A METHOD AND A DEVICE FOR PRODUCING FUELS

Abstract: A method for producing fuels based on solid carbonaceous natural fuels which are particularly suited for non-polluting thermal power generation with gas and steam turbines in a combined cycle which is characterized in that the flow of finely-divided natural fuel is pyrolyzed at superatmospheric pressure, suitably 5 to 20 bar, and >700 DEG C in a cascade of a number of reactors, preferably >3 reactors, and in that the pyrolysis gas is reformed, preferably in the presence of burnt lime and/or dolomite for desulphuration, is brought into fluidizing contact with the char recirculated from the last reactor in said cascade, with a flow which is >5 times larger than the flow of fuel, the fluidizing contact between the pyrogas formed and the char being continued in the following reactors and the temperature in said reactors preferably being maintained at a level higher than in said first reactor, whereas the temperature in the last reactor in said cascade is suitably maintained at a lower level than in said first reactor, whereas produced "reformed gas" and netto char withdrawn from said last reactor after separation are preferably used as fuel in a combined cycle, whereas the recirculating char withdrawn from said last reactor is after a suitable temperature increase by partial combustion with oxygen containing gas recirculated to said first reactor in said cascade. A device for carrying out said method.

Description: A METHOD AND A DEVICE FOR PRODUCING FUELS In thermo-electric power generation processes the old, established steam turbine cycle is increasingly substituted with a combined cycle comprising gas as well as steam turbine. In this way power generation can be performed with higher efficiency and 45-47% can be reached compared with 39-41% in the steam turbine cycle. Said high efficiency of the combined cycle is, however, obtained only when using natural gas as fuel, and for solid natural fuels, such as coal and bio (biological) fuels the efficiency is restricted to 42-44% because of the complications caused by transforming the fuel to a form which is acceptable for the gas turbine. A number or processes, such as pressure (super-atmospheric) combustion, complete and partial gasification, etc. have been developed for making possible the use of solid natural fuels in connection with a combined cycle. All said processes are characterized by a high level of complexity and are therefore subjected to operation disturbances in a more than normal degree. This fact and the moderate efficiency of 42-44% have caused that said processes have not been commonly accepted. The present invention is directed to an uncomplicated method for transforming solid natural fuels, such as coal, prefer- ably with 5-45% of volatile constituents, lignites, peat and bio fuels, to a form which is suited for a combined cycle, wherein the end product of said method is pressurized clean hot combustable gas with a high heat value, "reformed gas", suited for the gas turbine, and finely-divided hot char with a high heat value, which is suitable as a fuel for all types of steam generators. Char is here intended to be interpreted as the coke-like residue comprising low levels of H, O, N and S, which remains after pyrolysis of solid carbonaceous fuels. The method according to this invention is characterized by transforming the solid natural fuel to a form suited for the combined cycle by pyrolysis in combination with reformation of the pyro gas in the presence of water vapour, wherein the flow of finely-divided fuel at super-atmospheric pressure, suitably 5-20 bars, and >700°C in a first reactor in a cascade of reactors, suitably ≥3, in the presence of finely- divided burnt lime and/or dolomite (when "lime" is used in the following in the specification said expression comprises also dolomite) for desulphurization, is brought into fluid¬ izing contact with char recirculated from the last reactor in said cascade with a flow >5 times larger than the flow of fuel, whereafter fluidizing contact between formed pyro gas and char is continued in the subsequent reactors and the temperature in said reactors is suitably maintained at a higher level than in said first reactor, whereas the tempera¬ ture in the last reactor in said cascade is suitably main¬ tained at a lower level than in said first reactor, where¬ after produced pyro gas and net char are separated, and recirculated char discharged from said last reactor, after adapted temperature increase by partial combustion with oxygen containing gas, is recirculated to said first reactor, the pyrolysis reactor, in said cascade. According to the invention the fluidizing contact between the gas and the char in all the reactors in said cascade is suitably performed in a fluidized bed of classical type, i.e. with the relative void volume € in the fluidized bed main¬ tained within the range 0.4<€<0.8. For achieving a good contact and rapid pyrolysis the dried natural fuel is finely- divided prior to the pyrolysis so that suitably 50% thereof has a particle size <150 μm and 90% <250 μm. The contact of the finely-divided natural fuel and the recirculating char with adapted temperature is performed by blowing the fuel with the aid of inert gas, suitably N (when N2 is stated to be the fluidizing gas in the following, said gas can also be substituted with another inert gas) against the surface of the fluidized char bed in the first reactor in said cascade, wherein said char bed is "minifluidized" with inert gas, suitably N2, supplied to the bottom zone of said fluidized bed through distribution means for fluidizing gas arranged there. "Minifluidizing" should be understood as fluidizing with a gas speed in the range u^ < u ≤5 u m f, where u mf = the minifluidizing speed according to the standard definition. When brought into contact with the "minifluidized" char bed with a temperature of >700°C, suitably 800-900°C, the finely- divided fuel is pyrolyzed very rapidly and >90% of its con¬ tent of volatile constituents are stripped within <1 second. The pyrolysis products consist of tar vapours (tar fumes), vapours (fumes) of light oils, steam and non-condensable gases such as CO, H2, CH4, C2H4, etc. Depending upon the content of oxygen in the natural fuel the pyro gas contains more or less of autogenous steam. For natural fuels with a high oxygen content the quantity of steam formed in the pyrolysis is sufficient for the reforming process, but for fuels with a low oxygen content compensation of the shortage by addition of externally produced steam is required. Reforming of the pyrolysis products is according to the invention achieved by bringing said products into a continued fluidized contact with the catalytically very active char for an adapted period of time and at an adapted temperature in the subsequent reactors in said cascade. Thus, char and pyro gas are transferred in the form of a suspension to the second reactor in said cascade, where the fluidized contact is continued in a fluidized bed of classical type which, however, in this case is "mini- fluidized", suitably with N2 with a small added amount of oxygen containing gas. The combustion reactions taking place hereby with mainly CO as the final product cover the heat demand in the endothermal reforming reactions in said second reactor. In the following reactors in the cascade the fluidizing contact between the reformed pyro gas and char is according to the invention repeated, wherein the bed temperature is suitably increased from one reactor to the following one. The reformed gas, which leaves the last but one reactor in said cascade in a suspension with char, consists essentially of CO, H2 and N2 and the suspension is fed to the last reactor where "minifluidizing" is performed with Ν2 with an adapted addition of steam. Said steam reacts with the char forming CO and H2 which causes a decrease of the temperature, suitably to about 800°C, since the reaction is endothermic. The decrease of the bed temperature in the last reactor in the cascade causes the small remaining amount of tar vapours which optionally may be present in the reformed gas from the last but one reactor to condense on the char and thereby to be made harmless for the filtering process which according to this invention is used for separating the fine-grained frac¬ tion of the suspension of net char and reformed gas, which is discharged from the last reactor of said cascade. The coarse fraction is suitably first separated in a hot cyclone prior to the filtering process. Furthermore, from the bottom zone of the last reactor in the cascade there is a separate discharge of the char which is recirculated to the first reactor (the pyrolysis reactor) after increasing the temperature of said char to the pyro¬ lysis temperature by partial combustion with oxygen contain¬ ing gas. Said partial combustion of the recirculating char is accord¬ ing to this invention preferably performed under fluidizing transportation to a hot cyclone arranged at a suitable level, in which hot cyclone the char is separated. After adjustment of the temperature of said combustion gas to 1000-1200°C by burning a part of the CO content of said gas with oxygen containing gas, said combustion gas is used for calcination to burnt lime of a flow of finely-divided lime which flow is adapted to the S content of said fuel. The char separated in said hot cyclone is mixed with the burnt lime and the mixture is fed into the fluidized bed in said first reactor in said cascade. In the pyrolysis of the fuel therein about half of the S content of the fuel is transformed into H2S which is bonded as CaS by the burnt lime present. The rest of the S content of the fuel is present in bonded state in the net char which is separated from the suspension of reformed gas and char which is discharged from the upper part of the last reactor in said cascade. The remaining sulphur in the net char is set free as SO2 when burning the char in connection with the use thereof for generating steam. SO2 is thereby bonded as CaSO^ provided that the addition of CaO is correctly adapted to the recirculating char. By adding burnt lime to the recirculating char in a flow corresponding to a molar ratio Ca/S = 1.5-3.0, where S = the content of S in the fuel flow, >90% of the S content of the fuel can be neutral¬ ized. Calcining of the finely-divided lime stone is according to this invention suitably performed in a fluidized bed of venturi type which is directly connected to the hot cyclone in which the recirculating char is separated from the temperature adjusted transportation gas. The separation of the burnt lime (quick lime) in the suspension from the venturi bed is performed in a hot cyclone, from which the gas is fed to the last but one reactor in the cascade, whereby the content of not combusted CO and the heat content are recovered. The content of carbon dioxide in the gas will then also participate in the cooling of the bed material in the last reactor by reduction of a part of the carbon dioxide to CO, which is a highly endothermal reaction. When using the net char for generating steam in an ACFB ("atmospheric circulating fluidized bed") a substantial advantage is achieved with the method according to this invention with regard to the content of CaS in the char. The presence thereof in the primary air zone in the ACFB steam generator thus causes decomposition of >.70% of 2O formed therein which is derived from bonded nitrogen in fuel. The decomposition proceeds to N2 and can be illustrated with the following formulas: ΔG kcal N 2 0 + 1/5 CaS + 1/5 C = 1/5 CaS0 4 + 1/5 CO + N 2 -71.1 N 2 0 + 1/5 CaS + 1/5 CO = 1/5 CaS0 4 + 1/5 C0 2 + N 2 -83.5 N 2 0 + 1/4 CaS = 1/4 CaS0 4 + N 2 -74.5 It may be observed that the thermodynamic "driving power" (ΔG) for all reactions is high and about the same under reducing as well as neutral conditions. This means that the lower part of the combustion shaft of the CFB steam gener¬ ator, at the bottom of which the primary air or about 1/2 of the flow of combustion air and the char together with CaS from the last reactor in the cascade are introduced, exhibits ideal conditions for decomposition of the nitrous oxide. Reduction of N2O is highly desirable since nitrous oxide, contrary to NO and N0 2 , is able to penetrate into the stratosphere where it decomposes under the influence of sunlight and forms free oxygen radicals which, in turn, cause decomposition of the ozon layer. The suspension of reformed gas and net char discharged from the last reactor in the cascade has a temperature of about 800 C C. The main part of the char contained by said suspension is separated in a hot cyclone with simultaneous cooling to <600 β C by mixing the suspension prior to the cyclone with an adapted flow of wet steam and/or finely distributed water. Cooling is suitable for condensing vapours of optional alkali chlorides in the reformed gas, which could damage the gas turbine when using the gas as a gas turbine fuel. The reformed gas leaving the hot cyclone and containing the finest char fraction is thereafter filtered in hot filters of ceramic type, and the separated fine fraction is combined with the char separated in the hot cyclone. The char material obtained is a highly efficient fuel in all types of pressur¬ ized (super-atmospheric) as well as atmospheric steam generators. With the aid of the method according to this invention >50% of a solid carbonaceous fuel may in the way described above be transformed to a hot clean pressurized gas with a high heat value, which is directly suited as a gas turbine fuel, and hot fine-grained char, which is directly suited as a fuel in all types of steam generators. Such of the ACFB type are preferred since it is thereby possible to achieve a highly environmental-friendly (non-polluting) combined power gener¬ ation with high efficiency and low emissions of SO2 as well as NO and N 2 0. For additional illustration of the invention an embodiment thereof is described with reference to Fig. 1 and based on a bituminous coal with 50% of volatiles and the analysis, etc. stated below: % C H 0 N S ash 62.1 5.8 25.3 1.2 0.8 4.8 raw coal, water content = 10% dry coal, heat value = 6190 kcal/kg waf The fluidizing contact between the gas and the char in this embodiment takes place in a cascade of five reactors of a classical fluid bed type (l)-(5) which are arranged verti¬ cally directly below each other. The first reactor (1), the pyrolysis reactor, comprises an annular fluid bed chamber (12) with a centrally arranged overflow shaft (13). Recirculated char (14) with an adapted addition of burnt lime (15) and a temperature adjusted to 900°C is supplied to the fluid bed chamber (12) in the tangential direction and parallel to the bottom (16) thereof, said char flow being adapted so that it is, based on the weight, 10 x larger than the flow of coal dust (17) which in suspension with N2 is supplied to the fluid bed surface (18) from the distribution device (8) through an adapted number of evenly distributed injection tubes (19). The fluidized bed in the annular chamber (12) is "minifluidized" with N2 (20), which is supplied to the distribution means (21) through the annular channels (22), making possible different fluidizing gas flows in various bottom zones. The method of supplying the recirculating char (14) and the "minifluidizing gas" (21) makes it possible to bring the fluid in the annular chamber (12) to macro-rotate in the horizontal as well as vertical directions and thereby to perform a spiral (helical) movement in the annular chamber (12) around the central outlet shaft (13). A larger "mini¬ fluidizing gas flow" in the bottom zone close to the outlet shaft (13) causes the fluidized bed material to flow down¬ wards in the outer zone of the annular chamber (12) and upwards in its inner zone, from which the bed material over¬ flows to the outlet shaft (13). The injection tubes (19) for the coal dust, which extend up through the bottom of the distribution device (8), which is shaped as an annular classical N2 fluidized fluid bed, in which the injection tubes (19) act as overflows, end in the reactor (1) above the outer zone of the fluid bed surface (18) where the macro-movement of the bed material is directed downwards. The coal dust in the suspension with N2 blows downwards through the injection tubes (19) and hits the fluid bed surface (18) and is rapidly mixed into the char fluid bed, whereby very quick heating and pyrolysis is achieved. Produced pyro gas and char which overflow to the outlet shaft (13) form there together a suspension which is blown down through the shaft. The reactor (2) is connected directly under the reactor (1), and the outlet shaft (13) thereof ends close to the bottom of the reactor (2). The reactor (2) as well as the reactor (1) are provided with distributing means for "minifluidizing gas" which, however, in this case consists of N2 with an adapted minor addition of air. The char fluid bed in the reactor (2) is maintained at an adapted depth with regard to the desired dwell time of the char therein with the aid of a suitable number of evenly distributed overflow outlet tubes (23) which discharge close to the bottom of the reactor (3). The suspension of pyro gas and char blowing down through the outlet shaft (13) bubbles up like a plume therearound with violent mixing of the fluid bed material (char) in the reactor (2), whereby a desired fluidizing contact between the catalytically active char and the pyro gas from the reactor (1) is obtained. Thereby reforming of the pyro gas to "reformed gas" is obtained comprising an increase of the content of CO and H 2 in the gas with a reduction of the content of tar vapours, vapours of light oils and water therein. In order to achieve an even distribution around the periphery of the outlet shaft (13) of the pyro gas-char suspension flowing out into the fluid bed of the reactor (2), the wall of the shaft (13) is suitably provided with a number of slots (24). Such slots have proved to be beneficial also in the inlet end of the outlet shaft and around the inlet and outlet ends of the overflow outlet tubes (23). The char-"reformed gas" suspension blowing down through the overflow outlet tubes (23) to the bottom zone of the reactor (3) directly connected under the reactor (2) bubbles up in the shape of plumes through the fluid bed of catalytically active char in the reactor (3), whereby stripping, pyrolysis and reforming of optional remnants of volatile substances in the char is achieved. For promoting said reactions in the reactor (3) the fluid bed therein is "minifluidized" with N2 + an adapted minor flow of air, whereby the temperature is increased by partial combustion, suitably to >30°C. In the reactor (4) which is connected directly below the reactor (3) the procedure from the reactor (3) is repeated and the temperature in the fluid bed in the reactor (4) is increased, suitably with >30°C, by adding a small air flow to the N2 which is supplied as a "minifluidizing gas". Suitably the temperature increase in the reactors (2), (3) and (4) is adjusted so that the temperature in the reactor (4) can be maintained at about 1000°C. The suspension of reformed gas and char which blows down through the overflow outlet tubes in the reactor (4) bubbles up through the fluid bed in the reactor (5). Said reactor is "minifluidized" with N2 with an adjusted addition of water vapour which causes a reduction of the bed temperature, suitably to about 800 C C, by endothermal reduction of water vapour with char with the formation of CO and H2. From the last reactor (5) of said cascade recirculating char is discharged (26) from the bottom zone in a flow which, based on the weight, is 10 x larger than the flow of coal (17). With the aid of preheated, optionally oxygen enriched air (27) the char is transported (28), with simultaneous partial combustion and temperature increase to the pyrolysis temperature (900°C), to the hot cyclone (9) where the char is separated and, after mixing with burnt lime (15), is fed to the pyrolysis reactor (1). The hot cyclone (9) is directly connected to the venturi fluid bed reactor (10) where calcining of finely-divided limestone (29) is carried out by bringing it into fluidizing contact with the transport gas from the cyclone (9), 'the temperature of which is adjusted to 1000-1200°C. Said tem¬ perature adjustment is performed by adding to the transport gas an adjusted flow of 0 2 (air) with which a part of the CO content of the transport gas is combusted. The suspension of burnt lime and transport gas which leaves the venturi reactor (10) is blown directly into the hot cyclone (11), from which separated burnt lime is fed to the flow of char from the cyclone (9). The hot gas leaving the cyclone (11) and which in addition to CO2 and N2 contains also non-combusted CO is according to this invention used by being fed (30) to the reactor (4) where it is mixed with the suspension of char and reformed gas blowing down through the overflow outlet tubes to the bottom zone of the fluid bed of char in the reactor (5). The suspension of net char and "reformed gas" produced is discharged from the reactor (5) at the level of the surface of the fluid bed and is blown through the conduit (31) to the hot cyclone (6). In said conduit (31) an adjusted flow of wet water vapour (32) is added for cooling down the suspension to <600°C, whereby optional vapours of alkali chlorides are brought to condense. In the hot cyclone (6) net production of char with particles with particle size > about 10 μm is separated and fed to the outlet part (33) of the filter unit (7) whereas the "reformed gas" with the smallest particles is fed to the filter part (34) of the filter unit. This consists of vertical tubes of porous ceramic material with a bottom, on which tubes the finest char particles build up a layer which acts as the true filter material. By periodic "back blowing" of said filter tubes clogging of said filter tubes is prevented and knocked- off char material falls down in the outlet part (33) of the filter unit where the material separated by the filter is combined with the coarser char fraction from the cyclone (6). From the filter unit (7) the char is fed to closed "lock hoppers" which are alternatingly subjected to pressure relief and make possible the use of the char as a fuel also in atmospheric steam generators of all kinds. The reactors (l)-(5) are according to this invention of such dimensions that the total dwell time of the net char flow amounts to >5 seconds, suitably 10-100 seconds. The higher the temperature maintained in the reactors in said cascade is, the shorter is the dwell time required for complete stripping of the volatile substances of the fuel and complete reforming of the vapours of tars and light oils in the pyro gas. At a high temperature also a part of the active fine fraction of the char is gasified by reaction with water vapour. The method according to this invention gives per kg of coal waf of the gas flame coal mentioned above net char and "reformed gas" from the last reactor in the cascade with the following yields, analyses and characteristics: 1.51 Nm 3 "reformed gas", 800°C and 15 bars analysis CO C0 2 H 2 N 2 % 30.5 7.8 43.5 18.2 heat value = 2050 kcal/Nm 3 (Hu) 0.33 kg char waf, 800°C analysis C H 0 N S ashes % 81.6 0.6 1.3 1.3 0.7 14.5 heat value = 7990 kcal/kg waf (Hu) The solid coal fuel is thus by the method according to this invention divided into on one hand gas with a high heat value corresponding to 56.3%, and on the other hand fine-grained and thereby easily combusted char with likewise a high heat value corresponding to 43.7% of the energy content of the coal. A fuel with a high content of volatile substances gives the best result in the method according to this invention. Thus, as regards for instance (black) coal (mineral coal), coal with 35-45% of volatiles (gas flame coal and flame coal) are preferred since these materials give the highest yield of "reformed gas". A way to improve the possible uses of (black) coal with a lower content of volatiles is to compensate the lack of volatile material with oil. This oil is according to this invention added to the pyrolysis reactor (1), suitably by being sprayed on the surface of the fluid bed or onto char which overflows and falls down into the outlet shaft (13) of the reactor. Economically important is that by this invention it is possible to use cheap sulphur and vanadium containing residual oils, which today do not have a market for the main part of power generating methods. Thus, sulphur as well as vanadium are captured as sulphate and vanadate resp. in the combustion of char produced according to this invention because of the content of burnt lime therein. A plant for carrying out the method according to this invention, for which also patent protection is sought, comprises the following main parts, of which, however, the embodiments may vary within comparatively broad limits without deviating from the scope of invention: - a number of fluid bed reactors (l)-(5) with corresponding distribution chamber for "minifluidizing gas" arranged in a cascade below each other in a common pressure supporting cylindrical shell, where all reactors, besides the lowest, are provided with overflow outlets for transferring char and gas in the form of a suspension to the underneath reactor; - a pressurized distribution means (8) with flow controlling feeder for finely-divided fuel and with a chamber for fluidizing gas and overflow outlet for a suspension of fuel and gas discharging in the first reactor (1) of the cascade; - a separating and filtering unit (6)+(7) for separating char and "reformed gas" in the suspension from the last reactor in the cascade; - a "pipe-lift" including hot cyclone (28)+(9) for recirculation of char from the last to the first reactor in the cascade with simultaneous partial combustion thereof; and optionally a venturi reactor (10) with flow controlling feeder directly connected to the "pipe-lift" cyclone (9) and to the cyclone (11) for burnt lime and/or dolomite.

Claims: CLAIMS 1. A method for producing fuels, based on solid carbonaceous natural fuels, particularly adapted for environ¬ mental-friendly (non-polluting) thermal power generation with gas and steam turbines in combined cycle, c h a r a c t e r ¬ i z e d in that the flow of finely-divided natural fuel at super-atmospheric pressure, suitably 5-20 bars, and >700°C in a cascade of several reactors, suitably >3 reactors, is pyrolyzed and the pyro gas is reformed by being brought into fluidizing contact, suitably in the presence of burnt lime and/or dolomite for desulphurization, with char recirculated from the last reactor in said cascade with a flow >5 x larger than the flow of fuel, whereafter the fluidizing contact between formed pyro gas and char is continued in subsequent reactors and the temperature in said reactors is suitably maintained at a level higher than in said first reactor, whereas the temperature in the last reactor in said cascade is suitably maintained at a level lower than in said first reactor, whereafter produced "reformed gas" and net char, which are discharged from the last reactor, after separation are suitably used as fuels in a combined cycle, whereas the recirculating char discharged from said last reactor after adapted temperature increase by partial combustion with oxygen containing gas is recirculated to said first reactor in said cascade. 2. A method according to claim 1, c h a r a c t e r ¬ i z e d in that the fluidizing contact between gas and bed material in the reactors in the cascade is performed in fluid beds of classical type (0.4<e<0.8), wherein the fluid bed in the first reactor is "minifluidized" with inert gas, suitably N2, suitably in such a way that the bed is brought into a spiral shaped (helically shaped) macro-movement, whereas the following reactors, besides the last one, are "minifluidized" with inert gas, suitably N2, with adapted addition of air for achieving a temperature increase of suitably >30°C in the fluid bed of said reactors, whereas the last reactor in the cascade is "minifluidized" with inert gas, suitably N2, with adapted addition of water vapour for achieving a temperature decrease in the fluid bed of said reactor. 3. A method according to claims 1-2, c h a r a c t e r ¬ i z e d in that the total dwell time of the net char in the fluid beds of the cascade is >5 seconds, suitably 10-100 seconds. 4. A method according to claims 1-3, c h a r a c t e r ¬ i z e d in that the temperature in the suspension of net char and "reformed gas", which is discharged from the last reactor in the cascade, is reduced to <600°C by addition of wet water vapour and/or finely-divided water, whereafter the "reformed gas" is separated from the net char, suitably in a hot cyclone + a ceramic high temperature filter. 5. A method according to claims 1-4, c h a r.a c t e r - i z e d in that the transport gas for recirculating char, suitably combustion gas after partial combustion, after separation of char and adjustment of the gas temperature to 1000-1200°C, is used for calcining finely-divided limestone (lime) and/or dolomite, suitably in fluid bed of venturi type, whereafter the burnt lime and dolomite resp. are separated, suitably in a hot cyclone, and for desulphurizing purpose is mixed into the recirculating char, which is fed to the first reactor in the cascade. 6. A method according to claims 1-5, c h a r a c t e r ¬ i z e d by using a solid carbonaceous natural fuel with a low content of volatile materials, wherein the shortage of volatiles is compensated by addition of oil, suitably residual oil, to the first reactor in the cascade, wherein said oil is suitably sprayed on the surface of the fluid bed and/or bed material which overflows to the outlet shaft of the reactor. 7. A device for carrying out the method according to any of claims 1-6, c h a r a c t e r i z e d by comprising the following main parts: - a number of fluid bed reactors (l)-(5) with corresponding distribution chambers for "minifluidizing gas" arranged in a cascade below each other within a common cylindrical pressure supporting shell, where all reactors, besides the lowest one, are provided with overflow outlet tubes for transferring char and gas in the form of a suspension to the nearest underlying reactor; - a pressurized distribution means (8) with flow controlling feeder for finely-divided fuel and with a chamber for fluidizing gas and overflow outlet tube for a suspension of char and fluidizing gas, which discharges in the first reactor in the cascade; - a separation and filtering unit (6)+(7) for separating char and "reformed gas" in the suspension from the last reactor in the cascade; - a pipe-lift including hot cyclone (28)+(9) for recirculating char from the last to the first reactor in the cascade with simultaneous partial combustion thereof; and optionally - a venturi reactor (10) with flow controlling feeder directly connected to the pipe-lift cyclone (9) and to the cyclone (11) for burnt lime and/or dolomite.

Inventors: COLLIN PER, COLLIN, PER
Applicants: COLLIN PER, NONOX ENG AB, NONOX ENGINEERING AB
Application year: 1993
Main classification: C10J3
IPC codes: C10J3