Treatment system for recycling oil gas and BOG through BOG low-temperature cold energy cycle condensation

Abstract

The invention relates to the technical field of energy conservation, in particular to a treatment system for recycling oil gas and BOG through BOG low-temperature cold energy cycle condensation. Emptying treatment of BOG and oil gas in an LNG oil gas combined building station can cause the problems of serious environmental pollution, environmental safety and resource waste. In order to solve the technical problems, the treatment system for recycling oil gas and BOG through BOG low-temperature cold energy cycle condensation of the LNG oil gas co-construction station is provided, on the basis of normal-temperature compression and normal-temperature water cooling, oil gas discharged in the operation process of the refueling part of the co-construction station is recycled only through low-temperature cold energy condensation of BOG discharged by an LNG storage tank; condensed exhaust gas meets the national environmental protection emission requirement, and the oil gas recovery rate reaches 99% or above, so that in the oil gas recovery process, a tail gas adsorption link does not need to be arranged, a refrigerating system does not need to be additionally arranged, and potential safety hazards and operation investment cost of oil gas recovery are greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of energy conservation, and particularly relates to a processing system for recycling oil and gas and BOG by using the low-temperature cold energy cycle of BOG through condensation. Background Art

[0002] The high-concentration hydrocarbon mixture gas emitted during the production, transportation, and use of light oil products, abbreviated as oil and gas, is the main source of VOCs in the urban atmospheric environment. The contribution rate of oil and gas emissions to the generation of ozone in the urban sky cannot be ignored. One of the main sources of oil and gas emissions in cities is urban gas stations. Since the vast majority of urban gas stations are located in relatively crowded places such as urban transportation arteries, and oil and gas itself also has certain toxicity and strong flammable and explosive characteristics, its oil and gas emissions pose a greater potential danger to urban society and the environment. Therefore, gas stations need to carry out end-of-pipe recovery treatment for oil and gas. Among them, the common methods for separating and recovering oil and gas from air are the condensation method or the condensation-adsorption integrated method. The oil and gas recovery method of the condensation-adsorption integrated method uses the condensation method as the front-end method of the integrated process to separate most of the oil and gas and air, and then uses the adsorption method as the back-end treatment method of the integrated technology for tail gas treatment. When the mixed gas enters the recovery device of the condensation-adsorption integrated method, the temperature of the oil and gas-air mixed gas is first reduced to -50 to 80°C by the low temperature generated by the refrigeration device in the condensation process section, so that most of the heavier oil and gas components are condensed into liquid and separated. Then, the unliquefied gas discharged from the condenser enters the adsorption process section. By utilizing the difference in the binding force between each component in the mixed gas and the adsorbent, the air component that is difficult to adsorb in the mixed gas and the oil and gas component that is easy to adsorb are further separated, so that the tail gas emission concentration is controlled within a lower index. Compared with the single condensation method, this integrated method requires an additional large-scale adsorption operation system, resulting in an increase in processing equipment and a complex recovery process system. At the same time, it also brings a series of problems such as a high heat effect during the adsorption process in the adsorption section, a high desorption temperature, difficult and incomplete desorption regeneration, an increase in the subsequent treatment cost of the adsorbent, and potential safety hazards. The simple condensation method can directly recover oil products, with a relatively simple process and little influence from external temperature and pressure. However, application examples of the simple condensation method show that the condensation temperature needs to be reduced to a very low level to make the tail gas emissions meet the national emission standards. Usually, the corresponding refrigeration system mostly adopts a multi-stage mechanical refrigeration system, resulting in a complex refrigeration process system and relatively high investment and operation costs.

[0003] In addition, against the backdrop of the increasing consumption of LNG in China, many gas stations have been retrofitted with LNG refueling facilities or co-built with LNG refueling stations due to their geographical coverage advantages, becoming LNG-oil gas combined stations. In LNG-oil gas combined stations, the gas emissions to be treated include not only the oil gas emissions from the gas station part but also the BOG gas emissions generated during the storage and loading / unloading of LNG in the retrofitted LNG refueling station part. These emissions are caused by factors such as environmental heat leakage, heat generated by the operation of loading / unloading equipment, and changes in storage pressure during loading / unloading. The main existing methods for treating BOG gas emissions are as follows: One is to heat the low-temperature BOG gas to room temperature through a heater and then treat it. The treatment methods include on-site storage, atmospheric emission, or re-pressurization and feeding it into the gas pipeline, etc. The characteristics of this type of method are that the treatment process is simple, but it causes waste of the low-temperature cold energy of BOG. If the BOG is finally discharged, it will further waste fuel energy and also bring problems such as environmental pollution and environmental safety. The second is to directly re-liquefy the low-temperature BOG by using sub-cooled LNG or low-temperature nitrogen and then recover it. However, this method usually requires compressing the low-temperature BOG or low-temperature nitrogen using a low-temperature compressor, resulting in a sharp increase in equipment investment and operating costs. The third is to liquefy and recover the BOG gas by consuming liquid nitrogen, but this causes continuous loss of liquid nitrogen and its cold energy, and the long-term operating economy is not good.

[0004] Chinese invention patent CN106402644A discloses a BOG and oil gas combined recovery system for an LNG-oil gas combined station. Although this patent proposes a recovery system for jointly recovering oil gas and BOG by utilizing the cold energy of BOG in an LNG-oil gas combined station, to a certain extent, it realizes the ingenious recovery and utilization of the cold energy of BOG, reduces the combined recovery cost, and improves the efficiency. However, in the combined recovery of oil gas and BOG, the cold energy transferred from BOG to oil gas and purified gas after the condensation and separation of the mixed gas is not fully utilized, resulting in a relatively low recovery rate of the cold energy of BOG, and the combined recovery efficiency still needs to be further improved.

[0005] In view of the above situation, for LNG-oil gas combined stations, the present invention proposes a method and device for efficiently jointly recovering oil gas and BOG by making full use of the high-quality low-temperature cold energy of the discharged BOG, combined with normal-temperature compression and normal-temperature cooling. This device and method are of great significance for economically and effectively solving the serious environmental pollution, environmental safety, and resource waste problems caused by the venting of oil gas and BOG in LNG-oil gas combined stations, and will surely demonstrate better social, environmental, and economic benefits in the near future. Summary of the Invention

[0006] The problems existing in the prior art are as follows: The evacuation treatment of BOG and oil-gas in the LNG oil-gas combined station will cause serious environmental pollution, environmental safety and resource waste problems. In view of the above technical problems, the present invention provides a treatment system for recycling oil-gas and BOG by using the low-temperature cold energy of BOG, which includes an oil-gas condensation separation system and a BOG cold energy recycling system. The mixed gas (oil-gas and air) formed by volatilization in the oil-gas condensation separation system is gradually condensed by means of the low-temperature cold energy of BOG in the BOG cold energy recycling system, so as to realize the separation of the heavy components and light components in the mixed gas. The separated light components are evacuated, and the separated heavy components are recovered into the gasoline storage tank.

[0007] Preferably, the BOG cold energy recycling system includes a BOG cold energy recycling system and an LNG cryogenic liquid recycling system. The BOG cold energy recycling system releases cold energy by passing the BOG generated by the LNG storage tank through the gas-phase outlet at the top of the LNG storage tank in a way of overpressure release, adjusting the flow rate, and then sequentially entering the cold fluid channels of the BOG tertiary heat exchanger, the oil-gas secondary condenser, and the oil-gas primary condenser. After that, it is sequentially compressed by a natural gas compressor and cooled by a BOG water cooler to no more than 30°C, and then enters the hot fluid channels of the BOG primary heat exchanger, the BOG secondary heat exchanger, and the BOG tertiary heat exchanger for heat exchange, and then enters the hot fluid channel of the BOG quaternary heat exchanger for heat exchange and condensation and liquefaction to a temperature not higher than -160.9°C. Then it enters the BOG throttle expansion valve for throttling and pressure reduction to 0.6 MPa, and then enters the BOG equilibrium tank for gas-liquid separation. The separated gas enters the LNG storage tank, and the separated liquid enters the LNG cryogenic liquid recycling system through the output pipeline in the LNG cryogenic liquid recycling system.

[0008] Preferably, a second control valve, a first one-way valve, and a BOG flow meter are sequentially arranged between the gas-phase outlet at the top of the LNG storage tank and the BOG tertiary heat exchanger.

[0009] Preferably, the LNG cryogenic liquid recycling system pumps the LNG in the LNG storage tank through the output pipeline into the LNC cryogenic pump, then pumps it into the cold fluid channel of the BOG quaternary heat exchanger by the LNC cryogenic pump, and finally returns to the LNG storage tank through the return pipeline.

[0010] Preferably, the mixed gas (the mixed gas formed by oil and gas and air) in the oil and gas buffer tank flows out from the gas-phase outlet at the top of the oil and gas buffer tank, and then successively passes through flow regulation and compression by an oil and gas compressor. After being cooled to a temperature not exceeding 30°C in an oil and gas water cooler, it enters the hot fluid flow channel of the primary oil and gas condenser for heat exchange and temperature reduction, and then enters the primary oil and gas separator for gas-liquid separation. The separated gas phase enters the hot fluid flow channel of the secondary oil and gas condenser from the top of the primary oil and gas condenser for heat exchange and temperature reduction, and then enters the secondary oil and gas separator for gas-liquid separation. When the separated gas phase is cooled by throttling expansion to below -99.3°C, it successively enters the second cold fluid flow channels of the BOG secondary heat exchanger and the BOG primary heat exchanger for heat exchange and then is emptied. The pressure of the gas phase separated in the secondary oil and gas separator after being cooled by throttling expansion is 0.15 - 0.16 MPa.

[0011] Preferably, a first control valve, an oil and gas regulating valve, and an oil and gas flowmeter are successively arranged between the gas-phase outlet at the top of the oil and gas buffer tank and the oil and gas compressor.

[0012] Preferably, the opening and closing of the first control valve and the second control valve are controlled by the signal of the pressure detection device. When the gas-phase outlet pressure of the LNG storage tank reaches 0.6 - 0.8 MPa, the first control valve and the second control valve are simultaneously opened under the control of the signal of the pressure detection device.

[0013] Preferably, the opening of the oil and gas regulating valve is jointly controlled by the signals of the BOG flowmeter and the oil and gas flowmeter to achieve the matching of the mixed gas flow and the BOG flow.

[0014] Preferably, the liquid phase separated by the primary oil and gas separator is cooled by throttling expansion to not exceed 0.3°C, then exchanges heat in the first cold fluid flow channel of the BOG primary heat exchanger, and then enters the oil and gas condensate separator for gas-liquid separation. The separated gas phase enters the oil and gas buffer tank through a pipeline, and the separated liquid phase enters the gasoline storage tank through the bottom of the oil and gas condensate separator.

[0015] Preferably, the liquid phase separated by the secondary oil and gas separator is cooled by throttling expansion to below -95.4°C, then successively enters the BOG secondary heat exchanger and the BOG primary heat exchanger for heat exchange, and then enters the oil and gas condensate separator for oil and gas separation. The separated gas phase enters the oil and gas buffer tank through a pipeline, and the separated liquid phase enters the gasoline storage tank through the bottom of the oil and gas condensate separator. The pressure of the liquid phase separated by the secondary oil and gas separator after being cooled by throttling expansion is 0.15 - 0.16 MPa.

[0016] Preferably, the mass flow ratio of the oil and gas volatilized in the oil and gas condensation separation system to the BOG in the BOG cold energy recycling system is 5:7 - 3:4.

[0017] Preferably, the optimal mass flow ratio of the oil and gas vapor formed by volatilization in the oil and gas condensation separation system to the BOG in the BOG cold energy recycling system is 5:7.

[0018] The present invention has the following beneficial effects:

[0019] (1) Based on normal temperature compression and normal temperature water cooling, the present invention only utilizes the low-temperature cold energy of the BOG discharged from the LNG storage tank to condense and recover the oil and gas discharged during the operation of the refueling part of the combined station, so that the discharged gas after condensation meets the national environmental protection emission requirements, and the oil and gas recovery rate reaches 99% and above. Therefore, in the present invention, neither a tail gas adsorption link nor an additional refrigeration system needs to be set for oil and gas recovery, which greatly reduces the safety hazards and operation investment costs of oil and gas recovery. At the same time, during the process of oil and gas cooling and condensation recovery, the low-temperature BOG is heated to normal temperature, compressed at normal temperature, and then cooled and condensed for recovery. During the process of BOG cooling and condensation recovery, the cold energy transferred to the mixed gas for oil and gas recovery before is fully recovered, so that the BOG cold energy can be fully utilized. Therefore, in the present invention, no additional refrigeration system needs to be set for BOG recovery, and the equipment used is all ordinary compression and heat exchange equipment, which are relatively common in the domestic market, making the investment in the entire process equipment, subsequent operation energy consumption, and maintenance costs all greatly reduced. Therefore, the present invention makes full use of the cold energy of BOG in the LNG combined station to jointly recover oil and gas and BOG, greatly reducing the capital investment, operation energy consumption, and maintenance costs of BOG and oil and gas recovery, improving the safety and stability of the recovery process, and realizing the low-cost, energy-saving, and safe joint recovery of BOG and oil and gas, having good industrial promotion and market application prospects;

[0020] (2) Throttle expansion valves are respectively arranged at the gas and liquid outlets of the oil and gas secondary separator and the liquid outlet of the oil and gas primary separator to reduce the outlet fluid pressure to not less than 0.15 MPa, 0.15 MPa, and 0.14 MPa respectively, so as to make full use of the remaining pressure energy of the outlet fluid for refrigeration, increase the cold energy recovery amount in the subsequent cold energy recovery link, and enable the energy in the entire treatment system to be fully recycled and the energy utilization rate to be fully optimized;

[0021] (3) The BOG flowmeter and the oil and gas flowmeter are respectively used to measure the flow rates of the BOG flowing out of the LNG storage tank and the mixed gas flowing out of the oil and gas buffer tank. The system sets the ratio of the BOG flow rate to the mixed gas flow rate to be between 5:7 and 3:4. When the flow rate ratio is not within this range, the opening of the oil and gas regulating valve is adjusted through the control system to eliminate the flow rate ratio deviation. Such a setting can ensure that the oil and gas concentration in the mixed gas tail gas is lower than the emission standard, and at the same time can fully recover and utilize the BOG cold energy, reducing the amount of subcooled pressurized LNG required for liquefying and condensing BOG. Description of the Drawings

[0022] Figure 1: It is a processing system for recycling oil and gas and BOG by utilizing the low-temperature cold energy of BOG provided by the present invention.

[0023] 101. Oil and gas buffer tank, 102. Oil and gas compressor, 103. Oil and gas water cooler, 104. Primary oil and gas condenser, 105. Primary oil and gas separator, 106. Secondary oil and gas condenser, 107. Secondary oil and gas separator, 108. Oil and gas condensate separator, 201. LNG storage tank, 202. Natural gas compressor, 203. BOG water cooler, 204. Primary BOG heat exchanger, 205. Secondary BOG heat exchanger, 206. Tertiary BOG heat exchanger, 207. Quaternary BOG heat exchanger, 208. BOG balance tank, 209. LNG cryogenic pump, 210. Output pipeline, 211. Return pipeline, V1. First control valve, V2. Oil and gas regulating valve, V3. First throttle expansion valve for oil and gas, V4. Second throttle expansion valve for oil and gas, V5. Tail gas throttle expansion valve, V6. Second control valve, V7. First check valve, V8. BOG throttle expansion valve, FM2. BOG flowmeter, FM1. Oil and gas flowmeter. Detailed implementation mode

[0024] The present invention will be described in detail below in conjunction with embodiments. However, it should be understood that the following embodiments are only illustrative examples of the implementation modes of the present invention, rather than limiting the scope of the present invention.

[0025] As Figure 1 shown, it is a processing system for recycling oil and gas and BOG by utilizing the low-temperature cold energy of BOG provided by the present invention. In this system, the gas phase outlet of the oil and gas buffer tank (101) is successively connected to the inlet of the oil and gas compressor (102) through the first control valve (V1), the oil and gas regulating valve (V2) and the oil and gas flowmeter (FM1). The outlet of the oil and gas compressor (102) is connected to the inlet of the oil and gas water cooler (103). The outlet of the oil and gas water cooler (103) is connected to the hot fluid inlet of the primary oil and gas condenser (104). The hot fluid outlet of the primary oil and gas condenser (104) is connected to the inlet of the primary oil and gas separator (105). The gas phase outlet of the primary oil and gas separator (105) is connected to the hot fluid inlet of the secondary oil and gas condenser (106). The hot fluid outlet of the secondary oil and gas condenser (106) is connected to the inlet of the secondary oil and gas separator (107). The gas phase outlet of the secondary oil and gas separator (107) is connected to the inlet of the second cold fluid flow channel of the secondary BOG heat exchanger (205) via the tail gas throttle expansion valve (V5). The outlet of the second cold fluid flow channel of the secondary BOG heat exchanger (205) is connected to the inlet of the second cold fluid flow channel of the primary BOG heat exchanger (204). The second cold fluid outlet of the primary BOG heat exchanger (204) is connected to a vent pipeline for direct venting;

[0026] The liquid phase outlet of the oil and gas secondary separator (107) is connected to the first cold fluid inlet of the BOG secondary heat exchanger (205) via the oil and gas first throttle expansion valve (V4). The liquid phase outlet of the oil and gas primary separator (104) is connected to the first cold fluid outlet manifold of the BOG secondary heat exchanger (205) via the oil and gas first throttle expansion valve (V3) and then connected to the first cold fluid inlet of the BOG primary heat exchanger (204). The first cold fluid outlet of the BOG primary heat exchanger (204) is connected to the inlet of the oil and gas condensate separator (108). The gas phase outlet at the top of the oil and gas condensate separator (108) is connected to the inlet of the oil and gas buffer tank (101). The liquid phase outlet at the bottom of the oil and gas condensate separator (108) is connected to the gasoline storage tank;

[0027] The gas phase outlet of the LNG storage tank (201) is sequentially connected to the cold fluid inlet of the BOG tertiary heat exchanger (206) through the second control valve (V6), the first check valve (V7) and the BOG flowmeter (FM2). The cold fluid outlet of the BOG tertiary heat exchanger (206) is connected to the cold fluid inlet of the oil and gas secondary condenser (106). The cold fluid outlet of the oil and gas secondary condenser (106) is connected to the cold fluid inlet of the oil and gas primary condenser (104). The cold fluid outlet of the oil and gas primary condenser (104) is connected to the inlet of the natural gas compressor (202). The outlet of the natural gas compressor (202) is connected to the inlet of the BOG water cooler (203). The outlet of the BOG water cooler (203) is connected to the hot fluid inlet of the BOG primary heat exchanger (204). The hot fluid outlet of the BOG primary heat exchanger (204) is connected to the hot fluid inlet of the BOG secondary heat exchanger (205). The hot fluid outlet of the BOG secondary heat exchanger (205) is connected to the hot fluid inlet of the BOG tertiary heat exchanger (206). The hot fluid outlet of the BOG tertiary heat exchanger (206) is connected to the hot fluid inlet of the BOG quaternary heat exchanger (207). The hot fluid outlet of the BOG quaternary heat exchanger (207) is connected to the inlet of the BOG balance tank (208) through the BOG throttle expansion valve (V8). The liquid phase outlet of the BOG balance tank (208) converges with the liquid phase outlet of the LNG storage tank (201) and then is connected to the inlet of the LNG cryogenic pump (209). The outlet of the LNG cryogenic pump (209) is connected to the cold fluid inlet of the BOG quaternary heat exchanger (207). The cold fluid outlet of the BOG quaternary heat exchanger (207) is connected to the output pipeline of the LNG storage tank (201). The gas phase outlet of the BOG balance tank (208) is connected to a position on the top of the LNG storage tank (201) different from the gas phase opening of the LNG storage tank (201).

[0028] Both the oil and gas compressor (102) and the natural gas compressor (202) are normal temperature compressors.

[0029] The primary oil and gas separator (105), the secondary oil and gas separator (107), and the BOG balance tank (208) are all vacuum-insulated tanks, and the connecting pipelines between the various devices are all insulated pipes.

[0030] A pressure detection device is provided at the top of the LNG storage tank (202), and the opening and closing of the first control valve (V1) and the second control valve (V6) are controlled by the signals of the pressure detection device; the opening degree of the oil and gas control valve (V2) is jointly controlled by the signals of the BOG flowmeter (FM2) and the oil and gas flowmeter (FM1) to achieve the flow matching of the mixed gas and the BOG flow.

[0031] The oil and gas buffer tank (101) is equipped with a liquid level monitoring device, a liquid outlet pipe and a control valve are provided at the bottom, and the opening and closing of the control valve are controlled by the signal of the liquid level detection device. When the liquid level reaches the set maximum liquid level, the liquid level detection device issues a control signal to open the control valve. The bottom liquid phase outlet pipe and the liquid outlet pipe of the oil and gas condensate separator (108) converge into one pipeline and then connect to the inlet pipe of the gasoline storage tank. The maximum liquid level is located below the gas phase outlet at the top of the oil and gas condensate separator (108) and the connection port of the inlet of the oil and gas buffer tank (101).

[0032] The specific method for realizing the recovery of light and heavy components in the oil and gas in the oil and gas buffer tank (101) and the BOG by making full use of a treatment system for recycling oil and gas and BOG using BOG low-temperature cold energy is as follows:

[0033] Step 1: When the gas phase outlet pressure of the LNG storage tank (201) reaches 0.6 MPa, the first control valve (V1) and the second control valve (V6) are simultaneously opened under the control of the signals of the pressure detection device;

[0034] Oil and gas condensation separation system:

[0035] Step 1-2: The mixed gas at 20°C, 120 kPa, and 56 kg / h flowing out of the oil and gas buffer tank (101) passes through the first control valve (V1) and the oil and gas regulating valve (V2), is metered by the oil and gas flowmeter (FM1), and then enters the oil and gas compressor (102) to be pressurized to 129.7°C and 800 kPa. After that, it enters the oil and gas water cooler (103) and is cooled to 30°C. The cooled mixed gas at 30°C and 790 kPa enters the hot fluid flow channel of the primary oil and gas condenser (104), and is cooled by the BOG at -44.2°C, 580 kPa, and 40 kg / h in the cold fluid flow channel of the primary oil and gas condenser (104) to 2°C, and then enters the primary oil and gas separator (105) for gas-liquid separation. The mixed gas at 2°C, 780 kPa, and 28.6 kg / h flowing out from the gas phase outlet of the primary oil and gas separator (105) enters the hot fluid flow channel of the secondary oil and gas condenser (106). The primary cooled oil and gas condensate at 2°C, 780 kPa, and 27.4 kg / h flowing out from the liquid phase outlet of the primary oil and gas separator (105) is throttled and cooled to 0.3°C by the first oil and gas throttling expansion valve (V3);

[0036] Step 1-3: The mixed gas at 2°C, 780 kPa, and 28.6 kg / h entering the hot fluid flow channel of the secondary oil and gas condenser (106) is cooled by the BOG at -110°C, 590 kPa, and 40 kg / h flowing into the cold fluid flow channel of the secondary oil and gas condenser (106) from the cold fluid outlet of the BOG tertiary heat exchanger (206) to -95.0°C, and then enters the secondary oil and gas separator (107) for gas-liquid separation. The purified gas at -95.0°C, 770 kPa, and 23.3 kg / h obtained after gas-liquid separation flows out from the gas phase outlet of the secondary oil and gas separator (107), is throttled and cooled to -99.3°C by the tail gas throttling expansion valve (V5), and then enters the second cold fluid flow channel of the BOG secondary heat exchanger. The cryogenic oil and gas condensate at -95.0°C, 770 kPa, and 5.33 kg / h flowing out from the liquid phase outlet of the secondary oil and gas separator (107) is throttled and cooled to -95.4°C by the second oil and gas expansion valve (V4) and then enters the first cold fluid flow channel of the BOG secondary heat exchanger (205);

[0037] Steps 1-4: The purified gas at -99.3°C, 150 kPa, and 23.3 kg / h entering the second cold fluid flow channel of the BOG secondary heat exchanger (205) and the cryogenic oil and gas condensate at -95.4°C, 150 kPa, and 5.33 kg / h entering the first cold fluid flow channel of the BOG secondary heat exchanger (205) simultaneously release cold energy to the BOG at 5°C, 3480 kPa, and 40 kg / h entering the hot fluid flow channel of the BOG secondary heat exchanger (205). Then, the purified gas at 2°C, 140 kPa, and 23.3 kg / h flows from the second cold fluid outlet of the BOG secondary heat exchanger (205) into the second cold fluid inlet of the BOG primary heat exchanger (204). The cryogenic oil and gas condensate at 2°C, 140 kPa, and 23.3 kg / h flows out from the second cold fluid outlet of the BOG secondary heat exchanger (205) and converges with the primary cooled oil and gas condensate at 0.33°C, 140 kPa, and 27.4 kg / h that has been throttled and cooled by the oil and gas No. 1 throttle expansion valve (V3) and then flows into the first cold fluid flow channel of the BOG primary heat exchanger (204).

[0038] Steps 1-5: The purified gas at 2°C, 140 kPa, and 23.3 kg / h flowing into the second cold fluid flow channel of the BOG primary heat exchanger (204) and the oil and gas condensate at 4.9°C, 140 kPa, and 32.7 kg / h flowing into the first cold fluid flow channel of the BOG primary heat exchanger (204) simultaneously release cold energy to the BOG at 30°C, 3.49 Mpa, and 40 kg / h entering the hot fluid flow channel of the BOG primary heat exchanger (206). Then, the heated purified gas at 20°C, 130 kPa, and 35.8 kg / h flows from the second cold fluid outlet of the BOG primary heat exchanger (204) into the vent pipeline for venting. The heated oil and gas condensate is heated to 14.8°C and then flows out from the first cold fluid flow channel outlet of the BOG primary heat exchanger (204) into the oil and gas condensate separator (108) for gas-liquid separation. The oil and gas condensate at 14.8°C, 130 kPa, and 28.5 kg / h obtained after gas-liquid separation flows through a pipeline from the liquid phase outlet of the oil and gas condensate separator (108) into the gasoline storage tank for recovery. The oil and gas at 14.8°C, 130 kPa, and 4.2 kg / h obtained after gas-liquid separation flows back from the gas phase outlet of the oil and gas condensate separator (108) into the oil and gas buffer tank (101).

[0039] BOG Cold Energy Recycling and Recovery System:

[0040] Step 2-2: The BOG at -145°C and 600 kPa flows into the cold fluid flow path of the BOG three-stage heat exchanger (206) from the gas-phase outlet of the LNG storage tank (201) through the second control valve (V6), the first check valve (V7), and the BOG flowmeter (FM1) at a flow rate of 40 kg / h to release cold energy. After the cold energy is released, the BOG is heated to 260°C, and then enters the cold fluid flow path of the oil-gas secondary condenser (106) to exchange heat and be heated with the 2°C, 780 kPa, 28.6 kg / h mixed gas entering the hot fluid flow path of the oil-gas secondary condenser (106). The BOG at -44.2°C, 580 kPa, 40 kg / h flowing out of the cold fluid flow path of the oil-gas secondary condenser (106) enters the cold fluid flow path of the oil-gas primary condenser (104) to further exchange heat and be heated with the 30°C, 790 kPa, 56 kg / h mixed gas entering the hot fluid flow path of the oil-gas primary condenser (104). The BOG at 20°C, 570 kPa, 40 kg / h heated by the mixed gas flows out from the outlet of the cold fluid flow path of the oil-gas primary condenser (104) and enters the natural gas compressor (202);

[0041] Step 2-3: The BOG flowing into the natural gas compressor (202) is pressurized to 3.5 MPa, and then enters the BOG water cooler (203) for water cooling to 30°C, 3.49 MPa, 40 kg / h. After that, it enters the hot fluid flow path of the BOG primary heat exchanger (204) to receive the combined cold energy from the 2°C, 140 kPa, 23.3 kg / h purified gas entering the BOG primary heat exchanger (204) from the second cold fluid inlet pipe of the BOG primary heat exchanger (204) and the 4.9°C, 140 kPa, 32.7 kg / h oil-gas condensate entering the BOG primary heat exchanger (204) from the first cold fluid inlet pipe of the BOG primary heat exchanger (204), and is cooled to 5°C and then flows into the hot fluid flow path of the BOG secondary heat exchanger (205);

[0042] Step 2-4: The BOG at 5°C, 3.58 MPa, 40 kg / h flowing into the hot fluid flow path of the BOG secondary heat exchanger (205) receives the combined cold energy from the BOG secondary heat exchanger (205) -99.3°C, 150 kPa, 23.3 kg / h purified gas in the second cold fluid flow path of the BOG secondary heat exchanger (205) and the -95.4°C, 150 kPa, 5.33 kg / h cryogenic oil-gas condensate entering the first cold fluid flow path of the BOG secondary heat exchanger (205), and is cooled to -37.6°C, and then flows into the hot fluid flow path of the BOG three-stage heat exchanger (206);

[0043] Step 2-5: The BOG at -37.6°C, 3.47 Mpa, and 40 kg / h flowing into the hot fluid flow path of the BOG tertiary heat exchanger (206) exchanges heat with the BOG at -145°C, 600 kPa, and 40 kg / h flowing into the cold fluid flow path of the BOG tertiary heat exchanger (206) from the gas-phase outlet of the LNG storage tank (201), and the temperature drops to -110.3°C, then enters the hot fluid flow path of the BOG quaternary heat exchanger (207);

[0044] Step 2-6: The BOG at -110.3°C, 3.46 MPa, and 40 kg / h flowing into the hot fluid flow path of the BOG quaternary heat exchanger (207) is condensed and liquefied in the BOG quaternary heat exchanger (207) by the LNG at -162°C, 1.6 MPa, and 18.12 m 3 / h formed by being pressurized by the LNG cryogenic pump (209) flowing into the cold fluid flow path of the BOG quaternary heat exchanger (207). The pressurized LNG in the LNG cryogenic pump (209) is from the output pipeline of the LNG storage tank (201). The LNG at -160.9°C, 3.45 MPa, and 40 kg / h flowing out of the hot fluid flow path of the BOG quaternary heat exchanger (207) is throttled to 0.6 MPa by the BOG throttle expansion valve and then enters the BOG balance tank (208) to balance the pressure. The liquid phase at -160°C, 0.6 MPa, and 0.12 m 3 / h flowing out from the bottom of the BOG balance tank (208) enters the output pipeline connected between the LNG storage tank and the LNG cryogenic pump (209). The LNG at -161°C, 1.59 MPa, and 18.12 m3 / h flowing out of the cold fluid flow path of the BOG quaternary heat exchanger (207) is pressurized and then flows back to the LNG storage tank (201) through the return pipeline connected between the LNG storage tank and the LNG cryogenic pump (209). The gas phase flowing out from the top of the BOG balance tank (208) after balancing the pressure enters the LNG storage tank from a position different from the gas-phase outlet at the top of the LNG storage tank at the top of the LNG storage tank.

[0045] Using the above processing system for recycling oil and gas and BOG by utilizing the low-temperature cold energy of BOG to achieve the recovery of light and heavy components in the oil and gas in the oil and gas buffer tank (101) and BOG, the oil and gas recovery rate reaches 99%, and the BOG liquefaction recovery rate reaches 100%.

[0046] The set temperature and pressure parameters in the above process are values in a relatively optimal state. During actual operation, affected by environmental factors, those skilled in the art can make corresponding adjustments to achieve the purpose of simultaneously recovering BOG and oil and gas.

[0047] The LNG storage tank (201) is the LNG storage tank set in the LNG filling part of the co-location station and is not specially set.

[0048] Based on the above-mentioned ideal embodiments of the present invention as inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A processing system for recycling oil and gas and BOG by using the cryogenic cold energy cycle condensation of BOG, characterized in that, It includes an oil and gas condensation separation system and a BOG cold energy recycling and recovery system. The mixed gas formed by volatilization in the oil and gas condensation separation system is gradually condensed by means of the low-temperature cold energy of BOG in the BOG cold energy recycling and recovery system, so as to realize the separation of heavy components and light components in the mixed gas. The separated light components are emptied, and the separated heavy components are recovered into the gasoline storage tank.

2. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, as claimed in claim 1, wherein, The BOG cold energy recycling and recovery system includes a BOG cold energy recycling system and an LNG cryogenic liquid recycling system. The BOG cold energy recycling system releases cold energy by allowing the BOG generated in the LNG storage tank to enter the cold fluid channels of the BOG three-stage heat exchanger, the oil and gas secondary condenser, and the oil and gas primary condenser in sequence through overpressure release from the gas-phase outlet at the top of the LNG storage tank after flow regulation. Then, after being compressed by the natural gas compressor and cooled to no more than 30°C by the BOG water cooler in sequence, it enters the hot fluid channels of the BOG primary heat exchanger, the BOG secondary heat exchanger, and the BOG three-stage heat exchanger for heat exchange, and then enters the hot fluid channel of the BOG four-stage heat exchanger for heat exchange and condensation to a temperature not higher than -160.9°C. After that, it enters the BOG throttle expansion valve for throttling and pressure reduction to a pressure not lower than the outlet pressure of the LNG cryogenic pump, and then enters the BOG equilibrium tank for gas-liquid separation. The separated gas enters the LNG storage tank, and the separated liquid enters the LNG cryogenic liquid recycling system through the connecting pipeline between the BOG four-stage heat exchanger and the LNG cryogenic pump.

3. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation according to claim 2, characterized in that, A second control valve, a first one-way valve, and a BOG flowmeter are sequentially arranged between the gas-phase outlet at the top of the LNG storage tank and the BOG three-stage heat exchanger.

4. A treatment system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, according to claim 1, characterized in that, The LNG cryogenic liquid recycling system allows the LNG in the LNG storage tank to enter the LNC cryogenic pump through the output pipeline to form pressurized subcooled LNG at 1.5 - 1.7 MPa, and then is pumped into the cold fluid channel of the BOG four-stage heat exchanger by the LNC cryogenic pump, and finally flows back into the LNG storage tank through the return pipeline.

5. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, as claimed in claim 1, wherein In the oil and gas condensation separation system, the mixed gas formed in the oil and gas buffer tank flows out from the gas-phase outlet at the top of the oil and gas buffer tank, and then after flow regulation and compression by the oil and gas compressor in sequence, it enters the oil and gas water cooler for cooling to a temperature not more than 30°C, and then enters the hot fluid channel of the oil and gas primary condenser for heat exchange and temperature reduction. After that, it enters the oil and gas primary separator for gas-liquid separation. The separated gas phase enters the hot fluid channel of the oil and gas secondary condenser from the top of the oil and gas primary condenser for heat exchange and temperature reduction, and then enters the oil and gas secondary separator for gas-liquid separation. When the separated gas phase is cooled by throttling and expansion to below -99.3°C, it enters the second cold fluid channels of the BOG secondary heat exchanger and the BOG primary heat exchanger for heat exchange and then is emptied. The pressure of the gas phase separated in the oil and gas secondary separator after throttling and expansion cooling is 0.15 - 0.16 MPa.

6. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, according to claim 5, characterized in that, A first control valve, an oil and gas regulating valve, and an oil and gas flowmeter are sequentially arranged between the gas-phase outlet at the top of the oil and gas buffer tank and the oil and gas compressor.

7. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation according to claim 5, characterized in that, After the liquid phase separated by the primary oil and gas separator is cooled by throttling expansion to no more than 0.3 °C, it exchanges heat in the first cold fluid flow channel of the BOG primary heat exchanger and then enters the oil and gas condensate separator for gas-liquid separation. The separated gas phase enters the oil and gas buffer tank through a pipeline, and the separated liquid phase enters the gasoline storage tank through the bottom of the oil and gas condensate separator.

8. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation according to claim 5, characterized in that, After the liquid phase separated by the secondary oil and gas separator is cooled by throttling expansion to below -95.4 °C, it successively enters the BOG secondary heat exchanger and the BOG primary heat exchanger for heat exchange, and then enters the oil and gas condensate separator for oil and gas separation. The separated gas phase enters the oil and gas buffer tank through a pipeline, and the separated liquid phase enters the gasoline storage tank through the bottom of the oil and gas condensate separator. The pressure of the liquid phase separated by the secondary oil and gas separator after throttling expansion and cooling is 0.15 - 0.16 MPa.

9. A treatment system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, according to claim 1, characterized in that The mass flow ratio of the oil and gas volatilized in the oil and gas condensation separation system to the BOG in the BOG cold energy recycling and recovery system is 5:7 - 3:

4.

10. A processing system for recycling oil and gas and BOG by using BOG low-temperature cold energy cycle condensation, as claimed in claim 9, wherein The optimal mass flow ratio of the oil and gas volatilized in the oil and gas condensation separation system to the BOG in the BOG cold energy recycling and recovery system is 5:7.

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