DE2543500A1 - PROCESS FOR CONVERTING CARBON MATERIAL INTO A GAS MIXTURE CONTAINING CO AND H LOW 2 AND DEVICE FOR CARRYING OUT THE PROCESS - Google Patents

Description

The invention relates to a method for converting carbonaceous material into a _{gas mixture containing CO and H 2} by gasifying finely divided solid and / or liquid carbonaceous materials containing bonded carbon, volatile constituents and possibly ash and moisture. Solid carbonaceous material includes, for example, finely divided coke, anthracite, hard coal or lignite or a mixture of two or more of these materials

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to understand. Liquid carbonaceous materials are hydrocarbons that are liquid at moderate temperatures, such as fuel oils, tar oils and topped Crude oil.

According to the invention, the carbonaceous materials are after crushing optionally solid carbonaceous material to a grain size of less than about 3 mm, preferably less than 1 mm, gasified at elevated temperature and optionally increased pressure with a gasifying agent containing water vapor and oxygen gas. The gasification takes place in a so-called circulating fluidized bed - for the definition compare, for example, Chemical Engineering Progress, Volume 67, February 1971, pages 58 to 63; L. Reh: Fluidized Bed Processing - which contains fine-grained solid material and is held in a vertical elongated reaction zone - to which regulated flow rates of the carbonaceous material and the gasification agent are fed. The fine-grained solid material in the fluidized bed can consist of fed in fine-grained solid, pyrolysis residues and ashes from the carbon-containing solid material or optionally an inert material, for example Al ₂ O-. The fluidization in the lower part of the zone is generated by the introduction of a non-oxidizing or slightly oxidizing gas with less than 10% O ₂ / for example a partial flow of the _{gas mixture containing CO and H 2} , in the part of the zone below the inlet of the gasifying agent, usually maintained at the bottom of the zone. In the fluidized bed that has flowed up in this way, the gasification agent is divided into several sub-flows so that it can be rapidly displaced

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mixed with the flowing mixture of gas and solid material and so local overheating of the gasification agent is limited and controlled by partial combustion with the oxygen. In order to prevent deposits on the wall of the reaction space, local overheating close to the wall must be avoided in a suitable manner, for example by diverting the flows of the gasifying agent away from the wall. The angle between the river and the wall should expediently be at least about 10.
In addition, the currents must not be so strong that they penetrate through the layer and come close to the opposite wall, which is avoided by choosing a sufficiently large number of small partial flows. These are suitably distributed both in the vertical direction and around the zone, ie over the circumference of the reaction zone. According to the invention, the temperature in the reaction zone is at the desired level
from 800 to 1200 C by regulating the percentage of oxygen gas in the gasifying agent.

A mixture of gas and solid material exits from the upper part of the reaction zone and is subjected to separation. Solid material so separated is returned to the lower part of the zone. The hot gas freed from solids consists essentially of CO, CO ₂ / H "and H" 0. After cooling down and
simultaneous recovery of their physical heat content, for example to generate steam for gasification and
After washing and absorption of the main part of the CO ₂ content in a known manner, a high-quality gas mixture consisting of CO and H- is obtained. This mixture can advantageously be used as synthesis gas and / or, after methanation, as artificial natural gas.

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To maintain an acceptable level of solid carbonaceous materials in the reaction zone during gasification Ashes formed, a regulated flow of bed material is discharged from the bottom of the reaction zone. The admissible Ash content depends on the properties of the ashes and the coal. In favorable cases, an ash content of over 90% can be permitted which means that only a few percent of the supplied carbon goes off with the ashes. In certain cases the Ash content can be kept lower, and it may then be appropriate to reduce the carbon content of the ashes in some way to take advantage of.

According to one embodiment of the invention, the stages of a Sulfur purification of the fuel and, if necessary, sulfur recovery be included. The carbonaceous materials suitable for the process are often high in sulfur. In this case, CaO containing materials become the reaction zone fed. The sulfur released by the supplied carbonaceous materials is then converted to CaO in the form of CaS bound. Good sulfur removal can be achieved if the CaO content of the reaction zone is kept higher than its CaS content will. This can be achieved by regulating the supply of CaO

according to the material and by cooling a regulated flow of the sheet materials from the lower part of the reaction zone. In this In connection with this, it is expedient to remove ash and sulfur from the latter river and then return it to the reaction zone .

The CaO-containing material can either be fine-bodied like that Remainder of the sheet materials, i.e. less than about 3 mm, and can

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then introduced into any part of the reaction zone. However, the material can also be coarse, i.e. larger than about 3 mm and up to about 10 mm. Then it won't be complete transferred to the fluidized bed state, but sinks in the bed downwards. In this case it should therefore be at the top of the Reaction zone are added. After extraction at the bottom, it can be separated from the rest of the layer materials by sieving Sulfur can be released and fed back again.

Ashes can penetrate from the protruding layer materials two fundamentally different methods can be removed, hereinafter referred to as the mechanical and the magnetic method will.

According to the mechanical method, the temperature in the reaction zone chosen so high that the ashes soften and clump together. Since ashes agglomerate only with ashes and not with coke, the aseh agglomerates gradually grow into one Size that they settle at the bottom of the reaction zone. When layered materials are removed from them, a mixture is obtained of materials that contain ace agglomerates that are present in the With regard to their size can be separated mechanically, for example by sieving, and then tipped off. If for the purpose of sulfur removal CaO-containing material is added, it should be so fine-grained that it is finally freed from ashes in the th parliamentary group is located. The remainder of the layer material discharged is then, in a known manner, from the main part of its sulfur content freed and returned to the reaction zone.

The mechanical method of removing the ashes works satisfactorily, when the solid carbon dioxide fed to the reaction zone

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the material containing the substance has a uniform composition. In view of that most such materials will vary relatively widely in composition, are comprehensive arrangements required in this case to equalize the properties, such as stratification or bedding.

According to the magnetic method of removing the ashes from the discharged layer material, the gasification takes place just below the softening temperature of the ashes in the solid carbonaceous material fed in. That from the lower part of the reaction zone In this case, discharged layer material is cooled below the Curie point of the iron content of the ashes, whereupon the material is magnetically fractionated. Here, the cooling is carried out in such a way that heat is recovered becomes what is expediently done by using the gasifying agent as a coolant. In fractionation, a Magnetic fraction obtained, which essentially contains ashes, the iron content of which as a result of the reducing conditions in the lower part of the reaction zone partly made of Fe or Fe_O. consists. This fraction is dumped. The non-magnetic fraction obtained, which essentially consists of coke and CaO / CaS components contains, is then known by their sulfur content in Freed way and then returned to the reaction zone.

The magnetic method for removing the ashes works satisfactorily provided that the Fe ₂ O_ content of the ashes of the solid carbonaceous material fed in is less than 5%. This is the case with most types of hard coal and lignite, and in this respect the magnetic method has been found to be essentially independent of normal fluctuations in the

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Properties of the solid carbonaceous material fed proven.

The flow of the sheet material discharged from the lower part of the reaction zone is according to the invention in connection with FIG Separation of magnetic ash is controlled in such a way that the ash content of the zone is maintained on a mirror which allows undisturbed operation. This level depends on the properties of the ashes and has to be determined on a case-by-case basis will.

In order to enrich certain substances, such as Al "O and SiO", such as they are in small proportions in the non-magnetic fraction to avoid in the system becomes a small part of expediently dumped less than 10% of the non-magnetic fraction according to the invention. The loss that occurs here Ca content is compensated by giving the fraction a balanced flow of CaO-containing material, such as limestone, dolomite or burnt dolomite, supplied from the outside. Since in principle Ca circulates within the system, the CaO content in the Reaction zone almost to the desired level through intermittent excess or insufficient supply of CaO-containing Maintain foreign material.

Sulfur can be removed from the stratified material from which the ashes have been removed in various ways. The known method of bringing the material into contact with a gas mixture containing _{H 3} O and CO ₂ at elevated pressure and elevated temperature has proven to be particularly useful. The CaS content is converted into H ₃ S and CaCO. In a Claus process, H ₃ S becomes elementary

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Converted sulfur, which is tradable, while the CaCO-containing component formed is returned to the reaction zone together with the coke content of the material. Under the influence of the high temperature, CaCO _{3 is} thermally decomposed to CaO, which binds further amounts of sulfur.

In a particularly advantageous embodiment of the invention, the CaCO ₃ formed during the sulfur removal is decomposed in a separate measure in a venturi layer by means of the hot gas which emerges from the upper part of the reaction zone after dust has been freed. CaCO-. is thermally decomposed to CaO, and the mixture of gas and solid material obtained in this way is separated. The solid material (component containing coke + CaO) is returned to the reaction zone. This embodiment provides for sulfur purification in two stages and therefore leads to an extremely low sulfur content in the gas produced.

In the following the invention with reference to the drawing described in more detail, the schematically an apparatus for Shows implementation of the invention.

The device according to the invention consists of a refractory lined Oven shaft with a reaction zone elongated in the vertical direction and separating devices connected at the top 2, 3, from which lines 4 and 5 return retained solid material to the shaft. Located at the bottom of the shaft openings 6 for the introduction of upflow gas through the bottom surface of the zone. There are openings in the shaft wall for the introduction of gasification agent in the form of jets directed inward from the wall and inlets 8 for the supply of carbon

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Substance-containing material and inlets 9 for the supply of CaO-containing material. At the bottom of the shaft there is also a discharge line 10 for solid material. From the separators 2 and 3, the CO, CO ₂ , H ₂ and HO-containing gases that are formed go through a line 11 to a cooling and cleaning system 12; This consists of a waste heat boiler 13, in which a substantial part of the physical heat content of the gas is recovered in the form of water vapor, a water scrubber 14, in which the gas is washed with cold water to remove its dust content and water vapor, and a device 15 for the absorption of carbon dioxide , wherein the gas is _{brought into contact with a suitable absorption solution, for example K 2} CO ₃ solution, in order to remove _{its CO 2 content.} The openings 7 should preferably be at a height between the center of the reaction zone and approximately 1/2 m above the openings 6.

From the boiler 13 steam is passed through line 16 to the inlet openings 8 for carbonaceous material and also for mixing with oxygen from line 17 to a heat exchanger 18, from which the mixture passes through a line 19 to the inlet openings 7 for the gasifying agent. Part of the purified gas in line 20 goes through a line 21, 22 to the inlet openings 6 at the bottom of the shaft and thus serves as an upflow gas in that part of the reaction chamber ^! which is below the inlet openings 7 for the gasification agent. Another part goes through a branch line 23 to a fluidized bed 24 of the usual type for the solid material exiting from the bottom of the shaft through line 10. This material exchanges its heat with the entering gasification agent with the help of the heat exchangers

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exchange areas 18. After cooling below the Curie point it will the solid material is magnetically separated by means of the magnetic separator 25. This results in a magnetic fraction that through Line 26 goes off and consists essentially of ash, the iron content of which is partly as Fe or Fe_O. is to be specified. These Fraction is dumped.

The non-magnetic fraction in line 27 is _{brought into contact in a known manner with a gas mixture containing H 9} O and CO ₉ in a fluidized bed vessel 28 at elevated temperature and pressure. The result is a removal of the main part of the sulfur content of the fraction in the form of H ₉ S in line 35, which is converted in a Claus plant 29 into elemental sulfur, which is discharged through line 30.

The content of the layer materials in the sulfur removal vessel 28 is kept constant by the controlled discharge of layer material through line 31. This material consists essentially of coke and CaCO ₃ "components and, after branching off and removing a small proportion through line 32 and replacing the loss of CaO by the controlled addition of CaO-containing foreign material from line 33, e.g. burnt and unburned limestone and dolomite, returned to the reaction zone.

example

As a practical example of the method according to the invention as described above, the following values can be given will. The reaction chamber has a clear width of 6.6 m and a height of 25 m.

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Material flow C. t / h Nm 0 ³ Zh Temp. ⁰ C 8.4% Coal (8) 45.3 65 4.8 200 Gas (11) CO 188 , 7 ^H 2 ° .000 9OO _% Steam (16) 49.9 33.4 ? 5.7 29Ο Oxygen (17) 39 .000 2OO Gas (22) 19th .000 20th Ashes (26) 6.1 350 Coal analysis ^CH 1.7 Moisture ashes 39.0 2.5 Gas analysis (11) CO ₀ CH ₁ ^H 2 t- I
5.5 1, 37.8

The gas pressure within the layer is about 5 at. The amount of water vapor from the boiler 13 is 76 t / h, of which 33.4 t / h as saturated steam is generated at 290 C and fed into line 16. The remainder produced as superheated steam at 450 ° C from pipes not shown, e.g. for oxygen preheating from line 17 or the water supply to the boiler 13.

About 10% of the amount of gas produced passing through line 11 is returned through line 22.

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Claims (9)

Claims 1. Process for converting carbonaceous material into a Gas mixture containing CO and H “by gasification at increased Temperature and possibly increased pressure, characterized in that that the carbonaceous material after fine comminution, optionally the solid constituents on a Grain size of less than 3 mm, preferably less than 1 mm, is gasified in a circulating fluidized bed, which in a perpendicular elongated reaction zone is maintained wherein regulated flows of carbonaceous material and water vapor and gasifying agent containing oxygen gas are supplied through the wall of the reaction zone during the fluidized bed condition of the lower part of the reaction zone by means of a regulated flow which is non-oxidizing or less oxidizing Gas introduced into this zone is maintained, the gasification agent being divided into several in the fluidized bed Partial streams introduced the temperature in the reaction zone by controlling the percentage of molecular oxygen in the gasification agent controlled and a controlled ratio of ashes is maintained in the reaction zone by having a regulated flow of bed material discharged from the lower part of the reaction zone. 2. The method according to claim 1, characterized in that the generated CO and H ₂ -containing gas is cooled in a waste heat boiler with the generation of water vapor. 609816/0772 3. The method according to claim 1 or 2, characterized in that the generated gas is freed from water and carbon dioxide in a known manner. 4 .. The method according to any one of claims 1 to 3, characterized in that that a partial flow of the gas generated is used for fluidization in the lower part of the reaction zone. 5. The method according to any one of claims 1 to 4, characterized in that that the CaO-containing material for binding sulfur is fed as CaS to the reaction zone. 6. The method according to claim 5, characterized in that the feed of CaO-containing material and the removal of layer material are regulated in such a way that the content of CaO in the layer is higher than the CaS content. 7. The method according to claim 5 or 6, characterized in that the removed layer material is separated into an ash-containing fraction and a CaO / CaS-containing fraction. 8. The method according to claim 7, characterized in that the component containing CaO / CaS is _{heated under pressure with steam and CO 2} , the major part of its sulfur being converted into H ₃ S, which is obtained in a known manner. 9. Device for carrying out the method according to claim 1 for the purpose of converting carbonaceous material into a _{gas mixture containing CO and H 2} by gasification at elevated temperature and possibly elevated pressure, characterized by a vertical, refractory-lined shaft (1), the upper part of which is connected to separating devices ( 2, 3) for the separation of solid material from the generated gas is completed by pipes 609816/0772 (4, 5) for returning separated pest to the shaft (1) of
Openings (6) in the floor / shaft for the introduction of upflow gas , openings (7) in the wall for the introduction of gasifying agent in the form of jets directed inward from the wall, inlet openings (8, 9) for solid material and a discharge line (10) at the bottom of the shaft. S09816 / 0772