Recycling method and system of polycrystalline silicon slag slurry

Abstract

The invention provides a method and a system for recycling polycrystalline silicon slag slurry. The recycling method of the polycrystalline silicon slag slurry comprises the following steps: enabling kettle residual liquid output by a high-boiling reaction kettle to enter a catalyst concentration kettle for concentration treatment to obtain gas-phase chlorosilane and a concentrated product; and enabling the concentrated product to enter a conversion residual liquid neutralization kettle for hydrolysis treatment to obtain hydrogen and waste liquid. According to the recycling method, chlorosilane in the kettle residual liquid obtained through catalytic cracking can be recycled, the kettle residual liquid can be treated with small water consumption, generated waste liquid can be directly discharged to a wastewater treatment facility, the conveying steps are simple, and the treatment process is simple.

Description

Technical Field

[0001] The invention relates to a method and system for recovering polysilicon slag slurry, belonging to the technical field of chemical separation. Background Art

[0002] With the increase in demand, the photovoltaic industry and the integrated circuit industry have developed rapidly. Polysilicon is the core raw material of the photovoltaic industry and the integrated circuit industry, so more and more companies have begun to produce polysilicon.

[0003] At present, almost all polysilicon production enterprises adopt the modified Siemens method. In the process of producing polysilicon by the modified Siemens method, a large amount of slurry is generated. The slurry mainly includes silicon powder, metal chloride, polychlorosilane, silicon tetrachloride, trichlorosilane and dichlorosilane. After separation, the slurry removes silicon powder and metal chloride, recovers part of silicon tetrachloride, trichlorosilane and dichlorosilane, and the remaining polysilane with a boiling point higher than silicon tetrachloride and trichlorosilane is high-boiling products. This part of the material needs to be recycled and used by catalytic cracking. However, after catalytic cracking of high-boiling products, a kettle residue containing chlorosilane, waste catalyst and polysiloxane will be obtained. At present, the kettle residue is mainly discharged after hydrolysis treatment. However, the hydrolysis treatment consumes a lot of water, and the hydrolysis wastewater is difficult to transport and the treatment process is complicated. Summary of the invention

[0004] The present invention provides a method for recovering polysilicon slurry. The method can recover and utilize chlorosilane in kettle residual liquid obtained by catalytic cracking, and can treat the kettle residual liquid with a small amount of water consumption. The generated waste liquid can be directly discharged to a wastewater treatment facility, and the transportation steps and treatment process are simple.

[0005] The present invention provides a polysilicon slurry recovery system, which is used to implement the above-mentioned recovery method. The recovery system can recover chlorosilanes in the kettle residual liquid obtained by catalytic cracking, and can treat the kettle residual liquid with a small water consumption. The generated waste liquid can be directly discharged to a wastewater treatment facility, and the transportation steps and treatment process are simple.

[0006] The present invention provides a method for recovering polysilicon slurry, which comprises the following steps:

[0007] The residual liquid outputted from the high-boiling reactor is fed into a catalyst concentration reactor for concentration treatment to obtain gaseous chlorosilane and concentrated products;

[0008] The concentrated product is introduced into the conversion residual liquid neutralization kettle for hydrolysis treatment to obtain hydrogen and waste liquid.

[0009] In the above-mentioned recovery method, the kettle residue comprises, in terms of mass percentage, 0.3-3% of chlorosilane, 90-99% of polysiloxane and 1.2-7% of waste catalyst.

[0010] The recovery method as described above, wherein, further comprises: allowing the gaseous chlorosilane to enter a high-boiling distillation tower for distillation treatment.

[0011] The recovery method as described above, further comprises: allowing the hydrogen to enter a tail gas washing tower for washing treatment.

[0012] In the recovery method as described above, during the concentration treatment, the temperature is 130 to 180° C. and the pressure is 0.05 to 0.15 MPaG.

[0013] In the recovery method as described above, the concentrated product is hydrolyzed using a sodium hydroxide solution.

[0014] In the recovery method as described above, the sodium hydroxide solution is an aqueous sodium hydroxide solution, and the concentration of the aqueous sodium hydroxide solution is 5-35%.

[0015] The recovery method as described above, wherein the flow rate of the sodium hydroxide solution is 5-10m 3 / h.

[0016] In the recovery method as described above, during the hydrolysis treatment, the temperature is 50-80°C and the pressure is 0.02-0.06MPaG.

[0017] The present invention provides a polysilicon slurry recovery system, wherein the recovery system is used to implement the above-mentioned recovery method;

[0018] The recovery system comprises: a catalyst concentration kettle and a conversion residual liquid neutralization kettle;

[0019] The concentrated product outlet of the catalyst concentration kettle is communicated with the inlet of the conversion residual liquid neutralization kettle.

[0020] The present invention provides a method for recovering polysilicon slurry, wherein the method first concentrates the residual liquid in the kettle to obtain gaseous chlorosilane and a concentrated product, and then hydrolyzes the concentrated product to obtain hydrogen and waste liquid. The obtained gaseous chlorosilane and hydrogen can be recycled, and the obtained waste liquid can be directly discharged to a wastewater treatment facility. The waste liquid has a simple transportation step and a simple treatment process, and the water consumption of the recovery method is low, so the method is suitable for wide promotion and application.

[0021] The present invention provides a polysilicon slurry recovery system for implementing the above-mentioned recovery method. The recovery system can recover chlorosilanes in the kettle residual liquid obtained by catalytic cracking, and can treat the kettle residual liquid with a small water consumption. The generated waste liquid can be directly discharged to a wastewater treatment facility, and the transportation steps and treatment process are simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 Schematic diagram of the polysilicon slurry recovery process in some embodiments of the present invention.

[0024] Description of reference numerals:

[0025] 1: Catalyst concentration kettle;

[0026] 2: Conversion residual liquid neutralization kettle. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Figure 1 Schematic diagram of the polysilicon slurry recovery process in some embodiments of the present invention. Figure 1 As shown, the first aspect of the present invention provides a method for recovering polysilicon slurry, which comprises the following steps:

[0029] The residual liquid outputted from the high-boiling reactor enters the catalyst concentration reactor 1 for concentration treatment to obtain gaseous chlorosilane and concentrated products;

[0030] The concentrated product is allowed to enter the conversion residual liquid and reactor 2 for hydrolysis treatment to obtain hydrogen and waste liquid.

[0031] The slurry in the polysilicon production process mainly includes silicon powder, metal chloride, polychlorosilane, silicon tetrachloride, trichlorosilane and dichlorosilane. Usually, after the slurry is separated, silicon powder and metal chloride are removed, and some polysilane high-boiling products with boiling points higher than silicon tetrachloride and trichlorosilane will remain after recovering some silicon tetrachloride, trichlorosilane and dichlorosilane. The polysilane high-boiling products need to be catalytically cracked and recovered in a high-boiling reactor under the action of a catalyst. After catalytic cracking, the reactor residue including chlorosilane, waste catalyst and polysiloxane will be obtained. Among them, the catalyst can be a composite organic ammonium, which has weak toxicity, and the waste liquid including the composite organic ammonium does not need to be treated.

[0032] The recovery method of the present invention specifically comprises: the kettle residual liquid including chlorosilane, waste catalyst and polysiloxane obtained after catalytic cracking is outputted from a high-boiling reactor, and is concentrated in a catalyst concentration kettle 1. During the concentration, the chlorosilane will volatilize, thereby obtaining gaseous chlorosilane and a concentrated product including waste catalyst and polysiloxane, and the obtained gaseous chlorosilane can be recycled; then the concentrated product is allowed to enter the conversion residual liquid neutralization kettle 2 for hydrolysis treatment, so that the polysiloxane is hydrolyzed to obtain hydrogen and waste liquid, the waste catalyst is deposited in the waste liquid, the obtained hydrogen can be recycled, and the obtained waste liquid can enter the wastewater treatment facility.

[0033] The recovery method of the present invention can recycle chlorosilane and hydrogen in the kettle residue obtained by catalytic cracking, and can achieve the treatment of the kettle residue with a small amount of water consumption, and the generated waste liquid can be directly discharged to the wastewater treatment facility, with simple transportation steps and simple treatment process. Therefore, the recovery method of the present invention can efficiently remove waste in the slurry and improve the recycling efficiency of resources.

[0034] In some embodiments of the present invention, when the kettle residue includes, by mass percentage, 0.3-3% chlorosilane, 90-99% polysiloxane and 1.2-7% waste catalyst, the recovery method can more efficiently remove waste from the slurry and improve the recycling efficiency of resources.

[0035] In some embodiments of the present invention, the recovery method further comprises: allowing the gaseous chlorosilane to enter a high-boiling distillation tower for distillation treatment.

[0036] Specifically, gaseous chlorosilane is fed into a high-boiling distillation tower for distillation treatment to further separate impurities in the gaseous chlorosilane to obtain high-purity chlorosilane. The obtained chlorosilane can be reused, thereby improving the recycling efficiency of resources.

[0037] In some embodiments of the present invention, the recovery method further comprises: allowing the hydrogen to enter a tail gas scrubber for scrubbing.

[0038] Specifically, hydrogen enters the tail gas washing tower for washing treatment to further remove impurities in the hydrogen and obtain high-purity hydrogen. The obtained hydrogen can be reused, thereby further improving the recycling efficiency of resources.

[0039] The inventors also found in their research that by limiting the specific parameters of the concentration process, the processing efficiency of the concentration process can be further improved, and the yield and purity of gas-phase chlorosilane can be improved. For example, in some embodiments of the present invention, during the concentration process, the temperature is 130 to 180° C. and the pressure is 0.05 to 0.15 MPaG.

[0040] For example, during the concentration process, the temperature may be in the range of one of 130° C., 135° C., 140° C., 150° C., 170° C., and 180° C., or any two thereof;

[0041] The pressure may be in a range consisting of one or any two of 0.05 MPaG, 0.06 MPaG, 0.07 MPaG, 0.09 MPaG, 0.1 MPaG, 0.13 MPaG, and 0.15 MPaG.

[0042] In some embodiments of the present invention, when the concentrated product is hydrolyzed using a sodium hydroxide solution, the efficiency of the hydrolysis treatment is improved, and the polysiloxane in the concentrated product is more fully converted into hydrogen and waste liquid.

[0043] Furthermore, when the sodium hydroxide solution is an aqueous sodium hydroxide solution, the concentration of the aqueous sodium hydroxide solution is 5-35%. Using the aqueous sodium hydroxide solution of the above concentration for hydrolysis treatment can save sodium hydroxide while improving the efficiency of the hydrolysis treatment, and more fully convert the polysiloxane in the concentrated product into hydrogen and waste liquid.

[0044] Illustratively, the concentration of the sodium hydroxide aqueous solution may be any one of 5%, 6%, 7%, 9%, 12%, 17%, 30%, 35%, or a range consisting of any two of them.

[0045] In the present invention, the efficiency of the hydrolysis treatment can be further controlled by controlling the flow rate of the sodium hydroxide solution, so that the polysiloxane in the concentrated product can be more fully converted into hydrogen and waste liquid while saving sodium hydroxide. For example, in some embodiments of the present invention, the flow rate of the sodium hydroxide solution is 5-10m / s. 3 / h.

[0046] Exemplarily, the flow rate of the sodium hydroxide solution can be 5m 3 / h、6m 3 / h、8m 3 / h、10m 3 / h or a range consisting of any two of them.

[0047] In some embodiments of the present invention, when the temperature is 50-80°C and the pressure is 0.02-0.06MPaG during the hydrolysis treatment, the efficiency of the hydrolysis treatment can be further improved while saving energy consumption, so that the polysiloxane in the concentrated product can be more fully converted into hydrogen and waste liquid, thereby achieving efficient treatment of waste in the slurry and improving the recycling efficiency of resources.

[0048] For example, during the hydrolysis treatment, the temperature may be any one of 50°C, 60°C, 70°C, 75°C, 80°C, or a range consisting of any two thereof;

[0049] The pressure may be any one of 0.02 MPaG, 0.03 MPaG, 0.05 MPaG, 0.06 MPaG, or a range consisting of any two of them.

[0050] A second aspect of the present invention provides a polysilicon slurry recovery system, wherein the recovery system is used to implement the recovery method of the first aspect;

[0051] The recovery system includes: a catalyst concentration kettle 1 and a conversion residual liquid neutralization kettle 2;

[0052] The concentrated product outlet of the catalyst concentration kettle 1 is connected to the inlet of the conversion residual liquid neutralization kettle 2.

[0053] Specifically, the kettle residue including chlorosilane, waste catalyst and polysiloxane obtained after catalytic cracking is output through the high boiling reactor, and is put into the catalyst concentration kettle 1 through the inlet of the catalyst concentration kettle 1, and is concentrated in the catalyst concentration kettle 1. During the concentration, the chlorosilane will volatilize, thereby obtaining gaseous chlorosilane and concentrated products including waste catalyst and polysiloxane, and the obtained gaseous chlorosilane can be recycled; then the concentrated product is output through the concentrated product outlet of the catalyst concentration kettle 1, and enters the conversion residual liquid neutralization kettle 2 through the inlet of the conversion residual liquid neutralization kettle 2. In the conversion residual liquid neutralization kettle 2, the concentrated product will be hydrolyzed, wherein the polysiloxane is hydrolyzed to obtain hydrogen and waste liquid, the waste catalyst is deposited in the waste liquid, the obtained hydrogen can be recycled, and the obtained waste liquid can enter the wastewater treatment facility.

[0054] The recovery system of the present invention can recover chlorosilane and hydrogen in the kettle residual liquid obtained by catalytic cracking, and can realize the treatment of the kettle residual liquid with a small amount of water consumption, and the generated waste liquid can be directly discharged to the wastewater treatment facility, with simple transportation steps and simple treatment process. The recovery system can efficiently remove waste in the slurry and improve the recycling efficiency of resources.

[0055] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0056] Example 1

[0057] The polysilicon slurry recovery system of this embodiment is as follows: Figure 1 As shown, it comprises: a catalyst concentration kettle 1 and a conversion residual liquid neutralization kettle 2;

[0058] The concentrated product outlet of the catalyst concentration kettle 1 is connected to the inlet of the conversion residual liquid neutralization kettle 2.

[0059] Example 2

[0060] The method for recovering polysilicon slurry in this embodiment is carried out using the recovery system in Embodiment 1, and specifically includes:

[0061] The residual liquid outputted from the high-boiling reactor enters the catalyst concentration reactor 1 for concentration treatment to obtain gaseous chlorosilane and concentrated products;

[0062] The gaseous chlorosilane enters a high-boiling distillation tower for distillation treatment;

[0063] The concentrated product is fed into the conversion residual liquid neutralization kettle 2, and in the conversion residual liquid neutralization kettle 2, a sodium hydroxide aqueous solution is used for hydrolysis treatment to obtain hydrogen and waste liquid;

[0064] The hydrogen gas is sent to the tail gas scrubber for scrubbing, and the resulting waste liquid is sent to the wastewater treatment facility for treatment;

[0065] The kettle residue includes, by mass percentage, 1% chlorosilane, 96% polysiloxane and 3% waste catalyst, wherein the waste catalyst is an organic amine compound;

[0066] During the concentration process, the temperature is 156°C and the pressure is 0.05MPaG;

[0067] The mass percentage of sodium hydroxide aqueous solution is 20%, and the flow rate of sodium hydroxide aqueous solution is 10m 3 / h;

[0068] During the hydrolysis treatment, the temperature was 55°C and the pressure was 0.06MPaG;

[0069] The temperature rise in the hydrolysis treatment is small, the temperature changes between 40 and 58°C, and the consumption of sodium hydroxide is small.

[0070] Comparative Example

[0071] The method for recovering polysilicon slurry in this comparative example is basically the same as that in Example 2, except that:

[0072] The residual liquid in the kettle is directly hydrolyzed without concentration treatment;

[0073] In the hydrolysis treatment, the amount of sodium chloride used is 2.3 times the amount of sodium hydroxide used in Example 2, and the wastewater generated is 1.53 times the wastewater in Example 2. In addition, in the hydrolysis treatment, a heat exchanger is required to reduce the temperature of the hydrolysis cycle spray wastewater. The temperature rises too high during the hydrolysis treatment, and the water temperature can reach above 65°C.

[0074] It can be seen from the embodiments and comparative examples that the present invention, by concentrating the residual liquid output from the high-boiling reactor and then performing a hydrolysis treatment, can reduce the temperature change in the hydrolysis treatment and reduce the amount of wastewater without adding a heat exchanger while reducing the amount of sodium hydroxide used.

[0075] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for recovering polysilicon slurry, characterized in that: The following steps are involved: The residual liquid outputted from the high-boiling reactor is fed into a catalyst concentration reactor for concentration treatment to obtain gaseous chlorosilane and concentrated products; The concentrated product is introduced into the conversion residual liquid neutralization kettle for hydrolysis treatment to obtain hydrogen and waste liquid.

2. The recycling method according to claim 1, characterized in that: The kettle residual liquid comprises, in terms of mass percentage, 0.3-3% of chlorosilane, 90-99% of polysiloxane and 1.2-7% of waste catalyst.

3. The recovery method according to claim 1 or 2, characterized in that: Also includes: The gaseous chlorosilane is allowed to enter a high-boiling distillation tower for distillation treatment.

4. The recycling method according to any one of claims 1 to 3, characterized in that: Also includes: The hydrogen is allowed to enter a tail gas scrubbing tower for scrubbing treatment.

5. The recycling method according to any one of claims 1 to 4, characterized in that: During the concentration treatment, the temperature is 130 to 180° C. and the pressure is 0.05 to 0.15 MPaG.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The concentrated product is subjected to a hydrolysis treatment using a sodium hydroxide solution.

7. The recycling method according to claim 6, characterized in that: The sodium hydroxide solution is a sodium hydroxide aqueous solution, and the concentration of the sodium hydroxide aqueous solution is 5-35%.

8. The recycling method according to claim 6 or 7, characterized in that: The flow rate of the sodium hydroxide solution is 5-10m 3 / h.

9. The recycling method according to any one of claims 1 to 8, characterized in that: During the hydrolysis treatment, the temperature is 50-80° C. and the pressure is 0.02-0.06 MPaG.

10. A polysilicon slurry recovery system, characterized in that: The recycling system is used to implement the recycling method according to any one of claims 1 to 9; The recovery system comprises: a catalyst concentration kettle and a conversion residual liquid neutralization kettle; The concentrated product outlet of the catalyst concentration kettle is communicated with the inlet of the conversion residual liquid neutralization kettle.

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