Cooling system suitable for methyl chlorosilane and control method thereof

Abstract

The invention discloses a cooling system suitable for methyl chlorosilane and a control method thereof.In the cooling system, a process gas storage tank is connected with a screw compressor, the screw compressor is connected with a gas-liquid separator, the gas-liquid separator is in pipeline connection with a liquid spraying tank cooler through a fourth control valve, and the liquid spraying tank cooler is connected with a liquid spraying tank; the liquid spraying tank is connected with a liquid spraying pump, and the liquid spraying pump is connected with a screw compressor pipeline through a first control valve; according to the control method, the opening degree of the control valve is adjusted through liquid level remote transmission or temperature remote transmission interlocking, so that the flow in the cooling system is controlled, and the cooling effect is kept stable. The screw compressor effectively prevents the female and male rotors in the screw compressor from being locked due to too high temperature, effectively solves the problem of temperature rise in the compression process, reduces the equipment failure rate, and improves the safety and stability of operation of the screw compressor.

Description

Technical Field

[0001] The invention belongs to the technical field of organosilicon production, and in particular relates to a cooling system suitable for methylchlorosilane and a control method thereof. Background Art

[0002] Methylchlorosilane is an organic compound with the chemical formula CH5ClSi. It is the main monomer for synthesizing silicone polymers. It is used to manufacture silicone resins and silicone rubbers, prepare silicone adhesives and sealants, and is also used to produce silane coupling agents. Therefore, the production of methylchlorosilane has become the technical pillar of the silicone industry. At present, the industrial production of methylchlorosilane monomers adopts the direct synthesis method. The specific method is to first synthesize a crude monomer using silicon powder, catalyst copper powder and superheated methyl chloride gas, and then remove silicon and copper fine powders through cyclone dust removal to obtain a methylchlorosilane mixed monomer containing methyl chloride. Then, in the crude monomer tower, methyl chloride and methylchlorosilane are separated by separation, fractionation and other methods to obtain a crude methylchlorosilane mixed monomer and methyl chloride. Among them, methyl chloride and crude methylchlorosilane mixed monomers are generally transported by screw compressors when transported to the next process. The high speed and high efficiency of the screw compressor are used to improve the gas transportation efficiency, thereby improving production efficiency. However, during the use of screw compressors, the secondary exhaust temperature is likely to rise, affecting the cooling effect; and the reaction temperature should not be too high when producing methylchlorosilane by the direct method, otherwise the yield of dimethyldichlorosilane will be reduced, the content of polychlorosilane will increase, and thus the content of by-products will increase. Therefore, the reaction temperature of methylchlorosilane needs to be strictly controlled, which puts forward higher requirements on the cooling performance of the screw compressor.

[0003] Common cooling methods for screw compressors are air cooling, water cooling and refrigerant cooling. Refrigerant cooling uses refrigerant to pass through the radiator of the screw compressor so that the heat it emits is absorbed by the coolant, thereby achieving cooling of the screw compressor.

[0004] Chinese patent CN201330707Y discloses a screw compressor refrigeration oil cooling system, the screw compressor is connected to the oil separator through a pipeline, the air supply interface is connected to the screw compressor inlet pipeline and the oil cooler pipe inlet through a pipeline with a control valve, the oil cooler pipe outlet is connected to the screw compressor inlet pipeline through a pipeline with a control valve, the oil separator refrigeration oil outlet is connected to the oil cooler shell inlet through a pipeline, and the oil cooler shell outlet is connected to the oil separator refrigeration oil inlet through a pipeline with a filter. The utility model has a simple and reasonable structure, can effectively improve the heat exchange effect of the oil cooler, the screw compressor can operate normally, and the refrigerant it uses is propane, which is different from the type of products cooled by the screw compressor.

[0005] Conventional coolant circulation pipelines and material delivery pipelines in screw compressors need to be independent of each other, but when the screw compressor leaks or equipment fails, the coolant will mix with the delivered material, introducing new impurities, thereby affecting the reaction. In addition, when the cooling effect of the coolant does not match the requirements of the delivered material, it is easy to cause the screw compressor to operate unstably, affecting the cooling effect. For example, in the production and delivery process of methylchlorosilane, when pure methyl chloride is used as a coolant, its cooling effect after vaporization is better, but it is easy to cause high exhaust pressure of the screw compressor, and at the same time, there will be a pressure drop when the spray pump is running, which is not conducive to stable operation; when pure methylchlorosilane is used for cooling, although it can achieve a cooling effect, the amount of liquid sprayed per hour is large, and a large amount of monomer circulation is not conducive to the stability of the entire production system, and increases processing energy consumption. Summary of the invention

[0006] In view of the above technical problems, the present invention provides a cooling system suitable for methylchlorosilane and a control method thereof, which effectively prevents the yin and yang rotors in the screw compressor from locking due to excessive temperature, effectively solves the problem of temperature rise during the compression process, reduces the equipment failure rate, and improves the safety and stability of the screw compressor operation.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a cooling system suitable for methylchlorosilane, wherein the process gas storage tank is connected to the screw compressor, the screw compressor is connected to the gas-liquid separator, the gas-liquid separator is connected to the spray tank cooler pipeline via a fourth control valve, the spray tank cooler is connected to the spray tank, the spray tank is connected to the spray pump, and the spray pump is connected to the screw compressor pipeline via a first control valve.

[0008] Preferably, the screw compressor is connected to a reflux cooler, and the reflux cooler is connected to a pipeline of the screw compressor via a fifth control valve; a pressure remote transmission is provided on the pipeline connecting the fifth control valve and the screw compressor.

[0009] Preferably, the screw compressor is connected to a gas-liquid separator, and the gas-liquid separator is connected to a crude monomer tower.

[0010] Preferably, the spray tank cooler is cyclically connected to the cooling water storage tank.

[0011] Preferably, a temperature remote transmitter is provided on the pipeline connecting the screw compressor and the gas-liquid separator, and the temperature remote transmitter is interlocked with the first control valve.

[0012] Preferably, the gas-liquid separator is provided with a second liquid level remote transmitter and a sixth control valve; the second liquid level remote transmitter is interlocked with the fourth control valve.

[0013] Preferably, the liquid spray tank is connected to a liquid spray pump, and the liquid spray pump is connected to the liquid spray tank via a second control valve.

[0014] Preferably, the liquid spray tank is connected to the liquid replenishment tank pipeline via a third control valve; the liquid spray tank is provided with a first liquid level remote transmitter, and the first liquid level remote transmitter is interlocked with the third control valve.

[0015] Preferably, the spray medium in the spray tank is composed of 60% of methylchlorosilane mixed monomers and 40% of methyl chloride; the temperature of the spray medium is -5°C to 0°C.

[0016] The present invention also provides a control method for a cooling system suitable for methylchlorosilane, the control method comprising: According to the temperature of the screw compressor outlet, the opening of the first control valve and the second control valve are interlocked and controlled; Control the start and stop of the fourth control valve according to the liquid level interlock transmitted by the second liquid level remotely; The start and stop of the third control valve is controlled according to the liquid level interlock transmitted by the first liquid level remotely; The opening of the fifth control valve is interlocked and controlled according to the remotely transmitted pressure at the screw compressor inlet.

[0017] Preferably, the sum of the openings of the first control valve and the second control valve is 100%; when the temperature of the temperature transmission is less than 50°C, the spray system stops running, the opening of the first control valve is 3% of the initial opening, and the opening of the second control valve is 97% of the initial opening; when the temperature of the temperature transmission is ≥50°C, the opening of the first control valve becomes 23%, and the opening of the second control valve becomes 77%. When the temperature of the temperature transmission increases by 1°C, the opening of the first control valve increases by 1.5%, and the opening of the second control valve decreases by 1.5%.

[0018] Preferably, when the second liquid level remote transmitter displays a liquid level ≥ 40 cm, the fourth control valve is opened to transport the liquid in the gas-liquid separator to the spray tank cooler.

[0019] Preferably, when the first liquid level remote transmitter shows that the liquid level is less than 40cm, the third control valve is opened to replenish the spray medium stored in the replenishment tank into the spray tank. When the liquid level reaches 60cm, the third control valve is closed to keep the liquid level of the cooling medium in the spray tank at 40-60cm, thereby meeting the cooling needs of the screw compressor.

[0020] Further preferably, the cooling medium is a liquid containing a mixed monomer of methyl chloride and methylchlorosilane, wherein the mass percentage of methyl chloride in the cooling medium is 40%, and the mass percentage of the mixed monomer of methylchlorosilane is 60%.

[0021] Preferably, when the pressure value of the remote pressure transmission changes by 5 kPa, the opening of the fifth control valve changes in the opposite direction by 3%; the pressure value of the remote pressure transmission is maintained at 90±5 kPa.

[0022] The beneficial effects of the present invention are: 1. The cooling medium that has passed through the screw compressor is recovered and recycled through the gas-liquid separator and the spray tank cooler, which saves cooling medium and reduces energy consumption.

[0023] 2. A temperature remote transmitter is installed on the outlet pipeline of the screw compressor. The temperature remote transmitter is interlocked with the first control valve on the outlet pipeline of the spray tank. The amount of cooling medium in the spray tank entering the screw compressor can be controlled in real time according to the outlet temperature of the screw compressor, so as to keep the exhaust temperature at the outlet of the screw compressor constant.

[0024] 3. The screw compressor is connected to the reflux cooler in a loop, and the return opening is controlled by the fifth control valve frequency conversion. The frequency is adjusted in real time according to the production situation to maximize the efficiency of the screw compressor, thereby saving energy consumption.

[0025] 4. Methylchlorosilane mixed monomer is used as cooling medium, so it can directly enter the cooling system and participate in the system reaction without introducing new impurities; the methylchlorosilane mixed monomer contains 60% methylchlorosilane monomer and 40% methyl chloride, which can not only ensure that the cooling medium has a good cooling effect, but also has a certain lubrication effect, preventing the yin and yang rotors in the screw compressor from locking due to excessive temperature, effectively solving the problem of temperature rise during compression, reducing the equipment failure rate, and improving the safety and stability of the screw compressor operation. It not only solves the problem of poor cooling effect, but also solves the problem of large liquid injection volume and increased energy consumption when using only methyl chloride or only methylchlorosilane monomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the overall structure of the present invention, in which 1 is a screw compressor, 2 is a gas-liquid separator, 3 is a reflux cooler, 4 is a spray tank cooler, 5 is a spray tank, 6 is a spray pump, 7 is a first control valve, 8 is a second control valve, 9 is a third control valve, 10 is a first liquid level remote transmission, 11 is a fourth control valve, 12 is a second liquid level remote transmission, 13 is a temperature remote transmission, 14 is a fifth control valve, 15 is a sixth control valve, 16 is a crude monomer tower, 17 is a liquid replenishment tank, 18 is a cooling water storage tank, 19 is a process gas storage tank, and 20 is a pressure remote transmission. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It is worth noting that the following embodiments are only preferred embodiments of the present invention and should not be understood as limiting the present invention. The protection scope of the present invention shall be based on the contents recorded in the claims. Any modification or replacement made by those skilled in the art to the technical solution of the present invention without creative work shall fall within the protection scope of the present invention.

[0028] Example 1 like Figure 1As shown, a cooling system suitable for methylchlorosilane, the process gas storage tank 19 is connected to the screw compressor 1, the screw compressor 1 is connected to the gas-liquid separator 2, the gas-liquid separator 2 is connected to the spray tank cooler 4 pipeline via the fourth control valve 11, the spray tank cooler 4 is connected to the spray tank 5, the spray tank 5 is connected to the spray pump 6, and the spray pump 6 is connected to the screw compressor 1 pipeline via the first control valve 7; the mixed monomer in the spray tank 5 is transported to the screw compressor 1 through the spray pump 6 to cool it, the gas and liquid processed by the screw compressor 1 are transported to the gas-liquid separator 2 through the pipeline, when the liquid level in the gas-liquid separator 2 reaches a certain level, the fourth control valve 11 is automatically opened, and the separated liquid is transported to the spray tank cooler 4 for cooling, and then transported to the spray tank 5 for recycling.

[0029] Preferably, the screw compressor 1 is connected to the reflux cooler 3 to reflux part of the liquid for cooling. The reflux cooler 3 is connected to the screw compressor 1 pipeline via the fifth control valve 14 to reflux the cooled liquid to the screw compressor 1 for recycling. The fifth control valve 14 can control the return opening of the screw compressor 1, and realize it through frequency conversion, and adjust the frequency in real time according to the production situation. By adjusting the return opening, the efficiency of the screw compressor is maximized and energy consumption is saved to the greatest extent. A pressure transmitter 20 is provided on the pipeline connecting the fifth control valve 14 and the screw compressor 1, and the pressure transmitter 20 is used to detect the pressure at the inlet of the screw compressor 1, so as to interlock and control the opening of the fifth control valve 14.

[0030] Preferably, the screw compressor 1 is connected to the gas-liquid separator 2, and the gas-liquid separator 2 is connected to the crude monomer tower 16, and the gas separated in the gas-liquid separator 2 is transported to the crude monomer tower for cooling and condensation, and the generated liquid is transported to the screw compressor 1 again for recycling.

[0031] Preferably, the spray tank cooler 4 is cyclically connected to the cooling water storage tank 18 to circulate cooling water for the spray tank cooler 4 to cool the liquid to -5°C~0°C.

[0032] Preferably, a temperature transmitter 13 is provided on the pipeline connecting the screw compressor 1 and the gas-liquid separator 2 to monitor the temperature at the outlet of the screw compressor 1 in real time; the temperature transmitter 13 is interlocked with the first control valve 7 to realize automatic control of the first control valve 7; when the data in the temperature transmitter 13 increases, the opening of the first control valve 7 is automatically increased, and when the data in the temperature transmitter 13 increases, the opening of the first control valve 7 is automatically decreased.

[0033] Preferably, the gas-liquid separator 2 is provided with a second liquid level remote transmitter 12 and a sixth control valve 15, wherein the sixth control valve 15 is arranged on the external discharge pipe at the bottom of the gas-liquid separator 2 to control the external discharge of the liquid; the second liquid level remote transmitter 12 is interlocked with the fourth control valve 11 to realize automatic control of the fourth control valve 11. When the second liquid level remote transmitter 12 detects that the liquid level in the gas-liquid separator 2 reaches a certain height, the fourth control valve 11 automatically opens to discharge the liquid in the gas-liquid separator 2 and transport it to the spray tank cooler 4.

[0034] Preferably, the spray tank 5 is connected to the spray pump 6, and the spray pump 6 is connected to the spray tank 5 via a second control valve 8, so that part of the pumped liquid flows back to the spray tank 5 to control the flow rate of the liquid entering the screw compressor 1.

[0035] Preferably, the spray tank 5 is connected to the replenishing tank 17 pipeline via the third control valve 9; the spray tank 5 is provided with a first liquid level remote transmitter 10, and the first liquid level remote transmitter 10 is interlocked with the third control valve 9. When the liquid in the spray tank 5 is lower than a certain height, the third control valve 9 is automatically opened to replenish the liquid stored in the replenishing tank 17 into the spray tank 5, so that the liquid in the spray tank 5 always maintains a certain liquid level, thereby ensuring the amount of liquid entering the screw compressor 1, thereby ensuring the cooling effect.

[0036] Preferably, the spray medium in the spray tank is composed of 60% of methylchlorosilane mixed monomers and 40% of methyl chloride; the temperature of the spray medium is -5°C to 0°C; and the gas separated in the gas-liquid separator 2 is methyl chloride.

[0037] Example 2 A control method for a cooling system applicable to methylchlorosilane, wherein the cooling system applicable to methylchlorosilane is as described in Example 1, and the specific control method is as follows: (1) The process gas is transported to the screw compressor, mixed with the spray medium, and cooled. After cooling, it is transported to the gas-liquid separator 2 through a pipeline to separate the gas-phase methylchlorosilane from the liquid-phase methylchlorosilane. When the liquid level of the liquid-phase methylchlorosilane in the gas-liquid separator 2 exceeds 40 cm, the second liquid level remote transmission 12 detects this situation, and the interlock control opens the fourth control valve 11 to transport the liquid-phase methylchlorosilane to the spray tank cooler for cooling. When the second liquid level remote transmission 12 detects that the liquid level is lower than 40 cm, the fourth control valve 11 is closed to keep the liquid level in the gas-liquid separator 2 constant at 40 cm.

[0038] (2) Liquid methylchlorosilane cooled by the spray tank cooler and having a temperature of -5°C to 0°C enters the spray tank 5 and is then pumped out by the spray pump 6. A portion of the liquid enters the screw compressor 1 as a cooling medium through the first control valve 7, and the other portion flows back to the spray tank 5 through the second control valve 8. A temperature remote transmitter 13 is provided on the outlet pipeline of the screw compressor 1. (3) When the load of the screw compressor 1 increases to 60%, and the temperature remote transmitter 13 detects that its outlet temperature is ≥50°C, the opening of the first control valve 7 is adjusted from the initial 23% to 24.5%, and the opening of the second control valve 8 is adjusted from the initial 77% to 75.5%, so that the amount of cooling medium entering the screw compressor 1 is increased, the cooling effect is improved, and the load and outlet temperature of the screw compressor are reduced; and when the temperature increases by 1°C on the basis of 50°C, the opening of the first control valve 7 increases by 1.5%, and the opening of the second control valve decreases by 1.5%; When the load of the screw compressor 1 is reduced to 30%, and the temperature remote transmitter 13 detects that its outlet temperature is ≤90°C, the opening of the first control valve 7 is adjusted from the initial 100% to 98.5%, and the opening of the second control valve 8 is adjusted from the initial 0% to 1.5%, so that the amount of cooling medium entering the screw compressor 1 is reduced, the cooling effect is improved, and thus the load and outlet temperature of the screw compressor are increased; and when the temperature is reduced by 1°C on the basis of 90°C, the opening of the first control valve 7 is reduced by 1.5%, and the opening of the second control valve is increased by 1.5%; finally, the outlet temperature fluctuation of the screw compressor 1 is kept within 75°C±5°C, and the stable operation of the cooling system is improved; (4) When the first liquid level remote transmitter 10 on the spray tank 5 detects that the liquid level in the spray tank 5 is lower than 40 cm, the third control valve 9 is interlocked to open, and the liquid stored in the replenishment tank 17 is replenished into the spray tank 5. When the liquid level reaches 60 cm, the third control valve 9 is closed, and the replenishment is stopped, so that the liquid level in the spray tank 5 is constant at 40-60 cm. (5) Control the opening of the fifth control valve 14 to reflux the liquid phase cooled in the reflux cooler 3 to the screw compressor 1. The efficiency of the screw compressor is improved and the energy consumption is reduced by controlling the opening of the fifth control valve 14. When the pressure transmitter 20 at the inlet of the screw compressor 1 shows that the pressure is reduced and the pressure is lower than 85 kPa, the opening of the fifth control valve 14 is adjusted to 15% to increase the reflux flow rate, thereby reducing the temperature of the screw compressor. When the pressure transmitter 20 at the inlet of the screw compressor 1 shows that the pressure is increased and the pressure is higher than 95 kPa, the opening of the fifth control valve 14 is adjusted to 0% to reduce the reflux flow rate, so that the inlet pressure of the screw compressor 1 is always maintained at 90±5 kPa. For every 5 kPa change in pressure, the opening of the fifth control valve 14 is adjusted by 3%. Before the screw compressor 1 is started, the initial opening of the fifth control valve 14 is 100%. After the screw compressor 1 is started, the fifth control valve 14 is gradually closed to a suitable opening according to the load adjustment.

[0039] (6) After the gas-liquid separator has been running for 24 hours, samples are taken for analysis. When the methylchlorosilane content is higher than 70%, in order to avoid poor cooling effect, the sixth control valve 15 is opened to discharge the liquid phase in the gas-liquid separator 2 out of the system, and the third control valve 9 is opened to replenish the liquid to ensure that the methylchlorosilane mixed monomer component in the system is constant, thereby ensuring the cooling effect.

[0040] Preferably, the process gas in step (1) is methyl chloride gas containing a small amount of methylchlorosilane.

[0041] Preferably, in step (4), liquid methyl chloride is stored in the liquid replenishment tank 17.

[0042] Preferably, the methylchlorosilane mixed monomer in the system of step (6) consists of 40% methyl chloride and 60% methylchlorosilane.

Claims

1. A cooling system suitable for methylchlorosilane, characterized in that: The process gas storage tank (19) is connected to the screw compressor (1), the screw compressor (1) is connected to the gas-liquid separator (2), the gas-liquid separator (2) is connected to the liquid spray tank cooler (4) pipeline via the fourth control valve (11), the liquid spray tank cooler (4) is connected to the liquid spray tank (5), the liquid spray tank (5) is connected to the liquid spray pump (6), and the liquid spray pump (6) is connected to the screw compressor (1) pipeline via the first control valve (7).

2. A cooling system suitable for methylchlorosilane according to claim 1, characterized in that: The screw compressor (1) is connected to a reflux cooler (3), and the reflux cooler (3) is connected to the screw compressor (1) pipeline via a fifth control valve (14); a pressure remote transmitter (20) is provided on the pipeline connecting the fifth control valve (14) and the screw compressor (1).

3. A cooling system suitable for methylchlorosilane according to claim 1, characterized in that: The screw compressor (1) is connected to a gas-liquid separator (2), and the gas-liquid separator (2) is connected to a crude monomer tower (16); the liquid spray tank cooler (4) is cyclically connected to a cooling water storage tank (18).

4. A cooling system suitable for methylchlorosilane according to claim 1 or 3, characterized in that: A temperature remote transmitter (13) is provided on the pipeline connecting the screw compressor (1) and the gas-liquid separator (2), and the temperature remote transmitter (13) is interlocked with the first control valve (7).

5. A cooling system suitable for methylchlorosilane according to claim 1, characterized in that: The gas-liquid separator (2) is provided with a second liquid level remote transmitter (12) and a sixth control valve (15); the second liquid level remote transmitter (12) is interlocked with the fourth control valve (11).

6. A cooling system suitable for methylchlorosilane according to claim 1, characterized in that: The liquid spray tank (5) is connected to the liquid spray pump (6), and the liquid spray pump (6) is connected to the liquid spray tank (5) via a second control valve (8).

7. A cooling system suitable for methylchlorosilane according to claim 1, characterized in that: The liquid spray tank (5) is connected to the liquid replenishment tank (17) through a pipeline via a third control valve (9); a first liquid level remote transmitter (10) is provided on the liquid spray tank (5), and the first liquid level remote transmitter (10) is interlocked with the third control valve (9).

8. A cooling system suitable for methylchlorosilane according to claim 1 or 7, characterized in that: The spray medium in the spray tank is composed of 60% of methylchlorosilane mixed monomers and 40% of methyl chloride; the temperature of the spray medium is -5°C to 0°C.

9. A control method for a cooling system for methylchlorosilane, characterized in that: The control method is used to control the cooling system applicable to methylchlorosilane according to any one of claims 1 to 8, and the control method comprises: Interlocking and controlling the openings of the first control valve (7) and the second control valve (8) according to the temperature of the remote temperature transmitter (13) at the outlet of the screw compressor (1); Controlling the start and stop of the fourth control valve (11) according to the liquid level interlock of the second liquid level remote transmitter (12); Controlling the start and stop of the third control valve (9) according to the liquid level interlock of the first liquid level remote transmitter (10); The opening degree of the fifth control valve (14) is interlocked and controlled according to the pressure of the remote pressure transmitter (20) at the inlet of the screw compressor (1).

10. The control method according to claim 9, characterized in that: The sum of the openings of the first control valve (7) and the second control valve (8) is 100%; when the temperature of the temperature remote transmitter (13) is less than 50°C, the opening of the first control valve (7) is 3% and the opening of the second control valve (8) is 97%; when the temperature of the temperature remote transmitter (13) is ≥50°C, the opening of the first control valve (7) is 23% and the opening of the second control valve (8) is 77%; when the temperature of the temperature remote transmitter (13) increases by 1°C, the opening of the first control valve (7) increases by 1.5% and the opening of the second control valve (8) decreases by 1.5%.

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