Polysilicon reduction tail gas heat energy recycling system
By designing a polycrystalline silicon reduction tail gas heat energy recovery and utilization system, the reduction tail gas is used to heat the polycrystalline silicon reduction reaction materials, which solves the problem of insufficient heat energy recovery from the reduction tail gas and achieves more efficient energy utilization and energy saving effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- XINTE ENERGY CO LTD
- Filing Date
- 2025-09-01
- Publication Date
- 2026-08-04
AI Technical Summary
In existing technologies, the heat energy recovery from the reduction tail gas during polysilicon production is insufficient, resulting in energy waste.
A polycrystalline silicon reduction tail gas heat energy recovery and utilization system is designed, including a tail gas cooler, a first vaporizer, a first preheater, a mixer, a second preheater, and a second vaporizer. The system heats the polycrystalline silicon reduction reaction material with the reduction tail gas and combines a gas-solid separation device and a compressor to achieve more complete heat energy recovery.
It effectively reduces steam consumption during the vaporization process of reactants, reduces the consumption of circulating water and cooling media, improves energy utilization efficiency, and achieves the goal of energy saving.
Smart Images
Figure CN224593747U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of heat energy recovery technology of reduction furnace tail gas in polycrystalline silicon production process, specifically relating to a polycrystalline silicon reduction tail gas heat energy recovery and utilization system. Background Technology
[0002] Currently, bell-type reactors are commonly used to produce polysilicon. During the reaction process, the bell-type reactor needs to maintain a high temperature of 1000–1100°C. Correspondingly, the temperature of the reduction tail gas exiting the bell-type reactor is also relatively high. If its thermal energy is recovered and utilized, the energy consumption and cost in the polysilicon production process can be effectively reduced.
[0003] Existing technologies can recover and utilize the heat energy from reduction exhaust gases. However, problems of insufficient energy recovery and energy waste still exist. Utility Model Content
[0004] The technical problem to be solved by this utility model is to address the above-mentioned deficiencies in the existing technology by providing a polycrystalline silicon reduction tail gas heat energy recovery and utilization system. The system uses reduction tail gas and compressed hydrogen to heat the polycrystalline silicon reduction reaction materials, thereby more fully recovering the heat energy of the reduction tail gas during the recovery process, effectively reducing the steam consumption during the vaporization process of the reaction materials, and reducing the consumption of circulating water and cooling medium required for the downstream tail gas cooling, thus achieving the purpose of energy saving.
[0005] The technical solution adopted to solve the technical problem of this utility model is to provide a polycrystalline silicon reduction tail gas heat energy recovery and utilization system, including:
[0006] The exhaust gas cooler includes: an exhaust gas cooler body, an inlet of a first heat exchange channel disposed on the exhaust gas cooler body, an outlet of the first heat exchange channel, an inlet of a second heat exchange channel, and an outlet of the second heat exchange channel. The inlet of the first heat exchange channel is used to introduce polysilicon reduction exhaust gas, and the inlet of the second heat exchange channel is connected to the outlet of a mixer. The trichlorosilane discharged from the outlet of the second heat exchange channel and the raw material hydrogen are used to react in the polysilicon reduction furnace. The exhaust gas cooler is used to heat the reaction raw materials in the polysilicon reduction furnace using the heat from the polysilicon reduction exhaust gas, and to cool down the reduction exhaust gas.
[0007] A first vaporizer includes: a first vaporizer body, an inlet of a first heat exchange channel disposed on the first vaporizer body, an outlet of the first heat exchange channel, an inlet of a second heat exchange channel, a first outlet of the second heat exchange channel, and a second outlet of the second heat exchange channel. The first outlet of the second heat exchange channel is used to discharge vaporized trichlorosilane, and the second outlet of the second heat exchange channel is used to discharge unvaporized trichlorosilane. The inlet of the first heat exchange channel is connected to the outlet of the first heat exchange channel of the exhaust gas cooler, and the inlet of the second heat exchange channel is connected to the outlet of the second heat exchange channel of the first preheater. The first vaporizer is used to vaporize trichlorosilane.
[0008] The first preheater includes: a first preheater body, an inlet of a first heat exchange channel of the first preheater disposed on the first preheater body, an outlet of the first heat exchange channel of the first preheater, an inlet of a second heat exchange channel of the first preheater, and an outlet of the second heat exchange channel of the first preheater. The inlet of the first heat exchange channel of the first preheater is connected to the outlet of the first heat exchange channel of the first vaporizer. The inlet of the second heat exchange channel of the first preheater is used to introduce trichlorosilane (TCS), a raw material for polycrystalline silicon production. The first preheater is used to preheat the trichlorosilane.
[0009] The mixer includes: a mixer body, a first mixer inlet, a second mixer inlet, and a mixer outlet disposed on the mixer body. The first mixer inlet is connected to the first outlet of the second heat exchange channel of the first vaporizer, and the second mixer inlet is also connected to the outlet of the second heat exchange channel of the second preheater.
[0010] The second preheater includes: a second preheater body, an inlet of a first heat exchange channel of the second preheater disposed on the second preheater body, an outlet of the first heat exchange channel of the second preheater, an inlet of a second heat exchange channel of the second preheater, and an outlet of the second heat exchange channel of the second preheater. The inlet of the first heat exchange channel of the second preheater is connected to the outlet of the first heat exchange channel of the first preheater. The inlet of the second heat exchange channel of the second preheater is used to introduce hydrogen gas, a raw material for polycrystalline silicon production. The second preheater is used to preheat the hydrogen gas, a raw material for polycrystalline silicon production.
[0011] The second vaporizer includes: a second vaporizer body, an inlet of a first heat exchange channel of the second vaporizer disposed on the second vaporizer body, an outlet of the first heat exchange channel of the second vaporizer, an inlet of a second heat exchange channel of the second vaporizer, and an outlet of the second heat exchange channel of the second vaporizer. The inlet of the second heat exchange channel of the second vaporizer is connected to the second outlet of the second heat exchange channel of the first vaporizer. The outlet of the second heat exchange channel of the second vaporizer is used to discharge vaporized trichlorosilane. The inlet of the first heat exchange channel of the second vaporizer is used to introduce a heat source to vaporize the trichlorosilane within the second heat exchange channel of the second vaporizer. The outlet of the first heat exchange channel of the second vaporizer is used to discharge the heat source. The second vaporizer is used to vaporize the trichlorosilane that was not vaporized in the first vaporizer.
[0012] Optionally, the outlet of the second heat exchange channel of the second vaporizer is also connected to the inlet of the mixer.
[0013] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0014] A gas-solid separation device, the inlet of which is connected to the outlet of the first heat exchange channel of the first preheater; the gas-solid separation device is used to perform gas-solid separation.
[0015] The exhaust gas low-pressure condenser is connected to the gas outlet of the gas-solid separation device. The exhaust gas low-pressure condenser is used to condense trichlorosilane and separate out the recovered hydrogen.
[0016] The compressor has its inlet connected to the outlet of the low-pressure condenser for exhaust gas, and its outlet connected to the inlet of the first heat exchange channel of the second preheater. The compressor is used to compress the recovered hydrogen to raise its temperature.
[0017] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0018] The first buffer tank is located between the exhaust gas low-pressure condensation unit and the compressor, and is connected to both the exhaust gas low-pressure condensation unit and the compressor. The first buffer tank is used to buffer the raw material hydrogen gas.
[0019] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0020] The second buffer tank is located between the compressor and the second preheater, and is connected to both the compressor and the second preheater. The second buffer tank is used to buffer the raw material hydrogen.
[0021] Optionally, the gas-solid separation device includes:
[0022] The cyclone separator has its inlet connected to the outlet of the first heat exchange channel of the first preheater.
[0023] The filter is connected to the gas outlet of the cyclone separator. The filter is used to remove silicon powder. The gas outlet of the filter is connected to the inlet of the exhaust gas low-pressure condenser.
[0024] Optionally, the exhaust gas low-pressure condensation unit includes: a primary air cooler, a primary circulating water cooler, a primary exhaust gas integrated heat exchanger, a secondary exhaust gas integrated heat exchanger, a primary seven-degree water heat exchanger, a chlorosilane condensate tank, an exhaust gas cryocooler, and a chlorosilane gas-liquid separator.
[0025] The primary air cooler is connected to the filter, and the secondary exhaust gas heat exchanger is connected to the primary buffer tank. The secondary exhaust gas heat exchanger is used to discharge hydrogen gas, which then enters the compressor's pre-compressor buffer tank.
[0026] The primary circulating water cooler is connected to the primary air cooler; the primary exhaust gas integrated heat exchanger is connected to the primary circulating water cooler; the primary seven-degree water heat exchanger is connected to the primary exhaust gas integrated heat exchanger; the secondary exhaust gas integrated heat exchanger is connected to the primary seven-degree water heat exchanger; the exhaust gas cryostat is connected to the secondary exhaust gas integrated heat exchanger; the chlorosilane gas-liquid separator is connected to the secondary exhaust gas integrated heat exchanger; and the chlorosilane gas-liquid separator is connected to the exhaust gas cryostat.
[0027] The primary tail gas integrated heat exchanger is used to cool the reducing tail gas from the low-temperature chlorosilane condensate and the chlorosilane-rich liquid containing hydrogen chloride absorbed in the bottom of the tail gas recovery absorption tower. The chlorosilane then enters the hydrogen chloride desorption tower of the tail gas recovery unit for hydrogen chloride desorption.
[0028] The primary circulating water cooler, primary exhaust gas integrated heat exchanger, secondary exhaust gas integrated heat exchanger, primary seven-degree water heat exchanger, exhaust gas cryocooler, and chlorosilane gas-liquid separator are all connected to the chlorosilane condensate tank, which is used to collect chlorosilane condensate.
[0029] The exhaust gas low-pressure condensation device also includes a chlorosilane condensate transfer pump, which is connected to a chlorosilane condensate tank.
[0030] Optionally, the exhaust gas cooler, the first preheater, and the second preheater are all fixed tube sheet heat exchangers.
[0031] Optionally, the first vaporizer and the second vaporizer are one of the following: jacketed tube vaporizer, U-tube vaporizer, and shell-and-tube vaporizer.
[0032] Optionally, the mixer may include either a static mixer or a pipeline gas mixer.
[0033] Optionally, the compressor includes either a reciprocating compressor or a centrifugal compressor.
[0034] Compared with the prior art, this utility model adds a first-stage vaporizer while using the reduction tail gas to preheat the TCS feedstock. This allows for more complete recovery and utilization of the heat from the reduction tail gas, reducing the temperature of the reduction tail gas from 100-170℃ in the prior art to 90℃. The heat recovery from the reduction tail gas is more complete. With the same TCS feed rate, the steam consumption of the TCS steam vaporizer is reduced by 25%-27%. Based on a TCS feed rate of 120t / h, this can save 7.12t / h of steam. Attached Figure Description
[0035] Figure 1 This is a schematic diagram of the polycrystalline silicon reduction tail gas heat energy recovery and utilization system in embodiments 2 and 3 of this utility model;
[0036] Figure 2 This is a schematic diagram of the structure of the exhaust gas low-pressure condensation device in embodiments 2 and 3 of this utility model.
[0037] In the diagram: 1-Exhaust gas cooler, 2-First vaporizer, 3-First preheater, 4-Mixer, 5-Second preheater, 6-Second vaporizer, 7-Low-pressure condenser for exhaust gas, 8-First buffer tank, 9-Compressor, 10-Second buffer tank, 11-Cyclone separator, 12-Filter, 13-Inlet of the first heat exchange channel of the exhaust gas cooler, 14-Outlet of the first heat exchange channel of the exhaust gas cooler, 15-Inlet of the second heat exchange channel of the exhaust gas cooler, 16-Outlet of the second heat exchange channel of the exhaust gas cooler, 21-Inlet of the first heat exchange channel of the first vaporizer, 22-Outlet of the first heat exchange channel of the first vaporizer, 23-Inlet of the second heat exchange channel of the first vaporizer, 24-First outlet of the second heat exchange channel of the first vaporizer, 25-Second heat exchange channel of the first vaporizer 31-Second outlet of the hot channel, 32-Inlet of the first heat exchange channel of the first preheater, 33-Inlet of the second heat exchange channel of the first preheater, 34-Outlet of the second heat exchange channel of the first preheater, 41-First inlet of the mixer, 42-Outlet of the mixer, 43-Second inlet of the mixer, 51-Inlet of the first heat exchange channel of the second preheater, 52-Outlet of the first heat exchange channel of the second preheater, 53-Inlet of the second heat exchange channel of the second preheater, 54-Outlet of the second heat exchange channel of the second preheater, 61-Inlet of the first heat exchange channel of the second vaporizer, 62-Outlet of the first heat exchange channel of the second vaporizer, 63-Inlet of the second heat exchange channel of the second vaporizer, 64-Outlet of the second heat exchange channel of the second vaporizer. Detailed Implementation
[0038] To enable those skilled in the art to better understand the technical solution of this utility model, the present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0039] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.
[0040] In the description of this patent, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this patent 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 patent.
[0041] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.
[0042] Example 1
[0043] This embodiment provides a polysilicon reduction tail gas heat energy recovery and utilization system, including:
[0044] The exhaust gas cooler includes: an exhaust gas cooler body, an inlet of a first heat exchange channel disposed on the exhaust gas cooler body, an outlet of the first heat exchange channel, an inlet of a second heat exchange channel, and an outlet of the second heat exchange channel. The inlet of the first heat exchange channel is used to introduce polysilicon reduction exhaust gas, and the inlet of the second heat exchange channel is connected to the outlet of a mixer. The trichlorosilane discharged from the outlet of the second heat exchange channel and the raw material hydrogen are used to react in the polysilicon reduction furnace. The exhaust gas cooler is used to heat the reaction raw materials in the polysilicon reduction furnace using the heat from the polysilicon reduction exhaust gas, and to cool down the reduction exhaust gas.
[0045] A first vaporizer includes: a first vaporizer body, an inlet of a first heat exchange channel of the first vaporizer disposed on the first vaporizer body, an outlet of the first heat exchange channel of the first vaporizer, an inlet of a second heat exchange channel of the first vaporizer, a first outlet of the second heat exchange channel of the first vaporizer, and a second outlet of the second heat exchange channel of the first vaporizer. The inlet of the first heat exchange channel of the first vaporizer is connected to the outlet of the first heat exchange channel of the exhaust gas cooler, and the inlet of the second heat exchange channel of the first vaporizer is connected to the outlet of the second heat exchange channel of the first preheater. The first vaporizer is used for vaporizing trichlorosilane.
[0046] The first preheater includes: a first preheater body, an inlet of a first heat exchange channel of the first preheater disposed on the first preheater body, an outlet of the first heat exchange channel of the first preheater, an inlet of a second heat exchange channel of the first preheater, and an outlet of the second heat exchange channel of the first preheater. The inlet of the first heat exchange channel of the first preheater is connected to the outlet of the first heat exchange channel of the first vaporizer. The inlet of the second heat exchange channel of the first preheater is used to introduce trichlorosilane, a raw material for polycrystalline silicon production. The first preheater is used to preheat trichlorosilane.
[0047] The mixer inlet is connected to the first outlet of the second heat exchange channel of the first vaporizer, and the mixer inlet is also connected to the outlet of the second heat exchange channel of the second preheater.
[0048] The mixer includes: a mixer body, a first mixer inlet, a second mixer inlet, and a mixer outlet disposed on the mixer body. The first mixer inlet is connected to the first outlet of the second heat exchange channel of the first vaporizer, and the second mixer inlet is also connected to the outlet of the second heat exchange channel of the second preheater.
[0049] The second preheater includes: a second preheater body, an inlet of a first heat exchange channel of the second preheater disposed on the second preheater body, an outlet of the first heat exchange channel of the second preheater, an inlet of a second heat exchange channel of the second preheater, and an outlet of the second heat exchange channel of the second preheater. The inlet of the first heat exchange channel of the second preheater is connected to the outlet of the first heat exchange channel of the first preheater. The inlet of the second heat exchange channel of the second preheater is used to introduce hydrogen gas, a raw material for polycrystalline silicon production. The second preheater is used to preheat the hydrogen gas, a raw material for polycrystalline silicon production.
[0050] The second vaporizer includes: a second vaporizer body, an inlet of a first heat exchange channel of the second vaporizer disposed on the second vaporizer body, an outlet of the first heat exchange channel of the second vaporizer, an inlet of a second heat exchange channel of the second vaporizer, and an outlet of the second heat exchange channel of the second vaporizer. The inlet of the second heat exchange channel of the second vaporizer is connected to the second outlet of the second heat exchange channel of the first vaporizer. The outlet of the second heat exchange channel of the second vaporizer is used to discharge vaporized trichlorosilane. The inlet of the first heat exchange channel of the second vaporizer is used to introduce a heat source to vaporize the trichlorosilane within the second heat exchange channel of the second vaporizer. The outlet of the first heat exchange channel of the second vaporizer is used to discharge the heat source. The second vaporizer is used to vaporize the trichlorosilane that was not vaporized in the first vaporizer.
[0051] Compared with the prior art, this utility model adds a first-stage vaporizer while using the reduction tail gas to preheat the TCS feedstock. This allows for more complete recovery and utilization of the heat from the reduction tail gas, reducing the temperature of the reduction tail gas from 100-170℃ in the prior art to 90℃. The heat recovery from the reduction tail gas is more complete. With the same TCS feed rate, the steam consumption of the TCS steam vaporizer is reduced by 25%-27%. Based on a TCS feed rate of 120t / h, this can save 7.12t / h of steam.
[0052] Example 2
[0053] like Figure 1 As shown, this embodiment provides a polysilicon reduction tail gas heat energy recovery and utilization system, including:
[0054] The exhaust gas cooler 1 includes: an exhaust gas cooler body, an inlet 13 of a first heat exchange channel of the exhaust gas cooler disposed on the exhaust gas cooler body, an outlet 14 of the first heat exchange channel of the exhaust gas cooler, an inlet 15 of a second heat exchange channel of the exhaust gas cooler, and an outlet 16 of the second heat exchange channel of the exhaust gas cooler. The inlet 13 of the first heat exchange channel of the exhaust gas cooler is used to introduce polysilicon reduction exhaust gas. The inlet 15 of the second heat exchange channel of the exhaust gas cooler is connected to the mixer outlet 42. The trichlorosilane (TCS) discharged from the outlet 16 of the second heat exchange channel of the exhaust gas cooler and the raw material hydrogen are used to react in the polysilicon reduction furnace. The exhaust gas cooler 1 is used to heat the reaction raw materials in the polysilicon reduction furnace by the heat of the polysilicon reduction exhaust gas, and to cool down the reduction exhaust gas.
[0055] The first vaporizer 2 includes: a first vaporizer body, an inlet 21 of a first heat exchange channel of the first vaporizer disposed on the first vaporizer body, an outlet 22 of the first heat exchange channel of the first vaporizer, an inlet 23 of a second heat exchange channel of the first vaporizer, a first outlet 24 of the second heat exchange channel of the first vaporizer, and a second outlet 25 of the second heat exchange channel of the first vaporizer. The first outlet 24 of the second heat exchange channel of the first vaporizer is used to discharge vaporized trichlorosilane, and the second outlet 25 of the second heat exchange channel of the first vaporizer is used to discharge unvaporized trichlorosilane. The inlet 21 of the first heat exchange channel of the first vaporizer is connected to the outlet 14 of the first heat exchange channel of the exhaust gas cooler, and the inlet 23 of the second heat exchange channel of the first vaporizer is connected to the outlet 34 of the second heat exchange channel of the first preheater. The first vaporizer 2 is used to vaporize trichlorosilane.
[0056] The first preheater 3 includes: a first preheater body, an inlet 31 of a first heat exchange channel of the first preheater disposed on the first preheater body, an outlet 32 of the first heat exchange channel of the first preheater, an inlet 33 of a second heat exchange channel of the first preheater, and an outlet 34 of the second heat exchange channel of the first preheater. The inlet 31 of the first heat exchange channel of the first preheater is connected to the outlet 22 of the first heat exchange channel of the first vaporizer. The inlet 33 of the second heat exchange channel of the first preheater is used to introduce trichlorosilane, a raw material for polycrystalline silicon production. The first preheater 3 is used to preheat trichlorosilane.
[0057] The mixer 4 includes: a mixer body, a first mixer inlet 41, a second mixer inlet 43, and a mixer outlet 42 disposed on the mixer body. The first mixer inlet 41 is connected to the first outlet 24 of the second heat exchange channel of the first vaporizer, and the second mixer inlet 43 is connected to the outlet 54 of the second heat exchange channel of the second preheater. The mixer 4 is used for mixing materials.
[0058] The second preheater 5 includes: a second preheater body, an inlet 51 of the first heat exchange channel of the second preheater disposed on the second preheater body, an outlet 52 of the first heat exchange channel of the second preheater, an inlet 53 of the second heat exchange channel of the second preheater, and an outlet 54 of the second heat exchange channel of the second preheater. The inlet 51 of the first heat exchange channel of the second preheater is connected to the outlet 32 of the first heat exchange channel of the first preheater. The inlet 53 of the second heat exchange channel of the second preheater is used to introduce hydrogen gas, a raw material for polycrystalline silicon production. The second preheater 5 is used to preheat the hydrogen gas, a raw material for polycrystalline silicon production.
[0059] The second vaporizer 6 includes: a second vaporizer body, an inlet 61 of a first heat exchange channel of the second vaporizer disposed on the second vaporizer body, an outlet 62 of the first heat exchange channel of the second vaporizer, an inlet 63 of a second heat exchange channel of the second vaporizer, and an outlet 64 of the second heat exchange channel of the second vaporizer. The inlet 63 of the second heat exchange channel of the second vaporizer is connected to the second outlet 25 of the second heat exchange channel of the first vaporizer. The outlet 64 of the second heat exchange channel of the second vaporizer is used to discharge vaporized trichlorosilane. The inlet 61 of the first heat exchange channel of the second vaporizer is used to introduce a heat source to vaporize the trichlorosilane in the second heat exchange channel of the second vaporizer 6. The outlet 62 of the first heat exchange channel of the second vaporizer is used to discharge the heat source. The second vaporizer 6 is used to vaporize the trichlorosilane that was not vaporized in the first vaporizer 2.
[0060] Based on process calculations, two vaporizers can be used. The existing process uses steam to heat and vaporize trichlorosilane, with the steam source being 0.4 MPaG steam obtained from water flash evaporation in the reduction furnace drum at a temperature of 170℃. This proposed solution uses reduction tail gas at 170–176℃ to heat and vaporize trichlorosilane, effectively reducing steam consumption in the second vaporizer 6, achieving more complete heat recovery from the reduction tail gas, and not affecting the heat utilization efficiency of the first preheater 3 and the second preheater 5, thus achieving energy savings.
[0061] The first vaporizer 2 has two channels and five ports. The shell side of the first vaporizer 2 is the second heat exchange channel of the first vaporizer. The second heat exchange channel of the first vaporizer includes the inlet (trichlorosilane inlet) 23, the first outlet 24 and the second outlet 25 of the first vaporizer. The first heat exchange channel of the first vaporizer contains reducing tail gas at 170-176°C, which is used for heating and vaporizing the trichlorosilane in the second heat exchange channel of the first vaporizer.
[0062] The first heat exchange channel of the first preheater is the tube side of the first preheater, which is connected to the reducing tail gas outlet of the tube side of the first vaporizer and serves as a hot flow channel. The second heat exchange channel of the first preheater is the shell side of the first preheater and is used to introduce trichlorosilane pigment that needs to be heated.
[0063] The first inlet 41 of the mixer is fed with vaporized trichlorosilane. The mixer 4 mixes the preheated hydrogen with the vaporized trichlorosilane. The material ratio in the process of hydrogen reducing trichlorosilane can be precisely adjusted by regulating valves and flow meters.
[0064] The first heat exchange channel of the second preheater receives recovered hydrogen gas from the compressor of the exhaust gas recovery device. After compression, the gas has a temperature of 150-153°C and has heat recovery value.
[0065] The heat source for the second vaporizer 6 is S4 (i.e., 4 kg of steam).
[0066] Optionally, the outlet 64 of the second heat exchange channel of the second vaporizer is also connected to the inlet of the mixer 4.
[0067] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0068] A gas-solid separation device, the inlet of which is connected to the outlet 32 of the first heat exchange channel of the first preheater; the gas-solid separation device is used to perform gas-solid separation.
[0069] The exhaust gas low-pressure condensing device 7 has its inlet connected to the gas outlet of the gas-solid separation device; the exhaust gas low-pressure condensing device 7 is used to condense trichlorosilane and separate out the recovered hydrogen.
[0070] The compressor 9 has its inlet connected to the outlet of the exhaust gas low-pressure condensation device 7, and its outlet connected to the inlet 51 of the first heat exchange channel of the second preheater. The compressor 9 is used to compress the recovered hydrogen to raise its temperature.
[0071] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0072] The first buffer tank 8 is located between the exhaust gas low-pressure condensing device 7 and the compressor 9, and is connected to both the exhaust gas low-pressure condensing device 7 and the compressor 9. The first buffer tank 8 is used to buffer the raw material hydrogen gas.
[0073] Optionally, the polysilicon reduction tail gas heat energy recovery and utilization system further includes:
[0074] The second buffer tank 10 is located between the compressor 9 and the second preheater 5, and is connected to both the compressor 9 and the second preheater 5. The second buffer tank 10 is used to buffer the raw material hydrogen.
[0075] Optionally, the gas-solid separation device includes:
[0076] Cyclone separator 11, the inlet of which is connected to the outlet 32 of the first heat exchange channel of the first preheater;
[0077] Filter 12 is connected to the gas outlet of cyclone separator 11. Filter 12 is used to filter out silicon powder. The gas outlet of filter 12 is connected to the inlet of exhaust gas low-pressure condenser 7.
[0078] Optionally, such as Figure 2As shown, the exhaust gas low-pressure condensation device includes: a primary air cooler 71, a primary circulating water cooler 72, a primary exhaust gas integrated heat exchanger 73, a secondary exhaust gas integrated heat exchanger 74, a primary seven-degree water heat exchanger 75, a chlorosilane condensate tank 76, an exhaust gas cryocooler 77, and a chlorosilane gas-liquid separator 78.
[0079] The primary air cooler 71 is connected to the filter 12, and the secondary exhaust gas heat exchanger 74 is connected to the first buffer tank 8. The secondary exhaust gas heat exchanger 74 is used to discharge hydrogen gas, which then enters the compressor pre-buffer tank.
[0080] The primary circulating water cooler 72 is connected to the primary air cooler 71; the primary exhaust gas integrated heat exchanger 73 is connected to the primary circulating water cooler 72; the primary seven-degree water heat exchanger 75 is connected to the primary exhaust gas integrated heat exchanger 73; the secondary exhaust gas integrated heat exchanger 74 is connected to the primary seven-degree water heat exchanger 75; the exhaust gas cryocooler 77 is connected to the secondary exhaust gas integrated heat exchanger 74; the chlorosilane gas-liquid separator 78 is connected to the secondary exhaust gas integrated heat exchanger 74; and the chlorosilane gas-liquid separator 78 is connected to the exhaust gas cryocooler 77.
[0081] The primary tail gas integrated heat exchanger 73 is used to cool the reducing tail gas by absorbing the low-temperature chlorosilane condensate and the chlorosilane-rich liquid containing hydrogen chloride in the bottom of the tail gas recovery absorption tower. The chlorosilane enters the hydrogen chloride desorption tower of the tail gas recovery device for hydrogen chloride desorption.
[0082] The primary circulating water cooler 72, the primary exhaust gas integrated heat exchanger 73, the secondary exhaust gas integrated heat exchanger 74, the primary seven-degree water heat exchanger 75, the exhaust gas deep cooler 77, and the chlorosilane gas-liquid separator 78 are all connected to the chlorosilane condensate tank 76, which is used to collect chlorosilane condensate.
[0083] The exhaust gas low-pressure condensation device also includes a chlorosilane condensate transfer pump 79, which is connected to a chlorosilane condensate tank 76.
[0084] The chlorosilane condensate transfer pump 79 is also connected to the primary tail gas integrated heat exchanger 73, and the chlorosilane condensate collected by the chlorosilane condensate tank 76 is input into the primary tail gas integrated heat exchanger 73.
[0085] Optionally, the exhaust gas cooler 1, the first preheater 3, and the second preheater 5 are all fixed tube sheet heat exchangers (BEM).
[0086] Optionally, the first vaporizer 2 and the second vaporizer 6 are one of the following: jacketed tube vaporizer, U-tube vaporizer, and shell-and-tube vaporizer.
[0087] Specifically, in this embodiment, both the first vaporizer 2 and the second vaporizer 6 are jacketed vaporizers.
[0088] Optionally, mixer 4 includes either a static mixer or a pipeline gas mixer.
[0089] Specifically, in this embodiment, mixer 4 is a static mixer.
[0090] Optionally, the compressor 9 includes either a reciprocating compressor 9 or a centrifugal compressor 9.
[0091] Specifically, the compressor 9 in this embodiment is a reciprocating compressor 9.
[0092] Specifically, this embodiment provides a method for recovering and utilizing the heat energy from polycrystalline silicon reduction tail gas using the polycrystalline silicon reduction tail gas heat recovery and utilization system of this embodiment, including the following steps:
[0093] 1) The reduction tail gas discharged from the tail gas outlet of the polysilicon reduction furnace is cooled by the jacketed heat exchanger, and the temperature drops from 450-600℃ to 245℃. After passing through the tail gas cooler 1 to exchange heat with the reaction mixture, the temperature of the reduction tail gas is further reduced to 176.5℃. The reaction mixture is heated from 101℃ to 175℃ and enters the polysilicon reduction furnace for reduction reaction to produce polysilicon.
[0094] 2) The reduction tail gas, cooled by the tail gas cooler 1, is used in the first vaporizer 2 to heat the preheated TCS, causing some of the TCS to vaporize directly. The remaining unvaporized TCS is sent from the bottom of the first vaporizer 2 to the second vaporizer 6 for heating with steam to vaporize. The vaporized TCS is then sent to the mixer 4, mixed with heated H2, and then sent to the tail gas cooler 1 for further heating. The reduction tail gas is further cooled to 120℃~125℃. The reaction pressure in the first vaporizer 2 is controlled at 0.85~1.0MPaG, and the pressure in the second vaporizer 6 is specifically controlled at 0.8PaG.
[0095] 3) The reduction tail gas from the first vaporizer 2 is preheated by the first preheater 3 to the raw material TCS at a temperature of 40-60℃. After the raw material TCS is heated to 90-95.5℃, the reduction tail gas is cooled again to 90-100℃ and then enters the gas-solid separation unit to separate and obtain recovered hydrogen. After being cooled by the tail gas low-pressure condensing unit 7 (first-stage air cooler 71, first-stage circulating water cooler 72, first-stage tail gas integrated heat exchanger 73, second-stage tail gas integrated heat exchanger 74, first-stage seven-degree water heat exchanger 75, chlorosilane condensate tank 76, tail gas deep cooler 77, chlorosilane gas-liquid separator 78, chlorosilane condensate transfer pump 79), the temperature of the recovered hydrogen drops to 7℃ and then enters the compressor 9 for compression, raising the temperature to 150℃. The low-pressure condensing process of the tail gas low-pressure condensing unit 7 is as follows: the recovered hydrogen is first cooled by the first-stage air cooler 71 to a temperature of 55℃ and then enters the first-stage circulating water cooler 72. The process begins by using circulating water to recover hydrogen, which is then cooled to 44°C for gas-liquid separation. The condensed chlorosilane enters the chlorosilane condensate tank 76, while the non-condensable gas enters the first-stage tail gas integrated heat exchanger 73 to exchange heat with the absorber bottom liquid and the chlorosilane in the chlorosilane condensate tank 76. This reduces the recovered hydrogen temperature to 28-30°C. After further gas-liquid separation, the liquid chlorosilane enters the chlorosilane condensate tank 76, while the non-condensable gas is cooled again with 7°C water, further reducing the recovered hydrogen temperature to 12°C. The first-stage tail gas integrated heat exchanger 73 then further reduces the recovered hydrogen temperature to 3°C, and gas-liquid separation is performed again. The condensed liquid phase enters the chlorosilane condensate tank 76, while the non-condensable gas is cooled again to -20°C with -25°C Freon for gas-liquid separation. The condensed liquid phase then enters the chlorosilane condensate tank 76. The non-condensable gas then exchanges heat with the recovered hydrogen in the second-stage tail gas integrated heat exchanger 74. Finally, the recovered hydrogen is cooled to 7°C and then enters the compressor for compression.
[0096] 4) After the compressor 9, the recovered hydrogen is used to exchange heat with the raw material hydrogen, so that the temperature of the raw material hydrogen is heated from 10-15℃ to 90℃. It is then sent to the mixer 4, mixed with the vaporized TCS, and then sent to the tail gas cooler 1 for heating before being sent to the reduction furnace. It is cooled to 56.2℃.
[0097] The material consumption in the existing technology process is compared with the process consumption of the method for recovering and utilizing the polysilicon reduction tail gas heat energy using the polysilicon reduction tail gas heat energy recovery and utilization system in this embodiment. The comparison is shown in Table 1 below:
[0098] Before process optimization 26 208.89 After process optimization 18.88 165.03 Savings 7.12 43.86
[0099] Table 1
[0100] The polycrystalline silicon reduction tail gas heat energy recovery and utilization system in this embodiment uses the reduction tail gas and compressed hydrogen to heat the polycrystalline silicon reduction reaction materials, which more fully recovers the heat energy of the reduction tail gas in the recovery process, effectively reduces the steam consumption in the vaporization process of the reaction materials, and at the same time reduces the consumption of circulating water and cold medium required for cooling the tail gas at the back end, thus achieving the purpose of energy saving.
[0101] Compared with existing technologies, this invention adds a first-stage vaporizer while preheating the TCS feedstock using reduction tail gas. This allows for more efficient recovery and utilization of the heat from the reduction tail gas, reducing the temperature of the reduction tail gas from 100-170℃ in existing technologies to 90℃. The heat recovery is more thorough, and with the same TCS feed rate, the steam consumption of the TCS steam vaporizer is reduced by 25%-27%. Based on a TCS feed rate of 120t / h, this saves 7.12t / h of steam, and the circulating water cooler after compressor 9 saves 43.86m³. 3 / h.
[0102] Example 3
[0103] like Figure 1 , 2 As shown, this embodiment provides a polysilicon reduction tail gas heat energy recovery and utilization system, which differs from the polysilicon reduction tail gas heat energy recovery and utilization system in Embodiment 2 in the following ways:
[0104] Specifically, in this embodiment, both the first vaporizer 2 and the second vaporizer 6 are fixed tube sheet heat exchangers. It is recommended that the first vaporizer be of the BKM type and the second vaporizer of the BKU type.
[0105] Specifically, in this embodiment, the mixer 4 is a pipeline gas mixer.
[0106] This embodiment provides a method for recovering and utilizing the heat energy from polycrystalline silicon reduction tail gas using the polycrystalline silicon reduction tail gas heat recovery and utilization system of this embodiment, including the following steps:
[0107] Refined TCS from the distillation workshop is pumped to the first preheater 3, where it is heated to 95°C. It then passes through the first vaporizer 2 for further vaporization, raising the TCS temperature to 115°C. The liquid TCS is then sent to the second vaporizer 6, where it is heated with 0.4 MPaG steam until completely vaporized. The pressure in the first vaporizer 2 is controlled at 0.85 MPaG, and the pressure in the second vaporizer 6 is controlled at 0.8 MPaG. The vaporized TCS, along with the gaseous phase from the first vaporizer 2, is sent to the mixer 4 to mix with the heated feed hydrogen. The feed hydrogen is heated in the second preheater 5 using recovered hydrogen from compressor 9, raising its temperature from 10°C to 90°C before being sent to the mixer 4 to mix with the vaporized TCS. The temperature of the mixed material is 101°C. The mixture is then heated to 175°C by the reduction tail gas before being sent to the polycrystalline silicon reduction furnace for reaction to produce polycrystalline silicon.
[0108] The reduction tail gas originates from a bell-type polycrystalline silicon reduction furnace. It first passes through a jacketed heat exchanger, where its temperature drops to 210–245°C. Then, it passes through a tail gas cooler 1 to heat a mixture of TCS and raw material hydrogen, reducing its temperature to 176°C. Next, it goes to the first vaporizer 2 to heat and vaporize the TCS, further reducing its temperature to 120°C. This 120°C reduction tail gas is then used to preheat the TCS raw material at 40–60°C. After the temperature of the reduction tail gas drops to 90°C, it passes through a cyclone separator 11 and a filter 12 to remove any silicon it contains. The powder is then reduced and the tail gas is sent to the tail gas low-pressure condenser 7 for separation of chlorosilanes and hydrogen. In the tail gas low-pressure condenser 7, most of the dichlorosilane, trichlorosilane and silicon tetrachloride contained in the tail gas are condensed. Hydrogen, hydrogen chloride and a small amount of chlorosilane are cooled to 3-10°C and fed into compressor 9. The recovered hydrogen is compressed and the temperature is raised to 150°C. The high temperature of the recovered hydrogen after compression is used to preheat the raw material hydrogen. After the temperature of the recovered hydrogen drops to 56°C, it is cooled, absorbed by hydrogen chloride and adsorbed by impurities before being used as raw material hydrogen for the production of polycrystalline silicon.
[0109] The polycrystalline silicon reduction tail gas heat energy recovery and utilization system in this embodiment uses the reduction tail gas and compressed hydrogen to heat the polycrystalline silicon reduction reaction materials, which more fully recovers the heat energy of the reduction tail gas in the recovery process, effectively reduces the steam consumption in the vaporization process of the reaction materials, and at the same time reduces the consumption of circulating water and cold medium required for cooling the tail gas at the back end, thus achieving the purpose of energy saving.
[0110] Example 4
[0111] This embodiment provides a polysilicon reduction tail gas heat recovery and utilization system, which differs from the polysilicon reduction tail gas heat recovery and utilization system in Embodiment 2 in the following ways:
[0112] Specifically, in this embodiment, the exhaust gas cooler, the first preheater, and the second preheater are all shell-and-tube heat exchangers.
[0113] Specifically, in this embodiment, the first vaporizer is a U-tube vaporizer and the second vaporizer is a shell-and-tube vaporizer.
[0114] Specifically, the compressor in this embodiment is a centrifugal compressor.
[0115] The polycrystalline silicon reduction tail gas heat energy recovery and utilization system in this embodiment uses the reduction tail gas and compressed hydrogen to heat the polycrystalline silicon reduction reaction materials, which more fully recovers the heat energy of the reduction tail gas in the recovery process, effectively reduces the steam consumption in the vaporization process of the reaction materials, and at the same time reduces the consumption of circulating water and cold medium required for cooling the tail gas at the back end, thus achieving the purpose of energy saving.
[0116] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this utility model, and the utility model is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of this utility model, and these modifications and improvements are also considered to be within the protection scope of this utility model.
Claims
1. A polysilicon reduction tail gas heat energy recycling system, characterized in that, include: The exhaust gas cooler includes: an exhaust gas cooler body, an inlet of a first heat exchange channel of the exhaust gas cooler disposed on the exhaust gas cooler body, an outlet of the first heat exchange channel of the exhaust gas cooler, an inlet of a second heat exchange channel of the exhaust gas cooler, and an outlet of the second heat exchange channel of the exhaust gas cooler. The inlet of the first heat exchange channel of the exhaust gas cooler is used to introduce polysilicon reduction exhaust gas. The inlet of the second heat exchange channel of the exhaust gas cooler is connected to the outlet of a mixer. The trichlorosilane discharged from the outlet of the second heat exchange channel of the exhaust gas cooler and the raw material hydrogen are used to react in the polysilicon reduction furnace. The exhaust gas cooler is used to heat the reaction raw materials in the polysilicon reduction furnace by the heat of the polysilicon reduction exhaust gas, and to cool down the reduction exhaust gas. The first vaporizer includes: a first vaporizer body, an inlet of a first heat exchange channel of the first vaporizer disposed on the first vaporizer body, an outlet of the first heat exchange channel of the first vaporizer, an inlet of a second heat exchange channel of the first vaporizer, a first outlet of the second heat exchange channel of the first vaporizer, and a second outlet of the second heat exchange channel of the first vaporizer. The first outlet of the second heat exchange channel of the first vaporizer is used to discharge vaporized trichlorosilane, and the second outlet of the second heat exchange channel of the first vaporizer is used to discharge unvaporized trichlorosilane. The inlet of the first heat exchange channel of the first vaporizer is connected to the outlet of the first heat exchange channel of the exhaust gas cooler, and the inlet of the second heat exchange channel of the first vaporizer is connected to the outlet of the second heat exchange channel of the first preheater. The first vaporizer is used to vaporize trichlorosilane. The first preheater includes: a first preheater body, an inlet of a first heat exchange channel of the first preheater disposed on the first preheater body, an outlet of the first heat exchange channel of the first preheater, an inlet of a second heat exchange channel of the first preheater, and an outlet of the second heat exchange channel of the first preheater. The inlet of the first heat exchange channel of the first preheater is connected to the outlet of the first heat exchange channel of the first vaporizer. The inlet of the second heat exchange channel of the first preheater is used to introduce trichlorosilane, a raw material for polycrystalline silicon production. The first preheater is used to preheat the trichlorosilane. The mixer includes: a mixer body, a first mixer inlet, a second mixer inlet, and a mixer outlet disposed on the mixer body. The first mixer inlet is connected to the first outlet of the second heat exchange channel of the first vaporizer, and the second mixer inlet is also connected to the outlet of the second heat exchange channel of the second preheater. The second preheater includes: a second preheater body, an inlet of a first heat exchange channel of the second preheater disposed on the second preheater body, an outlet of the first heat exchange channel of the second preheater, an inlet of a second heat exchange channel of the second preheater, and an outlet of the second heat exchange channel of the second preheater. The inlet of the first heat exchange channel of the second preheater is connected to the outlet of the first heat exchange channel of the first preheater. The inlet of the second heat exchange channel of the second preheater is used to introduce hydrogen gas, a raw material for polycrystalline silicon production. The second preheater is used to preheat the hydrogen gas, a raw material for polycrystalline silicon production. The second vaporizer includes: a second vaporizer body, an inlet of a first heat exchange channel of the second vaporizer disposed on the second vaporizer body, an outlet of the first heat exchange channel of the second vaporizer, an inlet of a second heat exchange channel of the second vaporizer, and an outlet of the second heat exchange channel of the second vaporizer. The inlet of the second heat exchange channel of the second vaporizer is connected to the second outlet of the second heat exchange channel of the first vaporizer. The outlet of the second heat exchange channel of the second vaporizer is used to discharge vaporized trichlorosilane. The inlet of the first heat exchange channel of the second vaporizer is used to introduce a heat source to vaporize the trichlorosilane in the second heat exchange channel of the second vaporizer. The outlet of the first heat exchange channel of the second vaporizer is used to discharge the heat source. The second vaporizer is used to vaporize the trichlorosilane that was not vaporized in the first vaporizer.
2. The polysilicon reduction tail gas heat energy recycling system according to claim 1, characterized in that, The outlet of the second heat exchange channel of the second vaporizer is also connected to the inlet of the mixer.
3. The polysilicon reduction tail gas heat energy recycling system according to claim 1, characterized in that, Also includes: A gas-solid separation device, the inlet of which is connected to the outlet of the first heat exchange channel of the first preheater, is used to perform gas-solid separation. The exhaust gas low-pressure condenser is connected to the gas outlet of the gas-solid separation device. The exhaust gas low-pressure condenser is used to condense trichlorosilane and separate out the recovered hydrogen. The compressor has its inlet connected to the outlet of the low-pressure condenser for exhaust gas, and its outlet connected to the inlet of the first heat exchange channel of the second preheater. The compressor is used to compress the recovered hydrogen to raise its temperature.
4. The polysilicon reduction tail gas heat energy recovery system according to claim 3, characterized in that, Also includes: The first buffer tank is located between the tail gas low-pressure condensation device and the compressor. The first buffer tank is connected to the tail gas low-pressure condensation device and the compressor respectively. The first buffer tank is used to buffer the raw material hydrogen.
5. The polysilicon reduction tail gas heat energy recovery system according to claim 3, wherein, Also includes: The second buffer tank is located between the compressor and the second preheater. The second buffer tank is connected to both the compressor and the second preheater and is used to buffer the raw material hydrogen.
6. The polysilicon reduction tail gas heat energy recovery system according to claim 3, wherein, The gas-solid separation device includes: The cyclone separator has its inlet connected to the outlet of the first heat exchange channel of the first preheater. The filter is connected to the gas outlet of the cyclone separator. The filter is used to remove amorphous silica powder from the reduction tail gas. The gas outlet of the filter is connected to the inlet of the tail gas low-pressure condenser.
7. The polysilicon reduction tail gas heat energy recovery system according to claim 3, wherein, The exhaust gas low-pressure condensation unit includes: a primary air cooler, a primary circulating water cooler, a primary exhaust gas integrated heat exchanger, a secondary exhaust gas integrated heat exchanger, a primary seven-degree water heat exchanger, a chlorosilane condensate tank, an exhaust gas cryocooler, and a chlorosilane gas-liquid separator. The primary air cooler is connected to the filter, and the secondary exhaust gas heat exchanger is connected to the primary buffer tank. The secondary exhaust gas heat exchanger is used to discharge hydrogen gas. The primary circulating water cooler is connected to the primary air cooler; the primary exhaust gas integrated heat exchanger is connected to the primary circulating water cooler; the primary seven-degree water heat exchanger is connected to the primary exhaust gas integrated heat exchanger; the secondary exhaust gas integrated heat exchanger is connected to the primary seven-degree water heat exchanger; the exhaust gas cryostat is connected to the secondary exhaust gas integrated heat exchanger; the chlorosilane gas-liquid separator is connected to the secondary exhaust gas integrated heat exchanger; and the chlorosilane gas-liquid separator is connected to the exhaust gas cryostat. The primary tail gas integrated heat exchanger is used to cool the reducing tail gas from the low-temperature chlorosilane condensate and the bottom of the tail gas recovery absorption tower, which absorbs the chlorosilane-rich liquid containing hydrogen chloride. The primary circulating water cooler, primary exhaust gas integrated heat exchanger, secondary exhaust gas integrated heat exchanger, primary seven-degree water heat exchanger, exhaust gas cryocooler, and chlorosilane gas-liquid separator are all connected to the chlorosilane condensate tank, which is used to collect chlorosilane condensate.
8. The polysilicon reduction tail gas heat energy recovery system according to claim 3, characterized in that, The compressor includes: Any one of reciprocating compressors and centrifugal compressors.
9. The polysilicon reduction off-gas heat energy recovery system of claim 1, wherein, The exhaust gas cooler, the first preheater, and the second preheater are all fixed tube sheet heat exchangers.
10. The polysilicon reduction tail gas heat energy recovery system of claim 1, wherein, The first vaporizer and the second vaporizer are one of the following: jacketed tube vaporizer, U-tube vaporizer, and shell-and-tube vaporizer.
11. The polysilicon reduction tail gas heat energy recovery system according to claim 1, wherein, The mixer includes either a static mixer or a pipeline gas mixer.