Apparatus for producing amorphous silica and method for producing amorphous silica

Abstract

To provide an apparatus for producing an amorphous silica which can produce an amorphous silica having different degrees of purity according to various applications using a biomass derived from a silicic acid plant as a raw material.SOLUTION: An apparatus for producing an amorphous silica, which includes a reaction furnace 2, a raw material supply mechanism 4 for supplying a biomass derived from a silicic acid plant as a raw material to the reaction furnace 2, and a gas supply mechanism 3 for supplying water vapor and oxygen-containing gas from the lower part of the reaction furnace 2, and produces an amorphous silica by heat-treating the raw material while being brought into contact with gas supplied through the gas supply mechanism 3, includes a heat treatment state adjustment mechanism A for adjusting a ratio of carbon contained in the amorphous silica produced by adjusting a ratio of the oxygen-containing gas supplied from the gas supply mechanism to a supply amount of the raw material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a reactor, a raw material supply mechanism for supplying biomass derived from siliceous plants to the reactor as a raw material, a gas supply mechanism for supplying steam and oxygen-containing gas from below the reactor, and an apparatus for producing amorphous silica and a method for producing amorphous silica, which produce amorphous silica by heat treatment while contacting with the gas supplied through the gas supply mechanism.

Background Art

[0002] Patent Document 1 proposes a method and an apparatus for producing amorphous silica that can efficiently recover energy and obtain high-quality silica with high purity using biomass derived from siliceous plants as a raw material.

[0003] The method for producing amorphous silica includes a gasification step of thermally decomposing and gasifying biomass derived from siliceous plants, and a firing step of firing the biomass residue generated in the gasification step.

[0004] The apparatus for producing amorphous silica includes a gasification furnace for thermally decomposing and gasifying biomass containing siliceous plants, a separation mechanism for separating biomass residue from a mixture of pyrolysis gas and biomass residue discharged from the gasification furnace, and a firing furnace for firing the biomass residue separated by the separation mechanism to obtain amorphous silica.

[0005] According to the above-described method for producing amorphous silica, the biomass derived from siliceous plants is thermally decomposed and recovered as fuel in the gasification step, and impurities such as carbon components remaining in the biomass residue are removed by firing the remaining biomass residue, and white amorphous silica with high purity can be obtained.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The method for producing amorphous silica disclosed in Patent Document 1 is a production method and a production apparatus for obtaining high-purity amorphous silica by removing impurities such as a carbon component.

[0008] However, there has been found a use in which amorphous silica containing impurities such as a carbon component can be effectively utilized as a recycled resource, and a shared production apparatus capable of producing amorphous silica having different purities according to the use is desired.

[0009] An object of the present invention is to provide an apparatus for producing amorphous silica and a method for producing amorphous silica, in which amorphous silica having different purities can be obtained according to various uses, using biomass derived from siliceous plants as a raw material.

MEANS FOR SOLVING THE PROBLEMS

[0010] To achieve the above object, a first characteristic configuration of an apparatus for producing amorphous silica according to the present invention includes a reactor, a raw material supply mechanism for supplying biomass derived from siliceous plants to the reactor as a raw material, a gas supply mechanism for supplying steam and an oxygen-containing gas from the bottom of the reactor where the raw material stays, and an apparatus for producing amorphous silica that generates amorphous silica by heat-treating while bringing the raw material into contact with the steam and the oxygen-containing gas and flowing it, The gas supply mechanism includes a plurality of ejection holes for ejecting the gas. supplied from the gas supply mechanism In plan view, the of the gas distribution of the ejection holes or the difference in the supply amount of the gas ejected from each of the ejection holes It is characterized in that it is provided with a flow state adjusting mechanism for adjusting the flow state of the raw material by adjusting at least one of the supply distributions and adjusting the ratio of carbon contained in the generated amorphous silica.

[0011] Using a production apparatus including a reactor, a raw material supply mechanism, and a gas supply mechanism, during heat treatment, through a flow state adjusting mechanism, The supply distribution, which is the distribution of the ejection holes of the gas in plan view supplied from the gas supply mechanism or the difference in the supply amount of the gas ejected from each of the ejection holes By adjusting at least any one of them, the flow state of the raw material is adjusted, and amorphous silica having different properties is produced.

[0012] In addition to the first characteristic configuration described above, the second characteristic configuration further includes a heat treatment state adjustment mechanism that adjusts the ratio of carbon contained in the amorphous silica produced by adjusting the ratio of the oxygen-containing gas supplied from the gas supply mechanism to the supply amount of the raw material.

[0013] By adjusting the ratio of the oxygen-containing gas to the supply amount of the raw material through the heat treatment state adjustment mechanism during heat treatment, the ratio of carbon contained in the amorphous silica can be adjusted, and amorphous silica having different properties can be produced. For example, white amorphous silica with high purity or black amorphous silica containing carbon can be obtained.

[0014] In addition to the first or second characteristic configuration described above, the third characteristic configuration is such that the flow state adjustment mechanism includes the gas supplied by the gas supply mechanism The ejection holes The distribution of is made dense to stir the raw material in a state where the contact opportunity with the gas is uniform, and the distribution of the gas supplied by the gas supply mechanism The ejection holes Is made rough to stir the raw material in a state where the contact opportunity with the gas is non-uniform, and is at least adjustable to the first flow state and the second flow state.

[0015] In the first flow state, the distribution of the gas supplied from the gas supply mechanism Ejection holes Becomes dense, the gas is uniformly supplied to the raw material, and a good combustion reaction is promoted. In the second flow state, the distribution of the gas supplied from the gas supply mechanism Ejection holes Becomes rough, and a region where the raw material rises along with the upward flow of the gas and a region where the raw material descends without the gas being supplied are generated, and a good gasification reaction is promoted.

[0016] The fourth characteristic configuration is the above-mentioned first Two In addition to the characteristic configuration, the heat treatment state adjustment mechanism includes a temperature adjustment mechanism that maintains the combustion temperature in the internal space of the reactor at a predetermined temperature or lower that suppresses the crystallization of the amorphous silica.

[0017] If the temperature that rises due to the combustion reaction of biomass inside the reactor exceeds the predetermined temperature, there is a risk that amorphous silica will crystallize and cristobalite, which exhibits carcinogenicity, will be generated. Even in such a case, by adjusting the combustion temperature to a predetermined temperature or lower by the temperature adjustment mechanism, crystallization of the amorphous silica can be prevented and amorphous silica can be stably obtained.

[0018] Further, the first characteristic configuration of the method for producing amorphous silica according to the present invention is a raw material supply step of supplying a raw material to a reactor by a raw material supply mechanism, a gas supply step of supplying steam and an oxygen-containing gas from the bottom where the raw material in the reactor stays by a gas supply mechanism, and a method for producing amorphous silica by heat-treating while bringing the raw material into contact with the steam and the oxygen-containing gas and flowing it, The gas supply mechanism includes a plurality of ejection holes for ejecting the gas. in the In plan view, the gas distribution of the ejection holes or the difference in the supply amount of the gas ejected from each of the ejection holes It is provided with a flow state adjustment step of adjusting the flow state of the raw material by adjusting at least one of the supply distributions to adjust the ratio of carbon contained in the produced amorphous silica.

[0019] The second characteristic configuration is, in addition to the first characteristic configuration described above, a heat treatment state adjustment step of adjusting the ratio of carbon contained in the produced amorphous silica by adjusting the ratio of the oxygen-containing gas supplied in the gas supply step to the supply amount of the raw material.

[0020] The third characteristic configuration is, in addition to the first or second characteristic configuration described above, the flow state adjustment step includes the The ejection holes distribution of the gas supplied in the gas supply step to make it dense and stir the raw material in a state where the contact opportunity with the gas is uniform, a first flow state, and the The ejection holes The step is at least to coarsen the distribution and stir the raw material in a state where the contact opportunity with the gas is non-uniform, i.e., the second flow state.

[0021] The same fourth characteristic configuration is the above-mentioned first Two In addition to the characteristic configuration, the heat treatment state adjustment step includes a temperature adjustment step of maintaining the combustion temperature in the internal space of the reactor below a predetermined temperature that suppresses the crystallization of the amorphous silica.

Advantages of the Invention

[0022] As described above, according to the present invention, it has become possible to provide an apparatus for producing amorphous silica and a method for producing amorphous silica in which amorphous silica having different purities can be obtained according to various applications using biomass derived from siliceous plants as a raw material.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0024] Hereinafter, an example of an apparatus for producing amorphous silica and a method for producing amorphous silica according to the present invention will be described. [Configuration of the apparatus for producing amorphous silica] FIG. 1 shows one aspect of an apparatus 1 for producing amorphous silica according to the present invention. The apparatus 1 for producing amorphous silica includes a cylindrical reactor 2 having a constriction formed in the central portion in the vertical direction and having a reduced diameter at the lower part than at the upper part, a raw material supply mechanism 4 for supplying a biomass derived from siliceous plants to the reactor 2 as a raw material, a gas supply mechanism 3 for supplying a mixed gas of steam and air, which is an example of an oxygen-containing gas, from below the reactor 2, etc. A predetermined amount of silica sand for forming a fluidized bed is filled at the bottom of the reactor 2.

[0025] The raw material supply mechanism 4 is composed of a screw conveyor mechanism including a cylindrical casing and screw blades housed in the cylindrical casing, and the tip side of the casing is flange-connected to the side wall below the constriction of the reactor 2. Although not shown, a hopper equipped with a metering supply mechanism is provided on the base end side of the casing.

[0026] The biomass filled in the hopper is compactly conveyed by the screw blades and introduced into the reactor 2. As the biomass, a large amount of rice husks generated after paddy rice produced by farmers is husked is used.

[0027] The gas supply mechanism 3 includes a header pipe 30 disposed on the lower side of the reactor 2 and a plurality of diffuser pipes 31 having a circular cross section connected to the header pipe 30 in a parallel posture. 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 diffuser pipe 31 via the header pipe 30. Saturated steam or superheated steam is used as the steam.

[0028] A small amount of silica sand is filled at the bottom of the reactor 2, and a jet fluidized bed 9 is formed at the lower part of the reactor 2, where the silica sand flows due to the mixed gas supplied from the gas supply mechanism 3. In the jet fluidized bed 9, the raw material rice husk is stirred by the silica sand and heated by steam in the presence of air while flowing, so that it is heat-treated to produce amorphous silica. The heat treatment includes a combustion reaction in which the carbon component contained in the rice husk combines with oxygen, and a gasification reaction in which the carbon component contained in the rice husk reacts with steam to produce carbon monoxide and hydrogen.

[0029] The amorphous silica that has been heat-treated into fine powder at the lower part of the reactor 2, that is, the reduced diameter part, rises in the furnace together with the combustion exhaust gas and is discharged from the exhaust pipe 10 connected to the top of the reactor 2. Since the flow rate of the combustion exhaust gas decreases in the upper part of the reactor 2, that is, the enlarged diameter part, the rice husk with insufficient heat treatment falls downward due to its own weight.

[0030] The amorphous silica discharged from the exhaust pipe 10 is guided to the cyclone 7, separated from the combustion exhaust gas and recovered. The combustion exhaust gas after the amorphous silica is separated is secondarily combusted in the secondary combustion facility 8 and then discharged to the atmosphere.

[0031] [Configuration of the heat treatment state adjustment mechanism] The manufacturing apparatus 1 for amorphous silica described above further includes a heat treatment state adjustment mechanism A. The heat treatment state adjustment mechanism A is a mechanism for adjusting the heat treatment conditions of the raw material supplied to the reactor 2. By switching whether the raw material mainly undergoes a combustion reaction or a gasification reaction while being the same manufacturing apparatus 1, it is a mechanism for adjusting the proportion of carbon contained in the produced amorphous silica.

[0032] By adjusting the heat treatment state adjustment mechanism A so that a combustion reaction mainly occurs to sufficiently burn impurities such as carbon contained in the raw material, high-purity amorphous white silica can be obtained. Also, by adjusting the heat treatment state adjustment mechanism A so that a gasification reaction mainly occurs in a state where impurities such as carbon contained in the raw material remain, amorphous black silica can be obtained.

[0033] In the present specification, white silica refers to amorphous silica in which the proportion of carbon contained therein is less than 5% by weight and which appears white or whitish, and black silica refers to amorphous silica in which the proportion of carbon contained therein exceeds 5% by weight and which appears black or blackish.

[0034] White silica is effectively used as a white cosmetic raw material, an adsorbent, an additive for industrial materials such as white paints and resins, and an agricultural material such as a fertilizer for imparting silica to crops. Black silica is effectively used as a black cosmetic raw material, an adsorbent, an additive for industrial materials such as black paints and resins and additives for tires, and an agricultural material such as a fertilizer for imparting silica and carbon to crops.

[0035] The heat treatment state adjustment mechanism A includes an oxygen-containing gas ratio adjustment mechanism (which becomes an air ratio adjustment mechanism in this embodiment because air is used as the oxygen-containing gas in this embodiment) that adjusts the ratio of the supply amount of the raw material of the oxygen-containing gas supplied from the gas supply mechanism 3, and a fluid state adjustment mechanism that adjusts at least one of the total amount, supply position, and supply distribution of the gas supplied from the gas supply mechanism 3 to adjust the fluid state of the raw material in the jet fluidized bed formed inside the reactor 2.

[0036] Increasing the total amount of the gas makes the fluid state of the raw material intense, and decreasing the total amount of the gas makes the fluid state of the raw material gentle. By densely adjusting the distribution of the gas supply positions, the raw material can be agitated so that the contact opportunities between the raw material and the gas become uniform, and by coarsely adjusting the distribution of the gas supply positions, the raw material can be agitated so that the contact opportunities between the raw material and the gas become non-uniform. By densely adjusting the gas supply distribution, the raw material can be agitated so that the contact opportunities between the raw material and the gas become uniform, and by coarsely adjusting the gas supply distribution, the raw material can be agitated so that the contact opportunities between the raw material and the gas become non-uniform. For example, even if the distribution of the gas supply positions is the same, the gas supply distribution can be adjusted by individually varying the gas supply amounts ejected from each nozzle.

[0037] Figures 2(a) and (b) show a gas supply mechanism 3(3A) for mainly causing a combustion reaction in the reactor 2 to obtain white silica, and Figures 3(a) and (b) show a gas supply mechanism 3(3B) for mainly causing a gasification reaction in the reactor 2 to obtain black silica. As described above, the gas supply mechanisms 3(3A, 3B) include a header pipe 30 disposed on the lower side of the reactor 2 and a plurality of diffuser pipes 31 having a circular cross-section connected to the header pipe 30 in a parallel posture. 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 diffuser pipe 31 through the header pipe 30.

[0038] Each diffuser pipe 31 is supported by an attachment 31F having an arcuate cross-section along the lower peripheral wall of the reactor 2. The attachment 31F is formed in a shape covering an arcuate notch formed in the lower side wall of the reactor 2, and by fixing the attachment 31F to the side wall of the reactor 2 with the tip side of each diffuser pipe 31 entering the reactor 2, the plurality of diffuser pipes 31 are fixed to the reactor 2 in a parallel posture with each other.

[0039] As shown in Figures 2(a) and (b), the diffuser pipes 31 constituting the gas supply mechanism 3(3A) for the combustion reaction are composed of a small diameter and a large number so that the rice husks supplied from the raw material supply mechanism 4 are uniformly stirred and burned without locally generating a high temperature region in an arbitrary plane orthogonal to the axis of the reactor 2.

[0040] Specifically, ejection holes 31H for the mixed gas directed in two directions inclined obliquely downward at an angle θ with respect to the horizontal direction are formed in the diffuser pipes 31. The ejection holes 31H formed in each diffuser pipe 31 are set so that the pitches L2 in the axial direction and the direction intersecting the axial direction are substantially equal, and the pitch L3 between the diffuser pipes 31 is set to L3≒2L2 so that the pitch of the ejection holes 31H is substantially equal along the direction intersecting the axial direction.

[0041] The mixed gas discharged downward from the ejection holes 31H toward the lower part of the reactor 2 blows up the silica sand upward to form a spouted bed and uniformly stirs the rice husks supplied from the raw material supply mechanism 4. The angle θ is set in the range of 30° to 60°, preferably in the range of 40° to 50°, centered on 45°. The diameter and number of each diffuser pipe 31 are set according to the diameter of the lower part of the reactor 2. For example, if the diameter L1 of the lower part of the reactor 2 is in the range of 300 mm to 1800 mm, the diameter of the diffuser pipe 31 can be selected in the range of 20A (27.2 mm) to 80A (89.1 mm), and the number can be selected in the range of 6 to 30.

[0042] As shown in FIGS. 3(a) and 3(b), the diffuser pipes 31 constituting the gas supply mechanism 3(3B) for the gasification reaction are configured with a large diameter and a small number so that the rice husks supplied from the raw material supply mechanism 4 flow unevenly in an arbitrary plane perpendicular to the axis of the reactor 2 to obtain a large stirring effect.

[0043] Specifically, the diffuser pipe 31 is formed with ejection holes 31H for the mixed gas directed in two directions inclined obliquely downward at an angle θ with respect to the horizontal direction and ejection holes 31H directed vertically downward. The ejection holes 31H formed in each diffuser pipe 31 are set so that the pitches L2 in the axial direction and the direction intersecting the axial direction are substantially equal, and the pitch L3 between the diffuser pipes 31 is set to L3 > L2.

[0044] The mixed gas discharged downward from the ejection holes 31H toward the lower part of the reactor 2 blows up the silica sand upward to form a spouted bed and stirs the rice husks supplied from the raw material supply mechanism 4 by lifting them upward. Since L3 > L2 is set, the rice husks lifted upward by the mixed gas flow unevenly and are greatly stirred along a large circulation path in which they descend in the weak region of the upward flow between the diffuser pipes 31.

[0045] The angle θ is set in the range of 30° to 60°, preferably 40° to 50°, centered around 45°. The diameter and number of each gas diffusing pipe 31 are set according to the diameter of the lower part of the reactor 2. For example, if the diameter of the lower part of the reactor 2 is in the range of 300 mm to 1800 mm, the diameter of the gas diffusing pipe 31 can be selected in the range of 40A (48.6 mm) to 80A (89.1 mm), and the number can be selected in the range of 3 to 6.

[0046] That is, the gas supply mechanism 3 (3A, 3B) constitutes a fluidization state adjustment mechanism, and the fluidization state of the rice husk is adjusted according to which of the gas supply mechanisms 3A and 3B is used, and it is possible to switch mainly between combustion reaction and gasification reaction. By replacing the gas supply mechanism 3A with the gas supply mechanism 3B, the raw material can be mainly subjected to a combustion reaction, and by replacing the gas supply mechanism 3B with the gas supply mechanism 3A, the raw material can be mainly subjected to a gasification reaction. That is, a fluidization state adjustment process for switching the fluidization state of the raw material in the spouted bed by the gas supply mechanism 3 (3A, 3B) is executed. Note that the numerical values of L1, L2, and L3 described above are examples and are not limited to the shown numerical values.

[0047] In other words, the fluidization state adjustment mechanism includes a first fluidization state in which the distribution of the gas supply positions by the gas supply mechanism 3 is made dense to mainly cause the raw material to undergo a combustion reaction, and the raw material is stirred in a state where the contact opportunity with the gas is uniform, and a second fluidization state in which the distribution of the gas supply positions by the gas supply mechanism 3 is made coarse to mainly cause the raw material to undergo a gasification reaction, and the raw material is stirred in a state where the contact opportunity with the gas is non-uniform, and it is configured to be adjustable to either state.

[0048] In the first fluidization state, the distribution of the gas supply positions of the gas supplied from the gas supply mechanism 3 becomes dense, so that the gas is uniformly supplied to the raw material, promoting a good combustion reaction. In the second fluidization state, the distribution of the gas supply positions of the gas supplied from the gas supply mechanism 3 becomes coarse, and a region where the raw material rises along with the upward flow of the gas and a region where the raw material descends without the gas being supplied are generated, promoting a good gasification reaction.

[0049] In the first flow state, the distribution of the air supply positions in a plan view supplied from the gas supply mechanism 3 becomes dense, and the rice husks flow uniformly in the fluidized bed and the space above it, obtaining a stable contact opportunity with air, and a good combustion reaction is promoted. In the second flow state, the distribution of the air supply positions in a plan view supplied from the gas supply mechanism 3 becomes coarse, and a region where air is supplied and a large upward flow is generated with respect to the rice husks and a region where air is not supplied and a downward flow is generated with respect to the rice husks are generated, and due to the stirring effect in which the upward and downward movements of the rice husks are repeated in a non-uniform state in the fluidized bed and the space above it, a good gasification reaction is promoted.

[0050] In the above description, an example of adjusting the distribution of the gas supply positions to adjust the flow state has been described. However, in order to adjust the flow state, at least any one of the total amount of gas, the supply position, and the supply distribution may be adjusted, and it is also possible to adjust by combining any of the total amount of gas, the supply position, and the supply distribution.

[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 supply amount is adjusted by a valve 32V (which may be a damper) provided in the air supply pipe 32. Further, superheated steam generated by a heat exchanger provided in the secondary combustion facility 8 or superheated steam generated by a heat recovery 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 supply amount is adjusted by a valve 33V (which may be a damper) provided in the steam supply pipe 33. Reference numeral 34 is a steam flow meter.

[0052] The valve 32V functions as an air ratio adjustment mechanism, and by adjusting the air ratio with respect to the rice husks supplied from the raw material supply mechanism 4, it is possible to adjust to either a combustion reaction or a gasification reaction of the rice husks.

[0053] The air ratio adjustment mechanism is a mechanism for adjusting to either a first range in which the theoretical air ratio with respect to rice husks is greater than 1 for mainly causing a combustion reaction of the rice husks, or a second range in which the theoretical air ratio is less than 1 for mainly causing a gasification reaction of the rice husks. An air ratio adjustment step is executed by the air ratio adjustment mechanism.

[0054] By adjusting the air ratio with respect to the rice husks to a first range where the value is greater than 1 which is the theoretical air ratio, the rice husks can be favorably caused to undergo a combustion reaction, and by adjusting to a second range where the value is less than 1 which is the theoretical air ratio, the rice husks can be favorably caused to undergo a gasification reaction.

[0055] The first range is preferably a range where the air ratio is 1.3 or more and 1.5 or less. If the air ratio is less than 1.3, a carbon component remains in the silica and high-quality white silica cannot be obtained. If the air ratio is greater than 1.5, the heat carried out by the excess air increases, the combustion temperature decreases, and a good combustion state cannot be maintained. Also, the second range is preferably a range where the air ratio is 0.2 or more and 0.5 or less. If the air ratio is less than 0.2, thermal decomposition is not promoted. If the air ratio is greater than 0.5, part of the carbon burns and good black silica cannot be obtained.

[0056] In addition, when using something other than air, such as oxygen-enriched air, as the oxygen-containing gas, by adjusting, via an oxygen-containing gas ratio adjustment mechanism, the ratio of the oxygen-containing gas with respect to the raw material to a first range where the value is greater than 1 which is the theoretical air ratio in terms of air ratio conversion, the rice husks as the raw material can be favorably caused to undergo a combustion reaction, and by adjusting the ratio of the oxygen-containing gas with respect to the raw material to a second range where the value is less than 1 which is the theoretical air ratio in terms of air ratio conversion, the rice husks as the raw material can be favorably caused to undergo a gasification reaction. When using oxygen-enriched air, since the gas amount decreases, the flow state of the raw material may be adjusted by adjusting the total amount of the gas supplied from the gas supply mechanism.

[0057] Similarly, the first range is preferably a range of 1.3 or more and 1.5 or less, and the second range is preferably a range of 0.2 or more and 0.5 or less.

[0058] Figs. 4(a) and 4(b) show a production apparatus 1 and a gas supply mechanism 3A that are adjusted by a heat treatment state adjustment mechanism to mainly cause the rice husks to undergo a combustion reaction to obtain white amorphous silica. By a control device (see Fig. 6), the opening degree of valve 32V is adjusted so that the air ratio falls within the range of 1.3 or more and 1.5 or less, and the temperature at the reduced-diameter portion of reactor 2 is adjusted within the range of 500°C to 600°C. Also, so that the temperature at the enlarged-diameter portion falls within the range of 750°C to 800°C, the amount of supplied air from the upper air supply mechanism 6 via valve 6V and the amount of heat recovered by the heat recovery mechanism 5 via valve 5V are adjusted. For this purpose, the outputs of first and second temperature sensors TH1 and TH2 installed on the downstream side and upstream side of the heat recovery mechanism 5 are input to the control device.

[0059] The combustion reaction at this time is represented by the following reaction formula. C + O2 → CO2 CO + (1 / 2)·O2 → CO2

[0060] Figs. 5(a) and 5(b) show a production apparatus 1 and a gas supply mechanism 3B that are adjusted by a heat treatment state adjustment mechanism to mainly cause the rice husks to undergo a gasification reaction to obtain black amorphous silica. By a control device (not shown), the opening degree of valve 32V is adjusted so that the air ratio falls within the range of 0.2 or more and 0.5 or less, and the temperature at the reduced-diameter portion of reactor 2 is within the range of 500°C to 600°C, and the amount of supplied air from the upper air supply mechanism 6 via valve 6V and the like are adjusted so that the temperature at the enlarged-diameter portion falls within the range of 700°C to 750°C. At this time, the steam supplied to the steam supply pipe 33 is superheated steam generated by a heat exchanger provided in the secondary combustion facility 8.

[0061] The gasification reaction at this time is mainly a water gas reaction and is represented by the following reaction formula.

[0062] The water gas reaction refers to an endothermic reaction in which carbon monoxide (CO) and hydrogen (H2) are produced from solid carbon (C), which is biomass, and water vapor (H2O) in a high-temperature environment of 500 °C or higher, as shown in the following equation. By supplying a small amount of air in addition to the steam to the reactor 2, the necessary reaction heat is provided by the combustion of a part of the rice husks, and the temperature inside the furnace is maintained in a high-temperature environment of 500 °C or higher. C + H2O → CO + H2

[0063] In this embodiment, superheated steam at a pressure of 1 MPa or less and a temperature of 120 °C to 160 °C is supplied from the steam supply pipe 33. The steam supplied to the reactor 2 is used for the initial heating of the raw materials, for activation including an increase in the specific surface area of silica due to the water gas reaction and combustion reaction, and for suppressing an abnormal increase in the ambient temperature inside the furnace due to the subsequent combustion reaction. The supply amount thereof is appropriately adjusted by the valve 33V. When mainly performing the water gas reaction, the ratio of water vapor is increased to promote activation, and the oxygen-containing gas is supplied in the minimum amount that can maintain the furnace temperature. When mainly performing the combustion reaction, the ratio of the oxygen-containing gas is increased to promote the combustion reaction, and water vapor has the effect of suppressing the generation of a local high-temperature field due to the combustion reaction.

[0064] In this embodiment, rice husks are used as biomass. About 70% of rice husks are carbohydrates such as cellulose, hemicellulose, and lignin, about 15 - 20% are silica, and most of the remainder is moisture, containing a small amount of alkaline impurities. The present invention is preferably used when recycling biomass containing such silica as a resource. Therefore, the application target of the present invention is not limited to rice husks, and it is also possible to use biomass derived from siliceous plants such as rice straw, wheat straw, bamboo, corn, sugarcane, reed, and rush.

[0065] That is, by the amorphous silica manufacturing apparatus 1 described above, a raw material supply step of supplying a raw material to the reactor by a raw material supply mechanism, a gas supply step of supplying water vapor and an oxygen-containing gas from the bottom where the raw material of the reactor stays by a gas supply mechanism, and a method for manufacturing amorphous silica by heat-treating the raw material while bringing it into contact with water vapor and an oxygen-containing gas are realized.

[0066] Then, an oxygen-containing gas ratio adjustment step (air ratio adjustment step) is executed by an oxygen-containing gas ratio adjustment mechanism (air ratio adjustment mechanism) provided in the heat treatment state adjustment mechanism, and the ratio of carbon contained in the amorphous silica generated by adjusting the ratio of the raw material supply amount of the oxygen-containing gas supplied in the gas supply step is adjusted.

[0067] Also, a fluid state adjustment step for adjusting the fluid state of the raw material is executed by adjusting at least one of the total amount, supply position, and supply distribution of the gas supplied in the gas supply step by the fluid state adjustment mechanism.

[0068] Furthermore, the heat treatment state adjustment mechanism includes a temperature adjustment mechanism that maintains the combustion temperature in the internal space of the reactor 2 at a predetermined temperature or lower, specifically about 800 °C or lower, when burning rice husks. The heat recovery mechanism 5 provided in the reactor 2 functions as the temperature adjustment mechanism. That is, when the raw material is subjected to a combustion reaction, a temperature adjustment step for maintaining the combustion temperature in the internal space of the reactor 2 at a predetermined temperature or lower that suppresses the crystallization of amorphous silica is executed by the heat recovery mechanism 5.

[0069] If the temperature in the furnace exceeds the above-mentioned predetermined temperature due to the combustion reaction of the rice husks being an exothermic reaction in the reactor 2, there is a risk that the amorphous silica will crystallize and cristobalite, which exhibits carcinogenicity, will be generated. Even in such a case, by adjusting the combustion temperature to a predetermined temperature or lower by the heat recovery mechanism 5, it becomes possible to prevent the crystallization of amorphous silica and stably obtain amorphous silica. When the rice husks mainly undergo a gasification reaction inside the reactor 2, since it is an endothermic reaction, the combustion temperature in the internal space of the reactor 2 may be below the predetermined temperature even without using the heat recovery mechanism 5. However, when the above-mentioned predetermined temperature is exceeded due to an accompanying combustion reaction, it is also possible to provide the heat recovery mechanism 5.

[0070] FIG. 6 shows the configuration of a control device C for controlling a manufacturing apparatus 1 for amorphous silica. Values of sensors such as a first temperature sensor TH1, a second temperature sensor TH2, a steam flow meter 34, and a steam temperature sensor TH3 for detecting the temperature of steam output from a boiler provided in a secondary combustion facility 8 are input to the control device C, and an identification signal indicating whether the heat treatment state adjusted by the heat treatment state adjustment mechanism mainly promotes a combustion reaction or mainly promotes a gasification reaction is input.

[0071] When the heat treatment state adjusted by the heat treatment state adjustment mechanism is mainly a combustion reaction, the control device C adjusts the opening degree of a valve 32V and the opening degree of a valve 6V based on the value of the second temperature sensor TH2 so that the combustion temperature in the reduced-diameter portion of the reactor 2 falls within 500°C to 600°C, thereby adjusting the air supply amount from the upper air supply mechanism 6, and also adjusts the opening degree of a valve 33V. Further, based on the value of the first temperature sensor TH1, the opening degree of a valve 5V is adjusted to adjust the flow rate of boiler water supplied to the heat recovery mechanism 5 so that the combustion temperature in the enlarged-diameter portion of the reactor 2 falls within 750°C to 800°C, in other words, so that the temperature is lower than the phase transition temperature range at which amorphous silica crystallizes.

[0072] For example, by controlling the reduction of the air supply amount from the air supply mechanism, the temperature of the reactor 2 can be lowered, and by controlling the increase of the flow rate of boiler water, the temperature of the enlarged-diameter portion of the reactor 2 can be lowered. As a result, the combustion temperature can be adjusted so as not to exceed a predetermined temperature.

[0073] When the heat treatment state adjusted by the heat treatment state adjustment mechanism is mainly a gasification reaction, the control device C adjusts the opening degree of the valve 32V and the air supply amount from the upper air supply mechanism 6 based on the value of the second temperature sensor TH2 so that the combustion temperature in the reduced-diameter portion of the reactor 2 falls within 500°C to 600°C, and also adjusts the opening degree of the valve 33V based on the value of the first temperature sensor TH1 so that the combustion temperature in the enlarged-diameter portion falls within 700°C to 750°C.

[0074] Similarly to the above, by controlling the reduction of the air supply amount from the air supply mechanism, the temperature of the reactor 2 can be decreased, and by controlling the increase of the flow rate of the boiler water, the temperature of the enlarged diameter portion of the reactor 2 can be decreased. As a result, the combustion temperature can be adjusted so as not to exceed a predetermined temperature. In this case, if the combustion temperature of the enlarged diameter portion does not exceed 800°C, it is not necessary to adjust the flow rate of the boiler water supplied to the heat recovery mechanism 5. The second temperature sensor TH2 may be located at a position where the temperature of the reduced diameter portion can be monitored, and may be installed in either the reduced diameter portion or the enlarged diameter portion as long as it is upstream of the heat recovery mechanism 5.

[0075] In FIGS. 1, 4, and 5, as the upper air supply mechanism 6 for adjusting the combustion state in the space above the spouted bed 9, a configuration in which an air supply pipe is inserted from the side wall near the throttle portion of the reactor 2 and an air supply nozzle for supplying air downward from the central portion of the reactor 2 is provided at the tip of the air supply pipe has been described. However, the configuration of the upper air supply mechanism 6 is not limited to this example and can be appropriately configured according to the size of the reactor 2 and the like.

[0076] For example, as shown in FIG. 7(a), an air supply pipe provided with an air supply nozzle at its tip may be provided so as to hang down from the zenith of the reactor 2, or as shown in FIG. 7(b), a plurality of air supply nozzles may be provided near the throttle portion of the reactor 2. For example, a plurality of air supply nozzles can be evenly arranged on concentric circles in a plan view.

[0077] In the above-described embodiment, an example in which the gas supply mechanism 3 is configured to supply a mixed gas of steam and air, which is an example of an oxygen-containing gas, has been described. However, as long as each configuration of the above-described oxygen-containing gas ratio adjustment mechanism and the flow state adjustment mechanism is provided, the steam and the oxygen-containing gas may be configured to be supplied individually.

[0078] In the above-described embodiment, the mode of forming a jet fluidized bed inside the reactor 2 to heat-treat the raw material and stirring and fluidizing the raw material together with silica sand in the jet fluidized bed has been described. However, a mode of forming a fluidized bed near the bottom of the reactor 2 and stirring and fluidizing the raw material together with silica sand in the fluidized bed may be adopted. In any case, in order to bring the raw material into good contact with the gas by the jet fluidized bed or the fluidized bed, the particle size of the silica sand is preferably in the range of 0.05 mm to 2 mm. Further, if the raw material can be heat-treated while being brought into contact with the gas inside the reactor 2, it is not essential to introduce silica sand into the reactor 2.

[0079] The above-described embodiment merely explains a specific example of the apparatus for producing amorphous silica and the production apparatus according to the present invention, and the scope of the present invention is not limited by the description. Needless to say, the specific configuration of each part can be appropriately changed and designed within the range where the functions and effects of the present invention are achieved.

Explanation of Reference Numerals

[0080] 1: Apparatus for producing amorphous silica 2: Reactor 3: Gas supply mechanism 30: Header pipe 31: Diffuser pipe 32: Air supply pipe 32V: Valve 33: Steam supply pipe 33V: Valve 4: Raw material supply mechanism 5: Heat recovery mechanism 6: Upper air supply mechanism 7: Cyclone 8: Secondary combustion equipment 9: Jet fluidized bed 10: Exhaust pipe A: Heat treatment state adjustment mechanism

Claims

1. A manufacturing apparatus for amorphous silica, comprising a reactor, a raw material supply mechanism for supplying biomass derived from siliceous plants as a raw material to the reactor, a gas supply mechanism for supplying steam and an oxygen-containing gas from the bottom where the raw material in the reactor stays, and heat-treating the raw material while making it contact with and flow with the steam and the oxygen-containing gas to produce amorphous silica, wherein the gas supply mechanism is provided with a plurality of ejection holes for ejecting the gas, and having a flow state adjustment mechanism for adjusting at least one of the distribution of the ejection holes of the gas in a plan view supplied from the gas supply mechanism or the supply distribution which is the difference in the supply amount of the gas ejected from each ejection hole, thereby adjusting the flow state of the raw material and adjusting the ratio of carbon contained in the produced amorphous silica.

2. The manufacturing apparatus for amorphous silica according to claim 1, further comprising a heat treatment state adjustment mechanism for adjusting the ratio of carbon contained in the produced amorphous silica by adjusting the ratio of the oxygen-containing gas supplied from the gas supply mechanism to the supply amount of the raw material.

3. The manufacturing apparatus for amorphous silica according to claim 1 or 2, wherein the flow state adjustment mechanism is configured to be adjustable to at least a first flow state in which the distribution of the ejection holes of the gas by the gas supply mechanism is made dense to stir the raw material in a state where the contact opportunity with the gas is uniform, and a second flow state in which the distribution of the ejection holes of the gas by the gas supply mechanism is made coarse to stir the raw material in a state where the contact opportunity with the gas is non-uniform.

4. The manufacturing apparatus for amorphous silica according to claim 2, wherein the heat treatment state adjustment mechanism includes a temperature adjustment mechanism for maintaining the combustion temperature in the internal space of the reactor at a predetermined temperature or lower that suppresses crystallization of the amorphous silica.

5. A raw material supply step of supplying raw materials to a reactor by a raw material supply mechanism, a gas supply step of supplying steam and an oxygen-containing gas from the bottom where the raw materials in the reactor stay by a gas supply mechanism, and a method for producing amorphous silica by heat-treating while bringing the raw materials into contact with the steam and the oxygen-containing gas and flowing them, comprising: The gas supply mechanism includes a plurality of ejection holes for ejecting the gas, A flow state adjustment step of adjusting at least one of the distribution of the ejection holes of the gas in a plan view supplied in the gas supply step or the supply distribution which is the difference in the supply amount of the gas ejected from each of the ejection holes, thereby adjusting the flow state of the raw materials and adjusting the proportion of carbon contained in the produced amorphous silica. A method for producing amorphous silica comprising the flow state adjustment step.

6. A heat treatment state adjustment step of adjusting the proportion of carbon contained in the produced amorphous silica by adjusting the ratio of the oxygen-containing gas supplied in the gas supply step to the supply amount of the raw materials. The method for producing amorphous silica according to claim 5, comprising the heat treatment state adjustment step.

7. The flow state adjustment step includes a first flow state in which the distribution of the ejection holes of the gas supplied in the gas supply step is made dense and the raw materials are stirred in a state where the contact opportunity with the gas is uniform, and a second flow state in which the distribution of the ejection holes of the gas supplied in the gas supply step is made rough and the raw materials are stirred in a state where the contact opportunity with the gas is non-uniform. The method for producing amorphous silica according to claim 5 or 6, which is at least a step of adjusting to the second flow state.

8. The heat treatment state adjustment step includes a temperature adjustment step of maintaining the combustion temperature in the internal space of the reactor at a predetermined temperature or lower that suppresses the crystallization of the amorphous silica. The apparatus for producing amorphous silica according to claim 6.

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