AU3645700A

AU3645700A - Process and device to enable autothermic gasification of solid fuels

Info

Publication number: AU3645700A
Application number: AU36457/00A
Authority: AU
Inventors: Klaus Knop; Helmut Kubiak; Hans-Jurgen Muhlen; Paul van den Oosterkamp
Original assignee: Ferrostaal AG; DMT GmbH and Co KG; Technip Benelux BV
Current assignee: Ferrostaal AG; DMT GmbH and Co KG; TEn Netherlands BV
Priority date: 1999-05-27
Filing date: 2000-05-26
Publication date: 2000-11-30
Also published as: GB2350370A; FR2794128A1; ES2190695A1; GB0012957D0; ZA200002647B; DE19925316A1; ES2190695B1

Description

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AUSTRALIA

Patents Act 1990 Technip Benelux B.V., DMT GmbH, Ferrostaal AG

ORIGINAL

COMPLETE

SPECIFICATION

STANDARD PATENT Invention Title: Process and device to enable autothernic gasification of solid fuels The following statement is a full description of this invention including the best method of performing it known to us:ill Process and device to enable autothermic gasification of solid fuels Description The invention relates to a process for the autothermic gasification of solid fuels in accordance with the preamble to patent claim 1 and to a device with which to carry out the process.

A process for the gasification of organic raw and waste materials or raw and waste materials containing organic materials is known from DE 42 38 934 C2, where the raw and waste materials are initially heated by means of direct contact with a heated flow of gas around a circuit to a final temperature of t 10 between 120 and 350°C, whereby this preliminary chemical treatment allows the raw and waste materials to be converted into a brittle intermediate product 0:00 once the gases and vapours have been separated off. The separated gases vapours only contain negligible amounts of combustible materials. The flow of gas conveyed around a circuit is heated by means of mixing a fresh gas obtained by burning a heating gas. The heating gas used should 0...preferably be a part of the synthetic gas generated as a result of the process.

A proportion of the gas flow circuit equivalent to the total volume of the fresh gas and the gases and vapours separated at the preliminary heat treatment stage is separated off from the circuit gas flow each time. At the preliminary heat treatment stage, a brittle intermediate product is separated, before being crushed to a fine material with grains significantly smaller than 1 mm and ~subjected to an entrained flow gasification process which generates a gas which is rich in CO and H 2 The best temperatures are in the region of 180 to 190'C for wood and straw, between 220 and 2300C for a domestic waste fraction containing plastic and around 3000C for shredder material with a high PVC content.

The combustion chamber used for heating at the preliminary thermal treatment stage is connected directly to this preliminary treatment stage. The proportion which has to be separated from the circuit gas flow is therefore set aside from the flow of gas which leaves the preliminary treatment stage, i.e.

once the heat content of the waste gas has been utilised. This means that this proportion also contains some of the gases and vapours released during the initial treatment stage, which means that it cannot be diverted into the atmosphere without further treatment. The known process therefore proposes the use of an active carbon filter to clean the separated gas flow. The filtered material in the active carbon filter is removed at regular intervals by passing it through the gasification stage. This means that this procedure requires expenditure on equipment and operation for the filter arrangement.

In the known process, the gasification is carried out without steam and with the introduction of pure oxygen in the form of a flame reaction at a relatively high temperature of around 1300'C. This high temperature is required on the one hand in order to break down the toxins contained in the filter mass, which largely consist of higher hydrocarbons, with an adequate degree of safety, and on the other hand to produce a molten clinker. This molten clinker and the synthetic gas produced in the gasifier are cooled with quenching water in a quenching chamber immediately below the gasification reaction chamber such that the clinker solidifies into a granulate. The gas :9 •*•separated off from the quenching chamber is saturated with steam before being subjected to a gas cooling and gas purification process, it is then used, for example, in a block-type thermal power station with gas motors. However, not all of the synthetic gas generated can be used for this purpose, as some of °o the gas is fed into the gas generator in order to generate a support flame for the flame reaction and or into the combustion chamber for heating at the o" :preliminary thermal treatment stage. Otherwise gas from sources outside the process has to be used for this purpose. If it has not evaporated, the quenching water used in the quenching chamber must be removed and then undergo a waste water purification process at some expense because of the toxins which have dissolved in it.

The aim of this invention is to further develop a process of the type detailed above such that it is no longer necessary to filter the waste gas to remove hydrocarbons from the waste gas.

The aim is also to minimise the cost of waste water purification. Finally, gasification should be able to be carried out at as low an operating temperature as possible, and the synthetic gas generated should be able to be used for other technical processes, especially as a reduction gas for pig-iron production by means of direct reduction of iron oxide, without being subjected to an expensive gas purification process. Another function of the invention is to propose a device with which to carry out the process as detailed in the invention.

This function is resolved in accordance with the invention with respect to the characteristics outlined in patent claim 1. Advantageous further developments of this process are detailed in the subsidiary claims below. A device to carry out this process, in accordance with the invention, exhibits the characteristics detailed in the independent subsidiary claim 18 and could be further developed by the addition of the features detailed in the dependent subsidiary claims.

The major consideration for this invention was the fact that the fuel is crushed in advance before being subjected to pyrolysis, which guarantees almost complete degasification of the fuel. After separation of the gases and vapours from the fine coke-like fuel generated as an intermediate product in this way, this fuel is introduced into the gasification stage without the pyrolysis gases. At around 700 to 9000C, for example, and preferably around 750C, the temperature is relatively low compared to that used for a flame reaction.

15 The gases and vapours released during the pyrolysis, which largely consist of °combustible materials, undergo combustion which is as complete as possible in a combustion chamber, thus providing the hot smoke gas to enable direct heating at the pyrolysis stage. This guarantees that higher hydrocarbons and toxins and the majority of the sulphur compounds are safely removed from the pre-treated fuel before it gets to the gasification stage. This makes it possible to generate a synthetic gas which exhibits a high level of purity from the outset and is especially free from higher hydrocarbons and contains only low levels of sulphur compounds. The procedure to which the invention relates is also characterised in that the combustion of the gases and vapours generated in the pyrolysis stage produces smoke gas, from which heat is extracted to produce the mixture of water vapour and gas containing 02 required for the gasification stage before the smoke gas is used to heat the pyrolysis stage.

This considerably reduces the temperature of the smoke gas such that the partial flow of the smoke gas which has to be taken away from the circuit for reasons of mass conservation can be separated before the pyrolysis stage without any excessive loss of heat.

In the following, the invention is explained in more detail on the basis of the numbering scheme used in the diagram.

The scheme used in the diagram reflects a possible embodiment of the invention. The main components of the system are an unit 1 for carrying out the pyrolysis, a gasifier 2, which takes the form of a horizontal gas generator in the preferred embodiment, and a combustion chamber 3. A feed line 20 from a supply container 4 feeds fine fuel into the unit 1 and is preferably pneumatic in design. The fuel, which is preferable ground and dried hard coal or brown coal, is fed into the supply container 4 via an application device 15. Although they are not preferred, other solid materials with a high organic material content could also be considered as the fuel, such as shredded wood, biomass or waste material. If coal is used, it can still be processed easily by the procedure to which the invention relates if it has a relatively high ash 10 content.

In order to avoid spontaneous combustion of the prepared fine, dry fuel in the supply container 4, the container is flooded with an inert gas (e.g.

nitrogen). The inert gas is introduced via the inert gas feed line 16.

The pyrolysis stage is shown in the diagram of the preferred embodiment as a circulating fluidised bed (unit 1, separation mechanism but could also be in the form of an entrained flow reactor, for example, if required. The pyrolysis is carried out such that the fuel, which has grains of less than 5 mm in size, preferably mostly under 1 mm, is introduced with an oxygen seal and heated by means of direct contact with a hot smoke gas at the pyrolysis temperature. The smoke gas is introduced into the unit 1 from the combustion chamber 3 via a line 34.

The fine fuel is degasified during pyrolysis. Together with the fine degasified fuel (coke), the gases and vapours released are fed through a pipe 21 into a separation mechanism 5 which takes the form of a cyclon, in which the coke is separated from the gases and vapours. A volume of the separated coke equivalent to the volume of fuel fed in is also fed into the gasifier 2 through a pipe 25, while the remainder of the volume is fed back into the unit 1 via a return pipe 26, The separated gases and vapour are fed from the separation mechanism 5 through a pipe 22 to the burner 8 in the combustion chamber 3 as fuel. This ensures complete oxidation of the higher hydrocarbons in the pyrolysis gas. The combustion air is supplied via a feed line 19 at an appropriate level of pressure. An advantageous development of the invention would incorporate a heat exchanger 12 positioned in the feed line 19 whose heat exchange surfaces were arranged within the combustion chamber 3 such that the combustion air is preheated.

In the combustion chamber 3, there is a heat exchanger 9 to which steam can be introduced via a feed line 17 for the purposes of superheating.

There is also a development of the invention whereby a heat exchanger 10 is arranged in the combustion chamber, to which a gas containing oxygen, preferably air or pure oxygen, can be fed via feed line 18 for the purposes of preheating. The outlet of this heat exchanger 10 is connected to the feed line 17 such that a mixture of water vapour and the preheated gas containing oxygen is introduced into the heat exchanger 9. Once this mixture is superheated, it is fed into the gasifier 2 via pipe 31.

The heat exchangers 9, 10 and 12, and heat exchanger 11 to be ~explained below, remove a significant amount of the heat from the smoke gas produced in combustion chamber 3, such that it exits the combustion chamber 3 through the smoke gas pipe 32 in a significantly cooler form. This smoke gas pipe 32 branches into a smoke gas diversion line 33 and the feed line 34 which leads to the unit 1. The flow volume in the smoke gas feed pipe 32 is separated such that the proportion of the flow gas separated off into the smoke gas diversion line 33 is equivalent to the sum of the volume of the combustion air fed into the burner 8 via the feed line 19 and the volume of the gases and vapours released as a result of the pyrolysis in the unit 1, which are introduced into the burner 8 together with the flow of smoke gas flowing through the unit 1.

~This means that some of the smoke gas is permanently flowing in a circuit around the system. To ensure that the circulating smoke gas is fed back into the combustion chamber at an appropriate level of pressure, a compressor 13 is incorporated into the feed line 34. As the fresh smoke gas flowing out of the combustion chamber 3 is considerably reduced in temperature due to the heat exchanger, the aforementioned heat exchanger 11 is positioned behind compressor 13 and has its heat exchange surfaces inside the combustion chamber 3, which means that before the fresh smoke gas is introduced into the unit 1, it is heated to the appropriate temperature for pyrolysis. This pyrolysis temperature is at least 450 0 C. The pyrolysis temperature, i.e. the temperature of the material leaving the pyrolysis stage, should preferably be at least 600°C and ideally around 7000C. Because the fuel introduced is so fine and a circulating fluidised bed or an entrained flow reaction is used, the individual fuel particles heat up extremely quickly. The 6 rapid temperature rise and the avoidance of excessively high temperatures at the pyrolysis stage favour the formation of pyrolysis coke with a fine pore structure, i.e. a large surface area and thus high levels of reactivity. Therefore, if possible, a temperature of around 700 to 750'C should not be exceeded for pyrolysis. On the other hand, an adequately high pyrolysis temperature in the region of, for example, 600 or 7000C, represents a guarantee of almost perfect degasification of the fuel used within a short space of time.

It is worth noting that the combustion of the gases and vapours released during pyrolysis generates enough heat to power the pyrolysis on the 10 one hand and to provide heat to generate the mixture of steam and gas containing 02 required for gasification. It also means that it is not necessary to provide either part of the synthetic gas produced during the procedure to which the invention relates or fuel from other sources for this purpose.

Appropriately, the heat exchangers inside the combustion chamber 3 are arranged in the direction of the flow of fresh smoke gas, such that the flow of smoke gas is heated for pyrolysis first, and then the mixture of steam and ~gas containing oxygen is heated, before the preheating of the gas containing oxygen required for gasification. It is also appropriate that the preheating of the combustion air for the generation of the smoke gas is the last thing that 20 happens before the smoke gas exits the combustion chamber 3. If there is still surplus energy in the combustion chamber, this can be used to generate and or superheat steam by means of an additional heat exchanger which is not shown in the diagram, this steam can then released on a steam turbine to generate mechanical or electrical energy.

The mixture of water vapour and gas containing 02 required for gasification in the gasifier is supplied at a temperature which is roughly equivalent to the gasification temperature, or which is at least not significantly above or below the gasification temperature. As gasification is an endothermic reaction whereby the carbon content of the pyrolysis coke removes it from the unit 1 and part of the water vapour is converted into a synthetic gas rich in H 2 and CO, there must be an appropriate amount of heat available for this reaction. This is achieved in that part of the carbon is combusted with the volume of oxygen introduced. The more oxygen is introduced, the higher the temperature and the proportion of CO 2 in the synthetic gas produced. In order for the gasification process to take place at a comparably low temperature, there is an advantageous further development of the invention in which there is a feed line 24 from a supply container 6 through which a fine-grain catalyst material is fed into the gasifier. The catalyst material is filled into the supply container 6 using a loading mechanism 14. The catalyst material is conveyed in a similar way to the way in which the fuel is transported into the unit 1, on a pneumatic basis with the aid of a stream of inert gas, which is fed into the supply container 6 via a pipe 23.

Potassium carbonate is particularly suitable as a catalyst material for the gasification process. Naturally, other catalysts can also be used. For 10 example, certain sodium or calcium compounds could be considered.

However, potassium carbonate is considered particularly appropriate.

0The real benefit of the catalyst is the possibility of achieving high throughput levels at relatively low temperatures. Alternatively, high throughput rates could also be achieved at lower temperatures without using a catalyst if the reaction volumes were sufficiently increased: but this would involve considerable "expenditure in equipment and would therefore not be economically viable.

Another alternative for the gasification would be not to use a catalyst, to maintain the same reaction volumes and increase the gasification temperature, which involves burning a greater percentage of the pyrolysis 20 coke.

The gasifier 2 appropriately takes the form of a horizontal gas generator which works with a stationary fluidised bed. For this purpose, the pyrolysis coke is introduced into the chamber above an inflow base inside the gasifier 2.

With the aid of the inflow base, the superheated mixture of water vapour and gas containing oxygen, which fed is in through pipe 31, is introduced such that the fine coke swirls up accordingly. There are insets inside the gasifier 2 which divide the reaction chamber into gasification zones. These can take the form of vertical partition walls which stretch out across part of the height of the horizontal gasifier 2. In the embodiment shown, there are two such dividing walls, thus creating three gasification zones 2a 2c. The aim of this is to limit back-mixing within the gasifier to a minimum, i.e. there should be no significant back-mixing between the individual gasification zones, but only within the different gasification zones. The horizontal arrangement of the gasifier 2 guarantees an adequate average dwell time for the individual particles of the pyrolysis coke, as is particularly appropriate when processing hard coal. A vertical gas generator can also be appropriate for pyrolysed fuels with particularly high levels of reactivity, because the dwell time for the individual particles can be less, It is clear from the diagram that there is a funnel-shaped outlet mechanism 2d at the right hand end of the gasifier 2. This outlet mechanism 2d collects the residual ash after gasification and removed via a pipe 30. The synthetic gas formed in the gasifier 2, which is rich in CO and H 2 is initially fed into a cyclon 7, where any dust it contains is separated off and passed into the ash diversion line 30 via a pipe 29.

1. The synthetic gas which forms can be removed via pipe 28. Because it exhibits a comparatively high level of purity from the outset, and especially -because it does not contain significant levels of sulphur compounds, this gas is particularly suited to being used as a reduction gas for the direct reduction of iron oxide to produce pig-iron. Therefore it is especially advantageous if the pipe 28 for the synthetic gas produced is connected with a direct reduction system, which is not shown in the diagram.

Generally, before the synthetic gas from pipe 28 can be used, it is subjected to a gas cooling process whereby the volume of steam required for the procedure to which the invention relates is generated. A gas conditioning process is also often recommendable.

20 Another advantageous application of the synthetic gas produced is in the generation of pure hydrogen and or carbon monoxide for chemical or petrochemical processes. The synthetic gas can also be used in line with the generation of electrical energy using a combined gas steam turbine process.

The following two embodiments, in which only the volumes of vapour and air (as a gas containing 02) introduced to the gasification process differ, emphasise the effectiveness of this invention. Hard coal was dried in a ground coal drying machine to a residual moisture of approx. 1 to 2 and crushed to a size no greater than 1 mm. This coal dust was introduced into a pyrolysis reactor, brought into direct contact with smoke gas generated by the combustion of the gases and vapours produced by the pyrolysis and thus heated. The release of gases and vapours resulted in the formation of pyrolysis coke. The gases and vapours and the dust-like pyrolysis coke exited the pyrolysis stage at a temperature of around 700°C. Once the pyrolysis coke had been separated off from the gases and vapours in a cyclon, the pyrolysis coke was introduced into a gasification reactor. The gases and vapours were 9 combusted completely under pressure in air, so that all higher hydrocarbons, including tars, were oxidised. The heat generated was used to superheat the water vapour required for gasification and to preheat the air used as a gas containing oxygen for the gasification process.

The combustion heat was also used to reheat the smoke flow used to heat the pyrolysis process. Approx. 4 by weight of potassium carbonate was added as a catalyst to the flow of pyrolysis coke and fed into the gasifier via a cell-wheel valve. In order to achieve the same throughput using the same equipment without a catalyst, the temperature would have to be increased by 10 around 170 0 C. In the first stage of the gasifier's fluidised bed, the coke mixed in with the catalyst added, so that the gasification reaction took place at a temperature of around 750°C and pressure of 15 bar. As shown in the embodiment in the diagram, the gasifier used also exhibited three gasification zones, of which the second and third had the same volume. At the transition from the first to the second gasifier zone, a conversion rate of around 26 was determined. At the same temperature, the conversion rate in the two .subsequent gasifier zones was significantly higher, and an overall conversion rate of 95 of the pyrolysis coke was determined when the ashes were removed from the gasifier. In order to enable further energetic use of the 20 remaining carbon content, the ashes removed were fed into a fluidised bed combustion system. The dust removed in the cyclon to which the raw synthetic gas was introduced after the gasifier was also added to this fluidised bed combustion.

In both examples of the implementation of the procedure, a volume of 100 t/h of coal was fed into the pyrolysis. The pyrolysis produced an output of around 70 t/h of pyrolysis coke in each case, which was all introduced into the gasifier. After gasification, a volume of 8.7 t/h of solids (ash residual coke) was removed from the gasifier in each case. A flow of 252,500 Nm 3 /h of hot smoke gas was introduced into the pyrolysis stage in each case, while a total of 273,200 Nm 3 /h of pyrolysis gas was removed from the pyrolysis stage in both cases. In the first example, 209 t/h of water vapour and 61,000 Nm 3 /h air (as a gas containing oxygen) was introduced into the gasification stage. With these parameters, the result was a raw gas flow of 392,750 Nm 3 /h in the gasifier. In the second example, the amount of water vapour introduced at the gasification stage was significantly increased to 311 t/h, while the volume of air fed in remained almost unchanged at 61,200 Nm 3 In the second example, this resulted in a flow of 538,650 Nm 3 /h of raw gas from the gasifier. The composition of the raw gas can be seen in the table below, Bearing in mind the proportion of water vapour retained in the synthetic gas in each instance, it becomes clear that the significant increase in steam added in the second example results in a significantly higher oxygen yield. The content of CO and CH 4 in the synthetic gas in the second example are both lower than in the first.

H

2 CO CO2 CH4 N2 H 2 S H 2 0 Example 1 23.11 8.96 13.48 4.54 12.57 0.14 37.20 Example 2 23.20 6.35 11.60 1.88 8.22 0.11 47.72 The particular advantages of this invention can be summarised in the following points: simplified gas and water purification simplified coal measurement in the gasification process electrically independent process control (export of electrical energy also possible) improved utilisation of heat waste gas can be purified at high pressure suitable for a wide range of coals and other solid fuels 20 simple to incorporate into gas or steam turbine process for electricity generation high levels of efficiency in comparison to processes which consume oxygen.

Claims

1. Process for autothermic gasification of solid fuels under excess pressure with a gas containing 02, whereby the fuel first undergoes preliminary heat treatment by means of direct contact with a flow of hot smoke gas, gases and vapours are separated off and a brittle intermediate product is formed, whereby the flow of hot smoke gas is generated by combustion in the presence of the gases and vapours separated off during the preliminary heat treatment and whereby the intermediate product produced in the preliminary 10 treatment stage is subjected to gasification in fine powdered form from which a synthetic gas rich in H 2 and CO is produced, characterised in that: the fuel used is in a fine powdered form, the preliminary heat treatment takes the form of pyrolysis with a final temperature of at least 4500C, the gasification takes place in the presence of water vapour and heat is extracted from the flow of hot smoke gas, before it its introduced into the preliminary heat treatment stage, in order to generate the mixture of steam and gas containing 02 required for gasification.

2. Process in accordance with claim 1 characterised in that the 20 preliminary heat treatment is carried out with a final temperature of 600°C, but preferably around 700°C.

3. Process in accordance with one of claims 1 to 2, characterised in that hard coal or brown coal is used as the solid fuel.

4. Process in accordance with one of claims 1 to 3, characterised in that the flow of hot smoke gas is generated exclusively by combustion of the gases and vapours separated off at the preliminary heat treatment stage. 12 Process in accordance with one of claims 1 to 4, characterised in that the smoke gas is fed around a circuit, whereby a volume of smoke gas equivalent to the volume of the gases and vapours introduced into the combustion stage and the volume of combustion air is separated off.

6. Process in accordance with one of claims 1 to 5, characterised in that the combustion is complete combustion.

7. Process in accordance with one of claims 1 to 6, characterised in that the combustion takes place under pressure charging.

8. Process in accordance with one of claims 1 to 7, characterised in 10 that, once the heat has been extracted for the mixture of water vapour and gas containing 02 and before it is introduced into the preliminary heat treatment 9% 0 stage, the flow of hot smoke gas is heated up to the temperature required for the preliminary heat treatment by means of indirect heat exchange with freshly generated smoke gas.

9. Process in accordance with one of claims 1 to 8, characterised in that the combustion air for the combustion of the gases and vapours extracted from the preliminary heat treatment is preheated by means of indirect heat exchange with the freshly generated smoke gas. Process in accordance with one of claims 1 to 9, characterised in that the preliminary heat treatment takes place in a circulating fluidised bed.

11. Process in accordance with one of claims 1 to 9, characterised in that the preliminary heat treatment takes place in an entrained flow reactor. o

12. Process in accordance with one of claims 1 to 11, characterised in that the gasification takes place in a horizontal gas generator with a fluidised bed,

13. Process in accordance with claim 12, characterised in that the gasification takes place in a series of subsequent zones between which there is only negligible back-mixing.

14. Process in accordance with one of claims 1 to 13, characterised in that air or pure oxygen is used as the gas containing 02 for gasification. Process in accordance with one of claims 1 to 14, characterised 10 in that a volume of fine powder catalyst, especially fine potassium carbonate powder, is added at the gasification stage.

16. Process in accordance with one of claims 1 to 15, characterised in that the mixture of water vapour and gas containing 02 is fed into the gasification stage at a temperature roughly equivalent to the final gasification temperature.

17. Process in accordance with one of claims 1 to 16, characterised in that excess heat from the combustion of gases and vapours from the preliminary heat treatment is used for generating and or superheating steam :which is then released on a steam turbine to generate mechanical or electrical oo 20 energy.

18. Device for carrying out the process in accordance with claim 1, with a unit for the preliminary heat treatment of a solid fuel, with a feed pipe (34) for a hot smoke gas and a feed line (15) for the fuel to the unit with a gasifier into which the fuel previously treated in the unit and a gas containing 02 and water vapour can be fed and which exhibits an outlet (27) for the gas rich in H 2 and CO generated in the gasifier an ash removal mechanism (2d, 30) and a combustion chamber to generate the hot smoke gas, whereby the combustion chamber is connected to the unit via a pipe (22) through which the gases and vapours generated at the preliminary heat treatment stage can be introduced as fuel, characterised in that the solid fuel is introduced in fine powdered form through a feed pipe into the unit for preliminary heat treatment, the unit is designed as a pyrolysis unit for a minimum end temperature of the pre-treated fuel of 450°C and the combustion chamber incorporates at least one heat.exchanger 1) to generate the mixture of water vapour and gas containing 02 required in the gasifier

19. Device in accordance with claim 18, characterised in that the unit for the preliminary heat treatment is designed for a final temperature of at least 600 0 C, but preferably around 700°C. Device in accordance with one of claims 18 to 19, characterised in that the unit for the preliminary heat treatment is connected to a separation mechanism especially in the form of a cyclon which enables 10 the separation of gases and vapours on the one hand and fine powder pre- treated fuel on the other.

21. Device in accordance with one of claims 18 to 20, characterised in that the pipe (22) is the only feed line for fuel to the combustion chamber.

22. Device in accordance with one of claims 18 to 21, characterised in that the unit is part of a circulating fluidised bed.

23. Device in accordance with one of claims 18 to 21, characterised ,in that the unit is in the form of an entrained flow reactor.

24. Device in accordance with one of claims 18 to 23, characterised in that the combustion chamber incorporates a first heat exchanger (10) for preheating the gas containing 02 for the gasification, the outlet of which is connected to a feed line (17) for steam, to which a second heat exchanger which is arranged in the combustion chamber and used to superheat the mixture of water vapour and gas containing 02, is connected. Device in accordance with one of claims 18 to 24, characterised in that there is a smoke gas pipe (32) at the outlet from the combustion chamber which branches into a smoke gas diversion line (33) to take the hot smoke gas to the unit

26. Device in accordance with claim 25, characterised in that the feed line (34) incorporates a condenser (13) in to raise the pressure of the flow of smoke gas and the combustion chamber incorporates a third heat exchanger (11) to increase the temperature of the flow of smoke gas.

27. Device in accordance with one of claims 18 to 26, characterised in that the combustion chamber is attached to at least one burner into which both the gases and vapours extracted from the unit and the combustion air required can be introduced at increased pressure to guarantee pressure-charged combustion.

28. Device in accordance with one of claims 18 to 27, characterised in that there is a fourth heat exchanger (12) in the combustion chamber (3) which is incorporated into a feed line (18) for the combustion air to the burner of the combustion chamber

29. Device in accordance with one of claims 18 to 28, characterised in that the gasifier is in the form of a horizontal gas generator with a fluidised bed.

30. Device in accordance with claim 29, characterised in that the gasifier is divided by means of insets into a series of gasifier zones between which there is only negligible back-mixing of the fuel to be gasified.

31. Device in accordance with one of claims 18 to 30, characterised in that the gasifier has a feed line (24) for supplying catalyst material in fine powdered form.

32. Device in accordance with one of claims 18 to 26, characterised in that there is an additional heat exchanger in the combustion chamber for generating and or superheating steam which can then be used on a steam turbine to generate mechanical or electrical energy.

33. Use of a device in accordance with one of claims 18 to 32 to supply the synthetic gas as a reduction gas for a system producing pig-iron by means of direct reduction of iron oxide.

34. Use of a device in accordance with one of claims 18 to 32 to supply synthetic gas as the material used in a system to produce pure 25 hydrogen and or carbon monoxide for chemical or petrochemical processes. Use of a device in accordance with one of claims 18 to 32 to supply synthetic gas as the fuel for a system to generate electricity or a combined gas steam turbine process. DATED THIS 26 DAY OF MAY 2000 TECHNIP BENELUX B.V. DMT GmbH FERROSTAAL AG PATENT ATTORNEYS FOR THE APPLICANT:- F B RICE Co