CA1107071A

CA1107071A - Process of producing fuel gas and fluidized bed reactor for carrying out the process

Info

Publication number: CA1107071A
Application number: CA312,053A
Authority: CA
Inventors: Hans Linneborn
Original assignee: NEUHAUS-SCHWERMANN ALBERT
Current assignee: NEUHAUS-SCHWERMANN ALBERT
Priority date: 1977-09-27
Filing date: 1978-09-25
Publication date: 1981-08-18
Also published as: BE870797A; LU80286A1; DK423178A; NL7809805A; FR2404041A1; GB2009226B; JPS5456608A; SE7810102L; GB2009226A; DE2743392A1; BR7806339A

Abstract

PROCESS OF PRODUCING FUEL GAS AND FLUIDIZED BED REACTOR FOR
CARRYING OUT THE PROCESS
ABSTRACT
Fine-grained to coarse-grained or fibrous fuels of organic origin are processed with omnidirectional relative move-ments of fuel particles and gasifying agent particles and with subsequent formation of a combustible mixture from the fuel gas product and oxygen, followed by a combustion of the mixture in a prime mover. The fuel is gasified in a fluidized bed under such conditions that the fuel gas product is entirely or sub-stantially free from contents of heavy hydrocarbons, hydrocarbon compounds, substances which form tarlike condensates when cooled below their dew point temperature, as well as phenols and phenol compounds. These conditions can be adjusted by any person skilled in the art in that the height of the fluidized bed is maintained below an upper limit at which the fluidized bed is torn open more than locally and that the height of the fluidized bed is maintained above a lower limit at which the fuel gas still contains the above mentioned substances.

Description

BACKGRO~ND OF THE INVENTION
Whereas the Earth's reserves of petroleum and fossil coal are limited, the consumption of these energy carriers con-tinues to ~row steeply so that such reserves approach exhaustion at an increasing rate. For this reason it is essential to use yeolo~ically younger fuels, which are either directly available, such as . ~ .

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- wood, or become available ~s residual or waste ma-terials in the production of foodstuffs for human beings and animals. Such residual or waste materials include straw, shells, husks, skins, peel, pods, tuhular stalks (ba~assel etc. They become available in a perpetual sequence and in large quantities as the crops are harvestea. A basic disadvantage of these residual or waste mat-erlals resides in that they contain substances which during a heat treatment of these residual or was-te materials by degasification, ~asification and combustion form heavy hydrocarbons, hydrocarbon compounds, phenols and other substances which form tarlike condensates when cooled below their dew point temperature. The ` presence of these substances in the residual or waste materials is due to the fact that the latter have not been subjected to a geologically induced transformation process under high pressures and temperatures in the absence of air. The reaction of fuel gases which can be derived from said residual or waste materials in a prime mover inevitably results in an expansion of gas in the piston-cylinder assemblies of internal combustion engines or in the nozzles and blade systems of turbines so that condensates will be separated and tar will deposit in the form of crists on the pistons and valves of engines or will clog the flow paths in the nozzles and blade systems or turbines. For these reasons it has previously believed that gases produced by a heat treatment of ~eologically young fuels cannot be used in engines.
But what seemed to be impossible has been accomplished by an intermittent treatment of wood 7~

and brown coal in shafts. A shaft for holdiny and preheating the fuel has been provided and has at-tached to said shaft a diabolo-shaped extension, i.e., a nozzle defining a convergent-divergent path for the flow o~ fuel. In the operation of such a system, the level of the hottest zones will depend on the loading of the shaft. In these zones the tar vapors are cracked to form innocuous fuel gas components.
SU~l~RY OF THE INVENTION

.____ _ ___ It is an object of -the invention to accomplish -the same result in continuous operation. This has been enabled by the recognition that any fluidized bed can be operated under conditions which ensure that a fuel gas produced therein from geolo~ically youngfuels is free from heavy hydrocarbons, hydro-carbon compounds, phenols and other substances which form tarlike condensates when cooled under its dew point.
The recognition underlying the present invention resides in that such fluidized bed reactor can be operated under such conditions that the fuel gas product is free from heavy hydro-carbons, hydrocarbon compounds, phenols and phenol compounds os that it can be burnt in engines or turbines in continuous operation without damage to the prime mover. For this purpose it is ne-cessary to take into consideration the material/constants of the fuels to be gasified, their specific gravities and bulk densities their particle size and fibrous structures, their particle or ~iber shapes, the surface ~07~7~

characteristics of such particles or fibers, the weight and surface area ratios of particulate matter to fibrous matter, their chemical compositions, their response to heat regarding the formation of gas produced by low temperature distillation and of combustion gas, particularly during a transition between endothermic and exothermic states and during such states, also t:he material constants of gasifying agen~s and combustion-assisting agellts regarding inlet temperatures, subatmospheric and superatmospheric pressures, specific gravi.ties and bulk densities moisture contents, degrees of ionization, as well as operational data which can be determined by preliminary experiments, such as patterns of movement or flow behavior of the fuel and of the yasifying agents or the combustion-assisting agents during and/
or after the supply of such materials to heat-treating spaces.
The values of the corresponding parameters must be measured so that the average values of all stated parameters can be de-termined.
Based on that basic recognition the process proposed according to the invention for the production of combustible gases from fine-grained to coarse-grained and/or fibrous fuels, preferably of organie origin, with omnidirectional relative motions between fuel partieles and gasifying agent particles and particularly with a subsequent formation of an ignitable mixture of the produet gas and oxygen and with eombustion of the mixture in a prime mover, is eharacterized accordina to -the invention in that the :Euel is gasified in a fluidized bed under such con-ditions that the combustible gas product ~ 4 is entirely or substantially free from heavy hydrocarbons, hydro-carbon compounds which when cooled under their dew point tem-perature form tarlike condensates, phenols and phenol compounds.
Any person having average skill in the art concerned here can determine the average value o~ each of the above-men-tioned parameters and can determine by a subsequent experiment the upper limit of the height of the fluidized bed at which the latter is not longer torn apart or is torn apart only ]ocally.
In this wa~ the conditions can be determined which ensure that the hëight of -the fluidized bed will not exceed an upper limit.
The same average values, can be used by the person skilled in the art to find out in what lower height range of the fluidized bed the latter produces a combustible gas product which still contains tar vapors and phenol vapors and what is the smallest height of a fluidized bed which'produces a gas that is entirely free from both substances. In this wayr the conditions which ensure that the height of the fluidized bed will exceed a lower limit can be determined for the investigated reactor so that it will then be sufficient to adjust the corresponding operating data so as to operate the fluidized bed at a height between the upper and lower limits which have been ascertained and thus -to maintain in continuous operation the conditions which are required ~r the fuel being processed and -the gasifying agent which is available.
After the above mentioned basic recognition the inventor required additional deliberations and insights before he could define the teaching which constitutes the invention.
An increase in per~ormance will always require an increase of the reaction surface area which becomes effective per unit of time. This can be accomplished by an increase of the fuel surface area if the fuel is first disintegrated to form a fine-grained to coarse-grained and/or fibrous material which is capable ~r ._~

of trIckling, i~ the fuel does n~-t already constitute such a material in ~ts natural state and/or as a result of this pro-duction. When subjected to extraneous heat, such fuel will first be effectively degasified on a relatively large surface area per unit of welght of fuel. This is also applicable to the ~asifi-cation, provided that each of the particles of the ~ine-grained to coarse-grained and/or fibrous fuel - these particles will briefly be referred to as `'fuel par-ticles" hereinafter - is supplied with o~gen in a quantity which is sufficient for gasi-tO fication. That quantity is known to be smaller than the quan-tity of oxygen required for combustion. For this reason these remarks are even more applicable to the combustion of the particle. Wlth respect to all ~uel particles being considered, such combustion will be a partial combustion because the particles will be in-itially burnt only in the amount which is required to produce -the heat that is necessary for degasification and gasificationA
Because the gasifying agent constitutes a second reactant and must contact each fuel particle, a second deliberation shows that with particulate fuel best results will be produced if the process just described is carried out as a dynamic rather than as a static process, in a fluidized bed, such as is known from other technologies. Whereas in such other technologies, e.g., in drying processes, the fluidized bed can be used in a relatively simple manller, the use of the fluidized bed in the present process gives rise to a multitude of highly complicated phenomena, which must be controlled in that certain operating conditions are maintained. In the first place, a homogeneous fluidized bed must be produced and maintained in a stable state. Thorough tests have confirmed that this requirement can be met if the heiyht of the fluidized bed is maint~ined below an upper limit. Otherwise the fluidized bed will pulsate and will be torn open with formation of channels which extend deeply into or-e~ven throughout the ~ ~ . .

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- fluidized bed. Adjacent to such channels, -the fuel in the fluidized bed will fail to exhibit the turbulent up-and-down motion which is typical of a fluidized bed and the latter will be permanently fissured. It might be believed that in these torn-apart regions the fluidized bed is not sufficiently loaded and for this reason the height of the fluidized bed should be increased. But with an increased height the fluidized bed would be torn open even more strongly, contrary to all expectations.
~ccordin~ to further recognitions underlying the invention, the pulsation and channeling can be suppressed by flow-dynamical measures. For instance, a swirl of the gasifying agent will cause the solid particles to gyrate and to be transversely shifted so that fuel particles will enter the channels and the fluidized bed will thus be permanently maintained in a filled state. If the 1uidized bed is maintained at a height below the above-mentioned upper limit, the fluidized bed can be maintained in a homogeneous, stable condition in operation.
Additional problems arise and additional measures must be adopted to solve them. Degasification and gasification pro-cesses depend on time because the fuel particles in the fluidizedbed must be supplied with heat during a minimum residence time, which is functionally dependent on a minimum height of the fluidized bed. If the height of the fluidized bed is less that that minimum the temperatures at which the resulting hydrocarbons and hydrocarbon compounds as well as the phenols and phenol compounds are chemically decomposed or cracked are not obtained for a sufficiently long time. On the other hand, the mi~imum height of the fluidized bed cannot be fully utilized unless the statistical mean of the motion of the particles when projected on an imaginary lateral vertical plane generally increases from the bottom to the top of the fluidized bed. This can be accomplished in a simple manner in that the fuel is supplied ` ~ !

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to the fluidized bed on the bottom level of the fluidized bed, i.e., on the level o~ a support, e.g , a supporting grate, for the fluidized bed. This recognition leads to the requirement that the fluid bed must be maintained in a height which is above a lower limit and ensures that the residence time of the fuel particles in the fluidized bed is as long as or longer than the time re-cluired for the decomposition of the heavy hydrocarbons and pheno:Ls contained in the fuel gas.
In a process of the kind discussed here, the thermal and chemical processes, which may briefly be described as the chemism of the process, are of great importance too and mus-t be comt:rolled so that the above mentioned conditions of the fluidized ~ed are maintained. It is significant that endothermic and ex-othermic processes take place even during the degasification and must be taken i~to account in controlling the conditions.
It is also significant that the transistion between the two phases is sudden rather that gradual. There is initially a violent outbreak burst of gases produced by dry distillation and these gases breaking out remove air which has been occluded to or disposed between the particles so that the latter are approached by gasifying agents and the presence of the two re-actants under the thermal conditions required for-the reaction results in an initiation of the gasification, whcih then proceeds to completion, followed by partial combustion. As has been mentioned hereinbefore, the partial combustion is required for the generation of temperatures required for the degasification, gasi-facation and cracking processes. If the heiyht of the fluidized bed would decrease below the lower limit, the above~mentioned bursts of gases produced by dry distillation could displace fuel particles ana could interfere with the distribution and agitation of such fuel particles~ prevent the formation of a homogeneous and stable fluidized bed, and permit of the production . ~ ~

o~ a gas which contains non~decomposed hy~rocarbons and phenols as it is wi~thdrawn so tllat the combustion of such gas in a prime mover would involve a condensation of tar- and phenol-containing vapors and would also result in pollution.
The need for a matching of the parameters which are of main significance has been indicated by an observation made during tile gasification of palm kernelsA When the above-mentioned parameters were initially matched in a manner which appeared to be appropriate, the product gas was free from tar but very thin Eilms of fat or oil were formed on those parts of the reactor which were at a lower temperature than the gas as it was with-drawn. Because palm kernels are relatively large compared to other fuels, such as chopped cereal s-traw, and may be fingerlike, the converntional control of the residence time was not sufficient to suppress the formation of the oil or fat. Whereas these residues are not deleterious, they are undersirable. Two methodsare apparently available for sùppressing the formation of such films. The palm kernels can be disintegrated before being fed to the reactor but this is not economical. Alternatively, the fluidized bed can be supplied with leaning materials, such as previously degasified palm kernels. It is thus apparent that the formation of the films cannot be suppressed unless the parameters being matched include the ratios of surface area and particle size to the mass of the particles.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, Fig. 1 is a diagrammatic view showing a fluidized bed reactor plant in which a cyclone disposed on the cen-ter line of the reactor and other parts of the plant serve to supply fuel to the reactor, Fig. 2 is in its left-hand half a top plan view showing a part of the reactor of Fig l and in its right-hand half : "

a transvelse sectional view taken on line II-II in Eic3. 1, Fi~. 3 is a fragmentary sectional view showing a grate for supporting the fluidized bed produced in the reactor of Fig. 1, Fig. 4 shows a fluidized bed reactor in whieh the fuel is caused to trickle into the fuel-gasifying chamber laterally from a fuel supply eontained in a bin disposed beside the reactor whereas in the reactor of Fig. 1 the fuel is centrally supplied by means of a cyelone, Fig. 5 is a horizontal seetional view taken on line V-V in Fig. 4, Fig. 6 shows a modifieation of the support of Fig. 1, Flg. 7 shows a hemispherieal grate and Fig. 8 a grate having the shape of a eomplete sphere, Fig. 9 shows a reaetor having an annular cylindrieal spaee for aecommodating a fluidized bed for produeing gas, as well as an inner jaeket space for preheating the eombustion air, and a eombustion ehamber for produeing fuel gases, and Fig. ~0 shows a fluidized bed reaetor having eornbustion ehamber for melting ash.

DESCRIPTION OF THE PREFERRED EMBODIMENT
_ .
In the plant shown in Fig. 1, the fluidized bed reactor comprises an outer casing 1, a shell body 3 for accommodating the fluidized bed 2, and a diagrammatieally indieated grate 4 for supporting the fluidized bed. The fluidized bed may be supported by any means whieh maintain the fluidized bed in position and in sueh a shape during the operation of the reae-tor that the eon-ditions of the fluidized bed ensure the formation of a eombustible gas that is free from tars and phenols~ For this purpose it will be suffieient to provide the surfaces whieh define the space for aceommodating the fluidized bed with projections or other ob-staeles whieh prevent an unintended emptying of the reaetion spaee.

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The reactor shown in Fig. 1 also comprises a hood 5, which is remote from the supporting grate and has an end por-tion 51 that extends into a space 6 between the outer housing 1 and the shell body 2. As a result, the combustib~e yas product to be withdrawn ~lows along a path indicated by an arrow 61 and another flow path, indicated by an arrow 62, is provided, in which par~ of the yas produced in the fluidized bed 2 is branched off and recycled through the chamber 6 into tlle flui~ized bed 2.
There is also a cyclone assembly which is generally designated 7 and may be designed in various ways for continuously feeding fuel to the fluidized bed reactor. The cyclone 7 has a housing 72, which surrounds a working chamber 71 and at least adjacent to the latter is double-walled so that the chamber 71 can be heated or cooled, e.g., to cause preheated fuel to be discharged through the outlet 73 so that the reactivity of the fuel in the fluidized bed is improved. The working chamber 71 is preceded by generally known means for measurement and contro], including automatic control, such as valves, hinged valves, change-over valves, limit switches, thermostats and other con-ventional devices and instruments for supervising the proce~ses in the reactor and controlling them in an intended manner~
Below said means for measurement and control, conveying and meteriny means 74 and 75 are shown and may be replaced by any other conveyor or pump. These means serve generally to produce a gaseous or vaporous fuel-entraining stream, -to which fuel is supplied from a storage bin 76 through a star wheel feeder 73 at a controlled or automatically controlled rate. The automatic control may be effected, e.g. in dependence on the load on an engine or turbine which is fed with a mixture of ~uel yas produced in the fluidized bed and of combustion air which contains the re-quired quantity of oxygen. Combustion air of normal composition may ~e replaced by oxy~en-enriched air. The automatic control may also include an automatic controi of a heating or cooling fluid which is supplied to the heat exchanger chamber of the jacket 77 surrounding the working chamber 71 of ~he cyclone and ls withdrawn therefrom after a heat exchange has been effected.
If a contact be~ween the fluid which entrains the fuel and the 1uidized bed 2 is to be prevented and a control of the height of the fluidi~ed bed 2 is desired, the conduit 78 of the reactor shown in Fig. 1 may contain a downpipe 79, which is vertically adjustable and can be fixed in position and may be used to with-draw the entraining fluid, e.g., when the fluidized bed departs from the desired conditions under which the gas product is entirely or virtually free from substances which could adversely affect the operation of succeeding engines, turbines, other equipment, or parts of plants or could result in pollution, e.g., by escaping phenols. The downpipe 79 can become effective even if one cyclone 7 is not provided with control means because the space which accommodates the fluidized bed 2 will be automatically shut off as a result of the dynamic and static pressure gradients ln the vorte~ of the cyclone and any pressure gradients which may arise in the flow path of the entraining fluid before the vortex will remain ineffective. The position of the downpipe 79 re-lative to the surrounding tube 78 can be automatically adjusted and fixed, e.g., by automatic control operations which are initiated by the prime mover which is supplied with the fuel gas as the load on said prime mover is increased or decreased. The positioning means may be of hydraulic or pneumatic type and may be similar to parts 42 shown in Fig. 1 and will be described hereinafter. Fig. 1 shows also that the supporting grate 4 may carry a pointed cone 41, which is vertically adjustable in unison with the grate 4 by means of a slidable positioning and fixing member, which constitutes a piston having a pis-ton face, tv which ~ 7~

fluid pressure can be applied to adjust the parts and hold them in position. such piston may be autom~tically controlled, e.g., in response to output signals o~ detectors wh~ch are responsive to the presence ~f heavy hydrocarbons or phenols in the gas.
In that case even unpredictable changes in the feeding of the xeactor and resulting changes of material constants and con-ditions of supplies cannot give rise to undesired results.
The grate 4 serves also to admit the gasifying agent, which consists of air that is under a slightly superatmospheric pressure and may have been enriched with oxygen. The gasifying agent is supplied to the reactor through the conduit 43 and the chamber 44. An e~ample of the design of the grate plates, not shown in Fig. 1 is represented in Figs. 2 and 3, which will be described hereinafter.
Except for special cases, a single coarse axial adjust-ment of the supporting grate 4 by the mechanism 42, 421-426 will be sufficient when the desired operating conditions of the reactor have been determined. A fine adjustment of the height of the ~luidized bed will have to effected by a control of the pressure (superatmospheric or subatmospheric) of the gasifying agent. This feature may also be used for automatic control.
For this purpose is may be suitable to provide thermosensors 32, 33, 34 etc. in the walls of the body 3 and/or to provide thermosensors 15, 16, 17 etc. in the walls of the outer housing 1 on certain levels, particularly on, above and below the highest and lowest permissible levels of the fluidized bed, and to apply the output signals of said thermosensors to the inputs of a small computer. Such computer may comprise processing means, program control means, command-generating means and pulse gen-erators and may be connected to servomotors, posi-tioning motors and adjusting motors. The output signals oE the thermosensors may also be used to control certain controlling elements, such as . ~ , - .

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hinged throttle valves, servovalves, other valves etc. ~n the computer, the output signal of the thermosensors may be processed with significant other operational data, which may be constant and/or variable, and depend on the nature, shape, surface configuration, specific gravity, and bulk density of the fuel its surface finish, particle shape etc. The processing is ef~ected in consideration of temperatures, pressures, flow conditions and other controlling parameters which prevail in the fluidized bed and can be ascertained, suitably with a deter-mination of average and means values as controlling values.The resulting control pulses are applied to positioning motors by which the pressure and rate of the gasifying agent supplied to the fluidized bed is controlled in such a manner, inter alia, that the fluidized bed 42 is operated under the conditions required for a satisfactory production of gas. If during such control the conditions depart from the range within which the input data are effective in this manner, limit comparators, processors, pulse generators, program controlimeans and command-generating means as well as the con-trol means are used to control a positioning motor, which by means of the positioning member 42 in Fig. 1 causes the grate 4 to perform a vertical movement in such a direction that the desired conditions are re-established.
Such movement may be accomplished in several steps in response to the output signals from successive thermosensors 32, 33 etc.
and/or 15,15 etc.
Figs. 2 and 3 show how the gasifying agent is intro-duced with a swirl through the supply chamber 44 and the grate shown in Fig. 3 and how the gas product is withdrawn through the pipe 63 so as to produce a swirl in the chamber 64. For this purpose, the grate plate 45 is formed with struck-out tongues 46 which are upwardly inclined and with oppositely direction tongue 47 and these tongues 46, 47 define passages 4~ which are .~

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inclined to the plane of -the swirl-generating grate. The gas outlet p~pe 6~ is tangentially attached to the outer housing 1 of the reactor so that said pipe imparts to the fuel gas to be withdrawn a swirl, which is effective also in the space 6~ and even in the adjoining fluidized bed 2 and assists the swirl imparted to the gasifying agent by the tongues 46 and47 and imparts a st~irl to the fluidlzed bed as is required. The conditions which result in the production of a Euel gas which is free from tar and phenol vapors are thus established.
Fig. 4 shows a reactor which :is basically similar to the one described hereinbefore but difEers from it as regards the means for supplying fuel and as regards the supporting characters designate similar parts explained with reference to Figs~ 1 to 3.
The means for supplying fuel to the fluidized bed 2 comprise a lateral feed pipe 8 by which the supply of fuel is automatically controlled. For this purpose the outer housing 1 comprises an upper portion 11 and a lower portion 12, which is much smaller in cross-section than the upper portion 11 and connected thereto by a transition cone 13. The lowermost genera-trix 81 of the fuel-feeding pipe 8 is longitudinally aligned with a generatrix of the transition cone 13. The pipe 8 is disposed at such a height relative to the shell body 3 -that the lower edge 31 of the shell body 3 extends through a space which con-stitutes an axial extension of the cavity 82 of the pipe 8. As a result, the lower edge 31 constitutes an underflow weir, under which the flowable fuel can trickle like a liquid under control of the edge 31, which permits fuel to pass to the fluidized bed ~ only from a retaining space 83, which is defined by the walls adjacent to the generatrix 81 and the edge 31. When the ~o conditions change in such a manner that the fuel is admitted to the fluidized bed at a rate which is too low or too high, a ring member (not shown), which constltutes the lowermost part oE the ~, i shell body 3 and is formed with the lower edge 31 thereof and surrounds another part of the shell body and can be vertically adjusted and fixed in position may be sligh-tly lifted in -the first case or lowered in the second case~ This permits o~ an arbitrary, coarse adaptation of the fuel rate to existing cond~tions in a simple manner whereas the fine adaptation is effected by auto-matic control.
As is apparent from Fig. 4, the gas-with-drawing pipe 63 is tangentially attached to the upper portion 11 of the outer housing 1 of the reactor so that a swirl is imparted to the air as it is withdrawn. As has been explained with reference to Fi~s. 1 to 3, that swirling action augments the swirl which is g~nera~ed in the fluidized bed within the shell body 3 by the means shown in Figs. 2 and 3. Parts 46, 47 and 63 can be matched in such a manner that the s~irling actions are produced in the same sense to cumulatively or even exponentially augment each other so that the required flow conditions in the fluid bed can easily be established particularly because the swirling action can be further intensified by the means provided in the further embodiment shown in Figs. 4 and 5~
In accordance with Fig. 5 the fluidized bed reactor may differ from the one shown in Figs. 1 to 3 also in that the grate 4 has an imperforate central portion 148.
~n the flow path of the gasifying agent, the grate 4 shown in Figs. 4 is preceded by a circular series of guide vanes 49, which impart a strong swirl to the gasifying ayent leaving the space 44 (Fig. 1). The swirling gasifying agent enters the space 016, which is defined at the top by -the grate 4 and at the bottom by the bottom wall 19 of the houslng portion 12.
The central portion 48 or 148 of the grate 4 shown in Fi~s. 4 or 5 may be used to support a pointed cone 41, such as is shown in Figs. 1 and 5, or may carry a body having a different shape. Such an extension may be used to define an annular - ~luidized bed or to ensure the presence in ~he reactor of a core space in which there is no fluid flow.
It ls apparent from Fig 4 .hat the grate 4 is formed with slots through which the gasifying agent enters the f]uidized bed 2. The design in accordance with Figs. 2 and 3 has already been described. In this way, the swirl of the gasifying agent leaving the guide vanes 49 is augmented. Owing to the swirl previously imparted to the gasifyingagent, the swirling action exerted by the tongues near the periphery of the grate on the entering gasifying air is stronger than the swirl imparted by the tongues which are nearer to the center of the grate so that the motion imparted to the gasifying agent near the periphery is much stronger than the motion imparted near the center. This effect is promoted in that, in accordance with Fig. 5, the central portion 148 of the grate is entirely imperforate. Where a preliminary swirl is not produced, there is no need for an imperforate central portion 148 of the grate. This design has been adopted, e.g., also in the grate shown in Fig. 6 in conjunction with the pointed cone 41 shown in Fig. 1. The previously described struckout tongues previously described have been provided elsewhere. The pointed cone 41 prevents a formation of columns of fuel which could otherwise form in the central portion of the gas producer and by their presence or their collapse could disturb the fluid-ized bed 2 or could increase the density thereof near its peri-phery so that it would be less liable to be torn open.
Fig. 7 shows a hermispherical grate 4 having an im-perforate central portion 48 and tongues 47 in a peripheral portion. The imperforate central portion 148 of the grate may carry a core body having any desired shape, e.g., a hollow cy-lindrical shape (Figs. 9,10), which extends into or through ihe gasifying space that accommodates the fluidized bed.

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The grate shown in F~g, 7 is hemispherical. It is also provided with tongues 46, 47 as shown in Fig. 3. Instead of these tongues, means m~y be provided which force the gasifying agent to flow in a predetermined, preferred pattern. In the present embodiment, a stronger swirl is imparted to the gasifying agent in the outer zones and the resistance in the outer zones is increased because -the fluidi~ed bed is enriched with larger fuel particles adjacent to its periphery so that the gasifying agent may be distributed even more uniformly over the grate area which is available.
Fig. 8 shows a grate ~ in the shape of a complete sphere having a continuous imperforate belt portion 56. The grate 4 is rotatably mounted and the gasifying agen-t enters through hollow trunnions, which are sealed in the belt portion 58.
~hen one hemisphere has been clogged with slag, the grate can be turned through 180 so that the other hemisphere, which may not be clogged with slag, e.g., because it has been cleaned before, takes the position of the hemisphere which has been clogged with slag. The sphere may be drawn-in near its edge and the hollow-spherical cavity which is formed in the gas producer andaccommodate the sphere may be rotated so as to produce a ball mill action by which slag crusts are crushed and eliminated.
The swirl produced by the illustrated tongues may be assisted by guide vanes of suitable shape.
Fig. 9 shows a reactor design which may be adopted when the fuel gas produced in the fluidized bed 2 is to be used immediately thereafter for a generation of heat by a combustion in a combustion chamber together with combustion air which has been preheated to a high temperature, praticularly if the burners are closely succeeded or surrounded by heat exchangers used to minimize the heat losses. For this purpose the gasification is effected in a fluidized bed reactor which is generally similar to the one shown in Fig. 4 but differs fr~m it by having a fluidized bed in the shape oE a cylindrical ring, which surrounds a dead core space having the shape shown in Fig. 9, and surrounded by the inner wall 01, which together with an outer wall 011 def:ines a jacket space 09 flown through by air supplied through inlet pipe 08. secause the outer jacket wall 011 forms the ;nner ioundary of the fluidized bed and the latter is supplied with fuel through the inclined pipe 8, heat is trans-ferred at an extremely high rate to the combustion air, which is supplied through 08 and flows into the space 012 at the top end of the inner wall 01 through an annular clearance 010 between the _ inner wall 01 and the outer wall 011 of the jacket. The space 012 is defined by a mushroom-shaped extension, which has per-forations 013 or tongues 46, 47, as shown in Fig. 3, permitting the high-temperature combustion air to flow from space 012 into space 014, which constitutes part of a combustion chamber. The gas produced in the fluidized bed flows in the directions in-dicated in Fig. 1 by the arrows 61,62. In the direction in-dicated by the arrow 61, fuel gas flows into the combustion chamber 014. The remaining gas is recycled in the direction of the arrow 62 to the fluidized bed. The drive mechanism 02 for revolving the annular grate 4 comprises a motor-driven pinion in mesh with a gear provided on the grate 4.
Fig. 10 shows the design of a reactor which can be used when ash is to be discharged in a molten state. The basic arrange-ment is highly similar to that of Fig. 9. A difference resides in that the dead core space defined in Fig. 9 by the wall 01 is replaced by a meltina chamber 04, which is provided with an outlet 05 for a continuous discharge of molten slag. In the embodiment shown in Fig. 10, the combustion air is heated to a high temp-erature in the jacket space 09 and through the oblique slots 05 directly enters the melting chamber 04. For this reason, the ~ ' -- 19 --lleat e~chanqer can also be accommodated in the comhustion chamber, whIch succeeds the transition cone 07. Part of the product gas is recycled in the direction indicated by the arrow 62. Another part of the product gas flows in the direction in-dicated by the arrow 61 from the slots 05 which communicates with the retaining space 010 above the fluidized bed so that the melting chamber 04 fed with high-temperature combustion air is also fed with fuel gas at a rate which ensures that the ash in the melting chamber 04 is melted, particularly because the outer 10 wall 011 defining the jacket space 09 constitutes the inside boundary of the fluidized bedand for this reason transfers heat at a high rate so that the combustion air which has flown through said jacket space supplied the ash from above with the heat re-~uired to melt the ash and turn it into slag.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for producing a gaseous fuel from organic particulates of a fluidizable mass in a reactor having an oxygen source, comprising supplying a quantity of oxygen to said reac-tor; agitating said organic particulates with said oxygen; said agitation shifting said organic particulates relatively to said oxygen; igniting said organic particulates in the presence of said oxygen to form a heated fluidized bed having a selectable height; gasifying said organic particulates with a gasifying agent to produce a gaseous fuel containing an amount of hydro-carbons, phenols, and phenolic compounds; and simultaneously varying the height of said fluidized bed between a highest and lowest level, the highest level defining a level when the fluidized bed is torn apart by permanent fissures, the lowest level defining a level when said organic particulates have a minimum residence time in said fluidized bed, so that the hydro-carbons, phenols and phenolic compounds produced from said gasi-fying step undergo thermal decomposition.

2. A process as claimed in claim 1, which includes the step of adjusting the level of a bottom support of said fluid-ized bed and maintaining said adjusted level.

3. A process as claimed in claim 1 which includes the step of varying the level of the bottom support for said fluid-ized bed in automatic dependence of the load on consumers of the gaseous fuel.

4. A process as claimed in claim 1 which includes controlling the supply of gasifying agent supplied to said fluidized bed as regards to the pressure of said gasifying agent, its supply rate and temperature and humidity in auto-matic dependence on the content in the gaseous fuel of heavy hydrocarbons, hydrocarbon compounds, substances adapted to form tarlike condensates, phenols and phenol compounds, by means of detectors for such substances, said control being adapted to eliminate any of said substances in said fuel gas.

5. A process as claimed in claim 1 which includes moving said particulates and said gasifying agent so as to exhibit a liquid-like behavior in said fluidized bed.

6. A process as claimed in claim 1 which includes aadding said particulates to a stream of said gasifying agent, which is additionally fed to said fluidized bed.

7. A process as claimed in claim 1 which includes imparting to said gasifying agent a swirl and feeding said gasi-fying agent with said swirl to said fluidized bed.

8. A process as claimed in claim 1 which includes combining said particulates and said gasifying agent in a common stream, separating said particulates from said stream, and using said separated particulates jointly with said gasifying agent to form said fluidized bed.

9. A process as claimed in claim 1 which includes melting ash, particulate coke and other meltable substances formed in said fluidized bed to form molten slag and discharging said slag in a molten state.

10. A process as set forth in claim 1 which includes feeding leaning material to said fluidized bed, which leaning material is adapted to suppress a formation of fatty films on any surfaces which are at a temperature below the minimum temper-ature in the fluidized bed.

11. A fluidized bed reactor adapted to carry out a process as set forth in claim 1 which fluidized bed reactor comprises in combination a hollow container adapted to accom-modate a fluidized bed, a supporting element which closes said hollow container adjacent its bottom and is adapted to support a fluidized bed in said hollow container, and a hood, which covers and laterally protrudes beyond the open end of said tubular shell at the end thereof which is remote from said supporting element, said hood in conjunction with said tubular shell defining gas flow passages for feeding part of the fuel gas product formed in said fluidized bed to a consumer and for recycling another part of said fuel gas product to said fluidized bed through the space between said hollow container and said tubular shell means for feeding organic particulates to said bed, means for feeding oxygen to said bed, means for feeding a gasifying agent to said bed and means for varying the height of the bed to between said highest and lowest levels.

12. A fluidized bed reactor as set forth in claim 11 including a cyclone assembly which is disposed in the cavities of the reactors and adapted to feed fuel and a gasifying agent for said fuel to a space which is disposed in said reactor and adapted to accommodate a fluidized bed.

13. A fluidized bed reactor as set forth in claim 11 comprising a transition cone between said hollow container and said supporting element, and a pipe adapted to supply fuel to said fluidized bed and having a lowermost generatrix which is longitudinally aligned with a generatrix of said transition cone, whereby said pipe and cone are adapted to cause said fuel to trickle into said fluidizing bed at a rate corresponding to the consumption of fuel.

14. A fluidized bed reactor as set forth in claim 11 in which said supporting element consists of a plate-like grate at the end of a piston, which is guided in a cylinder for adjust-ment in height, said piston and cylinder constituting parts of a control system which is adapted to move said grate to any desired level and to maintain said grate on such adjusted level.

15. A fluidized bed reactor as set forth in claim 11 in which a gas-withdrawing pipe is tangentially attached to said hollow container and adapted to impart a swirl to said gas as it is withdrawn and in said hollow container.