Note: Descriptions are shown in the official language in which they were submitted.
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A MULTI-ZONE CARBON CONVERSION SYSTEM WITH PLASMA
MELTING
FIELD OF THE INVENTION
This invention pertains to the field of carbonaceous feedstock gasification
and in
particular, to a multi-zone carbon converter.
BACKGROUND OF THE INVENTION
Gasification is a process that enables the conversion of carbonaceous
feedstock, such
as municipal solid waste (MSW) or coal, into a combustible gas. The gas can be
used
to generate electricity, steam or as a basic raw material to produce chemicals
and
liquid fuels.
I5
Possible uses for the gas include: the combustion in a boiler for the
production of
steam for internal processing and/or other external purposes, or for the
generation of
electricity through a steam turbine; the combustion directly in a gas turbine
or a gas
engine for the production of electricity; fuel cells; the production of
methanol and
other liquid fuels; as a further feedstock for the production of chemicals
such as
plastics and fertilizers; the extraction of both hydrogen and carbon monoxide
as
discrete industrial fuel gases; and other industrial applications.
Generally, the gasification process consists of feeding carbonaceous feedstock
into a
heated chamber (the gasifier) along with a controlled and/or limited amount of
oxygen
and optionally steam. In contrast to incineration or combustion, which
operates with
excess oxygen to produce C02, H20, SON, and NOx, gasification processes
produce a
raw gas composition comprising CO, H2, H2S, and NIL. After clean-up, the
primary
gasification products of interest are H2 and CO.
Useful feedstock can include any municipal waste, waste produced by industrial
activity and biomedical waste, sewage, sludge, coal, heavy oils, petroleum
coke,
heavy refinery residuals, refinery wastes, hydrocarbon contaminated soils,
biomass,
and agricultural wastes, tires, and other hazardous waste. Depending on the
origin of
RECTIFIED SHEET (RULE 91)
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the feedstock, the volatiles may include H2O, H2, N2, 02, C02, CO, CH4, H2S,
NH3,
C2H6, unsaturated hydrocarbons such as acetylenes, olefins, aromatics, tars,
hydrocarbon liquids (oils) and char (carbon black and ash).
As the feedstock is heated, water is the first constituent to evolve. As the
temperature
of the dry feedstock increases, pyrolysis takes place. During pyrolysis the
feedstock
is thermally decomposed to release tars, phenols, and light volatile
hydrocarbon gases
while the feedstock is converted to char.
to Char comprises the residual solids consisting of organic and inorganic
materials.
After pyrolysis, the char has a higher concentration of carbon than the dry
feedstock
and may serve as a source of activated carbon. In gasifiers operating at a
high
temperature (> 1,200 C) or in systems with a high temperature zone, inorganic
mineral matter is fused or vitrified to form a molten glass-like substance
called slag.
Since the slag is in a fused, vitrified state, it is usually found to be non-
hazardous and
may be disposed of in a landfill as a non-hazardous material, or sold as an
ore, road-
bed, or other construction material. It is becoming less desirable to dispose
of waste
material by incineration because of the extreme waste of fuel in the heating
process
and the further waste of disposing, as a residual waste, material that can be
converted
into a useful syngas and solid material.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a multi-zone carbon converter
for
converting processed feedstock into syngas and slag. In accordance with an
aspect of
the invention, there is provided a multi-zone carbon converter comprising a
carbon
conversion zone having one or more processed feedstock inputs, one or more
syngas
outlets and a heated air input in communication with a slag zone for melting
ash
and/or for maintaining slag in a molten state comprising a plasma heat source
and slag
outlet. The carbon conversion and slag zones are separated by an inter-zonal
region
or inter-zone comprising an impediment for restricting or limiting movement of
material between the carbon conversion zone and the slag zone.
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In accordance with another aspect of the invention, there is provided a multi-
zone
carbon converter for converting processed feedstock to syngas and slag
comprising a
chamber comprising a carbon conversion zone in communication with a slag zone,
wherein the carbon conversion zone and the slag zone are separated by an inter-
zonal
region or inter-zone; the carbon conversion zone comprising a processed
feedstock
input for receiving processed feedstock from a source, a syngas outlet and a
heated
air input; the inter-zonal region or inter-zone comprising an impediment to
limit the
flow of material between the carbon conversion zone and the slag zone by
either
partial or intermittently occluding the inter-zonal region or inter-zone and
optionally,
comprising heat transfer elements to provide for initial ash melting; the slag
zone
comprising a plasma heat source and a slag outlet; wherein the processed
feedstock is
converted to a syngas and ash in the carbon conversion zone, and the ash is
converted
into molten slag in the inter-zonal region or inter-zone and/or the slag zone
through
the application of heat from the plasma heat source.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments of the present invention will now be described, by way of example
only, by reference to the attached Figures, wherein:
Figure 1 is a block flow diagram showing the different zones of the multi-zone
carbon
converter. in general terms, namely showing the carbon conversion zone in
communication with a slag zone for melting ash and/or maintaining slag in a
molten
state.
Figure 2 is a block flow diagram showing the inputs of a multi-zone carbon
converter
comprising a carbon conversion zone in communication with a slag zone for
melting
ash and/or for maintaining slag in a molten state in combination with a
carbonaceous
feedstock gasifier.
Figure 3 is a schematic representation of the multi-zone carbon converter in
general
terms, namely showing the general features of the carbon conversion zone,
inter-zonal
region or inter-zone and the slag zone.
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Figure 4 is a schematic representation of one embodiment of the multi-zone
carbon
converter in association with a main gasification chamber.
Figure 5 illustrates a flange chamber design of the multi-zone carbon
converter which
would facilitate replacement of the impediment and allow for the use of
multiple
impediment configurations.
Figure 6 is a partial longitudinal-section view of one embodiment of the multi-
zone
carbon converter in which the impediment comprises a plurality of ceramic
balls.
Figure 7 is a longitudinal-sectional view of the inter-zonal region or inter-
zone and
slag zone of one embodiment of the multi-zone carbon converter detailing a
domed
cogwheel-shaped impediment.
Figure 8(A) is a partial longitudinal-section view of one embodiment of the
multi-
zone carbon converter detailing various ports for process air, a start-up
burner port, a
port for gas from a hot gas generator, slag outlet and impediment. 8(B) is a
cross-
sectional view of the embodiment illustrated in 8(A) at level A-A. 8(C) is a
top view
of the impediment and supporting wedges.
Figure 9 is a cross-sectional view of one embodiment of the multi-zone carbon
converter in which the impediment comprises a series of interconnected bricks.
Figure 10 is an illustration of an impediment comprising a grate.
Figure I 1 is a longitudinal-sectional view of the inter-zonal region or inter-
zone and
slag zone of the multi-zone carbon converter of one embodiment of the multi-
zone
carbon converter.
Figure 12 is a longitudinal-sectional view of one embodiment of the multi-zone
carbon converter in which the impediment comprises a moving grate. Figures
12(A)
and (B) detail moving grate designs.
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Figure 13A is a cross-sectional view detailing the ports in the slag zone of
one
embodiment of the multi-zone carbon converter including oxygen and/or air
inputs
(0), carbon inputs (C), ports for plasma torches (P) and gas burner port (G).
13B is a
partial longitudinal view of the embodiment of the multi-zone carbon converter
shown in 13A.
Figure 14 is an enlargement of Figure 13B.
Figure 15 is a partial longitudinal-sectional view of one embodiment of the
two zone
carbon converter detailing the slag zone with plasma heat deflector.
Figure 16 illustrates a modification of the multi-zone carbon converter in
which the
slag zone further comprises a weir to form a slag pool to facilitate slag
mixing.
Figure 17 is a partial longitudinal-sectional view of one embodiment of the
multi-
zone carbon converter detailing one embodiment of the slag cooling system
including
a water spray and drag chain.
Figure 18 is a perspective view of one embodiment of the multi-zone carbon
converter detailing processed feedstock inputs and various ports.
Figure 19 is an alternative perspective view of the embodiment of the multi-
zone
carbon converter illustrated in Figure 18 detailing the processed feedstock
input, the
syngas outlet and plasma torch.
Figure 20 is a longitudinal-sectional view through the multi-zone carbon
converter
illustrated in Figure 18 and 19, detailing the impediment between the carbon
conversion zone and the slag zone.
Figure 21 details the impediment between the carbon conversion zone and the
slag
zone of the multi-zone carbon converter illustrated in Figures 18 to 20.
Figure 22 is a cross-sectional view through the air box of the multi-zone
carbon
converter illustrated in Figures 18 to 21.
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Figure 23 is a cross-sectional view through the multi-zone carbon converter of
Figures
18 to 22 at torch level detailing the tangentially located air inputs and
plasma torch.
Figure 24 is a cross-sectional view through the multi-zone carbon converter of
Figures
18 to 23 at burner level.
Figure 25 illustrates alternative views of the multi-zone carbon converter of
Figures
18 to 23.
Figure 26 is a perspective view of one embodiment of the multi-zone carbon
converter detailing processed feedstock inputs and various ports comprising a
grate
impediment.
Figure 27 is an illustration of one embodiment of the multi-zone carbon
converter in
which the impediment comprises a series of interconnected bricks.
Figure 28 is an illustration of one embodiment of the multi-zone carbon
converter in
which the impediment comprises a vertically-oriented grate.
Figure 29 is an illustration of one embodiment of the multi-zone carbon
converter in
which the impediment comprises a cogwheel-shaped dome.
Figure 30 is an illustration of detailing an alternative embodiment of the
multi-zone
carbon converter.
Figure 31A and B are illustrations of the air flow with one embodiment of the
multi-
zone carbon converter.
Figure 32 is an illustration of detailing an alternative embodiment of the
multi-zone
carbon converter.
Figure 33 is an illustration of detailing an alternative embodiment of the
multi-zone
carbon converter.
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DETAILED DESCRIPTION OF THE INVENTION
Definitions
Unless defined otherwise, all technical and scientific terms used herein have
the same
meaning as commonly understood by, one of ordinary skill in the art to which
this
invention belongs.
As used herein, the term "processed feedstock" includes char, low and ultra-
low
volatile feedstocks with fixed carbon and ash components, the by-products of a
carbonaceous feedstock gasification or pyrolysis process, products obtained
from the
incomplete combustion of carbonaceous feedstock, or the solids collected in
gas
conditioning and/or cleanup systems with the heat source inputs from plasma
torch.
As used herein, the term "syngas" is defined as a gas mixture that contains
varying
amounts of carbon monoxide and hydrogen generated by the gasification of a
carbon
containing fuel to a gaseous product with a heating value. Syngas consists
primarily
of carbon monoxide, carbon dioxide and hydrogen, and has less than half the
energy
density of natural gas. Syngas is combustible and often used as a fuel source
or as an
intermediate for the production of other chemicals.
"Processed syngas" refers to syngas reformulate or refined using a plasma heat
gas
refining or reformulating system.
As used herein, the term "sensing element" is defined to describe any element
of the
system configured to sense a characteristic of a process, a process device, a
process
input or process output, wherein such characteristic may be represented by a
characteristic value useable in monitoring, regulating and/or controlling one
or more
local, regional and/or global processes of the system. Sensing elements
considered
within the context of the system may include, but are not limited to, sensors,
detectors, monitors, analyzers or any combination thereof for the sensing of
process,
fluid and/or material temperature, pressure, flow, composition and/or other
such
characteristics, as well as material position and/or disposition at any given
point
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within the system and any operating characteristic of any process device used
within
the system. It will be appreciated by the person of ordinary skill in the art
that the
above examples of sensing elements, though each relevant within the context of
the
system, may not be specifically relevant within the context of the present
disclosure,
and as such, elements identified herein as sensing elements should not be
limited
and/or inappropriately construed in light of these examples.
As used herein, the term "response element" is defined to describe any element
of the
system configured to respond to a sensed characteristic in order to operate a
process
device operatively associated therewith in accordance with one or more pre-
determined, computed, fixed and/or adjustable control parameters, wherein the
one or
more control parameters are defined to provide a desired process result.
Response
elements considered within the context of the system may include, but are not
limited
to static, pre-set and/or dynamically variable drivers, power sources, and any
other
element configurable to impart an action, which may be mechanical, electrical,
magnetic, pneumatic, hydraulic or a combination thereof, to a device based on
one or
more control parameters. Process devices considered within the context of the
system,
and to which one or more response elements may be operatively coupled, may
include, but are not limited to, material and/or feedstock input means, heat
sources
such as plasma heat sources, additive input means, various gas blowers and/or
other
such gas circulation devices, various gas flow and/or pressure regulators, and
other
process devices operable to affect any local, regional and/or global process
within the
system. It will be appreciated by the person of ordinary skill in the art that
the above
examples of response elements, though each relevant within the context of the
system,
may not be specifically relevant within the context of the present disclosure,
and as
such, elements identified herein as response elements should not be limited
and/or
inappropriately construed in light of these examples.
Overview of the System
Referring to Figure 1, there is provided a multi-zone carbon converter for the
conversion of processed feedstock into a syngas and an inert slag product. The
multi-
zone carbon converter comprises a multi-zone refractory-lined chamber having
one or
more input(s) for receiving processed feedstock, one or more gas outlet(s), a
slag
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outlet, heated air inputs to facilitate the conversion of the processed
feedstock into
syngas and ash and a plasma heat source to provide the heat necessary to melt
the ash
into slag and optionally steam or process additive inputs. Optionally, the
processed
feedstock is pre-treated (homogenized, ground, shredded and/or pulverized)
prior to
being fed into the converter. In particular, the multi-zone carbon converter
comprises
a first zone or carbon conversion zone in communication with a second zone or
slag
zone for melting residual substantially carbon free solid material into molten
slag
and/or for maintaining slag in a molten state. The carbon conversion zone and
the
slag zone are separated by the inter-zonal region or inter-zone that comprises
an
impediment for restricting or limiting the movement of material between the
two
zones and, in some embodiments, may also provide for the initial melting of
the
residual substantially carbon free solid material (i.e. ash) into molten slag.
The present multi-zone carbon converter is optionally for use in conjunction
with a
system: for generating processed feedstock from carbonaceous feedstocks. For
example, the multi-zone carbon converter (10) can receive processed feedstock
from a
low-temperature gasifier (15) (see Figures 2 and 4). In such configurations,
the multi-
zone carbon converter may be considered as an extension of the gasifier in
that the
third stage of the gasification process (i.e. carbon conversion) is
substantially
completed within the multi-zone carbon converter.
Generally, the gasification of the carbonaceous feedstock can be subdivided
into three
stages, namely, drying, volatization and char-to-ash (or carbon) conversion.
Stage I: Drying of the Material
The first stage of the gasification process is drying, which occurs mainly
between
25 C and 400 C. Some volatilization and some carbon-to-ash conversion may also
take place at these lower temperatures.
Stage II: Volatilization of the Material
The second stage of the gasification process is volatilization, which occurs
mainly
between 400 C and 700 C. A small degree (the remainder) of the drying
operation as
well as some carbon conversion (char to syngas) will also take place at this
temperature.
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Stage III: Char-to-Ash Conversion
The third stage of the gasification process is that of carbon conversion which
takes
place at a temperature range of between 600 C and 1000 C. A small degree (the
remainder) of volatilization will also take place at this temperature. After
this stage,
the major products are a substantially carbon-free solid residue (ash) and
syngas. In
order to avoid agglomeration of the ash, the maximum temperature in this
region
should not exceed about 950 C.
During gasification, in order to increase the yield of the desired syngas
products, it is
necessary to maximize the conversion of the carbonaceous feedstock into the
desired
gaseous products. The multi-zone carbon converter therefore provides a system
for
ensuring the complete conversion of the available carbon remaining in the
processed
feedstock into a syngas, while also providing for the recovery of the syngas
and a slag
product. The multi-zone carbon converter therefore also provides for the
addition of
heated air, and optionally process additives such as steam and/or carbon rich
gas
and/or carbon, to facilitate the conversion of the carbon to the desired
syngas product.
The multi-zone carbon converter also provides plasma heat to facilitate the
complete
conversion of the residual inorganic materials (i.e. ash) into a vitrified
substance or
slag.
The multi-zone carbon converter comprises a multi-zone refractory-lined
chamber
comprising: one or more processed feedstock inlet(s), a syngas outlet, heated
air
inlets, a slag outlet, and one or more ports for a plasma heat source such as
a plasma
torch and optionally one or more process additive inlets or ports. The multi-
zone
carbon converter also optionally comprises a control subsystem for monitoring
operating parameters and adjusting operating conditions within the converter
to
optimize the conversion reaction. Sensing elements and response elements are
integrated within the converter, and the response elements adjust the
operating
conditions within the converter according to the data obtained from the
sensing
elements.
The multi-zone carbon converter comprises a first zone or carbon conversion
zone in
communication with a second zone or slag zone for melting residual solid
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(i.e. ash) and/or for maintaining slag in a molten state. The carbon
conversion zone
and the slag zone are separated by the inter-zonal region or inter-zone that
comprises
an impediment for guiding and/or restricting the movement of material between
the
two zones. The inter-zonal region or inter-zone may, optionally also provide
for the
initial melting of the residual substantially carbon free solid material (i.e.
ash) into
molten slag and/or facilitate air diffusion and/or mixing.
Figure 3 is a schematic depiction of one embodiment of the multi-zone carbon
converter (10). The multi-zone carbon converter (10) comprises processed
feedstock
inputs (20) into the carbon conversion zone (11) of the refractory-lined
chamber (15),
where heated air inputs (35) convert the unreacted carbon in the processed
feedstock
into a syngas. Residual substantially carbon-free solid material (i.e. ash) is
subsequently converted into a molten slag material in either the inter-zonal
region or
inter-zone and/or the slag zone by the direct or indirect (i.e. via heat
transfer elements)
application of plasma heat. Optionally, the impediment of the inter-zonal
region or
inter-zone acts as a heat transfer element for transferring the heat of the
plasma heat
source to the residual solid material (i.e. ash) thereby affecting its initial
melting. The
inter-zonal region or inter-zone may further comprise additional heat transfer
element
for efficiently transferring the plasma heat. The molten slag material is
output from
the slag zone of the multi-zone carbon converter and passed into an optional
slag
cooling subsystem for cooling. The syngas is output from the converter and is
optionally passed back into a main gasification chamber where it is combined
with the
gaseous products of the main gasification process or is subjected to further
downstream processing and/or is stored in a storage tank-
The processed feedstock for input into the multi-zone carbon-converter may be
from a
variety of sources including by-products of a carbonaceous feedstock
gasification or
pyrolysis process, obtained from the incomplete combustion of carbonaceous
feedstock, or the solids collected in gas conditioning and/or cleanup systems
with the
heat source inputs from plasma torch.
The multi-zone carbon converter facilitates the production of syngas and slag
by
sequentially promoting carbon conversion and residual substantially carbon-
free solid
(i.e. ash) melting. This is accomplished by allowing carbon conversion to
occur at a
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certain temperature range prior to exposing the residual substantially carbon-
free solid
(i.e. ash) to a higher temperature range. The multi-zone carbon converter
minimizes
or eliminates the amount of carbon trapped in the melt.
In particular, the carbon conversion process is accomplished by providing the
appropriate level of oxygen to the processed feedstock and raising the
temperature of
the processed feedstock to the level required to convert carbon in the
processed
feedstock to a syngas by exposing the processed feedstock to the specific
environment
of the carbon conversion zone. The syngas produced in the conversion process
exits
the chamber via a gas outlet.
The resulting syngas may comprise heavy metal and particulate contaminants.
Accordingly, in one embodiment, the multi-zone carbon converter optionally
further
comprises a gas conditioning subsystem for cooling and conditioning the
residue gas
as required for downstream applications. Alternatively, the multi-zone carbon
converter may be connected to downstream gas condition and/or gas storage
systems.
The source of the processed feedstock may be, but is not limited to, a low
temperature
or high temperature gasifier or pyrolyser, a hopper in which the residue is
stored, or
particulate matter separators within a gas conditioning system, for example, a
baghouse filter or cyclone. The multi-zone carbon converter may be directly or
indirectly connected to the source of the processed feedstock. The processed
feedstock is conveyed, continuously or intermittently, from the source of the
processed feedstock through appropriately adapted outlets and/or conveyance
means
to the processed feedstock inlet of the chamber, as would be known to the
skilled
worker, according to the requirements of the system and the type of by-product
to be
removed. Optionally, the processed feedstock is pre-treated prior to input
into the
chamber. Pre-treatment can include but is not limited to homogenizing,
grinding,
pulverizing, shredding, source separation or magnetic metal-removal.
The molten slag, at a temperature of, for example, about 1200 C to about 1800
C,
may continuously be output from the multi-zone carbon converter and thereafter
cooled to form a solid slag material. Such slag material may be intended for
landfill
disposal or may further be broken into aggregates for conventional uses.
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Alternatively, the molten slag can be poured into containers to form ingots,
bricks
tiles or similar construction material. The resulting slag material may also
be used as
a supplementary cementing material in concrete, in the production of a
lightweight
aggregate or mineral wool, in the manufacture of foam glass, or in the
development of
packaging materials.
Accordingly, the multi-zone carbon converter may also include a subsystem for
cooling the molten slag to its solid form. The slag cooling subsystem is
provided as
appropriate to afford the cooled slag product in the desired format.
The multi-zone carbon converter also optionally comprises a control system for
managing the carbon conversion and melting process. In particular, the multi-
zone
carbon converter comprises a control subsystem comprising sensing elements for
monitoring operating parameters of the system, and response elements for
adjusting
operating conditions within the system to manage the conversion process,
wherein the
response elements adjust the operating conditions within the system according
to the
data obtained from the sensing elements, thereby promoting efficient and
complete
carbon conversion and melting. The adjustable operating parameters include,
for
example, plasma heat rate (power) and position, processed feedstock feed rate,
and air
and/or steam and/or carbon rich gas and/or carbon-containing gas inputs and/or
carbon inputs.
Multi-zone Carbon Converter
Referring now to Figure 3, the multi-zone carbon converter (10) comprises a
refractory-lined chamber (15) having a first end or processed feedstock input
end and
a second end or slag output end. The converter further comprises a processed
feedstock input (20), syngas outlet (25) and slag outlet (30), a plasma heat
source
(40), hot air inputs (35), one or more additive input(s) (not shown) and,
optionally, a
control system.
Referring now to Figure 4, which is a schematic depiction of representative
multi-
zone carbon converters in association with a main gasification chamber. The
multi-
zone carbon converter (10) comprises processed feedstock inputs (20) into a
carbon
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conversion zone (11), where heated air inputs (35) convert the processed
feedstock
into a syngas product and a residual substantially carbon-free solid (i.e.
ash). The
syngas product escapes through the syngas outlet (25). The residual solid
material (i.e.
ash) is melted in the inter-zonal region or inter-zone (12) and/or the slag
zone (13)
into slag via the indirect (i.e. via the use of heat transfer elements) or
direct
application of plasma heat. The molten slag material is output from the slag
zone and
passed into an optional slag cooling subsystem for cooling. The syngas output
from
the chamber is optionally passed back into a main gasification chamber where
it is
combined with the gaseous products of the main gasification process or is
passed to
downstream processing and/or storage systems.
Design Considerations for the Chamber
The chamber of the multi-zone carbon converter is designed to provide a
sealed,
insulated space for processing of processed feedstock into syngas and to allow
for the
passage of syngas to downstream process such as cooling or refining or other
and for
processing of ash into slag. The design of the chamber promotes the formation
of the
two zones and reflects the specific requirements of each of these zones. The
design
may optionally provide for access to the interior of the multi-zone carbon
converter
for inspection, maintenance and repair. Referring to Figure 5, the chamber is
optionally a flanged chamber to facilitate the replacement of the individual
zones or
the inter-zonal region or inter-zone or parts of individual zones.
The multi-zone carbon converter comprises a carbon conversion zone, an inter-
zonal
region or inter-zone and a slag zone. The carbon conversion zone is adapted to
i)
input the processed feedstock to be conditioned, ii) input heated air to
convert
unreacted carbon in the processed feedstock to a syngas having a heating value
and
substantially carbon-free solid residue, iii) input optional process additives
such as
steam and/or carbon rich gas, iv) output the syngas and the solid residue. The
inter-
zonal region or inter-zone is designed to segregate the carbon conversion zone
and the
slag zone. and to regulate the flow of material there between and may
optionally
provide for the initial melting of the solid residue into slag by effecting
the transfer of
plasma heat to the solid residue. The slag zone is designed to input heat to
condition
the substantially carbon free solid residue from the carbon conversion to form
a
molten slag material (and optionally convert any residual carbon to gas) or to
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maintain molten slag in its molten state, and output the molten slag and where
appropriate, gaseous product. Optionally, the slag zone can further comprise
or be
connected to a slag cooling subsystem to facilitate the solidification of the
molten
slag. Accordingly, the chamber of the two zone carbon converter is a
refractory-
lined, generally vertically-oriented chamber comprising a processed feedstock
inlet,
heated air inlets, a gas outlet, a slag outlet, and a plasma heat source and
optionally
one or more process additive inlets.
In determining the sizing of the individual zones, the function of the
individual zone
to can be considered. In the carbon conversion zone, as much carbon as
possible is
being converted to the gas phase. The slag zone functions to melt the ash
completely.
The carbon conversion zone is sized by the air flow at those quantity the most
of
carbon being converted meanwhile still in substoichoimentric environment with
highest possible operating temperature. The cross section area is based on the
superficial velocity required so that the operating conditions are in fixed-
bed mode
instead of fluidization. The slag zone dimension if based on heat balance
calculation
to maintain at high level temperature to ensure the ash melting with the heat
inputs
from plasma heat sources.
The multi-zone carbon conversion chamber is designed to ensure that the carbon
conversion and ash processing is carried out efficiently and completely, in
order to
use a minimum amount of energy to effectly complete these processes.
Accordingly,
factors such as efficient heat transfer, adequate heat temperatures, residence
time,
molten slag flow, input residue volume and composition, and size and
insulation of
the chamber are taken into account when designing the chamber. The chamber is
also
designed to ensure that the processes are carried out in a safe manner.
Accordingly,
the multi-zone carbon converter is designed to isolate the processing
environments
from the external environment. Generally, the chamber is designed such that
the
upstream end, proximal to the processed feedstock input is specifically
adapted for the
carbon conversion process and the proximal to the slag outlet is specifically
adapted
for the melting process.
Alternatively, the chamber is designed such that the carbon conversion zone is
a
centrally located zone and the slag zone encircles the carbon conversion zone.
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such embodiments, the segregation of the carbon conversion zone and the slag
zone
may be accomplished by elevating the carbon conversion zone in comparison to
the
slag by use of a sloped floor.
Optionally, the chamber is shaped to promote or facilitate the separation of
the carbon
conversion zone and slag zone. Accordingly, in one embodiment, the inter-zonal
region or inter-zone forms a constriction of the chamber (See Figure 20).
Materials
The multi-zone carbon conversion chamber is refractory-lined chamber with an
internal volume sized to accommodate the appropriate amount of material for
the
required solids residence time.
The chamber is typically manufactured with multiple layers of materials as are
appropriate. For example, the outer layer, or shell, of the chamber is
typically steel.
Moreover, it may be beneficial to provide one or more insulating layers
between the
inner refractory layer and the outer steel shell to reduce the temperature of
the steel
casing. An insulating board around the outer surface of the slag reservoir may
also
be provided to reduce the temperature of the steel casing. Optionally, a
ceramic
blanket may be used as an insulator. When room for expansion of the refractory
without cracking is required, a compressible material, such as a ceramic
blanket, can
be used against the steel shell. The insulating materials are selected to
provide a shell
temperature high enough to avoid acid gas condensation if such an issue is
relevant,
but not so high as to compromise the integrity of the outer shell.
The refractory protects the chamber from the high temperature and corrosive
gases
and minimizes unnecessary loss of heat from the process. The refractory
material can
be a conventional refractory material well-known to those skilled in the art
and which
is suitable for use for a high temperature e.g., a temperature of about 1100 C
to
1800 C), un-pressurized reaction. When choosing a refractory system factors to
be
considered include internal temperature, abrasion; erosion and corrosion;
desired beat
conservationilimitation of temperature of the external vessel; desired life of
the
refractory. Examples of appropriate refractory material include high
temperature
fired ceramics, i.e., aluminum oxide, aluminum nitride, aluminum silicate
boron
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nitride, zirconium phosphate, glass ceramics and high alumina brick containing
principally, silica, alumina, chromia and titania. To further protect the
chamber from
corrosive gases the chamber is, optionally, partially or fully lined with a
protective
membrane. Such membranes are known in the art and, as such, a worker skilled
in
the art would readily be able to identify appropriate membranes based on the
requirements of the system and, for example, include Sauereisen High
Temperature
Membrane No 49.
In one embodiment, the refractory is a multilayer design with a high density
layer on
the inside to resist the high temperature, abrasion, erosion and corrosion.
Outside the
high density material is a lower density material with lower resistance
properties but
higher insulation factor. Optionally, outside this layer is a very low density
foam
board material with very high insulation factor and can be used because it
will not be
exposed to abrasion of erosion. Appropriate materials for use in a multilayer
refractory are well known in the art.
In one embodiment, the multilayer refractory comprises an internally oriented
chromia layer; a middle alumina layer and an outer inboard layer.
Optionally, the refractory in the individual zones and regions may be
specifically
adapted for the environment within that particular area of the chamber. For
example,
the bottom part of the chamber may have a thicker refractory where the working
temperature is higher. In addition, the refractory of the slag zone may be
adapted to
withstand higher temperatures and be designed to limit slag penetration into
the
refractory thereby reduce corrosion of the refractory.
The wall of the chamber can optionally incorporate supports for the refractory
lining
or refractory anchors. Appropriate refractory supports and anchors are known
in the
art.
Due to the severe operating conditions, it is anticipated that the refractory
may require
periodic maintenance. Accordingly, in one embodiment, the chamber is flanged
such
that separable upper and lower portions are provided, wherein the chamber
lower
portion (where the reservoir is located) is removable from the chamber upper
portion.
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In one embodiment, the chamber is suspended from a support structure such that
the
lower portion can be dropped away from the upper portion to facilitate
maintenance.
This embodiment provides for removing the lower portion without disturbing any
connections between the chamber upper portion and upstream or downstream
components of the system.
Carbon Conversion Zone
The carbon conversion process is accomplished by raising the temperature of
the
processed feedstock to the level required to convert carbon in the processed
feedstock
to a syngas by exposing the processed feedstock to the specific environment of
the
carbon conversion zone. The syngas produced in the conversion process exits
the
chamber via a gas outlet. In one embodiment, the syngas is passed back into a
gasification chamber, where it combines with the gases produced during the
main
gasification process.
Referring to Figure 4, the carbon conversion zone (11) comprises one or more
input(s) (20) for receiving processed feedstock, one or more syngas outlet(s)
(25) and
is in communication via the inter-zonal region or inter-zone (12) with the
slag zone
(13).
The carbon conversion zone (11) is provided with heated air inlets (35) to
provide the
required temperature for converting any remaining volatiles and carbon to a
syngas.
The chamber is also designed to ensure highly efficient exposure of the
residue to the
heated air to minimize the amount of sensible heat that is lost via the
product gas.
Therefore, the position and orientation of the heated air inlets are
additional factors to
be considered in the design of the carbon conversion zone.
Processed Feedstock Input
The multi-zone carbon converter comprises a processed feedstock input in
association
with the processed feedstock inlet of the converter chamber. The processed
feedstock
inlet is adapted to receive the processed feedstock into the carbon conversion
zone of
the chamber. The input of processed feedstock into the chamber may be passive
(i.e.
by gravity) or active. Optionally, the processed feedstock input actively
conveys the
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processed feedstock from a source to the inlet of the converter chamber.
Appropriate
active conveyance mechanisms are known in the art and include double locked-
hoppers, screw conveyors, drag chains, pneumatically pushed and other means
known
in the art.
Processed feedstock entering the chamber may come from one or multiple
sources.
Sources of the processed feedstock may include, but are not limited to, a low
temperature or high temperature gasifier, a hopper in which the residue of a
gasification process is stored, or upstream gas conditioning systems, for
example, a
baghouse filter or fly ash from cyclones.
Where the processed feedstock is provided in more than one input stream, or
from
more than one source, the different streams may each be passed into the
chamber
through a dedicated processed feedstock inlet, or they may be combined prior
to
introduction into the chamber. In the latter embodiment, there is provided one
processed feedstock inlet through which all processed feedstock are provided.
Accordingly, the chamber may comprise a common inlet or multiple inlets.
The source of the processed feedstock may be provided in direct communication
with
the multi-zone carbon converter chamber, i.e., each processed feedstock input
is fed
directly from the source into the chamber. Alternatively, the source may be
provided
in indirect communication with the chamber, wherein the residue inputs are
conveyed
from the source into the chamber via a system of conveyor means.
Where the multi-zone carbon converter chamber is indirectly connected to the
source
of the processed feedstock, the processed feedstock input comprises one or
more
means for conveying the processed feedstock from the source into the chamber.
For
example, the processed feedstock may include a single screw conveyor or a
series of
screw conveyors, belts, rams, plows, rotating arms, rotating chains, traveling
grates
and pusher rams.
The multi-zone carbon converter chamber is optionally provided with an air
lock in
association with the processed feedstock input. This optional air lock may be
located
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to provide a barrier between the source of the processed feedstock (and the
ambient
air to guard against excessive air ingestion )and the interior of the chamber.
The processed feedstock input optionally includes a control mechanism such
that the
input rate of the processed feedstock can be controlled to ensure optimal
carbon
conversion and melting and homogenization of the residual material.
The processed feedstock input optionally includes or is optionally connected
to a pre-
treatment module. Pre-treatment includes treatments that homogenize or reduce
the
size of processed feedstock particles and include, for example, grinding,
pulverizing
and homogenizing. Appropriate grinders, pulverizers and homogenizers are known
in
the art.
Carbon Conversion Zone Heating Sys
tem
The carbon conversion process requires heat. Heat addition can occur directly
by
partial oxidation of the processed feedstock (i.e. by the exothermic reaction
of
oxygen in the air inputs with carbon and volatiles present in the processed
feedstock)
or indirectly by the use of one or more heat sources know in the art.
The heat required to convert the unreacted carbon in processed feedstock is
provided
(at least partially) through the use of heated air inputs.
The hot air can be supplied from, for example, air boxes, air heaters or heat
exchangers, all of which are known in the art.
In one embodiment, hot air is feed into the carbon conversion zone by air feed
and
distribution system with inputs proximal to the inter-zonal region or inter-
zone.
Appropriate air feed and distribution systems are known in the art and include
air
boxes for each step level from which hot air can pass through perforations in
the wall
of the chamber or via air nozzles or spargers.
Additional or supplemental heating as may be required can be provided by one
or
more heating means known in the art including, but not limited to, a gas
burner.
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In one embodiment, the additional heat source can be circulating hot sand.
In one embodiment, the additional heat source can be an electrical heater or
electrical
heating elements.
In order to facilitate initial start up of the multi-zone carbon converter,
the chamber
can include access ports sized to accommodate various conventional burners,
for
example natural gas, oil/gas or propane burners, to pre-heat the chamber.
Also,
wood/biomass sources, engine exhausts, electric heaters could be used to
preheat the
chamber.
Process Additive Inputs
Process additives may optionally be added to the carbon conversion zone to
facilitate
efficient conversion of processed feedstock into syngas. Steam input can be
used to
ensure sufficient free oxygen and hydrogen to maximize the conversion of
decomposed elements of the input processed feedstock into product gas and/or
non-
hazardous compounds. Air input can be used to assist in processing chemistry
balancing to maximize carbon conversion to a fuel gas (minimize free carbon)
and to
maintain the optimum processing temperatures while minimizing the cost of
input
heat. In addition, oxygen and/or ozone may be inputted through process
additive ports
into the carbon conversion zone.
Optionally, other additives may be used to optimize the carbon conversion
process
and thereby improve emissions.
Optionally, carbon-rich gas can be used as a process additive.
The carbon conversion zone, therefore, can include one or more process
additive
inputs. These include inputs for steam injection and/or air injection and/or
carbon-rich
gas. The steam inputs can be strategically located to direct steam into high
temperature regions and into the product gas mass just prior to its exit from
the
converter. The air inputs can be strategically located in and around the
chamber to
ensure full coverage of process additives into the carbon conversion zone.
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In one embodiment, the process additive inputs are located proximal to the
inter-zonal
region or inter-zone.
In one embodiment, the process additive inputs provide diffuse, low
velocity.input of
additives.
In embodiments in which hot air is used to heat the chamber additional
air/oxygen
injection inputs may optionally be provided.
Inter-Zonal Region or Inter Zone
The inter-zonal region or inter-zone functions to substantially spatially
segregate the
carbon conversion zone from the slag zone and optionally provides for the
initial
melting of the residual solid material (i.e. ash) of carbon conversion by
effectively
transferring plasma heat to the residual solid material. The inter-zonal
region or inter-
zone further provides a conduit or connection between the two zones. The inter-
zonal
region or inter-zone comprises an impediment that limits or regulates the
movement
of material between the carbon conversion and slag zone by either partial or
intermittently occluding the inter-zonal region or inter-zone, impedes
excessive
migration of unconverted carbon into the melt and may optionally further
comprise
heat transfer elements.
Referring to Figure 6, in one embodiment, the inter-zonal may optionally be
substantially contiguous with the slag zone.
Impediment
The impediment limits or regulates the movement of material between the carbon
conversion and slag zone by either partial or intermittently occluding the
inter-zonal
region or inter-zone and may optionally further provide for heat transfer.
The impediment is mounted within the inter-zonal region or inter-zone and can
be of
various shapes or designs, including but not limited to dome shaped, pyramidal
shaped, grates, moving grates, brick grate; plurality of ceramic balls,
plurality of
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tubes; cogwheel-shaped etc. The shape and size of the impediment may in part
be
dictated by shape and orientation of the chamber.
The impediment and any necessary mounting elements must be able to effectively
operate in the harsh conditions of the multi-zone carbon converter and in
particular
must be able to operate at high temperatures. Accordingly, the impediment is
constructed of materials designed to withstand high temperature. Optionally,
the
impediment may be refractory-lined or manufactured from solid refractory.
Referring to Figures 6 to 10, which detail various alternative, non-limiting
impediments.
In one embodiment as illustrated in Figure 6, the impediment comprises a
plurality of
ceramic balls.
In the embodiment as illustrated in Figure 7, the impediment comprises a
cogwheel-
shaped refractory dome.
In one embodiment as illustrated in Figure 8, the impediment is a solid
refractory
dome (145) mounted by wedge-shaped mounting bricks (150) in the inter-zonal
region. The solid refractory dome is sized such that there is a gap (155)
between the
outside edge of the dome and the inner wall of the chamber. Optionally, the
refractory dome further comprises a plurality of holes (160).
In the illustrated embodiment, an optional plurality of alumina or ceramic
balls (165)
between 20 to 100mm in diameter rest on top of the refractory dome to form a
bed
and provide for diffusion of heated air and to promote the transfer of plasma
heat to
the ash to initially melt the ash into slag. In this embodiment, as the ash
melts it
transits the inter-zonal region through the gap (160) between the outside edge
of the
dome (145) and the inner wall of the chamber and into the slag zone.
Referring to Figure 9, the impediment comprises a solid refractory brick
grate. The
refractory brick grate (245) is provided with gaps (255) between the
individual bricks
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to allow for communication between the carbon conversion zone and the slag
zone via
the inter-zonal region.
Referring to Figure 10, the impediment comprises a grate structure
manufactured
from refractory-lined tubes (345) mounted within a mounting ring (350).
Referring to Figure 12, the impediment comprises a moving grate.
Heat transfer elements and Diffusion Elements
to Optionally, the inter-zonal region may further comprise heat transfer or
diffusion
elements to facilitate the transfer of plasma heat to the ash. Heat transfer
elements are
known in the art and include ceramic balls, pebbles, bricks.
in one embodiment, the heat transfer element comprises plurality of alumina or
ceramic balls (165) between 20 to 100mm in diameter rest on top of the
refractory
dome to form a bed and provide for diffusion of heated air and to promote the
transfer
of plasma heat to the ash to initial melt the ash into slag.
Optionally, the impediment may be or comprise the heat transfer element.
Optional Heating Elements
Optionally, the inter-zonal region or inter-zone may be equipped with a source
heat.
Appropriate sources of heat include an air tuyere, an electrical heater or
electrical
heating elements, burners or sources of plasma heat including plasma torches.
The optional plasma torches can be placed in the inter-zonal region and/or at
the
carbon-conversion zone / inter-zonal region interface and/or at the inter-
zonal region /
slag zone interface
Optionally, any carbon remaining in the ash is converted to a syngas by the
application of plasma heat in inter-zonal region or inter-zone.
Accordingly, the chamber wall of the inter-zonal region can include access
ports sized
to accommodate various sources of heat.
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Slag Zone
The melting process is accomplished by raising the temperature of the residual
substantially carbon-free solid material (ash) to the level required to melt
the
remaining residue and occurs within the inter-zonal region and/or the slag
zone. The
heat required for the melting process is provided by one or more plasma heat
sources.
This heat may be directly applied or indirectly applied via heat transfer
elements. The
plasma heat will also serve to convert any small amounts of carbon remaining
in the
residue after the carbon conversion by the heated air inputs. Additional or
supplemental heating as may be required can be provided by one or more heating
means known in the art including, but not limited to, induction heating or
joule
heating.
The slag zone is provided with a plasma heat source that meets the required
temperature for heating the ash (directly or indirectly) to levels required to
melt and
homogenize the residual solid to provide a molten slag at a temperature
sufficient to
flow out of the multi-zone carbon converter. Optionally, any carbon remaining
in the
ash is converted to a syngas. The slag zone is also designed to ensure highly
efficient
heat transfer between the plasma gases and the residue or slag, to minimize
the
amount of sensible heat that is lost. Therefore, the type of plasma heat
source used, as
well as the position and orientation, of the plasma heating means are
additional factors
to be considered in the design of the slag zone.
The slag zone is also designed to ensure that the residue residence time is
sufficient to
bring the residue up to an adequate temperature to fully melt and homogenize
the
residual inorganic materials.
Referring to Figures 13 and 16, optionally, the slag zone is provided with a
reservoir
in which the residue accumulates while being heated by the plasma heat source.
The
reservoir also allows mixing of the solid and molten materials during the
conditioning
process. Sufficient residence time and adequate mixing ensures that the
conditioning
process is completely carried out, and that the resulting slag has the desired
composition.
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The slag zone may be tapered towards the slag outlet or have a sloped floor to
facilitate escape of molten slag.
The slag zone is designed for continuous output of the molten slag material.
Continuous slag removal allows the conditioning process to be carried out on a
continual basis, wherein the residue to be conditioned may be continuously
input and
processed by the plasma heat, without interruption as would be required for
periodic
slag removal.
In one embodiment, continuous slag exhaust is achieved by using a reservoir
bounded
on one side by a weir (33) that allows the slag pool to accumulate until it
exceeds a
certain level, at which point the molten slag runs over the weir and out of
the
chamber.
Where the processed feedstock being conditioned contains a significant amount
of
metal, and the slag zone comprises a reservoir bounded by a weir, the metals,
due to
their higher melting temperature and density, typically accumulate in the
reservoir
until such time as they are removed. Accordingly, in one embodiment of the
multi-
zone converter, the reservoir is optionally provided with a metal tap port,
whereby the
tap port is plugged with a soft refractory paste, through which a hole may be
periodically opened using the heat from an oxygen lance. Once the tap port has
been
opened and the chamber temperature has been raised sufficiently to melt the
accumulated metals, the molten metals are tapped off from the bottom of the
reservoir. The outlet is resealed by placing refractory or other suitable
material into
the hole.
Due to the very high temperatures needed to condition the ash, and
particularly to
melt any metals that may be present, the chamber wall and floor in the slag
zone may
optionally be lined with a refractory material that will be subjected to very
severe
operational demands. The selection of appropriate materials for the design of
the slag
zone is made according to a number of criteria, such as the operating
temperature that
will be achieved during typical residue conditioning processes, resistance to
thermal
shock, and resistance to abrasion and erosion/corrosion due to the molten slag
and/or
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hot gases that are generated during the melting process. The porosity of the
material
may be considered when choosing material for the slag zone.
The slag zone may also include one or more ports to accommodate additional
structural elements or instruments that may optionally be required. In one
embodiment, the port may be a viewport that optionally includes a closed
circuit
television to maintain operator full visibility of aspects of the ash
processing,
including monitoring of the slag outlet for formation of blockages. The
chamber may
also include service ports to allow for entry or access into the chamber for
maintenance and repair. Such ports are known in the art and can include
sealable port
holes of various sizes.
Plasma Heat
The slag zone employs one or more plasma heating sources to convert the ash
material produced by the carbon conversion processes. The plasma heat sources
may
be movable, fixed or a combination thereof.
The plasma heat sources may comprise a variety of commercially available
plasma
torches that provide suitably high temperature gases for sustained periods at
the point
of application. In general, such plasma torches are available in sizes from
about 100
kW to over 6 MW in output power. The plasma torch can employ one or a
combination of suitable working gases. Examples of suitable working gases
include,
but are not limited to, air, argon, helium, neon, hydrogen, methane, ammonia,
carbon
monoxide, oxygen, nitrogen, and carbon dioxide. In one embodiment of the
present
invention, the plasma heating means is continuously operating so as to produce
a
temperature in excess of about 900 C to about 1800 C as required for
converting the
residue material to the inert slag product.
In this respect, a number of alternative plasma technologies are suitable for
use in the
slag zone. For example, it is understood that transferred are and non-
transferred are
torches (both AC and DC), using appropriately selected electrode materials,
may be
employed. It is also understood that inductively coupled plasma torches (ICP)
may
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also be employed. Selection of an appropriate plasma heat source is within the
ordinary skills of a worker in the art.
The use of transferred are, torches instead of non-transferred arc torches may
improve
the efficiency of the residue conditioning process due to their higher
electrical to
thermal efficiency, as well as the higher heat transfer efficiency between the
hot
plasma gases and the material being melted because the are passes directly
through
the melt. Where transferred arc torches are used, it is necessary to ensure
that the slag
zone is electrically isolated since the slag zone outer shell will be
electrically
connected to the power supply.
In one embodiment, the plasma heat source is a DC non-transferred arc torch.
In one embodiment, the plasma torch is a graphite torch.
In one embodiment of the multi-zone carbon converter, the one or more plasma
heat
sources are positioned to optimize the conversion of the residue material to
inert slag.
The position of the plasma heat source(s) is selected according to the design
of the
residue conditioning chamber. For example, where a single plasma heat source
is
employed, the plasma heat source may be mounted in the top of the chamber and
disposed in a position relative to the slag pool collecting at the bottom of
the chamber
to ensure sufficient heat exposure to melt the residue material and force the
slag to
flow. In one embodiment, the plasma heat source is a plasma torch vertically
mounted in the top of the chamber.
All plasma heat sources are controllable for power and optionally (where
movable
heat sources are used) position. In one embodiment, the plasma heat rate is
varied to
accommodate varying residue input rate. The plasma heat rate can also be
varied to
accommodate varying residue melting temperature properties.
The plasma heat sources may be operated on a continuous or non-continuous
basis at
the discretion of the operator to accommodate varying residue input rate and
melting
temperature properties.
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Optionally, the slag zone may be equipped with a deflector (61) to deflect or
direct the
plasma heat (see Figures 15 and 16).
Process Additives
Process additives may optionally be added to the slag zone including steam,
air,
carbon and/or carbon-rich gas and/or oxygen-rich gas and/or bag ash.
Accordingly,
the slag zone may be equipped with various inputs and/or the chamber at the
slag
zone may further comprising a number of ports for these inputs.
Slag Output
The slag zone comprises a slag output. The slag output includes an outlet on
the
chamber through which molten slag is exhausted. The outlet is typically
located at or
near the bottom of the chamber to facilitate the gravity flow of the molten
slag pool
out of the chamber. The slag output also optionally includes a slag cooling
subsystem
to facilitate the cooling of the molten slag to its solid form. Such a cooling
subsystem
can for example include a pool of water or water spray.
The molten slag can be extracted in a continuous manner throughout the full
duration
of processing. The molten slag can be cooled and collected in a variety of
ways that
will be apparent to a person skilled in the art to form a dense, non-
leachable, solid
slag.
Optionally, as the ash is conditioned by the plasma heat, the resulting molten
slag
accumulates in a reservoir. The resulting molten slag is extracted in a
continuous
manner, i.e., as the volume of molten slag in the reservoir increases, it
passes over a
weir and exits the conditioning chamber through an outlet.
Continuous extraction embodiments are particularly suitable for systems that
are
designed to operate on a continuous basis.
In one embodiment, the slag output means also comprises a slag cooling
subsystem
for cooling the molten slag to provide a solid slag product. In one
embodiment, the
molten slag is poured into a quench water bath (78). The water bath provides
an
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efficient system for cooling the slag and causing it to shatter into granules
suitable for
commercial uses, such as for the manufacture of concrete or for road building.
The
water bath may also provide a seal to the environment in the form of a shroud
that
extends from the base of the slag chamber down into the water bath, thereby
providing a barrier preventing outside gases from entering the residue
conditioning
chamber. The solid slag product may be removed from the water bath by a
conveyor
system. Alternatively, the slag cooling subsystem may comprise a water spray.
In one embodiment of the slag cooling subsystem, the molten slag is dropped
into a
thick walled steel catch container for cooling. In one embodiment, the molten
slag is
received in an environmentally sealed bed of silica sand or into moulds to
provide
solid slag suitable for small scale processing or for testing certain
parameters
whenever such testing is performed. The small moulds can be control cooled in
a
preheated oven.
In one embodiment of the slag cooling subsystem, the molten slag is converted
to a
commercial product such as glass wool.
Control
In one embodiment of the multi-zone carbon converter, a control system may be
provided to control one or more processes implemented in, and/or by, multi-
zone
carbon converter. In general, the control system would monitor and regulate
the
different processes to ensure the efficient and complete conversion of the
processed
feedstock into a syngas product and efficient and melting of the residual
solid (i.e ash)
into slag.
The control system comprises one or more sensing elements for real-time
monitoring
of operating parameters of the system; and one or more response elements for
adjusting operating conditions within the system to optimize the conversion
reaction,
wherein the sensing elements and the response elements are integrated within
the
system, and wherein the response elements adjust the operating conditions
within the
system according to the data obtained from the sensing elements.
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Control Elements
Sensing elements contemplated within the present context can include, but are
not
limited to, means for monitoring operational parameters such as gas flow,
temperature
and pressure at various locations within the system, as well as means for
analyzing the
chemical composition of the syngas product.
The data obtained from the sensing elements is used to determine if any
adjustments
to the conditions and operating parameters within the multi-zone carbon
converter are
required to optimize the efficiency of the processes and the composition of
the
product syngas. Ongoing adjustments to the reactants (for example, rate of
processed
feedstock addition, input of heated air and/or steam), as well as to certain
operating
conditions, such as pressure within various components within the system,
enable this
process to be conducted under conditions that enable the consistent and
efficient
production of the syngas.
The control system can be designed and configured with the objective of
optimizing
the efficiency of the conversion process and to mitigate environmental impacts
caused
by the process. The control system can also be designed to operate the multi-
zone
carbon converter under continuous operating conditions.
The following operational parameters may be intermittently or continuously
monitored by the sensing elements, and the data obtained are used to determine
whether the system is operating within the optimal set point, and whether, for
example, there needs to be more power delivered by the torches, more air or
steam
injected into the system, or if the processed feedstock input rate needs to be
adjusted.
Temperature
In one embodiment, the control system comprises means to monitor the
temperature
3o at sites located throughout the multi-zone carbon converter as required for
example,
inside the carbon conversion zone, inter-zonal region, or slag zone. The means
for
monitoring the temperature may be thermocouples or optical thermometers
installed
at locations in the system as required.
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Means for monitoring the temperature of the hot syngas product may also be
located
at the syngas outlet of the carbon conversion zone.
System Pressure
In one embodiment, the control system comprises means to monitor the pressure
at
locations throughout the multi-zone carbon converter. These pressure
monitoring
means may include pressure sensors such as pressure transducers, pressure
transmitters or pressure taps located anywhere in the system, for example, on
a
vertical wall of the chamber.
Gas Flow Rate
In one embodiment, the control system comprises means to monitor the rate of
syngas
flow. Fluctuations in the gas flow may be the result of non-homogeneous
conditions
(e.g. torch malfunction or interruptions in the material feed), therefore if
fluctuations
in gas flow persist, the system may be shut down until the problem is solved.
Gas Composition
In one embodiment, the control system comprises means to monitor the
composition
of the syngas product. The gases produced during the conversion process can be
sampled and analyzed using methods well known to the skilled worker.
In one embodiment, the syngas composition is monitored by means of a gas
monitor,
which is used to determine the chemical composition of the syngas, for
example, the
hydrogen, carbon monoxide and carbon dioxide content of the synthesis gas. In
one
embodiment, the chemical composition of the syngas product is monitored
through
gas chromatography (GC) analysis. Sample points for these analyses can be
located
throughout the system. In one embodiment, the gas composition is monitored
using a
Fourier Transform Infrared (FTIR) Analyser, which measures the infrared
spectrum
of the gas.
Although high temperature gas analysis means exist, one skilled in the art can
appreciate that it may be required to cool the gas prior to analyzing its
composition,
depending upon the type of system used for gas analysis.
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Response Elements
Response elements contemplated within the present context can include, but are
not
limited to, various control elements operatively coupled to process-related
devices
configured to affect a given process by adjustment of a given control
parameter
related thereto. For instance, process devices operable within the present
context via
one or more response elements, may include, but are not limited to, means for
adjusting various operational parameters such as the rate of addition of the
processed
feedstock, air and/or steam, as well as operating conditions, such as power to
the torch
and torch position.
Plasma Heat Source
The present carbon converter uses the controllability of plasma heat to ensure
the
complete melting and vitrification of ash to slag.
In one embodiment of the invention, the control system comprises means to
adjust the
power, and optionally the position, of the plasma heat source. For example,
when the
temperature of the melt is too low, the control system may command an increase
in
the power rating of the plasma heat source; conversely, when the temperature
of the
chamber is too high, the control system may command a drop in the power rating
of
the plasma heat source.
In one embodiment, the power of the torch is maintained at a level that is
proportional
to the rate of the residue addition, i.e., an increase in the residue feed
rate results in an
increase in the torch power. The torch power can also be adjusted to react to
changes
in the characteristics and composition of the residue, for example, with
respect to its
melting properties such as temperature, specific heat capacity, and heat of
fusion.
In one embodiment, the position of the plasma heat source is adjustable to
ensure
complete coverage of the melt pool, and the elimination of areas of
incompletely
reacted materials.
The Rate of Processed Feedstock Addition
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In one embodiment of the invention, the control system comprises means to
adjust the
supply rate of processed feedstock to the carbon conversion zone. The
processed
feedstock may be added in a continuous manner, for example, by using a
rotating
screw or auger mechanism, or it can be added in a discontinuous fashion.
In each case, where the processed feedstock input means comprises a series of
pusher
rams, the control system may optionally employ limit switches or other means
of
travel control such as computer controlled variable speed motor drives to
control the
length, speed and/or frequency of the rain stroke so that the amount of
material fed
into the respective chamber with each stroke can be controlled. Where the
input
means comprises one or more screw conveyors, the rate of addition of the
material to
the carbon conversion zone may be controlled by adjusting the conveyor speed
via
drive motor variable frequency drives.
The input rates are adjusted as required to ensure acceptable control over the
processed feedstock conversion steps, thereby preventing the conveyance of
incompletely converted materials out of the carbon conversion zone.
Addition of Process Additives
In one embodiment of the invention, the control system comprises means to
adjust the
rate and/or amounts of air inputs into carbon conversion and/or slag zone or
the inputs
of other process additives including carbon and steam.
Heated air inputs may be provided as required to maintain optimum processed
feedstock conversion temperatures.
In one embodiment, the control system comprises process control means for
adjusting
the process additives based on data obtained from monitoring and analyzing the
composition of the syngas. The gas composition data may be obtained on a
continuous basis, thereby allowing the adjustments to additive inputs such as
air and
steam to be made on a real-time basis. The type and quantity of the process
additives
are very carefully selected to optimize the chemical composition of the syngas
while
maintaining adherence to regulatory authority emission limits and minimizing
operating costs.
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EXAMPLES
Example 1
Referring to Figures 8, 11, 18 to 25, the multi-zone carbon converter (110) is
zonally
segregated by an interzonal region (112) into a upper carbon conversion zone
(111)
and lower slag melting zone (113). The carbon conversion zone (111) is
maintained
at a temperature of about 950 C to about 1100 C and the slag melting zone is
maintained at a temperature of about 1350 C to about 1600 C.
Referring to Figures 8, 11, 18 to 25, in the illustrated embodiment the multi-
zone
carbon converter (110) comprises a refractory-lined vertically-oriented
chamber (115)
having a processed feedstock input (120), gas outlet (125), a slag outlet
(130), and
zone-specific heating system (i.e. a system that can establish two temperature
zones)
comprising an air box (135) and plasma torch (140). If necessary, the
processed
feedstock input is optionally equipped with a grinder (not shown) to
homogenize the
size of the inputted material.
The chamber (115) is a refractory-lined steel weldment having a substantially
cylindrical shape with a roof and has a length-to-diameter ratio of about
3.6:1 at it
widest point. The diameter of the chamber is narrowed in the inter-zonal
region at
throat and further tapers towards the slag outlet. The chamber is constructed
in
segments to facilitate the replacement of components including those within
the inter-
zonal region.
The refractory comprises three layers, the internal layer is: chromia-alumina
type
cartable, for high temperature resistance, the middle layer and outer layer
are plicaste
insulating castable refractory and insulboard respectfully. For the lower part
of
chamber vessel, the refractory is thicker due to the higher operating
temperature,
190mm shamrock 493, 115mm plicast LWI-28 and 76 mm insboard 2300HD and
25mm durablanket are applied. The refractory at the top section is composed by
190mm Plicast Hymor 2800, 114mm IFB and 100 mm Legrit super lite CD.
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Referring to Figure 22, heated air is introduced into the carbon conversion
zone via
an air box (135) located proximal to the downstream end of this zone. The air
feed to
the air box is controllable allowing for regulation of the conversion process.
The air
flow rate is controlled by the feed/air ratio and operating temperature
change.
Optionally, steam may be injected into the carbon conversion zone via the
steam
injection ports (136).
Referring to Figure 21, the carbon conversion zone (111) tapers to the
narrowed
l0 inter-zonal region (112). The inter-zonal region comprises a physical
impediment
(145) to guide the flow of material from the carbon conversion zone to the
slag zone.
Referring to Figures 8 and 11, the physical impediment comprises a solid pre-
cast
refractory dome (145) mounted in the inter-zonal region via four wedge-shaped
refractory bricks (150). The refractory dome is sized to provide a gap (155)
or space
between the internal wall of the multi-zone carbon converter and the dome
thereby
allowing for transfer of material between zones. The gap is sized
appropriately to
allow molten slag to pass through. Optionally, the refractory dome can have a
plurality of holes (151).
A plurality of alumina or ceramic balls (165) between 20 to 100mm in diameter
rest
on top of the refractory dome to form a bed and provide for diffusion of
heated air and
to promote the transfer of plasma beat to the ash to initially melt the ash
into slag in
the inter-zonal region. In this embodiment, as the ash melts it transits the
inter-zonal
region through the gap (155) between the outside edge of the dome and the
inner wall
of the chamber and into the slag zone.
Located downstream of the inter-zonal region is the slag zone (113). The slag
zone
(113) is a refractory-lined cylinder having a single conically shaped slag
outlet (130).
The slag zone comprises various ports including a plasma torch port, burner
port to
accommodate a burner (139) to pre-heat the chamber, and ports for various
process
additives including hot air and carbon and/or bag ash. Referring to Figure 23,
the
slag melting zone is equipped with a plasma torch (140) and tangentially mount
air
nozzle (141) with pneumatic conveyor gas and hot air injection nozzles. The
hot air,
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carbon and/or bag ash and plasma torch form a hot gas generator (HGG) and
achieve
high temperature gas (>1600 C) to promote ash melting. The plasma torch is
rated at
300kW, water cooled, copper electrode, NTAT, DC plasma. Optionally, carbon
and/or bag ash can be injected using carbon input or through the air nozzles.
Referring to Figure 24, the chamber further comprises a port to accommodate a
burner (139) to facilitate start-up.
Referring to Figure 25, upon exiting the slag zone the molten slag passes
through a
water spray (113) thereby solidifying the slag into pieces. The pieces of slag
are
removed via a drag chain assembly (114).
The plasma torch (140) is mounted on a sliding mechanism that can move the
torch
(140) into and out of the slag melting zone. Optionally, the torch can be
brought
closer for higher heat intensity. The torch (140) is sealed to the chamber by
means of
a sealing gland. This gland is sealed against a gate valve, which is, in turn,
mounted
on and sealed to the vessel. To remove a torch (140), it is pulled out of the
chamber
(115) by the slide mechanism. Initial movement of the slide disables the high
voltage
torch power supply for safety purposes. The gate valve shuts automatically
when the
torch (140) has retracted past the valve and the coolant circulation is
stopped. The
hoses and cable are disconnected from the torch (140), the gland is released
from the
gate valve and the torch (140) is lifted away by a hoist.
Replacement of a torch (140) is done using the reverse of the above procedure;
the
slide mechanism can be adjusted to permit variation of the insertion depth of
the torch
(140).
The gate valve is operated mechanically so that operation is automatic. A
pneumatic
actuator is used to automatically withdraw the torch in the event of cooling
system
failure. Compressed air for operating the actuator is supplied from a
dedicated air
reservoir so that power is always available even in the event of electrical
power
failure. The same air reservoir provides the air for the gate valve. An
electrically
interlocked cover is used a further safety feature by preventing access to the
high
voltage torch connections.
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Thermocouples are positioned at various locations with the carbon converter
such that
the temperature within the zones is maintained at pre-determined temperature
and if it
falls below this temperature power to the plasma torches or air injection is
increased
Example 2
The general structure and design of the multi-zone carbon converter is as
described
above, in that the carbon conversion zone and slag zone are substantially the
same as
that described in Example 1. Referring to Figures 10 and 26, in the
illustrated
embodiment the multi-zone carbon converter (310) comprises a refractory-lined
vertically-oriented chamber (315) having a processed feedstock input (not
shown),
syngas outlet (325), a slag outlet (330), and zone-specific heating system
(i.e. a
system that can establish two temperature zones) comprising an air inlets (not
shown)
and plasma torch (340).
Referring to Figures 10 and 26, the inter-zonal region comprises a physical
impediment to regulate the flow of material from the carbon conversion zone to
the
slag zone. In the instant embodiment, the physical impediment comprises a
series of
substantially parallel refractory line tubes (345) mounted within a mounted
with a
mounting ring (350). The tubes are mounted such that there is a gap (355)
between
adjacent tubes. Optionally, a plurality of alumina or ceramic balls between 20
to
100mm in diameter rest on top of the impediment to form a bed and provide for
diffusion and to promote the transfer of plasma heat to the ash to initially
melt the ash
into slag in the inter-zonal region.
Hot air is feed into the carbon conversion zone through perforations in the
upper
surface of the substantially parallel refractory line tubes (345).
Example 3
The general structure and design of the multi-zone carbon converter is as
described
above, in that the carbon conversion zone and slag zone are substantially the
same as
that described in Example 1. Referring to Figure 27, in the illustrated
embodiment
the multi-zone carbon converter (210) comprises a refractory-lined vertically-
oriented
chamber (315) having a processed feedstock input (not shown), syngas outlet
(not
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shown), a slag outlet (230), and zone-specific heating system (i.e. a system
that can
establish two temperature zones) comprising an air inlets (not shown) and
plasma
torch (240).
Referring to Figure 27, the inter-zonal region comprises a physical impediment
to
regulate the flow of material from the carbon conversion zone to the slag
zone. In the
instant embodiment, the physical impediment comprises a series of
interconnected
refractory bricks (245). The bricks are mounted on a mounting element (250)
such
that there are gaps (255) between adjacent bricks.
Example 4
Referring to Figures 28, in the illustrated embodiment the multi-zone carbon
converter (partially shown) comprises a refractory-lined vertically-oriented
chamber
(415) having a processed feedstock input (not shown), syngas outlet (not
shown), a
slag outlet (430), and zone-specific heating system (i.e. a system that can
establish
two temperature zones) comprising an air inlets (435) and plasma torch (440)
and
optional tapping spout (446).
Referring to Figure 28, the carbon conversion zone is central located and the
slag
zone is located towards the periphery of the chamber. The floor of the chamber
is
sloped such that the carbon conversion zone is upstream of the slag zone
thereby
promoting uni-directional movement of material between these zones. The two
zones
are separated by the inter-zonal region. The inter-zonal region comprises a
physical
impediment to regulate the flow of material from the carbon conversion zone to
the
slag zone. In the instant embodiment, the physical impediment comprises a
series of
substantially vertically-oriented, substantially parallel refractory-lined
perforated
pipes (445). Heated air is introduced into the carbon conversion zone through
the
perforations in the pipes to the center of the pile of processed feedstock
thereby
converting and heating the carbon in the processed feedstock. The air is
heated
slightly as it comes from the bottom, while cooling the pipes. Through air
inlets (441)
in the slag zone air is injected outside the row of pipes and serves to keep
the outer
surface of the pipes very hot so as to keep the slag from freezing.
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The sloped bottom of the slag zone serves to drain the residue towards the
side of the
chamber where the plasma torch is located such that the residue is melted into
molten
slag. As the slag exits it drops through a water spray into a hopper below.
Example 5
The general structure and design of the multi-zone carbon converter is as
described
above, in that the carbon conversion zone and slag zone are substantially the
same as
that described in Example 1. Referring to Figure 29 which illustrates part of
the
carbon conversion zone, the inter-zonal region and the slag zone, the multi-
zone
carbon converter (510) comprises a refractory-lined vertically-oriented
chamber (515)
having a processed feedstock input (not shown), syngas outlet (not shown), a
slag
outlet (530), and zone-specific heating system (i.e. a system that can
establish two
temperature zones) comprising an air inlets (not shown) and plasma torch
(540).
Referring to Figure 29, the inter-zonal region comprises a physical impediment
to
regulate the flow of material from the carbon conversion zone to the slag
zone. In the
instant embodiment, the physical impediment comprises a cogwheel-shaped dome
(545).
Example 6
The structure and design of the multi-zone carbon converter is as described
above, in
that the carbon conversion zone and slag zone are substantially the same as
that
described in Example 1, except for the design of the slag zone. Referring to
Figure
(which illustrates part of the carbon conversion zone, the inter-zonal region
and the
slag zone), the chamber at the slag zone includes a branch or hot gas
generator (622)
having a plasma torch (640), carbon and/or bag ash inputs (642) and hot air
inlets
(641).
Example 7
Referring to Figure 6, the general structure and design of the multi-zone
carbon
converter is as described above, in that the carbon conversion zone and slag
zone are
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substantially the same as that described in Example 1. Referring to Figure 6
which
illustrates part of the carbon conversion zone, the inter-zonal region and the
slag zone,
the multi-zone carbon converter (610) comprises a refractory-lined vertically-
oriented
chamber (615) having a processed feedstock input (not shown), syngas outlet
(not
shown), a slag outlet (630), and zone-specific heating system (i.e. a system
that can
establish two temperature zones) comprising an air inlets (not shown) and
plasma
torch (640).
Referring to Figure 6, the inter-zonal region (which is contiguous with the
slag zone)
comprises a physical impediment to regulate the flow of material from the
carbon
conversion zone to the slag zone. In the instant embodiment, the physical
impediment
comprises a plurality of ceramic balls (645).
Example 8
Referring to Figure 32, the general structure and design of the multi-zone
carbon
converter is as described above, in that the carbon conversion zone and the
inter-zonal
region are substantially the same as that described in. Example 1. The floor
of the slag
zone comprises a rotating slanted refractory table. The rotation of the table
top
facilitates the evacuation of the molten slag. Optionally, table can include a
plurality
of ceramic balls to facilitate plasma heat transfer. The floor of the slag
zone can be
elevated and retracted from the processing zones.
Referring to Figure 32 which illustrates part of the carbon conversion zone,
the inter-
zonal region and the slag zone, the multi-zone carbon converter (810)
comprises a
refractory-lined vertically-oriented chamber (815) having a processed
feedstock input
(not shown), syngas outlet (not shown), a slag outlet (830), and zone-specific
heating
system (i.e. a system that can establish two temperature zones) comprising an
air
inlets (not shown) and plasma torch (840) and impediment (845).
The refractory-line table top is mounted on a drive shaft (846) operatively
connected
to an externally mounted motor (847). The slag-floor assembly is readily
detachable
from the inter-zonal region and the carbon-converter zone and is mounted on an
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elevating table on rails to facilitate clean out. A plurality of ceramic balls
(848)
promotes the transfer of plasma heat.
Optionally, molten slag is cooled by a water spray upon exiting the slag
outlet (830)
and the solidified slag falls onto a drag chain for removal.
Example 9
Figure 33 illustrates part of the carbon conversion zone, the inter-zonal
region and the
slag zone, the multi-zone carbon converter (910) comprises a refractory-lined
vertically-oriented chamber (915) having a processed feedstock input (not
shown),
syngas outlet (not shown), a slag outlet (930), and zone-specific heating
system (i.e. a
system that can establish two temperature zones) comprising an air inlets (not
shown), plasma torch (940), propane or natural gas burner (937) and impediment
(945).
The impediment comprises a rotating refractory cone (921) mounted on a drive
pedestal having a drive shaft (933) linked to an external motor (942). The
lower
portion of the rotating refractory comprises a well (978) in which slag
accumulates
prior to exiting the chamber. The impediment / slag-floor assembly is readily
detachable from the inter-zonal region and the carbon-converter zone and is
mounted
on an elevating table on rails to facilitate clean out.
Optionally, molten slag is cooled by a water spray upon exiting the slag
outlet (930)
and the solidified slag falls onto a drag chain for removal.
Example 10
Referring to Figure 12, in the illustrated embodiment the multi-zone carbon
converter
(1010) comprises a refractory-lined vertically-oriented chamber (1015) having
a
processed feedstock input (1020), syngas outlet (1025) in communication with a
plasma gas refining chamber (1066), a slag outlet (1030), an agitator (1031)
with
externally mounted motor assembly (1032) , and zone-specific heating system
(i.e. a
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system that can establish two temperature zones) comprising air inlets (1041)
and
plasma torch (1040).
The inter-zonal region comprises a physical impediment to regulate the flow of
material from the carbon conversion zone to the slag zone. In the instant
embodiment, the physical impediment comprises a rotating grate (1045) mounted
within the inter-zonal region. Residual solid material transits the inter-
zonal region
and melts within the slag zone. Figures 12A and B illustrate exemplary grate
designs.
43
