Note: Descriptions are shown in the official language in which they were submitted.
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A GAS REFORMULATING SYSTEM USING PLASMA TORCH HEAT
FIELD OF THE INVENTION
This invention pertains to the field of carbonaceous feedstock gasification.
In particular, to a gas
refining system using plasma torch heat.
BACKGROUND TO 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.
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 operate with excess
oxygen to produce
C02, H20, SOR, and NOx, gasification processes produce a raw gas composition
comprising CO,
H2, H2S, and NH3. 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 the feedstock, the volatiles
may include H20,
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).
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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.
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.
The means of accomplishing a gasification process vary in many ways, but rely
on four key
engineering factors: the atmosphere (level of oxygen or air or steam content)
in the gasifier; the
design of the gasifier; the internal and external heating means; and the
operating temperature for
the process. Factors that affect the quality of the product gas include:
feedstock composition,
preparation and particle size; gasifier heating rate; residence time; the
plant configuration
including whether it employs a dry or slurry feed system, the feedstock-
reactant flow geometry,
the design of the dry ash or slag mineral removal system; whether it uses a
direct or indirect heat
generation and transfer method; and the syngas cleanup system. Gasification is
usually carried
out at a temperature in the range of about 650 C to 1200 C, either under
vacuum, at atmospheric
pressure or at pressures up to about 100 atmospheres.
There are a number of systems that have been proposed for capturing heat
produced by the
gasification process and utilizing such heat to generate electricity,
generally known as combined
cycle systems.
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The energy in the product gas coupled with substantial amounts of recoverable
sensible heat
produced by the process and throughout the gasification system can generally
produce sufficient
electricity to drive the process, thereby alleviating the expense of local
electricity consumption.
The amount of electrical power that is required to gasify a ton of a
carbonaceous feedstock
depends directly upon the chemical composition of the feedstock.
If the gas generated in the gasification process comprises a wide variety of
volatiles, such as the
kind of gas that tends to be generated in a low temperature gasifier with a
"low quality"
carbonaceous feedstock, it is generally referred to as off-gas. If the
characteristics of the
feedstock and the conditions in the gasifier generate a gas in which CO and H2
are the
predominant chemical species, the gas is referred to as syngas. Some
gasification facilities
employ technologies to convert the raw off-gas or the raw syngas to a more
defined gas
composition prior to cooling and cleaning through a gas quality conditioning
system.
Utilizing plasma heating technology to gasify a material is a technology that
has been used
commercially for many years. Plasma is a high temperature luminous gas that is
at least partially
ionized, and is made up of gas atoms, gas ions, and electrons. Plasma can be
produced with any
gas in this manner. This gives excellent control over chemical reactions in
the plasma as the gas
might be neutral (for example, argon, helium, neon), reductive (for example,
hydrogen, methane,
ammonia, carbon monoxide), or oxidative (for example, oxygen, carbon dioxide).
In the bulk
phase, a plasma is electrically neutral.
Some gasification systems employ plasma heat to drive the gasification process
at a high
temperature and/or to refine the offgas/syngas by converting, reconstituting,
or reforming longer
chain volatiles and tars into smaller molecules with or without the addition
of other inputs or
reactants. When gaseous molecules come into contact with the plasma heat, they
will
disassociate into their constituent atoms. Many of these atoms will react with
other input
molecules to form new molecules, while others may recombine with like atoms.
As the
temperature of the molecules in contact with the plasma heat decreases all
atoms fully
recombine. As input gases can be controlled stoichiometrically, output gases
can be controlled
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to, for example, produce substantial levels of carbon monoxide and
insubstantial levels of carbon
dioxide.
The very high temperatures (3000 to 7000 C) achievable with plasma heating
enable a high
temperature gasification process where virtually any input feedstock including
waste in as-
received condition, including liquids, gases, and solids in any form or
combination can be
accommodated. The plasma technology can be positioned within a primary
gasification chamber
to make all the reactions happen simultaneously (high temperature
gasification), can be
positioned within the system to make them happen sequentially (low temperature
gasification
with high temperature refinement), or some combination thereof.
The gas produced during the gasification of carbonaceous feedstock is usually
very hot but may
contain small amounts of unwanted compounds and requires further treatment to
convert it into a
useable product. Once a carbonaceous material is converted to a gaseous state,
undesirable
substances such as metals, sulfur compounds and ash may be removed from the
gas. For
example, dry filtration systems and wet scrubbers are often used to remove
particulate matter and
acid gases from the gas produced during gasification. A number of gasification
systems have
been developed which include systems to treat the gas produced during the
gasification process.
These factors have been taken into account in the design of various different
systems which are
described, for example, in U.S. Patent Nos. 6,686,556, 6,630,113, 6,380,507;
6,215,678,
5,666,891, 5,798,497, 5,756,957, and U.S. Patent Application Nos.
2004/0251241,
2002/0144981. There are also a number of patents relating to different
technologies for the
gasification of coal for the production of synthesis gases for use in various
applications,
including U.S. patent Nos. 4,141,694; 4,181,504; 4,208,191; 4,410,336;
4,472,172; 4,606,799;
3o 5,331,906; 5,486,269, and 6,200,430.
U.S. Patent No. 6,810,821 describes an apparatus and method for treating the
gas byproduct of a
waste treatment system using a plasma torch which employs a working gas
including a mixture
of carbon dioxide and oxygen and excluding nitrogen. The exclusion of nitrogen
is to prevent
the formation of nitrogen oxides and hydrogen cyanide which are produced due
to the reactions
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of the nitrogen in the air plasma working gas with oxygen and the hydrocarbons
in the
vessel/reactor at high temperatures.
U.S. Patent No. 5,785,923 describes an apparatus for continuous feed material
melting which
includes an input gas receiving chamber having an input gas torch heater, such
as a plasma torch,
for destroying the volatile material.
Prior systems and processes have not adequately addressed the problems that
must be dealt with
on a continuously changing basis. Some of these types of gasification systems
describe means
for adjusting the process of generating a useful gas from the gasification
reaction. Accordingly,
it would be a significant advancement in the art to provide a system that can
efficiently gasify
carbonaceous feedstock in a manner that maximizes the overall efficiency of
the process, and/or
the steps comprising the overall process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a gas refining system using
plasma torch heat. In
accordance with an aspect of the invention, there is provided a system for
reformulating of an
input gas from a gasification reaction to a reformulated gas of defined
chemical composition
comprising a refractory-lined cylindrical chamber having a first end and a
second end, said
chamber comprising an input for receiving the input gas positioned at or near
the first end of the
chamber; an output for releasing the reformulated gas positioned at or near
the second end of the
chamber; one or more oxygen source(s) inputs in fluid communication with the
chamber; and
one or more plasma torches; wherein said plasma torch(es) heat the chamber and
the input gas is
thereby converted to reformulated gas.
In accordance with another aspect of the invention, there is provided a method
for reformulating
an input gas from a gasification reaction into a reformulated gas, comprising
the steps of
delivering the input gas at an inlet of a refractory-lined chamber; injecting
an oxygen source into
the chamber; torch heating the chamber with one or more plasma torches, and
thereby producing
the reformulated gas.
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This invention provides a gas reformulating system for the reformulating of
input gas derived
from gasification of carbonaceous feedstock into reformulated gas of a defined
chemical
composition. In particular, the gas reformulating system uses torch heat from
a plasma torch to
dissociate the gaseous molecules thereby allowing their recombination into
smaller molecules
useful for downstream application, such as energy generation. The system may
also comprise
gas mixing means, process additive means, and a control system with one or
more sensors, one
or more process effectors and computing means to monitor and/or regulate the
reformulating
reaction.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent in the
following detailed
description in which reference is made to the appended drawings.
Figure 1 is a schematic of the gas reformulating system according to an
embodiment of the
invention.
Figure 2 is a schematic of one embodiment of a gas reformulating system of the
invention
coupled to a gasifier.
Figure 3 is a schematic of one embodiment of a gas reformulating system of the
invention
coupled to two gasifiers.
Figure 4 is a schematic of a gas reformulating chamber according to an
embodiment of the
invention.
Figure 5 is a schematic of one embodiment of the gas reformulating chamber.
Figure 6 A and B illustrates an arrangement of baffles in one embodiment of
the gas
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reformulating chamber. Figure 6A is a diagram illustrating air-flow within the
gas reformulating
chamber comprising bridge wall baffles. Figure 6B is a diagram illustrating
air-flow within the
gas reformulating chamber comprising turbulator or choke ring baffles.
Figure 7A is a diagram illustrating air-flow out of a Type A nozzle. Figure 7B
is a diagram
illustrating air-flow out of a Type B nozzle.
Figure 8 is a schematic illustrating the orientation of the inlets and plasma
torch ports of one
embodiment.
Figure 9A is a cross-sectional view of the gas reformulating chamber of Figure
5. Figure 9B is a
diagram illustrating the air-flow within a gasifier comprising a gas
reformulating system of the
invention including the gas reformulating chamber of Figure 5. Figure 9C
illustrates the
injection of air from the air inputs into the chamber and its effect on air-
flow in the chamber of
Figure 5.
Figure 10 is a schematic of a transport reactor coupled to one embodiment of
the gas
reformulating system.
Figure 11 is a schematic of two entrained flow gasifiers, each coupled to one
embodiment of the
gas reformulating system.
Figure 12 is a schematic of two fixed bed gasifier, each coupled to one
embodiment of the gas
reformulating system.
Figure 13 is a schematic of a cyclonic gasifier coupled to one embodiment of
the gas
reformulating system.
Figure 14 is a schematic of a horizontally-oriented gasifier comprising one
embodiment of the
gas reformulating system including the gas reformulating chamber of Figure 5.
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Figure 15 is an alternative view of the gasifier and gas reformulating system
of Figure 14.
Figure 16 is a cross sectional view of the gasifier and gas reformulating
system of Figure 14.
Figure 17 illustrates a blown up cross sectional view of the gasifier shown in
Figure 14 detailing
the air boxes, carrier ram fingers, ash extractor screw and serrated edge of
step C.
Figure 18 details the carrier ram enclosure of the gasifier illustrated in
Figures 14.
Figure 19 is a cross sectional view of the gas reformulating chamber of Figure
5 detailing the
refractory supports.
Figure 20 is a schematic of a portion of the gas reformulating system of
Example 1 detailing the
torch mounting system and according to an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
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 "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 a gasification
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 within the
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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 a gasification 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 a
gasification
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 a
gasification system, and to which one or more response elements may be
operatively coupled,
may include, but are not limited to, material and/or feedstrock 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 a gasification 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 a gasification 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, this invention provides a gas reformulating system
(GRS) 3000
comprising a gas reformulating chamber 3002 having one or more input gas
inlets 3004, one or
more reformulated gas outlets 3006, one or more plasma torches 3008, one or
more oxygen
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source(s) inputs 3010 and a control system.
The invention provides a GRS for converting raw input gas comprising volatile
molecules that
can include, for example, carbon monoxide, hydrogen, light hydrocarbons, and
carbon dioxide
and contaminating particulate matter such as soot and carbon black produced
during the
gasification of carbonaceous feedstock. This GRS provides a sealed environment
for containing
and controlling the process. It uses plasma torch heat to disassociate the
volatile molecules into
their constituent elements that then recombine as a reformulated gas of a
defined chemical
composition. Process additives such as air and/or oxygen and optionally steam
are used to
provide the necessary molecular species for recombination. The plasma torch
heat also removes
unwanted substances such as paraffins, tars, chlorinated compounds among
others, by
decomposing and converting these unwanted substances to smaller molecules such
as H2 and
CO. The GRS further comprises a control system that regulates the process and
thereby enables
the process to be optimized.
The GRS is designed to be able to convert the input gas from a gasification
reaction into a gas of
defined composition, with a chemical makeup comprising smaller molecules in
proportion and
composition desirable for downstream considerations.
Gas Reformulating System (GRS)
Referring to Figure 1, the GRS 3000 comprises a gas reformulating chamber 3002
having one or
more input gas inlet(s) 3004, one or more reformulated gas outlet(s) 3006, one
or more plasma
torch(es) 3008, one or more oxygen source(s) input(s) 3010 and a control
system.
Downstream of the GRS an induction blower in gaseous communication with the
gas
reformulating chamber may be provided to maintain the pressure of the gas
reformulating
chamber at a desired pressure, for example a pressure of about 0 to -5 mbar.
Referring to Figure 2, in one embodiment, the GRS 3000 is designed to be
coupled directly to a
gasifier 2000 such that the gas reformulating chamber 3002 is in gaseous
communication with
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the gasifier 2000. The gas reformulating chamber 3002 therefore receives input
gas directly
from the gasifier 2000. In such embodiments, the GRS 3000 may further comprise
a mounting
flange 3014 or connector for coupling the gas reformulating chamber 3002 to
the gasifier 2000.
To facilitate maintenance or repair, the GRS 3000 may optionally be reversibly
coupled to the
gasifier 2000 such that the GRS 3000, if necessary, may be removed.
In one embodiment as demonstrated by Figure 3, the GRS 3000 is a stand-alone
unit which
receives input gas from one or more storage tank(s) or one or more gasifier(s)
2000 via piping
3009 or appropriate conduits. In such stand-alone units, the GRS may further
comprise
appropriate support structures.
The Gas Reformulating Chamber
Referring to Figures 1 to 4, the gas reformulating chamber 3002 has one or
more input gas inlets
3004, one or more reformulated gas outlets 3006, one or more ports for heaters
3016 and one or
more ports for oxygen source(s) inputs.
Input gas enters the plasma-torch heated gas reformulating chamber 3002
through one or more
input gas inlet(s) 3004 in the chamber 3002 and is optionally blended by gas
mixers 3012. One
or more input(s) 3010 are provided through which the oxygen source(s) are
injected into the gas
reformulating chamber 3002. The one or more reformulated gas outlets 3006
enable the
reformulated gas to exit the GRS 3000 and to be passed to downstream
processes, for example
for further refinement or for storage at storage facilities.
Design Objectives
The gas reformulating chamber 3002 is a chamber with a sufficient internal
volume to
accommodate the residence time required for the reformulating of input gas
into reformulated
gas to occur.
Accordingly, in designing the gas reformulating chamber, the required gas
residence time can be
considered. Gas residence time is a function of the gas reformulating chamber
volume and
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geometry, gas flow rate, the distance the gas travels and/or the path of the
gas through the
chamber (i.e., a straight linear passage or a swirling, cyclonic, helical or
other non-linear path).
The gas reformulating chamber must, therefore, be shaped and sized in such a
manner that the
flow dynamics of the gas through the chamber allows for an adequate gas
residence time. The
gas residence time can be modified by the use of air jets that promote a
swirling flow of the gas
through the gas reformulating chamber, such that the passage of the gas is non-
linear and
therefore has a longer residence time.
In one embodiment, the gas residence time is about 0.5 to about 2.0 seconds.
In one
embodiment, the gas residence time is about 0.75 to about 1.5 seconds. In a
further embodiment,
the gas residence time is about 1 to about 1.25 seconds. In a still further
embodiment, the gas
residence time is about 1.2 seconds.
Flow modeling of the GRS can be performed to ensure that a particular design
of a gas
reformulating chamber promotes proper mixing of process inputs, and proper
conditions
formation to enable the required chemical reformulatings to occur.
Shape and Orientation
The gas reformulating chamber 3002 may be any shape so long as it allows for
the appropriate
residence time to enable sufficient reformulating of the input gas into
reformulated gas. The gas
reformulating chamber 3002 may be disposed in a variety of positions so long
as appropriate
mixing of the input gas occurs and a desired residence time is maintained.
The gas reformulating chamber can be oriented substantially vertically,
substantially horizontally
or angularly and have a wide range of length-to-diameter ratios ranging from
about 2:1 to about
6:1. In one embodiment, the length-to-diameter ratio of the gas reformulating
chamber 3002 is
3:1.
In one embodiment, the gas reformulating chamber 3002 is a straight tubular or
venturi shaped
structure comprising a first (upstream) end and a second (downstream) end and
is oriented in a
substantially vertical position or a substantially horizontal position.
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In one embodiment, the gas reformulating chamber 3002 is positioned
substantially horizontally
or substantially vertically, has a volume designed to allow a sufficient gas
residence time to
complete the cracking of hydrocarbon organic compounds in the input gas, and a
length /
diameter ratio designed to ensure the gas velocity is in the optimization
range.
In one embodiment as depicted in Figure 5 in which the GRS 3202 is configured
for coupling to
a gasifier, the gas reformulating chamber 3202 is a straight, substantially,
vertical refractory-
lined capped cylindrical structure having an open bottom (upstream) end 3204
for direct gaseous
communication with a gasifier 2000 and one reformulated gas outlet 3206
proximal to or at the
top (downstream) end of the chamber. The cylindrical chamber is formed by
capping the top
(downstream) end of a refractory-lined cylinder with a refractory-lined lid
3203. In order to
facilitate maintenance or repair, the lid is removeably sealed to the
cylinder.
The wall of the gas reformulating chamber can be lined with refractory
material and/or a water
jacket can encapsulate the gas reformulating chamber for cooling and/or
generation of steam or
recovery of usable torch heat.
The gas reformulating chamber may have multiple walls, along with a cooling
mechanism for
heat recovery, and the gas reformulating system may also include heat
exchangers for high
pressure/high temperature steam production, or other heat recovery capability.
Optionally, the gas reformulating chamber can include one or more chambers,
can be vertically
or horizontally oriented, and can have internal components, such as baffles,
to promote back
mixing and turbulence of the gas.
The gas reformulating chamber may optionally have a collector for solid
particulate matter that
can be collected and optionally fed into the gasifier for further processing
or the solid residue
compartments of a gasification system, such as a solid residue conditioning
chamber, for further
processing.
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Collectors for solid particulate matter are known in the art and include but
not limited to
centrifugal separators, inertial impingement baffles, filters or the like.
In embodiments in which the GRS is directly coupled to the gasifier additional
solid particulate
collectors may not be necessary as particulates formed may, in part, fall
directly back into the
gasifier.
The temperature of the reformulated gas exiting the GRS 3000 will range from
about 400 C to
over 1000 C. The temperature may be optionally reduced by a downstream heat
exchange
system used to recover heat and cool the reformulated gas. If necessitated by
downstream
applications or components, the exit temperature of the reformulated gas can
be reduced by
recirculating cooled reformulated gas at the top of the gas reformulating
chamber 3002 such that
the cooled reformulated gas and the newly produced reformulated gas mix. The
gas
reformulating chamber 3002 therefore can optionally include inlets proximal to
the downstream
end of the chamber for injecting cooled reformulated gas into the newly formed
hot reformulated
gas.
Materials
The gas reformulating chamber is generally a refractory-lined chamber with an
internal volume
sized to accommodate the appropriate amount of gas for the required gas
residence time or
otherwise fabricated so that it is able to withstand high temperatures.
Conventional refractory materials that are suitable for use in a high
temperature (e.g. up to about
1200 C), un-pressurized chamber are well-known to those skilled in the art.
Examples of
suitable refractory materials include, but are not limited to, high
temperature fired ceramics, i.e.,
aluminum oxide, aluminum nitride, aluminum silicate boron nitride, zirconium
phosphate, glass
ceramics and high alumina brick containing principally, silica, alumina,
chromia and titania,
ceramic blanket and insulating firebrick. Where a more robust refractory
material is required,
materials such as Didier Didoflo 89CR and Radex Compacflo V253 may be used.
In one embodiment, the refractory can be a multilayer design with a high
density layer on the
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inside to resist the high temperature, erosion and corrosion that is present
in the gas
reformulating chamber. 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 that can be used
because it will not
be exposed to a corrosive environment which can exist within the gas
reformulating chamber.
The multilayer design can further optionally comprise an outside layer,
between the foam board
and the vessel shell that is a ceramic blanket material to provide a compliant
layer to allow for
differential expansion between the solid refractory and the vessel shell.
Appropriate materials
for use in a multilayer refractory are well known in the art.
In one embodiment, the multilayer refractory can further comprise segments of
compressible
refractory separating sections of a non-compressible refractory to allow for
vertical expansion of
the refractory. The compressible layer can optionally be protected from
erosion by overlapping
extendible high density refractory.
In one embodiment, the multilayer refractory can comprise an internally
oriented chromia layer;
a middle alumina layer and an outer insboard layer.
In some embodiments of the invention, the gas reformulating chamber includes a
layer of up to
about seventeen inches, or more, of specially selected refractory lining
throughout the entire gas
reformulating chamber to ensure maximum retention of processing torch heat
while being
impervious to chemical reaction from the intermediate chemical constituents
formed during
processing.
The refractory lining in the bottom section of the gas reformulating chamber
can be more prone
to wear and deterioration since it must withstand higher temperatures from the
operating sources
of plasma torch heat. In one embodiment, therefore, the refractory in the
lower section is
designed to comprise a more durable "hot face" refractory than the refractory
on the gas
reformulating chamber walls and top. For example, the refractory on the walls
and top can be
made of DIDIER RK30 brick, and the different "hot face" refractory for the
lower section can be
made with RADEX COMPAC-FLO V253.
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In embodiments in which the gas reformulating chamber is refractory-lined, the
wall of the gas
reformulating chamber can optionally incorporate supports for the refractory
lining or refractory
anchors.
Gas Inlets and Outlets
The gas reformulating chamber 3002 comprises one or more input gas inlets 3004
to feed input
gas into the chamber for processing and one or more reformulated gas outlets
or ports 3006 to
pass the reformulated gas produced in the reformulating reactions to
downstream processing or
storage. The inlet(s) for input gas is located at or near the first or
upstream end. The inlet may
comprise an opening or, alternatively, may comprise a device to control the
flow of input gas
into the gas reformulating chamber and/or a device to inject the input gas
into the gas
reformulating chamber.
In one embodiment, the one or more input gas inlets 3004 for delivering the
input gas to the gas
reformulating chamber can be incorporated in a manner to promote concurrent,
countercurrent,
radial, tangential, or other feed flow directions.
In one embodiment, there is provided a single input gas inlet with an
increasing conical shape.
In one embodiment, the inlet comprises the open first end of the gas
reformulating chamber,
whereby it is in direct gaseous communication with the gasifier.
In embodiments in which the gasifier and GRS are directly coupled, the
attachment site on the
gasifier for coupling to the GRS may be strategically located to optimize gas
flow and/or
maximize mixing of the input gas prior to entering the gas reformulating
chamber.
In one embodiment, the gas reformulating chamber is located at the center of
the gasifier,
thereby optimizing mixing of the input gas prior to entering the gas
reformulating chamber.
In one embodiment, the inlet comprises an opening located in the closed first
(upstream) end of
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the gas reformulating chamber. This embodiment uses an input gas inlet port to
deliver the
volatiles generated during gasification of carbonaceous feedstock into the
chamber.
In one embodiment, the inlet comprises one or more openings in the wall of the
gas
reformulating chamber proximal to the first (upstream) end.
Referring to Figure 3, in embodiments in which the gas reformulating chamber
3000 is
connected to one or more gasifiers 2000, one or more inlets in the gas
reformulating chamber
3002 may be in direct communication with the one or more gasifier 2000 through
a common
opening or may be connected to the gasifier 2000 via piping 3009 or via
appropriate conduits.
The reformulated gas produced in the reformulating reaction exits the gas
reformulating chamber
through one or more reformulated gas outlets 3006.
One or more outlets 3006 for the reformulated gas produced in the gas
reformulating chamber
are located at or near the second or downstream end. The outlet may comprise
an opening or,
alternatively, may comprise a device to control the flow of the reformulated
gas out of the gas
reformulating chamber.
In one embodiment, the outlet comprises the open second (downstream) end of
the gas
reformulating chamber.
In one embodiment, the outlet comprises one or more openings located in the
closed second
(downstream) end of the gas reformulating chamber.
In one embodiment, the outlet comprises an opening in the wall of the gas
reformulating
chamber near the second (downstream) end.
Ports
The gas reformulating chamber comprises various ports including one or more
ports for heaters,
one or more process additive ports, and optionally one or more access ports,
view ports and/or
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instrumentation ports.
Heater ports include ports for primary heat sources including plasma torches
and optional
secondary sources.
In one embodiment, the gas reformulating chamber comprises one or more port(s)
for mounting
plasma torches 3016.
In one embodiment, the gas reformulating chamber 3002 comprises two or more
ports for
mounting plasma torches 3016.
In one embodiment, the gas reformulating chamber comprises three or more ports
for mounting
plasma torches.
In one embodiment, the gas reformulating chamber comprises four or more ports
for mounting
plasma torches.
In one embodiment, there is provided two ports for plasma torches positioned
at diametric
locations along the circumference of the gas reformulating chamber.
In one embodiment, two ports are provided for tangentially mounting two plasma
torches.
In one embodiment, the ports for the tangentially mounted plasma torches are
located above the
air inlets to provide maximum exposure to plasma torch heat.
Optionally, ports for mounting plasma torches may be fitted with a sliding
mounting mechanism
to facilitate the insertion and removal of the plasma torch(es) from the gas
reformulating
chamber and may include an automatic gate valve for sealing the port following
retraction of the
plasma torch(es).
Optionally, one or more process additive port(s) or inlet(s) are included to
enable process
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additives, such as carbon dioxide, other hydrocarbons or additional gases to
be injected into the
gas reformulating chamber. Optionally, ports or inlets are provided such that
reformulated gas
not meeting quality standards may be re-circulated into the gas reformulating
chamber for further
processing. Ports or inlets may be located at various angles and/or locations
to promote turbulent
mixing of the materials within the gas reformulating chamber.
One or more ports can be included to allow measurements of process
temperatures, pressures,
gas composition and other conditions of interest.
In addition, the gas reformulating chamber 3002 may further include one or
more ports for
secondary torch heat sources to assist in the pre- heating or torch heating of
the gas reformulating
chamber.
Optionally, plugs, covers, valves and/or gates are provided to seal one or
more of the ports or
inlets in the gas reformulating chamber 3002. Appropriate plugs, covers,
valves and/or gates are
known in the art and can include those that are manually operated or
automatic. The ports may
further include appropriate seals such as sealing glands.
Oxygen Source(s) Ports
As noted above, the GRS comprises one or more inputs for oxygen source(s), the
oxygen
source(s) includes oxygen, oxygen-enriched air, air, oxidizing medium, steam
and other oxygen
sources as would be readily understood. Thus the gas conversion chamber
comprises one or
more ports for oxygen source(s) inputs.
In one embodiment, the gas reformulating chamber comprises one or more port(s)
for air and/or
oxygen inputs and optionally one or more ports for steam inputs.
In one embodiment, the gas reformulating chamber 3002 comprises one or more
oxygen
source(s) port(s). In one embodiment, the gas reformulating chamber comprises
two or more
oxygen source(s) ports. In one embodiment, the gas reformulating chamber
comprises four or
more oxygen source(s) ports. In one embodiment, the gas reformulating chamber
comprises six
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oxygen source(s) ports. In one embodiment, there is provided nine oxygen
source(s) ports
arranged in three layers around the circumference of the gas reformulating
chamber. The oxygen
source(s) ports may be in various arrangements so long as the arrangements
provide sufficient
mixing of the oxygen source(s) with the input gas.
Gas Mixers
The gas reformulating chamber 3002 may further optionally include one or more
additional or
supplementary gas mixers at or near the input gas inlet to mix the input gas
such that the input
gas is of more uniform composition and/or temperature and/or to mix the input
gas with process
additives or oxygen source(s). The mixers may include one or more air jets
(air swirl jets) at or
near the input gas inlet which inject a small amount of air into the input gas
and create a swirling
motion or turbulence in the input gas stream and thereby mix the input gas.
In one embodiment, the mixer comprises two or more air swirl jets at or near
the input gas inlet
which inject a small amount of air into the input gas and create a swirling
motion or turbulence
in the input gas stream and thereby mix the input gas by taking advantage of
the injected air's
velocity.
In one embodiment, the mixer comprises three or more air swirl jets at or near
the inlet which
inject a small amount of air into the input gas and create a swirling motion
or turbulence in the
input gas stream and thereby mix the input gas.
In one embodiment, the mixer comprises four or more air swirl jets at or near
the inlet which
inject a small amount of air into the input gas and create a swirling motion
or turbulence in the
input gas stream and thereby mix the input gas. The number of air swirl jets
can be designed to
provide substantially maximum mixing and swirl based on the designed air flow
and exit
velocity, so that the jet could penetrate to the center of the chamber.
Baffles may also be used to induce mixing of the input gas by creating
turbulence in the input
gas. A baffle is a mechanical obstruction to the normal flow pattern. Baffles
serve to block a
section of the gas reformulation chamber cross section, resulting in a rapid
increase in flow
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velocity and a corresponding rapid decrease on the downstream side of the
baffle. This generates
a high level of turbulence and speeds local mixing.
Baffles may be located at various locations in the gas reformulating chamber.
Baffle
arrangements are known in the art and, include but are not limited, to cross
bar baffles, bridge
wall baffles (Figure 6A), choke ring baffle (Figure 6B) arrangements and the
like. Accordingly,
in one embodiment, the gas mixer comprises baffles.
Oxygen Source(s)
As noted above, the GRS comprises one or more oxygen source(s) inputs, the
oxygen source(s)
can include but not limited to oxygen, oxygen-enriched air, air, oxidizing
medium and steam.
In one embodiment, the one or more oxygen source(s) input(s) comprise one or
more air and/or
oxygen and optionally one or more steam input(s).
In one embodiment, the air and/or oxygen and steam inputs comprise high
temperature resistance
atomizing nozzles or jets. Appropriate air nozzles are known in the art and
can include
commercially available types. A single type of nozzle or multiple different
types of nozzles may
be used in the GRS. Example nozzles include type A nozzles and type B nozzles
as illustrated in
Figure 7. The type of nozzles can be chosen based on functional requirements,
for example a
type A nozzle is for changing the direction of air flows for creating the
desired swirls and a type
B nozzle is for creating high velocity of air flow to achieve certain
penetrations, and maximum
mixing.
The nozzles can direct the air to a desired angle which is effective for
mixing the gas. In one
embodiment, the air jets are positioned tangentially. In one embodiment,
angular blowing is
achieved by having a deflector at the tip of the input nozzle, thus allowing
the inlet pipes and
flanges to be square with the gas reformulating chamber.
The arrangement of air and/or oxygen inputs is based on the diameter of the
gas reformulating
chamber, the designed flow and jet velocity, so that adequate penetration,
substantially
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maximum swirl and mixing can be achieved. Various arrangements of the oxygen
inputs or
ports, steam inputs or ports and ports for plasma torches which provide
sufficient mixing of the
input gas with the injected oxygen and steam and sufficient residence time for
the reformulating
reaction to occur are contemplated by the invention. For example, the oxygen
inputs or ports,
steam inputs or ports and ports for the plasma torches may be arranged in
layers around the
circumference of the gas reformulating chamber. This arrangement allows for
the tangential and
layered injection of plasma gases, oxygen and steam which results in a
swirling motion and
adequate mixing of the input gas with the oxygen and steam and provides a
sufficient residence
time for the reformulating reaction to occur.
In embodiments in which the air and/or oxygen input ports are arranged in
layers, the air and/or
oxygen input ports can optionally be arranged to substantially maximize the
mixing effects.
In one embodiment, all the air and/or oxygen input ports are positioned
tangentially thereby
allowing the lower level input ports to premix the gas, torch heat it up, and
start a swirl motion in
the gas. The upper level air input ports cab accelerate the swirl motion
thereby allowing a re-
circulating vortex pattern to be developed and persisted.
Referring to Figure 9, in one embodiment, the lowest level of air input ports
is composed of four
jets, 3212, which will premix the gases generated from a lower gasifier, torch
heat it up. The
other upper two levels of air nozzles, 3211, will provide main momentum and
oxygen to mix
gases and torch heat up to the temperature required.
The arrangements of steam inputs or ports is flexible in number, levels,
orientations and angle as
long as they are located in a position to provide optimized capabilities to
temperature control.
In one embodiment, the gas reformulating chamber comprises one or more steam
inputs or ports.
In one embodiment, the gas reformulating chamber comprises two or more steam
inputs or ports.
The steam inputs or ports may be in various arrangements so long as the
arrangements provide
sufficient mixing with the input gas. In one embodiment there is provided two
steam input ports
arranged in two layers around the circumference of the gas reformulating
chamber and
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positioned at diametric locations.
The oxygen and/or steam input ports may also be positioned such that they
inject oxygen and
steam into the gas reformulating chamber at an angle to the interior wall of
the gas reformulating
chamber which promotes turbulence or a swirling of the gases. The angle is
chosen to achieve
enough jet penetration and maximum mixing based on chamber diameter and
designed air input
port flow and velocity.
In one embodiment, the oxygen and/or steam inputs inject air and steam at an
angle between
about 50-70 from the interior wall of the gas reformulating chamber. In one
embodiment, the
oxygen and steam inputs inject air and steam at an angle between about 55-65
from the interior
wall of the gas reformulating chamber. In one embodiment, the oxygen and steam
inputs inject
oxygen and steam at an about 60 angle from the interior wall of the gas
reformulating chamber.
In one embodiment, the air input ports can be arranged such that they are all
in the same plane,
or they can be arranged in sequential planes. The arrangement of air input
ports is designed to
achieve maximum mixing effects. In one embodiment the air input ports are
arranged in lower
and upper levels. In one embodiment, there are four air input ports at the
lower level and another
six air input ports at upper level in which three input ports are slightly
higher than the other three
to create cross-jet mixing effects to achieve better mixing.
In one embodiment, the gas reformulating chamber includes oxygen inputs, steam
input ports,
and ports for plasma torches that are arranged such that there is adequate
mixing of the gases and
steam throughout the chamber.
Optionally, air can be blown into the chamber angularly so that the air
creates a rotation or
cyclonic movement of the gases passing through the chamber. The plasma torches
may also be
angled to provide further rotation of the stream.
Plasma Torches and Secondary Torch Heat Sources
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In order for the reformulating reaction to occur, the gas reformulating
chamber 3002 must be
torch heated to a sufficiently high temperature. A worker skilled in the art
could readily
determine an adequate temperature for the reformulating reaction. In one
embodiment, the
temperature is about 800 C to about 1200 C. In one embodiment, the temperature
is about
950 C to about 1050 C. In one embodiment the temperature is about 1000 C to
1200 C.
The GRS therefore further comprises one or more non-transferred arc plasma
torches 3008. Non-
transferred arc plasma torches are known in the art and include non-
transferred arc A.C. and
D.C. plasma torches. A variety of gases have been used with plasma torches
including but not
limited to air, 02, N2, Ar, CH4, C2H2 and C3H6. A worker skilled in the art
could readily
determine the type of plasma torches that may be used in the GRS.
In one embodiment, the plasma torch is one or more non-transferred arc A.C.
plasma torch(es).
In one embodiment, the plasma torch is one or more non-transferred D.C. plasma
torch(es). In
one embodiment, the plasma torch is two non-transferred, reverse polarity D.C.
plasma torches.
In one embodiment, there are two plasma torches that are positioned
tangentially to create same
swirl directions as air and/or oxygen inputs do. In one embodiment, the plasma
torch is two 300
kW plasma torches each operating at the (partial) capacity required.
In one embodiment, the gas reformulating system comprises one or more plasma
torch(es). In
one embodiment, the gas reformulating system comprises two or more plasma
torches. In one
embodiment, the gas reformulating system comprises two water cooled, copper
electrode, NTAT
DC plasma torches.
In one embodiment, the use of plasma torch heat is minimized by maximizing the
release of
torch heat that occurs during the reformulating of carbon or multi-carbon
molecules to mainly
CO and H2 by optimizing the amount of air and/or oxygen injected into the gas
reformulating
chamber.
The Control System
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In one embodiment of the present invention, a control system may be provided
to control one or
more processes implemented in, and/or by, the various systems and/or
subsystems disclosed
herein, and/or provide control of one or more process devices contemplated
herein for affecting
such processes. In general, the control system may operatively control various
local and/or
regional processes related to a given system, subsystem or component thereof,
and/or related to
one or more global processes implemented within a system, such as a
gasification system, within
or in cooperation with which the various embodiments of the present invention
may be operated,
and thereby adjusts various control parameters thereof adapted to affect these
processes for a
defined result. Various sensing elements and response elements may therefore
be distributed
throughout the controlled system(s), or in relation to one or more components
thereof, and used
to acquire various process, reactant and/or product characteristics, compare
these characteristics
to suitable ranges of such characteristics conducive to achieving the desired
result, and respond
by implementing changes in one or more of the ongoing processes via one or
more controllable
process devices.
The control system generally comprises, for example, one or more sensing
elements for sensing
one or more characteristics related to the system(s), process(es) implemented
therein, input(s)
provided therefor, and/or output(s) generated thereby. One or more computing
platforms are
communicatively linked to these sensing elements for accessing a
characteristic value
representative of the sensed characteristic(s), and configured to compare the
characteristic
value(s) with a predetermined range of such values defined to characterise
these characteristics
as suitable for selected operational and/or downstream results, and compute
one or more process
control parameters conducive to maintaining the characteristic value with this
predetermined
range. A plurality of response elements may thus be operatively linked to one
or more process
devices operable to affect the system, process, input and/or output and
thereby adjust the sensed
characteristic, and communicatively linked to the computing platform(s) for
accessing the
computed process control parameter(s) and operating the process device(s) in
accordance
therewith.
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In one embodiment, the control system provides a feedback, feedforward and/or
predictive
control of various systems, processes, inputs and/or outputs related to the
conversion of
carbonaceous feedstock into a gas, so to promote an efficiency of one or more
processes
implemented in relation thereto. For instance, various process characteristics
may be evaluated
and controllably adjusted to influence these processes, which may include, but
are not limited to,
the heating value and/or composition of the feedstock, the characteristics of
the product gas (e.g.
heating value, temperature, pressure, flow, composition, carbon content,
etc.), the degree of
variation allowed for such characteristics, and the cost of the inputs versus
the value of the
outputs. Continuous and/or real-time adjustments to various control
parameters, which may
include, but are not limited to, heat source power, additive feed rate(s)
(e.g. oxygen, oxidants,
steam, etc.), feedstock feed rate(s) (e.g. one or more distinct and/or mixed
feeds), gas and/or
system pressure/flow regulators (e.g. blowers, relief and/or control valves,
flares, etc.), and the
like, can be executed in a manner whereby one or more process-related
characteristics are
assessed and optimized according to design and/or downstream specifications.
Alternatively, or in addition thereto, the control system may be configured to
monitor operation
of the various components of a given system for assuring proper operation, and
optionally, for
ensuring that the process(es) implemented thereby are within regulatory
standards, when such
standards apply.
In accordance with one embodiment, the control system may further be used in
monitoring and
controlling the total energetic impact of a given system. For instance, a a
given system may be
operated such that an energetic impact thereof is reduced, or again minimized,
for example, by
optimising one or more of the processes implemented thereby, or again by
increasing the
recuperation of energy (e.g. waste heat) generated by these processes.
Alternatively, or in
addition thereto, the control system may be configured to adjust a composition
and/or other
characteristics (e.g. temperature, pressure, flow, etc.) of a product gas
generated via the
controlled process(es) such that such characteristics are not only suitable
for downstream use, but
also substantially optimised for efficient and/or optimal use. For example, in
an embodiment
where the product gas is used for driving a gas engine of a given type for the
production of
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electricity, the characteristics of the product gas may be adjusted such that
these characteristics
are best matched to optimal input characteristics for such engines.
In one embodiment, the control system may be configured to adjust a given
process such that
limitations or performance guidelines with regards to reactant and/or product
residence times in
various components, or with respect to various processes of the overall
process are met and/or
optimised for. For example, an upstream process rate may be controlled so to
substantially match
one or more subsequent downstream processes.
In addition, the control system may, in various embodiments, be adapted for
the sequential
and/or simultaneous control of various aspects of a given process in a
continuous and/or real
time manner.
In general, the control system may comprise any type of control system
architecture suitable for
the application at hand. For example, the control system may comprise a
substantially centralized
control system, a distributed control system, or a combination thereof. A
centralized control
system will generally comprise a central controller configured to communicate
with various local
and/or remote sensing devices and response elements configured to respectively
sense various
characteristics relevant to the controlled process, and respond thereto via
one or more
controllable process devices adapted to directly or indirectly affect the
controlled process. Using
a centralized architecture, most computations are implemented centrally via a
centralized
processor or processors, such that most of the necessary hardware and/or
software for
implementing control of the process is located in a same location.
A distributed control system will generally comprise two or more distributed
controllers which
may each communicate with respective sensing and response elements for
monitoring local
and/or regional characteristics, and respond thereto via local and/or regional
process devices
configured to affect a local process or sub-process. Communication may also
take place between
distributed controllers via various network configurations, wherein a
characteristics sensed via a
first controller may be communicated to a second controller for response
thereat, wherein such
distal response may have an impact on the characteristic sensed at the first
location. For example,
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a characteristic of a downstream product gas may be sensed by a downstream
monitoring device,
and adjusted by adjusting a control parameter associated with the converter
that is controlled by
an upstream controller. In a distributed architecture, control hardware and/or
software is also
distributed between controllers, wherein a same but modularly configured
control scheme may
be implemented on each controller, or various cooperative modular control
schemes may be
implemented on respective controllers.
Alternatively, the control system may be subdivided into separate yet
communicatively linked
local, regional and/or global control subsystems. Such an architecture could
allow a given
process, or series of interrelated processes to take place and be controlled
locally with minimal
interaction with other local control subsystems. A global master control
system could then
communicate with each respective local control subsystems to direct necessary
adjustments to
local processes for a global result.
The control system of the present invention may use any of the above
architectures, or any other
architecture commonly known in the art, which are considered to be within the
general scope and
nature of the present disclosure. For instance, processes controlled and
implemented within the
context of the present invention may be controlled in a dedicated local
environment, with
optional external communication to any central and/or remote control system
used for related
upstream or downstream processes, when applicable. Alternatively, the control
system may
comprise a sub-component of a regional an/or global control system designed to
cooperatively
control a regional and/or global process. For instance, a modular control
system may be designed
such that control modules interactively control various sub-components of a
system, while
providing for inter-modular communications as needed for regional and/or
global control.
The control system generally comprises one or more central, networked and/or
distributed
processors, one or more inputs for receiving current sensed characteristics
from the various
sensing elements, and one or more outputs for communicating new or updated
control
parameters to the various response elements. The one or more computing
platforms of the
control system may also comprise one or more local and/or remote computer
readable media
(e.g. ROM, RAM, removable media, local and/or network access media, etc.) for
storing therein
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various predetermined and/or readjusted control parameters, set or preferred
system and process
characteristic operating ranges, system monitoring and control software,
operational data, and the
like. Optionally, the computing platforms may also have access, either
directly or via various
data storage devices, to process simulation data and/or system parameter
optimization and
modeling means. Also, the computing platforms may be equipped with one or more
optional
graphical user interfaces and input peripherals for providing managerial
access to the control
system (system upgrades, maintenance, modification, adaptation to new system
modules and/or
equipment, etc.), as well as various optional output peripherals for
communicating data and
information with external sources (e.g. modem, network connection, printer,
etc.).
The processing system and any one of the sub-processing systems can comprise
exclusively
hardware or any combination of hardware and software. Any of the sub-
processing systems can
comprise any combination of none or more proportional (P), integral (I) or
differential (D)
controllers, for example, a P-controller, an I-controller, a PI-controller, a
PD controller, a PID
controller etc. It will be apparent to a person skilled in the art that the
ideal choice of
combinations of P, I, and D controllers depends on the dynamics and delay time
of the part of the
reaction process of the gasification system and the range of operating
conditions that the
combination is intended to control, and the dynamics and delay time of the
combination
controller. It will be apparent to a person skilled in the art that these
combinations can be
implemented in an analog hardwired form which can continuously monitor, via
sensing
elements, the value of a characteristic and compare it with a specified value
to influence a
respective control element to make an adequate adjustment, via response
elements, to reduce the
difference between the observed and the specified value. It will further be
apparent to a person
skilled in the art that the combinations can be implemented in a mixed digital
hardware software
environment. Relevant effects of the additionally discretionary sampling, data
acquisition, and
digital processing are well known to a person skilled in the art. P, I, D
combination control can
be implemented in feed forward and feedback control schemes.
In corrective, or feedback, control the value of a control parameter or
control variable, monitored
via an appropriate sensing element, is compared to a specified value or range.
A control signal is
determined based on the deviation between the two values and provided to a
control element in
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order to reduce the deviation. It will be appreciated that a conventional
feedback or responsive
control system may further be adapted to comprise an adaptive and/or
predictive component,
wherein response to a given condition may be tailored in accordance with
modeled and/or
previously monitored reactions to provide a reactive response to a sensed
characteristic while
limiting potential overshoots in compensatory action. For instance, acquired
and/or historical
data provided for a given system configuration may be used cooperatively to
adjust a response to
a system and/or process characteristic being sensed to be within a given range
from an optimal
value for which previous responses have been monitored and adjusted to provide
a desired result.
Such adaptive and/or predictive control schemes are well known in the art, and
as such, are not
considered to depart from the general scope and nature of the present
disclosure.
Control Elements
Sensing elements contemplated within the present context, as defined and
described above, can
include, but are not limited to, elements that monitor gas chemical
composition, flow rate and
temperature of the product gas, monitor temperature, monitor the pressure,
monitor opacity of
the gas and various parameters relating to the torch (i.e., torch power and
position)
Monitored Parameters
Gasification technologies generally yield a product gas whose H2:CO ratio
varies from as high as
about 6:1 to as low as about 1:1 with the downstream application dictating the
optimal H2:CO
ratio. In one embodiment, the resulting H2:CO ratio is 1.1-1.2:1. In one
embodiment, the
resulting H2:CO ratio is 1.1:1.
The resulting H2:CO ratio in the reformulated gas is dependant on the
operating scenario
(pyrolytic or with adequate 02/Air), on the processing temperature, the
moisture content and the
relative C,H content of the feedstock gasified as well as the amount of
supplementary carbon
feed.
Taking into account one or more of the above factors, the control system of
the invention
regulates the composition of the reformulated gas over a range of possible
H2:CO ratios by
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adjusting the balance between applied plasma torch heat, air and/or oxygen,
carbon and steam
thereby allowing reformulated gas composition to be optimized for a specific
downstream
application.
A number of operational parameters may be regularly or continuously monitored
to determine
whether the system is operating within the optimal set point. The parameters
being monitored
may include, but are not limited to, the chemical composition, flow rate and
temperature of the
product gas, the temperature at various points within the system, the pressure
of the system, and
various parameters relating to the torch (i.e., torch power and position) and
the data are used to
determine if there needs to be an adjustment to the system parameters.
The Composition and Opacity of the Reformulated Gas
The product gas can be sampled and analyzed using methods well known to the
skilled
technician. One method that can be used to determine the chemical composition
of the product
gas is through gas chromatography (GC) analysis. Sample points for these
analyses can be
located throughout the system. In one embodiment, the gas composition is
measured using a
Fourier Transform Infrared (FTIR) Analyser, which measures the infrared
spectrum of the gas.
A part of this invention is determining whether too much or too little oxygen
is present in the
outlet stream and adjusting the process accordingly. In one embodiment, an
analyzer or sensor in
the carbon monoxide stream detects the presence and concentration of carbon
dioxide or other
suitable reference oxygen rich material. In one embodiment, oxygen is measured
directly.
In one embodiment, the sensors analyze the composition of the reformulated gas
for carbon
monoxide, hydrogen, hydrocarbons and carbon dioxide and from the data
analyzed, a controller
sends a signal to the oxygen and/or steam inlets to control the amount of
oxygen and/or steam
injected into the gas reformulating chamber and/or a signal to the plasma
torches
In one embodiment, one or more optional opacity monitors are installed within
the system to
provide real-time feedback of opacity, thereby providing an optional mechanism
for automation
of process additive input rates, primarily steam, to maintain the level of
particulate matter below
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the maximum allowable concentration.
The Temperature at Various Locations in System
In an embodiment, there is provided means to monitor the temperature of the
reformulated gas
and the temperature at sites located throughout the system, wherein such data
are acquired on a
continuous basis. Means for monitoring the temperature in the chamber, for
example, may be
located on the outside wall of the chamber, or inside the refractory at the
top, middle and bottom
of the chamber. Additionally, sensors for monitoring the exit temperature of
the reformulated gas
are provided.
In an embodiment, the means for monitoring the temperature is provided by
thermocouples
installed at locations in the system as required.
The Pressure of S, s~
In one embodiment, there is provided means to monitor the pressure within the
reaction vessel,
wherein such data are acquired on a continuous, real time basis. In a further
embodiment, these
pressure monitoring means comprise pressure sensors such as pressure
transducers or pressure
taps located anywhere on the reaction vessel, for example on a vertical wall
of the reaction
vessel.
The Rate of Gas Flow
In an embodiment, there is provided means to monitor the rate of product gas
flow at sites
located throughout the system, wherein such data are acquired on a continuous
basis.
Fluctuations in the gas flow may be the result of non-homogeneous conditions
(e.g. torch
malfunction or out for electrode change or other support equipment
malfunction). As a
temporary measure fluctuations in gas flow may be corrected by feedback
control of blower
speed, feed rates of material, secondary feedstock, air, steam, and torch
power. If fluctuations in
gas flow persist, the system may be shut down until the problem is solved.
Addition of Process Additives
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In an embodiment, the control system comprises response elements to adjust the
reactants,
including any process additives, to manage the chemical reformulating of input
gas to
reformulated gas. For example, process additives may be fed into the chamber
to facilitate the
efficient reformulating of an input gas of a certain chemical composition into
a reformulated gas
of a different desired chemical composition.
In one embodiment, if the sensors detect excess carbon dioxide in the
reformulated gas, the
steam and/or oxygen injection is decreased.
Response elements contemplated within the present context, as defined and
described above, 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 elements that regulate
oxygen source(s)
inputs and plasma torch heat.
Adjusting Power to a Torch (Torch Heat)
The process of the invention uses the controllability of plasma torch heat to
drive the reaction.
Addition of process air into the refining chamber also bears part of the torch
heat load by
releasing torch heat energy with combustion of reformulated gas. The flow rate
of process air is
adjusted to keep torch power in a good operating range.
Plasma torch power is adjusted to stabilize the reformulated gas exit
temperatures at the design
set point. In one embodiment, to ensure that the tars and soot formed in the
gasifier are fully
decomposed the design set point is about 1000 C.
Adjusting Pressure within the System
In one embodiment, the control system comprises a response element for
controlling the internal
pressure of the chamber. In one embodiment, the internal pressure is
maintained at a negative
pressure, i.e., a pressure slightly below atmospheric pressure. For example,
the pressure of the
reactor will be maintained at about 1-3 mbar vacuum. In one embodiment, the
pressure of the
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system is maintained at a positive pressure.
An exemplary embodiment of such means for controlling the internal pressure is
provided by an
induction blower in gaseous communication with the GRS. The induction blower
thus employed
maintains the system at a negative pressure. In systems in which positive
pressure is maintained
the blower is commanded to operate at lower RPM than the negative pressure
case or a
compressor may be used.
In response to data acquired by pressure sensors located throughout the
system, the speed of the
induction blower will be adjusted according to whether the pressure in the
system is increasing
(whereby the fan will increase in speed) or decreasing (whereby the fan will
decrease in speed).
Moreover, according to the process of the invention, the system may be
maintained under slight
negative pressure relative to atmospheric pressure to prevent gases being
expelled into the
environment.
Pressure can be stabilized by adjusting the reformulated gas blower's speed.
Optionally, at
speeds below the blower's minimum operating frequency, a secondary control
overrides and
adjusts the recirculation valve instead. Once the recirculation valve returns
to fully closed, the
primary control re-engages.
Gasifiers for Use with the GRS
The invention is adapted for use with one or more gasifiers and for use with
various types of
gasifiers. The gasifier converts carbonaceous feedstock to an input gas
product. The stages of
the feedstock gasification include: i) drying of the feedstock to remove
residual moisture, ii)
volatilization of volatile constituents of the dried feedstock to produce a
char intermediate, and
iii) reformulating of the char to input gas and ash. The gaseous products of
the gasification
process therefore include the volatile constituents and input gas, which are
subjected to the
plasma reformation step of the invention to provide the raw reformulated gas
product.
Generally, a gasifier comprises a refractory-lined chamber having one or more
feedstock inlets, a
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torch heating means, one or more optional process additive inlets, a gas
outlet, and an optional
solid residue or slag outlet or removal system.
The gasification process can be carried out in a variety of different
gasifiers including the
gasifier described below in the example or one of a number of standard
gasifiers as are known in
the art. Examples of gasifiers known in the art include, but are not limited
to entrained flow
reactor vessels, fluidized bed reactors, and rotary kiln reactors, each of
which is adapted to
accept feedstock in the form of solids, particulates, slurry, liquids, gases,
or a combination
thereof. The gasifier can have a wide range of length-to-diameter ratios and
can be oriented
either vertically or horizontally.
In one embodiment, the gasifier for use with the invention is a transport
reactor gasifier 3401
(Figure 10) which entrained the feedstock in the gas stream and recycles it
through the
gasification zone to ensure maximum reformulating of feedstock into input gas.
The GRS 3000
can optionally be directly coupled to the transport reactor gasifier at the
gas exit.
In one embodiment, the gasifier for use with the invention is an entrained
flow gasifier 3402A,
3402B (Figure 11). The coupling of the GRS 3000 to the entrained flow gasifier
will increase
the residence time for the reactions to be completed and add a second high
temperature zone to
further ensure gas quality.
In one embodiment, the gasifier for use with the invention is a fixed bed
gasifier 3403A, 3403B
(Figure 12). The fixed bed gasifier can be of multitude of designs which
control the flow and
characteristics of the pile for gasification (and pyrolysis). The GRS 3000 is
coupled to the input
gas outlet to ensure complete reaction of the gas to simpler gas molecules.
In one embodiment, the gasifier for use with the invention is a cyclone
gasifier 3404 (Figure 13).
Example
Figures 14 to 18 show a converter incorporating an embodiment of the GRS
comprising the gas
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reformulating chamber shown in Figure 5.
The gasifier 2200 comprises a refractory-lined horizontally-oriented stepped-
floor gasification
chamber 2202 having a feedstock input 2204, gas outlet 2206 and a solid
residue outlet 2208.
The gasification chamber 2202 is a refractory-lined steel weldment having a
stepped floor with a
plurality of floor levels 2212, 2214, 2216.
The solid residue outlet is equipped with an ash extractor comprising an
extractor screw 2209
which will pull the ash out of the gasifier and feed it into an ash conveyor
system.
Each step has a perforated floor 2270 through which heated air can be
introduced. To avoid
blockage of the air holes during processing, the air hole size is selected
such that it creates a
restriction and thus a pressure drop across each hole. This pressure drop is
sufficient to prevent
waste particles from entering the holes.
The air feed for each level or step is independently controllable. Independent
air feed and
distribution through the perforated floor 2270 is achieved by a separate air
box 2272, 2274, 2276
which forms the floor of each step.
Movement through the steps is facilitated by a series of multiple-finger
carrier rams 2228, 2230,
2232, with the floor of each step being serviced by a single multiple-finger
carrier ram. The
series of carrier rams further allows for the control of the height of the
pile at each step and the
total residence time of the reactant material in the gasification chamber.
Each ram is capable of
movement over the full or partial length of that step, at variable speeds.
Each ram unit comprises an externally mounted guide portion, a multiple finger
ram having
optional guide portion engagement members, externally mounted drive system and
an externally
mounted control means. The guide portion comprises a pair of generally
horizontal, generally
parallel elongated tracks 2240(a), 2240(b) (not shown) mounted on a frame.
Each of the tracks
has a substantially L-shaped cross-section. The ram comprises a ram body 2326
and a series of
elongated, substantially rectangular ram fingers 2328 sized to slidably move
through
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corresponding sealable opening in the chamber wall.
Power to propel the rams along the tracks is supplied by a externally mounted
electric variable
speed motor 2256 which drives a motor output shaft 2258 selectably in the
forward or reverse
direction allowing for extension and retraction of the ram at a controlled
rate. Position sensors
2269 transmit ram position information to the control system. Optionally, the
motor may further
comprise a gear box. Two driver sprocket gears 2260 are mounted on the motor
output shaft.
The driver sprockets 2260 and corresponding driven sprockets 2262mounted on an
axle 2264
operatively mesh with chain members 2266 which are secured by brackets 2268to
the elongated
rectangular block 2244.
In the step-floor gasifier, conditions at the individual steps are optimized
for different degrees of
drying, volatilization and carbon reformulating.
The feedstock is introduced into the chamber, onto the first step via the
feedstock input (421).
The normal temperature range for this step (as measured at the bottom of the
material pile) lies
between 300 and 900 C. The major process here is that of drying with some
volatilization and
carbon conversion.
Step II is designed to have a bottom temperature range between 400 and 950 C.
The main
process is that of volatilization with a small degree (the remainder) of the
drying operation as
well as a substantial amount of carbon conversion.
Step III temperature range lies between 600 and 1000 C. The major process in
Step III is that of
carbon conversion with a lesser amount (the remainder) of volatilization.
As the solid feed material progresses through the chamber it loses its mass
and volume as its
volatile fraction is volatilized to form input gas and the resulting char is
reacted to form
additional input gas and ash.
The unrefined input gas exits through the gas outlet 2206 of the gasifier 2200
into the GRS 3200
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which is sealably coupled to the gasifier via a mounting flange 3214 which
directly connects the
gasifier gas outlet with the single conically shaped input gas inlet of the
GRS. Air is injected
into the input gas stream through swirl ports 3212 to create a swirling motion
or turbulence in the
input gas stream thereby mixing the input gas and creating a re-circulating
vortex pattern within
the GRS. The residence time of the gas within the GRS is about 1.2 seconds
Referring to Figure 5, the GRS comprises a substantially vertically mounted
refractory-lined
cylindrical chamber having a length-to-diameter ration of about 3:1 and a
single conically shaped
input gas inlet to which the gasifier is connected to via a mounting flange
3214. The chamber is
capped with a refractory-lined lid 3203 thereby creating a sealed gas
reformulating chamber
3202.
The gas reformulating chamber comprises various ports including one or more
ports for heaters
3216, one or more ports for one or more oxygen sources 3210, and optionally
one or more access
or view ports 3326 and/or instrumentation ports 3226. In addition, the gas
reformulating chamber
is equipped with lifting points 3230.
The refractory used on the wall of the chamber is a multilayer design with a
high density layer on
the inside to resist the high temperature, erosion and corrosion that is
present in the chamber, a
middle lower density material layer with lower resistance properties but
higher insulation factor
and an outer very low density foam board layer with very high insulation
factor. The outside
layer, between the foam board and the vessel steel shell is a ceramic blanket
material to provide a
compliant layer to allow for differential expansion between the solid
refractory and the vessel
shell. Vertical expansion of the refractory is provided for by means of a
compressible refractory
layer separating sections of the non-compressible refractory. The compressible
layer is protected
from erosion by overlapping but extendible high density refractory.
Referring to Figure 19, the gas reformulating chamber further comprises a
refractory support
system comprising a series of circumferential extending shelves 3220. Each
shelf is segmented
and includes gaps to allow for expansion. Each shelf segment 3222 is supported
by a series of
support brackets 3224.
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In this embodiment of the GRS, the one or more inputs for one or more oxygen
source(s) include
air and steam inputs.
The GRS further comprises three levels of tangentially positioned air nozzles,
two tangentially
located plasma torches, six thermocouple ports, two burner ports, two pressure
transmitter ports
and several spare ports.
Referring to Figure 9, air is injected into the gas stream by three levels of
air nozzles that include
four jets at the lower leve13212 and another six jets at upper leve13211 in
which three jets are
slightly higher than other three to create cross-jet mixing effects to achieve
better mixing.
The GRS further includes two-tangentially mounted 300kW, water cooled, copper
electrode,
NTAT, DC plasma torches mounted on a sliding mechanism. The two plasma torches
are
located above the air nozzles to provide maximum exposure to plasma torch heat
(see Figure 9,
2o 3216).
The plasma power supply converts three phase AC power into DC power for each
plasma torch.
As an intermediate step, the unit first converts the three phase AC input into
a single high
frequency phase. This allows for better linearization of the eventual DC
output in the chopper
section. The unit allows output DC voltage is allowed to fluctuate in order to
maintain stable DC
current.
Each plasma torch 3208 is mounted on a sliding mechanism that can move the
torch 3208 into
and out of the gas reformulating chamber. The torch 3208 is sealed to the gas
reformulating
chamber 3202 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 3208, it is
pulled out of the
reformulating chamber 3202 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 3208 has retracted past the valve and the coolant circulation is
stopped. The hoses and
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cable are disconnected from the torch 3208, the gland is released from the
gate valve and the
torch 3208 is lifted away by a hoist.
Replacement of a torch 3208 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 3208.
The gate valve is operated mechanically so that operation is automatic. A
pneumatic actuator
3233 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 3234. An electrically interlocked cover is used a
further safety feature
by preventing access to the high voltage torch connections.
Thermocouples are positioned at various locations with the gas reformulating
chamber such that
the temperature of the reformulated gas within the GRS is maintained at about
1000 C and if it
falls below this temperature power to the plasma torches or air injection is
increased.
In this embodiment, the air flow at each step is pre-set to maintain
substantially constant
temperature ranges and ratios between steps. For example, about 36% of the
total air flow may
be directed to Step A, about 18% to Step B, and about 6% to Step C, the
remainder being
directed to an attached GRS (e.g. 40% of total air flow). Alternatively, air
input ratios may be
varied dynamically to adjust temperatures and processes occurring within each
step of the
gasifier and/or GRS
The molecules within the gaseous mixture within the gas reformulating chamber
disassociate
into their constituent elements in the plasma arc zone and then reformed into
reformulated gas.
The hot crude reformulated gas exits the GRS via the reformulated gas outlet
3206.
The invention being thus described, it will be apparent that the same may be
varied in many
ways. Such variations are not to be regarded as a departure from the spirit
and scope of the
invention, and all such modifications as would be apparent to one skilled in
the art are intended
to be included within the scope of the following claims.
