CN111234875A

CN111234875A - Preparation method and preparation system for preparing synthetic gas from RDF-5 fuel and fluidized bed gasification RDF-5

Info

Publication number: CN111234875A
Application number: CN202010124357.6A
Authority: CN
Inventors: 蒋正兴; 蒋伟伟; 朱振鑫; 张博; 王志锋; 吴建平; 吕响荣; 袁梦霞; 丁雅倩
Original assignee: Atea (shanghai) Environmental Ltd
Current assignee: Atea (shanghai) Environmental Ltd
Priority date: 2020-02-27
Filing date: 2020-02-27
Publication date: 2020-06-05

Abstract

The invention relates to a preparation method and a preparation system for preparing synthetic gas by RDF-5 fuel and fluidized bed gasification RDF-5, belonging to the technical field of waste treatment, firstly, RDF-4 fuel is added with a batching additive to prepare RDF-5 fuel with certain particle size and higher ash melting point, and then carrier gas is blown into a dense-phase bed layer of a fluidized bed through a batching and conveying unit, at the temperature of about 1000 ℃, the RDF-5 fuel and the return material of the dipleg separated by the cyclone separator, the preheated air and the superheated steam are subjected to sufficient gasification reaction for enough time, can directly synthesize the synthesis gas without tar and dioxin, can be directly conveyed to a gas holder or a synthesis gas output pipeline through common waste heat recovery and purification, has thorough purification, effectively reduces the cost of enterprises, and the application of RDF gasification to the field of clean industrial synthesis gas or industrial gas with higher value is expanded.

Description

Preparation method and preparation system for preparing synthetic gas from RDF-5 fuel and fluidized bed gasification RDF-5

Technical Field

The invention relates to the technical field of waste treatment, in particular to a preparation method and a preparation system for preparing synthesis gas by using RDF-5 fuel and fluidized bed gasification RDF-5.

Background

The Municipal Solid Waste (MSW) mainly refers to domestic waste produced by urban residents, commercial waste, waste produced in municipal maintenance and management, such as waste paper, waste plastics, waste furniture, waste glass products, waste porcelain, kitchen waste and the like. At present, the quantity of urban domestic garbage in the world is increased at a speed 2.5-3 times faster than the average economic growth speed, and according to statistics, the urban domestic garbage in China is increased at an average speed of 10% per year, but the per capita cultivated land in China is less than 3.85% of the United states, and the precious land resources for garbage landfill are increasingly reduced. In addition, the landfill easily causes pollution to underground water, soil and atmosphere, and threatens the health and living environment of people. Landfills or open-air landfills are therefore not the ultimate solution for waste disposal. The garbage incineration can achieve the purposes of volume reduction, weight reduction and high-temperature sterilization, and the generated energy can be used for power generation, so the garbage incineration technology is researched and applied in industrially developed countries.

Various types of garbage incinerators around the world are over 200, but the most representative garbage incinerator technologies at present mainly include fluidized bed incinerator (including RDF incinerator) technology, rotary kiln incinerator technology, and grate type incinerator technology. The circulating fluidized bed has many advantages in terms of incineration mode, but has many problems when being used for treating low-calorific-value urban domestic garbage in China. Such as: the garbage entering the furnace needs to be sorted, and the heat value of the garbage entering the furnace is required to be higher. Sometimes, in order to improve the calorific value of the garbage and stabilize the incineration, a certain proportion (more than or equal to 20 percent) of auxiliary fuel is required to be added. The rotary kiln incinerator is mainly suitable for treating hazardous wastes, has small capacity and is not applied to the treatment of municipal wastes. Grate furnaces are currently in more use and are recommended by the nation. The grate furnace is mainly characterized in that the garbage entering the furnace does not need to be sorted, but the operation of the grate furnace also meets the problems of low combustion temperature, uncontrolled combustion, local collapse, unqualified tail gas black smoke pollutant discharge and the like caused by the garbage entering the furnace with high moisture and low heat value, the discharged smoke gas can reach the standard through a complicated treatment process, otherwise, the smoke gas is discharged in an overproof manner, and the combustion-supporting fuel cost and the smoke gas treatment cost are extremely high.

The above problems have led the industry to recognize that there are still many problems in direct incineration of raw garbage, and it is important and necessary to prepare raw garbage into garbage derived fuel (RDF-5) with uniform size and uniform and stable calorific value, and then to incinerate or pyrolyze and gasify the raw garbage through the pretreatment of sorting, removing iron and inorganic matters.

Chinese patents CN105351019A, CN105363756A, CN204113363U, CN105983568A and the like disclose processes of preparing RDF from domestic garbage, pyrolyzing and gasifying the RDF, burning fuel gas to generate power, wherein the raw garbage is separated, crushed and dried to prepare RDF solid fuel, the RDF solid fuel is pyrolyzed and gasified to generate combustible gas, the combustible gas is burned at the temperature of more than 850 ℃, and the waste heat of the flue gas is recovered to generate steam and generate power. Compared with the primary garbage, the domestic garbage is made into combustible RDF solid fuel, and the RDF fuel is pyrolyzed and gasified under the condition of oxygen deficiency or oxygen deficiency, so that the formation of dioxin can be effectively inhibited. After the rod is formed, the water content is reduced, the heat value is improved, the power generation efficiency is improved, and the generated combustible gas is subjected to secondary high-temperature heat storage incineration to thoroughly decompose dioxin. However, like all the RDF fuels, the fuel gas produced by low-temperature pyrolysis gasification in the above patent inevitably contains tar and dioxin, and the fuel gas does not reach the quality of industrial fuel gas, and can only be completely eliminated by on-site secondary combustion. In addition, the fuel gas is directly combusted without deacidification, desulfurization and purification, and the content of acid gas in the flue gas is still higher, so that the grade of the steam generated by the high-temperature flue gas waste heat boiler is limited, and the efficiency of steam power generation is also influenced. On the other hand, the garbage incineration power generation internet access is always limited by local power grid peak shaving, the coal-fired boiler thermal power generation is stable in operation, the garbage power generation internet access influences the power peak shaving, the effect of saving the coal-fired consumption of the local power grid is not large, and the whole resource waste is caused in principle.

Chinese patent CN108033446A discloses a cogeneration process of thermoelectric carbon fertilizer and activated carbon by taking municipal refuse derived fuel RDF 5 as a raw material, which discloses the utilization value and the approach of residual biochar after the RDF fuel is pyrolyzed and gasified, but the pyrolysis and gasification process can not avoid the generation of tar and dioxin, and needs on-site secondary high-temperature combustion to thoroughly eliminate the toxic and harmful pollutants which are extremely difficult to decompose.

Chinese patent CN107057794A discloses a method for modifying, forming and gasifying household garbage, which comprises the procedures of bag breaking, magnetic separation, screening, coarse breaking, medium breaking and fine breaking of the household garbage. This patent proposes an improved process for the solidification of RDF-5 fuel in order to increase the fuel strength in fixed bed pyrolysis gasification, rather than the ash fusion point. RDF fuel is fed from the top of the fixed bed and contacts with ascending fuel gas in a countercurrent mode to complete low-temperature dry distillation, and tar and dioxin are generated. Different from gasified coal quality, the RDF fuel is mainly volatile, most of the RDF fuel is subjected to pyrolysis gasification consumption at the top of a fixed bed, only a small amount of carbonized fuel moves downwards to enter a gasification layer, and the gasification temperature is not obviously changed from that of the ordinary unblended RDF fuel, so that ash slag at the bottom of the bed layer is prevented from melting, and slag discharge is prevented from being influenced. The RDF ingredient forming process of the patent does not solve the problem that fuel gas contains tar and dioxin.

Chinese patent CN107365614A discloses a resource recycling method of tobacco stem bio-forming fuel, which proposes that coal powder is added into RDF fuel to increase the heat value, quicklime is added to absorb carbon dioxide in fuel gas, carbon dioxide in biomass fuel gas is solidified in carbon slag, the proportion of carbon in the carbon slag is increased to be used as a raw material for producing carbon-based fertilizer, and simultaneously, the carbon dioxide emission during the combustion of the biomass fuel gas is reduced. However, the RDF proportioning method proposed by the patent does not improve the ash melting point of the RDF, the RDF fuel is pyrolyzed and gasified to still generate fuel gas containing tar and dioxin, and the steam level generated by combustion of the fuel gas is not high, so that the use is limited.

Japanese patent JP2016044819A discloses a method for configuring a high temperature cyclone combustion chamber for RDF fluidized bed gasification, wherein tar and dioxin generated by RDF gasification are completely decomposed in the high temperature cyclone combustion chamber, fly ash possibly carried by fuel gas is also melted at high temperature to form liquid slag, and high temperature flue gas is subjected to waste heat recovery to generate steam. Also, the patent still focuses on a gas combustion method containing tar and dioxin, and does not solve the problems of tar and dioxin and the like in the gasification stage of the RDF fluidized bed.

In summary, the gasification technology of the current RDF fuel is focused on low-temperature pyrolysis gasification, and tar and dioxin in fuel gas are removed by cooling and electric tar capture or direct high-temperature combustion. However, from the technical and economic point of view, the RDF fuel gasification and gas combustion are not as energy-efficient as the RDF fuel direct combustion without any way, which greatly limits the application prospect of the RDF fuel pyrolysis gasification technology.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method and a preparation system for preparing synthesis gas from RDF-5 fuel and fluidized bed gasification RDF-5, raw garbage is treated to obtain bulk RDF-4 fuel, and then the bulk RDF-4 fuel is added with a batching additive to prepare RDF-5 fuel, and then the RDF-5 fuel is gasified at high temperature by a fluidized bed, and sufficient residence time is controlled, so that the synthesis gas without tar and dioxin can be prepared.

The technical scheme for realizing the purpose is as follows:

the invention provides RDF-5 fuel, which is obtained by mixing and extrusion molding of RDF-4 fuel and blending additives, wherein the blending additives comprise high-alumina pulverized coal or high-alumina pulverized coal ash, coke, RDF-5 extrusion molding adhesive and quicklime, the ratio of the RDF-4 fuel to the blending additives is as follows: high-alumina pulverized coal or high-alumina fly ash: coke: RDF-5 extrusion Binder: quick lime 1: 0.1-0.5: 0.1-0.5: 0.1-0.5: 0 to 0.5, preferably in a ratio of 1: 0.1-0.3: 0.1-0.3: 0.1-0.3: 0-0.3, the ash melting point of the RDF-5 fuel generated after the mixture is prepared reaches more than 1000 ℃, the extruded particle size is controlled to be 5-10mm, and besides the ash melting point, the mixture additive is also used for adjusting the heat value of the RDF-5 fuel within a set range, thereby being beneficial to stabilizing the gasification system of the fluidized bed.

Further, the RDF-5 extrusion forming adhesive is tar or cellulose biomass.

Further, in the ash content of the high-alumina pulverized coal or the high-alumina pulverized coal ash, the content of alumina is 30% -50%, and preferably 35% -45%.

The application also provides a preparation method for preparing synthesis gas by fluidized bed gasification RDF-5, which comprises the following steps:

s1, mixing the RDF-4 fuel and the dosing additive, and performing extrusion forming to prepare the RDF-5 fuel;

s2, conveying the RDF-5 fuel to a dense-phase bed of the fluidized bed by carrier gas pneumatic force, and simultaneously introducing superheated steam and preheated air, wherein the temperature of the superheated steam is 250-;

s3, separating the suspended synthetic gas in the dilute phase section of the fluidized bed, cooling and purifying and discharging.

Further, the carrier gas in step S2 is air, nitrogen or CO₂。

Further, between the steps S2 and S3, a step S2-1 is included, wherein the quicklime is blown into the dilute phase section of the fluidized bed by a carrier gas, wherein the carrier gas is nitrogen or CO₂If the method is used for producing synthetic ammonia or methanol by RDF-5 auxiliary coal gasification, the surplus CO2 in the whole plant can be used for pneumatic transmission of a screw feeder and quicklime blowing of a fluidized bed dilute phase section.

Further, in step S2, the retention time of the RDF-5 fuel in the dense-phase bed is controlled by the bed height of the dense-phase bed, the bed height of the dense-phase bed is controlled by the slag discharge rate of the spiral slag cooler, and the bottom slag is discharged by the rotation speed of the spiral slag cooler according to the components of the fuel in the fluidized bed, the specification and the model of the spiral slag cooler, and the like.

The application also provides a preparation system for preparing the synthesis gas by fluidized bed gasification RDF-5, which comprises:

the mixing and conveying unit comprises a screw stirring kneader and a screw feeder, the screw stirring kneader is provided with a feeding hole and a discharging hole, the discharging hole is communicated with a hopper of the screw feeder, the RDF-4 fuel becomes composite rod-shaped or granular RDF-5 fuel with higher ash melting point after mixing, mixing and extruding, and the RDF-5 fuel is pneumatically conveyed to a dense-phase bed layer of the fluidized bed by carrier gas of the screw feeder;

the high-temperature gasification unit comprises a gasification furnace and a cyclone separator, a fluidized bed and an air inlet chamber are arranged in the gasification furnace, the fluidized bed is provided with a dilute phase section and a dense phase bed layer which are distributed up and down, the bottom of the dense phase bed layer is provided with a gas distribution plate for isolating the air inlet chamber, the distribution plate is provided with a sieve pore and a slag discharge pipe, and the slag discharge pipe is connected with a spiral slag cooler; the side wall of the fluidized bed is provided with a first inlet and a second inlet which are communicated with the dense-phase bed, the first inlet is communicated with the screw feeder, the second inlet is communicated with a dipleg return material of the cyclone separator, the top of the dilute phase section is communicated with one inlet of the cyclone separator, RDF-5 fuel enters the dense-phase bed through the first inlet, the dipleg return material of the cyclone separator enters the dense-phase bed through the second inlet, simultaneously preheated air provided by a high-temperature preheater and steam provided by a waste heat boiler enter the dense-phase bed through sieve holes, so that the fuel is fully gasified at high temperature, and the spiral slag cooler controls the height of the dense-phase bed through bottom slag discharged from the dense-phase bed, so that the fuel can stay in the dense-phase bed for enough time to completely decompose tar and dioxin which can be generated by common pyrolysis gasification;

the waste heat recovery and purification unit comprises a high-temperature preheater, a waste heat boiler and a purification device which are sequentially connected, wherein the high-temperature preheater is communicated with a synthesis gas outlet of the cyclone separator, the purification device is communicated with a gas cabinet or a synthesis gas outward conveying pipeline through an induced draft fan, and the high-temperature preheater and the waste heat boiler are communicated with the gas inlet chamber; and

and a DCS control system is arranged in the control device and is used for controlling the fluidized bed, the cyclone separator and the waste heat recovery and purification unit.

Further, the fluidized bed is a circulating fluidized bed or a bubbling fluidized bed, so that the RDF-5 fuel is rapidly mixed with a large amount of high-temperature bed materials and transfers heat to the gasification temperature.

Furthermore, the dilute phase section is communicated with a quicklime nozzle, and quicklime is blown into the dilute phase section of the fluidized bed by carrier gas and is used for deacidification in a fluidized bed by a dry method.

Furthermore, a jacket ash cooler is arranged between the slag discharging pipe and the spiral slag cooler, the bottom slag is cooled to 550 ℃ through the jacket ash cooler, and then the bottom slag is cooled to about 100 ℃ through the spiral slag cooler to discharge a fluidized bed.

Further, the purification device comprises a bag-type dust collector, and an activated carbon blowing device is arranged in the bag-type dust collector and used for adsorbing tar possibly contained in the initial stage of the fluidized bed gasification system.

Further, the high-temperature preheater is an air preheater or an oxygen-enriched preheater.

Has the advantages that: compared with the prior art, the RDF-5 fuel and the preparation method and the preparation system for preparing the synthesis gas by fluidized bed gasification RDF-5 provided by the invention have the difference that firstly, the RDF-5 fuel with a certain particle size and a higher ash melting point is prepared by adding a batching additive into the RDF-4 fuel, and then, the RDF-5 fuel is blown into a dense bed layer of a fluidized bed by carrier gas of a batching and conveying unit, the RDF-5 fuel, the return material of a dipleg separated by a cyclone separator, preheated air and superheated steam carry out sufficient gasification reaction for enough time at the temperature of about 1000 ℃, synthesis gas without tar and dioxin can be directly generated, and the synthesis gas can be directly conveyed to a gas holder by common waste heat recovery and purification, so that the purification is thorough, and the cost of enterprises is effectively reduced;

in addition, the pyrolysis gasification fuel gas is limited to be used for on-site steam production and power generation, and the power generation is limited by local power peak regulation and power grid construction if the power generation is connected to the Internet, so that the application range of the RDF-5 fuel is expanded, the application of the RDF-5 fuel is expanded to RDF-5 high-temperature gasification, synthesis gas waste heat recovery, purification and downstream coal chemical industry application from pyrolysis gasification, combustion, steam and power generation or used as industrial fuel gas, and the situation that dioxin exceeds the standard is not needed to be worried about, namely the RDF-5 fuel is gasified at high temperature to obtain clean industrial synthesis gas with higher value or fuel gas capable of being conveyed for a long distance;

this application can match with coal chemical production devices such as current synthetic ammonia or methyl alcohol, as the auxiliary fuel of current coal gasification gas making coal as fired, only need with current coal as fired blending can normal use, do benefit to low reaches synthetic gas waste heat recovery and clean system, can reduce RDF gasification project investment by a wide margin, promote current apparatus for producing's economic benefits by a wide margin.

Drawings

FIG. 1 is a block diagram of a process for generating RDF-4 fuel from raw refuse.

FIG. 2 is a block diagram of a process for preparing syngas from fluidized bed gasification RDF-5 according to the present application.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

Referring to figure 1, the raw garbage (LHV-6748 kJ/kg, moisture Mt-56%) is changed into 20-30 cm garbage by a large-object crusher, the garbage is subjected to primary iron removal to a drum sieve, the diameter of the screen of the drum sieve is 90mm, oversize materials are larger than 90mm to a secondary crusher, undersize materials are high-moisture organic matters and are subjected to biological drying or fermentation or directly used as organic humus soil for treatment, the oversize materials are subjected to secondary crushing and secondary iron removal to a vibrating sieve of 60-80 mm, the undersize materials are inorganic matters such as glass, ash and the like, the oversize materials are subjected to turbine air separation, other metals and possible glass and the like are removed, and the bulk RDF-4 fuel with high heat value (LHV-16700 kJ/kg, Mt-20%) and equivalent grain size of less than 25mm is obtained;

referring to fig. 2, the blending and conveying unit comprises a screw stirring kneader and a screw feeder, the screw stirring kneader is provided with a feed inlet for receiving the RDF-4 fuel, blending additives are added in the screw stirring kneader for blending, mixing and extrusion molding, a discharge outlet of the screw stirring kneader is communicated with a hopper of the screw feeder, the blending additives are high-alumina pulverized coal or high-alumina fly ash, coke, RDF-5 extrusion molding adhesive and quicklime, wherein the ratio of the RDF-4 fuel to each blending additive is RDF-4 fuel: high-alumina pulverized coal or high-alumina fly ash: coke: RDF-5 extrusion Binder: quick lime 1: 0.1-0.5: 0.1-0.5: 0.1-0.5: 0-0.5, preferably, the ratio is 1: 0.1-0.3: 0.1-0.3: 0.1-0.3: 0-0.3, the ash melting point of RDF-5 fuel generated after batching reaches above 1000 ℃, the extruded particle size is controlled to be 5-10mm, then the screw feeder is conveyed to a dense-phase bed layer of a fluidized bed through carrier gas pneumatic, except for the ash melting point, the batching additive is also used for adjusting the heat value of the RDF-5 fuel to be within a set range, the stability of a fluidized bed gasification system is facilitated, the RDF-4 fuel is batched according to the table 1 to become composite fuel, the heat value is further increased (LHV-18200 kJ/kg), the ash melting point reaches 1000 ℃, the problem that the fluidized bed is gasified at high temperature and the fluidization is not influenced by melting can be met, the operation temperature is higher than the temperature (600-;

table 1: compound RDF-5 ingredient composition, analysis and heat value

Preferably, the alumina content in the ash of the high alumina fly ash or high alumina fly ash in the dosing additive is 30% to 50%, more preferably 35% to 45%.

Table 2 shows the ash content analysis of high-alumina pulverized coal required for blending, and the RDF-5 fuel extrusion particle size is 5-10mm in equivalent diameter;

table 2: ash analysis of high alumina fine coal for RDF-5 fuels

The high-temperature gasification unit comprises a gasification furnace and a cyclone separator, a fluidized bed and an air inlet chamber are arranged in the gasification furnace, the fluidized bed is provided with a dilute phase section and a dense phase bed layer which are distributed up and down, a distribution plate for isolating the air inlet chamber is arranged below the dense phase bed layer, and the distribution plate is provided withThe side wall of the fluidized bed is provided with a first inlet and a second inlet which are communicated with a dense-phase bed layer, the first inlet is communicated with the screw feeder, 127kg/hr of composite rod-shaped RDF-5 fuel is metered and conveyed to the dense-phase bed layer of the fluidized bed through the screw feeder and is rapidly mixed with a large amount of bed materials, the heat transfer, the devolatilization, the pyrolysis and the high-temperature gasification are carried out, and a gasification agent is superheated steam (0.5Mpag, 250 ℃) of 60-75 kg/hr and 60-70% of oxygen enrichment 55-65 Nm/hr³The second inlet is communicated with a dipleg of the cyclone separator, the top of the dilute phase section is communicated with the inlet of the cyclone separator, high-temperature synthesis gas carries fine particle bed materials to the cyclone separator, the high-temperature cyclone catches most of the fine particle bed materials and returns to the dense-phase bed layer through the dipleg and a material sealing valve, so that a large amount of high-temperature bed materials circulate, the fluidized-bed layer is favorably maintained, the mixing and heat transfer between a large amount of bed materials and relatively small amount of incoming RDF-5 fuel are promoted, the slag discharge pipe is communicated with a spiral slag cooler, bottom slag in the fluidized bed is discharged through the spiral slag cooler, the height of the dense-phase bed layer is controlled by the continuous slag discharge of the spiral slag cooler through the control of a slag discharge system, and the retention time of the RDF-5 fuel in the dense-phase bed layer is kept at 10-80min, preferably 30-50min, and fully reacting to completely decompose tar and dioxin possibly generated by common pyrolysis gasification;

the waste heat recovery and purification unit comprises a high-temperature preheater, a waste heat boiler and a purification device which are sequentially connected, wherein the purification device comprises a bag-type dust collector, preferably, an active carbon injection device is arranged in the bag-type dust collector and is used for adsorbing tar possibly contained in the initial stage of the fluidized bed gasification system, the high-temperature preheater is communicated with a synthesis gas outlet of the cyclone separator, the synthesis gas recovers heat through the high-temperature preheater and the waste heat boiler, the temperature is reduced to 150-plus-200 ℃ for purification, then the synthesis gas is conveyed to a system gas cabinet or a synthesis gas outward conveying pipeline through an induced draft fan, the byproduct steam of the waste heat boiler is 06-0.9MPag low-pressure steam which is only used for gasification and possibly RDF-4 fuel drying, the high-temperature preheater is preheated to 300-plus-700 ℃, preferably 500-plus-600 ℃ and is used₂S content is less than or equal to 50mg/Nm3, and the dust content is less than or equal to 10mg/Nm³The content of HCL is less than or equal to 5mg/Nm³(well below GB 18484-2014 hazardous waste incineration pollution control standard (petition draft)), the high-temperature preheater and the waste heat boiler are both also communicated with the air inlet chamber to provide superheated steam and preheated air required by a fluidized bed;

in addition, a DCS control system is arranged in the control device and used for controlling the automatic operation of the fluidized bed, the cyclone separator, the waste heat recovery and purification unit and the like.

Preferably, the dilute phase section is communicated with a quicklime nozzle, quicklime is blown into the fluidized bed by a carrier gas and is used for deacidifying in the fluidized bed by a dry method to remove HC1 and H which may be contained₂S, and the carrier gas can be nitrogen or CO₂Gas, if used for the RDF-5 fuel auxiliary coal gasification to produce synthetic ammonia or methanol, the surplus CO is left in the whole plant₂The method can be used for pneumatic transmission of a screw feeder and jetting of the quicklime at the dilute phase section of the fluidized bed, excessive quicklime is separated by a cyclone separator, and most of the excessive quicklime is captured and returned to a dense phase bed layer and discharged as bottom slag.

Preferably, a jacket ash cooler is arranged between the slag discharge pipe and the spiral slag cooler, bottom slag is cooled to 550 ℃ through the jacket ash cooler, and then the bottom slag is cooled to about 100 ℃ through the spiral slag cooler to discharge a fluidized bed.

Preferably, the residence time of the RDF-5 fuel in the dense-phase bed is controlled by the rotating speed or frequency of a spiral slag cooler communicated with a slag discharge pipe, and the residence time of the fuel is controlled by controlling the volume of the bed through the slag discharge rate of the spiral slag cooler according to the components and the volume flow of the fed materials in the fluidized bed.

According to the method, common RDF-4 fuel is made into bar-shaped or granular RDF-5 fuel with a higher ash melting point through batching, then high-temperature gasification is carried out in a circulating fluidized bed, bed materials are not melted and keep a good fluidized state, the circulating fluidized bed is attached with a cyclone separator, sufficient heat transfer between the high-temperature bed materials and the RDF-5 fuel is ensured, the bed temperature is uniform, and sufficient retention time of the RDF-5 fuel in the fluidized bed is ensured by keeping the bed height of a high-temperature dense-phase bed, so that tar and dioxin possibly generated by common pyrolysis gasification can be completely decomposed.

The syngas composition in this example is shown in table 3:

components

CO

H2

CH4

CO2

N2

Tar oil

Dioxin (DIOXIN)

The content is vol%

30.0～33.0

30.0～36.0

1.0～2.0

20.0～24.0

8.0～12.0

Not detected out

The common pyrolysis gasification can only be directly combusted at high temperature on site to eliminate tar and dioxin in fuel gas, so that steam with low value is obtained, and if steam is used for power generation, the online of the steam is also limited by power grid regulation and the like. The synthesis gas (gas with a certain heat value) produced by the method does not contain tar and dioxin, and can become normal-temperature industrial gas and industrial synthesis gas with higher values through common waste heat recovery and purification treatment. The application can expand the application of RDF to the field of industrial synthesis gas production, and is particularly suitable for the auxiliary synthesis gas production of the existing fluidized bed coal gasification.

The above embodiments are merely preferred embodiments of the present disclosure, which are not intended to limit the present disclosure, and any modifications, equivalents, improvements and the like, which are within the spirit and principle of the present disclosure, should be included in the scope of the present disclosure.

Claims

1. The RDF-5 fuel is obtained by mixing and extruding RDF-4 fuel and a blending additive, and is characterized in that the blending additive comprises high-alumina pulverized coal or high-alumina fly ash, coke, RDF-5 extrusion molding adhesive and quicklime, wherein the ratio of the RDF-4 fuel to each blending additive is as follows: high-alumina pulverized coal or high-alumina fly ash: coke: RDF-5 extrusion Binder: quick lime 1: 0.1-0.5: 0.1-0.5: 0.1-0.5: 0 to 0.5, preferably in a ratio of 1: 0.1-0.3: 0.1-0.3: 0.1-0.3: 0-0.3.

2. The RDF-5 fuel of claim 1, wherein: the RDF-5 extrusion forming adhesive is tar or cellulose biomass.

3. The RDF-5 fuel of claim 1, wherein: in the ash content of the high-alumina pulverized coal or the high-alumina pulverized coal ash, the content of alumina is 30-50%, preferably 35-45%.

4. A preparation method for preparing synthesis gas by fluidized bed gasification RDF-5 is characterized by comprising the following steps:

s1, mixing the RDF-4 fuel and the blending additives, and carrying out extrusion forming to obtain the RDF-5 fuel as claimed in claims 1-3;

s2, conveying the RDF-5 fuel to a dense-phase bed of a fluidized bed through carrier gas pneumatic force, and simultaneously introducing superheated steam and preheated air, wherein the temperature of the superheated steam is 250-300 ℃, the temperature of the preheated air is 300-700 ℃, preferably 400-600 ℃, and the residence time of the RDF-5 fuel in the dense-phase bed is controlled to be 10-80min, preferably 30-50 min;

5. The method of claim 4, wherein the carrier gas in step S2 is air, nitrogen or CO₂。

6. The method of claim 4, wherein: between the steps S2 and S3, the method further comprises a step S2-1 of blowing quicklime into the dilute phase section of the fluidized bed by a carrier gas, wherein the carrier gas is nitrogen or CO₂。

7. The method of claim 4, wherein: in step S2, the residence time of the RDF-5 fuel in the dense bed is controlled by the bed height of the dense bed, which is controlled by the slag removal rate of the spiral slag cooler.

8. A preparation system for preparing synthesis gas by fluidized bed gasification RDF-5 as claimed in claims 4-7, comprising:

the device comprises a batching and conveying unit, a feeding unit and a discharging unit, wherein the batching and conveying unit comprises a screw stirring and kneading machine and a screw feeder, the screw stirring and kneading machine is provided with a feeding hole and a discharging hole, and the discharging hole is communicated with a hopper of the screw feeder;

the high-temperature gasification unit comprises a gasification furnace and a cyclone separator, a fluidized bed and an air inlet chamber are arranged in the gasification furnace, the fluidized bed is provided with a dilute phase section and a dense phase bed layer which are distributed up and down, the bottom of the dense phase bed layer is provided with a gas distribution plate for isolating the air inlet chamber, the distribution plate is provided with a sieve pore and a slag discharge pipe, and the slag discharge pipe is connected with a spiral slag cooler; the side wall of the fluidized bed is provided with a first inlet and a second inlet which are communicated with the dense phase bed, the first inlet is communicated with the screw feeder, the second inlet is communicated with the dipleg of the cyclone separator, and the top of the dilute phase section is communicated with an inlet of the cyclone separator;

the control device is internally provided with a DCS control system.

9. The manufacturing system of claim 8, wherein the fluidized bed is a circulating fluidized bed or a bubbling fluidized bed.

10. The production system of claim 8, wherein the dilute phase section is in communication with a quicklime nozzle.

11. The manufacturing system of claim 8, further comprising a jacketed ash cooler disposed between said slag discharge pipe and said spiral slag cooler.

12. The manufacturing system of claim 8, wherein the purification device comprises a bag-type dust collector, and an activated carbon blowing device is arranged in the bag-type dust collector.

13. The production system of claim 8, wherein the high temperature preheater is an air preheater or an oxygen-rich preheater.