Propylene refrigeration integrated system and propylene refrigeration consumption reduction method

Abstract

The invention relates to the technical field of propylene refrigeration, and provides a propylene refrigeration integrated system and a propylene refrigeration consumption reduction method.The propylene refrigeration integrated system comprises a propylene compressor, a first-section inlet separator, a second-section inlet separator, a propylene condenser, a propylene buffer tank, a propylene flash tank, a propylene subcooler and a propylene evaporator; the propylene evaporator is provided with a water bath heater; the propylene evaporator is provided with three functional interfaces, namely a first interface, a second interface and a third interface, the non-condensable gas treatment subsystem comprises at least one non-condensable gas cooler, the tube pass of the non-condensable gas cooler is used for circulating and cooling non-condensable gas from the system, and the shell pass of the non-condensable gas cooler is used for circulating liquid-phase propylene from the propylene buffer tank to provide cooling capacity; and a shell pass gas phase outlet is connected with the first-section inlet separator. According to the propylene refrigeration integrated system, through collaborative integration of the propylene whole-process recovery network and the low-level heat energy utilization system, the dual purposes of propylene consumption reduction and system energy saving in the whole stages of driving, running and parking are achieved.

Description

Technical Field

[0001] This application relates to the field of propylene refrigeration technology, and more specifically, to an integrated propylene refrigeration system and a method for reducing propylene refrigeration consumption. Background Technology

[0002] Currently, existing propylene refrigeration systems are widely used in coal chemical and other fields to provide cooling for units such as cryogenic methanol washing. While their conventional processes are relatively mature, they still face significant challenges in actual production, including high propylene consumption and high system energy consumption. Regarding propylene consumption, during the start-up phase, medium-pressure nitrogen is typically introduced as the dry gas seal gas for the compressor, resulting in a large amount of non-condensable nitrogen entering the system. To maintain stable operating pressure, this non-condensable gas, along with a large amount of entrained propylene, must be discharged into the flare, causing severe propylene waste. During normal operation, liquid propylene discharged from the compressor inlet separator to avoid liquid carryover, propylene entrained in the system's non-condensable gas, and leaks from the dry gas seal all directly or indirectly lead to continuous propylene loss. During shutdown and unloading, residual liquid propylene at low points in pipelines and equipment is often difficult to recover and is ultimately forced to be discharged. Regarding system energy consumption, both the propylene condenser and the turbine condenser driving the compressor rely on large amounts of circulating water for cooling, resulting in enormous water resource consumption. Simultaneously, the low-grade heat energy contained in the turbine exhaust is not effectively utilized, leading to low energy efficiency. Furthermore, traditional air-cooled or water-cooled condenser methods also have their own drawbacks, such as susceptibility to ambient temperature fluctuations, susceptibility to clogging, high antifreeze pressure, or high water consumption. Therefore, there is an urgent need for an integrated propylene refrigeration solution that can systematically reduce propylene loss and effectively recover and utilize low-grade heat energy to reduce circulating water consumption and overall energy consumption, thereby improving the economic efficiency and environmental friendliness of operation. Summary of the Invention

[0003] This application aims to at least address the technical problems of traditional propylene refrigeration systems in the relevant technologies, such as large propylene loss, large system circulating water consumption, and low energy utilization during operation.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows: In one aspect, this application provides an integrated propylene refrigeration system for reducing propylene consumption and energy consumption, comprising: a propylene compressor, the propylene compressor including a first stage compressor and a second stage compressor; a first stage inlet separator, the gas phase outlet of the first stage inlet separator being connected to the inlet of the first stage compressor of the propylene compressor; a second stage inlet separator, the gas phase outlet of the second stage inlet separator being connected to the inlet of the second stage compressor of the propylene compressor; a propylene condenser, the inlet of the propylene condenser being connected to the outlet of the second stage compressor of the propylene compressor; a propylene buffer tank, the inlet of the propylene buffer tank being connected to the liquid phase outlet of the propylene condenser; a propylene flash evaporator, the inlet of the propylene flash evaporator being connected to the liquid phase outlet of the propylene buffer tank, and its gas phase outlet being connected to the second stage inlet separator; a propylene subcooler, the tube-side inlet of the propylene subcooler being connected to the liquid phase outlet of the propylene flash evaporator; and a propylene evaporator... The propylene evaporator is equipped with a water bath heater. The propylene evaporator has three functional interfaces: a first interface, serving as a liquid propylene receiving port, for receiving liquid propylene from a first-stage inlet separator and / or the system's liquid propylene discharge collection pipeline; a second interface, serving as a first gas phase outlet, selectively connected to the outlet pipeline of the propylene compressor via a first gas phase pipeline, which is equipped with a heating device; and a third interface, serving as a second gas phase outlet, selectively connected to a first-stage inlet separator via a second gas phase pipeline. A non-condensable gas treatment subsystem includes at least one non-condensable gas cooler. The tube side of the non-condensable gas cooler is used to circulate and cool non-condensable gas from the system, while its shell side is used to circulate liquid propylene from the propylene buffer tank to provide cooling. Its shell-side gas phase outlet is connected to a first-stage inlet separator.

[0005] This application provides an integrated propylene refrigeration system to reduce propylene consumption and energy consumption. Through the synergistic integration of a full-process propylene recovery network and a low-grade heat energy utilization system, it achieves the dual goals of reducing propylene consumption and saving system energy throughout the start-up, operation, and shutdown phases. In the full-process propylene recovery scenario, the core of this application lies in the installation of a propylene evaporator with a water bath heater and its configuration with multiple switchable connection pipelines. During the start-up phase, liquid propylene from the propylene buffer tank is heated in the evaporator. The resulting high-pressure saturated propylene gas is then heated via a dedicated superheated pipeline and can be directly used as the dry sealing gas for the compressor, completely eliminating the use of nitrogen and preventing the massive propylene loss during start-up caused by the emission of non-condensable nitrogen. During normal operation, liquid propylene emitted from the inlet separator and other sources is introduced into the evaporator and gently evaporated at low pressure. The resulting gaseous propylene can be returned to the compressor inlet to re-participate in the refrigeration cycle, achieving "zero flare" recovery of liquid propylene. During the shutdown and material return phase, residual liquid propylene from various parts of the system collects in the evaporator, is vaporized, and then sent to the main process, where it is re-condensed and recovered using the existing air cooler and condenser. In the scenario of deep non-condensable gas treatment, this application includes a subsystem containing at least one non-condensable gas cooler. Non-condensable gas from the main condenser and leaked gas from the dry gas seal can be introduced into the tube side of the non-condensable gas cooler, respectively. Low-temperature liquid propylene from the propylene buffer tank evaporates in its shell side, providing cooling capacity. This ensures that the propylene component in the non-condensable gas is fully condensed, separated, and recovered to the system, significantly reducing propylene loss caused by non-condensable gas emissions during normal operation. In the scenario of system energy saving and waste heat utilization, this application integrates an energy recovery subsystem centered on a lithium bromide refrigeration unit. This unit uses the exhaust steam from the turbine driving the compressor as a heat source to produce low-temperature chilled water, which is then supplied to the propylene condenser as a cooling medium. This significantly replaces the circulating water consumption in the original process, achieving effective utilization of low-grade heat energy. Furthermore, the exhaust steam from the lithium bromide unit can enter an optimized hybrid condenser for final condensation. This condenser combines the advantages of air-cooled water saving and water-cooled stability, and controls back pressure by flexibly adjusting the spray water volume and cooling load, thus improving the economic efficiency and flexibility of turbine operation. Through the organic integration of the above modules, the entire system achieves a significant reduction in both propylene consumption and system energy consumption without significantly increasing investment.

[0006] Secondly, this application proposes a method for reducing propylene refrigeration consumption, employing an integrated propylene refrigeration system as described above. The method includes the following steps: S1, Start-up stage: Liquid propylene from the propylene buffer tank is introduced into the propylene evaporator and heated using a water bath heater to generate saturated propylene gas at 1.1 MPaG~1.3 MPaG. The saturated propylene gas is then superheated through a first gas phase pipeline and led to the dry gas sealing device of the propylene compressor as sealing gas; S2, Normal operation stage: Liquid propylene from the first inlet separator and the system liquid propylene discharge collection pipeline is... The liquid phase propylene is introduced into the propylene evaporator through the first interface, and the propylene evaporator is controlled to operate at low pressure. The liquid phase propylene is evaporated using a water bath heater, and the resulting gaseous phase propylene is returned to the first inlet separator through the second gas phase pipeline. At the same time, the non-condensable gas in the system is introduced into the non-condensable gas treatment subsystem to recover the propylene entrained therein. S3, shutdown and material return stage: The remaining liquid phase propylene in the system is introduced into the propylene evaporator and heated and evaporated using a water bath heater. The resulting propylene gas is introduced into the outlet pipeline of the propylene compressor through the first gas phase pipeline, and condensed and recovered to the propylene buffer tank using the compressor outlet air cooler and propylene condenser.

[0007] The propylene refrigeration energy saving method provided in this application, since it is used in the propylene refrigeration integrated system of the above scheme, has all the beneficial effects of the propylene refrigeration integrated system, which will not be repeated here.

[0008] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0009] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the piping structure of a propylene refrigeration integrated system according to an embodiment of this application; Figure 2 This is a schematic diagram of the piping structure of the energy recovery subsystem in a propylene refrigeration integrated system according to an embodiment of this application; Figure 3 This is a flowchart of a propylene refrigeration energy-saving method according to an embodiment of this application.

[0010] in, Figure 1 and Figure 2 The correspondence between the reference numerals and component names in the attached drawings is as follows: 100 Propylene Refrigeration Integrated System, 102 Compressor Outlet Air Cooler, 110 Propylene Compressor, 120 First Stage Inlet Separator, 130 Second Stage Inlet Separator, 140 Propylene Condenser, 150 Propylene Buffer Tank, 160 Propylene Flash Tank, 170 Propylene Subcooler, 180 Propylene Evaporator, 190 Non-condensable Gas Treatment Subsystem, 192 First Non-condensable Gas Cooler, 194 Second Non-condensable Gas Cooler, 200 Energy Recovery Subsystem, 210 Lithium Bromide Refrigeration Unit, 220 Mixed Condenser, 221 Exhaust Condenser, 222 Ejector System, 223 Water Cooler, 224 Air Cooler, 225 Condensate Pump. Detailed Implementation

[0011] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0012] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0013] The following reference Figures 1 to 3 This application describes a propylene refrigeration integrated system 100 and a propylene refrigeration energy-saving method for reducing propylene consumption and energy consumption, provided according to some embodiments of the present application.

[0014] According to the first aspect of this application, Figure 1 and Figure 2As shown, one embodiment of this application provides a propylene refrigeration integrated system 100 for reducing propylene consumption and energy consumption, comprising: a propylene compressor 110, which includes a compressor stage 1 and a compressor stage 2; a first-stage inlet separator 120, the gas phase outlet of which is connected to the compressor stage 1 inlet of the propylene compressor 110; a second-stage inlet separator 130, the gas phase outlet of which is connected to the compressor stage 2 inlet of the propylene compressor 110; a propylene condenser 140, the inlet of which is connected to the compressor stage 2 outlet of the propylene compressor 110; a propylene buffer tank 150, the inlet of which is connected to the liquid phase outlet of the propylene condenser 140; a propylene flash evaporator 160, the inlet of which is connected to the liquid phase outlet of the propylene buffer tank 150, and its gas phase outlet connected to the second-stage inlet separator 130; and a propylene subcooler 170, the tube side inlet of which is connected to the propylene subcooler 170. The system includes: a propylene flash tank 160 connected to the liquid phase outlet; a propylene evaporator 180 equipped with a water bath heater; the propylene evaporator 180 having three functional interfaces: a first interface, serving as a liquid phase propylene receiving port for receiving liquid phase propylene from a first-stage inlet separator 120 and / or the system's liquid phase propylene discharge collection pipeline; a second interface, serving as a first gas phase outlet, selectively connected to the outlet pipeline of the propylene compressor 110 via a first gas phase pipeline, the first gas phase pipeline being equipped with a heating device; and a third interface, serving as a second gas phase outlet, selectively connected to a first-stage inlet separator 120 via a second gas phase pipeline; and a non-condensable gas treatment subsystem 190, including at least one non-condensable gas cooler, the tube side of which is used to circulate and cool non-condensable gas from the system, its shell side for circulating liquid phase propylene from the propylene buffer tank 150 to provide cooling, and its shell side gas phase outlet connected to the first-stage inlet separator 120.

[0015] Specifically, such as Figure 1As shown, the propylene refrigeration integrated system 100 for reducing propylene consumption and energy consumption provided in the embodiments of this application includes a propylene compressor 110, a first-stage inlet separator 120, a second-stage inlet separator 130, a propylene condenser 140, a propylene buffer tank 150, a propylene flash evaporator 160, a propylene subcooler 170, a propylene evaporator 180, and a non-condensable gas treatment subsystem 190. The propylene compressor 110 includes a first-stage compressor and a second-stage compressor. The gas phase outlet of the first-stage inlet separator 120 is connected to the first-stage compressor inlet of the propylene compressor 110. The gas phase outlet of the second-stage inlet separator 130 is connected to the second-stage compressor inlet of the propylene compressor 110. The inlet of the propylene condenser 140 is connected to the second-stage compressor outlet of the propylene compressor 110. The inlet of the propylene buffer tank 150 is connected to the liquid phase outlet of the propylene condenser 140. The inlet of the propylene flash tank 160 is connected to the liquid phase outlet of the propylene buffer tank 150, and its gas phase outlet is connected to the second-stage inlet separator 130. The tube-side inlet of the propylene subcooler 170 is connected to the liquid phase outlet of the propylene flash tank 160. The propylene evaporator 180 is equipped with a water bath heater. The propylene evaporator 180 has three functional interfaces: a first interface, a second interface, and a third interface. The system comprises the following subsystems: a first interface serves as a liquid propylene receiving port, used to receive liquid propylene from the first-stage inlet separator 120 and / or the system's liquid propylene discharge collection pipeline; a second interface serves as a first gas phase outlet, selectively connected to the outlet pipeline of the propylene compressor 110 via a first gas phase pipeline, the first gas phase pipeline being equipped with a heating device; and a third interface serves as a second gas phase outlet, selectively connected to the first-stage inlet separator 120 via a second gas phase pipeline. The non-condensable gas treatment subsystem 190 includes at least one non-condensable gas cooler, the tube side of which circulates and cools non-condensable gas from the system, the shell side of which circulates liquid propylene from the propylene buffer tank 150 to provide cooling, and the shell-side gas phase outlet connected to the first-stage inlet separator 120.

[0016] Thus, by setting up a propylene evaporator 180 with three functional interfaces, this system establishes a centralized, controllable, and multifunctional processing hub for the discharge and recovery of liquid propylene in the propylene refrigeration process. Its first interface collects the liquid propylene to be discharged during normal operation, mainly from the first-stage inlet separator 120; the second interface connects to the compressor outlet via a first gas phase pipeline equipped with a heating device, specifically for start-up and shutdown phases; the third interface connects to the first-stage inlet separator 120 via a second gas phase pipeline for steam recovery during normal operation. These three interfaces, in conjunction with a water bath heater, enable the propylene evaporator 180 to switch connection paths under different operating conditions, respectively: producing high-pressure propylene gas to replace nitrogen as a sealing gas during start-up; vaporizing and returning the discharged liquid propylene to the system during normal operation; and vaporizing and recovering residual liquid in the system during shutdown. Simultaneously, the integrated non-condensable gas treatment subsystem 190 utilizes low-temperature liquid propylene from the propylene buffer tank 150 as a cold source to deeply cool and separate propylene components entrained in the non-condensable gas, further reducing propylene process emission losses. The above design systematically closes off multiple propylene loss points in the process, directly realizing closed-loop management and efficient recovery of propylene materials within the system.

[0017] Compared with existing technologies, the propylene refrigeration integrated system 100 provided in this application, which reduces propylene consumption and energy consumption, has the following advantages: First, it achieves full-process, multi-condition propylene recovery. Through the ingenious design and path switching of the three functional interfaces of the propylene evaporator 180, the propylene recovery problem in each stage of start-up, normal operation, and shutdown is systematically solved, significantly reducing propylene consumption throughout the entire life cycle; Second, it eliminates the dependence on nitrogen during the start-up phase. By using the system's self-produced high-pressure superheated propylene gas as a dry gas sealing gas source, the huge losses caused by non-condensable nitrogen entering the system and subsequent entrainment of propylene in the flare are fundamentally avoided; Third, it enhances the deep recovery of propylene from non-condensable gas. The non-condensable gas treatment subsystem 190 adopts a low-temperature propylene cooling process to efficiently separate and recover propylene components from non-condensable gas and sealing leakage gas, further reducing propylene emission losses during normal operation; Fourth, it integrates energy recovery and water-saving functions. By introducing a lithium bromide refrigeration unit 210 that uses turbine exhaust steam as a heat source, chilled water is produced for the propylene condenser 140, effectively utilizing low-grade heat energy and significantly reducing the system's consumption of circulating water and overall operating energy consumption.

[0018] Specifically, existing propylene refrigeration systems are widely used in coal chemical and other fields to provide cooling for units such as cryogenic methanol washing. While their conventional processes are relatively mature, they still face significant challenges in actual production, including high propylene consumption and high system energy consumption. Regarding propylene consumption, during the start-up phase, medium-pressure nitrogen is typically introduced as the dry gas seal gas for the compressor, resulting in a large amount of non-condensable nitrogen entering the system. To maintain stable operating pressure, this non-condensable gas, along with a large amount of entrained propylene, must be discharged into the flare, causing severe propylene waste. During normal operation, liquid propylene discharged from the compressor inlet separator to avoid liquid carryover, propylene entrained in the system's non-condensable gas, and leaks from the dry gas seal all directly or indirectly lead to continuous propylene loss. During shutdown and unloading, residual liquid propylene in pipelines and equipment at low points is often difficult to recover and is ultimately forced to be discharged. Regarding system energy consumption, both the propylene condenser and the turbine condenser driving the compressor rely on large amounts of circulating water for cooling, resulting in huge water resource consumption. Simultaneously, the low-grade heat energy contained in the turbine exhaust is not effectively utilized, leading to low energy efficiency. In addition, traditional air-cooled or water-cooled condenser methods also have their own disadvantages, such as being easily affected by ambient temperature, being prone to clogging, having high antifreeze pressure, or high water consumption.

[0019] To address the shortcomings of existing technologies, such as Figure 1As shown, the propylene refrigeration integrated system 100 provided in this application, which reduces propylene consumption and energy consumption, achieves the dual goals of reducing propylene consumption and saving system energy throughout the entire process of start-up, operation, and shutdown by synergistically integrating a full-process propylene recovery network and a low-grade heat energy utilization system. In the full-process propylene recovery scenario, the core of this application lies in the installation of a propylene evaporator 180 with a water bath heater and its configuration with multiple switchable connection pipelines. During start-up, liquid propylene from the propylene buffer tank 150 is heated in the evaporator. The resulting high-pressure saturated propylene gas, after being heated through a dedicated superheated pipeline, can be directly used as the dry sealing gas for the compressor, completely eliminating the use of nitrogen and removing the massive propylene loss during start-up caused by the emission of non-condensable nitrogen. During normal operation, liquid propylene emitted from the inlet separator and other sources is introduced into the evaporator and gently evaporated under low pressure. The resulting gaseous propylene can be returned to the compressor inlet to re-participate in the refrigeration cycle, achieving "zero flare" recovery of liquid propylene. During the shutdown and material return phase, residual liquid propylene from various parts of the system collects in the evaporator, is vaporized, and then sent to the main process, where it is re-condensed and recovered using the existing air cooler and condenser. In the scenario of deep non-condensable gas treatment, this application includes a subsystem containing at least one non-condensable gas cooler. Non-condensable gas from the main condenser and leaked gas from the dry gas seal can be introduced into the tube side of the non-condensable gas cooler, respectively. Low-temperature liquid propylene from the propylene buffer tank 150 evaporates in its shell side to provide cooling, ensuring that the propylene component in the non-condensable gas is fully condensed, separated, and recovered to the system, significantly reducing propylene loss caused by non-condensable gas emissions during normal operation. In the scenario of system energy saving and waste heat utilization, this application integrates an energy recovery subsystem 200 with a lithium bromide refrigeration unit 210 as its core. This unit uses the exhaust steam from the turbine driving the compressor as a heat source to produce low-temperature chilled water, which is then supplied to the propylene condenser 140 as a cooling medium, thereby significantly replacing the circulating water consumption in the original process and achieving effective utilization of low-grade heat energy. Furthermore, the exhaust steam from the lithium bromide refrigeration unit 210 can enter the optimized hybrid condenser 220 for final condensation. This condenser combines the advantages of air-cooled water saving and water-cooled stability, and controls back pressure by flexibly adjusting the spray water volume and cooling load, thereby improving the economy and flexibility of turbine operation. Through the organic integration of the above modules, the entire system achieves a significant reduction in both propylene consumption and system energy consumption without significantly increasing investment.

[0020] In specific applications, the propylene flash tank 160 in this application is specifically an energy-saving device with a pressure of 0.55 MPaG. The gas phase is used as the second-stage inlet gas for the compressor, and the liquid phase is divided into two streams.

[0021] In some embodiments, optionally, such as Figure 1As shown, it also includes a compressor outlet air cooler 102, which is installed on the pipeline between the compressor second stage outlet of the propylene compressor 110 and the air inlet of the propylene condenser 140.

[0022] Specifically, such as Figure 1 As shown, the compressor outlet air cooler 102 can be used for preliminary cooling of the high-temperature propylene gas at the compressor outlet during normal operation to reduce the heat load on the subsequent condenser. More importantly, during the system shutdown and material return phase, when the residual liquid propylene that cannot be recovered through the conventional process is vaporized in the propylene evaporator 180 and returned to the compressor outlet pipeline via the first gas phase pipeline, the compressor outlet air cooler 102 works in conjunction with the propylene condenser 140 to gradually cool and condense this portion of recovered propylene gas into a liquid state, which is then ultimately recovered into the propylene buffer tank 150, thereby ensuring the integrity and feasibility of the propylene recovery process during the shutdown phase.

[0023] In some embodiments, optionally, such as Figure 1 As shown, the non-condensable gas treatment subsystem 190 includes a first non-condensable gas cooler 192 and a second non-condensable gas cooler 194 arranged in parallel; the tube-side inlet of the first non-condensable gas cooler 192 is connected to the non-condensable gas discharge port of the propylene condenser 140, and its tube-side liquid phase outlet is connected to the propylene buffer tank 150; the tube-side inlet of the second non-condensable gas cooler 194 is used to receive the leaked gas from the dry gas seal of the propylene compressor 110, and its tube-side liquid phase outlet is connected to the propylene evaporator 180.

[0024] Specifically, such as Figure 1As shown, the first non-condensable gas cooler 192 and the second non-condensable gas cooler 194 are connected in parallel to form a non-condensable gas treatment subsystem 190. The tube-side inlet of the first non-condensable gas cooler 192 is connected via pipeline to the non-condensable gas discharge port at the top of the propylene condenser 140 to receive relatively high-pressure non-condensable gas from the main process. The tube-side inlet of the second non-condensable gas cooler 194 is connected via pipeline to receive primary leakage gas from the dry gas sealing device of the propylene compressor 110; this gas typically has lower pressure and a smaller flow rate. The shell-side inlets of both non-condensable gas coolers are connected via pipeline to the liquid phase outlet of the propylene buffer tank 150 and are equipped with pressure reducing valves. The higher-pressure liquid propylene from the propylene buffer tank 150 is depressurized here, enters the shell side, and undergoes evaporation and heat absorption, providing cooling for the non-condensable gas in the tube side. The propylene gas phase generated by evaporation is drawn out from the shell-side gas phase outlet of each cooler, merges, and returns to the gas phase space of the first-stage inlet separator 120 to re-participate in the compression refrigeration cycle, achieving efficient utilization of the cooling capacity. After cooling, the propylene component in the non-condensable gas is condensed. For the first non-condensable gas cooler 192, the propylene liquid phase condensed in its tubes flows out from its tube-side liquid phase outlet under gravity and returns directly to the pressure-matched propylene buffer tank 150. For the second non-condensable gas cooler 194, the propylene liquid phase condensed in its tubes is discharged from its tube-side liquid phase outlet and sent to the low-pressure operating propylene evaporator 180 for recovery. This differentiated liquid phase recovery path design is an optimization based on the different pressures and characteristics of the two non-condensable gas sources, ensuring smooth and efficient propylene recovery. The remaining non-condensable gas after propylene separation is discharged from the tube-side gas phase outlets of the two coolers and finally sent to the flare system for processing.

[0025] In some embodiments, optionally, such as Figure 2 As shown, it also includes an energy recovery subsystem 200, which includes a lithium bromide refrigeration unit 210; the heat source inlet of the lithium bromide refrigeration unit 210 is used to receive exhaust steam from the turbine driving the propylene compressor 110, and the chilled water outlet of the lithium bromide refrigeration unit 210 is connected to the cooling medium inlet of the propylene condenser 140.

[0026] Specifically, such as Figure 2As shown, the exhaust steam generated by the turbine driving the propylene compressor 110 is entirely or partially used as a driving heat source and is introduced into the heat source inlet of the lithium bromide refrigeration unit 210 through a pipeline. The lithium bromide refrigeration unit 210 utilizes this low-grade heat energy to produce chilled water (e.g., no higher than 5°C) at a temperature significantly lower than conventional cooling water through its internal absorption refrigeration cycle. The chilled water outlet of the lithium bromide refrigeration unit 210 is connected to the cooling medium inlet of the propylene condenser 140 through a pipeline, thereby transporting the produced chilled water to the propylene condenser 140, partially or completely replacing the original circulating cooling water for condensing the high-temperature propylene gas from the compressor outlet. This design converts the waste heat from the turbine exhaust steam, which was originally discharged or difficult to utilize, into valuable cooling energy, directly reducing the demand and consumption of external circulating water by the propylene condenser 140, and achieving efficient cascade utilization of system energy and a reduction in overall energy consumption.

[0027] In some embodiments, optionally, such as Figure 2 As shown, the energy recovery subsystem 200 also includes a hybrid condenser 220, which is connected in series with the lithium bromide refrigeration unit 210 and is used to condense the turbine exhaust steam flowing out of the lithium bromide refrigeration unit 210.

[0028] Specifically, such as Figure 2 As shown, the hybrid condenser 220 is arranged in series with the lithium bromide refrigeration unit 210 in terms of process flow. The exhaust steam from the turbine driving the propylene compressor 110 flows through the lithium bromide refrigeration unit 210 and releases some low-grade heat energy. Then it is drawn out from the heat source outlet of the lithium bromide refrigeration unit 210 and enters the air inlet at the bottom of the hybrid condenser 220.

[0029] Specifically, the mixing condenser 220 is preferably a packed tower structure with a high-efficiency packing layer inside to increase the gas-liquid contact area. A spray device is installed at the top of the mixing condenser 220. The condensate collected at the bottom of the mixing condenser 220 is pressurized by the condensate pump 225 and divided into two streams. One stream is sent out of the system as product condensate for recycling; the other stream is used as a cooling medium, flowing sequentially through an air cooler 224 and a water cooler 223 for staged cooling. This fully cooled condensate is atomized by the spray device and sprayed from top to bottom, making full counter-current contact with the turbine exhaust steam flowing from bottom to top in the packing layer, which has undergone waste heat recovery from the lithium bromide refrigeration unit 210, for direct contact condensation. The condensed condensate falls back to the bottom of the condenser, completing the cycle. Trace amounts of uncondensed non-condensable gases are extracted from the top of the mixing condenser 220 by an extraction device to maintain the required vacuum level of the system. This hybrid design combines the water-saving advantages of air cooler 224 with the stable cooling effect of water cooler 223: pre-cooling with air cooler 224 significantly reduces the load and size of water cooler 223, while the flowing condensate avoids the risk of air cooler tube bundle freezing in winter; finally, water cooler 223 ensures that the cooling effect is unaffected by ambient temperature fluctuations. By adjusting one or more of the following: spray water volume, air cooler fan frequency (or frequency converter control), and water cooler 223 circulating water valve opening, the turbine exhaust back pressure can be flexibly and precisely controlled, thereby optimizing operating efficiency and saving energy and water.

[0030] In specific applications, such as Figure 2 As shown, the specific working process of the propylene refrigeration integrated system 100 for reducing propylene consumption and energy consumption provided in this application is as follows: Gaseous propylene (0.04 MPaG, -40°C) from the refrigeration unit enters the first-stage inlet separator 120. After droplet separation, the gas phase enters the first-stage inlet of the compressor. When the liquid phase in the first-stage inlet separator 120 is high, it is discharged to the propylene evaporator 180. The gas phase from the propylene flash tank 160 enters the second-stage inlet separator 130. After entrained droplets are separated, the gas phase enters the second-stage inlet of the compressor, and the liquid phase is discharged to the first-stage inlet separator 120. The compressor outlet pressure is 1.85 MPaG. The propylene gas at the compressor outlet is condensed into 40°C liquid propylene through the compressor outlet air cooler 102 and the propylene condenser 140. Propylene in its initial state, after passing through the propylene buffer tank 150, enters the propylene flash tank 160 (i.e., the economizer). The pressure in the propylene flash tank 160 is 0.55 MPaG. The vapor phase serves as the inlet gas for the second stage of the compressor. The liquid phase is split into two streams: one enters the shell side of the propylene subcooler 170, and the other enters the tube side. The shell-side propylene is depressurized to 0.04 MPaG and its temperature drops to -40°C. The propylene in the shell side evaporates, absorbing heat to lower the temperature of the tube-side propylene, which drops to -20°C. The subcooled propylene in the shell side, at a pressure of 0.55 MPaG and a temperature of -20°C, is then sent to the downstream refrigeration section. The propylene vapor phase after heat exchange in the downstream refrigeration section returns to the first-stage inlet separator 120 to perform refrigeration work again.

[0031] The propylene refrigeration system's low-point discharge, pipeline low-point discharge, first-stage inlet separator 120 liquid phase discharge pipeline, and second non-condensable gas cooler 194 liquid phase discharge pipeline are all connected to the propylene evaporator 180. The vapor phase pipeline of the propylene evaporator 180 splits into two lines: one goes to the propylene compressor 110 outlet pipeline, which is a jacketed heating pipeline used for start-up and shutdown processes; the other goes to the first-stage inlet separator 120, used for normal production processes. The propylene evaporator 180 is heated by a water bath heater.

[0032] Non-condensable gas from propylene condenser 140 enters the tube side of the first non-condensable gas cooler 192. After being cooled by the shell side of the first non-condensable gas cooler 192, it is separated into gas and liquid phases. The gas phase is discharged to the flare system after being depressurized by the pressure regulating valve, and the liquid phase is discharged to the propylene buffer tank 150 by gravity. The shell side of the first non-condensable gas cooler 192 contains liquid propylene from the propylene buffer tank 150. The shell side of the first non-condensable gas cooler 192 cools the propylene in the tube side of the non-condensable gas cooler by the heat absorption of propylene evaporation. The gas phase in the shell side of the first non-condensable gas cooler 192 returns to the first inlet separator 120. The leaking gas from the dry gas seal stage of the propylene compressor 110 enters the tube side of the second non-condensable gas cooler 194. After being cooled by the shell side of the second non-condensable gas cooler 194, it is separated into gas and liquid phases. The gas phase is directly discharged to the flare system, and the liquid phase is intermittently discharged to the propylene evaporator 180 by gravity through a regulating valve. The shell side of the second non-condensable gas cooler 194 contains liquid propylene from the propylene buffer tank 150. The shell side of the second non-condensable gas cooler 194 cools the propylene in the tube side of the non-condensable gas cooler by absorbing heat through the evaporation of propylene. The gas phase in the shell side of the second non-condensable gas cooler 194 returns to the first-stage inlet separator 120.

[0033] Propylene compressor 110 start-up phase: Before starting the propylene flash compressor, valves V3 and V5 are closed, and valves V6 and V4 are open. The compressor outlet air cooler 102 and propylene condenser 140 are not in use (no cooling). Liquid propylene from the propylene buffer tank 150 enters the propylene evaporator 180. The propylene evaporator 180 is heated by a water bath heater and produces saturated high-pressure propylene gas of 1.1MPaG~1.3MPaG. The gas is superheated to about 70°C through the propylene jacket heating pipeline and enters the outlet pipeline of the propylene compressor 110. The superheated propylene gas is then used in the dry gas seal. After the propylene compressor 110 is successfully started, when the outlet pressure of the propylene compressor 110 exceeds 1.1 MPa, valves V6 and V4 are slowly closed. The propylene gas from the outlet of the propylene compressor 110 is used to provide sealing gas for the dry gas seal. After valves V6 and V4 are closed, the outlet pressure of the propylene compressor 110 gradually increases. When it exceeds 1.4 MPa, the compressor outlet air cooler 102 and the propylene condenser 140 can be slowly put into operation, and valve V5 is slowly opened. This design allows the compressor to be started without the use of medium-pressure nitrogen, avoiding the accumulation of non-condensable gases in the system and thus reducing propylene loss.

[0034] During normal operation of the propylene refrigeration system: Valves V3, V6, and V5 are open, and valve V4 is closed. The liquid inlet and gas outlet of the propylene evaporator 180 are connected to the first-stage inlet separator 120. During normal production, the liquid propylene discharged from the propylene refrigeration system enters the propylene evaporator 180. After being heated by the water bath heater in the propylene evaporator 180, the vaporized propylene enters the first-stage inlet separator 120 of the propylene compressor 110. This allows the propylene discharged during normal operation to be discharged into the propylene evaporator 180, thereby reducing the need for flare discharge and minimizing propylene consumption during normal operation.

[0035] Specifically, the system also includes a non-condensable gas treatment subsystem 190. The non-condensable gas treatment subsystem 190 includes a first non-condensable gas cooler 192 and a second non-condensable gas cooler 194. The non-condensable gas treatment subsystem 190 is used to treat the non-condensable gas vented from the propylene refrigeration system to the flare and the primary leakage gas from the compressor dry gas seal flare. During normal production, non-condensable gas (1.85 MPaG, 40°C) from propylene condenser 140 enters the tube side of the first non-condensable gas cooler 192. After being cooled by the shell side of the first non-condensable gas cooler 192, it is separated into gas and liquid phases. The gas phase is discharged to the flare system after being depressurized by pressure regulating valve V7, and the liquid phase is discharged to the propylene buffer tank 150 by gravity. The shell side of the first non-condensable gas cooler 192 contains liquid propylene from the propylene buffer tank 150. The shell side of the first non-condensable gas cooler 192 cools the propylene in the tube side of the first non-condensable gas cooler 192 by the heat absorption of propylene evaporation. The gas phase in the shell side of the first non-condensable gas cooler 192 returns to the first inlet separator 120. The leaking gas from the dry gas seal stage of the propylene compressor 110 enters the tube side of the second non-condensable gas cooler 194. After being cooled by the shell side of the second non-condensable gas cooler 194, it is separated into gas and liquid phases. The gas phase is directly discharged to the flare system, and the liquid phase is intermittently discharged to the propylene evaporator 180 by gravity through a regulating valve. The shell side of the second non-condensable gas cooler 194 contains liquid propylene from the propylene buffer tank 150. The shell side of the second non-condensable gas cooler 194 cools the propylene in the tube side of the second non-condensable gas cooler 194 by absorbing heat through the evaporation of propylene. The gas phase in the shell side of the second non-condensable gas cooler 194 returns to the first-stage inlet separator 120.

[0036] Propylene refrigeration system shutdown and liquid return / replacement phase: During the shutdown and liquid return phase of the propylene refrigeration system, the propylene compressor 110 is stopped, valve V3 is closed, and valves V4, V5, and V6 are opened. The propylene evaporator 180 and the propylene jacket heating pipeline are connected to the compressor outlet pipeline. All liquid propylene that cannot be recovered by the propylene refrigeration system (liquid propylene that cannot be recovered from the pipeline and equipment low points) is discharged into the propylene evaporator 180. The jacket steam in the propylene jacket heating pipeline is stopped. The vapor phase propylene, heated by the water bath heater of the propylene evaporator 180, enters the outlet pipeline of the propylene compressor 110. It is cooled by the compressor outlet air cooler 102, causing the vapor phase propylene to condense and be recovered into the propylene buffer tank 150. Then, the recovered liquid propylene is sent to the tank area through the normal process.

[0037] In specific applications, such as Figure 2 As shown, the specific working process of the propylene refrigeration integrated system 100 for reducing propylene consumption and energy consumption and recovering low-grade heat energy provided in this application is as follows: The exhaust steam from the turbine outlet of the propylene compressor 110 first enters the lithium bromide refrigeration unit 210 to recover low-grade heat energy. Chilled water is obtained in the lithium bromide refrigeration unit 210 for use in the propylene refrigeration system, and then enters the lower part of the exhaust steam condenser 221.

[0038] Specifically, the mixed condenser 220 includes: an exhaust condenser 221, an ejector system 222, a water cooler 223, an air cooler 224, and a condensate pump 225. Non-condensable gases passing through the exhaust condenser 221 are extracted from the top and enter the ejector system 222 to maintain the turbine's vacuum level.

[0039] Specifically, the exhaust steam condenser 221 is preferably designed as a packed tower. After the condensate is collected at the bottom of the exhaust steam condenser 221, it is pressurized by the condensate pump 225. The condensate at the outlet of the condensate pump 225 is divided into two streams. One stream is directly sent outside the boundary for recycling through the regulating valve V1, which controls the liquid level of the exhaust steam condenser 221. The other stream is cooled successively by the air cooler 224 and the water cooler 223, and then enters the upper part of the exhaust steam condenser 221 through the regulating valve V2. It is atomized by nozzles and comes into counter-current contact with the turbine exhaust steam from top to bottom in the exhaust steam condenser 221, condensing the turbine exhaust steam into condensate.

[0040] Specifically, the turbine exhaust pressure control is flexible and employs multiple methods: Method one is to control the condensate return flow rate via the regulating valve V2 of the condensate return valve to the exhaust condenser 221. Method two is to control the condensate temperature returning to the exhaust condenser 221 by controlling the frequency of the air cooler's inverter and thus the load on the air cooler. Method three is to control the circulating water flow rate via the circulating water regulating valve V8 of the water cooler 223, thereby controlling the condensate temperature returning to the exhaust condenser 221.

[0041] Specifically, the turbine exhaust pressure is controlled as follows: when the turbine exhaust pressure is high, the condensate return valve V2 is opened first, then the frequency converter of air cooler 224 is used to increase the air cooler load, and finally the circulating water regulating valve V8 of water cooler 223 is opened. When the turbine exhaust pressure is low, the circulating water regulating valve V8 of water cooler 223 is closed first, then the frequency converter of air cooler 224 is used to reduce the air cooler load, and finally the condensate return valve V2 is reduced, thereby achieving the purpose of energy and water conservation.

[0042] According to the second aspect of this application, such as Figure 3 As shown in the embodiments of this application, a method for reducing propylene refrigeration consumption is also proposed, which uses the propylene refrigeration integrated system as described in the above embodiments. The method for reducing propylene refrigeration consumption includes the following steps: S1, Start-up phase: Liquid propylene from the propylene buffer tank is introduced into the propylene evaporator and heated by a water bath heater to produce saturated propylene gas of 1.1MPaG~1.3MPaG. The saturated propylene gas is then superheated through the first gas phase pipeline and led to the dry gas sealing device of the propylene compressor as sealing gas. S2. Normal operation phase: Liquid propylene from the first inlet separator and the system liquid propylene discharge collection pipeline is introduced into the propylene evaporator through the first interface, and the propylene evaporator is controlled to operate at low pressure. The liquid propylene is evaporated using a water bath heater, and the generated gaseous propylene is returned to the first inlet separator through the second gas pipeline. At the same time, the system non-condensable gas is introduced into the non-condensable gas treatment subsystem to recover the propylene entrained therein. S3, Shutdown and Material Removal Stage: The residual liquid propylene in the system is introduced into the propylene evaporator and heated and evaporated using a water bath heater. The resulting propylene gas is introduced into the outlet pipeline of the propylene compressor through the first gas phase pipeline and condensed and recovered into the propylene buffer tank using the compressor outlet air cooler and propylene condenser.

[0043] Specifically, such as Figure 3As shown, in step S1, the second gas phase line is closed, and the first gas phase line and its heating device are opened. A portion of liquid propylene is drawn from the propylene buffer tank and introduced into the propylene evaporator. Its water bath heater is started, and the pressure of the propylene evaporator is controlled at approximately 1.1 MPaG~1.3 MPaG, causing the internal liquid propylene to evaporate and produce corresponding saturated propylene gas. This saturated propylene gas is introduced into the first gas phase line, and superheated to approximately 70°C~95°C using a heating device on the line (such as jacket steam), forming stable, clean superheated propylene gas. This superheated propylene gas is delivered to the dry gas sealing device of the propylene compressor as the primary sealing gas, thus completely replacing the medium-pressure nitrogen used in the traditional start-up process. Once the propylene compressor has successfully started and its outlet pipeline pressure has steadily risen above 1.1 MPaG, the supply to this first gas phase line is slowly cut off, and the propylene process gas from the propylene compressor's own outlet is switched to be used as the sealing gas.

[0044] In step S2, the first gas phase line is closed and the second gas phase line is opened. Liquid propylene discharged from the inlet separator when the liquid level is too high, as well as liquid propylene collected from other low-level discharges in the system, is introduced through the first interface of the propylene evaporator. The propylene evaporator is controlled to operate at a low pressure (e.g., 0.04 MPaG~0.1 MPaG), utilizing the heating effect of the water bath heater to gently evaporate the incoming liquid propylene. The resulting gaseous propylene is returned to the gas phase space of the inlet separator through the second gas phase line, re-entering the first stage of the compressor for compression circulation, thus avoiding losses caused by direct discharge of liquid propylene into the flare. Simultaneously, non-condensable gas from the propylene condenser is introduced into the tube side of the first non-condensable gas cooler, and leaked gas from the compressor dry gas seal is introduced into the tube side of the second non-condensable gas cooler. Utilizing the cooling provided by the low-temperature liquid propylene from the propylene buffer tank evaporating in the shell sides of the two coolers, the propylene components in the two non-condensable gases are condensed, separated, and recovered, while the remaining non-condensable gas is discharged into the flare system.

[0045] In step S3, after the main process of the propylene refrigeration system is shut down, the second gas phase pipeline is closed and the first gas phase pipeline is reopened. All liquid propylene remaining in the system pipelines and at low points of equipment, which cannot be recovered through conventional methods, is introduced into the propylene evaporator. A water bath heater is used to heat this residual liquid, causing it to completely evaporate into propylene gas. The generated propylene gas is then introduced into the outlet pipeline of the propylene compressor via the first gas phase pipeline. Using the existing compressor outlet air cooler and propylene condenser in the system, this portion of propylene gas is gradually cooled and condensed into a liquid state, ultimately recovered into the propylene buffer tank, completing the complete recovery of propylene material within the system.

[0046] Thus, the propylene refrigeration energy-saving method provided in this application systematically constructs a propylene recovery and energy utilization path covering the entire process of start-up, normal operation, and shutdown through the synergy of an integrated system and phased operations. This method not only directly and significantly reduces propylene material loss at each stage and improves operational economy, but also achieves energy saving and consumption reduction by recovering low-grade heat energy to replace circulating water cooling, effectively solving the dual problems of high propylene consumption and high system energy consumption in existing technologies.

[0047] In some embodiments, optionally, such as Figure 3 As shown, during the start-up phase, when the outlet pressure of the propylene compressor stabilizes above 1.1 MPaG, the propylene gas from the propylene compressor outlet is switched to be used as the sealing gas, and the first gas phase pipeline is shut off.

[0048] Specifically, such as Figure 3 As shown, during the start-up phase, when the propylene compressor successfully starts and operates stably, and the process propylene gas pressure in its outlet pipeline rises and stabilizes at 1.1 MPaG or higher, it is ready to use its own process gas as the dry gas sealing gas source. At this point, a switching operation for the sealing gas source is required. First, slowly open the process gas supply valve from the propylene compressor outlet pipeline to its dry gas sealing device. Simultaneously, slowly close and eventually completely shut off the control valve on the first gas phase pipeline, cutting off the supply of superheated propylene gas from the propylene evaporator. This switching process must be performed smoothly to ensure stable gas source pressure in the dry gas sealing device and not affect the safe operation of the compressor. After the switching is completed, the dry gas sealing device of the propylene compressor is completely sealed by the process propylene gas at the compressor outlet. The first gas phase pipeline and related heating devices are then shut down, and the propylene evaporator enters standby or preparation state for the next operating condition.

[0049] In some embodiments, optionally, such as Figure 3 As shown, during normal operation, the non-condensable gas treatment process includes: passing non-condensable gas from the propylene condenser into the tube side of the first non-condensable gas cooler for cooling, the separated non-condensable gas is discharged through the flare, and the condensed propylene liquid is returned to the propylene buffer tank; passing leaking gas from the dry gas seal of the propylene compressor into the tube side of the second non-condensable gas cooler for cooling, the separated non-condensable gas is discharged through the flare, and the condensed propylene liquid is discharged into the propylene evaporator.

[0050] Specifically, such as Figure 3As shown, during normal operation, the non-condensable gas treatment process executes the following two sub-processes in parallel: For non-condensable gas from the propylene condenser, the high-pressure (e.g., approximately 1.8 MPaG) non-condensable gas accumulated at the top of the propylene condenser is introduced into the tube-side inlet of the first non-condensable gas cooler through a pipeline. Simultaneously, a portion of the liquid propylene from the propylene buffer tank, after being throttled and depressurized by a pressure-reducing valve (e.g., V1), enters the shell side of the first non-condensable gas cooler and evaporates, absorbing heat to provide cooling for the non-condensable gas in the tube side. The non-condensable gas is cooled in the tube side, and the propylene component contained therein is condensed. The gas-liquid mixture is separated in the lower part or outlet tube box of the first non-condensable gas cooler: the separated liquid propylene flows out from its tube-side liquid outlet by gravity and system pressure difference, returning to the pressure-matched propylene buffer tank; the separated gaseous phase, mainly non-condensable gases such as nitrogen, is depressurized by a pressure regulating valve and discharged into the flare system from its tube-side gaseous outlet. For leaking gas from the dry gas seal of the propylene compressor: the primary leaking gas discharged from the dry gas seal (pressure typically close to or slightly higher than atmospheric pressure) is piped into the tube-side inlet of the second non-condensable gas cooler. Similarly, another portion of liquid propylene from the propylene buffer tank is depressurized and enters its shell side to provide cooling. The leaking gas is cooled within the tube side, where the propylene vapor is condensed. After separation, the condensed liquid propylene phase is discharged from its tube-side liquid phase outlet and, due to its lower pressure, is sent to the propylene evaporator, which is also operating at low pressure, for recovery and vaporization; the remaining non-condensable gas is directly discharged from its tube-side gas phase outlet into the flare system. The propylene vapor phase produced by evaporation in the shell sides of both non-condensable gas coolers is drawn from its respective shell-side gas phase outlet, merges, and returns to the first-stage inlet separator, thus achieving refrigerant recycling.

[0051] In some embodiments, optionally, such as Figure 3 As shown, it also includes an energy recovery step: introducing the exhaust steam from the turbine driving the propylene compressor into the lithium bromide refrigeration unit as a heat source to produce chilled water; and supplying the chilled water to the propylene condenser as a cooling medium.

[0052] Specifically, such as Figure 3As shown, the energy recovery step operates independently of the propylene recovery process. The low-pressure exhaust steam generated by the turbine driving the propylene compressor is piped out in whole or in part and delivered as a driving heat source to the heat source inlet of the lithium bromide refrigeration unit. The lithium bromide refrigeration unit employs the absorption refrigeration principle, using water as the refrigerant and lithium bromide solution as the absorbent. It utilizes the heat energy from the input turbine exhaust steam to drive a refrigeration cycle within its generator, ultimately producing significantly cooled chilled water (e.g., at 5°C or lower) in its evaporator. The produced low-temperature chilled water is pumped out through the chilled water outlet of the lithium bromide refrigeration unit and transported through a piping system to the propylene condenser as its cooling medium, thus partially or completely replacing the traditional process's complete reliance on external circulating water for cooling. This step converts the low-grade waste heat from the turbine exhaust into high-value chilled water cooling capacity, directly reducing the cooling water consumption of the propylene condenser and the overall system energy consumption, achieving efficient cascade utilization of energy.

[0053] In some embodiments, optionally, such as Figure 3 As shown, the turbine exhaust steam, after heat recovery by the lithium bromide refrigeration unit, is further condensed by a mixing condenser, and the turbine exhaust back pressure is controlled by adjusting the spray water volume and / or cooling load returning to the condenser.

[0054] Specifically, such as Figure 3As shown, the turbine exhaust steam, which has released some heat after exiting the lithium bromide refrigeration unit, is introduced into the mixing condenser for final condensation. Turbine exhaust back pressure control is achieved through a multi-stage, prioritized adjustment mechanism, the core of which lies in adjusting the spray water flow rate and temperature (i.e., cooling load) returning to the mixing condenser. When it is necessary to reduce the turbine exhaust back pressure (e.g., when the back pressure is too high), the following priority order is followed: First, the condensate return regulating valve V2 is opened wider to increase the amount of cooling water sprayed to the top of the mixing condenser, enhancing the condensation effect by increasing direct contact heat exchange and rapidly reducing the exhaust pressure. This method has the lowest energy consumption. If increasing regulating valve V2 to its maximum still cannot meet the back pressure requirement, then the air cooler fan frequency is increased to increase its load, thereby reducing the condensate temperature flowing through the air cooler, indirectly reducing the spray water temperature, and enhancing the condensation driving force. If the above methods are still insufficient, finally, the water cooler circulating water regulating valve V8 is opened wider to further reduce the spray water temperature by increasing the water cooler's cooling water flow rate. This method consumes more circulating water and is therefore used as a last resort for regulation. Conversely, when it is necessary to increase the turbine exhaust back pressure (e.g., when the back pressure is too low), the operation is performed in the opposite priority order: first, close the water cooler circulating water regulating valve; second, reduce the air cooler load; and finally, close the condensate return regulating valve V2. Through the above-mentioned graded and optimized control method, it is possible to maximize the use of air cooling water conservation while ensuring the efficient and stable operation of the turbine, flexibly respond to changes in ambient temperature and load fluctuations, and achieve a balance between operational economy and water conservation.

[0055] In the description of this application, the term "multiple" refers to two or more. Unless otherwise expressly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0056] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0057] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A propylene refrigeration integrated system for reducing propylene consumption and energy consumption, characterized in that, include: A propylene compressor, wherein the propylene compressor comprises a first stage compressor and a second stage compressor; A first-stage inlet separator, the gas phase outlet of which is connected to the first-stage inlet of the propylene compressor; A two-stage inlet separator is connected to the second-stage inlet of the propylene compressor via its gas phase outlet. A propylene condenser, wherein the inlet of the propylene condenser is connected to the second-stage outlet of the propylene compressor; A propylene buffer tank, the inlet of which is connected to the liquid phase outlet of the propylene condenser; A propylene flash evaporator, the inlet of which is connected to the liquid phase outlet of the propylene buffer tank, and the gas phase outlet of which is connected to the two-stage inlet separator; A propylene subcooler, wherein the tube-side inlet of the propylene subcooler is connected to the liquid phase outlet of the propylene flash tank; A propylene evaporator, wherein the propylene evaporator is equipped with a water bath heater; wherein the propylene evaporator has three functional interfaces: The first interface serves as a liquid propylene receiving port, used to receive liquid propylene from the aforementioned inlet separator and / or the system liquid propylene discharge collection pipeline; The second interface, serving as the first gas phase outlet, is selectively connected to the outlet pipeline of the propylene compressor via the first gas phase pipeline, and a heating device is provided on the first gas phase pipeline. The third interface, serving as the second gas phase outlet, is selectively connected to the aforementioned inlet separator via a second gas phase pipeline; The non-condensable gas treatment subsystem includes at least one non-condensable gas cooler, the tube side of which is used to flow and cool non-condensable gas from the system, the shell side of which is used to flow liquid propylene from the propylene buffer tank to provide cooling, and the shell side gas phase outlet of which is connected to the first-stage inlet separator.

2. The propylene refrigeration integrated system for reducing propylene consumption and energy consumption according to claim 1, characterized in that, It also includes a compressor outlet air cooler, which is installed on the pipeline between the compressor stage outlet of the propylene compressor and the air inlet of the propylene condenser.

3. The propylene refrigeration integrated system for reducing propylene consumption and energy consumption according to claim 1, characterized in that, The non-condensable gas treatment subsystem includes a first non-condensable gas cooler and a second non-condensable gas cooler connected in parallel. The tube-side inlet of the first non-condensable gas cooler is connected to the non-condensable gas outlet of the propylene condenser, and its tube-side liquid phase outlet is connected to the propylene buffer tank. The tube-side inlet of the second non-condensable gas cooler is used to receive leaked gas from the dry gas seal of the propylene compressor, and its tube-side liquid phase outlet is connected to the propylene evaporator.

4. The propylene refrigeration integrated system for reducing propylene consumption and energy consumption according to claim 1, characterized in that, It also includes an energy recovery subsystem, which includes a lithium bromide refrigeration unit; The heat source inlet of the lithium bromide refrigeration unit is used to receive exhaust steam from the turbine driving the propylene compressor, and the chilled water outlet of the lithium bromide refrigeration unit is connected to the cooling medium inlet of the propylene condenser.

5. The propylene refrigeration integrated system for reducing propylene consumption and energy consumption according to claim 4, characterized in that, The energy recovery subsystem also includes a hybrid condenser connected in series with the lithium bromide refrigeration unit for condensing the turbine exhaust steam flowing out of the lithium bromide refrigeration unit.

6. A method for reducing energy consumption in propylene refrigeration, characterized in that, The propylene refrigeration integrated system as described in any one of claims 2 to 5, wherein the propylene refrigeration energy saving method comprises the following steps: S1. Start-up phase: Liquid propylene from the propylene buffer tank is introduced into the propylene evaporator and heated by the water bath heater to produce saturated propylene gas of 1.1 MPaG to 1.3 MPaG. The saturated propylene gas is then superheated through the first gas phase pipeline and led to the dry gas sealing device of the propylene compressor as sealing gas. S2. Normal operation phase: Liquid propylene from the first inlet separator and the system liquid propylene discharge collection pipeline is introduced into the propylene evaporator through the first interface, and the propylene evaporator is controlled to operate at low pressure. The liquid propylene is evaporated using the water bath heater, and the generated gaseous propylene is returned to the first inlet separator through the second gas pipeline. At the same time, the system non-condensable gas is introduced into the non-condensable gas treatment subsystem to recover the propylene entrained therein. S3, Shutdown and Material Removal Stage: The residual liquid propylene in the system is introduced into the propylene evaporator and heated and evaporated using the water bath heater. The generated propylene gas is introduced into the outlet pipeline of the propylene compressor through the first gas phase pipeline and condensed and recovered into the propylene buffer tank using the compressor outlet air cooler and the propylene condenser.

7. The propylene refrigeration energy-saving method according to claim 6, characterized in that, During the start-up phase, when the outlet pressure of the propylene compressor stabilizes at 1.1 MPaG or higher, the propylene gas from the outlet of the propylene compressor is switched to be used as the sealing gas, and the first gas phase pipeline is shut off.

8. The propylene refrigeration energy-saving method according to claim 6, characterized in that, During the normal operation phase, the non-condensable gas treatment process includes: The non-condensable gas from the propylene condenser is passed into the tube side of the first non-condensable gas cooler for cooling. The separated non-condensable gas is discharged from the flare, and the condensed propylene liquid is returned to the propylene buffer tank. The leaking gas from the dry gas seal of the propylene compressor is passed into the tube side of the second non-condensable gas cooler for cooling. The separated non-condensable gas is discharged to the flare, and the condensed propylene liquid is discharged into the propylene evaporator.

9. The propylene refrigeration energy-saving method according to claim 6, characterized in that, It also includes energy recovery steps: The exhaust steam from the turbine driving the propylene compressor is introduced into the lithium bromide refrigeration unit as a heat source to produce chilled water; The chilled water is supplied to the propylene condenser as a cooling medium.

10. The propylene refrigeration energy-saving method according to claim 9, characterized in that, The turbine exhaust steam, after heat recovery by the lithium bromide refrigeration unit, is further condensed in a mixing condenser, and the turbine exhaust back pressure is controlled by adjusting the spray water volume and / or cooling load returning to the condenser.

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