GB1597691A

GB1597691A - Process and plant for the gasification of solid fuels particularly of bituminous coal

Info

Publication number: GB1597691A
Application number: GB130/78A
Authority: GB
Original assignee: Ruhrkohle AG
Current assignee: RAG AG
Priority date: 1977-01-05
Filing date: 1978-01-04
Publication date: 1981-09-09
Also published as: PL112063B1; IN148689B; BR7800070A; PL203826A1; JPS53104607A

Description

(54) "PROCESS AND PLANT FOR THE GASIFICATION OF SOLID FUELS, PARTICULARLY OF BITUMINOUS COAL7' (71) We, RUHRKoHLE AKTENGESEL LSCHAFT, a German Body Corporate, of 1, Rellinghauser Strasse, D-4300 Essen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: This invention relates to processes and plants for the gasification of solid fuels, more particularly, but not exclusively, bituminous coral, in which fuel having a granular size of about 0 to 10 mm is fed from a bunker into the reaction chamber of a 'fixed bed" or "fluid bed" reactor, together with additives if necessary, a gasification agent, e.g. a mixture of (i) steam or carbon dioxide and (ii) air or oxygen, is introduced into the reaction chamber, and the ash which is produced during the gasification is removed from the reaction chamber.

A "fixed bed" reactor is one in which gasification is essentially carried out with the solid fuel lying on a grate, whereas a "fluid bed" reactor is one in which the solid fuel is gasified during falling or whirling through the reaction chamber.

For gasification in a fluid bed reactor, fuels are usually preferred which have a relatively high reaction capability. For this reason, the process according to the invention is applicable not only to bituminous coal, but also to brown coal, oil coke, low temperature coke and similar solid fuels or other substances containing hydrocarbons which are available in a fine granular state. Insofar as additives are provided in the process, these principally serve to influence the melting point of the ash in order to prevent clogging up by liquefied ash, which can occur at relatively high gasification temperatures. Also the additives can be used for desulphurising the gas and for facilitating the subsequent processing of the ash, for example processing of the ash for use in cement.

Fluid bed gasification in this form is already known (W. Peters, Kohlevergasgung, Verlag Glückauf 1976,77,87). With the known process, gasification takes place under atmospheric pressure. It is true that attempts have been made to raise the temperature of gasification to about 15000C in order to obtain a better quality gas, in which the carbon monoxide content is raised in favour of the carbon dioxide content.

However, this does not increase the throughput quantities in the long run. From the point of view of equipment, the disadvantage exists with the known fluid bed gasification plants that a relatively complicated charging gate arrangement is necessary, which must provide protection against gas over-pressure in order to avoid explosions in the supply bunker. As a means of conveying and supplying the fuel and removing the ash, screw conveyors are usually used. These conveyors have, amongst others, the disadvantage that they cannot convey against a pressure differential, i.e. approximately the same pressure must prevail in front of as behind the screw conveyor.

The aim of the invention is essentially, with the process outlined in the introduction, to simplify the to and away conveying necessary for the supply of the fuel and the removal of the ash and thus to achieve an increased throughput with an adequately accurate quantification of the fuel supply and the amount of ash produced, independently of the pressure in the gasification zone of the reactor.

According to the invention there is provided a process for gasification of solid fuel from a bulker to a pressurised gasification zone within a reaction chamber by successively compressing discrete portions of fuel to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber to a pressure substantially below that of the gasification zone, introducing a gasification agent into the reaction chamber, and removing the ash produced during gasification from the reaction chamber in such a manner that the reaction chamber is at no time subjected to atmospheric pressure, the fuel supply and/ or ash removal being achieved by pumping.

Self-energising gasification carried out under over-pressure by such a process leads to an appreciable increase in throughput, as well as the methane content in the gas; moreover, it does not have a detrimental effect on the conveying to and away of the materials. The pumping of the fuel and/or ash not only makes the conventional fuel supply or ash removal gate arrangement superfluous because of the pressure-tight shutting off of the fuel portions which is achieved, but also enables accurate quantification of the amount of fuel or amount of ash. By "selfenergising gasification" is meant an autothermic gasification, an autothermic reaction being a coupled exothermic - endothermic reaction.

For this reason the invention has the advantage that the economy of the process is considerably enhanced by higher throughput quantities and by simplification of the plant.

According to a preferred embodiment of the process, the gasification zone pressure is set at approximately 200 bars and the gasification temperature is in the range from approximately 900"C to 12000C. It is thereby possible to carry out the known high temperature fluid bed gasification with substantially increased throughput because of the considerable gasification pressure.

Preferably, the ash is cooled off before it is extracted. In an embodiment of the process given as an example, the ash is cooled to about 200 C. This cooling of the ash is most economically carried out by employing the gasification agent.

In a further embodiment of the process, utilizing a fluid bed reactor, the introduction of the portion of fuel above the fluid bed takes place from above in the reaction chamber of the reactor. With fuels with a large proportion of fine grain material, the introduction of a part of the gasification agent can also take place from above, so as to reduce or prevent losses by non-converted small particles of material being carried along by the producer gas. As, on selecting the temperature of gasification, the sinter point of the ash can be extended, an agglomeration of the particles of slack takes place within the fluid bed, which particles, influenced by their higher density as well as the increased particle diameter, tend to sink to the bottom of the fluid bed. The continuous feeding of fuel from above results in a partial countercurrent of the gas in the reaction chamber.

Thus heat, which otherwise could only be retrieved outside the reaction chamber, can be retained in the reaction chamber. In total, this leads to a reduced oxygen requirement and to a higher gas yield in relation to fuel consumption.

If, on the other hand, the temperature is reduced, a gas can be produced which is relattively rich in methane and is very suitable for the creation of a natural gas exchange.

With another embodiment of the invention, the release of the fuel takes place directly into the fluid bed. This embodiment has the advantage that the carrying away of fine granulated material (coal or ash, respectively) with the stream of gas is considerably reduced due to the reduction of the free path lengths in the column of material of the fluid bed. Thereby, in particular, the dust content of the gases produced is reduced.

This effect can be enhanced by introducing tar or similar materials into the upper zone of the fluid bed, where there is a particular concentration of fine granules. Here the tar leads to an advantageous agglomeration of the finely granulated dust into larger particles. As a result excessive carrying away of dust can also be combatted.

The invention is also applicable to processes for the self-energising pressure gasification of solid fuels, preferably lumpy bituminous coal, with a gasification agent, for example a mixture of (i) steam or carbon dioxide and (ii) oxygen or air, in a packet or fixed bed reactor. Fuel is continuously introduced, for example from above, into the reaction chamber of the reactor first being cut off from the amosphere in portions. The fuel portions are brought to zonal pressure prevailing in the reactor, and are fed continuously into the reaction chamber of the reactor, the ash produced during gasification being transferred to the exterior and brought to atmospheric pressure.

Fixed bed gasification is known per se in several embodiments (W. Peters, Kohlevergasung, Verlag Gliickauf 1976, 64, 76 Y). The gasification gas and/or crude gas can be used after suitable processing as a synthetic gas and also as a replacement for natural gas or town gas. A known process works with zonal pressures, that is pressures in the gasification zone of the reactor, of 25 bars. Because of this, the fuel must be brought by way of a comparatively complicated gate arrangement into the reactor. Filling of the gate requires a relatively large amount of fuel to be supplied. This leads to difficulties in the regulation and control of the gasification process. Similar difficulties arise at the ash extraction gate. Furthermore, with each operational cycle of the gate, production gas is lost. These losses would increase with an increase in gasification pressure proportionally to the gasification pressure. Noncaking or only weakly caking bituminous coals serve as fuel. Generally, granulation fractions between about 6 and 30 mm are used. Unclassified coal can be used in the known process but then, however, the standard operational conditions must be essentially modified. The proportion of fine coal may not exceed certain limit values, as otherwise a severe reduction of the throughput performance would occur.

Accordingly, the known process also has the disadvantage that untreated raw coal cannot be used under standard conditions. Operation of the known reactors is also impeded by the relaively high tar and dust content on the crude gas. The invention enables simplification of the known process by an improvement of the fuel feed and/or the ash extraction and by creating the conditions for a pressure increase in the reaction chamber of the reactor which, in particular, simplifies the fuel feed and the treatment of the gasification gas in the reactor.

By pumping the fuel, a continuous delivery of fuel into the reactor is achieved and thus an accurate quantification of the fuel is made possible which. in turn, enables better control of the gasification process. The fuel gate arrangement may be dispensed with because the portion of fuel, together with the displacement element of the pump, ensures a tight seal to the outside between the reactor and the pump. As, under certain conditions, the pump pressure is increased greatly beyond the reactor pressure which until now has been considered as the upper limit, the throughput of fuel and the quality of the gasification or production gas is considerably increased.On the other hand, by sealing the displacement element against reactor pressure with supply portions of fuel, sealing of the displacement element from the atmosphere can be dispensed with and thus a very high compression of the fuel achieved. If the process is applied to the extraction of the ash from the reactor, then the exit gate arrangement which has so far been used is eliminated, even at considerably increased pressures in the reactor. The overall advantage that the economy of the process is considerably increased by higher throughput quantities and by simplification of the plant is thus achieved.

This simplification also applies to tbe fuel fed into the reactor. This consists, according to one embodiment of the invention, of run-ofmine coal classified at 20 mm, with which the zonal pressure in the reactor at a gasification temperatures in the range from 900 C to 1200 C can be set at up to 200 bars.

In an embodiment of the invention, the supply of fuel is preheated to 3000C and is fed continuously from above into the reaction chamber. On increased pressure of the gasification zone it is possible, by the return of hydrogen-containing gasification gas, to initiate hydrogenation reactions for increasing the methane output. This gas, drawn off from the lower section of the reaction chamber, is cooled, compressed and heated up to about 750"C, and introduced into the reactor.

In this process, in the upper part of the reaction chamber, part of the fuel is already partially oxidised and gasified, especially its finely granulated part. Only the coarser particles of fuel reach the fixed bed of the reactor. By the partial gasification of the finely granulated part, or by hydrogenation reactions, the necessary reaction temperature for the gasification is adjusted from 750 to 950"C. The gasification agent and the recycled gas flow together through the upper part of the reactor, whilst the fuel which is building up in the fixed bed is gasified in the countercurrent.

Preferably, additives are made to the fuel, e.g. in the shape of lime. On the one hand, at comparatively high reaction chamber temperatures, this can simplify the treatment of the ash because clogging by ash is avoided. On the other hand, desulphurisation of the production gas can be carried out simultaneously in the reaction chamber In another embodiment of the invention, the fuel is pumped from below through the fixed bed. By this means the raking arms which have so far been necessary for the distribution of the fuel in the gasifier may be dispensed with.

Strongly caking coals can also be used without mechanical means having to be provided for breaking up the fuel bed, as the caking characteristics are to a large extent lost by partial oxidation.

According to another embodiment of the invention, the fuel and the gasification agent are fed into the reaction chamber from above whilst the production gas is drawn off from below the fixed bed and the liquid ashes are granulated and removed as a granulate. Also in this process, a pre-degassing of the fuel is involved which, in the case of caking coals, leads to a large part of the caking capability being lost. This leads to a wider spectrum of coals being suitable for gasification without complicating the operation of the reactor.

Furthermore, the invention is applicable to a process for the self-energising gasification of granular fuel, in particular bituminous coal, with a gasification agent, for example oxygen and steam, in which the fuel is led from a bunker into a mixing head in a controlled quantity, where it is entrained by the gasification agent stream and blown into the reaction chamber by a burner. The gasification may take place at a standard temperature, i.e. at atmospheric temperature. The preferred fields of application of the invention are, however, further developments of the above described gasification process, aimed at increasing of the gasification pressure. Instead of with bituminous coal, the invention can be carried out with other types of coal and other fuels, for example with brown coal and oil coke.As gasification agents, besides oxygen and steam, also air and steam, oxygen and carbon dioxide or air and carbon dioxide could be used.

A process is known (W. Peters, Kohlvergasung, Verlag Gluckauf 1976, 88, 97) which works at normal pressures with coal dust, which should be of size 70% < 0.075 mm. (or leave no more than 10% residue on a 0.09 DIN sieve).

The coal which is used is fed continuously at at controlled rate into a mixing head by a screw conveyor. The temperatures of gasification are relatively high at 1500 to 1900 C. Synthetic gas is produced. The cost of producing usable coal from the coal which is delivered is a dis advantageous factor, because the necessary milling is expensive and demands a considerable technical effort. Furthermore, the regulating and control expenses are considerable. Also the continuous feeding of the fuel in the regulated quantities by means of a screw conveyor causes problems, especially with coarse grained fuel.

The invention provides improved means for feeding fuel, thus permitting simplification of the above described process and also, in a further development of this process, permitting gasification under increased pressure thus resulting in improved throughput and/or higher grade producer gas.

The pumping in of the fuel can take place at pressures of up to 200 bars and has the advantage that a prescribed supply of fuel can be achieved even with considerably coarser granulation, for example up to about 2 mm.

The size of granulation creates no difficulties for the gasification as, because of the high gasification temperature, a sudden heating up to the reaction temperature occurs which leads to a reduction in size of the coarse grain in the flame. Thus an advantage of the invention is that fine milling of the fuel can be dispensed with. In practice, it is only necessary to sieve the run-of-the-mine coal, for example with a grain size limit of about 2 mm, which coal, because of the progressive mechanisation below ground, contains enough fine coal below this grain size in any case.The process furthermore has the advantage that it permits a considerable over-pressure in the reaction chamber, because the portions of fuel in front of the displacement element are sealed off from the outside, making special delivery gate arrangements and blowback protection devices superfluous, which until now have had to be employed in order to avoid explosions, particularly in the fuel storage bunkers.

Dividing the fuel into portions of prescribed quantity which are subsequently fed as a substantially continuous stream has the advantage that regulated amounts of fuel can be very accurately maintained. Consequently a considerable amount of the previous control and regulation requirement is dispensed with.

Furthermore, the fuel is capable of being pumped dry. Thus the heat equilibrim of the gasification is improved as compared to processes which work with suspensions of fuel in water, because the heat expended in the reactor to vapourise the water vehicle is saved and preheated steam can be fed in according to the reactor requirements.

In a preferred embodiment of the invention, the fuel is prepared by breaking or classifying and is bunkered under standard pressure undried. This is possible even with increased pressure in the reaction chamber, because flame blowbacks are eliminated for the reasons explained above.

In a further embodiment of the invention which is provided particularly for considerably increased pressures in the reaction chamber, the ashes resulting from the reaction are pumped out of the reaction chamber by being divided into portions which are brought individually to atmospheric pressure and subsequently released.

In this manner it is possible to prevent pressure escape from the gasification zone of the reactor to the exterior during ash removal.

With another embodiment of the invention an unprepared settlement of filter mud is used as fuel. In this case also the fuel is of granular nature. The employment of such mud is possible because the process is independent of the moisture content of the fuel to be fed in. Thus a considerable economic advantage is gained because the available filter muds can be considered as preparation by-products which are very difficult to dispose of, if at all. The invention also provides a plant for carrying out the above described process in accordance with the invention.

Various plants embodying the invention will now be described, by way of example, with reference to the accompanying drawings, in which : Figure lisa sdematic view ofa plant for the gasification of bituminous coal in a fluid bed, Figure 2 is a view similar to Figure 1 but of a modified plant, Figure 3 is a side view of a pump for feeding the fuel, Figure 4 is a plan view of the pump shown in Figure 3, Figure 5 is a schematic view of a plant for the generation of synthetic gas by pressure gasification of bituminous coal, Figure 6 is a schematic view of a fixed bed reactor for the generation of high methane content producer gas.

Figure 7 is a schematic view of a modified plant in which fuel is introduced from below by way of a burner through a fixed bed and the gasification agent is introduced through the grate of the reactor, Figure 8 shows a further modified plant for the generation of synthetic gas, and Figure 9 is a schematic view of a plant for the gasification of granular bituminous coal with oxygen and steam and employing a mixing head.

In the figures, the same reference numerals relate to parts corresponding to each other.

Prepared bituminous coal, of granular size in the range 0 - 10 mm, is supplied by way of a duct 2 to a bunker 1. From the bunker 1, a pump 3 pumps the fuel 4 in discrete portions, as described below, by displacing a portion of fuel, sealing it from the body of fuel 4, pressurising it and introducing it by way of a conduct 5 and a nozzle 6 into the top 19 of a reactor 7. By employing a combination of several, preferably three, alternately driven pistons in the pump, and uniting the portions of fuel supplied by the pumps in one conduit, an even flow of fuel is achieved. In the reactor there is a fluid bed, shown schematically at 8, to which a gasification agent is fed from below at 9. A mixture of steam and air or a mixture of steam the oxygen serves as gasification agent.

The gas is generated in the fluid bed 8 and is led off at approximately 3 to 4 m above the fluid bed through a conduit 10, if necessary after an after-gasification step, that is after burning off of the remaining gasification agent.

The ash is drawn from the lower truncated conical part 11 of the reactor by way of a shaft 12. For this, a pump 13 is used which is constructed similarly to the pump 3 and is described in greater detail below. Air with steam or oxygen with steam is fed in by way of a duct 18 in order to cool off the ash. As the reactor 7 operates at considerably above atmospheric pressure, for example about 200 bars at gasification temperatures of 900 to 12000C, the ash which is divided into discrete portions is first reduced to atmospheric pressure with the aid of the pump 13 before it is discharged at 14.

In the modified embodiment shown in Figure 2, the fuel is fed from the supply bunker 1 by the pump 3 through a cooled lance 15 directly into the fluid bed 8'. On the other hand, the supply of the gasification agent takes place through an annular tuyere 9' which is arranged below the fluid bed 8'. For this reason, the reactor 7' has a somewhat different shape.

Whilst in the embodiment shown in Figure 1 the part 11 is conically narrowed towards the bottom, in the case of the reactor 7' in the embodiment shown in Figure 2, it is a practically cylindrical pressure vessel with a lightly domed top 16 below which the exit pipe 17 for the generated gas is arranged. The lower part 11' of the reactor 7' is conically reduced in size and ends in a relatively narrow shaft 12' below which the pump 13 is arranged for the removal of the ash. Again, an annular conduit 18' for a branch of the stream of gasification agent is provided which serves to cool the ash before this is fed into the pump 13.

Both of the pump 3 and 13 are double piston pumps each having two parallel cylinders 20 and 21 as shown in Figures 3 and 4, the references 13 (3) and 3 (13) in these figures being intended that the pump shown in these figures may be used either as a fuel pump 3 or as an ash pump 13. However a three cylinder pump could be used with advantage. In each of the cylinders there runs a displacer piston 23, 24 respectively. The rear side of each piston is exposed to hydraulic pressure means at 25 or 26, respectively. Considering operation of the pump in relation to the supply of fuel, from the unpressurised bunker 1, the first piston 23 pushes a portion of fuel 29 into the cylinder 20. As can be seen in Figure 4, a rotary valve 28 associated with the cylinder 20 is initially closed, so that when the piston 23 moves into the position shown, the portion of fuel 29 is compressed.The final pressure corresponds to the internal pressure of the reactor . After the reactor pressure has been attained, the cylindrically shaped valve 28 opens to the position of the valve 30 in Figure 4 by rotating through an angle of 90 , the valve 30 being associated with the cylinder 21 but otherwise being similar to the trip valve 28. The bore 31 of the valve 28, which has the same diameter as the cylinder bore 32, is thus brought into alignment with the cylinder 20. The compressed fuel may then enter the reactor as shown at 27 in relation to the cylinder 21. As the same pressure prevails on either side of the valves 28 and 30, the load applied to the surfaces definer the bores of these valves 28 and 30 is very low.Furthermore the ensuing introduction of the portions of fuel into the pressure chamber when the valves are opened takes place at very low piston speed.

A blocking switch (not shown) only allows the return of the piston when the valve has been closed again (see position of the valve 28 in Figure 4). During the filling and pressurising procedure of the piston 23, the second piston 24 delivers a corresponding portion of fuel into the pressure chamber. Slight dead periods in the supply of fuel arise with the reciprocal closing and opening of the valves 28 and 30.

Of course, more than two pistons 23 and 24 with associated cylinders 20 and 21 can be provided. In the event of three piston and cyllinder combinations of this kind being used, the dead periods can be practically eliminated.

It can also be arranged that the portion of fuel, as represented in the example of the piston 24 and cylinder 21, is only released into the pressure chamber by the valve 30 if the pressure of the piston 23, by suitably timing the opening of the valve 30.

In the embodiment shown in Figure 2, tar is fed, by way of a pipe 40 and a nozzle 41 above fluid bed 8', into the pressure chamber of the reactor 7'. In all cases, the pump 13 which serves to extract the ash is formed similarly to the pump 3 which is used for feeding the fuel.

Consequently, the valves of the ash pump 13 are subject to atmospheric pressure on the delivery side.

In the embodiment shown in Figure 5, a fuel storage bunker 103 is arranged to supply fuel to a fixed bed reactor 100. The coal is supplied to the bunker by was of a duct 101, and is held in readiness in the bunker at 102.

Coal is supplied by a pump 104 from the store at 102; the piston of this pump is schematically shown at 105. The fuel is supplied by way of a conduit 106 to an inlet nozzle 108 in the roof 107 of the pressure chamber 109 of the reactor 100. In the reaction chamber 109 there prevails a pressure of, for example, 200 bars. Gasification agent is supplied to the pressure chamber 109 by way of a conduit 110 and the inlet nozzle 108. The coal falls from above through the reaction chamber 109 of the reactor 100 on to a fixed bed 112, which rests on a grate 113.

Gasification agent is also supplied from below, by way of a conduit 114, through the grate 113. Here also the gasification agent is steam or carbon dioxide and oxygen or air.

In the upper part 115 of the reaction chamber 109 a partial oxidation of gasification of the introduced fuel takes place, so that here the necessary reaction is commenced. The nonconverted larger particles of the fuel build up on the fixed bed 112 above the grate 113. The gasification zone 116 is formed in the upper part of the fixed bed, whilst the lower part forms the combustion zone. The particles of fuel in the fixed bed 112 react with the gasification agent introduced at 114. The relatively cold gasification agent acts simul taneously as a cooling agent fot the grate 113, which is subjected to intense heat.

The crude gas which is generated is drawn off through the duct 117 in the direction of the arrow 118.

To facilitate the reaction, the upper part 119 of the reactor is drawn-in, as shown, in the manner of a truncated cone. Furthermore, the reactor is surrounded by a water jacket 120 to recover the heat generated.

The grate 113 is designed so that it can be rotated. This facilitates extraction of the ash, which is taken out of the reactor 100 at 121 by a pump which corresponds to the pump 104 but is not shown.

In the embodiment shown in Figure 6, the reactor is divided, by a partition 123 having an opening 124, into a lower part 122, which forms the reaction chamber, and an upper part 125. The coal is introduced into the upper part 125 of the reactor by way of a conduit 127 by means of a pump which is not shown but corresponds to the pump 104 of Figure 5.

Production gas is introduced by way of a pipe 128 leading from the lower part 122 of the reactor, where it is drawn off by way of a pipe 129, and consequently contains mainly carbon monoxide and hydrogen. Part of the gas which is drawn off is taken away at 130. The remainder goes by way of a by-pass pipe 131 into a gas scrubber 133 which is only shown schematically and from which the gas is recycled by way of the pipe 128 into the upper part 125.

The ash is extracted at 134 by way of a pump corresponding to pump 104 but which is not shown. Gasification agent, comprising oxygen or air fed by way of a pipe 136 and steam or carbon dioxide fed by way of a pipe 137, passes into the reactor through a grate 135, which is shown schematically and which is preferably rotatable. A fixed bed forms on the grate 135.

By means of the scrubbed gas, which is precompressed and fed back by way of the pipe 128 into the upper part 125 of the reaction chamber, a low temperature hydrogenation reaction takes place with the fuel which has been introduced 127 by way of the conduit.

This forms production gas having a high methane content, which can be drawn off by way of a pipe 138. If necessary, this production gas may be subjected to a gas scrubbing process before it is used further.

Simultaneously, gasification agents, namely (i) oxygen or air and (ii) steam or carbon dioxide, are added by way of a pipe 139 with the fuel which is introduced.

Accumulated fuel in a hopper 140 formed in the partition 123 passes through the opening 124 on to the fixed bed on the grate 135 which lies below. In view of the natural cone of poured fuel which is thus formed, an optimum distribution of the ungasified fuel in the lower part 122 of the reaction chamber is achieved because of the conical formation of the grate 135.

In the embodiment shown in Figure 7, in which the corresponding parts are marked in agreement with Figure 5, the fuel is fed continuously to a burner 108 in the grate 113 by the pump 104 by way of the conduit 106, to which burner 108 the gasification agent, namely a mixture of (i) steam or carbon dioxide and (ii) oxygen or air, is also fed by way of the pipe 111. As shown, the burner 108 lies directly at the tip of the truncated conical grate 113. Thus the fuel can be distributed over the surfact of the grate in an optimum manner.

The ash is extracted at 121 by a pump (not shown) corresponding to the pump 104. The production gas is drawn off along a conduit situated in the upper part 119 of the reactor 110' by way of pipe 118'. The reactor 110' is surrounded by a water jacket 120' to recover the heat generated.

Also in Figure 8 the reference numerals relate to corresponding parts in Figures 5 and 7.

Accordingly, the fuel is fed from the store 102 by the pump 104 along the conduit 106 to the fuel and gasification agent inlet nozzle 108 in tile upper part 119 of the reactor 110',, to whicli the gasification agent, namely a mixture of (i) steam or carbon dioxide and (ii) oxygen or air, is added by the pipe 111'. In the upper part of the pressure chamber 109 a partial gasification takes place. The gas which is thus pro duced, together with the remaining gasification agent and fuel, travels into the lower part of the reactor towards the fixed bed 112 of the grate 113', where the fuel accumulates. Gasification agent, as well as the producer gas, pass downwardly through the fixed bed. Thus complete conversion of the still available fuel occurs. The gas is drawn off by way of a withdrawal conduit 117, situated below the grate 113' and the fixed bed, in the direction of the arrow 118'. The ash falls into a water bath 141 where it breaks down into granules. An extraction device 142 takes care of the withdrawal of the granulated ash.

The grate 113 consists of fire resistant materials, because it cannot be cooled by the relatively cool gasification agents as in previous embodiments. On the other hand, the water jacket 120" surrounding the pressure chamber 109 need not extend below the level of the grate 113'.

In the plant shown in Figure 9, classified coal with an upper grain size limit of about 2 mm is loaded by way of a conduit 201 into a bunker 202, which maintains a store of fuel at 203. A pump 204 takes fuel portions from this store 203 and feeds them by way of the valve 205 and a conduit 206 to a mixing head 207.

Thus, the fuel is continuously conveyed and introduced into the mixing head 207. In the mixing head 207, the fuel is entrained in a stream of gasification agent, for example a mixture of oxygen and steam, which is fed in by way of a pipe 208, and is blown into the reaction chamber by a burner 207a, which is only schematically shown, of the gasifier 209.

As can be seen, the burner 207a is located in the truncated conical roof 210 of the gasifier 209. The control means which on the one hand control the feed rate of gasification agent are not shown in the drawing. However, the gasifying process can be regulated by controlling gasification agent feed rate in relation to the fuel feed rate. Most of the fuel gasifies in the upper part of the reaction chamber 211.

Synthetic gas (H2 + CO2) is thereby generated and is drawn off by way of a conduit 212.

The ash which occurs during the gasification process is drawn off through the conical lower part 213 of the gasifier 209 by way of an opening 214 and falls into a granulating bath 215 from which the granulated ash can be drawn off by an extraction device 21.

The gasifier 209 is provided with a fireproof brick lining 217.

A further pump corresponding to the pump 204 can be utilised for removing in place of the bath 215 and extraction device 216.

WHAT WE CLAIM IS: 1. A process for gasification of solid fuel, which process includes the steps of supplying fuel from a bunker to a pressurised gasification zone within a reaction chamber by successively comprising discrete portions of fuel to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber to a pressure substantially below that of the gasification zone, introducing a gasification agent into the reaction chamber, and removing the ash produced during gasification from the reaction chamber in such a manner that the reaction chamber is at no time subjected to atmospheric pressure, the fuel supply and/or ash removal being achieved by pumping.

2. A process according to Claim 1, wherein the ash is removed from the reaction chamber by successively isolating discrete portions of the ash from the gasification zone in pressure tight manner, reducing these portions to atmospheric pressure and discharging the portions of ash.

3. A process according to Claim 1 or 2, wherein the pressure of the gasification zone is up to 200 bars and the gasification temperature is in the range from about 900"C to 12000C.

4. A process according to Claim 1, 2 or 3, wherein, in the case where the ash is removed by pumping, the ash is cooled off before it is pumped.

5. A process according to Claim 4, wherein the ash is cooled off to about 200"C.

6. A process according to Claim 4 or 5, wherein the gasification agent is used for cooling the ash.

7. A process according to any one of Claims 1 to 6, wherein the reaction chamber is a fluid bed reaction chamber.

8. A process according to Claim 7, wherein the fuel is bituminous coal, and the gasification agent is a mixture of(i) steam or carbon dioxide and (ii) oxygen or air.

9. A process according to Claim 7 or 8, wherein the portions of fuel are introduced into the upper part of the reaction chamber from above the fluid bed.

10. Aprocess according to Claim 9, wherein, with fuel containing a high proportion of fine material, part of the gasification agent is also fed into the reaction chamber from above.

11. A process according to Claim 7 or 8, wherein the portions of fuel are introduced directly into the fluid bed.

12. A process according to Claim 7, 8 or 9, wherein tar and/or similar material is introduced into the reaction chamber above the fluid bed.

13. A process according to any one of Claims 1 to 6, wherein the reaction chamber is a fixed bed reaction chamber.

14. A process according to Claim 13, wherein the fuel is lumpy bituminous coal, and the gasification agent is a mixture of (i) steam or carbon dioxide and (ii) oxygen or air.

15. A process according to Claim 13 or 14, wherein the fuel consists of run-of-the-mine coal which is classified at 20 mm, predried and preheated to a temperature of 200 to 3000C.

16. A process according to Claim 13, 14 or 15, wherein the fuel is fed from above into the reaction chamber, and gasification gas is recycled from a lower section of the reaction chamber into a upper section of the reaction chamber, from which the gasification gas is drawn off as producer gas.

17. A process according to Claim 16, wherein gasification gas which has been drawn off from the lower section of the reaction chamber is cooled, subsequently compressed, reheated to about 750"C, and only then recycled into the upper part of the reaction chamber.

18. A process according to any one of Claims 13 to 17, wherein the fuel is supplemented by additives.

19. A process according to Claim 13, 14 or 15, wherein the fuel is introduced from below

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. grate 113'. In the plant shown in Figure 9, classified coal with an upper grain size limit of about 2 mm is loaded by way of a conduit 201 into a bunker 202, which maintains a store of fuel at 203. A pump 204 takes fuel portions from this store 203 and feeds them by way of the valve 205 and a conduit 206 to a mixing head 207. Thus, the fuel is continuously conveyed and introduced into the mixing head 207. In the mixing head 207, the fuel is entrained in a stream of gasification agent, for example a mixture of oxygen and steam, which is fed in by way of a pipe 208, and is blown into the reaction chamber by a burner 207a, which is only schematically shown, of the gasifier 209. As can be seen, the burner 207a is located in the truncated conical roof 210 of the gasifier 209. The control means which on the one hand control the feed rate of gasification agent are not shown in the drawing. However, the gasifying process can be regulated by controlling gasification agent feed rate in relation to the fuel feed rate. Most of the fuel gasifies in the upper part of the reaction chamber 211. Synthetic gas (H2 + CO2) is thereby generated and is drawn off by way of a conduit 212. The ash which occurs during the gasification process is drawn off through the conical lower part 213 of the gasifier 209 by way of an opening 214 and falls into a granulating bath 215 from which the granulated ash can be drawn off by an extraction device 21. The gasifier 209 is provided with a fireproof brick lining 217. A further pump corresponding to the pump 204 can be utilised for removing in place of the bath 215 and extraction device 216. WHAT WE CLAIM IS:

1. A process for gasification of solid fuel, which process includes the steps of supplying fuel from a bunker to a pressurised gasification zone within a reaction chamber by successively comprising discrete portions of fuel to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber to a pressure substantially below that of the gasification zone, introducing a gasification agent into the reaction chamber, and removing the ash produced during gasification from the reaction chamber in such a manner that the reaction chamber is at no time subjected to atmospheric pressure, the fuel supply and/or ash removal being achieved by pumping.

through the fixed bed into the reaction chamber by means of a cooled burner.

20. A process according to Claim 13 or 14, wherein the fuel and the gasification agent are introduced into the reaction chamber from above, and the producer gas is drawn off from below the fixed bed, whilst the liquid ash is granulated and removed as granulate.

21. A process according to Claim 13 or 14, wherein the fuel and a part of the gasification agent are introduced into the reaction chamber from above, and the remaining gasification agent is fed through a grate, whilst the producer gas is led off from above the grate.

22. A process according to any of Claims 1 to 6, wherein the fuel is delivered to a mixing head where it is entrained by a stream of gasification agent and blown into the reaction chamber by a burner.

23. A process according to Claim 22, wherein the fuel is pumped into the mixing head by means of three piston and cylinders arrangements, whereby a substantially continuous stream of fuel is produced.

24. A process according to Claim 22 or 23, wherein the fuel is prepared by breaking or classifying, and the prepared fuel is bunkered undried under atmospheric pressure.

25. A process according to Claim 22, 23 or 24, wherein an unprepared settlement or filter mud is employed as fuel.

26. A plant for gasification of solid fuel, which plant includes a bunker for solid fuel, a reaction chamber adapted to contain a pressurised gasification zone, fuel supply means for conveying fuel from the bunker to the reaction chamber by successively compressing discrete portions of fuel to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressuretight manner, and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber to a pressure substantially below that of the gasification zone, gasification agent supply means for introducing gasification agent into the reaction chamber, and ash removal means for removing the ash produced during gasification from the reaction chamber in such a manner that the reaction chamber is at no time subjected to atmospheric pressure, the fuel supply means and/or the ash removal means incorporating a pump.

27. A plant according to Claim 26, wherein the or each pump comprises one or more pistons for compressing the portions of fuel, and one more outlet valves for introducing the compressed portions of fuel into the reaction chamber.

28. A plant according to Claim 26 or 27, wherein the reaction chamber comprises a lower part having the shape of a truncated cone.

29. A plant according to Claim 26, 27 or 28, wherein the reaction chamber is a fluid bed reaction chamber.

30. A plant according to Claim 29, wherein fuel is fed into the top of the reaction chamber, which widens out downwardly from the point where the fuel is delivered in a hemispherical manner.

31. A plant according to Claim 29, wherein a cooled lance is provided for carrying the fuel to the fluid bed.

32. A plant according to Claim 29, wherein one or more nozzles are arranged in the fluid bed and serve for the introduction of the portions of fuel.

33. A plant according to any one of Claims 29 to 32, wherein a tar feed is provided above the fluid bed.

34. A plant according to Claim 26, 27 or 28, wherein the reaction chamber is a fixed bed reaction chamber.

35. A plant according to Claim 34, wherein the fuel and at least a part of the gasification agent are fed into the top of the reaction chamber, which widens conically in a downward direction, starting from the feed point.

36. A plant according to Claim 34 or 35, wherein a lead-off is arranged in the top of the reactor which widens conically in a downward direction, for gas generated in the reaction chamber.

37. A plant according to Claim 35, wherein a feed inlet is arranged in the upper section of the reaction chamber for fuel, recycled gas and gasification agent, and the reaction chamber is divided into two parts by a partition having a hopper-shaped opening therein for feeding nonconverted fuel in the upper part of the reaction chamber to a grate arranged in the lower part of the reaction chamber.

38. A plant according to Claim 37, including a lead-off conduit for gas from the lower part of the reaction chamber and a by-pass conduit provided with a gas scrubber for gas which is to be fed back into the upper part of the reaction chamber.

39. A plant according to any one of Claims 34 to 38, including a conical grate beneath which is arranged a withdrawal conduit for gas, a water bath to receive and granulate the ash, and ash extraction means.

40. A plant according to Claim 34, including a burner for introducing the fuel and gasification agent into the tip of a truncated conical grate for the fixed bed.

41. A plant according to Claim 26, 27 or 28 wherein a mixing head is provided for delivering fuel entrained by a stream of gasification agent to a burner.

42. A plant according to Claim 41, including a pump for the removal of the ash with one or more pistons which feature on the pressure side one or more outlet valves which are adapted to be under atmospheric pressure on their delivery side.

43. A plant according to Claim 41 or 42, wherein the mixing head and the burner are arranged in a truncated conical upper section of the reaction chamber.

44. A plant according to Claim 41,42 or 43, wherein an ash granulation bath with an ash extraction device is provided below the reaction chamber.

45. A plant for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 1 or 2 and Figures 3 and 4 of the accompanying drawings.

46. A plant for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 5, 6, 7 or 8 of the accompanying drawings.

47. A plant for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 9 of the accompanying drawings.

48. A process for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 1 or 2 and Figures 3 and 4 of the accompanying drawings.

49. A process for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 5, 6, 7 or 8 of the accompanying drawings.

50. A process for gasification of solid fuel, substantially as hereinbefore described with reference to Figure 9 of the accompanying drawings.