Complexing agent for separating and purifying high-boiling residues in polycrystalline silicon slurry and preparation method of complexing agent

Abstract

The invention discloses a complexing agent for separating and purifying high-boiling residues in polycrystalline silicon slag slurry and a preparation method of the complexing agent, and relates to the technical field of complexing agents, the complexing agent comprises secondary recrystallization sodium chloride, crown ether, a dispersing agent and an anti-caking agent calcium silicate, and a complexing agent product is obtained through ball milling homogenization and air jet pulverization; the secondary recrystallized sodium chloride accounts for 90-110 parts; 0.1 to 0.3 part of crown ether; 1-3 parts of a dispersing agent; the anti-caking agent is 0.1 to 0.3 part of calcium silicate. The crown ether and the anti-caking agent calcium silicate are adopted in the complexing agent, the efficiency of the complexing agent is improved, the complexing agent is added according to the mass ratio of 1.5-2% of the mass of the high-boiling residues, the optimal aluminum removal capacity is shown at the temperature of 150-160 DEG C, and the recovery quality of the high-boiling residues is improved.

Description

Technical Field

[0001] The invention relates to the technical field of complexing agents, in particular to a complexing agent for separating and purifying high-boiling substances in polysilicon slurry and a preparation method thereof. Background Art

[0002] In the process of polysilicon production, the polymerization reaction of trichlorosilane (boiling point: 31.8℃) and silicon tetrachloride (boiling point: 57.6℃) will occur during the silicon rod deposition and cold hydrogenation fluidized bed reaction, and a certain amount of high-boiling substances (polychlorosilane) will be produced as by-products, the main components of which are tetrachlorodisilane (boiling point: 128-130℃), pentachlorodisilane (boiling point: 131℃), hexachlorodisilane (boiling point: 145℃), etc. These high-boiling substances are active in nature, and their hydrolyzates have the characteristics of spontaneous combustion, which can spontaneously combust even in water, making them extremely dangerous. In the existing polysilicon production process, these high-boiling substances are usually mixed with slurry materials. After passing through the dryer, the high-boiling substances do not enter the gas phase, but remain in the silicon powder to form a paste material with the silicon powder, and are finally sent to the hydrolysis system for hydrolysis together with the silicon powder. This results in a waste of chlorosilane (trichlorosilane and silicon tetrachloride) resources, reduces the economic efficiency of the system, consumes a large amount of lime milk and water, and produces salt-containing wastewater and filter press solid waste, which has high disposal costs and pollutes the environment.

[0003] In order to recover high-boiling products such as polychlorosilane in the slurry, the slag-slurry mixture needs to be effectively separated, and a complexing agent is added to the separated high-boiling products to remove metal impurities and improve the quality of the high-boiling products. The high-quality high-boiling products are cracked into trichlorosilane and silicon tetrachloride under the action of the catalyst and returned to the system as polysilicon raw materials, thereby achieving the purpose of reducing the cost of polysilicon.

[0004] At present, alkali metal chlorides, alkaline earth metal chlorides and transition metal chlorides are used as dealuminizing agents to remove metal impurities from high boiling points. However, when it comes to chlorosilane systems, the reaction is a liquid-solid surface reaction, the utilization rate of the dealuminizing agent is low, and a large amount of dealuminizing agent needs to be added. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a complexing agent for separating and purifying high-boiling substances in polysilicon slurry and a preparation method thereof, so as to solve the above-mentioned technical problems.

[0006] The invention protects a complexing agent for separating and purifying high-boiling substances in polysilicon slurry, and the components thereof include: secondary recrystallized sodium chloride, crown ether, dispersant, and anti-caking agent calcium silicate.

[0007] The present invention also protects a preparation method of a complexing agent for separating and purifying high-boiling substances in polysilicon slurry, which comprises the following method: homogenizing secondary recrystallized sodium chloride, crown ether, dispersant and anti-caking agent calcium silicate by ball milling, and then air flow pulverizing to obtain a complexing agent product.

[0008] Furthermore, the secondary recrystallized sodium chloride is 90-110 parts; the crown ether is 0.1-0.3 parts; the dispersant is 1-3 parts; and the anti-caking agent calcium silicate is 0.1-0.3 parts, wherein the parts are parts by weight.

[0009] Furthermore, the secondary recrystallized sodium chloride is 100 parts, the crown ether is 0.2 parts, the dispersant is 2 parts, and the anti-caking agent calcium silicate is 0.2 parts, wherein the parts are parts by weight.

[0010] Furthermore, the secondary recrystallized sodium chloride is dried in a fluidized bed; the fluidized bed has a large contact area between hot air and the material, good heat transfer effect, fast drying rate, and can ensure the uniformity of the drying effect. The material is not easy to agglomerate or stick during the drying process.

[0011] Furthermore, the dispersant is a crown ether dispersant, and the crown ether dispersant is isooctyl alcohol; the crown ether dispersant reduces the time and energy required to complete the dispersion process, effectively improves the lubricity of the complexing agent, and naturally dissipates during the ball milling homogenization process without being brought into the complexing agent;

[0012] The anti-caking agent calcium silicate can effectively prevent the complexing agent from agglomerating or coagulating. Considering safety and introducing as few new elements as possible, calcium silicate is the best choice.

[0013] The present invention also protects the application of a complexing agent for separating and purifying high-boiling substances in polysilicon slurry. The complexing agent is used for separating and purifying high-boiling substances in polysilicon slurry. The specific application is: the slurry produced by polysilicon production contains silicon powder, trichlorosilane, silicon tetrachloride and high-boiling substances; first, the trichlorosilane, silicon tetrachloride and high-boiling substances are physically separated from the silicon powder through a precipitation separation device, and then the trichlorosilane, silicon tetrachloride and high-boiling substances are separated through a clear liquid distillation device based on the principle of different boiling points; the separated high-boiling substances are passed into an aluminum removal evaporator at a temperature of 150-160°C, and a complexing agent is added at 1.5-2% of the mass of the high-boiling substances to complex metal impurities in the high-boiling substances, and the high-boiling substances are recovered by vaporization and condensation at different boiling points, and the unevaporated high-boiling substances and the complexing agent are retained in the aluminum removal evaporator and discharged regularly.

[0014] Aluminum chloride, a metal impurity in high-boiling products, will form a high-boiling-point complex with sodium chloride under certain conditions, thereby effectively reducing the aluminum chloride from entering the gas phase; when there is an excess of sodium chloride and the aluminum chloride is completely complexed, the complex system becomes liquid when the temperature is higher than 152 degrees, and at this time, it has the best complexing effect;

[0015] The complexing agent is added at a mass ratio of 1.5-2% of the high boiling mass, and the best aluminum removal ability is demonstrated at a temperature between 150-160°C.

[0016] After use, the complexing agent is still discharged from the aluminum removal evaporator in solid form together with the unevaporated high boiling point. At this time, the complexing agent forms a complex with aluminum. The molecular formula of the complex is NaAlCl 4 The substance has a molecular weight of 191.78, is a white or yellowish crystalline powder, is deliquescent, has a melting point of 185°C, and is soluble in water. Its properties are similar to those of aluminum chloride, and it undergoes a more violent hydrolysis reaction with water. The hydrolysis products are aluminum hydroxide and hydrogen chloride. In production, it is neutralized with 8% lime milk, and the final products are aluminum hydroxide (solid) and calcium chloride (aqueous solution).

[0017] The beneficial effects of the present invention are as follows: crown ether and anti-caking agent calcium silicate are used in the complexing agent to improve the efficiency of the complexing agent, the complexing agent is added at a mass ratio of 1.5-2% of the mass of the high-boiling substance, and the best aluminum removal ability is exhibited at a temperature between 150-160° C., thereby improving the recovery quality of the high-boiling substance; the removal of metal impurities avoids catalyst poisoning, thereby improving the efficiency of subsequent catalytic cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] none DETAILED DESCRIPTION

[0019] The invention provides a complexing agent for separating and purifying high-boiling substances in polysilicon slurry. The components of the complexing agent include: secondary recrystallized sodium chloride, crown ether, dispersant and anti-caking agent calcium silicate.

[0020] Example 1

[0021] The present invention provides a complexing agent for separating and purifying high-boiling substances in polysilicon slurry and a preparation method thereof. The components thereof include, by weight, 90 parts of secondary recrystallized sodium chloride, 0.1 parts of crown ether, 1 part of dispersant, and 0.1 parts of anti-caking agent calcium silicate. The complexing agent product L1 is obtained by ball milling homogenization and air flow pulverization.

[0022] Example 2

[0023] The present invention provides a complexing agent for separating and purifying high-boiling substances in polysilicon slurry and a preparation method thereof. The components thereof include, by weight, 100 parts of secondary recrystallized sodium chloride, 0.2 parts of crown ether, 2 parts of dispersant, and 0.2 parts of anti-caking agent calcium silicate. The complexing agent product L2 is obtained by ball milling homogenization and air flow pulverization.

[0024] Example 3

[0025] The present invention provides a complexing agent for separating and purifying high-boiling substances in polysilicon slurry and a preparation method thereof. The components thereof include, by weight, 110 parts of secondary recrystallized sodium chloride, 0.3 parts of crown ether, 3 parts of dispersant, and 0.3 parts of anti-caking agent calcium silicate. The complexing agent product L3 is obtained by ball milling homogenization and air flow pulverization.

[0026] Example 4

[0027] The slurry produced in the production of polysilicon contains silicon powder, trichlorosilane, silicon tetrachloride, high-boiling substances, etc. First, trichlorosilane, silicon tetrachloride, high-boiling substances are physically separated from silicon powder through a precipitation separation device, and then trichlorosilane, silicon tetrachloride, and high-boiling substances are separated through a clear liquid distillation device based on the principle of different boiling points; the separated high-boiling substances are divided into three parts, and the mass of each part of high-boiling substances is 2kg.

[0028] Example 5

[0029] The three portions of high boiling materials in Example 4 were respectively introduced into the aluminum removal evaporator. When the temperature reached 150°C, the complexing agent products L1, L2, and L3 obtained in Examples 1, 2, and 3 were respectively added at 1.5% of the mass of the high boiling materials to complex the metal impurities in the high boiling materials. The high boiling materials were vaporized, condensed, and recovered based on the principle of different boiling points. The unevaporated high boiling materials and the complexing agent were left in the aluminum removal evaporator and discharged regularly. The reaction time and content were recorded and compared.

[0030] Reaction time and impurity removal efficiency: When the temperature is stabilized at 150°C, after adding complexing agent products L1, L2, and L3 at 1.5% of the mass of high-boiling substances, the reaction time shows differences. In the L1 reactor, the reaction gradually stabilizes after about 5 hours. During this period, the aluminum content in the high-boiling substances gradually decreases from the initial average of 500ppm to about 200ppm, and the iron content decreases from 150ppm to about 80ppm; the L2 reaction system reacts quickly and reaches equilibrium in about 4 hours. The aluminum content drops significantly to less than 150ppm, and the iron content is as low as about 60ppm. This high efficiency is due to its precise formula. The crown ether, dispersant, and calcium silicate work well together to accelerate the capture and complexation precipitation of metal ions; the L3 reaction time is the same as L1, but the removal of aluminum and iron impurities is slightly inferior, with final concentrations of about 180ppm and 70ppm respectively; the proportion of recovered high-boiling substances reaches 80%, and the purity increases from the original 70% to 87.5%, effectively improving the quality of raw materials and reducing raw material costs;

[0031] Unevaporated high-boiling substances: The L1 system has slight agglomeration, which increases the energy consumption for transportation and subsequent processing; L2 is evenly dispersed without agglomeration, and aluminum complexes account for about 25% of the unevaporated substances. It has a small particle size and is evenly distributed, which ensures the fluidity and stability of the system, greatly reduces the risk of pipeline blockage, and reduces maintenance costs by about 20%; L3 has a small amount of agglomeration, and aluminum complexes account for 28%, and the processing difficulty is medium.

[0032] Example 6

[0033] The three portions of high boiling materials in Example 4 were respectively introduced into the aluminum removal evaporator. When the temperature reached 155°C, the complexing agent products L1, L2, and L3 obtained in Examples 1, 2, and 3 were respectively added at 1.8% of the mass of the high boiling materials to complex the metal impurities in the high boiling materials. The high boiling materials were vaporized, condensed, and recovered based on the principle of different boiling points. The unevaporated high boiling materials and complexing agents were retained in the aluminum removal evaporator and discharged regularly. The reaction time and content were recorded and compared.

[0034] Reaction time and impurity removal efficiency: When the temperature is stabilized at 155°C, after adding complexing agent products L1, L2, and L3 at 1.8% of the mass of high-boiling substances, the reaction of L1 is shortened to 4 hours, and the aluminum content is reduced to 120ppm, and the iron to 40ppm; L2 reaches the best effect in only 3.5 hours, and the aluminum content is about 80ppm, and the iron is as low as 30ppm; L3 reacts for 4 hours, and the aluminum and iron contents are about 110ppm and 35ppm respectively; the proportion of recovered high-boiling substances is 85%, and the purity is increased to 91%.

[0035] The fluidity of the unevaporated mixed system L2 is the best, L1 is acceptable but viscous, L3 is slightly inferior, and the proportion of aluminum complex in L2 increases to 35%. The structure is dense and stable, which is conducive to subsequent neutralization. During the treatment, the amount of lime milk was reduced by 25%, the amount of waste residue generated was reduced by 30%, the comprehensive treatment cost was reduced by about 25%, and the calcium concentration of wastewater was reduced by 40%.

[0036] Example 7

[0037] The three portions of high boiling materials in Example 4 were respectively introduced into the aluminum removal evaporator. When the temperature reached 160°C, the complexing agent products L1, L2, and L3 obtained in Examples 1, 2, and 3 were respectively added at 1.5% of the mass of the high boiling materials to complex the metal impurities in the high boiling materials. The high boiling materials were vaporized, condensed, and recovered based on the principle of different boiling points. The unevaporated high boiling materials and the complexing agent were retained in the aluminum removal evaporator and discharged regularly. The reaction time and content were recorded and compared.

[0038] Reaction time and impurity removal efficiency: When the temperature is stabilized at 160°C, after adding complexing agent products L1, L2, and L3 at 2.0% of the mass of high-boiling substances, L1 reacts for 3.5 hours, and the aluminum and iron contents are 80ppm and 25ppm respectively; the reaction of L2 is completed within 3 hours, and the aluminum content is less than 60ppm and the iron content is 20ppm; L3 reacts for 3.5 hours, and the aluminum content is 70ppm and the iron content is 22ppm; the proportion of recovered high-boiling substances is as high as 90%, and the purity reaches 93.5%, which is close to excellent grade.

[0039] Among the unevaporated materials, the L2 system aluminum complex is produced in large quantities, of high quality, with low activity and dispersion.

[0040] Comprehensive reaction time trends of Examples 5, 6, and 7: With increasing temperature and the amount of complexing agent added, the reaction time shows a decreasing trend, and the optimal efficiency is reached at 160°C and 2.0% addition. The overall reaction rate of formula L2 is faster and the aluminum content is more effectively reduced, indicating that the synergy of its ingredients has advantages under all working conditions, which is conducive to the design of industrial rapid processing flow.

[0041] Improved purity of recovered high-boiling materials: The purity of recovered high-boiling materials continues to increase with the optimization of reaction conditions. At 160°C and 2.0% addition, the purity of high-boiling materials recovered with the assistance of L2 increases by more than 35%, which strongly supports the reuse of high-boiling materials, reduces the cost of polysilicon raw materials, increases system economy, and reduces environmental burden. It is a key breakthrough in the resource utilization of high-boiling materials in the polysilicon industry and guides the direction of complexing agent optimization and process adaptation.

Claims

1. A complexing agent for separating and purifying high boiling points in polysilicon slurry, characterized in that: It includes secondary recrystallized sodium chloride, crown ether, dispersant and anti-caking agent calcium silicate.

2. The complexing agent for separating and purifying high boiling points in polysilicon slurry according to claim 1, characterized in that: The secondary recrystallized sodium chloride is 90-110 parts; the crown ether is 0.1-0.3 parts; the dispersant is 1-3 parts; and the anti-caking agent calcium silicate is 0.1-0.3 parts.

3. The complexing agent for separating and purifying high boiling points in polysilicon slurry according to claim 2, characterized in that: The secondary recrystallized sodium chloride is 100 parts, the crown ether is 0.2 parts, the dispersant is 2 parts, and the anti-caking agent calcium silicate is 0.2 parts.

4. The method for preparing a complexing agent for separating and purifying high boiling points in polysilicon slurry according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: homogenizing secondary recrystallized sodium chloride, crown ether, dispersant and anti-caking agent calcium silicate through ball milling, and then air flow pulverizing to obtain a complexing agent product.

5. The method for preparing a complexing agent for separating and purifying high boiling points in polysilicon slurry according to claim 4, characterized in that: The secondary recrystallized sodium chloride is dried in a fluidized bed.

6. The method for preparing a complexing agent for separating and purifying high boiling points in polysilicon slurry according to claim 4, characterized in that: The dispersant is a crown ether dispersant, and the crown ether dispersant is isooctyl alcohol.

7. The use of a complexing agent for separating and purifying high boiling points in polysilicon slurry according to any one of claims 1 to 3, characterized in that: The complexing agent is used for separating and purifying high-boiling substances in polysilicon slurry, and is specifically applied as follows: the slurry produced by polysilicon production contains silicon powder, trichlorosilane, silicon tetrachloride and high-boiling substances; firstly, trichlorosilane, silicon tetrachloride and high-boiling substances are physically separated from silicon powder by a precipitation separation device, and then trichlorosilane, silicon tetrachloride and high-boiling substances are separated by a clear liquid distillation device based on the principle of different boiling points; the separated high-boiling substances are passed into an aluminum removal evaporator at a temperature of 150-160° C., and a complexing agent is added at 1.5-2% of the mass of the high-boiling substances to complex metal impurities in the high-boiling substances, and the high-boiling substances are recovered by vaporization and condensation at different boiling points, and the unevaporated high-boiling substances and the complexing agent are retained in the aluminum removal evaporator and discharged regularly.