Low-temperature ethylene storage system suitable for total storage capacity less than or equal to 500 cubic meters

Abstract

The application discloses a low-temperature ethylene storage system suitable for total reserves less than or equal to 500 cubic meters, which comprises a low-temperature ethylene storage tank, a variable-frequency ethylene conveying pump, a liquid-phase ethylene distributor and an ice machine set. A high-temperature liquid-phase ethylene outlet is arranged at the bottom of the low-temperature ethylene storage tank and is communicated with a pipeline of the variable-frequency ethylene conveying pump. A discharge port of the variable-frequency ethylene conveying pump is communicated with a feeding port pipeline of the ice machine set. The liquid-phase ethylene distributor is arranged in the top of the low-temperature ethylene storage tank and is communicated with a liquid outlet pipeline of the ice machine set. The device can replace a diaphragm compressor and the ice machine set to realize the same cooling loss effect, effectively reduce production cost, improve production safety and reduce production energy consumption.

Description

Technical Field

[0001] This application relates to the field of VOC emission reduction technology, and in particular to a low-temperature ethylene storage system suitable for a total storage capacity of less than or equal to 500 cubic meters. Background Technology

[0002] Ethylene is liquid at -104℃ and normal pressure. Low-temperature ethylene storage tanks are commonly used to store ethylene. The design temperature of these tanks is -196℃ and the design pressure is 0.84MPaG. Under normal operation, the tank pressure is 0.1~0.6MPaG and the tank temperature is -63~-93℃.

[0003] During the daily operation of a cryogenic ethylene storage system, some ethylene will vaporize due to the rise in temperature inside the storage tank caused by ambient temperature, leading to an increase in tank pressure. The pressure relief and discharge to prevent overpressure in the storage tank is called cold loss. The causes of ethylene discharge losses from ethylene storage tanks include: "static evaporation losses from ethylene storage tank cold loss, tank truck unloading losses, heat transfer losses during the operation of ethylene transfer pumps, and heat leakage losses from cryogenic liquid ethylene pipes," etc., resulting in annual ethylene losses in cryogenic ethylene storage systems accounting for more than 10% of the total storage volume.

[0004] All gaseous ethylene leaks from the low-temperature ethylene storage system can only be discharged to the flare system through pipelines. After ignition and combustion, the gas is safely released into the atmosphere. High-frequency and large-volume ethylene gas emissions from the flare system will increase the risk of black smoke from the flare system, affecting the environmental compliance requirements of continuous production. At the same time, in order to eliminate the black smoke in time, the consumption of smoke-extinguishing steam will also increase. In addition, high-frequency and large-volume ethylene gas emissions will also increase the total carbon emissions of the unit.

[0005] To eliminate cold loss in low-temperature ethylene storage systems, existing ethylene storage systems generally use a "compressor + ice machine" as a system-supporting cold loss reduction device, with the specific structure as follows: Figure 1 As shown, the compressor and ice machine pipelines are connected; the compressor is connected to the gas outlet pipeline on the top of the ethylene storage tank; the ice machine is connected to the liquid inlet pipeline of the ethylene storage tank; the vaporized ethylene enters the compressor for pressurization, then enters the ice machine for cooling and liquefaction before entering the ethylene storage tank for storage.

[0006] The device uses a compressor to extract high-temperature gaseous ethylene from the top of the cryogenic ethylene storage tank and send it to an ultra-low temperature ice machine. After cooling the high-temperature ethylene gas into cryogenic liquid ethylene, it is sent back to the cryogenic ethylene storage tank, eliminating the gaseous ethylene emission loss caused by the cold loss of the storage tank, the heat transfer loss of the transfer pump, and the heat leakage loss of the cryogenic pipe of the liquid ethylene.

[0007] Existing "compressor + ice machine" cooling loss reduction devices are applied in areas with a total storage capacity ≤ 500m³. 3 When used in small-scale low-temperature ethylene storage systems, the following shortcomings exist:

[0008] 1) High investment ratio: To avoid the impact of compressor lubricating oil on the quality of ethylene feedstock, the existing units use diaphragm compressors. Diaphragm compressors are expensive, resulting in the investment in existing loss reduction units exceeding the total storage capacity by ≤500m³. 3 The total investment in a small-scale low-temperature ethylene storage system accounts for 50%.

[0009] 2) High operating costs: The existing loss reduction unit includes a compressor and an ice machine, resulting in high overall energy consumption. The unit consumes more than 1341 kWh of electricity to liquefy 1 ton of gaseous ethylene.

[0010] 3) High risk of leakage: Existing loss reduction devices require the installation of compressors, ice machines, and many supporting auxiliary devices. The connection relationship of related pipelines and fittings is complex, which can easily lead to leakage during the cooling process of the vaporized ethylene device.

[0011] The information disclosed in the background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art. Summary of the Invention

[0012] This application addresses the aforementioned technical problems by providing a low-temperature ethylene storage system suitable for a total storage capacity of 500 cubic meters or less. This system is particularly suitable for total storage capacities ≤ 500 cubic meters. 3 In the cooling and liquefaction of cold-loss gaseous ethylene generated by the low-temperature ethylene storage system, this effectively solves the problem of loss reduction devices in existing low-temperature ethylene storage systems with a total storage capacity ≤500m³. 3 The application of small-scale low-temperature ethylene storage systems faces challenges such as high investment ratios, high operating costs, and significant leakage risks.

[0013] This application provides a cryogenic ethylene storage system suitable for a total storage capacity of less than or equal to 500 cubic meters, including: a cryogenic ethylene storage tank, a variable frequency ethylene transfer pump, a liquid phase ethylene distributor, and an ice unit;

[0014] The bottom of the low-temperature ethylene storage tank is equipped with a high-temperature liquid ethylene outlet, which is connected to the pipeline of the variable frequency ethylene delivery pump; the outlet of the variable frequency ethylene delivery pump is connected to the inlet pipeline of the ice unit; the liquid phase ethylene distributor is housed inside the top of the low-temperature ethylene storage tank and is connected to the outlet pipeline of the ice unit.

[0015] Preferably, the liquid phase ethylene distributor includes: a liquid phase ethylene distributor feed pipe, multiple liquid phase ethylene distributor claw-type distribution pipes, and multiple liquid phase ethylene distributor nozzles; one end of each liquid phase ethylene distributor claw-type distribution pipe is connected to the bottom end of the liquid phase ethylene distributor feed pipe and is at the same height; the liquid phase ethylene distributor claw-type distribution pipes are evenly distributed along the circumference of the liquid phase ethylene distributor feed pipe; the included angle between adjacent liquid phase ethylene distributor claw-type distribution pipes is 120°.

[0016] The nozzles of the liquid phase ethylene distributor are spaced apart on the bottom surface of the claw-type distribution pipe of the ethylene distributor and are connected to the claw-type distribution pipe of the ethylene distributor.

[0017] Preferably, the liquid phase ethylene distributor nozzle includes: a liquid phase ethylene distributor nozzle body, a liquid phase ethylene distributor nozzle distribution disk lug, and a liquid phase ethylene distributor nozzle distribution disk;

[0018] The nozzle body of the liquid phase ethylene distributor is connected to the claw-type distribution pipe of the ethylene distributor and is located on the bottom surface of the claw-type distribution pipe of the ethylene distributor.

[0019] The lugs of the liquid phase ethylene distributor nozzle distribution plate are symmetrically arranged in pairs on both sides of the liquid phase ethylene distributor nozzle cylinder, and the extended ends are connected to both sides of the liquid phase ethylene distributor nozzle distribution plate.

[0020] Preferably, it includes: an ice machine bypass pipe, an ice machine feed end isolation valve, and an ice machine discharge end isolation valve; the two ends of the ice machine bypass pipe are respectively connected to the feed pipe and discharge pipe of the ice machine unit.

[0021] Preferably, it includes: an ice machine bypass valve; an ice machine bypass valve is installed on the ice machine bypass pipe.

[0022] Preferably, it includes: a third emergency shut-off valve and a reflux regulating valve; a reflux regulating valve is installed on the feed pipe outside the connection point between the ice machine bypass pipe and the ice machine unit's feed pipe; a third emergency shut-off valve is installed on the feed pipe outside the connection point between the ice machine bypass pipe and the ice machine unit.

[0023] Preferably, it includes: a first emergency shut-off valve and a cryogenic vacuum pipeline; a variable frequency ethylene delivery pump is installed on the cryogenic vacuum pipeline.

[0024] Preferably, a first emergency shut-off valve is installed on the feed end pipe section of the variable frequency ethylene conveying pump; the discharge end of the low temperature vacuum pipeline is connected to the reflux regulating valve and the ethylene conveying pipeline respectively.

[0025] Preferably, the ice machine feed end isolation valve is installed on the feed pipe of the ice machine unit; the ice machine discharge end isolation valve is installed on the discharge pipe of the ice machine unit.

[0026] The beneficial effects that this application can produce include:

[0027] 1) The low-temperature ethylene storage system provided in this application is applicable to low-temperature ethylene storage systems with a total storage capacity of less than or equal to 500 cubic meters. This system can replace the diaphragm compressor + ice unit to achieve the same cooling loss reduction effect, effectively reducing production costs. At the same time, it does not require the use of complex supporting pipeline components, reducing the risk of gasified ethylene leakage and improving production safety. It can effectively reduce production energy consumption while maintaining environmental assessment requirements during continuous production and avoiding the occurrence of continuous black smoke emissions.

[0028] 2) The cryogenic ethylene storage system provided in this application, applicable to a total storage capacity of 500 cubic meters or less, reduces the investment ratio of the ethylene storage system from 50% in existing processes to below 25%, effectively lowering production costs. It eliminates the need for high-power-consuming membrane compressors, thus effectively reducing the energy loss required to recover and liquefy 1 ton of ethylene, decreasing power consumption from 1341 kWh in existing processes to 1058 kWh. The ice unit is located on the return bypass of the ethylene transfer pump, effectively isolating the ice unit for maintenance without affecting the operation of the cryogenic ethylene storage system. It allows for cold energy recovery from the storage tanks under low-load ethylene delivery, and the cold energy recovery load can be adjusted.

[0029] 3) The cryogenic ethylene storage system provided in this application is applicable to cryogenic ethylene storage systems with a total storage capacity of less than or equal to 500 cubic meters. The system is equipped with a liquid phase ethylene distributor on the internal reflux pipe assembly at the top of the cryogenic ethylene storage tank to ensure uniform heat transfer between cryogenic liquid phase ethylene and high-temperature gas phase ethylene, thereby improving the liquefaction efficiency of high-temperature gas phase ethylene. It can achieve the liquefaction pressure reduction effect of existing cooling loss reduction devices and effectively avoid the overflow of gas phase ethylene caused by overpressure in the ethylene storage tank, which would lead to the generation of black smoke.

[0030] 4) The cryogenic ethylene storage system provided in this application, applicable to systems with a total storage capacity of 500 cubic meters or less, features a first emergency shut-off valve on the cryogenic vacuum pipeline between the bottom outlet of the cryogenic ethylene storage tank and the variable frequency ethylene transfer pump; a third emergency shut-off valve on the return pipeline between the ice unit and the top return outlet of the cryogenic ethylene storage tank; and a second emergency shut-off valve on the ethylene transfer pipeline. When an abnormal ethylene leak occurs in the ethylene storage loss reduction system, the first, second, and third emergency shut-off valves can be remotely and promptly shut off to quickly isolate the source of the flammable and explosive ethylene leak, eliminating the leak immediately. This avoids the leakage risks associated with adding an ice unit and related piping and fittings to existing loss reduction devices. The added ice unit and related piping and fittings are equipped with electrostatic grounding and electrostatic bridging to eliminate electrostatic hazards. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of an existing loss reduction device.

[0032] Figure 2 A schematic diagram of the structure of a low-temperature ethylene storage system with a total storage capacity of less than or equal to 500 cubic meters, provided in at least one embodiment of this application;

[0033] Figure 3 A schematic diagram of the liquid phase ethylene distributor provided in this application;

[0034] Figure 4 A schematic diagram of the nozzle arrangement for the liquid phase ethylene distributor provided in this application;

[0035] Figure 5 A schematic diagram of the liquid phase ethylene distributor nozzle structure provided in this application;

[0036] Figure 6 This is a schematic diagram of the ethylene tanker unloading process provided in this application;

[0037] Legend:

[0038] 1. Low-temperature ethylene storage tank; 2. Low-temperature vacuum pipeline; 3. First emergency shut-off valve; 4. Variable frequency ethylene transfer pump; 5. Liquid phase ethylene distributor; 6. Second emergency shut-off valve; 7. Ice machine bypass valve; 8. Ice machine feed end isolation valve; 9. Ice machine discharge end isolation valve; 10. Third emergency shut-off valve; 11. Reflux regulating valve; 12. Reflux pipeline; 13. Ice machine bypass pipe; 14. Ethylene transfer pipeline; 15. Liquid phase ethylene distributor feed pipe; 16. Liquid phase ethylene distributor claw-type distribution pipe; 17. Liquid phase ethylene distributor nozzle; 18. Liquid phase ethylene distributor nozzle cylinder; 19. Liquid phase ethylene distributor nozzle distribution plate lug; 20. Liquid phase ethylene distributor nozzle distribution plate; 21. Tank; 22. First gas connection pipe; 23. Upper liquid inlet pipe; 24. Lower liquid inlet pipe; 25. Detailed Implementation

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this does not limit the present invention in any way. Any modifications or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0040] Unless otherwise specified, all materials and instruments used in the following embodiments were obtained through commercial channels; and all detection methods used are existing methods unless otherwise specified.

[0041] Example 1

[0042] like Figure 2 As shown, the low-temperature ethylene storage tank loss reduction device includes: a low-temperature ethylene storage tank 1, a low-temperature vacuum pipeline 2, a first emergency shut-off valve 3, a variable frequency ethylene transfer pump 4, a liquid phase ethylene distributor 5, a second emergency shut-off valve 6, an ice machine bypass valve 7, an ice machine feed end isolation valve 8, an ice machine unit 9, an ice machine discharge end isolation valve 10, a third emergency shut-off valve 11, a reflux regulating valve 12, a reflux pipeline 13, an ice machine bypass pipe 14, and an ethylene transfer pipeline 15;

[0043] The bottom outlet of the cryogenic ethylene storage tank 1 is connected to one end of the cryogenic vacuum pipeline 2. The cryogenic vacuum pipeline 2 is sequentially equipped with a first emergency shut-off valve 3, a variable frequency ethylene transfer pump 4, a return pipeline 13, and an ethylene transfer pipeline 15. The return pipeline 13 is connected to one end of the cryogenic vacuum pipeline 2 and the other end is connected to the top return outlet of the cryogenic ethylene storage tank 1. The return pipeline 13 is sequentially equipped with a return regulating valve 12, an ice machine feed end isolation valve 8, an ice machine unit 9, an ice machine discharge end isolation valve 10, and a third emergency shut-off valve 11. Ice machine bypass pipes 14 are connected to the outer pipes at both ends of the ice machine feed end isolation valve 8 and the ice machine discharge end isolation valve 10 on the return pipeline 13. An ice machine bypass valve 7 is installed on the ice machine bypass pipe 14.

[0044] The ethylene conveying pipeline 15 is connected to one end of the cryogenic vacuum pipeline 2, and the other end of the ethylene conveying pipeline 15 is connected to the ethylene user; the ethylene conveying pipeline 15 is equipped with a second emergency shut-off valve 6.

[0045] The liquid phase ethylene distributor 5 includes: a liquid phase ethylene distributor feed pipe 16 and a liquid phase ethylene distributor claw-type distribution pipe 17; three liquid phase ethylene distributor claw-type distribution pipes 17 are arranged at the bottom of the liquid phase ethylene distributor feed pipe 16; one end of the liquid phase ethylene distributor claw-type distribution pipes 17 is connected to the bottom of the liquid phase ethylene distributor feed pipe 16 at the same height, and the included angle between adjacent liquid phase ethylene distributor claw-type distribution pipes 17 is 120°, and they are evenly distributed at the same height.

[0046] Each liquid ethylene distributor claw-type distribution pipe 17 has multiple liquid ethylene distributor nozzles 18 spaced apart at its bottom. This allows the cooled liquid ethylene to be sprayed from each ethylene distributor claw-type distribution pipe 17 into the cryogenic ethylene storage tank 1.

[0047] The liquid ethylene distributor nozzle 18 includes: a liquid ethylene distributor nozzle body 19 and liquid ethylene distributor nozzle distribution disk lugs 20; the liquid ethylene distributor nozzle body 19 is installed on the bottom surface of the liquid ethylene distributor claw-type distribution pipe 17 and is connected to the liquid ethylene distributor claw-type distribution pipe 17; the liquid ethylene distributor nozzle distribution disk lugs 20 are symmetrically arranged on opposite side walls at the bottom of the liquid ethylene distributor nozzle body 19; the liquid ethylene distributor nozzle distribution disk lugs 20 are connected to both sides of the liquid ethylene distributor nozzle distribution disk 21.

[0048] During use, when the difference between the measured pressure of the cryogenic ethylene storage tank 1 and the tank's control limit pressure (0.6 MPaG) is 0.02 MPaG, the ice unit 9 and the ethylene transfer pump 4 are started to cool and depressurize the tank. When the difference is 0.02 MPaG, the measured pressure of the cryogenic ethylene storage tank 1 is 0.58 MPaG, and the temperature of the liquid ethylene corresponding to this pressure value is -63.55℃.

[0049] At this time, the first emergency shut-off valve 3 at the bottom of the cryogenic ethylene storage tank 1 is opened, allowing the liquefied liquid ethylene affected by the high temperature to flow out. After being pressurized by the variable frequency ethylene transfer pump 4, the liquid ethylene is sent to the ice unit 9 through the return pipe 13. The ice unit 9 cools the high-temperature liquid ethylene into cryogenic liquid ethylene. The cryogenic liquid ethylene enters the cryogenic ethylene storage tank 1 from the top return end through the ethylene return pipe 13, passes through the liquid ethylene distributor 5, and falls from the top of the tank. It then undergoes mass transfer and heat exchange with the high-temperature gaseous ethylene in the upper part of the cryogenic ethylene storage tank 1, cooling the high-temperature gaseous ethylene into liquid ethylene. With the continuous operation of the variable frequency ethylene transfer pump 4 and the ice unit 9, the high-temperature gaseous ethylene in the upper part of the cryogenic ethylene storage tank 1 is continuously cooled and liquefied, reducing the tank pressure. Consequently, the temperature of the liquid ethylene in the lower part of the cryogenic ethylene storage tank gradually decreases, thereby maintaining the pressure of the cryogenic ethylene storage tank below the safe value, eliminating the overpressure discharge caused by the cold loss of the cryogenic ethylene storage tank, and realizing the elimination of ethylene loss in the cryogenic ethylene storage tank.

[0050] When the measured pressure of the cryogenic ethylene storage tank 1 drops to ≤0.35 MPaG, the pressure reduction stops after the icing unit 9 and the variable frequency ethylene transfer pump 4 are stopped. At this point, the ethylene temperature corresponding to the pressure value of the cryogenic ethylene storage tank 1 is -80℃. It is evident that this device can effectively achieve rapid pressure reduction by liquefying the high-temperature ethylene at the top of the ethylene storage tank, continuously lowering the temperature of the liquid ethylene inside the cryogenic ethylene storage tank 1, and maintaining the ethylene storage tank pressure below a safe value for a long time, thereby achieving a pressure reduction effect. The temperature reduction can reach 25%. The ethylene liquefaction pressure reduction and temperature reduction effects are significant.

[0051] 1. Reduced investment costs:

[0052] like Figure 1 , 2 As shown, compared with existing loss reduction devices, the system provided in this application does not require the use of a high-investment membrane compressor. It can achieve the liquefaction of high-temperature gaseous ethylene at the top of the tank by simply adding an ice unit and a liquid phase ethylene distributor 5 in the low-temperature ethylene storage tank 1. This effectively avoids the leakage of ethylene vaporized in the low-temperature ethylene storage tank 1, which would lead to ethylene loss. At the same time, the cooled liquid phase ethylene can be refluxed into the low-temperature ethylene storage tank 1 to reduce the ethylene temperature in the low-temperature ethylene storage tank 1, thereby maintaining the tank in a low-pressure state for a long time and avoiding overpressure discharge losses.

[0053] The temperature of the liquid ethylene is lowered, and the reflux is returned to the low-temperature ethylene storage tank 1 to further reduce the temperature of the liquid ethylene in the low-temperature ethylene storage tank 1.

[0054] This device is applied to 2×200m 3 The investment comparison for low-temperature ethylene storage systems is shown in the table below:

[0055] Technology Name Ice unit membrane compressor ethylene distributor Material costs Construction cost Tank system investment Investment ratio Compressor + Ice Machine 550,000 yuan 650,000 yuan 0 million yuan 450,000 yuan 550,000 yuan 4.4 million yuan 50％ Process optimization + ice machine 550,000 yuan 0 million yuan 10,000 yuan 210,000 yuan 260,000 yuan 4.4 million yuan 23.4％

[0056] The low-temperature ethylene loss reduction device provided in this application reduces the investment ratio of the ethylene storage system from 50% in the existing process to less than 23.4%.

[0057] 2. Energy consumption reduction effect:

[0058] This system eliminates the need for high-power membrane compressors; this device is applicable to 2×200m 3 The table below shows the consumption comparison for handling 1 ton of gaseous ethylene loss in a low-temperature ethylene storage system:

[0059] Technology Name Ice machine rated power membrane compressor rated power Ethylene transfer pump rated power Power consumption Compressor + Ice Machine 75kW 34kW 0.0kW 1341 kWh / t ethylene Process optimization + ice machine 75kW 0.0kW 11kW 1058 kWh / t ethylene

[0060] Note: The rated cooling capacity of the 75kW ice machine is 10kW. It requires a cooling capacity of approximately 123kW to cool 1 ton of -78℃ gaseous ethylene to -80℃ liquid ethylene.

[0061] After adopting this application, the power consumption is reduced from 1341kWh to 1058kWh by the existing loss reduction device.

[0062] 3. The device and its operating process provided in Example 1: The ice machine unit 9 is installed on the return path of the variable frequency ethylene conveying pump 4. The inlet and outlet ends of the ice machine unit 9 are respectively equipped with an ice machine inlet isolation valve 8 and an ice machine outlet isolation valve 10, which can isolate the ice machine unit 9 for maintenance without affecting the normal operation of the low temperature ethylene storage system.

[0063] When the ice machine malfunctions and needs maintenance, the bypass valve 7 can be opened, and the feed isolation valve 8 and the discharge isolation valve 10 can be closed. Maintenance can be carried out in a safe isolation manner between the rear flange of the feed isolation valve 8 and the front flange and blind plate of the discharge isolation valve 10. The variable frequency ethylene transfer pump 4 can be started to supply ethylene to the outside normally.

[0064] 4. Comparison of start-stop conditions:

[0065] The apparatus and its operating process provided in Example 1 are applied to a 2×200m 3 The power consumption of the low-temperature ethylene storage system is shown in the table below;

[0066] Comparative Example

[0067] The difference from Example 1 is that the ice unit 9 is turned on when the measured pressure inside the cryogenic ethylene storage tank 1 is 0.35 MPaG; the ice unit 9 is turned off when the pressure is 0.26 MPaG. This condition is applied to a 2×200m² ice unit. 3 The power consumption of the low-temperature ethylene storage system is shown in the table below;

[0068]

[0069] Note: The rated power of the ice chiller unit is 75KW, and the rated power of the ethylene transfer pump is 11kW; the ice chiller unit runs from 20℃ to -105℃ each time it starts up.

[0070] As can be seen from the above, adopting the start-stop conditions provided in this application can effectively reduce energy consumption while achieving a better loss reduction effect.

[0071] 5. The apparatus and its operating process provided in Example 1 are applied to a 2×200m 3 The low-temperature ethylene storage system avoids the pressure relief and discharge of ethylene from the tank truck to the flare system after unloading, reducing ethylene loss by 0.3 tons / truck and reducing ethylene flare smoke elimination steam consumption by 0.6 tons / truck.

[0072] See Figure 6 During unloading, the cryogenic ethylene storage tank 1 is connected to the tank 22 installed on the tank truck via a pipeline; the cryogenic ethylene storage tank 1 and the tank 22 are connected through the first gas connection pipe 23 to equalize the pressure.

[0073] The upper liquid inlet pipe 24 is connected to the upper part of the ethylene tanker and then to the unloading port of the cryogenic ethylene tanker for upper liquid inlet, and the lower liquid inlet pipe 25 is connected to the lower part of the ethylene tanker and then to the unloading port of the cryogenic ethylene tanker for lower liquid inlet.

[0074] When the cryogenic ethylene storage tank 1 reaches the unloading liquid level, unloading is required. Before unloading, the ice unit 9 and the variable frequency ethylene transfer pump 4 of the device in Example 1 are started to cool and depressurize to 0.2 MPaG (at which time the ethylene temperature is -83.15℃). During unloading, the third emergency shut-off valve 11 at the top of the cryogenic ethylene storage tank 1 is opened to allow liquid to enter from the top. After unloading, the pressure of the cryogenic ethylene storage tank 1 drops to 0.17 MPaG. The tank 22 is installed on the tank truck. The high-pressure ethylene in the tank 22 can be evenly compressed to the cryogenic ethylene storage tank 1 through the first gas connection pipe 23 from the ethylene tank truck tank to the cryogenic ethylene tank, and the pressure of the tank truck tank 22 is released to below 0.25 MPaG to avoid ethylene loss due to pressure relief and discharge from the tank 22 to the flare system.

[0075] 6. Ethylene emissions:

[0076] Before using the device provided in this application, at an ambient temperature of 20°C, 2×200m 3 The low-temperature ethylene storage tank 1 suffers from heat loss due to ambient temperature heat transfer, with a measured daily evaporation rate of 0.191% (daily evaporation loss of 0.458 tons of ethylene); the unloading emission loss per truck of ethylene is 0.469 tons (annual unloading volume of approximately 70 trucks); the heat transfer loss during the operation of the ethylene transfer pump is estimated to result in an annual loss of approximately 3 tons of ethylene; and the heat leakage loss from the liquid phase ethylene low-temperature pipe is estimated to result in an annual loss of approximately 2 tons of ethylene.

[0077] After adopting the system provided in this application and using the cooling system, 2*200m3 The annual ethylene emissions from cryogenic ethylene storage tank 1 will be reduced by 205 tons (the specific calculation is based on 200m³). 3 *0.00191*0.6 (density of liquid ethylene)*2*365+0.469(≈0.458)*70+3+2=205), based on an ethylene unit price of approximately 10,000 yuan / ton, steam cost of 180 yuan / ton, and the consumption of ethylene emission smoke-extinguishing steam being twice that of ethylene, the carbon conversion factor for ethylene emissions is 3.14. The carbon conversion factor for 1.6MPaG flare smoke-extinguishing steam is 0.09444, electricity cost is 0.45 / kWh, depreciation is calculated over 10 years, the annual maintenance cost of refrigeration unit 9 is 50,000 yuan, the annual revenue is approximately 1.87 million yuan, and the company reduces carbon emissions by 682 tons annually.

[0078] Example 2

[0079] The difference from Example 1 is that the ethylene inlet and outlet pipes connected to the ice unit 9 are covered with a 100mm thick polyurethane for insulation, reducing heat loss from the new pipeline.

[0080] Example 3

[0081] The difference from Example 1 is that the operation information, fault information and alarm information of the optimized ice machine unit 9 are communicated to the main control DCS system; the DCS system sets up remote shutdown control for the optimized ice machine unit.

[0082] During use, the main controller can monitor the operation of ice unit 9 in real time. If an abnormal alarm is detected, the controller can promptly contact the inspection team for confirmation and maintenance to eliminate potential hazards. In the event of a leak, the main controller can immediately shut down the ice unit to prevent the accident from escalating.

[0083] Example 4

[0084] The difference from Example 1 is that the heat exchange and cooling method between the ice unit 9 and ethylene is an indirect cooling method: the high-pressure ice machine refrigerant cools the slightly positive pressure refrigerant system, and the refrigerant then cools the high-pressure process ethylene medium.

[0085] During use, when an internal leak occurs in the heat exchanger, regardless of whether it is high-pressure refrigerant or high-pressure ethylene, it will only leak into the slightly positive pressure refrigerant system. The high-pressure refrigerant or ethylene leaking into the slightly positive pressure system will be safely discharged into the flare system, effectively preventing fire and explosion accidents caused by cross-contamination of refrigerant and ethylene media in the ice unit.

[0086] Example 5

[0087] The difference from Example 1 is that: Ice unit 9 adopts a multi-component mixed refrigerant formula and an externally balanced low-temperature electronic expansion valve. A filter is installed on the refrigerant liquid pipeline of ice unit 9, and multi-stage cascade is achieved by driving a single screw compressor to achieve a general low-temperature refrigeration range from -110°C to -30°C. During normal operation, the unit's power consumption is automatically adjusted according to the operating conditions, which greatly simplifies the refrigeration system. The ice unit uses PLC programming and a touch screen controller to achieve precise automatic control, high reliability, and stable operation of the unit.

[0088] In use, compared with multi-unit cascade refrigeration systems, the number of compressors is reduced by two. The unit structure is simplified, the unit failure rate is low, and the cooling capacity consumption is reduced by 2.5 kWh.

[0089] Example 6

[0090] The difference from Example 1 is that the evaporator of the ice unit 9 is a stainless steel plate evaporator with a high heat transfer coefficient.

[0091] In use, its heat transfer coefficient is 3 to 5 times that of a shell-and-tube evaporator; it occupies a small area, and its weight is generally only about 1 / 5 of that of a shell-and-tube evaporator, with an actual footprint of 20 square meters. Due to the full internal turbulence, it is not prone to scaling, and its scaling coefficient is only 1 / 3 to 1 / 10 of that of a shell-and-tube heat exchanger. As a result, the assembled ice unit has a compact structure, less cooling loss, good compressor oil return, can use a thermostatic expansion valve for liquid supply, facilitates cooling capacity adjustment, and requires less refrigerant charge.

[0092] Example 7

[0093] The difference from Example 1 is that the liquid phase ethylene distributor nozzle 18 is a high-throughput, high-intensity nozzle.

[0094] In use, the high-throughput, high-intensity nozzles achieve uniform spraying of liquid ethylene, ensuring uniform heat transfer between low-temperature liquid ethylene and high-temperature gaseous ethylene, and improving the liquefaction efficiency of high-temperature gaseous ethylene.

[0095] Example 8

[0096] The difference from Example 1 is that the liquid phase ethylene distributor nozzle 18 is model 0Cr18Ni9.

[0097] Example 9

[0098] The difference from Example 1 is that the liquid phase ethylene distributor nozzles 18 are arranged from the center outwards on the claw-type distribution pipe 17 of the liquid phase ethylene distributor (not evenly distributed, the nozzles 18 near the center are spaced further apart, so as to achieve uniform spraying of liquid phase ethylene inside the top of the low-temperature ethylene storage tank 1), and the diameter of the liquid phase ethylene nozzle outlets is arranged at intervals from small to large to ensure that the liquid phase ethylene is uniformly sprayed on the elevated plane inside the top of the low-temperature ethylene storage tank.

[0099] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-temperature ethylene storage system suitable for a total storage capacity of 500 cubic meters or less, characterized in that, include: Low-temperature ethylene storage tank (1), variable frequency ethylene transfer pump (4), liquid phase ethylene distributor (5), ice unit (9); The bottom of the low-temperature ethylene storage tank (1) is provided with a high-temperature liquid phase ethylene outlet, which is connected to the pipeline of the variable frequency ethylene transfer pump (4); the outlet of the variable frequency ethylene transfer pump (4) is connected to the inlet pipeline of the ice machine unit (9); the liquid phase ethylene distributor (5) is housed in the top of the low-temperature ethylene storage tank (1) and is connected to the outlet pipeline of the ice machine unit (9).

2. The low-temperature ethylene storage system according to claim 1, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that, The liquid phase ethylene distributor (5) includes: a liquid phase ethylene distributor feed pipe (16), multiple liquid phase ethylene distributor claw-type distribution pipes (17), and multiple liquid phase ethylene distributor nozzles (18); one end of each liquid phase ethylene distributor claw-type distribution pipe (17) is connected to the bottom end of the liquid phase ethylene distributor feed pipe (16) and is at the same height; the liquid phase ethylene distributor claw-type distribution pipes (17) are evenly distributed around the circumference of the liquid phase ethylene distributor feed pipe (16); the included angle between adjacent liquid phase ethylene distributor claw-type distribution pipes (17) is 120°. The liquid phase ethylene distributor nozzles (18) are spaced apart on the bottom surface of the ethylene distributor claw-type distribution pipe (17) and are connected to the ethylene distributor claw-type distribution pipe (17).

3. The low-temperature ethylene storage system according to claim 2, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... The liquid phase ethylene distributor nozzle (18) includes: liquid phase ethylene distributor nozzle body (19), liquid phase ethylene distributor nozzle distribution disk lug (20), and liquid phase ethylene distributor nozzle distribution disk (21); The nozzle body (19) of the liquid phase ethylene distributor is connected to the claw-type distribution pipe (17) of the ethylene distributor and is located on the bottom surface of the claw-type distribution pipe (17). The lugs (20) of the liquid phase ethylene distributor nozzle distribution disk are symmetrically arranged in pairs on both sides of the liquid phase ethylene distributor nozzle cylinder (19), and the extended ends are connected to both sides of the liquid phase ethylene distributor nozzle distribution disk (21).

4. The low-temperature ethylene storage system according to claim 1, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... include: Ice machine bypass pipe (14), ice machine feed end isolation valve (8), ice machine discharge end isolation valve (10); the two ends of the ice machine bypass pipe (14) are respectively connected to the feed pipe and discharge pipe of the ice machine unit (9).

5. The low-temperature ethylene storage system according to claim 4, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... include: Ice machine bypass valve (7); An ice machine bypass valve (7) is installed on the ice machine bypass pipe (14).

6. The low-temperature ethylene storage system according to claim 4, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... include: The third emergency shut-off valve (11) and the reflux regulating valve (12) are installed on the feed pipe outside the connection point between the ice machine bypass pipe (14) and the feed pipe of the ice machine unit (9); the third emergency shut-off valve (11) is installed on the feed pipe outside the connection point between the ice machine bypass pipe (14) and the ice machine unit (9).

7. The low-temperature ethylene storage system according to claim 4, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... include: First emergency shut-off valve (3), low temperature vacuum pipeline (2); variable frequency ethylene transfer pump (4) is installed on the low temperature vacuum pipeline (2).

8. The low-temperature ethylene storage system according to claim 7, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... The first emergency shut-off valve (3) is installed on the feed end pipe section of the variable frequency ethylene conveying pump (4); the discharge end of the low temperature vacuum pipeline (2) is connected to the reflux regulating valve (12) and the ethylene conveying pipeline (15) respectively.

9. The low-temperature ethylene storage system according to claim 4, applicable to a total storage capacity of 500 cubic meters or less, is characterized in that... The ice machine feed end isolation valve (8) is installed on the feed pipe of the ice machine unit (9); the ice machine discharge end isolation valve (10) is installed on the discharge pipe of the ice machine unit (9).

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