Note: Descriptions are shown in the official language in which they were submitted.
CA 02522384 2010-02-03
BIOMASS CONVERSION BY COMBUSTION
This invention relates to a method for combustion. The method may
be used for breaking down waste materials by pyrolysis, gasification and
combustion
in a close coupled combustion process. The method disclosed herein may be used
for animal waste including deadstock, animals parts, manure and can also be
used
for other waste organic materials including household, municipal, medical,
commercial and hazardous wastes.
The method and apparatus disclosed herein can be used for effectively
disposing of deadstock and animal materials while maintaining a temperature
sufficient to destroy pathogens including prions.
The method and apparatus disclosed herein can be used to effectively
dispose of animal waster material including materials having a moisture
content
greater than fifty percent with random batches consisting of 100% water (e.g.
contaminated blocks of ice) while maintaining the operation of the system and
the
required temperatures without the necessity for additional fossil fuels.
The method and apparatus disclosed herein can be used to extract
carbon. Where excess levels of carbon are produced beyond those necessary for
maintaining the required temperature, residual carbon can be extracted and
sequestered rather than released into the atmosphere as carbon dioxide.
BACKGROUND OF THE INVENTION
Many jurisdictions presently face a crisis in the disposal of deadstock,
offal and manure produced by the livestock industries. Disposal in landfill or
burial
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sites is of course highly undesirable since any pathogens remain in the soil
and
since the breakdown of the products is uncontrolled and can lead to
contamination.
Many landfill sites do not accept deadstock or offal and in many cases those
that do
require high charges for disposal fees.
Uncontrolled disposal can lead to the risk of disease transmission to,
and via, scavengers, insects, and the population at large. Composting either
can
require opening carcasses or carcass pathogen escape as carcasses decompose
and can produce contamination and unpleasant odours.
The disposal of manure from hogs is problematic in view of the facts
that it is primarily a slurry containing relatively high levels of water so
that
combustion is typically unavailable as a best method for disposal. Spread of
the
material on fields is costly and can lead to contamination.
There are combustion devices available for carrying out combustion of
deadstock and animal parts. Many of the machines are batch processes at
relatively
low productions rates so the individual animals must be inserted into a
containers
and combustion carried out until the materials are destroyed and expelled
through
flue gases leaving some solid materials for collection and potential use.
Often larger
animal carcasses require dissection or dismembering. Such batch processes
generally require the addition of fossil fuels to commence, and often to
maintain the
combustion at the temperatures required, even though in many cases the
materials
to be combusted generally have sufficient energy contained to maintain the
combustion through the process, provided the system is managed properly. If
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additional fuel is therefore used, excess energy is produced in some
situations
leading to inefficiency.
SUMMARY OF THE INVENTION
It is one object of the invention to provide a method for breaking down
materials by pyrolysis, gasification and combustion.
According to one aspect of the invention there is provided a method for
combustion comprising:
providing a combustible feed material;
providing a combustion container within which the combustion of the
feed material occurs;
the combustion container including a reactor portion for initial heating
of the feed material;
the combustion container including an exterior chamber within which at
least a part of the reaction portion is located such that combustion of
material in the
exterior chamber causes heating of the feed material in the reactor portion;
feeding the feed material into the reactor portion at a feed location;
the reactor portion including at least one contact surface onto which
the feed material is deposited and against which the feed material is in
contact when
heated;
causing the combustion in the exterior chamber to heat the feed
material in contact with said at least one contact surface of the reactor
portion to a
temperature above 600 degrees Celsius so as to cause the feed material in
contact
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with said at least one contact surface of the reactor portion to break down to
breakdown products comprising solid breakdown materials and gaseous breakdown
materials including combustible gases;
introducing combustion air into the exterior chamber for mixing with the
breakdown products to effect combustion thereof;
causing the breakdown products to exit the reactor portion into the
exterior chamber for combustion therein to form solid combustion products and
gaseous combustion products;
providing a flue for extraction of the gaseous combustion products from
the exterior chamber and generating a flow of the gaseous combustion products
from the exterior chamber into the flue;
providing an extraction system for the solid combustion products from
a bottom of the exterior chamber;
while the feed material is in contact with said at least one contact
surface of the reactor portion, causing downward movement of the feed material
by
gravity acting on the feed material from the feed location downwardly to a
bottom of
said at least one contact surface;
causing the solid breakdown products to exit downwardly under gravity
from the bottom of said at least one contact surface of the reactor portion
into said
exterior chamber;
and arranging the shape and orientation of said at least one contact
surface of the reactor portion and controlling the combustion in the exterior
chamber
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so as to maintain the feed materials in contact with said at least one contact
surface
of the reactor portion for a sufficient period of time to allow the breakdown
to occur.
According to one independently important feature of the invention the
reactor vessel is formed from a ceramic material.
5 Preferably the exterior vessel is lined with a ceramic material.
Preferably the ceramic material is a sintered silicon carbide similar to
the SAINT-GOBAIN ADVANCED CERAMICS structural ceramic product named
HEXOLOY.
According to one independently important feature of the invention the
reactor vessel includes a part which projects into the exterior vessel in a
manner
which allows the combustion gases to pass around the reactor vessel for
heating the
reactor vessel.
Preferably the combustion gases pass around four sides.
Preferably the reactor vessel descends down into the exterior vessel.
Preferably the reactor vessel is generally conical converging from an
upper mouth into which the feed materials are deposited to a bottom opening.
According to one independently important feature of the invention the
reactor vessel includes an upper mouth and a bottom discharge opening such
that
the feed materials pass therethrough by gravity and wherein the reactor vessel
is
shaped such that feed material fed into the reactor vessel is restricted in
flowing
downwards to the open bottom discharge opening sufficiently to allow the
breakdown to occur.
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Preferably the restriction is provided by a conical shape of the reactor
vessel.
Preferably the restriction is provided by members located on an inner
surface of the reactor vessel.
Preferably the members are movable relative to the inner surface.
According to one independently important feature of the invention there
is provided a bed of carbon at the bottom of the exterior vessel onto which
the solid
breakdown products from the reactor vessel fall.
According to one independently important feature of the invention the
breakdown products from the reactor vessel are free to fall onto the bed of
carbon
without any intervening grate such that the feed materials can fall from the
feed inlet
to the bottom of the exterior vessel by gravity and are maintained in the
reactor
vessel for breakdown by the shape and arrangement of the reactor vessel and
are
prevented from reaching the bottom of the exterior vessel by the carbon bed.
According to one independently important feature of the invention the
materials move from the feed opening to the bottom of the exterior vessel
solely by
gravity without assistance of moving elements providing motive power thereto.
Preferably wherein the temperature of the exterior vessel is maintained
at a required temperature above 600 degrees Celsius by controlling air inlet
into the
exterior vessel.
According to one independently important feature of the invention there
is provided a carbon bed in the exterior vessel from the carbon produced in
the
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breakdown and the variation of the air inlet causes air to increase or
decrease the
rate of combustion of the carbon bed.
Preferably heat from combustion of the carbon bed is used to maintain
the temperature at the required temperature without additional fuel.
Preferably the feed material can include more than 50% water content,
with random batches containing up to 100% water content, while the carbon bed
maintains the temperature at the required temperature without additional fuel.
Preferably the feed material includes a slurry containing at least 50%
water and wherein the reactor vessel is shaped and arranged to maintain the
slurry
in the reactor vessel for a sufficient period of time to effect said breakdown
while
allowing the breakdown products to fall from the reactor vessel under gravity.
Preferably the temperature is measured at the outlet of the exterior
vessel to maintain the temperature above the required temperature.
According to one independently important feature of the invention is
carbon being produced from the process to reduce the release of carbon dioxide
to
the atmosphere by removing carbon from a carbon bed at the bottom of the
exterior
vessel.
Preferably the feed material includes animal deadstock and parts and
wherein the temperature is maintained in the exterior vessel at above 1250
degrees
Celsius in order to destroy any pathogens.
Preferably there is provided a water injection system for adding water
into the reactor vessel.
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Preferably the combustion is effected without the addition of fossil fuel.
Preferably the air lock feed system is operated to add feed materials to
the reactor vessel to maintain feed products in the reactor vessel for
operation in a
continuous mode.
The invention also provides an apparatus having the same features as
set forth above.
According to one independently important feature of the invention, the
process involves configuring combustion regions to minimize, eliminate as
practicable, flame contact with component surfaces except the surfaces of
reactor
cones constructed of ceramic materials. Combustion air is dispersed into the
combustion chamber through a proprietary arrangement of perimeter openings in
the
combustion chamber perimeter such that, as practicable, the product gas flame
occurs "in space"; i.e. the cavity between the gasification cone and
combustion
chamber enclosure. The invention utilises radiation for the instantaneous
(speed of
light) transfer of product gas flame energy onto "line of sight" surfaces
that, due to
fundamentals of radiation at higher operating temperatures (above 1,000 deg.
C),
minimize temperature differentials between "line of sight" surfaces. This
allows
much higher operating temperatures for components fabricated of similar
materials
than possible where significant flame impingement occurs on combustion chamber
surfaces.
According to one independently important feature of the invention, the
process involves two negative pressure chambers, an upper wet feedstock
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conditioning chamber and a lower, in-line, high temperature reaction chamber.
Controlled volumes of preheated combustion air are drawn into the top of the
upper
chamber. A system of deflectors around the interior surface of the upper
chamber
provides an annular space around feedstock therein, creating a preheated
combustion air flow path down into the lower, high temperature reactor
chamber.
This feature facilitates evaporation of water that may be at or near the
vertical
perimeter surface of the feedstock charge, preventing liquid water flow onto
lower
chamber, high temperature surfaces.
Preferably air from the upper chamber fuels the random combustion
(depending on feedstock quality and moisture content) of mainly feedstock and
product gas generated at and near the feedstock-lower chamber surfaces
interface.
The combination of this combustion and radiation from the lower chamber
interior
surfaces collectively contribute to the feedstock destruction rate. The lower
chamber
is engulfed in flame resulting from combusting the remainder of product gas
that
exits the lower high temperature chamber and, when supplied with controlled
combustion air volumes, portions of the charcoal inventory at the bottom of
the
system.
Preferably the inner surface of the lower, high temperature chamber
contains both top-to-bottom gas passage ways and openings in the chamber wall
that allow unrestricted flow of gases around feed material therein and ready
escape
through numerous exits, including a bottom opening, into the external vessel
that
surrounds the lower, high temperature reaction chamber.
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The arrangement described in detail hereinafter can provide one or
more of the following features:
Complete organic materials combustion at high temperatures with no
requirement for supplemental fuels, all at feedstock moisture contents up to
the limit
5 of thermal energy in the organic component (as high as 70% water for
biomass) and
lump sizes up to whole, largest ruminant carcasses.
Dissociating and accumulating elemental carbon for either
sequestering/selling or combustion to sustain operation during low energy
feedstock
transients.
10 Continuous, sequential batch, high temperature, high rate,
pyrolysis/gasification process accomplished without flame impingement on
component surfaces.
Hazardous organics destruction ready to required Standards.
The system chambers have two second (minimum) retention (actual
gas volumes) at temperatures greater than 1,210 C (greater than 1,900 C
attainable
with feedstock energy only; special materials required in high temperature
regions).
No additional retention chambers or supplemental fossil fuel energy
required.
Universally configured component geometries facilitate continuous
feedstock material flow (by gravity) through combustion processes. No grates
or
internal mechanical conveyance systems are required,
Large turn down ratios (10:1) with fast recovery to high temperature
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operation by combusting portions of carbon reserve.
Adaptable internal component configurations customized to feedstock
characteristics.
No feedstock preparation is required, except for gross sizing for
passage through system openings.
No feedstock drying is required as long as average energy content of
organic component exceeds minimum necessary to maintain the minimal elemental
carbon reserve necessary to sustain desired operating temperatures during
transients.
The method tolerates (automatically) random, rapid and extreme
fluctuations in individual, or any combination or permutation thereof,
feedstock
quality, lump size and moisture content.
The method tolerates large and wide ranging fractions and shapes of
metal and mineral content in feedstock. Metal and mineral lump size limited
only by
the smallest passage dimension.
Capability to melt metals and minerals by burning elemental carbon
component of feedstock in dedicated, high temperature chamber.
These advantages can be obtained by an arrangement in which
organic materials are gravity fed into a conical shaped gasification chamber
where
the organics are gasified upon contact with interior surfaces. Gasification
occurs in
an oxygen free environment. Passageways on the inside of the gasification
chamber allow the unrestricted flow of vapours and gasification product gases
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towards the bottom of the cone. Ash, clinkers, and unburned carbon particles
exit
the bottom of the cone via gravity.
Carbon is sequestered from high energy feedstocks and is stored in a
chamber below the gasification cone. This carbon supplements the energy output
of
lower energy feedstocks to maintain desired operating temperatures at all
times.
The cone geometry supports organic feedstocks, eliminating the
requirement for grates or other combustion support systems. Organic material
that
may escape gasification and exit the bottom of the cone accumulates within the
ash
and carbon particle volume until burned along therewith; leaving only non
organic
ash as a solids emission.
The gasification cone is situated inside an enclosing container through
which thermal radiation can neither enter nor escape. Thermal energy from the
combustion of the product gas exiting the cone (and supplemental carbon
particle
combustion where required) is transferred via thermal radiation to both the
cone and
the enclosing container. Thermal radiation tends to equalize the surface
temperatures of both the cone and its enclosing container.
Combustion air used to oxidize the product gases leaving the
gasification chamber and carbon particles in the sump is preheated to over
1,000
degrees Fahrenheit.
A two stage combustion process is provided for the product gas
emitted from the gasifier chamber with the second stage operating at minimum
outlet
flue gas temperature of 2,500 F (attained with feedstock thermal energy only;
no
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fossil fuel or other auxiliary energy inputs) is accomplished by restricting
combustion
in the first stage to between about 70% to 85% of organic material with final,
complete combustion of gasses and gas conveyed organic materials occurring in
the
second stage.
A retention time of at least the order of two seconds in the second
stage combustion chamber (at actual gas flow rates and temperature therein)
facilitates complete combustion of organic materials and eliminates the
requirement
for gas emissions controls when processing biomass. Ash thereof consists of
minerals and metals only.
Carbon retained in the processor sump eliminates requirement for
feedstock drying and batch moisture management as long as one half hour
average
contains sufficient thermal energy to sustain process temperatures; e.g. one
feedstock batch can be 100% water (contaminated ice block for example).
Carbon retention for consumption, which acts to maintain temperatures
when processing low energy feedstock batches and rapid response first stage
combustion chamber temperature controls eliminate the requirement for
feedstock
quality management; e.g. the combustion can process a batch of relatively low
feedstock quality such as leather followed by a batch of rubber tires;
automatically
and unattended.
Rapid response anticipatory controls with a residual oxygen sensor in
the stack gas stream mitigates smoke emissions during extreme variations in
feedstock batch quality. A rapid rise in the stage one combustion chamber
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temperature indicates an event of extreme increase in feedstock quality
(energy
content). Such an occurrence causes the control system to
immediately reduce stage one combustion air supply (thus temperature
around the feedstock gasification cone; slowing processing rate),
initiate/increase combustion air bypass around the heat exchanger to
further cool stage 1 combustion chamber (if required),
and positions a second stage combustion air damper 100% open to
maximize organic burn rate therein and residual oxygen in stack gas stream.
The configuration is able to process hazardous materials to destruction
because of a negative pressure process (prevents material escape) and
retaining
materials for two seconds (minimum) in the second stage, high temperature
(2,500 F minimum), residual oxygen chamber.
The grate free configuration and a large diameter ash auger eliminates
the requirement to remove metal components from feedstock (e.g. rail tie
spikes,
hinges on demolition materials, etc.).
High temperature, radiant gasification eliminates the requirement for
sizing feedstock (other than to pass through the feed system openings) by
reducing
organic materials from outside surfaces inwardly. There is no requirement for
air or
gas flow through the feedstock. Gasification occurs at the feedstock plug
surfaces.
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High temperature flue gas-to-combustion air heat exchanger that
utilizes radiant energy distribution theory to mitigate hot spots at
continuous hot side
inlet temperatures of 2,500 F and periodic migrations up to 3,000 F.
The first stage of the two stage process converts biomass and non
5 toxic organics to three common components, product gas, carbon and water
vapor.
This facilitates predictable, repeatable conversion of product gas (similar
components but different proportions to natural gas) and carbon to particulate
free
gas emissions in the second stage; eliminating requirement for stack gas
processing
equipment/systems.
10 BRIEF DESCRIPTION OF THE DRAWINGS
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
Figure 1 is a cross sectional view of the combustion components only
of a combustion system according to the present invention.
15 Figure 2 is a schematic illustration of the system of Figure 1.
Figure 3 is a cross sectional view of a modified combustion chamber
for use with the system according to the present invention.
Figure 4 is a schematic illustration of the whole system including the
energy extraction systems.
Figure 5 is a schematic illustration of the complete system of a second
embodiment of combustion system according to the present invention wherein the
combustion chamber is formed in two parts.
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Figure 6 is a cross-sectional view of the combustion chamber of Figure
on an enlarged scale.
DETAILED DESCRIPTION
In Figure 1 is shown a combustion chamber generally indicated at 10
5 which includes an interior reaction vessel 11 and an exterior combustion
vessel 12
within which the combustion occurs. Feed materials are fed into the reaction
vessel
11 by a feeding system generally indicated at 13 which includes an air lock
system
defined by gates 14 and 15 which can be operated sequentially to allow
materials
between the gates to be deposited into the reaction vessel 11 for breakdown. A
conveyor 16 is provided in the form of an elevator which raises the materials
from
the ground to the necessary height above the feeding system 13 so that when
dropped into the feeding system, the remainder of the operation is effected by
gravity through the primary chamber 11 into the exterior chamber 12 without
the
necessity for any moving elements to carry the fed materials. From the feed
system
13, the feed materials are carried through a chute 17 and into the interior of
the
reaction vessel 11.
The reaction vessel 11 is shaped and arranged so that the feed
materials drop onto side walls of the vessel which are inclined downwardly and
inwardly underneath the chute 17 so that the materials are restricted from
falling
straight through the vessel 11 and initially engage surfaces of the vessel 11
so as to
receive heat from the walls of the vessel 11 to a degree sufficient to carry
out
breakdown of the materials.
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In the embodiment shown in Figure 1, vessel 11 is in the form of a
conical structure that extends from an open mouth 18 at the upper end
downwardly
to a bottom mouth 19 of smaller dimensions then the mouth 18 so that the walls
extend underneath the mouth 18.
The dimensions of the conical shape are selected so the materials can
fall through the bottom mouth 19 under gravity but are restrained within the
primary
sufficiently to at least commence and preferably complete the breakdown of the
materials to the components of carbon, water vapour and produce a gas. The
angle
of convergence of the side walls will vary depending upon the type of material
with
which the device is intended to operate. In a situation where the device is
intended
to operate with primarily or commonly slurry with very high water content, the
angle
of the surfaces may be significantly increased as shown in Figure 3 so that
the time
of dwell of the slurry material on the surfaces is increased sufficiently to
cause
heating of the slurry to drive off primarily the water vapour prior to
breakdown of the
remaining materials into carbon and producer gas while heating the materials
to the
required temperature described hereinafter.
It will be appreciated that a very high angle of inclination of the material
which assist in maintaining the flowable material to the slurry in the surface
may in
many cases be unsuitable for materials which has a higher content of solid
materials
since materials may collect on an inclined surface which has a higher angle
and
allows the material to discharge by gravity and such collection my interfere
with the
operation of the device.
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Though materials are fed in both solid and in slurry form, the solid
materials may collect on the surfaces thus impeding or slowing the flow of the
slurry
sufficiently to form a mass within the primary vessel which carries out the
heating
and breakdown of the materials within the primary vessel.
As the breakdown primarily occurs at the surface where the heat is at a
maximum, the materials sitting on the surface tend to breakdown from the
surface
allowing the remaining materials to migrate toward the surface for further
breakdown. Thus a combination of solid and liquid materials can provide in
effect a
plug of the feed materials within the vessel which moves towards the surfaces
and
then is carried by gravity acting upon the solid materials to move downwardly
through the bottom mouth 19.
In order to assist in maintaining the materials on the surface for an
extended period of teem, there may be provided on the surface baffles or guide
plates or other elements which assist in interfering with the simple sliding
movement
of the material over the surface. One preferred example of elements which can
be
carried on the surface which restrict the flow of the materials over the
surface but
can move to allow larger elements of the materials to pass by is provided by a
series
of chains 20 which are mounted on the surfaces defining the primary vessel at
the
top of the vessel and hang downwardly toward the bottom mouth 19. Such chains
are free to move about so that any larger solid elements can pass by the
chains and
through the open mouth, while the chains tend to restrict slurry or other
materials of
a smaller nature from sliding too quickly over the surface.
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The open mouth 19 may include one or more slots 21 around the
periphery so that the producer gas tends to escape from the vessel at a
position
spaced outwardly and upwardly from the open mouth so that the gas is free to
escape even if the bottom mouth 19 should be partly or wholly closed by
collecting
materials. The producer gas thus burns as it escapes through the slot around
the
periphery of the reaction vessel so that heating is applied directly to the
outside wall
of the reaction vessel.
The exterior vessel 12 surrounds the whole of the outside wall forming
the reaction vessel 11 so that combustion occurring within the exterior vessel
12
acts to heat the whole of the wall of the vessel 11. Above the vessel 11 the
chute 17
is located in an area which is insulated so that little or no heat or reduced
amount of
heat is applied in that area however the vessel 11 itself is simply formed by
a non-
insulted wall. Thus heat is transferred from the combustion occurring in the
exterior
chamber to the outside wall of the reaction vessel to effect the breakdown of
the
materials as described above at the temperatures described hereinafter.
The exterior chamber defines a bottom collection zone 22 for collecting
carbon in solid form falling from the open mouth 19. The carbon thus forms a
carbon bed which extends to the bottom of the chamber 12. The top of the
carbon
bed can vary in height within the chamber 12 and may indeed extend above the
height of the mouth 19. The carbon bed extends downwardly to a layer of ash 24
which is collected below the carbon bed 23. The ash is extracted from the
bottom of
the chamber 12 by an extraction auger (not shown). Duct 25 is a carbon sump
CA 02522384 2010-02-03
combustion air supply. Combustion air flow control gate 26 meters the entry of
air
through the ash layer 24 and into the carbon bed 23 through the outlet duct
25.
The carbon bed 23 provides two functions. Firstly it provides a source
of heat energy which can be assembled or collected during times of excess heat
5 energy within the feed material so that the carbon bed builds up during this
time
period. During time periods when the heat energy within the feed materials is
below
the requirement to reach the required temperature, carbon can be burned from
the
carbon bed thus depleting the carbon bed. This may occur when the feed
materials
are high in water content. Thus there is no necessity to add additional fossil
fuels
10 within the combustion chamber 12 due to the provision of the energy source
defined
by the carbon bed 23. It will be appreciated that suitable management of the
total
quantity of heat energy within the feed materials must be controlled so that
the
energy level must be sufficient so that the depletion of the carbon layer can
only be
temporary and cannot continue on a permanent basis since otherwise the carbon
15 material would be eventually completely depleted. For this purpose a sensor
27 can
be provided which detects the top level of the carbon bed. A second sensor 28
can
also be provided to detect the level of the bottom of the carbon bed at the
intersection with the ash 24. A duct 29 provides a combustion air supply to
the
product gas into chamber 12 above the carbon bed top surface.
20 Secondly the carbon bed provides a base onto which materials falling
from the primary vessel can drop. In most cases the material exiting from the
mouth
19 is the carbon itself which falls onto the bed and supplements the bed.
However
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in the case where some materials pass through the primary vessel without the
complete breakdown having occurred, such materials fall onto the top of the
carbon
bed and are maintained by the carbon bed supported within the burning carbon
so
that the further required breakdown can occur.
Thus there is no necessity for a grate or other horizontal support which
contains the carbon or other burning material so that the structure is in
effect
"grateless".
The top surface of the carbon layer can extend upwardly above the
mouth 19, in which case the carbon layer will begin to collect within the
interior of the
primary vessel 11 and thus restrict the volume remaining within the vessel for
the
breakdown of the feed materials. In the event that this is expected to be
temporary,
the carbon level can be left at the elevated position until it is again
depleted by
supply of feed materials of reduced thermal energy.
However in the event that the carbon production is expected to exceed
the carbon requirement for supplying heat, the discharge auger (not shown) can
be
operated to extract the carbon bed at a rate to maintain the upper level of
the carbon
bed at the required position or periodically depending upon a measured height
of the
carbon bed.
Combustion occurs within the exterior chamber 12 of both the carbon
in the carbon bed and of the production gases exiting from the mouth 19. This
combustion is contained within the chamber 12 which is surrounded by
insulating
material to maintain the temperature within the combustion chamber 12 at a
required
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elevated temperature.
The completely burnt gases within the combustion chamber exit
through a flue 30 into a heat exchanger 31 and from the heat exchanger into an
exit
system 32. The exit system is connected with a plurality of known elements for
extracting energy from the heated flue gases either in the form of motors such
as a
Stirling engine or as a heat exchanger from which the heat extracted is used
for
various purposes including heating other process, heating building, cooling
buildings
and the like. The heat exchanger 31 provides air into a chamber 33 which
supplies
air to ducts 25 and 29 via control dampers 26 and 34.
The arrangement described above therefore provides a system for
converting organic waste including harvested biomass and diseased plant and
animal material into electrical, heating and cooling energies, sterile water
and carbon
or charcoal.
The system operates at temperatures in excess of 1200 C (2200 F)
as detected by a temperature sensor 35 at the exit of the combustion chamber
12.
The system therefore transforms the feed materials containing potentially
dangerous
pathogens into emissions-compliant materials consisting mainly of carbon
dioxide,
water vapour and sterile ash. Emissions are greenhouse gas neutral when
processing untreated plant and animal materials.
The dual gate feedstock air lock at the inlet into the primary chamber
ensures that the primary chamber can operate at the required temperature
without
heat escaping through the feed system or air entering through the feed system
to
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interfere with the breakdown of the materials within the primary vessel. The
system
is maintained under negative pressure by an inducted draft fan 37 shown
schematically in the flue 32 so that it acts to draw air into the system
through the
ducts 25 and 29. Duct 29 via the control damper 34 provides combustion air
plus
residual oxygen to the producer gas.
The system can be started by operating the fan draft with both
feedstock air lock gates open while low moisture content biomass such as saw
dust,
sunflower seeds, wood shavings is burned in the primary chamber 11 until
minimum
system operating temperatures are obtained as detected by the temperature
sensor
35. In this case the system is changed to operating mode in which the feed
gates
are closed and the producer gas combustion/residual oxygen air is controlled
by the
dampers 34 and 26 which provide air to the charcoal bed to provide the burning
of
the charcoal bed and producer gas to provide the required temperature within
the
combustion chamber.
The system is operated by detecting the temperature 35 and supplying
sufficient air to burn the charcoal bed and producer gas to maintain the
required
temperature. Start of duration will range from approximately twenty to forty
minutes
depending upon the capacity.
The organic material is converted in an oxygen starved environment
into water vapour, producer a gas and carbon in the gasification chamber or
primary
chamber. Producer gas is similar in composition to natural gas but is at a
lower
energy content. The energy content of the producer gas will vary over a wide
range
CA 02522384 2010-02-03
24
depending upon feedstock quality and moisture content, likely between two
hundred
and five hundred btu/cubic foot which is approximately twenty percent to fifty
percent
of the energy of natural gas.
The feedstock air lock prevents oxygen entry into the primary chamber
11 during production of the super heated combustible gases. The superheated
combustible gases (mainly producer gas) exit the bottom of the reactor chamber
and
burn around the exterior thereof as permitted by the controlled inflow of flue
gas pre-
heated combustion air. The carbon component accumulates in the bed underneath
the mouth 19. The preheating of the inlet air in the heat exchanger 31 ensures
that
the maximum efficiency of combustion occurs within the chamber 12.
The system reduces feedstock to inert ash material volumes in the
range of 0.5 percent to 10 percent of the original depending upon the non
combustible material and moisture content of the feedstock. The matter
reduction
will depend upon the type of feedstock including wood, straw, deadstock,
offal,
manure, municipal/medical/industrial wastes together with the water content
and
voids within the feedstock which carry air into the system through the feed
air lock.
The system illustrated in Figures 5 and 6 comprises a combustion
chamber generally indicated at 40 defined by a reactor vessel 41 and an
exterior
combustion chamber 42. The combustion chamber 42 is divided into an interior
or
first combustion stage 43 and an exterior or second combustion stage 44.
The reactor vessel 41 includes an upper portion 45 which is fed with
the feed stock from a conveyor 46 which discharges the feed material through a
pair
CA 02522384 2010-02-03
of airlock gates 47. At the bottom of the first portion 45 of the reactor
vessel 41 is
provided a conical lower portion 48 which controls the gasification of the
feed stock
in the first gasification stage.
The conical portion 48 of the reactor vessel thus converges from an
5 upper mouth 50 downwardly to a bottom end 51 and provides an inner surface
which
controls the flow of the feed stock over the surface while the feed stock is
heated to
effect the gasification as discussed herein. The surface of the conical
section may
include channels and guides and elements which control the movement of the
material and allow the product gas to flow over the surface to the mouth 51
for
10 discharge.
The combustion chamber 40 includes an exterior wall 52 which is
covered by a layer of insulation 53. The first portion 45 of the reactor
vessel extends
through an opening in the upper horizontal wall portion of the chamber 52 so
that an
initial portion is exterior to the insulation 53 and a lower portion projects
into the
15 heated interior of the combustion chamber. The conical lower portion 48 is
located
wholly within the interior of the combustion chamber generally at a central
area
thereof so as to receive the maximum heat within the combustion chamber.
The combustion chamber 40 is divided into the inner combustion stage
43 and the outer combustion stage 44 by a cylindrical wall 54 which surrounds
the
20 reactor vessel. Thus the wall 54. includes a first upper cylindrical
portion 54A and a
second lower generally conical portion 54B which follows generally the angle
of the
lower conical portion 48 so as to define a conical channel outside the conical
portion
CA 02522384 2010-02-03
26
48 within which the main combustion occurs. The upper portion 54A defines a
channel 55 surrounding the upper portion 45 of the reactor vessel. The wall 54
terminates at an upper edge 56 which is spaced from the top wall of the
combustion
chamber so as to allow gases to escape from the channel 55 around the top edge
56 and into the second combustion stage 44. The stage 44 surrounds the wall 54
and is located within a generally annular chamber surrounding the wall 54 and
inside
a side wall 58 of the combustion chamber. A flue 59 is connected to the side
wall 58
of the second chamber 44 adjacent a bottom wall 60 of the combustion chamber.
Thus the combustible gases exiting the mouth 51 of the cone pass generally in
a
flow as indicated by arrows through the first combustion stage 43 and into the
second combustion stage 44 at the top and exit through the flue 59 at the
bottom.
Within the flue 59 is mounted a heat exchanger 61 which extracts heat
form the gases within the flue. A fan 62 draws the gases through the heat
exchanger and from the flue and expels those gases into a stack 63 for
suitable
discharge to the environment. A secondary flue discharge 64 is provided as an
emergency in event of key system component failure at the top of the second
combustion stage 48 so as to receive gases as they exit the first combustion
stage
43 at the top edge 56 of the wall 54. These gases also pass to the stack 63
for
discharge. Inlet combustion air is fed by a fan 65 into a duct 66. The duct
splits into
a first portion 67 and a second portion 68. These two portions reconnect at an
inlet
supply duct 69. The portion 67 of the duct bypasses the heat exchanger 61. The
portion 68 of the duct carries air through the heat exchanger 61 in the
opposite path
CA 02522384 2010-02-03
27
to the flue gases so as to receive heat from the flue gases. Thus the inlet
air in the
duct 69 can be heated to a controlled extent depending upon the amount of air
passed along the duct paths 67 and 68 and thus the amount that is heated by
the
heat exchanger 61.
A flue gas cooling air inlet is provided upstream of the induced draft fan
62so that, in the event that the flue gases exceed the induced draft fan 62
rating,
cooling air is metered into the fan inlet.
The inlet air duct 69 splits into two supply ducts 71 and 72. The duct
71 supplies an annular plenum 73 surrounding the conical portion 54B of the
wall 54.
The conical portion 54B has a series of holes allowing the entry of combustion
air
from the duct 71 into the plenum 73 and from that plenum into the first
combustion
stage 43 at the location surrounding the cone 48.
The second duct 72 communicates air to a second plenum 75 below
the cone 48. This plenum 75 has one or more openings 76 for feeding air into a
bottom chamber 77 below the cone 48. The bottom chamber 77 is defined by a
wall
portion 78 at the bottom of the conical section 54B and extending to the
bottom wall
60 of the combustion chamber. The bottom chamber 77 forms a receptacle for
carbon and residual organics which fall from the cone 48 at the mouth 51. Thus
the
air from the duct 72 which passes into the plenum 75 is supplied into the
carbon
collected within the chamber 77 below the mouth 51. Most of the combustion
product gasses escape from the plenum 77 into the bottom of the bed of carbon
by
passing through a pipe 79 having an upper cover 80 so that the air can escape
at
CA 02522384 2010-02-03
28
the top of the chamber 77 either above the bed of carbon or below the top of
the bed
of carbon depending upon the height of the bed which will vary as described
herein.
Below the chamber 77 is provided a collection duct 81 for collecting
ash and/or carbon so that the ash and any excess carbon can be removed through
the duct 81 and discharged through a conveyor 82.
The air supply ducts 71 and 72 contain suitable damper controls to
vary the amount of air flow into the plenums 73 and 75. The temperature of the
air
supply into these plenums can also be controlled as previously described by
varying
the ratio of air which is passed through the heat exchanger 61.
A further air inlet 83 is provided for allowing air into the top of the
second combustion stage 44. In this way the air supply to the carbon bed can
be
controlled independently of the air supply to the first combustion stage 43
and
independently of the air supply to the second combustion stage 44.
The temperature within the first combustion stage can be controlled to
control the heat applied to the reactor vessel since the heat supply to the
reactor
vessel is needed to be reduced and increased depending upon the fuel content
in
the feed stock supply.
As the temperature control within the first combustion stage is
independent of the combustion within the second combustion stage, the second
combustion stage can be maintained at a required level so that it maintains
the
necessary high temperature and the necessary dwell time of at least two
seconds to
ensure that the combustion is sufficiently complete to meet acceptable
standards.
CA 02522384 2010-02-03
29
The system illustrated in Figure 5 also includes the following sensors
and control valves (dampers):
Combustion air heat exchanger damper (CAHXD)
Induced draft fan cooling air damper (IDFCD)
Tertiary (stage 2 combustion chamber) combustion air damper (TCAD)
Carbon sump combustion air damper (CSCAD)
Product gas combustion air damper (PGCAD)
Emergency vent damper (EVD)
Feedstock air lock level sensor (FSALLS)
Feedstock makeup sensor, FSMUS
Combustion air bypass damper (CABD)
The combustion region beneath the conical portion is arranged so as
to minimize, or eliminate as practicable, flame contact with component
surfaces.
Combustion air is dispersed into the combustion chamber 43 through a plurality
of
perimeter openings in the combustion chamber perimeter at the plenum 73 such
that
the product gas flame occurs "in space"; i.e. in the cavity between the
gasification
cone 48 and combustion chamber enclosure 54. The invention utilises radiation
for
the instantaneous (speed of light) transfer of product gas flame energy onto
"line of
sight" surfaces that, due to fundamentals of radiation at higher operating
temperatures (above 1,000 deg. C), minimize temperature differentials between
surfaces. This allows much higher operating temperatures for components
fabricated of similar materials than possible where significant flame
impingement
CA 02522384 2010-02-03
occurs on combustion chamber surfaces.
The inner surface of the lower, high temperature chamber contains
both top-to-bottom gas passage ways and openings in the chamber wall that
allow
unrestricted flow of gases around feed material therein and ready escape
through
5 numerous exits, including a bottom opening, into the external vessel that
surrounds
the lower, high temperature reaction chamber.
The system provides the following features
The system converts, in a high temperature environment, organic
materials into a 2,200 F (plus) flue gas stream and sterile ash.
10 Integrated drying/sizing/combustion system eliminates feedstock
preparation requirements, other than gross lump sizing to accommodate
feedstock
system flow path dimensions;
Downward plug flow of feedstock undergoing surface gasification, no
flow required through feedstock plug in gasification chamber;
15 Integral, continuous, forced draft conveyance of charcoal fines down
through annular spaces around perimeter of feedstock plug 48 to primary
chamber
bottom outlet 81;
Feedstock plug surface agitation, where required, within the
gasification chamber bottom outlet 51;
20 Sequential, continuous gravity flow, and collectively controlled
gasification-producer gas combustion-charcoal combustion processes
automatically
maintain stable operation under rapidly and continuously changing permutations
and
CA 02522384 2010-02-03
31
combinations of feedstock quality, lump size and moisture content (up to
maximum
practicable moisture contents relative to feedstock energy; practical
limitation
anticipated in range of 80% moisture content);
High feedstock energy conversion efficiency attained by:
system insulation limiting exterior surface temperatures to 200 F;
high efficiency heat transfer from residual flue gas temperatures to
combustion air streams, condensing flue gas stream moisture and reducing stack
temperatures to below 200 F;
99% plus oxidation/removal of charcoal from ash stream;
Continuous, automatic ash extraction;
Minimal, if any, flue gas and ash treatment necessary to meet Kyoto
accord objectives and 2004 emissions standards when processing biomass;
High temperature operation makes each system hazardous waste
destruction ready, requiring only configuration, emissions testing and
licensing for
such applications;
Minimal materials handling;
High operating temperature materials lined containment vessel and
ceramic reactor;
Close coupled combustor capable of outlet gas stream temperatures
up to 2,000 C (3,600 F) and heat-up (from -40 to 2,000 C) and cool down in
less
then 1-'/2 hours;
Capable of rapid turn down to, and automatic control at 10% of rated
CA 02522384 2010-02-03
32
capacity. Temperatures at minimum capacity will be minimal required to sustain
operation and build charcoal for auto recovery to processing temperatures in
preparation for next production shift (e.g. hazardous waste destruction
operation);
Grate free;
Charcoal reserve. Process dries/gasifies feedstock, then combusts
charcoal;
No feedstock sizing (other then for feed hopper dimensions) or drying
of feedstock;
Process random, transient variations in organic energy content and
feedstock moisture levels up to self extinguishing values;
Tankless, atmospheric pressure steam generator; apparently product
recently introduced where water injected right into flame of fossil fuelled
burner;
Carbon lock up.
Further details of the specific construction of one example are set out
in the following specification:
Feedstock System
Hopper
304 stainless steel.
Capacity: 250 cubic feet at material densities ranging from 10 to 60
pounds/cubic foot.
Watertight.
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33
Bottom profiled to accommodate extension of feedstock conveyor
screw.
Structure and heavy duty thrust bearing mount at lower (back) end of
hopper to withstand shearing forces when cutting bone and large wood pieces at
hopper outlet.
Structural frame to support lowest portion of hopper 18" minimum
above floor surface.
Ladder up side of hopper for viewing contents.
Conveyor
304 stainless steel.
Conveying capacity: 75 cubic feet/hour at material density of 10
pounds/cubic foot ranging to 25 cubic feet/hour at 60 pound/cubic foot.
Conveyor: 40 feet long, 24" diameter, 30 degree incline. Conveyor
tube 30 feet long, bottom 10 feet of conveyor screw extends through feedstock
hopper. All flighting in hopper to 4" downstream of reinforced hopper exit
band shall
be heavy duty construction with leading edge saw tooth profiled for cutting
through
large ruminant bones and larger (up to 10"square) wood-plastic profiles. In-
hopper
portion has heavy duty shaft to take torque of cutter edged flighting.
Totally enclosed conveyor tube. Bottom 50% of tube welded
watertight; top 50% of tube hinged in 6' maximum lengths. Provide watertight
CA 02522384 2010-02-03
34
gasketting at all hinged top cover seams. Provide quick release latch(s) for
each
hinged section.
hp hydraulic motor and gear reduction unit for optimal combination of
conveying capacity and hopper outlet shearing performance.
5 Heavy duty bottom end thrust bearing for mounting onto hopper frame.
Screw flighting, tube profiles and "anti spin" features designed to, as
practicable, maximize feedstock lift performance (minimize material spinning
about
conveyor shaft) for complete range of materials ranging from liquid saturated
slurries
to dry "fluffy" products.
Painted conveyor support structure and full length inclined access stair
and handrails.
Carrier and top end bearings to suit specified application.
Discharge transition from 30" long x 24" wide to 17" square at
maximum angle of 20 degrees off vertical.
Air Lock
304 stainless steel.
Chute: 1/8" minimum thickness; horizontal air lock gates; '/" minimum
thickness.
Gate slide openings gasketted with high quality materials. Provide
gate wiper blades to minimize potential for leakage out of slide gate chamber.
17" square by 42" high.
CA 02522384 2010-02-03
Two slide gates in guide frames, each with hydraulic actuator and
mounting mechanism.
Top slide gate at connection to feedstock conveyor discharge chute,
bottom slide gate 34" below underside of top slide gate.
5 Processor
Shell
PYROCAST TG thermal shock resistant castable refractory, 3"
(minimum) thick, as fabricated by Pyrotek phone (519) 787-1421with exterior
insulation and weather covering such as aluminum cladding.
10 Annular combustion air plenums (around sloped portions of upper
product gas and lower carbon chambers) to be 3" (minimum) thick, PYROCAST TG.
Envelope insulation of material qualities and thickness necessary to
limit the outer surface temperatures to less than 200 F at inner surface
temperatures
of 2,500, (likely in range of 12" thick.
15 Provide 80" high x 36" wide removable panel in processor exterior shell
for access into secondary combustion chamber. Access panel shall be complete
with articulated structural support mechanism. Panel support mechanism to
support
panel at all times it is being moved completely clear of access opening; and
stowed
thereat.
20 Support structure, access stair and walkway around half of the top
perimeter.
CA 02522384 2010-02-03
36
Gasification Chamber
Hexoloy silicon carbide rated for continuous operation up to 4,000 F.
Heat Exchanger
Heat exchanger shell and all hot side plenums/partitions are 3" thick,
PYROCAST TG thermal shock resistant castable refractory as fabricated by
Pyrotek.
Hot side: Continuously modulates between 500 cfm and 2,500 cfm at
inlet temperatures ranging between 900 F and 2,700 F. Periodic, short duration
(5
minute maximum anticipated) hot side inlet temperature spikes as high as 3,000
F
possible. Ideally hot side inlet-outlet pressure differential less than 1"
water column.
Cold side: zero flow to 1,500 cfm max. (modulates) at inlet
temperatures ranging from -40 deg. F to 140 deg. F; design outlet temperature
in
range of 1,700 F at 2,500 F hot side entering temperatures. Ideally cold side
inlet-
outlet pressure differential less than 2" water column.
Heat exchanger tubes: type T-310 stainless steel, 9 of each 28" long,
3.5" O.D. pipe and serrated fin, 39 fins/ft; 0.05 thick fin; 1.25" fin height.
Insulated heat exchanger exterior with material qualities and thickness
necessary to limit outer surface temperatures to less than 200 F at inner
surface
temperatures of 2,200 F (approx. 8" thick). Apply weather protection
jacketing.
Induced Draft Fan
CA 02522384 2010-02-03
37
Rated (maximum) 6,000 scfm at 500 F and 6" water column; infinitely
variable capacity down to 500 scfm at 300 F and reduced associated system
curve
pressures.
Driven by approx. 8 hp. hydraulic motor.
Combustion Air Fan
Rated (maximum) 2,000 scfm at 140 F and 4" water column; infinitely
variable capacity down to 200 scfm at -40 F and reduced associated system
curve
pressures.
Driven by approx. 2 hp. hydraulic motor.
Ductwork
Type T-310 stainless steel rated for continuous operation at 2,100F for
emergency flue gas vent between processor and vent damper, type 304 stainless
steel from vent damper to stack connection.
Approximately 3" thick, PYROCAST TG for preheated combustion air
between heat exchanger outlet and processor product gas and carbon sump
combustion air plenums.
Type T-310 stainless steel for flue gas duct out of heat exchanger to
downstream edge of induced draft fan cooling air inlet. Type 304 stainless
steel
from that location to induced draft fan suction connection and for the induced
draft
fan discharge into stack.
CA 02522384 2010-02-03
38
Type 304 stainless steel from combustion air fan discharge to heat
exchanger connections.
Insulated exterior with material qualities and thickness necessary to
limit outer surface temperatures to less than 200F at inner surface
temperatures of
2,200 F. Apply weather protection jacketing; except where identified as "non
insulated" on system schematic drawing PS-1.
A stainless steel, expanded mesh heat shield over non insulated flue
gas ductwork and around the induced draft fan. Provide "quick release" access
doors in fan heat shield enclosure and at locations where access to mechanical
and
control system components is required.
Ash Extraction
Type 304 stainless steel, 10" diameter x 20' long screw conveyor at 30
deg. incline.
Type 304 stainless steel dual slide gate conveyor discharge air lock.
Hydraulic conveyor motor, 1/2 hp.
Two hydraulic actuators for hydraulic gates.
Dampers
Product gas and carbon sump dampers are Hexoloy silicon carbide
with V-notch orifice sliding plate overlapping a mating V-notch stationary
plate.
Both dampers in combustion air ductwork upstream of heat exchanger,
the secondary chamber combustion air inlet damper and the induced draft fan
inlet
CA 02522384 2010-02-03
39
cooling air damper shall be type 304 stainless steel, opposed blade,
industrial grade
design.
Emergency vent damper shall be T-310 stainless steel rated for
continuous operation at 2,100 F, spring returned to normally open position
guillotine
design.
Seven hydraulic damper actuators.
Chimney
Free standing, 24" diameter x 40' high, insulated double wall stainless
steel construction code approved for continuous industrial application
operation at
1,000 F.
Hydraulic Power Unit
Packaged, 3,000 psi output unit with factory electrical and control
panel.
Hydraulic pump with full modulation capability over complete range of
zero to full flow accomplished by unloading drive motor, not using pressure
relief
strategies.
Pump motor and drive coupling.
Full modulation controls over complete range from no load to 20 hp
hydraulic output capacity.
Oil reservoir and cooler.
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Hydraulic lines and control valves for 4 motors (2 conveyors and 2
fans), 4 two-position air lock gates, 1 two position guillotine emergency vent
damper
and 6 modulating dampers.
Propane Start Up Heater
5 1,000,000 Btuh output capacity manual insertion torch(s).
Operation is carried out in accordance with the following parameters:
General
PLC controlled with complete remote, real time process parameter display,
remote plant control capability and appropriate password/local operator
10 clearance/advisement of updates.
System graphic based data displays.
Capability to produce trend plots for selected system parameters.
All control setpoints fully adjustable.
Feedstock System
15 The feedstock system is locked out whenever the propane start up heater
is operating.
During automatic operation, a material level detector (feedstock makeup
sensor) below the lower feedstock air lock gate is operable.
CA 02522384 2010-02-03
41
Whenever no material is sensed by the sensor, the lower feedstock air
lock gate closes. When a sensor proves the lower gate has closed, the upper
feedstock
air lock gate opens.
The feedstock conveyor starts when a sensor proves the upper gate is
fully open, and operates until the feedstock air lock level sensor detects
material, closing
the upper feedstock gate.
Upon proof of upper gate closure, the lower feedstock gate opens,
discharging the feedstock batch into the gasification cone feed chute. The
lower
feedstock gate remains open until there is no material detected by the sensor
and the
Feedstock System process repeats.
The feedstock conveyor can be manually reversed by a control system
override.
Start Up
The following steps are carried out:
Ensure there is feedstock in conveyor hopper and the screw conveyor is
operated manually until full to discharge opening.
Select "start up" mode.
Control system positions dampers as follows:
Emergency vent damper closed
Product gas combustion air damper open
CA 02522384 2010-02-03
42
Carbon sump combustion air damper is closed unless required to
modulate to maintain the tertiary combustion air damper at about 15% open.
The combustion air damper of the second stage combustion chamber
modulates to maintain desired residual oxygen in heat exchanger flue gas
outlet.
Induced draft fan cooling air damper modulates to prevent induced draft
fan inlet temperature from exceeding 500F.
Combustion air bypass damper is closed
Combustion air heat exchanger damper is open
Air lock gate positions:
Feedstock upper air lock gate is closed
Feedstock lower air lock gate is open
Ash upper air lock gate is closed
Ash lower air lock gate is open
Start induced draft fan. Suction side static pressure sensor confirms
operation. Variable speed drive operates to maintain -0.25" we at heat
exchanger flue
gas inlet.
Start combustion air fan that is auto speed controlled to maintain -0.1" we
in heat exchanger combustion air outlet chamber.
Ignite propane torch(s) and insert into heat exchanger combustion air
outlet plenum.
CA 02522384 2010-02-03
43
When the primary combustion chamber outlet temperature reaches 2,300
F, manually switch controls to "Automatic" and shut off propane torch(s),
remove torch(s)
and replace insulated plug(s) in torch opening(s).
When the control system is switched to automatic, the combustion air fan
auto speed control resets to maintain 1.0" we in the heat exchanger combustion
air outlet
chamber and the heat exchanger inlet pressure resets to -0.5" wc; maintained
thereat by
the induced draft fan variable speed control.
Operation
The combustion is controlled by the combination of residual oxygen in the
heat exchanger flue gas outlet and the secondary combustion chamber outlet
temperature (same as heat exchanger inlet temperature).
All dampers modulate linearly over their full range (0% to 100%) within
temperature limits in the following table.
The EVD remains closed at all times the induced draft fan is proven
operational and, when operational, there is a negative pressure at the heat
exchanger
inlet. It only opens on the combination of control system calling for induced
draft fan
operation, no negative static pressure at heat exchanger inlet while the
system is
operating in the automatic mode.
The 1DFCD modulates to prevent induced draft fan inlet temperature from
exceeding 500F at any time. It is full closed whenever heat exchanger outlet
temperature is at or below 500F.
CA 02522384 2010-02-03
44
HX inlet (F) Damper Position Comment
2,700 TCAD modulating Modulates to maintain 15 ppm residual
oxygen in the heat exchanger flue gas outlet
stream, opens further if necessary to restrict
heat exchanger inlet to 2,700 F.
PGCAD modulating First priority is maintaining TCAD 15% open
until primary combustion chamber outlet
temperature reaches 2,500 F, then modulates
to hold that temperature while TCAD
modulates open beyond 15% to maintain heat
exchanger outlet oxygen.
CSCAD closed
CABD open
CAHXD closed
2,500* TCAD modulating Modulates to maintain 15 ppm residual
oxygen in heat exchanger outlet.
PGCAD modulating First priority is maintaining TCAD 15% open
until primary combustion chamber outlet
temperature rises to 200 F less than HX inlet,
then modulates to hold that reduced
CA 02522384 2010-02-03
temperature while TCAD modulates open
beyond 15% to maintain heat exchanger outlet
oxygen.
CSCAD modulating, Modulates, only if CAHXD full open, to
conditional maintain primary combustion chamber outlet
temperature 200E less than HX inlet. If no
carbon in sump, then TCAD will start
modulating closed because of excess
combustion air in processor. CSCAD
reference will be TCAD going less than 15%
open causing CSCAD to modulate first till it is
full closed then PGCAD modulates closed if
TCAD continues needing to reduce position
(in arriving at 15% open) because of to much
residual oxygen in stack.
CABD modulating As required io hold primary combustion
chamber outlet temperature at 200F less than
HX inlet temperature; opens when primary
combustion chamber outlet above that
condition; reverse operation when below that
condition
CAHXD modulating Linearly and opposite to CABD
CA 02522384 2010-02-03
46
' Normal operating condition.
Rich Fuel Batch Response
A rate of rise detector in the primary chamber outlet will cause the TCAD
and CABPD to rapidly position full open at a temperature rise rate equal or
exceeding
50F in 2 seconds. The CAHXD will rapidly and simultaneously position full
closed.
The dampers then migrate to positions necessary for 2,500 F operation.
Ash Removal
Operates off ash-charcoal interface level as sensed by temperature near
bottom of carbon sump. A continuous "trickle" of combustion air will cause
carbon in
bottom of sump to slowly turn to ash. When only ash, temperature of interface
will
approach combustion air temperature, initiating timed ash extraction cycle
after which
interface temperature check will repeat until interface temperature rises,
indicating
presence of charcoal in ash.
"OFF" status is bottom air lock gate open, top gate closed.
When ash is detected in bottom of the carbon sump 81, a bottom air lock
gate closes and a top gate opens (not shown). Ash conveyor 82 runs till air
lock level
detector senses ash pile just below top gate. The conveyor stops, the top gate
closes
and the bottom gate opens. The bottom gate then closes, the top gate opens and
the
cycle repeats till the ash-carbon interface temperature sensor detects a
temperature rise
due to charcoal burning.
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47
A rapid response anticipatory controls is operated with a residual
oxygen sensor in the gas stream in the stack 63 which mitigates smoke
emissions
during extreme variations in feedstock batch quality. A rapid rise in the
temperature
in the first stage combustion chamber 43 indicates an event of extreme
increase in
feedstock quality (energy content) in the retention cone 48. Such an
occurrence
causes the control system to:
immediately reduce first stage combustion air supply through plenum
73 (thus the temperature around the feedstock gasification cone 48 falls;
slowing the
processing rate),
initiate/increase combustion air bypass through the duct 67 around the
heat exchanger 61 to further cool the first stage combustion chamber 43 (if
required),
and positions the second stage combustion air damper TCAD 100%
open to maximize the organic burn rate therein to reduce residual oxygen in
stack
gas stream.
The evenly distributed (around chamber perimeter) and progressive
apportionment (vertical spacing of inlet ports) of preheated product gas
combustion air
from the plenum 73 causes burning in the primary combustion chamber 43 as long
as
any product gas exists therein.
The combustion gases stack 79 in the carbon sump and perimeter supply
of combustion air around the bottom thereof from the plenum 75 facilitates the
controlled
CA 02522384 2010-02-03
48
burn of carbon inventory at the bottom of the carbon sump 77 and allows
unrestricted hot
gas flow up the center of the carbon inventory. This provides essentially
instantaneous
heating of the gasification cone chamber 48 (when supplemental energy is
required to
sustain processor operation) as the hot combustion gases flow directly
upwardly from
the cap 80 at the top of the stack 79 into the mouth 51 instead of flowing
through and
heating up the carbon inventory. Flow through the carbon inventory is
undesirable
because it both changes the temperature and combustion performance thereof and
reduces combustion gas temperatures to essentially whatever the highest carbon
inventory temperature would be. The hot combustion gases stack 79 allows
maximum
temperature transfer directly into the chamber 43 surrounding the gasification
cone,
minimizing response time when low energy feedstock batches (up to and
including 100%
water) are processed.
A localized combustion zone (bottom of the carbon sump 77) provides
high rate, high temperature conversion/destruction of most carbon and residual
organics
before final, complete combustion occurs in the carbon sump ash discharge tube
81.
All processor ash flows through the discharge tube 81 against a low rate
counter flow of preheated combustion air from the plenum 75. The preheated
combustion air causes entrained organic material to combust at a flame front;
raising the
temperature thereat. That phenomenon is used to control the ash extraction
system. A
temperature sensor(s) in the ash tube will indicate whether the flame front
(of any
organic material that may be remaining in the ash) is at or downstream of the
sensor
location (temperature thereat higher than combustion air supply temperature)
or
CA 02522384 2010-02-03
49
upstream of the sensor(s) location when temperature in the tube is close to
that of the
combustion air supply. The ash extraction system will automatically operate
whenever
the temperature in the ash tube is at or near the combustion air supply
temperature;
stopping whenever the sensors detect a significantly higher temperature than
the
combustion air temperature.
In an alternative arrangement (not shown) two negative pressure
chambers are provided as the reactor vessel. This includes an upper wet
feedstock
conditioning chamber and a lower, in-line, high temperature reaction chamber.
Controlled volumes of preheated combustion air are drawn into the top of the
upper
chamber. A system of deflectors around the interior surface of the upper
chamber
provides an annular space around feedstock therein, creating a preheated
combustion air flow path down into the lower, high temperature reactor
chamber.
This feature facilitates evaporation of water that may be at or near the
vertical
perimeter surface of the feedstock charge, preventing liquid water flow onto
lower
chamber, high temperature surfaces.
Preferably air from the upper chamber fuels the random combustion
(depending on feedstock quality and moisture content) of mainly feedstock and
product gas generated at and near the feedstock-lower chamber surfaces
interface.
The combination of this combustion and radiation from the lower chamber
interior
surfaces collectively contribute to the feedstock destruction rate. The lower
chamber
is engulfed in flame resulting from combusting the remainder of product gas
that
exits the lower high temperature chamber and, when supplied with controlled
CA 02522384 2010-02-03
combustion air volumes, portions of the charcoal inventory at the bottom of
the
system.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
5 within the spirit and scope of the claims without department from such
spirit and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
