1
FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. GASIFICATION FURNACE, METHOD FOR OPERATING GASIFICATION
FURNACE, AND METHOD FOR BIOMASS GASIFICATION PROCESSING
2.
1. (A) KUBOTA CORPORATION
(B) Japan
(C) 1-2-47, Shikitsuhigashi, Naniwa-ku, Osaka-shi Osaka 5568601 Japan
The following specification particularly describes the invention and the manner in which it
is to be performed.
2
[TECHNICAL FIELD]
[0001] The present invention relates to a gasification furnace, a method for operating a
gasification furnace, and a method for biomass gasification processing with which gas as a
raw material of energy is obtained from biomass.
[BACKGROUND ART]
[0002] Biomass is a renewable biological organic resource other than fossil resources.
The biomass has attracted attention as a renewable energy source, because CO2 emitted due
to combustion of biomass can be considered as CO2 absorbed from the atmosphere through
photosynthesis by living organisms while they are growing, and thus does not count as a
cause of the global warming.
[0003] A technique of converting edible raw materials such as sugar cane and corn into
alcohol, through fermentation and filtration, to be alternative fuel has been established.
Unfortunately, this might result in food shortage or rise in the food price. Thus, recently, a
technique of gasifying non-edible raw materials such as rice straw, chaff, and wood waste in
a gasification furnace through water gas reaction, and converting the gas thus obtained into
liquid fuel through FT synthesis has attracted attention.
[0004] A water gas reaction generally employed for generating carbon monoxide and
hydrogen from biomass and water vapor is an endothermic reaction. To promote the
reaction, a temperature in the gasification furnace needs to be maintained at 500°C to
1200°C.
[0005] Various configurations have been employed to achieve this. Specifically, a
configuration in which water vapor is heated and then fed to the furnace, a configuration in
which a gasification furnace is heated with an external heat source such as an electrical
heater, a configuration of feeding fossil fuels, such as coal, as a heat source into the furnace,
a configuration of supplying oxygen in the furnace so that heat produced by partially
combusting biomass can be used as a heat source, or the other like configuration has been
employed. Still, many problems are yet to be solved for achieving a gasification furnace
with a high energy efficiency.
3
[0006] Patent document 1 discloses a biomass gasification furnace developed to achieve
an object of providing a biomass gasification furnace that can achieve full gasification of
biomass through clean and highly efficient gasification.
[0007] The biomass gasification furnace is an entrained bed gasification furnace
including: a biomass supplying unit that supplies crushed biomass with an average particle
diameter of 0.05 ≤ D ≤ 5mm; and a combustion oxidizing agent supplying unit that supplies
combustion oxidizing agent as a mixture of oxygen and water vapor. In the furnace, an
oxygen [O2]/carbon [C] molar ratio is set to be in a range of 0.1 ≤ O2/C < 1.0, and a water
vapor [H2O]/carbon [C] molar ratio is set to be in a range of 1 ≤ H2O/C, and a temperature
is set to 700 to 1200°C. The furnace includes the combustion oxidizing agent supplying
units provided in a plurality of stages so that the combustion oxidizing agent can be
supplied from a plurality of portions along a gas flow direction, and is operated at a furnace
pressure of 1 to 30 atmospheres. With the furnace pressure of 30 atmospheres, a low
superficial velocity in a tower can be achieved, whereby a compact device can be obtained.
[0008] In one mode of the disclosed gasification furnace, coal as a fossil fuel is supplied
and combusted for forming a high temperature field, so that a combustion aiding portion is
formed in a lower portion of a furnace main body. Biomass is fed to the combustion aiding
portion, whereby efficient thermal decomposition gasification involving no combustion of
the biomass can be achieved.
[0009] Patent document 2, with an object similar to that described above, discloses a
biomass gasification furnace including: a gasification furnace main body in which gas flows
from one side to another side in a vertical direction, a high temperature reaction field is
formed on the one side in the gasification furnace main body, and a gasification reaction
field is formed between the one side and the other side in the main body; a biomass
supplying unit that supplies biomass to the high temperature reaction field in the
gasification furnace main body; a combustion oxidizing agent supplying unit that supplies
oxygen to the high temperature reaction field in the gasification furnace main body; and a
water vapor supplying unit that supplies water vapor into the gasification furnace main
4
body. The water vapor supplying unit is configured to supply water vapor individually to
each of the high temperature reaction field and the gasification reaction field in the
gasification furnace main body. The biomass gasification furnace is operated at furnace
pressure of 1 to 30 atmospheres.
[0010] Patent document 3 discloses a fluidized bed gasification furnace including a
plurality of stages of gas supplying units that supply oxidizing gas, including oxygen to
water vapor, to each of a fluidized bed section and a freeboard section. In the fluidized bed
section, biomass is oxidized to be heated to a temperature of at least 500°C and no greater
than 750°C. A part of the biomass, oxidized in the previous step, is heated to a temperature
of at least 800°C and does not exceed 850°C on the upstream side in the freeboard section;
and a part of the biomass oxidized in the previous step is heated to a temperature of at least
900°C and does not exceed 1000°C on the downstream side in the freeboard section. The
gasification furnace is operated under a furnace pressure of 10 atmospheres to generate
synthesis gas in the manner described above.
PRIOR ART DOCUMENTS
PATENT DOCUMENTS
[0011]
[Patent document 1] Japanese Patent No. 4938920
[Patent document 2] Japanese Patent No. 4388245
[Patent document 3] Japanese Patent No. 5576394
SUMMARY OF INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0012] The technique of the gasification furnace disclosed in Patent document 1 is
described below. Specifically, the combustion oxidizing agent supplying unit is disposed in
an upstream portion of the furnace or a plurality of combustion oxidizing agent supplying
units are provided from the upstream side toward the downstream side. The unit supplies
the combustion oxidizing agent as a mixture of oxygen and water vapor in such a manner as
5
to achieve a ratio H2/CO between hydrogen gas and carbon monoxide gas of 2 or more
required for synthesizing methanol, considering the fact that generally, simple gasification
of biomass would not lead to the ratio H2/CO between hydrogen gas and carbon monoxide
gas exceeding 2. A molar ratio of oxygen [O2]/carbon [C] is adjusted to be in a range of 0.1
≤ O2/C < 1.0, and a molar ratio of water vapor [H2O]/carbon [C] is adjusted to be in a range
of 1 ≤ H2O/C. The water gas reaction is promoted by water vapor supplied by the
combustion oxidizing agent supplying unit. With oxygen also supplied, carbon monoxide
gas obtained by the water gas reaction is partially oxidized, whereby a temperature of 700 to
1200°C suitable for the water gas reaction is maintained.
[0013] The technique is for improving the [H2O]/[CO] ratio with the combustion
oxidizing agent fed into the furnace to partially combust the carbon monoxide gas (CO +
1/2O2 → CO2) for obtaining heat to be used, and with CO2 removed in the subsequent step.
A CO shift reaction device that adjusts a composition of gas including H2 and CO is
separately provided to a subsequent stage of the gasification furnace.
[0014] The gasification furnace disclosed in Patent document 2 also has an object of
achieving the ratio H2/CO between the hydrogen gas and the carbon monoxide gas of 2 or
more, required for synthesizing methanol, as in Patent document 1. With water vapor
individually provided to each of the high temperature reaction field and the gasification
reaction field in the gasification furnace main body, where the water gas reaction and a
water shift reaction respectively take place, a higher hydrogen gas yield rate in the
gasification reaction field can be achieved with temperature drop in the high temperature
reaction field prevented.
[0015] The fuel obtained through FT synthesis with gas obtained by the water gas reaction
is not limited to methanol. Thus, the ratio H2/CO between the hydrogen gas and the carbon
monoxide gas does not necessarily need to be adjusted to be 2 or more. For example, when
an iron-based catalyst is used to synthesize light oil from hydrogen gas and carbon
monoxide gas, the ratio H2/CO between the hydrogen gas and the carbon monoxide gas is
preferably adjusted to 1. It is a matter of course that the synthesizing of light oil is achieved
6
with the ratio H2/CO between the hydrogen gas and the carbon monoxide gas of a different
value, if the catalyst is different. The gasification furnaces disclosed in Patent documents 1
and 2 are difficult to adapt to such a variation.
[0016] Furthermore, when the type and a composition, including a water content, of
biomass as the raw material change, a preferable condition for the water gas reaction
changes and the ratio H2/CO of the hydrogen gas and the carbon monoxide gas generated
changes. Thus, a flexible gasification furnace with which gas with various target ratios
H2/CO can be easily obtained with various raw materials has been called for.
[0017] In each of the gasification furnaces disclosed in Patent documents 1 and 2, oxygen
gas and/or water vapor is supplied from multiple stages. Thus, a flowrate and thus a flow
speed of gas are higher at a portion more on the downstream side. Thus, there has been a
problem that the gasification furnace needs to have a large size to guarantee a sufficient
reaction time. The same applies to the gasification furnace disclosed in Patent document 3.
[0018] The conventional gasification furnaces each operate under pressure, and thus a
sealing property needs to be strictly guaranteed, leading to a problem of a high facility cost.
Furthermore, there has been a problem that the gasification furnaces need to have an even
larger size to operate under atmospheric pressure or negative pressure.
[0019] Although not elaborated in Patent documents 1, 2, and 3, an external heat source
such as a heater or heat obtained by combusting a fossil fuel such as coal are required for
maintaining a high temperature of 700 to 1200°C in the gasification furnace. Thus, there is
further a problem that this heating element, which is not carbon neutral as in the case of
biomass, needs to be taken into consideration for the sake of global warming.
[0020] In view of the above, an object of the present invention is to provide a gasification
furnace, a method for operating a gasification furnace, and a method for biomass
gasification processing with which synthesis gas of a desired ratio can be flexibly obtained
while using less external heat source.
MEANS FOR SOLVING THE PROBLEMS
7
[0021] To achieve the above-described object, a first characteristic configuration of a
gasification furnace according to the present invention is that, as described in claim 1 in the
appended claims, a biomass supplying unit; a water vapor supplying unit; a reaction tower
including: a first region in which biomass supplied from the biomass supplying unit flows in
an entrained bed formed with water vapor supplied from the water vapor supplying unit;
and a second region into which gas generated in the first region flows, the first region and
the second region being formed along a flow direction of the gas; a plurality of oxygen gas
supplying units that supply oxygen gas to each of the first region and the second region in
the reaction tower; and a supply amount adjustment mechanism that adjusts an amount of
the oxygen gas supplied from each of the oxygen gas supplying units are included.
[0022] The entrained bed in which the biomass, supplied from the biomass supplying unit,
flows due to the water vapor supplied from the water vapor supplying unit is formed in the
first region of the reaction tower. The biomass is gasified while flowing in the first region,
and the resultant gas flows to the second region on the downstream side in a gas flow
direction in the reaction tower. The oxygen gas supplying units, provided to the first region
and the second region, supply the oxygen gas so that a part of the biomass or the gas is
combusted. The resultant combustion heat is used for guaranteeing a temperature required
for the gasification reaction in each of the regions. At the same time, the combustion
changes the composition of the gas. The supply amount adjustment mechanism
individually adjusts the amounts of the oxygen gas supplied to the first region and the
second region. Thus, the temperature and the composition of the gas are adjusted for each
of the regions. As a result, the composition of the generated gas can be adjusted in each of
the regions, while using less external heat source.
[0023] A second characteristic configuration of the gasification furnace is that, as
described in claim 2 in the appended claims, in addition to the above-described first
characteristic configuration, in the first region a water gas reaction may mainly take place,
and in the second region a water gas shift reaction may mainly take place, and the supply
amount adjustment mechanism may be configured to adjust a composition of gas flowing
8
out from the reaction tower by adjusting the water gas reaction and the water gas shift
reaction.
[0024] In the first region where the water gas reaction mainly takes place, the biomass
mainly made of carbon is partially combusted by the oxygen gas supplied from the oxygen
gas supplying unit, and thus a temperature rises. With this combustion heat, the water gas
reaction as an endothermic reaction, that is, a reaction for generating the carbon monoxide
gas and the hydrogen gas from carbon and water vapor is promoted. In the second region,
the water gas shift reaction for generating the hydrogen gas from a part of the water vapor
supplied from the water vapor supplying unit that has not been used for the water gas
reaction and the carbon monoxide gas proceeds. Furthermore, a part of the carbon
monoxide gas is combusted by the oxygen gas supplied from the oxygen gas supplying unit.
[0025] When an amount of the oxygen gas supplied to the first region increases, the
reaction of combusting the biomass becomes the major reaction, resulting in a relatively
larger yield amount of the carbon monoxide and a smaller yield amount of the hydrogen
gas. When an amount of the oxygen gas supplied to the second region increases, the water
gas shift reaction is promoted by the heat as a result of combusting the carbon monoxide,
resulting in a relatively larger yield amount of the hydrogen gas and a smaller yield amount
of the carbon monoxide. Thus, the component ratio between the carbon monoxide gas and
the hydrogen gas to be finally generated can be adjusted as desired by adjusting the amounts
of the oxygen gas supplied to the first region and the second region.
[0026] The combustion of the oxygen gas supplied to the second region only results in a
change from carbon monoxide to carbon dioxide, involving no increase in the amount of
gas. Thus, a flowrate of the gas flowing from the first region to the second region does not
largely change. All things considered, a length of the space in the reaction tower where the
gas flows needs not to be increased to guarantee sufficient opportunities for the water gas
shift reaction or a cross-sectional area for the gas flow needs not to be increased to lower
the flowrate of the gas.
9
[0027] A third characteristic configuration of the gasification furnace is that, as described
in claim 3 in the appended claims, in addition to the above-described first or second
characteristic configuration, the supply amount adjustment mechanism may be configured
to adjust the amount of the supplied oxygen gas, by calculating an amount of the oxygen
gas required to be supplied to each of the oxygen gas supplying units based on a
composition and an amount of the biomass supplied.
[0028] The supply amount adjustment mechanism stoichiometrically calculates a level of
the water gas reaction in the first region, a level of the water gas shift reaction in the second
region, and an amount of the oxygen gas required for maintaining the temperature in the
regions suitable for the reactions, based on the composition and the amount of the biomass
supplied to the first region, that is, carbon C, hydrogen H, oxygen O, and water H2O in the
biomass supplied into the reaction tower. The amounts of the oxygen gas to be supplied
from the oxygen gas supplying units are adjusted based on a result of the calculation. Thus,
gas with a desired composition can be highly efficiently obtained while using less external
heat source.
[0029] A fourth characteristic configuration of the gasification furnace is that, as
described in claim 4 in the appended claims, in addition to any one of the above-described
first to third characteristic configurations, the supply amount adjustment mechanism may be
configured to adjust a ratio among amounts of the oxygen gas supplied from the oxygen gas
supplying units based on a composition of the gas flowing out from the reaction tower, with
a total amount of the supplied oxygen gas fixed.
[0030] In the configuration described above, the supply amount adjustment mechanism
adjusts the ratio among amounts of the oxygen gas supplied from the oxygen gas supplying
units based on the composition of the gas flowing out from the reaction tower, with the total
amount of the supplied oxygen gas fixed. Thus, a flexible configuration in which synthesis
gas of a desired composition can be accurately obtained with biomass of various
compositions can be achieved.
10
[0031] A fifth characteristic configuration of the gasification furnace is that, as described
in claim 5 in the appended claims, in addition to any one of the above-described first to
third characteristic configurations, the supply amount adjustment mechanism may be further
configured to adjust an amount of the water vapor supplied from the water vapor supplying
unit.
[0032] In the configuration described above, the supply amount adjustment mechanism
adjusts the amount of the water vapor supplied from the water vapor supplying unit in
accordance with the amounts of the oxygen gas supplied from the oxygen gas supplying
units. Thus, the levels of the water gas reaction and the water gas shift reaction can be
adjusted so that synthesis gas of a desired composition can be easily obtained.
[0033] A sixth characteristic configuration of the gasification furnace is that, as described
in claim 6 in the appended claims, a biomass supplying unit; a water vapor supplying unit; a
reaction tower including: a first region in which biomass supplied from the biomass
supplying unit flows in an entrained bed formed with water vapor supplied from the water
vapor supplying unit; and a second region into which gas generated in the first region flows,
the first region and the second region being formed along a flow direction of the gas; a
plurality of oxygen gas supplying units that supply oxygen gas to each of the first region
and the second region in the reaction tower; a communication portion through which the
generated gas and the biomass or a residue of the biomass are movable between the first
region and the second region; and a discharge port through which the generated gas and the
residue are discharged from the second region are included.
[0034] The entrained bed in which the biomass, supplied from the biomass supplying unit,
flows due to the water vapor supplied from the water vapor supplying unit is formed in the
first region of the reaction tower. The biomass is gasified while flowing in the first region,
and the resultant gas flows to the second region on the downstream side in a gas flow
direction in the reaction tower through the communication portion. The oxygen gas
supplying units, provided to the first region and the second region, supply the oxygen gas so
that a part of the biomass or the gas is combusted. The resultant combustion heat is used for
11
guaranteeing a temperature required for the gasification reaction in each of the regions. At
the same time, the combustion changes the composition of the gas. The supply amount
adjustment mechanism individually adjusts the amounts of the oxygen gas supplied to the
first region and the second region. Thus, the temperature and the composition of the gas are
adjusted for each of the regions. As a result, use of an external heat source can be reduced,
and the composition of the generated gas can be adjusted in each of the regions. The
biomass supplied to the reaction tower is gasified to be light-weight ash, and then is
discharged through the discharge port together with the gas.
[0035] In the first region where the water gas reaction mainly takes place, the biomass
mainly made of carbon is partially combusted by the oxygen gas supplied from the oxygen
gas supplying unit, and thus a temperature rises. With this combustion heat, the water gas
reaction as an endothermic reaction, that is, a reaction for generating the carbon monoxide
gas and the hydrogen gas from carbon and water vapor is promoted. In the second region,
the water gas shift reaction for generating the hydrogen gas from a part of the water vapor
supplied from the water vapor supplying unit that has not been used for the water gas
reaction and the carbon monoxide gas proceeds. Furthermore, a part of the carbon
monoxide gas is combusted by the oxygen gas supplied from the oxygen gas supplying unit.
As described above, the first region in which the water gas reaction mainly takes place and
the second region in which the water gas shift reaction mainly takes place are formed along
the gas flow in the reaction tower. The light-weight ash as a result of the gasification is
discharged from the second region together with the gas. With this configuration, a
compact gasification furnace can be achieved.
[0036] A seventh characteristic configuration of the gasification furnace is that, as
described in claim 7 in the appended claims, in addition to any one of the above-described
first to sixth characteristic configurations, the water vapor supplying unit may be disposed
more on an upstream side than the biomass supplying unit.
[0037] In the configuration described above, the biomass fed to the reaction tower is
prevented from falling down to a bottom portion due to an upward flow of the water vapor
12
supplied from the water vapor supplying unit, whereby the entrained bed of the biomass can
be effectively formed.
[0038] An eighth characteristic configuration of the gasification furnace is that, as
described in claim 8 in the appended claims, in addition to any one of the above-described
first to seventh characteristic configurations, an oxygen gas supplying unit among the
oxygen gas supplying units that corresponds to the first region may be disposed more on an
upstream side than at least the biomass supplying unit.
[0039] The water gas reaction between the biomass and the water vapor that mainly takes
place in the first region is an endothermic reaction. Thus, the water gas reaction is
suppressed when the temperature drops as a result of the reaction. In view of this, the
oxygen gas supplying unit corresponding to the first region is disposed at least on the
upstream side than the biomass supplying unit so that the biomass and the oxygen gas can
have a higher chance of being in contact with each other, whereby the combustion reaction
is promoted. All things considered, the combustion reaction can be used as the heat source
in the reaction tower, whereby the use of the external heat source can be effectively
reduced.
[0040] A ninth characteristic configuration of the gasification furnace is that, as described
in claim 9 in the appended claims, in addition to the above-described eighth characteristic
configuration, another oxygen gas supplying unit among the oxygen gas supplying units
that corresponds to the first region may be disposed more on a downstream side than the
biomass supplying unit.
[0041] Carbon monoxide generated by the water gas reaction is combusted by the oxygen
gas supplied from the downstream side of the biomass supplying unit. Thus, the water gas
reaction is further promoted, with the temperature drop on the downstream side of the
biomass supplying unit prevented. As a result, the generated gas with a sufficient
temperature can flow down to the second region.
[0042] A tenth characteristic configuration of the gasification furnace is that, as described
in claim 10 in the appended claims, in addition to any one of the above-described seventh to
13
ninth characteristic configurations, the water vapor supplying unit may be disposed more on
the upstream side than any one of the oxygen gas supplying units.
[0043] In the configuration described above, the oxygen gas is supplied to the biomass for
which the entrained bed is formed. Thus, the biomass and the water vapor or the oxygen
gas can have a higher chance of being in contact with each other, whereby an attempt to
increase the total amount of H2 and CO can be facilitated.
[0044] An eleventh characteristic configuration of the gasification furnace is that, as
described in claim 11 in the appended claims, in addition to any one of the above-described
first to tenth characteristic configurations, a gas flowrate adjustment portion may be further
included with which a gas flowrate in the second region becomes lower than a gas flowrate
in the first region.
[0045] In the configuration described above, the gas flowrate in the second region is lower
than the gas flowrate in the first region. Thus, the unreacted biomass that has failed to be
gasified in the first region having a large specific gravity may reach the second region but
cannot stay in the second region, and thus returns to the first region. The biomass that has
returned to the first region can have another chance of undergoing the water gas reaction or
the combustion reaction, and thus stays in the first region until to turn into ash with a small
specific gravity. Furthermore, a time required for the water gas shift reaction in the second
region can be guaranteed, so that the reaction tower can have a short length in the gas flow
direction. As a result, the water gas reaction with a high conversion rate of the biomass can
be achieved. The residue with a small specific gravity cannot stay in the first region with a
higher gas flowrate than the second region, and thus moves to the second region to be
discharged through the discharge port.
[0046] A twelfth characteristic configuration of the gasification furnace is that, as
described in claim 12 in the appended claims, in addition to the above-described eleventh
characteristic configuration, the gas flowrate adjustment portion may be implemented with a
shape of the reaction tower in which the second region has an average area of a crosssection
orthogonal to an inner gas flow that is larger than the average area in the first region.
14
[0047] A thirteenth characteristic configuration of the gasification furnace is that, as
described in claim 13 in the appended claims, in addition to the above-described eleventh or
twelfth characteristic configuration, the gas flowrate in the first region may be set to achieve
a flowrate with which the biomass floats, and the gas flowrate in the second region is set to
achieve a flowrate with which the biomass falls down to the first region.
[0048] In the configuration described above, the water gas reaction is promoted with the
entrained bed of the biomass formed in the first region. Unreacted biomass due to
insufficient water gas reaction might reach the second region but is unable to stay in the
second region and thus falls down to the first region, and thus can have another chance of
undergoing the water gas reaction or the combustion reaction. The biomass that has turned
into ash blows up to the second region together with the gas to be discharged through the
discharge port. Thus, the biomass can be gasified at high conversion rate in the first region.
[0049] A fourteenth characteristic configuration of the gasification furnace is that, as
described in claim 14 in the appended claims, in addition to the above-described sixth
characteristic configuration, a supply amount adjustment mechanism may be further
included that adjusts an amount of the oxygen gas supplied from each of the oxygen gas
supplying units, based on a composition of gas flowing out from the reaction tower.
[0050] The supply amount adjustment mechanism stoichiometrically calculates a level of
the water gas reaction in the first region, a level of the water gas shift reaction in the second
region, and an amount of the oxygen gas required for maintaining the temperature in the
regions suitable for the reactions, based on the composition and the amount of the biomass
supplied to the first region, that is, carbon C, hydrogen H, oxygen O, and water H2O in the
biomass supplied into the reaction tower. The amounts of the oxygen gas to be supplied
from the oxygen gas supplying units are adjusted based on a result of the calculation. Thus,
gas with a desired composition can be highly efficiently obtained while using less external
heat source.
[0051] A fifteenth characteristic configuration of the gasification furnace is that, as
described in claim 15 in the appended claims, in addition to the above-described sixth or
15
fourteenth characteristic configuration, a supply amount adjustment mechanism may be
further included that adjusts a ratio among amounts of the oxygen gas supplied from the
oxygen gas supplying units based on the composition of the gas flowing out from the
reaction tower, with a total amount of the supplied oxygen gas fixed.
[0052] In the configuration described above, the supply amount adjustment mechanism
adjusts the ratio among amounts of the oxygen gas supplied from the oxygen gas supplying
units based on the composition of the gas flowing out from the reaction tower, with a total
amount of the supplied oxygen gas fixed. Thus, a flexible configuration in which synthesis
gas of a desired composition can be accurately obtained with biomass of various
compositions can be achieved.
[0053] A first characteristic configuration of a method for operating a gasification furnace
according to the present invention is, as described in claim 16 in the appended claims, a
method for operating the gasification furnace including any one of the above-described first,
second, sixth, fourteenth, and fifteenth characteristic configurations including: measuring a
composition of the gas flowing out from the reaction tower; and adjusting amounts of the
oxygen gas supplied to the first region and the second region from the oxygen gas supplying
units in such a manner that the measured composition of the gas is obtained as a target gas
composition.
[0054] A second characteristic configuration of the method for operating a gasification
furnace is, as described in claim 17 in the appended claims, in addition to the abovedescribed
first characteristic configuration, a method for operating the gasification furnace
including any one of the above-described first, second, sixth, fourteenth, and fifteenth
characteristic configurations may further include: adjusting a ratio among amounts of the
oxygen gas supplied to the first region and the second region while maintaining a total
amount of the oxygen gas supplied from the oxygen gas supplying units, in such a manner
that the measured composition of the gas is obtained as the target gas composition.
[0055] A first characteristic configuration of a method for biomass gasification processing
according to the present invention is that, as described in claim 18 in the appended claims, a
16
water gas reaction promoting step in which an entrained bed is formed with water vapor
supplied to biomass in an upstream side in a reaction tower to mainly promote a water gas
reaction; a water gas shift reaction promoting step in which a water gas shift reaction is
mainly promoted involving water gas generated in the water gas reaction promoting step, in
a downstream side in the reaction tower; and an oxygen gas supplying step in which oxygen
gas is supplied for each of the water gas reaction promoting step and the water gas shift
reaction promoting step, and a ratio of amounts of the oxygen gas supplied to the respective
steps is adjusted to adjust a composition of gas flowing out from the reaction tower are
included.
[0056] A second characteristic configuration of the method for biomass gasification
processing is that, as described in claim 19 in the appended claims, in addition to the abovedescribed
first characteristic configuration, the oxygen gas supplying step may include
adjusting the composition of the gas flowing out from the reaction tower by adjusting the
ratio between the amounts of the supplied oxygen gas while maintaining a total amount of
the oxygen gas supplied for each of the water gas reaction promoting step and the water gas
shift reaction promoting step.
EFFECTS OF INVENTION
[0057] As described above, the present invention can provide a gasification furnace, a
method for operating a gasification furnace, and a method for biomass gasification
processing with which synthesis gas of a desired ratio can be flexibly obtained while using
less external heat source.
BRIEF DESCRIPTION OF DRAWINGS
[0058]
[Fig. 1] Fig. 1 is a partially cutout view of a gasification furnace according to the present
invention.
17
[Fig. 2] Fig. 2(a) is a diagram illustrating a main part of the gasification furnace
according to the present invention, and Fig. 2(b) is a cross-sectional view taken along a line
A-A in Fig. 2(a).
[Fig. 3] Fig. 3 is a diagram illustrating a supply amount control mechanism.
[Fig. 4] Figs. 4(a), 4(b), and 4(c) are each a diagram illustrating a biomass gasification
reaction, and Fig. 4(d) is a table illustrating experiment results.
[Fig. 5] Figs. 5(a), 5(b), 5(c), and 5(d) are each a diagram illustrating a main part of a
gasification furnace according to an alternative embodiment of the present invention.
[Fig. 6] Fig. 6 is a diagram illustrating a liquid fuel generation system that uses biomass
and includes the gasification furnace according to the present invention.
[Fig. 7] Fig. 7 is a diagram illustrating an energy generation system including the
gasification furnace according to the present invention.
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0059] An embodiment of a gasification furnace, a method for operating a gasification
furnace, and a method for biomass gasification processing according to the present
invention is described below.
A gasification furnace 10 according to the present invention illustrated in Fig. 6 can be
incorporated in a liquid fuel generation system 100 that generates liquid fuel from synthesis
gas generated by using biomass as a raw material. The synthesis gas generated by the
gasification furnace 10 can be used for power generation and for other heat sources.
[0060] The liquid fuel generation system 100 includes: the gasification furnace 10 that
generates the synthesis gas as a raw material of the liquid fuel from biomass; and an FT
synthesis device 104 that synthesizes fuel from synthesis gas. The synthesis gas in this
process has been refined by passing through a gas refining device 204 including a cyclone, a
scrubber, and an activated carbon adsorption tower for removing solids such as ash as well
as hydrogen sulfide gas, hydrogen chloride gas, ammonia, and the like from the synthesis
gas generated as described above.
18
[0061] The gasification furnace 10 includes a reaction tower that generates synthesis gas
(H2, CO) from the biomass through reduction heating with water vapor or superheated water
vapor, under a high furnace temperature that is equal to or higher than 500°C and equal to
or lower than 1000°C. The synthesis gas thus obtained with the reaction tower is refined by
the gas refining device 204 on the subsequent stage to have impurities removed. Then, the
synthesis gas is heated and pressurized to be at a high temperature and high pressure, and
then is fed to the FT synthesis device 104.
[0062] The term FT synthesis is short for Fischer-Tropsch synthesis, and is a series of
synthesis reaction processing for synthesizing liquid hydrocarbon from carbon monoxide
and hydrogen, through a catalytic reaction. The synthesis gas fed to the FT synthesis device
104 is fed to a solvent, in which a catalyst is dispersed, and thus is synthesized to be desired
hydrocarbon. For example, a ratio H2/CO between hydrogen and carbon monoxide may
preferably be approximately 2 for synthesizing methanol. The ratio H2/CO between
hydrogen and carbon monoxide is preferably approximately 1 when light oil is synthesized
in the present embodiment. The result of the synthesis varies depending on the type and the
property of the catalyst.
[0063] Thus, the ratio H2/CO between hydrogen and carbon monoxide is preferably
adjusted to efficiently obtain desired hydrocarbon through the FT synthesis. Even when the
type of hydrocarbon to be obtained is the same, the ratio might vary depending on the type
of the catalyst used in the FT synthesis.
[0064] Thus, the gasification furnace 10 has been demanded to be highly versatile so that
synthesis gas of various ratios of H2/CO can be obtained, and has been demanded to achieve
a high synthesis gas yield rate while having a compact size.
[0065] Fig. 1 illustrates one example of the gasification furnace 10 according to the
present invention.
The gasification furnace 10 includes: a reaction tower 4 that is supported by a frame,
made of corrosion resistance metal, and has a vertical cylindrical shape; a biomass
supplying unit 2 that supplies biomass to the reaction tower 4; a water vapor supplying unit
19
3 that supplies water vapor for causing water gas reaction to the reaction tower 4; and
oxygen gas supplying units 5 (5a, 5b, and 5c) that heat the reaction tower 4 to a desired
temperature and adjust the ratio H2/CO between hydrogen and carbon monoxide in the
synthesis gas.
[0066] For example, the water gas reaction and the water gas shift reaction between water
vapor and biomass, heated to approximately 500°C by high-frequency heating under normal
pressure, occur in the reaction tower 4. The resultant gas is discharged through a discharge
port 40 in an upper portion of the reaction tower 4, and is guided to the gas refining device
204 described above (see Fig. 6) through a discharge pipe 42. The water gas reaction
mainly takes place in a lower portion of the reaction tower 4, and the water gas shift
reaction mainly occurs in a process of rising in the reaction tower 4. The gas refining
device 204 (see Fig. 6) is provided with an induced draft fan. Thus, negative internal
pressure of the reaction tower 4 is maintained, and the gas generated in the reaction tower 4
is inducted to the gas refining device 204 (see Fig. 6) to be refined.
[0067] The biomass supplying unit 2 includes a screw conveyer including: a cylindrical
casing 20 having one end in flange connection with a lower portion of the reaction tower 4;
and a screw blade 21 contained in the cylindrical casing 20. The cylindrical casing 20
(hereinafter, simply referred to as "casing") has the other end provided with a feed port 22
for the biomass. A conveyance path 70 in a substantially vertical posture is connected to
the feed port 22. A hopper 7 including a fixed quantity supply mechanism 71 is provided to
an upper end of the conveyance path 70.
[0068] Dry biomass such as rice straw, chaff, wheat straw, and forage of corn is
preferably used as the biomass as the raw material. Such dry biomass is crushed to several
millimeters, filled in the hopper 7, and is conveyed to the feed port 22 through the
conveyance path 70. The biomass fed to the feed port 22 is compressed and conveyed and
consolidated by the screw blade 21 to be fed to the reaction tower 4. Thus, the inside of the
reaction tower 4 is sealed from outside air by the biomass filled and compressed in the
casing 20.
20
[0069] A first oxygen gas supplying unit 5 (5a) is provided below the biomass supplying
unit 2, and the water vapor supplying unit 3 is provided below the first oxygen gas
supplying unit 5 (5a). A plurality of oxygen gas supplying units 5 (5b and 5c) are provided
at different positions in a vertical direction above the biomass supplying unit 2.
[0070] The reaction tower 4 is provided with heat insulating walls W that surround the
reaction tower 4 for maintaining the temperature inside the tower. A plurality of heaters H
are embedded on the inner sides of the heat insulating walls W, on the lower side in the
reaction tower 4 in particular, for maintaining the reaction tower 4 at a desired temperature
(see Fig. 2(b)).
[0071] As illustrated in Fig. 2(a), an entrained bed (a self-fluidized bed) 8 flowing in the
reaction tower 4 is formed with biomass B supplied into the reaction tower 4 from the
biomass supplying unit 2 and water vapor injected from a nozzle 30 provided at a distal end
portion of the water vapor supplying unit 3.
[0072] The injection is performed from openings 30a of the nozzle 30 toward a bottom
portion 41 of the reaction tower 4, whereby the biomass that has fell on or currently falling
onto the bottom portion 41 is blown upward. A lower region in the reaction tower 4 in
which the entrained bed 8 is formed is a first region R1 where the water gas reaction mainly
takes place. A second region R2 (see Fig. 1) where the water gas shift reaction mainly takes
place is formed above the first region.
[0073] The water gas reaction is endothermic reaction, in a high temperature environment
of 500°C or higher, for generating carbon monoxide CO and hydrogen H2 from solid-state
carbon C as the biomass and water vapor H2O, as in the following formula:
C + H2O → CO + H2.
[0074] The water gas shift reaction is exothermic reaction, in a high temperature
environment of 800°C or higher, for generating carbon dioxide CO2 and hydrogen H2 from
carbon monoxide CO and water vapor H2O, as in the following formula:
CO + H2O → CO2 + H2.
21
[0075] A heat source is required for promoting the water gas reaction as the endothermic
reaction in the high temperature environment of 500°C or higher. Thus, the heater H and
the oxygen gas supplying unit 5 (5a) are provided as described above.
[0076] As illustrated in Fig. 2(b), the heater H is activated in a state where the reaction
tower 4 is surrounded by the heat insulating walls W, and thus the inside of the reaction
tower 4 is heated to 500°C or higher.
[0077] Referring back to Fig. 2(a), in the next process, the biomass B flowing in the first
region R1 is partially combusted by oxygen gas supplied from the first oxygen gas
supplying unit 5 (5a) to be carbon dioxide. With such exothermic reaction, the high
environmental temperature is maintained. Black particles in Fig. 2(a) represent the
combusted biomass. All things considered, the temperature is maintained by the external
heating by the heater H and the internal heating caused by partially combusting the biomass
B.
C + O2 → CO2
C + 1/2·O2 → CO
[0078] A second oxygen gas supplying unit 5 (5b) is also provided above the biomass
supplying unit 2 in the first region R1. The high environmental temperature is maintained
also with the biomass partially combusting due to oxygen supplied from the second oxygen
gas supplying unit 5 (5b). It is a matter of course that the amounts of the oxygen gas
supplied from these oxygen gas supplying units 5 are only enough for achieving stable
water gas reaction, and thus are not set to an amount that would almost completely combust
the biomass.
[0079] The biomass B supplied from the biomass supplying unit 2 is supplied to the
reaction tower 4 without being heated, and falls down in the reaction tower 4. Thus, a
portion around the lowest portion of the entrained bed has the lowest temperature. Thus, it
is important to provide the first oxygen gas supplying unit 5 (5a) around such a portion.
Furthermore, the position of the second oxygen gas supplying unit 5 (5b) is also important
to maintain sufficient environmental temperature above the biomass supplying unit 2 in the
22
first region. This is because the heater H is basically used as a startup heat source, and the
environmental temperature is maintained thereafter with the combustion reaction between
the oxygen gas and the biomass B.
[0080] The water vapor supplying unit 3 is disposed more on the upstream side than
(below in Fig. 2) the biomass supplying unit 2 in a gas flow direction. The oxygen gas
supplying unit 5a as one of the oxygen gas supplying units 5 that corresponds to the first
region R1 is at least disposed more on the upstream side than the biomass supplying unit 2.
[0081] Furthermore, the oxygen gas supplying unit 5b as another one of the oxygen gas
supplying units 5 that corresponds to the first region R1 is disposed on the downstream side
of the biomass supplying unit 2, and the water vapor supplying unit 3 is disposed more on
the upstream side than all of the oxygen gas supplying units 5.
[0082] The synthesis gas and char or ash generated from the biomass in the first region R1
rise to the second region R2 on the downstream side of the first region R1 in the gas flow
direction, whereby the water gas shift reaction is promoted. A third oxygen gas supplying
unit 5(5c) is disposed to have a distal end, facing downward, connected to an inlet portion
of the second region R2. The carbon monoxide, generated by the water gas reaction,
partially combusts due to the oxygen gas supplied from the third oxygen gas supplying unit
5 (5c).
CO + 1/2·O2 → CO2
[0083] The water gas shift reaction that mainly takes place in the second region is an
exothermic reaction. Thus, the oxygen gas supplied from the third oxygen gas supplying
unit 5 (5c) is more significant for adjusting the ratio between the carbon monoxide and the
hydrogen generated by the water gas reaction, and is less significant for maintaining the
environmental temperature. This is because a larger amount of combusted carbon
monoxide leads more hydrogen gas in the ratio H2/CO between hydrogen and carbon
monoxide.
[0084] The water vapor supplying unit 3 supplies water vapor required for the water gas
shift reaction. The water vapor that has not contributed to the water gas reaction in the first
23
region is consumed. The carbon monoxide is combusted by the oxygen gas supplied from
the third oxygen gas supplying unit 5 (5c) to turn into carbon dioxide, and thus the flowrate
of the gas rising in the reaction tower 4 does not largely change.
[0085] The gas and the biomass or char and ash generated in the first region can move
between the first region R1 and the second region R2 through a communication portion 43.
[0086] As described above, the water vapor supplying unit 3 supplies the water vapor
required for the water gas reaction and for the water gas shift reaction. The flowrate of the
water vapor is adjusted in such a manner that the entrained bed of the biomass is formed in
the first region.
[0087] More specifically, a gas flowrate adjustment portion c for achieving a lower gas
flowrate in the second region R2 compared with that in the first region R1 is formed in the
communication portion 43. The gas flowrate adjustment portion c is implemented with the
reaction tower 4 shaped in such a manner that the second region R2 has a larger inner
diameter, that is, a larger average area of an inner cross-section orthogonal to the inner gas
flow (an area of a plane of the reaction tower orthogonal to the sheet surface in Fig. 1),
compared with the first region R1.
[0088] The inner diameter increases smoothly without reducing so that the flow of the gas
from the first region R1 to the second region R2 is not disturbed, and a shape with a sharp
angle is employed so that the biomass and residues can be prevented from depositing on the
increased diameter portion.
[0089] The gas generated in the first region R1 rises with a slower speed upon reaching
the second region, due to the diameter increasing shape of the reaction tower 4. In this
process, unreacted biomass, rising together with the gas, falls to the first region with its own
weight. As a result, most of the unreacted biomass is used as the raw material for the water
gas reaction in the first region R1 or is combusted by the oxygen gas to be ash. The residue
of the biomass that has turned into ash to have a smaller specific gravity is blown up in the
entrained bed generated with the water vapor from the water vapor supplying unit 3, and
thus rises to the second region R2 together with the gas to be discharged through the
24
discharge port 40 together with the gas. Thus, no dedicated residue discharging portion for
taking out the residues needs to be provided in addition to the discharge port 40.
[0090] The flowrate of the gas flowing in the second region R2 is sufficiently low due to
the gas flowrate adjustment portion c as described above, whereby sufficient time can be
guaranteed for the water gas shift reaction. Thus, the second region R2 needs not to be
long, whereby the reaction tower 4 with a compact configuration can be achieved.
[0091] As described above, the reaction tower 4 includes the first region R1 where the
water gas reaction mainly takes place and the second region R2 where the water gas shift
reaction mainly takes place, arranged along the gas flow direction, and the ash with a light
weight is discharged from the second region. Thus, a compact gasification furnace can be
achieved with the first region R1 and the second region R2 integrally formed instead of
being separate devices.
[0092] As illustrated in Fig. 3, a process control unit 60 is further provided that manages
and controls biomass gasification processing in the gasification furnace 10 described above.
The process control unit 60 includes a general-purpose computer, a control program
installed in the general-purpose computer, and an expansion board. The expansion board is
provided with an input circuit and an output circuit. The input circuit receives detection
signals from a first temperature sensor S3 provided to the first region R1 and a second
temperature sensor S4 provided to the second region R2, as well as a hydrogen gas sensor
S1 and a carbon monoxide gas sensor S2 provided to the discharge pipe 42. The output
circuit outputs a driving signal to a motor that controls the rotation of the screw blade 21 of
the biomass supplying unit 2, and outputs opening adjustment signals to a control valve V1
for adjusting a flowrate of the water vapor supplied to the water vapor supplying unit 3 from
a water vapor supply source and to control valves Va, Vb, and Vc for adjusting the amount
of oxygen gas supplied to the oxygen gas supplying units 5 (5a, 5b, and 5c) from an oxygen
gas source.
[0093] A supply amount adjustment mechanism 50 that individually adjusts and controls
the amount of the oxygen gas supplied from each of the oxygen gas supplying units 5 (5a,
25
5b, and 5c) is embedded in the process control unit 60. The supply amount adjustment
mechanism 50 is configured to adjust the amount of the oxygen gas supplied from the
oxygen gas supplying units 5 to each of the first region R1 and the second region R2 so that
a target gas composition is achieved, that is, a desired ratio H2/CO between hydrogen and
carbon monoxide is achieved. The adjustment is based on the detection signals from the
hydrogen gas sensor S1 and the carbon monoxide gas sensor S2 that measure the
composition of the gas flowing out from the reaction tower 4.
[0094] As illustrated in Fig. 4(a), the oxygen gas supplied from the first oxygen gas
supplying unit 5a provided to the first region R1 is mainly consumed for combusting the
biomass, which is solid-state carbon, for compensating for temperature drop due to the
water gas reaction. The resultant combustion temperature leads to a rise in the
environmental temperature, whereby the water gas reaction is promoted. The combustion
of the solid-state carbon leads to the generation of and rise in the concentration of carbon
monoxide CO and carbon dioxide CO2, resulting in a relatively lower ratio H2/CO between
hydrogen and carbon monoxide. This effect is more pronounced when a larger amount of
oxygen is supplied from the first oxygen gas supplying unit 5a.
[0095] The oxygen gas supplied from the second oxygen gas supplying unit 5b, provided
on the downstream side of the first region R1, is for compensating for the temperature drop
due to the water gas reaction occurred on the upstream side. This gas works under the
mechanism that is the same as that of the oxygen gas supplied from the first oxygen gas
supplying unit 5a, and also somewhat promotes the water gas shift reaction between the
carbon monoxide that has been generated by the water gas reaction and the water vapor.
All things considered, a balance between the combustion of the solid-state carbon and the
water gas shift reaction is adjusted with the amount of oxygen gas supplied from the second
oxygen gas supplying unit 5b.
[0096] As illustrated in Fig. 4(b), the oxygen gas supplied from the third oxygen gas
supplying unit 5c provided to the second region R2 is mainly consumed for combusting the
carbon monoxide CO generated by the water gas reaction in the first region R1 or the
26
carbon monoxide CO generated by the combustion reaction, and for the water gas shift
reaction. As a result, the environmental temperature rises, whereby the water gas shift
reaction is promoted. As a result, the concentration of the hydrogen gas H2 rises, whereby a
relatively high ratio H2/CO between hydrogen and carbon monoxide is achieved. This
effect is more pronounced when a larger amount of oxygen is supplied.
[0097] As illustrated in Fig. 4(c), the amount of oxygen gas supplied from the three of the
oxygen gas supplying units 5 (5a, 5b, and 5c) is adjusted so that the ratio H2/CO between
hydrogen and carbon monoxide can be adjusted to a desired ratio.
[0098] An area of each circle surrounding a gas composition as illustrated in Figs. 4(a),
4(b), and 4(c) represents a schematic ratio of the corresponding generated gas.
[0099] Fig. 4(d) illustrates types and amount of gas generated as a result of operating the
gasification furnace 10 with the amounts of the oxygen gas supplied from the three of the
oxygen gas supplying units 5 (5a, 5b, and 5c) adjusted to various amounts.
[0100] Run 1 indicates a result of supplying the oxygen gas at an equal ratio among the
gas supplying units, with the total amount of oxygen gas supplied to the gasification furnace
10 fixed. Run 2 indicates a result of supplying a relatively large amount of oxygen gas to
the third gas supplying unit 5c with the total amount of oxygen gas supplied fixed. Run 3
indicates a result of supplying a relatively large amount of oxygen gas to the second gas
supplying unit 5b with the total amount of oxygen gas supplied fixed. Run 4 indicates a
result of supplying a relatively large amount of oxygen gas to the first gas supplying unit 5a
with the total amount of oxygen gas supplied fixed.
[0101] A description on the ratio H2/CO between hydrogen and carbon monoxide is given
below. In Run 2 in which the relatively large amount of oxygen gas is supplied to the third
gas supplying unit 5c, the ratio H2/CO is larger than that in Run 1 in which the oxygen gas
is equally supplied. In Run 4 in which the relatively large amount of oxygen gas is supplied
to the first gas supplying unit 5a, the ratio H2/CO is smaller than that in Run 1 in which the
oxygen gas is equally supplied. In Run 3 in which the relatively large amount of oxygen
27
gas is supplied to the second gas supplying unit 5b, the ratio H2/CO is smaller than that in
Run 1 in which the oxygen gas is equally supplied, as in Run 4.
[0102] Thus, the supply amount adjustment mechanism 50 is configured to adjust the ratio
between the amounts of oxygen gas supplied to the first region and the second region while
maintaining the total amount of the oxygen gas supplied from the oxygen gas supplying unit
5 at a constant amount, in such a manner that a target gas composition is obtained as a
measured gas composition.
[0103] More specifically, hydrogen can be relatively increased by increasing the amount
of oxygen gas supplied to the second region R2. Furthermore, carbon monoxide can be
relatively increased by increasing the amount of oxygen gas supplied to the first region R1,
more specifically to the upstream side of the first region R1.
[0104] For example, a heat input required for maintaining the environmental temperature
required for promoting the water gas reaction and the water gas shift reaction in the reaction
tower 4 is calculated based on the composition of the biomass and a water content. The
total amount of oxygen gas is determined in such a manner that the heat input can be
achieved with the heat as a result of combusting biomass and/or carbon monoxide in each of
the regions R1 and R2. Then, the ratio of the supplied amounts to the first region and the
second region is adjusted while maintaining the total amount thus determined.
[0105] The supply amount adjustment mechanism 50 in the gasification furnace 10
according to the present invention is not limited to the control mode described above. The
amount of oxygen gas supplied from the oxygen gas supplying units 5 (5a, 5b, and 5c) may
be adjusted to achieve a predetermined environmental temperature in the first region R1
and/or the second region R2 detected by the first temperature sensor S3 and the second
temperature sensor S4. This configuration also requires the amount of oxygen gas supplied
from the oxygen gas supplying units 5 (5a, 5b, and 5c) to be adjusted to achieve the target
gas compositions measured by the hydrogen gas sensor S1 and the carbon monoxide gas
sensor S2.
28
[0106] The number of temperature sensors and gas sensors may be increased so that the
amount of oxygen gas, temperature, and the ratio between hydrogen and carbon monoxide
can be more accurately adjusted.
[0107] The process control unit 60 is configured to perform adjustment to increase and
reduce the amount of biomass supplied from the biomass supplying unit 2 and/or the
amount of water vapor supplied from the water vapor supplying unit 3, when the supply
amount adjustment mechanism 50 fails to perform control for achieving the target gas
composition, or when the amount of gas decreases after the target gas composition is
achieved.
[0108] The supply amount adjustment mechanism 50 is configured to adjust the amount
of the oxygen gas required to be supplied and a ratio among the supplied amounts, based on
the change in the supplied amount of biomass and/or the supplied amount of water vapor.
[0109] As described above, with the gasification furnace 10 according to the present
invention, a method for biomass gasification processing is performed that includes: a water
gas reaction promoting step in which an entrained bed is formed with water vapor supplied
to biomass in an upstream side in a reaction tower to mainly promote a water gas reaction; a
water gas shift reaction promoting step in which a water gas shift reaction is mainly
promoted involving gas generated in the water gas reaction promoting step, in a
downstream side in the reaction tower; and an oxygen gas supplying step in which oxygen
gas is supplied for each of the water gas reaction promoting step and the water gas shift
reaction promoting step, with a ratio of amounts of the oxygen gas supplied for the
respective steps adjusted to adjust a composition of gas flowing out from the reaction tower.
[0110] The oxygen gas supplying step includes a step of adjusting the composition of the
gas flowing out from the reaction tower by adjusting a ratio between the amounts of the
supplied oxygen gas while maintaining a total amount of oxygen gas supplied for the water
gas reaction promoting step and for the water gas shift reaction promoting step.
[0111] With the gasification furnace according to the present invention, the amounts of
oxygen gas supplied from the oxygen gas supplying units 5 (5a, 5b, and 5c) are adjusted so
29
that synthesis gas with a ratio H2/CO between hydrogen and carbon monoxide being
approximately 2, and synthesis gas with a ratio H2/CO between hydrogen and carbon
monoxide being approximately 1 can be obtained.
[0112] Other embodiments of the gasification furnace according to the present invention
are described below.
In the exemplary configuration according to the embodiment described above, the
reaction tower 4 has the vertical cylindrical shape. An elliptical cylindrical shape or a
polygonal cylindrical shape may be employed as long as the reaction tower 4 has a vertical
form.
[0113] In the embodiment described above, a tapered portion in which an inner diameter
gradually increases from the first region R1 toward the second region R2 is formed in the
diameter increasing portion as the gas flowrate adjustment portion c formed in the
communication portion 43. The tapered portion is preferably formed to have a sharp angle.
This is because a sudden increase in the diameter might lead to ash and the like accumulated
in a step portion due to a separated flow, to hinder the reduction of the gas flowrate.
[0114] The embodiment described above can be applied to a fluidized bed gasification
furnace instead of the entrained bed gasification furnace described above. Furthermore, in
the entrained bed gasification furnace, the water gas reaction may be promoted with the
biomass crushed in the entrained bed with silica sand and ceramic particles slightly mixed
in the entrained bed.
[0115] In the example in the embodiment described above, the heater as an external heat
source is used for starting the furnace. The heater as the external heat source may also be
used to promote the water gas reaction. Also in this configuration, a power cost required for
the heater can be largely reduced with the oxygen gas supplying unit provided.
[0116] In a more preferable configuration, the gasification furnace can be operated with
biomass only, without feeding additional energy from the external source such as the heater
as the external heat source.
30
[0117] In the example of the embodiment described above, the three gas supplying units 5
are provided. Alternatively, another gas supplying unit 5d may be provided as illustrated in
a dashed line in Fig. 1. Such a gas supplying unit 5d may be provided not only for the first
region R1 but also for the second region R2. By increasing the number of gas supplying
units, the temperature in the reaction tower 4 and a component ratio between hydrogen and
carbon monoxide can be adjusted and controlled more in detail.
[0118] In the embodiment described above, the first and the second gas supplying units 5a
and 5b vertically supply the oxygen gas from a part of a circumference wall of the reaction
tower 4, and the third gas supplying unit 5c supplies the oxygen gas diagonally downward
from a part of the circumference wall of the reaction tower 4. However, such a
configuration should not be construed in a limiting sense.
[0119] For example, as illustrated in Fig. 5(a), the gas supplying unit 5 may include a
header pipe 50 that surrounds the reaction tower 4, and the oxygen gas may be supplied
from a plurality of gas supply pipes 51 formed on the header pipe 50, in directions for
producing swirling flow along an inner wall of the reaction tower 4. Furthermore, as
illustrated in Fig. 5(b), the oxygen gas may be supplied toward the center of the reaction
tower 4 from the plurality of gas supply pipes 51.
[0120] As illustrated in Figs. 5(c) and 5(d), the oxygen gas may be supplied upward or
downward relative to an axial direction of the reaction tower 4. The configuration
illustrated in Fig. 5(c), which is the same as that of the third gas supplying unit 5c as
illustrated in Fig. 1, may be combined with the configurations illustrated in Figs. 5(a) and
5(b). The same applies to the configuration illustrated in Fig. 5(d). The configuration is
particularly preferable for the first gas supplying unit 5a.
[0121] The oxygen gas supplied from the gas supplying unit 5 includes high purity
oxygen gas and further includes oxygen enriched gas obtained by adding oxygen to
atmospheric air for example.
[0122] In the example of the embodiment described above, superheated water vapor at
normal pressure is used as the water vapor. Alternatively, pressurized water vapor or
31
saturated water vapor may be employed. In the reaction tower at normal pressure as
described above, the superheated water vapor at normal pressure is preferably employed
considering the expansion of the water vapor in the reaction tower and a cost for
manufacturing the water vapor.
[0123] In the embodiment described above, an internal temperature of the entire reaction
tower 4 is maintained at 500°C or higher. Alternatively, a temperature distribution may be
formed in the reaction tower 4 for achieving a temperature required for each of the water
gas reaction and the water gas shift reaction. More specifically, the temperature distribution
may be formed with temperature for the first region R1 where the water gas reaction mainly
takes place and different temperature for the second region R2 where the water gas shift
reaction mainly takes place. Thus, the temperature required for each reaction can be
guaranteed, and the energy consumption can be reduced.
[0124] In the system according to the embodiment described above, the liquid fuel is
synthesized by generating the synthesis gas with biomass as a raw material. The synthesis
gas refined in the gasification furnace can be used as a gas fuel for power generation and the
like, and the synthesis gas may be used in any desired way.
[0125] In the example of the embodiment described above, the discharge port 40 is
provided at the top of the reaction tower 4 to be in connection with a space (second region)
in the upper portion of the reaction tower 4. For example, the discharge port 40 may be
formed on a side portion of an upper portion of the reaction tower 4 as long as the discharge
port 40 is connected to the second region.
[0126] In the example of the embodiment described above, dry biomass such as rice
straw, chaff, wheat straw, and forage of corn is used as the biomass as the raw material.
Furthermore, wood waste, bark, bamboo, and the like may be used. Chaff has a specific
gravity of approximately 0.1 and a water content of approximately 10%. Bark has a
specific gravity of approximately 0.6 and a water content of approximately 60%. Bamboo
has a specific gravity of approximately 0.7 and a water content of approximately 25%.
32
Thus, biomass of various properties may be used in the gasification furnace according to the
embodiment described above.
[0127] In the embodiment described above, char generated in the gasification furnace is
used for the water gas reaction in the gasification furnace. As illustrated in Fig. 7, char
generated in the gasification furnace 10 may be separated by a char separator 201 including
a cyclone and the like, and the char thus separated may be used as a fuel to generate hot
water in a combustion furnace 202. Then, the hot water may be heated by potential heat of
the synthesis gas in a waste heat boiler 203 so that water vapor can be generated to be used
for the gasification furnace 10, whereby the energy efficiency of the entire system can be
improved. A reference numeral 204 denotes the gas refining device and a reference
numeral 205 denotes a power generation device, the FT synthesis device, or the like.
[0128] The various embodiments described above are merely a specific example of a
gasification furnace, a method for operating a gasification furnace, and a method for
biomass gasification processing according to the present invention. Thus, the scope of the
present invention is not limited to the description above. It is a matter of course that the
specific configuration of the components can be modified as appropriate as long as the
effect of the present invention can be obtained.
33
WE CLAIM:
[Claim 1] A gasification furnace comprising:
a biomass supplying unit;
a water vapor supplying unit;
a reaction tower including: a first region in which biomass supplied from the biomass
supplying unit flows in an entrained bed formed with water vapor supplied from the water
vapor supplying unit; and a second region into which gas generated in the first region flows,
the first region and the second region being formed along a flow direction of the gas;
a plurality of oxygen gas supplying units that supply oxygen gas to each of the first
region and the second region in the reaction tower; and
a supply amount adjustment mechanism that adjusts an amount of the oxygen gas
supplied from each of the oxygen gas supplying units.
[Claim 2] The gasification furnace according to claim 1,
wherein in the first region, a water gas reaction mainly takes place, and in the second
region, a water gas shift reaction mainly takes place, and
wherein the supply amount adjustment mechanism is configured to adjust a composition
of gas flowing out from the reaction tower by adjusting the water gas reaction and the water
gas shift reaction.
[Claim 3] The gasification furnace according to claim 1 or 2, wherein the supply amount
adjustment mechanism is configured to adjust the amount of the supplied oxygen gas, by
calculating an amount of the oxygen gas required to be supplied to each of the oxygen gas
supplying units based on a composition and an amount of the biomass supplied.
[Claim 4] The gasification furnace according to any one of claims 1 to 3, wherein the
supply amount adjustment mechanism is configured to adjust a ratio among amounts of the
oxygen gas supplied from the oxygen gas supplying units based on a composition of the gas
flowing out from the reaction tower, with a total amount of the supplied oxygen gas fixed.
34
[Claim 5] The gasification furnace according to any one of claims 1 to 3, wherein the
supply amount adjustment mechanism is further configured to adjust an amount of the water
vapor supplied from the water vapor supplying unit.
[Claim 6] A gasification furnace comprising:
a biomass supplying unit;
a water vapor supplying unit;
a reaction tower including: a first region in which biomass supplied from the biomass
supplying unit flows in an entrained bed formed with water vapor supplied from the water
vapor supplying unit; and a second region into which gas generated in the first region flows,
the first region and the second region being formed along a flow direction of the gas;
a plurality of oxygen gas supplying units that supply oxygen gas to each of the first
region and the second region in the reaction tower;
a communication portion through which the generated gas and the biomass or a residue of
the biomass are movable between the first region and the second region; and
a discharge port through which the generated gas and the residue are discharged from the
second region.
[Claim 7] The gasification furnace according to any one of claims 1 to 6, wherein the
water vapor supplying unit is disposed more on an upstream side than the biomass
supplying unit.
[Claim 8] The gasification furnace according to any one of claims 1 to 7, wherein an
oxygen gas supplying unit among the oxygen gas supplying units that corresponds to the
first region is disposed more on an upstream side than the biomass supplying unit.
[Claim 9] The gasification furnace according to claim 8, wherein another oxygen gas
supplying unit among the oxygen gas supplying units that corresponds to the first region is
disposed more on a downstream side than the biomass supplying unit.
[Claim 10] The gasification furnace according to any one of claims 7 to 9, wherein the
water vapor supplying unit is disposed more on the upstream side than any one of the
oxygen gas supplying units.
35
[Claim 11] The gasification furnace according to any one of claims 1 to 10 further
comprising a gas flowrate adjustment portion with which a gas flowrate in the second
region becomes lower than a gas flowrate in the first region.
[Claim 12] The gasification furnace according to claim 11, wherein the gas flowrate
adjustment portion is implemented with a shape of the reaction tower in which the second
region has an average area of an inner cross-section orthogonal to an inner gas flow that is
larger than the average area in the first region.
[Claim 13] The gasification furnace according to claim 11 or 12,
wherein the gas flowrate in the first region is set to achieve a flowrate with which the
biomass floats, and
wherein the gas flowrate in the second region is set to achieve a flowrate with which the
biomass falls down to the first region.
[Claim 14] The gasification furnace according to claim 6 further comprising a supply
amount adjustment mechanism that adjusts an amount of the oxygen gas supplied from each
of the oxygen gas supplying units, based on a composition of gas flowing out from the
reaction tower.
[Claim 15] The gasification furnace according to claim 6 or 14 further comprising a
supply amount adjustment mechanism that adjusts a ratio among amounts of the oxygen gas
supplied from the oxygen gas supplying units based on the composition of the gas flowing
out from the reaction tower, with a total amount of the supplied oxygen gas fixed.
[Claim 16] A method for operating the gasification furnace according to any one of claims
1, 2, 6, 14, and 15, the method comprising:
measuring a composition of the gas flowing out from the reaction tower; and
adjusting amounts of the oxygen gas supplied to the first region and the second region
from the oxygen gas supplying units in such a manner that the measured composition of the
gas is obtained as a target gas composition.
[Claim 17] The method for operating the gasification furnace according to claim 16,
further comprising adjusting a ratio among amounts of the oxygen gas supplied to the first
36
region and the second region while maintaining a total amount of the oxygen gas supplied
from the oxygen gas supplying units, in such a manner that the measured composition of the
gas is obtained as the target gas composition.
[Claim 18] A method for biomass gasification processing, the method comprising:
a water gas reaction promoting step in which an entrained bed is formed with water vapor
supplied to biomass in an upstream side in a reaction tower to mainly promote a water gas
reaction;
a water gas shift reaction promoting step in which a water gas shift reaction is mainly
promoted involving water gas generated in the water gas reaction promoting step, in a
downstream side in the reaction tower; and
an oxygen gas supplying step in which oxygen gas is supplied for each of the water gas
reaction promoting step and the water gas shift reaction promoting step, and a ratio of
amounts of the oxygen gas supplied for the respective steps is adjusted to adjust a
composition of gas flowing out from the reaction tower.
[Claim 19] The method for biomass gasification processing according to claim 18,
wherein the oxygen gas supplying step includes adjusting the composition of the gas
flowing out from the reaction tower by adjusting the ratio between the amounts of the
supplied oxygen gas while maintaining a total amount of the oxygen gas supplied for the
water gas reaction promoting step and the water gas shift reaction promoting step.