1. A method for manufacturing amorphous silica using biomass derived from a silicicolous plant as a raw material, the method comprising: the gasification step of thermally decomposing the biomass for gasification; and the burning step of burning a biomass residue produced in the gasification step.

2. The method according to claim 1, wherein the gasification step gasifies the biomass in a temperature range below a phase transition temperature range in which amorphous silica is crystallized. 15 3. The method according to claim 2, wherein the gasification step is adjusted in such a manner that the biomass residue has a retention time shorter than or equal to a predetermined time.

4. The method according to claim 2 or 3, further comprising the 20 fuel generation step of generating fuel from a gas obtained in the gasification step.

5. The method according to any one of claims 1 to 4, further comprising, before the burning step, the pulverization step of pulverizing the biomass residue produced in the gasification step.

6. The method according to any one of claims 1 to 5, wherein the burning step includes: the first 5 burning step of burning the biomass residue for a! predetermined time in a carbon combustion temperature range; and after the first burning step, the second burning step of burning the biomass residue for a predetermined time in a temperature range below a phase transition temperature range in which amorphous silica is crystallized.

7. An apparatus for manufacturing amorphous silica for use in the method according to any one of claims 1 to 6, the apparatus comprising: a gasification furnace configured to thermally decompose biomass containing a silicicolous plant for gasification; a separation mechanism configured to separate a biomass residue from a mixture of a pyrolysis gas and the biomass residue discharged from the gasification furnace; and a burning furnace configured to burn the biomass residue separated by the separation mechanism to obtain amorphous silica.

8. The apparatus according to claim 7, further comprising a pulverizerconfigured to pulverizethe biomass residue separated by the separation mechanism.

9. The apparatus according to claim 7 or 8, further comprising, downstream Of the gasification furnace, a reaction device configured to generate fule from the pyrolysis gas That is generated by the gasification furnace and from which the biomass residue has been sperated By the separation mechanism.

1
FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. METHOD FOR MANUFACTURING AMORPHOUS SILICA AND
APPARATUS FOR MANUFACTURING AMORPHOUS SILICA
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 method and apparatus for
manufacturing amorphous silica that recovers energy from biomass
derived from a silicicolous plant such as rice hulls and that also
separates 5 and collects silica from the biomass in a high-value-added
condition.
Background Art
[0002] Patent Literature 1 discloses a method for manufacturing
10 granular silicate whereby white granular silicate is obtained through a
water gas reaction caused by supplying 1,000ºC or lower temperature
steam to rice-hull charcoal obtained by dry distillation of rice hulls.
[0003] Patent Literature 2 proposes a rice-hull-gasification residue
recycling system for the purpose of providing a rice-hull-gasification
15 residue recycling system completing in a paddy field district, by
developing a means for efficiently utilizing gasification residues that
are left after recovering energy from silicate-rich rice hulls through
thermal decomposition.
[0004] This rice-hull-gasification residue recycling system includes: a
20 gasification furnace for thermally decomposing rice hulls to obtain
decomposition gas and gasification residues; an energy conversion
facility for converting the decomposition gas to a source for energy such
as electricity, heat, or liquid fuel; and a grain size adjusting facility for
adjusting the grain diameters of the gasification residues, wherein the
25 grain-size-adjusted gasification residues are spread over an irrigated
paddy field as an adsorbent for paddy agrochemicals.
3
[0005] Patent Literature 3 proposes, as a method for obtaining high
purity amorphous silica from organic wastes such as agricultural
produce, edible plants, and wood without using mineral acids such as
sulfuric acid, hydrochloric acid, and nitric acid, a method for
manufacturing amorphous silica 5 including: the step of preparing an
organic waste containing silicon oxide as a starting material; the step of
immersing the organic waste in an aqueous solution of carboxylic acid
having hydroxy groups; the subsequent step of washing the organic
waste in water; and additionally the step of heating the organic waste
10 in the ambient atmosphere.
Citation List
Patent Literature
[0006] Patent Literature 1: Japanese Examined Patent Publication,
15 Tokukousho, No. 49-30353
Patent Literature 2: Japanese Unexamined Patent Application
Publication, Tokukai, No. 2009-23965
Patent Literature 3: PCT International Application Publication
No. WO2008/053711
20
Summary of Invention
Technical Problem
[0007] The method for manufacturing granular silicate disclosed in
Patent Literature 1 manufactures granular silicate by water
25 gasification of rice-hull charcoal obtained by dry distillation of rice hulls
to remove carbon content. The dry distillate gas produced in obtaining
4
rice-hull charcoal is wastefully discharged into the air without being
collected. The method has room for further improvement from the point
of view of recovering resources. The method also has a problem that the
obtained granular silicate has a purity of 90%, which is not very high
and limits 5 the usage of the granular silicate.
[0008] Meanwhile, attention has been paid to FT synthesis technology
whereby steam is supplied to biomass for a water gas reaction and a
water gas shift reaction to produce biofuels using resultant water gas
as a raw material for FT synthesis.
10 [0009] A highly efficient resource recycling system can be constructed
if biofuels are produced from the water gas obtained by using, for
example, rice hulls as biomass and supplying steam to, for example, the
rice hulls, and silica is collected from the biomass residues for recycling.
[0010] However, in such a resource recycling system, temperature in
15 the water gas shift reaction is set to as high as about 950ºC for
increased gasification efficiency. Some silica in the biomass residues
could be crystallized due to this high temperature and become difficult
to recycle.
[0011] In addition, if the carbon components themselves are
20 crystallized and acquired by silica, the carbon components cannot be
completely removed in subsequent burning of the biomass residues,
which lowers the purity of silica and produces grayish silica. Hence,
usage is limited in either case, which is undesirable.
[0012] The rice-hull-gasification residue recycling system disclosed in
25 Patent Literature 2 uses silica in gasification residues solely as an
adsorbent for paddy agrochemicals. If the silica is to be used for other
5
purposes, the system needs special arrangements to increase the purity.
[0013] The method for manufacturing amorphous silica disclosed in
Patent Literature 3 not only requires a water treatment facility for
post-processing an aqueous solution of carboxylic acid and like process
water, 5 but also causes energy loss in heating the processed organic
wastes in the ambient atmosphere. The method has room for further
improvement from the economic point of view.
[0014] In view of the aforementioned problems, it is an object of the
present invention to provide a method and apparatus for
10 manufacturing amorphous silica using biomass derived from a
silicicolous plant as a raw material, the method and apparatus being
capable of efficiently recovering energy and obtaining high purity, high
quality silica.
15 Solution to Problem
[0015] To achieve this object, a method for manufacturing amorphous
silica in accordance with the present invention has a first characteristic
feature that the method is a method for manufacturing amorphous
silica using biomass derived from a silicicolous plant as a raw material
20 and includes: the gasification step of thermally decomposing the
biomass for gasification; and the burning step of burning a biomass
residue produced in the gasification step.
[0016] The biomass derived from a silicicolous plant is thermally
decomposed and recovered as a fuel in the gasification step. The
25 remaining biomass residue is burned and hence rid of impurities, such
as carbon components, remaining in the biomass residue. High purity
6
silica is thereby obtained.
[0017] The method has, in addition to the first characteristic feature, a
second characteristic feature that the gasification step gasifies the
biomass in a temperature range below a phase transition temperature
5 range in which amorphous silica is crystallized.
[0018] Since the biomass is gasified in a temperature range below the
phase transition temperature range, amorphous silica is not
crystallized. Additionally, since the carbon components themselves are
neither crystallized nor acquired by silica, high purity silica can be
10 obtained in the subsequent burning step.
[0019] The method has, in addition to the second characteristic
feature, a third characteristic feature that the gasification step is
adjusted in such a manner that the biomass residue has a retention
time shorter than or equal to a prescribed time.
15 [0020] This adjustment of the retention time of the biomass residue
can reduce the possibility of silica being crystallized in the biomass
residue, thereby reducing the possibility of the carbon components
themselves being crystallized and acquired by silica. As a result, high
purity silica can be obtained in the subsequent burning step.
20 [0021] The method has, in addition to the second or third
characteristic feature, a fourth characteristic feature that the method
further includes the fuel generation step of generating fuel from a gas
obtained in the gasification step.
[0022] The fuel generation step converts the gas obtained in the
25 gasification step to a fuel, thereby expanding usage as a fuel.
[0023] The method has, in addition to any of the first to fourth
7
characteristic features, a fifth characteristic feature that the method
further includes, before the burning step, the pulverization step of
pulverizing the biomass residue produced in the gasification step.
[0024] The burning step is performed after pulverizing the biomass
residue produced in the gasification s 5 tep. Hence, impurities are
efficiently separated in burning, and silica can be obtained with
consistent grain diameters.
[0025] The method has, in addition to any of the first to fifth
characteristic features, a sixth characteristic feature that the burning
10 step includes: the first burning step of burning the biomass residue for
a prescribed time in a carbon combustion temperature range; and after
the first burning step, the second burning step of burning the biomass
residue for a prescribed time in a temperature range below a phase
transition temperature range in which amorphous silica is crystallized.
15 [0026] The first burning step of burning for a prescribed time in the
carbon combustion temperature range can efficiently combust the
carbon components in the biomass residue, thereby removing
carbon-derived black components. The second burning step of burning
for a prescribed time in a temperature range below the phase transition
20 temperature range can remove impurities and hence increase purity
without having to cause crystallization of silica.
[0027] An apparatus for manufacturing amorphous silica in
accordance with the present invention has a first characteristic feature
that the apparatus is an apparatus for manufacturing amorphous silica
25 for use in the method having any of the first to sixth characteristic
features and includes: a gasification furnace configured to thermally
8
decompose biomass containing a silicicolous plant for gasification; a
separation mechanism configured to separate a biomass residue from a
mixture of a pyrolysis gas and the biomass residue discharged from the
gasification furnace; and a burning furnace configured to burn the
biomass 5 residue separated by the separation mechanism to obtain
amorphous silica.
[0028] The gasification furnace thermally decomposes the biomass
containing a silicicolous plant, the centrifuge separates the pyrolysis
gas and the biomass residue, and the burning furnace burns the
10 biomass residue to obtain silica.
[0029] The apparatus has, in addition to the first characteristic
feature, a second characteristic feature that the apparatus further
includes a pulverizer configured to pulverize the biomass residue
separated by the separation mechanism.
15 [0030] The pulverizerpulverizes the biomass residue separated by the
centrifuge, to adjust grain size. The burning furnace can hence
efficiently burn the biomass residue.
[0031] The apparatus has, in addition to the first or second
characteristic feature, a third characteristic feature that the apparatus
20 further includes, downstream of the gasification furnace, a reaction
device configured to generate fuel from the pyrolysis gas that is
generated by the gasification furnace and from which the biomass
residue has been separated by the separation mechanism.
[0032] The reaction device configured to generate fuel from the
25 pyrolysis gas obtained by the gasification furnace can efficiently recycle
the energy of the biomass.
9
Advantageous Effects of Invention
[0033] As described above, the present invention can provide a method
and apparatus for manufacturing amorphous silica using biomass
derived from a silicicolous plant as a 5 raw material, the method and
apparatus being capable of efficiently recovering energy and obtaining
high purity, high quality silica.
Brief Description of Drawings
10 [0034] FIG. 1 is a diagram showing an exemplary method for
manufacturing amorphous silica in accordance with the present
invention.
FIG. 2 is a diagram showing a gasification furnace and an FT
synthesis reaction vessel in a BTL plant.
15 FIG. 3 is a diagram showing an exemplary apparatus for
manufacturing amorphous silica.
FIG. 4 is a diagram showing another exemplary apparatus for
manufacturing amorphous silica.
FIG. 5A is a diagram showing results of thermogravimetric
20 analysis of gasification ash in Experiment No. 3.
FIG. 5B is a diagram showing results of thermogravimetric
analysis of gasification ash under basic conditions.
FIG. 6 is a diagram showing results of a low-temperature
combustion experiment on a biomass residue.
25 FIG. 7 is a diagram showing results of the analysis of
components of white ash.
10
Description of Embodiments
[0035] The following will describe an exemplary method and
apparatus for manufacturing amorphous silica in accordance with the
5 present invention.
FIG. 1 shows an aspect of the method for manufacturing
amorphous silica in accordance with the present invention. Unhulled
rice produced by farmers is shipped to a rice center or stored in a grain
elevator. After the rice is hulled, a large amount of rice hulls is
10 transported as a raw material to a BTL (biomass to liquid) plant.
[0036] The BTL plant has a gasification furnace and an FT synthesis
reaction vessel. The synthetic gas produced by decomposing rice hulls
in the gasification furnace is fed to the FT synthesis reaction vessel
(alternatively referred to as the FT synthesis furnace) for FT synthesis,
15 thereby producing liquid biofuels (e.g., light oil and jet fuel).
[0037] The produced biofuels are used in transportation fuel and
agricultural fuel, and the waste heat produced in the BTL plant is fed
to a thermal insulation heat source in, for example, horticultural
facilities and hot springs. In addition, the off-gas obtained from the FT
20 synthesis in the FT synthesis reaction vessel is fed to machinery, such
as a gas engine power generator or a boiler, that operates on a heat
source, and the electric power generated by such machinery is used in
the facility.
[0038] The abundant silica content in the residues from the rice hulls
25 thermally decomposed in the gasification furnace is partly supplied to
agricultural fields as a fertilizer. The rest is utilized for industrial
11
purposes as a raw material, for example, for adsorbents.
[0039] FIG. 2 shows a basic structure of a BTL plant 100. The BTL
plant 100 includes: a gasification furnace 10 for producing, from
biomass, a synthetic gas that will be a raw material for liquid fuel; a
gas purifier 20 including, for 5 example, a cyclone,a scrubber, and an
activated carbon adsorption tower for removing, for example, ash and
other solid substances, hydrogen sulfide gas and hydrogen chloride gas,
and ammonia from the produced synthetic gas,; and an FT synthesis
reaction vessel 30 for synthesizing fuel from the synthetic gas refined in
10 the gas purifier 20.
[0040] The gasification furnace 10 includes a reaction tower for
reducing and heating the biomass in steam or superheated steam at
high temperature with a furnace temperature of from 500ºC to 1,000ºC,
to produce synthetic gas (H2, CO).
15 [0041] For instance, the steam and biomass heated to approximately
500ºC by, for example, high frequency heating under normal pressure
are subjected to a water gas reaction or a water gas shift reaction inside
the reaction tower. The produced gas is discharged via an exhaust port
located on an upper part of the reaction tower and guided into the gas
20 purifier 20 via an exhaust tube. The water gas reaction primarily
occurs in a lower part of the reaction tower, and the water gas shift
reaction primarily occurs whenthe steam and biomass rise in the
reaction tower. The gas purifier 20 includes an induced draft fan that
maintains the interior of the reaction tower under negative pressure, so
25 that the gas produced in the reaction tower is induced into the gas
purifier 20 where the gas is refined.
12
[0042] A biomass feeder includes, on one end thereof, a screw conveyor
mechanism including: a tubular casing connected by a flange to a lower
partof a side wall of the reaction tower; and screw blades housed in the
tubular casing and further includes, on the other end thereof, a hopper
including a 5 volumetric feeder mechanism. Dry biomass such as rice
hulls pulverized to approximately a few millimeters is fed to the hopper,
transported by the screw blades in a consolidated manner, and
introduced into the reaction tower. The steam supplied from an end of a
nozzle of a steam feeding unit disposed on the bottom of the biomass
10 feeder forms an entrained bed where the biomass flows in steam inside
the reaction tower.
[0043] The region in which the entrained bed is formed is a first region
R1 where the water gas reaction primarily occurs. A second region R2
where the water gas shift reaction primarily occurs is additionally
15 formed above the first region R1.
[0044] A water gas reaction is an endothermic reaction by which
carbon monoxide CO and hydrogen H2 are produced from solid carbon
C, which is biomass, and steam H2O in a high temperature
environment of not lower than 500ºC as represented by the formula
20 below. Besides the steam feeding unit, there is provided an oxygen
feeding unit for feeding a small amount of oxygen gas or air to the
reaction tower. Necessary reaction heat is delivered by the combustion
of a portion of the biomass.
C + H2O → CO + H2
25 [0045] A water gas shift reaction is generally an exothermic reaction
by which carbon dioxide CO2 and hydrogen H2 are produced from
13
carbon monoxide CO and steam H2O in a high temperature
environment of about 800ºC as represented by the formula below.
CO + H2O → CO2 + H2
[0046] The synthetic gas, char, and ash produced from the biomass in
the first region 5 R1 rise to the second region R2, which is located
downstream in the gas flow direction, to promote the aforementioned
water gas shift reaction. Note that the steam required in the water gas
shift reaction is fed from the steam feeding unit, so that the steam that
has not contributed to the water gas reaction in the first region R1 is
10 consumed.
[0047] The synthetic gas obtained in the reaction tower is refined in
the gas purifier 20 located downstream of the reaction tower, so that the
synthetic gas is rid of impurities. The synthetic gas is then heated and
pressurized to high temperature and high pressure in a heater and a
15 compressor and introduced to the FT synthesis reaction vessel 30 for
FT synthesis.
[0048] The term, “FT synthesis,” is an abbreviation of Fischer-Tropsch
synthesis and is alternatively referred to as an FT method or an FT
reaction. The term refers to a process that includes a series of synthesis
20 reactions for the synthesis of liquid hydrocarbon via catalytic reactions
from carbon monoxide and hydrogen.
[0049] The synthetic gas introduced to the FT synthesis reaction
vessel 30 is introduced into a medium in which a catalyst is dispersed,
to synthesize a desirable hydrocarbon. The ratio of hydrogen and
25 carbon monoxide, H2/CO, although variable depending on the type and
properties of the catalyst, is preferably approximately equal to 2 in the
14
synthesis of, for example, methanol. In synthesizing light oil in
accordance with the present embodiment, the ratio of hydrogen and
carbon monoxide, H2/CO, is preferably approximately equal to 1.
[0050] In other words, the ratio of hydrogen and carbon monoxide,
H2/CO, needs to be adjusted 5 so as to efficiently obtain a desirable
hydrocarbon through FT synthesis. This ratio can vary depending on
the type of catalyst used in the FT synthesis even when the same type
of hydrocarbon is to be produced.
[0051] The temperature at which rice hulls are thermally decomposed
10 in the gasification furnace needs to be in a temperature range below a
phase transition temperature range in which at least the silica
contained in the rice hulls is crystallized. If the silica is crystallized, it
is inappropriate to use such silica in industrial settings equally in view
of negative health effects. In addition, even amorphous silica, if having
15 such a low purity as to contain carbon components, will be colored black
and for this reason, cannot be used as ingredients of, for example,
foundation and other cosmetics, food additives, medicinal additives,
resin additives, paint additives, and rubber filling agents, and hence
limited in use.
20 [0052] The method for manufacturing amorphous silica in accordance
with the present invention can efficiently obtain high purity amorphous
silica while recovering energy from rice hulls. Rice hulls, which is a type
of agriculture waste, contain approximately 70% carbohydrate such as
cellulose, hemicellulose, and lignin and approximately 15 to 20% silica,
25 and the rest is mostly water and a trace of alkali impurities. The
present invention is suitably used in reusing such silica-containing
15
biomass as a new resource. Therefore, the present invention is
applicable not only to rice hulls, but also to biomass derived from
silicicolous plants such as rice straw, wheat straw, bamboo, corn, sugar
cane, silver grass, and rough horsetail.
5 [0053] The following will describe the method for manufacturing
amorphous silica in more detail.
The method for manufacturing amorphous silica using biomass
derived from a silicicolous plant as a raw material includes: the
gasification step of thermally decomposing the biomass in a gasification
10 furnace; and the burning step of burning, in a burning furnace, a
biomass residue produced in the gasification step. The biomass derived
from a silicicolous plant is thermally decomposed into hydrogen and
carbon monoxide and recovered as a fuel in the gasification step. The
remaining biomass residue is burned and hence rid of impurities, such
15 as carbon components, remaining in the biomass residue, to obtain high
purity silica.
[0054] As described above, in the process of causing a water gas
reaction and a water gas shift reaction by supplying steam to biomass
to produce synthetic gas such as hydrogen gas and carbon monoxide
20 gas, the water gas shift reaction preferably proceeds in a temperature
range below the phase transition temperature range in which the silica
in the biomass residue is crystallized, for example, in a temperature
range of not higher than 800ºC. Since the water gas shift reaction
proceeds in a temperature range below the phase transition
25 temperature range, the amorphous silica is not crystallized. In
addition, the carbon components themselves are not acquired by
16
crystallized silica, so that the carbon components can be efficiently
removed in the subsequent burning step. High purity silica can be thus
obtained.
[0055] In the gasification step, the supply rate of steam or the mixture
ratio of oxygen gas 5 in the steam is preferably adjusted in such a
manner that the flow time of the biomass residue, which is the time
until the biomass residue formed by the ashing in the water gas
reaction of the biomass introduced into the reaction tower flows out of
the reaction tower toward the gas purifier 20, is shorter than or equal to
10 a predeterminedtime.
[0056] The biomass is thermally decomposed in the water gas reaction
while flowing with the steam and further subjected to the water gas
shift reaction, which leaves the biomass residue. In this process, the
retention time of the biomass residue is adjusted by adjusting the
15 supply rate of the steam or the mixture ratio of oxygen gas in the
steam. As a result, the silica in the biomass residue is less likely to be
crystallized, and the carbon components themselves are less likely to be
crystallized and acquired by the silica. This adjustment enables the
subsequent burning step to produce high purity silica.
20 [0057] With a view to producing steam without having to consume
external energy, the manufacturing method preferably includes a steam
superheating step of heating steam through heat exchange utilizing the
sensible heat of the pyrolysis gas obtained in the gasification step,
which can improve economic efficiency.
25 [0058] In addition, the manufacturing method preferably includes a
biofuel generation step of producing biofuel through FT synthesis using
17
the gas obtained in the gasification step as a raw material. The biofuel
generation step can expand usage as a fuel in view of efficient use of
energy.
[0059] The manufacturing method preferably includes, before the
burning step, a pulverization s 5 tep of pulverizing the biomass residue
produced in the gasification step. The pulverization step enables
efficient separation of impurities by the burning and also enables
production of silica with consistent grain diameters, which is conducive
in producing whiter and more uniform granular silicate in the burning
10 step.
[0060] The burning step preferably includes: a first burning step of
burning the biomass residue for a prescribed time in a carbon
combustion temperature range; and after the first burning step, a
second burning step of burning the biomass residue for a
15 predeterminedtime in a temperature range above the first burning
temperature and below the phase transition temperature range.
[0061] The first burning step of burning for a prescribed time in the
carbon combustion temperature range, specifically, in a temperature
range of 400 to 600ºC, enables efficient combustion of the carbon
20 components contained in the biomass residue, thereby removing
carbon-derived black components. The second burning step of burning
for a predeterminedtime in a temperature range below the phase
transition temperature range, specifically, in a temperature range of
not higher than 800ºC enables removing impurities to increase purity,
25 without having to cause crystallization of silica.
[0062] The gasification step is not necessarily a water gas reaction and
18
may include a pyrolysis process by which, as an example, the biomass is
heated in a low oxygen concentration atmosphere for dry distillation.
[0063] FIG. 3 shows an exemplary apparatus for manufacturing
amorphous silica for using the aforementioned method for
5 manufacturing amorphous silica.
The apparatus for manufacturing amorphous silica includes: a
gasification furnace that thermally decomposes biomass containing a
silicicolous plant for gasification; a separation mechanism, such as a
centrifuge cyclone filter, that separates a biomass residue from a
10 mixture of a pyrolysis gas and the biomass residue discharged from the
gasification furnace; a pulverizerthat pulverisesthe biomass residue
separated by the separation mechanism; and a burning furnace that
burns the pulverizedbiomass residue to obtain amorphous silica. The
burning furnace may be, for example, an electricity-powered burning
15 furnace or a gas-powered burning furnace where approximate.
[0064] The gasification furnace includes an entrained-bed furnace
causing the biomass to flow with steam, thereby subjecting the biomass
to a water gas reaction and a water gas shift reaction, and further
includes a reaction device that produces fuel from the pyrolysis gas
20 obtained by separating, using the separation mechanism, the biomass
residue from a mixture of the pyrolysis gas and the biomass residue
discharged from the entrained-bed furnace.
[0065] Superheated steam produced in a boiler using biomass or fossil
fuel such as kerosene and the oxygen gas produced in an oxygen
25 generator PSA (pressure swing adsorption), as well as biomass, are
introduced to the gasification furnace. The biomass residue in the
19
synthetic gas produced in the water gas reaction and the water gas
shift reaction in the gasification furnace is separated by the cyclone,
pulverizedto a predeterminedgrain diameter in the pulverizer, then
introduced to the burning furnace, and burned, to obtain high purity
5 amorphous silica.
[0066] The synthetic gas from which the biomass residue has been
removed in the cyclone is guided into a heat exchanger for air
preheating and thereafter washed in a scrubber to remove, for example,
ammonia gas and hydrogen chloride gas. CO2 is removed in a CO2
10 adsorption tower from the synthetic gas refined by a gas purification
unit, and the synthetic gas heated and pressurized in a temperature
and pressure booster is introduced to an FT synthesis reaction vessel.
Oil is synthesized and gasified by the FT reaction. The resultant
gaseous components are liquefied in a condenser to produce a liquid
15 fuel as a fuel. The lower hydrocarbon gas having passed through the
condenser is used as an off-gas that powers a gas power generator.
[0067] FIG. 4 shows another exemplary apparatus for manufacturing
amorphous silica for using the aforementioned method for
manufacturing amorphous silica. FIGs. 3 and 4 show some common
20 features including the use of biomass as a raw material in gasification
in the gasification furnace, the pulverizingin the pulverizerof the
biomass residue separated in the cyclone, and the burning in the
burning furnace for the production of amorphous silica. FIG. 4 differs
from FIG. 3 in that the synthetic gas having passed through the cyclone
25 is used as a fuel for the gas power generator without being subjected to
the FT synthesis.
20
Examples
[0068] Experiments were conducted to design conditions for
manufacturing, from rice hulls, silica that can be used as a raw
material for cosmetics (raw material for a foundation) in the
5 aforementioned method for manufacturing amorphous silica.
Silica needs to satisfy three quality requirements such that the
silica can be used as a raw material for cosmetics: namely, silica should
be amorphous, have a grain diameter of approximately 10 μm, and
have a purity of 97% or higher. When the silica purity is 97% or higher,
10 the silica appears white and can be evaluated as free of toxic
ingredients.
[0069] Tests were conducted to find out how the gasification ratio, the
composition of the biomass residue, and the grain size of the biomass
residue change when the upper portion temperature of the gasification
15 furnace (operating condition 1), the steam-to-carbon ratio (operating
condition 2), the air-to-pure oxygen replacement ratio (operating
condition 3), and the process volume (operating condition 4), as
operating conditions for the gasification furnace, are changed relative
to basic conditions. The upper portion temperature of the gasification
20 furnace is the temperature of the second region R2 (see FIG. 2) where
the water gas shift reaction primarily occurs.
[0070] The basic conditions are conditions under which biofuel can be
obtained with maximum efficiency from the FT synthesis using
biomass. Specifically, the upper portion temperature of the gasification
25 furnace is set to 950ºC, the steam-to-carbon ratio is set to 1.7, the
air-to-pure oxygen replacement ratio is set to 0% (pure oxygen 100%),
21
and the process volume is set to 1 ton/day. The temperature of the first
region R1 is set to approximately 500 to 600ºC.
[0071] Tests were conducted under various operating conditions. The
results of the tests show that the biomass residue processed under
specific operating conditions where operating 5 condition 1 was set to
800ºC (basic condition is 950ºC), operating condition 2 was set to 1.7
(basic condition is 1.7), operating condition 3 was set to 100% (basic
condition is 0%), and operating condition 4 was set to 1 ton/day (basic
condition is 1 ton/day) produced white ash (specifically, light pink color)
10 if burned at 800ºC and whitish ash (specifically, very light gray color) if
burned at 600ºC or 550ºC. The results of the tests also show that the
biomass residue only produced gray or dark gray ash under other
conditions even if the burning conditions were similar.
[0072] FIGs. 5A and 5B show results of a thermogravimetric analysis.
15 Referring to FIG. 5B, if the biomass residue subjected to gasification
under the basic conditions was heated (burned), carbon combustion
showed two exothermic peaks (41.55 min. and 44.13 min.). Meanwhile,
in Experiment No. 3 shown in FIG. 5A, carbon combustion showed one
exothermic peak (42.83 min.).
20 [0073] It is envisaged that in the gasification under the basic
conditions, the carbon components were partially crystallized when
gasified at a high temperature of 950ºC and therefore less likely to
burn. In contrast, under mild conditions of Experiment No. 3 where the
carbon components were gasified at 800ºC, the carbon components
25 entirely turned into soft carbon, that is, easy-to-burn carbon with many
functional groups, so that the carbon was substantially completely
22
combusted and turned white.
[0074] Observation in SEM images reveals that the ash resulting from
the combustion experiments was composed mostly of silica and slightly
flattened in shape, but was not molten and retained the complex
structure that originated i 5 n rice hulls. However, in the silica resulting
from 3-hour, 800ºC combustion, crystalline silica, albeit in small
amounts (0.6% cristobalite and 0.3% quartz), was identified.
[0075] Next, the biomass residues gasified under the basic conditions
(the upper portion temperature of the gasification furnace was 950ºC)
10 (Samples No. 1, 2, and 3) and the biomass residues gasified under
specific operating conditions (the upper portion temperature of the
gasification furnace was 800ºC) (Samples No. 1 to 10) were pulverized
and thereafter heated in an electrical muffle furnace (air atmosphere)
under the various conditions described below to combust carbon. The
15 appearance (how well carbon was removed) of resulting grains was
observed.
[0076] The temperature boosting rate in combustion was set to either
one of two rates, namely, “rapid” (introduced into the furnace whose
temperature had been set to a setpoint temperature) and “slow” (placed
20 inside the furnace and subsequently heated at 200ºC/hour). The
combustion temperature was set to a temperature from 600 to 800ºC
(the silica is crystallized at or above 800ºC). The combustion time was
varied from 1 to 5 hours with an increment of 1 hour.
[0077] FIG. 6 shows results of the experiments.
25 The biomass residue gasified under the basic conditions (the
upper portion temperature of the gasification furnace was 950ºC) did
23
not produce white ash under any of these temperature boosting rate,
combustion temperature, and combustion time settings.
[0078] The biomass residues (Samples No. 1 to 10) gasified under
specific operating conditions (the upper portion temperature of the
gasification furnace wa 5 s 800ºC, which falls in a temperature range
below the phase transition temperature range in which silica is
crystallized) were more likely to produce white ash. This is presumably
because the decrease in the gasification temperature inhibited
crystallization of silica and allowed carbon to turn into easy-to-burn
10 soft carbon without being charred.
[0079] Furthermore, the results from Samples No. 2, 3, 6, and 8
indicate that the biomass residues were more likely to produce white
ash due to a decreased temperature boosting rate in combustion and
that the gasification ash turned white if combusted at 800ºC for at least
15 2 hours, at 750ºC for 4 hours, or at 700ºC for 5 hours.
[0080] The results from Samples No. 1, 4, 5, 7, 9, and 10 indicate that
rapid temperature boosting made it less likely to produce white ash.
This is presumably because silica partially melted and coated carbon,
which made the carbon less likely to burn.
20 [0081] FIG. 7 shows results of a component analysis on the white ash
of Sample No. 6. The results indicate that the white ash had a carbon
(C) concentration of 0.1% or less and contained 97% or higher, high
purity silica (SiO2), due to low-temperature combustion.
The white ash further contained a trace of components other
25 than silica such as potassium (K), sodium (Na), calcium (Ca), iron (Fe),
and phosphorus (P).
24
[0082] Meanwhile, the results indicate that the white ash had lead
(Pb) and arsenic (As) concentrations, regulated as toxic elements, not
exceeding respective standard values. Additionally, quartz, cristobalite,
and tridymite, which are silica crystals, were less than the minimum
quantifiable 5 amount, and silica remained amorphous after
low-temperature combustion. The results further indicate, regarding
the grain size distribution, that the biomass residue was pulverized to
approximately 10 μm by adjusting conditions in preparatory
pulverization (the pulverization volume, types and number of
10 pulverization media, and pulverization time).
[0083] These results of the experiments confirm that the gasification
step of causing biomass to flow with steam to subject the biomass to a
water gas reaction and a water gas shift reaction preferably causes the
water gas shift reaction in a temperature range below the phase
15 transition temperature range in which silica in the biomass residue is
crystallized and that the gasification step preferably adjusts the supply
rate of the steam or the mixture ratio of oxygen gas in the steam in such
a manner that the flow time of the biomass residue is shorter than or
equal to a predeterminedtime.
20 [0084] A pulverization step is preferably included before the burning
step, in order to pulverize the biomass residue produced in the
gasification step to approximately 5 to 15 μm. Additionally, the burning
step preferably includes: a first burning step of burning the biomass
residue for a prescribed time in the carbon combustion temperature
25 range; and after the first burning step, a second burning step of burning
in a temperature range below the phase transition temperature range
25
for a prescribed time.
[0085] By elevating temperature slowly at 100 to 200ºC/hour toward a
temperature range of 400 to 600ºC, which is a carbon combustion
temperature range, and retaining at 400 to 600ºC for 2 to 3 hours, the
carbon components contained 5 in the biomass residue can be efficiently
combusted so that the black components that originate in carbon can be
removed. Thereafter, by heating at a high temperature of 700 to 800ºC
for 1 to 3 hours, impurities can be removed to increase purity without
having to cause crystallization of silica.
10 [0086] It will be appreciated that the aforementioned, various
embodiments are a mere description of a specific example of a
gasification furnace, method of operating the gasification furnace, and
method of gasification of biomass in accordance with the present
invention. The description does not limit the scope of the present
15 invention. The specific structure of each member may be varied in a
suitable manner provided that these variations can achieve the
functions and effects of the present invention.
Reference Signs List
20 [0087] 10: Gasification Furnace
20: Gas Purifier
30: FT Synthesis Reaction Vessel
100: BTL Plant
R1: First Region
25 R2: Second region
WE CLAIM:-
1. A method for manufacturing amorphous silica using biomass
derived from a silicicolous plant as a raw material, the method
comprising:
the gasification step of thermally decomposing the biomass for
gasification; and
the burning step of burning a biomass residue produced in the
gasification step.
2. The method according to claim 1, wherein the gasification step
gasifies the biomass in a temperature range below a phase transition
temperature range in which amorphous silica is crystallized.
15 3. The method according to claim 2, wherein the gasification step
is adjusted in such a manner that the biomass residue has a retention
time shorter than or equal to a predetermined time.
4. The method according to claim 2 or 3, further comprising the
20 fuel generation step of generating fuel from a gas obtained in the
gasification step.
5. The method according to any one of claims 1 to 4, further
comprising, before the burning step, the pulverization step of
pulverizing the biomass residue produced in the gasification step.
6. The method according to any one of claims 1 to 5, wherein the
burning step includes:
the first 5 burning step of burning the biomass residue for a!
predetermined time in a carbon combustion temperature range; and
after the first burning step, the second burning step of burning
the biomass residue for a predetermined time in a temperature range
below a phase transition temperature range in which amorphous silica
is crystallized.
7. An apparatus for manufacturing amorphous silica for use in the
method according to any one of claims 1 to 6, the apparatus comprising:
a gasification furnace configured to thermally decompose
biomass containing a silicicolous plant for gasification;
a separation mechanism configured to separate a biomass
residue from a mixture of a pyrolysis gas and the biomass residue
discharged from the gasification furnace; and
a burning furnace configured to burn the biomass residue
separated by the separation mechanism to obtain amorphous silica.
8. The apparatus according to claim 7, further comprising a
pulverizerconfigured to pulverizethe biomass residue separated by the
separation mechanism.
9. The apparatus according to claim 7 or 8, further comprising, downstream
Of the gasification furnace, a reaction device configured to generate fule from the pyrolysis gas
That is generated by the gasification furnace and from which the biomass residue has been sperated
By the separation mechanism.