Cryogenic air separation steam condensate recovery system and control method thereof

Abstract

The invention relates to a deep cooling air separation steam condensate recovery system and a control method thereof, and relates to the technical field of condensate recovery, the deep cooling air separation steam condensate recovery system comprises a heat exchanger and a water collecting well, and the heat exchanger is provided with a cooling inlet, a cooling outlet, a heating inlet and a heating outlet; a condensate water input pipe, a first self-priming pump, a second self-priming pump and an overflow pipe are arranged on the water collecting well in a communicating mode, a condensate water input valve is arranged on the condensate water input pipe, an overflow valve is arranged on the overflow pipe, and the output end of the first self-priming pump and the output end of the second self-priming pump are both communicated with a cooling inlet. A circulating pump is arranged on the cooling outlet in a communicating manner, a waste nitrogen inlet pipe is arranged on the heating inlet in a communicating manner, a waste nitrogen inlet valve is arranged on the waste nitrogen inlet pipe, a waste nitrogen outlet pipe is arranged on the heating outlet in a communicating manner, a waste nitrogen bypass pipe is arranged on the waste nitrogen outlet in a communicating manner, and a silencer and an emptying valve are arranged on the waste nitrogen bypass pipe; and a waste nitrogen outlet valve is arranged on the waste nitrogen outlet pipe. The cooling device has the effect of reducing severe corrosion and blockage of the cooler.

Description

Technical Field

[0001] The present invention relates to the technical field of condensate recovery, and in particular to a deep-cold air separation steam condensate recovery system and a control method thereof. Background Art

[0002] The cryogenic air separation process is used to produce nitrogen, oxygen and argon in medium to large factories. For large factories in the metallurgy, petrochemical and other industries in China, it is the preferred technology for obtaining high-purity industrial oxygen and nitrogen.

[0003] The main equipment of cryogenic air separation is composed of: self-cleaning filter, air compressor, pre-cooling system, molecular sieve purification system, booster, expander, fractionation tower system, nitrogen compression system, spherical tank, liquid storage tank and backup system, etc. The basic principle of cryogenic air separation process is to cool the air to the liquefaction temperature, so that each component in it becomes liquid, and then separate them according to the difference in boiling points of different components.

[0004] For large factories located at the seaside, the chloride ion content in the raw water at the seaside is relatively high, resulting in poor water quality for the new water obtained after the water plant treats the raw water at the seaside. Using the new water obtained after treating the raw water at the seaside as circulating water for the air separation unit will cause serious corrosion of the interstage coolers of various compressors in the air separation unit, causing blockage of the cooler and affecting the heat exchange efficiency. Summary of the invention

[0005] In order to reduce the serious blockage of cooler corrosion and improve the stability of air separation unit operation, the present application provides a deep-cold air separation steam condensate recovery system and a control method thereof.

[0006] The present application provides a cryogenic air separation steam condensate recovery system that adopts the following technical solution: A deep cold air separation steam condensate recovery system comprises a heat exchanger, wherein the heat exchanger is provided with a cooling inlet, a cooling outlet, a heating inlet and a heating outlet, and also comprises a water collecting well, wherein a condensate input pipe, a first self-priming pump, a second self-priming pump and an overflow pipe are connected to the water collecting well, a condensate input valve is provided on the condensate input pipe, an overflow valve is provided on the overflow pipe, an output end of the first self-priming pump and an output end of the second self-priming pump are both connected to the cooling inlet, a circulating pump is provided on the cooling outlet, a dirty nitrogen inlet pipe is provided on the heating inlet, a dirty nitrogen inlet valve is provided on the dirty nitrogen inlet pipe, a dirty nitrogen outlet pipe is provided on the heating outlet, a dirty nitrogen outlet pipe is provided on the dirty nitrogen outlet pipe, a dirty nitrogen bypass pipe is provided on the dirty nitrogen bypass pipe, a muffler and a vent valve are provided on the dirty nitrogen outlet pipe, and a dirty nitrogen outlet valve is provided on the dirty nitrogen outlet pipe.

[0007] By adopting the above technical scheme, when the molecular sieve steam heater is not heating, the condensed water generated in the cryogenic air separation process enters the water collection well for storage through the condensed water inlet pipe. When the molecular sieve steam heater is heating, the heat exchanger is started, and the condensed water in the water collection well is passed into the heat exchanger through the cooling inlet, and the dirty nitrogen is passed into the heat exchanger through the dirty nitrogen inlet pipe. The condensed water and the dirty nitrogen are heat-exchanged in the heat exchanger. The dirty nitrogen is heated and discharged from the heating outlet. The condensed water is cooled and discharged from the cooling outlet. The dirty nitrogen discharged from the heating outlet enters the molecular sieve steam heater, and the condensed water discharged from the cooling outlet is pumped into the cooler. In the process, condensed water is used as circulating water of the air separation unit. Since the quality of condensed water is close to pure water, the circulating water quality of the air separation unit is improved and the blockage caused by serious corrosion of the cooler is reduced. Since the water temperature of condensed water is between 80-90℃, the condensed water is cooled before being incorporated into the circulating water network, which reduces the impact on the water temperature of the circulating water system and improves the operation stability of the air separation unit. In addition, the dirty nitrogen is used for heat exchange with the condensed water. While cooling the condensed water, the dirty nitrogen temperature is increased, the energy consumption of the molecular sieve steam heater is reduced, and the effect of condensed water heat recovery is achieved.

[0008] Preferably, the end of the condensate inlet pipe away from the water collection well is used to connect with the condensate outlet of the molecular sieve steam heater, the condensate outlet of the distillation tower steam ejector and the condensate outlet of the liquid storage tank water bath vaporizer. A maintenance manhole is provided on the water collection well, and a vacuum breaker and an automatic exhaust valve are provided on the top of the water collection well.

[0009] By adopting the above technical scheme, the condensed water produced by the molecular sieve steam heater, the distillation tower steam ejector and the liquid storage tank water bath vaporizer is discharged into the water collection well through the condensed water inlet pipe, the automatic exhaust valve discharges the secondary steam produced by the high-temperature condensed water inside the water collection well, the vacuum breaker makes it difficult for the high-temperature steam inside the water collection well to condense and produce negative pressure, so that the water collection well is not easy to crack or deform due to pressure buildup, and the inspection manhole facilitates the inspection and cleaning of the water collection well.

[0010] Preferably, a water level sensor is arranged in the water collection well, and the water level sensor is used to detect the internal height of the water collection well. The overflow pipe is located above the input end of the second self-priming pump, and the input end of the second self-priming pump is located above the input end of the first self-priming pump. A cooling inlet pipe is connected to the cooling inlet, a first water outlet pipe is connected between the output end of the first self-priming pump and the end of the cooling inlet pipe away from the cooling inlet, a first check valve is arranged on the first water outlet pipe, a second water outlet pipe is connected between the output end of the second self-priming pump and the end of the cooling inlet pipe away from the cooling inlet, and a second check valve is arranged on the second water outlet pipe.

[0011] By adopting the above technical solution, when the liquid level in the water collection well is too high, it is discharged into the stormwater channel through the overflow pipe. The first self-priming pump and the second self-priming pump are used in conjunction with each other to pump out the condensed water in the water collection well and pressurize it to provide kinetic energy for sending it into the heat exchanger. The first check valve and the second check valve prevent the condensed water from flowing back and damaging the first self-priming pump and the second self-priming pump.

[0012] Preferably, a cooling outlet pipe is provided between the cooling outlet and the input end of the circulation pump, and a temperature sensor is provided on the cooling outlet pipe.

[0013] By adopting the above technical solution, the temperature sensor detects the temperature of the condensed water after cooling, thereby controlling the amount of dirty nitrogen entering the heat exchanger.

[0014] Preferably, a condensate circulation pipe is connected to the output end of the circulation pump, a flow meter is provided on the condensate circulation pipe, and one end of the condensate circulation pipe away from the circulation pump is used for connection with a cooler.

[0015] By adopting the above technical solution, the flow meter detects the flow in the condensate circulation pipe, thereby controlling the start and stop of the circulation pump.

[0016] Preferably, a pressure sensor is provided on the dirty nitrogen outlet pipe, and the pressure sensor is located between the dirty nitrogen bypass pipe and the heat exchanger. The end of the dirty nitrogen outlet pipe away from the heat exchanger is used to be connected with the dirty nitrogen inlet of the molecular sieve steam heater. The dirty nitrogen outlet valve is located between the dirty nitrogen bypass pipe and the molecular sieve steam heater. The vent valve is located between the muffler and the dirty nitrogen outlet pipe.

[0017] By adopting the above technical solution, the pressure sensor detects the pressure in the dirty nitrogen outlet pipe and controls the start and stop of the vent valve and the muffler.

[0018] The present application provides a control method for a cryogenic air separation steam condensate recovery system using the following technical solution: A control method for a cryogenic air separation steam condensate recovery system comprises the following steps: S1, set the first water level threshold H1; set the third water level threshold H3; set the low temperature threshold T1; set the high temperature threshold T2; set the first flow value Q1; set the second flow value Q2; set the pressure value P; S2. Adjust the working status of the circulation pump, vent valve and muffler; S3, detecting the working status of the molecular sieve steam heater; S4, if the molecular sieve steam heater is heating, the heat exchanger works, the dirty nitrogen inlet pipe and the dirty nitrogen outlet pipe are connected, and step S5 is performed; if the molecular sieve steam heater is not heating, the heat exchanger stops working, and the dirty nitrogen inlet pipe and the dirty nitrogen outlet pipe are both cut off, and step S6 is performed; S5, adjust the water collection well to drainage mode and proceed to step S2; S6. Adjust the water collection well to the water storage mode and proceed to step S2.

[0019] By adopting the above technical scheme, when the molecular sieve steam heater is not heating, the condensed water generated in the cryogenic air separation process enters the water collection well for storage through the condensed water inlet pipe. When the molecular sieve steam heater is heating, the water collection well passes the condensed water into the heat exchanger to exchange heat with the contaminated nitrogen. The cooled condensed water is used as the circulating water of the air separation base, thereby achieving the effect of improving the water quality of the circulating water of the air separation base.

[0020] Preferably, step S2 comprises the following steps: S21, detecting the flow data q in the condensate circulation pipe; detecting the pressure data p in the dirty nitrogen outlet pipe; S22. If the flow data q in the condensate circulation pipe is not greater than the first flow value Q1, the circulation pump stops; if the flow data q in the condensate circulation pipe is greater than the second flow value Q2, the circulation pump stops; if the flow data q in the condensate circulation pipe is greater than the first flow value Q1, and the flow data q in the condensate circulation pipe is less than the second flow value Q2, the circulation pump runs; if the flow data q in the condensate circulation pipe is equal to the second flow value Q2, the circulation pump maintains the current state; if the pressure data p in the dirty nitrogen outlet pipe is greater than the pressure value P, the vent valve opens and the muffler runs; if the pressure data p in the dirty nitrogen outlet pipe is less than the pressure value P, the vent valve closes and the muffler stops; if the pressure data p in the dirty nitrogen outlet pipe is equal to the pressure value P, the vent valve and the muffler maintain the current state.

[0021] By adopting the above technical solution, the working states of the circulation pump, the vent valve and the muffler are dynamically adjusted, the degree of automation of the circulation pump, the vent valve and the muffler is improved, and the unnecessary working time of the circulation pump, the vent valve and the muffler is reduced.

[0022] Preferably, step S5 comprises the following steps: S51, reading the temperature data t of the condensed water in the cooling outlet pipe; S52, if the condensed water temperature data t at the cooling outlet is greater than the high temperature threshold value T2, the dirty nitrogen inlet valve opening is increased; if the condensed water temperature data t at the cooling outlet is less than the low temperature threshold value T1, the dirty nitrogen inlet valve opening is reduced; if the condensed water temperature data t at the cooling outlet is not greater than the high temperature threshold value T2, and the condensed water temperature data t at the cooling outlet is not less than the low temperature threshold value T1, the dirty nitrogen inlet valve opening remains unchanged; S53, reading the liquid level height data h in the water collection well; S54, if the water collection well liquid level height data h is greater than the third height threshold H3, then proceed to step S55; if the water collection well liquid level height data h is less than the first height threshold H1, then a low water level alarm is triggered, the condensate input valve is fully opened, the overflow valve is fully closed, the first self-priming pump, the second self-priming pump and the heat exchanger are adjusted to a stopped state, and step S2 is performed; if the water collection well liquid level height data h is not less than the first height threshold H1, and the water collection well liquid level height data h is not greater than the third height threshold H3, then the first self-priming pump is adjusted to a running state, and the second self-priming pump is adjusted to a stopped state, and step S2 is performed; S55, reducing the opening of the condensate input valve, increasing the opening of the overflow valve, and adjusting the first self-priming pump and the second self-priming pump to the operating state; S56, reading the liquid level height data h in the water collection well; S57. If the water collection well liquid level height data h is greater than the third height threshold H3, proceed to step S55; if the water collection well liquid level height data h is less than or equal to the third height threshold H3, increase the opening of the condensate input valve, reduce the opening of the overflow valve, set the second self-priming pump to close after one hour, and proceed to step S2.

[0023] By adopting the above technical scheme, during the heating process of the molecular sieve steam heater, when the liquid level of the water collection well is lower than the first height threshold, the water collection well only takes in water but does not discharge water. When the liquid level of the water collection well is between the first height threshold and the third height threshold, the first self-priming pump is operated to pump the condensed water in the water collection well into the heater. When the liquid level of the water collection well is higher than the third height threshold, the water inflow of the water collection well is reduced and the water discharge of the water collection well is increased until the liquid level of the water collection well is lower than the third height threshold, the water inflow of the water collection well is increased and the water discharge of the water collection well is gradually reduced. During the heating process of the molecular sieve steam heater, the dirty nitrogen enters the heat exchanger through the dirty nitrogen inlet pipe. When the temperature of the condensed water in the cooling outlet pipe exceeds the high temperature threshold, the amount of dirty nitrogen introduced is increased. When the temperature of the condensed water in the cooling outlet pipe is lower than the low temperature threshold, the amount of dirty nitrogen introduced is reduced. When the temperature of the condensed water in the cooling outlet pipe is between the low temperature threshold and the high temperature threshold, the amount of dirty nitrogen introduced remains unchanged, thereby achieving the effect of dynamically adjusting the heat exchange between condensed water and dirty nitrogen and rationally utilizing the thermal energy of condensed water.

[0024] Preferably, step S6 comprises the following steps: S61, adjusting the first self-priming pump and the second self-priming pump to a stopped state; S62, reading the liquid level height data h in the water collection well; S63. If the water collection well height data h is greater than the third height threshold H3, a high water level alarm is triggered, the condensate input valve is fully closed, the overflow valve is fully opened, and step S2 is performed; if the water collection well height data h is not greater than the third height threshold H3, the condensate input valve maintains a normal opening, the overflow valve is fully closed, and step S2 is performed.

[0025] By adopting the above technical solution, when the molecular sieve steam heater is not heating, when the liquid level in the water collection well is lower than the third height threshold, the condensate input pipe supplies water to the water collection well, and the overflow pipe is closed; when the liquid level in the water collection well exceeds the third height threshold, the condensate input pipe stops supplying water to the water collection well, and the overflow pipe is opened, and the condensate in the water collection well is discharged into the stormwater channel through the overflow pipe, so that the condensate generated in the cryogenic air separation process enters the water collection well through the condensate input pipe for storage.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. Use condensed water instead of raw water from the seaside to make new water, and use condensed water as circulating water for air separation units. Since the quality of condensed water is close to pure water, it can improve the quality of circulating water for air separation units and reduce the blockage caused by severe corrosion of coolers; 2. Cool the condensed water before adding it to the circulating water network, reducing the impact on the water temperature of the circulating water system, allowing the air separation unit to operate at a temperature, and using the dirty nitrogen to exchange heat with the condensed water. While cooling the condensed water, the dirty nitrogen temperature is increased, the energy consumption of the molecular sieve steam heater is reduced, and the effect of condensed water heat recovery is achieved; 3. The condensed water generated in the cryogenic air separation process enters the water collection well through the condensed water input pipe for storage. The condensed water in the water collection well is discharged into the heat exchanger for cooling. The cooled condensed water enters the air separation base, making full use of the steam condensed water generated in the heat exchange process of the air separation process to achieve the effect of water resource recycling and reduce the waste of water resources. According to the liquid level of the water collection well and the working mode of the molecular sieve steam heater, the water inlet and outlet of the water collection well are adjusted to reduce the overflow of the water collection well; 4. Dynamically adjust the working status of the circulating pump, vent valve and muffler, improve the automation level of the circulating pump, vent valve and muffler, and reduce the unnecessary working time of the circulating pump, vent valve and muffler; 5. Dynamically adjust the opening of the dirty nitrogen inlet valve to improve the utilization rate of condensed water heat recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a deep-cold air separation steam condensate recovery system in an embodiment of the present application.

[0028] Figure 2 It is a schematic diagram showing the connection relationship between the water collection well and the cooling inlet pipe in the embodiment of the present application.

[0029] Figure 3 It is a schematic diagram showing the connection relationship between the heat exchanger and the condensate circulation pipe in the embodiment of the present application.

[0030] Figure 4 It is a schematic diagram showing the connection relationship between the dirty nitrogen outlet pipe and the dirty nitrogen bypass pipe in the embodiment of the present application.

[0031] Figure 5 It is a flow chart of a method for controlling a deep-cold air separation steam condensate recovery system in an embodiment of the present application.

[0032] Figure 6 It is a flow chart showing the dynamic control of the circulation pump in the embodiment of the present application.

[0033] Figure 7 It is a flow chart showing the dynamic control of the vent valve and the muffler in the embodiment of the present application.

[0034] Figure 8 It is a flow chart showing the drainage mode of the water collection well in the embodiment of the present application.

[0035] Fig. 9 It is a flow chart showing the water storage mode of the water collection well in the embodiment of the present application.

[0036] Explanation of reference numerals: 1. heat exchanger; 11. cooling inlet; 111. cooling inlet pipe; 12. cooling outlet; 121. cooling outlet pipe; 122. temperature sensor; 13. heating inlet; 14. heating outlet; 2. water collection well; 21. condensate inlet pipe; 211. condensate inlet valve; 22. first self-priming pump; 221. first outlet pipe; 222. first check valve; 23. second self-priming pump; 231. second outlet pipe; 232. second check valve; 24. overflow pipe; 241. overflow valve; 25, inspection manhole; 26, vacuum breaker; 27, automatic exhaust valve; 28, water level sensor; 3, condensate circulation pipe; 31, circulation pump; 32, flow meter; 4, dirty nitrogen inlet pipe; 41, dirty nitrogen inlet valve; 5, dirty nitrogen outlet pipe; 51, dirty nitrogen outlet valve; 52, pressure sensor; 6, dirty nitrogen bypass pipe; 61, vent valve; 62, silencer; 7, cooler; 71, molecular sieve steam heater; 72, distillation tower steam ejector; 73, liquid storage tank water bath vaporizer; 74, stormwater drain. DETAILED DESCRIPTION

[0037] The following is combined with Figure 1-9 This application is described in further detail.

[0038] The present application embodiment discloses a deep cold air separation steam condensate water recovery system. Figures 1 to 4 , including a condensate input pipe 21, on which a condensate input valve 211 is installed. One end of the condensate input pipe 21 is connected to the condensate outlet of the molecular sieve steam heater 71, the condensate outlet of the fractionation tower steam ejector 72 and the condensate outlet of the liquid storage tank water bath vaporizer 73, and the other end of the condensate input pipe 21 is connected to the water collection well 2. When the molecular sieve steam heater 71 is not heated, the condensate generated in the cryogenic air separation process enters the water collection well 2 for storage through the condensate input pipe 21.

[0039] Reference Figures 1 to 4 A maintenance manhole 25, a vacuum breaker 26 and an automatic exhaust valve 27 are provided on the top of the water collection well 2. The maintenance manhole 25, the vacuum breaker 26 and the automatic exhaust valve 27 are all connected to the water collection well 2. The automatic exhaust valve 27 discharges the secondary steam generated by the high-temperature condensed water inside the water collection well 2. The vacuum breaker 26 makes it difficult for the high-temperature steam inside the water collection well 2 to condense and generate negative pressure, so that the water collection well 2 is not easy to crack or deform due to pressure holding. The maintenance manhole 25 facilitates the maintenance and cleaning of the water collection well 2.

[0040] Reference Figures 1 to 4 A water level sensor 28 is installed in the water collection well 2, and an overflow pipe 24 is installed on the side wall of the water collection well 2. One end of the overflow pipe 24 is connected to the water collection well 2, and the other end of the overflow pipe 24 is connected to the rainwater canal 74. An overflow valve 241 is installed on the overflow pipe 24. When the liquid level in the water collection well 2 is too high, it is discharged into the rainwater canal 74 through the overflow pipe 24.

[0041] Reference Figures 1 to 4 , the first self-priming pump 22 and the second self-priming pump 23 are installed on the water collection well 2, and the input end of the first self-priming pump 22 and the input end of the second self-priming pump 23 are both connected to the water collection well 2. The input end of the overflow pipe 24 is located above the input end of the second self-priming pump 23, and the input end of the second self-priming pump 23 is located above the input end of the first self-priming pump 22. The output end of the first self-priming pump 22 is connected to the first water outlet pipe 221, and the first check valve 222 is installed on the first water outlet pipe 221; the output end of the second self-priming pump 23 is connected to the second water outlet pipe 231, and the second check valve 232 is installed on the second water outlet pipe 231. The first self-priming pump 22 and the second self-priming pump 23 are used and the second self-priming pump 23 is used and the second self-priming pump 23 is used and the second self-priming pump 23 is used and the condensed water in the water collection well 2 is pumped out and pressurized to provide kinetic energy to be sent to the heat exchanger 1. The first check valve 222 and the second check valve 232 prevent the condensed water from flowing back and causing damage to the first self-priming pump 22 and the second self-priming pump 23.

[0042] Reference Figures 1 to 4 The first outlet pipe 221 is connected to one end of the first self-priming pump 22 and the second outlet pipe 231 is connected to one end of the second self-priming pump 23, and a cooling inlet pipe 111 is connected to the cooling inlet pipe 111. The heat exchanger 1 is provided with a cooling inlet 11, a cooling outlet 12, a heating inlet 13 and a heating outlet 14. A cooling channel is connected between the cooling inlet 11 and the cooling outlet 12, and a heating channel is connected between the heating inlet 13 and the heating outlet 14. The cooling inlet 11 is connected to the cooling inlet pipe 111, and the condensed water in the water collection well 2 enters the heat exchanger 1 for heat exchange and cooling.

[0043] Reference Figures 1 to 4The cooling outlet 12 is connected to a cooling outlet pipe 121, a circulating pump 31 is connected to the cooling outlet pipe 121, a condensed water circulating pipe 3 is connected to the output end of the circulating pump 31, a flow meter 32 is arranged on the condensed water circulating pipe 3, and the end of the condensed water circulating pipe 3 away from the circulating pump 31 is used to communicate with the cooler 7. The flow meter 32 detects the flow in the condensed water circulating pipe 3, thereby controlling the start and stop of the circulating pump 31, and sending the cooled condensed water into the air separation base, so that the condensed water is used as the circulating water of the air separation base, and the water quality of the circulating water of the air separation base is improved.

[0044] Reference Figures 1 to 4 , a temperature sensor 122 is installed on the cooling outlet pipe 121. A dirty nitrogen inlet pipe 4 is connected to the heating inlet 13, and a dirty nitrogen inlet valve 41 is installed on the dirty nitrogen inlet pipe 4. The temperature sensor 122 detects the temperature of the condensed water after cooling, thereby controlling the amount of dirty nitrogen entering the heat exchanger 1. A dirty nitrogen outlet pipe 5 is connected to the heating outlet pipe, and the end of the dirty nitrogen outlet pipe 5 away from the heat exchanger 1 is used to communicate with the dirty nitrogen inlet of the molecular sieve steam heater 71. A dirty nitrogen bypass pipe 6 is connected to the dirty nitrogen outlet pipe 5, and a muffler 62 and a vent valve 61 are installed on the dirty nitrogen bypass pipe 6 to reduce the pressure of the dirty nitrogen outlet pipe 5. The vent valve 61 is located between the muffler 62 and the dirty nitrogen outlet pipe 5. A dirty nitrogen outlet valve 51 and a pressure sensor 52 are installed on the dirty nitrogen outlet pipe 5, and the pressure sensor 52 is located between the dirty nitrogen bypass pipe 6 and the heat exchanger 1, and the dirty nitrogen outlet valve 51 is located between the dirty nitrogen bypass pipe 6 and the molecular sieve steam heater 71. By utilizing the waste nitrogen and condensed water for heat exchange, the waste nitrogen temperature is increased while the condensed water is cooled, thereby reducing the energy consumption of the molecular sieve steam heater 71 and achieving the effect of condensed water heat recovery.

[0045] The implementation principle of a deep cold air separation steam condensate recovery system in the embodiment of the present application is as follows: when the molecular sieve steam heater 71 is not heated, the condensate generated in the deep cold air separation process enters the water collection well 2 for storage through the condensate input pipe 21. When the molecular sieve steam heater 71 is heated, the heat exchanger 1 is started, the condensate in the water collection well 2 is passed into the heat exchanger 1 through the cooling inlet 11, and the dirty nitrogen is passed into the heat exchanger 1 through the dirty nitrogen inlet pipe 4. The condensate and the dirty nitrogen are heat exchanged in the heat exchanger 1. After the dirty nitrogen is heated, it is discharged from the heating outlet 14. After the condensate is cooled, it is discharged from the cooling outlet 12. The dirty nitrogen discharged from the heating outlet 14 enters the molecular sieve steam heater 71, and the condensate discharged from the cooling outlet 12 is pumped into the cooler 7. The condensate is used as the circulating water of the air separation unit. Since the quality of the condensate is close to that of pure water, the water quality of the circulating water of the air separation unit is improved, and the blockage caused by the serious corrosion of the cooler 7 is reduced. Since the condensate water temperature is between 80-90℃, the condensate water is cooled before being added to the circulating water network to reduce the impact on the circulating water system water temperature and improve the stability of the air separation unit operation. In addition, the waste nitrogen is used for heat exchange with the condensate water to increase the waste nitrogen temperature while cooling the condensate water, reduce the energy consumption of the molecular sieve steam heater 71, and achieve the effect of condensate water heat recovery.

[0046] The present application embodiment discloses a control method for a deep cold air separation steam condensate recovery system. Figures 1 to 9 , including the following steps.

[0047] S1. Set parameters. Set the first water level threshold H1; set the third water level threshold H3; set the low temperature threshold T1; set the high temperature threshold T2; set the first flow value Q1; set the second flow value Q2; set the pressure value P.

[0048] S2, dynamically adjust the working status of the circulation pump 31, the vent valve 61 and the muffler 62.

[0049] S21, detecting the flow data q in the condensate circulation pipe 3; detecting the pressure data p in the dirty nitrogen outlet pipe 5.

[0050] S22. If the flow data q in the condensate circulation pipe 3 is not greater than the first flow value Q1, the circulation pump 31 stops; if the flow data q in the condensate circulation pipe 3 is greater than the second flow value Q2, the circulation pump 31 stops; if the flow data q in the condensate circulation pipe 3 is greater than the first flow value Q1, and the flow data q in the condensate circulation pipe 3 is less than the second flow value Q2, the circulation pump 31 runs; if the flow data q in the condensate circulation pipe 3 is equal to the second flow value Q2, the circulation pump 31 maintains the current state; if the pressure data p in the dirty nitrogen outlet pipe 5 is greater than the pressure value P, the vent valve 61 is opened and the muffler 62 is operated; if the pressure data p in the dirty nitrogen outlet pipe 5 is less than the pressure value P, the vent valve 61 is closed and the muffler 62 stops; if the pressure data p in the dirty nitrogen outlet pipe 5 is equal to the pressure value P, the vent valve 61 and the muffler 62 maintain the current state.

[0051] S3, detecting the working status of the molecular sieve steam heater 71.

[0052] S4. If the molecular sieve steam heater 71 is heating, the heat exchanger 1 is working, the dirty nitrogen inlet pipe 4 and the dirty nitrogen outlet pipe 5 are connected, and step S5 is performed; if the molecular sieve steam heater 71 is not heating, the heat exchanger 1 stops working, and the dirty nitrogen inlet pipe 4 and the dirty nitrogen outlet pipe 5 are both cut off, and step S6 is performed.

[0053] S5, adjusting the water collection well 2 to the drainage mode, step S5 includes the following steps.

[0054] S51, reading the temperature data t of the condensed water in the cooling outlet pipe 121; S52, if the condensed water temperature data t at the cooling outlet 12 is greater than the high temperature threshold value T2, the opening of the dirty nitrogen inlet valve 41 increases; if the condensed water temperature data t at the cooling outlet 12 is less than the low temperature threshold value T1, the opening of the dirty nitrogen inlet valve 41 decreases; if the condensed water temperature data t at the cooling outlet 12 is not greater than the high temperature threshold value T2, and the condensed water temperature data t at the cooling outlet 12 is not less than the low temperature threshold value T1, the opening of the dirty nitrogen inlet valve 41 remains unchanged; S53, reading the liquid level height data h in the water collection well 2; S54, if the liquid level height data h of the water collection well 2 is greater than the third height threshold H3, then proceed to step S55; if the liquid level height data h of the water collection well 2 is less than the first height threshold H1, then a low water level alarm is triggered, the condensate input valve 211 is fully opened, the overflow valve 241 is fully closed, the first self-priming pump 22, the second self-priming pump 23 and the heat exchanger 1 are adjusted to a stopped state, and step S2 is performed; if the liquid level height data h of the water collection well 2 is not less than the first height threshold H1, and the liquid level height data h of the water collection well 2 is not greater than the third height threshold H3, then the first self-priming pump 22 is adjusted to a running state, and the second self-priming pump 23 is adjusted to a stopped state, and step S2 is performed; S55, reducing the opening of the condensate input valve 211, increasing the opening of the overflow valve 241, and adjusting the first self-priming pump 22 and the second self-priming pump 23 to the operating state; S56, reading the liquid level height data h in the water collection well 2; S57. If the liquid level height data h of the water collection well 2 is greater than the third height threshold H3, proceed to step S55; if the liquid level height data h of the water collection well 2 is less than or equal to the third height threshold H3, increase the opening of the condensate input valve 211, reduce the opening of the overflow valve 241, set the second self-priming pump 23 to close after one hour, and proceed to step S2.

[0055] S6. Adjust the water collection well 2 to the water storage mode. Step S6 includes the following steps.

[0056] S61, adjusting the first self-priming pump 22 and the second self-priming pump 23 to a stopped state; S62, reading the liquid level height data h in the water collection well 2; S63. If the height data h of the water collection well 2 is greater than the third height threshold H3, a high water level alarm is triggered, the condensate input valve 211 is fully closed, the overflow valve 241 is fully opened, and step S2 is performed; if the height data h of the water collection well 2 is not greater than the third height threshold H3, the condensate input valve 211 maintains a normal opening, the overflow valve 241 is fully closed, and step S2 is performed.

[0057] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A cryogenic air separation steam condensate recovery system, comprising a heat exchanger, wherein the heat exchanger is provided with a cooling inlet, a cooling outlet, a heating inlet and a heating outlet, and is characterized in that: It also includes a water collecting well, on which a condensate input pipe, a first self-priming pump, a second self-priming pump and an overflow pipe are connected. A condensate input valve is arranged on the condensate input pipe, and an overflow valve is arranged on the overflow pipe. The output end of the first self-priming pump and the output end of the second self-priming pump are both connected to the cooling inlet, and a circulating pump is arranged on the cooling outlet. A dirty nitrogen inlet pipe is arranged on the heating inlet, and a dirty nitrogen inlet valve is arranged on the dirty nitrogen inlet pipe. A dirty nitrogen outlet pipe is arranged on the heating outlet, and a dirty nitrogen bypass pipe is arranged on the dirty nitrogen bypass pipe. A muffler and a vent valve are arranged on the dirty nitrogen outlet pipe, and a dirty nitrogen outlet valve is arranged on the dirty nitrogen outlet pipe.

2. A cryogenic air separation steam condensate recovery system according to claim 1, characterized in that: The end of the condensate inlet pipe away from the water collection well is used to connect with the condensate outlet of the molecular sieve steam heater, the condensate outlet of the distillation tower steam ejector and the condensate outlet of the liquid storage tank water bath vaporizer. A maintenance manhole is arranged on the water collection well, and a vacuum breaker and an automatic exhaust valve are arranged on the top of the water collection well.

3. A cryogenic air separation steam condensate recovery system according to claim 1, characterized in that: A water level sensor is arranged in the water collection well, and the water level sensor is used to detect the internal height of the water collection well. The overflow pipe is located above the input end of the second self-priming pump, and the input end of the second self-priming pump is located above the input end of the first self-priming pump. A cooling inlet pipe is connected to the cooling inlet, a first water outlet pipe is connected between the output end of the first self-priming pump and the end of the cooling inlet pipe away from the cooling inlet, a first check valve is arranged on the first water outlet pipe, a second water outlet pipe is connected between the output end of the second self-priming pump and the end of the cooling inlet pipe away from the cooling inlet, and a second check valve is arranged on the second water outlet pipe.

4. A cryogenic air separation steam condensate recovery system according to claim 1, characterized in that: A cooling outlet pipe is arranged between the cooling outlet and the input end of the circulation pump, and a temperature sensor is arranged on the cooling outlet pipe.

5. The cryogenic air separation steam condensate recovery system according to claim 1, characterized in that: A condensate circulation pipe is connected to the output end of the circulation pump, a flow meter is arranged on the condensate circulation pipe, and one end of the condensate circulation pipe away from the circulation pump is used for communicating with a cooler.

6. A cryogenic air separation steam condensate recovery system according to claim 1, characterized in that: A pressure sensor is provided on the dirty nitrogen outlet pipe, and the pressure sensor is located between the dirty nitrogen bypass pipe and the heat exchanger. The end of the dirty nitrogen outlet pipe away from the heat exchanger is used to be connected with the dirty nitrogen inlet of the molecular sieve steam heater. The dirty nitrogen outlet valve is located between the dirty nitrogen bypass pipe and the molecular sieve steam heater. The vent valve is located between the muffler and the dirty nitrogen outlet pipe.

7. A control method for a cryogenic air separation steam condensate recovery system, used in the cryogenic air separation steam condensate recovery system according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, set the first water level threshold H1; set the third water level threshold H3; set the low temperature threshold T1; set the high temperature threshold T2; set the first flow value Q1; set the second flow value Q2; set the pressure value P; S2. Adjust the working status of the circulation pump, vent valve and muffler; S3, detecting the working status of the molecular sieve steam heater; S4, if the molecular sieve steam heater is heating, the heat exchanger works, the dirty nitrogen inlet pipe and the dirty nitrogen outlet pipe are connected, and step S5 is performed; if the molecular sieve steam heater is not heating, the heat exchanger stops working, and the dirty nitrogen inlet pipe and the dirty nitrogen outlet pipe are both cut off, and step S6 is performed; S5, adjust the water collection well to drainage mode and proceed to step S2; S6. Adjust the water collection well to the water storage mode and proceed to step S2.

8. A control method for a cryogenic air separation steam condensate recovery system according to claim 7, characterized in that: The step S2 comprises the following steps: S21, detecting the flow data q in the condensate circulation pipe; detecting the pressure data p in the dirty nitrogen outlet pipe; S22. If the flow data q in the condensate circulation pipe is not greater than the first flow value Q1, the circulation pump stops; if the flow data q in the condensate circulation pipe is greater than the second flow value Q2, the circulation pump stops; if the flow data q in the condensate circulation pipe is greater than the first flow value Q1, and the flow data q in the condensate circulation pipe is less than the second flow value Q2, the circulation pump runs; if the flow data q in the condensate circulation pipe is equal to the second flow value Q2, the circulation pump maintains the current state; if the pressure data p in the dirty nitrogen outlet pipe is greater than the pressure value P, the vent valve opens and the muffler runs; if the pressure data p in the dirty nitrogen outlet pipe is less than the pressure value P, the vent valve closes and the muffler stops; if the pressure data p in the dirty nitrogen outlet pipe is equal to the pressure value P, the vent valve and the muffler maintain the current state.

9. A control method for a cryogenic air separation steam condensate recovery system according to claim 7, characterized in that: The step S5 comprises the following steps: S51, reading the temperature data t of the condensed water in the cooling outlet pipe; S52, if the condensed water temperature data t at the cooling outlet is greater than the high temperature threshold value T2, the dirty nitrogen inlet valve opening is increased; if the condensed water temperature data t at the cooling outlet is less than the low temperature threshold value T1, the dirty nitrogen inlet valve opening is reduced; if the condensed water temperature data t at the cooling outlet is not greater than the high temperature threshold value T2, and the condensed water temperature data t at the cooling outlet is not less than the low temperature threshold value T1, the dirty nitrogen inlet valve opening remains unchanged; S53, reading the liquid level height data h in the water collection well; S54, if the water collection well liquid level height data h is greater than the third height threshold H3, then proceed to step S55; if the water collection well liquid level height data h is less than the first height threshold H1, then a low water level alarm is triggered, the condensate input valve is fully opened, the overflow valve is fully closed, the first self-priming pump, the second self-priming pump and the heat exchanger are adjusted to a stopped state, and step S2 is performed; if the water collection well liquid level height data h is not less than the first height threshold H1, and the water collection well liquid level height data h is not greater than the third height threshold H3, then the first self-priming pump is adjusted to a running state, and the second self-priming pump is adjusted to a stopped state, and step S2 is performed; S55, reducing the opening of the condensate input valve, increasing the opening of the overflow valve, and adjusting the first self-priming pump and the second self-priming pump to the operating state; S56, reading the liquid level height data h in the water collection well; S57. If the water collection well liquid level height data h is greater than the third height threshold H3, proceed to step S55; if the water collection well liquid level height data h is less than or equal to the third height threshold H3, increase the opening of the condensate input valve, reduce the opening of the overflow valve, set the second self-priming pump to close after one hour, and proceed to step S2.

10. A control method for a cryogenic air separation steam condensate recovery system according to claim 7, characterized in that: The step S6 comprises the following steps: S61, adjusting the first self-priming pump and the second self-priming pump to a stopped state; S62, reading the liquid level height data h in the water collection well; S63. If the water collection well height data h is greater than the third height threshold H3, a high water level alarm is triggered, the condensate input valve is fully closed, the overflow valve is fully opened, and step S2 is performed; if the water collection well height data h is not greater than the third height threshold H3, the condensate input valve maintains a normal opening, the overflow valve is fully closed, and step S2 is performed.

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