Note: Descriptions are shown in the official language in which they were submitted.
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
-- 5
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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
6 -
~ ~ . .
;37~)7~
- 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.
-- 10 --
~70~
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
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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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~`0~
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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i7~7~
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
15 -
~, 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
- 16 -
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.
~ 7~
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
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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.
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