CA2306889C

CA2306889C - Method and device for producing combustible gas, synthesis gas and reducing gas from solid fuels

Info

Publication number: CA2306889C
Application number: CA002306889A
Authority: CA
Inventors: Bodo Wolf
Original assignee: Individual
Current assignee: Linde GmbH
Priority date: 1997-10-28
Filing date: 1998-10-06
Publication date: 2008-12-16
Anticipated expiration: 2018-10-06
Also published as: PL190794B1; GR3036233T3; MY127842A; ZA989759B; ATE200791T1; DE19747324C2; AU754147B2; BR9813292A; EP1027407A1; JP2001521056A; TW518363B; NO328487B1; AR010952A1; EP1027407B1; JP4112173B2; ID21135A; WO1999021940A1; CN1278292A; ES2157673T3; AU9542798A

Abstract

The present invention relates to a process and an apparatus for generating fuel, synthesis and reduction gas. The reactor, according to the invention, comprises a combined fuel burner, a combustion chamber, an entrained flow gasifier, a heat compensating duct as well as a water bath, in which case the combined fuel burner is provided with means for the substoichiometric combustion of the gaseous low temperature carbonisation products and with vortex means flinging the liquid components towards the combustion chamber wall. The pulverised fuel can react endothermally with the gasifying agent from the combustion chamber into gasification gas, the residual coke being so swirled that it lowers the temperature of the combustion chamber wall below the slag melting temperature due to convective heat adsorption, a protective layer forming from solidified slag on the interior wall of the combustion chamber.

Description

Method and Device for Producing Combustible Gas, Synthesis Gas and Reducing Gas from Solid Fuels The invention relates to a process and an apparatus for generating fuel-, synthesis-and reduction gas from renewable and fossil fuels, other biomasses, refuse or sludges, preferably for pyrolysis products manufactured therefrom according to patent DE 44 04 673, in which case, if pyrolysis products are employed, these are separated to the largest possible extent, prior to being fed to the reactor, into solid and gaseous products, such as low temperature carbonisation gas and charcoal and are fed to the reactor separately.

The apparatus according to the invention is employed in energy generation, chemical industry and metallurgy for a highly efficient generation of fuel-, synthesis-and reduction gas for power engines, synthesis processes, ore reduction and pig iron production.

From FR 2177088 a process for the three-stage gasification of carbon. is known, wherein in a first process stage a synthesis gas containing hydrogen and carbon oxides is generated and wherein in the subsequent process stages methanation of this gas occurs. Since in this process a fuel gas having the highest possible methane content is to be obtained, high process pressures of at least 50 bar, preferably however of 70 bar, are required for methanation.

In a first stage first synthesis gas and liquid slag are generated, to -which, in a second stage, further fuel (carbon, water vapour) is added, in vvhich process, besides the formation of a product gas containing methane, hydrogen and carbon oxides, a carbon-slag mixture is formed by cooling off the slag.

The carbon-slag mixture obtained must subsequently be reduced to slurry in an additional process stage either by water vapour, in order to separate particies of carbonised material stili included therein and to return these in a third process stage or it must be removed in a third prodcess stage by fluidisation from the fluidised bed.

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Apart from the separation stage for the carbon-slag mixture, requiring additional energy expenditure, a drawback of this process is inter alia that the melted slag may cool off by adding cold- media such as water vapour, gas or carbon, resulting in uncontrollable agglomerations and caking.

Moreover, this process necessitates a third process stage, wherein the reactants must be maintained in a fluidised bed over an extended period of time.

Furthermore, there exists a relatively large number of gasification processes, which can subSt3ntialiy be classified into the 3 large groups of fixed bed gasification, fluidised bed gasification and entrained flow gasification. For gasification apparatus and in this context, in particLilar, for apparatus for entrained flow gasification into which group the apparatus according to the invention falls, many compromises must be made with regard to energy questions and gasifying agent requirements.
Entrained flow gasifiers involving melting down the mineral components are mostly single-stage operated, i.e. all media participating in the gasification reaction are conveyed to a single reaction chamber. This causes all media to be raised to the high temperature level above the slag melting temperature of the mineral components of the combustibles. This is the case both with reactors comprising a reactor wall which has both fire-proof brick-lining as well as those clad with a cooling screen. In the case of reactors with a cooling screen, as is typical in the case of the GSP entrained flow reactor (see literature [1,21), a substantial portion of the sensible heat of the gasification gas is surrendered to the cooled wall. Furthermore, in parallel flow reactors with water quenching of the gasification gas to a water vapour saturation temperature, whether with or without a cooled reactor wall,. a very large arriount of heat is reduced to a low exergy level. In the case of reactors comprising a cooled inner reactor wall, but also in the case of parallel flow reactors in which the gasification gas leaves the reactor in upward direction and the liquid slag in downward direction, the slag discharge must be kept flowing by means of additional heat or even by additional bumers. These measures result in a high oxygen requirement, reduction- of the calorific value of the gasification gas and thus in low exergy efficiency levels of the overall gasification. If these precautions are not taken, the function of the gasifier is disturbed as' the slag flow cannot be maintained.

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In entrained flow reactors operated with oxygen as gasifying agent, in particuiar, very short residence times of the reactants exist. In order to prevent break-through of oxygen in the event of fuel failure, very substantiat measuring and monitoring efforts are required.

Entrained flow reactors, supplied with fuel by separate pyrolysis, have the drawback that the pyrolysis products are cooled prior to being fed to the reactor and;
besides the heat losses, also require a high expenditure in gas processing and the handling of the liquid products.

An object of the invention to be attained resides in that a simplified process and a reactor are proposed which, compared with the state of the art, operate at a lower average temperature level with a higher exergy efficiency level, generating a gasification gas which is free of hydrocarbons and chlorinated hydrocarbons (dioxins, furanes) and which, by avoiding a separate separation stage, is suitable to be used as fuel gas for power generation, as synthesis gas or reduction gas in the same heating stage as the ore reduction.

Accordingly, in one aspect, there is provided a process for generating fuel, synthesis and reduction gas from renewable and fossil fuels, other biomasses, refuse or sludges by combustion in a combustor, admixing gaseous oxygen and/or oxygenaceous gases in substoichiometric ratios above the melting temperature of the inorganic portions into C02- and H20-containing gasifying agents, wherein:
fuel and/or gas is caused to spin when entering a combustion chamber, the liquid mineral components forming during combustion are flung against the substantially vertical combustor wall and they are separated from the gasifying agents forming in this process;
the gasifying agent is guided through a central aperture at the bottom of the combustion chamber into a gasification reactor, forming an immersion jet in the process;
the separated liquid components are discharged through the central aperture at the bottom of the combustion chamber, being entrained by the gasifying agent immersion jet as slag droplets, withdrawn parallel to the immersion jet and accelerated towards the reactor floor, collected there and discharged by the immersion jet;
the gasifying agent is supplied with solid carbonaceous fuel in a gasifier, in the course of the ensuing gasification reaction carbon dioxide is reduced to carbon monoxide and water vapour to hydrogen; and the gas immersion jet deflects above the reactor floor and the generated gasification gas in the upper portion of the reactor is discharged and processed to fuel, synthesis or reduction gas by subsequent dedusting and chemical cleaning.

In another aspect, the invention provides an apparatus for performing the process as previously described herein, comprising of a combined fuel burner as well as a combustion chamber provided thereunder, comprising fuel and gas supplies, wherein a) at the top of the combustion chamber a vortex means is provided via which the fuels and gases from the combined fuel burner are guided downwardly towards a gas outlet, provided centrally at the bottom of the the combined fuel burner, b) the gas outlet is surrounded by a slag trough at its upper end, c) an endothermic, entrained flow gasifier comp(sing a slag trough and a slag discharge means, into which the slag flows parallel to the gas, is provided underneath the gas outlet, and d) pulverised fuel lances are provided underneath the gas outlet extending into the gasifier.
The solution is attained in that the reactor is so constructed that the physical heat is basically maintained at a high temperature level with only minimal heat losses and is expfoited for increasing the chemically combined heat. For this purpose fuel and/or gas is first set into rotation at buming temperature at the entry to the burner, at the entry to the combustion chamber respectively, resulting in that hot slag droplets are flung against the wall, draining off the latter towards a slag trough at the bottom of the combustion chamber.

Mixing of liquid slag with solid fuel is therefore prevented. During this process the wall of the combustion chamber is maintained at such a temperature level that a layer of solidified slag melt forms on it, from which further slag formed drains off, (reflected) gasification gas flovving around its exterior.

The combustion chamber bottom comprises a central aperture from which the gas, freed from the slag droplets, exits as an immersion jet and enters the entrained flow 3a gasifier. The slag draining off the wall is collected in the trough surrounding the aperture, preferably equipped with radial drainage channels, draining off parallel to the gas in the entrained- flow gasifier. The gas outlet is in this context formed as a duct, causing the gasification gas to be (aminarised.

This attains two things. On the one hand, the gas escaping into the gasifier in downward direction is maintained relatively long as a jet, whereby the latter slows down by itself above the water bath due to compression effects and is deflected (reflected) in upward direction in order then to rise parallel to the immersion jet along the gasifier wall. The carbonaceous pulverised fuel is blown into the descending gas jet under reducing conditions, being first entrained while descending and then entering the jacket-like rising gas portion, the dimensioning of the apparatus and the flow velocity being so adapted as to result in a sufficient residence time and therefore a substantial gasification of the pulverised fuel.

In order to avoid reverse mixing of the rising gas portion with the exiting jet; a heat resistant steel or ceramics jacket may be provided around the gas outlet, through which the pulverised fuel can be conveyed via lances.

The rising gas reaches an intermediate chamber, e.g. via a guiding means, between an outer sleeve of the apparatus and the jacket of the combustion chamber, causirig a heat balance there and leaving the apparatus via the gasification gas outlet. =

The apparatus is provided with a heat protective lining and is preferably cooled. The gas formed is of high quality and can be used directly.

Prior to the entry of the rising gas into the heat balancing duct, the latter may be quenched by injecting water or cold gas, e.g. in the case of unstable operating conditions.

By way of the accompanying figure, the present invention is elucidated in detail with reference to a working example.

For this purpose a combined fuel bumer 1 is employed, absorbing hot, gaseous products from the low* temperature carbonisation process, including the vaporous components such as tar, oil, water and dust at the entry nozzle of the low temperature carbonisation product passage 4, guiding them into the combustion chamber 9 via the vortex means 33. In the low temperature carbonisation product passage of the combined fUel burner pipes for the conveyance of residual coke, ash and of additives into the reactor, are provided so as to swirl, heat up and fling the mineral components to be melted in the combustion chamber 9 towards the wall inside the combustion chamber in a liquid state. For the substoichiometric combustion into a gasifying agent above the ash melting temperature the combined fuel burner 1 is provided with further supply ducts for oxygen 7 or air 3, introduced into the combustion chamber 9 in the same direction as the low =temperature carbonisation products via vortex means 33 for the fast conversion with the low temperature carbonisation products into gasifying agents -and for the melting down of the mineral components of the residual coke, the ash and, as the case may be, the aggregates. In order to prevent critical heat introduction into the non-cooled structural components, the ignition fuel supply 2, the ignition air supply 5 and the ignition means as well as the ignition control 6, required for starting up and heating, are co-installed in the combined fuel bumer where these elements are protected by the .other flowing media in a stationary gasification operation.

The use of a known vortex bumer for pulverised carbon fuel is likewise possible.
The combustion chamber 9 is operated above the melting temperature of the mineral components of the residual coke, the ash and the aggregates. The wall of the combustion chamber 9 is heat conductive so that slag solidifies on it as a protective layer due to heat vvithdrawal towards the outside, while liquid slag drains off from the latter due to the temperature in the combustion chamber 9. The bottom of the reactor chamber 10 is designed as a slag collection trough 12 with buNn drainage channels in such a manner that a slag bath 13 may form, ensuring the slag flow at all times due to the direct contact of the slag with the gasifying agent 11 and due to the co-current flow with the gasifying agent 11, even when passing through the gas outlet 34. The gasifying agent 11 generated substoichiometrically in the.combustion chamber 9'under gasification conditions, serves as gasifying agent in the endothermic, entrained flow gasifier 14 because of its CO2- and HZO
content being set to a high level. The sensible heat introduced by the gasifying agent 11 is used for meeting the needs of the heat requirement for the endothermic gasification reaction between the pulverised fuel and the gasifying agent.. For this reason lances 15, 17 are provided for the pulverised fuel in the reactor. The gasifying agent 11 enters the endothermic, entrained flow gasifier 14 in the form of an immersion jet 16, accelerating the entrained slag droplets 18 so as to be brought into the water bath 19, solidifying there into an elution-proof granulate. The slag discharge means 22, the water supply 21 and the water overflow 20 were provided for the media discharge and for back-up of evaporated water. Together with the water bath 19 they form the lower end of the endothermic, entrained flow reactor 14.

The immersion jet can furthermore be stabilised and a reverse mixing with the reflected gas, rising sleeve-like parallel to the wall, can be prevented if a jacket 35 made of heat-proof steel or ceramics, through which the pulverised fuel lances pass, is provided undemeath the gas outlet 34. Additional lances 17 may be located thereunder.

By the supply of the oxygen-free gasifying agent 11 as well as by the pulverised fuel to be gasified in the endothermic, entrained flow reactor 14 and by the high gasification temperature above 500 C the design ensures that no oxygen- break-through can take place into the cold reactor regions.

The heat compensating duct 26, wherein, if required, guide means 24 are provided, serves to warm up the gasification gas, cooled due to the endothermic gasification process. They impart a turbulent vortex to the gasification gas flow 23, to increase the withdrawal of convective heat from the wall of the combustion chamber 9 in such a manner that the inner combustion chamber wall is cooled below the melting temperature of the slag, causing a protective layer to form from solidified slag. In addition, intensified cooling of the combustion chamber wall takes place by way of the cooling means 27, supplied via cooling agent supply and discharge means 28, 29. For lowering the gasification temperature which should be between 500 and 1200 C, the means 30 is provided for quenching the gasification gas, quenching nozzles 31 being mounted thereon. The gasification gas leaves the reactor via the gasification outlet 25 provided with fire-proof lining.

Further particulars of the multi-stage reactor permit a substantially broader field of application of the reactor. By replacing the residual coke, ash and pulverised fuel lances 8, 15, 17, parts of the combined fuel burner and the quenching nozzles 31, the facilities are thus provided to melt down extraneous mineral materials which may possibly be contaminated, as well as ores, and to gasify extraneous finely particulate fuels, to use own fuel gas or extraneously supplied gas for dosage or quenching with various means such as water, water vapour or cold gas.

The provision of a trough for the collection of slag draining in liquid f'orm from the combustion chamber 9 is provided as well, forming the lower end of the endothermic, entrained flow gasifier 14 instead of the water bath 19.

For chemical and thermal protection the reactor is provided with a fireproof lining 32. It can, however, also be designed with a heat and corrosion resistant material and thermal exterior insulation against pressures up to 10 Mpa.

As a safeguard against a breakthrough of the combustion chamber 9 into the endothermic, entrained flow gasifier 14, the lower portion of the heat compensating duct 26 is designed conically.

Literature:
[1] CARUFRITZ: "NOELL-CONVERSION PROCESS" EF publishers for Energy and Environment Technique GmbH 1994.

[2] LUCAS et al: "A comparison of carbon gasification processes under pressure in the entrained flow cloud" Chemische Technik 1988, issue 7, pages 282.

List of Reference Numerals 1 Combined fuel burner 19 Water bath 2 lgnifiort fuel supply 20 H20 overflow 3 Combustion air 21 Water supply 4 Low temperature carbonisation 22 Stag discharge products 23 Gasifiqtion gas flow Ignition air 24 Guide means 6 Monitoring 25 Gasification gas outlet 7 02 26 Heat compensating duct 8 Residual coke + ash 27 Cooling means 9 Combustion chamber 28 Cooling agent entry-Reaction chamber 29 Cooling agent exit 11 Gasifying agent 30 Quenches 12 Slag trough 31 Quenching nozzles 13 Stag bath 32 Heat protective lining 14 Endothermic 33 . Vortex means entrained flow gasifier 34 Gas outlet Pulverised fuel lance 35 Jacket 16 Immersion jet 17 Pulverised fuel lance 18 Slag droplets

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for generating fuel, synthesis and reduction gas from renewable and fossil fuels, other biomasses, refuse or sludges by combustion in a combustor, admixing gaseous oxygen and/or oxygenaceous gases in substoichiometric ratios above the melting temperature of the inorganic portions into CO2- and H2O-containing gasifying agents, wherein:
fuel and/or gas is caused to spin when entering a combustion chamber, the liquid mineral components forming during combustion are flung against the substantially vertical combustor wall and they are separated from the gasifying agents forming in this process;
the gasifying agent is guided through a central aperture at the bottom of the combustion chamber into a gasification reactor, forming an immersion jet in the process;
the separated liquid components are discharged through the central aperture at the bottom of the combustion chamber, being entrained by the gasifying agent immersion jet as slag droplets, withdrawn parallel to the immersion jet and accelerated towards the reactor floor, collected there and discharged by the immersion jet;
the gasifying agent is supplied with solid carbonaceous fuel in a gasifier, in the course of the ensuing gasification reaction carbon dioxide is reduced to carbon monoxide and water vapour to hydrogen; and the gas immersion jet deflects above the reactor floor and the generated gasification gas in the upper portion of the reactor is discharged and processed to fuel, synthesis or reduction gas by subsequent dedusting and chemical cleaning.

2. The process according to claim 1, wherein the fuels are heated allothermally or autothermally at 300 to 800°C, the products being separated into gaseous and solid carbonaceous fuels prior to being fed to the combustion chamber and being subsequently introduced separately to the process.

3. The process of claim 2, wherein the gaseous and solid carbonaceous fuels are low temperature carbonisation gas and charcoal, respectively.

4. The process according to any one of claims 1 to 3, wherein the solid carbonaceous fuel are ground to pulverised fuel.

5. The process according to any one of claims 1 to 4, wherein part of the heat requirement for the combustion is met by heat exchange with the gasification gas and/or the fuel, synthesis or reduction gas.

6. The process according to claim 5, wherein the gasification gas is guided through the chamber between the reactor wall and the exterior combustion chamber wall, absorbing a portion of the heat to be discharged from the combustion chamber.

7. The process according to claim 6, wherein the hot gasification gas is cooled prior to entry into the chamber or in the chamber between the reactor wall and the exterior combustion chamber wall.

8. The process according to any one of claims 1 to 7, wherein the slag is collected in a water bath on the reactor floor and is discharged therefrom.

9. The process according to claim 7, wherein cooling is performed directly by quenching with water, water vapour and/or cold gas or by means of a cooling surface connected to the reactor wall or its lining.

10. The process according to any one of claims 1 to 9, wherein extraneous mineral materials and/or ores are added to the solid carbonaceous fuel, being melt down during combustion.

11. The process according to any one of claims 4 to 10, wherein extraneous fuels of small particle size are admixed to the pulverised fuel.

12. The process according to any one of claims 4 to 11, wherein the pulverised fuel is injected into the immersion jet via one or more lances, directly below the combustion chamber floor.

13. The process according to any one of claims 1 to 12, wherein the slag is collected on the floor of the combustion chamber in a slag collection trough, conveyed to the central aperture via drainage pipes.

14. An apparatus for performing the process according to any one of claims 1 to 13, comprising of a combined fuel burner as well as a combustion chamber provided thereunder, comprising fuel and gas supplies, wherein:
a) at the top of the combustion chamber a vortex means is provided via which the fuels and gases from the combined fuel burner are guided downwardly towards a gas outlet, provided centrally at the bottom of the said combined fuel burner;
b) the gas outlet is surrounded by a slag trough at its upper end;
c) an endothermic, entrained flow gasifier comprising a slag trough and a slag discharge means, into which the slag flows parallel to the gas, is provided underneath the gas outlet; and d) pulverised fuel lances are provided underneath the gas outlet extending into the gasifier.

15. The apparatus according to claim 14, wherein the gas outlet in the upper region of the endothermic, entrained flow gasifier is surrounded by a jacket made of heat resistant material.

16. The apparatus according to claim 14 or 15, wherein upper and lower pulverised fuel lances are provided, the upper ones passing through the jacket.

17. The apparatus according to any one of claims 14 to 16, wherein the endothermic, entrained flow gasifier is enveloped by a heat protective lining.

18. The apparatus according to any one of claims 14 to 17, wherein a heat protective lining envelopes the combustion chamber in spaced apart relationship, forming a heat compensating duct in the form of an annular chamber.

19. The apparatus according to any one of claims 14 to 18, wherein a thermally protective lining is provided with a cooling means in the region of the combustion chamber.

20. The apparatus according to any one of claims 14 to 19, wherein guide means are provided in an annular chamber or a heat compensating duct.

21. The apparatus according to any one of claims 14 to 20, wherein quenching means are provided in the upper region of the endothermic entrained flow gasifier and/or in the heat compensating duct.

22. The apparatus according to any one of claims 14 to 21, wherein the slag trough is of conical design, comprising discharge channels for the slag.

23. The apparatus according to any one of claims 14 to 22, wherein the floor of the combustion chamber is conical and that the entrained flow gasifier comprises a counter cone as a safety means against flame breakthrough, surrounding the combustion chamber floor in spaced apart relationship.