Device for separating silicon powder from reduced tail gas

Abstract

The utility model provides a device for separating silicon powder from reduced tail gas. The device comprises a cyclone dust collector, a first filtering mechanism, a primary condenser, a secondary condenser, an air cooler, a multi-stage condenser, a condensate tank, a liquid phase filter and a machine pump, a gas phase outlet of the cyclone dust collector is connected with an inlet of the first filtering mechanism, a gas phase outlet of the first filtering mechanism is connected with a tube pass inlet of the first-stage condenser, a tube pass outlet of the second-stage condenser is connected with a gas phase inlet of the air cooler, and a liquid phase outlet of the air cooler is connected with an inlet of the condensate tank. A gas phase outlet of the air cooler is connected with a tube pass inlet of the multi-stage condenser, a tube pass outlet of the multi-stage condenser is connected with the condensate tank, an outlet of the condensate tank is connected with the liquid phase filter, and a liquid phase outlet of the liquid phase filter is connected with the pump so as to discharge a chlorosilane liquid phase; according to the scheme, large-particle silicon powder and small-particle silicon powder are separated according to the cyclone separation principle, then the silicon powder is separated through liquid-phase separation, liquid-phase chlorosilane is recycled, and grading and step-by-step separation and utilization of the silicon powder are achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of silicon powder recovery in polysilicon preparation, in particular to a silicon powder separation device for reducing tail gas. Background Art

[0002] At present, in the field of polysilicon, a small amount of elemental silicon is not deposited in the reduction reaction of hydrogen and trichlorosilane and enters the exhaust gas recovery system. The exhaust gas containing elemental silicon often uses gas phase and liquid phase filters to filter the silicon powder in the exhaust gas to prevent the silicon powder from entering the next process. The gas phase silicon powder filter is easy to clog the filter when filtering silicon powder. The clogged filter is usually purged with backblowing gas. Frequent backblowing of the filter will affect the stability of the subsequent system. In addition, the gas phase silicon powder filter will wear out due to long-term operation, resulting in the expansion of the pores of the filter element. Silicon powder will escape to the next process, causing wear and damage to the machine pump and compressor. In previous technologies, the liquid phase filter is usually located at the outlet of the machine pump. Under the long-term flushing of silicon powder, the machine pump is prone to wear and damage, affecting the stability of the system. Summary of the invention

[0003] In view of the above defects, the utility model proposes a reduction tail gas silicon powder separation device, comprising a cyclone dust collector, a first filtering mechanism, a first condenser, a second condenser, an air cooler, a multi-stage condenser, a condensate tank, a liquid phase filter, and a machine pump; the gas phase inlet of the cyclone dust collector is connected to the source of the reduced gas phase, the gas phase outlet is connected to the inlet of the first filtering mechanism, the gas phase outlet of the first filtering mechanism is connected to the tube side inlet of the first condenser, the tube side outlet of the first condenser is connected to the tube side inlet of the second condenser, the tube side outlet of the second condenser is connected to the gas phase inlet of the air cooler, the liquid phase outlet of the air cooler is connected to the inlet of the condensate tank, the gas phase outlet of the air cooler is connected to the tube side inlet of the multi-stage condenser, the tube side outlet of the multi-stage condenser is connected to the condensate tank, the outlet of the condensate tank is connected to the liquid phase filter, and the liquid phase outlet of the liquid phase filter is connected to the machine pump to discharge the chlorosilane liquid phase.

[0004] This scheme first separates large silicon powder particles through the cyclone separation principle, and then separates most of the small silicon powder particles through the gas phase separation principle. Then, through the liquid phase separation principle, the silicon powder in the liquid phase is separated and the liquid chlorosilane is recycled and utilized, thus forming a graded, step-by-step separation and utilization of silicon powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 This is the connection diagram of this solution.

[0006] In the figure: cyclone dust collector 10, first silicon powder collecting tank 11, first filtering mechanism 20, second silicon powder collecting tank 21, first condenser 30, second condenser 40, air cooler 50, third condenser 61, fourth condenser 62, fifth condenser 63, sixth condenser 64, condensate tank 70, liquid phase filter 80, machine pump 90, chlorosilane liquid collecting tank 901, reflux pipe 902, gas-liquid separator 100, second filtering mechanism 200, third silicon powder collecting tank 201, compressor 300, air intake buffer tank 301, exhaust buffer tank 302. DETAILED DESCRIPTION

[0007] See also Figure 1 The utility model provides a reduction tail gas silicon powder separation device, comprising a cyclone dust collector 10, a first filtering mechanism 20, a primary condenser 30, a secondary condenser 40, an air cooler 50, a multi-stage condenser, a condensate tank 70, a liquid phase filter 80, and a pump 90; the gas phase inlet of the cyclone dust collector 10 is connected to the source of the reduced gas phase, the gas phase outlet is connected to the inlet of the first filtering mechanism 20, the gas phase outlet of the first filtering mechanism 20 is connected to the pipe inlet of the primary condenser 30, and the primary cooler The tube-side outlet of the condenser 30 is connected to the tube-side inlet of the secondary condenser 40, the tube-side outlet of the secondary condenser 40 is connected to the gas phase inlet of the air cooler 50, the liquid phase outlet of the air cooler 50 is connected to the inlet of the condensate tank 70, the gas phase outlet of the air cooler 50 is connected to the tube-side inlet of the multi-stage condenser, the tube-side outlet of the multi-stage condenser is connected to the condensate tank 70, the outlet of the condensate tank 70 is connected to the liquid phase filter 80, and the liquid phase outlet of the liquid phase filter 80 is connected to the machine pump 90 to discharge the chlorosilane liquid phase.

[0008] In this solution, large particles in silicon powder are separated in advance by cyclone dust collector 10, and then silicon powder with smaller particles is separated by first filtering mechanism 20. After these two steps, 90% of silicon powder has been separated, and large particles of silicon powder will not enter the subsequent process and cause damage to the pump 90. Since the gas phase content of chlorosilane after reduction is extremely high, the recycling and reuse of chlorosilane is also very important while recovering silicon powder. The gas phase mixture after removing most of the silicon powder is condensed by multi-stage condenser, and the silicon powder in the condensate is first separated and processed by liquid phase filter 80 to avoid the silicon powder in the liquid phase chlorosilane from entering the distillation system when it is reused later. In the original design, the mixed gas after reduction directly enters the gas phase filter for separation. Although silicon powder can be collected, the presence of large particles of silicon powder can easily cause clogging or damage to the gas phase filter. In this solution, large particles of silicon powder are removed by the principle of cyclone separation and centrifugal principle. The large particles of silicon powder will not enter the subsequent system and will naturally not cause damage to the gas phase filter.

[0009] Furthermore, it also includes a gas-liquid separator 100, the tube-side outlet of the multi-stage condenser is connected to the inlet of the gas-liquid separator 100, the liquid phase outlet of the gas-liquid separator 100 is connected to the condensate tank 70, and the gas phase outlet of the gas-liquid separator 100 discharges the gas phase. Although the multi-stage condensation forms more liquid chlorosilane, there is still a part of the gas phase mixture, and there is a problem of waste of resources if it is directly discharged, so the gas-liquid separator 100 is set after the multi-stage condensation to separate the mixed gas phase in the liquid phase chlorosilane after the multi-stage condensation, and through the shell-side heat exchange of the four-stage condenser 62, part of the liquid phase in the gas phase is further converted into the gas phase, and enters the second gas phase filter for separation, so as to further remove and separate the silicon powder in the gas phase, and obtain an almost pure gas phase, which is then compressed by the compressor 300 and sent out.

[0010] Furthermore, a first silicon powder collecting tank 11 is provided at the solid phase outlet of the cyclone dust collector 10 to collect the separated silicon powder with a larger particle size, for example, >5 um.

[0011] Furthermore, a second silicon powder collecting tank 21 is provided at the solid phase outlet of the first filtering mechanism 20 to collect the separated silicon powder with a smaller particle size, for example, <5um. After passing through the first filtering mechanism, 90% of the silicon powder in the reduction tail gas has been filtered and collected.

[0012] Further, the multi-stage condenser includes a third-stage condenser 61, a fourth-stage condenser 62, a fifth-stage condenser 63, and a sixth-stage condenser 64, the tubes of which are sequentially connected. The tube inlet of the third-stage condenser 61 is connected to the gas phase inlet of the air cooler 50, and the tube outlet of the sixth-stage condenser 64 is connected to the inlet of the gas-liquid separator 100. The tube outlets of the third-stage condenser 61, the fourth-stage condenser 62, the fifth-stage condenser 63, and the sixth-stage condenser 64 are also connected to the inlet of the condensate tank 70. In the design of this solution, if a liquid phase mixture is formed in the tube of a certain stage condenser, it automatically flows into the condensate tank 70. If it is not completely liquefied, the gas phase mixture continues to enter the next stage condenser 30 along the tube to continue to be cooled. Therefore, the tube-side outlets of the third-stage condenser 61, the fourth-stage condenser 62, and the fifth-stage condenser 63 of this solution are not connected to the gas-liquid separator 100, and only the tube-side outlet of the sixth-stage condenser 64 is connected to the gas-liquid separator 100 to discharge the unliquefied gas mixture.

[0013] In a preferred embodiment, in this scheme, the gas temperature after reduction is an inlet temperature of 210°C, the first-stage condenser is cooled to 130°C, the second-stage condenser is cooled to 77°C, the air cooler 50 is cooled to 40°C, the third-stage condenser is cooled to 36°C, the fourth-stage condenser is cooled to 31°C, the fifth-stage condenser is cooled to 12°C, and the sixth-stage condenser is cooled to -20°C. The cooling medium of the fifth-stage condenser is low-temperature water, and the cooling medium of the sixth-stage condenser is Freon. After air cooling and multi-stage condensation, 90% of the chlorosilane gas phase in the reduction tail gas is converted into a liquid phase and collected in a condensate tank, while a large amount of hydrogen chloride and hydrogen are still not condensed. After heat exchange in the fourth-stage condenser, they are in a gas phase and filtered by the second filtering mechanism. After removing the silicon powder, a large amount of hydrogen chloride and hydrogen are separated.

[0014] Furthermore, it also includes a second filtering mechanism 200 and a compressor 300. The gas phase outlet of the gas-liquid separator 100 is connected to the shell side inlet of the fourth-stage condenser 62, and the shell side outlet of the fourth-stage condenser 62 is connected to the inlet of the second filtering mechanism 200. The solid phase outlet of the second filtering mechanism 200 is provided with a third silicon powder collecting tank 201 for collecting the separated silicon powder. The gas phase outlet of the second filtering mechanism 200 is connected to the compressor 300. The compressed gas is transported to the hydrogen chloride absorption process. The gas phase mixture separated from the gas-liquid separator 100 contains more or less liquid phase. If it is directly passed into the second filtering mechanism 200, the filtering efficiency of the gas phase filter will be greatly reduced. In order to remove the liquid phase in this part of the gas phase, no external structure is needed. Therefore, the gas phase after gas-liquid separation is passed into the shell side of the fourth-stage condenser 62 in this scheme, and the liquid phase part thereof is gasified by the heat in the tube side.

[0015] Furthermore, it also includes an intake buffer tank 301 and an exhaust buffer tank 302 which are respectively connected to the inlet and outlet of the compressor 300.

[0016] Furthermore, the first filtering mechanism 20 is a gas phase filter.

[0017] Furthermore, the second filter mechanism 200 is a gas phase filter. The gas phase filter and the liquid phase filter are both filter structures with filter elements disposed inside. The air cooler 50 is an air cooling structure.

[0018] Furthermore, it also includes a chlorosilane liquid collection tank 901 arranged between the liquid phase filter 80 and the machine pump 90, and the machine pump 90 is provided with a reflux pipe 902, which is connected to the chlorosilane collection tank; the outlet of the machine pump 90 is also connected to the shell side inlet of the three-stage condenser 61, and the shell side outlet of the three-stage condenser 61 discharges the chlorosilane liquid phase after heat exchange. The collected chlorosilane liquid phase is sent to the distillation process for recycling after heat exchange and temperature increase. The gas phase mixture entering the tube side of the three-stage condenser 61 is at a higher temperature at this time, and its heat can completely preheat the liquid chlorosilane, increase its temperature, and increase the basic temperature when entering the distillation process, which not only saves the distillation energy consumption, but also can replace the condensing medium of the three-stage condenser 61, and improve the condensation efficiency of the three-stage condenser 61. The chlorosilane liquid phase can completely replace the heat exchange medium in the original three-stage condenser 61, thereby saving the medium dosage, and can transfer heat to the chlorosilane liquid phase, providing basic heat for the distillation feed.

[0019] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of this patent.

Claims

1. Reduction tail gas silicon powder separation device, characterized by: It includes a cyclone dust collector, a first filtering mechanism, a first-stage condenser, a second-stage condenser, an air cooler, a multi-stage condenser, a condensate tank, a liquid phase filter, and a pump; the gas phase inlet of the cyclone dust collector is connected to the source of the reduced gas phase, the gas phase outlet is connected to the inlet of the first filtering mechanism, the gas phase outlet of the first filtering mechanism is connected to the tube-side inlet of the first-stage condenser, the tube-side outlet of the first-stage condenser is connected to the tube-side inlet of the second-stage condenser, the tube-side outlet of the second-stage condenser is connected to the gas phase inlet of the air cooler, the liquid phase outlet of the air cooler is connected to the inlet of the condensate tank, the gas phase outlet of the air cooler is connected to the tube-side inlet of the multi-stage condenser, the tube-side outlet of the multi-stage condenser is connected to the condensate tank, the outlet of the condensate tank is connected to the liquid phase filter, and the liquid phase outlet of the liquid phase filter is connected to the pump to discharge the chlorosilane liquid phase.

2. The silicon powder separation device for reducing tail gas according to claim 1, characterized in that: It also includes a gas-liquid separator, the tube outlet of the multi-stage condenser is connected to the inlet of the gas-liquid separator, the liquid phase outlet of the gas-liquid separator is connected to the condensate tank, and the gas phase outlet of the gas-liquid separator discharges the gas phase.

3. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: A first silicon powder collecting tank is also provided at the solid phase outlet of the cyclone dust collector.

4. The silicon powder separation device for reducing tail gas according to claim 1, characterized in that: A second silicon powder collecting tank is also arranged at the solid phase outlet of the first filtering mechanism.

5. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: The multi-stage condenser comprises a three-stage condenser, a four-stage condenser, a five-stage condenser and a six-stage condenser whose tubes are connected in sequence, the tube inlet of the three-stage condenser is connected to the gas phase inlet of the air cooler, the tube outlet of the six-stage condenser is connected to the inlet of the gas-liquid separator, and the tube outlets of the three-stage condenser, the four-stage condenser, the five-stage condenser and the six-stage condenser are also connected to the inlet of the condensate tank.

6. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: It also includes a second filtering mechanism and a compressor. The gas phase outlet of the gas-liquid separator is connected to the shell side inlet of the fourth-stage condenser, the shell side outlet of the fourth-stage condenser is connected to the inlet of the second filtering mechanism, a third silicon powder collection tank is arranged at the solid phase outlet of the second filtering mechanism, and the gas phase outlet of the second filtering mechanism is connected to the compressor.

7. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: It also includes an air intake buffer tank and an exhaust buffer tank which are respectively connected to the inlet and outlet of the compressor.

8. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: The first filtering mechanism is a gas phase filter.

9. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: The second filtering mechanism is a gas phase filter.

10. The reducing tail gas silicon powder separation device according to claim 1, characterized in that: It also includes a chlorosilane liquid collecting tank arranged between the liquid phase filter and the machine pump. The machine pump is provided with a reflux pipe, which is connected to the chlorosilane collecting tank. The outlet of the machine pump is also connected to the shell side inlet of the three-stage condenser, and the shell side outlet of the three-stage condenser discharges the chlorosilane liquid phase after heat exchange.

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