Movable recovery and purification treatment device for scattered gas in oil field
By designing a mobile oilfield scattered gas recovery and purification treatment device and utilizing a combination of a refrigeration system and a natural gas system, the problems of resource waste and environmental pollution in the treatment of scattered natural gas in oilfields are solved, and efficient purification and safe recovery of natural gas are achieved.
Patent Information
- Application Number
- CN202510862368.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2025-09-09
AI Technical Summary
In the existing technology, the scattered natural gas processing method in oil fields has problems such as resource waste, environmental pollution, safety hazards, and large investment but small returns. In particular, casing gas and associated gas in remote well sites are difficult to recycle and utilize efficiently.
A mobile oilfield scattered gas recovery and purification device has been designed. Utilizing a refrigeration system and a natural gas system, the device purifies natural gas through filtration, pressurization, cooling, and impurity removal, meeting the GB17820 Class II gas standard. The device, which includes a clever combination of filters, a booster, a refrigeration system, a natural gas air-cooled radiator, and a heat exchanger, enables continuous production and energy conservation and consumption reduction.
It realizes the effective utilization of scattered natural gas, achieves environmentally friendly and economical purification treatment effects, ensures the safe recovery and efficient utilization of natural gas, and avoids resource waste and environmental pollution.
Smart Images
Figure CN120607914A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of oilfield natural gas recovery, in particular to a movable oilfield scattered gas recovery and purification treatment device. Background Art
[0002] During the oil field production process, associated gas is divided into two parts. One part enters the oil pipeline network with the produced liquid and eventually enters the station oil collection tank, which is called "tank top gas". The other part remains in the annular space of the oil well production pipeline, which is called "casing gas". These "casing gases" need to be discharged regularly, otherwise it will affect production. However, due to environmental protection needs, associated gas is not allowed to be discharged at will. At the same time, the discharge of natural gas is also a waste of resources.
[0003] In the current production process, well sites with oil pipeline networks also have to deal with some "casing gas" with wellhead pressure lower than the technical dry pressure in individual wells, well groups, and well factories; associated gas from remote well sites without pipeline networks and far away from the main oil pipeline network; volatile gas and rich associated gas from tank tops of transfer stations and joint stations, as well as some associated gases with complex temperament and high difficulty in recycling, are all considered scattered gas, with daily gas production not exceeding 5000m3. 3 The cost of laying pipelines is too high, and there is no suitable technology and equipment for on-site treatment.
[0004] Traditionally, these scattered gases are treated on-site by venting and burning, which not only wastes high-quality resources but also pollutes the environment. Another method is to use them for on-site water-jacket furnace combustion heating at the well site, but there are problems with this method: first, due to the water content in the casing gas, the burner is prone to fire, causing safety problems; second, the gas utilization rate is insufficient; third, the gas is directly burned without being treated and the emission does not meet the standards; fourth, on-site gas-fired power generation equipment is used, which has the advantage of fully absorbing all the associated gas, but the investment is large, the return is small, and there are also problems such as substandard emissions.
[0005] Therefore, oil fields urgently need to develop a mobile oil field scattered gas recovery and purification treatment device. Summary of the Invention
[0006] The purpose of the present invention is to address the above-mentioned defects of the existing technology and provide a mobile oilfield scattered gas recovery and purification treatment device. By filtering and cooling the scattered natural gas in stages, particulate matter, water, heavy hydrocarbons above C4 and other substances are removed in sequence, so that it meets the standards of Class II gas specified in GB17820, and can then be used at the well site or exported.
[0007] The present invention relates to a mobile oilfield scattered gas recovery and purification device, the technical solution of which is as follows: comprising a natural gas system and a sewage discharge system, the natural gas system comprising a filter and a booster, the filter being used to filter impurities in the scattered gas, and the booster being used to increase the pressure of the scattered gas, wherein the natural gas system also comprises a refrigeration system, the natural gas system further comprising a natural gas air-cooled radiator and a natural gas heat exchanger, the output end of the booster being connected to the tube-side inlet of the natural gas heat exchanger via a pipeline and the natural gas air-cooled radiator, the tube-side outlet of the natural gas heat exchanger being connected to the shell-side inlets of the first and second evaporators of the refrigeration system via a pipeline and a natural gas proportion regulating electric three-way valve, the shell-side outlets of the first and second evaporators being respectively connected to the shell-side inlet of the natural gas heat exchanger via pipelines, and the shell-side outlets of the natural gas heat exchanger discharging the cooled scattered gas; The refrigeration system includes a low-temperature compressor, an oil separator, a four-way valve, a first solenoid valve, a second solenoid valve, a condenser, a drying filter, a first electronic expansion valve, a second electronic expansion valve, a first evaporator, and a second evaporator. The outlet of the low-temperature compressor is connected to the condenser through a pipeline, an oil separator, and a four-way valve. The output end of the condenser is connected to the first electronic expansion valve or the second electronic expansion valve through a pipeline and a drying filter. The output end of the first electronic expansion valve is connected to the pipe-side inlet of the first evaporator through a pipeline, and the output end of the second electronic expansion valve is connected to the pipe-side inlet of the second evaporator through a pipeline; the pipe-side outlet of the first evaporator is connected to the pipeline at the inlet end of the condenser through a pipeline and a second solenoid valve, and is connected to the air inlet end of the low-temperature compressor through a second pipeline and the first-circuit solenoid valve. The pipe-side outlet of the second evaporator is connected to the pipeline at the inlet end of the condenser through a pipeline and a first-circuit solenoid valve, and is connected to the air inlet end of the low-temperature compressor through a pipeline and a first-circuit solenoid valve.
[0008] Preferably, the above-mentioned four-way valve includes a first four-way valve, a second four-way valve, and a third four-way valve. The first output end of the first four-way valve is connected to the second four-way valve and the third four-way valve through a pipeline, the first output end of the second four-way valve is connected to the tube-side inlet of the second evaporator through a pipeline, the second output end of the second four-way valve is connected to the condenser through a pipeline, the first output end of the third four-way valve is connected to the tube-side inlet of the first evaporator through a pipeline, and the second output end of the third four-way valve is connected to the condenser through a pipeline.
[0009] Preferably, the second output end of the first four-way valve is connected to the first pressure relief valve through a pipeline, the second output end of the second four-way valve is also connected to the second pressure relief valve through a pipeline, and the second output end of the third four-way valve is also connected to the third pressure relief valve through a pipeline; the outer ends of the first pressure relief valve, the second pressure relief valve and the third pressure relief valve are converged to the pipeline at the air inlet end of the low-temperature compressor through a pipeline.
[0010] Preferably, the above-mentioned first evaporator includes an evaporator shell, a natural gas inlet, a natural gas outlet, a heat exchange coil, a shell-side cavity, and a frost and ice layer. The inner cavity of the evaporator shell is provided with a heat exchange coil, and a shell-side cavity is formed between the heat exchange coil and the inner wall of the evaporator shell. The two ends of the evaporator shell are respectively provided with a natural gas inlet and a natural gas outlet. High-temperature refrigerant is introduced into the inner cavity of the heat exchange coil to heat the frost and ice layer on the outer wall of the heat exchange coil, and the heat diffuses from the inside of the ice layer to the outside.
[0011] Preferably, the above-mentioned sewage discharge system includes a sewage storage tank, a first sewage discharge control valve, a second sewage discharge control valve, and a third sewage discharge control valve. The lower end of the shell side of the first evaporator is connected to the side line of the sewage storage tank through a pipeline and the first sewage discharge control valve, the lower end of the shell side of the second evaporator is connected to the side line of the sewage storage tank through a pipeline and the second sewage discharge control valve, and the lower end of the shell side of the natural gas heat exchanger is connected to the side line of the sewage storage tank through a pipeline and the third sewage discharge control valve.
[0012] Preferably, under the operating conditions that the first evaporator is freezing and the second evaporator is heating to melt ice, the purification process includes the following: The high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor enters the tube-side inlet of the second evaporator through the oil separator, the first four-way valve and the second four-way valve respectively. The heating and ice-melting mode is turned on, and the gas-liquid mixture flows out through the tube-side outlet of the second evaporator, enters the condenser through the pipeline and the first solenoid valve, and is further cooled and liquefied. Then, the medium-temperature and high-pressure liquid enters the tube-side inlet of the first evaporator through the drying filter and the first electronic expansion valve, evaporates and absorbs heat, and cools the natural gas from 0 to 5°C from the natural gas heat exchanger to -25 to -30°C. The refrigerant flows back from the tube-side outlet of the first evaporator through the first circuit solenoid valve to the air inlet of the low-temperature compressor to realize the circulation of the refrigerant.
[0013] Preferably, under the operating condition that the first evaporator is freezing and the second evaporator is pre-cooling, the process includes the following: When the second evaporator is finished heating and defrosting, instead of directly switching between the first and second evaporators, the second electronic expansion valve is opened slightly to flush a small amount of refrigerant into the valve. This pre-cools the second evaporator before allowing natural gas to enter the shell side of the second evaporator, thus preventing the natural gas output from the shell side of the second evaporator from failing to meet standards due to direct switching. During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor passes through the oil separator, the first four-way valve and the second four-way valve respectively into the condenser to be cooled and liquefied into medium-temperature and high-pressure refrigerant liquid, and then passes through the drying filter and the first electronic expansion valve and the second electronic expansion valve to form low-temperature and low-pressure refrigerant gas, which enters the first evaporator and the second evaporator respectively to achieve freezing of the first evaporator, and pre-cooling of the second evaporator by opening the second electronic expansion valve in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe-side outlets of the first evaporator and the second evaporator to the air inlet of the low-temperature compressor to realize the circulation of the refrigerant.
[0014] Preferably, under the operating condition that the first evaporator is heated to melt ice and the second evaporator is frozen, the method includes the following: When the first evaporator has been in freezing operation for a long time and a frost or ice layer forms on the outer wall of the heat exchange coil, which affects the freezing efficiency, the first evaporator and the second evaporator are switched on. At this time, the natural gas ratio regulating electric three-way valve gradually switches to connect the natural gas heat exchanger to the second evaporator and closes the connection with the first evaporator. Then, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor passes through the oil separator, the first four-way valve and the third four-way valve respectively into the first evaporator, and the defrosting mode is turned on. The high-temperature and high-pressure gas-liquid mixture flowing out of the first evaporator enters the condenser through the second solenoid valve, and is further cooled and liquefied to form a medium-temperature and high-pressure refrigerant liquid. Then, it passes through the drying filter and the second electronic expansion valve to form a low-temperature and low-pressure refrigerant gas, enters the second evaporator for evaporation and heat absorption, and cools the natural gas of 0 to 5°C from the natural gas heat exchanger to -25 to -30°C. The low-temperature and low-pressure refrigerant gas flows back from the pipe outlet of the second evaporator through the second circuit solenoid valve to the air inlet of the low-temperature compressor to realize the circulation of the refrigerant.
[0015] Preferably, under the operating conditions of pre-cooling the first evaporator and freezing the second evaporator, the following process is included: When ice or frost appears in the second evaporator, instead of directly switching between the first and second evaporators, the first electronic expansion valve is gradually opened to flush a small amount of refrigerant into the first evaporator. Before natural gas is allowed to enter the shell side of the first evaporator, the first evaporator is pre-cooled to avoid a sudden switch that may cause the output natural gas to not meet the standards. During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor passes through the oil separator, the first four-way valve and the third four-way valve respectively into the condenser to be cooled into a medium-temperature and high-pressure refrigerant liquid, then passes through the drying filter, and then passes through the first electronic expansion valve and the second electronic expansion valve to form a low-temperature and low-pressure refrigerant gas, which enters the first evaporator and the second evaporator respectively to achieve freezing of the second evaporator, and pre-cooling of the first evaporator is achieved by opening the first electronic expansion valve in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe-side outlets of the first evaporator and the second evaporator to the air inlet of the low-temperature compressor to realize the circulation of the refrigerant.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention utilizes a refrigeration system, a refrigeration compressor, ingenious process design and component matching, and utilizes the characteristics of a refrigeration system that can provide both cooling and cooling, as well as heating and de-icing. Two evaporators are set up, which operate alternately and are equipped with a pre-cooling function to ensure that the output of natural gas meets the standards. Among them, one evaporator dehydrates and removes heavy hydrocarbons above C4 by cooling and cooling, so that scattered natural gas is effectively utilized, and the other evaporator de-ices and defrosts by heating. In addition, by introducing high-temperature refrigerant into the inner cavity of the heat exchange coil to heat the frosted and iced layer on the outer wall of the heat exchange coil, the heat diffuses from the inside of the ice layer to the outside, and the de-icing effect is better, thereby achieving non-stop continuous production, energy-saving and consumption-reducing intelligent small module skid-mounted equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic diagram of the entire process of the present invention; Figure 2 This is a schematic diagram of the process of a refrigeration system in which the first evaporator freezes and the second evaporator heats to melt ice; Figure 3 This is a schematic diagram of the process of the refrigeration system when the first evaporator is freezing and the second evaporator is precooling; Figure 4 This is a schematic diagram of the process of a refrigeration system in which the first evaporator is heated to melt ice and the second evaporator is frozen; Figure 5 This is a schematic diagram of the process of the refrigeration system when the first evaporator is precooling and the second evaporator is freezing; Figure 6 It is a flow diagram of the natural gas system; Figure 7 This is a partial enlarged schematic diagram of hot fluorinated frost in a natural gas heat exchanger; Figure 8 It is a partially enlarged schematic diagram of hot gas defrosting in the prior art; Figure: cryogenic compressor 1, oil separator 2, first four-way valve 3, second four-way valve 4, third four-way valve 5, first solenoid valve 6, second solenoid valve 7, condenser 8, filter drier 9, sight glass 10, first electronic expansion valve 11, second electronic expansion valve 12, first evaporator 13, second evaporator 14, first pressure relief valve 15, second pressure relief valve 16, third pressure relief valve 17, natural gas proportional control electric three-way valve 18, first circuit solenoid valve 19, second circuit solenoid valve 20, natural gas heat exchanger 21, natural gas air-cooled radiator 22, sewage storage tank 23, first sewage control valve 24, second sewage control valve 25, third sewage control valve 26, evaporator shell 13.1, natural gas inlet 13.2, natural gas outlet 13.3, heat exchange coil 13.4, shell-side cavity 13.5, frost and ice layer 13.6. DETAILED DESCRIPTION
[0018] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.
[0019] Example 1, reference Figure 1-Figure 7 The present invention relates to a mobile oilfield scattered gas recovery and purification device, comprising a natural gas system and a sewage discharge system. The natural gas system comprises a filter and a booster, the filter is used to filter impurities in the scattered gas, and the booster is used to increase the pressure of the scattered gas. A refrigeration system is also included. The natural gas system further comprises a natural gas air-cooled radiator 22 and a natural gas heat exchanger 21. The output end of the booster is connected to the pipe-side inlet of the natural gas heat exchanger 21 through a pipeline and the natural gas air-cooled radiator 22. The pipe-side outlet of the natural gas heat exchanger 21 is connected to the shell-side inlet of the first evaporator 13 and the second evaporator 14 of the refrigeration system through a pipeline and a natural gas proportion adjustment electric three-way valve 18. The shell-side outlets of the first evaporator 13 and the second evaporator 14 are respectively connected to the shell-side inlet of the natural gas heat exchanger 21 through pipelines. The shell-side outlet of the natural gas heat exchanger 21 discharges the cooled scattered gas. The refrigeration system includes a low-temperature compressor 1, an oil separator 2, a four-way valve, a first solenoid valve 6, a second solenoid valve 7, a condenser 8, a drying filter 9, a liquid sight glass 10, a first electronic expansion valve 11, a second electronic expansion valve 12, a first evaporator 13, and a second evaporator 14. The outlet of the low-temperature compressor 1 is connected to the condenser 8 through a pipeline, an oil separator 2 and a four-way valve. The output end of the condenser 8 is connected to the first electronic expansion valve 11 or the second electronic expansion valve 12 through a pipeline, a drying filter 9 and a liquid sight glass 10. The output end of the first electronic expansion valve 11 is connected to the second electronic expansion valve 12 through a pipeline. The pipe-side inlet of the first evaporator 13 is connected, and the output end of the second electronic expansion valve 12 is connected to the pipe-side inlet of the second evaporator 14 through a pipeline; the pipe-side outlet of the first evaporator 13 is connected to the pipeline at the inlet end of the condenser 8 through a pipeline and the second solenoid valve 7, and is connected to the air inlet end of the low-temperature compressor 1 through a second pipeline and the first circuit solenoid valve 19. The pipe-side outlet of the second evaporator 14 is connected to the pipeline at the inlet end of the condenser 8 through a pipeline and the first solenoid valve 6, and is connected to the air inlet end of the low-temperature compressor 1 through a second pipeline and the second circuit solenoid valve 20.
[0020] The above-mentioned four-way valve includes a first four-way valve 3, a second four-way valve 4, and a third four-way valve 5. The first output end of the first four-way valve 3 is connected to the second four-way valve 4 and the third four-way valve 5 through a pipeline, the first output end of the second four-way valve 4 is connected to the pipe side inlet of the second evaporator 14 through a pipeline, the second output end of the second four-way valve 4 is connected to the condenser 8 through a pipeline, the first output end of the third four-way valve 5 is connected to the pipe side inlet of the first evaporator 13 through a pipeline, and the second output end of the third four-way valve 5 is connected to the condenser 8 through a pipeline.
[0021] The second output end of the first four-way valve 3 is connected to a first pressure relief valve 15 via a pipeline. The second output end of the second four-way valve 4 is also connected to a second pressure relief valve 16 via a pipeline. The second output end of the third four-way valve 5 is also connected to a third pressure relief valve 17 via a pipeline. The outer ends of the first pressure relief valve 15, the second pressure relief valve 16, and the third pressure relief valve 17 are connected to the pipeline at the intake end of the low-temperature compressor 1 via a pipeline. A liquid sight glass 10 is used to observe the liquid state of the refrigerant.
[0022] Reference Figure 7The first evaporator 13 mentioned in the present invention includes an evaporator shell 13.1, a natural gas inlet 13.2, a natural gas outlet 13.3, a heat exchange coil 13.4, a shell-side cavity 13.5, and a frost and ice layer 13.6. The heat exchange coil 13.4 is provided within the inner cavity of the evaporator shell 13.1, and the shell-side cavity 13.5 is formed between the heat exchange coil 13.4 and the inner wall of the evaporator shell 13.1. The natural gas inlet 13.2 and the natural gas outlet 13.3 are respectively provided at both ends of the evaporator shell 13.1. High-temperature refrigerant is introduced into the inner cavity of the heat exchange coil 13.4 to heat the frost and ice layer 13.6 on the outer wall of the heat exchange coil 13.4, and heat is diffused from the interior of the ice layer to the outside.
[0023] Reference Figure 1 The sewage discharge system mentioned in the present invention includes a sewage storage tank 23, a first sewage discharge control valve 24, a second sewage discharge control valve 25, and a third sewage discharge control valve 26. The lower end of the shell side of the first evaporator 13 is connected to the side line of the sewage storage tank 23 through a pipeline and the first sewage discharge control valve 24, the lower end of the shell side of the second evaporator 14 is connected to the side line of the sewage storage tank 23 through a pipeline and the second sewage discharge control valve 25, and the lower end of the shell side of the natural gas heat exchanger 21 is connected to the side line of the sewage storage tank 23 through a pipeline and the third sewage discharge control valve 26.
[0024] The method for using the mobile oilfield scattered gas recovery and purification device mentioned in the present invention has a technical solution that includes four operating conditions, specifically as follows: Working condition 1, refer to Figure 2 Under the operating conditions of freezing in the first evaporator 13 and melting ice in the second evaporator 14, the purification process includes the following: The high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor 1 passes through the oil separator 2, the first four-way valve 3, and the second four-way valve 4 respectively and enters the pipe-side inlet of the second evaporator 14. The heating and defrosting mode is turned on, and the gas-liquid mixture flows out through the pipe-side outlet of the second evaporator 14, passes through the pipeline and the first solenoid valve 6, and enters the condenser 8 for further cooling and liquefaction. Then, the medium-temperature and high-pressure liquid passes through the drying filter 9 and the first electronic expansion valve 11 and enters the pipe-side inlet of the first evaporator 13, evaporates and absorbs heat, and cools the natural gas of 0-5°C from the natural gas heat exchanger 21 to -25--30°C. The refrigerant flows back from the pipe-side outlet of the first evaporator 13 through the first circuit solenoid valve 19 to the air inlet of the low-temperature compressor 1 to complete the refrigerant circulation.
[0025] Working condition 2, refer to Figure 3 Under the condition that the first evaporator 13 is freezing and the second evaporator 14 is pre-cooling, the process includes the following: When the second evaporator 14 finishes heating and defrosting, instead of directly switching the functions of the first evaporator 13 and the second evaporator 14, the second electronic expansion valve 12 is opened slightly to flush a small amount of refrigerant into the second electronic expansion valve 12. Before the natural gas is opened to enter the shell side of the second evaporator 14, the second evaporator 14 is pre-cooled to avoid direct switching that may cause the natural gas output from the shell side of the second evaporator 14 to meet the standards. During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor 1 passes through the oil separator 2, the first four-way valve 3 and the second four-way valve 4 respectively, enters the condenser 8 to cool down and liquefy into a medium-temperature and high-pressure refrigerant liquid, then passes through the drying filter 9, and then passes through the first electronic expansion valve 11 and the second electronic expansion valve 12 to form a low-temperature and low-pressure refrigerant gas, and enters the first evaporator 13 and the second evaporator 14 respectively, to achieve freezing of the first evaporator 13, and pre-cooling of the second evaporator 14 by opening the second electronic expansion valve 12 in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe-side outlets of the first evaporator 13 and the second evaporator 14 to the air inlet of the low-temperature compressor 1 to achieve the circulation of the refrigerant.
[0026] Working condition three, refer to Figure 4 Under the operating conditions that the first evaporator 13 heats and melts ice, and the second evaporator 14 freezes ice, the following is included: When a frost layer 13.6 forms on the outer wall of the heat exchange coil 13.4 of the first evaporator 13 after a long period of freezing, affecting the freezing efficiency, the first evaporator 13 and the second evaporator 14 are switched. At this time, the natural gas ratio regulating electric three-way valve 18 gradually switches to connect the natural gas heat exchanger 21 to the second evaporator 14, closing the connection with the first evaporator 13. Then, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor 1 passes through the oil separator 2, the first four-way valve 3 and the third four-way valve 5 respectively and enters the first evaporator 13. The defrosting mode is turned on, and the high-temperature and high-pressure gas-liquid mixture flowing out of the first evaporator 13 passes through the second solenoid valve 7 and enters the condenser 8, where it is further cooled and liquefied to form a medium-temperature and high-pressure refrigerant liquid. Then, it passes through the drying filter 9 and the second electronic expansion valve 12 to form a low-temperature and low-pressure refrigerant gas, enters the second evaporator 14 to evaporate and absorb heat, and cools the natural gas of 0 to 5°C from the natural gas heat exchanger 21 to -25 to -30°C. The low-temperature and low-pressure refrigerant gas flows back from the pipe outlet of the second evaporator 14 through the second circuit solenoid valve 20 to the air inlet of the low-temperature compressor 1 to realize the circulation of the refrigerant.
[0027] Working condition 4, refer to Figure 5 Under the working conditions of pre-cooling in the first evaporator 13 and freezing in the second evaporator 14, the following process is included: When ice or frost appears in the second evaporator 14, instead of directly switching between the first and second evaporators 13 and 14, the first electronic expansion valve 11 is gradually opened to flush a small amount of refrigerant into the first evaporator 13. Before natural gas is allowed to enter the shell side of the first evaporator 13, the first evaporator 13 is pre-cooled to avoid a sudden switch that may result in substandard output natural gas. During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor 1 passes through the oil separator 2, the first four-way valve 3 and the third four-way valve 5 respectively into the condenser 8 to be cooled into a medium-temperature and high-pressure refrigerant liquid, then passes through the drying filter 9, and then passes through the first electronic expansion valve 11 and the second electronic expansion valve 12 to form a low-temperature and low-pressure refrigerant gas, and enters the first evaporator 13 and the second evaporator 14 respectively to achieve freezing of the second evaporator 14, and pre-cooling of the first evaporator 13 is achieved by opening the first electronic expansion valve 11 in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe-side outlets of the first evaporator 13 and the second evaporator 14 to the air inlet of the low-temperature compressor 1 to achieve the circulation of the refrigerant.
[0028] In addition, refer to Figure 6 , the cooling process of natural gas is as follows: After passing through the filter, the associated gas from the well site is pressurized and heated by a booster before entering the natural gas air-cooled radiator 22, where its temperature drops to a normal temperature of approximately 40°C. It is then sent to the natural gas heat exchanger 21 for pre-cooling. The pipe-side outlet of the natural gas heat exchanger 21 is connected to the shell-side inlets of the first evaporator 13 and the second evaporator 14 of the refrigeration system via a pipeline and a natural gas ratio-regulating electric three-way valve 18, thereby reducing the temperature of the natural gas to -25 to -30°C. The natural gas at -25 to -30°C is then sent to the shell-side inlet of the natural gas heat exchanger 21 to pre-cool the natural gas entering the pipe-side of the natural gas heat exchanger 21, reducing its temperature to 0 to 5°C. The natural gas, from which moisture and heavy hydrocarbons above C4 have been removed, is then connected to an external transmission pipeline or a well site pipeline from the shell-side outlet of the natural gas heat exchanger 21, completing the purification of the bulk gas here.
[0029] The above descriptions are merely some preferred embodiments of the present invention. Anyone skilled in the art may be able to modify the above-described technical solutions or convert them into equivalent technical solutions. Therefore, any corresponding simple modifications or equivalent transformations based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A mobile oilfield scattered gas recovery and purification device, comprising a natural gas system and a sewage discharge system. The natural gas system includes a filter and a supercharger. The filter is used to filter impurities in the scattered gas, and the supercharger is used to increase the pressure of the scattered gas. The device is characterized by: The refrigeration system is also included, and the natural gas system also includes a natural gas air-cooled radiator (22) and a natural gas heat exchanger (21). The output end of the booster is connected to the pipe-side inlet of the natural gas heat exchanger (21) through a pipeline and the natural gas air-cooled radiator (22). The pipe-side outlet of the natural gas heat exchanger (21) is connected to the shell-side inlet of the first evaporator (13) and the second evaporator (14) of the refrigeration system through a pipeline and a natural gas proportion adjustment electric three-way valve (18). The shell-side outlets of the first evaporator (13) and the second evaporator (14) are respectively connected to the shell-side inlet of the natural gas heat exchanger (21) through pipelines. The shell-side outlet of the natural gas heat exchanger (21) discharges the cooled scattered gas. The refrigeration system comprises a low-temperature compressor (1), an oil separator (2), a four-way valve, a first solenoid valve (6), a second solenoid valve (7), a condenser (8), a drying filter (9), a first electronic expansion valve (11), a second electronic expansion valve (12), a first evaporator (13), and a second evaporator (14). The outlet of the low-temperature compressor (1) is connected to the condenser (8) via a pipeline, an oil separator (2), and a four-way valve. The output end of the condenser (8) is connected to the first electronic expansion valve (11) or the second electronic expansion valve (12) via a pipeline and a drying filter (9). The output end of the first electronic expansion valve (11) is connected to the second electronic expansion valve (12) via a pipeline. The pipe-side inlet of the first evaporator (13) is connected, and the output end of the second electronic expansion valve (12) is connected to the pipe-side inlet of the second evaporator (14) through a pipeline; the pipe-side outlet of the first evaporator (13) is connected to the pipeline at the inlet end of the condenser (8) through a pipeline and a second solenoid valve (7), and is connected to the air inlet end of the low-temperature compressor (1) through a second pipeline and a first-circuit solenoid valve (19); the pipe-side outlet of the second evaporator (14) is connected to the pipeline at the inlet end of the condenser (8) through a pipeline and a first-circuit solenoid valve (6), and is connected to the air inlet end of the low-temperature compressor (1) through a second pipeline and a second-circuit solenoid valve (20).
2. The mobile oilfield scattered gas recovery and purification device according to claim 1 is characterized in that: The four-way valve comprises a first four-way valve (3), a second four-way valve (4), and a third four-way valve (5), wherein a first output end of the first four-way valve (3) is connected to the second four-way valve (4) and the third four-way valve (5) via a pipeline, a first output end of the second four-way valve (4) is connected to the pipe-side inlet of the second evaporator (14) via a pipeline, a second output end of the second four-way valve (4) is connected to the condenser (8) via a pipeline, a first output end of the third four-way valve (5) is connected to the pipe-side inlet of the first evaporator (13) via a pipeline, and a second output end of the third four-way valve (5) is connected to the condenser (8) via a pipeline.
3. The mobile oilfield scattered gas recovery and purification device according to claim 2 is characterized by: The second output end of the first four-way valve (3) is connected to the first pressure relief valve (15) through a pipeline, the second output end of the second four-way valve (4) is also connected to the second pressure relief valve (16) through a pipeline, and the second output end of the third four-way valve (5) is also connected to the third pressure relief valve (17) through a pipeline; the outer ends of the first pressure relief valve (15), the second pressure relief valve (16) and the third pressure relief valve (17) are connected to the pipeline at the air inlet end of the low-temperature compressor (1) through a pipeline.
4. The mobile oilfield scattered gas recovery and purification device according to claim 3 is characterized by: The first evaporator (13) comprises an evaporator shell (13.1), a natural gas inlet (13.2), a natural gas outlet (13.3), a heat exchange coil (13.4), a shell-side cavity (13.5), and a frosting and icing layer (13.6). The inner cavity of the evaporator shell (13.1) is provided with a heat exchange coil (13.4), a shell-side cavity (13.5) is formed between the heat exchange coil (13.4) and the inner wall of the evaporator shell (13.1), and a natural gas inlet (13.2) and a natural gas outlet (13.3) are respectively provided at both ends of the evaporator shell (13.1). A high-temperature refrigerant is introduced into the inner cavity of the heat exchange coil (13.4) to heat the frosting and icing layer (13.6) on the outer wall of the heat exchange coil (13.4), and heat diffuses from the inside of the ice layer to the outside.
5. The mobile oilfield scattered gas recovery and purification device according to claim 4 is characterized in that: The sewage discharge system includes a sewage storage tank (23), a first sewage discharge control valve (24), a second sewage discharge control valve (25), and a third sewage discharge control valve (26). The lower end of the shell side of the first evaporator (13) is connected to the side line of the sewage storage tank (23) through a pipeline and the first sewage discharge control valve (24). The lower end of the shell side of the second evaporator (14) is connected to the side line of the sewage storage tank (23) through a pipeline and the second sewage discharge control valve (25). The lower end of the shell side of the natural gas heat exchanger (21) is connected to the side line of the sewage storage tank (23) through a pipeline and the third sewage discharge control valve (26).
6. The mobile oilfield scattered gas recovery and purification device according to claim 5 is characterized by: Under the operating conditions where the first evaporator (13) is freezing and the second evaporator (14) is heating to melt ice, the purification process includes the following: The high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor (1) enters the pipe-side inlet of the second evaporator (14) through the oil separator (2), the first four-way valve (3) and the second four-way valve (4), respectively. The heating and de-icing mode is turned on, and the gas-liquid mixture flows out through the pipe-side outlet of the second evaporator (14), enters the condenser (8) through the pipeline and the first solenoid valve (6), and is further cooled and liquefied. Then, the medium-temperature and high-pressure liquid enters the pipe-side inlet of the first evaporator (13) through the drying filter (9) and the first electronic expansion valve (11), evaporates and absorbs heat, and cools the natural gas of 0 to 5°C from the natural gas heat exchanger (21) to -25 to -30°C. The refrigerant flows back from the pipe-side outlet of the first evaporator (13) through the first circuit solenoid valve (19) to the air inlet of the low-temperature compressor (1), realizing the circulation of the refrigerant.
7. The mobile oilfield scattered gas recovery and purification device according to claim 6 is characterized in that: Under the operating conditions where the first evaporator (13) is refrigerated and the second evaporator (14) is pre-cooled, the following is included: When the second evaporator (14) is heated and ice-melting is completed, at this time, instead of directly controlling the function conversion between the first evaporator (13) and the second evaporator (14), the second electronic expansion valve (12) is opened in a small amount, and a small amount of refrigerant is flushed into the second electronic expansion valve (12). Before the natural gas is opened to enter the shell side of the second evaporator (14), the second evaporator (14) is pre-cooled to avoid direct conversion resulting in the natural gas output from the shell side of the second evaporator (14) not meeting the standards; During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor (1) passes through the oil separator (2), the first four-way valve (3) and the second four-way valve (4) respectively, enters the condenser (8) to cool down and liquefy into a medium-temperature and high-pressure refrigerant liquid, then passes through the drying filter (9), and then passes through the first electronic expansion valve (11) and the second electronic expansion valve (12) to form a low-temperature and low-pressure refrigerant gas, which enters the first evaporator (13) and the second evaporator (14) respectively, thereby freezing the first evaporator (13) and pre-cooling the second evaporator (14) by opening the second electronic expansion valve (12) in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe outlets of the first evaporator (13) and the second evaporator (14) to the air inlet of the low-temperature compressor (1) to realize the circulation of the refrigerant.
8. The mobile oilfield scattered gas recovery and purification device according to claim 7 is characterized in that: Under the operating conditions where the first evaporator (13) heats and melts ice, and the second evaporator (14) freezes ice, the following is included: When the first evaporator (13) has been in a freezing state for a long time and a frost and ice layer (13.6) is formed on the outer wall of the heat exchange coil (13.4), which affects the freezing efficiency, the first evaporator (13) and the second evaporator (14) are switched on. At this time, the natural gas ratio regulating electric three-way valve (18) gradually switches to the natural gas heat exchanger (21) to connect to the second evaporator (14), and closes the connection with the first evaporator (13); Then, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor (1) passes through the oil separator (2), the first four-way valve (3) and the third four-way valve (5) and enters the first evaporator (13). The de-icing mode is turned on, and the high-temperature and high-pressure gas-liquid mixture flowing out of the first evaporator (13) passes through the second solenoid valve (7) and enters the condenser (8), where it is further cooled and liquefied to form a medium-temperature and high-pressure refrigerant liquid. Then, it passes through the drying filter (9) and the second electronic expansion valve (12) to form a low-temperature and low-pressure refrigerant gas, which enters the second evaporator (14) to evaporate and absorb heat, cooling the natural gas of 0 to 5°C from the natural gas heat exchanger (21) to -25 to -30°C. The low-temperature and low-pressure refrigerant gas flows back from the pipe outlet of the second evaporator (14) through the second circuit solenoid valve (20) to the air inlet of the low-temperature compressor (1) to realize the circulation of the refrigerant.
9. The mobile oilfield scattered gas recovery and purification device according to claim 8 is characterized in that: Under the operating conditions where the first evaporator (13) is pre-cooled and the second evaporator (14) is refrigerated, the following process is included: When ice or frost appears in the second evaporator (14), instead of directly switching the functions of the first evaporator (13) and the second evaporator (14), the first electronic expansion valve (11) is gradually opened to flush a small amount of refrigerant into the first evaporator (13). Before the natural gas is opened to enter the shell side of the first evaporator (13), the first evaporator (13) is pre-cooled to avoid sudden switching that causes the output natural gas to fail to meet the standards. During this period, the high-temperature and high-pressure refrigerant gas compressed by the low-temperature compressor (1) passes through the oil separator (2), the first four-way valve (3) and the third four-way valve (5) respectively and enters the condenser (8) to be cooled to a medium-temperature and high-pressure refrigerant liquid, then passes through the drying filter (9), and then passes through the first electronic expansion valve (11) and the second electronic expansion valve (12) to form a low-temperature and low-pressure refrigerant gas, which enters the first evaporator (13) and the second evaporator (14) respectively to achieve freezing of the second evaporator (14), and pre-cooling of the first evaporator (13) by opening the first electronic expansion valve (11) in a small amount; finally, the low-temperature and low-pressure refrigerant gas is converged from the pipe outlets of the first evaporator (13) and the second evaporator (14) to the air inlet of the low-temperature compressor (1) to achieve the circulation of the refrigerant.