BACKGROUND OF THE INVENTION
The present disclosure relates generally to methods for
activating carbon charcoal and, more particularly, to activating carbon charcoal
resulting from biomass gasification without the use of an external heat source, heat
treatment, and/or heat recovery.
At least some known gasification systems are integrated with
at least one power producing turbine system. Many of such systems include a gasifier
that creates a combustible gas or a combustible gas precursor, that undergoes
additional processing into a combustible gas, referred to as "producer gas". One
common source of producer gas or precursor feedstock is biomass material, as the use
of biomass material reduces the dependency on other sources of producer gas
feedstock, such as fossil fuel-based feedstocks including coal, andlor coke, for
example.
In use, the gasifier creates producer gas through a pyrolysis
reaction, whereby air is injected into the gasifier to completely burn the biomass
material to charcoal. The charcoal may then be activated and used for decolorization
purposes, purification of gases, adsorption of vapors, and purification of water, for
example. Conventionally, activation of charcoal is typically accomplished via
chemical or physicaVtherma1 processes. For example, in thermal activation, an
external heat source (e.g., a burner, or a reactor) heats the carbon-based charcoal
material, thereby burning the carbon and increasing its porosity.
This activation process can increase the marketable value of
charcoal when compared to inactivated charcoal. Accordingly, it would be
advantageous to provide alternative methods for activating the charcoal resulting from
biomass gasification that are more efficient and economical. More particularly, it
would be desirable to utilize heat generated internally within the biomass gasification
system to activate charcoal, thereby increasing the value of biomass gasification with
minimal investment in the process.
BRIEF DESCRIPTION OF THE INVENTION
In one aspect, a method of activating charcoal resulting from
gasification is provided. The method includes gasifying dried biomass material in a
gasification reactor of an integrated biomass gasification system to produce charcoal,
and activating the charcoal using heat generated from an integral heat source of the
integrated biomass gasification system.
In another aspect, a method of activating charcoal resulting
from gasification is provided. The method includes gasifying dried biomass material
in a gasification reactor of an integrated biomass gasification system to produce a
stream of charcoal and producer gas, separating the charcoal from the producer gas of
the stream using a hot screw conveyor, and activating the charcoal using heat
generated from an integral heat source of the integrated biomass gasification system.
In another aspect, a method of activating charcoal resulting
from gasification is provided. The method includes gasifying dried biomass material
in a gasification reactor of an integrated biomass gasification system to produce a
stream of charcoal and producer gas, separating the charcoal from the producer gas of
the stream using a hot screw conveyor, combusting the producer gas using a
combustor to generate hot exhaust gases, and activating the charcoal using heat from
the hot exhaust gases.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an exemplary system for use
in activating charcoal resulting from an integrated biomass gasification system using
heat from an integral heat source.
FIG. 2 is a schematic diagram of an alternative system for use
in activating charcoal resulting from an integrated biomass gasification system using
heat from an integral heat source.
DETAILED DESCRIPTION OF THE INVENTION
Although specific features of various exemplary embodiments
of the invention may be shown in some drawings and not in others, this is for
convenience only. In accordance with the principles of the invention, any feature of a
drawing may be referenced andor claimed in combination with any feature of any
other drawing.
The present invention is directed to an integrated biomass
gasification system capable of using heat produced within the system to activate
charcoal. This system includes an integral heat source for heating charcoal resulting
from the biomass gasification reactor of the system, thereby increasing its iodine
value to a level that may be useful as activated carbon in industries such as for
purification andor decolorization of water and vapors, for example. In some
embodiments, As used herein, the terms "integral heat source" and "integrated heat
source" are used interchangeably to refer to an internal component of the integrated
biomass gasification system that is incorporated for a primary purpose other than to
heat and activate charcoal resulting from the system.
In the exemplary embodiment, activation of charcoal occurs
either chemically or thermally. Thermal, also known as physical, activation occurs
after heating the charcoal material to a temperature where the carbon is at least
partially burned, and where its porosity is increased. Typically, charcoal is activated
at a temperature of at least 400°C.
FIG. 1 is a schematic diagram of an exemplary integrated
biomass gasification system 100 that may be used in generating charcoal for
activation. In the exemplary embodiment, System 100 includes a biomass dryer 102
that receives biomass material from a source 104. A biomass gasification reactor 106,
also referred to herein as a gasifier, receives dried biomass material 108 from biomass
dryer 102. Biomass dryer 102 may be any dryer known in the art, such as, but not
limited to, rotary dryers, flash dryers, superheated steam dryers, disk dryers, andlor
cascade dryers. Alternatively, in some embodiments, dried biomass material 108 is
produced by sun-drying. Dried biomass material 108 typically includes less than 12%
by weight moisture and includes approximately 6% by weight charcoal.
Once dried, dried biomass material 108 is conveyed to
biomass gasification reactor 106 for gasification. Biomass gasification reactor 106 is
coupled to a hot screw conveyor 112, wherein a stream (not shown) produced by
gasifier 106 is separated to remove solids such as charcoal 116 from producer gas
118. After separation from hot screw conveyor 112, charcoal 116 has a temperature
of approximately 200°C. Charcoal 116 may be subsequently treated with an acid
wash, such as with hydrogen chloride (HC1).
In one embodiment, charcoal 1 16 can contact outer walls 1 10
of screw conveyor 112, heating charcoal 116 to a temperature of between 400°C to
about 1 1 OO°C, such that charcoal 1 16 is activated.
Producer gas 11 8 is then channeled into a separator 114, such
as a cyclone separator, in which particulate matter 138 is separated from producer gas
118. The temperature of producer gas 118 channeled to separator 114 is typically
about 500°C. Accordingly, in one embodiment, heat from producer gas 118 can be
used for heating, and thereby activating, charcoal 116 through either air heating or
through steam generation as is known in the art.
It should be understood that although separator 114 is
described herein as a cyclone separator, any other separator known in the gasification
art may be used in system 100 without departing from the present invention. Producer
gas 118 is comprised primarily of hydrogen (H2), carbon dioxide (CO2) and carbon
monoxide (CO). Producer gas 118 is channeled into a combustor 122, wherein
producer gas 118 is combusted with air 126, typically ambient air, supplied by a
blower 128. As used herein, the term "blower" refers to a device that primarily serves
to propel a fluid while raising its pressure only slightly, whereas a "compressor"
refers to any device that discharges a fluid at a significantly higher pressure than the
pressure of fluid introduced into the compressor. As used herein, "pressurized" refers
to a fluid having a higher pressure than a "compressed" fluid. Combustor 122
discharges a combustor exhaust 146. Combustor 122 includes a heat exchanger
element 120, that is coupled in flow communication with a compressor 130 and a
turbine 124. Compressor 130 is rotationally coupled to turbine 124 via a transmission
structure 132.
Ambient air 134 is channeled into compressor 130.
Compressor 130 discharges a heated compressed air 136 that is channeled into
combustor 122. Combustor 122 discharges a heated pressurized air 140, that is
channeled towards turbine 124, and that is subsequently discharged from turbine 124
as an exhaust 142. Heated pressurized air 140 is expanded in turbine 124, causing
rotation of turbine 124. Turbine exhaust 142 is combined with combustor exhaust 146
to produce hot gases 148 that can be used to heat charcoal 116. In one embodiment,
gases 148 can heat charcoal 116 to a temperature of between about 400°C to about
1 1 OO°C, thereby activating charcoal 1 16.
FIG. 2 is a schematic diagram of an alternative integrated
biomass gasification system 200 for use in generating charcoal for activation. In the
exemplary embodiment, system 200 includes a biomass dryer 202, that receives
biomass material from a source 204. A biomass gasification reactor 206 receives dried
biomass material 208 from biomass dryer 202 for gasification. Similar to dryer 102
(shown in FIG. 1) used with system 100 (shown in FIG. I), biomass dryer 202 may be
any dryer known in the art. Alternatively, dried biomass material 208 may be
produced by sun-drying.
Biomass gasification reactor 206 is coupled to a hot screw
conveyor 212, wherein a stream (not shown) produced by biomass gasification reactor
206 is separated to remove solids including charcoal 216, from producer gas 218.
Similar to system 100, charcoal 216 in system 200 may contact outer walls 210 of
screw conveyor 212, thereby heating charcoal 116 to a temperature sufficient for
activation (i.e., between about 400°C to about 1100°C).
Similar to system 100, producer gas 21 8 generated in system
200 may be channeled to separator 214, such as a cyclone separator, in which
particulate matter 238 is separated from producer gas 218. Further, as the temperature
of producer gas 2 18 is typically about 500°C, heat from producer gas 2 18 can be used
for heating, and to thereby activate, charcoal 216 through either air heating or steam
generation.
Producer gas 21 8 is channeled into a combustor 222, wherein
the producer gas 218 is combusted with air 226 (typically ambient air) supplied by a
blower 228. Combustor 222 discharges a combustor exhaust 246. Combustor 222
includes a heat exchanger element 220, that is coupled in flow communication with
compressor 230 and turbine 224. Compressor 230 is rotationally coupled to turbine
224 via a transmission structure 232.
Ambient air 226 is channeled into compressor 230.
Compressor 230 discharges a compressed air 236 that is channeled into combustor
222. Combustor 222 discharges a heated pressurized air 240, that is channeled
towards turbine 224 prior to it subsequently being discharged from turbine 224 as
exhaust 242. Heated pressurized air 240 is expanded in turbine 224, causing rotation
of turbine 224.
6
Combustor 222 is coupled in flow communication with heat
exchanger 252. Combustor exhaust 246 is channeled to heat exchanger 252 to release
heat to a boiler feed water (BFW) 254, creating a heated boiler feed water 255.
Heated boiler feed water 255 is channeled to a heat exchanger 256 coupled in flow
communication with combustor 222, wherein heated boiler feed water 255 is heated
additionally by turbine exhaust 242, and is converted into a steam 258. Steam 258
may be used to heat charcoal 216 to a temperature between about 400°C to about
1 1 OO°C, to activate charcoal 2 16.
Alternatively, similar to system 100, turbine exhaust 242
generated in system 200 may be combined with combustor exhaust 246 to produce
hot gases 248 that can be used to heat charcoal 216. In one embodiment, hot gases
248 can heat charcoal 2 16 to a temperature of between about 400°C to about 1 1 OO°C,
thereby activating charcoal 21 6.
In contrast to known integrated biomass gasification systems,
the biomass gasification systems described herein enable charcoal resulting from
biomass gasification to be activated thermally using heat from an integral heat source;
more specifically, the systems described herein facilitate activating charcoal without
the use of an external heat source. The biomass gasification systems facilitate the
activation of charcoal resulting from biomass gasification in a more efficient and
economical manner, thereby increasing the value of biomass gasification with
minimal investment in the process. The activated charcoal may be used in many
industries, such as, for example, decolorization purposes, purification of air and gases,
adsorption of vapors, andor purification of water.
Exemplary embodiments of methods for activating charcoal
resulting from biomass gasification are described herein in detail. The methods and
systems are not limited to the specific embodiments described herein, but rather,
components of systems andor steps of the methods may be utilized independently and
separately from other components andlor steps described herein. For example, the
methods and systems described herein may also be used in combination with other
power generation schemes, and are not limited to practice with only the components
as described herein.
This written description uses examples to disclose the
invention, including the best mode, and also to enable any person skilled in the art to
practice the invention, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the invention is
defined by the claims, and may include other examples that occur to those skilled in
the art. Such other examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal language of the claims, or if
they include equivalent structural elements with insubstantial differences from the
literal language of the claims.
While the invention has been described in terms of various
specific embodiments, those skilled in the art will recognize that the invention can be
practiced with modification within the spirit and scope of the claims.

WE CLAIM
1. A method of activating charcoal resulting from gasification,
said method comprising:
gasifying dried biomass material (108) in a gasification reactor (106)
of an integrated biomass gasification system (100) to produce charcoal (1 16); and
activating the charcoal using heat generated from an integral heat
source of the integrated biomass gasification system.
2. The method in accordance with Claim 1 further comprising
drying the biomass material by at least one of using a dryer (102) and sun-drying the
biomass material.
3. The method in accordance with Claim 1, wherein the integrated
biomass gasification system also includes a combustor (122) and a turbine (124) in
flow communication with the gasification reactor, said method further comprises
contacting the biomass material with at least one of turbine exhaust (142) and
combustor exhaust (146).
4. The method in accordance with Claim 1, wherein activating the
charcoal comprises heating the charcoal to a temperature of from about 400°C to
about 1 100°C.
5. The method in accordance with Claim 4, wherein the integrated
biomass gasification system further includes a hot screw conveyor (1 12) coupled to
the gasification reactor, said method further comprises heating the charcoal with outer
walls (1 10) of the hot screw conveyor.
6. The method in accordance with Claim 4, wherein the integrated
biomass gasification system further includes a combustor (122) in flow
communication with the gasification reactor and a heat exchanger (120) in flow
communication with the combustor, said method further comprises heating the
charcoal with steam generated by the heat exchanger.
7. A method of activating charcoal resulting from gasification,
said method comprising:
gasifying dried biomass material (108) in a gasification reactor (106)
of an integrated biomass gasification system (100) to produce a stream of charcoal
(1 16) and producer gas (1 18);
separating the charcoal from the producer gas of the stream using a hot
screw conveyor (1 12); and
activating the charcoal using heat generated from an integral heat
source of the integrated biomass gasification system.
8. The method in accordance with Claim 7, wherein activating the
charcoal comprises heating the charcoal with the producer gas at a temperature of
about 500°C, wherein activating occurs subsequent to separating the charcoal from
the producer gas.
9. The method in accordance with Claim 7 further comprising
combusting the producer gas using a combustor (122) to generate hot
exhaust gases (142, 146); and
activating the charcoal using heat from the hot exhaust gases.
10. The method in accordance with Claim 7, wherein activating the
charcoal comprises heating the charcoal without the use of an external heat source.