DE102013113769A1 - Process for fixed-bed pressure gasification of carbonaceous fuels - Google Patents

Abstract

A process for producing a synthesis gas containing hydrogen and carbon oxides by gasification of coke or coal with oxygen and steam in a fixed bed carried by a discharge grate and producing ash in a fixed bed pressure reactor, wherein liquid, hydrocarbonaceous byproducts of gasification such as tars, oils, naphtha and Phenols are introduced into the fixed bed of the fixed bed pressure gasification reactor.

Description

Field of the invention

The invention relates to a process for producing a synthesis gas comprising hydrogen and carbon oxides by gasification of carbonaceous fuels, in particular coke or coal, with oxygen and steam in a fixed bed carried by a discharge grate and producing a solid ash in a fixed bed pressure gasification reactor Working up of the crude synthesis gas discharged from the fixed-bed pressure gasification reactor and containing hydrocarbon-containing by-products, for example tars, oils, naphtha or phenols, can be advantageously used.

State of the art

By means of fixed bed pressure gasification reactors, solid fuel such as coal, coke or other carbonaceous fuel is gasified with steam and oxygen as a gasifying agent at elevated temperature and, in most cases, under positive pressure to a syngas containing carbon monoxide and hydrogen to give a solid ash which overflows an ash discharge grate, which is designed in many cases as a rotary grate, is discharged from the reactor. This type of reactor is often referred to as FBDB (= Fixed Bed Dry Bottom) pressure carburetor.

In the fixed bed, the fuel passes from top to bottom following temperature zones with increasing temperature in this direction:

• Drying zone: In the drying zone, moisture bound in or on the fuel is desorbed and discharged from the fixed bed pressure gasification reactor with the crude synthesis gas stream.
• - Pyrolysis zone: Here, volatile compounds are released from the fuel and expelled. There is here a charring or coking of the fuel.
• - Gasification zone: In the gasification zone, the actual reaction of the fuel with the gasification agent, which usually contains air or oxygen, and water vapor and possibly carbon dioxide as a moderator, to the target products of gasification, namely hydrogen and carbon monoxide.
• - Combustion zone: Here, the heat energy required for gasification, pyrolysis and drying is generated by burning part of the fuel.

For further procedural details reference is made to the relevant literature, cf. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, page 367 ff , The gasification typically starts at temperatures of about 700 ° C and proceeds at high speed at temperatures of 800 ° C, see. Ullmanns Encyklopadie der Technischen Chemie, 4th Edition (1977), Volume 14, p. 384 , The local shows a typical temperature profile of the gas temperature in a fixed bed pressure gasification reactor, especially in the temperature zones discussed above.

In addition to the target products carbon monoxide and hydrogen, the crude synthesis gas after leaving the reactor but also obtained in the gasification by-products, such as tars, oils, naphtha, and phenols containing all hydrocarbons or consist of hydrocarbons and are liquid at ambient conditions or in liquid, liquid or dissolved in liquid-dispersed form (for example as an emulsion in water) during the work-up of the crude synthesis gas. All of these by-products are to be understood below as liquid by-products.

In addition, the raw gas from the fixed bed entrained dust, consisting of fuel and ash particles, and ammonia, which is also separated during the workup of the crude synthesis gas and obtained as a valuable material, cf. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, page 437, Figure 75 ,

Particularly in the case of smaller gasification plants, it is not always economical to process the liquid by-products into a salable state, for example with increased purity and / or freed of solid constituents. In these cases, the by-products must be disposed of in an orderly manner, resulting in disposal costs.

In the published patent application DE 2607745 A method is presented which disposes of the dust condensed tar separated from the gas condensate by returning it to the fixed bed pressure gasification reactor. A disadvantage of this method is that the recycled mass is only applied to the surface of the reactor bed. The tars contained in the mass are vaporized in this way before they reach the gasification zone of the fixed bed. The evaporated tars are discharged with the raw synthesis gas from the fixed bed pressure gasification reactor and washed out again from the gas condensate, so that they are driven only between the reactor and gas scrubbing in a circle.

The publication DE 19509570 A1 teaches a process for pyrolysis and fixed bed pressure gasification of carbonaceous materials. Among other things, a tar-oil-solids Water mixture applied to the surface of the fuel bed. Although some of the applied substances are pyrolyzed, a significant proportion is in turn discharged with the raw synthesis gas from the fixed-bed pressure gasification reactor.

In the published patent application DE 10 2013 202 356 A1 A method and apparatus for fixed bed pressure gasification of solid fuels with increased power and broader range of solid fuel applications is taught. There it is disclosed that powdered fuels are formed as secondary fuels by means of a briquetting press to form a fuel strand and then pressed into the fixed bed pressure gasification reactor. A tar-oil-solid mixture obtained in the fixed-bed pressure gasification serves as an agglomeration aid. Again, as the addition of the shaped secondary fuel into the drying and pyrolysis zone of the fixed bed pressure gasification reactor occurs, there are the above-described disadvantages of volatiles discharge with the raw synthesis gas.

The object of the invention is therefore to provide a process which is capable of recycling the by-products into the fixed-bed pressure gasification reactor in such a way that they are converted there into synthesis gas.

Description of the invention

The object has been achieved by a process for gasification of solid carbonaceous fuels, in particular coke or coal, with gasification agents in a fixed bed pressure gasification reactor comprising a gasification agent inlet, a product gas outlet, a fuel bed of solid carbonaceous fuel disposed on an ash discharge grid, a fuel supply device, an ash removal device; in which a synthesis gas comprising hydrogen and carbon oxides is obtained, discharged from the fixed bed pressure gasification reactor through the product gas outlet and subsequently processed into a pure synthesis gas, characterized in that hydrocarbonaceous by-products (liquid by-products) obtained in the preparation of the raw synthesis gas in liquid, liquid-dissolved or liquid-dispersed form Gasification, such as tars, oils, naphtha and phenols, introduced into the gasification zone and / or the combustion zone of the fixed-bed pressure gasification reactor and also at least partially converted to hydrogen and / or carbon oxides.

Further advantageous embodiments of the method according to the invention can be found in the subclaims 2 to 13.

As carbonaceous fuels, coke and coal are preferred because of their favorable combustion and gasification properties. However, the method according to the invention also includes the gasification of biomass with a sufficiently high carbon content if it can form a mechanically and hydrodynamically stable fuel bed under gasification conditions. Since in the implementation of the latter particularly high levels of liquid by-products are obtained, the application of the method according to the invention offers particular advantages here.

The gasification agents used are oxygen or air, preferably in conjunction with steam or carbon dioxide as moderator.

As a ash discharge grate, for example, a rotary grate can be used. The nature and use of this device is known per se to the person skilled in the art. With regard to the temperature control in the fixed-bed pressure gasification reactor, the thermal design limits for rotary grates must be taken into account. Maximum permissible temperatures for rotary grates are in the range of 300 to 400 ° C. This also limits the inlet temperature of the gasification agent added via a gasification agent inlet disposed below the rotary grate so that the gasification agent passes through the rotary grate before entering the fuel bed.

The preparation of the crude synthesis gas to a pure synthesis gas is known per se and is described in the relevant literature, cf. Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition (1977), Volume 14, p. 449 et seq , In particular, tar fractions, hydrocarbon fractions, eg. As naphtha, phenol-containing liquids and oil fractions to call. The oil fractions consist partly of foreign oils, which are used as a treatment aid and serve, for example, to reduce the viscosity and improve the filterability of tar fractions.

As stated in the discussion of the state of the art, by-products formed in the gasification, which contain hydrocarbons or consist of hydrocarbons and liquid under ambient conditions or in liquid, liquid-dissolved or in liquid-dispersed form (for example as an emulsion in water) in the workup of the crude synthesis gas, hereinafter to be understood as liquid by-products.

Of course, the transition between the above discussed temperature zones of the fixed bed pressure gasification reactor is fluid. These zones are not to be regarded as discrete areas with sharp transitions to the neighboring zones, they are rather defined by ideal typology. Decisive for the definition of the gasification zone is that in this zone, a significant conversion of the fuel to synthesis gas components takes place, or the gasification reaction proceeds with sufficient reaction rate. The location of this zone within the fixed bed pressure gasification reactor is, of course, dependent on its geometry and other characteristics as well as on its operating parameters, such as the mass flows and inlet temperatures of the gasification agent and fuel, the composition of the gasification agent, the ash effluent mass flow and the operating pressure. Experience has shown, however, that at temperatures above 700 ° C. a significant conversion of the fuel with the gasification agent to synthesis gas constituents takes place at temperatures above 800 ° C.

Preferred embodiments of the invention

The process according to the invention is preferably carried out such that at least part of the liquid by-products introduced into the fixed-bed pressure gasification reactor reaches a region in which the gas temperature is at least 700 ° C., preferably at least 800 ° C. As explained above, a significant conversion of the fuel with the gasification agent to synthesis gas constituents is achieved at temperatures above 700 ° C. and, at temperatures above 800 ° C., a significant conversion of the fuel. This is accomplished by introducing the liquid by-products into the fixed bed pressure gasification reactor in the gasification and / or combustion zone by pumping, injecting or spraying, using propellant gas in the event of injection or spraying. The introduction into the fixed-bed pressure gasification reactor by injection or spraying is suitable in particular for liquid by-products with low-viscosity addition conditions. Advantageously, a propellant gas is used for the injection or spraying of the liquid by-products which can behave either inertly or reactively with respect to the by-products and the reactions taking place in the gasification reactor. As an inert propellant, for example, nitrogen can serve. However, it is of particular advantage if, in the case of injection or spraying, a reactive propellant gas, for example the gasification agent or one or more of its constituents, is used. This eliminates the separate provision for the propellant gas, there is a further conversion to synthesis gas components and the product gas is not contaminated by non-process propellant gas components.

When using a propellant gas, the liquid by-products can be promoted on the principle of propulsion jet pump, so that below can be dispensed with a further pump to promote the liquid by-products.

If the viscosity permits, the injection or spraying of the liquid by-products is advantageously carried out so that they are atomized to a fine aerosol. In this way, a high penetration depth into the fuel fixed bed and a high conversion to synthesis gas components are ensured.

Liquid by-products with still high viscosity at addition conditions are preferably introduced by pumping into the fixed-bed pressure gasification reactor, wherein here too the addition takes place in the region of the gasification and / or combustion zone.

In a preferred embodiment of the invention, the injection or spraying of the liquid by-products in the fixed bed pressure gasification reactor via at least one, installed in the wall of the reactor and directed radially into the reactor chamber nozzle, wherein using multiple nozzles, these preferably at equal distances from each other and preferably at the same height distributed on the circumference of the reactor. By this symmetrical arrangement of the nozzles, a homogeneous distribution of the liquid by-products can be ensured on the individual nozzles. The nozzles may correspond in their design to the blow-molder process known for the production of pig iron, cf. Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 18, page 493 ,

Another particular embodiment of the invention is that the nozzle orifices complete with the lining of the reactor inner wall, so that they do not protrude into the reactor interior. In this way, the mechanical load on the nozzle orifice is reduced by the sinking material of the fixed bed.

Another particular embodiment of the invention is that carbon dioxide, water vapor, air or oxygen or any mixtures of these components are used as propellants. In the case of the addition of carbon dioxide or water vapor, the gas serves more as a propellant, in the case of the addition of air or oxygen, the propellant supports by its oxygen content, the oxidation and thus the gasification of the injected liquid by-products. It is advantageous that in all the above cases, a further implementation of the propellant gas components in the gasification reactor can take place or the propellant gas components are already present as components in the raw synthesis gas. The Introduction of extraneous components into the process is thus avoided.

In a particularly preferred embodiment of the invention, the nozzles are installed at a vertical distance of 1.0 to 2.0 m, preferably 1.5 m above the highest point of the Austragsrostes equidistant to each other on the circumference of the reactor in the reactor wall. At this distance is, with appropriate adjustment and tuning of the flow rates of fuel, oxygen and water vapor, the gasification zone of the fixed bed. The injected material thus enters the gasification zone and is reacted together with the material of the fixed bed to synthesis gas components. It has proved to be particularly favorable if the jet direction of the nozzles is directed downward with an angle deviating from the horizontal angle from 0 to 30 °, preferably 0 to 20 °, most preferably 0 to 10 °. As a result, the residence time of the liquid by-products introduced into the fixed-bed pressure gasification reactor in the hot regions is increased and their total path through the reactor is lengthened, which leads to an improved conversion of the liquid by-products to synthesis gas constituents. On the other hand, it is avoided in this way that the lying above the nozzle part of the fixed bed is loosened too much and that the jets may reach the ash layer and the rust.

A further particular embodiment of the invention consists in that the nozzle outlet speed related to the amount of propellant gas leaving the nozzle is between 50 and 150 m / s, preferably between 80 and 120 m / s. The volume of the vaporized liquid by-products is mathematically neglected. In this velocity range, a sufficient penetration depth of the jet into the fixed bed is given, so that high residence times and conversions of the liquid by-products are achieved.

Another particularly preferred embodiment of the invention is that the local temperature of the fixed bed is determined on the inside of the reactor wall by means of two installed on the circumference of the reactor rows of temperature sensors, wherein the temperature sensors are spaced apart within a row at equal intervals, wherein the vertical distance to the highest point of the discharge grate in the upper row 0.5 to 2.5 m, preferably 1.0 to 2.0 m and the vertical distance to the highest point of the discharge grate in the lower row 0 to 0.5 m, preferably 0.25 m and wherein the amount of ash discharged per unit time via the discharge grate is adjusted so that from the upper row of temperature sensors a temperature between 700 and 1300 ° C and from the lower row a temperature between 300 and 400 ° C measured becomes. In this way, the vertical position of the gasification zone of the fixed bed is adjusted so that the jets reach the gasification zone and a sufficient residence time of the introduced liquid by-products in the gasification zone results. The large temperature ranges in both cases are due to the different properties of the possible fuels used. If the temperature of the upper row of sensors is in the range of 700 to 1300 ° C, this indicates that the gasification zone is at the level of the nozzles as required.

If the temperature of the lower row of sensors is in the required range of 300 to 400 ° C, this ensures that a sufficiently thick ash zone is above the discharge grate and the discharge grate is thus protected against excessive temperatures.

The amount of ash discharged per unit time via the discharge grate can be regulated, for example when using a rotary grate by the rotational speed.

Another particular embodiment of the invention provides that the liquid by-products are mixed with one another in the fixed-bed pressure gasification reactor. In this way, for. As viscous, dust-laden tars lowered by the addition of oils in their viscosity and thus made more flowable, whereby the wear of the nozzle orifices is reduced. But it is also possible to introduce different liquid by-products separately via separate nozzles in the fixed-bed pressure gasification reactor. In this way, the wear can be limited to certain nozzles, or the nozzles can, according to the liquid by-product to be introduced, optimally designed, for example by using particularly abrasion resistant materials.

The by-products recirculated into the reactor according to the invention are liquid, although partly contaminated with dust, so that they are mixed with positive displacement pumps, e.g. multi-head plunger or diaphragm pumps can be pumped to the nozzles. Depending on the nature of the dust contained in the tar, it may be necessary to separate or crush coarser dust particles before introducing the tar. For this purpose, in connection with the treatment of tar products from the fixed bed coal gasification per se known mechanical separation processes, for. As the filtration, or crushing or homogenization can be used.

A further particular embodiment of the invention is that the inner wall of the reactor in the vicinity of the nozzle orifices is protected by panels, the panels consisting of ceramic material in which cooling elements made of metal, such as pipes, are contained, which are cooled by a cooling medium, like water, can be flowed through. The inner wall of the reactor is protected in this way in the vicinity of the nozzle openings from excessive heat. Because of malfunctions, such as damage to the nozzle orifice, the jet can be deflected and come close to the reactor wall.

embodiments

Further developments, advantages and applications of the invention will become apparent from the following description of non-limiting embodiment and numerical examples and the drawings. All described and / or illustrated features alone or in any combination form the invention, regardless of their combination in the claims or their dependency.

Show it

1 a longitudinal section through a fixed bed pressure gasification reactor with inlets for liquid by-products according to the invention,

2 a cross section through the fixed bed pressure gasification reactor at the level of the inlets for the liquid by-products.

1 shows by way of example how the inlets for liquid by-products in the same amount on the circumference of the fixed-bed pressure gasification reactor 1 are distributed. The fixed bed pressure gasification reactor is via the fuel addition 3 Fuel, in the present example charcoal fed. The ash obtained as a by-product of the gasification is passed through the ash discharge device 6 discharged from the fixed bed pressure gasification reactor. The gasification agent, steam and air or oxygen in the present example, passes through the gasification inlet after completion of the heating process 5 into the fixed bed pressure gasification reactor below the ash discharge grate 2 introduced, which is configured in the present example as a rotary grate. The raw synthesis gas produced in this process is transferred via the product gas outlet 6 discharged from the fixed-bed pressure gasification reactor and fed to the further work-up.

About the inlets 7 Liquid by-products, in this case a tar-oil-naphtha mixture, are introduced into the fixed bed of the fixed-bed pressure gasification reactor. The inlets are designed as nozzles and directed in a deviating by 10 ° from the horizontal angle downwards. The nozzles are installed at a vertical distance of 1.5 m above the highest point of the rotary grate equidistant to each other on the circumference of the reactor in the reactor wall. The nozzle openings close with the lining of the reactor inner wall and therefore do not protrude into the reactor interior.

As a propellant superheated high-pressure steam is used, the technical oxygen can be added. The nozzle outlet speed related to the amount of propellant gas leaving the nozzle is approximately 100 m / s.

The fixed bed pressure gasification reactor is equipped on the inside of the reactor wall with two rows of temperature sensors installed on the periphery of the reactor (not shown in the figure) with the temperature sensors spaced equidistant from each other within a row. The vertical distance to the highest point of the rotary grate is 1.8 m for the upper row of temperature sensors and 0.25 m for the lower row. By setting an appropriate rotational speed, the amount of ash discharged through the rotary grate per unit time is adjusted to measure a temperature between 700 and 1300 ° C from the upper row of temperature sensors and a temperature between 300 and 400 ° C from the lower row.

Industrial Applicability

With the invention, an economical method is provided to dispose of the by-products obtained in the gasification. The inventive method is particularly suitable for use in smaller gasification plants. This eliminates the processing of the liquid by-products in a salable condition and the disposal costs for these by-products are reduced.

LIST OF REFERENCE NUMBERS

1

 Fixed bed pressure gasification reactor

2

 Ascheaustragsrost

3

 fuel supply

4

 ash discharge

5

 Gasifying agent inlet

6

 product gas

7

 Inlets for liquid by-products

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 2607745 A [0008]
• DE 19509570 A1 [0009]
• DE 102013202356 A1 [0010]

Cited non-patent literature

• Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, page 367 et seq. [0004]
• Ullmanns Encyklopadie der Technischen Chemie, 4th Edition (1977), Vol. 14, p. 384 [0004]
• Ullmanns Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 15, page 437, Figure 75 [0006]
• Ullmanns Encyklopadie der Technischen Chemie, 4th Edition (1977), Vol. 14, p. 449 ff. [0017]
• Ullmann's Encyclopedia of Industrial Chemistry, Sixth Edition, Vol. 18, page 493 [0024]

Claims (13)

A method of gasifying solid carbonaceous fuels, particularly coke or coal, with gasification agents in a fixed bed pressure gasification reactor comprising a gasification agent inlet, a product gas outlet, a solid carbonaceous fuel bed disposed on an ash discharge grid, a fuel supply device, an ash removal device; in which a synthesis gas comprising hydrogen and carbon oxides is obtained, discharged from the fixed bed pressure gasification reactor through the product gas outlet and subsequently processed into a pure synthesis gas, characterized in that hydrocarbonaceous by-products (liquid by-products) obtained in the preparation of the raw synthesis gas in liquid, liquid-dissolved or liquid-dispersed form Gasification, such as tars, oils, naphtha and phenols, introduced into the gasification zone and / or the combustion zone of the fixed-bed pressure gasification reactor and also at least partially converted to hydrogen and / or carbon oxides. A process according to claim 1, characterized in that at least part of the liquid by-products introduced into the fixed-bed pressure gasification reactor reaches a region in which the gas temperature is at least 700 ° C, preferably at least 800 ° C. A method according to claim 1 or 2, characterized in that the liquid by-products are introduced by pumping, injecting or spraying in the fixed-bed pressure gasification reactor, wherein in the case of injection or spraying a propellant gas is used. A method according to claim 3, characterized in that the injection or spraying of the liquid by-products in the fixed bed pressure gasification reactor via at least one, installed in the wall of the reactor and directed radially into the reactor chamber nozzle, wherein when using multiple nozzles, these preferably at equal distances from each other and preferably distributed at the same height on the circumference of the reactor. A method according to claim 4, characterized in that the nozzle orifices terminate with the lining of the reactor inner wall, so that they do not protrude into the reactor interior. A method according to claim 3 to 5, characterized in that are used as propellants carbon dioxide, water vapor, air or oxygen or any mixtures of these components. A method according to claim 3 to 6, characterized in that the nozzles at a vertical distance of 1.0 to 2.0 m, preferably 1.5 m above the highest point of the Austragsrostes equidistant installed on the circumference of the reactor in the reactor wall are. A method according to claim 3 to 7, characterized in that the jet direction of the nozzles is directed with a between 0 to 30 °, preferably 0 to 20 °, most preferably 0 to 10 ° deviating from the horizontal angle downwards. Method according to one of Claims 3 to 8, characterized in that the nozzle exit speed related to the amount of propellant gas leaving the nozzle is between 50 and 150 m / s, preferably between 80 and 120 m / s. Process according to any one of Claims 3 to 9, characterized in that the local temperature of the packed bed is determined on the inside of the reactor wall by means of two rows of temperature sensors installed on the circumference of the reactor, the temperature sensors being equidistant from each other within a row, wherein the vertical distance to the highest point of the discharge grate in the upper row 0.5 to 2.5 m, preferably 1.0 to 2.0 m and the vertical distance to the highest point of the discharge grate in the lower row 0 to 0.5 m , preferably 0.25 m and wherein the amount of ashes discharged per unit time via the discharge grate is set so that from the upper row of temperature sensors a temperature between 700 and 1300 ° C and from the lower row a temperature between 300 and 400 ° C is measured. Method according to one of the preceding claims, characterized in that the liquid by-products are mixed with one another introduced into the fixed-bed pressure gasification reactor. Method according to one of the preceding claims, characterized in that different liquid by-products are introduced separately via separate nozzles in the fixed-bed pressure gasification reactor. Method according to at least one of the preceding claims, characterized in that the inner wall of the fixed-bed pressure gasification reactor in the vicinity of the nozzle orifices is protected by panels, the panels of ceramic material consisting in the cooling elements made of metal, such as pipes are, which can be traversed by a cooling medium, such as water.

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