CA1114179A - Process and apparatus for the self-energising gasification of solid fuels - Google Patents
Process and apparatus for the self-energising gasification of solid fuelsInfo
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- CA1114179A CA1114179A CA294,449A CA294449A CA1114179A CA 1114179 A CA1114179 A CA 1114179A CA 294449 A CA294449 A CA 294449A CA 1114179 A CA1114179 A CA 1114179A
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Abstract
ABSTRACT OF THE DISCLOSURE
Plant and process for the self-energising gasification of solid fuels in a pressurised reaction chamber of a fixed or fluid bed gasifier with a gasification agent, in which fuel is fed from a bunker into the gasifier by means of a fixed displacement pump which is separated from the reaction chamber by a rotary valve. The valve prevents gas escaping into the bunker and causing blowbacks. A similar pump may be used for extracting ash from the reaction chamber.
Plant and process for the self-energising gasification of solid fuels in a pressurised reaction chamber of a fixed or fluid bed gasifier with a gasification agent, in which fuel is fed from a bunker into the gasifier by means of a fixed displacement pump which is separated from the reaction chamber by a rotary valve. The valve prevents gas escaping into the bunker and causing blowbacks. A similar pump may be used for extracting ash from the reaction chamber.
Description
This invention relates to processes for the self-energising gasification of solid fuels, in particular bituminous coal? in a fluid bed with a gasification agent, e.g. steam, or carbon dioxide and air, or oxygen, in which fuel having a grannular size of about 0 to 10 mm. is fed from a bunker into a reaction chamber of a reactor, together with additives if necessary, is gasified on a fixed or fluid bed and the ash which is produced during the gasification is removed from -the chamber.
The invention also relates to plants for carrying out this process.
For gasification in a fluid bed, fuels are usually preferred which have a relatively high reaction capability. For this reason, the process according to the inYention is applicable not only to bituminous coal, but also to brown coal, oil coke, low temperature co~e 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, with respect to processing the ash for use in cement.
Fluid bed gasification in this form is already known (W. Peters, Kohlevergasung, Verlag Gl~ckauf 1976, 77, 87). With the known process, gasification takes place under atmospheric pressure. It is true that .
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attempts have been made to raise the temperature of gasification to about 1500C. 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., approx-imately the same pressure must prevail in front of and 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 supp:Ly of the fuel and the removal of the ash and thus to achiev~3 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 one aspect of the present invention, 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 compressing discrete portions of fuel by means of a source of compression pressure to substantially equal to the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating ~- '.
The invention also relates to plants for carrying out this process.
For gasification in a fluid bed, fuels are usually preferred which have a relatively high reaction capability. For this reason, the process according to the inYention is applicable not only to bituminous coal, but also to brown coal, oil coke, low temperature co~e 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, with respect to processing the ash for use in cement.
Fluid bed gasification in this form is already known (W. Peters, Kohlevergasung, Verlag Gl~ckauf 1976, 77, 87). With the known process, gasification takes place under atmospheric pressure. It is true that .
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attempts have been made to raise the temperature of gasification to about 1500C. 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., approx-imately the same pressure must prevail in front of and 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 supp:Ly of the fuel and the removal of the ash and thus to achiev~3 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 one aspect of the present invention, 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 compressing discrete portions of fuel by means of a source of compression pressure to substantially equal to the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating ~- '.
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: ' . : ' ' the discrete portions of fuel from the source of the com-pression pressure 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.
According to a further aspect of the present invention, 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 con-veying fuel from the bunker to the reaction chamber by succ-essively compressing discrete portions of fuel by means of a ` ~`
source of compression pressure to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating the discrete portions of fuel from the source of the compression pressure and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber ~.
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to a pressure substantially below that of the gasification zone, gasification agent supply means for introducing gasifi-cation 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 gasification carried out under over-pressure leads to an appreciable increase of the fuel throughput, as well as the methane content in the gas but, however, it ~ ~ 3 :
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does not have a detrimental effect on the conveying to and away o~ the materials because the pumping of the fuel not only makes the conventional supply gate arrangement super-fluous 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, respectively, and because the extraction of the ash is achieved for the same reasons without a conventional gate arrangement, even though a considerable over-pressure pre-vails in the reactor.
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 can be set at approximately 200 bar with gasification temperatures of approximately 900C.
to 1200C. 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 ..
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it is extracted. In an embodiment of -the process given as an example, the ash is cooled to about This cooling of the ash is most economically carried out by employing -the gasification agent. For this reason, one embodiment of the process is characterised in that for cooling -the ash at least one branch of the s-tream of gasification agent is employed.
In a further embodiment of the process, the freeing of the portion of fuel above the fluid bed takes place from above in the reaction chamber of the reactor. With ~uels with a large proportion of fine grain material, the introduction of a part of the gasi~ication agent can also take place from above, so as to reduce or prevent losses by non-converted small particles of material carried along by the producer gas. As, on selecting the temperature of gasification, the sinter point of the ash can be exceeded, an agglomeration of the particles of-slack takes place withi~ 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 ~rom above results in a partial countercurrent of the gas in the reaction chamber. Thus h-eat, 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 relati-rely ' ' 1 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 al.so applicable to processes for the self-energising pressure gasification of -~
solid fuels, preferably lumpy bituminous coal, with a gasification agent, for example steam, or carbon dioxide and 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 atmosphere in portions. Ihe fuel portion is brought under the zonal pressure prevailing in the reactor, and is ~ -fed continuously into the pressure chamber of the reactor, the ash produced during gasification being transferred to the exterior and brought to atmospheric pressure.
The fixed bed gasi~ication is known per se in several embodiments ( W0 Peters, Kohlevergasung, Verlag Gl~ckauf 1976, 6~, 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 ba~. 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 fed. This leads to difficulties in the regulation and control of the gasification process. Similar difficulties arise at the ash extraction gate.
Furt~ermore, 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.
Non-caking or only weakly caking bituminous coals serve as fuel. Generally, granulation fractions between about 6 and 30 mm. are used. Unolassified 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. ~peration of the ; 30 known reactors is also impeded by the relatively high tar and dust content of the crude gas. The invention enables simplification of the known process - : .
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, by an improvement of the fuel feed and/or the ash extraction and 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. ;~ ~ -According to the invention, this is achieved in that the fuel and/or the ash are pumped, so that separated-off portions of fuel are displaced, compressed ~ --to the zonal pressure of the reactor and released into the pressure chamber, the displacement element of the pump is shut off from the zonal pressure in the reactor and is returned, and portions of ash are extracted by a displacer, released to atmospheric -~
pressure and removed.
By pumping the fuel, a continuous delivery of fuel into the reactor is achieved and thus an accurate quantification of th~ fuel is made possible ~-which,in turn, enables better control of the gasification process. However, the ~uel gate arrangement is 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 rea~tor pressure which until now hàs been considered~as the upper limit, the throughput of fuel and the qua1ity of the gasification or production gas is coneiderably 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.
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If -the process is applied to the ex-traction of the ash from the reactor, then the exit gate arrangement which has so far been used is eliminated7 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 achived.
This simplification also applies to the fuel fed into the reactor. This consists, according to one embodiment of the invention, of a run-of-mine coal classified at 20 mm., with which the zonal pressure in the reactor at gasification temperatures of 900C. to 1200C. can be set at up to 200 bar.
In an embodiment of the invention, the supply of fuel is preheated to 300C. 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 750C.
and led 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 950C. The gasification agent and the recycled , - 8 - ~ ~`
-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 producer 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 are avoided. 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 producer 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 in~olved 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 suitable for gasification without complicating the operation o~ the reactor~
Furthermore, the invention is applicable to a process for the self-energising gasification o~
, 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 controlled quantity, where it is picked up by the gasification agent stream and blown into the -gasifier with a burner. These gasifications run at 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 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 monoxide could be used.
The process described in the introduction is known (W. Peters, Kohleverg~asung, Verlag Gl~ckauf 1976, 88, 97). The known process works so far 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 a controlled rate into the mixing head by a screw conveyor. The temperatures of gasification are relatively high at 1500 to 1900C. ;~
Synthetic gas is produced.
` The cost of producing usable coal from the coal which is delivered is a disadvantageous factor~
because the necessary milling is expensive and demands a considerable technical effort. Furthermore, the regulating and control expenses are considerable~
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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 ~uel, 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.
According to the invention this is made possible in that the fuel is pumped into the mixing -;~
head and divided into the required portions, which ~ -are pressurised by a displacement element, sealed off and fed into the reactor, a substantially continuous supply stream being produced by using a plurality of cylinders, preferably three.
The pumping in of the fuel can take place at pressures of up to 200 bar and has the advantage that a prescribed amount of fuel can be achieved even with considerably coarser granulation, for example up to about 2 mm. This size of granula-tion 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 inventlon is -that fine milling of the fuel can bs 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 because of the progressive mechanisation below ground contains enough fine coal below this grain size in any case. The process ~furthermore has the . : . . . : . . , advantage tha-t it permits a considerable over-pressure in the gasifier, because the portions of ~uel in front of the displacement element seal off to the outside, making special delivery gate arrangements and blow-back protection devices superfluous, which until now have had to be employed in order to avoid explosions, p~rticularly 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 the regulated amounts of fuel can be very accurately maintained and these quantities are easily controlled. 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 equilibrium 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 pressures 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 gasification chamber, the ashes resulting from the reaction are pumped out of the gasifier by being divided into portion~
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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 a granular nature. The employment of such mud is possible because the present process 1s 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 considere~d as preparation by-products which are very difficult to dispose if at all.
Various plants embo~ying the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a schematic view of a plant for the self-energising gasifLcation of bituminous coals 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 schematical view of a plant for the generation of synthetic gas by self-energising 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, Figure 9 is a view of a pump for the introduction of fuel or the extraction of ash, which is used in the plant shown in Figures 5 to 8, Figure 10 is a plan view of the pump shown in Figure 9, Figure 11 is a schematic view of a plant for the self-energising gasification of granular bituminous coal with oxygen and steam and employing a mixing head, Figure 12 is a side view of a pump for the introduction of fuel, and ~-Figure 13 is a plan view of the pump shown in Figure 12.
In the figures, the same refere~ce numerals relate to parts corresponding to each other. -~
-- Prepared bituminous coal, of granular size in the range 0 - 10 mm., is supplied at 2 to a bunker 1. From the bunker 19 a pump 3 pumps the fuel 4 in portions,~as described below, by displacing a portion of fuel, sealing it from the body of fuel 4, pressurising it and releasing it at 5 and 6 into a reactor 7~ By employing a combination of several, ..
preferably three? alternately driven pistons in the pump, and uniting the portions of ~uel in one conduit, an even flow of material is achieved. In the reactor ` there is a ~luid bed, shown schematically at 8, : , to which the gasifying agent is fed from below at 9. ~;
Steam together with air or oxygen serves as gasifying 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 a~ter an after-gasification. 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 i~
constructed similarly to the pump 3 and is descrlbed in greater detail below. Steam or oxygen with steam is fed in at 18 in order to cool off the ash. As .,. ~ . . .
the reactor 7 operates at considerably above atmospheric ~ --pressure, for example about 200 bar at gasification temperatures of 900 to 1200C., the ash which is divided into portions is first; released to atmospheric pressure with the aid o~ 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 othèr hand, the supply of the ; ~;~
gasification agent takes place through an annular -tuyère 9 which is arranged below the fluid bed 8 For this reason, the reactor 7 has a somewhat dif~erent shape. Whilst in the embodiment shown in Figure 1 the upper part ? is conically narrowed towards the bottom, in the case of the reactor 7 in the embodiment shown in Figure 29 it is a practically cylindrical pressure vessel with a lightly domed ;
top 15 below which thè exit pipe 17 for the generated gas is arranged. The lower part 11 of the reactor 7 1 5`
is conically reduced in size and ends in a relatively narrow sha~t 12 below which the pump 13 is arranged for the removal of the ash. Again, an annular conduit 18 for a branch o~ the stream of gasification agent is provided which serves to cool the ash before this is fed into the pump 13.
The pump 3 is a double piston pump having two parallel cylinders 20 and 21 as shown~in Figure 4. However a three cylinder pump could be used with ~ -advantage. In each of the cylinders there runs a fixed displacer piston 23, 24 respectively. The rear side of each piston is exposed to hydraulic pressure ~-means at 25 or 26, respectively. From the unpressurised bunker 1, the first piston 24 pushes a portion of fuel 27 into the cylinder 21. As can be seen in Figure 4, a rotary valve 28 associated with the cylinder 20 is ~irst of all closed, so that when the piston 23 moves into the position shown, the portionof 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 rotary through an angle of 90.
The bore 31 of the valve, which has the same diameter as the cylinder bore 32, is brought into alignment with the cylinder 21. As the same pressure prevails at either side of the the valves 28 and 30, the ; surface-loading of these valves 28 and 30 is very ~;
low. The same applies for the ensuing introduction of the portions of ~uel into the pressure chamber when the valves are opened, which takes place at very low piston speed.
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A blocking switch (not shown) only allows the return of the piston when the valve has been closed again (position of the valve 28 in Figure 4). -~ -During the filling and pressurising procedure of the piston 23, the second piston 24 delivers the corresponding portion of fuel into the pressure chamber. Thus slight dead periods 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 cylinder combinations of this kind being used, the dead periods can be prac~ically 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 i~ the pressure chamber is closed off ~rom the displacement pressure o~ the piston 23, which is produced by the position of the - valve 2~.
In the-embodiment shown in Figure 2, tar is fed, by way of a pipe 40 and a jet 41 above the ~
~luid 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
: ' . : ' ' the discrete portions of fuel from the source of the com-pression pressure 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.
According to a further aspect of the present invention, 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 con-veying fuel from the bunker to the reaction chamber by succ-essively compressing discrete portions of fuel by means of a ` ~`
source of compression pressure to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating the discrete portions of fuel from the source of the compression pressure 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 gasifi-cation 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 gasification carried out under over-pressure leads to an appreciable increase of the fuel throughput, as well as the methane content in the gas but, however, it ~ ~ 3 :
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does not have a detrimental effect on the conveying to and away o~ the materials because the pumping of the fuel not only makes the conventional supply gate arrangement super-fluous 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, respectively, and because the extraction of the ash is achieved for the same reasons without a conventional gate arrangement, even though a considerable over-pressure pre-vails in the reactor.
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 can be set at approximately 200 bar with gasification temperatures of approximately 900C.
to 1200C. 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 ..
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it is extracted. In an embodiment of -the process given as an example, the ash is cooled to about This cooling of the ash is most economically carried out by employing -the gasification agent. For this reason, one embodiment of the process is characterised in that for cooling -the ash at least one branch of the s-tream of gasification agent is employed.
In a further embodiment of the process, the freeing of the portion of fuel above the fluid bed takes place from above in the reaction chamber of the reactor. With ~uels with a large proportion of fine grain material, the introduction of a part of the gasi~ication agent can also take place from above, so as to reduce or prevent losses by non-converted small particles of material carried along by the producer gas. As, on selecting the temperature of gasification, the sinter point of the ash can be exceeded, an agglomeration of the particles of-slack takes place withi~ 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 ~rom above results in a partial countercurrent of the gas in the reaction chamber. Thus h-eat, 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 relati-rely ' ' 1 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 al.so applicable to processes for the self-energising pressure gasification of -~
solid fuels, preferably lumpy bituminous coal, with a gasification agent, for example steam, or carbon dioxide and 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 atmosphere in portions. Ihe fuel portion is brought under the zonal pressure prevailing in the reactor, and is ~ -fed continuously into the pressure chamber of the reactor, the ash produced during gasification being transferred to the exterior and brought to atmospheric pressure.
The fixed bed gasi~ication is known per se in several embodiments ( W0 Peters, Kohlevergasung, Verlag Gl~ckauf 1976, 6~, 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 ba~. 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 fed. This leads to difficulties in the regulation and control of the gasification process. Similar difficulties arise at the ash extraction gate.
Furt~ermore, 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.
Non-caking or only weakly caking bituminous coals serve as fuel. Generally, granulation fractions between about 6 and 30 mm. are used. Unolassified 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. ~peration of the ; 30 known reactors is also impeded by the relatively high tar and dust content of the crude gas. The invention enables simplification of the known process - : .
-~, .
. , ' ' , , ' " ' .
, by an improvement of the fuel feed and/or the ash extraction and 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. ;~ ~ -According to the invention, this is achieved in that the fuel and/or the ash are pumped, so that separated-off portions of fuel are displaced, compressed ~ --to the zonal pressure of the reactor and released into the pressure chamber, the displacement element of the pump is shut off from the zonal pressure in the reactor and is returned, and portions of ash are extracted by a displacer, released to atmospheric -~
pressure and removed.
By pumping the fuel, a continuous delivery of fuel into the reactor is achieved and thus an accurate quantification of th~ fuel is made possible ~-which,in turn, enables better control of the gasification process. However, the ~uel gate arrangement is 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 rea~tor pressure which until now hàs been considered~as the upper limit, the throughput of fuel and the qua1ity of the gasification or production gas is coneiderably 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 ex-traction of the ash from the reactor, then the exit gate arrangement which has so far been used is eliminated7 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 achived.
This simplification also applies to the fuel fed into the reactor. This consists, according to one embodiment of the invention, of a run-of-mine coal classified at 20 mm., with which the zonal pressure in the reactor at gasification temperatures of 900C. to 1200C. can be set at up to 200 bar.
In an embodiment of the invention, the supply of fuel is preheated to 300C. 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 750C.
and led 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 950C. The gasification agent and the recycled , - 8 - ~ ~`
-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 producer 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 are avoided. 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 producer 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 in~olved 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 suitable for gasification without complicating the operation o~ the reactor~
Furthermore, the invention is applicable to a process for the self-energising gasification o~
, 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 controlled quantity, where it is picked up by the gasification agent stream and blown into the -gasifier with a burner. These gasifications run at 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 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 monoxide could be used.
The process described in the introduction is known (W. Peters, Kohleverg~asung, Verlag Gl~ckauf 1976, 88, 97). The known process works so far 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 a controlled rate into the mixing head by a screw conveyor. The temperatures of gasification are relatively high at 1500 to 1900C. ;~
Synthetic gas is produced.
` The cost of producing usable coal from the coal which is delivered is a disadvantageous factor~
because the necessary milling is expensive and demands a considerable technical effort. Furthermore, the regulating and control expenses are considerable~
1 ~ :
:
. . .
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 ~uel, 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.
According to the invention this is made possible in that the fuel is pumped into the mixing -;~
head and divided into the required portions, which ~ -are pressurised by a displacement element, sealed off and fed into the reactor, a substantially continuous supply stream being produced by using a plurality of cylinders, preferably three.
The pumping in of the fuel can take place at pressures of up to 200 bar and has the advantage that a prescribed amount of fuel can be achieved even with considerably coarser granulation, for example up to about 2 mm. This size of granula-tion 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 inventlon is -that fine milling of the fuel can bs 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 because of the progressive mechanisation below ground contains enough fine coal below this grain size in any case. The process ~furthermore has the . : . . . : . . , advantage tha-t it permits a considerable over-pressure in the gasifier, because the portions of ~uel in front of the displacement element seal off to the outside, making special delivery gate arrangements and blow-back protection devices superfluous, which until now have had to be employed in order to avoid explosions, p~rticularly 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 the regulated amounts of fuel can be very accurately maintained and these quantities are easily controlled. 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 equilibrium 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 pressures 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 gasification chamber, the ashes resulting from the reaction are pumped out of the gasifier by being divided into portion~
.. .. . .
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 a granular nature. The employment of such mud is possible because the present process 1s 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 considere~d as preparation by-products which are very difficult to dispose if at all.
Various plants embo~ying the invention will now be described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a schematic view of a plant for the self-energising gasifLcation of bituminous coals 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 schematical view of a plant for the generation of synthetic gas by self-energising 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, Figure 9 is a view of a pump for the introduction of fuel or the extraction of ash, which is used in the plant shown in Figures 5 to 8, Figure 10 is a plan view of the pump shown in Figure 9, Figure 11 is a schematic view of a plant for the self-energising gasification of granular bituminous coal with oxygen and steam and employing a mixing head, Figure 12 is a side view of a pump for the introduction of fuel, and ~-Figure 13 is a plan view of the pump shown in Figure 12.
In the figures, the same refere~ce numerals relate to parts corresponding to each other. -~
-- Prepared bituminous coal, of granular size in the range 0 - 10 mm., is supplied at 2 to a bunker 1. From the bunker 19 a pump 3 pumps the fuel 4 in portions,~as described below, by displacing a portion of fuel, sealing it from the body of fuel 4, pressurising it and releasing it at 5 and 6 into a reactor 7~ By employing a combination of several, ..
preferably three? alternately driven pistons in the pump, and uniting the portions of ~uel in one conduit, an even flow of material is achieved. In the reactor ` there is a ~luid bed, shown schematically at 8, : , to which the gasifying agent is fed from below at 9. ~;
Steam together with air or oxygen serves as gasifying 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 a~ter an after-gasification. 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 i~
constructed similarly to the pump 3 and is descrlbed in greater detail below. Steam or oxygen with steam is fed in at 18 in order to cool off the ash. As .,. ~ . . .
the reactor 7 operates at considerably above atmospheric ~ --pressure, for example about 200 bar at gasification temperatures of 900 to 1200C., the ash which is divided into portions is first; released to atmospheric pressure with the aid o~ 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 othèr hand, the supply of the ; ~;~
gasification agent takes place through an annular -tuyère 9 which is arranged below the fluid bed 8 For this reason, the reactor 7 has a somewhat dif~erent shape. Whilst in the embodiment shown in Figure 1 the upper part ? is conically narrowed towards the bottom, in the case of the reactor 7 in the embodiment shown in Figure 29 it is a practically cylindrical pressure vessel with a lightly domed ;
top 15 below which thè exit pipe 17 for the generated gas is arranged. The lower part 11 of the reactor 7 1 5`
is conically reduced in size and ends in a relatively narrow sha~t 12 below which the pump 13 is arranged for the removal of the ash. Again, an annular conduit 18 for a branch o~ the stream of gasification agent is provided which serves to cool the ash before this is fed into the pump 13.
The pump 3 is a double piston pump having two parallel cylinders 20 and 21 as shown~in Figure 4. However a three cylinder pump could be used with ~ -advantage. In each of the cylinders there runs a fixed displacer piston 23, 24 respectively. The rear side of each piston is exposed to hydraulic pressure ~-means at 25 or 26, respectively. From the unpressurised bunker 1, the first piston 24 pushes a portion of fuel 27 into the cylinder 21. As can be seen in Figure 4, a rotary valve 28 associated with the cylinder 20 is ~irst of all closed, so that when the piston 23 moves into the position shown, the portionof 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 rotary through an angle of 90.
The bore 31 of the valve, which has the same diameter as the cylinder bore 32, is brought into alignment with the cylinder 21. As the same pressure prevails at either side of the the valves 28 and 30, the ; surface-loading of these valves 28 and 30 is very ~;
low. The same applies for the ensuing introduction of the portions of ~uel into the pressure chamber when the valves are opened, which takes place at very low piston speed.
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A blocking switch (not shown) only allows the return of the piston when the valve has been closed again (position of the valve 28 in Figure 4). -~ -During the filling and pressurising procedure of the piston 23, the second piston 24 delivers the corresponding portion of fuel into the pressure chamber. Thus slight dead periods 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 cylinder combinations of this kind being used, the dead periods can be prac~ically 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 i~ the pressure chamber is closed off ~rom the displacement pressure o~ the piston 23, which is produced by the position of the - valve 2~.
In the-embodiment shown in Figure 2, tar is fed, by way of a pipe 40 and a jet 41 above the ~
~luid 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 in the manner shown in Figures 3 and 4. Consequently, the valves -of the ash pump 13, which correspond tc the valvb~s~
28 and 30 o~ pump 3, are subject to atmospheric pressure on the delivery side~
The pump will now be described with referencs : . . , : , . .
- ~
b -to Figures 9 and 10 and the introduction of the fuel, although a sirnilar pump is also used for extracting the ash. ~;
This machine consists of two parallel pistons 151 and 152, the rear sides of which are acted upon by hydraulic pressure means at 153 and 154. The piston 151 pushes a fuel portion 155 taken from the hopper (not shown) into a sleeve 156 and compresses -it against a valve 156 which is closed. Pressure is 10 thereby built up behind the valve until the gasification pressure prevailing in the reactor is reached. Then the cylindrical valve 156 opens by rotating through an angle of about 90, whereby the condition is ~
reached represented by valve 157 which closes off `
15 ~ the sleeve 159, in which the piston 152 moves. As, in front of and behind the valve 157 the same pressure prevails, the driving and sliding surface-loadings of the valve are very low. The portion of fuel shown at 160 is introduced into the reactor. This takes 20 place at relatively low piston speed.
By rotating the valve 157 into the position of the ~alve 156, the displacer piston 152 is shut ;
off from the pressure in the reac*or, so that the piston can now return. Simple blocking switches - ;~
(not shown) only permit the return of the pistons 151 or 152 when valves 156 or 157, réspectively, have :
closed again. During the filling and compressing process of one piston, the other piston is feeding fuel, so that only slight dead periods occur with the reciprocal closing and opening of the valves 156 and 157. By the addition of a third displacer piston (not shown) such dead periods can in practice be f~
completely eliminated.
In the embodiment shown in Figure 5, a ~ ;
fuel storage bunker 103 is placed before the actual gasification plant; coal is supplied to the bunker ;~
at 101 and is held in readiness in the bunker at 102. ~ -Coal is supplled by a pump 104 from the store at 102; ~ ;
the piston of this pump is schematically shown at 105.
The fuel is supplied in the direction of the arrow 106 through an inlet conduit 108 in the roof 107 of the pressure chamber 109 of a reactor which is generally marked 100. In the reaction chamber 109 there prevails a pressure of, for example, 200 bar. Gasification agent is supplied to the pressure chamber 109 in the direction of the arrow 110 through the inlet conduit 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, as indicated by the arrow 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 or gasification of the introduced fuel takes place, so that here the necessary reaction is commenced. The non-converted larger particlesof fuel build up on the fixed bed 11Z above the grate 113. The gasification zone is formed in the upper part of the fixed bed, whilst the lower part forms the combustion zone`. me particles of fuel in the fixed bed 11,2 react with the gasification agent introduced at 114. The relatively cold gasification -; agent acts simultaneously as a cooling agent for 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 reco~Ter the heat generated.
The grate 113 is designed so that it can be rotated.t 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 i~ Figure 6, the reactor is designated 126. It is divided by a false bottom 123 having an opening 124, into a lower part 122, which forms the reaction chamber9 and an upper part 125. The coal is introduced into the` upper part 125 of the reactor 126 at 127 by means of a pump which is not shown but corresponds to the pum~p ;~
104. Producer gas is introduced by w~y of~a pipe ~-128 leading from the lower part 122 of the reactor 126 ? where it is drawn off by way o:E 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 scrrubber 133 which is only shown schematically and from which the gas is recycled by way of the pipe 128 into the chamber 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 at 128 into the upper section 125 of the reaction chamber, a low temperature hydrogenation reaction takes place with the fuel which has been introduced at 127. This forms a producer gas having a high methane content, which can be drawn off at 138. If necessary, this producer gas may be subjec~ed to a gas scrubbing process before it is used further.
Simultaneously, gasification agents, namely oxygen or air and steam or ca;rbon dioxide, are added at 139 with the fuel which is introduced~
Accumulated ~uel in a hopper 1~0 formed in the false bottom 123 passes through the opening 124 on to the fixed bed on the grate 135 which lies below.
Corresponding to the natural cone of poured fuel which is 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~in the ` direction of the arrow 106, to which burner 108 the gasification agent, namely steam or~carbon , ~$~
dioxide and oxygen or air is also fed, in the direction of the arrow 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 surface of the grate in an optimum manner. As schematically shown at 121, the ash is extracted by a pump corresponding to the pump 104. The producer gas is drawn off along a conduit situated in the upper part 119 of the reactor 110, in the direction of the arrow 118.
Also in Figure 8 the reference numerals relate to corresponding parts in Figures 5 and 7.
Accordingly, the fuel is led from the supply 102 by the pump 104 along the pipe 106 and the fuel and gasification agent inlet conduit 108 in the upper part 119 of the reactor 110, to which the gasification agent, namely steam or carbon dioxide and oxygen or air, are added at 111. In the upper part of the pressure chamber 109 a partial gasification takes place.
The gas which is thus produced, together with the remaining gasification agent and ~uel, travels into the lower part o~ the reactor -~owards the fixed bed 112 of the grate 113, where the fuel accumulates.
Gasification agent as well as the produced gas passes downwardly through the fixed bed 112. Thus complete conversion of the still available fuel occurs. The gas is drawn off by way of the withdrawal conduit 117, situated below the grate 113 and the fixed bed 112, 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 o~ 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.
With reference to~Figures 12 and 13 the fuel introduction pump is explained although, with a plant working with a mixing head, such a pump can also be used for removing the ashes.
As shown, this machine co~sists of two parallel pistons 251 and 252, the rear sides of which are acted upon b~ hydraulic pressure means at 253 and 254, respectively. The piston 251 pushes the portion f fuel 255 which has been removed from the hopper not shown in Figures 2 and 3, into a sleeve 258 and compresses it against a rotary valve 256 which is closed.
In this way, pressure is built up in front of the piston until the gasification pressure prevailing in the reactor is attained. Then the cylindrically shaped valve 256 opens by rotation through an angle of about 90, whereby the condition represented by the valve 257 is reached, in which the sleeve 259 is closed off by the piston 252. As the same pressure prevails in front of and behind the valve 257, the driving and sliding surface-loadings of the valve are very low. The portion of fuel shown at 260 is introduced at relatively low forward piston speed.
By rotating the valve 257 into the position shown for the valve 256, the displacer piston 252 is isolated from the pressure in the zone of the reactor into which the fuel is introduced. The displacer - ' ;~
: . ~
piston can now return. Simple blocking switches ~ -permit the return of the displacer piston 251 or 252 only when valve 256 or 257, respectlvely, has been closed.
During the filling and compressing process of one piston, the other piston is feeding fuel, so that only slight dead periods occur with the reciprical closing and opening of the valves 256 and 257. By the addition of a third displacer piston (not shown) such dead periods can in practice be completely eliminated.
In the plant shown in Figure 11, classified ~ ;
coal with an upper grain size limit of about 2 mm.
is loaded in the direction of the arrow 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, as described above, in the direction of the arrow `~
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 gasifying agent, for example oxygen and steam, which is fed in the direction of the arrow 208, and is blown into the burner at 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 operation of the pump and on the other hand control .
the feed rate of gasifying agent are not shown in ?
the drawing. However, the gasifying process can be regulated by controlling gasifying agent feed .
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rate in relation to the fuel feed rate. Most of the fuel gasifies in the upper part of the reaction chamber 211. Synthetic gas is thereby generated and is drawn off by way of a conduit at 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 ba-th 215 from which the granulated ash can be drawn off at 216.
The gasifier 209 is provided with a fireproof brick lining~217.
A further pump corresponding to the pump 204 can be utilised for pumping off the ash.
What we claim is:-., ',::
28 and 30 o~ pump 3, are subject to atmospheric pressure on the delivery side~
The pump will now be described with referencs : . . , : , . .
- ~
b -to Figures 9 and 10 and the introduction of the fuel, although a sirnilar pump is also used for extracting the ash. ~;
This machine consists of two parallel pistons 151 and 152, the rear sides of which are acted upon by hydraulic pressure means at 153 and 154. The piston 151 pushes a fuel portion 155 taken from the hopper (not shown) into a sleeve 156 and compresses -it against a valve 156 which is closed. Pressure is 10 thereby built up behind the valve until the gasification pressure prevailing in the reactor is reached. Then the cylindrical valve 156 opens by rotating through an angle of about 90, whereby the condition is ~
reached represented by valve 157 which closes off `
15 ~ the sleeve 159, in which the piston 152 moves. As, in front of and behind the valve 157 the same pressure prevails, the driving and sliding surface-loadings of the valve are very low. The portion of fuel shown at 160 is introduced into the reactor. This takes 20 place at relatively low piston speed.
By rotating the valve 157 into the position of the ~alve 156, the displacer piston 152 is shut ;
off from the pressure in the reac*or, so that the piston can now return. Simple blocking switches - ;~
(not shown) only permit the return of the pistons 151 or 152 when valves 156 or 157, réspectively, have :
closed again. During the filling and compressing process of one piston, the other piston is feeding fuel, so that only slight dead periods occur with the reciprocal closing and opening of the valves 156 and 157. By the addition of a third displacer piston (not shown) such dead periods can in practice be f~
completely eliminated.
In the embodiment shown in Figure 5, a ~ ;
fuel storage bunker 103 is placed before the actual gasification plant; coal is supplied to the bunker ;~
at 101 and is held in readiness in the bunker at 102. ~ -Coal is supplled by a pump 104 from the store at 102; ~ ;
the piston of this pump is schematically shown at 105.
The fuel is supplied in the direction of the arrow 106 through an inlet conduit 108 in the roof 107 of the pressure chamber 109 of a reactor which is generally marked 100. In the reaction chamber 109 there prevails a pressure of, for example, 200 bar. Gasification agent is supplied to the pressure chamber 109 in the direction of the arrow 110 through the inlet conduit 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, as indicated by the arrow 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 or gasification of the introduced fuel takes place, so that here the necessary reaction is commenced. The non-converted larger particlesof fuel build up on the fixed bed 11Z above the grate 113. The gasification zone is formed in the upper part of the fixed bed, whilst the lower part forms the combustion zone`. me particles of fuel in the fixed bed 11,2 react with the gasification agent introduced at 114. The relatively cold gasification -; agent acts simultaneously as a cooling agent for 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 reco~Ter the heat generated.
The grate 113 is designed so that it can be rotated.t 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 i~ Figure 6, the reactor is designated 126. It is divided by a false bottom 123 having an opening 124, into a lower part 122, which forms the reaction chamber9 and an upper part 125. The coal is introduced into the` upper part 125 of the reactor 126 at 127 by means of a pump which is not shown but corresponds to the pum~p ;~
104. Producer gas is introduced by w~y of~a pipe ~-128 leading from the lower part 122 of the reactor 126 ? where it is drawn off by way o:E 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 scrrubber 133 which is only shown schematically and from which the gas is recycled by way of the pipe 128 into the chamber 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 at 128 into the upper section 125 of the reaction chamber, a low temperature hydrogenation reaction takes place with the fuel which has been introduced at 127. This forms a producer gas having a high methane content, which can be drawn off at 138. If necessary, this producer gas may be subjec~ed to a gas scrubbing process before it is used further.
Simultaneously, gasification agents, namely oxygen or air and steam or ca;rbon dioxide, are added at 139 with the fuel which is introduced~
Accumulated ~uel in a hopper 1~0 formed in the false bottom 123 passes through the opening 124 on to the fixed bed on the grate 135 which lies below.
Corresponding to the natural cone of poured fuel which is 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~in the ` direction of the arrow 106, to which burner 108 the gasification agent, namely steam or~carbon , ~$~
dioxide and oxygen or air is also fed, in the direction of the arrow 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 surface of the grate in an optimum manner. As schematically shown at 121, the ash is extracted by a pump corresponding to the pump 104. The producer gas is drawn off along a conduit situated in the upper part 119 of the reactor 110, in the direction of the arrow 118.
Also in Figure 8 the reference numerals relate to corresponding parts in Figures 5 and 7.
Accordingly, the fuel is led from the supply 102 by the pump 104 along the pipe 106 and the fuel and gasification agent inlet conduit 108 in the upper part 119 of the reactor 110, to which the gasification agent, namely steam or carbon dioxide and oxygen or air, are added at 111. In the upper part of the pressure chamber 109 a partial gasification takes place.
The gas which is thus produced, together with the remaining gasification agent and ~uel, travels into the lower part o~ the reactor -~owards the fixed bed 112 of the grate 113, where the fuel accumulates.
Gasification agent as well as the produced gas passes downwardly through the fixed bed 112. Thus complete conversion of the still available fuel occurs. The gas is drawn off by way of the withdrawal conduit 117, situated below the grate 113 and the fixed bed 112, 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 o~ 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.
With reference to~Figures 12 and 13 the fuel introduction pump is explained although, with a plant working with a mixing head, such a pump can also be used for removing the ashes.
As shown, this machine co~sists of two parallel pistons 251 and 252, the rear sides of which are acted upon b~ hydraulic pressure means at 253 and 254, respectively. The piston 251 pushes the portion f fuel 255 which has been removed from the hopper not shown in Figures 2 and 3, into a sleeve 258 and compresses it against a rotary valve 256 which is closed.
In this way, pressure is built up in front of the piston until the gasification pressure prevailing in the reactor is attained. Then the cylindrically shaped valve 256 opens by rotation through an angle of about 90, whereby the condition represented by the valve 257 is reached, in which the sleeve 259 is closed off by the piston 252. As the same pressure prevails in front of and behind the valve 257, the driving and sliding surface-loadings of the valve are very low. The portion of fuel shown at 260 is introduced at relatively low forward piston speed.
By rotating the valve 257 into the position shown for the valve 256, the displacer piston 252 is isolated from the pressure in the zone of the reactor into which the fuel is introduced. The displacer - ' ;~
: . ~
piston can now return. Simple blocking switches ~ -permit the return of the displacer piston 251 or 252 only when valve 256 or 257, respectlvely, has been closed.
During the filling and compressing process of one piston, the other piston is feeding fuel, so that only slight dead periods occur with the reciprical closing and opening of the valves 256 and 257. By the addition of a third displacer piston (not shown) such dead periods can in practice be completely eliminated.
In the plant shown in Figure 11, classified ~ ;
coal with an upper grain size limit of about 2 mm.
is loaded in the direction of the arrow 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, as described above, in the direction of the arrow `~
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 gasifying agent, for example oxygen and steam, which is fed in the direction of the arrow 208, and is blown into the burner at 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 operation of the pump and on the other hand control .
the feed rate of gasifying agent are not shown in ?
the drawing. However, the gasifying process can be regulated by controlling gasifying 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 is thereby generated and is drawn off by way of a conduit at 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 ba-th 215 from which the granulated ash can be drawn off at 216.
The gasifier 209 is provided with a fireproof brick lining~217.
A further pump corresponding to the pump 204 can be utilised for pumping off the ash.
What we claim is:-., ',::
Claims (50)
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 compressing discrete portions of fuel by means of a source of compression pressure to substantially equal to the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating the discrete portions of fuel from the source of the compression pressure and introducing the compressed portions of fuel into the reaction chamber without subjecting the reaction chamber to a pressure substantially below that of the gasifi-cation 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.
2. A process according to Claim 1 wherein the source of compression pressure is a pump.
3. A process according to Claim 1 wherein the ash removal is achieved by pumping.
4. A process according to Claim 2 wherein the ash removal is achieved by pumping.
5. 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.
6. A process according to Claim 1 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 1200°C.
to 1200°C.
7. A process according to Claim 3 wherein the ash is cooled off before it is pumped.
8. A process according to Claim 7 wherein the ash is cooled off to about 200°C.
9. A process according to Claim 7 or 8 wherein the gasification agent is used for cooling the ash.
10. A process according to Claim 1 wherein the reaction chamber is a fluid bed reaction chamber.
11. A process according to Claim 10 wherein the fuel is bituminous coal, and the gasification agent is a mixture of (i) steam or carbon dioxide and (ii) oxygen or air.
12. A process according to Claim 10 wherein the portions of fuel are introduced into the upper part of the reaction chamber from above the fluid bed.
13. A process according to Claim 12 wherein, with fuel containing a high proportion of fine material, part of the gasification agent is also fed into the reaction chamber from above.
14. A process according to Claim 10 or 11 wherein the portions of fuel are introduced directly into the fluid bed.
15. A process according to Claim 10, 11 or 12 wherein tar and/or similar material is introduced into the reaction chamber above the fluid bed.
16. A process according to Claim 1 wherein the raction chamber is a fixed bed reaction chamber.
17. A process according to Claim 16 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.
18. A process according to Claim 16 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 300°C.
19. A process according to Claim 16 wherein the fuel is fed from above into the reaction chamber, and gasifi-cation gas is recycled from a lower section of the reaction chamber into an upper section of the reaction chamber, from which the gasification gas is drawn off as producer gas.
20. A process according to Claim 19 wherein gasification gas which has been drawn off from the lower section of the reaction chamber is cooled, subsequently com-pressed, reheated to about 750°C, and only then recycled into the upper part of the reaction chamber.
21. A process according to Claim 16 wherein the fuel is supplemented by additives.
22. A process according to Claim 16, 17 or 18 wherein the fuel is introduced from below through the fixed bed into the reaction chamber by means of a cooled burner.
23. A process according to Claim 16 or 17 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.
24. A Process according to Claim 16 or 17 wherein the fuel and a part of the gasification agent are introduced into the reaction chamber from above, and the remaining gasifi-cation agent is fed through a grate, whilst the producer gas is led off from above the grate.
25. A process according to Claim 1 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.
26. A process according to Claim 25 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.
27. A process according to Claim 25 wherein the fuel is prepared by breaking or classifying, and the prepared fuel is bunkered undried under atmospheric pressure.
28. A process according to Claim 25, 26 or 27 wherein an unprepared settlement or filter mud is employed as fuel.
29. 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 by means of a source of compression pressure to substantially the pressure of the gasification zone whilst isolating these portions from the gasification zone in pressure-tight manner, isolating the discrete portions of fuel from the source of the compression pressure and introducing the compressed portions of fuel into the reaction chamber without subjecting the re-action 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.
30. A plant according to Claim 29 wherein said source of compression pressure is a pump.
31. A plant according to Claim 29 wherein said ash removal means incorporates a pump.
32. A plant according to Claim 31 wherein said fuel supply means incorporates a pump.
33. A plant according to Claim 30 wherein said pump comprises one or more pistons for compressing the portions of fuel, and one or more outlet valves for introducing the compressed portions of fuel into the reaction chamber.
34. A plant according to Claim 29 wherein the reaction chamber comprises a lower part having the shape of a truncated cone.
35. A plant according to Claim 29 wherein the reaction chamber is a fluid bed reaction chamber.
36. A plant according to Claim 35 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.
37. A plant according to Claim 35 wherein a cooled lance is provided for carrying the fuel to the fluid bed.
38. A plant according to Claim 35 wherein one or more nozzles are arranged in the fluid bed and serve for the introduction of the portions of fuel.
39. A plant according to Claim 35, 36 or 37 wherein a tar feed is provided above the fluid bed.
40. A plant according to Claim 29 wherein the reaction chamber is a fixed bed reaction chamber.
41. A plant according to Claim 40 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.
42. A plant according to Claim 40 or 41 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.
43. A plant according to Claim 41 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 non-converted fuel in the upper part of the reaction chamber to a grate arranged in the lower part of the reaction chamber.
44. A plant according to Claim 43 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.
45. A plant according to Claim 40 or 41 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.
46. A plant according to Claim 40 including a burner for introducing the fuel and gasification agent into the tip of a truncated conical grate for the fixed bed.
47. A plant according to Claim 29 wherein a mixing head is provided for delivering fuel entrained by a stream of gasification agent to a burner.
48. A plant according to Claim 47 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.
49. A plant according to Claim 47 wherein the mixing head and the burner are arranged in a truncated conical upper section of the reaction chamber.
50. A plant according to Claim 47, 48 or 49 wherein an ash granulated bath with an ash extraction device is provided below the reaction chamber.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,449A CA1114179A (en) | 1978-01-06 | 1978-01-06 | Process and apparatus for the self-energising gasification of solid fuels |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA294,449A CA1114179A (en) | 1978-01-06 | 1978-01-06 | Process and apparatus for the self-energising gasification of solid fuels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1114179A true CA1114179A (en) | 1981-12-15 |
Family
ID=4110466
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA294,449A Expired CA1114179A (en) | 1978-01-06 | 1978-01-06 | Process and apparatus for the self-energising gasification of solid fuels |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1114179A (en) |
-
1978
- 1978-01-06 CA CA294,449A patent/CA1114179A/en not_active Expired
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