FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. APPARATUS FOR MANUFACTURING AMORPHOUS SILICA AND METHOD
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.
5
2
Technical Field
[0001] The present invention relates to an apparatus and method for manufacturing
amorphous silica, the apparatus including a reactor, a raw material supply mechanism to
supply biomass derived from a silicicolous plant as a raw material to the reactor, and a gas
5 supply mechanism to supply steam and an oxygen-containing gas from a lower section of the
reactor, the apparatus and method producing amorphous silica by heat-treating the raw material
while contacting it with the gas supplied via the gas supply mechanism.
Background Art
10 [0002] Patent Literature 1 proposes a method and apparatus for 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 and high
quality silica.
[0003] The proposed method for manufacturing amorphous silica includes: a gasification
15 step of thermally decomposing biomass derived from a silicicolous plant for gasification; and a
burning step of burning a biomass residue produced in the gasification step.
[0004] The proposed apparatus for manufacturing amorphous silica includes: 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
20 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.
[0005] The above method for manufacturing amorphous silica thermally decomposes the
biomass derived from a silicicolous plant to recover it as a fuel in the gasification step, and
25 burns the remaining biomass residue to remove impurities such as carbon components
remaining in the residue, resulting in high purity white silica.
Citation List
3
Patent Literature
[0006] Patent Literature 1: Japanese Unexamined Patent Application Publication No.
2020-040861
5 Summary of Invention
Technical Problem
[0007] The method and apparatus for manufacturing amorphous silica disclosed in Patent
Literature 1 is a manufacturing method and apparatus for obtaining high purity amorphous
silica from which impurities such as carbon components are removed.
10 [0008] However, even amorphous silica containing impurities such as carbon components
has found applications where it can be effectively utilized as a recycled resource, and thus a
need exists for a common-use manufacturing apparatus that can manufacture amorphous silica
of different purities for different applications.
[0009] It is an object of the present invention to provide an apparatus and method for
15 manufacturing amorphous silica using biomass derived from a silicicolous plant as a raw
material, the apparatus and method being capable of producing amorphous silica of different
purities for different applications.
Solution to Problem
20 [0010] To achieve the above object, an apparatus for manufacturing amorphous silica is
provided in accordance with the present invention, the apparatus including a reactor, a raw
material supply mechanism configured to supply biomass derived from a silicicolous plant as a
raw material to the reactor, and a gas supply mechanism configured to supply steam and an
oxygen-containing gas from a bottom of the reactor where the raw material is retained, the
25 apparatus being configured to produce amorphous silica by heat-treating the raw material
while contacting the raw material with the steam and the oxygen-containing gas. As a first
feature of the apparatus, the apparatus includes a heat treatment condition adjustment
mechanism configured to adjust a percentage of carbon contained in the produced amorphous
4
silica by adjusting a ratio of the oxygen-containing gas supplied from the gas supply
mechanism to an amount of the raw material supplied.
[0011] Using the manufacturing apparatus including the reactor, the raw material supply
mechanism, and the gas supply mechanism, the ratio of the oxygen-containing gas to the
5 amount of raw material supplied is adjusted during heat treatment via the heat treatment
condition adjustment mechanism to thereby adjust the percentage of carbon contained in the
amorphous silica, which can produce amorphous silica with different properties. For
example, high purity white amorphous silica and carbon-containing black amorphous silica
can be obtained.
10 [0012] In addition to the first feature above, the apparatus for manufacturing amorphous
silica has a second feature that the apparatus further includes a fluidized condition adjustment
mechanism configured to adjust a fluidized condition of the raw material by adjusting at least
one of a total amount, arrangement of supply positions, and supply distribution of the gas
supplied from the gas supply mechanism.
15 [0013] By adjusting at least one of the total amount, the arrangement of supply positions, and
the supply distribution of the gas, the fluidized condition of the raw material is adjusted to
produce amorphous silica with different properties.
[0014] In addition to the second feature above, the apparatus for manufacturing amorphous
silica has a third feature that the fluidized condition adjustment mechanism is configured to be
20 capable of adjusting the fluidized condition to at least a first fluidized condition and a second
fluidized condition, the first fluidized condition being where distribution of the supply
positions of the gas is made dense to cause the raw material to be stirred in uniform contact
with the gas, the second fluidized condition being where the distribution of the supply
positions of the gas from the gas supply mechanism is made coarse to cause the raw material to
25 be stirred in non-uniform contact with the gas.
[0015] In the first fluidized condition, the distribution of the supply positions of the gas from
the gas supply mechanism becomes dense, so that the gas is uniformly supplied to the raw
material, which facilitates a good combustion reaction. In the second fluidized condition, the
5
distribution of the supply positions of the gas from the gas supply mechanism 3 becomes
coarse, so that regions where the raw material rises with the upward streams of the gas and
regions where the raw material falls in the absence of the gas supply are created, which
facilitates a good gasification reaction.
5 [0016] In addition to any one of the first to third features above, the apparatus for
manufacturing amorphous silica has a fourth feature that the heat treatment condition
adjustment mechanism includes a temperature adjustment mechanism configured to maintain a
combustion temperature in an interior of the reactor at or below a predetermined temperature
at which crystallization of the amorphous silica is inhibited.
10 [0017] If the temperature elevated by the combustion reaction of the biomass inside the
reactor exceeds a predetermined temperature, the amorphous silica may crystallize to produce
carcinogenic cristobalite. Even in such a case, the temperature adjustment mechanism adjusts
the combustion temperature at or below the predetermined temperature to prevent the
crystallization of amorphous silica and thus obtain amorphous silica in a stable manner.
15 [0018] A method for manufacturing amorphous silica is also provided in accordance with the
present invention, the method including a raw material supply step of supplying, by a raw
material supply mechanism, a raw material to a reactor and a gas supply step of supplying, by
a gas supply mechanism, steam and an oxygen-containing gas from a bottom of the reactor
where the raw material is retained, the method producing amorphous silica by heat-treating the
20 raw material while contacting the raw material with the steam and the oxygen-containing gas.
As a first feature of the method, the method includes a heat treatment condition adjustment
step of adjusting a percentage of carbon contained in the produced amorphous silica by
adjusting a ratio of the oxygen-containing gas supplied in the gas supply step to an amount of
the raw material supplied.
25 [0019] In addition to the first feature above, the method for manufacturing amorphous silica
has a second feature that the method further includes a fluidized condition adjustment step of
adjusting a fluidized condition of the raw material by adjusting at least one of a total amount,
arrangement of supply positions, and supply distribution of the gas supplied in the gas supply
6
step.
[0020] In addition to the first or second feature above, the method for manufacturing
amorphous silica has a third feature that the fluidized condition adjustment step is a step of
adjusting the fluidized condition to at least between a first fluidized condition and a second
5 fluidized condition, the first fluidized condition being where distribution of the supply
positions of the gas is made dense to cause the raw material to be stirred in uniform contact
with the gas, the second fluidized condition being where the distribution of the supply
positions of the gas is made coarse to cause the raw material to be stirred in non-uniform
contact with the gas.
10 [0021] In addition to any one of the first to third features above, the method for
manufacturing amorphous silica has a fourth feature that the heat treatment condition
adjustment step includes a temperature adjustment step of maintaining a combustion
temperature in an interior of the reactor at or below a predetermined temperature at which
crystallization of the amorphous silica is inhibited.
15
Advantageous Effects of Invention
[0022] As described above, the present invention provides an apparatus and method for
manufacturing amorphous silica using biomass derived from a silicicolous plant as a raw
material, the apparatus and method being capable of producing amorphous silica of different
20 purities for different applications.
Brief Description of Drawings
[0023] FIG. 1 illustrates an exemplary apparatus for manufacturing amorphous silica in
accordance with the present invention.
25 FIG. 2Aillustrates a plan view of a gas supply mechanism where heat treatment
involves primarily a combustion reaction, and FIG. 2B illustrates a cross-section of major
components of the gas supply mechanism.
FIG. 3Aillustrates a plan view of a gas supply mechanism where heat treatment
7
involves primarily a gasification reaction, and FIG. 3B illustrates a cross-section of major
components of the gas supply mechanism.
FIG. 4Aillustrates an apparatus for manufacturing amorphous silica where heat
treatment involves primarily a combustion reaction, and FIG. 4B illustrates a gas supply
5 mechanism thereof.
FIG. 5Aillustrates an apparatus for manufacturing amorphous silica where heat
treatment involves primarily a gasification reaction, and FIG. 5B illustrates a gas supply
mechanism thereof.
FIG. 6 illustrates a control device provided in the apparatus for manufacturing
10 amorphous silica.
FIG. 7A illustrates an upper air supply mechanism in accordance with another
embodiment, and FIG. 7B illustrates an upper air supply mechanism in accordance with still
another embodiment.
15 Description of Embodiments
[0024] An exemplary apparatus and method for manufacturing amorphous silica will be
described below.
[Configuration of Apparatus for Manufacturing Amorphous Silica]
FIG. 1 shows an apparatus 1 for manufacturing amorphous silica in accordance with
20 an aspect of the present invention. The amorphous silica manufacturing apparatus 1 includes,
among others, a reactor 2of a tubular body with a circular cross-section and including a tapered
section at its center in the vertical direction, the tapered section gradually reducing in diameter
from above downward, a raw material supply mechanism 4 to supply biomass derived from a
silicicolous plant as a raw material to the reactor 2, and a gas supply mechanism 3 to supply a
25 mixed gas of steam and air, which is an example of the oxygen-containing gas, from a lower
section of the reactor 2.The bottom of the reactor 2 is filled with a predetermined amount of
silica sand that forms an entrained bed.
[0025] The raw material supply mechanism 4 is configured with a screw conveyor
8
mechanism including a tubular casing and screw blades housed in the tubular casing, and the
casing is connected by a flange at its distal end to a side wall of the reactor 2 below the tapered
section. Although not shown, the casing is provided at its proximal end with a hopper
including a raw material metered supply mechanism.
5 [0026] Biomass filled in the hopper is supplied in a metered amount into the screw conveyor
mechanism by the metered supply mechanism and conveyed by the screw blades through the
casing in a consolidated form to befed into the reactor 2. A large amount of rice hulls, which
are produced from dehulling unhulled rice produced by farmers, is used as the biomass.
[0027] The gas supply mechanism 3 is configured with a header pipe 30 located alongside
10 the lower section of the reactor 2 and multiple diffuser pipes 31 having a circular cross-section
and connected to the header pipe 30 in a mutually parallel orientation. An air supply pipe 32
and a steam supply pipe 33 are connected to the header pipe 30, and a mixed gas of air and
steam is supplied to each of the diffuser pipes 31 through the header pipe 30. Saturated steam
or superheated steam is used as the steam.
15 [0028] The bottom of the reactor 2 is filled with a small amount of silica sand, and the mixed
gas supplied from the gas supply mechanism 3 forms an entrained bed 9 where the silica sand
is fluidized in the lower section of the reactor 2.In the entrained bed 9, the rice hulls, which are
the raw material, are heat-treated as they are stirred by the silica sand and heated by the steam
in the presence of air while being fluidized, resulting in the production of amorphous silica.
20 The heat treatment includes a combustion reaction, in which carbon components contained in
the rice hulls are bonded with oxygen, and a gasification reaction, in which carbon components
contained in the rice hulls react with the steam to produce carbon monoxide and hydrogen.
[0029] The amorphous silica that has been heat-treated into fine powder in the reactor 2
below its tapered section, i.e., in the reduced diameter section, rises in the reactor2 together
25 with the combustion exhaust gas and is discharged from an exhaust pipe 10 connected to the
top of the reactor 2. It should be noted that the flow rate of the combustion exhaust gas
decreases in the reactor 2 above its tapered section, i.e., in the increased diameter section, so
that insufficiently heat-treated rice hulls fall downward due to their own weight.
9
[0030] The amorphous silica discharged together with the combustion exhaust gas from the
exhaust pipe 10 is introduced into a cyclone 7, where the amorphous silica is separated from
the combustion exhaust gas and recovered. The combustion exhaust gas from which the
amorphous silica has been separated is subjected to secondary combustion in a secondary
5 combustion facility 8before being released to the atmosphere.
[0031]
[Configuration of Heat Treatment Condition Adjustment Mechanism]
The amorphous silica manufacturing apparatus 1 described above further includes a
heat treatment condition adjustment mechanism A. The heat treatment condition adjustment
10 mechanism A is a mechanism to adjust heat treatment conditions for the raw material supplied
to the reactor 2. The heat treatment condition adjustment mechanism A switches whether the
raw material is to undergo primarily a combustion reaction or a gasification reaction, thereby
adjusting the percentage of carbon contained in the produced amorphous silica even in the
same manufacturing apparatus 1.
15 [0032] High purity, white amorphous silica can be obtained by adjusting the heat treatment
condition adjustment mechanism A so as to cause primarily a combustion reaction, in which
impurities such as carbon contained in the raw material are sufficiently burned. Also, black
amorphous silica can be obtained by adjusting the heat treatment condition adjustment
mechanism A so as to cause primarily a gasification reaction with impurities such as carbon
20 contained in the raw material remaining.
[0033] As used herein, white silica shall refer to amorphous silica that contains less than 5
wt. % of carbon in the amorphous silica and is white or whitish in appearance, and black silica
shall refer to amorphous silica that contains more than 5 wt. % of carbon in the amorphous
silica and is black or dark in appearance.
25 [0034] White silica is effectively used for industrial materials such as white cosmetic raw
materials, adsorbents, and additives for white paints, resins etc., as well as agricultural
materials such as fertilizers for supplying silica to crops. Black silica is effectively used for
industrial materials such as black cosmetics raw materials, adsorbents, additives for black
10
paints, resins, etc., and additives for tires, as well as agricultural materials such as fertilizers for
supplying silica and carbon to crops.
[0035] The heat treatment condition adjustment mechanism A includes an oxygen-containing
gas ratio adjustment mechanism and a fluidized condition adjustment mechanism. The
5 oxygen-containing gas ratio adjustment mechanism (or an air ratio adjustment mechanism in
the present embodiment because air is used as the oxygen-containing gas) adjusts the ratio of
the oxygen-containing gas supplied from the gas supply mechanism 3 to the amount of raw
material supplied. The fluidized condition adjustment mechanism adjusts the fluidized
condition of the raw material in the entrained bed formed inside the reactor 2 by adjusting at
10 least one of a total amount, arrangement of supply positions, and supply distribution of the gas
supplied from the gas supply mechanism 3.
[0036] Increasing the total gas amount leads to the raw material being more intensely
fluidized, and decreasing the total gas amount leads to the raw material being more gently
fluidized. Adjusting the distribution of nozzles, which define the gas supply positions, to make
15 it dense allows the raw material to be stirred in uniform contact with the gas. Adjusting the
distribution of the nozzles, which define the gas supply positions, to make it coarse allows the
raw material to be stirred in non-uniform contact with the gas. Adjusting the gas supply
distribution to make it dense allows the raw material to be stirred in uniform contact with the
gas. Adjusting the gas supply distribution to make it coarse allows the raw material to be
20 stirred in non-uniform contact with the gas. For example, even with the same distribution of
the gas supply positions, the gas supply distribution can be adjusted by individually varying
the gas supply amount emitted from each nozzle.
[0037] FIGS. 2A and 2B show a gas supply mechanism 3(3A) for obtaining white silica by
generating primarily a combustion reaction in the reactor 2. FIGS. 3A and 3B show a gas
25 supply mechanism 3(3B) for obtaining black silica by generating primarily a gasification
reaction in the reactor 2. As described above, the gas supply mechanisms 3 (3a, 3b) each
include the header pipe 30 located alongside the lower section of the reactor 2 and the multiple
diffuser pipes 31 having a circular cross-section and connected to the header pipe 30 in a
11
mutually parallel orientation. The air supply pipe 32 and the steam supply pipe 33 are
connected to the header pipe 30, and a mixed gas of air and steam is supplied to each of the
diffuser pipes 31 through the header pipe 30.
[0038] Each diffuser pipe 31 is supported by an attachment 31F having an arc-shaped cross
5 section and extending along the lower peripheral wall of the reactor 2. The attachment 31F is
shaped to cover an arc-shaped cutaway portion formed in the lower side wall of the reactor 2.
The attachment 31F is secured to the side wall of the reactor 2 with the distal end of each
diffuser pipe 31 entering the reactor 2, resulting in the multiple diffuser pipes 31 being secured
to the reactor 2 in a mutually parallel orientation.
10 [0039] As shown in FIGS. 2A and 2B, the diffuser pipes 31, which constitute the gas supply
mechanism 3 (3A) for combustion reactions, are small in diameter and include a large number
of pipes so that the rice hulls supplied from the raw material supply mechanism 4 are stirred
and burned uniformly without creating local high-temperature regions in any plane
perpendicular to the axis of the reactor 2.
15 [0040] More in detail, each diffuser pipe 31 includes, as the nozzles, bi-directional jets
31Hfor the mixed gas that are inclined downward at an angle θ relative to the horizontal
direction. The jets 31H formed in each diffuser pipe 31 are arranged to provide a substantially
constant pitch L2 in the axial direction and the direction intersecting the axial direction, and a
pitch L3 between two adjacent diffuser pipes 31 is set to L3≈2L2 so that the jets 31H are at a
20 substantially constant pitch along the direction intersecting the axial direction.
[0041] The mixed gas discharged from the jets 31H downwardly in the reactor 2 blows the
silica sand upward to form the entrained bed, uniformly stirring the rice hulls supplied from the
raw material supply mechanism 4. The angle θ is in the range of 30° to 60°, preferably in the
range of 40° to 50°, centered about45°. The diameter of each diffuser pipe 31and the number
25 of diffuser pipes 31 are set according to the diameter of the lower section of the reactor 2. For
example, if the diameter L1 of the lower section of the reactor 2 is in the range of 300 mm to
1800 mm, the diameter of each diffuser pipe 31 can be selected from the range of 20A (27.2
mm) to 80A (89.1 mm) and the number of diffuser pipes 31 can be selected from the range of 6
12
to 30.
[0042] As shown in FIGS. 3A and 3B, the diffuser pipes 31, which constitute the gas supply
mechanism 3 (3B) for gasification reactions, are large in diameter and include a small number
of pipes so that the rice hulls supplied from the raw material supply mechanism 4 are greatly
5 stirred by being non-uniformly fluidized in any plane perpendicular to the axis of the reactor 2.
[0043] More in detail, each diffuser pipe 31 includes, as the nozzles, bi-directional jets
31Hfor the mixed gas that are inclined downward at an angle θ relative to the horizontal
direction and a vertically downwardly directed jet 31H. The jets 31H formed in each diffuser
pipe 31 are arranged to provide a substantially constant pitch L2 in the axial direction and the
10 direction intersecting the axial direction, and a pitch L3 between two adjacent diffuser pipes 31
is set to L3> L2.
[0044] The mixed gas discharged from the jets 31H downwardly in the reactor 2 blows the
silica sand upward to form the entrained bed, swirling upward and stirring the rice hulls
supplied from the raw material supply mechanism 4.Since the pitch L3 is set to L3 > L2, the
15 rice hulls are greatly stirred as they are non-uniformly fluidized along a large circulation path
in which the rice hulls are swirled upward by the mixed gas and fall through regions between
the diffuser pipes 31 where the upward streams are weak.
[0045] The angle θ is in the range of 30° to 60°, preferably in the range of 40° to 50°,
centered about 45°.The diameter of each diffuser pipe 31and the number of diffuser pipes 31
20 are set according to the diameter of the lower section of the reactor 2.For example, if the
diameter of the lower section of the reactor 2 is in the range of 300 mm to 1800 mm, the
diameter of each diffuser pipe 31 can be selected from the range of 40A (48.6 mm) to 80A
(89.1 mm) and the number of diffuser pipes 31 can be selected from the range of 3 to 6.
[0046] In other words, the gas supply mechanisms 3 (3A, 3B) each constitute the fluidized
25 condition adjustment mechanism, and the fluidized condition of the rice hulls can be adjusted
depending on which of the gas supply mechanisms 3A or 3B is used, allowing for switching
whether the rice hulls are to undergo primarily a combustion reaction or a gasification reaction.
Replacing the gas supply mechanism 3B with the gas supply mechanism 3A allows the raw
13
material to undergo primarily a combustion reaction, and replacing the gas supply mechanism
3A with the gas supply mechanism 3B allows the raw material to undergo primarily a
gasification reaction. That is, the gas supply mechanisms 3 (3A, 3B) execute the fluidized
condition adjustment step of adjusting the fluidized condition of the raw material fluidized in
5 the entrained bed. It should be noted that the above values of L1, L2, and L3 are given by way
of example and not limiting.
[0047] In other words, the fluidized condition adjustment mechanism is configured to be
capable of adjusting the fluidized condition to one of a first fluidized condition and a second
fluidized condition, the first fluidized condition being where the distribution of the supply
10 positions of the gas from the gas supply mechanism 3 is made dense to stir the raw material in
uniform contact with the gas to cause the raw material to undergo primarily a combustion
reaction, the second fluidized condition being where the distribution of the supply positions of
the gas from the gas supply mechanism 3 is made coarse to stir the raw material in
non-uniform contact with the gas to cause the raw material to undergo primarily gasification
15 reaction.
[0048] In the first fluidized condition, the distribution of the supply positions of the gas from
the gas supply mechanism 3 becomes dense, so that gas is uniformly supplied to the raw
material, which facilitates a good combustion reaction. In the second fluidized condition, the
distribution of the supply positions of the gas from the gas supply mechanism 3 becomes
20 coarse, so that regions where the raw material rises with the upward streams of the gas and
regions where the raw material falls in the absence of gas supply are created, which facilitates
a good gasification reaction.
[0049] In the first fluidized condition, the distribution of the supply positions of the air from
the gas supply mechanism 3 in a plan view becomes dense, so that the rice hulls is fluidized
25 uniformly in the fluidized layer and the space there above to have stable contact with the air,
which facilitates a good combustion reaction. In the second fluidized condition, the distribution
of the supply positions of the air from the gas supply mechanism 3 in a plan view becomes
coarse, so that regions where large upward streams for the rice hulls occur in the presence of
14
air supply and regions where downward streams for the rise hulls occur in the absence of air
supply are created. Thus, the rice hulls are stirred as they repeatedly and non-uniformly rise
and fall in the fluidized layer and the space there above, which facilitates a good gasification
reaction.
5 [0050] While the above description has discussed an example of adjusting the distribution of
the gas supply positions to adjust the fluidized condition, at least one of the total gas amount,
the arrangement of gas supply positions, and the gas supply distribution may be adjusted to
adjust the fluidized condition. Some or all of the total gas amount, the arrangement of gas
supply positions, and the gas supply distribution may be adjusted in combination.
10 [0051] Returning to FIG. 1, compressed air supplied from a compressor or a blower fan is
supplied to the air supply pipe 32 connected to the header pipe 30, and the amount of
compressed air supplied is regulated by a valve 32V (which may alternatively be a damper)
provided in the air supply pipe 32. Superheated steam generated by a heat exchanger provided
in the secondary combustion facility 8 or superheated steam generated by a heat recovery
15 mechanism 5, which is a heat exchanger provided in the reactor 2, is supplied to the steam
supply pipe 33 connected to the header pipe 30, and the amount of steam supplied is regulated
by a valve 33V (which may alternatively be a damper) provided in the steam supply pipe
33.Reference numeral 34 denotes a steam flow meter.
[0052] The valve 32Vfunctions as an air ratio adjustment mechanism and adjusts the ratio of
20 air to the rice hulls supplied from the raw material supply mechanism 4. This adjustment
allows the rice hulls to undergo either a combustion reaction or a gasification reaction.
[0053] The air ratio adjustment mechanism is a mechanism to adjust the ratio of air to the
rice hulls between a first range and a second range, the first range being where the ratio is
greater than the theoretical air ratio of 1 to cause the rice hulls to undergo primarily a
25 combustion reaction, the second range being where the ratio is less than the theoretical air ratio
of 1to cause the rice hulls to undergo primarily a gasification reaction. As such, the air ratio
adjustment mechanism executes the air ratio adjustment step.
[0054] By adjusting the air ratio to the rice hulls to within the first range of values greater
15
than the theoretical air ratio of 1, the rice hulls can undergo a good combustion reaction. By
adjusting the air ratio to the rice hulls to within the second range of values less than the
theoretical air ratio of 1, the rice hulls can undergo a good gasification reaction.
[0055] The first range of air ratio is preferably from 1.3 to 1.5.If the air ratio is less than 1.3,
5 carbon components will remain in the silica, making it impossible to obtain high quality white
silica. If the air ratio is greater than 1.5, the amount of heat carried out by excess air will
increase and the combustion temperature will thus decrease, making it impossible to maintain
good combustion conditions. The second range of air ratio is preferably from 0.2 to 0.5. If the
air ratio is less than 0.2, pyrolysis will not be facilitated. If the air ratio is greater than 0.5,
10 some of the carbon will be burned, making it impossible to obtain good black silica.
[0056] When a gas other than air, such as oxygen-enriched air, is used as the
oxygen-containing gas, an oxygen-containing gas ratio adjustment mechanism can be used to
adjust the ratio of the oxygen-containing gas to the raw material to within a first range where
air ratio-equivalent values are greater than the theoretical air ratio of 1 to allow the raw
15 material, or the rice hulls, to undergo a good combustion reaction, or to within a second range
where air ratio-equivalent values are less than the theoretical air ratio of 1 to allow the raw
material, or the rice hulls, to undergo a good gasification reaction. The use of oxygen-enriched
air leads to a reduced gas amount. Accordingly, the total amount of gas supplied from the gas
supply mechanism may be controlled to adjust the fluidized condition of the raw material.
20 [0057] Similarly, the first range is preferably from 1.3 to 1.5, and the second range is
preferably from 0.2 to 0.5.
[0058] FIGS. 4A and 4B show the manufacturing apparatus 1 and the gas supply mechanism
3A, where the heat treatment condition adjustment mechanism performs an adjustment to
cause the rice hulls to undergo primarily a combustion reaction to obtain white amorphous
25 silica. A control device (see FIG. 6.) adjusts the opening of the valve 32V to cause the air ratio
to fall within the range of 1.3 to 1.5, thereby adjusting the temperature in the reduced diameter
section below the tapered section of the reactor 2 to fall within the range of 500°C to 600°C.
The control device also adjusts the amount of air supplied from the upper air supply
16
mechanism 6 and the amount of heat recovered by the heat recovery mechanism 5 via the
valve 6V and the valve 5V, respectively, to cause the temperature in the increased diameter
section above the tapered section of the reactor 2 to fall within the range of 750°C to 800°C.
To this end, outputs from a first temperature sensor TH1 and a second temperature sensor TH2
5 installed downstream and upstream, respectively, of the heat recovery mechanism 5 are input
to the control device.
[0059] The combustion reaction at this time is expressed by the following reaction formulae.
C+O2 → CO2
CO+(1/2)･O2 → CO2
10 [0060] FIGS. 5A and 5B show the manufacturing apparatus 1 and the gas supply mechanism
3B, where the heat treatment condition adjustment mechanism performs an adjustment to
cause the rice hulls to undergo primarily a gasification reaction to obtain black amorphous
silica. A control device (not shown) adjusts the opening of the valve 32V to cause the air ratio
to fall within the range of 0.2 to 0.5. The control device also adjusts, among others, the
15 amount of air supplied from the upper air supply mechanism 6 via the valve 6Vto cause the
temperature in the reduced diameter section of the reactor 2 to fall within the range of 500°C to
600°C and to cause the temperature in the increased diameter section of the reactor 2 to fall
within the range of 700°C to 750°C. At this time, superheated steam generated by the heat
exchanger provided in the secondary combustion facility 8 is used as the steam supplied to the
20 steam supply pipe 33.
[0061] The gasification reaction at this time is primarily an aqueous gas reaction, which is
expressed by the following reaction formula.
[0062] As indicated by the following formula, the aqueous gas reaction refers to an
endothermic reaction in which carbon monoxide CO and hydrogen H2 are produced from solid
25 carbon C, which is biomass, and steam H2O in a high temperature environment of 500°C or
higher. Supplying a small amount of air to the reactor 2 in addition to steam provides the
necessary reaction heat through combustion of some of the rice hulls and maintains the high
temperature environment of 500°C or higher in the reactor 2.
17
C+H2O → CO+H2
[0063] In the present embodiment, superheated steam of120°C to 160°C is supplied from the
steam supply pipe 33 at a pressure of 1 MPa or less.
Steam supplied to the reactor 2 is used for initial heating of the raw material, for
5 activation including increasing the specific surface area of silica through an aqueous gas
reaction or combustion reaction, and for inhibiting any abnormal rise in ambient temperature
in the reactor 2 due to subsequent combustion reactions, and the amount of steam supplied is
appropriately regulated with the valve 33V. In the case of causing primarily an aqueous gas
reaction, the ratio of steam is increased to facilitate activation, and the oxygen-containing gas
10 is supplied in a minimum amount enough to maintain the reactor temperature. In the case of
causing primarily a combustion reaction, the ratio of oxygen-containing gas is increased to
facilitate the combustion reaction, and the steam has the effect of inhibiting the creation of
local high-temperature fields due to the combustion reaction.
[0064] In the present embodiment, rice hulls are used as biomass. Rice hulls contain about
15 70% carbohydrates, such as cellulose, hemicellulose, and lignin, about 15-20% silica, with the
balance being dominantly water and trace amounts of alkali impurities. The present invention
is suitable for recycling such silica-containing biomass as a resource. Therefore, the invention
is applicable not only to rice hulls but also is applicable to the use of biomass derived from
silicicolous plants such as rice straw, wheat straw, bamboo, corn, sugarcane, silver grass, and
20 horsetail.
[0065] That is, the amorphous silica manufacturing apparatus 1 described above implements
the method for manufacturing amorphous silica, the method including the raw material supply
step of supplying, by the raw material supply mechanism, the raw material to the reactor and
the gas supply step of supplying, by the gas supply mechanism, steam and the
25 oxygen-containing gas from the lower section of the reactor where the raw material is retained,
the method producing the amorphous silica by heat-treating the raw material while contacting
it with the steam and the oxygen-containing gas.
[0066] The heat treatment condition adjustment mechanism executes the heat treatment
18
condition adjustment step, and the oxygen-containing gas ratio adjustment mechanism (air
ratio adjustment mechanism) provided in the heat treatment condition adjustment mechanism
executes the oxygen-containing gas ratio adjustment step (air ratio adjustment step), whereby
the ratio of the oxygen-containing gas supplied in the gas supply step to the amount of raw
5 material supplied is adjusted to control the percentage of carbon contained in the amorphous
silica produced.
[0067] The fluidized condition adjustment mechanism executes the fluidized condition
adjustment step of adjusting the fluidized condition of the raw material by adjusting at least
one of the total amount, the arrangement of supply positions, and the supply distribution of the
10 gas supplied in the gas supply step.
[0068] Additionally, the heat treatment condition adjustment mechanism includes the
temperature adjustment mechanism to maintain the combustion temperature in the interior of
the reactor 2 at or below a predetermined temperature, specifically at or below about 800°C,
when causing the rice hulls to undergo a combustion reaction. The heat recovery mechanism 5
15 provided in the reactor 2 functions as the temperature adjustment mechanism. That is, when
the raw material is caused to undergo a combustion reaction, the heat recovery mechanism 5
executes the temperature adjustment step of maintaining the combustion temperature in the
interior of the reactor 2 at or below a predetermined temperature at which crystallization of
amorphous silica is inhibited.
20 [0069] If the reactor temperature exceeds the above predetermined temperature due to the
exothermic combustion reaction of the rice hulls in the reactor 2, the amorphous silica may
crystallize to produce carcinogenic cristobalite. Even in such a case, the heat recovery
mechanism 5 adjusts the combustion temperature at or below the predetermined temperature to
prevent the crystallization of amorphous silica and thus obtain amorphous silica in a stable
25 manner. When the rice hulls are caused to undergo primarily a gasification reaction inside the
reactor 2, the combustion temperature in the interior of the reactor 2 may be kept at or below
the predetermined temperature even without the heat recovery mechanism 5 because the
gasification reaction is an endothermic reaction. However, if any accompanying combustion
19
reaction may cause the temperature to exceed the above predetermined temperature, the heat
recovery mechanism 5 may be provided as well.
[0070] FIG. 6 shows a configuration of a control device C to control the amorphous silica
manufacturing apparatus 1. The control device C receives sensor values from the first
5 temperature sensor TH1, the second temperature sensor TH2, the steam flow meter 34, and a
steam temperature sensor TH3thatdetects the temperature of steam output from the boiler
provided in the secondary combustion facility 8.The control device C also receives an
identification signal indicative of whether the heat treatment condition adjusted by the heat
treatment condition adjustment mechanism is to facilitate primarily a combustion reaction or a
10 gasification reaction.
[0071] When the heat treatment condition adjusted by the heat treatment condition
adjustment mechanism is to facilitate primarily a combustion reaction, the control device C
adjusts, based on the value of the second temperature sensor TH2, the opening of the valve
32V and the opening of the valve 6V to adjust the amount of air supplied by the upper air
15 supply mechanism 6 and also adjusts the opening of the valve 33V so that the combustion
temperature in the reduced diameter section of the reactor 2 falls within the range of 500°C to
600°C. Further, the control device C adjusts, based on the value of the first temperature
sensor TH1, the opening of the valve 5V to adjust the flow rate of boiler water supplied to the
heat recovery mechanism 5 so that the combustion temperature in the increased diameter
20 section of the reactor 2 falls within the range of 750°C to 800°C, in other words, is lower than
the phase transition temperature range in which amorphous silica crystallizes.
[0072] For example, the temperature in the reactor 2 can be lowered by reducing the air
supply from the air supply mechanism, and the temperature in the increased diameter section
of the reactor 2 can be lowered by increasing the flow rate of boiler water, thus allowing the
25 combustion temperature to be adjusted not to exceed the predetermined temperature.
[0073] When the heat treatment condition adjusted by the heat treatment condition
adjustment mechanism is to facilitate primarily a gasification reaction, the control device C
adjusts the opening of the valve 32V and the amount of air supply from the upper air supply
20
mechanism 6 and also adjusts the opening of the valve 33V based on the value of the second
temperature sensor TH2 so that the combustion temperature in the reduced diameter section of
the reactor 2 falls within the range of 500°C to 600°C, and based on the value of the first
temperature sensor TH1so that the combustion temperature in the increased diameter section
5 of the reactor 2 falls within the range of 700°C to 750°C.
[0074] Similarly to the above, the temperature in the reactor 2 can be lowered by reducing
the air supply from the air supply mechanism, and the temperature in the increased diameter
section of the reactor 2 can be lowered by increasing the flow rate of boiler water, thus
allowing the combustion temperature to be adjusted not to exceed the predetermined
10 temperature. It should be noted that, in this case, the flow rate of boiler water supplied to the
heat recovery mechanism 5 need not be adjusted if the combustion temperature in the
increased diameter section will not exceed 800°C. The second temperature sensor TH2 may be
located at any position where it can monitor the temperature in the reduced diameter section,
and thus may be installed either in the reduced diameter section or in the increased diameter
15 section as long as it is located upstream of the heat recovery mechanism 5.
[0075] In FIGS. 1, 4, and 5, the upper air supply mechanism 6 for adjusting the combustion
conditions in the space above the entrained bed 9 is illustrated as having the air supply pipe
that is inserted through the side wall of the reactor 2 near its tapered section and provided at its
distal end with the air supply nozzle for supplying air downwardly from the center of the
20 reactor 2. However, the configuration of the upper air supply mechanism 6 is not limited to
this example and may be configured as needed according to the size of the reactor 2 and other
factors.
[0076] For example, as shown in FIG. 7A, an air supply pipe provided at its distal end with
an air supply nozzle may be installed extending down through the top of the reactor 2. As
25 shown in FIG. 7B, multiple air supply nozzles may be installed near the tapered section of the
reactor 2. For example, multiple air supply nozzles can be evenly arranged on concentric
circles in a plan view.
[0077] In the above embodiments, the gas supply mechanism 3 is illustrated as being
21
configured to supply a mixed gas of steam and air, which is an example of the
oxygen-containing gas. However, the gas supply mechanism 3 may be configured to
individually supply the steam and the oxygen-containing gas, as long as the gas supply
mechanism 3 includes both of the oxygen-containing gas ratio adjustment mechanism and the
5 fluidized condition adjustment mechanism described above.
[0078] While the above embodiments have illustrated the formation of the entrained bed
inside the reactor 2 to cause the raw material to be stirred and be fluidized with the silica sand
in the entrained bed for heat treatment of the raw material, a fluidized bed may be formed near
the bottom of the reactor 2 to cause the raw material to be stirred and be fluidized with the
10 silica sand in the fluidized bed. In either case, the particle size of the silica sand is preferably
in the range of 0.05 mm to 2 mm to ensure good contact between the raw material and the gas
in the entrained bed or fluidized bed. It is not essential to introduce the silica sand into the
reactor 2 as long as the raw material can be heat-treated while in contact with the gas inside the
reactor 2.
15 [0079] It will be appreciated that the description of the above embodiments is given for
purposes of illustration of some specific examples of the apparatus and method for
manufacturing amorphous silica in accordance with the present invention. The description
does not limit the scope of the present invention, and specific configurations of the elements
may be varied as suited, as long as such variations provide the functions and effects of the
20 present invention as well.
Reference Signs List
[0080] 1: Apparatus for manufacturing amorphous silica
2: Reactor
25 3: Gas supply mechanism
30: Header pipe
31: Diffuser pipe
32: Air supply pipe
22
32V: Valve
33: Steam supply pipe
33V: Valve
4: Raw material supply mechanism
5 5: Heat recovery mechanism
6: Upper air supply mechanism
7: Cyclone
8: Secondary combustion facility
9: Entrained bed
10 10: Exhaust pipe
A: Heat treatment condition adjustment mechanism

\\ e Claim;
I . An apparatus for manufacturing amorphous silica including a reactor, a raw material
supply mechanism configured to supply biomass derived from a silicicolous plant as a raw
material to the reactor, and a gas supply mechanism configured to supply steam and an
oxygen-containing gas from a bottom ofthe reactor where the raw material is retained, the
apparatus being configured to produce amorphous silica by heat-treating the raw material
rrhilc contacting the ravv material with the steam and the oxygen-containing gas, the apparatus
comprising:
a heat treatment condition adjustrnent mechanism configured to adjus a percentage of
carbon contained in the produced amorphous silica by adjusting a ratio ofthe
oxygen-conlaining gas supplied from the gas supply mechanism to an amount ofthe raw
material supplied.
10
I ;) l. The apparatus for manufacturing amorphous silica according to claim 1, further
conrprising a lluidized condition adjustment mechanism configured to adjust a fluidized
condition ofthe raw material by adjusting at least one ofa total amount, arrangement of supply
positions. :rnd suppll'distribution olthe gas supplied from the gas supply mechanism.
20 3. The apparatus lor manufacturing amorphous silica according to claim 2, wherein the
fluidized condition adjustment mechanism is conligured to be capable ofadjusting the
fluidized condition to at least a first fluidized condition and a second fluidized condition, the
first fluidized condition being where distribution ofthe supply positions ofthe gas is made
dense to cause the raw material to be stined in uniform contact with the gas, the second
25 fluidized condition being where the distribution ofthe supply positions ofthe gas from the gas
supplv rnechanism is made c()arse to cause the raw material to be stirred in non-uniform
cr,Itaet $ ith thc gds.
23
5
4. The apparatus for manufacturing amorphous silica according to any one of claims 1 to
3. wherein the heat treatment condition adjustnent mechanism comprises a temperature
adiustment mechanism configured to maintain a combustion temperature in an interior of the
reactor ar or below a predetermined temperature at which crystallization of the amorphous
silica is inhibited.
5. A method tbr manulacturing amorphous silica including a raw material supply step of
supplr irrg. [r-r a rau nratcrial supply mcchanism, a raw material to a reactor and a gas supply
step ofsupplying, by a gas supply mechanism, steam and an oxygen-containing gas from a
bottom ofthe reactor where the raw material is retained, the method producing amorphous
silica by heat-treating the raw material while contacting the raw material with the steam and
the oxygen-containing gas, the method comprising:
a heat treatment condition adjustment step of adjusting a percentage of carbon
contained in the produced amorphous silica by adjusting a ratio of the oxygen-containing gas
supplied in the gas supply step to an amount ofthe raw material supplied.
6. The method for manufacturing amorphous silica according to claim 5, further
comprising a fluidized condition adjustment step ofadjusting a fluidized condition ofthe raw
material by ad.iusting at least one ofa total amount, arrangement of supply positions, and
supply distribution ofthe gas supplied in the gas supply step.
10
20
1 i)
7. The method for manufacturing amorphous silica according to claim 6, wherein the
lluidized condition adjustment step is a step of adjusting the fluidized condition to at least
between a first fluidized condition and a second fluidized condition, the fust fluidized
25 condition being where distribution ofthe supply positions ofthe gas is made dense to cause the
rau material to be stirred in uniform contact with the gaS. the second fluidized condition being
ulterc the distribution ofthe supply positiorrs ofthe gat iS inadb corirse to cause the raw
material to be stirred in non-uniform contact with the gas.
24
i)
8. The method fbr manufacturing amorphous silica according to any one of claims 5 to
7. wherein the heat treatment condition adiustment step comprises a temperafure adjustrnent
srep o1'maintaining a combustion temperatue in an interior of the reactor at or below a
predetermrned temperature at which crystallization of the amorphous silica is inhibited.