阅读说明：本技术 一种用含硅固体废弃物生产工业硅的方法 (Method for producing industrial silicon by using silicon-containing solid waste ) 是由 吴展平 赵云松 王元攀 吴小春 杨作荣 于 2021-09-29 设计创作，主要内容包括：本发明为一种用含硅固体废弃物生产工业硅的方法。一种用含硅固体废弃物生产工业硅的方法,包括：(1)将含硅固体废弃物置于酸性溶液中进行浸泡后,固液分离,对固相进行清洗,得硅渣；(2)将硅渣通过造粒机制成硅渣颗粒；(3)将硅渣颗粒和造渣剂混合均匀后,置于熔炼装置中,再在表面覆盖助剂,加热至完全融化后,去除表面渣液,得硅液；(4)将所述的硅液倒入模具中,冷却后,得工业硅。本发明所述的一种用含硅固体废弃物生产工业硅的方法,在熔炼之前,将硅渣中的主要杂质为二氧化硅和铁、铝、钙、铜等金属进行有效去除,从而使硅渣中的硅能够得到最大化的利用。(The invention relates to a method for producing industrial silicon by using silicon-containing solid waste. A method for producing industrial silicon by using silicon-containing solid waste comprises the following steps: (1) soaking the silicon-containing solid waste in an acid solution, performing solid-liquid separation, and cleaning a solid phase to obtain silicon slag; (2) preparing silicon slag into silicon slag particles through a granulator; (3) uniformly mixing the silicon slag particles and a slagging constituent, placing the mixture in a smelting device, covering an auxiliary agent on the surface, heating the mixture until the mixture is completely melted, and removing surface slag liquid to obtain silicon liquid; (4) and pouring the silicon liquid into a mold, and cooling to obtain the industrial silicon. According to the method for producing the industrial silicon by using the silicon-containing solid waste, disclosed by the invention, the main impurities in the silicon slag are effectively removed, such as silicon dioxide, iron, aluminum, calcium, copper and the like, before smelting, so that the silicon in the silicon slag can be utilized to the maximum extent.)

1. A method for producing industrial silicon by using silicon-containing solid waste is characterized by comprising the following steps:

(1) after the silicon-containing solid waste is placed in an acid solution for soaking treatment, solid-liquid separation is carried out, and the obtained solid phase is cleaned to obtain silicon slag;

(2) making the silicon slag into silicon slag particles with the water content of less than 8% by a granulator;

(3) uniformly mixing the silicon slag particles and a slagging constituent, placing the mixture in a smelting device, covering an auxiliary agent on the surface, heating the mixture until the mixture is completely melted, and removing surface slag liquid to obtain silicon liquid;

(4) and pouring the silicon liquid into a mold, and cooling to obtain the industrial silicon.

2. The method of claim 1,

in the step (1), the acidic solution contains hydrochloric acid, hydrofluoric acid and nitric acid.

3. The method of claim 2,

the mass fraction of the hydrochloric acid is 5-15%;

the mass fraction of the hydrofluoric acid is 0.5-8%;

the mass fraction of the nitric acid is 0.1-2%.

4. The method of claim 1,

in the step (1), stirring is carried out while soaking treatment is carried out, and soaking is carried out for not less than 24 hours.

5. The method of claim 1,

in the step (1), the mass ratio of the silicon-containing solid waste to the acidic solution is 1: 3.

6. The method of claim 1,

in the cleaning process of the step (1), the solid-liquid ratio is 1:10-15, the water temperature is higher than 4 ℃, and the cleaning is carried out for 6 hours.

7. The method of claim 1,

in the step (1), the water content of the solid phase is less than 30%, and the water content of the silicon slag is less than 30%.

8. The method of claim 1,

in the step (2), the silicon slag particles are 5-10mm spherical or cylindrical.

9. The method of claim 1,

in the step (3), the mass ratio of the silicon slag particles to the slagging agent to the auxiliary agent is 100: 0.5-2: 0.5-15.

10. The method of claim 1,

in the step (3), the slagging constituent is carbonate;

the auxiliary agent is one of fluoride, chloride, oxide and silicate.

Technical Field

The invention belongs to the technical field of polycrystalline silicon, and particularly relates to a method for producing industrial silicon by using silicon-containing solid waste.

Background

In the production process of the polycrystalline silicon, after materials in a cold hydrogenation and reduction section are recovered by chlorosilane, a certain amount of slurry materials containing silicon, chlorosilane and high-boiling residues are generated. The slag slurry mainly comprises solid-phase silicon powder particles, liquid-phase silicon tetrachloride, silicon trichloride, high-boiling residues, a small amount of metal chloride and the like.

In recent years, the main treatment methods of silicon slag slurry generated in the production process of polycrystalline silicon include hydrolysis method, cracking method, extraction method, rectification method, incineration method and the like, and the main purposes of the methods are to recover chlorosilane and reuse the chlorosilane or to perform harmless treatment and then landfill the chlorosilane, but no technology specially aiming at the reuse of solid silicon slag after the recovery of chlorosilane exists. For example, polysilicon production enterprises generally perform dry recovery and high-boiling cracking of silicon slag slurry, and not only recover chlorosilane and high-boiling residues in the slag slurry, but also recover silicon. And hydrolyzing and filter-pressing the waste residue to obtain solid-phase waste. The main body of the solid waste is silicon dioxide and silicon powder particles, and a small amount of ferric hydroxide, aluminum hydroxide and the like. However, at present, impurities such as silicon powder and the like cannot be sorted and utilized by a conventional method, so that the impurities cannot be utilized, precious resources are wasted, and finally, economic benefits are obviously affected.

With the expansion of the production capacity of the polycrystalline silicon, more silicon-containing solids are buried by industrial wastes; at present, the recovery technology of chlorosilane in silicon slag slurry by polysilicon manufacturers is mature day by day, and the technical research and development of how to recycle silicon-containing solid waste generated in the production process of polysilicon are urgently needed to solve the problems of land environmental pollution and waste of silicon resources caused by landfill.

Disclosure of Invention

The invention aims to provide a method for producing industrial silicon by using silicon-containing solid waste, which takes the silicon-containing solid waste in the production process of polycrystalline silicon as a raw material, is used for producing industrial silicon after impurities are removed, and realizes the effect of recycling the silicon-containing solid waste.

In order to realize the purpose, the adopted technical scheme is as follows:

a method for producing industrial silicon by using silicon-containing solid waste comprises the following steps:

(1) after the silicon-containing solid waste is placed in an acid solution for soaking treatment, solid-liquid separation is carried out, and the obtained solid phase is cleaned to obtain silicon slag;

(2) making the silicon slag into silicon slag particles with the water content of less than 8% by a granulator;

(3) uniformly mixing the silicon slag particles and a slagging constituent, placing the mixture in a smelting device, covering an auxiliary agent on the surface, heating the mixture until the mixture is completely melted, and removing surface slag liquid to obtain silicon liquid;

(4) and pouring the silicon liquid into a mold, and cooling to obtain the industrial silicon.

Further, in the step (1), the acid solution contains hydrochloric acid, hydrofluoric acid and nitric acid, and the mass fraction of the hydrochloric acid is 5-15%;

the mass fraction of the hydrofluoric acid is 0.5-8%;

the mass fraction of the nitric acid is 0.1-2%.

Further, in the step (1), stirring is carried out while soaking treatment is carried out, and soaking is carried out for not less than 24 hours.

Further, in the step (1), the mass ratio of the silicon-containing solid waste to the acidic solution is 1: 3.

Further, in the cleaning process of the step (1), the solid-liquid ratio is 1:10-15, the water temperature is higher than 4 ℃, and the cleaning is carried out for 6 hours.

Furthermore, the water content of the solid phase is less than 30 percent, and the water content of the silicon slag is less than 30 percent.

Further, in the step (2), the silicon slag particles are 5-10mm spherical or cylindrical.

Further, in the step (3), the mass ratio of the silicon slag particles, the slagging agent and the auxiliary agent is 100: 0.5-2: 0.5-15.

Further, in the step (3), the slag former is carbonate;

the auxiliary agent is one of fluoride, chloride, oxide and silicate.

Compared with the prior art, the invention has the beneficial effects that:

according to the technical scheme, the structure of the waste silicon slag is destroyed through acid leaching, metals such as iron, aluminum, calcium, copper and the like are removed, and then the silicon dioxide is removed through combination of smelting and deslagging, so that impurities in the silicon slag are removed to the greatest extent, the silicon content is improved, the silicon slag can be used for preparing industrial silicon, the waste silicon slag is recycled, and waste of silicon resources caused by landfill is avoided.

Detailed Description

In order to further illustrate the method for producing industrial silicon from silicon-containing solid waste according to the present invention and achieve the desired objects, the following embodiments, structures, features and effects thereof will be described in detail with reference to the accompanying drawings. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The method for producing industrial silicon from silicon-containing solid waste according to the present invention will be described in further detail with reference to the following specific examples:

the main components of the hydrolyzed silicon slag are as follows: 40-50% of silicon, 5-20% of iron, 15-25% of silicon dioxide and 5-10% of others. The silicon is simple substance silicon, and the iron is simple substance iron or iron compound. In order to make full use of silicon in the silicon slag, the silicon in the silicon slag is mainly separated from impurities such as silicon dioxide and the like. Impurities contained in the alloy are effectively removed before smelting, and then the alloy is smelted and cast, so that the product quality and the economic value can be improved. The technical scheme adopted by the invention is as follows:

a method for producing industrial silicon by using silicon-containing solid waste comprises the following steps:

(1) after the silicon-containing solid waste is placed in an acid solution for soaking treatment, solid-liquid separation is carried out, and the obtained solid phase is cleaned to obtain silicon slag;

(2) making the silicon slag into silicon slag particles with the water content of less than 8% by a granulator;

(3) uniformly mixing the silicon slag particles and a slagging constituent, placing the mixture in a smelting device, covering an auxiliary agent on the surface, heating the mixture until the mixture is completely melted, and removing surface slag liquid to obtain silicon liquid;

(4) and pouring the silicon liquid into a mold, and cooling to obtain the industrial silicon.

Preferably, in the step (1), the acidic solution contains hydrochloric acid, hydrofluoric acid and nitric acid, and further preferably, the mass fraction of the hydrochloric acid is 5-15%;

the mass fraction of the hydrofluoric acid is 0.5-8%;

the mass fraction of the nitric acid is 0.1-2%.

Preferably, in the step (1), the soaking treatment is performed while stirring, and the soaking time is not less than 24 hours.

Preferably, in the step (1), the mass ratio of the silicon-containing solid waste to the acidic solution is 1: 3.

Preferably, in the cleaning process of the step (1), the solid-liquid ratio is 1:10-15, the water temperature is higher than 4 ℃, and the cleaning is carried out for 6 hours.

Preferably, the water content of the solid phase is less than 30%, and the water content of the silicon slag is less than 30%.

Preferably, in the step (2), the silica fume particles are 5-10mm spherical or cylindrical.

Preferably, in the step (3), the mass ratio of the silicon slag particles to the slagging agent to the auxiliary agent is 100: 0.5-2: 0.5-15.

Preferably, in the step (3), the slag former is carbonate;

the auxiliary agent is one of fluoride, chloride, oxide and silicate.

Example 1.

The specific operation steps are as follows:

(1) soaking: soaking silicon-containing solid waste (silicon slag filter cake) generated in the production process of polycrystalline silicon, wherein the soaking solution is an acidic solution, and the mass fractions of hydrochloric acid, hydrofluoric acid and nitric acid contained in the acidic solution are 5-15%, 0.5-8% and 0.1-2% in sequence. And placing the silicon slag and the soak solution into a reaction kettle for stirring reaction, wherein the solid-liquid mass ratio is 1:3, and the stirring time is 24 hours.

And after stirring, carrying out solid-liquid separation on the solid-liquid mixture, recycling the liquid phase for reuse through plate-and-frame filter pressing, and cleaning the solid-phase silicon slag filter cake until the water content of the solid phase is less than 30%.

During the soaking process, a large amount of impurities such as silicon dioxide, iron, aluminum, calcium and the like contained in the silicon slag are removed through reaction. The hydrochloric acid and the hydrofluoric acid destroy the structure of the waste silicon slag, so that the waste silicon slag is reduced, and simultaneously, metal impurities in the middle of the waste silicon slag are exposed and removed; nitric acid can remove the silicon dioxide film coated on the silicon surface and separate the silicon dioxide and the silicon.

(2) Cleaning: and (3) placing the soaked silicon slag filter cake and water in a cleaning tank for stirring and cleaning according to the solid-liquid mass ratio of 1: 10-15. The temperature of the cleaning water is kept at 35-45 ℃, and the stirring and cleaning time is 6 h. And after stirring and cleaning, carrying out solid-liquid separation, and finishing the process when the water content of the solid-phase silicon slag is less than 30%.

(3) And (3) granulating and drying: adding the silicon slag into a stirrer, uniformly stirring, and conveying to a granulator, wherein the granulator can adopt an extrusion type, a disc type or a strand rotation type. The granulated silicon slag is spherical or cylindrical compact particles with the diameter of 5-10mm, and the final water content of the silicon slag particles is less than 8 percent.

(4) Smelting: dry-based silicon slag particles and a slagging agent (carbonate) are mixed according to the mass ratio of 100:0.5-2, placing the mixture into an induction furnace graphite crucible of an intermediate frequency furnace, covering the surface of the material with an auxiliary agent (fluoride, chloride or oxide, silicate and the like) with the mass ratio of silicon slag of 100:0.5-15, starting heating, and heating until the material is completely melted.

(5) Separating slag and silicon: covering the silicon liquid surface with the slag liquid (the scum is mainly silicon dioxide), pouring the slag liquid into a slag mold; returning to the furnace, replacing the mold, pouring the silicon liquid and the ingot mold again, and cooling to obtain the product.

(6) Product finishing: and taking the silicon ingot out of the ingot mold after cooling, processing a small amount of residual slag on the surface, crushing the large silicon ingot by using a crusher, and packaging in a classified manner to obtain a finished product.

Example 2.

The specific operation steps are as follows:

(1) 100KG (containing 30-60% of water) of filter cake silicon slag in the production of polycrystalline silicon is taken and placed in a reaction kettle, and 300KG of mixed liquid of hydrochloric acid, hydrofluoric acid, nitric acid and water in a mass ratio of 12:3:0.6:84.4 is prepared. Adding the prepared mixed soak solution into a reaction kettle, starting a stirring paddle of the reaction kettle to stir, sampling when the reaction stirring is carried out for 12 hours, sampling and stopping stirring when the reaction stirring is carried out for 24 hours, discharging and conveying to a plate-and-frame filter press for carrying out solid-liquid separation. And returning the filtrate to the reaction kettle for reuse, and press-filtering the solid-phase silicon slag until the water content is less than 30%, taking out and weighing for later use. And cleaning the sample to be neutral, and detecting the water content of a small amount of filter cake.

TABLE 1 data of dry base materials of silicon dioxide, Fe, Al, Ca and Cu

(2) Placing the soaked and filter-pressed silicon slag (65KG) in a cleaning tank, adding 10 times of tap water (650KG) into the cleaning tank, starting a cleaning tank stirrer, testing the pH value of the solution after stirring for 1h, testing the pH value to be 4 by using a pH test paper, stopping stirring for 5h, discharging the mixture to a self-discharging centrifuge for solid-liquid separation, adding tap water to wash the liquid phase to be neutral after the liquid phase is relatively dried, drying the liquid phase until the water content is less than 25%, testing the water content to be 23.6%, and discharging the solid-phase silicon slag for later use.

(3) And placing the cleaned silicon slag into a stirrer, starting a stirring device, unloading and conveying the silicon slag to a strip extruding granulator for granulation after uniform stirring, conveying the granular silicon slag to a mesh belt of a dryer through a belt conveyor for drying until the water content of the dry-based granular silicon slag is less than 8%, and drying to obtain the dry-based silicon slag granules with 48.3 KG.

(4) Uniformly mixing 48.3KG dried dry-based silicon slag particles with 0.72KG sodium carbonate (mass ratio is 100:1.5), and putting the uniformly mixed materials into a graphite crucible of an induction furnace of an intermediate frequency furnace; after the feeding is finished, 0.483KG of calcium fluoride and 0.241KG of sodium chloride are added, and the surface of the calcium fluoride is covered with 4.83KG of sodium silicate and 0.483KG of calcium silicate. And starting a heating system of the medium-frequency induction furnace to fully melt the materials in the furnace.

(5) And (4) tilting the furnace body to force slag, tilting the furnace body to a proper angle, and slowly lifting the furnace body to enable surface scum to flow into a slag mold through a furnace nozzle until the slag is forced to be clean and silicon water begins to be discharged. And replacing the ingot mold, and continuously pouring out the silicon water.

(6) And crushing and screening the cooled silicon ingot through a crusher and a screening machine to obtain a product silicon block. Weighing the silicon ingot with the weight of 34.29KG, and taking a comprehensive small sample for detection. The results are shown in Table 2.

TABLE 2

Name (R)	Si(％)	Fe(％)	Al(％)	Ca(％)	Cu(％)
						Silicon block	97.8	1.36	0.03	0.01	0.35

Example 3.

The specific operation steps are as follows

(1) 100KG (containing 30-60% of water) of hydrolyzed filter cake silicon slag in the production of polycrystalline silicon is placed in a reaction kettle, and 300KG of mixed liquid of hydrochloric acid, hydrofluoric acid, nitric acid and water in a mass ratio of 15:1:0.4:83.6 is prepared. Adding the prepared mixed soak solution into a reaction kettle, starting a stirring paddle of the reaction kettle to stir, sampling when the reaction stirring is carried out for 12 hours, sampling and stopping stirring when the reaction stirring is carried out for 24 hours, discharging and conveying to a plate-and-frame filter press for solid-liquid separation, returning filtrate to the reaction kettle for reuse, and carrying out filter pressing on solid-phase silicon slag until the water content is less than 30%, taking out and weighing for later use. And cleaning the sample to be neutral, and detecting the water content of a small amount of filter cake.

TABLE 3 data of dry base materials of silicon dioxide, Fe, Al, Ca and Cu

(2) Placing the silicon slag subjected to filter pressing in a cleaning tank, adding 350KG tap water into the cleaning tank, starting a cleaning tank stirrer, testing the pH value of the solution after stirring for 1h, testing the pH value to be 3 by using a pH test paper, stopping after continuously stirring for 3h, and discharging liquid after standing for 2h for silicon slag precipitation. And adding 350KG of tap water into the cleaning tank again, starting a stirrer of the cleaning tank, testing the pH value of the solution after stirring for 1h, testing the pH value to be 5 by using a pH test paper, stopping stirring after continuing for 3h, discharging the solution to a self-discharging centrifugal machine for solid-liquid separation, adding tap water to wash the solution to be neutral after the liquid phase is relatively dried, drying the solution until the water content is less than 25%, testing the water content to be 23.6%, and discharging the solid-phase silicon slag material for later use.

(3) And placing the cleaned silicon slag into a stirrer, starting a stirring device, unloading and conveying the silicon slag to a strip extruding granulator for granulation after uniform stirring, conveying the granular silicon slag to a mesh belt of a dryer through a belt conveyor for drying until the water content of the dry-based granular silicon slag is less than 8%, and drying to obtain 46.93KG dry-based silicon slag granules.

(4) Uniformly mixing 46.93KG dried dry-based silicon slag particles with 0.7KG sodium carbonate and 0.25KG calcium carbonate in a mass ratio of 100:2, and putting the uniformly mixed materials into a graphite crucible of an induction furnace of an intermediate frequency furnace; after the feeding is finished, adding sodium fluoride, aluminum fluoride 0.47KG and potassium chloride 0.24KG, wherein the salts are all in industrial grade; the surface is covered with 4.7KG of sodium silicate and 0.47KG of calcium silicate. And starting a heating system of the medium-frequency induction furnace to fully melt the materials in the furnace.

(5) And (4) tilting the furnace body to force slag, tilting the furnace body to a proper angle, and slowly lifting the furnace body to enable surface scum to flow into a slag mold through a furnace nozzle until the slag is forced to be clean and silicon water begins to be discharged. And replacing the ingot mold, and continuously pouring out the silicon water.

(6) And crushing and screening the cooled silicon ingot through a crusher and a screening machine to obtain a product silicon block. Weighing the silicon ingot with the weight of 33.78KG, and taking a comprehensive small sample for detection. The results are shown in Table 4.

TABLE 4

Name (R)	Si(％)	Fe(％)	Al(％)	Ca(％)	Cu(％)
						Silicon block	98.1	1.27	0.01	0.01	0.18

As can be seen from tables 2 and 4, the silicon content of the produced product silicon is high, and the industrial silicon requirement is met.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.