Method for preventing ammonium carbonate in working fluid of vacuum pump from being saturated

Abstract

The invention discloses a method for preventing ammonium carbonate in a vacuum pump working solution from being saturated, and belongs to the field of chemical production processes. The method comprises the following steps: a working solution is stored in a working solution buffer tank, ammonia gas enters the working solution buffer tank, and the working solution buffer tank feeds the ammonia gas into a liquid ring vacuum pump; working liquid in the liquid ring vacuum pump enters the working liquid buffer tank through pressure difference; part of the working solution in the working solution buffer tank enters a pipeline of a working solution rectifying tower through a working solution ammonium removal pump, the working solution is rectified, and ammonium carbonate solids are removed from the rectified working solution; and the rectified working solution enters a working solution buffer tank after passing through a tower kettle extraction pump of the working solution rectifying tower and a working solution cooler. The working liquid rectifying tower is arranged, so that the problem of crystallization of working liquid in the original liquid ring vacuum pump is solved, and the working time of the liquid ring vacuum pump is prolonged; the circulating use of the working solution is realized, the consumption of the working solution is reduced through the circulation of the working solution, and the cost is reduced.

Description

Technical Field

[0001] The invention relates to a post-processing method of ammonia produced by the reaction of propylene glycol and urea, and in particular to a method for preventing saturation of ammonium carbonate in a vacuum pump working fluid, belonging to the field of chemical production technology. Background Art

[0002] In chemical production, propylene glycol reacts with urea to produce propylene carbonate and ammonia. The generated ammonia contains a small amount of water, carbon dioxide, and organic matter (the main components are propylene glycol and a small amount of propylene carbonate). In order to recover the generated ammonia, it is necessary to compress the ammonia. The compression equipment needs to use a liquid ring vacuum pump. After being compressed by the liquid ring vacuum pump, the volume of the ammonia decreases and the pressure increases.

[0003] The working fluid used in the liquid ring vacuum pump is propylene carbonate, in which part of ammonia and carbon dioxide are dissolved. The dissolved carbon dioxide easily reacts with ammonia to produce ammonium carbonate dissolved in the working fluid. When the ammonium carbonate dissolved in the working fluid reaches saturation, solid ammonium carbonate precipitates. The solid ammonium carbonate will cause the temperature of the liquid ring vacuum pump to rise, abnormal noise will occur, and affect the normal operation of the liquid ring vacuum pump. In order to eliminate the influence of solid ammonium carbonate on the liquid ring pump, the process of the liquid ring vacuum pump is improved, and the technology of the present invention is proposed. Summary of the invention

[0004] The present invention aims to provide a method for preventing ammonium carbonate from being saturated in the working fluid of a vacuum pump, thereby solving the problem of damage to the liquid ring vacuum pump caused by ammonium carbonate solids generated when the liquid ring vacuum pump transports a large amount of ammonia and a small amount of carbon dioxide, and prolonging the operating time of the vacuum pump.

[0005] In the present invention, the working liquid medium of the liquid ring vacuum pump is replaced with propylene glycol, propylene glycol is used as the working liquid, and an operation flow of the working liquid to the distillation tower is added to prevent the working liquid from reaching saturation during operation; the mixed liquid in the working liquid buffer tank is transported to the working liquid distillation tower for heating and separation by the working liquid pump, and the ammonium carbonate is decomposed into ammonia and carbon dioxide after heating, thereby reducing the concentration of the ammonium carbonate dissolved in the working liquid. The working liquid in the working liquid buffer tank is transported to the vacuum pump by the working liquid pump, and the working liquid dissolves the ammonium carbonate to form an unsaturated solution, and the ammonium carbonate and the working liquid in the vacuum pump are transported to the working liquid buffer tank by the pressure difference. Since propylene glycol has a certain water absorption, the water content of the pure propylene glycol working liquid increases after running for a period of time, and after being rectified by the working liquid distillation tower, water, ammonia and carbon dioxide are separated from the top of the tower, and the working liquid in the tower bottom passes through the tower bottom working liquid extraction pump, and enters the working liquid buffer tank after cooling, and the cooled working liquid dissolves most of the ammonium carbonate solids in the working liquid tank.

[0006] The present invention provides a method for preventing ammonium carbonate from being saturated in a vacuum pump working fluid, comprising the following contents: (1) Circulation of working fluid in vacuum pump and compression and transportation of ammonia: The ammonia produced by the reaction is passed into the working liquid buffer tank, and enters the liquid ring vacuum pump from the gas outlet on the top of the working liquid buffer tank. The working liquid medium in the liquid ring vacuum pump uses propylene glycol. The function of the liquid ring vacuum pump is to provide suction for the ammonia in the working liquid buffer tank and compress the ammonia at the same time. The compressed ammonia is directly sent to the compression device for processing, and the ammonia forms liquid ammonia after passing through the compression device.

[0007] The working fluid in the liquid ring vacuum pump enters the working fluid buffer tank through the pressure difference; the working fluid in the working fluid buffer tank is respectively transported to the liquid ring vacuum pump through the working fluid pump and transported to the working fluid distillation tower through the working fluid ammonium removal pump.

[0008] Specifically, the mass content of propylene glycol in the propylene glycol working fluid is more than 90%, and the water content is less than 10%; the amount of propylene glycol used is related to the volume of the liquid ring vacuum pump and the volume of the working fluid buffer tank; the working fluid accounts for 20%~80% of the volume of the liquid ring vacuum pump, the working fluid accounts for 20%~50% of the volume of the working fluid buffer tank, and the working fluid accounts for 20%~50% of the volume of the bottom of the working fluid distillation tower; during operation, the stability of the liquid level in the liquid ring vacuum pump and the working fluid buffer tank must be ensured first.

[0009] (2) The working liquid containing unsaturated ammonium carbonate is sent to the distillation tower for heating and decomposition: A portion of the working fluid is transported to the working fluid distillation tower through the working fluid ammonium removal pump and enters the distillation tower for separation. The distillation tower kettle is equipped with a reboiler heater to heat the working fluid and the ammonium carbonate solid carried by the working fluid to 100°C~150°C. The ammonium carbonate is decomposed into ammonia and carbon dioxide by heat, and the water absorbed in the working fluid is also separated.

[0010] (3) The working fluid is recycled after being cooled: The working fluid extracted from the distillation tower kettle is cooled by a cooler and then enters the working fluid buffer tank. The working fluid is recycled and the temperature of the working fluid reaches 30°C~40°C after cooling.

[0011] The specific process of the above method is as follows: working fluid is stored in a working fluid buffer tank, and ammonia enters the working fluid buffer tank; the gas outlet of the working fluid buffer tank is connected to a liquid ring vacuum pump, and the liquid ring vacuum pump is used to compress ammonia. After the ammonia is compressed in the liquid ring vacuum pump, the gas phase outlet pressure of the liquid ring vacuum pump is higher than the gas phase inlet pressure; the working fluid pump provides power for the working fluid to enter the liquid ring vacuum pump, and the working fluid in the liquid ring vacuum pump enters the working fluid buffer tank through a pressure difference (forming a cycle); when the liquid ring vacuum pump is working, the pressure of the working fluid buffer tank and the front system pressure can reach -90kPa (G) ~ -10kPa (G), the outlet pressure can reach 50kPa (G) ~ 260kPa (G), and the suction volume can reach 1000kg / h ~ 3500kg / h.

[0012] Part of the working liquid enters the pipeline of the working liquid distillation tower through the working liquid ammonium removal pump to distill the working liquid. After distillation, the ammonia content and water content in the working liquid are reduced, and the ammonium carbonate solid is also removed, thereby achieving the purpose of making the liquid ring vacuum pump work for a long time; the working liquid after distillation is extracted through the working liquid distillation tower bottom extraction pump to extract the distillation tower bottom liquid (working liquid), and then the working liquid is cooled in the cooler and enters the working liquid buffer tank.

[0013] The invention provides a device for preventing ammonium carbonate from being saturated in the working fluid of a vacuum pump, comprising a working fluid buffer tank, a liquid ring vacuum pump, a compression device, a working fluid distillation tower, a working fluid distillation tower kettle extraction pump, a working fluid cooler, a working fluid pump and a working fluid ammonium removal pump; The liquid ring vacuum pump is provided with a gas phase inlet and a gas phase outlet at the top, a working fluid inlet at the middle, and a working fluid outlet at the bottom; The working liquid buffer tank provides a storage place for the working liquid and transports ammonia to the liquid ring vacuum pump; the bottom of the working liquid buffer tank is respectively connected to the working liquid pump and the working liquid ammonium removal pump, and the working liquid pump outlet is connected to the working liquid inlet of the liquid ring vacuum pump; the working liquid outlet of the liquid ring vacuum pump is connected to the working liquid buffer tank; the working liquid ammonium removal pump is connected to the working liquid distillation tower; ammonia enters the working liquid buffer tank from the ammonia inlet in the middle of the working liquid buffer tank, and the gas outlet at the top of the working liquid buffer tank is connected to the gas phase inlet of the liquid ring vacuum pump, so that the working liquid buffer tank realizes the function of transporting ammonia.

[0014] The bottom of the working liquid distillation tower is connected to the tower bottom extraction pump, the other end of the tower bottom extraction pump is connected to the working liquid cooler, and the working liquid cooler is connected to the working liquid buffer tank.

[0015] The flow rate of the working fluid pump and the working fluid ammonium removal pump should reach 50m 3 / h~80m 3 / h, head 50m~70m, design temperature of working fluid distillation tower is 105-200℃, design pressure of working fluid is 0.1-0.5MPa. Design working fluid inlet temperature of working fluid cooler is 100-200℃, working fluid outlet temperature is 30-40℃.

[0016] Beneficial effects of the present invention: (1) The additional working liquid distillation tower in the present invention solves the problem of crystallization of the working liquid in the original liquid ring vacuum pump and increases the working time of the liquid ring vacuum pump; (2) The cyclic operation of the working fluid buffer tank and the liquid ring vacuum pump provided by the present invention realizes the cyclic use of the working fluid, and the circulation of the working fluid reduces the consumption of the working fluid and reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1It is the working process diagram of the vacuum pump in the comparative example; Figure 2 This is a working diagram of the vacuum pump in Example 1 of the present invention.

[0018] In the figure: 1-working liquid buffer tank, 2-ammonia inlet, 3-liquid ring vacuum pump, 4-liquid ring vacuum pump gas phase inlet, 5-liquid ring vacuum pump gas phase outlet, 6-liquid ring vacuum pump working liquid inlet, 7-liquid ring vacuum pump working liquid outlet, 8-working liquid pump, 9-compression device, 10-working liquid distillation tower, 11-working liquid distillation tower kettle extraction pump, 12-working liquid cooler, 13-working liquid ammonium removal pump. DETAILED DESCRIPTION

[0019] Comparative Example: Using Propylene Carbonate as the Working Fluid Medium A company uses propylene glycol and urea to react to produce propylene carbonate and ammonia. In the process of producing propylene carbonate and ammonia, there are certain side reactions, which produce carbon dioxide and a small amount of water. Ammonia and carbon dioxide dissolve in the working fluid, which will cause ammonia and carbon dioxide to react to form ammonium carbonate solid, causing the liquid ring vacuum pump to shut down. Figure 1 The process shown in the figure is run with the following process parameters: propylene carbonate with a purity of 99.9% is used as the working fluid, 9-10m³ of working fluid is added to the liquid ring vacuum pump to reach 50-55% of the vacuum pump volume; 3-4m³ of working fluid is added to the buffer tank to reach 45-50% of the working fluid tank. Figure 1 The process compresses ammonia. At the beginning, the ammonia flow rate is 1000-1500kg / h, and the operating temperature of the vacuum pump is 30-40℃; within 1-2 hours of operation, the temperature of the vacuum pump rises to 38-45℃; within 2-4 hours of operation, the temperature of the vacuum pump rises to 40-50℃, and within 4-6 hours of operation, the temperature of the vacuum pump rises to 50-60℃; after 6 hours of operation, the vacuum pump makes an abnormal sound and stops. The liquid ring vacuum pump is disassembled for inspection. A large amount of solids are found inside, which are analyzed to be ammonium carbonate solids.

[0020] The specific process and implementation effect of the present invention are described in detail below: The method of the present invention is used to treat ammonia produced by the reaction of propylene glycol and urea, such as Figure 2 As shown, the device for preventing the saturation of ammonium carbonate in the working fluid of the vacuum pump comprises a working fluid buffer tank 1, a liquid ring vacuum pump 3, a compression device 9, a working fluid distillation tower 10, a working fluid distillation tower kettle extraction pump 11, a working fluid cooler 12, a working fluid pump 8 and a working fluid ammonium removal pump 13; The top of the liquid ring vacuum pump 3 is provided with a liquid ring vacuum pump gas phase inlet 4 and a liquid ring vacuum pump gas phase outlet 5, the middle is provided with a liquid ring vacuum pump working fluid inlet 6, and the bottom is provided with a liquid ring vacuum pump working fluid outlet 7; The working liquid buffer tank 1 provides a storage place for the working liquid, and an ammonia inlet 2 is arranged in the middle; the gas outlet at the top of the working liquid buffer tank is connected to the gas phase inlet 4 of the liquid ring vacuum pump, and the bottom of the working liquid buffer tank is respectively connected to the working liquid pump 8 and the working liquid ammonium removal pump 13, the working liquid pump 8 outlet is connected to the working liquid inlet 6 of the liquid ring vacuum pump, and the working liquid ammonium removal pump 13 is connected to the working liquid distillation tower 10; the working liquid outlet 7 of the liquid ring vacuum pump is connected to the working liquid buffer tank 1, so as to realize the recycling of the working liquid; ammonia enters the working liquid buffer tank from the ammonia inlet in the middle of the working liquid buffer tank, and the gas outlet at the top of the working liquid buffer tank is connected to the gas phase inlet of the liquid ring vacuum pump, so that the working liquid buffer tank realizes the function of conveying ammonia.

[0021] The bottom of the working liquid distillation tower 10 is connected to a working liquid distillation tower kettle extraction pump 11 , and the other end of the working liquid distillation tower kettle extraction pump is connected to a working liquid cooler 12 , and the working liquid cooler 12 is connected to the working liquid buffer tank 1 .

[0022] The flow rate of the working liquid ammonium removal pump and the working liquid pump should reach 50m 3 / h~80m 3 / h, head 50m~70m, design temperature of working fluid distillation tower is 105-200℃, design pressure of working fluid is 0.1-0.5MPa. Design working fluid inlet temperature of working fluid cooler is 100-200℃, working fluid outlet temperature is 30-40℃.

[0023] The method for preventing the saturation of ammonium carbonate in the working fluid of a vacuum pump by using the above device comprises the following contents: (1) The ammonia produced by the reaction is passed into the working liquid buffer tank and enters the liquid ring vacuum pump from the gas outlet at the top of the working liquid buffer tank. Propylene glycol is used as the working liquid medium in the liquid ring vacuum pump. The function of the liquid ring vacuum pump is to provide suction for the ammonia in the working liquid buffer tank and compress the ammonia at the same time. The gas outlet of the working liquid buffer tank is connected to the liquid ring vacuum pump, and the liquid ring vacuum pump is used to compress the ammonia. After the ammonia is compressed in the liquid ring vacuum pump, the gas phase outlet pressure of the liquid ring vacuum pump is higher than the gas phase inlet pressure. The working liquid pump provides power for the working liquid to enter the liquid ring vacuum pump. The working liquid in the liquid ring vacuum pump enters the working liquid buffer tank through the pressure difference, forming a cycle. The compressed ammonia gas is directly sent to the compression device 9 for processing, and after passing through the compression device, the ammonia gas becomes liquid ammonia.

[0024] The working liquid in the working liquid buffer tank 1 is transported to the liquid ring vacuum pump 3 through the working liquid pump 8 and transported to the working liquid distillation tower 10 through the working liquid ammonium removal pump 13 .

[0025] Specifically, the mass content of propylene glycol in the propylene glycol working fluid is more than 90%, and the water content is less than 10%; the amount of propylene glycol used is related to the volume of the liquid ring vacuum pump and the volume of the working fluid buffer tank; the working fluid accounts for 20%~80% of the volume of the liquid ring vacuum pump, and the working fluid accounts for 20%~50% of the volume of the working fluid buffer tank; during operation, the stability of the liquid level in the liquid ring vacuum pump and the working fluid buffer tank must be ensured first.

[0026] When the liquid ring vacuum pump is working, the pressure of the working liquid buffer tank and the front system pressure can reach -90kPa (G) ~ -10kPa (G), the outlet pressure can reach 50kPa (G) ~ 260kPa (G), and the suction volume can reach 1000kg / h ~ 3500kg / h.

[0027] (2) A portion of the working liquid is transported to the working liquid distillation tower through the working liquid ammonium removal pump and enters the distillation tower for separation. The distillation tower kettle is equipped with a reboiler heater to heat the working liquid and heat the ammonium carbonate solid carried by the working liquid to 100℃~150℃. The ammonium carbonate is decomposed into ammonia and carbon dioxide by heat, and the water absorbed in the working liquid is also separated. After distillation, the ammonia content and water content in the working liquid are reduced, and the ammonium carbonate solid is also removed, achieving the purpose of making the liquid ring vacuum pump work for a long time; the working liquid after distillation is extracted through the working liquid distillation tower kettle extraction pump to extract the distillation tower kettle liquid (working liquid), and then the working liquid is cooled by the cooler and enters the working liquid buffer tank.

[0028] (3) The working fluid is recycled after being cooled: The working fluid extracted from the distillation tower kettle is cooled by the working fluid cooler and then enters the working fluid buffer tank. The working fluid is recycled and the working fluid temperature reaches 30℃~40℃ after cooling.

[0029] The present invention is further described below by way of examples, but is not limited to the following examples. Specific process parameters and effects are described as follows: Example 1

[0030] according to Figure 2The device shown is implemented, the working liquid is replaced by propylene carbonate with propylene glycol, and the mass content of propylene glycol in the working liquid is 91%, that is, the water content is 9%. 9m³ of working liquid is added to the liquid ring vacuum pump, reaching 50% of the volume of the vacuum pump; 3m³ of working liquid is added to the buffer tank, reaching 50% of the volume of the working liquid tank; 8m³ of working liquid is added to the working liquid distillation tower kettle, reaching 55% of the working liquid distillation tower kettle volume, and 20 m³ of working liquid is added to the system. The ammonia flow rate is 1000kg / h for one day, the pressure of the working liquid buffer tank and the front system is -60kPa (G) ~ -50kPa (G), and the working temperature of the working liquid distillation tower kettle is 100 ~ 105℃. Samples are taken every 2 hours, and the water content of the working liquid in the working liquid distillation tower kettle is 5% to 6%, and the water content of the working liquid in the working liquid buffer tank is 7% to 8%. The working temperature of the vacuum pump is maintained at 35-45℃, the flow rate of the working liquid ammonium removal pump to the working liquid distillation tower is maintained at 30m³ / h, the flow rate of the working liquid pump to the liquid ring vacuum pump is maintained at 25m³ / h, and the liquid level of the liquid ring vacuum pump fluctuates between 40-60%, the liquid level of the buffer tank fluctuates between 40-50%, and the liquid level of the working liquid distillation tower fluctuates between 40-50%.

[0031] Subsequently, the ammonia flow rate was increased to 1500kg / h, and the working liquid pump was maintained at a flow rate of 25m³ / h to the liquid ring vacuum pump, and the working liquid ammonium removal pump was maintained at a flow rate of 30m³ / h to the working liquid distillation tower. The ammonia flow rate was increased to 1500kg / h and sampled after running for 1 hour. The water content of the working liquid in the working liquid distillation tower kettle was 5.5%, and the water content of the working liquid in the working liquid buffer tank was 8%. At this time, the pressure of the working liquid buffer tank and the front system was -55kPa (G), the working temperature of the vacuum pump was 35℃, and the working temperature of the working liquid distillation tower kettle was 105℃. The ammonia flow rate was increased to 1500kg / h and sampled after running for 2 hours. The water content of the working liquid in the working liquid distillation tower kettle was 6%, and the water content of the working liquid in the working liquid buffer tank was 9%. At this time, the pressure of the working liquid buffer tank and the front system was -58kPa (G), the working temperature of the vacuum pump was 37℃, and the working temperature of the working liquid distillation tower kettle was 101℃. The ammonia flow rate was increased to 1500kg / h and samples were taken after running for 3 hours. The water content of the working liquid in the working liquid distillation tower kettle was 8%, and the water content of the working liquid in the working liquid buffer tank was 10%. At this time, the pressure of the working liquid buffer tank and the front system was -50kPa (G), the operating temperature of the vacuum pump was 40°C, and the working temperature of the working liquid distillation tower kettle was.

[0032] The ammonia flow rate was increased to 1500kg / h and the operation was adjusted for 3-4h. The flow rate of the working liquid ammonium removal pump to the working liquid distillation tower was increased to 40m³ / h, the operating temperature of the working liquid distillation tower was increased to 120℃, and the ammonia flow rate was increased to 1500kg / h. After running for 4h, the sampling was taken. The water content of the working liquid in the working liquid distillation tower was 5%, and the water content of the working liquid in the working liquid buffer tank was 7%. At this time, the pressure of the working liquid buffer tank and the front system was -50kPa (G), the operating temperature of the vacuum pump was 35℃, and the working temperature of the working liquid distillation tower was 119℃. Subsequently, the operating temperature of the working liquid distillation tower was maintained at 115-120℃, and the ammonia flow rate was increased to 1500kg / h for 5-12h operation data. See Table 1.

[0033] Table 1

[0034] Subsequently, the ammonia flow rate was increased to 2000 kg / h and the system was operated for 7 days. The operating data are shown in Table 2.

[0035] Table 2

[0036] During the operation of ammonia flow, maintain the liquid level of the liquid ring vacuum pump at 40-60%, and the liquid level of the working liquid buffer tank at 40-50%. Maintain the working liquid distillation liquid level at 40-50%. Control the water content of the working liquid in the working liquid buffer tank at 6.0-7.0%, and control the water content of the working liquid in the working liquid distillation tower kettle at 4.0-6.5%. When the water content of the working liquid in the working liquid buffer tank continues to rise, under the premise of stabilizing the liquid level of the vacuum pump, the liquid level of the working liquid buffer tank, and the working liquid distillation liquid level, simultaneously increase the working temperature of the working liquid distillation tower kettle and the flow rate of the working liquid ammonium removal pump to the working liquid distillation tower.

Claims

1. A method for preventing saturation of ammonium carbonate in a vacuum pump working fluid, characterized in that The invention comprises the following contents: working liquid is stored in a working liquid buffer tank, ammonia enters the working liquid buffer tank, the working liquid buffer tank sends ammonia to a liquid ring vacuum pump, and ammonia is compressed in the liquid ring vacuum pump; the gas phase outlet pressure of the liquid ring vacuum pump is higher than the gas phase inlet pressure, and the working liquid in the liquid ring vacuum pump enters the working liquid buffer tank through the pressure difference; part of the working liquid in the working liquid buffer tank enters the pipeline of the working liquid distillation tower through the working liquid ammonium removal pump, and the working liquid is distilled. After distillation, the ammonia content and the water content in the working liquid are reduced, and the ammonium carbonate solid is also removed, so that the purpose of making the liquid ring vacuum pump work for a long time is achieved; the working liquid after distillation enters the working liquid buffer tank after passing through the working liquid distillation tower kettle extraction pump and the working liquid cooler.

2. The method for preventing ammonium carbonate saturation in a vacuum pump working fluid according to claim 1, characterized in that: (1) Circulation of working fluid in vacuum pump and compression and transportation of ammonia: The ammonia produced by the reaction is passed into the working liquid buffer tank, and enters the liquid ring vacuum pump from the gas outlet on the top of the working liquid buffer tank. The working liquid medium in the liquid ring vacuum pump uses propylene glycol; the liquid ring vacuum pump provides suction for the ammonia in the working liquid buffer tank and compresses the ammonia at the same time; the compressed ammonia is directly sent to the compression device for processing, and the ammonia becomes liquid ammonia after passing through the compression device; The working fluid in the liquid ring vacuum pump enters the working fluid buffer tank through the pressure difference; the working fluid in the working fluid buffer tank is respectively transported to the liquid ring vacuum pump through the working fluid pump and transported to the working fluid distillation tower through the working fluid ammonium removal pump; (2) The working liquid containing unsaturated ammonium carbonate is sent to the distillation tower for heating and decomposition: A part of the working liquid is transported to the working liquid distillation tower through the working liquid ammonium removal pump and enters the distillation tower for separation. The distillation tower kettle is equipped with a reboiler heater to heat the working liquid and the ammonium carbonate solid carried by the working liquid to 100℃~150℃. The ammonium carbonate is decomposed into ammonia and carbon dioxide by heat, and the water absorbed in the working liquid is also separated; (3) The working fluid is recycled after being cooled: The working fluid extracted from the distillation tower kettle is cooled by a cooler and then enters the working fluid buffer tank. The working fluid is recycled and the temperature of the working fluid reaches 30-40°C after cooling.

3. The method for preventing ammonium carbonate saturation in the working fluid of a vacuum pump according to claim 2, characterized in that: The mass content of propylene glycol in the propylene glycol working fluid is more than 90%, and the water content is less than 10%; the working fluid accounts for 20%~80% of the volume of the liquid ring vacuum pump, the working fluid accounts for 20%~50% of the volume of the working fluid buffer tank, and the working fluid accounts for 20%~50% of the volume at the bottom of the working fluid distillation tower; during operation, the liquid level in the liquid ring vacuum pump and the working fluid buffer tank is guaranteed to be stable.

4. The method for preventing saturation of ammonium carbonate in a vacuum pump working fluid according to claim 2, characterized in that: When the liquid ring vacuum pump is working, the gauge pressure of the working liquid buffer tank reaches -90kPa~-10kPa, the outlet gauge pressure reaches 50kPa~260kPa, and the suction volume reaches 1000kg / h~3500kg / h.

5. A device for preventing ammonium carbonate from being saturated in a vacuum pump working fluid, used for implementing the method for preventing ammonium carbonate from being saturated in a vacuum pump working fluid according to any one of claims 1 to 4, characterized in that: It includes a working liquid buffer tank, a liquid ring vacuum pump, a compression device, a working liquid distillation tower, a working liquid distillation tower kettle extraction pump, a working liquid cooler, a working liquid pump and a working liquid ammonium removal pump; The liquid ring vacuum pump is provided with a gas phase inlet and a gas phase outlet at the top, a working fluid inlet at the middle, and a working fluid outlet at the bottom; The working liquid buffer tank provides a storage place for the working liquid and transports ammonia to the liquid ring vacuum pump; the bottom of the working liquid buffer tank is respectively connected to the working liquid pump and the working liquid ammonium removal pump, and the working liquid outlet of the liquid ring vacuum pump is connected to the working liquid buffer tank; the working liquid ammonium removal pump is connected to the working liquid distillation tower; The bottom of the working liquid distillation tower is connected to the tower bottom extraction pump, the other end of the tower bottom extraction pump is connected to the working liquid cooler, and the working liquid cooler is connected to the working liquid buffer tank.

6. The device for preventing ammonium carbonate saturation in the working fluid of a vacuum pump according to claim 5, characterized in that: The gas outlet at the top of the working liquid buffer tank is connected to the gas phase inlet of the liquid ring vacuum pump, and the working liquid buffer tank realizes the function of conveying ammonia.

7. The device for preventing ammonium carbonate saturation in the working fluid of a vacuum pump according to claim 5, characterized in that: The flow rate of the working fluid pump and the working fluid ammonium removal pump should reach 50m 3 / h~80m 3 / h, head 50m~70m.

8. The device for preventing ammonium carbonate saturation in the working fluid of a vacuum pump according to claim 5, characterized in that: The design temperature of the working liquid distillation tower is 105-200°C, and the design pressure of the working liquid distillation tower is 0.1-0.5MPa; the working liquid inlet temperature of the working liquid cooler is 100-200°C, and the working liquid outlet temperature is 30-40°C.

Images