WO2018044251A1

WO2018044251A1 - Method of conversion of municipal solid waste and other carbon-containing feedstock with high content of tars into synthesis gas and the equipment used in this method

Info

Publication number: WO2018044251A1
Application number: PCT/UA2017/000085
Authority: WO
Inventors: Sergii Yu STRIZHAK
Original assignee: Strizhak Sergii Yu
Priority date: 2016-08-29
Filing date: 2017-08-23
Publication date: 2018-03-08

Abstract

The invention relates to a method and a device for thermochemical conversion of municipal solid waste and other carbon-rich feedstock with high content of tars into synthesis gas. Conversion occurs in a two-stage process of pyrolysis (zone 1-4) and subsequent downdraft gasification (zone 5-7) of viscous bed of carbonaceous feedstock residue in a slow air-and-gas flow. Viscous bed is a heated layer of pulverized friable mass of carbonaceous feedstock residue obtained in the process of high-temperature pyrolysis and conveyed into combustion and gasification zone 5 in the form of densified mass. The device consists of a feedstock loading device (1), a rotary kiln of indirect heating (2), a device for discharging dust gas residue (3), a unit for feeding carbonaceous feedstock residue (4), a gasifier (5) and a unit for unloading of the slag (6). The invention also describes use of synthesis gas in the ways presented herein.

Description

METHOD OF CONVERSION OF MUNICIPAL SOLID WASTE AND OTHER CARBON-CONTAINING FEEDSTOCK WITH HIGH CONTENT OF TARS INTO

SYNTHESIS GAS AND THE EQUIPMENT USED IN THIS METHOD

This invention consists of the method of thermo-chemical conversion into the synthesis gas of municipal solid waste (MSW) and other tar-rich carbon-containing waste into synthesis gas through the two-stage process of pyrolysis and subsequent viscous bed downdraft gasification of the carbon-containing residue of the process of pyrolysis.

"Viscous bed" is a layer of burning-hot crumbled mass of carbon-containing residue of carbonaceous feedstock residue of the process of high-temperature pyrolysis that comes into the zone of combustion and gasification as compact mass.

This invention is also a basis for a device realizing the method of thermo-chemical conversion into the synthesis gas of municipal solid waste (MSW) and other carbon- containing waste with large tar content into synthesis gas through the two-stage process of pyrolysis and subsequent viscous bed downdraft gasification of the carbon-containing residue of the process of pyrolysis.

PREREQUISITES FOR THIS INVENTION

Deficiencies of modern technologies of thermochemical conversion of MSW and other hydrocarbon materials into synthesis gas.

Pressing global need in the sources of renewable energy and alternative raw materials for the synthesis of nitrate fertilizers, like carbamide, exists today. These renewables could minimize environmental impact and display maximal economic effectiveness. Demand for energy and raw materials for synthesis of hydrocarbons generated from fossil fuels grows with continuing growth of population. This intensifies negative impact on the environment.

Some gasification technologies have recently shown significant progress in the conversion- of residential waste, especially in generation of thermal energy, although it constitutes comparatively small segment of energy markets of the developed nations. A number of technological and economic obstacles to the extension of this segment exist, and they should be removed.

The use of the majority of technologies of MSW conversion into syngas have not until now reached industrial scale owing either to their low efficiency, or to their inadequacy to the ever more strict environmental norms and standards, or a combination of these two factors.

The matter is that currently existing technologies of thermochemical conversion of MSW and other hydrocarbon-rich materials into syngas for further generation of electricity and synthesis of chemical products have until now used the so-called traditional updraft and traditional downdraft principles of gasification. These two principles are based on the three theories of gasification (reviewed in more details further on) that were developed in previous century and were meant for the conversion into the syngas of the traditional types of materials, like charcoal, coke and low-tar dry wood. These materials contain small amount of hydrocarbons (10-20%) in gas phase and large amount of residual carbon (80-90%).

As MSW and other types of hydrocarbon materials with large amounts of tar belong to an entirely different category of fuels with high amounts of hydrocarbons in gas phase (60- 70%) and small amounts of residual carbon (30-40%), they are not suitable for traditional methods of their conversion into syngas. That is to say that all current technologies attempt to convert these types of materials into synthesis gas applying those old traditional principles of gasification based on the theories of gasification oriented for the conversion of materials that have entirely different thermochemical characteristics.

This approach entails negative outcomes in the form of the barriers that slow down the development and usage of new thermochemical technologies of recycling of domestic waste.

Technological obstacles

■ Imperfect technologies

■ Low efficiency of syngas production, hence low efficiency of electricity generation and synthesis of hydrocarbons

■ High selectivity of composition of solid waste

■ Complex and cumbersome design of conversion plants and a large number of the units of equipment, including those for syngas and smoke gases purification

■ Low scaling capacity of existing technologies

■ High thermal and electric energy consumption of conversion process

■ Use of fossil fuels in the process of conversion

■ Use of combined generating cycles in generation of electricity

■ Complexity of service and maintenance of equipment

■ Other technological shortcomings

Economic barriers

■ Long periods of cost recovery of conversion plants due to high capital and service and maintenance expenditures

Environmental barriers

■ Excessive emissions into the atmosphere of NO_x, COS, N¾, S0₂, ¾S, HC1, dioxides, furans, various aromatic hydrocarbons and many other substances

^■ High levels of tars and oxides of heavy metals in synthesis gas, hence the need to recover them after costly purification of gases resulting from conversion

^■ High content of carbon in the ash residue of conversion process. Ash residue being toxic due to high concentration of heavy metals, hence the need to dispose of it at special landfills for hazardous and toxic discards.

In addition to the abovementioned, traditional updraft and traditional downdraft methods of gasification employed in the technologies of conversion of traditional fuels into synthesis gas have substantial deficiencies of their own.

From technological perspective the downdraft method of gasification has clear advantages, but as it too has some shortcomings, the updraft method is more used in modern technologies.

An undisputed advantage of the downdraft method is that the tars, acids and steams released at initial stages of thermal conversion of the feedstock undergo almost complete conversion while passing the zone of high temperatures. They become transformed into simple combustible gases usable for power generation by gas reciprocators or gas engines. The costs of gas cooling and cleaning are minimal. The downdraft method and the gasifiers based on its application have flaws.

Deficiencies of the traditional downdraft method of gasification:

• Impossibility to use plasticizing and coking types of feedstock;

• Limited use of feedstock with high content of tars because of them polluting recovered syngas and high costs of the system of gas cleaning;

• Impossibility to use small or very large fraction feedstock, heterogeneous or compressed mass, as well as high ash content feedstock and feedstock with low melting temperature of ash;

• Heterogeneity of the volumes, temperatures and composition of recovered gases due to instability of the process of gasification;

• The need to maintain very high temperatures at the gasification reactor exhauster in order that relatively clean syngas be obtained. This reduces significantly the efficiency of the technology in terms of «cool gas»;

• Insufficient use of the heat of recovered syngas in gasification process. Its better use increases overall efficiency of gasification process;

• Low efficiency of gasification reactors due to the need of comparatively slow air inflow avoiding initiation of the process of formation of fluid ash;

• Instability of gasification process because of the need to terminate completely the process of gasification to avoid the feedstock suspension inside gasification reactor;

• The need to periodically stop gasification process to clean internal surfaces of gasification reactors of feedstock, ash and slag formations;

• Difficult disposal of toxic carbon-containing slag residue;

• Large losses of heat due to designs of gasification reactors.

In an attempt to overcome these shortcomings a new theory (referred to further in the text as Theory 4) of gasification was developed for feedstock with high content of hydrocarbons in gaseous phase and low content of residual carbon.

This theory is the foundation of a new method of conversion of MSW and other types of hydrocarbon feedstock with high content of tars into synthesis gas. The process consists of two-stage pyrolysis and subsequent downdraft gasification in the air-and-gas flow of viscous bed of carbonaceous residue of pyrolysis. The process has a working name, not yet patented, of VGP4 (Viscous Bed Gasification Process 4). Devices based on this process have been developed.

Subsequently, these discoveries have been embodied in the new gasification technology with working pre-patent name SYNTENA 2-VGP4 (SYNTENA 2 - Viscous Bed Gasification Process 4).

Gasification technology SYNTENA 2-VGP4

Technology SYNTENA 2-VGP described hereinafter under the acronym SYN 2- VGP4 is based upon method of thermo-chemical conversion into the synthesis gas of municipal solid waste (MSW) and other carbon-containing waste with large tar content into synthesis gas through the two-stage process of pyrolysis and subsequent gasification of viscous bed of carbon-containing residue in the air-and-gas flow using downdraft process of gasification. Equipment was developed based on this technology.

This technology is defined as a two stage pyrolysis and gasification technology realized in a single or double vessel technological design.

Method of thermo-chemical conversion into the synthesis gas of municipal solid waste (MSW) and other carbon-containing waste with large tar content into synthesis gas described in this application is materialized through the two-stage process of pyrolysis and subsequent gasification of the viscous bed of carbon-containing residue in the air-and-gas flow through the downdraft process of gasification made possible the development of additional technological and environmental advantages of gasification reactors using the principle of downdraft gasification:

► Main technological advantages: ^■ Horizontal positioning of key gas generating equipment;

^■ Simplicity of design and minimal amount of the units of equipment including synthesis and smoke gas cleaning equipment;

^■ Good scalability of technology enabling conversion of up to 1000 tons of MSW per day;

^■ Only the heat of exothermal reactions of the process of gasification itself is used for the process of thermochemical conversion of domestic waste into syngas;

^■ This technology makes possible thermochemical conversion of MSW of different composition, fractions and highly humid, conversion of various materials that was not possible before;

^■ Increased productivity thanks to intensified reactions of gas formation;

^■ Improved quality and homogeneity, increase of the quantity of generated syngas;

^■ No need for additional sources of heat for pre-treatment drying of domestic waste as all necessary heat is provided by smoke gases from gas reciprocating machines of electricity generating cycle or from the process of synthesis of nitrogen fertilizers. This makes possible to convert domestic waste with humidity higher than 50% without any additional energy input;

■ Simplicity of technological maintenance, the need for overhauls and preventive maintenance is minimal thanks to special design of gasification reactor. Besides, costs of syngas cleaning are reduced substantially due to the fact that major cleaning of syngas occurs within the process of gasification;

■ 78-86% "cool gas" output efficiency of gasification process with the amount of gas double that of other technologies having output of only 40-50% as compared to technology SYNTENA 2-VGP;

■ Possibility to use synthesis gas in gas reciprocating machines or gas turbines with 35-42% efficiency for electricity generation, which is two times higher than the efficiency steam turbines with the efficiency of about 20%.

■ This technology makes possible intense synthesis of nitrate fertilizers like carbamide with no need for natural gas;

■ Oxygen and steam mixture can be used instead of air;

■ Other alternative fuels can be used, including hazardous.

► Environmental advantages

■ Efficient utilization of domestic waste as a source of renewable energy for generation of environmentally clean electric power and synthesis of nitrate fertilizers; ^■ No need to use any external fuel as the process is based on the heat of exothermal reactions only generated within the process of gasification;

Prevention of formation of NOx, COS, NH₃, S0₂, H₂S, HC1 thanks to special features of technology and design of gasification process;

^■ Recovered syngas does not contain any compounds of aromatic hydrocarbons, volatile organic compounds (VOCs) or tars, because they are destroyed in the course of thermochemical process. This simplifies significantly the system of gas cleaning and guarantees that they are not emitted in the environment;

^■ Non-hazardous silica slags are formed in the process of gasification of nonorganic fractions of MSW. Heavy metals from the MSW are encapsulated within those slags, which are insoluble in water and can be used for industrial purposes.

^■ In compliance with the provisions of Kyoto Protocol and Paris Climate Convention emissions of C0₂ are reduced two to three times per every kilowatt of electricity in comparison with now existing technologies.

All the advantages listed above permit to efficiently convert MSW and other hydrocarbon-rich feedstock into syngas with its further use for the generation of electric power and /or synthesis of nitrate fertilizers. This advanced technology achieves a new level of economic efficiency as compared to the existing technologies of gasification.

LIST OF FIGURES

Fig. 1 shows the scheme of calculation characteristics referred to in the part "Relative calculation of the amount of pyrocarbon formed in the process of thermal conversion of hydrocarbons and tars making part of pyrolysis gases".

Fig. 2 shows schematic diagram of gas generator.

Fig. 3 shows the sketch of gas generator unit.

Fig. 4 demonstrates the sketch of pyrolysis part.

Fig. 5 shows the sketch of gasification part.

Fig. 6 shows configuration of gasification zone of carbon-containing residue of feedstock.

Fig. 7 demonstrates the scheme of computations describing the principle of operation of gas generator based on the method of thermochemical conversion into syngas of MSW and other carbon-rich feedstock with high content of tars executed through two-stage process of pyrolysis and subsequent gasification in the air-and-gas flow of viscous bed of carbonaceous residue.

Fig. 8 in the form of Table 1.1 shows morphological content of solid waste used in this computation.

Fig. 9 in the form of Table 1.2 shows element composition of MSW.

Fig. 10 in Table 1.3 shows the percentage of water evaporated during the drying of feedstock.

Fig. 11 shows in Table 2.1 the feedstock residue after drying.

Fig. 12 demonstrates Table 2.2 with element composition of feedstock residue after the feedstock moisture recovery process.

Fig. 13 compares in Table 2.3 supposed composition of gases resulting from the process of moisture recovery from aforementioned feedstock and the data referred to in the literature.

Fig. 14 compares in Table 2.4 design data and literature data of changed elementary composition of fuel before and after the process of the recovery of moisture.

Fig. 15 shows in Table 3.1 of the feedstock residue entering the zone of low temperature pyrolysis.

Fig. 16 lists in Table 3.2 the products of low temperature pyrolysis.

Fig. 17 demonstrates in Table 3.3 the aggregate composition of gases of the processes of drying, moisture removal and low-temperature pyrolysis coming into the channel for pyrolysis gases of gasifier.

Fig. 18 with Table 3.4 compares the estimate and literature data of the products of low-temperature pyrolysis.

Fig. 19 compares in Table 3.5 the estimate and literature data on gases of low temperature pyrolysis.

Fig. 20 in Table 3.6 compares the estimate and literature data of the tar of low- temperature pyrolysis (primary tar oil).

Fig. 21 in Table 3.7 gives the composition of the tar of semi-coking of the coal.

Fig. 22 shows in Table 4.1 the composition of the residue of solid carbonaceous feedstock after low-temperature pyrolysis (semi-coke) conveyed into the zone of high- temperature pyrolysis.

Fig. 23 in its Table 4.2 demonstrates supposed ratio of the products of high- temperature pyrolysis, composition of gases and tars compiled from the literature and taking into consideration morphology of the feedstock.

Fig. 24 describes in Table 4.3 thermal conversion of primary tar oil conveyed from the zone of low-temperature pyrolysis.

Fig. 25 in Table 4.4 demonstrates the gases resulting from thermal breakdown of primary tar oil. Fig. 26 in Table 4.5 gives the aggregate composition of tars in the channel of pyrolysis gases formed in low- and high-temperature pyrolysis.

Fig. 27 in Table 4.6 gives aggregate composition of gases of drying, moisture removal and semi-coking.

Fig. 28 in Table 4.7 shows conversion of hydrocarbons contained in the producer gas of low-temperature pyrolysis.

Fig. 29 in Table 4.8 shows the products of conversion of hydrocarbons contained in the producer gas of low-temperature pyrolysis.

Fig. 30 in Table 4.9 illustrates composition of producer gas of low-temperature pyrolysis after hydrocarbon conversion.

Fig. 31 in Table 4.10 shows aggregate composition of the gases exiting the zone of high temperature pyrolysis, with all gaseous products mixing among themselves when they enter the channel for pyrolysis gases after partial conversion of hydrocarbons occurred.

Fig. 32 compares in Table 4.11 the estimate and literature data on the products of high-temperature pyrolysis.

Fig. 33 makes comparison in Table 4.12 of the estimate and literature data on the gases of high-temperature pyrolysis.

Fig. 34 shows in Table 4.13 a comparison between the estimate and literature data on the tars of high-temperature pyrolysis.

Fig. 35 compares in Table 4.14 the data of the estimate and from the literature on solid feedstock residue of high temperature pyrolysis (coke).

Fig. 36 demonstrates in Table 5.1 composition and amount of gas products entering combustion and gasification zone.

Fig. 37 shows in Table 5.2 the data of thermal conversion of solid carbonaceous feedstock residue.

Fig. 38 shows in Table 5.3 the data on combustion of a part of solid carbonaceous residue.

Fig. 39 shows in Table 5.4 the data for composition of carbonaceous residue that remained after its partial combustion.

Fig. 40 shows in Table 5.5 the data on combustion of the tars.

Fig. 41 shows in Table 5.6 the data on the tars not having combusted in combustion zone.

Fig. 42 gives in Table 5.7 the data on combustion of the gases of pyrolysis.

Fig. 43 shows in Table 5.8 the data on the gases not having combusted in combustion zone. Fig. 44 describes in Table 5.9 the aggregate of gases formed in the zone of combustion.

Fig. 45 shows in Table 5.10 the total amount of air consumed.

Fig. 46 lists in Table 5.11 the products conveyed from combustion zone.

Fig. 47 in Table 5.12 quotes the data on thermal conversion of tars.

Fig. 48 displays in Table 5.13 the reactions of C0₂.

Fig. 49 displays in Table 5.14 reactions of C.

Fig. 50 lists in Table 5.15 reactions of CO.

Fig. 51 shows in Table 5.16 reactions of CH₄.

Fig. 52 lists in Table 5.17 reactions of C2H4.

Fig. 53 displays in Table 5.18 the aggregate composition of gases and other products resulting from the reactions in the zone of combustion and gasification.

Fig. 54 compares in Table 5.19 effective experimental and literature data on the products of gasification.

Fig. 55 compares in Table 5.20 effective experimental data, estimate and literature data on resulting gases.

Fig. 56 represents basic technological outline of the process of synthesis of carbamide.

THEORETICAL FOUNDATION OF THE INVENTION

In their simplified form the processes of gasification of carbon feedstock can be viewed as the interaction only of carbon with oxygen and water steam. This is characteristic of traditional gasifiers used for the conversion into synthesis gas of traditional feedstocks like charcoal, coke and dry wood with low content of tars. These are the kinds of feedstocks, whose thermochemical parameters correspond to low content of hydrocarbons (10-20%) in gas phase and high content of residual carbon (80-90%).

Similar model describes quite accurately real processes occurring in these devices, because feedstock containing up 96% of carbon goes into gasification zone.

At present three theories exist that describe thermochemical interaction of carbon and oxygen, the so-called three theories of gasification. They can be symbolically designated Theory 1, 2 and 3:

Theory 1

The theory of primary formation of carbon oxide through reaction:

2C+0₂=2CO (1)

According to this theory, carbon dioxide is a secondary product of the following oxidation of carbon oxide through reaction:

2CO+0₂=2C0₂ (2)

This theory is taken as the basis for the design of the majority of gasification devices. Theory 2

The theory of primary formation of carbon dioxide through reaction:

C+0₂=C0₂ (3)

In accordance with this theory carbon oxide is a secondary product of the recovery of carbon dioxide by heated up carbon of the fuel as a result of reaction:

C0₂ + C = CO (4)

Theory 3

The theory of intermediary formation of complex carbon-oxygen compound from the reaction:

xC+y/20₂-CxOy (5)

This theory assumes that CO and C0₂ are formed in different proportions from the CxOy compound depending on the conditions in which occur the reactions:

CxOy=mC0₂+nCO (6)

C0₂ conversion occurs according to the equation:

Cx+yC0₂=CxOy+yCO (7)

Thus part of resulting CO is a product of primary reactions of gasification and another part is a product of secondary reactions.

It was established that with the temperature rising gasification process is ameliorated owing to the reactions balance shifting towards formation of larger amount of CO and also towards intensification of the reactions of water gas:

H₂0+C -CO+H₂ (8)

2H₂0+C = C0₂ +H₂ (9)

There are three theories describing interaction between steam and hot carbon of solid feedstock. All three are based on the same principles that are valid for the interaction of carbon with oxygen.

Of these three theories of carbon gasification the third theory can be considered most adequate, as it describes interim formation of a complex carbon-oxygen compound and subsequent transformation of this compound into simple gaseous products, carbon dioxide (C0₂) and carbon oxide (CO).

Despite that, it was Theory 1 on which the design of the majority of gasification devices was based. In this theory reactions of "primary gasification" (Formula 1) are considered main ones and reactions of "secondary gasification" auxiliary (Formula 4). In the designs of some gasifiers secondary reactions (Formula 4) are not taken into consideration at all.

In major part of gasification reactors the main process of primary oxygen gasification occurs through the so-called "incomplete burning" (Formula 1), to which carbon of the fuel is mainly subjected. The amount of carbon sufficient for this process is achieved by the usage of carbon-rich fuels, such as coke, wood charcoal, firewood, peat. Reactions of gasification are in this case heterogeneous, and, due to low intensity of those reactions, they do not develop high temperatures. This, in its turn, generates producer gas with low calorific value and with high content of the C0₂.

The use of MSW and other carbonaceous types of waste with high tar content as a feedstock that are the types of fuel thermochemical characteristics of which correspond to high content of hydrocarbons (60-70%) in gas phase and low content of residual carbon in gasifiers of classic design result in even higher content of C0₂ the gases thus generated. This is caused directly by the amount of carbon insufficient for the reactions of gasification.

A new theory of gasification has been developed to resolve this problem. If we use numbers to mark the existing theories of gasification, this new theory can be tentatively called "Theory 4".

Based on Theory 4 a new method was developed, the method of thermo-chemical conversion of municipal solid waste (MSW) and other carbon-containing waste with large content of tars into synthesis gas through the two-stage process of pyrolysis and subsequent viscous bed downdraft gasification of the carbon-containing residue in the air-and-gas flow. Its working unpatented name is VGP4 (Viscous Bed Gasification Process 4). Equipment for the implementation of this method has been developed.

This method has become a foundation of technology SYNTENA 2-VGP4, developed for conversion into syngas of the MSW and other carbon-containing feedstock with thermochemical characteristics corresponding to high content of hydrocarbons in gas phase and low content of residual carbon.

Unique aspects of the new method of thermo-chemical conversion of municipal solid waste (MSW) and other carbon-containing waste with large content of tars into synthesis gas through the two-stage process of pyrolysis and subsequent viscous bed downdraft gasification of the carbon-containing residue in the air-and-gas flow made it possible to modify classic scheme of gasification. A new device has been created that constitutes this invention representing a new design of a gasifier, which was given a tentative name SYN2-GG (SYNTENA 2 Gas Generator). The latter makes it possible to reach the content of carbon sufficient for full scale gasification of the abovementioned types of feedstock. Theory 4 of gasification of MSW

The concept of the new theory of gasification, Theory 4, which is a foundation of the method of thermochemical conversion into syngas of MSW and other carbon-containing waste with large content of tars into synthesis gas through the two-stage process of pyrolysis and subsequent downdraft viscous bed gasification of the carbon-containing residue in the air- and-gas flow is as follows. Gaseous products that are formed at the initial stage of thermochemical conversion of feedstock through its drying, removal of moisture, low- and high-temperature pyrolysis, contain large amount of various hydrocarbons and tars. They are conveyed into the zone of combustion and gasification, where part of them are burnt and thermally decomposed in a layer of carbonaceous residue resulting from the pyrolysis of this feedstock.

Partial combustion of pyrolysis gases occurs because the amount of oxygen conveyed into the fuel input unit of gasification reactor is insufficient for complete burning of these gases, which is the main condition for entire process of gasification.

As the speeds of homogenous reactions is one or two orders of value higher than the speeds of those heterogeneous, homogenous reactions of the combustion of gaseous products of pyrolysis first occur in the zone of combustion and gasification. Heterogeneous reaction between oxygen and solid carbon can only be secondary.

The carbon resulting from a preliminary pyrolysis of the feedstock, and pyro-carbon resulting from incomplete combustion of pyrolysis gases with high calorie values, are subjected to intense heating-up during the combustion of pyrolysis gases. This causes the intensification of the "secondary" reactions of gasification (Formula 4).

Reactions of water gas (8) are also enhanced by high temperatures, resulting in the increase of ¾, CO content in the gas, and respective decrease of N₂. Because of these processes synthesis gas is formed, which in fact consists of simple combustible gases CO and H₂, with small content of CH₄ and C_xH_y. Content of C0₂ remains minimal.

In conjunction with above mentioned, Theory 4 can be construed as a development of Theory 2.

Given the existing three theories of gasification, the new Theory 4 can be outlined as follows:

CxH_yO_z + ((2(x-a)+b-z)/2)0₂ = x-aC0₂ + bH₂0 + (y/2-b)H₂ + aC (10)

H₂0 + C = CO + H₂ (8)

2H₂0 + C = C0₂ + H₂ (9)

C0₂ + C = CO (4)

First equation (Formula 10) describes the process of incomplete burning of a part of pyrolysis gases in the zone of combustion and gasification with formation of carbon dioxide and water vapor, as well as partial thermal conversion of the residue of these gases with formation of hydrogen and residual pyro-carbon, generated by the reaction of de-hydration (Formula 1 1 and Formula 12):

C„H_2n+2→ C„H₂„ + H₂ (11)

CnH_2n H C_mH_2m+2→ (n+m)C + (2n+2m+2)H₂ (12)

Three subsequent reactions (Formula 4, Formula 8 and Formula 9) are the reactions of conversion of smoke gases into conventional flammable gases CO and H₂ occurring inside a layer of red-hot carbonaceous residue. Formula 8 and Formula 9 are the reactions of hydro- gasification of carbon, and Formula 4 is the reaction of the reduction of C0₂ into CO.

Another variant of the implementation of this invention is possible with another formulation of Theory 4:

CxHyOz→ C0₂ + CO + H₂0 + C_aH_b+ H₂ + C (13)

H2 + C0 + CaHb + 0₂→C0₂ + H₂0 + H₂ + C (14)

H₂0 + C = CO + H₂ (8)

2H₂0 + C - C0₂ + H₂ (9)

C0₂ + C - CO (4)

The equation of Formula 13 describes schematically the process of pyrolysis of hydrocarbon feedstock - C_xH_yO_z. In their simplified form the products of this pyrolysis are C0₂, H₂0, CO, H₂, hydrocarbons C_aH_B and pyro-carbon C.

Hydrogen, carbon monoxide and hydrocarbons partially burn in the process of gasification generating carbon dioxide and water vapor. Their residues become subjects of partial thermal conversion generating hydrogen and residual pyro-carbon, as schematically described by the equation of Formula 14.

Thus generated CO₂ and H₂0 are converted into the conventional flammable gases CO and H₂ within the layer of red-hot carbonaceous residue through the reactions of "secondary" gasification (Formula 4) and reactions of hydro-gasification (Formula 8 and Formula 9). The three latter equations (Formula 4, Formula 8 and Formula 9) are analogous to the previous scheme.

It is worth to note that pyro-carbon resulting from incomplete combustion and thermal conversion of pyrolysis gases (Formula 12) makes up for the overall deficiency of carbon in carbonaceous residue of the feedstock and is the first to enter the reactions of gasification and hydro-gasification (Formula 4, Formula 8 and Formula 9).

It must be noted also that in up-draft gasification highly wet feedstock can be used, or an additional amount of water together with air can be fed, resulting into an increase of methane CH₄ as in the reaction of methanization:

2H₂0 + 2C = CH₄ + CO (15)

This scheme of gasification makes it possible to process highly damp feedstock with high content of volatile substances, utilization of which in classic design gasifiers can be problematic due to the lack of carbon for the reactions of reduction. As a result, producer gas in them can have higher content of hydrocarbons, tars, C0₂, H₂0 and, respectively, N2.

For the sake of clarity of description of the benefits of the method of pyrolysis and subsequent gasification of viscous layer of feedstock in thermochemical conversion into synthesis gas of solid waste and other carbonaceous feedstock with high content of tars, it can be described with design parameters of "black box", as presented in Fig. 1. This scheme corresponds to the estimated parameters referred to in the chapter "Relative estimate of the amount of pyro-carbon formed in the process of thermal conversion of hydrocarbons and tars being part of pyrolysis gases".

Brief description of the method of thermochemical conversion into synthesis gas of MSW and other carbon-based feedstock with high content of tars, applied through the two-stage process of pyrolysis and subsequent downdraft viscous bed gasification of carbon-rich residue in the air-gas flow.

Method of thermochemical conversion into synthesis gas of MSW and other carbon- based feedstock with high content of tars, applied through the two-stage process of pyrolysis and subsequent downdraft viscous bed gasification of carbon-rich residue in the air-gas flow is used in the gasification reactor SYN2-GG, in which the entire process of generation of syngas is relatively divided into the seven separate temperature zones.

The first three zones are the zones of low-temperature processing of the feedstock. They are located in a pyrolysis section of the gasifier, which is a rotary kiln of special design (is referred to as SYN2-RK in the description annexed to this application) placed horizontally or slightly inclined vis-a-vis the horizon, and heated by the heat of syngas generated during gasification of feedstock. The other four zones are the zones of high temperature processing of feedstock. They are located in gasification section of gasification reactor, which is a downdraft gasifier (can be referred to in this application as SY 2-VG) of special design. The gasifier is connected to the rotary kiln by a body connector or by tubes. Design of the SYN2- GG is presented in Fig. 2.

Zones of low-temperature processing of feedstock:

Zone 1 - Drying section.

Temperatures: T - 30- 120°C.

Operations in this zone are: • sizing of feedstock through crushing of its lumps into smallest primary fractions, its drying and poking inside revolving internal body of rotary kiln;

• homogenization of feedstock:

• primary heating up of the feedstock with the heat of the syngas conveyed through the walls of the inner body of rotary kiln;

• final drying of the feedstock and intense formation of steam with boiling of recovered moisture;

• partial removal from the feedstock of the water tied in colloids and of adsorbed gases;

• beginning of the process of conversion of the state of the fusible elements of feedstock in the form of the softening of outer zones of these elements;

• initiation of the process of formation of gases.

Main feature of this zone is that during the pre-treatment of feedstock the largest part of its moisture and of the water tied in colloids are evaporated. Adsorbed gases are also released and decomposition of feedstock under these low temperatures is manifested in a weak manner, only through hardly noticeable formation of gases.

Zone 2 - moisture recovery zone

Temperatures: T - 120 - 300°C.

In this zone:

• final drying of the feedstock takes place and colloid water is removed;

• conversion of the state of matter of the feedstock occurs;

• processes of decomposition and destruction of organic polymers starts;

• initial formation of tars and of saturated and unsaturated hydrocarbons occurs. It is in this zone that gas starts to be released from the feedstock. This gas mainly consists of carbon dioxide and water. Amount of gas released under the temperature of 250°C can reach 2% - 2,5% of the total weight of feedstock fed into a gasifier. This conversion results in the loss of oxygen that is taken away from the feedstock in the form of water vapor, carbon dioxide and monoxide. Feedstock residue starts being enriched by carbon.

Zone 3 - low-temperature pyrolysis zone

Temperatures: T - 300 - 700°C.

In this zone the following processes occur:

• formation of saturated and non-saturated hydrocarbons, release of the vapors of light resinous substances;

• structural changes in the mass of feedstock, its conversion into homogenous crushed mass of carbonaceous feedstock residue;

• disintegration of some organic salts with formation of respective oxides;

• beginning of the process of reduction of oxides into metals.

This zone is characterized by increased formation of gases. Gases formed here have larger content of CO2 and of saturated and unsaturated hydrocarbons. Under the temperature of 350°C non-condensing gases start to be released. Condensing products start to be released at the same time, such as vapors of oil tar. Their amount increase and reaches maximum at the temperatures of 500° - 550°C. Large amount of the so-called pyroligneous water is also released from the feedstock, and the feedstock residue enriches significantly with carbon.

Zones of high-temperature processing of feedstock:

Zone 4 - zone of the high-temperature pyrolysis of feedstock

Temperatures: T - 700 - 1100°C

In this zone:

• reactions of high-temperature pyrolysis occur;

• decomposition and melting of some part of inorganic salts occurs, and their interaction with carbon and mineral components of carbonaceous residue of feedstock;

• reduction of metals from the oxides occur;

• reduced metals are oxidized under the influence of CO2 and H2O;

• conversion of the feedstock residue into a friable porous bed of carbon take place.

In this zone end gasification processes that occur in the zone of combustion and gasification. Also volatile hydrocarbons and tars some part of which under the impact of high temperatures are released, H2O and CO2 are converted into simple gases H₂ and CO.

Amount of carbon in feedstock residue reaches its maximum as a result of these processes.

Zone 5 - zone of combustion and gasification

Temperatures: T - 1100-1350°C.

The following processes take place in it:

• partial combustion of pyrolysis gases formed in the zones of low-temperature processing of feedstock and of high-temperature pyrolysis;

• conversion of carbon residue of the feedstock into the state of a "boiling" bed due to the dynamic of partial combustion of pyrolysis gases;

• gasification, or the process of reduction of combustion gases because of oxidation of burning hot carbonaceous residue of feedstock;

• thermal conversion of hydrocarbons and tars entering the zone of combustion and gasification;

• melting of inorganic component of carbonaceous residue;

• reactions of oxidation and reduction in inorganic component of carbonaceous residue;

• cleaning of the gases with the removal of hazardous components of gas;

• formation of slag.

The main processes in this zone are partial combustion in the oxygen of air flown inside, and thermal decomposition of gaseous products of pyrolysis. There is also intense interaction between burning-hot carbonaceous residue of feedstock with oxidizing gases resulting from combustion of some part of pyrolysis gases conveyed from the zones of low- temperature processing of feedstock. All the processes occur directly inside the bed of carbonaceous residue conveyed from the zone of high- temperature pyrolysis of feedstock.

Zone 6 - slag zone (zone of additional gasification)

Temperatures: T - 150 - 1100°C.

In this zone:

• the process of gasification of a part of red-hot carbon residue occurs, the residue coming from the zone of combustion and gasification under the impact of water steam conveyed into this zone;

• slag finishes forming and cools;

• slag is mechanically crushed;

• slag is removed from the gasifier.

In this zone the slag conveyed from the zone of combustion and gasification is cooled with air flown into the gasifier and water steam fed directly into the slag zone. It is then mechanically crushed and removed from the gasifier.

Zone 7 - gas zone

Temperatures: T- 120 - 900°C.

In this zone:

• hot synthesis gas is separated from slag- carbon dust;

• hot synthesis gas is cooled.

In this zone owing to the low speed of gas flow in the internal space of gas zone of gasifier SY 2-VG and natural gravitation hot syngas is separated from slag-carbon dust of carbonaceous feedstock residue. Synthesis gas is also cooled and cleaned of slag and carbon dust in the gas jacket of rotary kiln SYN2-RK. Description of the design and of the principle of operation of the device of this invention

The main device is gasification reactor SYN2-GG, representing a device executing pyrolysis and gasification, thermo-chemically converting solid waste and other carbon containing feedstock with high content of tars into syngas. Detailed design of the device is presented in Fig. 3.

Gasification reactor SYN2-GG consists of two parts:

A. Pyrolysis unit, which is a rotary kiln SYN2-RK for sloping heating. It has original design shown in Fig. 4, consisting of the following devices:

1. Input unit for feeding the feedstock into the rotary kiln.

2. Rotary kiln for indirect heating SYN2-RK.

3. Device for unloading dust gas residue from rotary kiln.

B. Gasification unit, which is gasifier SY 2-VG of downdraft gasification of the viscous bed of feedstock, shown in Fig. 5 and consisting of the following devices:

4. Unit for the feeding of carbonaceous feedstock residue into the gasifier.

5. Gasifier SYN2-VG.

6. Device for unloading the slag from the gasifier.

Input unit conveying the feedstock into the rotary kiln

Device that loads the feedstock into the rotary kiln (1) presented in Fig. 3 loads the feedstock (solid waste) into the rotary kiln for indirect heating (2).

It consists of the following components:

1. Bunker.

2. Vertical piston mechanism.

3. Slide gate.

4. Vertical loading channel.

5. Horizontal loading channel.

6. Horizontal piston mechanism.

PI. Hydraulic cylinder of vertical piston mechanism.

P2. Hydraulic cylinder of slide gate.

P3. Hydraulic cylinder of horizontal piston mechanism.

Design of the device that loads the feedstock into the rotary kiln for indirect heating

Device that feeds the rotary kiln (1) consists of the bunker 1 that has rectangular cross- section with vertical back wall and sloping side and front walls. Vertical piston mechanism 2 of the loading device with hydraulic cylinder PI is fastened to the vertical back wall of the bunker 1.

Vertical loading channel 4, divided into the upper and lower pipes of the vertical loading channel 4 that has rectangular or round cross-section, is weld onto the lower part of bunker 1. Between these two pipes there is slide gate 3 that has hydraulic cylinder P2. Lower part of the lower pipe of vertical loading channel 4 is weld on horizontal loading channel 5 that has round or rectangular cross-section and a mounting flange at its front end. Inside horizontal loading channel 5 there is horizontal piston mechanism 6 equipped with hydraulic cylinder P3 and attached to horizontal loading channel 5 with the bolt joining of coupling flange of horizontal piston mechanism 6 and horizontal loading channel 5.

Operation of the loading device of the rotary kiln for indirect heating

Pre-treated feedstock having passed through the system of feedstock pre-treatment (Fig. 3) of the technological complex SYN2-TC is conveyed by a conveyor belt to bunker 1 of the feedstock loading device (1), equipped with the vertical piston mechanism 2. In bunker 1, under the impact of movement of the piston of vertical piston mechanism 2, moved by hydraulic cylinder PI, the feedstock is compacted and conveyed through the vertical loading channel 4 into horizontal loading channel 5. In horizontal loading channel 5 under the impact of horizontal movement of the piston of horizontal piston mechanism 6, moved by hydraulic cylinder P3, the feedstock is conveyed into the tilted rotary kiln of indirect heating (2). At this time in horizontal loading channel 5, between the front end of the piston of horizontal piston mechanism 6 and back end of horizontal loading channel 5 a plug is formed by the feedstock. This plug prevents pyrolysis gases escape from the rotary kiln of indirect heating (2) into the atmosphere through the feedstock loading device (1).

In order to completely prevent the release of pyrolysis gases into the atmosphere from the rotary kiln of indirect heating (2), there is in the vertical loading channel 4 the slide gate 3. It is shut at all times and is only opened by hydraulic cylinder PI , when the piston of the vertical piston mechanism 2 moves down. When the piston of the vertical piston mechanism 2 moves up, the slide gate 3 shuts down, totally eliminating a possibility of escape of pyrolysis gases from the rotary kiln (2) into the atmosphere.

All mechanisms of the loading device (1) operate in full coordination among themselves allowing to manage the output and make the work of the device uninterrupted.

Rotary kiln of indirect heating

Inclined rotary kiln of indirect heating (2) is presented in Fig. 4. It is used for drying, moisture recovery and low temperature pyrolysis of feedstock.

Inclined rotary kiln of indirect heating is horizontally placed and consists of two bodies:

7. The inner body of the rotary kiln

8. The outer body of the rotary kiln

The inner body of the rotary kiln

The inner body of the rotary kiln is composed of the following components:

9. Round rib of the inner body

9.1. Outlets for pyrolysis gas and carbonaceous residue

9.2. External guide vanes

9.3. Internal guide vanes

10. Front oil seal hub of inner body

11. Back hub

12. Central hub

13. Supporting front wheel

14. Front supporting blocks

15. Supporting back wheel

16. Back supporting block

17. Back toe block

18. Ring gear

19. Pinion gear

20. Drive of rotary kiln

P4. Motor of rotary kiln

Design of the inner body of the rotary kiln

Design of the inner body of the rotary kiln 7 includes round rib of the inner body 9 with round cross-section. Inner guide vanes 9.2 are welded inside it, and spiral shape outer guide vanes 9.3 are welded to the outer surface of the rib. They are slightly inclined towards the rib's axis. In the back part of the rib of the inner body 9 there are outlets for pyrolysis gases and carbonaceous residue. Front oil seal hub 10 is welded to the front end of the rib of the inner body 9. In the headstock there is a channel for the installation of the feedstock loading unit, inside which there is an oil seal. In the front part of the front oil seal hub of inner body 10 there is a site for the supporting front wheel 13 bearing in its lower part on two supporting blocks 14. Ring gear 18 is welded to the central part of the front oil seal hub of inner body 10. Ring gear 20 meshes with the pinion gear 19 moved by electric or hydraulic drive of the rotary kiln 20.

Central hub 12 is welded to the central part of the rib of the inner body 9.

Back hub of the inner body 11 is welded to the back end of the rib of the inner body 9. Inside the tailstock there is a site, where back supporting wheel 15 is installed. In its lower part supporting wheel bears on the two back supporting blocks 16 and the side of the back supporting wheel 15 bears on the back toe block 17.

Outer body of the rotary kiln

Outer body of the rotary kiln SYN2-RK consists of the following components:

21. Front rib of the outer body

22. Front flange of the front rib of the outer body

23. Back oil seal flange of the front rib of the outer body

24. Front oil seal flange of the front rib of the outer body

25. Hot syngas inlet tube

26. Cold syngas outlet tube

27. Outlet tube for dust residue

28. Back rib of the outer body

29. Front oil seal flange of the back rib of the outer body

30. Back flange of the back rib of the outer body

31. Back oil seal flange of the back rib of the outer body

32. Hot pyrolysis gas outlet tube

33. Valve for emergency pressure relief

34. Carbonaceous residue outlet tube

35. Supporting feet of the front rib of the outer body

36. Supporting feet of the back rib of the outer body

37. Thermal insulation jacket of rotary kiln

38. Outer casing of rotary kiln

Design of the outer body of rotary kiln

Design of the outer body 8 of the rotary kiln includes the front rib of the outer body 21 and back rib of the outer body 28 having the heat insulation jacket of rotary kiln 37 and outer coat of rotary kiln 38.

Front flange of front rib of outer body 22 is welded to front end of front rib of outer body 21. Front oil seal flange of the front rib of outer body 24 is attached to front flange of front rib 22 with the bolts. Back oil seal flange of the front rib of outer body 23 is welded to back end of front rib of outer body 21. To the upper front part of the front rib of the outer body 21 cold syngas outlet tube 26 is welded, in the back part of front rib of outer body 21 there is tangentially welded hot syngas inlet tube 25 and the outlet tube of dust residue 27, which is welded in the lower part of the back of front rib of outer body 21.

There are four support feet 35 of the front rib of outer body 21 that are welded to the front rib of outer body 21. It is with these feet that it is attached to the frame structure of rotary kiln.

Front oil seal flange of the back rib of outer body 29 is welded to the front end of the back rib of outer body 28, and at the back part of back rib of outer body 29 the back flange of the back rib of outer body 30 is welded, to which the back oil seal flange of back rib of outer body 31 is attached with the bolts. In the upper central part of back rib of outer body 28 the hot pyrolysis gas outlet tube 32 is welded. It is equipped with the valve for emergency pressure relief 33. In the lower central part of the back rib of outer body 28 carbonaceous residue outlet tube 34 is welded. Also, four supporting feet of the back rib of the outer body 36 are welded to the back rib of outer body 28. It is with these feet that it is attached to the frame structure of rotary kiln at 3-5" to the horizon.

General description of the design of inclined rotary kiln for indirect heating

Rotary kiln for indirect heating SYN2-RK consists of rotating inner body of rotary kiln 7 and of outer body of rotary kiln 8 that is stationary and is fixed on the frame of its own.

Rotation of inner body of rotary kiln 7 occurs inside stationary outer body of rotary kiln 8. These are connected by gasproof oil seal systems located on the inner surfaces of the front oils seal flange of the front rib of outer body 24, of the back oil seal flange of the front rib of outer body 23, of the front oil seal flange of back rib of outer body 29 and of back oil seal flange of back rib of outer body 31. These gasproof oil seal systems make it possible to separate working zone of rotary kiln inside inner body of rotary kiln 7 from gas jacket located between inner body of rotary kiln 7 and outer body rotary kiln 8, and insulate both these zones from the atmosphere.

Calculation of dimensions of inner body of rotary kiln 7 and of outer body of rotary kiln 8, as well as calculations of all gas zones, is based on amounts of feedstock, its composition and moisture content.

Depending on installation of external compressor equipment, gas zones of rotary kiln can experience either heightened or lowered pressure of gas.

General dimensions of inclined rotary kiln for indirect heating (2), and an angle of its inclination with respect to the horizon and velocity of its rotation are calculated upon parameters of maximal thermal processing of feedstock in the inside zone of inner body of rotary kiln 7 by the heat of hot syngas, generated in the gasifier (5) and moving in the gas jacket located between inner body of rotary kiln 7 and its outer body 8.

Operation of inclined rotary kiln for indirect heating

Feedstock is fed into the inside zone of rotating inner body 7 of inclined rotary kiln for indirect heating (2) through an open end of horizontal loading channel 5 of the feeding unit (1) installed in the oil seal headstock of inner body 10.

Front oil seal hub of outer body 10 has gasproof oil seal hub system preventing the gases formed in the inside zone of inner body of rotary kiln 7 to be released into the atmosphere through a gap between the inner wall of the front oil seal hub of inner body 10 and the outer wall of horizontal loading channel 5 of the feeding unit of rotary kiln (1).

Inner body of rotary kiln 7 rotates due to the impact from electric or hydraulic drive of rotary kiln 20 conducted to inner body of rotary kiln 7 via pinion gear 19 and ring gear 18. While rotating, inner body of rotary kiln 7 bears with its supporting front wheel 13 on the two revolving front supporting blocks 14 and with its supporting back wheel 15 on the two back supporting blocks 16.

In the lower part of inclined rotary kiln of indirect heating (2) there is back toe block 17, against which rotating inner body 7 is set, making it possible to fix its back part relative to outer body of rotary kiln 8.

Feedstock fed into the working zone of rotary kiln (2) moves in there longitudinally thanks to the feedstock's sliding along internal guide vanes 9.1 and to the rotation of the inner body of rotary kiln 7. The feedstock is subjected to thermal processing by the heat conducted to it through the walls of the inner body of rotary kiln 7 from hot synthesis gas generated in gasifier SYN2-VG (5), and moving in gas jacket between the inner body 7 and outer body 8 of rotary kiln.

Inner body of rotary kiln 7 has on its outside external guide vanes 9.2 welded at some angle to inner body. They increase the area of heat transfer of the inner body of rotary kiln 7 and direct the movement of hot syngas in gas jacket along spiral trajectory along the surface of inner body of rotary kiln 7. These two factors significantly increase heat transfer and time of contact of hot syngas with inner body of rotary kiln 7 and with feedstock, reducing at the same time the overall size of rotary kiln.

Hot syngas is brought at the temperature of 500-700°C into the gas jacket between inner body 7 and outer body 8 of rotary kiln through the inlet tube of hot synthesis gas 25. Having moved in spiral trajectory along the surface of inner body of rotary kiln 7 and having given its heat to feedstock, syngas is cooled down to 120-150°C and taken out of gas jacket through the cold syngas outlet tube 26 and conveyed further through heat-insulated gas pipes into gas cleaning system. Besides, in gas jacket placed at small inclination relative to horizon, due to gravitational and centrifugal constituents of spiral movement of syngas, its primary cleaning of dust brought out of gasifier (5) together with syngas occurs. The dust at that time falls out along the walls of gas channel and in its lower part.

While in operation, the inner body of rotary kiln 7 makes revolving movement inside the outer body of rotary kiln 8 and with its external guide vanes 9.2 welded to the outer surface of its rib cleans the walls and all the space of gas jacket of dust residue. It also transports dust residue along the lower part of outer body of rotary kiln 8 to outlet tube of dust residue 27, located in the lower down part of the front rib of outer body 21, through which dust residue is taken out of inclined rotary kiln.

This unit operates as horizontal cyclone with mechanical cleaning of inside walls of the dust using rotation of the inside part, which is the inner body of rotary kiln 7.

As the feedstock is moving inside the working zone of rotary kiln, the process of its thermochemical conversion takes place that can be relatively divided into the three temperature zones:

Zone 1 - Drying zone: T 30 - 120°C;

Zone 2 - Moisture removal zone: T 120 ~ 300°C;

Zone 3 - Zone of low-temperature pyrolysis: T 300 - 700°C.

As a result of thermal processing of feedstock, in these zones hot pyrolysis gases are formed and hot carbonaceous feedstock residue, which are removed from the working zone of inner body of rotary kiln 7 through outlets for pyrolysis gas and carbonaceous residue 9.1. At this stage hot pyrolysis gases pass through gas interstice between inner body of rotary kiln 7 and outer body of rotary kiln 8 and are conveyed into gasifier SY 2-VG (5) through the hot pyrolysis gas outlet tube 32, and hot carbonaceous feedstock residue is put into vertical channel 43 of the device feeding carbonaceous feedstock residue into the gasifier (4).

Hot pyrolysis gas outlet tube 32 has an outer heat insulation jacket. At upper end of the tube's vertical portion there is the valve for emergency pressure relief 33, through which excessive gas pressure in the working zone of the inner body of rotary kiln 7 can be relieved should there be any unconventional situations during the operation of inclined rotary kiln of indirect heating (2).

Inclined rotary kiln of indirect heating (2) has thermal insulation jacket 37 and outer casing 38, minimizing heat loss into atmosphere. The work of the drive of rotary kiln 20 is synchronized with the work of all mechanisms of the input unit (1), of the device for unloading dust gas residue (3) and of unit for the feeding of carbonaceous feedstock residue into the gasifier (4). This makes it possible to manage the efficiency of gasification reactor SYN2-GG, make its operation uninterrupted and guarantee maximal low-temperature processing of feedstock in inclined rotary kiln for indirect heating (2).

Device for unloading dust gas residue from inclined rotary kiln

Device for unloading dust gas residue from rotary kiln (3) presented in Fig. 4 is used for the removal of dust from the syngas channel, located between inner body of rotary kiln 7 and outer body of rotary kiln 8.

It consists of the following components:

39. Sluice

40. Upper slide gate

41. Lower slide gate

42. Vertical channel

43. Horizontal channel

44. Screw mechanism

P5. Hydraulic cylinder of upper slide gate

P6. Hydraulic cylinder of lower slide gate

P7. Drive of screw mechanism

Design of the device for unloading dust gas residue from the rotary kiln

Device for unloading dust gas residue from rotary kiln (3) consists of sluice 39, equipped with upper slide gate 40, lower slide gate 41, put in motion by hydraulic cylinders P5 and P6. Sluice 39 is in its upper part attached by the bolts to the flange of outlet tube for dust residue 27. In its lower part sluice 39 is attached by its lower flange to the flange of the pipe of vertical channel 42 with the bolted-on attachment for a pair of flanges. The pipe of vertical channel 42 may have rectangular or round cross-section. The lower part of the pipe of vertical channel 42 is welded to horizontal channel 43 that has round cross-section and attachment flange at its front end. Its back end is welded to an opening in the carbonaceous residue outlet tube 34. Inside horizontal channel 43 there is a screw mechanism 44 equipped with an electric or hydraulic motor P7 and connected with horizontal channel 43 with the bolted-on attachment for a pair of flanges of screw mechanism 44 and horizontal channel 43.

Operation of the device for unloading dust gas residue from rotary kiln

Dust residue of synthesis gas goes from gas jacket of rotary kiln of indirect heating (2) into the device for unloading dust gas residue of rotary kiln (3) via the outlet tube for dust residue 27. At the beginning of unloading process the upper slide gate 40 is in the shut position and lower slide gate 41 is open. Because upper slide gate 40 is shut, dust residue accumulates in the outlet tube for dust residue 27 in the amount equal or smaller than the volume of inner chamber of sluice 39.

After calculated amount of dust residue has accumulated in the outlet tube for dust residue 27, upper slide gate 40 opens and lower slide gate 41 shuts down under the impact of the movement of hydraulic cylinders P5 and P6. Dust gas residue goes down from outlet tube for dust residue 27 into the internal space of the chamber of sluice 39. After that upper slide gate 40 shuts down under the impact of hydraulic cylinder of upper slide gate P5. After it is shut, lower slide gate 41 opens under the impact of the movement of hydraulic cylinder of lower slide gate P6, and all dust residue from the inner chamber of sluice 39 is unloaded through vertical channel 42 into horizontal channel 43. From there, under the impact of spiral movement of screw mechanism 44 driven by electric or hydraulic motor P7, dust residue moves into the carbonaceous residue outlet tube 34.

Afterwards this entire process is repeated automatically.

Unit for the feeding of carbonaceous feedstock residue into the gasifier

Unit for feeding of carbonaceous feedstock residue into the gasifier (4) outlined in Fig. 5 is used for loading into gasifier (5) of carbonaceous feedstock residue of MSW after thermal conversion of feedstock in rotary kiln for indirect heating (2).

It consists of the following parts:

45. Vertical channel

46. Horizontal channel

47. Screw mechanism

P8. Motor of screw mechanism

Design of the unit for the feeding of carbonaceous feedstock residue into the gasifier

Unit for the feeding of carbonaceous feedstock residue into the gasifier (4) consists of the pipe of vertical channel 45, the cross-section of which is round or rectangular, connected with the carbonaceous residue outlet tube 34 with flanges.

The lower part of the pipe of vertical channel 45 is welded to the pipe of horizontal channel 46 with round cross-section. In its central part horizontal channel 40 has securing flange, with which it is attached by the bolts to the flange of the pipe of the gasifier feeding unit 52.

Inside horizontal channel 46 there is screw mechanism 47 equipped with electric or hydraulic drive P8. The mechanism is attached to horizontal channel 46 with the bolted-on attachment for a pair of flanges.

Operation of the unit for the feeding of carbonaceous feedstock residue into the gasifier

After low-temperature pyrolysis of feedstock in inclined rotary kiln of indirect heating (2) carbonaceous residue of feedstock goes through carbonaceous residue outlet tube 34 into the vertical channel of the unit for feeding of carbonaceous feedstock residue into the gasifier (4)·

Carbonaceous residue from the vertical channel 45 pours into horizontal channel 46. From there, under the impact of spiral movement of screw mechanism 47, driven by electric or hydraulic drive P8, carbonaceous residue moves inside gasifier (5) through the open end of horizontal feeding channel 46.

Afterwards this process repeats automatically.

Design of gasification reactor SYN2-VG

Gasifier (5) is schematically presented in Fig. 5. It is used for generation of synthesis gas from pyrolysis gases and carbonaceous feedstock residue, resulting from low-temperature pyrolysis of MSW in inclined rotary kiln for indirect heating (2).

It consists of the following components:

48. Body of the gasifier

49. Upper flange

50. Lower flange

51. Branch pipe for the input of pyrolysis gases

52. Branch pipe for installation of feeding unit

53. Outlet branch pipe for hot synthesis gas

54. Heat insulation jacket

55. Outer protective casing

56. Fuel chamber

57. Inner wall of the fuel chamber

58. Outer wall of the fuel chamber

59. Air lances

60. Inner wall of the air channel

61. Air distribution box

62. Air channel

63. Hot synthesis gas channel

64. Feeder shaft

65. Channel for hot pyrolysis gases

66. Upper flange of the feeder shaft

67. Vanes of the feeder shaft

68. Lower gas slots

69. Upper gas slots

70. Screw mechanism

71. Supporting feet

P9. Motor of screw mechanism Design of gasification reactor of carbonaceous feedstock residue SYN2-VG

Gasification reactor's body 48 has outer heat insulation jacket 54 covered by outer protective casing 55. It also has the upper and lower ribs of different diameter welded with each other by connecting insert. Upper flange 49 is welded to the upper end of the rib of the body of the gasifier 48 and to the lower end of the rib of the body of the gasifier 48 the lower flange 50 is welded. Branch pipe for the input of hot pyrolysis gases 51 equipped in its upper part with connecting flange is welded by its lower end to the upper part of the upper rib of the body of the gasifier 48. Outlet branch pipe for hot synthesis gas 53 that has connecting flange in its upper part is welded to the upper part of the lower rib of the body of the gasifier 48.

In the lower part of the upper rib of gasifier' s body 48 fuel chamber 56 is located. It is a hollow structure, the body of which consists of the inner wall of the fuel chamber 57 and its outer wall 58, connected between themselves by upper and lower inserts. There are the slots for air channels in the upper insert.

In the upper part of the fuel chamber 57 the air lances 59 are located. They connect the hollow body of the fuel chamber 56 with its inner volume.

Between the wall of the lower rib of gasifier' s body 48 and inner wall of air channel 60 there is air channel 62 located, limited at its bottom part by lower flange 50, in which there are air flange channels 77. Air channel 62 in its upper part has the air distribution box 61.

Between the inner wall of air channel 60 and outer wall of fuel chamber 58 there is a channel of hot synthesis gas 63. In the upper part of the inner wall of air channel 60 the lower end of the outlet pipe for hot synthesis gases 53 is welded.

Inside the upper rib of the body of gasifier 48 there is a feeder shaft 64. It is a rib with its upper end welded to the upper flange of the feeder shaft 66. Special vanes of feeder shaft 64 are welded to the lower end of its rib. In between the vanes there are the upper gas slots 69 and lateral round opening for horizontal channel 46 of the carbonaceous feedstock residue loading into the gasifier. The upper flange of the feeder shaft 66 is attached with the bolts to the upper end 49 of the body of the gasifier 48. Screw mechanism 70 with hydraulic or electric drive P9 is located inside the rib of the feeder shaft 64. The screw mechanism is connected with the bolts by its upper flange to the upper flange of the feeder shaft 66.

Between the upper rib of the body of the gasifier 48 and the rib of the feeder shaft 64 there is a channel for the hot pyrolysis gases 65 connected to the inlet pipe of hot pyrolysis gases 51 welded by its lower end to the upper part of the upper rib of the body of the gasifier 48.

Four supporting feet 71 are welded from the outside to the lower part of the rib of the body of the gasifier 48 attaching it to the supporting structure. Operation of gasification reactor SYN2-VG

Entire gasification process in gasification reactor (5) occurs inside the body of gasification reactor 48.

The essence of gasification process is the interaction between heated oxygen of the air with hot pyrolysis gases and carbonaceous feedstock residue at the same time. Gasification process occurring inside gasification reactor can be tentatively divided into four temperature zones:

- Zone of high-temperature pyrolysis: T 700 - 1100°C;

- Zone of combustion and gasification: T 1100 - 1350°C;

- Slag zone: T 150 - 1100°C.

- Gas zone: T 120 - 900°C;

The process of gasification initiates when carbonaceous feedstock residue resulting from low-temperature pyrolysis of feedstock in inclined rotary kiln for indirect heating (2) is transferred into the feeding shaft 64 located at the centre of the body of the gasifier 48 through the open end of horizontal channel 46 of the feeding unit for carbonaceous feedstock residue (4) installed in the branch pipe for installation of gasifier's feeding unit 52. Automatic control system maintains velocity of the feeding of carbonaceous residue into the gasifier through the unit that feeds carbonaceous feedstock residue. The work of the feeding unit is synchronized with the work of the other parts and mechanisms of gasification reactor SYN2-GG

At the same time pyrolysis gases formed in inclined rotary kiln for indirect heating (2) are channeled through branch pipe for the input of pyrolysis gases 51 into the channel for pyrolysis gases 65. Moving down the channel for pyrolysis gases 65, pyrolysis gases are additionally heated up by infra-red radiation from the fuel chamber 56 through the open bottom end of the channel for pyrolysis gases 65.

Carbonaceous feedstock residue that entered feeding shaft 64 of the gasifier under the impact of the screw mechanism 70 also moves down inside the fuel chamber 58. Carbonaceous feedstock residue along with pyrolysis gases is heated by the heat from the processes of combustion and gasification taking place inside fuel chamber 56. Under the impact of high temperatures and due to virtual lack of free oxygen carbonaceous feedstock residue moving inside feeding shaft 64 undergoes structural transformations resulting from the process of high-temperature pyrolysis.

Gases resulting from high-temperature pyrolysis go through lower gas slots 68 and upper gas slots 69 into the channel for pyrolysis gases 65. There they mix with the gases of low-temperature pyrolysis and descend into the fuel chamber 56 through the open end of the channel for pyrolysis gases 65 constituted by the difference of diameters of the lower end of the feeding shaft 64 and the gasifier's body 48.

In the lower part of the feeder shaft 64 there are the vanes of the feeder shaft 67 constituting the plates widening down at an angle of appr. 30 degrees. These vanes are intended for supporting compacted carbonaceous feedstock residue moved by screw mechanism 70 and preventing it from abruptly falling from feeder shaft 64 into fuel chamber.

Feeder shaft vanes additionally serve for crumbling and separation of the mass of dense carbonaceous feedstock residue into segments, which facilitates the process of combustion and gasification in fuel chamber 56, as the air passing through air lances 59 and pyrolysis gases from the channel for pyrolysis gases 65 can penetrate freely the mass of carbonaceous feedstock residue through the slots thus formed.

Having passed through the zone of high-temperature pyrolysis, apportioned and crumbled by the vanes of the feeding shaft 67 carbonaceous feedstock residue descends inside fuel chamber 56, where the zone of combustion and gasification is located. It is in this zone that the main process of gasification occurs due to exothermal reactions of combustion of parts of gases of low- and high-temperature pyrolysis under the temperature of combustion of 1100-1350°C. The temperature of combustion of up to 1500°C can be developed in central part of the fuel chamber. Fuel chamber's diameter is calculated for a throughput of 500-700 kilogram of feedstock per 1 square meter of cross section of fuel chamber 58 under intense boiling of the bed of carbonaceous feedstock residue caused by high velocity of flow of air and by the process of formation of synthesis gas.

Heated to 250 - 300°C in air channel 82 of the device for unloading the slag and in air channel 62 of the gasifier the air due to the cooling of the components of gasifier is fed through air lances 59 into fuel chamber 56 at a speed of 35-50 m/s.

Besides exothermal reactions of combustion of some part of pyrolysis gases in this part of fuel chamber 56 primary gasification reactions take place having explicit endothermal effect limiting the development of too high temperatures in central part of fuel chamber 56. The gases thus formed descend into the bottom of fuel chamber 56 where there is the heated viscous mass of carbonaceous feedstock residue that fell there. Going through that layer formed in central part of fuel chamber 56 hot gases cool due to endothermal reactions of secondary gasification to the temperature of 700 - 1100°C. Resulting gases convert entirely into hot synthesis gas.

It should be mentioned that the air is pumped in an amount securing optimal composition and amount of generated synthesis gas.

Hot synthesis gas having the temperature of about 900C° enters gas zone of the gasifier located in the channel for hot synthesis gas 63. In this zone due to the lowering of the speed of its movement owing to the width of the zone and natural gravitation synthesis gas is partially cleaned of slag and feedstock dust.

Hot syngas, while rising up, cools to the temperature T 700°C due to heat losses occurring because of large surface of the walls of the channel for hot synthesis gas 63 that are cooled in their inside by the air pumped into the gasifier.

To lessen these losses of heat the walls of the hot synthesis gas channel 63 can have heat insulation.

Then through the outlet branch pipe for hot synthesis gas 53 it goes out of gasifier and transfers along heat-insulated gas channel into the gas jacket of the inclined rotary kiln for indirect heating (2), where synthesis gas is cleaned again of slag and carbon dust and cooled further to the T 120°C.

Slag formed under the impact of high temperatures in the zone of combustion and gasification enters slag zone in liquid, viscous or solid state depending on the temperatures, composition of feedstock, its moisture, share of inorganic ingredients and whether water steam is fed into the gasifier.

The slag zone is located in the bottom part of gasifier (5) and upper part of device for unloading the slag (6).

The cooling of hot slag in slag zone of gasifier (5) occurs through endothermal reactions of secondary gasification and its indirect cooling by the inner wall of air channel 60 cooled by colder air passing through air channel 62.

It cools to the T - 700-1100°C and transforms into solid silicate slag formation.

Then the slag goes into the lower part of slag zone located in the device for unloading of slag (6) from the gasifier (5), where it is cooled even more, is crushed and unloaded from the gasifier.

The gasifier (5) has thermal insulation jacket 52 and outer protective casing 53 that minimize heat losses into the atmosphere while gasifier is in operation.

Device for unloading the slag from the gasifier

Device for unloading the slag from the gasifier (6) is a part of gasifier (5). It is presented in general in Fig. 5 and is used for cooling, crushing and removal of the slag formed during gasification of carbonaceous feedstock residue.

It consists of the following components:

72. Outer body

73. Bottom

74. Inner body P T/UA2017/000085

75. Lower cone

76. Upper flange of the device for unloading the slag

77. Flange air channels

78. Crushing machine

79. Upper branch pipe of the channel for unloading the slag

80. Steam lances

81. Branch pipe of the air input channel

82. Air channel

83. Branch pipe for water/ water steam input

84. Distribution box

85. The sluice

86. Upper slide gate

87. Lower slide gate

88. Lower branch pipe of the slag output channel

P10. Hydraulic cylinder of the upper slide gate

PI 1. Hydraulic cylinder of the lower slide gate

Design of the device for unloading the slag from the gasifier

Device for unloading the slag (6) from the gasifier consists of the rib of its outer body 72, inside which there is the rib of the inner body 74, of upper flange 76 joining the two ribs in the upper part of the device, and of bottom 73 joining the ribs of the body in the lower part of the device. To the lower part of the inner body's rib 74 lower cone 75 is welded, in the lower part of which there is the channel for unloading the slag. The channel consists of upper branch pipe of the slag unloading channel 79, lower branch pipe of the slag unloading channel 88 and of the sluice 82 equipped with the lower slide gate 87 and upper slide gate 86.

Outside the upper branch pipe of the channel for unloading the slag 79 distribution box 84 is welded, into which the water or steam input channel 83 is tangentially welded. Steam lances 80 are also welded into the upper branch pipe of the channel for unloading the slag 79. Internal volume of distribution box 84 is connected through steam lances 80 with internal volume of the upper branch pipe of the channel for unloading the slag 79.

Specially designed crushing machine 78 is placed inside the rib of outer body 74. Crushing machine is equipped with the set of revolving disc mills mounted on water-cooled shafts.

Branch pipe of the air input channel 81 is welded tangentially to the bottom 73. Between the rib of the outer body 72 and the rib of the inner body 74 there is the air channel 82 connected with the air channel of the gasifier 62 by flange air channels 77 located in upper flange 76 of the slag unloading device and lower flange 50 of the gasifier (5).

Crushing machine 78 has a system of oil seals and bearings, and its own electric or hydraulic motor (not shown in the figures).

Operation of the device for unloading the slag from the gasifier

At the bottom of the gasifier (5) there is a device for unloading the slag (6) intended for cooling, crushing and subsequent removal of the slag formed in the process of gasification of carbonaceous feedstock residue in the gasifier.

In the lower part of the device for unloading the slag there is the air input branch pipe

81 through which cold air is supplied into the gasifier. Cold air, moving through air channel

82 located between the lower cone 75 and the bottom 73, and between outer body 72 and inner body 74 cools down their surfaces heated by the hot slag. The air is heated therewith.

Similarly, upper flange 76 is cooled down by supplied cold air that contacts with its lower part. The air is also cooled when it passes through flange air channels 77, connected with the same flange channels of lower flange 50 of the gasifier.

In the process of gasification of carbonaceous feedstock residue in the gasifier (5), the slag formed in fuel chamber 56 becomes hot monolith silicate formation and is transferred into the slag unloading device, where it is cooled and crushed by the disc mills of crashing machine 78.

Crushed slag is dropped into lower cone 75 and branch pipe of the slag unloading channel 79, where it is cooled further by supplied cold air going through air channel 62 cooling the inner wall of the channel 60 inside which there is hot slag.

Hot slag is also cooled through interaction with water or water steam supplied through the branch pipe of the water or water steam input channel 83, distribution box 84 and steam lances 80 into the upper branch pipe of the channel for slag unloading 79, where there is milled and still hot slag.

Apart from that, the cooling of the slag takes place thanks to endothermal reactions between water steam and residual carbon of the slag dropped into the device for unloading the slag from the zone of combustion and gasification of the gasifier (5). The slag thus cools to T - 300°C and frees itself from residual carbon. Synthesis gas thus obtains additional amount of combustible gases.

Cooled and milled slag is then removed from the device for unloading the slag (6) through the channel for unloading the slag.

Channel for unloading the slag consists of the upper branch pipe 79 of this channel, lower branch pipe 88 is equipped in the lower part of the upper branch pipe 79 with the sluice 82. This is done for additional air tightening of the gasifier (5). The sluice has an upper slide gate 86 and a lower slide gate 87.

At the initial stage of the slag unloading the upper slide gate 86 is shut and the lower slide gate 87 is open. Because the upper slide gate 86 is shut, the milled slag accumulates in the upper branch pipe of the channel for unloading the slag 79 and partially in the bottom part of the lower cone 75 in the amount equal or smaller than the inside volume of the inner chamber of the sluice 85.

After needed and sufficient amount of milled slag has accumulated inside this volume the lower slide gate 87 closes and upper slide gate 86 opens under the impact of hydraulic cylinders P10 and PI 1. Milled slag then goes down from the upper branch pipe of the channel for unloading the slag 79 into the sluice chamber 85. Put in motion by hydraulic cylinder P10 the upper slide gate 86 shuts down. After it is shut down the lower slide gate 87 opens under the impact of the movement of hydraulic cylinder PI 1 and all the slag drops from the inner chamber of the sluice 85 into the lower branch pipe of the channel for unloading the slag 88, from where it goes for recycling. The whole process is repeated automatically at later stages.

Crushing machine 78 and other devices of the channel of the device for unloading the slag (6) operate in sync with all the mechanisms and devices of gasifier SYN2-GG. This makes it possible to manage its efficiency, operate it uninterruptedly and achieve maximal thermochemical conversion of feedstock into synthesis gas in required composition, amount and quality.

DETAILED DESCRIPTION OF THE METHOD

Gas generator SYN2-GG was developed for thermochemical conversion of solid urban refuse and other carbon-containing tar-rich feedstock into synthesis gas through the two stage process of pyrolysis and ensuing down-draft gasification of viscous bed of carbonaceous feedstock residue of pyrolysis. Gasification reactor SYN2-GG performs phased thermochemical conversion of feedstock into syngas. Entire gasification process is relatively divided into seven separate temperature zones.

Zones of gasification reactor SYN2-GG for thermochemical conversion of feedstock into synthesis gas

The first three zones are the zones of low-temperature processing of the feedstock. Low-temperature pyrolysis of the feedstock (T<700°C) occurs in them. They are located in the pyrolysis part of gasifier SYN2-GG, which is a specially designed inclined rotary kiln for indirect heating SYN2-RK (Rotary Kiln SYNTENA2), installed at some angle to the horizon and heated by synthesis gas resulting from gasification of the feedstock. Remaining four zones are the zones of high-temperature processing of the feedstock (T>700°C). These zones are located in gasification part of gasifier SYN2-GG, which is a gasifier for downdraf gasification of the viscous bed SYN2-VG. Its design is based on the new theory of gasification making part of this invention. The gasifier is connected with inclined rotary kiln SYN2-RK by a body junction or by tubes.

Zones 1, 2, 3, 4 belong to pyrolysis area, and zones 5, 6, 7 pertain to the area of gasification process.

Processes of heating, drying, low-temperature and high-temperature pyrolysis occur in gasifier SYN2-GG at the same time. Gasification processes of interaction between oxidizing gases and the products of thermal break-down of the feedstock take place in it too. Division of the process of gasification into the zones is relative, as well as the subdivision of the processes that take place in these zones. Many gasification processes proceed in different zones with varying intensity, so this idealization is done for the purpose of theoretical computations and better understanding of the processes, occurring inside gasification reactor.

It needs to be noted that the sequence of parts in this chapter follows numerical order of the zones of the gasifier and is oriented towards succession of the processes of conversion of the solid part of solid urban refuse (or municipal solid waste, MSW).

Municipal solid waste processed in the gasifier as its feedstock are incredibly diverse and multicomponent in their organic and mineral parts, and also have varying moisture contents. These are the key aspects of their conversion, largely affecting the amount and composition of generated synthesis gas, and formation of slag residue.

For the purposes of description of the process of gasification VGP4, a MSW of the so- called "bottom" residue resulting from sorting of solid waste is used. Morphology and elemental structure of MSW referred to further in the description and theoretical calculations are shown in Tables 1 and 2.

Table 1. Morphological composition of MSW

Name of morphological type %

paper + cardboard 28.48

textile 4.00

plastic 26.49

rubber 2.50

wood (sawdust + straw) 24.48

metals (Al + Fe) 0.30

particulate waste (dust, sand, etc.) 6.25

food waste 7.50

Total 100.00

Table 2 Elemental composition of MSW Elements Mass, g %

C 484.40 48.44

H 59.40 5.94

0 279.60 27.96

N 7.70 0.77

CI - - s 2.40 0.24

moisture content 83.40 8.34

ash content 83.10 8.31

Total 1000.00 100.00

Morphology and elements presented in the tables above are real and were used in the tests of technological complex PGP-ITPD, described in the Gasifier Draft Test Report of the University of California Riverside (UCR), USA.

With regard to mineral part, not only its composition has an effect, but also the form of inorganic components in the feedstock.

Two categories can be distinguished among inorganic components: mechanical inclusions, and components that are chemically related with the feedstock.

• First category is the main one and can include 6% to 25% of inorganic components relative to the total mass of feedstock. These are mechanical inclusions such as ferrous and non-ferrous metals, ceramics, building refuse, particulate waste, glass, etc., forming its mineral part that includes such important elements as: CaC0₃, MgC0₃, FeC0₃, CaS0₄, Na₂S0₄, FeS0₄, FeS₂, S1O2, silicates with varying content of main oxides A1₂0₃, Si0₂, CaO, Na₂0, K₂0 and small content of the oxides of other metals.

These components can be relatively arranged by their lowering content in the feedstock in the following order:

o Si0₂ - dozens of percents of the total mass;

o Al, AI2O3, MgO, Fe, F₂0₃, CaSi0₃, CaC0₃ - a few percents, dozens of percents;

o Cu, Zn, S, T1O2, FeO, Ni, Pb, Na₂Si0₃, Sn, CaS0₄, MgS0₄, CI^", S^2", Na₂C0₃ - few percent, tenths of a percent;

o BaO, ZnO, Cd, NaCl, NaP0_4s MgC0₃, MgS0₄, MgSi0₃, K₃P0₄, CaCl₂, MgCb, K₂C0₃, Cr, Sb, SbO - tenths, hundredths of a percent;

o NaOH, LiOH, W, V₂0₅, Cr₂0₃, Ni₂0₃, PbO, ZnSi0₃, F^", S0₃ ^2", Mn, V, Mo, As, Co, Hg, As₂0₃, BeO - less than hundredths of a percent;

• Second category includes fewer compounds and may reach from 0,47% to 2,81% of the total mass of the feedstock. They are present in the feedstock as components that are chemically related with the feedstock, e.g. the metals, their oxides and salts making parts of paper, cardboard. They are present in the wood, dyes in textile refuse, polymeric materials. Zones of low-temperature processing of feedstock

Zone 1 - Zone of feedstock drying

Zone 1- Zone of feedstock drying is one of the zones of low-temperature processing of feedstock. The temperatures in it are: T 30 - 120 °C. It is located in the first section of the inner body of the rotary kiln for indirect heating SY 2-R .

The following processes take place inside this zone;

• Fragmentation of the lumps of grinded feedstock formed while being fed. It is grinded to the fraction of primary grinding due to its drying and mixing inside the inner body of the rotary kiln;

• Homogenization of the feedstock;

• Initial heating of feedstock by the heat of exiting synthesis gas, conveyed through the walls of the inner body of rotary kiln;

• Final drying of the feedstock and intensive formation of vapor during the boiling of released moisture;

• Partial removal of colloid-bound water and adsorbed gases from the feedstock;

• Beginning of the process of the change of the state of matter of the low melt components of feedstock in the form of the softening of their surfaces;

• Beginning of the process of formation of gases.

In the drying process there distinction can be made between the free moisture, hardly related with the feedstock because absorbed during direct contact of the feedstock with water, and the moisture related to the structure of the feedstock, hygroscopic and acquired through adsorption of the water vapors.

During feedstock's drying by the heat of outgoing synthesis gas conveyed through the inner walls of the body of rotary kiln, the speed of the drying grows rapidly, reaching its constant speed. The drying is accompanied by intensive formation of vapor caused by the boiling of free moisture in the feedstock.

Then the period of constant speed of the drying begins, and after feedstock reaches hygroscopic condition, the speed starts falling. This process is very dependent on the fraction composition of feedstock, on the load fed, and on the dynamic of its shuffling.

Thermal conductivity of feedstock constantly diminishes in the process of drying. Coefficient of thermal conductivity also reduces with diminishing moisture content, starting from critical point. Moisture content reduces due to deepening of the zone of evaporation and increase of thermal resistance of the dry outer layer of feedstock. These developments worsen the heating of inside layers of the feedstock, thereby prolonging the time of complete drying of internal layers of the feedstock.

But constant shuffling of the feedstock through rotation of the inner body of rotary kiln allows to level the temperature and homogenize the feedstock, distribute these processes through all the feedstock loaded, improving therewith the process of its drying.

Water vapor released during the drying goes into the upper part of inside body of rotary kiln, where it is partially heated up during the contact with the wall of the inner body of rotary kiln.

Natural moisture and part of colloid-tied water is removed from the feedstock, but most of colloid-bound water remains in the feedstock.

Adsorbed gases are also released from the feedstock during its drying. Decomposition of the feedstock is at this time manifested weakly with these temperatures, it is only expressed in hardly noticeable formation of gases.

Beginning of the process of the change of the state of the low-melting-point components of feedstock in the form of the softening of their surfaces is also seen.

The feedstock's mass reduces during the drying, but without shrinkage, that is to say that its volume does not diminish, and only its further heating causes more profound structural changes.

Zone 2 - Zone of moisture removal from the feedstock

Zone 2 - Zone of the removal of moisture from the feedstock is one of the zones of low-temperature processing of the feedstock with the temperatures of T 120 - 300°C. It is located in the second section of the inner body of the rotary kiln for indirect heating SYN2-

RK.

The following processes take place inside this zone:

• final drying of the feedstock and removal of colloid-bound water from it;

• conversion of the state of matter of the feedstock occurs;

• processes of decomposition and destruction of organic polymers starts;

• initial formation of tars and of saturated and unsaturated hydrocarbons occurs.

Final drying of the feedstock and removal of colloid water from it

Complete drying of the feedstock and removal of colloid-bound water from it occurs at the temperature approximately T 200 °C. Splitting off of the functional categories occurs at this time accompanied by the reactions of condensation of the radicals thus formed:

As a result of this process, mineral colloids go into the vapor phase and water vapors thus formed go into the upper part of the inner body of inclined rotary kiln.

Change of the state of matter

Along with this, fusible materials of organic and inorganic origin change their state into plastic or fluid. At the temperature of T 120°C polyethylene starts melting, then the other polymers representing low-melting-point part of the feedstock. At the temperature of T 200- 250°C all the polymers turn fluid, and owing to conglutination of the particles of the feedstock, all its mass turn into separate plastic lumpy formations, slowly revolving inside the second section of the inner body of inclined rotary kiln.

Structural changes that occur in this zone make all the mass of the feedstock shrink significantly and reduce its volume. Its thermal conductivity grows, helping quicker heating of the lumpy structures of the feedstock, including their inner strata. But, despite this, internal parts of the lumpy structures of the feedstock heat up slower than their outer parts.

Beginning of the processes of decomposition and destruction of organic polymers

Decomposition of organic polymers (breakup of polymer chains) starts at approximately T - 250 °C:

(-CH₂-CH₂-)„→ (-CH₂-CH2-)n-x, + (-CH₂-CH₂-)n-x₂ + (-CH₂-CH₂-)„._X„ (17)

Initial formation of saturated and unsaturated hydrocarbons and some other substances

The following processes occur in parallel with decomposition of polymers:

o Formation of saturated and unsaturated hydrocarbons, the reactions not being intensive:

R→CnH2„ + C_raH_2m+2 (18)

o Release of nitrogen, mainly molecular, in the form of ammonia and some other compounds containing nitrogen.

o Initiation of oxidation of hydrocarbons to phenols (Formula 21), acids

(Formula 19, Formula 20) and other compounds containing oxygen, owing to release of oxygen from the feedstock.

o Formation of considerable amount of phenols:

C„H_2n + 0₂→ Cn-lH_2n-2COOH (19)

C_mH2m+2 + 0₂→ C„-₁H2nCOOH (20)

O

(Formula 22)

C_nH_2n + H₂0→ C„H_2n+1OH (22)

This reaction is not sizeable.

As a result of these processes gases start to be released from the layer of feedstock in the form of oxide, carbon dioxide and tar. Methane, heavy hydrocarbon gases and hydrogen are released with further heating. The gases thus formed go into the upper part of the inner body of rotary kiln, where they mix up with water vapors.

At T 250°C the amount of released gas can be 2-2,5% of the weight of the feedstock loaded into the kiln.

These conversions result in feedstock losing both its weight and volume, and feedstock residue begins to be enriched by carbon.

Zone 3 - Zone of low-temperature pyrolysis of the feedstock

Zone 3 - Zone of low-temperature pyrolysis is one of the zones of low-temperature processing of feedstock. The temperatures in this zone are: T 300 - 700°C.

Zone of low-temperature pyrolysis of the feedstock is located in the third section of the inner body of rotary kiln for indirect heating SYN2-RK.

Processes inside this zone are:

• disintegration of some organic salts with formation of respective oxides;

• beginning of the process of reduction of oxides into metals.

Formation of saturated and non-saturated hydrocarbons, release of the vapors of light resinous substances

Reactions forming saturated and unsaturated hydrocarbons with small content of the atoms of C are predominant in this zone:

R→C„H₂„ + C_mH2m₊2, (23)

where n and m mainly have values 1-4.

Primary aromatic compounds are formed along with this process:

C„H₂„+2→ CnH„ +n/2H₂ (25)

It is caused by the fact that, when the temperatures reach T - 500°C, the process of condensation and aromatization of organic molecules intensifies, and its intensity peaks at the temperatures of 600 -700°C.

Among main reactions of this process are reactions of dehydration (Formula 11 and Formula 12) that can be divided into two parts:

o Primary reactions - reactions of milder dehydration with the release of unsaturated hydrocarbons (Formula 11).

o Final ones - reaction of total dehydration with formation of carbon and hydrogen (Formula 1 ).

Intensive formation of methane also occurs:

o Water vapors, released from the central part of the lumps of feedstock react with the carbon, formed on their surfaces and the walls of the device:

2C + 2H₂0 CH₄ + C0₂ (26)

o Methane as a consequence of interaction between carbon and hydrogen:

C + 2H₂ <^ CH₄ (27)

Equilibrium of this reaction in these conditions is shifted towards formation of methane by 60 % only. Therefore reverse reaction is also considerable.

o Methane forms as a result of catalytic decomposition of various hydrocarbons (Formula 28), Different metals are catalysts. These metals are always present in feedstock. It also occurs because of the contact with metal walls of inner body of rotary kiln:

C_nH_2n and/or Cmf a > CH₄ (28)

Structural changes in the mass of feedstock

The following processes take place under the impact of rising temperature:

• Plastic material of the lumpy formations of feedstock solidifies and then carbonizes starting from its outer layers;

• Carbon structure forms due to removal of hydrogen and formation of carbon- carbon bonds;

• Plastic lumps of feedstock residue disintegrate and all its mass turns into homogeneous ground mass of carbonaceous feedstock residue.

Metals and their salts contained in original feedstock and melt are incorporated into the forming carbon structure, producing significant impact on the process of pyrolysis, and later, on the process of gasification.

Decomposition of some organic salts with formation of related oxides

Initial temperature of decomposition of feedstock is determined mainly by its individual properties, and to some extent by the conditions in which its heating occurs.

The more there is bound oxygen the lower is the primary temperature of its decomposition. At initial stages of the heating of feedstock the first components that are released are components containing oxygen, and the last released are least oxidized tarry substances.

Large amount of oxygen in the feedstock causes exothermal effect in the process of the feedstock's heating. This happens because of reactions of oxidization, the feedstock is heated even more, which accelerates its destruction. This process is also sustained by decomposition of some inorganic salts, accompanied by formation of respective oxides in the process of heating of the feedstock loaded. H₂0, CO2 and N0₂ also decompose according to reactions cited in Formulas 29-33:

o Bases

Me(OH) —L→ MeO + H₂0, (29)

where Me - Ca(580°C), Be, Mg(550°C), Sr(500-850°C), A1(575°C), Cu(200°C), Zn(100-250^eC), Cd(170-300°C), Mn(220°C), Co(170°C), Ni(230-360°C), others,

o Nitrates

MeN0₃ -~L→ MeO + NC% (30)

where Me = Ni(500°C), Cu(250°C), Mg(300°C), Sr(570°C), Ba(670°C), and others, o Carbonates

MeCC —^→ MeO +C0₂, (31)

where Me = Mg (350-650°C), Pb (315°C), Be (180°C), Mn (100°C), Zn (357°C), Fe

(282°C), Cd (207°C) and others.

In other cases parts of organic salts break up and related oxides and oxygen O2 are formed:

o Peroxides

Me₂0₂— '→ Me₂0 + O2, (32)

where Me = K(500°C), Na(400°C), Li(200-400°C), and others,

o Sulphides

MeS0₄— !→ MeO + S0₂ + 0₂, (33)

where Me - Fe"(700°C), Fe^l"(600°C), Co(700°C), Ni(500°C), Sn(360°C), Cu(720°C), Ti(600°C), and others. With the oxygen released, reactions of oxidation in the layer of feedstock intensify, augmenting temperature increase in this zone and intensifying the release of various products of destruction of feedstock, mainly such as water vapor, carbonic gas, carbon oxide, acetic acid, methyl alcohol, formaldehyde, tar, methane, ethylene, propylene and hydrogen, as well as some other products of decomposition, amounts of which depend on the morphologic composition of the feedstock.

Beginning of the process of reduction of metals from the oxides

In this zone starts the process of reduction of metals from oxides that were fed with the feedstock. This reduction results from the reactions shown in Formulas 34-36:

MeO + CO— ^!→ Me + C0₂, (34)

where Me = Fe "Fe2"'(700°C), Pb(400°C), Cu(550°C), and others.

MeO + C— i→ Me + CO, (35)

where Me = Mn(600°-700°C), and others.

MeO + H₂— '→ Me + H₂0, (36)

where Me = Sn(500-600°C), Pb(350°C), Cu(250°C), Cd(300°C), Mo(700°C), Co(500°C), Ni(400°C), and others.

Large amounts of polymeric materials in the feedstock causes respective growth of output of saturated and unsaturated hydrocarbons. The polymers at this stage decompose practically entirely and no carbon residue is formed.

With the temperature reaching T - 350°C, along with non-condensing gases condensing products start to be released in the form of the vapors of tar oil (tar), their mass increasing with growing temperature of the feedstock, reaching the maximum at T - 500- 550°C. Abovementioned processes of destruction of the feedstock and of formation of gases cause significant shrinkage of the feedstock's volume and to the conversion of its structure to a porous dry carbon form.

With further heating the process of the release of tarry substances and other products that may condense, if cooled, terminates entirely. Formation of gases though continues, albeit less intensively.

The products resulting from low-temperature pyrolysis and the products of decomposition of the feedstock rise into the upper part of the inner body of the rotary kiln where they mix with water steam and with gases from the drying zone and zone of moisture recovery.

Pyrolysis gas thus obtained is subjected to heating with thermal radiation coming from the wall of the inner body of rotary kiln, or by direct contact with the wall. The tars and particles of carbon residue deposited on the inner wall of inner body of rotary kiln are removed under the impact of outside temperatures and water vapor coming from the zone of drying and zone of moisture removal, and through mechanical contact with carbonaceous feedstock residue occurring in the process of rotation of the inner body of rotary kiln.

After that, carbonaceous feedstock residue from the zone of low-temperature pyrolysis of the feedstock located inside inner body of rotary kiln SYN2-RK, goes into gasifier SYN2- VG, where its high-temperature pyrolysis and subsequent gasification take place.

Gases of low-temperature pyrolysis go out of inner body of rotary kiln SYN2-RK and go through a special channel into gasifier SYN2-VG, where they are subjected to thermal conversion, partial combustion and further conversion into syngas.

Zones of high-temperature treatment of the feedstock

Zone 4 - Zone of high-temperature pyrolysis

Zone of high-temperature pyrolysis is one of the zones of high-temperature processing of feedstock. Temperatures there vary between 700 and 1100°C.

The process of high-temperature pyrolysis of carbonaceous feedstock residue takes place in the zone of high-temperature pyrolysis, as well as the beginning of all reactions of the process of gasification.

The following processes take place within this zone:

• reactions of high-temperature pyrolysis;

• gasification process of carbonaceous feedstock residue starts;

• part of inorganic salts break down and melt. They interact with carbon and mineral components of carbonaceous feedstock residue;

• reduction of the metals from the oxides;

• oxidation of reduced metal after C0₂ and H₂0 act on them;

• feedstock residue turn into compressed, viscous mass of carbon.

Zone of high-temperature pyrolysis is formed out of solid feedstock residue transferred from inclined rotary kiln SYN2-RK in gasifier SYN2-SFG and heated up to the temperature of T - 700 - 1100°C due to thermal radiation coming from the zone of combustion and gasification.

Essential processes in this zone occur at the T - 700 - 1100°C, at this time continues the release of volatile hydrocarbons and tars, part of which, affected by high temperatures, convert into simple gases ¾ and CO. As a result of these processes the amount of carbon in feedstock residue reaches its maximum.

Also in this zone reactions of oxidation and reduction start. They take place in combustion and gasification zone. The process of high-temperature pyrolysis, in addition to the formation of primary gases H₂ and CO, is generally characterized by the formation of small amounts of methane, hydrogen, carbon dioxide, water vapor, and traces of some other hydrocarbon gases.

Development of the process of high-temperature pyrolysis

Volatile hydrocarbons and tars continue to be released from carbonaceous feedstock residue in the entire volume of the zone of high-temperature pyrolysis. Predominant reactions are those, in which saturated and unsaturated hydrocarbons are formed (23) and tars with high content of the atoms of C:

R→ CnH_2n + CmH_2m+2, (23)

where n and m equal 4 and more.

Hydrocarbons and tars generated in this zone as a result of high-temperature pyrolysis of carbonaceous feedstock residue, and those of them, which arrived from the zone of low- temperature pyrolysis, when acted on by high temperatures, remaining water vapors and carbon dioxide, begin conversion through the reactions of dehydration (Formula 11 and Formula 12), and vapor (Formula 37) and carbon dioxide conversion (Formula 38), during which primary flammable gases H₂ and CO are formed:

CnH_2n+2→ C_nH_2n + H₂ (11)

CnH₂„ H C_mH_2m+2→ (n+m)C + (2n+2m+2)H₂ (12)

CxH_y + X¾0 -→ XCO + (X + Y/2)H₂ (37)

CxH_y + X/2C02—→ ' (X + X/2)CO + Y/2H₂ (38)

Reactions of Formula 37 and Formula 38 are catalytic, the catalyzer being different metals present in carbonaceous feedstock residue.

Residual part of heavy hydrocarbons and tars together with the rest of the gases go down into the zone of combustion and gasification, where they partially combust and are finally converted into primary flammable gases H2 and CO.

Besides formation of simple gases H2 and CO, the process of high-temperature pyrolysis is characterized by formation of small amount of methane, and of the traces of some other hydrocarbon gases.

Methane is formed in this process as a product of interaction of carbon with water vapor and hydrogen through the reactions:

2C + 2H₂0 0· CH₄ + C0₂ (26)

C + 2H₂ C¾ (27)

This reactions is catalytic, its catalyzer, as in reactions with Formula 37 and Formula 38, are various metals present in carbonaceous feedstock residue.

Equilibrium of this reaction is in these conditions tipped towards formation of methane 60% only. Therefore reverse reaction is also tangible. Methane is also formed during catalytic cracking of various hydrocarbons (Formula 28). The catalyzer, as in reactions with Formula 26 and Formula 27, are different metals present in carbonaceous feedstock residue, for example, iron (Fe):

CnH_2n and/or C_mH_2m+₂ — CH₄ (28)

Conversion of pyrolysis gases in the channel for pyrolysis gases of the gasifier

In the zone of high-temperature pyrolysis there is a specially designed channel for pyrolysis gases of the gasifier, in which gases of low-temperature and high-temperature pyrolysis mix while descending into combustion and gasification zone.

In this channel under the temperatures of T - 700-1100 °C occur the following processes:

• Additional heating of pyrolysis gases;

• Intensification of the conversion of hydrocarbons in pyrolysis gases.

Mixture of pyrolysis gases forming in the zones of drying, moisture removal, low- and high-temperature pyrolysis undergo thermochemical conversion descending along the channel for pyrolysis gases. Both hydrocarbons and tars that they contain undergo conversion.

Reactions of dehydration presented earlier are main reactions of this conversion as shown by Formula Ϊ 1 and Formula 12:

C_nH_2n+2→C_nH₂„ + H₂ (11)

C„H_2n H C_mH_2m+2 - (n+m)C + (2n+2m+2)H₂ (12)

Transformations just described occur due to high temperatures conveyed from the red- hot rib of feedstock channel penetrating this zone from the open lower end of the channel for pyrolysis gases from the zone of combustion and gasification. These temperatures create conditions that are conducive to the reactions of conversion of hydrocarbons.

One of the main factors of reactions of conversion of hydrocarbons in the channel for pyrolysis gases of the gasifier is high content of water steam in the gases of low-temperature pyrolysis.

Partial pyrolysis of vapors of tars occurs here too with formation of primary tar that initiates in colder zones of low-temperature pyrolysis.

Because gas mixture stays in the channel for pyrolysis gases for limited period, only a part of gaseous hydrocarbons and tar vapors undergo conversion. But this process continues further in fuel chamber, combustion and gasification zone under higher temperatures.

Beginning of the process of gasification of the feedstock

In the lower part of the zone of high-temperature pyrolysis where the temperatures are higher, reactions of gasification begin. These reactions mainly take place in the zone of combustion and gasification.

Reactions of gasification (Formula 8, Formula 9 and Formula 4) that occur in this zone are explicitly endothermal. This is one of the factors that lower the overall temperature in this zone down to T - 700-1100 °C:

H₂0 + C = CO + Hi - 30 044 kcal/mole (8)

2H₂0 + C = C0₂ + H₂ - 20 195 kcal/mole (9)

C0₂ + C = 2CO - 39 893 kcal/mole (4)

Breakup of some part of inorganic salts and their interaction with carbon and other mineral components of carbonaceous feedstock residue

Originally there is in solid urban refuse a large mineral component, whose concentration grows at its entering the zone of high-temperature pyrolysis due to the reduction of volume of carbonaceous feedstock residue, caused by extraction of moisture from it alonfg with gaseous products and tars in the zones of low-temperature processing.

Some inorganic salts are decomposed through the reactions with Formulas 29-33. These are the salts that have not broken up in the zone of low-temperature pyrolysis with formation of respective oxides and of H2O, C0₂, N0₂ and 0₂ through the reactions with Formulas 29-33:

Me(OH)4— MeO + H₂0 (29)

eNOs— 1→ MeO + N0₂ (30)

MeC0₃—!→ MeO +C0₂ (31 )

Me₂0₂— '→ Me₂0 + 0₂ (32)

MeS0₄—→ ' MeO + S0₂ + 0₂ (33)

As a result of the processes in this zone, oxides of various metals are formed from the mineral part of the feedstock. These metal oxides have impurities of carbon and insignificant amounts of salts that have not yet decomposed, and some pure reduced metals. Depending on feedstock's original composition, some amount of metal alloys is formed. The bases of these alloys are iron, copper and silicon.

It needs to be mentioned that in these processes take part mineral components of feedstock that are both chemically bound with organic components (second category), and constitute mechanical impurities (first category).

Reduction of metals from oxides

Some part of metal oxides breaks up in the zone of high-temperature pyrolysis under the impact of high temperatures, especially in the lower part of this zone that borders on the zone of combustion and gasification: MeO— '→ Me + O, (39)

where Me = CdO (900°C), CuO (1026°C), and others.

Part of the metals is reduced from the oxides while contacting red-hot carbon:

MeO + C Me + CO, (40)

where Me = Na(900-1000°C), Ca(800-850°C), Ba(1000°C), Li(800°C), Sn(800- 900°C), Cd, Mn(600°-700°C), Cd, Ni, and others.

Oxidation of reduced metals under the impact of CC and H2O.

The process of oxidation of reduced metals brought into the zone of high-temperature pyrolysis together with carbonaceous feedstock residue from the zone of low-temperature pyrolysis and zone of gas filtration (Formulas 34-36), and of those formed in this zone as a result of reactions with Formulas 39-40 can occur under the impact of remaining water vapors (H₂0) and carbon dioxide (CO2), formed in this zone:

Me + H₂0 = MeO + H₂, (41)

where Me = Ti(800°C), Cr(700°C), Mo(700°C), and others.

Me + C0₂ = MeO + CO, (42)

where Me = Zn(600-700°C), and others.

Then the metals oxidized to oxides as a result of reactions with Formulas 41-42 are reduced again from the oxides in the reactions with Formulas 9-40. Alternating reactions of oxidation and reduction continue through all the period of the metals presence in the zone of high-temperature pyrolysis.

Reduced metals become acceptors of oxygen in the molecules of C02 and H₂0 in the reactions of Formulas 41-42, converting them in simple flammable gases CO and H₂.

Alternating processes of the reduction of metals from the oxides (Formulas 39-40) and subsequent oxidation of reduced metals (Formulas 41-42) reduces the content of C0₂ and H₂0 in the gases obtained in the zone of high-temperature pyrolysis and conveyed from the zone of combustion and gasification. Additional amounts of CO and H₂ are also generated in the process.

This process then expands down to the zone of combustion and gasification, where these reactions intensify.

Transformation of carbonaceous feedstock residue into compressed viscous mass of carbon

The process of melting of some mineral salts occurs in the zone of high-temperature pyrolysis.

All the chlorides are melted in this process (CaCl₂ - 787 °C, NaCl - 801 °C, and others), some carbonates ( 2CO3 - 618°C, Na₂C0₃ - 851°C, K₂C0₃ - 891°C, and others) and some oxides (K₂0 - 740°C, Mn0₂ - 847°C, PbO - 890°C, CdO - 900°C, SnO - 1040°C, and others).

Mineral components of feedstock undergo melting, both those bound with organic components (second category), and those that are mechanical impurities (first category).

Small mechanical inclusions of the first category, and particularly mineral components of the second category, evenly dispersed in the organic part of carbonaceous feedstock residue, are strongly shielded by carbon from the impact of high temperatures, so in the upper part of the zone of high-temperature pyrolysis they do not melt considerably. In the lower part of the zone of high-temperature pyrolysis bordering on the zone of combustion and gasification the melting of some part of inorganic salts largely intensifies, this melting being caused by general rise in temperatures and reduction of the shielding of the salts by carbon. This happens due to their higher concentration provoked by the process of secondary gasification.

General rise in temperature in the lower area of the zone of high-temperature pyrolysis and high concentration of mineral components with low melting point resulting from the reactions of reduction creates along with high-melting point components of feedstock also eutectic alloys with low melting points.

Due to high concentration of melted mineral salts these processes in the lower part of high-temperature pyrolysis zone cause transformation of carbonaceous feedstock residue into a red-hot crumbly porous mass of carbon slightly fractioned and divided into segments by the vanes of feedstock shaft.

Zone 5 - Zone of combustion and gasification

Zone of combustion and gasification of gasifier SYN2-VG is one of the zones of high- temperature treatment of the feedstock with the temperatures: T 1100 - 1350°C.

The process of gasification of carbonaceous residue is a very complex process. It is a part of high-temperature processing of the feedstock. It is executed simultaneously in all the seven zones of gasifier SYN2-VG, but the main process of gasification of carbonaceous feedstock residue generating very high quality synthesis gas takes place in the zone of combustion and gasification under the temperature T 1 100 - 1350°C.

Several processes take place in the zone of combustion and gasification. They occur in the inner volume of gasifier' s fuel chamber. These processes are the result of the complex interaction of hot pyrolysis gases coming from the channel for pyrolysis gases inside fuel chamber, of the oxygen of heated air conveyed into fuel chamber through air lances, and of red-hot carbonaceous feedstock residue.

These processes can be tentatively broken into a few closely tied processes going on in parallel:

• conversion of carbon residue of the feedstock into the state of a "boiling" or "fluidized" bed;

• partial combustion of pyrolysis gases formed in the zone of low temperature processing of feedstock;

• gasification of carbonaceous residue of feedstock;

• melting of inorganic component of carbonaceous residue;

• cleaning of the gases with the removal of hazardous components of gas;

• formation of slag.

Transformation of carbonaceous feedstock residue into the state of 'fluidized" bed

It needs to be pointed out that the processes of combustion and gasification in the fuel chamber of gasifier SYN2-VG differ in principle from similar processes in conventional gasification reactors. This difference can be shown in the diagram of horizontai cross-section of fuel chambers presented in Fig. 6.

A special feature of gasifier SYN2-VG is that the hot mixture of pyrolysis gases is conveyed into the space under the lances of fuel chamber from the channel for pyrolysis gases and from the zone of additional gasification. This mixture contains large amounts of simple hot gases H₂, CO, and CH₄, and certain portion of hydrocarbon gases and tars with high calorie value.

At the same time, carbonaceous feedstock residue, heated up to T - 1100°C, comes into the fuel chamber of the gasifier from the zone of high-temperature pyrolysis. In this heated bed of the residue rapid combustion take place of a part of pyrolysis gases composed mainly of simple hot gases H2, CO, and some amount of CH₄. Combustion occurs under the impact of the flow of hot air blown through the lances at a speed of up to 50 meters per second. This causes considerable local rise of temperature in this zone up to T - 1500°C.

Gas mixture, entering the fuel chamber, also contains water steams H2O and carbon dioxide gas C0₂. These actively participate in gasification process and themselves lower the temperature of combustion of gas mixture. This make it possible to control the temperature in the fuel chamber either through the general moisture content of loaded feedstock, or by feeding additional amounts of H2O or CO2 into the gasifier. Due to the high velocity of the air flow

Zone 5.1 - a zone of combustion of pyrolysis gases and

Zone 5.2 - a zone of gasification of carbonaceous feedstock residue

are formed in front of the air lances. Their general configuration is presented in Fig. 6.

Thanks to the advantageous design of gasifier SYN2-VG, processes of combustion and gasification occur in virtually all span of the fuel chamber located in front of the air lances, as shown in Fig. 6.

Combustion process is distributed evenly in the zone of combustion of pyrolysis gases and gasification process (Zone 5.1), and is distributed evenly in the zone of gasification of carbonaceous feedstock residue (Zone 5.2) thanks to the large number of air lances (2) as shown in Fig. 6 and high speed of the air blown through them. This, in turn, makes possible;

• maximally even supply of air over all the span of Zone 5.1, the zone of torch combustion of pyrolysis gases;

• to increase the depth of combustion to the very centre of the gasifier;

• to reduce the size of the segments of carbonaceous feedstock residue in Zone 5.2, gasification zone, which makes easier their faster heating and subsequent gasification;

• to cut, crush and loosen carbonaceous feedstock residue using powerful torch jets;

• to improve gas dynamic behavior in combustion zone by creating powerful effect of fluidization of carbonaceous residue in the volume of gases resulting from gasification. This, in its turn, allows us to avoid the formation of local stagnating cold areas (1), Fig. 6 in this zone;

• elutriate inorganic part of carbonaceous residue, when larger and heavier inclusions (first category) go down into the zone of additional gasification and then in the slag zone, and smaller ones (of the first and second categories) are melted in combustion zone;

• using the high velocity of torch jets, the not melted inorganic particles or the drops of melted slag can be transferred into the central part of the zone of combustion of pyrolysis gases, thus forming a slag cone in its centre (3) as shown in Fig.6.

• to raise the temperature not only in the area of air lances, but in all the volume of combustion zone, thus intensifying to maximal extent the process of gasification, to increase the level of conversion of the tars, acids and composite hydrocarbons in this zone.

These actions maximally intensify the processes of combustion of pyrolysis gases, thermochemical conversion of different hydrocarbons and tars, and gasification of carbonaceous feedstock residue in the area of fuel chamber of gasifier SYN2-VG.

The process of partial combustion of pyrolysis gases Partial combustion of pyrolysis gases in the bed of carbonaceous feedstock residue occurs in Zone 5.1, the zone of combustion of pyrolysis gases. Combustion occurs under the impact of oxygen of the air, conveyed into the fuel chamber of the gasifier that represents a system of torch combustion of gases shown in Fig. 6.

This is a diffusion process, because the air is fed into the fuel chamber through the air lances, and pyrolysis gases are conveyed through the diffusors or through the lower end of the fuel chamber. Air oxygen, as an oxidizer, and combustible pyrolysis gases are separated from each other in base mixture are transferred into the fuel chamber via diffusion.

Partial combustion of pyrolysis gases occurs due to the fact that the amount of air oxygen supplied into the fuel chamber of the gasifier is insufficient for complete burning out of these gases, the latter being key precondition for entire process of gasification.

During the combustion of a part of pyrolysis gases the reactions that occur first of all are homogenous reactions of oxidation with air oxygen of gaseous products specifically. Heterogeneous reactions of oxidation with air oxygen of the solid carbon are less frequent. This phenomenon is explained by the fact that the velocities of homogenous reactions (gas - gas) are higher of one or two orders than of those heterogeneous (gas - solid matter).

Besides, when part of pyrolysis gases combust in an oxygen-depleted environment, simple combustible gases ¾, CO and to some extent C¾ have priority in combustion due to high velocity of laminar expansion of fire in these gases. Only after combustion of these gases may various hydrocarbon gases and tars partake in combustion, and only after them carbon may combust.

The dynamic of reactions of combustion is branching-chain with progressing self- acceleration owing to the heat released in exothermal reactions, and the volume of air oxygen conveyed into the fuel chamber is calculated on the basis of thermal energy needed to maintain temperature regime in all the zones of the gasifier, and for generation of syngas of best possible composition and amounts.

The process of partial combustion of pyrolysis gases in an oxygen-depleted environment can be schematically presented in the equations of Formula 10 and Formula 13:

CxHyOz + ((2(x-a)+y/2-z)/2)0₂ = x-aC0₂ + y/2H₂0 + aC (10) or

H₂ + CO + C_aH_b + 0₂→C0₂ + H₂0 + H₂ + C (13) These equations (Formula 10 and Formula 13) describe the process of partial combustion in the zone of combustion and gasification of a part of products of low- temperature, and in part high-temperature pyrolysis with the release of residual pyro-carbon.

Equations of Formula 10 and Formula 13) may also be presented as a complex interaction of simple reactions of oxidation (Formulas 14-18), and of reactions of dehydration (Formula 11 and Formula 12);

CnH_2n+2 -» C„H₂„ + H₂ (11)

C_nH_2n H C_mH_2m+2→ (n+m)C + (2n+2m+2)H₂ (12)

2H₂ + 0₂ = H₂0 + 58 kcal/mole (14)

2CO + 0₂ = 2C0₂ + 136 kcal/mole (15)

CH₄ + 20₂ = C0₂ + H₂0 + 193 kcal/mole (16)

C₂H₄ + 30₂ = 2C0₂ + 2H₂0 + 316 kcal/mole (17)

C₃H₆ + 4,502 = 3C0₂ + 3H₂0 + 460 kcal/mole (18)

This presentation is based on the fact that gaseous products of pyrolysis are oxidized, first of all, by air oxygen, and only after that they start interacting with carbon dioxide gas and water steam formed during combustion of pyrolysis gases during pyrolysis of the feedstock. At that time the major part of the hydrocarbons and tars that make part of pyrolysis gases undergoes dehydration in this zone, and large amount of hydrogen (¾) and finely dispersed pyro-carbon (C) are generated.

To intensify the process of combustion and gasification hot air is conveyed at high speed into combustion and gasification zone. This air is heated as a result of the cooling of the components and parts of gasifier. If need be, water steam (H2O) and/or carbon dioxide (CO2) may be fed into this zone.

High speed of the air exiting air lances permits to loosen the carbonaceous feedstock residue mass in entire span of the fuel chamber, and in particular, in the area of the band of air lances. It makes possible to create in this zone a powerful effect of "boiling" of carbonaceous feedstock residue in the volume of gases formed in the process.

This circumstance makes possible considerable acceleration of the diffusion for interacting gases, and significant increase of the area of the surface of heterogeneous phase for carbonaceous residue. Velocity of adsorption of oxidizing gases and velocity of desorption of reaction products may be increased too. This substantially enhances reacti ons of oxidation, hence reactions of reduction in this zone, and, in turn, considerably improve the composition of generated synthesis gas.

Air oxygen in the process of combustion is virtually totally expended in the reactions of oxidation of a part of pyrolysis gases, in which mostly carbon dioxide, water steam and pyro-carbon are released. These then become the main agents together with carbonaceous feedstock residue in the process of gasification.

In this same zone the nitrogen (N) and sulphur (S) are oxidized to the oxides NO* and S0₂. Their amount depends on initial content of these elements in the feedstock and on the gas dynamic during diffusion combustion of the part of pyrolysis gases inside fuel chamber.

In the zone of combustion of pyrolysis gases reactions that form NH4, COS, ¾S, HC1 and other gases also occur. These, being hazardous components, ought to be removed from generated gas.

Gasification of carbonaceous feedstock residue

Gasification of carbonaceous feedstock residue is executed in Zone 5.2, the zone of gasification of carbonaceous feedstock residue. This process constitutes the conversion of combustion gases CO2 and H₂0 into the simple combustible gases H2 and CO due to their restoration in the fluidized bed of carbonaceous feedstock residue.

High velocity of homogeneous reactions of partial combustion of pyrolysis gases results in virtually all supplied oxygen reacting in a narrow space around air lances of fuel chamber. Thermal energy released in the process causes local overheating of carbonaceous feedstock residue in the area of the band of air lances, and significant rise in temperature in all the zone of combustion and gasification. This circumstance enables maximal intensification of gasification process, to raise the level of conversion of tars, acids and hydrocarbon compounds in this zone.

All the gases conveyed into the zone of combustion and gasification and formed as a result of the process of combustion as they interact with red-hot carbonaceous residue are mainly reduced to simple combustible gases in the reactions represented by Formula 4, Formula 8 and Formula 9:

H2O + C = CO + H₂ - 30 044 kcal/mole (8)

2H₂0 + C = C0₂ + H₂ - 20 195 kcal/mole (9)

C0₂ + C = CO - 39 893 kcal/mole (4)

These three reactions are main reactions of gasification, the first two (Formula 8 and Formula 9) being reactions of hydrogasification, and the last (Formula 4) is a reaction of carbon dioxide gasification when carbon monoxide is released.

Rising of the temperature in the zone of combustion and gasification accelerates and increases the rate of reactions of hydrogasification (Formula 8 and Formula 9) by additional heating of carbonaceous residue and water steam resulting both from combustion of pyrolysis gases (Formula 10), and from low-temperature processing of the feedstock. Increase of the rates of reactions of hydrogasification (Formula 8 and Formula 9) makes possible the use of the feedstock with high moisture content without its deep drying pre-treatment or additional feeding of water or water steam into the gasifier from the outside.

Under the impact of initial high temperatures the rate of reaction of carbon dioxide gasification of carbonaceous residue (Formula 4) also grows. This makes theoretically possible to use carbon dioxide fed from outside the gasifier as an additional oxidizer.

Reactions of Formula 4, Formula 8 and Formula 9 primarily occur at a boundary of the process of torch combustion of pyrolysis gases in the bed of carbonaceous residue and at the periphery of this process.

Because these reactions are reductive and are explicitly endothermal, the temperatures of the gases formed in the zone of combustion and gasification decrease to T - 1100-135O°C, limiting the overheating in this zone to T - 1500°C only in the area of torch combustion of pyrolysis gases.

Hot gases resulting from the process of gasification move upwards, thus towards a layer of carbonaceous feedstock residue moving down from the zone of high-temperature pyrolysis, heating it and setting it in motion in the form of suspension layer. At this time the temperature in the upper part of the zone of combustion and gasification rises to T - 1100 - 1200 °C.

Reactions of reduction (Formula 4, Formula 8 and Formula 9) continue in this part of the zone of combustion and gasification. These reactions result in continuing gasification - with remaining carbon dioxide and water steam - of the bed of the heated carbonaceous residue, rising into the zone of high-temperature pyrolysis.

In high-temperature pyrolysis zone the hot synthesis gas is additionally cooled to T 700 - 1100°C, heating to the same temperature carbonaceous feedstock residue in this zone, subjecting it to partial gasification and high-temperature pyrolysis.

Intensification of the reactions of gasification (Formula 4, Formula 8 and Formula 9) due to high temperatures and intense gas dynamic inside the bed of carbonaceous feedstock residue results in the gases with high content of H₂ and CO, thus lower content of C0₂ and N₂.

The process of thermal conversion of hydrocarbons and tars coming into gasification and combustion zone

In the zone of combustion and gasification a very important process occurs besides the processes of combustion of pyrolysis gases and of gasification of carbonaceous feedstock residue. This process has serious impact on the composition of the gases obtained in this zone. This process is thermal conversion of hydrocarbons and tars that within pyrolysis gases come into the zone of conversion and gasification from the channel of pyrolysis gases of the gasifier, from the zone of additional gasification and partially from the zone of high- temperature pyrolysis.

It should be noted that various hydrocarbons and tars in the pyrolysis gases going into the zone of combustion and gasification from aforementioned zones, have more carbon and hydrogen as compared to other combustible gases that are parts of pyrolysis gases.

Given the fact that during the combustion of pyrolysis gases simple combustible gases H2, CO and to some extent CH4 have a priority in combustion in a depleted oxygen environment, and that conditions of gas dynamics in the fuel chamber of the gasifier intensify combustion process and heighten the temperature of combustion to 1500 °C in the area of fuel chamber, where the air lances are situated, favourable conditions for thermal conversion are created in the zone of combustion of pyrolysis gases and in the zone of gasification of carbonaceous feedstock residue (Zone 6.1 and Zone 6.2 in Fig. 7), as well as in all of the gasifier.

Because of that the hydrocarbons and tars entering the zone of combustion and gasification from the channel for pyrolysis gases of the gasifier undergo dehydration through the reactions of Formula 1 1 and Formula 12:

Cntfen H C_mH2m+2 - (n+m)C + (2n+2m+2)H₂ (12)

The largest part of hydrocarbons and tars that are part of pyrolysis gases are subjected to the process of dehydration in this zone. At this stage large amount of hydrogen (H₂) and of fine-dispersed pyro-carbon (C) are released.

These capabilities of gasification reactor SYN2-VG and gasification process SYN2- VGP4 in general are well correlated for the processing of various types of feedstock with high content of hydrocarbons and chars in gas phase, and with low content of residual carbon. Municipal solid waste is exactly this kind of feedstock.

Besides the process of dehydration, the hydrocarbons and tars that are part of pyrolysis gases can undergo in this zone the steam and carbon dioxide conversion through the reactions shown in Formulas 37-38:

CxH_y + X/2C0₂—!→ (X + X 2)CO + Y/2H₂ (37)

CxHy + XH₂0—!→ XCO + (X + Y/2)H₂ (38)

Large amounts of water steam (H2O) and carbon dioxide (C0₂) that enter the zone of combustion and gasification along with pyrolysis gases, or resulting from combustion enhance this process.

Reactions of Formula 37 and Formula 38 are catalytic, the metals in carbonaceous feedstock residue serving as catalyzers.

As a result of thermal conversion of carbons and tars coming into the fuel chamber from the channel for pyrolysis gases as part of pyrolysis gases, in all of the zone of combustion and gasification simple combustible gases H₂, CO and fine-dispersed pyro-carbon are formed. Synthesis gas leaving this zone has maximal amount of simple combustible gases. Melting and breakdown of inorganic ingredients of carbonaceous residue

Inorganic ingredients of the feedstock come into the zone of combustion and gasification from high-temperature pyrolysis zone in the state differing from initial as a result of thermochemical transformation they have undergone in the zones preceding combustion and gasification zone.

Despite the fact that all inorganic ingredients in these zones were shielded by newly formed carbon and might have been subjected to only a weak impact from high temperature, one can assume that major part of them underwent structural changes within the range of the temperatures typical for various inorganic components.

This assumption is based on the following factors:

• continuous presence of inorganic components in these zones, hence their possible heating to relevant temperatures even when shielded by carbonaceous formations of feedstock;

• Mechanical impact on the feedstock inside rotary kiln due to its rotation and movements of the blades of the mixer in the gasifier;

• destruction of large carbonaceous lumps due to the gas dynamic inside gasifier' s body.

High temperature impact results in structural transformations of the feedstock. Inorganic ingredients thus proceed from the zone of high-temperature pyrolysis into the zone of combustion and gasification in the form of:

o the oxides resulting from the reactions shown in Formulas 29-33:

Me(OH)₄— '→ MeO + H₂0 (29)

MeNOa—!→ MeO + N0₂ (30)

MeCOs— ^ MeO +C0₂ (31)

Me₂0₂—L→ Me₂0 + 0₂ (32)

MeS0₄—L→ MeO + S0₂ + 0₂ (33)

o pure metals resulting from the reactions of Formulas 34-36 and Formulas 39-

40):

MeO + CO—t→ Me + C0₂ (34)

MeO + C—→ ' Me + CO (35)

MeO +H₂— Me + H₂0 (36)

MeO— !→ Me + 0 (39)

MeO + C—!→ Me + CO (40)

o sulphides, nitrides and chlorides resulting from the reactions in Formulas 43- 48, with practically all the chlorides coming in melted form

MeO + H₂S = Me S + H₂0 (43)

MeO + 2HC1 = MeCl₂ + H₂0 (44)

Me + H₂S - MeS (45)

Me + HC1 = MeCl (46)

Me + COS = MeS + CO (47)

Me + NH₄ = MeN+ 2H₂ (48)

o certain amount of other inorganic ingredients (first and second categories) coming into the gas reactor together with the feedstock.

Large inorganic components of the feedstock of the first category and small inorganic components shielded by the carbon inside large lumps of the feedstock may go into the zone of combustion and gasification without being affected by temperature in the zone of high- temperature pyrolysis. Therefore, due to high temperatures in the zone of combustion and gasification continue the following processes, initiated yet in the zone of low-temperature pyrolysis:

o decomposition of the salts of the mineral part of carbonaceous residue with relatively low temperature of destruction that were not broken down in the zone of high- temperature pyrolysis (Formulas 29-33);

o decomposition of the carbonates with high temperature of destruction:

MeCOs »MeO +C0₂ (49)

where Me = Ca(900-1200°C), Na(1000°C), K(1200°C), Ba(1000°C), Li(730-1230°C), and others;

o melting of some of the carbonates and final melting of all the chlorides. At this stage molten chlorides and carbonates may form eutectic mixtures with more refractory salts, lowering their melting temperature. This phenomenon eventually influences significantly formation of liquid slags with lowered temperature of melting.

Reactions of oxidation and reduction in inorganic constituent of carbonaceous residue

The process of reduction of metals from oxides and their subsequent oxidation in the zone of combustion and gasification occurs in exactly the same way as in the zone of high- temperature pyrolysis, albeit at a higher rate owing to higher temperatures and more intense gas dynamic in this zone.

In this process due to the reactions of Formula 39 and Formula 40 the main part of metal oxides conveyed in this zone is either broken down under the impact of high temperatures, or is reduced upon interaction with red-hot carbon. They are then oxidized to oxides while interacting with water steams (H₂0) and carbon dioxide (C0₂) through the reactions of Formula 41 and Formula 42, Reduced metals are in this process an acceptor of oxygen in molecules CO2 and H2O, transforming them in simple combustible gases CO and H₂.

These reactions alternate at high speed caused by high temperatures and elevated gas dynamic in this zone. This alternation continues until the moment when these metals start interacting with silicon dioxide (Si0₂) with formation of silicates and other elements like NH₄, H2S and HC1 through reactions of Formula 43 and Formula 44. Respective sulfides, nitrides and chlorides are formed in the process, the latter being resistant to destruction by high temperature.

Cleaning of gases by removing hazardous components

Main and highly efficient cleaning of generated gases takes place in the zone of gasification of carbonaceous feedstock residue. Gases are cleaned of ΝΟχ, S0₂, HC1, H₂S, NH₄ and COS that are hazardous components of gases formed in the zone of combustion of pyrolysis gases with the partial combustion of pyrolysis gases, part of which are all these components and some elements in them.

Three factors present in this zone make cleaning of gases efficient:

o high temperature from combustion of some part of pyrolysis gases;

o the presence of red-hot carbonaceous residue and of burning-hot micro- particles of pyro-carbon turned into the state of "fluidized" bed;

o the presence of various oxides and reduced metals of the first and second categories, deprived of shielding by carbon as a result of gasification.

Cleaning of generated gases of major pollutants like S0₂ and NOx occurs through their reactions with burning-hot carbon in the reactions (Formulas 50-51):

S0₂ + C = S + C0₂ (50)

N0₂ + C = N + C0₂ (51)

After that C0₂ can be reduced to CO through the reaction of Formula 4:

C0₂ + C = 2CO (4)

Cleaning of generated gases of HC1, H2S, NH₄ and COS can be executed with metal oxides and reduced metals. The metals can be solid, melted or gaseous.

This process occurs with oxides through the reactions of Formulas 43-44, and with reduced metals through the reactions of Formulas 45-48:

MeO + 2HC1 = MeCl₂ + H₂0 (44)

Me + H₂S = MeS + H₂ (45) Me + HC1 = MeCl + H₂ (46)

Me + COS = MeS + CO (47)

Me + N¾ = MeN+ 2H₂ (48)

Gases obtained as a result of combustion and gasification after going through all these reactions are cleaned of hazardous components and additional volumes of CO and H₂ are obtained along with some amounts of sulfides, chlorides and nitrides.

Generated gases are also cleaned of vapors of metals, including heavy metals, during the process of their transformation into respective sulfides, chlorides and nitrides that are resistant to destruction by temperature and subsequently become part of the slags.

Because the depth of gas cleaning directly depends on the components of inorganic constituent in carbonaceous residue, this depth can be augmented by special inorganic additives to the feedstock. These additives can be metal oxides, their salts and hydrates of oxides, and silicon dioxide.

Cleaned gases then descend into gas zone, and inorganic components of the newly formed slags descend into slag zone.

Formation of the slag

Inorganic constituent of carbonaceous feedstock residue undergoes cardinal chemical and structural transformations in the zone of combustion and gasification, being at the same time a catalyst of gasification and an acceptor. It takes active part in production of synthesis gas in large amounts and of great quality, and in its cleaning of hazardous impurities of heavy metals, compounds of sulfur and chloride, transforming them into an inactive, insoluble form representing in their major part compounds of silicon slag.

The main process of formation of the slag corresponds to a reaction of interaction of some metal oxides with silicon oxide (Formula 49):

MeO + SiOi = MeSi0₃, (49)

where M - Ca, Na, , Ba, Li, Fe, Cu, Zn, Cr, Mg, Pb, Ti, Cd and others.

These reactions primarily occur with the formation of liquid slag. This process is facilitated by the fact that the chlorides and carbonates present in the zone of combustion and gasification in molten state form eutectic mixtures with more refractory salts, lowering thereby their fusion temperature.

This circumstance considerably affects formation of fluid slags in this zone with reduced fusion temperature, which is T_sq.- 1100 - 1150°C.

The temperature of slag formation also directly depends on the components of inorganic constituent in carbonaceous residue, therefore the temperature of slag formation can be changed with special inorganic additives to the feedstock in the form of metal oxides, their salts, hydrate oxides and silicon dioxide.

As a result of the processes occurring in the zone of combustion and gasification, the slag is formed, the main components of which are metal and non-metal oxides, sulphides, chlorides, fluorides, inclusions of metal alloys and unreacted carbon. The slag thus formed represents complex amorphous-crystalline form of the silicates with variable composition with some mechanical inclusions.

The structure of the slag formation in the zone of combustion and gasification is a slag cone with a peak (3) in Fig. 6, located in the centre of fuel chamber at the level of air lances. Slowly cooling melt of the slag descends along the cone's slopes.

Slag cone's solid foundation is formed by unmelt inorganic inclusions (of the first category) of various sizes transferred into the central part of fuel chamber under the impact of high velocity of torch jets.

Smaller inorganic inclusion (of the first and second categories) molten at the boundaries of torch combustion, and those that came into this zone from high-temperature pyrolysis zone as separate drops are also blown into the central part of this zone under the impact of high velocity of torch jets.

Drops of melt slag moved into the central part of fuel chamber combine with unmelt inorganic inclusions having lower temperature. Molten slag cools down somewhat and together with unmelt inorganic inclusion forms a peak (3) in Fig. 6 of slag cone, along the slopes of which the drops of melt slag descend into the slag zone.

In the slag zone the slag continues cooling down, forming a mass of slag in conic shape.

Slag's cooling down in this zone results from the general lowering of temperatures in this zone caused by powerful endothermal reactions of gasification.

The slag then goes down into the slag zone, where it is transformed as it cools into a single mass of slag of a complex amorphous-crystalline form.

Zone 6 - Slag zone (Additional gasification zone)

Zone 6 - zone of additional gasification of gasifier SYN2-VG is one of the zones of high-temperature processing of the feedstock at the temperatures T 150 - 1 100°C.

Slag zone is situated in lower part of the inner volume of the body of gasifier, lower than fuel chamber, and inside the device for unloading the slag from the gasifier, as shown in Fig.5, pict. 4.

Within this zone the following processes occur:

• slag is formed and it is partially cooled down under indirect impact of the air fed into gasifier; • the process of gasification of a part of red-hot carbon residue occurs, the residue coming into this zone from the zone of combustion and gasification under the impact of water or steam additionally conveyed into slag zone;

• the slag is mechanically crushed and cooled under the impact of water or water steam;

• the slag is removed from the device for slag removal.

The slag is conveyed into the slag zone of gasifier SYN2-VG from the zone of combustion and gasification with the temperature of T - 900 - 1100°C in the form of monolithic hot slag, but some part of it can also be in liquid form, and some amount of slag may have a shape of separate solid formations.

In slag zone the slag is slowly cooled under indirect impact of cold atmospheric air pumped into the gasifier, then it is mechanically crushed in an impact crusher by means of disc cutters and subsequently removed from the gasifier through a sluice device into a receiving bunker.

The cooling of the slag is slow due to its large thermal capacity, which, in its turn, causes the need for a large volume of the slag zone, where the slag has to be kept for long periods of time.

Remaining in this zone, the slag cools down and acquires complex amorphous- crystalline form that depends on the conditions of the cooling, on initial morphological composition of the feedstock, its moisture content and possible inorganic additions to the feedstock, and on possible additional supply of water or water steam into this zone.

Feeding some water or water steam into the slag zone is needed because some part of burning-hot carbon from the zone of combustion and gasification, without being gasified, can fall through into the slag zone from where it is removed from the gasifier together with the slag.

For gasification of this carbon the steam is conveyed through steam lances into the device for slag unloading (6) in Fig. 5, pict. 4, where the lower part of the slag zone is. Steam lances are placed inside upper branch pipe of the channel for unloading the slag. The steam is pumped into the device through a branch pipe of the channel for water or steam feeding. Carbonaceous feedstock residue that has not been gasified in the zone of combustion and gasification undergoes final gasification under the impact of water steam once it is in the zone of additional gasification.

Reactions of gasification (Formula 8, Formula 9 and Formula 4) and reaction of methanization (Formula 26) occurring in this zone, are clearly endothermal, which contributes to the general lowering of temperature in this zone to T - 150 - 300 °C: H₂0 + C = CO + H₂ - 30 044 kcal/mole (8)

2H₂0 + C = C0₂ + H₂ - 20 195 kcal/mole (9)

2C + 2H₂0 CH₄ + C0₂ (26)

C0₂ + C = CO - 39 893 kcal/mole (4)

After that the gases formed in this zone go into gas zone where they mix with synthesis gas that comes from the zone of combustion and gasification thus increasing the concentration in it of flammable gases ¾, CH₄ and CO and its volume.

Thus the slag zone also functions as a zone of additional gasification of carbonaceous feedstock residue that was not gasified in the zone of combustion and gasification.

Excessive steam and gas pressure developed in slag zone reduces the pouring of carbon and small slag formations into it from the zone of combustion and gasification. Water steam partaking in the process of formation of the slag makes its structure crumbly. This positively affects the process of its further breaking up in the impactor.

Being in this zone for some time the slag slowly cools to the temperature of T- 150°C, turning into a complex amorphous-crystalline form of the silicates of variable composition with some mechanical inclusions.

Then solidified and crushed slag is taken out of the device for unloading the slag via the unloading channel equipped with a sluice mechanism, practically preventing any input of atmospheric air inside the gasifier that might have negatively affect final composition of synthesis gas.

Zone 7 - Gas zone

In zone 7 - the gas zone of gasifier SY 2-GG, one of the zones of both the low-and high-temperature treatment of the feedstock at T - 120 - 900°C, the process of the cleaning of synthesis gas of feedstock dust occurs.

Hot synthesis gas resulting from all thermochemical processes that occur in the gasifier SYN2-VG is released from the layer of feedstock in the zone of combustion and gasification at appr. T - 900°C, goes into the high-temperature part of gas zone situated inside the gasifier between the outer wall of the fuel chamber and internal wall of the air channel of the gasifier.

Synthesis gas generated in the zone of combustion and gasification mixes with the gas coming from the slag zone (zone of additional gasification) and slowly rises to the hot gas outlet branch pipe.

Diameter of this zone is designed so that the speed of the gas flow in it allows minimizing of any slag or carbon dust's going out the gasifier together with generated synthesis gas.

Hot syngas then goes through the gas outlet branch pipe into the jacket of rotary kiln, being a low-temperature part of gas zone, where it undergoes additional cleaning of slag and carbon dust and cools further from T 700°C to T - 120°C, giving its heat to MSW feedstock loaded inside rotary kiln.

Taking into consideration all the above, a conclusion can be made that gasification of MSW and of other and other carbon-containing feedstock with high content of tars with the method of thermochemical conversion consisting in two-stage process of pyrolysis and subsequent gasification in the flow of air and gas of the viscous bed of carbonaceous residue allow:

• higher general intensity of gasification of the feedstock in the fuel chamber of gasification reactor SYN2-VG, bringing its capacity from 350 kilogram per hour for 1 square meter of the overall cross-section of the fuel chamber (this being a norm for currently existing gasification reactors) to 700 kilogram per hour for 1 square meter of the cross-section of the fuel chamber (based on general intensity of gasification of pre-treated MSW of the gasification reactor SYN2-GG);

• larger amount of synthesis gas and its better composition thanks to higher content of simple combustible gases CO and ¾;

• the reduction in the overall volume of obtained synthesis gas of the unneeded substances like CO2, ¾0, O2, and of N2 as of a product of air gasification. This increases the efficiency of obtained gases for the generation of electric power;

• possibility to clean synthesis gas of hazardous gas components NOx, SO2, HC1, H₂S, NH₄ and COS, and of heavy metals directly in the process of gasification, including them into silicate slags in which there is practically no residual carbon.

Theoretical estimate of the method of thermochemical conversion into synthesis gas of municipal solid waste (MSW) and other carbon-containing feedstock with high content of tars executed in a two-stage process of pyrolysis and subsequent downdraft gasification of carbonaceous feedstock in a viscous bed air-and-gas flow

This theoretical estimate of gasification process is presented in the form of tables with calculations organized in accordance with the chart of the estimate in Fig. 7, where the principle of operation of gasification reactor SY 2-GG is shown. This operation is based on the method of thermochemical conversion into synthesis gas of municipal solid waste (MSW) and other carbon-containing feedstock with high content of tars executed in a two-stage process of pyrolysis and subsequent downdraft gasification of carbonaceous feedstock in a viscous bed air-and-gas flow.

Description of the theoretical estimate of the method of thermochemical conversion into synthesis gas of municipal solid waste (MSW) and other carbon- containing feedstock with high content of tars executed in a two-stage process of pyrolysis and subsequent downdraft gasification of carbonaceous feedstock in a viscous bed air-and-gas flow

Area of low-temperature processing of the feedstock

Zone 1 - Drying zone

The process of drying occurs in the zone of low-temperature processing of the feedstock and takes place in Zone 1 - Drying zone at the temperature T 30 - 120°C.

Solid urban refuse (municipal solid waste) in the form of "vat residue" after its sorting was taken as initial feedstock for this estimate.

Fig. 8 shows in Table 1.1 morphological composition of MSW used in this estimate.

This composition was used in the tests of technological complex PGP-1TPD, described in the Gasifier Draft Test Report of the University of California Riverside (UCR), USA.

Estimate of gasification process VGP4

Fig. 9 Table 1.2 demonstrates elemental composition of MSW.

In the drying process physical moisture and colloid water are removed from the feedstock, although the literature data points to the possibility that some part of colloid water might remain in the feedstock.

This estimate is based upon percentage of water evaporated during feedstock drying, as shown in Fig. 10, Table 1.3.

Zone 2 - Zone of moisture removal

Moisture removal zone is one of the zones of low-temperature processing of the feedstock. The process takes place in Zone 2 - Moisture removal zone under the T 120— 300°C. Fig. 11 Table 2.1 describes feedstock remaining after drying, and Fig. 12 gives in Table 2.2 elemental composition of the feedstock after moisture is removed.

Moisture removal process consists in the removal of remaining moisture and in low intensity release of gases, mainly water vapors and C0₂.

Fig. 13 gives in Table 2.3 an assumed composition of the gases after removal of moisture from the feedstock. It is compared to the data taken from the literature. Fig. 14 refers in Table 2.4 a comparison of estimated and literature data of the changes in elemental composition of the feedstock before and after moisture removal. Zone 3 - Zone of low-temperature pyrolysis

The process of low-temperature pyrolysis can be attributed to the zones of low- temperature processing of the feedstock. It takes place in Zone 3 - Zone of low-temperature pyrolysis under the T 300 - 700°C. Fig. 15 describes in Table 3.1 the feedstock residue, coming into the zone of low-temperature pyrolysis.

According to the literature data and due to peculiarities of the feedstock, massive percentage of the products of low-temperature pyrolysis is included, and composition of generated gases and elemental composition of primary tar oil. Elemental composition of residual solid feedstock that has not undergone pyrolysis is calculated based on the remaining mass of the elements after the other products of pyrolysis (gases, tars, water) have been removed. All this data is shown in Table 3.2 of Fig. 16. Table 3.3 in Fig. 17 shows aggregate composition of gases of the processes of drying, moisture removal and low-temperature pyrolysis entering the channel for pyrolysis gases of gasifier.

Table 3.4 in Fig. 18 compares literature and estimated data for products of low- temperature pyrolysis, and table 3.5 in Fig. 19 compares literature and estimated data for gases of low-temperature pyrolysis.

Table 3.6 in Fig. 20 compares the estimate and literature data for low-temperature pyrolysis tar (primary tar oil) and Fig. 21 in Table 3.7 compares estimated and literature data for the composition of the tar of semi-coked coal.

Area of high-temperature processing of feedstock

Zone of high-temperature pyrolysis

Zone of high-temperature pyrolysis is one of the zones of high-temperature processing of the feedstock with T 700 - 1100°C.

Composition of solid carbonaceous feedstock residue that has undergone low- temperature pyrolysis (semi-coke) and coming into the zone of high-temperature pyrolysis is shown in Fig. 22, Table 4.1.

Products of low-temperature pyrolysis are conveyed into the zone of high-temperature pyrolysis where there are higher temperatures. Further conversion of both carbonaceous feedstock residue (semi-coke) and, partially, of gases of low-temperature pyrolysis take place.

Table 4.2 of Fig. 23 displays supposed balance of the products of high-temperature pyrolysis, composition of gases and tars based on literature data with special features of consumed feedstock taken into consideration. Composition of solid carbonaceous residue is computed deriving from the mass of the other products of high-temperature pyrolysis.

In the zone of high-temperature pyrolysis of gasifier partial pyrolysis of primary tar oils occurs, these tar oils formed in a colder zone of low-temperature pyrolysis. This process occurs predominantly in the channel for pyrolysis gases, where the tar vapors come together with the gases. As the residence time of the gases and tar vapors in this zone is limited, not all the primary tar oil undergo thermal breakdown, therefore relative percentage value of its transformation is introduced into the estimate. On the basis of literature data, the elemental composition of the tar obtained after thermal conversion of primary tar oil was included in this estimate. This data is presented in Table 4.3 of Fig. 24.

Composition of gases resulting from thermal conversion of tar oil is shown in Fig. 25, Table 4.4. Composition of tar oil was determined based on literature data on the amounts and composition of tars.

In the channel for pyrolysis gases there are the tars of the low-temperature pyrolysis (primary tar oils), high-temperature pyrolysis tars and the tars that are a product of partial breakdown of primary tar oils. Their average composition is shown in Fig. 26, Table 4.5.

In the channel for pyrolysis gases there are also gases of drying, moisture removal and low-temperature pyrolysis. Their average composition is shown in Fig. 27, Table 4.6

Thanks to high temperature and high content of water steam in the zone of the channel for pyrolysis gases situated in the zone of high-temperature pyrolysis of the gasifier, the conditions conducive to the reactions of conversion of hydrocarbons in pyrolysis gases are created there. But because of the short residence time of gas mixture in this zone, only part of hydrocarbons undergoes thermal conversion. For the purposes of the estimate, percentage of hydrocarbons that entered into the reaction of water or carbon dioxide conversion is introduced. This data is presented in Table 4.7 of Fig. 28.

Table 4.8 of Fig. 29 shows composition of gases resulting from low-temperature pyrolysis, and Table 4.9 in Fig. 29 shows composition of primary gas of low-temperature pyrolysis after the conversion of hydrocarbons.

Table 4.10 in Fig. 31 shows the aggregate composition of gases leaving the zone of high-temperature pyrolysis. It accounts for the fact that all gaseous products that enter the channel for pyrolysis gases have mixed and hydrocarbons have partially converted.

Fig. 32, Table 4.11 compares estimated and literature data for the products of high- temperature pyrolysis, and Fig. 33 in its Table 4.12 compares estimated and literature data for high-temperature pyrolysis gases.

Fig. 34 compares in Table 4.13 the estimate and literature data the tars of high- temperature pyrolysis, and Table 4.14 compares estimate and literature data for solid residue after high-temperature pyrolysis (coke). Zone 5 - Zone of combustion and gasification

The process of combustion and gasification of carbonaceous residue occurs in the zone of high-temperature processing of the feedstock, in Zone 5 - Zone of combustion and gasification at T 1100 - 1350°C, and partially in Zone 4 - Zone of high-temperature pyrolysis at the temperature T 700 - 1100°C.

Because the process of combustion and gasification is very complex and occurs in the two zones at a time, an assumption was made for the clarity of the estimate that reactions of combustion occur in the Zone of combustion and gasification, and reactions of gasification take place in the Zone of high-temperature pyrolysis.

The process of combustion

The process of combustion of carbonaceous feedstock residue occurs in the zone of high-temperature processing of the feedstock, in Zone 5- Zone of combustion and gasification at the T 1100 - 1350°C.

Amount and composition of the products coming into the zone of combustion and gasification from the zone of high-temperature pyrolysis, and thermal conversion of these products in this zone are described in a number of tables below.

Table 5.1 in Fig. 36 demonstrates the amount and composition of the products coming into the zone of combustion and gasification.

Solid carbonaceous feedstock residue descends in the process of its gasification from high-temperature pyrolysis zone into the zone of combustion and gasification, undergoing processes of thermochemical conversion.

For clarity of the estimate it is assumed that having passed through high-temperature pyrolysis zone solid feedstock residue consists mainly of carbon.

The data for thermal conversion of solid carbonaceous feedstock residue is shown in Table 5.2 of Fig. 37.

It is also assumed that while going through the zone of combustion and gasification some very small part of carbonaceous feedstock residue burns down.

Two parameters are introduced into the estimate:

- Percentage of burned down carbonaceous feedstock residue with formed CO, not

C0₂.

- Percentage of carbonaceous feedstock residue burnt down forming CO and C0₂. The data on this process is presented in Tables 5.3 and 5.4 in Fig. 38 and 39.

As well as solid carbonaceous feedstock, vapors of resinous substances that come from the channel for pyrolysis gases do not combust there entirely. Percentage of combusted tar is introduced along with percentage of combustion gases thus formed. As tars are gaseous at these temperatures, larger percentage of tars combust than of carbonaceous residue.

The data on this process is presented in Tables 5.5 in Fig. 40 and Table 5.6 in Fig. 41.

Gaseous products of low-and high-temperature pyrolysis come into the zone of combustion and gasification from the channel for pyrolysis gases of the gasifier. It is these products that combust first, and the main part of air fed into the reactor is consumed by interaction with the gases. It is assumed though, that due to the high velocity of gas stream inside the gasifier some part of combustible gases does not burn and undergo conversion into simple combustible gases.

Percentage of gases that have reacted with oxygen and have formed combustible gases is introduced into the estimate. All the parameters of this process are referred in tables below.

Therefore the data on combustion of pyrolysis gases is given in Fig. 42, Table 5.7. The data for gases not combusted in the zone of combustion and gasification is shown in Table 5.8 of Fig. 43. The sum of the gases formed in the zone of combustion and gasification is shown in Table 5.9 of Fig. 44. Table 5.10 in Fig. 45 shows the total of the air consumed.

Gasification process

The process of gasification of carbonaceous residue occurs in the zone of high- temperature processing of the feedstock, namely in Zone 5 - Zone of combustion and gasification at T 1100 - 1350°C.

The process of gasification takes place in the zone of combustion and gasification situated inside fuel chamber of the gasifier. It is a complex interaction of hot pyrolysis gases coming from the channel for pyrolysis gases into the fuel chamber, of the oxygen of heated air fed into fuel chamber through air vanes, and of burning-hot carbonaceous feedstock residue.

All these processes are illustrated with the tables shown in the Figures below. Thus the products that came from combustion zone are shown in Table 5.11 of Fig.46.

Part of the tars that has not burned in combustion zone goes into the lower part of the zone of combustion and gasification, where under high temperatures their breakdown occurs. All the parameters of this process are shown in the Table 5.12 of Fig. 47.

Similarly, interaction occurs between water steam, gases and carbonaceous residue arriving in this zone. All these processes are demonstrated in Tables 5.13-5.17 in Fig. 48-52. Information about interaction between some gases and carbon, about interaction of gases among themselves, about the amount of gases entering various reactions, and information about the amounts of resulting products is laid out in these tables.

Table 5.18 in Fig. 53 shows aggregate composition of gases and other products resulting from all reactions in combustion and gasification zone.

Table 5.19 in Fig. 54 compares the estimate data of the products of the process of gasification obtained during the experiment, and their estimated values.

Table 5.20 in Fig. 55 compares literature, estimate and experimental parameters of resulting gases.

Energy balance of gasification process

In this estimate the highest calorie value of feedstock (MSW) combustion is used including the energy of condensation of water steam formed at combustion of hydrogen. Table 3 shows thermal losses due to thermal energy taken away by generated hot gases (wet), and Table 4 shows thermal losses into the environment (design losses), and Table 5 demonstrates physical losses caused by the heat taken away by slag residue. Table 6 demonstrates evaporation of primary moisture (phase transition), in Table 7 physical losses caused by the heat taken away by tars are shown, and Table 8 displays thermal effect of gasification process,

Table Γ» 3. Thermal losses. Thermal energy of resulting hot gases (wet)

thermal effect of the phase transition of water kJ/mole 43.8

Table JVs 4. Thermal losses into the environment (design losses)

Table 9 shows general energy balance. Table 10 compares the results of the energy balance estimate with literature data, and Table 11 presents estimated energy parameters of the process. Table JYs 9. General energy balance

Table 10. Comparison of the results of the computed energy balance estimate with literature data

7 - L.K. Kolerov. «Gas Engine Machinery*). Moscow 1951.

Table JVa 11. Estimated ener arameters of the rocess of asification .

Compared characteristics of main technologies of thermochemical conversion of Existing technologies of thermochemical conversion of MSW: 1. Incineration - direct combustion of MSW in air medium.

2. Low-temperature pyrolysis - thermal conversion of MSW at the temperature lower than 700°C without oxygen.

3. High-temperature pyrolysis - thermal conversion of MSW at the temperature higher than 700°C without oxygen.

4. Gasification pyrolysis - thermal conversion of MSW at the temperature higher than 700°C without oxygen with subsequent gasification of carbonaceous residue of MSW in traditional updraft or downdraft gasifiers.

5. Thermal conversion of MSW under the impact of plasma in traditional updraft gasifiers with liquid slag removal.

6. Technology SYNTENA2-VGP4 - gasification pyrolysis technology of thermal conversion of MSW into synthesis gas in an updraft gasification reactor based on the new Theory of Gasification of MSW and Other Carbonaceous Feedstock with High Content of Tars.

MSW characteristics used for the reckoning of the technologies of thermal conversion

Table 12. Thermal arameters of MSW

value of pre- technologies ( h d f f d k d i ) Conditional estimate of the amount of pyro-carbon formed in the process of thermal conversion of hydrocarbons and tars making part of pyrolysis gases

This estimate should be considered conditional, because a computation of the amount of pyro-carbon is extremely complicated. It is conditioned by a multitude of factors that are difficult to take account of, as they are related to the reactions of combustion. This estimate may be computed though, if some conditional assumptions are allowed for.

The basis of this estimate is the process of partial combustion of pyrolysis gases and tars in the zone of combustion and gasification, accompanied by formation of carbon dioxide and water steam, during which their remaining portions are subjected to thermal conversion generating hydrogen and residual pyro-carbon resultant from the reactions of dehydration (Π):

CnH_2n H C_mH_2ra+2→ (n+m)C + (2n+2m+2)H₂ (11)

The data for estimated composition of pyrolysis gases and tars is given in Table 14.

Table 14. Gaseous products of pyrolysis

The estimate of combustion of a part of pyrolysis gases is based on a conditional assumption about priority combustion of simple combustible gases H₂, CO and partially CH₄ in a depleted oxygen environment, conditioned by high velocity of laminar diffusion of flame in these gases.

The data on the combustion of pyrolysis gases is shown in Table 15. Table 15. Combustion of rol sis ases

The estimate of the volume of oxygen (Table 14), needed in the process of gasification of the feedstock derived from the need to maintain certain temperatures in all the zones of gasification reactor. In the general estimate of gasification processes however exothermal effect of some of the reactions was not taken into account, specifically of the reactions of thermochemicai conversion of inorganic constituent of the feedstock. Neither was taken into account the influence that catalytic effect exerts on the process of obtaining of synthesis gas. Catalytic effect is caused by various metals that have been reduced from their oxides in the process of feedstock processing. As a practical consequence of this fact, the amount of oxygen needed for feedstock gasification may be much smaller than estimated. This brings us to the conclusion that an indicator of the amount of pyro-carbon resulting from incomplete combustion of pyrolysis gases can be much higher than estimated, because it has inverse correlation on the volumes of oxygen needed for feedstock gasification.

As a result of this estimate and with assumptions made hitherto, a conclusion can be made that residual carbon can be obtained in the amount exceeding the estimated 1 15.85 grams per each kilogram of processed feedstock. Larger amounts can be obtained through reactions of dehydration occurring during partial combustion of pyrolysis gases and tars in the zone of combustion and gasification and subsequent thermal conversion of their residues.

This option makes possible the processing of hydrocarbon feedstock with high content of hydrocarbons in gas phase and with low content of residual carbon. MSW is one of the types of such feedstock, and with this option synthesis gas of better quality and in larger amounts can be obtained from every kilogram of processed feedstock. Description and data of the process of synthesis of carbamide from synthesis gas resulting from gasification of MSW with the method of thermochemical transformation into synthesis gas of MSW and other carbon-containing feedstock with high content of tars through a two-stage process of pyrolysis and subsequent downdraft gasification of carbon residue of pyrolysis in the air-and gas flow of viscous bed

In the process of thermochemical conversion of any MSW into synthesis gas through the method of pyrolysis and subsequent downdraft gasification of viscous bed of feedstock pyrolysis residue with thermochemical conversion into synthesis gas of solid urban refuse and other carbon-containing feedstock with high content of tars in this invention the gases are formed that besides nitrogen N₂ contain large amount of hydrogen H₂ and carbon monoxide CO, and smaller amount of carbon dioxide CO2. The increase of hydrogen is possible through conversion of CO with addition of water steam. H₂ and CO2 also form in the process. After the elutriation of the CO2 hydrogen ¾ together with N2 are used for the synthesis of ammonia NH3, and the CO2 released during regeneration of absorbing solution is used for the synthesis of carbamide CO(NH₂)₂.

The chain of the transformations of the CO is described by this sequence of equations:

CO + H₂0 = C0₂ (52);

N2 + 3H₂ = 2NH3 (ammonia) (53)

C0₂ + 2NH₃ = H₂0 + CO(NH₂)₂ (carbamide) (54).

A primary technological scheme of the process of synthesis of carbamide through the reactions of Formulas 52-54 is shown in Fig. 56.

The composition of the synthesis gas obtained through the gasification technology SYNTENA2-VGP4 is shown in Fig. 54.

According to the technological scheme (Fig. 56), the separation of nitrogen is performed:

Hence the com osition of the as mixture after nitrogen se aration will be:

Next is steam conversion of CO in synthesis gas.

In this variant of implementation of the invention an assumption is made that only CO undergoes steam conversion through the reaction:

CO+H2O = CO2+H2+Q (+9,86 kcal) (52)

Conventional two-stage process of CO conversion is considered:

• The first stage is done under T 350-450°C with catalysts (Fe₃O₄ + 8-10% Cr₂03), resulting gases have residual content of CO - 1-3%.

• Second stage is low-temperature 180~250°C of Cu-Zn-Al(Cr) oxide catalyst, with residual content of CO - 0,1-0,6%.

To sustain the temperature in the CO steam converter, relief gases are used. These gases are obtained at membrane separator ¾, consisting mainly of CH₄ and C_nH_m.

Listed below are the gases that take part in the reaction of conversion:

Gas mixture after CO conversion:

In accordance with technological scheme (Fig. 56), C0₂ is removed from synthesis

It makes followin as mixture com osition after C0₂ removal:

According to technological scheme (Fig. 56), membrane separation of hydrogen from synthesis gas is done:

In accordance with technological scheme (Fig. 56), ammonia NH₃ is synthesized.

Industrial production of ammonia is based on direct interaction of hydrogen and nitrogen according to the reaction of Formula 53, Gaber process:

N₂+3H₂ = 2NH₃ +Q (+22,04 kCal) (53)

Standard synthesis of ammonia takes place under the T 500°C and pressure of 350 atmospheres with catalyst porous iron +A1₂0 +K₂0. Product output in one cycle in ammonia synthesis reactor is approximately 30%, but due to circulation ammonia output is actually 100%.

Below are the gases used for synthesis of ammonia:

N₂ (released from synthesis gas) 423.78 529.73

Gas residue not used in the synthesis of NH₃

801.84 1002.30

Final product

NH₃ 847.57 643.24

Technology also provides (Fig. 56) for the synthesis of carbamide CO(NH₂)2. Synthesis process is based on traditional Bazarov reaction in two stages:

- Formation of ammonium carbamate: 2NH₃+C02=NH4COONH₂ +Q (+38,0 Kicaji);

- Dehydration of ammonium carbamate:

kcal). For this reaction liquid ammonia NH₃ is used and gaseous carbon dioxide CO2, their proportions being 2,8-3, INH3 : ICO2. The process is done under the temperature 180-185°C and pressure 13,4 - 14,4 mPa. The reagents are in the synthesis tower for 45-60 min. C0₂ conversion rate is 60%. For this variant of the invention's execution proportion of NH₃ : CO2 was chosen to be 3:1.

For the 100% carbamide output various known technologies can be used.

They differ in methods of distillation and use of not reacted NH₃ and CO2, and in ways of manufacturing finished carbamide from its solutions:

a) Partial recycling processes:

- Partial recycle of liquid ammonia;

- Partial recycle of liquid ammonia and solution of carbon-ammonia salts of «Toyo Kazeu» company.

6) Full recycling processes:

- Recycling of dissolved NH3 and CO2;

- Recycling of suspension of ammonium carbamate;

- Separation of not reacted NH3 and CO2 and their return into a cycle;

- Recirculation of hot gases;

- Stripping, i.e. process of synthesis and distillation.

The following are the substances for the production of carbamide:

Substances used in the reaction

Products volume, 1 mass, g

NH3 (liquid) 643.24

CO2 (used for synthesis) 423.78 832.43

C0₂ (surplus, not used in synthesis) 424.66 834.16

degree of conversion of CO2, % 100

Final products

Carbamide CO(NH₂)2 1135.13 NH3 that has not reacted 0

CO2 that has not reacted 0

H₂0 340.54

Carbamide output (% of theoretical) 1< )0

Therefore, one of the options of this invention is a method of pyrolysis and subsequent gasification of viscous bed of feedstock through thermochemical conversion into synthesis gas of solid urban refuse and various other carbon- and tar-rich feedstock resulting in the output of up to 1 135,13 grams of carbamide (urea) for each kilogram of prepared solid urban refuse.

In its entirety, this invention is a method of thermochemical conversion into synthesis gas of municipal solid waste (MSW) and other carbonaceous and tar-rich feedstock through a two-stage process of two-stage pyrolysis with its subsequent downdraft gasification in the air- and gas flow of viscous bed in an integrated technological process.

This method of thermochemical conversion into synthesis gas and following gasification of MSW and other carbonaceous and tar-rich feedstock through a two-stage process of pyrolysis and downdraft gasification in the viscous bed of carbonaceous residue is fulfilled for technological complex SYN2-TC (VGP4) and is presented in Fig. 57.

The technological complex for this invention is a device for thermochemical conversion into synthesis gas of MSW and other carbonaceous tar-rich feedstock, this conversion being a two-stage process of pyrolysis and ensuing gasification in an air-and-gas flow of viscous bed of carbonaceous residue of pyrolysis of the feedstock. It uses downdraft principle of gasification and known technological methods of MSW processing used here for explanatory purposes with a yet unpatented title SYN2-TC (SFGP4). Realization described hereto does not in any way limit possible adaptations and equivalents.

Structure of technological complex SYN2-TC (VGP4).

MSW after its sorting at a refuse sorting plant was identified in the form of the so- called "vat residue" as a key feedstock in terms of the structure of technological complex, its configuration and technical devices needed for it. MSW is a feedstock that can be processed into producer and synthesis gas, electric power or nitrogen fertilizers. This does not in any way preclude, though, the use by technological complex SYN2-TC of other carbonaceous feedstocks with various structures, ash and moisture contents after its slight re-configuring. In this variant the feedstock is transported to the site of the technological complex by cargo transport in the amounts needed for its uninterrupted operation for 3 days and stored in a storage bunker. Then the feedstock is transferred to the conveyor belt which feeds it into a mill, where it is crushed, homogenized and partially dried. The milled feedstock is transported by conveyor belt into a specially designed rotary dryer of indirect heating, where the feedstock is dried by smoke gases coming from the power unit of technological complex. The temperature of the gases is 400-500°C. The heat of the power unit's radiator can be used in the drying process. It can heat the flowing air fed into internal volume of rotary dryer so that water steam can be removed from it. Depending on the composition of the loaded feedstock limestone, dolomite, depleted iron ores may be added through dosing units. The products from the system of synthesis gas cleaning can be added too, including carbon, slag dust, and chemical cleaning agents, such as Na2S, NaCl, NaOH, FeO, Fe₂03, and some others. The feedstock is dried in the rotary dryer from the level of original moisture content of 40-50% to 5-10% moisture content. Smoke gases cool to the temperature of 120-150°C and are released into the atmosphere through smoke pipe. Steam formed in the process of feedstock drying is conveyed together with hot flowing air into the heat exchanger so that moisture is condensed. It can be partially transferred into gasification reactor, where it takes part in the process of gasification. The water condensed in the heat exchanger goes into the system of water cleaning and treatment equipped with cleaning, pre-treatment and accumulation devices for further use in technological complex. The cooled air is conveyed into the gasifier for gasification of the feedstock. Dried feedstock is conveyed from rotary dryer by the conveyor to a magnetic separator, where metal is extracted from the feedstock, the metal can be eventually sold as scrap metal. The feedstock is then transferred by the conveyor to the mechanical sifter, where remaining inorganic components are separated from dried feedstock. About 10% of inorganic components remain in the feedstock, and resultant sifting with small amount of organic components is stored in containers for further transportation to landfills. After inorganic ingredients are separated the feedstock is transferred by the conveyor to the daily storage bunker with 12 hours storage capacity. From there the feedstock is fed by the screw feeder into receiving hopper of an input device. It is then fed into gasification reactor SYN2-GG consisting of horizontal rotary kiln for low-temperature pyrolysis of the feedstock SYN2-RK, in which the processes of low-temperature pyrolysis occurs, and of gasification reactor SYN2-VG for downdraft viscous bed gasification. The slags formed in the process of gasification are crushed inside the gasifier SYN2-VG body and are removed from it for eventual utilization. Hot synthesis gas is conveyed through a heat-insulated channel into the pyrolysis rotary kiln SYN2-RK. Synthesis gas that left its excessive heat in pyrolysis rotary kiln SY 2-RK is removed from it with the temperature 120-150°C and goes through heat- insulated channel into the system of gas cleaning operating on the principle of "wet" cleaning of gas.

One of the main devices of the "wet" gas cleaning system is a water scrubber, in which synthesis gas is cleaned of fine-dispersed dust carbonaceous and slag components. Gas is cleaned by a spray of cold water counter-current to the flow of synthesis gas. Due to the low temperature of the water spray inside water scrubber, synthesis gas is cooled to the temperature of 20-40°C. Synthesis gas goes then into a disintegrator, where it is dried of water dust, and then it goes into a filter of chemical cleaning. In chemical cleaning filter synthesis gas is cleaned of residual hazardous gaseous components - HC1, H₂S, S0₂ and some others. Filtering element of chemical filter constitutes a solid porous object made of iron oxides Fe₂03 and FeO. Going through it, synthesis gas is cleaned, and components that include sulfur, chlorine and other noxious components are bound on the surfaces of filtering element. Cleaning and regeneration of filtering element is done by its cyclical washing with NaOH solution. After the washing the alkali solution contains sulfides and chlorides of sodium Na₂S, NaCl, and some amount of dissolved iron oxides in the form of compounds of different composition, such as Na[Fe(OH)₄], Na-iFeOa etc. After maximum concentration of these substances is reached in the washing water solution NaOH solution is replaced with a new one. Used solution with the particles of filtering element dissolved in it as Fe₂0₃ and FeO and some other compounds are recycled. There is an option of mixing the components of washing solution with other ingredients used in gas cleaning system and transferring this mixture into a storage bunker of a dosing unit (located at the inlet of rotary drier) to be added to feedstock as an additive. After chemical cleaning filter synthesis gas goes into the filter of fine gas cleaning. After its final cleaning there synthesis gas goes into gasholder, where it is stored and homogenized.

In Option 1 synthesis gas goes from the gasholder into gas reciprocator of power generator for generation of electric energy, and hot smoke gases with the temperature of 400- 500°C, formed as a result of combustion of synthesis gases in it, go through the heat-insulated channel into the rotary drier for feedstock drying.

In Option 2 synthesis gas goes from the gasholder into a unit for synthesis of chemical products, such as carbamide, and relief gases that remain after the process of synthesis are conveyed for the burning that can help drying the feedstock in rotary drier.

Technological complex SYN2-TC (VGP4) operates automatically.

Albeit a description is completed by the formula of an invention that specifies and clearly state an invention, it was though that the options of realization of this invention would be better understood from this description. In all the options of realization of this invention all the mass percentages are presented as mass of the overall mass of the composition, if there are no specific indications otherwise. All the ranges are inclusive and combinable. The number of significant digits is not transferable for limitation of numbers indicated, nor for accuracy of measurements.

Sizes and values used in this document should not be construed as strictly limited by exact numerical values referred herein. Rather, if there are no indications otherwise, each value is supposed to indicate both the value referred to, and functionally equivalent range surrounding that value.

Every document, cited in this description, including any cross-references, is included in this document as a reference in its entirety, if something different is not explicitly excluded or in any way limited. The citing of any document does not acknowledge that it is a known level of technology concerning any invention presented or claimed in this document, or if any reference in itself or combined with any other reference or references informs of, suggests or discovers any such invention. In addition, to the extent that any meaning of a term or its definition in this document contravenes any meaning or definition of the same term in a document used foe reference, the meaning or definition attributed to that term in this document shall prevail.

As a number of specific options of the materialization of this invention are illustrated and described herein, it must be obvious to skilled experts in this field that various other alterations and modifications can be made without major changes to the essence and scope of this invention. Its purpose therefore is to encompass in the enclosed formula of the invention any modifications and improvements that are within the scope of this invention.

Claims

1. Method of thermochemical conversion into synthesis gas of municipal solid waste (MSW) and other carbon-containing feedstock with high content of tars executed in a two- stage process of pyrolysis and downdraft gasification of carbonaceous feedstock in a viscous bed air-and-gas flow, with

pyrolysis executed in a rotary kiln place horizontally or slightly inclined versus the horizon, rotary kiln heated with the heat of synthesis gas resulting from gasification of the feedstock. The process is divided into the sequence of stages:

- crushing of the lumps of the feedstock loaded into gasification complex to small fractions;

- homogenization of the feedstock;

- heating of feedstock with the heat of synthesis gas transferred through the walls of the inner body of rotary kiln;

- partial removal of colloid water and adsorbed gases;

- state of the low-fusion elements of the feedstock is changed;

- gas formation is initiated;

- the feedstock is dried completely and colloid water is removed;

- state of the matter of the feedstock is changed;

- process of decomposition and/or destruction of organic polymers is initiated;

- formation of tars and/or saturated or unsaturated hydrocarbons and/or vapors of light resinaceous substances is initiated;

- the structure of feedstock is changed into a crushed mass of carbonaceous feedstock residue;

- reduction of metals from oxides is started.

Gasification occurs in gasification reactor, which in this invention is a downdraft gasifier. Gasification includes the sequence of:

- decomposition and melting of some inorganic salts starts along with their interaction with carbon and mineral ingredients of carbonaceous feedstock residue;

- metals are reduced from the oxides, then earlier reduced metals are oxidized under the impact of CO2 and H2O;

-feedstock residue starts forming crumbly porous carbons mass;

- pyrolysis gases are partially combusted, thereby converting carbonaceous residue into the state of «fluidized» bed;

- combustion gases are reduced through oxidization of hot carbonaceous residue; - thermal conversion of hydrocarbons and/or tars occurs;

- inorganic ingredient of carbonaceous residue fuses;

- gasification of a part of burning carbonaceous residue initiates under the impact of water steam;

at the same time:

- slag forms and is partially cooled;

- slag is grinded and removed from the gasifier;

- resulting hot synthesis gas is separated from the dust of slag and carbon;

- synthesis gas is cooled by pumping it through rotary kiln.

2. Device for therrnochemical conversion into synthesis of solid urban refuse and other carbon-containing feedstock with high content of tars consists of:

1) pyrolysis part designed as a rotary kiln of indirect heating. Consists of feedstock loading device, rotary kiln of indirect heating and device for discharging dust gas residue.

Device for loading feedstock into rotary kiln consists of:

- the bunker;

- vertical piston mechanism;

- slide gate;

- vertical loading channel;

- horizontal loading channel;

- horizontal piston mechanism;

- motor of vertical piston mechanism;

- motor of slide gate;

- motor of horizontal piston mechanism.

Vertical piston mechanism is attached to the bunker. This mechanism is connected to its motor. Vertical loading channel is attached to the lower part of the bunker. Vertical loading channel is divided into upper and lower pipes. The channel can have rectangular or round cross-section. Between upper and lower pipes of vertical loading channel there is a slide gate connected with its motor. Lower part of lower pipe of vertical loading channel is fastened to horizontal loading channel that has rectangular or round cross-section. Horizontal piston mechanism is located inside horizontal loading channel. Horizontal piston mechanism is joined with hydraulic cylinder of horizontal piston mechanism.

Rotary kiln consists of:

- inner body of the rotary kiln;

- outer body of the rotary kiln. Inner body of the rotary kiln for indirect heating has a rib of the inner body that has rounded cross-section. Inside it there are internal guide vans, and on its outer surface there are outer guide vans of spiral shape attached to external surface of the rib and slightly inclined vis-a-vis its axis. In the rear part of the rib of inner body there are outlets for pyrolysis gas and carbonaceous residue. Front oil seal hub is welded to the front end of the rib of the inner body. In the seal hub there is a channel for the installation of the feedstock loading unit, inside which there is an oil seal. In the front part of the front oil seal hub of inner body there is a site for the supporting front wheel that can bear in its lower part on supporting blocks. Motor unit, specifically its ring gear is welded to the central part of the front oil seal hub of inner body. Ring gear meshes with the pinion gear moved by electric or hydraulic motor of the rotary kiln. Central hub is welded to the central part of the rib of the inner body. Back hub of the inner body is welded to the back end of the rib of the inner body. Inside the tailstock there is a site, where back supporting wheel is installed. In its lower part supporting wheel bears on the two back supporting blocks and the side of the back supporting wheel bears on the back toe block.

Outer body of rotary kiln consists of front rib of outer body and its rear rib having heat insulation jacket of rotary kiln and outer coat of rotary kiln.

Front flange of front rib of outer body is welded to front end of front rib of outer body. Front oil seal flange of the front rib of outer body is attached to front flange of front rib with the bolts. Back oil seal flange of the front rib of outer body is welded to back end of front rib of outer body. To the upper front part of the front rib of the outer body cold syngas outlet branch tube (or tubes) is welded, in the back part of front rib of outer body there is tangentially welded hot syngas inlet branch tube and the outlet tube of dust residue, which is welded in the lower part of the back of front rib of outer body.

Four support feet are welded to the front rib of outer body. It is with these feet that it is attached to the frame structure of rotary kiln.

Front oil seal flange of the back rib of outer body is welded to the front end of the back rib of outer body, and at the part of back rib of outer body the back flange of the back rib of outer body is welded, to which the back oil seal flange of back rib of outer body is attached with the bolts. In the upper central part of back rib of outer body the hot pyrolysis gas outlet tube is welded. It is equipped with the valve for emergency pressure relief. In the lower central part of the back rib of outer body carbonaceous residue outlet branch tube (or tubes) is welded. Also, four supporting feet of the back rib of the outer body are welded to the back rib of outer body. It is with these feet that the outer body of rotary kiln is attached to its frame structure inclined at 3-5 degrees to the horizon.

The back rib of the outer body is designed so that it can be attached to the support structure of the rotary kiln with inclination of 2-22 degrees vis-a vis the horizon.

Device for unloading dust gas residue consists of the following components:

- the sluice;

- upper slide gate;

- lower slide gate;

- vertical channel;

- horizontal channel;

- screw mechanism;

- motor of the upper slide gate ;

- motor of the lower slide gate;

- motor of screw mechanism.

Device for unloading dust gas residue from rotary kiln consists of sluice equipped with upper slide gate, lower slide gate, both can be activated by respective motors. The sluice is in its upper part attached to the flange of outlet tube for dust residue. In its lower part the sluice is connected with vertical channel. The lower part of the pipe of vertical channel is welded to horizontal channel. Screw mechanism can be placed inside horizontal channel, and the mechanism can be connected with the motor of screw mechanism.

Gasification part is represented by a downdraft gasifier for gasification in air-and-gas flow of viscous bed of carbonaceous residue of the process of pyrolysis of feedstock. Gasification part consists of a unit for feeding carbonaceous feedstock residue, of the gasifier, and of a unit for unloading of the slag.

Unit for the feeding of carbonaceous feedstock residue into the gasifier consists of the:

- vertical channel of the unit for the feeding of carbonaceous feedstock residue;

- horizontal channel;

- screw mechanism;

- motor of screw mechanism.

Unit for the feeding of carbonaceous feedstock residue into the gasifier consists of the pipe of vertical channel that can have rectangular or round cross-section. It is connected to the outlet branch pipe for carbonaceous feedstock residue of rotary kiln by flange connection. Lower part of the branch pipe of vertical channel is attached to horizontal channel. In its central part horizontal channel is attached to the pipe of the gasifier feeding unit. Inside horizontal channel there is screw mechanism equipped with electric or hydraulic motor. The mechanism is attached to the horizontal channel. The gasifier consists of the following components:

- the body of the gasifier;

- upper flange;

- lower flange;

- branch pipe for input of pyrolysis gases;

- branch pipe for installation of feeding unit;

- outlet branch pipe for hot synthesis gas;

- heat insulation jacket;

- outer protective casing;

- fuel chamber;

- inner wall of the fuel chamber;

- outer wall of the fuel chamber;

- multitude of air lances;

- air channel;

- inner wall of the air channel;

- air distribution box;

- hot synthesis gases channel;

- feedstock shaft;

- hot pyrolysis gases channel;

- feedstock shaft blades;

- lower gas slits;

- upper gas slits;

- screw mechanism;

- motor of screw mechanism.

The body of gasification reactor consists of the lower and upper ribs having different diameter and connected with one another by a connecting insert. Gasifier's body has outer heat insulation jacket covered by outer protective casing. Upper flange is welded to the upper end of the rib of the body of the gasifier. Lower flange is welded to the lower end of the rib of the gasifier. Branch pipe(-s) for the input of pyrolysis gases is (are) welded by its lower end to the upper part of the gasifier's upper rib. Outlet branch pipe(-s) for hot synthesis gas is (are) welded to the upper part of the gasifier's lower rib. In the lower part of gasifier's body fuel chamber is located. It is a hollow structure, the body of which consists of the inner wall of the fuel chamber and its outer wall, connected in the upper and lower part by inserts.

In the upper insert there are apertures of air channels, and in upper part of the inner wall of the fuel chamber air lances are located, connecting the hollow body of the fuel chamber with its internal volume. Between the wall of the lower rib of gasifier' s body and inner wall of air channel there is an air channel in the upper part of which there is the air distribution box. The air channel is limited at its bottom part by lower flange, in which there are air flange channels. In between the inner wall of air channel and outer wall of the fuel chamber there is a channel for hot synthesis gas. In the upper part of the inner wall of the air channel the lower end of the hot synthesis gases outlet branch pipe is fixed. Feedstock shaft representing a rib is inside upper rib of the gasifier's body. The feedstock shaft's upper end is welded to upper flange of the feedstock shaft. Tailor-made blades of the feedstock shaft are attached to the lower end of the rib of the feedstock shaft. There are lower gas slits between the blades. In the of the feedstock shaft rib's upper part there are upper gas apertures and round side opening for the installation of carbonaceous feedstock residue feeding unit into the horizontal channel. Upper flange of the feedstock shaft can be attached to the upper flange of the body of gasifier. The inside of the rib of the feeding shaft is designed to allow screw mechanism to be placed. Screw mechanism is connected with its motor; between upper rib of the body of the gasifier and the rib of the feeding shaft there is a channel for hot pyrolysis gases connected with the hot pyrolysis gases input pipe(-s). This (these) is (are) connected with their lower end to the upper part of the upper rib of the gasifier's body. The upper part of the lower rib can be connected to supporting structure.

Device for unloading the slag from the gasifier consists of the following components:

- outer body;

- bottom;

- inner body;

- lower cone;

- upper flange of the device for unloading the slag;

- flange air channels;

- crushing machine;

- upper branch pipe of the slag unloading channel;

- steam lances;

- branch pipe of the air input channel;

- air channel;

- branch pipe for water/ water steam input

- distribution box

- sluice;

- upper slide gate; - lower slide gate;

- lower branch pipe of the slag unloading channel;

- motor of the upper slide gate;

- motor of the lower slide gate.

Device for unloading the slag from the gasifier consists of the rib of the outer body, inside which there is the rib of the inner body, and upper flange joining both ribs in in the upper part of the device. To the lower part of the inner body's rib lower cone is welded, to lower part of which the upper branch pipe of the slag unloading channel is welded. In the lower part of the device for unloading the slag from the gasifier there is the bottom, to which lower part of the rib of the outer body and lower part of the lower cone are welded. It is also equipped with a sluice that has upper slide gate and lower slide gate. Outside of the upper branch pipe of the channel for slag unloading there is a distribution box, to which a branch pipe of the water/water steam input channel is connected. Steam lances are in the upper branch pipe of the slag unloading channel. Internal volume of distribution box joins internal volume of the upper branch pipe of the slag unloading channel through steam lances. Inside the rib of gasifier's inner body there is a crushing machine that is fitted with a set of revolving disc mills mounted on water-cooled shafts. Branch pipe of the air input channel is attached to the bottom, and air channel joined with air channel of the gasifier is between the ribs of the inner and outer bodies. It is connected gasifier's air channel by means of flange air channels that are in the upper flange of the device for unloading the slag from the gasifier.

3. Production of synthesis gas according to p. 1 for electricity generation with gas engine.

4. Use of synthesis gas according to p. 1 for synthesis of nitrogen fertilizers.