A transcritical co2 ejector heat pump oilfield waste heat recovery system and method

Abstract

The application discloses a transcritical CO2 ejector heat pump oilfield waste heat recovery system and method, and relates to the field of oilfield waste heat recovery. The system comprises a CO2 ejector heat pump unit, a solar photothermal unit and an oilfield waste heat recovery unit. The CO2 ejector heat pump unit is connected with the solar photothermal unit through an air cooler and a thermoelectric generator, and is connected with the oilfield waste heat recovery unit through a regenerator and a gas-liquid separator. The method comprises heat exchange through the air cooler, adjustment of the thermoelectric generator and a throttle valve to obtain working fluid in different states, data collection and processing and analysis. Through the system and the method, efficient recovery and utilization of oilfield waste heat can be realized, and resource utilization and economic benefits can be improved.

Description

Technical Field

[0001] This invention relates to the field of heat pump technology, and in particular to a transcritical CO2 jet heat pump oilfield waste heat recovery system and method. Background Technology

[0002] During the extraction process of most domestic oilfields, natural gas, water, and oil are extracted simultaneously. However, the produced fluids have a water content as high as 70%, and are mostly wastewater at 70℃~80℃. This wastewater is usually directly discharged or injected back into the ground, resulting in significant energy waste. Oilfield production also generates a large amount of waste heat. If this waste heat is not effectively recovered and utilized, it will waste a significant amount of energy, causing environmental pollution and economic losses. Therefore, finding technical means to utilize oilfield waste heat is an important research direction.

[0003] Existing technologies still have problems such as excessive energy consumption and high pollution emissions from traditional heating methods during oilfield production, collection, and transportation, as well as the problem of low-temperature hot water recovery and utilization. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the current transcritical CO2 jet heat pump oilfield waste heat recovery method, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a transcritical CO2 jet heat pump method for waste heat recovery in oil fields.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] Transcritical CO2 jet heat pump unit, solar thermal unit, oilfield waste heat recovery unit;

[0009] The transcritical CO2 jet heat pump unit includes an ejector, a gas-liquid separator, a T-valve, a regenerator, a compressor, an air cooler, a throttling valve, and a thermoelectric generator. The T-valve includes a first T-valve and a second T-valve.

[0010] The solar thermal unit includes a solar collector, a phase change heat storage box, a generator, and a circulating water pump. The circulating water pump includes a first circulating water pump, a second circulating water pump, and a third circulating water pump. One end of the solar collector is connected to the phase change heat storage box and the other end is connected to the generator. One end of the first circulating water pump is connected to the phase change heat storage box and the other end is connected to the generator to form a loop. The generator is also connected to a second T-valve.

[0011] The solar thermal unit is connected to the thermoelectric generator via the transcritical CO2 jet heat pump unit, and the oilfield waste heat recovery unit is connected to the transcritical CO2 jet heat pump unit via the air cooler and the thermoelectric generator.

[0012] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery system of the present invention, the system further includes a T-type valve including a third T-type valve and a fourth T-type valve, and one end of the ejector is connected to a gas-liquid separator, while the other end is connected to a first T-type valve.

[0013] The other end of the first T-valve is connected to a regenerator, one end of the regenerator is connected to a compressor and a second T-valve, and the other end of the second T-valve is connected to an air cooler.

[0014] The third T-valve is connected to the compressor and the air cooler, as well as the fourth T-valve. The fourth T-valve is connected to the gas-liquid separator, the regenerator, and the third T-valve.

[0015] One end of the gas-liquid separator is also connected to a throttle valve, and the other end of the throttle valve is connected to a thermoelectric generator. The thermoelectric generator is connected to an emitter to form a circuit.

[0016] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery system described in this invention, the oilfield waste heat recovery unit comprises a crude oil heat exchanger, a three-phase separator, an air flotation tank, a second circulating water pump, a settling tank, a filter tank, a desulfurization tower, and a thermoelectric generator.

[0017] The three-phase separator is connected to the crude oil heat exchanger at one end and to the flotation tank at the other end. The second circulating water pump is connected to the flotation tank at one end and to the settling tank at the other end. The filter tank is connected to the settling tank at one end and to the thermoelectric generator at the other end. The desulfurization tower is connected to the thermoelectric generator.

[0018] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, when there is insufficient sunlight, the evaporation temperature of the working fluid in the thermoelectric generator is maintained at 0°C by adjusting the water flow rate and the opening of the throttle valve, thereby producing hot water with a temperature between 55-75°C.

[0019] During the data acquisition process, data such as temperature, pressure, and enthalpy at both ends of the thermoelectric generator (cold and hot ends) are collected using data acquisition instruments and sent to a PC via a serial communication interface.

[0020] In the CO2 cycle system, CO2 is compressed into a supercritical fluid by the compressor and exchanges heat with the cooling water in the air cooler. The cooling water becomes hot water. After being cooled by the air cooler, the supercritical fluid enters the regenerator and is then separated by the gas-liquid separator. The separated gas phase fluid returns to the regenerator and exchanges heat with the transcritical fluid before entering the compressor for compression.

[0021] During the refrigeration cycle, the cooled supercritical fluid is transformed into a low-pressure, high-speed fluid through an ejector. This fluid mixes with the low-pressure fluid from the thermoelectric generator in the mixing chamber of the ejector. After energy exchange, the fluid passes through the diffuser, where its pressure increases. The fluid then enters the gas-liquid separator in a two-phase state. The gaseous refrigerant returns to the compressor, while the liquid refrigerant, after being cooled and depressurized by the expansion valve, enters the thermoelectric generator to absorb heat and then becomes the ejector fluid to complete the cycle.

[0022] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, after the first T-valve and the second T-valve are opened, the two-phase working fluid enters the ejector and the generator for mixing, and CO2 enters the air cooler using a spiral grooved tube heat exchanger through a pipeline. The fluid flowing in the thin tube is CO2, and the fluid flowing in the spiral grooved tube is water. The two exchange heat in countercurrent flow. After being cooled by the air cooler, the supercritical fluid enters the regenerator, and after being separated by the gas-liquid separator, it enters the compressor for compression.

[0023] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, the evaporation temperature is maintained at 0°C by adjusting the hot water flow rate, the cold end water flow rate of the thermoelectric generator, and the opening of the throttle valve, thereby producing hot water at a temperature of 55-75°C. The changes in inlet and outlet data show that the cold end inlet water temperature and the hot water inlet water temperature of the thermoelectric generator are both 14.5°C, the hot water flow rate varies from 2.8 to 4.6 L / min, and the cold end water flow rate of the thermoelectric generator varies from 8 to 20 L / min.

[0024] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, in the experiment, a data acquisition instrument is connected to both ends of the thermoelectric generator (the cold end and the hot end of the thermoelectric generator) to measure the changes in temperature, pressure and enthalpy. Temperature and pressure signals are acquired through the 34901A module of the data acquisition instrument and sent to a PC through a serial communication interface.

[0025] Emerson's mass flow meters communicate with a PC via the ModBus protocol by calling the MSCOMM control in Visual Basic.

[0026] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, CO2 is compressed into a supercritical fluid by a compressor and enters an air cooler to exchange heat with cooling water, and the cooling water outputs hot water to users.

[0027] After being cooled by the air cooler, the supercritical fluid exchanges heat with the fluid in the regenerator and then enters the nozzle of the ejector for expansion and pressure reduction to mix with the low-pressure CO2 fluid. After being pressurized in the diffuser, it enters the gas-liquid separator.

[0028] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, the CO2 saturated liquid and gas are separated in the gas-liquid separator. The liquid enters the thermoelectric generator to exchange heat with the chilled water after being throttled by the throttling valve, and the gas enters the compressor to complete the cycle after being exchanged heat with the regenerator.

[0029] As a preferred embodiment of the transcritical CO2 jet heat pump oilfield waste heat recovery method described in this invention, the supercritical fluid after cooling enters the ejector and becomes a low-pressure, high-speed fluid. It mixes with the low-pressure fluid from the thermoelectric generator in the mixing chamber of the ejector, exchanging momentum and energy. Then, it passes through the diffuser chamber, where the pressure increases, and enters the gas-liquid separator in a two-phase state. The gas phase refrigerant returns to the compressor, while the liquid phase refrigerant, after being cooled and depressurized by the throttling valve, enters the cold end of the thermoelectric generator to absorb heat and then enters the ejector as the entrainer to complete the cycle.

[0030] The beneficial effects of this invention are as follows: The system includes a CO2 jet heat pump unit, a solar thermal unit, and an oilfield waste heat recovery unit. The CO2 jet heat pump unit is connected to the solar thermal unit via an air cooler and a thermoelectric generator, and to the oilfield waste heat recovery unit via a regenerator and a gas-liquid separator. The method includes heat exchange using an air cooler, adjusting the thermoelectric generator and a throttling valve to obtain supercritical fluids in different states, data acquisition, and data processing and analysis. This system and method enable efficient recovery and utilization of oilfield waste heat, improving resource utilization and economic benefits. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0032] Figure 1This is a flowchart of a transcritical CO2 jet heat pump oilfield waste heat recovery method according to the present invention.

[0033] Figure 2 This is a pressure-enthalpy diagram for a transcritical CO2 jet heat pump cycle. Detailed Implementation

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0037] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth. Example

[0038] Reference Figure 1 A transcritical CO2 jet heat pump oilfield waste heat recovery system includes:

[0039] Specifically, the CO2 jet heat pump unit 100 includes an ejector 101 and a T-valve 103a. The T-valve 103a includes a first T-valve 103, a second T-valve 103b, a third T-valve 103c, and a fourth T-valve 103d. One end of the ejector 101 is connected to a gas-liquid separator 102, and the other end is connected to the first T-valve 103a. The other end of the first T-valve 103a is connected to a regenerator 104. One end is connected to the compressor 105 and the second T-valve 103b, and the other end of the second T-valve 103b is connected to the air cooler 106; the third T-valve 103c is connected to the compressor 105, the air cooler 106 and the fourth T-valve 103d respectively, and the fourth T-valve 103d is connected to the gas-liquid separator 102, the regenerator 104 and the third T-valve 103c respectively; one end of the gas-liquid separator 102 is also connected to the throttle valve 107, and the other end of the throttle valve 107 is connected to the thermoelectric generator 108, forming a circuit.

[0040] The solar thermal unit 200 includes a solar collector plate 201, a phase change heat storage box 202, a generator 203, and a circulating water pump 204 forming a loop. The circulating water pump 204 includes a first circulating water pump 204a, a second circulating water pump 204b, and a third circulating water pump 204c. One end of the solar collector plate 201 is connected to the phase change heat storage box 202, and the other end is connected to the generator 203. One end of the first circulating water pump 204a is connected to the phase change heat storage box 202, and the other end is connected to the generator 203 to form a loop. The generator 203 is also connected to a second T-valve 103b.

[0041] The oilfield waste heat recovery unit 300 comprises a crude oil heat exchanger 301, a three-phase separator 302, a flotation tank 303, a second circulating water pump 204b, a settling tank 304, a filter tank 305, a desulfurization tower 306, and a thermoelectric generator 108. One end of the three-phase separator 302 is connected to the crude oil heat exchanger 301, and the other end is connected to the flotation tank 303. One end of the second circulating water pump 204b is connected to the flotation tank 303, and the other end is connected to the settling tank 304. One end of the filter tank 305 is connected to the settling tank 304, and the other end is connected to the thermoelectric generator 108. The desulfurization tower 306 is connected to the thermoelectric generator 108.

[0042] The solar thermal unit 200 is connected to the transcritical CO2 jet heat pump system via the generator 203, and the oilfield waste heat recovery system is connected to the transcritical CO2 jet heat pump system via the thermoelectric generator 108.

[0043] Furthermore, when sunlight is abundant, the solar collector heats water and delivers it to the generator 203 for heat exchange with the refrigerant, maintaining the generating temperature between 66°C and 88°C. This provides a high-pressure steam source for the transcritical CO2 jet heat pump, achieving the optimal ejection coefficient (COP). The cooled water is pumped back to the phase change heat storage tank 202 for storage, while a portion is sent to the solar collector to further heat the solar collector panels 201. Meanwhile, the refrigerant in the generator 203, after being heated to a high-temperature and high-pressure state, passes through the second T-valve 103. b enters the ejector 101, where it acts as a high-pressure supercritical fluid, attracting a low-pressure ejector fluid from the cold end of the thermoelectric generator 108. The two fluids mix inside the ejector 101 to form a medium-pressure mixed fluid, which is then discharged. The medium-pressure mixed fluid enters the gas-liquid separator 102. The gas portion after gas-liquid separation enters the air cooler 106 through a pipeline for heat release and cooling. The cooled fluid returns to the generator 203 through the third T-valve 103c. The liquid portion enters the throttle valve 107 for cooling and depressurization, and finally returns to the ejector 101 after the thermoelectric generator 108 outputs cooling capacity.

[0044] Furthermore, under conditions of insufficient sunlight, the T-valve 103 switches to the compressor 105 side, and the first circulating water pump 204a in the solar thermal system stops. At this time, the medium-pressure mixed fluid discharged by the ejector 101 enters the gas-liquid separator 102. The separated gaseous working fluid first enters the regenerator 104 to cool the refrigerant at the outlet of the air cooler 106, and then enters the compressor 105 to be upgraded to a high-temperature and high-pressure refrigerant working fluid. After the air cooler 106 releases heat, it returns to the ejector 101. The liquid portion separated enters the throttle valve 107 and the thermoelectric generator 108 to absorb heat and then returns to the ejector 101. The liquid refrigerant working fluid delivers cooling capacity to the cold end of the thermoelectric generator 108 through direct expansion.

[0045] In the oilfield waste heat recovery system, natural gas from the three-phase separator 302 is directly exported. Heavy oil enters the crude oil heat exchanger 301 and is then exported for further refining and processing under the heat provided by the air cooler. Low-temperature hot water, after passing through the flotation tank 303, settling tank 304, and filter tank 305, provides a low-temperature heat source to the hot end of the thermoelectric generator 108 for waste heat recovery. After being treated by the desulfurization tower 306, it is injected back into the ground. The thermoelectric generator 108 receives the cold energy from the heat pump working fluid and the heat energy from the low-temperature hot water, creating a temperature difference at both ends of the device. Utilizing the Seebeck effect, the thermoelectric element in the middle of the device generates current, part of which is supplied to the compressor 105, and the excess is output to the outside for other uses.

[0046] The solar thermal system adopts a closed-loop circulation, and the supercritical fluid is a 25% ethylene glycol solution. The air cooler 106 and the crude oil heat exchanger 301 adopt a closed-loop circulation, and the supercritical fluid is a 25% ethylene glycol solution. Example

[0047] Reference Figure 2 Transcritical CO2 jet heat pump oilfield waste heat recovery methods include:

[0048] Specifically, when there is insufficient sunlight, the evaporation temperature of the working fluid in the thermoelectric generator 108 is maintained at 0°C by adjusting the water flow rate and the opening of the throttle valve 107, thereby producing hot water with a temperature between 55-75°C.

[0049] During the data acquisition process, data such as temperature, pressure and enthalpy at both ends of the cold end and hot end of the thermoelectric generator 108 are collected using a data acquisition instrument, and the data is sent to the PC through a serial communication interface.

[0050] In the CO2 cycle system, CO2 is compressed into a supercritical fluid by the compressor 105 and exchanges heat with the cooling water in the air cooler 106. The cooling water becomes hot water. After being cooled by the air cooler 106, the supercritical fluid enters the regenerator 104 and is then separated by the gas-liquid separator 102. The separated gas phase fluid returns to the regenerator 104 and exchanges heat with the transcritical fluid before entering the compressor 105 for compression.

[0051] In the refrigeration cycle, the cooled supercritical fluid is transformed into a low-pressure, high-speed fluid through ejector 101, and then mixed with the low-pressure fluid from thermoelectric generator 108 in the mixing chamber. The refrigeration system is then circulated after energy exchange, diffusion, and gas-liquid separation.

[0052] S1: Power is switched on, putting the reciprocating CO2 compressor in a loaded state. The nominal power is 4kW, and the theoretical displacement is 3.5m³. 3 / h. The first T-valve (103a) and the second T-valve (103b) open, allowing the two-phase working fluid to enter the ejector 101 and generator 203 for mixing. CO2 enters the air cooler 106 through a pipeline. The air cooler 106 uses a spiral grooved tube heat exchanger, with CO2 flowing in the thin tubes and water flowing in the spiral grooved tubes, resulting in counter-current heat exchange. The cold end of the thermoelectric generator 108 and the regenerator 104 use a counter-current shell-and-tube heat exchanger, with CO2 flowing in the inner tube and water flowing in the outer tube. The water flow rate in the air cooler 106 and the cold end of the thermoelectric generator 108 is adjusted by changing the opening of the pipeline valves. The gas-liquid separator uses a U-shaped tube structure with an internal oil return port and a volume of 0.01 m³. 3 .

[0053] The supercritical fluid is cooled by the air cooler 106 and then enters the regenerator 104. It is then separated by the gas-liquid separator 102 and then enters the compressor 105 for compression.

[0054] S2: Adjust the hot water flow rate, the cold end water flow rate of the thermoelectric generator 108, and the opening of the throttle valve to keep the evaporation temperature constant at 0℃, and produce hot water at a temperature of 55-75℃. In the experiment studying the changes in the inlet and outlet data of the evaporator and condenser, the cold end inlet water temperature and the hot water inlet water temperature of the thermoelectric generator 108 are both 14.5℃, the hot water flow rate varies from 2.8 to 4.6 L / min, and the cold end water flow rate of the thermoelectric generator 108 varies from 8 to 20 L / min.

[0055] S3: Connect the data acquisition instrument to both the cold and hot ends of the thermoelectric generator 108 to measure the changes in temperature, pressure, and enthalpy during operation. The temperature and pressure signals in the experiment are acquired through the 34901A module of the Agilent 34970A data acquisition instrument and sent to the PC via the RS-232 serial communication interface. The Emerson mass flow meter communicates with the PC via the ModBus protocol using the Visual Basic MSCOMM control.

[0056] S4: CO2 is compressed into a high-temperature and high-pressure supercritical fluid by compressor 105. The supercritical fluid enters air cooler 106 to exchange heat with cooling water. After absorbing heat, the cooling water outputs hot water to the user.

[0057] After being cooled by the air cooler 106, the supercritical fluid enters the regenerator 104 to exchange heat with the fluid returning from the gas-liquid separator 102 to the compressor 105, and then enters the nozzle of the ejector 101 to expand and depressurize, entraining the low-pressure CO2 fluid (ejector fluid) coming out of the cold end of the thermoelectric generator 108.

[0058] The two fluids exchange momentum and energy in the mixing section of the ejector 101. After mixing, they are decelerated and pressurized in the diffuser chamber and leave the ejector 101 with a certain degree of dryness before entering the gas-liquid separator 102.

[0059] In the gas-liquid separator 102, CO2 liquid and gas are separated. The saturated liquid is throttled by the throttle valve 107 and then enters the cold end of the thermoelectric generator 108 to exchange heat with the chilled water. The saturated gas enters the regenerator 104 to exchange heat and then enters the compressor 105 to complete the cycle.

[0060] The supercritical fluid at the outlet of compressor 105 releases heat in air cooler 106, its temperature decreases, and it enters the nozzle of ejector 101 as supercritical fluid, becoming a high-speed flowing low-pressure fluid. It entrains the low-pressure fluid coming out of the cold end of thermoelectric generator 108. The two fluids mix in the mixing chamber of ejector 101, exchanging momentum and energy. Then, they pass through the diffuser, where the pressure increases, and they enter the gas-liquid separator 102 in a two-phase state. The gaseous refrigerant returns to compressor 105, while the liquid refrigerant, after being cooled and depressurized by throttling valve 107, enters the cold end of thermoelectric generator 108, absorbs heat, and then enters ejector 101 as an entrainer fluid to complete the cycle.

[0061] The supercritical fluid at the outlet of compressor 105 releases heat in air cooler 106, its temperature decreases, and it enters the nozzle of ejector 101 as supercritical fluid, becoming a high-speed flowing low-pressure fluid. It entrains the low-pressure fluid coming out of the cold end of thermoelectric generator 108. The two fluids mix in the mixing chamber of ejector 101, exchanging momentum and energy. Then, they pass through the diffuser chamber, where the pressure increases, and they enter the gas-liquid separator 102 in a two-phase state. The gaseous refrigerant returns to compressor 105, while the liquid refrigerant, after being cooled and depressurized by throttle valve 107, enters the cold end of thermoelectric generator 108, absorbs heat, and then enters thermoelectric generator 108 as an entrainer fluid to complete the cycle.

[0062] S5: Experimental data processing and analysis. The collected data is tabulated, and the operating line segment is plotted on the pressure-enthalpy graph. Processing and calculations are performed according to relevant formulas and modeling. Analysis and conclusions are drawn.

[0063] The system works as follows: the supercritical fluid at the outlet of compressor 105 releases heat in air cooler 106, its temperature decreases, and it enters the nozzle of ejector 101 as supercritical fluid, becoming a high-speed flowing low-pressure fluid. It entrains the low-pressure fluid coming out of the cold end of thermoelectric generator 108. The two fluids mix in the mixing chamber of ejector 101, exchanging momentum and energy. Then, they pass through the diffuser chamber, where the pressure increases, and they enter the gas-liquid separator 102 in a two-phase state. The gaseous refrigerant returns to compressor 105, and the liquid refrigerant, after being cooled and depressurized by throttle valve 107, enters the cold end of thermoelectric generator 108 to absorb heat and then enters ejector 101 as an entrainer fluid to complete the cycle.

[0064] Depend on Figure 2It can be seen that: the supercritical gas exiting the compressor at point 1 becomes a high-temperature and high-pressure state at point 2. After passing through the cooler, the temperature decreases and reaches point 3. The supercritical fluid is approximately isentropic during the depressurization and acceleration process in the absorption chamber, reaching point 4 at the nozzle outlet. Then it mixes with the low-temperature and low-pressure fluid in point 4”, reaching point 5. After passing through the diffuser, it reaches point 6. The gaseous working fluid returns to the compressor at point 1 for the next cycle. The rest passes through the gas-liquid separator and reaches point 7 as a pure liquid. After isentropic throttling, it reaches point 8. Points 8 to 9 are the working fluid evaporation process. After that, it returns to point 4” and enters the next cycle.

[0065] The main calculation model for the system's circulating thermodynamics can be summarized as follows:

[0066] Compressor power consumption:

[0067] W=h2-h1

[0068] Heat dissipation of the cooler:

[0069] Q1 = h2 - h3

[0070] Throttling processes 3-4 and 7-8 are considered isenthalpic processes:

[0071] h7=h8, h3=h4

[0072] Evaporator heat absorption:

[0073] Q2 = (h9 - h8) + (h1 - h6)

[0074] Circulating heating coefficient:

[0075] COP = Q1 / W

[0076] Cycle cooling coefficient:

[0077] EER=Q2 / W

[0078] Where h1, h2, h3, h4, h6, h7, h8, and h9 represent the enthalpy values ​​of points 1, 2, 3, 4, 6, 7, 8, and 9.

[0079] Example 3

[0080] This embodiment is the third embodiment of the present invention. Unlike the first embodiment, this embodiment provides an operational test of a transcritical CO2 jet heat pump oilfield waste heat recovery system and method, and obtains two sets of operational data to verify and explain the technical effects adopted in this method.

[0081]

[0082] Based on the comparison of the above charts and data, it can be seen that the transcritical CO2 jet heat pump cycle is superior to the CO2 vapor compression heat pump cycle in terms of operating data. The comparison data shows that the transcritical CO2 jet heat pump cycle has a COP of 2.64, an EER of 9.02, and evaporator-side inlet and outlet enthalpies of 320 kJ and 438 kJ, respectively, and condenser-side inlet and outlet enthalpies of 483 kJ and 320 kJ, respectively, which are all superior to the traditional heat pump cycle. The traditional heat pump cycle has a COP of 1.75, an EER of 7.67, and evaporator-side inlet and outlet enthalpies of 272 kJ and 372 kJ, respectively, and condenser-side inlet and outlet enthalpies of 410 kJ and 272 kJ, respectively.

[0083] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A transcritical CO2 jet heat pump oilfield waste heat recovery system, characterized in that: include, Transcritical CO2 jet heat pump unit (100), solar thermal unit (200), oilfield waste heat recovery unit (300). The transcritical CO2 jet heat pump unit (100) includes an ejector (101), a gas-liquid separator (102), a T-valve (103), a regenerator (104), a compressor (105), an air cooler (106), a throttle valve (107), and a thermoelectric generator (108). The T-valve (103) includes a first T-valve (103a) and a second T-valve (103b). The solar thermal unit (200) includes a solar collector (201), a phase change heat storage box (202), a generator (203), and a circulating water pump (204). The circulating water pump (204) includes a first circulating water pump (204a), a second circulating water pump (204b), and a third circulating water pump (204c). The solar collector (201) is connected at one end to the phase change heat storage box (202) and at the other end to the generator (203). The first circulating water pump (204a) is connected at one end to the phase change heat storage box (202) and at the other end to the generator (203) to form a circuit. The generator (203) is also connected to the second T-valve (103b). The solar thermal unit (200) is connected to the thermoelectric generator (108) through the transcritical CO2 jet heat pump unit (100), and the oilfield waste heat recovery unit (300) is connected to the transcritical CO2 jet heat pump unit (100) through the air cooler (106) and the thermoelectric generator (108).

2. The transcritical CO2 jet heat pump oilfield waste heat recovery system as described in claim 1, characterized in that: The T-valve (103) also includes a third T-valve (103c) and a fourth T-valve (103d). One end of the injector (101) is connected to the gas-liquid separator (102), and the other end is connected to the first T-valve (103a). The other end of the first T-valve (103a) is connected to the regenerator (104), one end of the regenerator (104) is connected to the compressor (105) and the second T-valve (103b), and the other end of the second T-valve (103b) is connected to the air cooler (106). The third T-valve (103c) is connected to the compressor (105) and the air cooler (106) and the fourth T-valve (103d), respectively. The fourth T-valve (103d) is connected to the gas-liquid separator (102) and the regenerator (104) and the third T-valve (103c), respectively. One end of the gas-liquid separator (102) is also connected to a throttle valve (107), and the other end of the throttle valve (107) is connected to a thermoelectric generator (108). The thermoelectric generator (108) is connected to an injector (101) to form a circuit.

3. The transcritical CO2 jet heat pump oilfield waste heat recovery system as described in claim 2, characterized in that: The oilfield waste heat recovery unit (300) comprises a crude oil heat exchanger (301), a three-phase separator (302), an air flotation tank (303), a second circulating water pump (204b), a settling tank (304), a filter tank (305), a desulfurization tower (306), and a thermoelectric generator (108). The three-phase separator (302) is connected at one end to the crude oil heat exchanger (301) and at the other end to the flotation tank (303). The second circulating water pump (204b) is connected at one end to the flotation tank (303) and at the other end to the settling tank (304). The filter tank (305) is connected at one end to the settling tank (304) and at the other end to the thermoelectric generator (108). The desulfurization tower (306) is connected to the thermoelectric generator (108).

4. A method for waste heat recovery in a transcritical CO2 jet heat pump oilfield, based on a transcritical CO2 jet heat pump oilfield waste heat recovery system as described in any one of claims 1-3, characterized in that: It also includes, When there is insufficient sunlight, the working fluid in the thermoelectric generator (108) is kept at 0°C by adjusting the water flow rate and the opening of the throttle valve (107), thereby producing hot water at a temperature between 55-75°C. During the data acquisition process, data such as temperature, pressure and enthalpy at both ends of the cold end and the hot end of the thermoelectric generator (108) are collected using a data acquisition instrument, and the data is sent to the PC through a serial communication interface. In the CO2 cycle system, CO2 is compressed into a supercritical fluid by the compressor (105), and exchanges heat with the cooling water in the air cooler (106). The cooling water becomes hot water. After being cooled by the air cooler (106), the supercritical fluid enters the regenerator (104) and is then separated by the gas-liquid separator (102). The separated gaseous fluid returns to the regenerator (104) to exchange heat with the transcritical fluid before entering the compressor (105) for compression. During the refrigeration cycle, the cooled supercritical fluid is passed through the ejector (101) to become a low-pressure, high-speed fluid. It is mixed with the low-pressure fluid from the thermoelectric generator (108) in the mixing chamber of the ejector (101). After energy exchange, it passes through the diffuser chamber, where the pressure increases. It then enters the gas-liquid separator (102) in a two-phase state. The gaseous refrigerant returns to the compressor (105), while the liquid refrigerant, after being cooled and depressurized by the throttle valve (107), enters the thermoelectric generator (108) to absorb heat and then enters the ejector (101) as an ejector fluid to complete the cycle.

5. The method for waste heat recovery in oilfields using a transcritical CO2 jet heat pump as described in claim 4, characterized in that: After the first T-valve (103a) and the second T-valve (103b) are opened, the two-phase working fluid enters the ejector (101) and the generator (203) for mixing. CO2 enters the air cooler (106) with a spiral grooved tube heat exchanger through the pipe. The medium flowing in the thin tube is CO2, and the medium flowing in the spiral grooved tube is water. The two exchange heat in countercurrent. After being cooled by the air cooler (106), the supercritical fluid enters the regenerator (104), and after being separated by the gas-liquid separator (102), it enters the compressor (105) for compression.

6. The method for waste heat recovery in oilfields using a transcritical CO2 jet heat pump as described in claim 5, characterized in that: By adjusting the hot water flow rate, the cold end water flow rate of the thermoelectric generator (108), and the opening of the throttle valve, the evaporation temperature is kept constant at 0℃, thereby producing hot water with a temperature of 55-75℃. The changes in the inlet and outlet data show that the cold end inlet water temperature and the hot water inlet water temperature of the thermoelectric generator (108) are both 14.5℃, the hot water flow rate varies from 2.8 to 4.6 L / min, and the cold end water flow rate of the thermoelectric generator (108) varies from 8 to 20 L / min.

7. The method for waste heat recovery in oilfields using a transcritical CO2 jet heat pump as described in claim 6, characterized in that: In the experiment, the data acquisition instrument was connected to the cold end and the hot end of the thermoelectric generator (108) to measure the changes in temperature, pressure and enthalpy. The temperature and pressure signals were collected by the 34901A module of the data acquisition instrument and sent to the PC through the serial communication interface. Emerson's mass flow meters communicate with a PC via the ModBus protocol by calling the MSCOMM control in Visual Basic.

8. The method for waste heat recovery in oilfields using a transcritical CO2 jet heat pump as described in claim 7, characterized in that: CO2 is compressed into a supercritical fluid by the compressor (105) and enters the air cooler (106) to exchange heat with the cooling water. The cooling water outputs hot water to the user. After being cooled by the air cooler (106), the supercritical fluid exchanges heat with the fluid in the regenerator (104) and then enters the nozzle of the ejector (101) for expansion and pressure reduction to mix with the low-pressure CO2 fluid. After being pressurized by the diffuser, it enters the gas-liquid separator (102).

9. The method for recovering waste heat from an oilfield using a transcritical CO2 jet heat pump as described in claim 8, characterized in that: In the gas-liquid separator (102), CO2 saturated liquid and gas are separated. The liquid is throttled by the throttle valve (107) and then enters the thermoelectric generator (108) to exchange heat with the chilled water. The gas is exchanged heat by the regenerator (104) and then enters the compressor (105) to complete the cycle.

10. The method for recovering waste heat from an oilfield using a transcritical CO2 jet heat pump as described in claim 9, characterized in that: The cooled supercritical fluid enters the ejector (101) and becomes a low-pressure, high-speed fluid. It mixes with the low-pressure fluid from the thermoelectric generator (108) in the mixing chamber of the ejector (101) to exchange momentum and energy. Then, it passes through the diffuser chamber, where the pressure increases, and enters the gas-liquid separator (102) in a two-phase state. The gaseous refrigerant returns to the compressor (105), and the liquid refrigerant, after being cooled and depressurized by the throttle valve (107), enters the cold end of the thermoelectric generator (108) to absorb heat and then enters the ejector (101) as an ejector fluid to complete the cycle.

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