Note: Descriptions are shown in the official language in which they were submitted.
131 1923
The present invention relates to a process and apparatus for
the gasification of solid or solid and liquid organic, i.e.
carbonaceous matter by partial combustion with a gasifying
medium comprising oxygen or oxygen and steam or oxygen and
carbon dioxide. The invention can be applied to a large
variety of different uses, including waste dlsposal (solid
as well as liquid by incineration with or without
utilisation of the gas and sensible heat generated by the
process, fuel gas production (ranging from lean producer gas
to higher grade fuel gases).useful for heating purposes,
steam raising and the like as well as for fuelling internal
combustion engines ~diesel engines, spark ignition engines
and gas turbines) and for the manufacture of varioùs grades
of synthesis gas.
lS According to its main aspects the invention relates to
improvements and/or modifications of the invention desc~ibed
and claimed in Canadian patent ap411Lation No.~073,7~Inter
alia the invention can be applied to a very complete
gasification of the gasifiable content of a wide variety of
carbonaceous materials, including waste materials such as
sawdust and other sawmill wastes, forestry wastes,
agricultureal wastes, domestic and other refuse, various
industrial wastes, but also various grades of solid
fossilised fuels, ranging from peat through lignite, oil
shale, tar sand to black coal. It is a feature of the
invention that effective pyrolysis with partial combustion
of such materials can be achieved at relatively modest
temperatures, whereby it is often possible to avoid or
mitigate ash fusion or ash softening problems as well as
certain heavy metal volatilisation problems sometimes
ex~perienced with more conventional gasification processes
operating at higher temperaturqs.
Waste incineration processes of the kind to which
ce~r~tai~n aspects of the invention relate are known; for
example~from Maschinenmarkt, WUrzburg, 81 (1975) 69, page
1923, a process is known referred to as high temperature
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. ~., ~.~.. ...... .
731 lq~3
process according to which refuse is incinerated and in
whicll the combustion of the pyrolysis gases takes place in a
separate coml)ustion chamber. Also from DE-PS 26 04 408 a
process is known in which the gases arising during the
pyrolysis of waste materials are supplied to a combustion
chamber, there to be combusted.
In the combustion of flue gases it is desirable for
these to be burnt off as completely as possible, even when
considering only the generation of residual gases friendly
to the environment, and particularly, if the sensible heat
arising from the combustion of the gases is desirable in
order to improve the energy balance. However, the complete
combustion of the flue gases in which the aromatics in the
flue gases are converted, is possible only at relatively
high temperatures in the combustion chamber which must be
higher than 1000C. Such high temperatures are indeed
possible also in conducting the known processes, e.g.
according to DE-PS 26 04 409. However, to set up such high
temperatures, results in difficulties in the known processes
due to the fact that the melting of the ash, whilst in the
combustion chamber, cannot be avoided. This results in
undesirable deposit formations in the combustion chamber and
thus in faulty operation.
A need therefore exists in the art to provide a process
of the type referred to in the introduction which permits as
complete a combustion of the gases as possible without
operating problems.
Liquid wastes which can be disposed of in accordance
with the invention include for example lacquer sludges which
are left behind as soiled residual liquids after the
application or spraying of lacquers onto workpieces to l)e
painted. In lacquer workshops and spray painting shops such
sludges are formed as a waste material in considerable
quantities. Lacquer residues w~ich cannot be further
utilised are, however, also unavoidable in the manufacture
of lacquers. These include for example reject batches.
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1 3 1 1 923
Lacquer sludges - optionally after having been
concentrated - are dumped on special dumping sites. This
not only involves expense. For such dumping moreover only a
small number of dumping sites are available which as time
progresses are becoming increasingly scarce due to extensive
utilisation.
Similar difficulties are also caused by paint and
solvent wastes.
It is also known in double or multiple stage
gasification of the down draft type for the gas formed in
the first gasification stage to pass through one or more
subsequent high temperature zones in the subsequent one or
more gasification stages. However, in that case the maxirnum
temperatures of all the high temperature zones are limited
by the restraints imposed by the ash fusion or softening
temperature of the solid carbonaceous matter.
There exists a need for a gasification process of the
type indicated above which permits the cracking of tars and
tar oils contained in the gas emerging from the first high
temperature zone in a second high temperature zone, the
temperature of which is not limited by the gas fusion or
softening temperature of the solid carbonaceous matter from
which the gas was formed and wherein cracking of the tars
and tar oils and cleaning of the gas preferably proceeds as
far as possible not at the expense of gas already forrned.
The gasification of many solid fuels, in particular
coal is generally carried out with greater or lesser
additions of water, usually in the form of steam, to the
gasifying medium in order to promote the complete
gasification of the solid carbonaceous matter and to
increase the hydrogen content of the gas, some of which
hydrogen may be in tne forM of hydrocarbons such as methane.
In such processes it is important to regulate the rate
at which water is introduced into the gasifier.
35The present invention proposes a method and means for
regulating the feed rate of water vapour to the gasiPier in
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a particularly simple manner. At the same time the
invention can be used to permit parts of the gasifier
apparatus exposed to high temperatures to be constructed of
materials of relatively modest temperature resistance.
In accordance with the present invention there is
provided a process for the gasification of solid or solid
and liquid organic, i.e. carbonaceous matter by partial
combustion with a gasifying medium comprising oxygen or
oxygen and steam or oxygen and carbon dioxide, wherein the
10 organic matter is first subjected to partial combustion and
pyrolysis at a temperature within the range of from about
400C upwards, but below the ash fusion or softening
temperature of the organic matter in a first gasification
treatment, whilst being supported above a fire grate or
15 equivalent partition means in the presence of
substochiometrical amounts of oxygen introduced with the
gasifying medium, whereafter gases generated in the first
gasification treatment are subjected to thermal cracking in
at least one further heat treatment, again in the presence
20 of oxygen, the further heat treatment being carried out
either whilst avoiding direct contact with the ash or ash
containing residue of the organ~c matter formed in the first
gasification treatment, also in the presence of oxygen - or,
provided the ash of the organic matter has a melting or
25 softening temperature above the temperature of the further
heat treatment, in an embers bed including said ash,
confined in a constricted passage supported by the same or
yet a further fire grate defining at least one variable gap
constituting the lower limits of the passage and controlling
30 the rate of gradual downwards travel of the embers bed.
In the latter modification it is due to the constricted
passage defining the outlines of the embers bed and leading
towards a relatively narrow gap of variable width that the
~pyrol~sis gases are subjected to particularly intimate
35 contact with the embers bed to resultin cracking of tar and
oil constituents still contained in the gas. The gap is
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1~1 19~3
variable and by alternating the increasing and decreasing
the size of the gap from time to time, it is possible to
regu~ate the rate of downward travel of the embers beds and
thereby the completeness to which combustible matter of the
5 embers bed is utilised before the ash or ash containing
residue of the organic matter is discharged through the gap
into an ash pit or the like for eventual disposal.
One embodiment according to which the gases may be
subjected to a further heat treatment may be carried out in
10 that gases formed in the first gasification treatrnent are
recycled to where the first gasification treatment takes
place, thereby being subjected to thermal -cracking by
further heat treatment in the presence of oxygen introduced
with the gasifying medium.
According to preferred embodiments of the invention,
the partial combustion and pyrolysis takes place under
downdraft conditions in a bed subjected to mechanical
internal reconstitution by back and forth agitation in
predominantly horizontal direction, more particularly in an
20 embodiment, wherein simultaneously with the back and forth
agitation the size of a variable gap constituting the lower
limit of a passage through which the bed travels gradually
downward is increased and decreased, thereby regulating the
rate at which the bed travels, preferably wherein the
25 mechanical agitation is brought about by back and forth
tilting about a horizontal axis of an agitating member.
It is particularly preferred that simultaneously with
the back and forth horizontal agitation the bed is subjected
to an up and down displacement action. Preferab7y the
30 agitating member is also used for feeding gasifying medium
into th bed.
Advantageously the agitating member projects upwardly
from a fire grate member defining the lower limit of the
bed, mounted pivotally about a substantially horizontal axis
35 and comprising on both sides of the axis upwardly directed,
downwardly sloping flanking surfaces which carry the bed,
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131 19~
tne lower edges of the flanking surfaces each defining one
side of a gap controlling the passage of bed material, the
width of the gap being varied when the fire grate member is
tilted back and forth, thereby subjecting the bed to the
5 horizontal agitation and the up and down displacement action.
What has been described above in relation to the
partial combustion and pyrolysis step, is preferably also
applied in the same or an analogous manner to the further
heat treatment when carried out under downdraft conditions
10 in a bed subjected to mechanical internal reconstition by
back and forth agitation in predominantly horizontal
direction.
A particular embodiment which is considered
particularly useful for the gasification of relatively
15 unreactive carbonaceous matter such as coal, and in
particular black coal the partial combustion and pyrolysis
takes place under downdraft conditions in a first bed
supported by a fire grate member defining the lower limit of
the bed, mounted pivotally about a substantially horizontal
20 axis and comprising on both sides of the axis upwardly
directed, downwardly sloping flanking surfaces which carry
the bed, the lower edges of the flanking surfces each
defining one side of a gap controlling the passage of bed
material, the width of the gap being varied when the fire
25 grate member is tilted back and forth, and wherein the bed
material discharged from the first bed drops onto and forms
a second bed underneath the first bed, supported in
substantially the same or similar manner as the first bed,
the gas generated in the first bed in the first gasification
30 treatment leaving the first bed through the gaps at the
bottom of the first bed being passed under downdraft
conditions through the second bed for further heat
treatment.
Preferably at least one of the beds is subjected to
35 mechanical internal reconstitution by the back a.nd forth
agitation action of an agitating ~ember projecting upwardly
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131 1923
from the fire grate member supporting the bed.
Advantageously at least one of the beds is supplied with
gasifying medium or steam or both through a feed member
projecting upwardly from the apex of the fire grate member
5 supporting the bed.
A different embodiment according to the invention is
provided wherein a further heat treatment of the gas takes
place -substantially out of direct contact with the ash or
ash-containing residue formed in the first gasification
10 treatment, which comprises passing the gases emerging from
the first gasification treatment into a combustion chamber
and there adding to the gas further oxygen or oxygen-
containing gas in an amount sufficient to raise the
temperature of the gas by combustion reactions above the
15 temperature of the first gasification to bring about
thermal cracking of crackable compounds of the gas.
Preferably air or oxygen is first added in
substochiometrical proportions whereafter the hot gases are
led into a duct where further air or oxygen is added to
20 complete the combustion of the gas. In that embodiment
generally the sensible heat of the combustion gases is used
for heating purposes.
In the lastmentioned embodiment the gases from within
the combustion chamber to its outlet or outlets are
25 conducted separately, fresh air being admixed to the
separately conducted gases. The separate conductance of the
gases permits - in conjuntion with the easily controllable
feeding of fresh air to the separately conducted gases - to
set up the temperatures required for the complete combustion
30 within a defined region. The remaining region of the
combustion chamber may then be kept at a lower temperature
level, whereby the adverse effect of high ternperature on the
combustion chamber walls may be reduced and other drawbacks
such as for example, the melting of the ash, can be avoided.
35 This applies particularly to an advantageous embodiment of
the process according to the invention in which the gases
._ ,., .. _ .. , .. , .. . ..... _. . _ _ _ _
., - . :
- : ' '. ' ' ''''' ' ,'
- . . ~ .
~ - 131 1~2~
are conducted separately starting from the centre of the
combustion chamber or respectively passing through the
centre of the combustion chamber.
The separate conductance of the gases furthermore makes
5 possible particularly favourable starting-up conditions for
the combustion chamber. The reason is that if the gases are
ignited in the defined region of separate conductance, this
region can be raised very rapidly to the temperature of
about 800C required for the formation of clean residual
10 gases.
- A particularly advantageous modification of the process
according to the invention resides in that the gases fed
into the combustion chamber are supplied with fresh air in
sub-stochiometrical ratio and additionally thereto fresh
15 air is supplied to the conducted gases in a ratio which is
at least stochiometrical. By this expedient - the
appropriate proportioning of the amounts of fresh air - it
is possible in an optimal manner to adjust the desired high
temperatures in the defined region of the separately
20 conducted gases whilst lower temperatures are maintained in
the remaining region of the combustion chamber.
The invention also provides another type of process
modification wherein the further heat treatment takes place
out of direct contact with the ash or ash-containing residue
25 of the organic matter and which comprises maintaining a
second high temperature zone, separated and rernote from the
first gasification zone and maintained at a temperature
sufficiently high for substantially complete cracking oF
tars and tar oils, wherein the second high temperature zone
30 comprises an embers bed formed by a solid carbonaceous fuel
producing substantially no fused or softened ash at that
temperature. Such process may for example be applied to the
higll temperature gasification of solid carbonaceous matter
by partial combustion.
This procedure may also be applied advantageously to
the gasification of liquid wastes comprising organic
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cor,lponents, ~ilerein the liquid wastes are applied onto an
embers bed to convert the liquid wastes into gaseous
products, the gaseous products being withdrawn through the
embers bed and in the course thereof being so heated in the
5 embers bed that high molecular mass organic components in
the gas are cracked, the withdrawn gas mixture cleared off
ash particles, serving as a fuel gas.
The term "embers" as herein employed is intended to
denote glowing particles of carbonaceous matter, e.g. char
10 or coal of greater or lesser size and includes such matter
in an incandescent state of greater or lesser intensity.
The liquid waste is applied onto an embers bed at a
controlled rate such that the liquid waste is evaporated.
Gaseous products and solid residual components are formed.
l5 The gaseous products are drawn through the embers bed,
thereby being so heated that high molecular weight organic
components in the gas are cracked. For that purpose the
embers bed in accordance with a further preferred feature
of the invention comprises at least one temperature zone
20 having a temperature in the range of from 800C upwards,
e.g, 800 - 1000C through which the gaseous products have to
pass. A readily ignitable gas mixture comprising low
molecular weight gas components such as H2, C0, CH4 is
formed. The gas mixture withdrawn from the embers bed can
25 therefore be utilised as a fuel gas for energy generation,
optionally with the introduction of additional oxygen. The
fuel gas is already cleaned to a substantial extent of the
solid residual components formed during the conversion of
the liquid waste. The residual components form part of the
30 embers bed and are withdrawn from the embers bed in the form
of ash.
It is advantageous to pass the gaseous product,
preferably after a first separation of ash particles through
a cracking and cleaning stage following thereafter having a
35 temperature which is preferably higher than that of the
aforesaid embers bed, e.g. between 900 and 1500-C, say
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131 1923
1000C. In that stage a cracking of residual high molecular
weight organic components still contained in the gas mixture
being discharged takes place. In addition the fuel gas is
cleaned of dust particles which are still entrained. This
5 takes place in an embers bed through which the gaseous
products pass. From the cracking and cleaning stage a fuel
gas emerges which has a low tar and oil content.
For forming the embers bed degassed high carbon
material, for example coke or charcoal is used. In the
lO first embers bed it is possible in addition to employ
grinding mill balls which cause the comminution of the
material particles which form the embers bed.
By spraying the waste liquid over the embers bed of the
first stage and by its distribution in small droplets
15 evaporation is facilitated and a uniform distribution in the
shaft space above the embers bed is attained.
As already indicated, a particular aspect of the
invention provides a process for the high temperature
gasification of solid carbonaceous matter by partial
20 combustion with a gasifying medium comprising oxygen in a
first high temperature zone to form a combustible gas
followed by passing the combustible gas through a second
high temperature zone, separated and remote from the first
zone and rnaintained at a temperature sufficiently high for
25 substantially complete cracking of tars and tar oils,
wherein the second high temperature zone comprises àn embers
bed formed by a solid carbonaceous fuel producing
substantially no fused or softened ash at that temperature.
~ ~Accordingly it is now possible to subject to the high
30 temperature gasification in the first high temperature zone
a solid carbonaceous matter which has an ash fusion or
softening temperature below the temperature maintained in
the second high temperature zone, the temperature of the
first high temperature zone being maintained at a level to
35 gasify the carbonaceous matter without fusing or softening
the ash. This means that the gasification of the solid
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131 1923
carbonaceous matter can proceed at a relatively low
temperature from 450 upwards, e.g. in the range of 600 to
lOOO~C, more particularly frorn 700 to 900 and in any event
below the ash fusing or softening temperature of the solid
5 carbonaceous matter. This also means that relatively low
quality solid carbonaceous matter having a relatively low
ash fusion or softening temperature can be gasified without
ash fusion or ash agglomeration problems occurring.
Also it is possible to gasify materials containing
lO heavy metals whilst avoiding wholly or in part the
volatilisation of such heavy metals. This can be important
in two contexts. Firstly it may be desired to recover the
heavy metals in the ash. Secondly, if the heavy metals are
toxic their volatilisation may be environmentally undesirable.
The second high temperature zone is operated at
temperatures from 800~C upwards, e.g. from 900 to 1300C,
preferably at 1000 - 1200C. ~
The second high temperature zone may be operated under
down-draft conditions, which means that any higher molecular
20 weight components such as tars or tar oils which may be
formed in the higher region of the fuel bed which forms the
second high temperature zone will be conducted through the
regions of highest temperature of the second high
temperature zone and be subjected to cracking as well.
The solid carbonaceous fuel used for producing the
second high temperature zone is selected from those
producing substant~ally no ash which is fused or softened at
the temperature of the second high temperature zone. In
general this will be a material having an ash fusion or
30 softening temperature substantially higher than that of the
solid carbonaceous matter subjected to gasification in the
first high temperature zone.
This means that the second high temperature zone can be
operated under process conditions which would have resulted
35 in ash fusion and a~glomeration problems if the solid
carbonaceous matter present in the first high temperature
,. 11
, , .
... , . ~ . . .. ~ , . . _ . . .. . .... . . .
~ . .... .
-- 1 31 1 9~3
zone had been present there as well. The separation of the
first high temperature zone from the second high temperature
zone avoids these problems, because the ash from the first
zone can thus be withdrawn separately without entering the
5 second zone.
The terms "first" and "second" zone are intended to
include the case where either or both of these zones are in
their-turn subdivided into a succession of zones. For
example, the gasification of the solid carbonaceous matter
lO passing through the first zone may in fact proceed in more
than one stage, provided the ash fusion or softening
temperature is not reached in any of these stages.
If the solid fuel in the second high temperature zone
is substantially free of tar or oil-yielding volatiles, e.g.
15 coke or charcoal, it is possible to operate the second high
temperature zone not necessarily under down-draft
conditions, but also optionally under updraft conditions,
without creating additional tar and tar oil problems.
This can have the advantage that higher temperatures
20 may be attained without excessively exposing the fire grate
to heat.
The gasification of the solid carbonaceous matter in
the first high temperature zone can be carried out under any
suitable gasification conditions, including fluidised bed or
25 circulatory fluidised conditions, although a solid bed
gasification is preferred. Preferably the first high
temperature zone is operated under down-draft conditions and
; the first high temperature zone is provided by an embers
bed formed by the solid carbonaceo~s matter.
The solid carbonaceous matter may for example be brown
coal or black coal. The process may for example be
conducted using high ash, high volatile duff coal which is a
very cheap material, serving as the solid carbonaceous
matter for the gasification. The solid carbonaceous matter
35 may comprise waste coal or low grade coal having an ash
content, e.g. in excess of 25~ by mass based on dry matter,
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131 1923
e.g. as high as 50% ash. However, the process can also be
applied to the gasification of other low grade fossilised
solid fuels, e.g. so-called oil shale or tar sands. Thus
the process can be applied to the gasification of waste
5 materials from coal mines which at present are dumped,
because they are below marketable grade. Besides the energy
content of such materials being irretrievably lost by
dumping, these dumps constitute an environmental hazard.
These dumps are subject to spontaneous ignition and then
10 give rise to noxious fumes and smoke.
According to a further embodiment, the solid
carbonaceous matter comprises domestic garbage, e.g.
introduced in pel~et form or other suitable compacted
particle form. The gasification of such materials is
15 problematic because of the low ash fusion temperature of
garbage.
The invention may also be applied to the gasification
of solid carbonaceous matter comprising bagasse or wood,
e.g. bagasse which has been pelletised and dried, e.g.
20 according to technology which is now in commercial use in
Brazil. By passing the gas produced in the first high
temperature zone by the gasification of bagasse or wood
through a second high temperature zone maintained at a
sufficiently high temperature, e.g. fuelled with charcoal,
25 it is possible to produce fuel 9ases which require
relatively little further cleaning in order to be usable for
the fuelling of internal combustion engines. It is also
possible to avoid or mitigate tar formation problems which
arise from the gasification of biomass having a relatively
30 high moisture content. This is particularly so, if in the
second high temperature zone a fuel is used which requires
some moisture for optimum gasification.
The solid fuel used in the second high temperature zone
may for example bç anthracite or coke having a high ash
35 softening temperature, or charcoal. These fuels are usually
more expensive than the solid carbonaceous matter gasified
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131 1923
in the first high temperature zone. However, the
consumption of the more expensive solid fuel is generally
very much less than the consumption of solid carbonaceous
matter in the first high temperature zone. For example,
S generally the solid fuel consumed in the second high
temperature zone constitutes in terms of fuel value less
than half the amount of solid carbonaceous matter gasified
in the first high temperature zone, e.g. Iess than 30~ and
may be as little as lO~. This may be achieved by
lO restricting the dimensions of the second high temperature
zon~ to smaller dimensions than those of the first high
temperature zone. Moreover, the admission or feeding of
gasification medium, in particular air or oxygen or oxygen-
containing gases is so restricted so that the required high15 ternperature is maintained, preferably in a concentrated
region whilst fuel consumption is restricted.
It is furthermore possible to include in the second
high temperature zone substances which catalise the cracking
of tars and tar oils and other substances, e.g. ammonia.
20The, fuel gas produced according to the invention may
for example be cooled and - if necessary after further
cleaning - be used to power an internal combustion engine.
For example, the process may be used to produce gaseous fuel
for diesel generators or gas turbines or generators powered
25 by spark ign~tion engines. The practising of the process is
not limited to any particular scale. It can be applied to
relatively small power generating plant, or to relatively
large plant, e.g. to supply peak power requirements. In
this context it is an advantage that the process can be
30 adapted for intermittent operation, since the embe.rs bed of
gasification furnaces as used in the process can be kept
"dormant" for relatively long periods, ready for a
;resumption of the gasification by the renewed introduction
~ of gasification medium at relatively short notice..
~ The process may also be applied to the powering of
mobile units, e.g. for powering the diesel engines of ships.
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1 3 1 1 923
However, the invention may also be applied to the powering
of smaller mobile equipment, e.g. tractors or trucks. In
that case the solid carbonaceous matter may for example be
wood or bagasse pellets whilst the second high temperature
5 zone is fuelled with relatively small amounts of charcoal,
thereby minimising the tar and tar oil content of the gas.
The process may also be applied to the production of gas
for industrial or domestic heating purposes or to the
production of synthesis gas.
The gasification may be carried out at substantially
atmospheric pressure or at elevated pressure in accordance
with generally known principles. Depending on the purpose
for which the gas is to be used, the gasifying medium
comprising oxygen may be air or air enriched with oxygen or
15 pure oxygen. Air enriched with oxygen or pure oxygen may
for example be introduced into the second high temperature
zone where generally a high temperature is desirable.
However, in order to promote high temperatures, particularly
in the second high temperature zone, it is also possible to
20 preheat the gasifying medium, e.g. air before its
introduction into the high temperature zone. This may for
example be done by heat exchange to recover the sensible
heat of the gas produced.
It is also possible to introduce water into the
25 gasification medium and/or one of the embers beds, e.g. at a
locality in or preceding the first embers bed. Such
introduction of water is particularly desirable if the solid
carbonaceous matter is coal of relatively low moisture
content. The water may be introduced in the forrn of steam,
30 such steam being for example generated and/or heated using
sensible heat generated by the gasification process.
As mentioned above, it is desirable in certain cases
for steam to be included in the gasifying medium or to be
injected into the bed of solid carbonaceous matter being
35 gasified. According to one aspect of the present invention,
such a process is provided wherein the water is introduced
131 lq23
in the form of steam into the gasification chamber from a
water jacket means forming-part of the confining outlines of
the gasifier furnace in contact with an incandescent region
of the furnace interior, the rate of steam introduction
5 being controlled by controlling the water level in the water
jacket means.
According to one embodiment, the water jacket means
form part of the outer upright confining outlines of the
incandescent region. According to another embodiment, the
10 water jacket means form part of fire grate means of the
gasifier.
The aforegoing two possibilities may of course be
combined in a single process or apparatus.
The invention also provides apparatus for carrying o~t
15 the various process modifications described in the
aforegoing.
Thus, for carrying out that process in which the gases
from the first gasification zone are subjected to combustion
out of contact with the ash combustion chamber an apparatus
20 is suitable in which at least one gas duct comprising one or
more apertures leading into the combustion chamber, is
provided passing through or starting from the interior of
the combustion chamber and the one end of which constitutes
the outlet of the combustion chamber or is connected
25 thereto, and which is adapted to be connected ta a fresh air
feedline. The gas duct in this context is made
advantageously of refractory material such as ceramic or
heat-resistant steel.
An advantageous embodiment of the combustion chamber
30 comprises the feature that the gas duct passes through the
centre of the combustion chamber or starts from the centre
of the combustion chamber.
A simple embodiment of the combustion chamber according
to the invention provides for a gas duct comprising a pipe
35 having lateral apertures. In this context the lateral
apertures may be directed towards the upper part, the sides
.
16
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-`` 131 1923
of t~e combustion chamber or even to the ash discharge
means. Preferably the lateral apertures are directed
towards the ash discharge means in order to avoid as far as
possible, an entry of fly ash or other dust particles into
5 the gas duct. In this context it is advantageous for the
gas duct to pass through the interior of the combustion
chamber and for the fresh air feedline to be adapted to be
connected to that end of the gas duct which is opposite to
the outlet of the combustion chamber. However, the fresh
lO air feed may proceed also, for example, through a fresh air
feedline projecting into the gas duct. The resulting
selection of the fresh air inlet position provides the
possibility to influence the combustion procedures in the
combustion chamber or in the gas duct respectively, not only
15 by controlling the amounts of fresh air, but also by the
selection of the position of introduction of the fresh air.
In determining the feed position regard may be had for
example, to the residence period of the gases in that
portion of the gas duct which succeeds the feed position.
The combustion chamber according to the invention may
be applied in an advantageous manner to a combustion plant
for the combustion of combustible material in which the
combustible material is first pyrolised in a chamber
provided therefore and the flue gases resulting from the
25 pyrolysis are fed to the combustion chamber. The employment
of the combustion chamber according to the invention wlll
then permit a particularly effective control of the
combustion processes taking place in the combustion chamber.
~ epending on the selection of the manner of feeding
30 fresh air into the gas duct, the separate conductance of the
gases into the combustion chamber combined with an intense
combllstion of the gases, results in a concentrated flame jet
extending beyond the region of the combustion chamber. In
order to attain a flame jet extending, if possible beyond
35 tlle combustion chamber, it may thus be advantageous to feed
the fresh air to the separately conducted gases only close
, ~
~ .................................................................. .
- 1 31 1 923
to the outlet of the combustion chamber or optionally even
outside the combustion chamber. In that case the combustion
chamber according to the invention may be employed
particularly advantageously in the context of a combustion
5 plant for the combustion of combustible material in which
the combustion chamber is succeeded by a means for utilising
the sensible heat. Thus, for example, the combustion
chamber may be succeeded by a boiler of a heating plant, the
flame jet emerging from the gas duct of the combustion
10 chamber being directed onto the heat exchanger o~ the
boiler.
For those process embodiments requiring steam injection
the invention also provides a gasification apparatus
comprising a furnace adapted to hold solid carbonaceous
15 matter to be gasified, including at least a region thereof
in a more or less intense incandescent state, comprising a
water jacket device or devices bordering the region and
forming a confining outline thereof, a level regulating
device for controlling the level of water maintained in the
20 jacket and ducts or passage means for releasing steam
generated ~n the jacket into the interior of the furnace.
The level regulating device may for example comprise a
float valve, various suitable designs of which are known per
se and therefore require no description.
In accordance with one preferred embodiment the water
~acket device forms upright walls of the furnace. According
to a further preferred embodiment, the features of which may
be combined with the previous embodiment, the water jacket
device is incorporated in a fire grate devtce of the
30-furnace.
For the gasifiction of liquid wastes the invention also
provides a shaft furnace for carrying out the process of
the invention comprising
a) a shaft space adapted to be closed in a gas-tight
manner in its upper region and limited in a downward
direction by a grate serving to support an embers bed
18
.. . , . ~ ,. ...
131 lq23
to be formed in the shaft space and provided in a
rotatable or pivotal fashion in the shaft in such a
manner that between the margin of the grate and the
wall of the shaft a gap acting as a passage is left for
ash particles to be withdrawn under the action of
gravity from the embers bed,
b) a feed means for a liquid waste material to be
applied onto the embers bed and comprising organic
components and entering into the shaft space above the
embers bed,
c) a gas duct for introducing an oxidising agent into
the embers bed, and
d) a withdrawal means connected below the grate for
the gas mixture formed in the embers bed by evaporation
and gasification of the liquid waste.
The shaft furnace comprises a shaft space which in its
upper region is adapted to be closed in a gas-tight manner
and which in a downward direction is limited by a grate
serving for supporting an embers bed. The embers bed is
20 maintained by charging solid fuel from above. The shaft
furnace is preferably operated under down-draft conditions.
The grate is rotatable or pivotal in the shaft and so
provided that between its edge and the shaft wall a gap for
the passage therethrough of ash particles remains which are
25 discharged from the embers bed under the action of gravity.
Above the embers bed a feed duct enters into the shaft for a
liquid waste material to be applied onto the embers bed and
comprising the organic components. A gas duct leading into
the shaft serves for feeding an oxidising agent into the
30 embers bed. The gas mixture formed in the embers bed due to
the evaporation and gasification of the liquid waste is
withdrawn in the lower region of the shaft furnace. The
withdrawal means required therefore is connected below the
grate. The gas mixture withdrawn can be employed directly
35 for heat generation as a fuel gas. The embers bed has a
temperature zone at a teMperature in the range between 800
.,, 19
~: !
-
131 1923
and 1000C, or somewhat higher or lower, depending on the
fuel.
A gas mixture containing very little or no tar residues
is generated by adding in series a second cracking and
5 cleaning stage. The second stage in the same manner as the
shaft furnace comprises an embers bed. The embers bed has a
temperature e.g. of 900 to 1000C. The second stage is
operated under updraft conditions, i.e. the gaseous
products withdrawn from the shaft furnace flow through the
10 embers bed in countercurrent to the embers bed material
which under the action of gravity moves downwardly in the
cracking reactor. In the embers bed the high molecular
weight organic gas components still contained in the gas
mixture are cracked. In addition fine ash particles
15 entrained in the gas are retained.
The embers beds are composed of degassed high carbon
material, for example of coke or charcoal. A comminution
action is attained by the addition of grinding mill balls
which are added to the embers bed in the shaft furnace.
According to a different aspect of the invention the
apparatus according to the invention may also be defined as
an apparatus for the gasification of liquid wastes
comprising organic components, comprising two furnaces, the
first one being adapted to maintain a first charge of
25 glowing solid embers and comprising means for feeding liquid
waste material comprising organic wastes to that charge of
embers and the ~econd furnace being adapted to maintain a
high ternperature second charge of embers substantially free
of volatiles, and further comprising means for feeding gas
30 from underneath the first charge of embers through the
second charge of embers to a withdrawal locality.
Preferably the first furnace comprises a grate adapted
to support a solid fuel and first embers bed under down
draft conditlons.
Preferably the second furnace is adapted to support
the second charge of embers in the form of a second embers
'
1 31 1 923
bed and to be operated under updraft conditions.
According to a specific aspect of the present
invention, there is provided a process for the high
temperature gasification of solid carbonaceous matter by
5 partial combustion with a gasifying medium comprising oxygen
in a first high temperature zone to form a combustible gas
followed by passing the combustible gas through a second
high temperature zone, separated and remote from the first
zone and maintained at a temperature sùfficiently high for
lO substantially complete cracking of tars and tar oils,
wherein the second high temperature zone comprises an embers
bed formed by a solid carbonaceous fuel producing
substantially no fused or softened ash at that temperature.
According to a further aspect of the invention there is
15 provided an apparatus for carrying out the process as set
out above comprising two gasification furnaces connected in
series and wherein the first gasification furnace comprises
a duct for passing gas generated in the first furnace to the
top of the second gasification furnace which is of the down
20 draft type. Preferably the first furnace is also of the
down draft type, the reason being that any volatiles
including tars and tar oils generated in the second
gasification furnace will also pass through the high
temperature zone in the second furnace, there to be
25 subjected to cracking into low molecular mass constituents.
The apparatus may comprise means for injecting water or
steam into eitller or both of the reactors. Preferably the
means for injecting water or steam is in the first reactor.
Also preferably the apparatus comprises means for
30 transferring sensible heat from the gas discharged from the
second gasification furnace to the water or steam prior to
its being injected.
The apparatus may comprise heat exchanger means for
cooling the gas discharged from the second furnace and for
35 transferriny the heat withdrawn from the gas to one or more
of the gasification media introduced into either or both of
. . .
131 ~9~3
the furnaces~ preferably at least the second furnace.
In the following the invention will be further
described and explained with reference to the accompanying
drawings.
There is shown in:
Fig. 1, an incinerator or gasification apparatus
including a gas duct passing through the centre of the
combustion chamber and a feed means for fresh air provided
at the start of the gas duct,
Fig. 2, the combustion chamber according to Fig. 1 in a
sectional line A - B taken normal to the plane of the
drawing of Fig. I,
Fig. 3, the combustion chamber including a gas duct
passing through the centre of the combustion chamber and a
15 feed means for fresh air provided near the outlet of the gas
Fig. 4, the combustion chamber, inc1uding a gas duct
starting from the centre of the combustion chamber.
F;g. 5 a diagrammatic vertical sect~on of a multiple
stage gasification apparatus according to the invention
20 comprising two beds one above the other supported by fire
grate members (sluice members) as described in relation to
Figs. 1 to 4;
Fig. 6 a diagrammatic vertical section showing the
arrangement side by side of several fire grate members
25 (sluice members) as described in relation to Figs. 1 to 4 to
support an embers bed in a gasification or incineration
apparatus according to the invention.
Fig. 7 a shaft furnace apparatus acccording to the
invention in vertical section adapted for the disposal and
30 gasification of liquid wastes;
Fig. 8 a diagrammatic view, partly in section and not
strictly to scale of an apparatus in accordance with the
invention for gasifying solid carbonaceous matter followed
by cracking of the gas and vapour in a separate embers bed;
Fig. 9 a diagrammatic vertical section of a gasifier
apparatus according to the invention, applicable to any of
22
.
~ 131 1923
the embodiments in -the aforegoing, where steam injection is
desired;
Fig. 10 a fire grate device of an apparatus according
to the invention in vertical section, adapted for
embodiments where steam injection is desired.
In the incinerator illustrated in Figs. 1 to 4, the
combustion chamber 1 follows a pyrolysis chamber 2 in
series; Both chambers are separated from one another by the
gate member 3, also referred to herein as a sluice member or
10 fire grate member.
In the case of the combustion chamber illustrated in
Figs. 1 and 2, the gas duct 4 passes through the centre of
the combustion chamber 1. At the beginning of the gas duct
4 a gas burner 5 is provided servin~ for ignition to start
15 the combustion process in the combustion chamber. The fresh
air feedlines 6 is connected to the gas duct 4.
For operating the incinerator, combustible material is
charged into the pyrolysis chamber 2 through the upper
sluice gate 7. For starting the pyrolysis gas burners 8 are
20 employed. The combustible flue gases formed in the
pyrolysis chamber are withdrawn downwardly into the
combustion chamber 1. They enter through apertures 9 into
the gas duct 4. The apertures 9 are provided on that side
of the gas duct which faces the ash discharge means 10, i.e.
25 on the downward side.
During the operation of the incinerator, fresh air is
conducted by way of the sluice gate member 3 via the fresh
air feedline 11 in a sub-stochiornetrical ratio, both
upwardly into the pyrolysis chamber 2 as well as into the
30 combustion chamber 1. As a result, an embers bed is formed
above the sluice rnember 3 at a temperature of up to about
800C in which the pyrolysls gases are cracked down
substantially or at least partly into short-chain
hydrocarbon molecules. The heat generated in the embers bed
35 by partial combustion of the material, results in the
pyrolysis of the material prevailing above the embers bed.
131 1923
The fresh air introduced into the combustion chamber
1 by way o~ the sluice 3, results in a partial combustion of
the combustible gases at a temperature not exceeding 800C
in that portion of the combustion chamber 1 which is outside
5 the gas duct 4, resulting in further cracking of tars and
tar oils.
Fresh air in at least stochiometrical ratio to the
gases is fed into the gas duct 4 by way of the fresh air
feedline 6. This results in a complete combustion of the
10 flue gases introduced into the gas duct 4 so that a
temperature of about 1100C is attained.
In the embodiment of the combustion chamber illustrated
in Fig. 3, the fresh air feedline 6 projects by way of an
additional duct member 6a beyond the centre of the
15 combustion chamber into the gas duct 4. The feed position
for the fresh air is accordingly close to the outlet of the
combustion chamber such that the region of complete
combustion of the gases is also positioned close to the
outlet of the combustion chamber and the resulting hot flame
20 projects beyond the region of the combustion chamber.
In the embodiment of the combustion chamber 1
111ustrated in Fig. 4 the gas duct 4 starts from the centre
of the combustion chamber 1. The gas duct in this case
takes the form of a pipe of which the end provided in the
25 combustion chamber is open towards the combustion chamber.
The introduction of fresh air proceeds by suction by way of
the duct member 6a projecting into the pipe 4 and which
after the swinging down of the gas burner S is open towards
the outside.
Departing from the embodiments of the combustion
chamber according to the invention illustrated in the
drawing,-it may be advantageous, depending on the dimensions
of the combustion chamber and for optimising the combustion
procedure, to provide more than one gas duct 4 in the
35 combustion chamber, e.g. side by side.
The use of a single duct 4 passing all or part-way
,....
24
,,"~":
~: ~ . .. .. .. . . . .
;.
131 1~23
through the combustion chamber 2, as described above, is
particularly useful in furnaces in which the combustion
chamber, or indeed the entire structure, is basically
cylindrical. Particularly in the case of furnaces of
5 rectangular horizontal cross-section it may be convenient to
provide a co~bustion chamber according to the invention with
two or more gas ducts for leading combustible gases out of
the combustion chamber in a path where they can be consumed
at a temperature higher than that which is found in the
10 remainder of the combustion chamber. The plural gas ducts
are preferably of the same construction, but they may be of
any of the kinds illustrated in the other figures, for
exarnple. Furthermore, although horizontal disposition of
the gas ducts, in which the high temperature complete
15 combustion takes place, is particularly convenient in an
incinerator furnace in which there is a pyrolysis chamber
above the combustion chamber constituted according to the
invention, it is evident that there may be applications of
the combustion chamber according to the invention in which
20 the gas duct leading out of the combustion chamber is
disposed obliquely or vertically.
An important aspect of the invention, and which has
utility regardless of whether or not the pyrolysis gases are
combusted in a combustion chamber as described above, or are
25 subjected to other uses (e.g. for suitable combustion
engines), or regardless of whether or not the pyrolysis
apparatus is operated with air or oxygen or oxygen-enriched
air and with or without injection of steam - regardless of
the pressure at which the apparatus is operated - resides in
30 the following features of the sluice member 3.
According to this aspect of the invention there is
provided a gasification apparatus for converting solid
combustible materials into combustible gases ~which term may
include generator gas, water gas and various grades of
35 synthesis gas, comprising a sluice member 3, sub-dividing
the interior of the gasification apparatus to an upper,
'' 25
'
'
131 1923
first pyrolysis stage or chamber 2 and a lower, second
partial combustion stage or chamber 1. According to this
further aspect of the invention, the sluice member 3 has
downwardly inclined flanking faces, the lower edges of which
5 each define a gap for the passage of the glowingembers from
the first pyrolysis chamber 2 into the second partial
combustion chamber 1. The sluice member 3 is mounted
pivotally as shown in the drawing, in end bearings
permitting back- and forth-tilting (e.g. intermittently) of
10 the sluice member 3 to increase or decrease the size of the
gaps on either side, thereby promoting the passage of the
material.
As a preferred feature the sluice member 3 comprises
one or more upwardly projecting members (which, as shown in
15 the drawings) serve to supply sub-stochiometrical amounts of
air or oxygen to the upper first pyrolysis stage. However,
in accordance with the present further feature of the
present aspect of the invention, these upwardly projecting
member(s) provide an important function as well in that they
20 participate in the pivoting or tilting movements of the
sluice member and thereby also act mechanically on the
embers in a manner which promotes the desirable physical
structure of that bed.
Important further aspects of the invention relate to
25 certain features of the sluice device 3. These aspects have
utility not only if the apparatus according to the invention
is employed as an incinerator and/or for the production of a
heating gas~to be burned for heat generation in the devices
4 illustrated in the drawings. These aspects may also find
30 utility in the generation of producer goes for powering
internal combustion engines ~in particular diesel or spark
ignition) or for producing synthesis gas from solid fuels
such as wood, peat, brown coal or hlack coal. In the case
af synthesis gas production, it is normally the practice to
35 employ oxygen or oxygen-enriched air and steam as a
~ gasifying medium, rather than air alone. Moreover, it is
,~
2G
r ~ ~ -
1 3 1 ~ 9 2~
- generally advantageous in that case to operate the generator
at a pressure exceeding atmospheric pressure to a greater or
lesser extent. These are matters readily understood by
persons skilled in the art.
As will be apparent from the drawings already described
and in particular Fig. 2, read with Fig. 1. the invention
according to the further aspects now to be described
provides an apparatus for converting a bed (the top level of
which is shown in chamber 2) composed of solid combustible
carbonaceous materials (e.g. wood or other biomass, or coal)
by reaction with substochiometrical amounts of oxygen in a
gasifying medium, introduced to the various feed means
described above into combustible gases, namely carbon
monoxide and hydrogen and greater or lesser amounts of
volatile hydrocarbons and other gas~s.
The bed comprises a plurality of zones, namely (from
the top downwards): an upper drying zone reaching e.g. down
to about the level halfway between the top of the bed and
the upwardly projecting member of the sluice device 3; a
degassing zone in which volatile constituents are driven
off, reaching down to about halfway between the top of the
upwardly projecting member of the sluice device 3 and the
bottom; and a gasification zone (e.g. at 800C) in which the
residual char of the degassing zone ~in form of glowing
embers) is converted into C0, H2 and C02 reaching down to
the level of the gap between the sluice device 3 and the
wall of the reactor.
The combustible gases are withdrawn generally
downwardly through the bed into and through the chamber 1
for further combustion in means 4 or for withdrawal to other
uses through the pipe 4.
; The~apparatus comprises at least one sluice device 3
defining the lower limit of a zone of the bed. As will be
seen, the sluice device is similar to that shown in Fig. 2
of D~E-PS 27 34 973, being mounted pivotally about a
s~ubstantially horizontal axis, being the axis of the pipe
-~ ~ 27
,,
,, ~f
~: ,:
- 131 1923
l1. The sluice device 3 comprises on both sides of the axis
upwardly directed, downwardly sloping, flanking surfaces for
carrying the bed, ter~inating in lower edges, each defining
one side of a gap for the controlled passage of bed
5 material. The other side of the gap is formed by the walls
of the generator vessel.
The passage of the bed material through the gap is
assisted by alternatingly increasing and decreasing the size
of the gap. This is done by the up and down tilting
lO movements of the sluice device (3). So far the operation of
the sluice device is identical to that described in DE-PS 27
34 973.
According to the invention the sluice device carries
substantially vertically upwardly projecting means, which
15 may be in the form of individual upwardly projecting pipes
or may take the form of a continuous upwardly extending web
or fin. In either case these means will participate in the
back and forth tilting movement of the sluice member,
thereby exercising a desirable mechanical disturbing action
20 on the bed. These means projecting upwardly from the apex
formed by the sloping flanking surface include discharge
apertures capped by roof-shaped formations for introducing
gasifying medium, e.g. air, 1nto the bed.
In addition the sluice member includes discharge
25 apertures for the separately controlled introduction of
gasifying medium, respectively combustion medium, directed
downward from the underside of the sluice device.
The apparatus may comprise two or more of the sluice
devices side by side, separated by the gaps, to form a grid.
30 In this manner it is possible to increase the size and
capacity of the apparatus, whilst maintaining a bed of good
quality. ~It is also possible to install two or more of the
sluice members one above the other to define different zones
of the bed. These possibilities will be described with
35 reference to Figs. 5 and 6, wherein in general the same
reference numbers are employed as in Figs. 1 to 4.
~- ~ 28
~
1 31 1 92~
It is also possible to apply the apparatus to the
gasification of liquid wastes as will be explained more
fully with reference to Fig. 7. Figs. 7 to 8 moreover
illustrate the upgrading of gases produced in any of the
5 embodiments of the invention by cracking in a separate and
distinct embers bed.
Finally Figs. 9 and 10 demonstrate how steam injection
can be applied to the embodiments according to the remaining
figures.
Referring first to Fig. 5, two fire grate members 3'
and 3" are provided one above the other, each supporting a
bed in upper portion 2' and lower portion 2" of the
- pyrolysis chamber. The intermittent tilting movement of
fire grate member 3' controls the rate at which the embers
bed in portion 2' passes the gaps between member 3 and the
walls of the furnace to form a further bed in lower portion
2". The intermittent tilting movement of the lower fire
grate member 3" in likewise manner to member 3' controls
the reconstitution of the bed due to the horizontal to and
fro agitation exercised by the upwardly projecting part 3a
and the up and down displacing action exercised by ~he
inclined flanks. In addition the tilting movement, by
increasing and decreasing the sizes of the gaps at the
opposite lower edges of the inclined flanks controls the
rate of downward travel of the bed by contro11ing the rate
at which the gasification residue, mostly ash, is discharged
into the ash pit of the apparatus. The embodiment according
to Fig. 5 is particularly intended for the gasification of
solid fuels such as coal which are relatively inert.
2eferring now to Fig. 6, the fire grate member 3 which
is considered novel per se is also particularly suitable for
large gaslfiers or incinerators in which a plurality of such
members 3 are placed side by side, spaced apart by gaps
controlled by the above-described tilting movement to form a
composite fire grate. Above the fire grate and horizontally
staggered in relation to the fire grate members 3 may be
:
29
' ::
----" 1 31 1 923
.
additional feed means 8' for air or gasifying medium. These
may be similarly pivotally mounted about their respective
axis, thus serving as agitating means which also assist in
maintaining a favourable bed condition.
In contrast to what is shown in Figs. 1 to 4 the
upward projecting parts 3a of the fire grate members in
Figs. 5 and ~ take the form of continuous double-walled webs
extending over the full length of the fire grate member.
This can have a configuration as illustrated or a
lO different configuration achieving the same purpose. For
example the sides of the upwardly projecting part may have
sides inclined at a wider angle to one ano~her than that
shown, provided such angle is an acute angle, i.e. of less
than 9O~C, preferably not more than 45C. Also the angle
l5 between the flanking sides of the fire grate member may be
more acute than that shown in Figs. 5 and 6 and may be from
about 45~C upward, as long as it is not less than the
overall angle of taper of the sides of the upwardly
projecting part. Generally the upwardly projecting part
20 extends a distance from the tilting axis 3b as large or
larger than the distance by which the flanking sides extend
sideways from the tilting axis 3b.
Referring now to Fig. 7, a shaft furnace is illustrated
the shaft space 2a of which is adapted to be closed in a
gas-tight manner in its upper region at 7a. A shaft wall 2b
in the downward direction comprises an aperture for
accommodating a grate 3"' which in the working example is
provided in the shaft in a manner rotatable about its shaft
axis 16. The grate 3"' is so inserted in the shaft that a
gap 15 serving as a passage is left between the edge of the
grate 3"' and the shaft wall 2b. Ash is withdrawn through
the gap under the action of gravity from an embers bed 2c
formed above the grate and supported by the grate. The
grate 3"' is of conical configuration. The ash which is to
be withdrawn slides over the conical surface towards the gap
15 serving as a passage.
:: .
,: 30
:~ , :
'
~. ~ . ,.,~, .
-- 131 1923
The withdrawal of the ash is controlled by the rotation
of the grate. For that purpose the grate 3"' is fixed to a
drive shaft 17 which is adapted to be turned stepwise by a
motor 28 by way of a transmission 29. As the frequency of
steps is increased and as the amplitude of thesteps and the
rate of rotation of the grate is increased, the rate of ash
withdrawal increases.
Instead of a rotating grate it is also possible and in
fact preferred to employ a grate as described with reference
to Figs. 1 to 6 which is pivotal to tilt back and forth
about an axis normal to the axis 16 of the shaft. In the
case of a tilting grate a gap for the passage of material is
formed between the edge of the grate and the wall of the
shaft, the width of the gap being varied by the movement of
the grate. As the selected angle by whi-ch the grate is
deflected by the pivotal tilting movement is increased, the
variation of the width of the gap between a minimum and a
maximum value is also increased. Blockage of the gap for
passing material due to jamming of ash particles is
counteracted thereby. A tilting grate is possible even if
the shaft furnace is cylindrical as shown and also offers
advantages when the shaft furnace has to be cleaned. For
cleaning the gap serving as a passage is widened by tilting
the grate to such an extent that all solid pieces present in
the shaft furnace can be discharged in a downward direction.
If the tilting grate is made of a prismatic configuration,
the ash to be discharged from the embers bed will also with
this grate slide towards the gap serving as a passage over
an inclined surface. Above the embers bed 6 a feed duct lO
- 30 for the liquid wastes enters into the shaft 2a of the shaft
- furnace. The duct 30 is connected to a metering device 31
connected to a storage vessel for the liquid waste. The
storage vessel is not illustrated in the drawing. The
quid waste comprises organic components. The working
example relates to paint wastes comprising organic
components such as solvents, thixotropic agents or dyes as
~ 31
131 lq23
well as inorganic additives such as pigment or fillers.
However, it is also possibie to process lacquer sludges.
The metering device 31 comprises a liquid pump which
can be regulated or an adjustable valve by means of which
5 the feed rate of the liquid wastes to the shaft furnace can
be regulated. Nozzles for spraying the liquid waste may be
provided at the outlet of the feed means 30 in the shaft
space above the embers bed 2c. In the working example the
liquid waste is simply fed dropwise onto the embers bed.
In order to feed oxygen to the embers bed 2c, the drive
shaft 17 of the grate 3"' takes the form of a hollow tube,
the outer end 13 of which, downwardly projecting from the
bottom 12 of the shaft being connected to a gas duct 14
supplying oxygen or air. The oxygen flows in the hollow
15 tube to the apex 35 of the cone of the grate 3"' and is
introduced into the embers bed 2c by way of outlet apertures
37 symmetrically provided around the cone axis 16. In the
working example the cone axis 16 coincides with the shaft
axis 16. The conical grate may, however, also be fitted in
20 the shaft furnace to move in a tumbling manner.such that the
width of the slot for the passage between the edge of the
grate and the shaft wall undergoes local variation when the
grate ls turned.
Departing from the working example illustrated in the
~5 drawing, the grate 3"' may also be provided with outlet
apertures for oxygen or air at various levels of the conical
grate. For example it is also possible for oxygen or air to
be fed in addition into the embers bed only slightly above
the gap 15 serving as the passage. This is desirable in
30 particular if the fuel gas to be withdrawn from the shaft
furnace is to be converted immediately and be burned for
heat generation.
The amount of oxygen introduced at the apex 35 of the
cone is preferably so dimensioned that the temperature of
35 the embers bed required for the cracking of the gases is
maintained within the shaft furnace by the partial
32
, :
.
131 1923
combustion of the gases formed in the embers bed. In the
working example the embers bed is composed of coke which can
be charged through a closable aperture 7a at the top of the
shaft. The embers bed has a temperature between 800 and
5 1000C. The temperature of the embers bed must be so
adjusted that the organic products formed by the
gasification of the paint wastes are cracked when the gases
pass through the high temperature zone. In the working
example the temperature is set to 800 to 900C because the
10 shaft furnace is followed in series by a cracking and
cl'eaning stage 23.,
The gas mixture generated in the embers bed 2c is
sucked off by way of a withdrawal duct 18 in the lower
region of the shaft furnace. Accordingly the gas flows
l5 through the shaft furnace in cocurrent with,the liquid
wastes being fed into the shaft. A blower 20 installed in
the discharge duct 19 provides in the working example the
necessary suction pressure. The gas mixture and the ash
particles are separated from one another after the passage
20 through the gap 5. The ash particles initially collect at
the shaft bottom 12 and are conveyed by scoops 12a to the
withdrawal duct 18 through which they drop into an ashpit
21. From there they can be discharged by way of a sluice
22.'
In the working example the shaft furnace described
above is followed in series by a second cracking and
cleaning stage 23 for cracking the residual high molecular
weight hydrocarbons of the gas mixture generated. The
cracking and cleaning stage 23 similarly comprises an embers
bed 24, the embers bed being supported by a grate 24a, the
temperature of the embers bed being set to a range between
900 and 1000C. The discharge duct 18 connected to the
shaft furnace enters below the embers bed 24 into the
cracking and cleaning stage. The gas mixture introduced is
subse~uently discharged at the head of this stage by way of
the outlet 19. Not only are the high molecular weight
131 1923
organic gas components still contained in the gas mixture
subjected to cracking in the embers bed 24, but a cleaning
effect is also attained. Ash particles entrained by the gas
mixture are retained. From the cracking and cleaning stage
5 23 a gas mixture emerges which essentially comprises H2. CO,
CH4 and which can immediately be utilised as a fuel gas
optionally after intermediate storage, e.g. in pressurised
storage means.
Above the embers bed 24 a closable charging aperture 25
10 is provided for coke which in the working example serves as
the fuel for the embers bed 24. However, charcoal may also
be used as a degassed material rich in carbon. Oxygen is
not fed to the cracking and cleaning stage 23 in the working
example. It is assumed that the oxygen fed to the fuel gas
15 in the shaft furnace is also sufficient for a partial
combustion of the fuel gas in the cracking and cleaning
stage 23 in order to maintain in the cracking and cleaning
stage the temperature of the embers bed required for cracking
the gas components. This reduces the fuel requirements for
20 this stage.
In a shaft furnace of the above described type having
a shaft volume of 100 dm3 up to 50 kg lacquer sludge per
hour were gasified. The lacquer sludge contained between 40
and 50 mass percent of inorganic additives. The temperature
25 in the embers bed 2c was set to approximately 900C and the
temperature in the embers 24 to about 1000C. Coke having
an average particle size of from 10 to 30 mm diameter was
used for forming the embers beds.
The fuel gas emerging from the outlet 19 had producer ?
30 gas quality. The combustible gas components such as CO, H2,
CH4 made up 55 volume percent. It was possible to generate
gas in an~amount of 250 normal m3 per hour having a heating
value of 5000 kilojoules/Nm3,
Other liquid wastes comprising organic components which
35 may be used include for example oily or fatty solutions or
slurries. from such waste liquids as well it is possible to
34
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-~ 131 1923
generate fuel gas in the same manner. Besides the disposal
of such liquids, the process at the same time serves to save
fossil fuels.
The invention as exemplified was found to provide a
5 process for the disposal of liquid wastes comprising organic
components which is friendly to the environment and which
moreover can be operated with useful energy gains. In
addition the process was found to be suitable for being
practised in a simple manner.
It will be understood that the invention can be
practised to produce mixtures of gases derived in optional
ratios within wide limits of gas derived from the liquid
wastes and gas derived from the embers beds.
Referring now to Fig. 8, there is shown a first
l5 gasification furnace or generator 51 connected in series by
way of a connecting duct 53 to a much smaller second
gasification or generator furnace 52 of similar design to
the first furnace 51. The furnaces 51 and 52 comprise fuel
hoppers 53 and 54 respectively each feeding through a sluice
20 lock device 55 and 56 respectively, having top and bottom
slider gates 57, 58 and 59, 60 respectively or equivalent
means, whlch are known per se and require no detailed
description.
Each gaslfication furnace furthermore comprises a grate
25 device 61 and 62 respectively ~corresponding to grate 3 in
Figs. 1 to 4) in the form of a prismatic member comprising
downwardly ~nclined flanks 63 and 64 respective1y, the lower
edges of which stop just short of the walls of the
respective furnace 51, 52 to form gaps 65 and 66
30 respectively for the controlled passage of solid matter.
Each grate member 61 and 62 is adapted to be pivoted back
and forth about an axis 67 and 68 respectively to cause a
mechanical disturbance of the fuel bed supported by each of
the grates and to cause alternating narrowing and widening
35 of the gaps 65 and 66, whereby the discharge of solid
matter, more particularly ash through the gaps i s
,
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131 1923
controlled.
Each grate member 61, 62 furthermore comprises coaxial
with its pivoting axis 67 or 68 a feed duct 69 or 70
respectively for the introduction of gasification medium.
5 These feed ducts feed at least in part into upwardly
directed hollow webs 71 and 72 respectively, terminating in
outlets 73 and 74 respectively, protected in an upward
direction by roof-like baffles 75 and 76 respectively.
In the case of the grate member 61 of the first
lO gasification furnace 51, the feed duct 69 is subdivided into
two parts, only one of which feeds into the upwardly
directed web 71, whilst the other one is adapted to
discharge the same or a different gasification medium
through gaps 77 in the inclined flanks 63 of the grate
15 device 61.
In the drawing only a single grate device 61, 62 is
shown in each of the gasification furnaces. However, two or
more such devices may be provided side by side separated by
gaps 65 to provide a grate of double or multiple cross
20 sect~onal area. The grates each support a solid fuel bed,
the tops of which are denoted as 78 and 79 respectively.
Near the tops of the beds 78 and 79 the furnaces furthermore
each provide additional feed means 80 and 81 respectively
for an oxygen-containing gasification medium, e.g. air blown
25 into the furnaces by blowers 82 and 83 respectively.
Each gasification furnace 51, 52 furtherrnore comprises
an ash pit 84 and 85 respectively and an ash discharge
sluice 86 and 87 respectively.
The connecting duct 53 has its inlet aperture 88
30 immediately below and sheltered by the grate member 61 and
enters the second furnace 52 at a locality near the top 79 of
the fuel bed.
The inlet aperture 89 of the discharge duct 40 of the
second furnace 52 also is positioned immediately below the
35 grate member 62. It passes into a heat exchanger device 41
for cooling the gas which may for example comprise separate
36
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1 31 1 9~3
sections 42 and 43. Section 42 receives at 44 water or
steam which in section 42 picks up serlsible heat from the
hot gases. Hot steam is discharged through duct 45 to be
passed for example to the first gasification furnace, e.g.
5 to the duct means 69 and/or to the inlet means 80 for
gasification medium.
The second heat exchanger section 43 is fed at 46 with
oxygen-containing gasification medium, e.g. air or oxygen-
enriched air which is heated in section 43 and then passed
10 to duct 70. The gas leaving the heat exchanger at 47, e.g.
withdrawn by a sustion fan (not shown) may if necessary,
pass through further cleaning means, e.g. a gas scrubber
and/or a filter, before being fed at 48 to an internal
combustion engine 49 which drives a generator 90.
It will be appreciated of course that instead of a
single gasification furnace 51 being connected in series
with the gasification furnace 52, there could be two or more
gas generators 51 feeding into a single furnace 52.
The fire grate members 61 and 62 are mounted pivotally
20 about their axes 67 and 68 respectively and are connected to
a mechanism (not shown) adapted to impart a to and fro
pivoting movement about an angle and with a speed and
fre4uency which can be adjusted at will. The angle
determines the degree of variation of the s1zes of the gaps
25 65 and 66, and the factors just described, determine the
rate at which ash is withdrawn from the bottom of the embers
bed into the ash pits 84 and 85 respectively. For cleaning
of the apparatus the grate member may be tilted more
substantially so that any solid matter supported by the
30 grate will fall through.
The pivoting movement also has a further desired effect
in that the upright web members 71 and 72 respectively rock
to and fro, thereby to disturb the bed supported by the
grate. This assists in the avoidance of channelling and
35 generally modifies the structure of the bed in a desired
manner.
1 3 1 1 923
The apparatus according to Fig. 8 may be operated as
follows:
Gas generator 51 is charged with a high volatile South
African duff coal having a high ash content of between 20 and
25%, about 25% by mass volatile content based on dry matter
and an ash softening temperature in the region of 1000C.
The particle size ranges from about 1 mm upwards to nut
size, although larger pieces may be present.
Generator 52 is supplied with anthracite having a
volatile content of between 5 and 6%, an ash content of
about 6% and an ash softening temperature in the region of
1500 C.
During the starting up phase the fuel beds in both
generators are ignited with a propane gas burner (not shown)
and by introducing air through the blowers 82 and 83
respectively. In the case of gas generator 52 the air
introduction at 81 using blower 83 is employed only during
the starting up phase, until a strongly incandescent high
temperature embers bed has been formed. In the case of
generator 51, air introduction at 80 by means of the blower
82 is continued throughout the process and regulated to
maintain the desired temperature conditions.
In generator 51 a mixture of air and steam is
introduced via duct 69 through outlet apertures 73 and 77.
The overall ratio of air to steam in generator 51 is
adjusted to that ratio which corresponds to steam saturation
at 50 C. Blowing of air and steam is also so adjusted that
the temperature in the region of highest incandescence just
above gaps 65 is about 900 C. The first high temperature
gasification zone where the temperature ranges from about
700 to 900 C which is below the ash softening temperature of
the coal extends from about the level of baffle 75 to the
gaps 65. The degassing zone in the fuel bed where the
temperature ranges from about 400 to 700 C extends from
approximately the level of baffle 75 to the level of air
inlet nozzles 80. The steam which is introduced through pipe
38
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131 lq23
45 has been preheated by heat exchange to utilise some of
the sensible heat of the gases produced, and this is a
further factor which can be used to control the temperature
in the gasification zone. The steam lowers the temperature
in the first high temperature zone, due to the reaction of
coal with water being endothermal. On the other hand in the
presence of water the temperature required for total
gasification of coal is also lower than in the absence of
water. At the relatively low temperatures prevailing in the
gasification zone, the carbon content of the embers bed is
converted into a mixture of carbon dioxide, hydrogen and
carbon monoxide, some methane being also formed. More
methane results from the degassing reaction and the partial
cracking of volatiles liberated in the degassing zone and
drawn through the embers bed.
In the generator 52 a highly incandescent embers bed
having a temperature of 1000 to 1400 C, preferably 1000 -
1200 C that is below the ash softening temperature of the
anthracite, is maintained in the region between gaps 66 and
the feed apertures 74 for the gasification medium. The high
temperature is maintained by the blowing of air preheated in
heat exchanger section 43 through duct 70 and feed outlets
74. Optionally the air may be enriched with oxygen, or pure
oxygen may be employed or oxygen and steam or oxygen and
C02. ~ptionally some air or oxygen may also be introduced
into the gas in the connecting duct 53 to raise the
temperature of the gas entering the second gasifier 52 by
partial combustion. The temperature maintained in the
embers bed of gas generator 52 is maintained at such a high
level that the gas withdrawn through outlet 89, 40 is
substantially free of tars and tar oils. The fuel
consumption in generator 52, based on fuel value of the
combustible matter is maintained at between 10 and 15% the
consumption in generator 51.
In a different embodiment generator 51 is fuelled with
domestic garbage pellets produced according to the process
39
1 31 1 923
of the Swiss firm Orfa. In that case no steam injection is
resorted to, generator 51 being operated with air only,
introduced at 80 and 83.
The invention as set out above can also be applied to
5 enable the first high temperature zone to be maintained in a
temperature range in which exposure of various parts of the
first gasifier furnace to excessively high temperatures is
avoided or minimised, as a result the life expectancy of
heat exposed components may be improved or such components
10 can be manufactured of less expensive materials which would
not survive at much higher temperatures.
The invention can also be conducted as a pressure ?
gasification process, and even using only oxygen and steam
and optionally CO2 as gasification medium. The oxygen tends
15 to raise the temperature of the high temperature zones,
whilst the steam tends to depress this temperature. Because
of the splitting of the gasification apparatus into two
furnaces as taught by the present invention, it is possible
to operate the first furnace under relatively depressed
20 temperature conditions which may be preferred for a variety
of reasons, be it to ensure that the ash softening
temperature or the temperature of volatilisation of certain
components, e.g. heavy metals, in the first high temperature
zone is not exceeded, or be it to restrict thermal loading
25 of the equipment of the first furnace, or be it merely to
promote the complete gasification of the material in the
first high temperature zone by the maintenance of a
relatively high water content, and regardless of whether or
not the resultant gas already has the desired composition
30 and purity. The latter two factors may then be modified to
the desired extent in the second high temperature zone.
The claims that follow are to be considered an integral
part of the present disclosure.
.
