Chlorosilane recovery system capable of efficiently utilizing HCl

Abstract

The invention provides a chlorosilane recovery system capable of efficiently utilizing HCl, which comprises a first storage tank (D01) used for receiving chlorosilane waste liquid generated by an upstream system, the first storage tank (D01) is connected with a rectification device (T01) through a first pump (P01), a gas-phase substance generated by the rectification device (T01) is condensed through a two-stage condensation device, and the condensation device is connected with a second storage tank (D01) through a second pump (P01); a liquid-phase substance generated by condensation is stored in a second storage tank (D02), and a gas-phase substance which is not condensed is subjected to heat exchange through a fourth heat exchanger (E04) and then is fed into the fixed bed reactor (R02); and a liquid-phase substance generated by the rectification device (T01) is fed into the reaction kettle (R01). According to the invention, the chlorosilane residual liquid is effectively treated and utilized, another waste silicon powder of the slag slurry treatment device is also effectively treated, and meanwhile, HCl gas is utilized to the greatest extent after being desorbed, so that resources are saved to a certain extent while the environment is protected.

Description

Technical Field

[0001] The invention relates to a chlorosilane recovery system, in particular to a chlorosilane recovery system which efficiently utilizes HCl. Background Art

[0002] This section merely provides background information related to the present disclosure and is not necessarily prior art.

[0003] Both the silane fluidized bed method and the modified Siemens method use a cold hydrogenation process to prepare SiHCl3. This process will produce a large amount of chlorosilane waste liquid (SiCl4, Si2Cl6, silicon powder, metal chloride, etc.), which needs to be sent to the slurry high-boiling device for treatment and recycling. The silicon powder is treated as waste slag after being hydrolyzed. For high-boiling substances represented by Si2Cl6 (Si2OCl6, Si2HCl5, etc.), it is necessary to react with HCl under the action of a catalyst, catalytically crack to generate SiCl4 and SiHCl3, and then return to the system for reuse (Si2Cl6+HCl——SiHCl3+SiCl4). This process requires the continuous introduction of a large amount of HCl gas. During the process, the unreacted HCl will re-enter the system through the compressor. Due to the continuous enrichment of non-condensable gas N2 in the system (which cannot be removed without process venting), the concentration of HCL will decrease (N2 enrichment), reducing the reaction efficiency.

[0004] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a chlorosilane recovery system for efficiently utilizing HCl in view of the deficiencies in the prior art.

[0006] In order to solve the above technical problems, the present invention discloses a chlorosilane recovery system for efficiently utilizing HCl, comprising:

[0007] A first storage tank for receiving chlorosilane waste liquid generated by an upstream system, wherein the first storage tank is connected to a distillation device via a first pump, the gaseous phase material generated by the distillation device is condensed via a two-stage condensation device, the liquid phase material generated by the condensation is stored in a second storage tank, and the uncondensed gaseous phase material is sent to a fixed bed reactor after heat exchange via a fourth heat exchanger; the liquid phase material generated by the bottom of the distillation device is sent to a reactor.

[0008] Furthermore, the system also includes:

[0009] An adsorption device disposed between the distillation device and the reactor, for adsorbing metal ions;

[0010] The adsorption device is an adsorption column for removing metal ions, and there are two adsorption columns, one in operation and one in reserve.

[0011] Furthermore, the liquid phase material stored in the second storage tank is sent through a third pump as reflux to the distillation tower and also sent to a downstream cold hydrogenation device as a raw material.

[0012] Furthermore, a heating device is provided in the fixed bed reactor to control the reaction temperature therein at 400-450°C;

[0013] The external silicon powder is transported into the fixed bed reactor to react with the gas phase material input from the upstream. The high-temperature gas phase gas after the reaction enters the filter to remove solid impurities and then passes through the three-stage heat exchange device. The liquid phase material enters the third storage tank for storage; the gas phase material enters the spray scrubber;

[0014] The liquid in the third storage tank is transported to the first storage tank by the fourth pump.

[0015] Furthermore, the three-stage heat exchange device includes: a fourth heat exchanger for heat exchange with the gas phase feed, a fifth heat exchanger whose refrigerant is circulating water, and a sixth heat exchanger whose refrigerant is ethylene glycol;

[0016] Furthermore, the two-stage condensing device comprises:

[0017] The primary condenser uses circulating water for heat exchange and the secondary condenser uses ethylene glycol for heat exchange.

[0018] Furthermore, the temperature of the gaseous substance produced by the condensation is 150-170°C.

[0019] Furthermore, the distillation device is a plate distillation tower with a top pressure of 120-150 Kpa and a temperature of 75-85°C.

[0020] Furthermore, the spray washing tower adopts three-stage spraying to absorb HCl gas in the input gas, and uses the bottom liquid of the tower as spraying through the fifth pump. When the concentration of hydrochloric acid obtained after elution and absorption reaches 20-25%, it is sent to the downstream hydrochloric acid analysis device, and the gas not absorbed at the top of the tower enters the downstream tail gas treatment system.

[0021] Furthermore, the reactor is a steam-heated reactor, a catalyst is added to the reactor, and the steam flow rate is controlled so that the reaction temperature is 100-110°C and the pressure is 140-170 kPa. After the HCl gas output by the downstream hydrochloric acid analysis device is introduced into the bottom of the reactor, the gaseous product enters the stripping section at the bottom of the distillation device.

[0022] Beneficial effects:

[0023] The system proposed in the present invention combines a distillation tower, a reaction kettle, a fixed bed reactor, and a spray washing tower, which not only effectively treats and utilizes the chlorosilane residual liquid, but also effectively treats another waste silicon powder of the slurry treatment device. At the same time, the HCl gas is utilized to the maximum extent after being analyzed, and the remaining HCl in the tail gas is also recycled by spray absorption, which protects the environment while saving resources to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0025] Figure 1 This is a schematic diagram of the overall system architecture proposed by the present invention. DETAILED DESCRIPTION

[0026] The overall idea of ​​the present invention is as follows: design a new resource recovery process to recycle HCl in two steps: participate in the cracking reaction, and then pass the remaining HCl into a reaction tower equipped with an electric heating device to react with the recovered silicon powder to generate chlorosilane for reuse; finally, the remaining HCl is recovered by elution. This method effectively disposes of the waste generated in the production of polysilicon to the maximum extent and reduces the waste of resources. Figure 1 As shown, the present invention proposes a chlorosilane recovery system for efficiently utilizing HCl, and the specific technical scheme is as follows:

[0027] 1. In this technical solution, the system receives chlorosilane waste liquid (SiCl4, Si2Cl6, silicon powder, metal chloride, etc., Note: the main components of polysilicon by-product chlorosilane residual liquid include monosilane mainly composed of SiCl4 and SiHCl3, high boiling point components represented by Si2Cl6, metal chloride introduced when adding catalyst, solid impurity Si powder and SiO2, etc.) generated from the cold hydrogenation device. After solid-liquid separation in the previous system (SiCl4, Si2Cl6), they are stored in D01, and the chlorosilane is sent to the distillation device T01 through the P01 pump.

[0028] 2. The distillation device distills chlorosilane (the distillation tower adopts a plate tower), and the top output (SiCl4, HCl, non-condensable gas) enters the condenser in the gas phase. The top of the tower is 120-150Kpa and the temperature is 75-85°C. The bottom output (Si2Cl6, Si2OCl6) is pumped to the V01 adsorption column through P02 to remove metal ions such as Al and Ti (a set of adsorption columns consists of 2, one is open and the other is standby. The use of the adsorption column can effectively prevent metal ions such as Al and Ti from entering R01, avoid catalyst deactivation, and extend the service life of the catalyst).

[0029] 3. The output from the top of the tower is condensed into most of SiCl4 and SiHCl3 by two-stage condensation (one-stage condensation in the prior art, using ethylene glycol for heat exchange, consuming a large amount of cold). The first-stage condenser E02 uses circulating water for heat exchange, and the second-stage condenser E03 uses ethylene glycol for heat exchange. The condensate of E02 and E03 enters the condensate tank D02 at the top of the tower for storage, and the condensate is sent back to the top of the tower for reflux through the P03 pump, and is sent out to the cold hydrogenation device for production. The uncondensed gas phase (N2, HCl) enters the gas-to-gas heat exchanger E04 and exchanges heat with the outlet gas phase of the tail gas F01 (the gas phase product after the reaction of silicon powder and hydrogen chloride in the fixed bed R02), and the temperature reaches 150-170 degrees Celsius (the gas phase inlet and the gas phase outlet are heat exchanged, so that the heat is effectively utilized) and enters the fixed bed reactor R02.

[0030] 4. After the high-boiling substances at the bottom of the tower are adsorbed to remove metal ions, they enter the steam-heated reactor R01. Catalysts (organic amine catalysts, which can be one of N-methylglucose amine amine, diethylenetriamine amine, benzonitrile, tri-n-butylamine, 1,6-hexanediamine or N,N-dimethylaniline) are added to the reactor regularly, and the steam flow rate is controlled to keep the reaction temperature at 100-110°C and the pressure at 140-170 kPa. Excess HCl gas from the hydrochloric acid analysis device (the source is 32% hydrochloric acid analyzed in the analysis device) is introduced into the bottom of R01, and a catalytic cracking reaction occurs: Si2Cl6+HCl——SiHCl3+SiCl4, and the gaseous product enters T01 from the stripping section at the bottom of the tower for further purification and separation.

[0031] 5. The R02 fixed bed reactor is equipped with an electric heating device to control the reaction temperature at 400-450 degrees Celsius. Si powder is transported into the reactor by pneumatic conveying and reacts with the introduced HCl, Si+4HCl-SiCl4+2H2. The high-temperature gas phase after the reaction (SiCl4, H2 generated by the reaction, unreacted HCl) enters the filter F01 to remove solid impurities and then passes through three-stage heat exchange: E04, E05 (E05 refrigerant is circulating water), E06 (ethylene glycol); the liquid phase enters D03 and is transported to the distillation tower feed tank D01 through P04, and the gas phase (unreacted HCl, H2, N2) enters the HCl spray washing tower T02.

[0032] 6. The spray washing tower T02 adopts three-stage spraying to absorb HCl gas, and the bottom liquid of the tower is used for spraying through the P05 pump. When the hydrochloric acid concentration reaches 20-25% after elution and absorption, it is sent to the hydrochloric acid analysis device for concentration and reuse. The tail gas not absorbed at the top of the tower enters the tail gas system for treatment.

[0033] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, the invention content of a chlorosilane recovery system for efficiently utilizing HCl provided by the present invention and some or all of the steps in each embodiment can be executed. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0034] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on such an understanding, the technical solutions in the embodiments of the present invention can be essentially or partly contributed to the prior art in the form of computer programs, i.e., software products, which can be stored in a storage medium and include several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, an MCU or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.

[0035] The present invention provides a concept and method for a chlorosilane recovery system that efficiently utilizes HCl. There are many methods and approaches to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be considered as the scope of protection of the present invention. All components not specified in this embodiment can be implemented using existing technologies.

Claims

1. A chlorosilane recovery system for efficiently utilizing HCl, characterized in that: The system comprises: A first storage tank (D01) for receiving chlorosilane waste liquid generated by an upstream system, wherein the first storage tank (D01) is connected to a distillation device (T01) via a first pump (P01), the gaseous phase material generated by the distillation device (T01) is condensed via a two-stage condensation device, the liquid phase material generated by the condensation is stored in a second storage tank (D02), and the uncondensed gaseous phase material is sent to a fixed bed reactor (R02) after heat exchange via a fourth heat exchanger (E04); the liquid phase material generated by the distillation device (T01) is sent to a reactor (R01).

2. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The system further comprises: An adsorption device (V01) disposed between the distillation device (T01) and the reactor (R01), for adsorbing metal ions; The adsorption device (V01) is an adsorption column for removing metal ions, and there are two adsorption columns.

3. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The liquid phase material stored in the second storage tank (D02) is sent to the distillation device (T01) or to the downstream cold hydrogenation device as a raw material through the third pump (P03).

4. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The fixed bed reactor (R02) is provided with a heating device to control the reaction temperature therein at 400-450°C; The external silicon powder is transported into the fixed bed reactor (R02) to react with the gas phase material input from the upstream. The high-temperature gas phase gas after the reaction enters the filter (F01) to remove solid impurities and then passes through the three-stage heat exchange device. The liquid phase material enters the third storage tank (D03) for storage; the gas phase material enters the spray washing tower (T02); The liquid in the third storage tank (D03) is transported to the first storage tank (D01) by a fourth pump (P04).

5. A chlorosilane recovery system for efficiently utilizing HCl according to claim 4, characterized in that: The three-stage heat exchange device comprises: a fourth heat exchanger (E04) for performing heat exchange with gaseous feed, a fifth heat exchanger (E05) whose refrigerant is circulating water, and a sixth heat exchanger (E06) whose refrigerant is ethylene glycol.

6. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The two-stage condensing device comprises: The primary condenser (E02) uses circulating water for heat exchange and the secondary condenser (E03) uses ethylene glycol for heat exchange.

7. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The temperature of the gaseous substance produced by the condensation is 150-170°C.

8. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The distillation device (T01) is a plate distillation tower with a top pressure of 120-150 Kpa and a temperature of 75-85°C.

9. A chlorosilane recovery system for efficiently utilizing HCl according to claim 4, characterized in that: The spray washing tower (T02) adopts three-stage spraying to absorb HCl gas in the input gas, and uses the bottom liquid of the tower as spraying through the fifth pump (P05). When the concentration of hydrochloric acid obtained after elution and absorption reaches 20-25%, it is sent to the downstream hydrochloric acid analysis device, and the gas not absorbed at the top of the tower enters the downstream tail gas treatment system.

10. A chlorosilane recovery system for efficiently utilizing HCl according to claim 1, characterized in that: The reactor (R01) is a steam-heated reactor. A catalyst is added to the reactor (R01), and the steam flow rate is controlled to make the reaction temperature 100-110°C and the pressure 140-170 kPa. After the HCl gas output by the downstream hydrochloric acid analysis device is introduced into the bottom of the reactor (R01), the gaseous product enters the stripping section at the bottom of the distillation device (T01).

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