DD147549A1 - PROCESS FOR GAS PRODUCTION FROM SOLID FUELS - Google Patents

Abstract

The invention relates to the field of coal refinement. The aim of the invention is to find a way to gasify coal, which disintegrate disproportionately strong under thermal stress and are bad to gasify by conventional methods. The object of the invention is to develop a suitable method. According to the invention this is achieved by the fact that after a conventional drying the fuel is degassed, preferably under pressure, partially degassed, dried or preheated before it enters a gasification zone in this preheated state. The gasification takes place in a fluidized bed or in a partially in fluidized state layer with the supply of air or oxygen and a temperature moderator. Part of the gas produced in the gasification is used as spuel gas for degassing. The resulting dust is separated and gasified in a melt chamber dust gasification together with other dust.

Description

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Title of the invention

Process for the production of gas from solid fuels

Field of application of the invention

The invention relates to a process for the production of gas from solid fuels by partial oxidation with gasifying agents, taking into account particularly unfavorable properties of the fuel.

Characteristic of the known technical solutions

For the gasification of solid fuels, various methods are known, each of which is suitable for fuels of a certain nature.

Gasification in a fixed bed is suitable for lumpy fuels with a small amount of undersize. The lumpy nature jäarf while the countercurrent to the gas passing through drying, degassing and gasification are not lost substantially.

Fine-grained fractions may not practically form due to thermal decomposition of the fuel pieces, so that the void volume in the fixed bed is maintained. 20. The gasification residues are usually fine-grained, because the mass of lumpy fuel during the gasification reaction passes into the gaseous phase and

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essentially unburned residues are to be discharged at the end of the process via a grate.

. Therefore, this solid gasification residue must be coarse-grained and thus flowed through in a resting bed. With the gas in the quiescent bed uphill pea grain may arise only in such small quantities that the void volume is not displaced. The dust retained by the action of the plague bed must be gasified with the sinking bed; if it consists of ashes it must agglomerate so that it can be discharged with the remaining grainy ash. On the other hand, no unwanted agglomeration should occur, such as baking phenomena in the degassing zone, slagging in the ash zone. Finally, the fuel must bring about a certain minimum gas outlet temperature, so that the process works trouble-free and technically safe.

This multiplicity of requirements of the process must be inherent in the fuel or prior art fueling processes must impart it. At least the required pieceiness is to be produced by classification methods. Coals that do not have such properties can not be gasified in the plague bed.

Pressure gasification processes in the plague bed are u. a. by E. Rammler and H.J. Alberti in "Chemistry and Technology of Lignite", Berlin 1962 and in "Ulimann's Encyclopedia of Industrial Chemistry" Volume 10, pages 418 to 424 described.

Another method gasifies granular fuel in the fluidized bed. The grain size of the fuel to be gasified in this process can be present within wide limits in accordance with the fluidic requirements. The permissible dust content is stated differently depending on the economic limits of the

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casual dust discharge in the raw gas as well as technological conditions, such as a dust return in the fluidized bed.

DE-PS 1023 844 gives information on the permissible content of the fluidized material with regard to pebble with minimal dust losses.The fluidized bed gasification is described, inter alia, in the abovementioned literature source by RAMMLER and v. ALBERTI and by L. LENZ in the "Lehrbuch der Winklergaserzeugung", Leuna SETSCHMOW and ALTSCHULER also put specific pressure on the operation of this process.

A process of fluidized bed gasification under pressure is also described by LANGHOPP, K. and others in DE-O. 27 00281. The requirements of the method for the classification of the fuel and its reactivity limit the applicability of this method. The processes of dust gasification also make demands on the fuel. The required purity of the dust is related to the reactivity and the technical equipment of the process. In processes which usually work with reaction temperatures above the slag melting point, the dependence on reactivity and ash softening temperature, which hinders the gasification in the fluidized bed, does not matter. On the contrary, the ash melting temperature must be below the technically controllable limit. Pressurized process

85th of this type are u. a. described in the following places:

ROSSBACH, MÜLLER, KUPPLER, Energie Grafelfing, 30

(1978) p.194-195 VÖLKEL Energie Grafelfing, 30

(1978) S. 196 - 198 concerning these basic methods of gasification

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In addition, process combinations have become known, which in turn require very specific fuel properties.

The WP C 10 J / 197 287 describes "method and apparatus for combined fluidized bed and Pestbettverggasung of coal" · The process is carried out in a common reaction chamber · In the upper part of this reactor, a lumpy fuel in the plague bed is degassed and partially gasified In this treatment, the lumpy fuel becomes granular, according to the precondition, without forming substantial amounts of dust. It passes in this state into the lower part of the reactor where it is gasified in a fluidized bed. The entire gas of the oil bed zone flows through the pest bed located above it , The dust content of the gas of the fluidized-bed gasification is not greater than is presumed by the action of the peat bed as a result of the peat. Thus, this process combination is suitable only for lumpy fuels with good thermal stability, because the entire gasification gas flow through the Pestbettschicht uncontrolled. The energy loss of the gasification gas occurring with this process restricts the generation of waste heat steam.

The required for the gasification in the plague bed good flow through a granular ash layer must not be met by the fuel in this combination of methods. It is possible to gasify non-baking, thermally stable fuels leaving behind a limited amount of powdery ash as a gasification residue with this combination of methods. Methane, tars and oils remain in static charge as in countercurrent gasification, but must be separated from an unnecessarily large amount of gas.

The gas is not suitable for syntheses without further process steps of gas conversion.

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The DE-OS. 26 40 180 relates to a further process combination of fluidized bed, dust and fixed bed gasification with the name "method and apparatus for gas production from solid fuels" · The fuel is gasified with fractions of different particle size in a reactor in the fluidized bed. The coarsest pieces sink down through the fluidized bed and settle on a grate, where they gas together with lumpy Vergasungsrückständen the fluidized bed in quiescent or quasi-stationary bed completely. Above the fluidized bed is the part of the reactor in which the dust entrained from the fluidized bed is regasified.

This method places very low demands on the classification of the fuel. Baking ability of the coal does not bother. However, there are the following disadvantages:

Thermal decomposition of the fuel to dust may occur only insofar as the dust can still be gasified with sufficient economic effect in the dust gasification zone. In most cases, this requires a high reaction temperature of the dust gasification zone and requires a fuel whose ashes have a high softening temperature. The gasification zone in the plague bed requires, as mentioned above, a coarse-grained ash, so that a flow of gasification agent in the entire cross section of the quiescent bed occurs. Under the reaction conditions of the dust gasification zone, which is traversed by the entire gas stream, a synthesis gas is formed. Partly methane, tars and oils are completely gasified. The gas is not as a long-distance gas without carburation or other gas-converting process steps

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suitable·

Object of the invention

The invention has the goal to produce by combining known gasification processes of solid fuels under pressure gas, with low demands on the grain size and sustainability of the undersized, are provided. In particular, coal should be gasified, which decompose relatively strong under thermal stress and can be gasified, for example, in the plague bed only with loss of power. The quiescent bulk of this coal does not have the required void volume to achieve the peat effect presumed for the combination of pest bed / aerated gasification referred to in the prior art. The reactivity and the low softening temperature of the ash do not allow a significant gasification effect in the dust gasification zone over the fluidized bed of the process combination Pestbett-, fluidized bed and dust gasification according to DE-OS 26 40 180. The gasification of this coal in a resting bed on a grate leads to extraordinarily powdery ashes. The softening and agglomeration behavior of the ash is so unfavorable that unintentional slags are formed when ash sintering is desired.

The extraction of tars and oils and the requirements of Perngas quality should be made possible by the combination of processes. If necessary, synthesis gas should be generated.

Explanation of the essence of the invention

The technical problem relates to the gasification of a fuel with the aforementioned unfavorable properties, with known gasification processes and

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known process combinations not or only with poor economic efficiency or under. Loss of tars, oils and methane and plug dust or with extensive processing and other prior to gasification process steps are controlled.

The main process of the process combination according to the invention is the gasification in the fluidized bed or quasi-fluidized bed. The latter state should designate the transition between fixed bed and fluidized bed fluidically. Part of the gasification gas from the fluidized bed enters a degassing zone in which the fuel is degassed in a static bed. This part of the gasification gas is sized so that its sensible heat the heat demand of the degassing according to the principle of. Spülgasschwelung covers. The temperature of the carbonization gas outlet must be above the dew point of the tar, so that the carbonization gas passages function trouble-free. This condition is met, in which the fuel is preferably predried in tube dryers. The Spülgasschwelraum usually forms a unit with the fluidized bed reactor, wherein the Entgasungsrückstand passes without cooling in the gasification. Another part of the gasification gas passes through a dust gasification zone, which is used for

^ ¹ 5 layer gasification is usually placed over the <* fluidized bed, in a dust separator. The dust deposited there is coarse and is wholly or partially returned to the fluidized bed. The gas then passes into the high-pressure waste heat boiler, which is usually designed as a water tube boiler. The steam generated there makes the process combination steam-economically self-sufficient. Only after the boiler is the dry separation of the fine dust arranged, followed immediately by a wet separation. The gas of the gasification is cooled together or. Separately from the carbonization gas. This is Uiederdruckdampf won for the predrying. For cooling the gas, in particular

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The gasification gas can also be admixed with pulverized coal, which is thereby subjected to further drying and optionally also degassing. This dust is separated by known methods bodice. Tar vapors from coal dust can also be separated and partly used as tar. The process conditions of the interconnected to the process combination individual methods are substantially known. Special features of the combination are the following states:

Discharge temperature of the degassing gas above tar dew point preferably more than 450 ⁰ C at 2.5 MPa.

The pre-dried fuel has a maximum water content of 15 % and a grain size 0-15 mm, preferably 3-15 mm.

The degassed fuel enters the fluidized bed at temperatures of up to 800 ^° C. The fluidized bed temperature is at least 825 ^° C. This temperature is set by the concentration of oxygen in the gasification agent.

The pressure is 0.2 to 10 MPa, preferably 2.5 MPa. In general, one can dispense with the process combination on secondary nozzles for the gasification agent.

The dust is fed with 20 to 25 MJ / kg calorific value, 35 to 45 % ash of the melting chamber dust gasification. 75 %. of the dust are smaller than 0.09 mm. The upper grain size is 0.2 mm.

The discharge bag has a grain size of 0 to 3 mm, 13 »5 to 14.6 MJ / kg calorific value, 60 - 70 % ash. Further details can be found in the following embodiment

 The process combination can be operated partly under pressure, partly without pressure.

embodiment

The solution will be explained below for two possible process schemes.

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For a certain lignite the following execution is appropriate:

The pit-dried coal is classified · The fraction greater than 6 mm grain size is comminuted to the grain size 0 - .15 mm. In tube dryers of known type, the pre-drying is 55 - carried out 58% water content to 15 20% water content. The dried granular fuel with 19 MJ / kg calorific value and a grain size of 0.2 - 15 mm is fed to a working under 2.5 MPa pressure reactor, which includes the process steps degassing and gasification in two sections and the Staubnachvergasung.

Under the supply of 5,600 nr / h of oxygen in a mixture with 2.5 times the amount of steam produced gasification gas, part of which flows through the degassing as a heat transfer medium. The two partial streams are combined after the wet dedusting and cooling to give a total amount of 33,000 r / h and reactor of the following composition:

Calorific value 9.65 MJ / nr CO 22.2 "

H ₂ 42.0 VoI .56 CO 22.2 ti CH ₄ 5.5 It C n H m 0.3 Il II ₂ 1.0 ti CO ₂ + H ₂ S 29.0 ti

After leaching of the CO ₉ , a clean gas follows with the after-

C.

standing composition:

H ₂ 57.4 % Vol. Calorific value 13.20 MJ / m ³ CO 30.3 tt CH ₄ 7.5 tt C n H m 0.4 ti 295 ^ ₂ 1.4 It CO ₀ 3.0 ti

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From the raw gas 40 g / nr dry dust are obtained and fed together with the dry coal dust of grain size 0 - 0.2 mm of the melting chamber dust gasification.

The combined degassing gasification reactor, including the proportionate amount of dry coal dust, delivers 4.5 t / h of 0-0.2 mm filament grit with 21 to 23 MJ / kg calorific value. It is gasified in the melt chamber dust gasification process. The results of this method are known and require no further explanation (see DD-WP C 10 J / 205 679 as well as the already cited publications) ·

The high pressure steam of both gas generating processes is partly consumed in the gas generating process, partly fed into a grid.

The waste heat low-pressure steam is used essentially for drying the coal, for treating the gas water and the tars and oils and in the gas purification process.

Pur heat-related purposes hot water is also generated as a heat carrier.

The coal gasification effluent discharge gas is either burned or gasified in steams for energetic purposes including coal drying with steam or fire gases, or used as an absorbent for water management purposes by known methods.

The gas water of the degassing gas is dephenolated and purified by known methods, the gas water of the two gasification processes are only after purified according to the discharge conditions for the receiving water.

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The cooled and purified gas from the process combination is converted in part or in whole according to the intended use in its composition, and known methods can be used.

The combined degasification and gasification process allows for demand-based control of the degassing, with maximum gas production associated with minimal specific coal consumption and elimination of any degassing products.

The gasification of granular coal then provides 60 000 nr / h and reactor gas. The specific coal use for this

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Gas drops from 0.77 kg / nr to 0.65 kg / m. The specific one

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Oxygen consumption increases from 0.17 m oxygen / m raw gas

3 3 from 0.19 ra / m. Gasification steam is used in 2 times the quantity of oxygen

The crude gas had the following composition: H ₂ 42.9 vol.% CO 27.2 "CH ₄ 7.0" H ₂ 1.0 "CO ₂ + H ₂ S 25.0"

Dry dust generation including coal dust is 12 t / h and combined reactor.

Conversely, at maximum recovery of degassing

3 products 30 000 nr raw gas / h and reactor produced. The

3 3 specific oxygen demand drops to 0.16 nr / nr raw gas.

The steam input increases to 4.2 times the amount of oxygen. The composition of the raw gas from the combined degassing-gasification process is now:

H ₂ 43.0 CO 23.0 CH ₄ 9.0 C n H m 0.3 U ₂ 1.0 CO ₂ + H ₂ S 32.0

tt

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The production of dry dust is 4.5 to 5 t / h and combined degassing-gasification reactor, the proportion of coal dust compared to the aforementioned Fahrwieisen the combination of methods is higher. The production of tars and oils is 75 to 80 % of the tar yield according to the FISCHER method.

The dust gasification process in smelting reactors, for example, is equipped with three reactors and processes the dust from a plant of 18 reactors using the combined process. The advantages of the aforementioned method example are:

• Minimal effort for the treatment of coal and coal dust}

· Processing of thermally unstable coals with very unfavorable characteristics of the ash;

• high efficiency;

• flexibility of gas production with constant consumption of coal;

, high carbon gasification grade and gasification grade;

• Coverage of self-consumption of steam from waste heat.

The last-mentioned preference is needed above all for coal, which is not suitable for combustion in boiler furnaces.

Claims (7)

21 7253 1 ^ Invention claim. 1. A process for producing gas from solid fuels granular to lumpy texture by partial oxidation at reduced by drying water content, characterized in that the fuel is preferably degassed in a static bed under pressure, partially deaerated, dried or preheated before it enters the preheated state in a gasification zone in that the tar yield and gas composition are adjusted by adjusting the amount of purge gas and the conversion rate, that gasification in a fluidized bed or in a partially fluidized bed layer is partially oxidized with supply of oxygen, possibly also air and a temperature moderator, preferably steam, and that a portion of the gasification gas thus produced is used as a pressurized purge gas for degassing. 2. The method according to item 1, characterized in that ^ the preheating and degassing of the fuel is controlled by adjusting the serving as a purge gas portion of the gasification gas. 3 _# Method according to item 1, characterized in that by increasing the turnover speed in the gasification zone, the dry dust generation for the melting chamber dust gasification is set. 4 · The method of item 1, characterized in that the _aua (j _it is burnt partially or totally gasification of the granular carbonaceous fuel accumulating ash and the thus generated heat to the drying of the fuel is used. 5 * Method according to item 1, characterized in that the Hiederdruckdampf generated from the heat of the two gasification processes is used to dry the coal, Ή - ?. ™. nc \ p.-r that produces Hfiiwasser and as a heat carrier 2172 53 is used for the process associated cleaning and conversion of the gas, and or or that high-pressure steam is generated and used in the gasification processes and optionally for gas conversion. 6 · Method according to item 1, characterized in that the dust from the gas is at least partially deposited dry and as well as the dust from the drying and processing of the granular fuel or a portion of this dust is gasified in a melt chamber dust gasification. Process according to item 1, characterized in that the degassing gas is partially dedusted by the action of the carbon granulate. 4308. The method according to item 1, characterized in that coal dust for cooling the gasification gas is mixed with the gas stream and the mixture is optionally after removal of the Teernebel and a part of the gas of a coal dust-Schmelzkammerfeuerung or gasification.