Ethylene storage and transportation system

Abstract

According to the ethylene storage and transportation system, cooling capacity of liquid-phase ethylene and cooling capacity of gas-phase ethylene are recycled in a unified mode by arranging the low-temperature cold storage assembly, the temperature of the gas-phase ethylene needing to be cooled is reduced, and power consumption of the propylene ice maker is saved. The high-temperature heat storage assembly is arranged to absorb heat of gas-phase ethylene and is used for heating liquid-phase ethylene needing to be heated, and steam consumption in the ethylene vaporization heating process is reduced. According to the scheme, the propylene ice maker, the circulating water guarantee heat exchanger, the cold water guarantee heat exchanger and the heaters are arranged, the working condition that the heat and the cold of the system are not matched due to flow fluctuation of ethylene BOG and low-temperature liquid-phase ethylene can be overcome, and efficient and stable operation of the system is achieved.

Description

Technical Field

[0001] The present application belongs to the technical field of ethylene storage and transportation, and specifically, relates to an ethylene storage and transportation system. Background Art

[0002] With the development of the petroleum industry and the national economy, the demand for ethylene has increased. In addition to the ethylene products produced by the ethylene plant, a large amount of ethylene needs to be purchased from outside, which needs to be stored during transportation. At present, the main storage method for ethylene is the fully refrigerated ethylene storage method.

[0003] The ethylene produced by the ethylene plant and the ethylene purchased by the atmospheric low-temperature tank truck or tank ship need to be stored in the low-temperature liquid phase ethylene storage tank. According to the needs of downstream users, the liquid phase ethylene (about -103°C) in the storage tank is pressurized to the pressure required by the downstream users through the ethylene pump outside the storage tank, and then enters the ethylene vaporizer for heating to obtain high-temperature and high-pressure gaseous ethylene for use by the downstream device. The heat source used by the industrial ethylene vaporizer is generally steam. The process of ethylene pressurization and reheating not only consumes a large amount of steam, but also the cold capacity of the ethylene itself is not recycled. Usually, the temperature difference between the low-temperature liquid phase ethylene storage tank and the environment can reach about 140°C. Therefore, during the process of ethylene pump pressurization, precooling of the ethylene pipeline for unloading from the ship / truck, pipeline transportation, storage in the storage tank, etc., the low-temperature liquid phase ethylene absorbs the heat of the ambient temperature to produce a large amount of ethylene evaporation (BOG, Boil Off Gas) gas. The temperature fluctuation of the ethylene product produced by the ethylene plant and the temperature fluctuation of the purchased ethylene will also cause the increase of BOG gas. The existing technology generally compresses the atmospheric pressure ethylene BOG gas into high-pressure and high-temperature gas-phase ethylene, condenses it into high-pressure and low-temperature liquid-phase ethylene through an ethylene ice machine, and then returns it to the ethylene storage tank after throttling. In this process, the BOG compressor and the ethylene ice machine consume a lot of electricity, and the high-temperature heat of the gas-phase ethylene between the stages and at the outlet of the BOG compressor is basically wasted, resulting in high overall energy consumption of the ethylene storage and transportation device. Summary of the invention

[0004] In view of this, the purpose of the present application is to propose an ethylene storage and transportation system to solve the technical problem of high overall energy consumption of ethylene storage and transportation devices in the prior art.

[0005] The technical solution of the present application provides an ethylene storage and transportation system, including an ethylene tank for storing liquid ethylene; and also includes a cold storage component, a heat storage component and an output component:

[0006] The cold storage assembly comprises a first heater, an ethylene condenser, a first buffer tank, a first circulation pump and a second heater connected to each other, and the cold storage assembly further comprises a propylene ice machine connected to the ethylene condenser; the first heater, the second heater and the propylene ice machine in the cold storage assembly are all connected to the ethylene tank;

[0007] The heat storage component comprises a third heater, a first cooler, a second cooler, a second buffer tank, a second circulation pump, a circulating water guarantee heat exchanger and a cold water guarantee heat exchanger connected to each other; the third heater in the heat storage component is connected to the first heater, the first cooler is connected to the second heater, and the second cooler is connected to the ethylene condenser;

[0008] The output component comprises a fourth heater, an input end of the fourth heater is connected to the third heater, and an output end of the fourth heater is connected to an ethylene demand end.

[0009] In some schemes, the ethylene storage and transportation system is characterized in that the first heater, the third heater and the fourth heater heat the liquid ethylene output from the ethylene tank in sequence, vaporize the liquid ethylene into gaseous ethylene that meets the temperature requirement of the ethylene demand end, and then transport the gaseous ethylene to the ethylene demand end.

[0010] In some schemes, the ethylene storage and transportation system described in the cold storage component, the first buffer tank outputs a first intermediate medium, the first intermediate medium is pressurized by the first circulation pump and transported to the hot flow channels of the first heater and the second heater respectively, for heat exchange with liquid ethylene and gaseous ethylene; the first intermediate medium recovers the cold of liquid ethylene and gaseous ethylene and its temperature is reduced; the first intermediate medium with reduced temperature is transported to the cold flow channel of the ethylene condenser, for heat exchange with the gaseous ethylene, the first intermediate medium releases the cold to condense the gaseous ethylene into liquid ethylene, and the first intermediate medium releases the cold and is transported back to the first buffer tank.

[0011] In some schemes of the ethylene storage and transportation system, the first intermediate medium includes ethylene or Freon; the temperature of the first intermediate medium is reduced to -50 to -70°C in the first heater and the second heater; the temperature of the first intermediate medium is increased to -20 to 10°C after releasing cold in the ethylene condenser.

[0012] In some schemes, the ethylene storage and transportation system described in the heat storage component, the second buffer tank outputs the second intermediate medium, and the second intermediate medium enters the hot flow channel of the third heater after being pressurized and heated by the second circulation pump, and is used to exchange heat with the liquid ethylene in the cold flow channel, so that the liquid ethylene is heated and vaporized to gaseous ethylene; after the temperature of the second intermediate medium is reduced, it enters the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; the temperature of the second intermediate medium is adjusted by the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger, and then enters the cold flow channels of the first cooler and the second cooler respectively, and exchanges heat with the gaseous ethylene in the hot flow channels of the first cooler and the second cooler, the gaseous ethylene is cooled, and the temperature of the second intermediate medium is increased and transported to the second buffer tank.

[0013] In some schemes of the ethylene storage and transportation system, the second intermediate medium includes an ethylene glycol aqueous solution, water or heat transfer oil; the temperature of the second intermediate medium is reduced to -20 to 50°C in the third heater; the temperature of the second intermediate medium is adjusted to 15 to 30°C by the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; the temperature of the second intermediate medium is increased to 60 to 85°C after passing through the first cooler and the second cooler.

[0014] In some embodiments of the ethylene storage and transportation system, at least one first compressor is connected between the second heater and the first cooler; at least one second compressor is connected between the first cooler and the second cooler;

[0015] The liquid ethylene output from the ethylene tank passes through the cold flow channel of the second heater, and then is pressurized and heated by the first compressor, cooled by the first cooler, and pressurized and heated by the second compressor to obtain gaseous ethylene which enters the hot flow channel of the second cooler; the second cooler cools the gaseous ethylene and then transports it to the propylene ice machine, and the propylene ice machine outputs liquid ethylene to the ethylene tank.

[0016] In some embodiments of the ethylene storage and transportation system, a throttle valve is provided between the propylene ice machine and the ethylene tank.

[0017] The ethylene storage and transportation system described in some embodiments further comprises:

[0018] The first temperature sensor is arranged at the outlet of the circulating water protection heat exchanger and the cold water protection heat exchanger; the first temperature sensor is used to detect the temperature of the second intermediate medium output by the circulating water protection heat exchanger and the cold water protection heat exchanger; the system controller adjusts the circulating water and cold water flow of the circulating water protection heat exchanger and the cold water protection heat exchanger according to the temperature of the second intermediate medium.

[0019] The ethylene storage and transportation system described in some embodiments further comprises:

[0020] The second temperature sensor is arranged at the outlet of the propylene ice machine; the second temperature sensor is used to detect the temperature of ethylene output by the propylene ice machine; the system controller adjusts the operating load of the propylene ice machine and the opening of the throttle valve according to the temperature of ethylene output by the propylene ice machine.

[0021] Compared with the prior art, the above solution provided in the embodiment of the present application has the following advantages:

[0022] The ethylene storage and transportation system provided by the present application recovers the cold of liquid-phase ethylene and gas-phase ethylene in a unified manner by setting a low-temperature cold storage component, which is used to reduce the temperature of gas-phase ethylene that needs to be cooled, thereby saving the power consumption of the propylene ice machine. By setting a high-temperature heat storage component to absorb the heat of gas-phase ethylene and use it to heat the liquid-phase ethylene that needs to be heated, the steam consumption in the ethylene vaporization and heating process is saved. The present solution is provided with a propylene ice machine, a circulating water guarantee heat exchanger, a cold water guarantee heat exchanger and multiple heaters, which can overcome the operating conditions where the heat and cold of the system are mismatched due to fluctuations in the flow of ethylene BOG and low-temperature liquid-phase ethylene, and achieve efficient and stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above-mentioned features and technical advantages of the present application will become clearer and easier to understand through the following description of its embodiments in conjunction with the accompanying drawings.

[0024] Figure 1 This is a structural schematic diagram of an ethylene storage and transportation system according to an embodiment of the present application;

[0025] Figure 2 This is a structural block diagram of the control part of the ethylene storage and transportation system described in one embodiment of the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. The same parts are represented by the same figure numerals. It should be noted that the words "front", "rear", "left", "right", "up" and "down" used in the following description refer to the directions in the accompanying drawings. The words "inside" and "outside" used refer to the direction toward or away from the geometric center of a specific component, respectively.

[0027] The present application embodiment provides an ethylene storage and transportation system, such as Figure 1As shown, it includes an ethylene tank 1 for storing liquid ethylene; it also includes a cold storage component, a heat storage component and an output component as shown in the figure, the output component corresponds to the ethylene pipeline channel, and the output component is used to connect with the ethylene demand end. Among them, the cold storage component includes a first heater 3, an ethylene condenser 11, a first buffer tank 14, a first circulation pump 15 and a second heater 6 connected to each other, and the cold storage component also includes a propylene ice machine 12 connected to the ethylene condenser 11; the first heater 3, the second heater 6 and the propylene ice machine 12 in the cold storage component are all connected to the ethylene tank 1, the propylene ice machine 12 is connected to one inlet end of the ethylene tank 1, and the first heater 3 and the second heater 6 are connected to the two outlet ends of the ethylene tank 1. The heat storage component includes a third heater 4, a first cooler 8, a second cooler 10, a second buffer tank 16, a second circulation pump 17, a circulating water guarantee heat exchanger 18 and a cold water guarantee heat exchanger 19 connected to each other; the third heater 4 in the heat storage component is connected to the first heater 3, the first cooler 8 is connected to the second heater 10, and the second cooler 10 is connected to the ethylene condenser 11. The output component includes a fourth heater 5, the input end of the fourth heater 5 is connected to the third heater 4, and the output end of the fourth heater 5 is connected to the ethylene demand end.

[0028] In the ethylene storage and transportation system of the above embodiment, the ethylene feed sources of the ethylene tank 1 of low-temperature liquid ethylene include ethylene unloaded from ships, ethylene unloaded from trucks, and ethylene products produced by ethylene plants. The generation of ethylene BOG at the top of the ethylene tank 1 is due to changes in ambient temperature, the operation of the ethylene pump 2, precooling of the unloading and unloading pipelines, temperature fluctuations of ethylene products produced by the ethylene plant, etc., and the flow rate of ethylene BOG fluctuates randomly; the flow rate of low-temperature liquid ethylene output from the bottom of the ethylene tank 1 is determined by the operating load of the user demand side. The ethylene demand side includes one or more devices of VCM, PO / SM, PP, HDPE, LLDPE, EO, etc.

[0029] The low-temperature liquid ethylene stored in the low-temperature liquid ethylene tank 1 is pressurized to the pressure required by the ethylene demand end by the ethylene pump 2, and then enters the cold flow channels of the first heater 3, the third heater 4 and the fourth heater 5 in sequence, and the low-temperature liquid ethylene is heated and vaporized into high-temperature gas-phase ethylene and enters the ethylene demand end; the low-temperature normal-pressure ethylene BOG from the top of the low-temperature liquid ethylene storage tank 1 enters the cold flow channel of the second heater 6, and the low-temperature ethylene BOG is heated and reheated and enters the hot flow channels of the first cooler 8 and the second cooler 10, and the high-temperature gas-phase ethylene is cooled and enters the hot flow channel of the ethylene condenser 11, and the gas-phase ethylene is condensed into low-temperature liquid-phase ethylene and then enters the propylene ice machine 12 for further cooling, and the low-temperature liquid-phase ethylene coming out of the propylene ice machine 12 returns to the low-temperature liquid ethylene storage tank 1.

[0030] In the cold storage component, the first buffer tank 14 stores a low-temperature first intermediate medium, which is mainly used to recover the cold of low-temperature liquid ethylene and gaseous ethylene, and use the recovered cold to condense the gaseous ethylene in the hot flow channel into low-temperature liquid ethylene.

[0031] The second buffer tank 16 in the heat storage component stores a high-temperature second intermediate medium, which is used to heat the low-temperature liquid ethylene in the cold flow channel and heat it to vaporize it into high-temperature gas-phase ethylene, that is, to absorb the cold energy of the low liquid-phase ethylene, and use the absorbed cold energy, the cold energy obtained by the regulating functions of the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19, and the cold energy provided by the first cooler 8 and the second cooler 10 to cool the high-temperature gas-phase ethylene in the hot flow channel to a lower temperature.

[0032] The ethylene storage and transportation system in the above scheme recovers the cold of liquid and gaseous ethylene in a unified manner by setting up a low-temperature cold storage component, which is used to reduce the temperature of gaseous ethylene that needs to be cooled, saving the power consumption of the propylene ice machine. By setting up a high-temperature heat storage component to absorb the heat of gaseous ethylene, it is used to heat the liquid ethylene that needs to be heated, saving the steam consumption in the ethylene vaporization and heating process. This scheme is equipped with a propylene ice machine, a circulating water guarantee heat exchanger, a cold water guarantee heat exchanger and multiple heaters, which can overcome the operating conditions where the system heat and cold are mismatched due to fluctuations in the flow of ethylene BOG and low-temperature liquid ethylene, and achieve efficient and stable operation of the system.

[0033] In some embodiments of the ethylene storage and transportation system, the first heater 3, the third heater 4 and the fourth heater 5 heat the liquid ethylene output from the ethylene tank in sequence, vaporize the liquid ethylene into gaseous ethylene that meets the temperature requirement of the ethylene demand end, and then transport the gaseous ethylene to the ethylene demand end. Preferably, the fourth heater 5 uses steam as a heat source to heat the high-temperature gaseous ethylene output from the third heater 4 to the temperature required by the ethylene demand end. Specifically, when practical, the steam flow rate can be accurately controlled by the ethylene outlet temperature of the fourth heater 5.

[0034] Preferably, in the ethylene storage and transportation system, in the cold storage component, the first buffer tank 14 outputs the first intermediate medium, which is pressurized by the first circulation pump 15 and transported to the heat flow channels of the first heater 3 and the second heater 6 respectively, for heat exchange with liquid ethylene and gaseous ethylene; the first intermediate medium recovers the cold of liquid ethylene and gaseous ethylene and its temperature is reduced; the first intermediate medium with reduced temperature is transported to the cold flow channel of the ethylene condenser 11, for heat exchange with the gaseous ethylene, the first intermediate medium releases cold to condense the gaseous ethylene into liquid ethylene, and the first intermediate medium releases cold and transports back to the first buffer tank 14. Further preferably, the first intermediate medium includes ethylene or Freon; the temperature of the first intermediate medium is reduced to -50 to -70°C in the first heater 3 and the second heater 6; the temperature of the first intermediate medium increases to -20 to 10°C after releasing cold in the ethylene condenser 11. That is, the first intermediate medium is cooled to -50 to -70°C in the first heater 3 and the second heater 6, and the first intermediate medium at -50 to -70°C is heated to -20 to 10°C in the ethylene condenser 11. In actual application, the temperature value can be selected within the above range and can be a fluctuating value.

[0035] Furthermore, in the ethylene storage and transportation system, in the heat storage component, the second buffer tank 16 outputs a second intermediate medium, and the second intermediate medium is pressurized and heated by the second circulation pump 17 and enters the hot flow channel of the third heater 4, for heat exchange with the liquid ethylene in the cold flow channel, so that the liquid ethylene is heated and vaporized to gaseous ethylene; after the temperature of the second intermediate medium is reduced, it enters the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19; the temperature of the second intermediate medium is adjusted by the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19, and then enters the cold flow channels of the first cooler 8 and the second cooler 10 respectively, and exchanges heat with the gaseous ethylene in the hot flow channels of the first cooler 8 and the second cooler 10, the gaseous ethylene is cooled, and the temperature of the second intermediate medium is increased and transported to the second buffer tank 16. Preferably, the second intermediate medium includes ethylene glycol aqueous solution, water or heat transfer oil; the temperature of the second intermediate medium is reduced to -20 to 50°C in the third heater 4; the temperature of the second intermediate medium is adjusted to 15 to 30°C by the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19; the temperature of the second intermediate medium is increased to 60 to 85°C after passing through the first cooler 8 and the second cooler 10. That is, the second intermediate medium is cooled to -20 to 50°C in the third heater 4, the second intermediate medium of -20 to 50°C is adjusted to 15 to 30°C in the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19, and then enters the first cooler 8 and the second cooler 10 to be heated to 60 to 85°C. In actual application, the temperature value can be selected within the above range and can be a fluctuating value.

[0036] As shown in the figure, preferably, a throttle valve 13 is arranged between the propylene ice machine and the ethylene tank; at least one first compressor 7 including a first compressor in the figure is connected between the second heater 6 and the first cooler 8; at least one second compressor 9 including a second compressor in the figure is connected between the first cooler 8 and the second cooler 10; the liquid ethylene output from the ethylene tank 1 passes through the cold flow channel of the second heater 6, and then is pressurized and heated by the first compressor 7, cooled by the first cooler 8 and pressurized and heated by the second compressor 9 to obtain gaseous ethylene that enters the hot flow channel of the second cooler 10; the second cooler 10 cools the gaseous ethylene and transports it to the propylene ice machine 12, and the propylene ice machine 12 outputs liquid ethylene to the ethylene tank 1. The whole cycle process is as follows: low-temperature normal-pressure ethylene BOG from the top of the ethylene tank 1 enters the cold flow channel of the second heater 6, the low-temperature ethylene BOG is heated and then enters the first compressor 7 for pressurization, the high-temperature gaseous ethylene coming out of the first compressor 7 enters the hot flow channel of the first cooler 8, the high-temperature gaseous ethylene is cooled and then enters the second compressor 9 for further pressurization, the high-temperature and high-pressure gaseous ethylene at the outlet of the second compressor 9 enters the hot flow channel of the second cooler 10, the high-temperature gaseous ethylene is cooled and then enters the hot flow channel of the ethylene condenser 11, the gaseous ethylene is condensed into low-temperature liquid ethylene, and then enters the propylene ice machine 12 for further cooling, and the low-temperature liquid ethylene coming out of the propylene ice machine 12 is decompressed by the throttle valve 13 and then returns to the low-temperature liquid ethylene storage tank 1.

[0037] Furthermore, the ethylene storage and transportation system provided in the embodiment of the present application also includes a first temperature sensor TS1, which is arranged at the outlet of the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19; the first temperature sensor TS1 is used to detect the temperature of the second intermediate medium output by the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19; the system controller adjusts the circulating water and cold water flow of the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19 according to the temperature of the second intermediate medium. Specifically, the system controller controls the opening of the circulating water guarantee heat exchanger valve CW and the cold water guarantee heat exchanger valve BS. In the scheme of this embodiment, a first TS1 temperature controller is arranged on the second intermediate medium pipeline of the guarantee heat exchanger outlet, and the opening of the inlet valve of the circulating water and the cold water is controlled by the temperature of the second intermediate medium at the guarantee heat exchanger outlet. When the ethylene BOG flow rate is large and the required liquid ethylene flow rate at the downstream ethylene demand end is small, the operating temperature of the second intermediate medium exceeds 30°C, indicating that the heat of high-temperature gas-phase ethylene recovered from the first cooler 8 and the second cooler 10 is greater than the heat required for heating ethylene at the third heater 4. The system controller issues an instruction to reduce the opening of the circulating water guarantee heat exchanger valve CW and increase the opening of the cold water guarantee heat exchanger valve BS to cool the second intermediate medium to 15°C to reduce the compressor inlet gas ethylene temperature, improve the compressor efficiency, and reduce compression energy consumption; when the ethylene BOG flow rate is small and the required liquid ethylene flow rate at the downstream ethylene demand end is large, the operating temperature of the second intermediate medium is lower than 15 ℃, it indicates that the heat of high-temperature gas-phase ethylene recovered from the first cooler 8 and the second cooler 10 is less than the heat required for heating ethylene at the third heater 4, and the system controller issues an instruction to reduce the opening of the cold water protection heat exchanger valve BS and increase the opening of the circulating water protection heat exchanger valve CW, and heat the second intermediate medium to 30℃ to input the heat of the circulating water into the second intermediate medium, thereby heating the ethylene at the outlet of the third heater 4 to a higher temperature, thereby reducing the steam consumption at the fourth heater 5; when the intermediate medium temperature is between 15 and 30℃, the openings of the two inlet valves CW and BS of the circulating water protection heat exchanger 18 and the cold water protection heat exchanger 19 for circulating water and cold water are not adjusted.

[0038] Further preferably, the ethylene storage and transportation system further includes a second temperature sensor TS2, which is arranged at the outlet of the propylene ice machine 12; the second temperature sensor TS2 is used to detect the temperature of ethylene output by the propylene ice machine 12; the system controller adjusts the operating load of the propylene ice machine 12 and the opening of the throttle valve 13 according to the temperature of ethylene output by the propylene ice machine 12. In specific application, when the ethylene BOG flow rate is large and the liquid-phase ethylene flow rate required by the ethylene demand side is small, the liquid-phase ethylene cooling capacity recovered from the first heater 3 and the second heater 6 cannot meet the demand for gas-phase ethylene condensation at the ethylene condenser 11, and the propylene ice machine 12 is turned on, and the operating load of the propylene ice machine 12 is controlled by the ethylene temperature at the outlet of the propylene ice machine 12; when the ethylene BOG flow rate is small and the liquid-phase ethylene flow rate required by the ethylene demand side is large, the liquid-phase ethylene cooling capacity recovered from the first heater 3 and the second heater 6 can cool the ethylene at the outlet of the ethylene condenser 11 to a lower temperature, which can reduce the gas-phase ethylene flow rate flashed after the throttle valve 13, which is beneficial to reducing the BOG flow rate at the top of the low-temperature liquid ethylene storage tank 1 and reducing the compression power consumption.

[0039] Below, the implementation process and effect of the solution in the above embodiment of the present application are further explained in conjunction with a specific application example:

[0040] A large chemical park has an ethylene plant, a VCM plant, a POSM plant and an ethylene storage and transportation plant. The ethylene products produced by the ethylene plant and the ethylene unloaded from the dock are stored in a low-temperature liquid phase ethylene tank 1 in the storage and transportation plant. The pressure of the ethylene tank 1 is normal pressure and the temperature is about -102°C. According to the ethylene demand of the downstream VCM plant and POSM plant, the ethylene pump 2 delivers the corresponding flow of ethylene from the low-temperature liquid phase ethylene tank 1; the ethylene BOG gas flow rate at the top of the low-temperature liquid phase ethylene tank 1 changes with the changes in factors such as the ambient temperature, the power of the ethylene pump, the temperature of ethylene produced by the ethylene plant, and the precooling of the unloading ethylene pipeline. Now, taking the operating conditions of low-temperature liquid phase ethylene output flow rate of 20t / h, liquid phase ethylene output pressure of 4.8MPaG, ethylene BOG flow rate of 10t / h, and ethylene BOG temperature of -80°C as an example, the above scheme is explained.

[0041] The normal pressure and -102°C liquid ethylene from the low-temperature liquid ethylene tank 1 is pressurized to 4.8MPaG and -100°C by the ethylene pump 2, and then enters the cold flow channel of the first heater 3 to be heated to -20°C. The -20°C liquid ethylene then enters the cold flow channel of the third heater 4 to be heated and vaporized to 60°C. The 60°C gaseous ethylene enters the cold flow channel of the fourth heater 5, is heated to 200°C with S20 steam, and then enters the downstream VCM and POSM units, i.e., the ethylene demand end reactor, for reaction. The fourth heater 5 consumes about 2.8 t / h of S20 steam.

[0042] The ethylene BOG at normal pressure and -80°C from the tank top of the low-temperature liquid phase ethylene tank 1 enters the cold flow channel of the second heater 6 and is heated to -20°C. The low-temperature ethylene BOG is heated and then reheated and enters the first compressor 7 to be pressurized to 0.6 MPaG and 126°C. The high-temperature gas-phase ethylene coming out of the first compressor 7 enters the hot flow channel of the first cooler 8. The high-temperature gas-phase ethylene is cooled to 35°C and enters the second compressor 9 to be further pressurized to 2.1 MPaG and 127°C. The high-temperature and high-pressure gas-phase ethylene at the outlet of the second compressor 9 enters the hot flow channel of the second cooler 10. The high-temperature gas-phase ethylene is cooled to 35°C and enters the hot flow channel of the ethylene condenser 11. The gas-phase ethylene is completely condensed to liquid-phase ethylene at -47°C, and is directly returned to the low-temperature liquid-phase ethylene tank 1 after being depressurized by the throttle valve 13. The propylene ice machine 12 does not operate.

[0043] The first heater 3, the second heater 6, the ethylene condenser 11, the propylene ice machine 12, the first buffer tank 14 and the first circulation pump 15 constitute a low-temperature cold storage component. The first intermediate medium used in the cold storage component is liquid ethylene. The first intermediate medium ethylene at -15°C is output from the first buffer tank 14, and after being pressurized by the first circulation pump 15, it enters the hot flow channels of the first heater 3 and the second heater 6 respectively, and heats the -100°C liquid ethylene and the -80°C gaseous ethylene in the cold flow channel to -20°C respectively. 1.2MW and 0.2MW of cold energy are recovered respectively, the temperature of the first intermediate medium ethylene is reduced to -65°C, the intermediate medium ethylene at -65°C enters the cold flow channel of the ethylene condenser 11 again, and the gas phase ethylene in the hot flow channel is condensed from 35°C to liquid phase ethylene at -47°C. The temperature of the first intermediate medium ethylene is restored to -15°C and then circulated back to the first buffer tank 14. This process recovers a total of about 1.4MW of low-temperature ethylene cold energy, which is used to completely condense the ethylene BOG. ​​The propylene ice machine does not need to be turned on at all, saving 1060kW of electricity consumption;

[0044] The third heater 4, the first cooler 8, the second cooler 10, the second buffer tank 16, the second circulation pump 17, the circulating water guarantee heat exchanger 18 and the cold water guarantee heat exchanger 19 constitute a heat storage component. The second intermediate medium ethylene glycol aqueous solution of 70°C is output from the second buffer tank 16, and after being pressurized by the second circulation pump 17, it enters the hot flow channel of the third heater 4, and heats and vaporizes the -20°C liquid ethylene in the cold flow channel to 60°C, with a heat exchange load of 2.2MW. The temperature of the second intermediate medium ethylene glycol aqueous solution is reduced to -15°C, and the -15°C ethylene glycol aqueous solution It enters the circulating water guarantee heat exchanger 18, is heated to 30°C by 40°C circulating water, with a heat exchange load of 1.2MW, and then enters the cold flow channels of the first cooler 8 and the second cooler 10 to take heat, and cools the high-temperature gas-phase ethylene of 125°C and 127°C in the hot flow channels of the first cooler 8 and the second cooler 10 to 35°C, with heat exchange loads of 0.5MW and 0.5MW respectively. The second intermediate medium ethylene glycol aqueous solution takes heat and raises the temperature to 70°C and then circulates back to the second buffer tank 16. In this process, a total of 2.2MW of compressor interstage heat and circulating water heat are recovered for vaporization heating of ethylene.

[0045] In the above example, 1.2MW of gas-phase ethylene condensation heat, 2.2MW of compressor interstage heat and circulating water heat are recovered. Only 2.8t / h S20 steam is consumed in the entire liquid-phase ethylene vaporization and heating process, which reduces 5.6t / h S20 steam consumption compared to the complete vaporization and heating process of liquid-phase ethylene. The scheme in the above example recovers 1.4MW of low-temperature ethylene cooling capacity, which completely saves 1060kW of ice machine power consumption compared to ice machine refrigeration and condensation of ethylene BOG; the scheme in the above example fully realizes the recovery and utilization of compressor interstage heat and low-temperature ethylene cooling capacity.

[0046] A person skilled in the art should understand that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present application should be included in the protection scope of the present application.

Claims

1. An ethylene storage and transportation system, comprising an ethylene tank for storing liquid ethylene; characterized in that: It also includes cold storage components, heat storage components and output components: The cold storage assembly comprises a first heater, an ethylene condenser, a first buffer tank, a first circulation pump and a second heater connected to each other, and the cold storage assembly further comprises a propylene ice machine connected to the ethylene condenser; the first heater, the second heater and the propylene ice machine in the cold storage assembly are all connected to the ethylene tank; The heat storage component comprises a third heater, a first cooler, a second cooler, a second buffer tank, a second circulation pump, a circulating water guarantee heat exchanger and a cold water guarantee heat exchanger connected to each other; the third heater in the heat storage component is connected to the first heater, the first cooler is connected to the second heater, and the second cooler is connected to the ethylene condenser; The output component comprises a fourth heater, an input end of the fourth heater is connected to the third heater, and an output end of the fourth heater is connected to an ethylene demand end.

2. The ethylene storage and transportation system according to claim 1, characterized in that: The first heater, the third heater and the fourth heater heat the liquid ethylene output from the ethylene tank in sequence, vaporize the liquid ethylene into gaseous ethylene that meets the temperature requirement of the ethylene demand end, and then transport the gaseous ethylene to the ethylene demand end.

3. The ethylene storage and transportation system according to claim 1, characterized in that: In the cold storage component, the first buffer tank outputs a first intermediate medium, which is pressurized by the first circulation pump and transported to the heat flow channels of the first heater and the second heater respectively for heat exchange with liquid ethylene and gaseous ethylene; the temperature of the first intermediate medium is reduced after recovering the cold of the liquid ethylene and the gaseous ethylene; The first intermediate medium after the temperature is reduced is transported to the cold flow channel of the ethylene condenser to exchange heat with the gas phase ethylene. The first intermediate medium releases cold energy to condense the gas phase ethylene into liquid phase ethylene. The first intermediate medium releases cold energy and is transported back to the first buffer tank.

4. The ethylene storage and transportation system according to claim 3, characterized in that: The first intermediate medium includes ethylene or Freon; the temperature of the first intermediate medium is reduced to -50 to -70°C in the first heater and the second heater; the temperature of the first intermediate medium is increased to -20 to 10°C after releasing cold in the ethylene condenser.

5. The ethylene storage and transportation system according to claim 1, characterized in that: In the heat storage component, the second buffer tank outputs the second intermediate medium, and the second intermediate medium enters the hot flow channel of the third heater after being pressurized and heated by the second circulation pump, and is used to exchange heat with the liquid ethylene in the cold flow channel, so that the liquid ethylene is heated and vaporized to gaseous ethylene; after the temperature of the second intermediate medium is reduced, it enters the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; the temperature of the second intermediate medium is adjusted by the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger, and then enters the cold flow channels of the first cooler and the second cooler respectively, and exchanges heat with the gaseous ethylene in the hot flow channels of the first cooler and the second cooler, the gaseous ethylene is cooled, and the temperature of the second intermediate medium is increased and transported to the second buffer tank.

6. The ethylene storage and transportation system according to claim 5, characterized in that: The second intermediate medium includes ethylene glycol aqueous solution, water or heat transfer oil; the temperature of the second intermediate medium is reduced to -20 to 50°C in the third heater; the temperature of the second intermediate medium is adjusted to 15 to 30°C by the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; the temperature of the second intermediate medium is increased to 60 to 85°C after passing through the first cooler and the second cooler.

7. The ethylene storage and transportation system according to claim 1, characterized in that: At least one first compressor is connected between the second heater and the first cooler; at least one second compressor is connected between the first cooler and the second cooler; The liquid ethylene output from the ethylene tank passes through the cold flow channel of the second heater, and then is pressurized and heated by the first compressor, cooled by the first cooler, and pressurized and heated by the second compressor to obtain gaseous ethylene which enters the hot flow channel of the second cooler; the second cooler cools the gaseous ethylene and then transports it to the propylene ice machine, and the propylene ice machine outputs liquid ethylene to the ethylene tank.

8. The ethylene storage and transportation system according to claim 7, characterized in that: A throttle valve is provided between the propylene ice machine and the ethylene tank.

9. The ethylene storage and transportation system according to claim 8, characterized in that: Also includes: A first temperature sensor is arranged at the outlet of the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; The first temperature sensor is used to detect the temperature of the second intermediate medium output by the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger; the system controller adjusts the circulating water and cold water flow of the circulating water guarantee heat exchanger and the cold water guarantee heat exchanger according to the temperature of the second intermediate medium.

10. The ethylene storage and transportation system according to claim 9, characterized in that: Also includes: A second temperature sensor is disposed at the outlet of the propylene ice machine; the second temperature sensor is used to detect the temperature of ethylene output by the propylene ice machine; The system controller adjusts the operating load of the propylene ice machine and the opening of the throttle valve according to the temperature of ethylene output from the propylene ice machine.

Images