Waste heat comprehensive utilization system in polycrystalline silicon production
By introducing a -15℃ liquid ammonia refrigerant heat exchanger in the polysilicon production system, the problems of low waste heat recovery rate and large deep refrigerant usage are solved, and efficient waste heat utilization and cost reduction are achieved.
Patent Information
- Application Number
- CN202422195635.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-09
- Publication Date
- 2025-09-02
- Estimated Expiration
- 2034-09-09
AI Technical Summary
The waste heat recovery rate in polysilicon production is low, and the high-grade deep refrigerant consumption is large, resulting in high load on the ice machine and high production costs.
The -15℃ liquid ammonia refrigerant heat exchanger is introduced into the reducing exhaust gas recovery system and the cold hydrogenation condensation system. The liquid ammonia generator and the circulating water cooler are connected through pipelines. The -15℃ liquid ammonia refrigerant is prepared using surplus steam, and the intermediate heat exchanger is added to improve the heat recovery rate and reduce the use of deep-cooled refrigerant.
Significantly improve heat utilization, reduce power consumption and operating costs, reduce deep refrigerant usage, reduce ice machine load, and improve system energy utilization efficiency.
Smart Images
Figure CN223295054U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of waste heat recovery and utilization equipment, and in particular relates to a comprehensive waste heat utilization system in polysilicon production. Background Art
[0002] In the production of polysilicon, with the continuous increase in the output of polysilicon products in the reduction section and the decreasing steam consumption, the company's Phase I and Phase II projects currently have a surplus of 70t / h of steam. With the completion and commissioning of the Phase III project, the surplus steam will increase to about 132t / h.
[0003] To maintain system balance, existing technology requires cooling large amounts of steam through the primary reduction furnace, the chassis plate-and-frame heat exchanger, and the secondary reduction air cooler. This excess steam treatment not only wastes significant thermal energy but also consumes significant amounts of circulating water and electricity. As the plant expands, the overall system load increases. Furthermore, due to the limited capacity of the plate-and-frame heat exchanger and air cooler, the reduction section frequently experiences overpressure in the chassis water tank, which cannot be regulated. This leads to elevated chassis water temperatures and an increasing incidence of overheated return water vaporization, posing significant challenges to the safe and stable operation of the production system.
[0004] In the chemical production process, energy recovery and utilization is a crucial component for improving quality and reducing costs. In polysilicon production, heat recovery is particularly common in the recovery and hydrogenation stages, and is a crucial process for energy conservation and cost reduction. For example, in the traditional recovery process, hydrogen is purified using five stages of heat exchange before the compressor and six stages after the compressor, deep cooling the hydrogen to below -60°C. While existing technologies include heat recovery, the efficiency of recovering the cooling capacity of high-grade refrigerants is low. For example, there is no heat recovery between the fourth and fifth stages (which cool the material from -8°C to -35°C). Under this process, the load on the chiller corresponding to the deep refrigerant is very high. Because the heat exchanger in the previous stage needs to cool the material to a lower temperature, the load is transferred entirely to the high-grade refrigerant, placing relatively high demands on the chiller.
[0005] For example, in the condensation process of the cold hydrogenation section, the traditional process uses 33°C circulating water to cool the material, and then enters the -40°C deep cooling system after only one stage of heat exchange. The temperature difference between the circulating water and the -40°C refrigerant is about 70°C. Even if a first-stage intermediate heat exchange is used for recovery, less than 20% of the heat is recovered.
[0006] Therefore, it is still a major challenge for the industry to rationally, efficiently and continuously utilize waste heat in production, improve the heat recovery rate and achieve the goal of energy saving and consumption reduction. Utility Model Content
[0007] The utility model aims to solve the problems in the prior art of polysilicon production reduction tail gas recovery systems, low heat recovery rate in reduction tail gas recovery systems, and large consumption of high-grade deep refrigerant, which results in a large load on the electric ice machine corresponding to the high-grade deep refrigerant and high production costs.
[0008] In order to achieve the above-mentioned purpose of the invention, the technical solution of the present utility model is as follows:
[0009] The waste heat comprehensive utilization system in polysilicon production adds a -15°C liquid ammonia refrigerant heat exchanger to the reduction tail gas recovery system, and / or the -15°C liquid ammonia refrigerant heat exchanger is installed between the fourth-stage condenser and the fifth-stage condenser of the reduction tail gas recovery system;
[0010] And / or a -15°C liquid ammonia refrigerant heat exchanger is added to the cold hydrogenation condensation system, and / or the -15°C liquid ammonia refrigerant heat exchanger is installed between the circulating water cooler and the -40°C Freon condenser of the cold hydrogenation condensation system.
[0011] Furthermore, the fourth-stage condenser in the reduction tail gas recovery system is a condenser through which a -10°C Freon medium is passed, and the fifth-stage condenser is a condenser through which a -40°C Freon medium is passed.
[0012] Furthermore, the circulating water cooler of the cold hydrogenation condensation system is 33°C cooling water.
[0013] Furthermore, the medium inlet of the liquid ammonia refrigerant heat exchanger is connected to a circulating water cooler through pipeline I, and the circulating water cooler is connected to a liquid ammonia generator containing ammonia and N,N-diethylaniline solution through pipeline II. A jacket or heating pipe is provided on the outside of the liquid ammonia generator, or a heating pipe is provided on the inside of the liquid ammonia generator, and the jacket or heating pipe is connected to a steam pipeline.
[0014] The medium outlet of the liquid ammonia refrigerant heat exchanger is connected to an absorption device containing N,N-diethylaniline solution through pipeline III, and the outlet of the absorption device is connected to a booster pump and then to a liquid ammonia generator through pipeline IV.
[0015] Furthermore, the heating tube is a coil or a tube array.
[0016] Furthermore, a storage tank is provided between the circulating water cooler and the liquid ammonia refrigerant heat exchanger.
[0017] Furthermore, the outside of the storage tank is coated with a heat insulation layer, and the outside of the heat insulation layer is provided with a heat preservation sleeve.
[0018] Furthermore, the liquid ammonia generator is provided with a liquid ammonia supply pipeline and a solvent supply pipeline.
[0019] Beneficial effects of the utility model:
[0020] First, this utility model proposes a comprehensive waste heat utilization system for polysilicon production. First, it introduces a heat exchanger using a liquid ammonia refrigerant at -15°C, increasing heat conversion efficiency from approximately 20% to approximately 50%, significantly improving heat utilization. This system improves existing polysilicon production reduction tail gas recovery systems, which suffer from low heat recovery rates and high usage of high-grade deep refrigerant, resulting in heavy loads on the corresponding electric refrigeration units, thereby reducing production costs.
[0021] 2. In the present invention, a new device for preparing -15°C liquid ammonia refrigerant is proposed. The surplus steam generated by the polysilicon production system can be introduced into the steam pipeline, and the surplus steam can be used as power to prepare -15°C liquid ammonia refrigerant for use in the system, which significantly reduces the power consumption cost, that is, reduces the operating cost of the heat exchange process.
[0022] 3. In this utility model, the fourth-stage condenser in the reduction tail gas recovery system is fed with -10°C Freon, and the fifth-stage condenser is fed with -40°C Freon. In this solution, an intermediate heat exchanger (liquid ammonia refrigerant heat exchanger) using -15°C liquid ammonia refrigerant is installed between the fourth and fifth-stage condensers, recovering approximately 50% of the heat. While maintaining the same final temperature drop, this reduces the use of -40°C cryogenic refrigerant by approximately 30%, lowering the load on the refrigeration unit corresponding to the -40°C refrigerant by approximately 80%, and reducing equipment operating costs.
[0023] 4. In the present invention, an intermediate heat exchanger (liquid ammonia refrigerant heat exchanger) for -15°C liquid ammonia refrigerant is added between the circulating water cooler and the -40°C Freon condenser in the cold hydrogenation condensation system, which can reduce the load of the -40°C cryogenic refrigerant by about 80% and reduce the power consumption of the -40°C electric ice machine by 80%.
[0024] 5. In the present invention, the liquid ammonia generator can be heated by a jacket or a heating tube according to needs. In addition, the heating tube can be built-in or external to the liquid ammonia generator. The heating tube can be a coil or a tube. When a jacket is used to pass steam, an external jacket is generally used.
[0025] 6. In the present invention, a storage tank is provided between the circulating water cooler and the liquid ammonia refrigerant heat exchanger, which can be used to temporarily store -15°C liquid ammonia refrigerant to ensure stable delivery of refrigerant to the rear end.
[0026] 7. In the present invention, the outside of the storage tank is coated with a heat-insulating layer, and a heat-insulating sleeve is provided outside the heat-insulating layer to prevent the loss of cold.
[0027] 8. In the present invention, a liquid ammonia supply pipeline and a solvent supply pipeline are provided on the liquid ammonia generator, and liquid ammonia and solvent are supplied to the liquid ammonia generator through the provided liquid ammonia supply pipeline and solvent supply pipeline. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a structural diagram of the waste heat comprehensive utilization system.
[0029] Figure 2 It is a structural diagram of a liquid ammonia generator (with built-in shell-and-tube heat exchange tubes).
[0030] Figure 3 It is a structural schematic diagram of another embodiment of a liquid ammonia generator.
[0031] Figure 4 This is a partial enlarged view of the tank pipe wall.
[0032] Figure 5 It is a structural diagram of another implementation method of the waste heat comprehensive utilization system.
[0033] Figure 6 It is a structural diagram of another implementation method of the waste heat comprehensive utilization system.
[0034] Among them, 1. Liquid ammonia refrigerant heat exchanger; 2. Fourth-stage condenser; 3. Fifth-stage condenser; 4. Circulating water cooler; 5. -40℃ Freon condenser; 6. Pipeline I; 7. Pipeline II; 8. Liquid ammonia generator; 9. Jacket; 10. Heating pipe; 11. Steam pipeline; 12. Pipeline III; 13. Absorption device; 14. Booster pump; 15. Pipeline IV; 16. Storage tank; 17. Insulation layer; 18. Insulation jacket; 19. Liquid ammonia supply pipeline; 20. Solvent replenishment pipeline; 21. Reduction tail gas transmission pipeline; 22. Cold hydrogenation condensed gas transmission pipeline; 1.1. Medium inlet; 1.2. Medium outlet; 13.1. Outlet. DETAILED DESCRIPTION
[0035] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.
[0036] Example 1
[0037] To facilitate public understanding of the present solution, this embodiment takes the addition of a -15°C liquid ammonia refrigerant heat exchanger in the reduction tail gas recovery system as an example, and further illustrates the present solution in conjunction with the accompanying drawings.
[0038] Waste heat comprehensive utilization system in polysilicon production, reference Figure 1A -15°C liquid ammonia refrigerant heat exchanger 1 is installed between the fourth-stage condenser 2 and the fifth-stage condenser 3 of the reduction tail gas delivery pipeline 21 in the reduction tail gas recovery system. The fourth-stage condenser 2 in the reduction tail gas recovery system is a condenser that flows with a -10°C Freon medium, while the fifth-stage condenser 3 is a condenser that flows with a -40°C Freon medium. At this point, after the material passes through the fourth-stage condenser 2, the liquid ammonia refrigerant heat exchanger 1, and the fifth-stage condenser 3, it is necessary to cool the material before the compressor from -8°C to -35°C.
[0039] Preferably, the medium inlet 1.1 of the liquid ammonia refrigerant heat exchanger 1 is connected to the circulating water cooler 4 through pipeline I6, and the circulating water cooler 4 is connected to the liquid ammonia generator 8 containing ammonia and N,N-diethylaniline solution through pipeline II7. A jacket 9 is provided on the outside of the liquid ammonia generator 8, and the jacket 9 is connected to the steam pipeline 11.
[0040] In this embodiment, the medium outlet 13.1.2 of the liquid ammonia refrigerant heat exchanger 1 is connected to the absorption device 13 containing N,N-diethylaniline solution through pipeline III 12, and the outlet 13.1 of the absorption device 13 is connected to the booster pump 14 and then connected to the liquid ammonia generator 8 through pipeline IV 15.
[0041] Compared with the traditional technology (no liquid ammonia refrigerant heat exchanger 1 is provided between the fourth-stage condenser 2 and the fifth-stage condenser 3), the waste heat comprehensive utilization system in this embodiment can significantly reduce the -40°C cryogenic refrigerant load, reduce the power consumption of the -40°C ice machine, and significantly reduce the operating cost.
[0042] Example 2
[0043] The only difference between this embodiment and embodiment 1 is that a heating pipe 10 is provided on the outside of the liquid ammonia generator 8 , the heating pipe 10 is connected to the steam pipeline 11 , and the heating pipe 10 can be designed as a coil or a tube array according to demand, and the heating pipe 10 is in close contact with the outer wall of the liquid ammonia generator 8 .
[0044] Example 3
[0045] The only difference between this embodiment and embodiment 1 is that a heating pipe 10 is provided inside the liquid ammonia generator 8 , and the heating pipe 10 is connected to the steam pipeline 11 .
[0046] The heating tube 10 can be designed as a coil or a tube array according to the requirements. Figure 2 The diagram shows the structure of the built-in tube. Figure 3 The diagram shows the structure of the built-in coil.
[0047] Example 4
[0048] The only difference between this embodiment and embodiments 1-3 is that
[0049] refer to Figure 5A storage tank 16 is provided between the circulating water cooler 4 and the liquid ammonia refrigerant heat exchanger 1 .
[0050] Example 5
[0051] The only difference between this embodiment and embodiments 1-4 is that the exterior of the storage tank 16 is coated with a heat insulation layer 17 , and a heat preservation sleeve 18 is provided on the exterior of the heat insulation layer 17 .
[0052] Preferably, the liquid ammonia generator 8 is provided with a liquid ammonia supply pipeline 19 and a solvent supply pipeline 20.
[0053] Example 7
[0054] This embodiment takes the liquid ammonia refrigerant heat exchanger 1 with a temperature of -15°C added in the cold hydrogenation condensation system as an example, and further illustrates this solution with reference to the accompanying drawings.
[0055] refer to Figure 6 In the waste heat comprehensive utilization system for polysilicon production, a -15°C liquid ammonia refrigerant heat exchanger (1) is installed between the cold hydrogenation condensation system's circulating water cooler (4) and the -40°C Freon condenser (5). The cold hydrogenation condensation system's circulating water cooler (4) uses 33°C cooling water. After passing through the circulating water cooler (4), the liquid ammonia refrigerant heat exchanger (1), and the -40°C Freon condenser (5), the material before the compressor needs to be cooled from -100°C to -35°C.
[0056] Preferably, the medium inlet 1.1 of the liquid ammonia refrigerant heat exchanger 1 is connected to the circulating water cooler 4 through pipeline I6, and the circulating water cooler 4 is connected to the liquid ammonia generator 8 containing ammonia and N,N-diethylaniline solution through pipeline II7. A jacket 9 is provided on the outside of the liquid ammonia generator 8, and the jacket 9 is connected to the steam pipeline 11.
[0057] In this embodiment, the medium outlet 13.1.2 of the liquid ammonia refrigerant heat exchanger 1 is connected to the absorption device 13 containing N,N-diethylaniline solution through pipeline III 12, and the outlet 13.1 of the absorption device 13 is connected to the booster pump 14 and then connected to the liquid ammonia generator 8 through pipeline IV 15.
[0058] In this embodiment, the outside of the storage tank 16 is coated with a heat insulation layer 17, and the outside of the heat insulation layer 17 is provided with a heat preservation sleeve 18. Figure 4 The liquid ammonia generator 8 is provided with a liquid ammonia supply pipeline 19 and a solvent supply pipeline 20.
[0059] Compared with the traditional technology (no liquid ammonia refrigerant heat exchanger 1 is provided between the circulating water cooler 4 and the -40°C Freon condenser 5), the waste heat comprehensive utilization system in this embodiment can significantly reduce the -40°C cryogenic refrigerant load in a 50,000-ton polysilicon supporting system and reduce the power consumption of the -40°C ice machine by about 80%. It is estimated that the power consumption of the -40°C ice machine can be reduced by 19 million kW throughout the year, and the operating cost is expected to be reduced by 9 million yuan.
Claims
1. Comprehensive utilization system of waste heat in polysilicon production, characterized by: A -15°C liquid ammonia refrigerant heat exchanger (1) is added to the reduction tail gas recovery system, and / or the -15°C liquid ammonia refrigerant heat exchanger (1) is arranged between the fourth stage condenser (2) and the fifth stage condenser (3) of the reduction tail gas recovery system; and / or adding a -15°C liquid ammonia refrigerant heat exchanger (1) in the cold hydrogenation condensation system, and / or the -15°C liquid ammonia refrigerant heat exchanger (1) is provided between the circulating water cooler (4) and the -40°C Freon condenser (5) of the cold hydrogenation condensation system; The medium inlet (1.1) of the liquid ammonia refrigerant heat exchanger (1) is connected to the circulating water cooler (4) through the pipeline I (6), and the circulating water cooler (4) is connected to the liquid ammonia generator (8) containing ammonia and N,N-diethylaniline solution through the pipeline II (7). The outer side of the liquid ammonia generator (8) is provided with a jacket (9) or a heating pipe (10), or the inner side of the liquid ammonia generator (8) is provided with a heating pipe (10), and the jacket (9) or the heating pipe (10) is connected to the steam pipeline (11). The medium outlet (1.2) of the liquid ammonia refrigerant heat exchanger (1) is connected to an absorption device (13) containing N,N-diethylaniline solution through a pipeline III (12). The outlet (13.1) of the absorption device (13) is connected to a booster pump (14) and then to a liquid ammonia generator (8) through a pipeline IV (15).
2. The waste heat comprehensive utilization system in polysilicon production according to claim 1, characterized in that: The fourth-stage condenser (2) in the reduction tail gas recovery system is a condenser through which a -10°C Freon medium is passed, and the fifth-stage condenser (3) is a condenser through which a -40°C Freon medium is passed.
3. The waste heat comprehensive utilization system in polysilicon production according to claim 1, characterized in that: The circulating water cooler (4) of the cold hydrogenation condensation system is 33°C cooling water.
4. The waste heat comprehensive utilization system in polysilicon production according to claim 1, characterized in that: The heating tube (10) is a coil or a tube array.
5. The waste heat comprehensive utilization system in polysilicon production according to claim 1, characterized in that: A storage tank (16) is provided between the circulating water cooler (4) and the liquid ammonia refrigerant heat exchanger (1).
6. The waste heat comprehensive utilization system in polysilicon production according to claim 5, characterized in that: The outside of the storage tank (16) is coated with a heat insulation layer (17), and the outside of the heat insulation layer (17) is provided with a heat insulation sleeve (18).
7. The waste heat comprehensive utilization system in polysilicon production according to claim 1, characterized in that: The liquid ammonia generator (8) is provided with a liquid ammonia supply pipeline (19) and a solvent supply pipeline (20).