Method and system for preparing cryogenic refrigerant by using composite refrigerant in polycrystalline silicon production
By using ammonia and N,N-diethylaniline solutions to prepare deep refrigerant, the problems of poor stability and high power consumption of screw compressors in the traditional polysilicon industry are solved, low-cost and efficient cooling effect are achieved, and production costs are reduced and equipment operation risks.
Patent Information
- Application Number
- CN202411528213.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-09-09
- Filing Date
- 2024-10-30
- Publication Date
- 2025-01-10
AI Technical Summary
The screw compressors used in the traditional polysilicon industry have poor stability, high power consumption, high investment costs, and the deep-cooled refrigerant refrigerant refrigerant refrigerant refrigerant has complex structure and consumable parts problems, resulting in increased production costs.
Ammonia is used as a refrigerant, combined with N,N-diethylaniline solution as solvent, and the ammonia is vaporized by heating and pressurization, condensed into liquid ammonia, which is used to prepare deep refrigerant and to achieve the absorption of cold and heat through the circulation system. and volatile, replacing traditional Freon refrigerant.
It reduces the load and power consumption of ice machines in polysilicon production, significantly reduces production costs, simplifies the equipment structure, improves the stability and safety of the system, and reduces the equipment operation costs.
Smart Images
Figure CN119289551A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of efficient utilization of energy, and in particular to a method and system for preparing a cryogenic refrigerant by using a composite refrigerant in the production of polysilicon. Background Art
[0002] In the traditional polysilicon industry, deep cold refrigerants usually use Freon as a refrigerant, and the refrigeration method uses a screw compressor pressurization method, which has been common in the polysilicon industry and has been used for many years. Although the mode of using screw compressors to refrigerate Freon gas phase compressors is widely used, there are still many problems that need to be solved, such as: 1. The stability of screw compressors is difficult to guarantee. Liquid inlet or high temperature alarm tripping of rotors and windings often occurs. In addition, there are many types of evaporative cooling and economizer storage tank equipment in the subsequent system, with complex structures, high investment costs, and many vulnerable parts. 2. The use of compressors, evaporative cooling and other equipment has very high power consumption in long-term operation. Taking a 3000kW -10℃ ice machine as an example, its motor power is basically around 900kW, plus the consumption of evaporative cooling, the COP value during actual operation is generally less than 3. The annual electricity consumption of an ice machine can be as high as more than 4 million.
[0003] With the continuous increase in polysilicon production capacity, the number of supporting ice machines is increasing. The annual electricity consumption of ice machines in a 200,000-ton polysilicon production plant can reach over 100 million yuan.
[0004] Based on the above reasons, technicians in this industry are still constantly exploring, trying to find heat exchange equipment with simpler structure and lower operating costs, and / or find more suitable refrigerants to replace or partially replace ice machine operations to provide cooling for multiple systems, thereby reducing the load of the original ice machine and reducing production costs. Summary of the invention
[0005] The inventor of the present invention has found through relevant data research that ammonia can volatilize at a temperature of dozens of degrees below zero, and has a high thermal enthalpy value, and can absorb a large amount of heat, thereby achieving the purpose of refrigeration. Therefore, in this scheme, ammonia is considered as a refrigerant to achieve the absorption and volatilization of cold and heat, thereby providing cooling for the system. As for the solvent, in this scheme, ammonia is easily soluble at room temperature, ammonia is easily volatilized when the temperature rises to 100°C or above, and a substance that is not easy to vaporize in the range of room temperature to 130°C is selected - N, N-diethylaniline solution.
[0006] In order to solve the above technical problems, the present invention is implemented by the following technical solutions: A method for preparing a cryogenic refrigerant using a composite refrigerant in polysilicon production comprises the following steps: S1. Heating and pressurizing the ammonia-solvent composite refrigerant at room temperature or low temperature and at normal pressure or low pressure, so that the ammonia in the ammonia composite refrigerant is vaporized and the remaining solvent is in liquid state; S2, maintaining the high pressure state in step S1, condensing the gaseous ammonia into liquid ammonia, that is, obtaining cryogenic refrigerant liquid ammonia for use by the user end; S3. After the deep cold refrigerant liquid ammonia in step S2 is heat exchanged at the user end, gaseous ammonia at room temperature or low temperature and normal pressure or low pressure is obtained. The gaseous ammonia is sent to a storage tank containing a solvent. After the gaseous ammonia is absorbed, an ammonia-solvent composite refrigerant is obtained for the next recycling.
[0007] Furthermore, the solvent is N,N-diethylaniline solution.
[0008] Furthermore, in step S1, the surplus steam generated in the production of polysilicon is used to heat the ammonia-solvent composite refrigerant.
[0009] Furthermore, in step S1, when the ammonia-solvent composite refrigerant is pressurized, the pressure is controlled to be 1.5 MPa.
[0010] Furthermore, in step S2, 33° C. cooling water is used to condense gaseous ammonia into liquid ammonia to obtain liquid ammonia cryogenic refrigerant.
[0011] A circulation system used in the above method comprises a storage tank I for storing ammonia-solvent composite refrigerant, wherein the storage tank I is connected to a cooling device and a storage tank II in sequence, and the storage tank II is used for temporarily storing liquid ammonia deep-cold refrigerant, and the storage tank II is connected to the medium inlet of the user-end heat exchanger through the pipeline I, and the medium outlet of the user-end heat exchanger is connected to an absorption device containing a solvent through the pipeline II, and the outlet of the absorption device is connected to the storage tank I through the pipeline III, and the outer side of the storage tank I is provided with a jacket or a heating pipe through which steam passes, or the inner side of the storage tank I is provided with a heating pipe through which steam passes.
[0012] Furthermore, the cooling device is a shell and tube heat exchanger with a 33°C cooling water medium passing therethrough; the storage tank I is provided with a liquid ammonia supply pipeline and a solvent supply pipeline.
[0013] Furthermore, the heating tube is a coil or a tube array.
[0014] Furthermore, the exterior of the storage tank II is coated with a heat insulation layer, and the exterior of the heat insulation layer is provided with a heat preservation sleeve.
[0015] Furthermore, a compressor is provided between the storage tank I and the cooling device.
[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, an ammonia-solvent composite refrigerant is proposed. The ammonia-solvent composite refrigerant is in liquid state at room temperature, and ammonia will automatically volatilize under certain temperature and pressure conditions. In the actual application process, it can be designed to use the waste heat in the factory area to heat the ammonia-solvent composite refrigerant solution, volatilize gaseous ammonia under a certain high pressure, and then cool the gaseous ammonia to liquid phase through a condenser under this pressure, and then supply the liquid ammonia rich in cold to the user side. The ammonia after decompression absorbs the heat on the user side and volatilizes into a gas phase, and then the gaseous ammonia is absorbed by the aforementioned solvent, and after mixing with the solvent, it forms an ammonia-solvent composite refrigerant in liquid state, and then it is sent to the high-pressure side by a pump. In this cycle, the refrigeration effect of ammonia can be achieved. The whole method is easy to operate, involves fewer steps, and is easy to control.
[0017] 2. In the present invention, liquid ammonia and soluble salts constitute an ammonia-solvent composite refrigerant. This solution can be separated under the condition of steam heat input, and then cooled by circulating water, evaporating and absorbing heat under low pressure conditions. The system is refrigerated under such a circulating condition, and the source power of this process is the surplus steam generated in the polysilicon production process. For polysilicon production companies, deep cold refrigerants can be obtained at a very low refrigeration cost, which significantly reduces the load and power consumption of traditional -10℃ and -40℃ ice machines. With the increase in electricity price costs in the manufacturing industry, reducing the unit power consumption is also a key factor for the survival of enterprises. In addition, this method can consume a part of the surplus steam generated in the production of polysilicon, and can also reduce the process links and processing costs of processing surplus steam.
[0018] 3. In the present invention, the solvent is preferably N,N-diethylaniline solution. Ammonia is easily soluble in N,N-diethylaniline solution under normal temperature and pressure. The mixed solution of ammonia dissolved in N,N-diethylaniline solution is easily volatilized after the temperature is raised to 100°C or above, and has the characteristics of not being easy to vaporize in the range of room temperature to 130°C, and is suitable for preparing liquid ammonia cryogenic refrigerant.
[0019] 4. In the present invention, when the ammonia-solvent composite refrigerant is pressurized, the pressure is controlled to 1.5MPa, and 33°C cooling water is used to condense gaseous ammonia into liquid ammonia, so that liquid ammonia cryogenic refrigerant at room temperature can be obtained. The liquid ammonia cryogenic refrigerant under high pressure is sent to the user end to release the pressure, absorb heat, and then quickly vaporize and convert into -15°C cryogenic refrigerant, which can replace traditional Freon ice-making agents to provide cooling for the system, thereby reducing the load of the original ice machine and reducing production costs.
[0020] 5. In the present invention, the circulation system involved in the method has a relatively simple structure, mainly involving a storage tank I, a cooling device, a storage tank II, an absorption device and a booster pump, with very little power consumption and very low electricity cost. There are fewer devices, and the equipment procurement cost is also very low. The risk of system tripping composed of heat exchangers is also significantly reduced, ensuring safe and stable production while significantly reducing equipment operating costs.
[0021] 6. In the production of polysilicon, the system's deep cold refrigerant (-10℃, -40℃, -70℃) generally uses Freon and dichloromethane as the medium to cool the system. The present invention first proposes to use -15℃ liquid ammonia to cool the system. Liquid ammonia can also be used to evaporate and condense Freon, which is an indirect cooling form. The former is that liquid ammonia directly cools, which is suitable for the initial design of new projects. For existing systems that have been put into operation, liquid ammonia can be used to cool Freon, and an indirect cooling mode can be adopted. This does not require replacement of the original heat exchanger, saving equipment investment.
[0022] 7. In the present invention, the heating pipe in the circulation system is a steam-permeable structure. The heating pipe can be involved in a coil or a tube array, built into the storage tank I, or close to the outer wall of the storage tank I to ensure the heat exchange efficiency of the equipment.
[0023] 8. In the present invention, the outside of the storage tank II is coated with a heat insulation layer, and a heat preservation sleeve is provided outside the heat insulation layer to prevent the loss of cold.
[0024] IX. In the present invention, a liquid ammonia supply pipeline and a solvent supply pipeline are provided on the storage tank I, and the circulation system can replenish liquid ammonia and solvent through the provided liquid ammonia supply pipeline and solvent supply pipeline. A compressor is provided between the storage tank I and the cooling device to further ensure that the pressure is controlled to 1.5MPa. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a structural diagram of the circulatory system.
[0026] Figure 2 It is a schematic diagram of the structure of storage tank I.
[0027] Figure 3 It is a structural schematic diagram of another implementation method of storage tank I.
[0028] Figure 4 This is a partial enlarged view of the tank wall of tank II.
[0029] Figure 5 It is a structural schematic diagram of another embodiment of the circulation system.
[0030] Among them, 1. Storage tank I; 2. Compressor; 3. Cooling device; 4. Storage tank II; 5. Pipeline I; 6. User-end heat exchanger; 7. Pipeline II; 8. Absorption device; 9. Booster pump; 10. Pipeline III; 11. Jacket; 12. Heating pipe; 13. Liquid ammonia supply pipeline; 14. Solvent replenishment pipeline; 15. Insulation layer; 16. Insulation jacket; 17. Steam pipeline; 3.1. Cooling water pipeline; 6.1. Medium inlet; 6.2. Medium outlet; 8.1. Outlet. DETAILED DESCRIPTION
[0031] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.
[0032] Example 1 A method for preparing a cryogenic refrigerant by using a composite refrigerant in polysilicon production relates to the technical field of efficient utilization of energy, and comprises the following steps: S1. Heating and pressurizing the ammonia-solvent composite refrigerant at 30°C and 0.2MPa low pressure to vaporize the ammonia in the ammonia composite refrigerant and leave the remaining solvent in liquid state; S2, maintaining the high pressure state in step S1, condensing the gaseous ammonia into liquid ammonia, that is, obtaining cryogenic refrigerant liquid ammonia for use by the user end; S3. After the deep cold refrigerant liquid ammonia in step S2 is heat exchanged at the user end, gaseous ammonia at room temperature and low pressure (close to 0.2MPa) is obtained. The gaseous ammonia is sent to a storage tank containing a solvent. After the gaseous ammonia is absorbed, an ammonia-solvent composite refrigerant is obtained for the next recycling.
[0033] Example 2 To facilitate the public's understanding of the present scheme, this embodiment takes the preparation of -15°C liquid ammonia cryogenic refrigerant as an example, and combines the method of preparing cryogenic refrigerant using composite refrigerant in polysilicon production with a circulating system as an example to further illustrate the present scheme.
[0034] refer to Figure 1 In this embodiment, the circulation system includes a storage tank Ⅰ1 for storing ammonia-solvent composite refrigerant, and the storage tank Ⅰ1 is connected to the cooling device 3 and the storage tank Ⅱ4 in sequence. The storage tank Ⅱ4 is used to temporarily store liquid ammonia deep cold refrigerant. The storage tank Ⅱ4 is connected to the medium inlet 6.1 of the user-end heat exchanger 6 through the pipeline Ⅰ5, and the medium outlet 6.2 of the user-end heat exchanger 6 is connected to the absorption device 8 containing the solvent through the pipeline Ⅱ7. The outlet 8.1 of the absorption device 8 is connected to the storage tank Ⅰ1 through the pipeline Ⅲ10. The outer side of the storage tank Ⅰ1 is provided with a steam jacket 11.
[0035] In this embodiment, the cooling device 3 is a shell and tube heat exchanger through which a 33° C. cooling water medium is passed; the storage tank Ⅰ1 is provided with a liquid ammonia supply pipeline 13 and a solvent supply pipeline 14.
[0036] Based on the above circulation system, a method for preparing a cryogenic refrigerant using a composite refrigerant in polysilicon production includes the following steps: S1, passing the surplus steam generated in the production of polysilicon into the jacket 11 outside the storage tank Ⅰ1 through the steam pipeline 17, heating the ammonia-solvent composite refrigerant at 30°C and 0.2MPa low pressure in the storage tank Ⅰ1, wherein the solvent is N,N-diethylaniline solution, so that the ammonia in the ammonia composite refrigerant is vaporized, at which time the temperature of the gaseous ammonia is 130°C and the pressure is 1.5MPa, and the remaining solvent is in liquid state; S2. Maintain the high pressure (1.5 MPa) state in step S1, and transport the gaseous ammonia to the cooling device 3. The cooling device 3 supplies cooling water at 33°C through the cooling water pipeline to condense the gaseous ammonia into liquid ammonia, that is, obtain room temperature deep cold refrigerant liquid ammonia, which is temporarily stored in the storage tank II4 for use by the user end; S3. The liquid ammonia cryogenic refrigerant temporarily stored in the storage tank II4 in step S2 is transported to the user-side heat exchanger 6 via pipeline I5. After the pressure is released at the user side and the liquid ammonia absorbs heat, it is rapidly vaporized and converted into -15°C cryogenic refrigerant liquid ammonia. After complete heat exchange, the -15°C cryogenic refrigerant liquid ammonia is obtained to obtain gaseous ammonia at a low pressure of about 30°C and 0.2MPa. The gaseous ammonia is then transported to the absorption device 8 containing the solvent via pipeline II7. The gaseous ammonia is absorbed by the N,N-diethylaniline solvent to obtain an ammonia-solvent composite refrigerant, which is then pumped to the storage tank I1 via pipeline III10 by a booster pump 9 for the next recycling.
[0037] In this embodiment, taking the preparation of 10,000kW of refrigerant as an example, the adoption of this solution can save 28 million kW / year, and reduce the production cost by about 14 million yuan / year in total. It can replace more than 3 -10℃ ice machines and be used by a polysilicon production enterprise with a capacity of more than 50,000 tons. In addition, the refrigerant production system has a simple structure and small moving equipment, and is not prone to the risk of system tripping, which ensures the safe and stable operation of the production system and reduces the operating costs.
[0038] Example 3 The difference between this embodiment and embodiment 2 is that: The storage tank Ⅰ1 is equipped with a heating pipe 12, which is a tube array. Figure 2 .
[0039] The jacket 11 and the heat exchange tube each have their own advantages, and can be selected according to the specific working conditions on site. If the design volume is not large, it is recommended to use the form of the outer jacket 11. This form has a simple structure, uncomplicated welding process, can ensure stable heat transfer, and has low manufacturing cost. If the design volume is large and the tank size is large, then the use of the outer jacket 11 may result in uneven heating. It is recommended to use the form of an inner coil to ensure constant heating. However, compared with the jacket 11 structure, the internal heating tube 12 has a more complex structure, a difficult welding process, and a high cost.
[0040] Example 4 The difference between this embodiment and embodiment 2-3 is that: The storage tank Ⅰ1 is provided with a heating tube 12, which is a coil. Figure 3 .
[0041] Example 5 The difference between this embodiment and embodiment 2-4 is that the reference Figure 1 ,4 The outside of the storage tank II 4 is coated with a heat insulation layer 15 , and the outside of the heat insulation layer 15 is provided with a heat preservation sleeve 16 .
[0042] Example 6 The difference between this embodiment and embodiments 2-4 is that: A compressor 2 is provided between the storage tank Ⅰ3 and the cooling device 3 to ensure that the pressure of the material in the pipeline is stable so as to obtain a refrigerant with a desired temperature.
[0043] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.
Claims
1. A method for preparing a cryogenic refrigerant using a composite refrigerant in polysilicon production, characterized in that: The steps include: S1. Heating and pressurizing the ammonia-solvent composite refrigerant at room temperature or low temperature and at normal pressure or low pressure, so that the ammonia in the ammonia composite refrigerant is vaporized and the remaining solvent is in liquid state; S2, maintaining the high pressure state in step S1, condensing the gaseous ammonia into liquid ammonia, that is, obtaining cryogenic refrigerant liquid ammonia for use by the user end; S3. After the deep cold refrigerant liquid ammonia in step S2 is heat exchanged at the user end, gaseous ammonia at room temperature or low temperature and normal pressure or low pressure is obtained. The gaseous ammonia is sent to a storage tank containing a solvent. After the gaseous ammonia is absorbed, an ammonia-solvent composite refrigerant is obtained for the next recycling.
2. The method for preparing a cryogenic refrigerant using a composite refrigerant in polysilicon production according to claim 1, characterized in that: The solvent is N,N-diethylaniline solution.
3. The method for preparing a cryogenic refrigerant using a composite refrigerant in polysilicon production according to claim 1, characterized in that: In step S1, the surplus steam generated in the production of polysilicon is used to heat the ammonia-solvent composite refrigerant.
4. The method for preparing a cryogenic refrigerant using a composite refrigerant in the production of polysilicon according to claim 1, characterized in that: In step S1, when the ammonia-solvent composite refrigerant is pressurized, the pressure is controlled to be 1.5 MPa.
5. The method for preparing a cryogenic refrigerant using a composite refrigerant in the production of polysilicon according to claim 4, characterized in that: In step S2, 33° C. cooling water is used to condense gaseous ammonia into liquid ammonia to obtain liquid ammonia cryogenic refrigerant.
6. A circulation system for the method according to claim 1, characterized in that: The invention comprises a storage tank I (1) for storing an ammonia-solvent composite refrigerant, wherein the storage tank I (1) is connected in sequence to a cooling device (3) and a storage tank II (4), wherein the storage tank II (4) is used for temporarily storing a liquid ammonia deep-cold refrigerant, and the storage tank II (4) is connected to a medium inlet (6.1) of a user-end heat exchanger (6) through a pipeline I (5), and a medium outlet (6.2) of the user-end heat exchanger (6) is connected to an absorption device (8) containing a solvent through a pipeline II (7), and an outlet (8.1) of the absorption device (8) is connected to the storage tank I (1) through a pipeline III (10), and a jacket (11) or a heating pipe (12) through which steam flows is provided on the outside of the storage tank I (1), or a heating pipe (12) through which steam flows is provided on the inside of the storage tank I (1).
7. A circulation system according to claim 6, characterized in that: The cooling device (3) is a shell and tube heat exchanger through which a cooling water medium at 33°C is passed; the storage tank I (1) is provided with a liquid ammonia supply pipeline (13) and a solvent supply pipeline (14).
8. A circulation system according to claim 6, characterized in that: The heating tube (12) is a coil or a tube array.
9. A circulation system according to claim 6, characterized in that: The storage tank II (4) is coated with a heat insulation layer (15) on the outside, and a heat insulation sleeve (16) is provided on the outside of the heat insulation layer (15).
10. A circulation system according to claim 6, characterized in that: A compressor (2) is provided between the storage tank I (1) and the cooling device (3).