阅读说明：本技术 肥料及包含硅酸盐水溶液的肥料的制备方法 (Fertilizer and method for producing fertilizer containing silicate aqueous solution ) 是由 徐盟贵 黄汉璋 李东峯 邹易谚 于 2019-04-23 设计创作，主要内容包括：一种肥料及一种包含硅酸盐水溶液的肥料的制备方法,所述肥料包含硅酸盐水溶液,该硅酸盐水溶液的碱度小于1％,并该硅酸盐水溶液含有水溶性金属氧化物及盐酸溶性氧化硅,该盐酸溶性氧化硅与该水溶性金属氧化物的重量比值范围为0.9～1.4。前述肥料其碱度及盐酸溶性氧化硅与水溶性金属氧化物的重量比值皆更符合目前应用上的需求。(A fertilizer and a preparation method of the fertilizer containing aqueous silicate solution are provided, wherein the fertilizer contains aqueous silicate solution, the alkalinity of the aqueous silicate solution is less than 1%, the aqueous silicate solution contains water-soluble metal oxide and hydrochloric acid-soluble silicon oxide, and the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide is 0.9-1.4. The alkalinity of the fertilizer and the weight ratio of the hydrochloric acid soluble silicon oxide to the water soluble metal oxide all meet the requirements of the current application.)

1. A fertilizer, characterized in that: the fertilizer comprises a silicate aqueous solution, wherein the alkalinity of the silicate aqueous solution is less than 1%, the silicate aqueous solution contains water-soluble metal oxide and hydrochloric acid-soluble silicon oxide, and the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide ranges from 0.9 to 1.4.

2. The fertilizer according to claim 1, characterized in that: the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide is 1-1.3.

3. The fertilizer according to claim 1, characterized in that: the aqueous silicate solution has a pH greater than 13.

4. The fertilizer according to claim 1, characterized in that: the water-soluble metal oxide is selected from water-soluble alkali metal oxides.

5. Fertilizer according to claim 4, characterized in that: the water-soluble metal oxide is water-soluble potassium oxide.

6. Fertilizer according to any one of claims 1 to 5, characterized in that: the alkalinity of the silicate aqueous solution is less than 0.5 percent.

7. The fertilizer according to claim 6, characterized in that: the alkalinity of the silicate aqueous solution is less than 0.1%.

8. The fertilizer according to claim 1, characterized in that: the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide ranges from 1 to 1.3, the pH value of the silicate aqueous solution is greater than 13, and the alkalinity of the silicate aqueous solution is less than 0.5%.

9. Fertilizer according to claim 1 or 8, characterized in that: the silicate is present in an amount ranging from 35 to 45 wt% based on 100 wt% of the total weight of the aqueous silicate solution.

10. A method for producing a fertilizer comprising an aqueous silicate solution, characterized in that: the preparation method comprises a step of mixing a purified powder with an aqueous hydroxide solution to obtain the aqueous silicate solution, the purified powder including a plurality of primary particles containing silicon and being prepared by the steps of:

(1) providing a silicon filter cake containing silicon, water and organic matters; and

(2) turning the silicon filter cake into a plurality of reaction particles to obtain the purified powder,

wherein the step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

11. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the method of mixing the purified powder with the aqueous hydroxide solution is to mix the purified powder with a solvent containing water to obtain a mixed slurry, and then mix the mixed slurry with the aqueous hydroxide solution to obtain the aqueous silicate solution.

12. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the number of moles of silicon in the purified powder is not less than the number of moles of hydroxide in the aqueous hydroxide solution.

13. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the ratio of the mole ratio of silicon in the purified powder to the hydroxide in the aqueous hydroxide solution is in the range of 1 to 2.1.

14. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: d of the primary particle₅₀The particle size is 0.4 to 0.9 μm.

15. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the silicon filter cake is prepared by filter pressing the silicon powder water solution generated in the slicing process of the silicon crystal bar.

16. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the aqueous hydroxide solution is an aqueous potassium hydroxide solution.

17. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the step (2) is to change the silicon filter cake into the reaction particles, and then remove the organic substances in the reaction particles to obtain the purified powder.

18. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10, characterized in that: the aqueous silicate solution has a pH greater than 13.

19. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10 or 17, characterized in that: the method for changing the silicon filter cake into the reaction particles in the step (2) is as follows:

(2-1) dehydrating the silica filter cake to obtain a dehydrated silica filter cake; and

(2-2) pulverizing the dehydrated silica cake to obtain the reaction particles.

20. The method of producing a fertilizer comprising an aqueous silicate solution according to claim 19, characterized in that: in this step (2-2), D of the reaction particles₅₀The particle size range is 0.7 mu m-10 mm.

21. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10 or 17, characterized in that: the method for changing the silicon filter cake into the reaction particles in the step (2) is as follows:

(2-1) mixing the silicon filter cake with water and stirring and dispersing to obtain a mixed solution; and

(2-2) spray-drying the mixed solution to obtain the reaction particles.

22. The method of producing a fertilizer comprising an aqueous silicate solution according to claim 21, characterized in that: in this step (2), the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter in the range of 20 to 50 μm, each secondary particle being composed of a plurality of primary particles containing silicon.

23. The method of producing a fertilizer comprising an aqueous silicate solution according to claim 22, characterized in that: the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter of 30 to 45 μm.

24. The method for producing a fertilizer containing an aqueous silicate solution according to claim 10 or 17, characterized in that: the step (2) is to knead and dry the silicon filter cake in a negative pressure environment to obtain the reaction particles.

25. The method of producing a fertilizer comprising an aqueous silicate solution according to claim 24, characterized in that: in this step (2), the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter in the range of 0.7 to 20 μm, each secondary particle being composed of a plurality of primary particles containing silicon.

26. The method of producing a fertilizer comprising an aqueous silicate solution according to claim 25, characterized in that: the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter of 1 to 3 μm.

27. A fertilizer, characterized in that: the fertilizer comprises a purified powder and an additive selected from a potassium salt, a phosphate salt, an organic fertilizer or a combination of the foregoing, the purified powder comprising a plurality of primary particles comprising silicon and being prepared by the steps of:

(1) providing a silicon filter cake containing silicon, water and organic matters; and

(2) turning the silicon filter cake into a plurality of reaction particles to obtain the purified powder,

wherein the step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

28. The fertilizer material of claim 27, wherein: d of the primary particle₅₀The particle size is 0.4 to 0.9 μm.

Technical Field

The present invention relates to a fertilizer and a method for producing a fertilizer containing an aqueous silicate solution, and more particularly to a fertilizer containing silicon and a method for producing a fertilizer containing an aqueous silicate solution including a step of removing organic substances.

Background

Silicon-containing fertilizers can be classified as liquid silicon fertilizers, which typically comprise an aqueous silicate solution (e.g., an aqueous potassium silicate solution), or solid silicon fertilizers, which typically comprise silicon and other fertilizer additives.

The existing preparation method of liquid silicon fertilizer or solid silicon fertilizer usually uses silicon as raw material. TW200502164 discloses a method for preparing silicate aqueous solution as liquid silicon fertilizer, which is prepared by directly using waste silicon generated in semiconductor manufacturing process to perform oxidation reaction with hydroxide aqueous solution. However, the long time required for the reaction between silicon and hydroxide in the above preparation method leads to high time cost when waste silicon is directly used as a raw material for preparing a silicate aqueous solution, and since the waste silicon contains organic impurities such as sealing resin, the organic matters remain in the fertilizer prepared subsequently when the waste silicon is directly used as a raw material for preparing a silicon-containing fertilizer, and the organic matters are difficult to be removed from the fertilizer; in addition, the alkalinity of the preparation method is higher than that of the existing liquid fertilizer taking silicate aqueous solution as the main component, and the weight ratio of the hydrochloric acid soluble silicon oxide to the water soluble metal oxide is not in line with the requirement of the current application.

Therefore, it is a direction of research to find a liquid fertilizer with alkalinity and weight ratio of hydrochloric acid soluble silicon oxide to water soluble metal oxide meeting the current application requirements, and how to solve the problems of residual organic matters difficult to remove in the silicon-containing fertilizer and long reaction time of silicon and hydroxide caused by the preparation method.

Disclosure of Invention

A first object of the present invention is to provide a liquid fertilizer.

Thus, the fertilizer comprises a silicate aqueous solution having a basicity of less than 1%, and the silicate aqueous solution contains a water-soluble metal oxide and a hydrochloric acid-soluble silicon oxide, the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide being in the range of 0.9 to 1.4.

A second object of the present invention is to provide a method for preparing a fertilizer comprising an aqueous silicate solution.

The method for preparing a fertilizer comprising an aqueous silicate solution according to the present invention comprises a step of mixing a purified powder comprising a plurality of primary particles containing silicon with an aqueous hydroxide solution to obtain the aqueous silicate solution, and is prepared by the steps of:

(1) providing a silicon filter cake containing silicon, water and organic matters;

(2) turning the silicon filter cake into a plurality of reaction particles to obtain the purified powder,

wherein the step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

A third object of the present invention is to provide a fertilizer in a solid state.

The fertilizer thus comprises a purified powder and an additive selected from a potassium salt, a phosphate, an organic fertilizer or a combination of the foregoing, the purified powder comprising a plurality of primary particles comprising silicon and being prepared by the steps of:

(1) providing a silicon filter cake containing silicon, water and organic matters; and

(2) turning the silicon filter cake into a plurality of reaction particles to obtain the purified powder,

wherein the step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

The invention has the following effects: the alkalinity of the silicate aqueous solution contained in the liquid fertilizer is less than 1 percent, and the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide is 0.9-1.4, so the liquid fertilizer can meet the requirements of the current application. In addition, because the purified powder of the primary particles containing silicon is used as a raw material for preparing the fertilizer, and organic matters in the silicon filter cake or the reaction particles are removed in the process of preparing the purified powder, the fertilizer does not have organic matters which are difficult to remove; in the production method of the present invention, the purified powder is reacted with an aqueous hydroxide solution, so that the reaction time of silicon and hydroxide is short.

In view of the above effects, it is added that the preparation method of the present invention is a method of converting a silica cake into a plurality of reaction particles including a plurality of primary particles and then reacting the reaction particles with an aqueous hydroxide solution, and compared to the conventional method of directly reacting a silica cake (i.e., conventional waste silica cake), the reaction particles including a plurality of primary particles can increase the contact (reaction) area between silica and hydroxide, thereby promoting the reaction and increasing the reaction rate (i.e., reducing the reaction time), and therefore, compared to the conventional method, the preparation method of the present invention can reduce the reaction time between silica and hydroxide. In addition, organic matters in the silicon filter cake or the reaction particles need to be removed firstly in the preparation process of the purified powder, so organic matters which are difficult to remove do not remain in the fertilizer.

The present invention will be described in detail below:

[ Fertilizer ]

The following description will be made for the first fertilizer and the second fertilizer of the present invention, respectively:

a. a first fertilizer:

the first fertilizer is a liquid fertilizer and comprises a silicate aqueous solution, wherein the alkalinity of the silicate aqueous solution is less than 1%, the silicate aqueous solution comprises a water-soluble metal oxide and a hydrochloric acid-soluble silicon oxide, and the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide is in the range of 0.9-1.4.

The metal species in the water-soluble metal oxide is determined by the metal ion species in the aqueous hydroxide solution selected for the preparation of the aqueous silicate solution, and for example, when the aqueous hydroxide solution is an aqueous alkali metal hydroxide solution, the water-soluble metal oxide is a water-soluble alkali metal oxide. Preferably, the water-soluble metal oxide is selected from the group consisting of water-soluble alkali metal oxides, water-soluble alkaline earth metal oxides, and combinations thereof. More preferably, the water-soluble metal oxide is selected from the group consisting of water-soluble sodium oxide, water-soluble potassium oxide, water-soluble magnesium oxide, water-soluble calcium oxide, and combinations thereof. Still more preferably, the water-soluble metal oxide is water-soluble sodium oxide, water-soluble potassium oxide, or a combination of the foregoing. Still more preferably, the water-soluble metal oxide is water-soluble potassium oxide.

Preferably, the alkalinity is less than 0.5%. More preferably, the alkalinity is less than 0.1%.

Preferably, the weight ratio of the hydrochloric acid-soluble silica to the water-soluble metal oxide is in the range of 0.9 to 1.4 (wt%/wt%). More preferably, the weight ratio of the hydrochloric acid-soluble silicon oxide to the water-soluble metal oxide is 1 to 1.3.

Preferably, the aqueous silicate solution has a pH greater than 13.

Preferably, the silicate is present in an amount ranging from 35 to 45 wt% based on 100 wt% of the total weight of the aqueous silicate solution.

Preferably, the fertilizer also contains any ingredients currently available for addition to fertilizers (e.g., humates, total nitrogen, total phosphorous anhydride, or total potassium oxide, etc.).

b. A second fertilizer:

a second fertilizer of the invention is a solid fertilizer and comprises a purified powder and an additive selected from the group consisting of potassium salts, phosphates, organic fertilizers, and combinations of the foregoing, the purified powder being prepared by the steps of:

(1) providing a silicon filter cake containing silicon, water and organic matters; and

(2) turning the silicon filter cake into a plurality of reaction particles to obtain the purified powder,

wherein the step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

Such as, but not limited to, plant ash; the main component is carbonic acidPotassium (K)₂CO₃)]Potassium bicarbonate (KHCO)₃) Or a combination of the foregoing. Such as, but not limited to, ammonium dihydrogen phosphate (NH)₄H₂PO₄) Calcium superphosphate (calcium superphosphate), or combinations of the foregoing.

The organic fertilizer can be the existing fertilizer containing organic matters. Preferably, the organic fertilizer further comprises any ingredients currently available for addition to fertilizers (e.g., total nitrogen, total phosphoric anhydride, or total potassium oxide, etc.).

Preferably, the pH of the organic fertilizer is greater than 7. More preferably, the pH of the organic fertilizer is greater than 8.

Preferably, D of the primary particle₅₀The particle size is 0.4 to 0.9 μm.

Preferably, the purified powder is present in an amount ranging from 7 to 11 wt% and the additive is present in an amount ranging from 89 to 93 wt%, based on 100 wt% of the total weight of the second fertilizer. More preferably, the purified powder is in a weight range of 8 to 10 wt%, and the additive is in a weight range of 90 to 92 wt%.

[ method for producing a Fertilizer containing an aqueous silicate solution ]

The method for producing a fertilizer containing an aqueous silicate solution of the present invention comprises a step of mixing a purified powder with an aqueous hydroxide solution to obtain the aqueous silicate solution, wherein the purified powder comprises a plurality of primary particles containing silicon.

Preferably, D of the primary particle₅₀The particle size is 0.4 to 0.9 μm. More preferably, D of the primary particle₅₀The particle size is 0.5 to 0.8 μm.

Preferably, the aqueous hydroxide solution is selected from the group consisting of aqueous alkali metal hydroxide solutions, aqueous alkaline earth metal hydroxide solutions, and combinations thereof. More preferably, the aqueous hydroxide solution is selected from the group consisting of aqueous sodium hydroxide solution, aqueous potassium hydroxide solution, aqueous magnesium hydroxide solution, aqueous calcium hydroxide solution, and combinations thereof. Still more preferably, the water-soluble metal oxide is water-soluble sodium oxide, water-soluble potassium oxide, or a combination of the foregoing. Still more preferably, the aqueous hydroxide solution is an aqueous potassium hydroxide solution.

Preferably, the purified powder and the aqueous hydroxide solution are mixed by mixing the purified powder with a solvent containing water to obtain a mixed slurry, and then mixing the mixed slurry with the aqueous hydroxide solution to obtain the aqueous silicate solution. More preferably, the solvent further comprises an alcohol. Still more preferably, the alcohol is present in an amount ranging from 1 to 5 wt% based on 100 wt% of the total solvent. More preferably, the solid content of the slurry is 20-40 wt%.

Preferably, the number of moles of silicon in the purified powder is not less than the number of moles of hydroxide in the aqueous hydroxide solution.

Preferably, the mole ratio of silicon in the purified powder to hydroxide in the aqueous hydroxide solution is in the range of 1 to 2.1. More preferably, the mole ratio of silicon in the purified powder to hydroxide in the aqueous hydroxide solution is in the range of 1 to 2.0.

Preferably, the purified powder and the aqueous hydroxide solution are mixed at 65 to 95 ℃. More preferably, the purified powder and the aqueous hydroxide solution are mixed at 65 to 75 ℃.

Preferably, the silicate is present in an amount ranging from 35 to 45 wt% based on 100 wt% of the total weight of the aqueous silicate solution.

[ Process for producing purified powder ]

The following is a detailed description of the preparation of the purified powder:

the silicon filter cake is a cake-shaped filter cake obtained by filter-pressing an aqueous solution containing silicon powder and organic matters through a plate frame.

Preferably, the aqueous solution containing silicon powder and organic substances is obtained from a semiconductor process in which an aqueous solution (containing organic substances) of silicon powder is generated. Preferably, the silicon filter cake is prepared by press-filtering a silicon powder aqueous solution generated in the slicing process of the solar silicon crystal bar by a plate frame. More preferably, D of the silicon powder in the aqueous solution of silicon powder₅₀The particle size is 0.4 to 0.9 μm. More preferably, D of the silicon powder in the aqueous solution of silicon powder₅₀The particle size is 0.5 to 0.8 μm.

The organic matter is any organic impurity that is typically present in a silicon filter cake, for example, when the aqueous solution containing silicon powder and organic matter is obtained from a semiconductor process that produces an aqueous solution of silicon powder during the process, the organic matter is an organic impurity that is present in an aqueous solution of silicon powder during a conventional semiconductor process.

Preferably, the water content is 35 to 45 wt% based on 100 wt% of the total weight of the silica cake.

The step (2) further comprises a step of removing organic matters from the silicon cake before the silicon cake becomes the reaction particles, or a step of removing organic matters from the reaction particles before the purified powder is obtained.

It should be noted that the aforementioned method for removing organic matter from the silicon filter cake or the reaction particles can be any method (physical formula or chemical formula) capable of removing organic matter from silicon, such as but not limited to, removing organic matter from the silicon filter cake or the reaction particles by using an organic solvent (such as alcohol or ketone) or an acid (such as nitric acid or hydrofluoric acid).

Preferably, the step (2) is a method for converting the silicon filter cake into the reactive particles as follows:

(2-1) dehydrating the silica filter cake to obtain a dehydrated silica filter cake; and

(2-2) pulverizing the dehydrated silica cake to obtain the reaction particles.

More preferably, the step (2-1) is performed by removing water at 150-170 ℃.

More preferably, in the step (2-1), the solid content of the dehydrated silica filter cake ranges from 98 to 99.5 wt%.

More preferably, in the step (2-2), D of the reaction particles₅₀The particle size range is 0.7 mu m-10 mm. Still more preferably, in the step (2-2), D of the reaction particles₅₀The particle size is 0.7-1.3 mm. Still more preferably, in the step (2-2), D of the reaction particles₅₀The particle size is 0.9-1.1 mm.

More preferably, in the step (2), the reaction particles from which the organic substances are removed are pulverized to obtain the purified powder.

Preferably, the step (2) is a method for converting the silicon filter cake into the reactive particles as follows:

(2-1) mixing the silicon filter cake with water and stirring and dispersing to obtain a mixed solution; and

(2-2) spray-drying the mixed solution to obtain the reaction particles.

Preferably, the silicon filter cake is mixed with water and stirred for dispersion, and then filtered by a screen mesh of 130-170 meshes (mesh) to obtain the mixed solution. More preferably, the silicon filter cake is mixed with water and stirred and dispersed, and then filtered by a screen mesh of 140-160 meshes to obtain the mixed solution. More preferably, the weight of the powder formed from the silica cake is 15 to 20 wt% based on 100 wt% of the total weight of the aqueous solution after the stirring and dispersing and before the filtering.

More preferably, D of the reaction particles₅₀The particle size range is 20-50 μm, and each reaction particle is composed of a plurality of primary particles. Still more preferably, D of the reactive particles₅₀The particle size is 30 to 45 μm. Still more preferably, D of the reactive particles₅₀The particle size is 35 to 40 μm. More preferably, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.4-0.9 μm. More preferably, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.7-0.9 μm. More preferably still, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.5-0.8 μm.

More preferably, the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter in the range of 20 to 50 μm, each secondary particle being composed of a plurality of primary particles containing silicon. Still more preferably, the purified powder comprises a plurality of D₅₀Secondary particles each having a particle diameter of 30 to 45 μm. More preferably, each secondary particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.4 to 0.9 μm and containing silicon. More preferably, each secondary particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.7 to 0.9 μm and containing silicon. More preferably, each secondary pelletA plurality of D₅₀Primary particles having a particle diameter of 0.5 to 0.8 μm and containing silicon.

Preferably, the step (2) is to knead and dry the silica filter cake in a negative pressure environment to obtain the reaction particles. In detail, the silicon filter cake is crushed into a plurality of reaction particles during the kneading and drying process under the negative pressure environment.

More preferably, the silica filter cake is kneaded and dried at a pressure greater than-75 cmHg.

More preferably, the silicon filter cake is kneaded and dried at a temperature of 80 to 150 ℃. More preferably, the silica cake is kneaded and dried at a temperature of 130 to 150 ℃.

More preferably, the silica cake is kneaded and dried by a kneading dryer.

More preferably, D of the reaction particles₅₀The particle size range is 0.7-20 μm, and each reaction particle is composed of a plurality of primary particles. Still more preferably, D of the reactive particles₅₀The particle size is 1 to 3 μm. More preferably, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.4-0.9 μm. More preferably, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.5-0.9 μm. More preferably, each reaction particle is composed of a plurality of D₅₀Primary particles with a particle size of 0.5-0.8 μm.

More preferably, the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter in the range of 0.7 to 20 μm, each secondary particle being composed of a plurality of primary particles containing silicon. Still more preferably, the purified powder comprises a plurality of D₅₀Secondary particles each having a particle diameter in the range of 1 to 3 μm. More preferably, each secondary particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.4 to 0.9 μm and containing silicon. More preferably, each secondary particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.5 to 0.9 μm and containing silicon. More preferably, each secondary particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.5 to 0.8 μm and containing silicon.

Detailed Description

The invention will be further described in the following examples, but it should be understood that these examples are illustrative only and should not be construed as limiting the practice of the invention.

< preparation example 1>

Preparation of purified powder

The purified powder of preparation 1 was prepared by the following steps:

step (1): a silicon cake containing silicon, water and organic matter is provided. The silicon filter cake is waste silicon powder (D) produced in the slicing process of the solar silicon crystal bar_50-Particle size of 0.8 μm) was subjected to plate-and-frame filter pressing using a plate-and-frame filter press. Wherein the water content is 40 wt%, based on the total weight of the silica filter cake being 100 wt%.

Step (2-1): and (3) dehydrating the silicon filter cake in a 160 ℃ vacuum box to ensure that the solid content in the silicon filter cake is 99-99.5 wt%, thus obtaining a dehydrated silicon filter cake.

Step (2-2): crushing the dewatered cake with a crusher to obtain a plurality of D₅₀Reaction particles having a particle diameter of 1mm and containing silicon and an organic substance.

Step (2-3): the organic matter in the reaction particles was removed, and then the reaction particles from which the organic matter was removed were pulverized by a high-speed pulverizer (rotation speed of 30000rpm/10 seconds) to obtain dispersed purified powder. Wherein the purified powder comprises a plurality of silicon-containing particles D₅₀Primary particles having a particle diameter of 0.8. mu.m.

It should be noted that, in the step (2-1) of the present preparation example 1, the organic material in the silica cake may be removed, and then the silica cake from which the organic material is removed is formed into a water-removed silica cake, in this case, the step (2-2) is to obtain the reaction particles containing silica, and the step (2-3) is to obtain the purified powder by directly pulverizing the reaction particles obtained in the step (2-2).

< preparation example 2>

Preparation of purified powder

The purified powder of preparation 2 was prepared by the following steps:

step (1): same as in step (1) of preparation example 1.

Step (2-1): the silica cake was mixed with reverse osmosis water (RO water), and the mixture was stirred and dispersed in a high-speed stirrer, and then filtered through a 150 mesh screen to obtain a mixed solution. Wherein the silica filter cake forms a powder having a weight of 20 wt% based on 100 wt% of the total weight of the solution after dispersion by stirring and before filtration.

Step (2-2): spray-drying the mixed solution to obtain a plurality of D₅₀Black reaction particles having a particle diameter of 36.11 μm, containing silicon and organic matter, and being spherical. The spray drying method comprises the steps of conveying the mixed solution to a centrifugal atomizing nozzle by a quantitative pump at a feeding amount of 40g per minute, carrying out centrifugal atomization on the mixed solution into liquid drops at 15000-20000 revolutions per minute, and drying the liquid drops under hot air at 250 ℃ to obtain the reaction particles. It is to be further noted that each reaction particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.8 μm and containing silicon and organic substances.

Step (2-3): removing organic matters in the reaction particles to obtain purified powder. Wherein the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter of 37 μm and being spherical, each secondary particle consisting of a plurality of D₅₀Primary particles having a particle diameter of 0.8 μm and containing silicon.

It should be noted that, in the step (2-1) of the present production example 2, the organic material in the silica cake may be removed, and then the silica cake from which the organic material is removed may be mixed with reverse osmosis water, and in this case, the purified powder may be obtained after the step (2-2) [ the purified powder obtained in the step (2-3) described above ].

< preparation example 3>

Preparation of purified powder

The purified powder of preparation 3 was prepared by the following steps:

step (1): same as in step (1) of preparation example 1.

Step (2-1): kneading and pumping the silicon filter cake in a kneading dryerAir drying (temperature 150 deg.C; pressure is pumping to-70 cmHg) to obtain multiple D₅₀The reaction particles had a particle size of 2.58 μm and were irregular. It is to be further noted that each reaction particle is composed of a plurality of D₅₀Primary particles having a particle diameter of 0.8 μm and containing silicon and organic substances.

Step (2-2): removing organic matters in the reaction particles to obtain purified powder. Wherein the purified powder comprises a plurality of D₅₀Secondary particles having a particle diameter of 2.5 μm and being irregular, each secondary particle consisting of a plurality of D₅₀Primary particles having a particle diameter of 0.8 μm and containing silicon.

It should be noted that, in the step (2-1) of the present production example 3, the organic material in the silica cake may be removed, and then the silica cake from which the organic material is removed may be kneaded and dried, and in this case, the purified powder may be obtained after the step (2-1) [ the purified powder obtained in the same manner as in the step (2-2) ].

In more detail, the method for removing organic substances in the above preparation examples 1 to 3 may be a method for removing organic substances from the silicon cake (or the reaction particles) by using an organic solvent (e.g., alcohol or ketone), or a method for removing organic substances from the silicon cake (or the reaction particles) by using an acid (e.g., nitric acid or hydrofluoric acid). If organic solvent is used for removing organic matters, the silicon filter cake (or the reaction particles) is washed by the organic solvent, and then the organic solvent remained in the reaction particles is removed; if the organic matter in the silicon filter cake (or the reaction particles) is removed by acid, the silicon filter cake (or the reaction particles) is washed by acid, then the silicon filter cake (or the reaction particles) after acid washing is washed by water to be neutral, and finally the silicon filter cake (or the reaction particles) after water washing is filtered and dried.

< comparative preparation example >

Preparation of the pulverized powder

Crushing the solar crystal growth raw material into millimeter (mm) grade silicon material by a coarse crusher, and crushing into D by a medium crusher₅₀Crushed powder having a particle size of 11 μm.

< example 1>

Preparation of aqueous Potassium silicate solution