CN112503782B - Oilfield waste heat recovery system and method using solar energy and lithium bromide heat pump - Google Patents

Abstract

The invention discloses an oilfield waste heat recovery system and method applying solar energy and a lithium bromide heat pump. The invention utilizes the heat pump technology to extract the waste heat of the produced water of oil extraction, reduces the conversion of taste heat energy into high-grade heat energy, and the high-temperature heat source is provided by a renewable energy solar energy system, and the prepared high-temperature hot water is used for crude oil external heating, clear water heating, domestic water heating, and the like. Solves the technical problems of the prior art that the original external pipeline consumes no renewable energy such as electricity or natural gas, the temperature for preparing hot water is low, and the energy consumption of the oil well water-mixing heating system is large.

Description

Oilfield waste heat recovery system and method using solar energy and lithium bromide heat pump

Technical Field

The invention relates to a waste heat recovery system integrating the conversion of renewable energy solar energy into thermal energy and the extraction of waste heat of oil field produced water by an absorption heat pump, belonging to the technical field of heat recovery in energy conservation and environmental protection.

Background technique

The oil field has entered the middle and late stages of "high water content and high recovery" development. The existing oil field heat circulation system uses phase change heating furnaces for stable heating of crude oil or heating of external oil, steam boilers for heating, heating of process facilities and treatment of aged oil, hot water boilers for fresh water heating, and hot water transportation for well washing. The heating furnace in the station uses natural gas as energy, and the gas source is dry gas exported from the natural gas production and sales plant. The flow of produced water in the oil field is sufficient. After the crude oil is separated into oil, gas and water at the oil field joint station, the produced water is directly injected into the oil field after treatment, resulting in a large waste of waste heat, which is not in line with the concept of energy conservation and environmental protection. At the same time, the oil field is located in a large space, rich in solar energy resources, and has a large idle area. The original system did not effectively and reasonably utilize clean and renewable solar energy.

In response to global environmental pollution, global warming, unreasonable energy structure, waste of resources and other issues, many experts at home and abroad have conducted extensive research on energy-saving and emission reduction technologies. Among them, patent 201910227884.7 mentions the use of low-temperature waste heat lost by cooling industrial kilns by setting up oil circulation loops, organic Rankine cycles and water cooling circulation loops. Although this patent utilizes the low-temperature waste heat of industrial kilns, a considerable part of the waste heat is still lost through cooling towers with heat transfer oil as the medium, resulting in waste heat resources. Patent CN201922498185.4 mentions the use of lithium bromide solution heat exchange and heat medium water heat exchange to combine industrial waste heat recovery, absorption heat pumps and salt energy storage technology, and uses air source heat pump technology to heat the salt energy storage system and provide heat to users. However, this patent does not consider the frosting problem of air source heat pumps in low temperature environments; when the required heat is relatively large, the heating capacity of the air source heat pump is insufficient and the reliability is poor. At the same time, in low temperature environments, the energy efficiency ratio of the air source heat pump will drop rapidly.

The proposal of effective utilization of renewable energy solar energy and waste heat recovery can not only solve the problems of single energy structure of oil fields, outdated traditional heating equipment, difficult system optimization, waste of waste heat of oil field produced water, but also meet the environmental protection requirements of energy conservation and emission reduction, and consider the best match between the net zero emission target of oil fields and their project benefits. After the crude oil is separated into oil, gas and water at the oil field joint station, all the produced water is used to inject into the oil field. This patent adopts heat pump technology to extract the heat of produced water, increase its temperature for utilization, and replace the existing gas heating furnace and hot water boiler in the station. The oil field waste heat recovery system using solar energy and lithium bromide heat pump proposed in this patent has energy-saving economic benefits and environmental benefits, will not cause pollution to the ecological environment, has a simple system principle, reduces power generation energy consumption, and better responds to my country's "energy conservation and emission reduction" policy requirements. At the same time, this patent takes into account that solar energy resources can also be utilized, and through the use of waste heat, multi-energy complementarity, resources can be saved, atmospheric pollutant emissions can be reduced, and the level of safety and environmental protection management can be improved to achieve green development.

Summary of the invention

An oilfield waste heat recovery system using solar energy and lithium bromide heat pumps comprises a solar collector array 101, a hot water storage tank 102, an underground heat storage system 103, a heat exchange water supply tank 104, a circulating water tank 105, an auxiliary heat source 106, a generator 203, a condenser 204, an evaporator 202, an absorber 201, a solution heat exchanger 205, a throttle valve 206, an overflow pipe 207, a temperature difference circulation pump 1001, a temperature circulation pump 1002, a constant temperature circulation pump 1003, a solution pump 1004, and a water supply pump 1005.

The solar collector array 101 has one inlet and one outlet, the hot water storage tank 102 has four inlets and four outlets, the underground heat storage system 103 has one inlet and one outlet, the heat exchange water tank 104 has two inlets and two outlets, the circulating water tank 105 has three inlets and two outlets, the auxiliary heat source 106 has one inlet and one outlet, the generator 203 has two inlets and four outlets, the condenser 204 has two inlets and two outlets, the evaporator 202 has two inlets and two outlets, the absorber 201 has four inlets and two outlets, and the solution heat exchanger 205 has two inlets and two outlets.

The inlet of the solar thermal collector array 101 is connected to the first outlet of the hot water storage tank 102, the outlet of the solar thermal collector array 101 is connected to the first inlet of the hot water storage tank 102, the second inlet of the hot water storage tank 102 is connected to the outlet of the underground heat storage system 103, the second outlet of the hot water storage tank 102 is connected to the inlet of the underground heat storage system 103, the third inlet of the hot water storage tank 102 is connected to the first outlet of the circulating water tank 105, the third outlet of the hot water storage tank 102 is connected to the first inlet of the circulating water tank 105, the fourth inlet of the hot water storage tank 102 is connected to the first outlet of the heat exchange replenishment tank 104, the fourth outlet of the hot water storage tank 102 is connected to the first inlet of the heat exchange replenishment tank 104, the inlet of the auxiliary heat source 106 is connected to the third outlet of the hot water storage tank 102, the outlet of the auxiliary heat source 106 is connected to the third inlet of the circulating water tank 105, and the second inlet of the circulating water tank 105 is connected to the first outlet of the generator 203, The second outlet of the circulating water tank 105 is connected to the first inlet of the generator 203, the second inlet of the generator 203 is connected to the first outlet of the solution heat exchanger 205, the second outlet of the generator 203 is connected to the first inlet of the condenser 204, the third outlet of the generator 203 is connected to the third inlet of the absorber 201, the fourth outlet of the generator 203 is connected to the first inlet of the solution heat exchanger 205, the first outlet of the condenser 204 is connected to the first inlet of the evaporator 202, the second inlet of the condenser 204 is connected to the first outlet of the absorber 201, and the first outlet of the evaporator 202 is connected to the fourth inlet of the absorber 201; the second inlet of the absorber 201 is connected to the second outlet of the solution heat exchanger 205, the second outlet of the absorber 201 is connected to the second inlet of the solution heat exchanger 205, and the pipeline connecting the third outlet of the generator 203 and the third inlet of the absorber 201 is the overflow pipe 207.

A method for an oilfield waste heat recovery system using solar energy and a lithium bromide heat pump comprises a water cycle and a lithium bromide solution cycle.

Water circulation: the solar collector array 101 and the hot water storage tank 102 form a closed loop. The solar collector array 101 absorbs solar energy and converts it into heat energy. The hot water flows out from the outlet of the solar collector array 101 through the medium, and then flows into the hot water storage tank 102 from the first inlet of the hot water storage tank 102. The underground heat storage system 103 and the hot water storage tank 102 form a closed loop. The underground heat storage system 103 stores heat when solar energy resources are abundant, and provides heat to the hot water storage tank 102 when solar energy resources are scarce.

The heat exchange make-up water tank 104 and the hot water storage tank 102 form a circulating closed circuit for heat exchange between the hot water storage tank 102 and the heat exchange make-up water tank 104. Hot water flows out from the fourth outlet of the hot water storage tank 102 and then flows into the heat exchange make-up water tank 104 from the first inlet of the heat exchange make-up water tank 104, satisfying the requirement of cold water entering the heat exchange make-up water tank 104 to absorb heat and provide hot water for users.

Cold make-up water enters the heat exchange make-up water tank 104 from the second inlet of the heat exchange make-up water tank 104, and hot water flows out from the second outlet of the heat exchange make-up water tank 104 for use by users.

The hot water storage tank 102 and the circulating water tank 105 form a loop for heat exchange between the hot water storage tank 102 and the circulating water tank 105 . Hot water flows out from the third outlet of the hot water storage tank 102 and then flows into the circulating water tank 105 from the first inlet of the circulating water tank 105 .

The hot water storage tank 102, the auxiliary heat source 106 and the circulating water tank 105 form a loop. When the water temperature of the circulating water tank 105 does not reach the design temperature, the constant temperature circulation pump 1003 is turned on, and the auxiliary heat source 106 supplements heat to the circulating water tank 105 to reach the design water temperature. When the circulating water tank 105 has reached the design temperature, the constant temperature circulation pump 1003 is turned off, and the hot water storage tank 102 directly supplies heat to the circulating water tank 105.

The circulating water tank 105 and the generator 203 form a loop. The hot water in the circulating water tank 105 serves as a high-temperature heat source for the generator 203 and exchanges heat with the dilute lithium bromide solution in the generator 203 .

The low-temperature waste heat produced water enters the evaporator 202 from the second inlet of the evaporator 202 , exchanges heat with the water vapor in the evaporator 202 , and then flows out from the second outlet of the evaporator 202 .

The cold water that is required to be heated enters the absorber 201 from the first inlet of the absorber 201, absorbs the absorption heat in the absorber 201, and then flows out from the first outlet of the absorber 201. The cold water that is heated once flows out from the first outlet of the absorber 201, enters the condenser 204 from the second inlet of the condenser 204, exchanges heat with the high-temperature water vapor in the condenser 204, absorbs the condensation heat, and flows out from the second outlet of the condenser 204 to complete the secondary heating for user use.

Lithium bromide solution circulation: The dilute lithium bromide solution in the generator 203 absorbs heat from the high-temperature heat source and is heated and boiled, wherein the water with a low boiling point is vaporized into high-pressure water vapor, which is separated from the absorbent lithium bromide concentrated solution and enters the condenser 204 through a pipeline connected to the second outlet of the generator 203 and the first inlet of the condenser 204.

The high-pressure water vapor generated in the generator 203 releases heat to the cooling medium cold water in the condenser 204, condenses into condensed water, flows out from the first outlet of the condenser 204, is reduced in pressure and cooled by the throttle valve 206, enters the evaporator 202 from the first inlet of the evaporator 202, exchanges heat with the low-temperature waste heat produced water, and evaporates into water vapor. The water vapor in the evaporator 202 flows out from the first outlet of the evaporator 202, enters the absorber 201 from the fourth inlet of the absorber 201, and in the absorber 201, the low-pressure water vapor generated by the evaporator 202 is continuously absorbed by the absorbent lithium bromide concentrated solution to maintain the low pressure in the evaporator 202. The lithium bromide dilute solution formed by the absorption of water vapor by the absorbent lithium bromide concentrated solution flows out from the second outlet of the absorber 201, enters the solution heat exchanger 205 from the second inlet of the solution heat exchanger 205 after being pressurized by the solution pump 1004, flows out from the first outlet of the solution heat exchanger 205 after heat exchange with the lithium bromide concentrated solution flowing out of the generator 203, and then flows into the generator 203 from the fourth inlet of the generator 203. In the generator 203, the lithium bromide dilute solution absorbs the heat of the high-temperature heat source and boils, and the water with a low boiling point vaporizes into high-pressure water vapor and separates from the absorbent lithium bromide and enters the condenser 204. The concentrated lithium bromide concentrated solution flows out from the fourth outlet of the generator 203 and then enters the solution heat exchanger 205 from the first inlet of the solution heat exchanger 205, flows out from the second outlet of the solution heat exchanger 205 after heat exchange with the lithium bromide dilute solution, and then enters the absorber 201 from the second inlet of the absorber 201.

When the lithium bromide concentrated solution passage of the solution heat exchanger 205 is blocked due to crystallization, the liquid level of the generator 203 rises, and the lithium bromide concentrated solution directly enters the absorber 201 through the overflow pipe 207.

A temperature difference circulation pump 1001 is provided on the pipeline connecting the outlet of the solar collector array 101 and the first inlet of the hot water storage tank 102, a temperature circulation pump 1002 is provided on the pipeline connecting the second outlet of the hot water storage tank 102 and the inlet of the underground heat storage system 103, a constant temperature circulation pump 1003 is provided on the pipeline connecting the outlet of the auxiliary heat source 106 and the third inlet of the circulating water tank 105, a solution pump 1004 is provided on the pipeline connecting the second inlet of the solution heat exchanger 205 and the second outlet of the absorber 201, a water supply pump 1005 is provided on the pipeline through which the cold make-up water enters the second inlet of the heat exchange make-up water tank 104, and a throttle valve 206 is provided on the pipeline connecting the first inlet of the evaporator 202 and the third outlet of the condenser 204.

The underground heat storage system 103 adopts a water kiln heat storage system, the circulating water tank 105 adopts a square water tank, the heat exchange water tank 104 adopts a stainless steel water tank, the auxiliary heat source 106 adopts an auxiliary electric heating system or a heat pump, etc., the generator 203 adopts a falling film generator, the condenser 204 adopts a shell and tube heat exchanger, the evaporator 202 adopts a spray evaporator, the absorber 201 adopts a spray heat exchanger, and the solution heat exchanger 205 adopts a shell and tube heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system flow chart of the present invention.

The reference numerals in FIG1 are: 101. solar collector array, 102. heat storage tank, 103. underground heat storage system, 104. heat exchange water supply tank, 105. circulating water tank, 106. auxiliary heat source, 201. absorber, 202. evaporator, 203. generator, 204. condenser, 205. solution heat exchanger, 206. throttle valve, 207. overflow pipe, 1001. temperature difference circulation pump, 1002. temperature circulation pump, 1003. constant temperature circulation pump, 1004. solution pump, 1005. water supply pump.

Detailed ways

The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

The system flow chart of this embodiment is shown in Figure 1. The oilfield produced water waste heat recovery system of this embodiment includes a solar collector array 101, a heat storage tank 102, an underground heat storage system 103, a heat exchange water supply tank 104, a circulating water tank 105, an auxiliary heat source 106, an absorber 201, an evaporator 202, a generator 203, a condenser 204, a solution heat exchanger 205, a throttle valve 206, an overflow pipe 207, a temperature difference circulation pump 1001, a temperature circulation pump 1002, a constant temperature circulation pump 1003, a solution pump 1004, and a water supply pump 1005.

When the waste heat recovery system of this example is in operation, the interface between the system and the outside world includes the second inlet of the heat exchange water supply tank 104, the second outlet of the heat exchange water supply tank 104, the first inlet of the absorber 201, the second inlet of the evaporator 202, and the second outlet of the evaporator 202; wherein the second inlet of the heat exchange water supply tank 104 flows in cold water, the second outlet of the heat exchange water supply tank 104 flows out hot water, the first inlet of the absorber 201 flows in cold water required to be heated for use in the oil field, the second outlet of the condenser 204 flows out cold water required to be heated for use in the oil field, and the second inlet of the evaporator 202 flows in water. The second outlet of the evaporator 202 flows out produced water; the circulating medium in the system includes circulating water, lithium bromide solution, water vapor and condensed water; the circulating water circulates among the solar collector array 101, the hot water storage tank 102, the underground heat storage system 103, the heat exchange water tank 104, the circulating water tank 105 and the auxiliary heat source 106; the lithium bromide solution circulates among the absorber 201, the generator 203 and the solution heat exchanger 205; the water vapor circulates between the absorber 201 and the evaporator 202, the generator 203 and the condenser 204; the condensed water circulates between the condenser 204 and the evaporator 202.

The functions of each component are as follows:

Solar thermal collector array 101: absorbs solar radiation and transfers the generated heat energy to the circulating water in the solar thermal collector array 101 to transfer heat to the system;

Hot water storage tank 102: Due to the instability of solar energy, the hot water generated by the solar collector array 101 needs to be temporarily stored for use;

Underground heat storage system 103: Stores solar radiation energy in spring, summer and autumn for use in winter;

Heat exchange water supply tank 104: provides water for system startup, operation and user water supply;

Circulating water tank 105: maintains a certain amount of circulating hot water and transfers heat to the generator 203;

Auxiliary heat source 106: To solve the intermittent disadvantage of solar energy, it provides heat to the system when the system is insufficient in heating or fails;

Absorber 201: The low-pressure water vapor generated by the evaporator 202 is absorbed by the dilute lithium bromide solution in the absorber 201 to maintain the low pressure in the evaporator 202;

Evaporator 202: condensed water from condenser 204 absorbs heat in evaporator 202 and evaporates into water vapor;

Generator 203: The dilute lithium bromide solution from the absorber 201 is heated and boiled in the generator 203, wherein the water vapor with a low boiling point evaporates into water vapor and enters the condenser 204 to be separated from the lithium bromide. The dilute lithium bromide solution is concentrated into a concentrated lithium bromide solution, which is then returned to the absorber 201 after being depressurized, and absorbs the low-pressure water vapor in the evaporator 202 again;

Condenser 204: condenses the water vapor from generator 203 into liquid water;

Solution heat exchanger 205: The cold dilute solution from the absorber 201 and the hot concentrated solution from the generator 203 are heat exchanged in the solution heat exchanger 205;

Throttle valve 206: The water vapor from the generator 203 is condensed into liquid water in the condenser 204, and then enters the evaporator 202 through the throttle valve 206 with reduced pressure and temperature;

Overflow pipe 207: When the lithium bromide concentrated solution passage of the solution heat exchanger 205 is blocked due to crystallization, the liquid level of the generator 203 rises, and the lithium bromide concentrated solution directly enters the absorber 201 through the overflow pipe 207;

Temperature difference circulation pump 1001: adjusts the operating temperature of the solar collector array 101 according to the temperature of the hot water storage tank 102. When the temperature difference between the solar collector array 101 and the hot water storage tank 102 is greater than the set temperature, the temperature difference circulation pump 1001 is turned on, the system operates, and heat is transferred from the solar collector array 101 to the hot water storage tank 102. When the temperature difference is less than the set value, the temperature difference circulation pump 1001 stops running;

Temperature circulation pump 1002: provides stable pressure and flow rate for the circulating water in the system, completes the heat storage from the solar thermal collection system to the underground heat storage system 103, and releases heat from the underground heat storage system 103 to the hot water storage tank 102 on cloudy days or in weather with poor sunshine intensity;

Constant temperature circulation pump 1003: completes the mutual switching between the solar energy heat collection system and the auxiliary heat source 106. When the temperature of the circulating water in the circulating water tank 105 drops to the set low-temperature start temperature, the auxiliary heat source 106 can start to supply heat to the system. When the temperature of the circulating water in the circulating water tank 105 rises to the set stop temperature, the auxiliary heat source 106 stops working, which not only ensures the normal heating of the system, but also maximizes the use of solar energy.

Solution pump 1004: sends the dilute lithium bromide solution from the absorber 201 to the generator 203;

Make-up water pump 1005: Provides secondary water supply when the circulating water in the system is insufficient or missing.

When the system is actually running, the solar collector array 101 and the hot water storage tank 102 form a closed loop, and the solar collector array 101 collects solar heat to heat the circulating water in the solar collector array 101 to provide heat to the hot water storage tank 102. The underground heat storage system 103 stores heat when solar energy resources are abundant, and provides heat to the hot water storage tank 102 when solar energy resources are scarce.

The hot water storage tank 102 and the heat exchange water supply tank 104 form a closed loop, which is used for the hot water storage tank 102 to provide heat to the heat exchange water supply tank 104, so that cold water from the outside enters the heat exchange water supply tank 104 to absorb heat and provide hot water for users. The hot water storage tank 102 and the circulating water tank 105 form a loop, which is used for the hot water storage tank 102 to provide heat to the circulating water tank 105. The hot water storage tank 102, the auxiliary heat source 106 and the circulating water tank 105 form a loop. When the water temperature of the circulating water tank 105 does not reach the design temperature, the constant temperature circulation pump 1003 is turned on, and the auxiliary heat source 106 supplements heat to the circulating water tank 105 to reach the design water temperature. When the circulating water tank 105 has reached the design temperature, the constant temperature circulation pump 1003 is turned off, and the hot water storage tank 102 directly supplies heat to the circulating water tank 105.

The circulating water tank 105 and the generator 203 form a closed loop, and the hot water in the circulating water tank 105 serves as a high-temperature heat source to provide heat for the generator 203. When the system is running, the hot water in the circulating water tank 105 that reaches the design temperature serves as the high-temperature heat source of the generator 203, and exchanges heat with the dilute lithium bromide solution in the generator 203. The dilute lithium bromide solution from the absorber 201 in the generator 203 absorbs the heat of the high-temperature heat source and evaporates into high-temperature water vapor; the high-temperature water vapor in the generator 203 enters the condenser 204 and exchanges heat with the heated cold water to condense into condensed water; the condensed water in the condenser 204 is reduced in pressure by the throttle valve 206 and enters the evaporator 202, and exchanges heat with the produced water from the oil field in the evaporator 202, and evaporates using the waste heat of the produced water in the oil field. The water vapor in the evaporator 202 enters the absorber 201 and is absorbed by the lithium bromide concentrated solution to become a lithium bromide dilute solution. The lithium bromide dilute solution in the absorber 201 exchanges heat with the lithium bromide concentrated solution from the generator 203 through the solution heat exchanger 205. The lithium bromide dilute solution in the absorber 201 enters the generator 203 and circulates again as described above. When the lithium bromide concentrated solution passage of the solution heat exchanger 205 is blocked due to crystallization, the liquid level of the generator 203 rises, and the lithium bromide concentrated solution directly enters the absorber 201 through the overflow pipe 207. The cold water required to be heated from the outside enters the absorber 201 to absorb the absorption heat in the absorber 201. The cold water that has been heated once comes out of the absorber 201 and enters the condenser 204 to exchange heat with the high-temperature water vapor in the condenser 204. The cold water is heated twice to reach the design temperature for users.

Claims (1)

1. The method for the oil field waste heat recovery system by using the solar energy and the lithium bromide heat pump is characterized by comprising the following steps of:

The oilfield waste heat recovery system applying the solar energy and the lithium bromide heat pump consists of a solar heat collector array (101), a heat storage water tank (102), an underground heat storage system (103), a heat exchange water supplementing tank (104), a circulating water tank (105), an auxiliary heat source (106), a generator (203), a condenser (204), an evaporator (202), an absorber (201), a solution heat exchanger (205), a throttle valve (206), an overflow pipe (207) and the like;

The solar heat collector array (101) has one inlet and one outlet, the heat storage tank (102) has four inlets and four outlets, the underground heat storage system (103) has one inlet and one outlet, the heat exchange water supplementing tank (104) has two inlets and two outlets, the circulating water tank (105) has three inlets and two outlets, the auxiliary heat source (106) has one inlet and one outlet, the generator (203) has two inlets and four outlets, the condenser (204) has two inlets and two outlets, the evaporator (202) has two inlets and two outlets, the absorber (201) has four inlets and two outlets, and the solution heat exchanger (205) has two inlets and two outlets;

An inlet of the solar heat collector array (101) is connected with a first outlet of the heat storage water tank (102), an outlet of the solar heat collector array (101) is connected with a first inlet of the heat storage water tank (102), a second inlet of the heat storage water tank (102) is connected with an outlet of the underground heat storage system (103), a second outlet of the heat storage water tank (102) is connected with an inlet of the underground heat storage system (103), a third inlet of the heat storage water tank (102) is connected with a first outlet of the circulating water tank (105), a third outlet of the heat storage water tank (102) is connected with a first inlet of the circulating water tank (105), a fourth inlet of the heat storage water tank (102) is connected with a first outlet of the heat exchange water supplementing tank (104), an inlet of the auxiliary heat source (106) is connected with a third outlet of the heat storage water tank (102), a second inlet of the circulating water tank (105) is connected with a first outlet of the generator (203), a second outlet of the circulating water tank (105) is connected with a first inlet of the generator (203) of the second generator (203) and a second outlet of the generator (203) is connected with a second inlet of the generator (203), the third outlet of the generator (203) is connected with the third inlet of the absorber (201), the fourth outlet of the generator (203) is connected with the first inlet of the solution heat exchanger (205), the first outlet of the condenser (204) is connected with the first inlet of the evaporator (202), the second inlet of the condenser (204) is connected with the first outlet of the absorber (201), the first outlet of the evaporator (202) is connected with the fourth inlet of the absorber (201), the second inlet of the absorber (201) is connected with the second outlet of the solution heat exchanger (205), the second outlet of the absorber (201) is connected with the second inlet of the solution heat exchanger (205), and the pipeline connecting the third outlet of the generator (203) with the third inlet of the absorber (201) is an overflow pipe (207);

A temperature difference circulating pump (1001) is arranged on a pipeline connected with the outlet of the solar heat collector array (101) and the first inlet of the heat storage water tank (102); a temperature circulating pump (1002) is arranged on a pipeline of the second outlet of the heat storage water tank (102) connected with the inlet of the underground heat storage system (103); a constant temperature circulating pump (1003) is arranged on a pipeline of the outlet of the auxiliary heat source (106) connected with the third inlet of the circulating water tank (105);

the method for the oilfield waste heat recovery system applying the solar energy and the lithium bromide heat pump comprises the following steps of:

Water circulation: the solar heat collector array (101) and the heat storage water tank (102) form a circulation closed circuit, the solar heat collector array (101) absorbs solar energy and converts the solar energy into heat energy, the heat energy flows out of an outlet of the solar heat collector array (101) through medium hot water and flows into the heat storage water tank (102) from a first inlet of the heat storage water tank (102), the underground heat storage system (103) and the heat storage water tank (102) form a circulation closed circuit, the underground heat storage system (103) stores heat when solar energy resources are abundant, and the underground heat storage system provides heat for the heat storage water tank (102) when the solar energy resources are deficient;

the heat exchange water supplementing tank (104) and the heat storage water tank (102) form a circulation closed circuit, and the circulation closed circuit is used for heat exchange between the heat storage water tank (102) and the heat exchange water supplementing tank (104), hot water flows out of a fourth outlet of the heat storage water tank (102), flows into the heat exchange water supplementing tank (104) from a first inlet of the heat exchange water supplementing tank (104), meets the heat absorption requirement of cold water entering the heat exchange water supplementing tank (104), and provides hot water for a user;

Cold water enters the heat exchange water supplementing tank (104) from a second inlet of the heat exchange water supplementing tank (104), and hot water flows out of a second outlet of the heat exchange water supplementing tank (104) for a user to use;

The heat storage water tank (102) and the circulating water tank (105) form a loop, and the loop is used for exchanging heat between the heat storage water tank (102) and the circulating water tank (105), hot water flows out of a third outlet of the heat storage water tank (102) and flows into the circulating water tank (105) from a first inlet of the circulating water tank (105);

The heat storage water tank (102), the auxiliary heat source (106) and the circulating water tank (105) form a loop, when the water temperature of the circulating water tank (105) does not reach the design temperature, the constant temperature circulating pump (1003) is started, the auxiliary heat source (106) supplements heat for the circulating water tank (105) to reach the design water temperature, when the circulating water tank (105) reaches the design temperature, the constant temperature circulating pump (1003) is closed, and the heat storage water tank (102) directly supplies heat for the circulating water tank (105);

The circulating water tank (105) and the generator (203) form a loop, and hot water of the circulating water tank (105) is used as a high-temperature heat source of the generator (203) to exchange heat with the lithium bromide dilute solution in the generator (203);

The low-temperature waste heat produced water enters the evaporator (202) from a second inlet of the evaporator (202), exchanges heat with water vapor in the evaporator (202), and flows out from a second outlet of the evaporator (202);

Cold water required to be heated enters the absorber (201) from a first inlet of the absorber (201) to absorb heat absorbed in the absorber (201) and flows out from a first outlet of the absorber (201), cold water required to be heated at one time flows out from a first outlet of the absorber (201) and then enters the condenser (204) from a second inlet of the condenser (204) to exchange heat with high-temperature water vapor in the condenser (204), and after the heat absorbed is condensed, the cold water flows out from a second outlet of the condenser (204) to finish secondary heating for users;

Circulating lithium bromide solution; the lithium bromide dilute solution in the generator (203) absorbs heat of a high-temperature heat source and is heated and boiled, wherein water with low boiling point is gasified into high-pressure water vapor, and the high-pressure water vapor is separated from the absorbent lithium bromide concentrated solution and enters the condenser (204) through a pipeline connected with a second outlet of the generator (203) and a first inlet of the condenser (204);

The high-pressure steam generated in the generator (203) releases heat to the cooling medium cold water in the condenser (204) and condenses into condensed water, then flows out of the first outlet of the condenser (204), is decompressed and cooled through the throttle valve (206), enters the evaporator (202) from the first inlet of the evaporator (202), exchanges heat with the low-temperature waste heat produced water and evaporates into steam;

the water vapor in the evaporator (202) flows out of a first outlet of the evaporator (202), enters the absorber (201) from a fourth inlet of the absorber (201), continuously absorbs low-pressure water vapor generated by the evaporator (202) by using an absorbent lithium bromide concentrated solution in the absorber (201) to maintain the low pressure in the evaporator (202), absorbs the lithium bromide dilute solution formed by the water vapor by the absorbent lithium bromide concentrated solution, flows out of a second outlet of the absorber (201), is boosted by a solution pump (1004), enters the solution heat exchanger (205) from a second inlet of the solution heat exchanger (205), exchanges heat with the lithium bromide concentrated solution flowing out of the generator (203), flows out of the first outlet of the solution heat exchanger (205), and flows into the generator (203) from the fourth inlet of the generator (203);

In the generator (203), the lithium bromide dilute solution absorbs heat of a high-temperature heat source and boils, water with low boiling point is gasified into high-pressure water vapor which is separated from absorbent lithium bromide and enters a condenser (204), concentrated lithium bromide concentrated solution flows out of a fourth outlet of the generator (203) and then enters the solution heat exchanger (205) from a first inlet of the solution heat exchanger (205), exchanges heat with the lithium bromide dilute solution and then flows out of a second outlet of the solution heat exchanger (205), and then enters the absorber (201) from a second inlet of the absorber (201);

when the lithium bromide concentrated solution passage of the solution heat exchanger (205) is blocked due to crystallization, the liquid level of the generator (203) is increased, and the lithium bromide concentrated solution directly enters the absorber (201) through the overflow pipe (207);

The temperature difference circulating pump (1001) adjusts the operation temperature of the solar heat collector array (101) according to the temperature of the heat storage water tank (102), when the temperature difference between the solar heat collector array (101) and the heat storage water tank (102) is larger than the set temperature, the temperature difference circulating pump (1001) is started, the system operates, heat is transmitted from the solar heat collector array (101) to the heat storage water tank (102), and when the temperature difference is smaller than the set value, the temperature difference circulating pump (1001) stops operating;

The temperature circulating pump (1002) provides stable pressure and flow rate for circulating water in the system, so that the solar heat collection system is used for storing heat to the underground heat storage system (103), and the underground heat storage system (103) is used for releasing heat to the heat storage water tank (102) in overcast days and on days with poor sunlight intensity;

The constant temperature circulating pump (1003) completes the mutual switching of the solar heat collection system and the auxiliary heat source (106), when the temperature of circulating water in the circulating water tank (105) is reduced to a set low temperature starting temperature, the auxiliary heat source (106) can start to work to supply heat to the system, and when the temperature of the circulating water in the circulating water tank (105) is increased to a set stopping temperature, the auxiliary heat source (106) stops working, so that the normal heat supply of the system is ensured, and the solar energy is utilized to the maximum extent.