A device for removing silicon powder in a VTH pipe network

Abstract

The utility model relates to the field, specifically disclose a device for removing silicon powder in VTH pipe network. The device includes exhaust buffer tank, chlorosilane storage tank, primary heat exchanger, spray tower, secondary heat exchanger and exhaust compressor, and exhaust buffer tank exhaust port and primary heat exchanger, spray tower, secondary heat exchanger and exhaust compressor are connected in proper order. Exhaust buffer tank is with chlorosilane as adsorbing medium, and the silicon powder containing exhaust gas is dispersed and passed into liquid phase through branch pipeline, and the silicon powder is adsorbed and precipitated after gas-liquid exchange, and is regularly discharged through tank bottom deslagging valve, and low liquid level transmitter, high liquid level transmitter and overflow valve are arranged in the tank to maintain liquid level stability, and chlorosilane temperature transmitter interlocking cooling valve is arranged to pass into low temperature hydrogen gas to control tank temperature below 15 DEG C. The device significantly reduces the amount of silicon powder entering the front heat exchanger and spray tower through pre-treatment, reduces the frequency of equipment blockage and operation and maintenance cost, and ensures the continuous and stable operation of the tail gas recovery system.

Description

Technical Field

[0001] This utility model relates to the field of polysilicon production tail gas treatment technology, and in particular to a device for removing silicon powder from VTH pipelines. Background Technology

[0002] The exhaust gases generated during polysilicon production mainly contain N2, H2, SiH2Cl2, SiHCl3, and HCl, among which non-condensable gases (N2 and H2) account for approximately 80%, with the remainder being chlorosilane gases. To reduce hydrogen venting and save costs, two exhaust gas pipelines are typically designed, VTH (Vent To Hydrogen) and VTN (Vent To Nitrogen), depending on the hydrogen content in the exhaust gas. The VTH pipeline network contains a large amount of solid silicon powder generated during production. These particles are very small (some reaching ultrafine dust levels, D50 < 10 μm), easily agglomerating and adhering. If they cannot be effectively separated, they will seriously affect the stable operation of the production system and product quality.

[0003] Currently, one of the mainstream methods for silicon powder separation in polysilicon production tail gas recovery systems is through a liquid-phase filter at the bottom of a scrubbing tower. Its core working principle is as follows: after the tail gas containing silicon powder enters the scrubbing tower, it comes into full contact with the scrubbing liquid sprayed inside the tower. Some of the silicon powder entrained in the tail gas is captured by the scrubbing liquid, forming a slurry containing silicon powder. The slurry collects at the bottom of the scrubbing tower and is then filtered through a liquid-phase filter to separate the silicon powder from the slurry. The filtered scrubbing liquid is recycled, and the separated silicon powder is centrally processed. However, this method of separating silicon powder using a liquid-phase filter at the bottom of a scrubbing tower has significant technical drawbacks. Specifically, the silicon powder is not pretreated before entering the scrubbing tower, and a large amount of silicon powder directly enters the scrubbing tower and related upstream equipment with the tail gas, leading to two major problems that seriously affect the normal operation of the system. On the one hand, after a large amount of silicon powder enters the scrubbing tower, the slurry formed by mixing with the washing liquid has an excessively high silicon powder content. The liquid phase filter at the bottom of the scrubbing tower needs to filter silicon powder frequently, which easily causes the filter element to become clogged. This requires staff to frequently stop the machine to clean the clog and replace the filter element, which not only increases the labor maintenance cost, but also seriously interrupts the continuous operation of the exhaust gas recovery system and reduces production efficiency. At the same time, frequent filter cleaning will also lead to an increase in the number of start-ups and shutdowns of the exhaust gas compressor in the downstream system, which will aggravate the wear of the compressor, shorten the service life of the equipment, and increase the equipment maintenance cost.

[0004] On the other hand, the heat exchangers (core equipment for exhaust gas cooling and heat exchange) before entering the scrubbing tower are frequently clogged due to silicon powder entrained in the exhaust gas adhering to the tube walls and inside the tubes. This is especially true for heat exchanger tubes with small diameters (some only 10mm), where silicon powder blockage is difficult to clean, directly causing a significant reduction in heat exchange efficiency, increased exhaust temperature, and consequently affecting the normal operation of subsequent processes such as distillation purification and hydrogen reduction. It may even lead to subsequent equipment malfunctions due to excessive temperature, resulting in greater production losses and safety hazards. In addition, long-term accumulation of silicon powder can scratch the inner walls of the equipment, forming a rough surface, further aggravating silicon powder adsorption, creating a vicious cycle of "blockage-adsorption-more severe blockage," which seriously restricts the continuity and stability of polysilicon production and cannot meet the industry's needs for large-scale, high-efficiency production. Utility Model Content

[0005] The purpose of this invention is to provide a device for removing silicon powder from VTH pipelines, so as to solve the problems existing in the prior art.

[0006] This utility model is implemented by the following technical solution: A device for removing silicon powder from a VTH pipeline network, comprising an exhaust gas buffer tank, a chlorosilane storage tank, a primary heat exchanger, a spray tower, a secondary heat exchanger, and an exhaust gas compressor. The VTH pipeline network is connected to the inlet of the exhaust gas buffer tank via a pipeline. The exhaust port of the exhaust gas buffer tank is sequentially connected to the primary heat exchanger, the spray tower, the secondary heat exchanger, and the exhaust gas compressor via pipelines. The chlorosilane storage tank is connected to the inlet of the buffer tank replenishment pump, and the outlet of the buffer tank replenishment pump is connected to the exhaust gas buffer tank. The chlorosilane storage tank is connected to the inlet of the spray tower replenishment pump, and the outlet of the spray tower replenishment pump is connected to the outlet of the buffer tank. The outlet is connected to the spray tower. A low-level transmitter, a high-level transmitter, and an overflow valve are installed on the waste gas buffer tank. The replenishment pump is electrically connected to the low-level transmitter, and the overflow valve is electrically connected to the high-level transmitter. A waste gas temperature transmitter is installed at the inlet pipe of the waste gas compressor. A first control valve is installed at the cooling water inlet of the first-stage heat exchanger, and a second control valve is installed at the cooling water inlet of the second-stage heat exchanger. The waste gas temperature transmitter is electrically connected to the first control valve and the second control valve, respectively. A slag discharge valve is installed at the bottom of the waste gas buffer tank, and the slag discharge valve is connected to the slurry treatment system through a pipeline.

[0007] Furthermore, it also includes a silica powder filter, with a circulating pump connected to the bottom outlet of the spray tower. The outlet of the circulating pump is connected to the inlet of the silica powder filter, and the outlet of the silica powder filter is connected to the liquid inlet of the spray tower.

[0008] Furthermore, a chlorosilane temperature transmitter is installed on the waste gas buffer tank, and a low-temperature hydrogen inlet is connected to the bottom of the waste gas buffer tank. A cooling valve is installed at the low-temperature hydrogen inlet, and the cooling valve is electrically connected to the chlorosilane temperature transmitter.

[0009] The advantages of this utility model are: chlorosilane is used as the adsorption medium in the waste gas buffer tank. The VTH waste gas is dispersed into multiple gas streams and introduced into the liquid phase through branch pipes. After gas-liquid exchange, the silicon powder is adsorbed by chlorosilane and settles to the bottom of the conical tank by gravity. It is then discharged periodically through the slag discharge valve. This pretreatment significantly reduces the amount of silicon powder entering the first-stage heat exchanger, thereby reducing the frequency of heat exchanger tube blockage.

[0010] The low-level transmitter and the high-level transmitter are interlocked with the buffer tank replenishment pump and the overflow valve, respectively, to maintain a stable liquid level in the waste gas buffer tank, ensuring that the gas outlet at the bottom of the inlet pipe is always more than 1.5 meters deep into the liquid surface, thus guaranteeing the contact time between the waste gas and the chlorosilane. The chlorosilane temperature transmitter is interlocked with the cooling valve, which introduces low-temperature hydrogen to maintain the temperature inside the tank below 15°C, suppressing the volatilization of chlorosilane and stabilizing the adsorption efficiency.

[0011] The exhaust gas temperature transmitter is interlocked with the first control valve of the cooling water inlet of the primary heat exchanger and the second control valve of the cooling water inlet of the secondary heat exchanger. The cooling water volume is adjusted in stages according to the exhaust gas temperature at the compressor inlet and its rising slope to control the inlet gas temperature at 10℃–12℃. The circulating liquid at the bottom of the spray tower is pumped into the silicon powder filter for filtration and reused, reducing the frequency of cleaning the silicon powder filter and the number of start-ups and shutdowns of the exhaust gas compressor. Attached Figure Description

[0012] Figure 1 This is a system connection diagram of the present invention.

[0013] In the diagram: 1. Waste gas buffer tank; 2. Chlorosilane storage tank; 3. Primary heat exchanger; 4. Spray tower; 5. Secondary heat exchanger; 6. Waste gas compressor; 7. Silica powder filter; 101. Low level transmitter; 102. High level transmitter; 103. Overflow valve; 104. Cooling valve; 105. Slag discharge valve; 106. Chlorosilane temperature transmitter; 201. Buffer tank replenishment pump; 202. Spray tower replenishment pump; 601. Waste gas temperature transmitter; 602. First control valve; 603. Second control valve; 701. Circulation pump. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0015] like Figure 1The diagram illustrates an embodiment of the present invention: a device for removing silicon powder from a VTH (Vacuum-Through-Heat) pipeline network. The device includes a waste gas buffer tank 1, a chlorosilane storage tank 2, a primary heat exchanger 3, a spray tower 4, a secondary heat exchanger 5, and a waste gas compressor 6. The VTH pipeline network is connected to the inlet of the waste gas buffer tank 1 via a pipe. The temperature of the waste gas from the VTH pipeline network is between 17-25°C. To maintain the temperature of the waste gas buffer tank 1 below 15°C, a chlorosilane temperature transmitter 106 is installed on the waste gas buffer tank 1. The chlorosilane temperature transmitter 106 monitors the temperature of the chlorosilane inside the waste gas buffer tank 1. A low-temperature hydrogen inlet is connected to the bottom of the waste gas buffer tank 1, and a cooling valve 104 is installed at the low-temperature hydrogen inlet. The cooling valve 104 is electrically connected to the chlorosilane temperature transmitter 106. The DCS (Distributed Control System) reads the temperature of the chlorosilane temperature transmitter 106. When the temperature exceeds 15°C, the cooling valve 104 is opened to introduce low-temperature hydrogen gas for cooling, preventing the chlorosilane from continuously being heated by the exhaust gas and causing it to volatilize. When the exhaust gas enters the exhaust gas buffer tank 1, the tank has multiple branch pipes that divide the exhaust gas into multiple streams that are introduced into the chlorosilane. The silicon powder in the gas exchanges with the chlorosilane. Most of the silicon powder is adsorbed by the chlorosilane and settles to the bottom of the tank by gravity. The bottom of the exhaust gas buffer tank 1 is conical, and a slag discharge valve 105 is installed at the bottom of the cone. The slag discharge valve 105 is connected to the slurry treatment system through a pipe. The silicon powder that settles to the bottom is periodically sent to the slurry treatment system through the slag discharge valve 105 for desliming and drying before being recycled.

[0016] The exhaust port of the waste gas buffer tank 1 is sequentially connected to the primary heat exchanger 3, the spray tower 4, the secondary heat exchanger 5, and the waste gas compressor 6 via pipelines. After pretreatment in the waste gas buffer tank 1, most of the silicon powder is adsorbed. Passing through the primary heat exchanger 3 and the spray tower 4 effectively reduces the frequency of blockage in the primary heat exchanger 3, and significantly reduces the silicon powder content in the bottom liquid of the spray tower 4. A circulation pump 701 is connected to the bottom outlet of the spray tower 4, and the outlet of the circulation pump 701 is connected to the inlet of the silicon powder filter 7. The outlet of the silicon powder filter 7 is connected to the liquid inlet of the spray tower 4. The cleaning frequency of the silicon powder filter 7 can also be significantly reduced.

[0017] The chlorosilane storage tank 2 is connected to the inlet of the buffer tank replenishment pump 201, and the outlet of the buffer tank replenishment pump 201 is connected to the waste gas buffer tank 1. The chlorosilane storage tank 2 is connected to the inlet of the spray tower replenishment pump 202, and the outlet of the spray tower replenishment pump 202 is connected to the spray tower 4. A low-level transmitter 101, a high-level transmitter 102, and an overflow valve 103 are installed on the waste gas buffer tank 1. The buffer tank replenishment pump 201 is electrically connected to the low-level transmitter 101, and the overflow valve 103 is electrically connected to the high-level transmitter 102. Depending on the production rhythm, the waste gas in the VTH pipeline network periodically contains a large amount of chlorosilane gas, and some... The condensate is sent to the compressor and downstream system for processing. A large amount of chlorosilane in the condensate condenses and remains in the waste gas buffer tank 1 when it enters the waste gas buffer tank 1, which will cause the liquid level in the waste gas buffer tank 1 to rise. When the liquid level rises, the DCS reads the signal of the high liquid level transmitter 102. When the high liquid level transmitter 102 is triggered, the DCS controls the overflow valve 103 to open and return the chlorosilane in the waste gas buffer tank 1 to the chlorosilane storage tank 2. At this time, the chlorosilane storage tank 2 should be set at a position lower than the waste gas buffer tank 1 so that it can return by gravity. The overflow valve 103 should be set at the position of the clear liquid above the liquid level to reduce the amount of silicon powder entering the chlorosilane storage tank 2. When the chlorosilane content in the exhaust gas of the VTH pipeline decreases, or when the exhaust gas buffer tank 1 starts to discharge slurry, the liquid level in the exhaust gas buffer tank 1 will drop. If the liquid level is insufficient, the contact time between the exhaust gas and the chlorosilane will be insufficient, resulting in a decrease in the adsorption rate. Therefore, the bottom outlet of the inlet pipe needs to be at least 1.5 meters deep into the liquid surface. When the liquid level is lower than this position, the DCS reads the low liquid level transmitter 101, and the low liquid level transmitter 101 sends a signal to the DCS. The DCS controls the closure of the overflow valve 103 and opens the buffer tank replenishment pump 201 and its associated valves. The buffer tank replenishment pump 201 replenishes the chlorosilane from the chlorosilane storage tank 2 into the exhaust gas buffer tank 1. When the liquid level returns to the low liquid level transmitter 101, the DCS controls the closure of the buffer tank replenishment pump 201 and closes the associated valves to complete the replenishment operation.

[0018] When the exhaust gas enters the exhaust gas compressor 6, its temperature needs to be controlled between 10℃ and 12℃. Cooling of the exhaust gas is mainly achieved through the primary heat exchanger 3 and the secondary heat exchanger 5. An exhaust gas temperature transmitter 601 is installed at the inlet pipe of the exhaust gas compressor 6. A first control valve 602 is installed at the cooling water inlet of the primary heat exchanger 3, and a second control valve 603 is installed at the cooling water inlet of the secondary heat exchanger 5. The exhaust gas temperature transmitter 601 is electrically connected to both the first and second control valves 602 and 603. The DCS reads the temperature rise rate from the exhaust gas temperature transmitter 601. If the temperature exceeds 10℃, the second control valve 603 for cooling water before the secondary heat exchanger 5 is opened wider. If the temperature rise rate exceeds 1℃ / minute, both the first and second control valves 602 and 603 are opened simultaneously, thus cooling both the inlet and outlet air of the spray tower 4 and maintaining the temperature between 10℃ and 12℃.

[0019] In the description of this utility model, it should be noted that the terms "center", "upper", "lower", "front", "rear", "top", "bottom", "left", "right", "vertical", "horizontal", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

Claims

1. An apparatus for removing silicon powder from a VTH pipeline network, characterized in that, The system includes an exhaust gas buffer tank (1), a chlorosilane storage tank (2), a primary heat exchanger (3), a spray tower (4), a secondary heat exchanger (5), and an exhaust gas compressor (6). The VTH pipeline is connected to the inlet of the exhaust gas buffer tank (1) via a pipeline. The exhaust outlet of the exhaust gas buffer tank (1) is connected to the primary heat exchanger (3), the spray tower (4), the secondary heat exchanger (5), and the exhaust gas compressor (6) in sequence via pipelines. The chlorosilane storage tank (2) is connected to the inlet of the buffer tank replenishment pump (201), and the outlet of the buffer tank replenishment pump (201) is connected to the exhaust gas buffer tank (1). The chlorosilane storage tank (2) is connected to the inlet of the spray tower replenishment pump (202), and the outlet of the spray tower replenishment pump (202) is connected to the spray tower (4). A low-level transmitter is installed on the exhaust gas buffer tank (1). 101) A high level transmitter (102) and an overflow valve (103) are installed. The buffer tank replenishment pump (201) is electrically connected to the low level transmitter (101), and the overflow valve (103) is electrically connected to the high level transmitter (102). An exhaust gas temperature transmitter (601) is installed at the inlet pipe of the exhaust gas compressor (6). A first control valve (602) is installed at the cooling water inlet of the first heat exchanger (3), and a second control valve (603) is installed at the cooling water inlet of the second heat exchanger (5). The exhaust gas temperature transmitter (601) is electrically connected to the first control valve (602) and the second control valve (603) respectively. A slag discharge valve (105) is provided at the bottom of the exhaust gas buffer tank (1). The slag discharge valve (105) is connected to the slurry treatment system through a pipeline.

2. The apparatus for removing silicon powder from a VTH pipeline according to claim 1, characterized in that, It also includes a silicon powder filter (7), and a circulating pump (701) is connected to the bottom outlet of the spray tower (4). The outlet of the circulating pump (701) is connected to the inlet of the silicon powder filter (7), and the outlet of the silicon powder filter (7) is connected to the liquid inlet of the spray tower (4).

3. The apparatus for removing silicon powder from a VTH pipeline according to claim 1, characterized in that, A chlorosilane temperature transmitter (106) is installed on the waste gas buffer tank (1). A low-temperature hydrogen inlet is connected to the bottom of the waste gas buffer tank (1). A cooling valve (104) is provided at the low-temperature hydrogen inlet. The cooling valve (104) is electrically connected to the chlorosilane temperature transmitter (106).

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