Particle manufacturing method and particle manufacturing apparatus

Abstract

To provide a particle manufacturing method that can manufacture a particle having a larger particle size than conventional and a relatively high uniformity in particle size.SOLUTION: The particle manufacturing method according to the present invention comprises a granulation step in which a composition is dropped from a vibrating nozzle into a solvent stirred by a stirrer to granulate a particle containing the composition (step S1), and a solvent removal step in which the solvent is removed from the solvent-containing particle obtained in the granulation step (step S1) to yield particle (step S2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a particle manufacturing method and a particle manufacturing apparatus suitable for manufacturing porous particles that can be filled in a column for chromatography or the like.

Background Art

[0002] Particles produced by granulation or the like can be used, for example, as an adsorbent carrier (stationary phase) such as a catalyst. Such particles carrying a catalyst can be used for applications such as separation and removal of metals in a solution, or separation and purification of compounds in the pharmaceutical, food, and chemical industries.

[0003] Particles as described above can be produced, for example, by granulation using a freeze-drying method. Patent Document 1 (International Publication No. WO2019 / 175954) describes a technique related to the production of spray freeze granulation dry powder, in which a freeze granule is generated in a freeze granulation chamber by cooling a continuously supplied stock solution, and the generated freeze granule is freeze-dried to produce a dry powder.

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In extraction chromatography carried out to separate minor actinides from high-level radioactive waste liquid, research using an adsorbent with porous silica particles as a carrier has been underway.

[0005] In the above extraction chromatography, when feeding high-level radioactive waste liquid to the porous particles filled in the column, it is preferable to avoid pressurization in the liquid feeding as much as possible in order to enhance safety.

[0006] However, with conventional granulation methods, the small particle size results in a large pressure loss in the column. This poses a problem because when high-level radioactive waste liquid is introduced through the porous granulated particles packed into the column, it is necessary to introduce the liquid under a predetermined pressure. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the particle manufacturing method according to the present invention comprises a granulation step in which a composition obtained by mixing a first composition and a second composition is dropped from a nozzle that vibrates vertically into a solvent stirred by a stirrer, and particles containing the composition are granulated; and a solvent removal step in which the solvent is removed from the solvent-containing particles obtained in the granulation step to obtain particles. A drying step in which particles obtained in the solvent removal step are dried, and a calcination step in which particles dried in the drying step are calcined. Includes, The first composition is a silica colloid solution, The second composition is characterized by being an aqueous solution containing a mixture of ammonium molybdate, sodium dihydrogen phosphate, and salts of disodium molybdate.

[0010] Furthermore, the particle manufacturing method according to the present invention is characterized by further including a washing step of washing the particles that have been fired in the firing step.

[0011] Furthermore, the particle manufacturing apparatus according to the present invention includes at least a granulation section comprising: a nozzle that vibrates vertically; piping for supplying a composition in which a first composition and a second composition are mixed to the nozzle; and a granulation tank in which particles of the composition dropped from the nozzle are granulated into a solvent stirred by a stirrer. and, A solvent removal unit removes the solvent from the solvent-containing particles obtained in the granulation unit to obtain particles, A drying section for drying the particles obtained in the solvent removal section, and a firing section for firing the particles dried in the drying section, It has, The first composition is a silica colloid solution, The second composition is characterized by being an aqueous solution containing a mixture of ammonium molybdate, sodium dihydrogen phosphate, and salts of disodium molybdate.

[0013] Furthermore, the particle manufacturing apparatus according to the present invention is characterized in that a static mixer is used for mixing the first composition and the second composition. [Effects of the Invention]

[0015] The particle manufacturing method according to the present invention includes a granulation step in which a composition is dropped from a vibrating nozzle into a solvent stirred by a stirrer to granulate particles containing the composition, and a solvent removal step in which the solvent is removed from the solvent-containing particles obtained in the granulation step to obtain particles. With such a particle manufacturing method, it is possible to manufacture particles with a larger particle size and relatively high uniformity of particle size than conventional methods, and when used in an extraction chromatography column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0016] Furthermore, according to the particle manufacturing method of claims 3 and 4, porous particles with a large particle size and large pore volume and pore size can be obtained. When used packed into a column, the pressure loss is reduced, enabling safer transport of high-level radioactive waste liquid.

[0017] Furthermore, the particle manufacturing apparatus according to the present invention has a granulation section that includes at least a nozzle that vibrates up and down, a pipe for supplying a composition to the nozzle, and a granulation tank in which particles of the composition dropped from the nozzle are granulated into a solvent stirred by a stirrer. With such a particle manufacturing apparatus according to the present invention, it is possible to manufacture particles with a larger particle size and higher uniformity of particle size than conventional particles. When these are used in an extraction chromatography column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0018] Furthermore, according to the particle manufacturing apparatus of claim 8, porous particles with a large particle size and large pore volume and pore diameter can be manufactured. Therefore, from the viewpoint of pore diameter, when used packed into a column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0019] Further, in the particle manufacturing method and particle manufacturing apparatus according to the present invention, a solid spherical porous particle with relatively high strength can be obtained, and porous particles with relatively high particle size uniformity can be manufactured. According to such a particle manufacturing method and particle manufacturing apparatus according to the present invention, after the manufacture of the porous particles, the classification operation is labor-saving, so that the manufacturing cost can be reduced.

Brief Description of Drawings

[0020] [Figure 1] It is a diagram showing the flow of the particle manufacturing method according to an embodiment of the present invention. [Figure 2] It is a diagram showing the device configuration of the granulation unit 10 in the particle manufacturing apparatus 1 according to an embodiment of the present invention. [Figure 3] (A) A photograph of droplets of the mixed solution from the nozzle 21 when there is no vertical vibration by the vibrator 20, (B) A photograph of droplets of the mixed solution from the nozzle 21 when there is vertical vibration by the vibrator 20. [Figure 4] It is a schematic diagram explaining the solvent removal step in the particle manufacturing method according to an embodiment of the present invention. [Figure 5] It is a schematic diagram explaining the drying step in the particle manufacturing method according to an embodiment of the present invention. [Figure 6] It is a schematic diagram explaining the change in the internal structure of silica particles (porous particles). [Figure 7] It is a SEM image of silica particles 50 manufactured based on the particle manufacturing method and manufacturing apparatus according to an embodiment of the present invention. [Figure 8] It is a graph showing the relationship between the liquid feeding speed - pressure when silica particles 50 manufactured by the particle manufacturing method according to the present invention and conventional silica particles are each filled in a column. (Including the case where the column is not filled.) [Figure 9] It is a table showing the parameters set at the time of manufacturing silica particles 50 according to each example. [Figure 10] It is a table showing the characteristics of silica particles 50 according to each example.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be described while referring to the drawings. FIG. 1 is a diagram showing the flow of a particle manufacturing method according to an embodiment of the present invention. Further, FIG. 2 is a diagram showing the device configuration of the granulation unit 10 in the particle manufacturing apparatus 1 according to an embodiment of the present invention.

[0022] In the following embodiments, the description will be made by exemplifying a method for manufacturing porous silica particles and a manufacturing apparatus according to the present invention. However, the particle manufacturing method and the particle manufacturing apparatus 1 according to the present invention are not precluded from being applied to the manufacture of porous particles having a material other than silica as the main material. The particle manufacturing method and the particle manufacturing apparatus 1 according to the present invention can be applied to porous particles having an arbitrary material as the main material.

[0023] As shown in FIG. 1, in the particle manufacturing method according to an embodiment of the present invention, a granulation step by dropping into a solvent in step S1 is carried out. The device configuration for specifically carrying out such a granulation step is the granulation unit 10 in the particle manufacturing apparatus 1 shown in FIG. 2.

[0024] The compositions serving as raw materials for the porous silica particles granulated in the granulation unit 10 are respectively stored in the first composition storage tank 11 and the second composition storage tank 12. In the first composition storage tank 11, a colloidal solution of silica (SiO2), which is a weakly basic aqueous solution of nano-sized silica particles serving as the skeleton of the porous particles, is stored. In the second composition storage tank 12, a pore-forming agent solution is stored.

[0025] Note that the pore-forming agent solution stored in the second composition storage tank 12 is added for pore formation in the porous particles. The pore-forming agent solution is preferably an aqueous solution in which salts such as ammonium molybdate (NH4)6Mo7O 24 ·4H2O, sodium dihydrogen phosphate NaH2PO4, and disodium molybdate Na2MoO4·2H2O are mixed.

[0026] The silica (SiO2) colloidal solution stored in the first composition storage tank 11 and the pore-forming agent solution stored in the second composition storage tank 12 are transferred to the static mixer 15 by the first pump 13 and the second pump 14, which are located in the piping 17 connected to the respective storage tanks.

[0027] In the static mixer 15, the silica (SiO2) colloidal solution and the pore-forming agent solution are mixed. However, in this invention, it is not essential to use the static mixer 15 to mix the silica (SiO2) colloidal solution and the pore-forming agent solution; other means of solution mixing may be used.

[0028] The mixed solution of silica (SiO2) colloidal solution and pore-forming agent solution, discharged downstream from the static mixer 15, is supplied to the nozzle 21. The nozzle diameter at the tip of the nozzle 21 is approximately 0.5 mm. The mixed solution of silica (SiO2) colloidal solution and pore-forming agent solution is discharged from the tip of the nozzle 21.

[0029] A granulation tank 25 containing liquid nitrogen 23 is provided vertically below the nozzle 21. Although liquid nitrogen 23 is used as an example of the solvent stored in the granulation tank 25, other liquid refrigerants such as liquid argon or liquid helium can also be used instead of liquid nitrogen.

[0030] The fins 28, which are immersed in liquid nitrogen 23, are rotated via rods 27 by a motor (not shown) in the main body of the agitator 26. As a result, the liquid nitrogen 23 stored in the granulation tank 25 is agitated.

[0031] On the other hand, the aforementioned nozzle 21 is attached to a vibrator 20 that performs vibration in the vertical direction. The vibration characteristics (frequency, amplitude, etc.) of this vibrator 20 are controlled by a controller 19.

[0032] A mixed solution of a silica (SiO2) colloidal solution and a pore-forming agent solution is supplied to the nozzle 21, which is vibrating up and down by the vibrator 20, via piping 17. Due to the up and down vibration of the nozzle 21, the mixed solution is discharged from the nozzle 21 as nearly spherical droplets with uniform shape and diameter, and is dropped into the liquid nitrogen 23 being stirred in the granulation tank 25.

[0033] Figure 3(A) is a photograph of droplets of the mixed solution discharged from the nozzle 21 when there is no vertical vibration by the vibrator 20, and Figure 3(B) is a photograph of droplets of the mixed solution discharged from the nozzle 21 when there is vertical vibration by the vibrator 20. As shown in Figure 3(B), it can be seen that the droplets of the mixed solution discharged from the nozzle 21 due to the vertical vibration by the vibrator 20 are uniform in shape and are approximately spherical with a consistent diameter.

[0034] The droplets of the mixed solution dropped from the nozzle 21 into the liquid nitrogen 23 first freeze (solidify) in the liquid nitrogen 23, becoming spherical particles (hereinafter referred to as "silica particles 50"). The droplets of the mixed solution dropped into the liquid nitrogen 23 freeze (solidify) the water contained within them, becoming frozen spherical particles.

[0035] Here, since the liquid nitrogen 23 is agitated by the fins 28, it is prevented from the multiple silica particles 50 from bonding together to form a single particle. Therefore, the silica particles 50 become spherical particles with uniform particle sizes (for example, particle size of about 1 mm).

[0036] On the other hand, if we assume that the liquid nitrogen 23 is not stirred in the granulation tank 25, the particles generated by a single droplet dropped from the nozzle 21 will coalesce, resulting in particles of uneven size and a large number of non-spherical particles.

[0037] Now, the process of treating the large-particle-sized silica particles 50 obtained through the granulation process described above to create the finished silica particles 50 with pores will be explained below.

[0038] Returning to Figure 1, in step S2, a solvent removal step is performed to remove the liquid nitrogen 23 (solvent) remaining around the silica particles 50. Figure 4 is a schematic diagram illustrating the solvent removal step in the particle manufacturing method according to an embodiment of the present invention.

[0039] The silica particles 50 granulated in liquid nitrogen 23 in the granulation tank 25 are collected in a glass container 30, such as a flask. Antifreeze 44 is stored in the chamber 43. In the solvent removal process, the glass container 30 is brought into contact with the antifreeze 44 cooled to below 0°C in the chamber 43, thereby evaporating the excess liquid nitrogen 23 without melting the frozen water in the silica particles 50.

[0040] Following step S2, a drying process is carried out in step S3. Figure 5 is a schematic diagram illustrating the drying process in the particle production method according to an embodiment of the present invention.

[0041] As shown in Figure 5, a rubber stopper 35 through which an exhaust pipe 36 is inserted is fitted to the opening of the glass container 30 after the solvent removal process. A vacuum pump (not shown) is attached to the end of the exhaust pipe 36 that is not inside the glass container 30. By operating this vacuum pump, the pressure inside the glass container 30 is reduced to remove moisture from the silica particles 50.

[0042] Following step S3, a pre-firing process is carried out in step S4, and then, following step S4, the main firing process is carried out in step S5.

[0043] To carry out the pre-firing and main firing processes, the silica particles 50 in the glass container 30 are transferred to a heat-resistant container (not shown), such as a crucible, and the crucible is placed in an electric furnace (not shown) to perform each firing process. The pre-firing process is carried out at a temperature of, for example, 350°C, and the main firing process is carried out at a temperature of, for example, 690°C for a predetermined time (for example, about 1 hour). Note that the crucible and electric furnace are not essential equipment for carrying out each firing process and are shown only as examples.

[0044] The purpose of carrying out the pre-calcination and final calcination processes described above is to induce phase separation using spinodal decomposition. Of the two phases separated, the first phase is the phase that forms the framework of silica particles, mainly composed of SiO2, and the second phase is the phase of complex salts such as phosphomolybdic acid.

[0045] After each of the above firing processes has been carried out, a washing process is performed as step S6. In this washing process, a 1 mol / L nitric acid solution and 90°C hot water are used to wash and remove the second phase of the separated material, which is the complex salt, etc.

[0046] After the washing step in step S6, the drying step in step S7 can be performed to obtain porous silica particles 50 remaining as the first phase.

[0047] The changes in the internal structure of the silica particles 50 during steps S4 to S7 will be explained using the schematic diagram in Figure 6. Each figure in Figure 6 is a magnified view of a part of the silica particles 50. The leftmost figure in Figure 6 shows the internal structure of the silica particles 50 in the unseparated state after step S3.

[0048] By performing the S4 and S5 calcination processes on these unseparated silica particles 50, the particles are separated into a phase mainly composed of SiO2 and a phase mainly composed of complex salts, etc. (Center diagram in Figure 6) In step S6, the phase-separated silica particles 50 are washed with acid and hot water to remove the complex salt and other phases, and in the drying step S7, excess moisture is removed to finally obtain porous silica particles 50 with pores.

[0049] Figure 7 shows SEM images of silica particles 50 manufactured according to the particle manufacturing method and apparatus according to an embodiment of the present invention. Figure 7(A) shows the entire silica particle 50, and Figure 7(B) shows the surface of the silica particle 50. As can be seen from Figure 7(A), the particle size of the porous silica particles 50 produced by the present invention approaches approximately 1 mm. Furthermore, from Figure 7(B), numerous pores can be seen on the surface of the silica particle 50.

[0050] A comparison was made between silica particles 50 produced by the particle manufacturing method according to the present invention described above and conventional silica particles. Commercially available silica particles were used as the conventional particles. Particle size distribution measurements were performed on the silica particles 50 produced according to the present invention and the conventional silica particles. The average particle size of the former was approximately 1 mm, while the average particle size of the latter was approximately 50 μm. As can be seen from this, the particle size of the silica particles 50 produced according to the present invention is approximately two orders of magnitude larger than that of the conventional silica particles. Laser diffraction and scattering methods were used to measure the average particle size.

[0051] As described above, the silica particles 50 produced by the particle production method and apparatus according to the present invention can produce particles with a larger particle size than conventional particles.

[0052] Next, silica particles 50 produced by the particle manufacturing method according to the present invention and conventional silica particles were packed into columns, and the relationship between the liquid delivery rate and pressure was investigated. For reference, the relationship between the liquid delivery rate and pressure was also investigated in the case of an unpacked column. Figure 8 is a graph showing the liquid delivery rate-pressure relationship for these three cases.

[0053] The procedure for obtaining the relationship between liquid delivery rate and pressure was as follows: First, particles that had been thoroughly mixed with deionized water were packed into a glass column (10 mmφ × 400 mmH) to a height of 380 mm, taking care to prevent air from entering.

[0054] Next, after connecting the plunger pump and pressure sensor (PA-750 amplifier-equipped pressure sensor manufactured by Nidec Copal Electronics Corporation), deionized water (25°C) is pumped, and the voltage value of the pressure sensor is measured as the pumping speed is increased.

[0055] The pressure was determined by converting the voltage value from the pressure sensor into a pressure value.

[0056] For the conventional silica particles, commercially available products were used.

[0057] As shown in Figure 8, the relationship between liquid delivery rate and pressure in a column packed with silica particles 50 produced by the particle manufacturing method according to the present invention was almost the same as when the column was empty. In contrast, it can be seen that the pressure of a conventional column packed with silica particles increased significantly with increasing liquid delivery rate.

[0058] Verifications related to Figure 8 also show that the silica particles 50 produced by the particle production method and apparatus according to the present invention can be used, for example, by packing them into a column when separating minor actinides from high-level radioactive waste liquid, thereby reducing pressure loss and enabling safer delivery of high-level radioactive waste liquid. (Examples) Below, we will describe the production of several examples of silica particles 50 based on the particle production method and particle production apparatus according to the present invention. The parameters set during production differ in each embodiment, and these are shown in the table in Figure 9. Figure 10 is a table showing the characteristics of the silica particles 50 according to each embodiment.

[0059] In the table in Figure 9, column (a) shows that the stirrer 26 used is the M-102 manufactured by Shibata Scientific Co., Ltd. The diameter of the 4-blade fin is 60 mm, and the diameter of the 6-blade fin is 120 mm. The granulation tank 25 in which the liquid nitrogen 23 to be stirred by the stirrer 26 is stored is the BT-100 manufactured by Sugiyama Gen Co., Ltd. The internal dimensions of this product are φ200 mm × 140 mm, and the material is SUS304t1.0.

[0060] In the table in Figure 9, Snowtex®, listed in column (c), is a colloidal solution of silica (SiO2) (a weakly basic aqueous solution of nano-sized silica particles that form the backbone of porous particles), and is a product of Nissan Chemical Corporation. Snowtex® model number N-40 has a silica concentration of 40% and the silica particle diameter in the colloidal solution is 22 nm.

[0061] Furthermore, in the pore-forming agent solution shown in column (e) of the table in Figure 9, the mixing ratio of ammonium molybdate, sodium dihydrogen phosphate, and disodium molybdate was 1.5:1:0.75 by weight, respectively.

[0062] Furthermore, in relation to column (g) of the table in Figure 9, the exciter 20 used was the PET-05 manufactured by IMV Corporation.

[0063] Furthermore, the "fluid delivery rate" in column (h) of the table in Figure 9 refers to the flow rates of the first pump 13 and the second pump 14.

[0064] Furthermore, in the table in Figure 10, column (i) "Average particle size" was measured using a Mastersizer 3000 from Malvern Panalytical (measured using dry dispersion with AeroS), and the average particle size was defined as the 50% volume-based particle size.

[0065] Furthermore, the "uniformity" in column (j) of the table in Figure 10 was calculated by measuring the particle size distribution using the Mastersizer 3000 (measured using dry dispersion with AeroS) manufactured by Malvern Panalytical, and applying the result of the particle size distribution to the following formula.

[0066]

number

[0067] however,

[0068]

number

[0069] These represent the volume [%] and particle size [mm] of size class i.

[0070]

number

[0071] This is the median diameter (average particle diameter) [mm]. Uniformity is a numerical indicator that shows the distribution of particle sizes; a smaller value indicates a narrower distribution of particles relative to the average particle size (higher particle size uniformity).

[0072] Furthermore, to obtain the data related to "pores" in columns (k) and (l) of the table in Figure 10, the pore distribution was measured using the mercury intrusion method with a PoreMaster 60 manufactured by Quantachrome Instruments (now Anton Paar). The average pore diameter is based on the 50% pore diameter by volume.

[0073] From the above, it was confirmed that, by appropriately setting each parameter, silica particles 50 having a particle diameter of 1.07 to 1.38 mm can be produced using the particle manufacturing method and particle manufacturing apparatus according to the present invention.

[0074] Furthermore, it was confirmed that, by appropriately setting each parameter, silica particles 50 with relatively good uniformity of 0.27 to 0.40 can be produced using the particle manufacturing method and particle manufacturing apparatus according to the present invention.

[0075] Furthermore, according to the particle manufacturing method and particle manufacturing apparatus of the present invention, by appropriately setting each parameter, it was possible to manufacture silica particles 50 having a relatively large pore volume, with a total pore volume of 1.67 mL / g or more.

[0076] Furthermore, according to the particle manufacturing method and particle manufacturing apparatus of the present invention, by appropriately setting each parameter, it was possible to manufacture silica particles 50 having a large pore size, with an average pore size of 0.90 μm or more.

[0077] Thus, the silica particles 50 produced by the particle manufacturing method and apparatus according to the present invention are silica particles 50 with a large particle size and large pore volume and pore diameter.

[0078] As described above, the particle manufacturing method according to the present invention includes a granulation step in which a composition is dropped from a vibrating nozzle into a solvent stirred by a stirrer to granulate particles containing the composition, and a solvent removal step in which the solvent is removed from the solvent-containing particles obtained in the granulation step to obtain particles. With such a particle manufacturing method, it is possible to manufacture particles with a larger particle size and higher uniformity of particle size than conventional methods, and when used in an extraction chromatography column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0079] Furthermore, according to the particle manufacturing method of claims 3 and 4, porous particles with a large particle size and large pore volume and pore size can be obtained. When used packed into a column, the pressure loss is reduced, enabling safer transport of high-level radioactive waste liquid.

[0080] Furthermore, the particle manufacturing apparatus 1 according to the present invention has a granulation section 10 that includes at least a nozzle 21 that vibrates up and down, a pipe 17 for supplying a composition to the nozzle 21, and a granulation tank 25 in which particles of the composition dropped from the nozzle 21 are granulated into a solvent stirred by a stirrer 26. With such a particle manufacturing apparatus 1 according to the present invention, it is possible to manufacture particles with a larger particle size and relatively high uniformity of particle size than conventional particles. When these are used in an extraction chromatography column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0081] Furthermore, according to the particle manufacturing apparatus 1 of claim 8, porous particles with a large particle size and large pore volume and pore size can be manufactured. When used packed into a column, the pressure loss is reduced, enabling safer delivery of high-level radioactive waste liquid.

[0082] Furthermore, the particle manufacturing method and particle manufacturing apparatus 1 according to the present invention can produce porous particles that are solid and spherical, have relatively high strength, and have relatively high uniformity in particle size. With such a particle manufacturing method and particle manufacturing apparatus 1 according to the present invention, the classification operation after the production of porous particles is reduced, making it possible to reduce manufacturing costs. [Explanation of Symbols]

[0083] 1...Particle production equipment 10. Granulation section 11...first composition storage tank 12...Second composition storage tank 13. Pump No. 1 14. Pump No. 2 15. Static Mixer 17. Piping 19. Controller 20. Vibrator 21... Nozzle 23. Liquid nitrogen (solvent) 25... Granulation tank 26...Agitator 27.. ​​Rod 28.. Finn 30... Glass containers 35... Rubber stopper 36. Exhaust pipe 43... Chamber 44. Antifreeze 50... Silica particles (porous particles) Step S1... Granulation process by dropping into solvent Step S2... Solvent removal process Step S3... Drying process Step S4... Pre-firing process Step S5... Firing Process Step S6... Cleaning process Step S7... Drying process

Claims

1. A granulation step is performed in which a composition obtained by mixing the first composition and the second composition is dropped from a nozzle that vibrates vertically into a solvent stirred by a stirrer, thereby granulating particles containing the composition. A solvent removal step is performed to remove the solvent from the solvent-containing particles obtained in the granulation step to obtain particles, A drying step to dry the particles obtained in the solvent removal step, The process includes a firing step in which the particles dried in the above drying step are fired, The first composition is a silica colloid solution, A method for producing particles, characterized in that the second composition is an aqueous solution containing a mixture of ammonium molybdate, sodium dihydrogen phosphate, and salts of disodium molybdate.

2. The particle manufacturing method according to claim 1, further comprising a washing step of washing the particles that have been fired in the aforementioned firing step.

3. A nozzle that vibrates up and down, A pipe for supplying a composition, which is a mixture of the first composition and the second composition, to the nozzle, A granulation tank in which particles of a composition dropped from a nozzle are granulated into a solvent stirred by a stirrer, and a granulation section comprising at least A solvent removal unit removes the solvent from the solvent-containing particles obtained in the granulation unit to obtain particles, A drying section for drying the particles obtained in the solvent removal section, It has a firing section for firing the particles dried in the drying section, The first composition is a silica colloid solution, A particle manufacturing apparatus characterized in that the second composition is an aqueous solution containing a mixture of ammonium molybdate, sodium dihydrogen phosphate, and salts of disodium molybdate.

4. The particle manufacturing apparatus according to claim 3, characterized in that a static mixer is used for mixing the first composition and the second composition.

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