Hydrogen grading purification pretreatment system for polysilicon production

Abstract

The utility model provides a kind of hydrogen grading purification pretreatment system for polysilicon production, it is related to polysilicon production technical field.The utility model includes hydrogen chloride absorption tower, gas-liquid separation device, three-stage condensing device, shunt device by pipeline sequential connection, and one way of shunt device output two-way, and one way has active carbon adsorption tower group, hydrogen buffer tank, reduction furnace in order, and another way has heat exchanger, first storage tank, compressor, second storage tank and cold hydrogenation device in order.The utility model solves the prior art active carbon adsorption tower easy " penetration " failure, output hydrogen quality does not reach standard, and the problem of energy waste and high processing cost caused by cold hydrogenation device and reduction furnace share high-purity hydrogen.

Description

Technical Field

[0001] This utility model relates to the field of polysilicon production technology, specifically to a hydrogen graded purification pretreatment system for polysilicon production. Background Technology

[0002] Polycrystalline silicon production refers to the industrial process of converting industrial silicon into high-purity polycrystalline silicon material through chemical purification and physical deposition. Currently, the widely used modified Siemens process involves the following core steps: first, reacting industrial silicon with hydrogen chloride to synthesize trichlorosilane; then purifying the trichlorosilane using precision separation techniques such as distillation; next, reducing the high-purity trichlorosilane with hydrogen in a reduction furnace, causing silicon to deposit on a heating element to form rod-shaped polycrystalline silicon. Simultaneously, the exhaust gases generated during production undergo a highly efficient recovery and separation system to separate and utilize hydrogen from chlorosilanes and hydrogen from hydrogen chloride, thereby reducing costs and energy consumption.

[0003] In the polysilicon production process, the hydrogen in the reduction tail gas, after purification, needs to be supplied to both the reduction furnace and the cold hydrogenation unit. Since the cold hydrogenation unit has lower requirements for hydrogen quality, while the reduction furnace requires extremely high-purity hydrogen, the original system uniformly passed all hydrogen through an activated carbon adsorption tower group for deep purification, inputting some of the purified hydrogen into the cold hydrogenation unit, which has lower hydrogen quality requirements, resulting in a waste of energy and operating costs. Furthermore, the hydrogen produced by the upstream hydrogen chloride stripping tower carries mist; even after three-stage condensation, trace amounts of silane liquid still enter the adsorption tower, causing the activated carbon adsorbent to rapidly "penetrate" and fail, resulting in acidic produced hydrogen with excessive levels of metal impurities, boron, and phosphorus, severely affecting the quality of the polysilicon product from the reduction process. Therefore, the following solutions are proposed to address these issues. Utility Model Content

[0004] The purpose of this invention is to develop a hydrogen graded purification and pretreatment system for polysilicon production. By setting up a gas-liquid separator at the front end and a diversion branch before activated carbon adsorption, and equipping it with cryogenic and pressurization equipment, the system achieves graded purification and precise utilization of hydrogen. This solves the problems in the prior art, such as the activated carbon adsorption tower being prone to "penetration" failure, the substandard quality of the produced hydrogen, and the energy waste and high processing costs caused by the cold hydrogenation unit and the reduction furnace sharing high-purity hydrogen.

[0005] This utility model is achieved through the following technical solution:

[0006] A hydrogen staged purification pretreatment system for polysilicon production includes:

[0007] The hydrogen chloride absorption tower, gas-liquid separation unit, three-stage condenser, and diversion unit are connected sequentially by pipelines.

[0008] The diversion device outputs two paths, one of which is sequentially connected to the activated carbon adsorption tower group, the hydrogen buffer tank, and the reduction furnace, and the other is sequentially connected to the heat exchanger, the first storage tank, the compressor, the second storage tank, and the cold hydrogenation device.

[0009] The hydrogen gas at the top of the hydrogen chloride absorption tower flows sequentially through a gas-liquid separator for preliminary gas-liquid separation and a three-stage condenser for deep condensation and liquid removal. Then, it is divided into two streams by the diversion device. One stream of hydrogen gas enters the activated carbon adsorption tower group for purification, is stored in the hydrogen buffer tank, and is supplied to the reduction furnace. The other stream of hydrogen gas enters the heat exchanger for deep cooling, is buffered in the first storage tank, pressurized by the compressor, and buffered in the second storage tank before being directly supplied to the cold hydrogenation unit.

[0010] Optionally, the gas-liquid separation device is a gas-liquid separation tank with an internal wire mesh demister, used to intercept and separate mist droplets entrained in the hydrogen gas from the top of the hydrogen chloride absorption tower.

[0011] Optionally, the three-stage condensation device consists of three condensers connected in series, used to cool the temperature of hydrogen gas step by step to -20°C to -30°C, thereby achieving condensation and removing residual silane liquid.

[0012] Optionally, the diversion device is a three-way valve or a diversion valve, which diverts the hydrogen from the three-stage condenser into two outputs according to a predetermined ratio.

[0013] Optionally, the heat exchanger uses a refrigerant with a temperature of -40°C to cool the hydrogen to -35°C to -40°C.

[0014] Optionally, the compressor is used to pressurize the cryogenic hydrogen to 2.5MPa~3.0MPa to meet the feed pressure requirements of the cold hydrogenation device.

[0015] Optionally, the activated carbon adsorption tower group includes multiple adsorption towers, each group including three adsorption towers. The three adsorption towers are used in a cycle, with one in operation, one regenerating, and one on standby. The entire process is sequentially controlled.

[0016] The beneficial effects of this utility model are:

[0017] This invention improves the hydrogen treatment process, enabling the staged utilization of hydrogen, effectively reducing the load on the activated carbon adsorption tower, preventing adsorbent breakthrough, improving hydrogen quality, and reducing treatment costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a system structure diagram of the present invention. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] In this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0022] The embodiments of this utility model will now be described in detail with reference to the accompanying drawings.

[0023] This utility model discloses a hydrogen graded purification pretreatment system for polycrystalline silicon production, such as... Figure 1 As shown, it includes a hydrogen chloride absorption tower, a gas-liquid separation device, a three-stage condensation device, a diversion device, an activated carbon adsorption tower group, a hydrogen buffer tank, and a reduction furnace, which are connected in sequence by pipelines. The diversion device is connected in sequence by pipelines to a heat exchanger, a first storage tank, a compressor, a second storage tank, and a cold hydrogenation device.

[0024] The hydrogen gas containing a small amount of silane droplets at the top of the hydrogen chloride absorption tower flows sequentially through a gas-liquid separator for preliminary gas-liquid separation, a three-stage condenser for deep condensation and liquid removal, and then is split into two outputs by a diversion device.

[0025] After the first stream enters the activated carbon adsorption tower group for deep purification, the high-quality hydrogen obtained is stored in the hydrogen buffer tank and supplied to the reduction furnace.

[0026] The second line passes through a heat exchanger for deep cooling, a first storage tank for buffering, a compressor for pressurization, and a second storage tank for buffering before being directly supplied to the cold hydrogenation unit.

[0027] The gas-liquid separation device is a gas-liquid separation tank with an internal wire mesh demister, used to intercept and separate droplets entrained in hydrogen gas from the top of the hydrogen chloride absorption tower.

[0028] The three-stage condensation unit consists of three condensers connected in series, used to cool the temperature of hydrogen gas step by step to -20°C to -30°C, thereby achieving condensation and removing residual silane liquid.

[0029] The diversion device is a three-way valve or a diversion valve, used to divert hydrogen from the three-stage condenser to the main pipeline and branch pipelines in a predetermined ratio.

[0030] The heat exchanger uses a refrigerant with a temperature of -40°C to cool the hydrogen output from the splitter to -35°C to -40°C.

[0031] The compressor is used to pressurize the cryogenic hydrogen to 2.5MPa~3.0MPa to meet the feed pressure requirements of the cold hydrogenation unit.

[0032] The activated carbon adsorption tower group consists of multiple adsorption towers, each group containing three adsorption towers. The three adsorption towers are used in a cycle, with one in operation, one regenerating, and one on standby. The entire process is sequentially controlled. The adsorption towers are used to adsorb and remove acidic impurities, metallic impurities, and impurities such as boron and phosphorus from hydrogen, so that they meet the hydrogen quality requirements of the reduction furnace.

[0033] The hydrogen buffer tank, the first storage tank, and the second storage tank are all used to stabilize the system pressure and ensure a continuous and controllable supply of hydrogen to downstream units or furnaces.

[0034] One specific application of this embodiment is:

[0035] Step S1. Draw out the hydrogen mixture containing droplets from the hydrogen chloride absorption tower:

[0036] A mixture of hydrogen gas containing mist entrained in the hydrogen chloride absorption tower is drawn out from the top outlet. This mixture includes hydrogen gas, hydrogen chloride gas, and entrained silane droplets.

[0037] Step S2. The gas-liquid separation device performs preliminary gas-liquid separation:

[0038] The hydrogen mixture obtained in step S1 is introduced into a gas-liquid separation device. The device is equipped with a wire mesh interception structure. When the hydrogen mixture passes through the wire mesh, the droplets are intercepted by the wire mesh and fall down, thus achieving gas-liquid separation. After separation, preliminary purified hydrogen and separated liquid (mainly silane liquid) are obtained. This step removes most of the entrained droplets, reducing the load on the subsequent three-stage condensation device.

[0039] Step S3. Three-stage condensation device for step-by-step cooling and condensation:

[0040] The pre-purified hydrogen obtained in step S2 is introduced into a three-stage condenser, which consists of multiple condensers connected in series to progressively reduce the temperature of the hydrogen. Specifically:

[0041] The first-stage condenser cools the hydrogen gas to below room temperature, and the condenser leaves behind liquid silane.

[0042] The second-stage condenser further cools the liquid silane to a lower temperature (e.g., 0°C to -10°C), condensing more silane liquid.

[0043] The third stage of condensation finally cools the temperature to -20°C to -30°C, completely condensing and removing residual silane liquid;

[0044] During the condensation process, the silane liquid is collected and discharged from the system, yielding cooled hydrogen gas;

[0045] Step S4. The splitter separates the hydrogen gas into two streams:

[0046] The cooled hydrogen obtained in step S3 is introduced into a splitting device (e.g., a three-way valve or a splitter), which divides the hydrogen into two streams:

[0047] The first stream of hydrogen is directed to the activated carbon adsorption tower group for subsequent deep purification.

[0048] The second stream of hydrogen flows to the cold hydrogenation unit, which is used for cold hydrogenation processes where the quality requirements of hydrogen are not high.

[0049] The split ratio can be adjusted according to actual production needs. Usually, the second hydrogen stream accounts for 20% to 40% of the total flow to effectively reduce the processing load of the activated carbon adsorption tower group.

[0050] A portion of the hydrogen is introduced directly into the cold hydrogenation unit, avoiding the need for all the hydrogen to pass through the activated carbon adsorption tower group before entering the cold hydrogenation unit, thus reducing the load on the adsorption tower and preventing adsorbent breakthrough.

[0051] Step S5. The heat exchanger undergoes cryogenic treatment:

[0052] The second hydrogen gas in step S4 is introduced into a heat exchanger. The heat exchanger uses a refrigerant with a temperature of -40°C (such as liquid nitrogen or low-temperature refrigerant) to perform deep cryogenic treatment on the hydrogen gas, so that the temperature of the hydrogen gas drops to -35°C to -40°C. This step further condenses any trace amounts of silane liquid that may remain in the hydrogen gas, ensuring that the hydrogen gas meets the usage requirements of the cold hydrogenation device.

[0053] Step S6. After cryogenic cooling, the hydrogen is temporarily stored in the first storage tank:

[0054] The hydrogen gas after deep cooling in step S5 is introduced into the first storage tank (e.g., a buffer tank) for temporary storage and stabilization. The first storage tank is used to balance gas flow fluctuations and ensure continuous and stable feed to the subsequent compressor.

[0055] Step S7. The compressor pressurizes the hydrogen gas:

[0056] The hydrogen in the first storage tank is pressurized by a compressor to raise the hydrogen pressure to 2.5 MPa to 3.0 MPa; the pressurization process uses a reciprocating or centrifugal compressor to ensure that the hydrogen reaches the operating pressure required by the cold hydrogenation unit;

[0057] Step S8. After pressurization, the hydrogen is temporarily stored in the second storage tank:

[0058] The pressurized hydrogen from step S7 is introduced into a second storage tank (e.g., a high-pressure buffer tank) for further buffering and stabilization. The second storage tank is used to regulate the flow rate and pressure to ensure that the hydrogen supplied to the cold hydrogenation unit is continuous and controllable.

[0059] Step S9. Hydrogen is delivered to the cold hydrogenation unit:

[0060] Hydrogen from the second storage tank is transported to the cold hydrogenation unit for use in the cold hydrogenation synthesis process. Since the cold hydrogenation process does not have high requirements for hydrogen quality, the hydrogen does not need to pass through the activated carbon adsorption tower group and can be used directly to meet the process requirements. It also has no negative impact on the quality, conversion rate and process control of cold hydrogenation synthesis.

[0061] Step S10. The activated carbon adsorption tower group performs deep adsorption and purification:

[0062] The first stream of hydrogen gas in step S4 is introduced into the activated carbon adsorption tower group, which consists of multiple activated carbon adsorption towers connected in parallel or in series. When the hydrogen gas passes through the activated carbon bed, impurities such as metallic impurities, boron (B), and phosphorus (P) are adsorbed and removed. The adsorption tower group operates at room temperature or slightly above room temperature to ensure that the hydrogen gas meets high quality standards (B content less than 0.01 ppbw, impurity content less than 1.2 ppbw).

[0063] Step S11. The purified hydrogen is temporarily stored in a hydrogen buffer tank:

[0064] The high-quality hydrogen after deep purification in step S10 is introduced into a hydrogen buffer tank. This buffer tank is used to ensure the stability, continuity and controllability of the feed, buffer pressure fluctuations, and provide a constant hydrogen supply for the subsequent reduction furnace.

[0065] Step S12. Hydrogen gas is supplied to the reduction furnace:

[0066] High-quality hydrogen from the hydrogen buffer tank is delivered to the reduction furnace for the polysilicon reduction process. This hydrogen meets the high quality requirements of the reduction furnace, ensuring the purity of the polysilicon product, reducing impurity deposition, and improving the quality of the polysilicon product.

[0067] This invention improves the hydrogen treatment process, enabling the staged utilization of hydrogen, effectively reducing the load on the activated carbon adsorption tower, preventing adsorbent breakthrough, improving hydrogen quality, and reducing treatment costs.

[0068] The above embodiments are merely preferred embodiments of this utility model and are not intended to limit the technical solutions of this utility model. Any technical solution that can be implemented based on the above embodiments without creative effort should be considered to fall within the scope of protection of this utility model patent.

Claims

1. A hydrogen staged purification pretreatment system for polysilicon production, characterized in that, include: The hydrogen chloride absorption tower, gas-liquid separation unit, three-stage condenser, and diversion unit are connected sequentially by pipelines. The diversion device outputs two paths, one of which is sequentially connected to the activated carbon adsorption tower group, the hydrogen buffer tank, and the reduction furnace, and the other is sequentially connected to the heat exchanger, the first storage tank, the compressor, the second storage tank, and the cold hydrogenation device. The hydrogen gas at the top of the hydrogen chloride absorption tower flows sequentially through a gas-liquid separator for preliminary gas-liquid separation and a three-stage condenser for deep condensation and liquid removal. Then, it is divided into two streams by the diversion device. One stream of hydrogen gas enters the activated carbon adsorption tower group for purification, is stored in the hydrogen buffer tank, and is supplied to the reduction furnace. The other stream of hydrogen gas enters the heat exchanger for deep cooling, is buffered in the first storage tank, pressurized by the compressor, and buffered in the second storage tank before being directly supplied to the cold hydrogenation unit.

2. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The gas-liquid separation device is a gas-liquid separation tank with an internal wire mesh demister, used to intercept and separate droplets entrained in the hydrogen gas from the top of the hydrogen chloride absorption tower.

3. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The three-stage condensation device consists of three condensers connected in series, used to cool the temperature of hydrogen gas step by step to -20°C to -30°C, thereby condensing and removing residual silane liquid.

4. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The diversion device is a three-way valve or a diversion valve, which divides the hydrogen from the three-stage condenser into two outputs according to a predetermined ratio.

5. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The heat exchanger uses a refrigerant with a temperature of -40°C to cool the hydrogen gas to -35°C to -40°C.

6. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The compressor is used to pressurize the cryogenic hydrogen to 2.5MPa~3.0MPa to meet the feed pressure requirements of the cold hydrogenation device.

7. The hydrogen staged purification pretreatment system for polycrystalline silicon production according to claim 1, characterized in that, The activated carbon adsorption tower group includes multiple adsorption towers, each group including three adsorption towers. The three adsorption towers are used in a cycle, with one in operation, one in regeneration, and one in standby. The entire process is sequentially controlled.

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