Amorphous silica manufacturing apparatus and method for manufacturing amorphous silica

Abstract

To provide an apparatus for producing an amorphous silica which can efficiently produce an amorphous silica 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 properties of the amorphous silica produced by switching to mainly subject the raw material to a combustion reaction or a gasification reaction by the heat treatment.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a reactor, a raw material supply mechanism that supplies biomass derived from a silicic acid plant as a raw material to the reactor, a gas supply mechanism that supplies water vapor and an oxygen-containing gas from below the reactor, and an apparatus and method for producing amorphous silica that produces amorphous silica by heat treating the amorphous silica while contacting it with the gas supplied via the gas supply mechanism. [Background technology]

[0002] Patent Document 1 proposes a method and an apparatus for producing amorphous silica that uses biomass derived from silicic acid plants as a raw material, and that can efficiently recover energy while obtaining high-purity, high-quality silica.

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

[0004] The amorphous silica manufacturing apparatus also includes a gasification furnace that pyrolyzes and gasifies biomass including silicic acid plants, a separation mechanism that separates the biomass residue from a mixture of pyrolysis gas and biomass residue discharged from the gasification furnace, and a calcination furnace that calcines the biomass residue separated by the separation mechanism to obtain amorphous silica.

[0005] According to the above-mentioned method for producing amorphous silica, the biomass derived from silicic acid plants is pyrolyzed in the gasification step and recovered as fuel, and the remaining biomass residue is subjected to a calcination process to remove impurities such as carbon components remaining in the biomass residue, thereby obtaining white amorphous silica with high purity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-040861 A Summary of the Invention [Problem to be solved by the invention]

[0007] The method for producing amorphous silica disclosed in Patent Document 1 requires a further calcination treatment of the biomass residue obtained in the gasification step, and it is desirable to obtain amorphous silica without carrying out the time-consuming calcination treatment.

[0008] In addition, the supply of water vapor is essential for activating the silica produced and for preventing the temperature from rising to the range where silica crystallizes during the heat treatment process, and it is uneconomical to require a separate heat source to obtain such water vapor.

[0009] An object of the present invention is to provide an apparatus and method for producing amorphous silica that can efficiently obtain amorphous silica using biomass derived from a silicic acid plant as a raw material. [Means for solving the problem]

[0010] In order to achieve the above object, a first characteristic configuration of an amorphous silica production apparatus according to the present invention includes a reactor, a raw material supply mechanism for supplying biomass derived from a silicic acid plant as a raw material to the reactor, a gas supply mechanism for supplying steam and an oxygen-containing gas from a bottom of the reactor where the raw material is retained, and a temperature control mechanism for maintaining a temperature of an internal space of the reactor at or below a predetermined temperature that suppresses crystallization of the amorphous silica, the temperature control mechanism comprising: a heat exchanger that uses water as a heat medium; an upper air supply mechanism that supplies air between the gas supply mechanism and the heat exchanger to combust the raw material; and the water vapor generated in the heat exchanger is supplied to the reactor via the gas supply mechanism.

[0011] Biomass derived from silicic acid plants is supplied to a reactor, and is heat-treated by contacting it with steam and an oxygen-containing gas. A part of the biomass undergoes a water-gas reaction, and a part of the biomass undergoes a combustion reaction, producing amorphous silica. During this process, The upper air supply mechanism adjusts the amount of air supplied between the gas supply mechanism and the heat exchanger, and the combustion state in the space adjacent to the upper air supply mechanism is adjusted, and the amount of heat recovered by the heat recovery mechanism is adjusted in accordance with the combustion state in the space adjacent to the upper air supply mechanism. The temperature of the inner space of the reactor is maintained below the phase transition temperature range where amorphous silica crystallizes. Furthermore, the water vapor generated in the heat exchanger is supplied into the reactor via the gas supply mechanism, thereby enabling the efficient production of amorphous silica.

[0012] The second characteristic configuration is, in addition to the first characteristic configuration described above, an oxygen-containing gas ratio adjusting mechanism that adjusts the ratio of the oxygen-containing gas to the supply amount of the raw material, converted into an air ratio, to a range of 1.3 to 1.5.

[0013] The oxygen-containing gas ratio adjustment mechanism adjusts the ratio of the oxygen-containing gas to the raw material, converted into an air ratio, to a range of 1.3 to 1.5, thereby burning the carbon components contained in the raw material and efficiently producing white amorphous silica.

[0014] The third characteristic configuration of the present invention is, in addition to the first or second characteristic configuration described above, that the temperature adjustment mechanism is provided downstream of the heat exchanger provided in the reactor. Between the heat exchanger and the upper air supply mechanism The point is that the temperature sensor is provided in the

[0015] The amount of heat exchanged by the heat exchanger can be appropriately adjusted based on the value of a temperature sensor provided downstream of the heat exchanger provided in the reactor.

[0016] A first characteristic configuration of the method for producing amorphous silica according to the present invention is a method for producing amorphous silica, comprising: a raw material supplying step of supplying a raw material made of biomass derived from a silicic acid plant to a reactor by a raw material supply mechanism; a gas supplying step of supplying steam and an oxygen-containing gas from a bottom of the reactor where the raw material is retained by a gas supplying mechanism; and a temperature adjusting step of producing amorphous silica by heat-treating the raw material while contacting it with the steam and the oxygen-containing gas, the temperature of the inner space of the reactor being maintained at or below a predetermined temperature that inhibits crystallization of the amorphous silica, the temperature adjusting step being performed by using a heat exchanger using water as a heat medium. an upper air supply mechanism that supplies air between the gas supply mechanism and the heat exchanger to combust the raw material; and the steam generated in the heat exchanger is supplied to the reactor via the gas supply mechanism.

[0017] The second characteristic configuration is, in addition to the first characteristic configuration described above, an oxygen-containing gas ratio adjusting mechanism that adjusts the ratio of the oxygen-containing gas to the supply amount of the raw material, converted into an air ratio, to a range of 1.3 to 1.5.

[0018] The third characteristic configuration of the present invention is, in addition to the first or second characteristic configuration described above, that the temperature adjustment step is performed by Between the heat exchanger and the upper air supply mechanism The point is that the temperature is measured based on the value of a temperature sensor disposed in the Effect of the Invention

[0019] As described above, according to the present invention, it is possible to provide an apparatus for producing amorphous silica and a method for producing amorphous silica, which can efficiently obtain amorphous silica using biomass derived from a silicic acid plant as a raw material. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an explanatory diagram showing an example of an apparatus for producing amorphous silica according to the present invention. [Diagram 2] FIG. 1A is a plan view of a gas supply mechanism for a case where the heat treatment is mainly a combustion reaction, and FIG. 1B is a cross-sectional view of the main part of the gas supply mechanism. [Diagram 3]FIG. 1A is a plan view of a gas supply mechanism when the heat treatment is mainly a gasification reaction, and FIG. 1B is a cross-sectional view of the main part of the gas supply mechanism. [Figure 4] An explanatory diagram of an amorphous silica production apparatus in which the heat treatment is mainly a combustion reaction. [Diagram 5] An explanatory diagram of an amorphous silica manufacturing apparatus in which the heat treatment is mainly a gasification reaction. [Figure 6] An explanatory diagram of a control device provided in an amorphous silica manufacturing apparatus. [Figure 7] 1A and 1B are explanatory diagrams of an upper air supply mechanism showing another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] An example of the apparatus for producing amorphous silica and the method for producing amorphous silica according to the present invention will be described below. [Configuration of amorphous silica manufacturing equipment] One embodiment of an amorphous silica production apparatus 1 according to the present invention is shown in Fig. 1. The amorphous silica production apparatus 1 includes a cylindrical reactor 2 having a constricted portion formed in the vertical center and a diameter reduced from the top to the bottom, a raw material supply mechanism 4 for supplying biomass derived from silicic acid plants as a raw material to the reactor 2, and a gas supply mechanism 3 for supplying a mixed gas of water vapor and air, which is an example of an oxygen-containing gas, from the bottom of the reactor 2, and the bottom of the reactor 2 is filled with a predetermined amount of silica sand to form a spouted bed.

[0022] The raw material supply mechanism 4 is composed of a screw conveyor mechanism equipped with a cylindrical casing and a screw blade housed in the cylindrical casing, and the tip side of the casing is flange-connected to the side wall below the narrowed portion of the reactor 2. Although not shown, a hopper equipped with a quantitative supply mechanism is provided at the base end side of the casing.

[0023] The biomass filled in the hopper is transported compactly by the screw blade and fed into the reactor 2. The biomass used is a large amount of rice husks that are generated after the unhulled rice produced by farmers is hulled.

[0024] The gas supply mechanism 3 is configured with a header pipe 30 arranged on the lower lateral side of the reactor 2, and a plurality of aeration pipes 31 with a circular cross section connected to the header pipe 30 in a parallel orientation. An air supply pipe 32 and a steam supply pipe 33 are connected to the header pipe 30, and a mixture of air and steam is supplied to each aeration pipe 31 through the header pipe 30. Saturated steam or superheated steam is used as the steam.

[0025] A small amount of silica sand is filled at the bottom of the reactor 2, and the mixed gas supplied from the gas supply mechanism 3 causes the silica sand to flow in the lower part of the reactor 2 to form an entrained bed 9. In the entrained bed 9, the raw material rice husks are agitated by the silica sand and heated by steam in the presence of air while flowing, thereby producing amorphous silica through heat treatment. The heat treatment involves a combustion reaction in which the carbon components contained in the rice husks combine with oxygen, and a gasification reaction in which the carbon components contained in the rice husks react with steam to produce carbon monoxide and hydrogen.

[0026] The amorphous silica that has been heat-treated and turned into fine powder in the lower part of the reactor 2, i.e., the narrowed diameter part, rises inside the furnace together with the combustion exhaust gas and is discharged from the exhaust pipe 10 connected to the top of the reactor 2. Note that, since the flow rate of the combustion exhaust gas decreases in the upper part of the reactor 2, i.e., the expanded diameter part, rice husks that have not been sufficiently heat-treated fall downward due to their own weight.

[0027] The amorphous silica discharged from the exhaust pipe 10 is guided to a cyclone 7 where it is separated from the combustion exhaust gas and recovered, and the combustion exhaust gas from which the amorphous silica has been separated is subjected to secondary combustion in a secondary combustion facility 8 and then released into the atmosphere.

[0028] [Structure of heat treatment condition adjustment mechanism] The above-mentioned amorphous silica manufacturing apparatus 1 further includes a heat treatment condition adjusting mechanism A. The heat treatment condition adjusting mechanism A is a mechanism for adjusting the heat treatment conditions of the raw material supplied to the reaction furnace 2, and even though it is the same manufacturing apparatus 1, it is a mechanism for adjusting the proportion of carbon contained in the generated amorphous silica by switching between mainly subjecting the raw material to a combustion reaction or mainly subjecting the raw material to a gasification reaction.

[0029] High-purity amorphous white silica can be obtained by adjusting the heat treatment condition adjusting mechanism A so that the combustion reaction that sufficiently burns impurities such as carbon contained in the raw material occurs primarily. Also, amorphous black silica can be obtained by adjusting the heat treatment condition adjusting mechanism A so that the gasification reaction occurs primarily while impurities such as carbon contained in the raw material remain.

[0030] In this specification, white silica refers to amorphous silica in which the proportion of carbon contained in the amorphous silica is less than 5% by weight and which has a white or whitish appearance, and black silica refers to amorphous silica in which the proportion of carbon contained in the amorphous silica is more than 5% by weight and which has a black or blackish appearance.

[0031] White silica is effectively utilized in industrial materials such as a raw material for white cosmetics, an adsorbent, and an additive for white paints and resins, and in agricultural materials such as fertilizers for adding silica to crops, while black silica is effectively utilized in industrial materials such as a raw material for black cosmetics, an adsorbent, and an additive for black paints and resins, and an additive for tires, and in agricultural materials such as fertilizers for adding silica and carbon to crops.

[0032] The heat treatment condition adjusting mechanism A includes an oxygen-containing gas ratio adjusting mechanism (in this embodiment, air is used as the oxygen-containing gas, so it is an air ratio adjusting mechanism) that adjusts the ratio of the oxygen-containing gas supplied from the gas supply mechanism 3 to the supply amount of the raw material, and a fluidization condition adjusting mechanism that adjusts the fluidization condition of the raw material in the entrained bed formed inside the reaction furnace 2 by adjusting at least one of the total amount, supply position, and supply distribution of gas supplied from the gas supply mechanism 3.

[0033] By increasing the total amount of gas, the flow state of the raw material becomes intense, and by decreasing the total amount of gas, the flow state of the raw material becomes gentle. By adjusting the distribution of the gas supply positions to be dense, the raw material can be agitated so that the raw material and the gas have a uniform contact opportunity, and by adjusting the distribution of the gas supply positions to be coarse, the raw material can be agitated so that the raw material and the gas have a non-uniform contact opportunity. By adjusting the gas supply distribution to be dense, the raw material can be agitated so that the raw material and the gas have a uniform contact opportunity, and by adjusting the gas supply distribution to be coarse, the raw material can be agitated so that the raw material and the gas have a non-uniform contact opportunity. 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 amount ejected from each nozzle.

[0034] 2(a) and (b) show a gas supply mechanism 3 (3A) for obtaining white silica by mainly inducing a combustion reaction in the reactor 2, and FIG. 3(a) and (b) show a gas supply mechanism 3 (3B) for obtaining black silica by mainly inducing a gasification reaction in the reactor 2. As described above, the gas supply mechanism 3 (3A, 3B) includes a header pipe 30 disposed on the lower side of the reactor 2, and a plurality of aeration pipes 31 with a circular cross section connected to the header pipe 30 in a parallel position to each other. 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 aeration pipe 31 via the header pipe 30.

[0035] Each of the air diffuser pipes 31 is supported by an attachment 31F having an arc-shaped cross section that is aligned along the lower peripheral wall of the reactor 2. The attachment 31F is formed in a shape that covers an arc-shaped cutout 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 of the air diffuser pipes 31 inserted into the reactor 2, the multiple air diffuser pipes 31 are fixed to the reactor 2 in a parallel posture to each other.

[0036] As shown in Figures 2(a) and (b), the gas supply mechanism 3 (3A) for the combustion reaction has a small diameter diffuser tube 31, which is made up of many diffusers, so that the rice husks supplied from the raw material supply mechanism 4 are uniformly stirred and combusted within any plane perpendicular to the axis of the reactor 2 without generating localized high-temperature regions.

[0037] More specifically, mixed gas outlet holes 31H facing two directions inclined obliquely downward at an angle θ with respect to the horizontal direction are formed in the air diffuser pipe 31. The outlet holes 31H formed in each air diffuser pipe 31 are set so that the pitch L2 in the axial direction and in the direction intersecting the axial direction are approximately equal, and the pitch L3 between the air diffuser pipes 31 is set to L3 ≈ 2L2 so that the pitches of the outlet holes 31H in the direction intersecting the axial direction are approximately equal.

[0038] The mixed gas discharged from the nozzle 31H toward the bottom of the reactor 2 blows 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 40° to 50°, with 45° as the center. 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.

[0039] As shown in Figures 3(a) and (b), the diffuser pipes 31 constituting the gas supply mechanism 3 (3B) for the gasification reaction are configured with a small number of large diameter diffusers 31 so that the rice husks supplied from the raw material supply mechanism 4 flow non-uniformly within any plane perpendicular to the axis of the reactor 2, thereby achieving a large stirring effect.

[0040] More specifically, mixed gas ejection holes 31H facing two directions inclined obliquely downward at an angle θ with respect to the horizontal direction and ejection holes 31H facing vertically downward are formed in the air diffusion pipe 31. The ejection holes 31H formed in each air diffusion pipe 31 are set so that the pitches L2 in the axial direction and in the direction intersecting the axial direction are approximately equal, and the pitch L3 between the air diffusion pipes 31 is set so that L3>L2.

[0041] The mixed gas discharged from the nozzle 31H toward the bottom of the reactor 2 blows 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 up. Since L3>L2 is set, the rice husks stirred up by the mixed gas flow unevenly along a large circulation path, descending through the areas between the air diffusers 31 where the upward flow is weak, and are stirred significantly.

[0042] The angle θ is set in the range of 30° to 60°, preferably 40° to 50°, with 45° as the center. The diameter and number of each aeration 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 300mm to 1800mm, the diameter of the aeration pipe 31 can be selected in the range of 40A (48.6mm) to 80A (89.1mm), and the number can be selected in the range of 3 to 6.

[0043] In other words, the gas supply mechanism 3 (3A, 3B) constitutes a fluidization state adjustment mechanism, and the fluidization state of the rice husks is adjusted depending on which of the gas supply mechanisms 3A and 3B is used, making it possible to adjust whether the reaction is mainly combustion or gasification. The gas supply mechanism 3 (3A, 3B) executes a fluidization state adjustment process that switches the fluidization state of the raw material by the entrained bed. Note that the values ​​of L1, L2, and L3 mentioned above are examples and are not limited to the values ​​shown.

[0044] In other words, the fluidization state adjustment mechanism is configured to be adjustable to either a first fluidization state in which the distribution of gas supply positions by the gas supply mechanism 3 is dense so that the raw materials are agitated with a uniform opportunity for contact with the gas, in order to mainly cause the raw materials to undergo a combustion reaction, or a second fluidization state in which the distribution of gas supply positions by the gas supply mechanism 3 is sparse so that the raw materials are agitated with an uneven opportunity for contact with the gas, in order to mainly cause the raw materials to undergo a gasification reaction.

[0045] In the first flow state, the distribution of the supply positions of the gas supplied from the gas supply mechanism 3 is dense, so that the gas is supplied evenly to the raw material, promoting a good combustion reaction, and in the second flow state, the distribution of the supply positions of the gas supplied from the gas supply mechanism 3 is sparse, so that there are areas where the raw material rises with the upward flow of gas and areas where the raw material descends without being supplied with gas, promoting a good gasification reaction.

[0046] In the first fluidization state, the distribution of the supply positions of the air supplied from the gas supply mechanism 3 in a plan view becomes dense, and the rice husks flow evenly in the fluidized bed and in the space above it, providing a stable contact opportunity with the air, promoting a good combustion reaction. In the second fluidization state, the distribution of the supply positions of the air supplied from the gas supply mechanism 3 in a plan view becomes sparse, creating areas where air is supplied and a large upward flow occurs over the rice husks, and areas where no air is supplied and a downward flow occurs over the rice husks, creating a stirring effect where the rice husks rise and fall unevenly in the fluidized bed and in the space above it, promoting a good gasification reaction.

[0047] In the above explanation, an example has been described in which the distribution of gas supply positions is adjusted to adjust the flow state. However, in order to adjust the flow state, it is sufficient to adjust at least one of the total amount of gas, the supply positions, and the supply distribution, and it is also possible to adjust a combination of the total amount of gas, the supply positions, and the supply distribution.

[0048] Returning to Fig. 1, compressed air is supplied from a compressor or a blower fan to an air supply pipe 32 connected to the header pipe 30, and the amount of the air supplied is adjusted by a valve 32V (which may be a damper) provided on the air supply pipe 32. In addition, superheated steam generated in a heat exchanger provided in the secondary combustion equipment 8 or superheated steam generated in a heat recovery mechanism 5, which is a heat exchanger provided in the reactor 2, is supplied to a steam supply pipe 33 connected to the header pipe 30, and the amount of the steam supplied is adjusted by a valve 33V (which may be a damper) provided on the steam supply pipe 33. Reference numeral 34 denotes a steam flow meter.

[0049] The valve 32V functions as an air ratio adjusting mechanism, and by adjusting the air ratio to the rice husks supplied from the raw material supply mechanism 4, it is possible to adjust the rice husks to either undergo a combustion reaction or a gasification reaction.

[0050] The air ratio adjustment mechanism adjusts the theoretical air ratio to the rice husks to either a first range in which the theoretical air ratio is greater than 1 so that the rice husks are primarily subjected to a combustion reaction, or a second range in which the theoretical air ratio is less than 1 so that the rice husks are primarily subjected to a gasification reaction, and the air ratio adjustment process is carried out by the air ratio adjustment mechanism.

[0051] By adjusting the air ratio to rice husks to a first range greater than the theoretical air ratio of 1, the rice husks can be combusted well, and by adjusting the air ratio to a second range less than the theoretical air ratio of 1, the rice husks can be gasified well.

[0052] The first range is preferably an air ratio of 1.3 or more and 1.5 or less. If the air ratio is less than 1.3, carbon components remain in the silica, making it impossible to obtain high-quality white silica, and if the air ratio is greater than 1.5, the amount of heat taken out by the excess air increases, the combustion temperature drops, and good combustion conditions cannot be maintained. The second range is preferably an air ratio of 0.2 or more and 0.5 or less. If the air ratio is less than 0.2, pyrolysis is not promoted, and if the air ratio is greater than 0.5, a part of the carbon is burned, making it impossible to obtain good black silica.

[0053] When using oxygen-containing gas other than air, such as oxygen-enriched air, the ratio of the oxygen-containing gas to the raw material can be adjusted via the oxygen-containing gas ratio adjustment mechanism to a first range in which the ratio, converted into an air ratio, is greater than the theoretical air ratio of 1, thereby enabling a good combustion reaction of the raw material rice husks, and the ratio of the oxygen-containing gas to the raw material can be adjusted to a second range in which the ratio, converted into an air ratio, is less than the theoretical air ratio of 1, thereby enabling a good gasification reaction of the raw material rice husks. When oxygen-enriched air is used, the amount of gas decreases, so the flow state of the raw material may be adjusted by adjusting the total amount of gas supplied from the gas supply mechanism.

[0054] Similarly, the first range is preferably from 1.3 to 1.5, and the second range is preferably from 0.2 to 0.5.

[0055] 4(a) and (b) show a manufacturing apparatus 1 and a gas supply mechanism 3A for obtaining white amorphous silica by adjusting the heat treatment state adjusting mechanism so that rice husks are mainly subjected to a combustion reaction. The opening of the valve 32V is adjusted by the control device (see FIG. 6) so that the air ratio is in the range of 1.3 to 1.5, and the temperature at the reduced diameter part of the reactor 2 is adjusted to the range of 500°C to 600°C. Also, the amount of air supplied from the upper air supply mechanism 6 is adjusted via the valve 6V, and the amount of heat recovered by the heat recovery mechanism 5 is adjusted via the valve 5V so that the temperature at the expanded diameter part is in the range of 750°C to 800°C. For this purpose, the outputs of the first and second temperature sensors TH1 and TH2 installed on the downstream and upstream sides of the heat recovery mechanism 5 are input to the control device.

[0056] The combustion reaction at this time is expressed by the following reaction formula. C+O2→ CO2 CO+(1 / 2)·O2 → CO2

[0057] 5(a) and (b) show a manufacturing apparatus 1 and a gas supply mechanism 3B for obtaining black amorphous silica by adjusting the heat treatment state adjusting mechanism so that the rice husks are mainly gasified. A control device (not shown) adjusts the opening of a valve 32V so that the air ratio is in the range of 0.2 to 0.5, and adjusts the amount of air supplied from the upper air supply mechanism 6 via a valve 6V so that the temperature at the narrowing part of the reactor 2 is in the range of 500°C to 600°C and the temperature at the expanding part is in the range of 700°C to 750°C. The steam supplied to the steam supply pipe 33 at this time is superheated steam generated in a heat exchanger provided in the secondary combustion equipment 8.

[0058] The gasification reaction at this time is mainly a water-gas reaction, and is represented by the following reaction formula.

[0059] The water-gas reaction is an endothermic reaction in which carbon monoxide CO and hydrogen H2 are produced from solid carbon C (biomass) and water vapor H2O in a high-temperature environment of 500°C or higher, as shown in the following formula. 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 some 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

[0060] In this embodiment, superheated steam at a temperature of 120° C. to 160° C. is supplied from the steam supply pipe 33 at a pressure of 1 MPa or less. The steam supplied to reactor 2 is used for 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 atmospheric temperature inside the furnace due to the subsequent combustion reaction, and the amount supplied is appropriately adjusted by valve 33V. When the water-gas reaction is mainly performed, the ratio of water steam is increased to promote activation, and the minimum amount of oxygen-containing gas that can maintain the temperature inside the furnace is supplied. When the combustion reaction is mainly performed, the ratio of oxygen-containing gas is increased to promote the combustion reaction, and the water steam has the effect of suppressing the generation of a local high-temperature field due to the combustion reaction.

[0061] In this embodiment, rice husks are used as biomass. Rice husks are about 70% carbohydrates such as cellulose, hemicellulose, and lignin, about 15 to 20% silica, and the majority of the remainder is water, with a small amount of alkaline impurities. The present invention is preferably used when such biomass containing silica is to be regenerated as a resource. Therefore, the application 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, thin grass, and horsetail.

[0062] That is, the above-mentioned amorphous silica manufacturing apparatus 1 realizes a raw material supplying process in which raw material is supplied to the reactor by a raw material supply mechanism, a gas supplying process in which steam and an oxygen-containing gas are supplied by a gas supplying mechanism from the bottom of the reactor where the raw material is retained, and an amorphous silica manufacturing method in which amorphous silica is produced by heat-treating the raw material while contacting it with the steam and the oxygen-containing gas.

[0063] Then, an oxygen-containing gas ratio adjustment process (air ratio adjustment process) is carried out by an oxygen-containing gas ratio adjustment mechanism (air ratio adjustment mechanism) provided in the heat treatment condition adjustment mechanism, and the proportion of carbon contained in the generated amorphous silica is adjusted by adjusting the ratio of the oxygen-containing gas supplied in the gas supply process to the supply amount of the raw material.

[0064] In addition, a flow condition adjusting mechanism adjusts at least one of the total amount, supply position, and supply distribution of gas supplied in the gas supply step, thereby adjusting the flow condition of the raw material.

[0065] Furthermore, the heat treatment state adjusting mechanism includes a temperature adjusting mechanism that maintains the combustion temperature in the internal space of the reactor 2 at a predetermined temperature or lower, specifically, at approximately 800°C or lower, when the rice husks are subjected to a combustion reaction. The heat recovery mechanism 5 provided in the reactor 2 functions as the temperature adjusting mechanism. That is, when the raw material is subjected to a combustion reaction, the heat recovery mechanism 5 executes a temperature adjusting step of maintaining the combustion temperature in the internal space of the reactor 2 at a predetermined temperature or lower that inhibits the crystallization of amorphous silica.

[0066] When the temperature inside the reactor 2 exceeds the above-mentioned predetermined temperature due to the combustion reaction of rice husks, which is an exothermic reaction, there is a risk that amorphous silica will crystallize and cristobalite, which is carcinogenic, will be generated. Even in such a case, the heat recovery mechanism 5 adjusts the combustion temperature to a predetermined temperature or lower, thereby preventing the crystallization of amorphous silica and enabling amorphous silica to be obtained stably. When the gasification reaction of rice husks mainly occurs inside the reactor 2, it is an endothermic reaction, so the combustion temperature in the internal space of the reactor 2 may be kept below the predetermined temperature even without the heat recovery mechanism 5, but when the accompanying combustion reaction exceeds the above-mentioned predetermined temperature, it is also possible to provide the heat recovery mechanism 5.

[0067] 6 shows the configuration of a control device C that controls the amorphous silica manufacturing apparatus 1. The control device C receives inputs of sensor values ​​such as the first temperature sensor TH1, the second temperature sensor TH2, the steam flow meter 34, and the steam temperature sensor TH3 that detects the temperature of steam output from the boiler provided in the secondary combustion facility 8, as well as an identification signal indicating whether the heat treatment state adjusted by the heat treatment state adjustment mechanism is one that mainly promotes a combustion reaction or one that mainly promotes a gasification reaction.

[0068] When the heat treatment state adjusted by the heat treatment state adjusting mechanism is mainly a combustion reaction, the control device C adjusts the aperture of the valve 32V based on the value of the second temperature sensor TH2 so that the combustion temperature of the narrowing diameter part of the reactor 2 is between 500°C and 600°C, adjusts the aperture of the valve 6V to adjust the amount of air supplied from the upper air supply mechanism 6, and also adjusts the aperture of the valve 33V. Furthermore, based on the value of the first temperature sensor TH1, the control device C adjusts the aperture of the valve 5V to adjust the flow rate of the boiler water supplied to the heat recovery mechanism 5 so that the combustion temperature of the expanding diameter part of the reactor 2 is between 750°C and 800°C, in other words, a temperature lower than the phase transition temperature range where amorphous silica crystallizes.

[0069] For example, the temperature of the reactor 2 can be lowered by controlling to decrease the amount of air supplied from the air supply mechanism, and the temperature of the expanded diameter section of the reactor 2 can be lowered by controlling to increase the flow rate of the boiler water, thereby making it possible to adjust the combustion temperature so that it does not exceed a predetermined temperature.

[0070] When the heat treatment state adjusted by the heat treatment state adjustment mechanism is mainly a gasification reaction, the control device C adjusts the aperture of valve 32V and the amount of air supplied from the upper air supply mechanism 6 so that the combustion temperature in the narrowed diameter section of the reactor 2 is between 500°C and 600°C based on the value of the second temperature sensor TH2, and so that the combustion temperature in the expanded diameter section is between 700°C and 750°C based on the value of the first temperature sensor TH1, and also adjusts the aperture of valve 33V.

[0071] As described above, the temperature of the reactor 2 can be lowered by controlling the amount of air supplied from the air supply mechanism to be decreased, and the temperature of the expanded diameter portion of the reactor 2 can be lowered by controlling the flow rate of the boiler water to be increased, so that the combustion temperature can be adjusted so as not to exceed a predetermined temperature. In this case, if the combustion temperature of the expanded diameter portion does not exceed 800°C, there is no need to adjust the flow rate of the boiler water supplied to the heat recovery mechanism 5. The second temperature sensor TH2 may be located in any position where the temperature of the contracted diameter portion can be monitored, and may be installed in either the contracted diameter portion or the expanded diameter portion as long as it is upstream of the heat recovery mechanism 5.

[0072] In Figures 1, 4, and 5, an upper air supply mechanism 6 for adjusting the combustion condition in the space above the entrained bed 9 is described in which an air supply pipe is inserted from the side wall near the narrowed portion of the reactor 2 and an air supply nozzle is provided at the tip of the air supply pipe to supply air downward from the center of the reactor 2. However, the configuration of the upper air supply mechanism 6 is not limited to this example and can be configured appropriately depending on the size of the reactor 2, etc.

[0073] For example, as shown in Fig. 7(a), an air supply pipe with an air supply nozzle at its tip may be provided so as to hang down from the top of the reactor 2, or as shown in Fig. 7(b), multiple air supply nozzles may be provided near the narrowed portion of the reactor 2. For example, multiple air supply nozzles may be evenly arranged on concentric circles in a plan view.

[0074] In the above-described embodiment, an example was described in which the gas supply mechanism 3 is configured to supply a mixed gas of water vapor and air, which is an example of an oxygen-containing gas. However, as long as the gas supply mechanism 3 is provided with the respective components of the oxygen-containing gas ratio adjustment mechanism and flow state adjustment mechanism described above, the gas supply mechanism 3 may be configured to supply water vapor and oxygen-containing gas separately.

[0075] In the above-mentioned embodiment, a spouted bed is formed inside the reactor 2 to heat-treat the raw material, and the raw material is stirred and fluidized together with the silica sand in the spouted bed. However, a fluidized bed may be formed near the bottom of the reactor 2, and the raw material is stirred and fluidized together with the silica sand in the fluidized bed. In either case, in order to bring the raw material into good contact with the gas by the spouted bed or the fluidized bed, the particle size of the silica sand is preferably in the range of 0.05 mm to 2 mm. Also, if the raw material can be heat-treated while being in contact with the gas inside the reactor 2, it is not essential to charge the silica sand inside the reactor 2.

[0076] The above-described embodiment merely describes one specific example of the amorphous silica manufacturing apparatus and manufacturing apparatus according to the present invention, and the scope of the present invention is not limited by the description. It goes without saying that the specific configuration of each part can be appropriately modified and designed within the scope in which the effects of the present invention are achieved. [Explanation of symbols]

[0077] 1: Amorphous silica manufacturing equipment 2: Reactor 3: Gas supply mechanism 30: Header pipe 31: Diffusion pipe 32: Air supply pipe 32V: Bulb 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: Spouted bed 10: Exhaust pipe A: Heat treatment condition control mechanism

Claims

1. An apparatus for producing amorphous silica, comprising: a reactor; a raw material supply mechanism for supplying biomass derived from a silicic acid plant as a raw material to the reactor; a gas supply mechanism for supplying steam and an oxygen-containing gas from a bottom of the reactor where the raw material is retained; and a heat treatment of the raw material while contacting it with the steam and the oxygen-containing gas to produce amorphous silica, a temperature control mechanism for maintaining the temperature of the inner space of the reactor at or below a predetermined temperature at which crystallization of the amorphous silica is inhibited; The temperature control mechanism is composed of a heat exchanger that uses water as a heat medium, and an upper air supply mechanism that supplies air between the gas supply mechanism and the heat exchanger to combust the raw material, and the water vapor generated in the heat exchanger is supplied to the reaction furnace via the gas supply mechanism.

2. 2. The apparatus for producing amorphous silica according to claim 1, further comprising an oxygen-containing gas ratio adjusting mechanism for adjusting the ratio of the oxygen-containing gas to the amount of the raw material supplied, converted into an air ratio, to a range of 1.3 to 1.

5.

3. 3. The apparatus for producing amorphous silica according to claim 1, wherein the temperature control mechanism includes temperature sensors downstream of the heat exchanger provided in the reactor and between the heat exchanger and the upper air supply mechanism.

4. A method for producing amorphous silica, comprising: a raw material supplying step of supplying a raw material made of biomass derived from a silicic acid plant to a reactor by a raw material supplying mechanism; a gas supplying step of supplying steam and an oxygen-containing gas from a bottom of the reactor where the raw material is retained by a gas supplying mechanism; and a heat treatment of the raw material while contacting it with the steam and the oxygen-containing gas to produce amorphous silica, A temperature control step of maintaining the temperature of the inner space of the reactor at or below a predetermined temperature that inhibits crystallization of the amorphous silica, A method for producing amorphous silica, wherein the temperature adjustment step is performed by a heat exchanger using water as a heat medium, and an upper air supply mechanism that supplies air between the gas supply mechanism and the heat exchanger to combust the raw material, and the water vapor generated in the heat exchanger is supplied to the reactor via the gas supply mechanism.

5. 5. The method for producing amorphous silica according to claim 4, further comprising an oxygen-containing gas ratio adjusting step of adjusting the ratio of the oxygen-containing gas to the raw material in terms of an air ratio within the range of 1.3 to 1.

5.

6. 6. The apparatus for producing amorphous silica according to claim 4 or 5, wherein the temperature adjustment step is performed based on the value of a temperature sensor disposed downstream of the heat exchanger provided in the reactor and between the heat exchanger and the upper air supply mechanism.

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