WO1997046639A1

WO1997046639A1 - Gas generation process

Info

Publication number: WO1997046639A1
Application number: PCT/EP1997/002485
Authority: WO
Inventors: Adrian Brandl; Volker Kaiser; Ralf Abraham; Werner Baumgartner; Christoph LÜTGE; Ci Liu; Marco Deutsch
Original assignee: Krupp Uhde Gmbh
Priority date: 1996-06-01
Filing date: 1997-05-15
Publication date: 1997-12-11
Also published as: DE19622152A1; AU2955397A; ZA974765B; ID18179A

Abstract

In a process for generating gas from at least one carbon-containing raw material which is partially oxidised by means of air or oxygen or oxygen-enriched air in a gasification reactor, as much residual carbon as possible which is also in the ash is to be converted into gas. This is achieved according to the invention in that the gasification residue is taken to a melt bath into which an oxidiser and additives are fed, by means of which a secondary raw gas, ceramic slag and alloyed melt are produced, and the secondary raw gas formed in the melt bath is mixed with the primary raw gas.

Description

"Process for the production of gas"

The invention relates to a process by means of which one or more carbon-containing feedstocks, including waste, by means of partial oxidation in a gasification reactor and an at least gas-side melt pool, gas, metal, sulfur and a base material for the Cement production.

To produce gas, e.g. Fuel gas or synthesis gas, from carbonaceous feedstocks, e.g. From coal, from wood or other biomass, from sewage sludge and / or from waste, these feedstocks are partially oxidized individually or in combination by means of air or oxygen or oxygen-enriched air. Fuel gas is fired under pressure, for example, in the combustion chamber of a gas turbine of a combined cycle power plant. Synthesis gas is used used for the production of methanol.

Adapted to the respective feedstocks, the partial oxidation takes place in gasification reactors, from which the gasification residue is drawn off either as a flowable slag or dry as ash.

The specialist book "Coal Gasification" [1] explains the form in which the gasification residue occurs in the different types of gasification reactors. The input materials are gasified either in the fixed bed, in the fluidized bed or in the entrained flow. If the gasification takes place in a fixed bed, such as in a rotary grate generator operated at approximately atmospheric pressure or in a rotary grate generator charged to about 30 bar, the gasification residue is obtained as largely unpolluted ash.

If the gasification takes place in the fluidized bed, for example in a Winkler generator operated at approximately atmospheric pressure or, for example, in a high-temperature Winkler gasifier (HTW gasifier) operated in a pressure-charged manner, the gasification residue forms in the fluidized bed granular ash granules which can no longer be fluidized once a certain grain size has been reached and which precipitate out of the fluidized bed as a bottom discharge.

In the specialist book "Coal Gasification" [1], page 89, it is stated, for example, that the ash of the Winkler generator contains approx. 5% non-gassed. Furthermore, it is stated in [2] that the ash removed from the bottom of the fluidized bed gasification, if it is "basic" in nature, is contaminated with water-soluble sulfides. As a result of the reducing conditions in the gasifier, the sulfur introduced with the feedstocks is converted into sulfides. Ash contaminated in this way is not suitable for landfill because the sulphides contained in it can be eluted and can move from rain to natural waste in the landfill. Chen waters can be transported.

If the gasification occurs in the entrained flow, the gasification residue is obtained as a liquid slag because of the high gasification temperatures of about 1500 ° to 1900 ° C. that result. In [1], page 96, it is reported that in the Koppers-Totzek gasifier, about half of the gasification residue flows downward as liquid slag on the gasifier walls, that it is quenched in a water-filled tank and that it is below the carburetor is withdrawn in granulated form. The other half of the gasification residue is discharged from the Koppers-Totzek gasifier with the crude gas generated as fly ash.

Regarding the Texaco gasifier, it is reported in [1], page 228, that the raw gas generated in the entrained flow, which carries the liquid slag, is cooled below the ash softening temperature in a radiation cooler. Subsequent redirection of the gas flow results in a separation between the solids carried in the gas flow and the raw gas. The separated part of the solids is collected in a water reservoir and discharged discontinuously via a lock. The remainder, which has not been separated off, is discharged from the Texaco gasifier as crude slag with the raw gas generated. For the Koppers-Totzek gasifier, [1] states a degree of coal conversion of 90-96%, under pressure up to 98%. For the Texaco carburetor, the corresponding statement is that the degree of coal conversion is 90-95%, sometimes higher. The coal which is not converted in the entrained-flow gasifier is obtained together with the gasification residue. As a result, the granulated slag produced as the bottom discharge in the entrained flow gasifiers also contains combustible components which can be used.

The crude gas formed in the gasification reactor is loaded with flyable gasification residue. Flight slag is discharged from the crude gas from the gasification reactor producing slag. Fly ash from the raw gas is discharged from the ash-producing gasification reactor.

Just like the gasification residue obtained as soil discharge, the flyable gasification residue also contains residues of the unreacted feed. In another specialist book "Coal Gasification Processes", [3], page 206, it is stated with a view of the Winkler gasifier that its fly ash transports 15 to 20% carbon with it.

From the journal article [4], which deals with the HTW gasification, it can be seen that the fly ash by means of Water washing is removed from the raw gas and that the fly ash is produced as sludge when the washing water is regenerated. The sludge is burned together with the ash, which itself has a residual carbon content of 25%, in a separate fluidized bed furnace.

Gasification could be made more economical if it were also possible to convert the residual carbon into gas.

As already mentioned above, the partial oxidation of carbonaceous feedstocks such as coal, oil, wood and waste in a fluidized bed, for example in an HTW gasifier, produces not only synthesis gas but also ash which contains a considerable proportion of residual carbon and contains considerable impurities, depending on the nature of the starting materials. The disposal of these contaminated, carbon-containing ashes is a problem. In addition, it is desirable to convert as much of the carbon as is contained in the carbon-containing feedstocks into synthesis gas.

The present invention solves the problems described by a method for the production of gas from at least one carbon-containing feedstock, which in one by means of air or oxygen or oxygen-enriched air The gasification reactor is partially oxidized and this results in primary raw gas and gasification residue; which process is characterized in that the gasification residue is placed in a molten bath, into the melt bath an oxidizer and additives are introduced, with which a secondary raw gas, ceramic slag and alloyed melt is produced from the gasification residue and that in Melting pool formed secondary raw gas is mixed with the primary raw gas.

A process for the gasification of waste materials is described in detail in the patent DE 43 39 973. There, two gasification reactors are interconnected, the first of which is operated as an HTW gasifier in a manner similar to that in the present invention. Following this first carburetor, the ash is ground, which is drawn off from this first carburetor. This ash is mixed together with flying dust, which comes from a dedusting device, and introduced together with additional fuel and gasification agent into a second gasification reactor, which is designed as an entrained flow gasifier of the Shell or Koppers-Totzek type and which, in addition to raw gas, exclusively contains slag Floor extraction produced.

In this, the present invention differs fundamentally legend of the technology described in the patent DE 43 39 973. The melt pool used in the present invention leads to a separation of the substances which collectively form slag in entrained-flow gasification into a ceramic phase and a metallic phase. In this way, in contrast to the technology described in patent specification DE 43 39 973, it is possible to recover the heavy metals which are contained in the ashes and are non-oxidizable and not gaseous at the prevailing temperatures, which is an advantage of the present invention.

For this purpose, according to the invention, a molten bath is used, as described in the patents US 5,491,279, WO 93/25277, US 4,574,714, US 5,298,233, US 5,443,572, US 5,301,620, US 5,358,549 and in the publication "Molten metal works waste wonders, by Peter Taffe, European Chemical News October 16-22, 1995, pp. 32-33 ".

Furthermore, by means of the present invention it is possible to dispose of lumpy residues, which cannot be done in an entrained flow gasifier and in a fluidized bed gasifier, such as, for example, an HTW gasifier, is only possible if the density of the lumpy pieces Residues is not too high for a fluidized bed. Such scrap is, for example, electronic scrap. This addresses another problem that is solved with the present invention. It is known that lumpy carbon-containing residues are viewed as problematic with regard to their disposal because they consist partly of carbon-containing fractions and equally of metals and / or metal compounds. Examples of such problematic residues are the plastic or elastomer refined with fillers, the metal-clad packaging films or the electronic scrap. These problematic residues are usually disposed of by incineration. However, their combustion in turn leads to exhaust gases contaminated with pollutants and to filter dust and ashes contaminated with heavy metals, which are then difficult to condition so that they can be safely returned to the environment.

Therefore, an embodiment of the invention is provided in which, in addition to the gasification residue, at least one lumpy residue is also added to the molten bath in order to generate additional secondary raw gas therefrom.

Furthermore, with the present invention, it is possible to dispense with fine grinding of the granulated slag or ash obtained as the bottom draw of the gasification reactor. The entry into the envisaged weld pool can either be pneumatic, then grinding is advisable. full, or the entry can take place via a lock system, in this case only a refraction of coarse parts is necessary.

For this purpose, the present invention has a configuration in which the carbon-containing slag or ash, which is obtained as the bottom discharge of the gasification reactor, is placed in a mixing and conveying device which also carries out a refraction on a predeterminable grain size.

As in the technology described by the patent specification DE 43 39 973, it is also possible to dispose of liquid residues which, however, should only have a low water content. Another advantage of the invention is that these residues are not only broken down thermally, but also catalytically in the molten bath, which increases the degree of decomposition.

This process of thermal / catalytic decomposition in the melt pool can be influenced by adding additives. The present invention therefore provides its own way of adding the additives to the molten bath, namely in such a way that, in addition to the carbon-containing slag or ash, mainly mineral additives are added to the mixing and conveying device, which are used to condition the Melting Ba of serve.

In a further embodiment of the present invention, these additives consist at least partly of mineralized ashes from other combustion processes. It will e.g. It is also possible to convert ashes containing heavy metals that result from the combustion or partial oxidation of heavy residues from petroleum processing into residues that are easier to deposit.

In a supplementary embodiment of the invention, it is provided that the carbon-containing slag or ash broken in the mixing and conveying device, if appropriate also together with the predominantly mineral aggregates introduced into the mixing and conveying device, either pneumatically or via a lock system to bring in the weld pool.

Another advantage of the present invention is that, in contrast to the entrained-flow gasification described in the patent DE 43 39 973, no additional fuel has to be provided for the operation of the melt pool. On the contrary, it is envisaged to use a little methane for cooling the entry elements of the melt bath or for cooling the melt bath itself and additionally optionally use water vapor for moderation. At the intended operating temperatures, the methane reacts endothermically with oxygen and water vapor to form carbon monoxide and hydrogen, which slightly increases the yield of synthesis gas and thus even generates additional fuel instead of using fuel.

Therefore, in a special embodiment of the present invention, methane is additionally introduced into the melt pool as cooling for the input organs.

The present invention also has another embodiment in which methane and / or additional steam is added to the melt pool as cooling when the melt bath temperature is to be reduced.

Electrical heating is usually required to maintain the melt bath temperature, which ensures the liquid state of the slag. Large amounts of electrical energy are usually consumed in this way. In the present invention, the electric heater is used only during the starting phase. During operation, the gasification parameters, for example the pressure-charged fluidized-bed gasification, are set such that a sufficiently large proportion of carbon remains in the extracted ash of the pressure-charged fluidized-bed reactor, so that an electrical heater only required in exceptional cases. As a further advantage of the invention, the possibility arises of designing the pressure-charged fluidized bed reactor with a shortened post-gasification zone, which saves considerable outlay on equipment. The shortening of the post-gasification zone, which begins immediately above the fluidized bed, causes a deterioration in the carbon conversion to primary raw gas and is usually undesirable. In this case, however, the unreacted carbon is completely converted into secondary raw gas in the downstream melt pool, so that no loss of raw gas occurs. Therefore, there is no disadvantage associated with the lower carbon conversion in the pressure-charged fluidized bed reactor.

In a similar way, as described in the patent DE 43 39 973 for the entrained-flow gasifier, it is possible according to the present invention to destroy the thermal energy of the secondary raw gas generated in the melt pool in a water wash and also to vaporize salt-like or metallic vapor Wash out connections.

The present invention is therefore designed such that the hot secondary raw gas is fed from the melt bath to a water wash, where it cools down and where the gaseous salt and metal compounds are washed out. As an alternative to this, the present invention provides for the use of a fluidized bed cooler, as described in US Pat. No. 4,936,872. Here, the vaporous, salt-like or metallic compounds are condensed or desublimated on the grains of the cooled fluidized bed material and are thus recovered. There are cooling coils in the fluidized bed, in which water vapor is generated. In this way, the thermal energy of the hot secondary raw gas is used as well as valuable ingredients are recovered and the accumulation of waste water is prevented, which are all further advantages of the invention.

In order to utilize these advantages, the present invention is also designed in such a way that the hot secondary raw gas is passed from the melt pool into a fluidized bed cooler in which the thermal energy of the hot secondary raw gas is used for steam generation and where the gaseous gases are used Condense or desublimate salt and metal compounds on the grains of the fluidized bed material and the fluidized bed material loaded in this way is drawn off.

The fluidized-bed particles loaded in this way are expediently continuously removed from the fluidized bed and returned to the molten bath. The entry in the weld pool can be done in the same way as previously described for ashes: either pneumatically as dust, which requires grinding, or via a lock system together with the other substances which are added to the molten bath.

For this purpose, a further embodiment of the present invention has been created, in which loaded fluidized bed material drawn off in this way is added to the mixing and conveying device to the gasification residue and, if appropriate, to the additives, and in this way reaches the melt pool.

The use of the molten bath also allows the production of a slag which is used as a cement base material. This is due on the one hand to the fact that the composition can be adjusted by adding additives to the molten bath and, on the other hand, to the fact that the heavy metals are absorbed by the metallic phase and can therefore only be found to a very small extent in the ceramic slag, which represents a further advantage of the invention. It is also possible through a suitable mixing ratio of the additives to influence the melting temperature of the liquid, ceramic phase. The substances calcium oxide (CaO), aluminum oxide (Al ₂ 0 ₃ ) and silicon dioxide (Si0 ₂ ) come into consideration as additives. Considering the mineral components in the ashes and in the dust that originates from the fluidized bed reactor, and on the basis of a state diagram of the system CaO / Al ₂ 0 ₃ / SiO _z , as described, for example, in Ullmann's Encyclopedia of Technical Chemistry, 4th, revised and expanded edition, 1975, Weinheim, volume 10 , P. 381, the operating temperature of the melting bath can be selected so that a low-melting eutectic is formed in the ceramic phase. If, on the other hand, base metals such as vanadium are also to be incorporated into noble metals that form the metallic phase of the molten pool, such as iron, the temperature of the molten pool must be raised accordingly, the relationship is described in Ullmann's Encyclopedia of Industrial Chemistry, 4. , revised and expanded edition, 1975, Weinheim, volume 10, p. 330, is shown in detail. In this case, the choice of a higher melting eutectic is recommended.

The present invention therefore provides in one of its embodiments that the molten bath has a liquid, ceramic phase and at least one liquid, metallic phase in which the starting materials are thermally and catalytically decomposed.

In addition, the present invention has a configuration in which a base material for cement production is made from the ceramic, liquid phase of the molten bath is obtained which contains the mineral additives and the mineral components of the carbonaceous feedstocks.

In addition, another embodiment of the present invention has therefore been supplemented in such a way that a metallurgical preliminary product is obtained from the metallic phase of the molten bath, which contains the metallic components of the carbon-containing feedstocks or residues.

If a fluidized bed cooler is used to cool the hot secondary raw gas generated in the melt pool, it is advisable to also select the fluidized bed material in the above-mentioned suitable mixing ratio, since this is also added to the melt pool and to form the liquid, contributes to the ceramic phase.

If the hot primary crude gas generated in the gasification reactor is treated in a water wash to remove dust, the sensible heat carried by the primary raw gas is devalued in a thermodynamic sense.

For this reason, the hot primary raw gas has recently been passed through filters fitted with ceramic filter cartridges. The major portion of the dust loading of the primary raw gas can thus be separated from it. All- However, with this hot gas dedusting, the hot primary raw gas must first be cooled to a temperature at which the filter candle material is still stable.

The fly ash in the hot gas filter must also be disposed of. In the context of the present invention, configurations were created with which the carbon content of the fly ash is particularly advantageously fed to recycling in a simple manner. For this, the waste heat of the primary raw gas generated in the gasification reactor is used for steam generation, the primary raw gas being cooled to a temperature which permits subsequent hot gas dedusting.

On the other hand, the flying dust separated from the cooled primary raw gas by means of hot gas dedusting is also added to the mixing and conveying device, into which the ashes from the bottom vent of the gasification reactor and possibly the mineral additives are also added. In this way, the flying dust from the primary raw gas is transferred to the melt pool in order to convert the carbon content of the flying dust into additional secondary raw gas there.

An alternative embodiment of the present invention fertilizer provides that the cooled primary raw gas is fed to a hot gas dedusting system and that the dust separated there is introduced directly into the melting bath through an injection pipe.

1 and 2 show two process flow diagrams, in which the process according to the invention is described by way of example.

The carbon-containing feed 1 and the oxygen-containing feed gas 2 are placed in a pressure-charged fluidized bed reactor 3 and converted to synthesis gas 4 and carbon-containing ash 10. The synthesis gas 4 is cooled in a steam generator 5, the cooled synthesis gas 6 is dedusted in a hot gas filter 7. The carbon-containing dust 8, the carbon-containing ash 10 and the additives 11 are placed in a mixing and conveying device which preferably consists of a cooling screw and is capable of crushing coarse pieces. The mixed ash 12, together with the lumpy residues 13 and the oxygen-containing feed gas 15, is introduced into the molten bath 16 by means of entry elements which are cooled with the methane / water vapor mixture 14. There a thermal and catalytic conversion to a metallic melt 18, a ceramic slag 17 and hot synthesis gas 19 takes place. 1 shows that the hot synthesis gas 19 is washed with water 21 in a water wash 20. A part of the supplied water 21 is discharged as waste water 22 into a waste water treatment plant, the rest of the water 21 evaporates, the synthesis gas cooling. The cleaned and cooled synthesis gas 23 is brought together with the dedusted synthesis gas 24 from the hot gas filter 7 and fed as a mixed synthesis gas 25 for further processing and use.

FIG. 2 shows that the hot synthesis gas 19 is passed into a fluidized bed cooler 26, where the condensable or desublimable, harmful gas components are separated and the synthesis gas is cooled. For this purpose, fresh fluidized bed material 27 is fed in and loaded fluidized bed material 28 is drawn off. The loaded fluidized bed material 28 is fed into the mixing and conveying device 9 and from there it is passed into the melt pool 16 in the mixed ash 12. The cleaned and cooled synthetic gas 23 is combined with the dedusted synthesis gas 24 from the hot gas filter 7 and fed as a mixed synthetic gas 25 for further processing and use. A calculated mass balance for FIG. 2 serves to further explain the method:

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20/3

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bibliography

[1] Dr. rer. nat Hans-Dieter Schilling, Dr. rer. nat. Bernhard Bonn, and

Dr. rer. nat. Ulrich Kraus, Coal Gasification, Existing Processes and New Developments, 3rd Edition of Volume 22 from "Mining, Raw Materials, Energy, Writings on Economic and Organizational Problems in the Extraction and Utilization of Mineral Raw Materials", Verlag Glückauf GmbH Essen 1981, ISBN 3 -7739-0354.5.

[2] Eberhard Nitschke, The Rheinbraun HTW Gasification

Technology for Combined Cycle Power Generation, paper presented at the TKK-VTT-IVO Seminar: "Pressurized Fluid Combustion and Gasification Power Systems, Hel¬ sinki November 23/24, 1987", printed in: Lectures and publications 1987, Uhde GmbH, Dortmund , February 1988.

[3] Perry Nowacki, Coal Gasification Processes, NOYES DATA CORPORATION, Park Ridge, New Jersey, USA, 1981, ISBN 0-8155-0864-6.

[4] Jochen Keller, Roland Meis, combined cycle power plant with HTW

Gasification for power generation from coal, peat and biomass, BRAUNKOHLE issue 6, 1990.

Claims

- 22 patent claims:

1. A process for the production of gas from at least one carbon-containing feedstock, which is partially oxidized in a gasification reactor by means of air or oxygen or oxygen-enriched air and thereby produces primary raw gas and gasification residue; characterized,

- that the gasification residue is placed in a molten bath,

- An oxidizer and additives are introduced into the molten bath, with which a secondary raw gas, ceramic slag and alloyed melt are generated from the gasification residue

- And the secondary raw gas formed in the melt pool is mixed with the primary raw gas.

2. The method according to claim 1, characterized in that in addition to the gasification residue at least one piece-containing carbon-containing residue is added to the melt pool and additional secondary raw gas is generated therefrom.

3. The method according to claim 1 or 2, characterized in - 23 -

that the carbon-containing slag or ash, which is obtained as a bottom draw from the gasification reactor, is placed in a mixing and conveying device which also carries out a refraction to a predeterminable grain size.

4. The method according to claim 3, characterized in that in the mixing and conveying device in addition to the carbon-containing slag or ash also mainly mineral additives are introduced, which are used to condition the melt pool.

5. The method according to claim 4, characterized in that these additives consist at least in part of mineralized ashes of other combustion processes.

6. The method according to any one of claims 3 to 5, characterized in that the ashes mixed in the mixing and conveying device and predominantly mineral additives are pneumatically introduced into the molten pool.

7. The method according to any one of claims 3 to 5, characterized in that the mixed in the mixing and conveying device - 24 -

Ashes and mainly mineral aggregates are introduced into the melt pool via a lock system.

8. The method according to any one of the preceding claims, characterized in that methane is added as cooling for the entry organs in the melt pool.

9. The method according to any one of the preceding claims, characterized in that additional water vapor is added as cooling in the molten bath when the molten bath temperature is to be reduced.

10. The method according to any one of the preceding claims, characterized in that the hot secondary raw gas is fed from the molten bath to a water wash, where it cools down and where the gaseous salt and metal compounds are washed out.

11. The method according to any one of claims 1 to 9, characterized in that the hot secondary raw gas from the melt is placed in a fluidized bed cooler in which the thermal energy of the hot secondary raw gas for steam generation - 25 -

is used and where the gaseous salt and metal compounds on the grains of the fluidized bed material condense or desublite and such loaded fluidized bed material is drawn off.

12. The method according to claim 11, characterized in that such removed, loaded fluidized bed material is added to the mixing and conveying device to the gasification residue and possibly to the additives and in this way reaches the molten bath.

13. The method according to any one of the preceding claims, characterized in that the Schraelz bath has a liquid, ceramic phase and at least one liquid, metallic phase in which there is a thermal and catalytic decomposition of the feedstocks.

14. The method according to any one of the preceding claims, characterized in that a base material for cement production is obtained from the ceramic, liquid phase of the molten bath, which contains the mineral additives and the mineral parts of the carbonaceous feedstocks. - 26 -

15. The method according to any one of the preceding claims, characterized in that a metallurgical primary product is obtained from the metallic phase of the molten bath, which contains the metallic portions of the carbonaceous feedstocks or residues.

16. The method according to any one of the preceding claims, characterized in that the waste heat of the primary raw gas generated in the gasification reactor is used for steam production, the primary raw gas being cooled to a temperature which permits subsequent hot gas dedusting.

17. The method according to claim 16, characterized in that the cooled primary raw gas is supplied to a hot gas dedusting and the dust separated there is added to the mixing and conveying device, in which the ash from the bottom extraction of the gasification reactor and possibly the mineral additives are added become.

18. The method according to claim 16, characterized in that the cooled primary raw gas is supplied to a hot gas dedusting and the dust separated there is introduced directly through an injection pipe into the weld pool.