Transcritical CO2 circulating system capable of realizing 120 DEG C high-temperature heat tracing in petroleum process and control method thereof

Abstract

The invention relates to the technical field of industrial heat pumps, in particular to a transcritical CO2 circulation system capable of achieving 120 DEG C high-temperature heat tracing in a petroleum process and a control method of the transcritical CO2 circulation system. The circulating system comprises a water pump, a gas cooler, an air source evaporation part, a waste heat superheater and a compressor. The gas cooler, the air source evaporation component, the waste heat superheater and the compressor are sequentially connected, and the water pump is connected with the gas cooler. The water pump is used for providing to-be-heated water for the gas cooler; the gas cooler is used for heat exchange between the supercritical carbon dioxide working medium and water to be heated; the air source evaporation part is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler; the waste heat superheater is used for heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component; the compressor is used for compressing the carbon dioxide working medium output by the waste heat superheater to obtain the supercritical carbon dioxide working medium. According to the embodiment of the invention, the heat supply temperature and stability can be improved.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of industrial heat pump, and in particular to a transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum process and a control method thereof. BACKGROUND

[0002] Heat pump technology is a high-efficiency energy transfer technology based on the inverse Carnot cycle, which realizes the efficient transport of heat energy from a low-temperature heat source to a high-temperature heat source through the phase change cycle of a working medium. In related technologies, a traditional heat pump system usually relies on a single low-temperature heat source (such as geothermal energy, etc.). However, the low-temperature heat source has temperature fluctuation characteristics. Therefore, the heat supply stability of the heat pump system using a single low-temperature heat source is poor. Moreover, the heat supply temperature of the heat pump system using a single low-temperature heat source is also low, and it is usually difficult to break through the upper limit of 80 degrees Celsius, which cannot meet the process demand for high-temperature heat sources (such as more than 120 degrees Celsius) in the petroleum industry. SUMMARY

[0003] The embodiments of the present specification provide a transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum process and a control method thereof, so as to improve the heat supply temperature and the stability of heat supply.

[0004] The embodiments of the present specification provide a transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum process, which comprises a water pump, a gas cooler, an air source evaporation component, a waste heat superheater and a compressor; the gas cooler, the air source evaporation component, the waste heat superheater and the compressor are connected in sequence, and the water pump is connected with the gas cooler. The water pump is configured to provide the water to be heated to the gas cooler. The gas cooler is configured to exchange heat between the supercritical carbon dioxide working medium and the water to be heated. The air source evaporation component is configured to exchange heat between the external environment and the carbon dioxide working medium output by the gas cooler. The waste heat superheater is configured to exchange heat between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component. The compressor is configured to compress the carbon dioxide working medium output by the waste heat superheater to obtain a supercritical carbon dioxide working medium.

[0005] The embodiments of the present specification also provide a control method of a transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum process, which comprises: controlling the water pump to provide the water to be heated to the gas cooler; controlling the gas cooler to exchange heat between the supercritical carbon dioxide working medium and the water to be heated; The air source evaporation component exchanges heat between the external environment and the carbon dioxide working medium output by the gas cooler; The waste heat superheater exchanges heat between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component; The compressor compresses the carbon dioxide working medium output by the waste heat superheater to obtain supercritical carbon dioxide working medium.

[0006] The cross-critical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing of the petroleum process in the embodiment of the present specification includes a water circuit and a carbon dioxide working medium circuit. The water circuit includes a water pump and a gas cooler. The carbon dioxide working medium circuit includes the gas cooler, an air source evaporation component, a waste heat superheater, and a compressor. The working fluid of the gas cooler includes carbon dioxide working medium and pressurized water. The two working fluids exchange heat in the gas cooler. By exchanging heat of the supercritical carbon dioxide working medium to the pressurized water, the gas cooler can output high-temperature hot water. In the carbon dioxide working medium circuit, the air source evaporation component is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler, and the waste heat superheater is used for heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component. Through the synergistic effect of the air source evaporation component and the waste heat superheater, the exhaust temperature of the compressor can be increased, for example, the exhaust temperature of the compressor can reach 120 degrees Celsius, so that the temperature of the hot water output by the gas cooler can be increased. Moreover, through the synergistic effect of the air source evaporation component and the waste heat superheater, the fluctuation degree of the compressor exhaust temperature can also be reduced, thereby reducing the fluctuation degree of the hot water output by the waste heat superheater and improving the stability of the cycle system heat supply. Thus, the cross-critical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing of the petroleum process in the embodiment of the present specification can be applied to the process links requiring 80-degree Celsius to 100-degree Celsius or above high-temperature heat source such as crude oil preheating, atmospheric and vacuum distillation, etc., and accurately matches the demand of the petroleum process for high-temperature heat source. In addition, the waste heat superheater is used for heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component, so that the recovery of industrial waste heat resources can be realized, the waste of industrial waste heat resources can be avoided, and the environmental burden is reduced. In addition, the carbon dioxide working medium has physical properties such as low critical temperature and high critical pressure, and its GWP (Global Warming Potential, global warming potential) is 1 and ODP (Ozone Depletion Potential, ozone depletion potential) is 0, so it has good environmental protection properties and meets the green transformation demand of the petroleum industry. BRIEF DESCRIPTION OF DRAWINGS

[0007] In order to more clearly illustrate the technical solutions in the embodiments of the present specification or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. The drawings in the following description are only some embodiments described in the present specification, and other drawings can be obtained by those of ordinary skill in the art without creative labor on the basis of these drawings.

[0008] Figure 1 A functional structure schematic diagram of a transcritical carbon dioxide cycle system capable of realizing 120 degrees Celsius high temperature heat tracing of petroleum processes in the embodiments of the present specification; Figure 2 A flowchart schematic diagram of a transcritical carbon dioxide cycle system control method capable of realizing 120 degrees Celsius high temperature heat tracing of petroleum processes in the embodiments of the present specification; Figure 3 A structure schematic diagram of a transcritical carbon dioxide cycle system control device capable of realizing 120 degrees Celsius high temperature heat tracing of petroleum processes in the embodiments of the present specification. DETAILED DESCRIPTION

[0009] The technical solutions in the embodiments of the present specification will be described clearly and completely in the following with reference to the drawings in the embodiments of the present specification. Obviously, the described embodiments are only some of the embodiments of the present specification, but not all the embodiments. The specific embodiments described herein are only used to explain the present disclosure, but not to limit the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present disclosure belong to the scope of protection of the present disclosure. In addition, the relationship terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations.

[0010] In the high energy consumption industries such as petroleum and steel, the inefficient recovery of industrial waste heat resources has become a core problem restricting the green transformation. According to statistics, about 70% of the waste heat generated in the industrial field is directly discharged in the form of hot flue gas, wastewater, etc., and the overall recovery and utilization rate is less than 30%. Taking the petroleum industry as an example, its core processes such as atmospheric distillation need to continuously supply high-temperature heat sources of 80-100 degrees Celsius or above, but the existing technology still relies on traditional heating methods with high energy consumption and heavy pollution, such as electric heating or direct combustion of primary energy. Such methods not only have high operating costs, but also emit a large amount of pollutants. In addition, the waste heat resources generated by the petroleum process, such as 10-15 degrees Celsius waste heat wastewater generated in the desalination of low-temperature water and pipeline cleaning, are not included in the recovery system, resulting in waste of waste heat resources. In addition, heat pump technology is a high-efficiency energy transfer technology based on the inverse Carnot cycle, which realizes the efficient transfer of low-temperature heat sources to high-temperature heat sources through the phase change cycle of the working medium. The existing heat pump system is still limited to a single heat source architecture, with poor heating stability and lower heating temperature. For example, when the temperature of a single low-temperature heat source is below 40 degrees Celsius or fluctuates dramatically, the heat pump system is difficult to maintain stable heating, making it difficult to meet the stringent requirements of petroleum processes for precise temperature control. In addition, the heat pump system uses traditional working media such as R134a. The traditional working media make the heat pump have lower energy efficiency at low temperatures, higher GWP (Global Warming Potential), and larger carbon emissions.

[0011] See Figure 1 The embodiment of the present specification provides a transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum processes. The transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum processes can include a water pump 1, a gas cooler 2, an air source evaporation component 3, a waste heat superheater 4, and a compressor 5. The transcritical carbon dioxide cycle system capable of realizing 120-degree Celsius high-temperature heat tracing for petroleum processes can include a water circuit and a carbon dioxide working medium circuit. The water circuit can include the water pump 1 and the gas cooler 2. The carbon dioxide working medium circuit can include the gas cooler 2, the air source evaporation component 3, the waste heat superheater 4, and the compressor 5.

[0012] The water pump 1 is connected to the gas cooler 2 through a pipeline. The water pump 1 is used to provide water to be heated to the gas cooler 2. The water pump 1 can be, for example, a centrifugal pump, a plunger pump, a magnetic drive pump, etc. The water to be heated can come from a water source such as surface water or underground water, etc. The water pump 1 can extract the water to be heated from the water source; can pump high-pressure water into the gas cooler 2 to push the flow of water in the water circuit.

[0013] In the carbon dioxide working fluid circuit, the carbon dioxide working fluid flows through the gas cooler 2, the air source evaporation component 3 and the waste heat superheater 4 in turn by the compression of the compressor 5, and finally returns to the inlet of the compressor 5, and repeats the above cycle.

[0014] The gas cooler 2 can be a heat exchanger for heat exchange between the supercritical carbon dioxide working fluid and the water to be heated. The gas cooler 2 can be, for example, a micro-channel heat exchanger, a double-pipe heat exchanger, a plate heat exchanger, etc. The working fluid of the gas cooler 2 includes the carbon dioxide working fluid and the pressurized water. The two working fluids exchange heat in the gas cooler 2. The carbon dioxide is in a supercritical state when the temperature is greater than a certain critical temperature (such as 31.1 degrees Celsius) and the pressure is greater than a certain critical pressure (such as 7.38 MPa). The supercritical carbon dioxide has a high temperature, which can reach 140 degrees Celsius to 150 degrees Celsius. The gas cooler 2 can exchange heat from the supercritical carbon dioxide working fluid to the pressurized water to increase the temperature of the water. In addition, the pressurized water in the gas cooler 2 has a high pressure, so that the boiling point of the water also increases. Thus, the gas cooler 2 can output high-temperature hot water after heating.

[0015] After the carbon dioxide working fluid exchanges heat in the gas cooler 2, the temperature and / or pressure decreases, and the phase state changes from supercritical state to subcritical state, for example, to gas-liquid two-phase state. The gas cooler 2 is connected to the air source evaporation component 3 through a pipeline. The carbon dioxide working fluid output by the gas cooler 2 can enter the air source evaporation component 3. The air source evaporation component 3 can be used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler 2. The carbon dioxide working fluid evaporates in the air source evaporation component 3. By absorbing environmental heat through evaporation, the temperature and / or pressure increases, so that the phase state of the carbon dioxide working fluid changes to saturated state.

[0016] The air source evaporation component 3 is connected to the waste heat superheater 4 through a pipeline. The carbon dioxide working fluid output by the air source evaporation component 3 can enter the waste heat superheater 4. The waste heat superheater 4 can be a heat exchanger for heat exchange between the waste heat resource and the carbon dioxide working fluid output by the air source evaporation component 3. The waste heat superheater 4 can be, for example, a micro-channel heat exchanger, a double-pipe heat exchanger, a plate heat exchanger, etc. Thus, after the carbon dioxide working fluid absorbs heat from the external environment in the air source evaporation component 3, it can further absorb heat from the waste heat resource in the waste heat superheater 4, and the temperature and / or pressure can further increase, and the phase state changes to superheated state.

[0017] The compressor 5 can be connected with the waste heat superheater 4 and the gas cooler 2 through pipelines respectively. The carbon dioxide working medium output by the waste heat superheater 4 can enter the compressor 5. The compressor 5 can compress the carbon dioxide working medium, so that the carbon dioxide working medium output by the waste heat superheater 4 is compressed to a high-temperature and high-pressure state, and supercritical carbon dioxide working medium is obtained. The supercritical carbon dioxide working medium output by the compressor 5 can enter the gas cooler 2, so as to exchange heat with the pressurized water to realize heating of the water. In this way, the carbon dioxide working medium can form a loop in the gas cooler 2, the air source evaporation component 3, the waste heat superheater 4 and the compressor 5. Through the phase change of the carbon dioxide working medium, the water can be heated, for example, the water can be heated to 120 degrees Celsius or above.

[0018] The transcritical carbon dioxide circulation system provided by the embodiment of the present specification can realize 120-degree Celsius high-temperature heat tracing of petroleum processes, solves the problems of strong dependence on single heat source, large heat supply fluctuation and low resource recycling rate, and significantly improves the flexibility of waste heat recovery. It provides a waste heat recovery technology covering all scenarios and all processes for the petroleum industry, and helps the industry to achieve energy saving, emission reduction and sustainable development. Specifically as follows.

[0019] (1) The transcritical carbon dioxide circulation system provided by the embodiment of the present specification can realize 120-degree Celsius high-temperature heat tracing of petroleum processes. In the carbon dioxide working medium loop, the air source evaporation component 3 is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler 2, and the waste heat superheater 4 is used for heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component 3. In this way, by innovatively integrating the air source and the waste heat resource, the suction temperature and / or suction pressure of the compressor 5 can be improved, so that the exhaust temperature of the compressor 5 can reach 140 degrees Celsius to 150 degrees Celsius or above, thereby improving the temperature of the hot water output by the gas cooler 2. In addition, by innovatively integrating the air source and the waste heat resource, the defects of strong fluctuation and poor stability of single low-temperature heat source can be overcome, the fluctuation degree of the exhaust temperature of the compressor 5 can be reduced, thereby reducing the fluctuation degree of the hot water output by the gas cooler 2 and improving the stability of the heat supply of the circulation system. In addition, by innovatively integrating the air source and the waste heat resource, when one of the air source evaporation component 3 and the waste heat superheater 4 fails, the system can automatically switch to the other normal low-temperature heat source, thereby improving the stability of the system. Therefore, the circulation system of the present specification can realize 120-degree Celsius high-temperature heat tracing of petroleum processes, and can be applied to multiple scenarios such as crude oil preheating and heat tracing, thereby providing an efficient, stable and environmentally friendly high-temperature heat management solution for the petroleum industry.

[0020] The suction temperature of the compressor 5 can refer to the temperature of the carbon dioxide working medium entering the compressor 5, for example, can be equal to the temperature of the carbon dioxide working medium output by the waste heat superheater 4. The suction pressure of the compressor 5 can refer to the pressure of the carbon dioxide working medium entering the compressor 5, for example, can be equal to the pressure of the carbon dioxide working medium output by the waste heat superheater 4. The exhaust pressure of the compressor 5 can refer to the pressure of the supercritical carbon dioxide working medium output by the compressor 5. The exhaust temperature of the compressor 5 can refer to the temperature of the supercritical carbon dioxide working medium output by the compressor 5.

[0021] (2) The transcritical carbon dioxide cycle system provided by the embodiment of the present specification can realize the high-temperature heating of 120 degrees Celsius of the petroleum process, and the waste heat superheater 4 is used for heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component 3. Thus, the cycle system can realize the recycling of industrial waste heat resources, avoid the waste of industrial waste heat resources, reduce the environmental burden, and improve the comprehensive energy efficiency of the system.

[0022] (3) The transcritical carbon dioxide cycle system provided by the embodiment of the present specification can realize the high-temperature heating of 120 degrees Celsius of the petroleum process, and adopts carbon dioxide as the working medium. The carbon dioxide working medium has the physical properties of low critical temperature and high critical pressure, has a GWP (Global Warming Potential, global warming potential) of 1 and an ODP (Ozone Depletion Potential, ozone depletion potential) of 0, has good environmental protection properties, has no pollutant emission, and is suitable for extreme environments, thereby meeting the green transformation needs of the petroleum industry. In addition, the carbon dioxide working medium has a low critical temperature (30.98 degrees Celsius) and a high critical pressure (7.38 MPa), and can realize non-phase-change heat transfer through counterflow heat exchange in a supercritical state, can raise the temperature of the water to be heated to more than 120 degrees Celsius, and accurately matches the demand of the petroleum process for a high-temperature heat source.

[0023] In some embodiments, the waste heat resource can include at least one of waste heat water and waste heat flue gas. The waste heat resource includes industrial waste heat resources generated in the fields of petroleum, steel, and the like. For example, the waste heat resource includes waste heat wastewater (10 degrees Celsius-15 degrees Celsius) or low-temperature cooling water generated in the links of low-temperature water desalination, pipeline cleaning, and the like. For another example, the waste heat resource can also include wastewater (50 degrees Celsius-60 degrees Celsius) obtained after separating the oil-water mixture pumped out by the oil pump in the oil extraction process of the petroleum industry.

[0024] In some embodiments, the air-source evaporation component 3 comprises an air-source evaporator 31 and a fan 32. The air-source evaporator 31 is connected to the gas cooler 2 and the waste heat superheater 4 through pipes. The air-source evaporator 31 is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler 2. The fan 32 is used to drive the external environment air to flow through the air-source evaporator 31. By driving the external environment air to flow through the air-source evaporator 31, the carbon dioxide working medium air-source evaporator 31 can absorb more heat.

[0025] In some embodiments, the carbon dioxide working medium circuit can further comprise a throttle valve 6. The throttle valve 6 is connected to the gas cooler 2 and the air-source evaporation component 3 (for example, the air-source evaporator 31) through pipes, respectively. The throttle valve 6 can depressurize the carbon dioxide working medium output by the gas cooler 2, so that the pressure of the carbon dioxide working medium is reduced to a low pressure state required by the air-source evaporation component 3. Thus, the phase state of the carbon dioxide working medium changes to a gas-liquid phase state. After the pressure is reduced, the boiling point of the carbon dioxide working medium also decreases. The two-phase carbon dioxide working medium can absorb heat from the air environment in the air-source evaporation component 3 and evaporate into gas, thereby realizing the heat absorption process. Thus, the phase state of the carbon dioxide working medium changes to a saturated state. The throttle valve 6 can be provided with a narrow flow channel. The carbon dioxide working medium output by the gas cooler 2 can realize rapid depressurization when passing through the narrow flow channel.

[0026] In some embodiments, the water circuit of the circulation system can further comprise a first water supply valve 7. The first water supply valve 7 can be connected to the gas cooler 2 through pipes. The first water supply valve 7 can provide the first hot water output by the gas cooler 2 to the outside. The first water supply valve 7 can be provided with a first water supply port 701. The first water supply valve 7 can adjust the flow of the first water supply port 701.

[0027] In some embodiments, the water circuit of the circulation system can further comprise a flash component, a second water supply valve 8 and a steam supply valve 9. The gas cooler 2 is connected to the flash component through a pipeline, and the flash component is connected to the second water supply valve 8 and the steam supply valve 9 through pipelines respectively. The flash component is used to depressurize the first hot water output by the gas cooler 2 to flash out the second hot water and steam. The second water supply valve 8 can provide the second hot water flashed out by the flash component. The second water supply valve 8 can be provided with a second water supply port 801. The second water supply valve 8 can adjust the flow of the second water supply port 801. The steam supply valve 9 can provide the water vapor flashed out by the flash component. The steam supply valve 9 can be provided with a steam supply port 901. The steam supply valve 9 can adjust the flow of the steam supply port 901. The temperature of the second hot water and the water vapor is lower than that of the first hot water. The pressure of the second hot water and the water vapor is lower than that of the first hot water. For example, the first hot water is high-temperature hot water, which can be, for example, 120 degrees Celsius hot water. The second hot water is medium-temperature hot water, which can be, for example, 100-110 degrees Celsius hot water. The water vapor is medium-temperature steam, which can be, for example, 100-110 degrees Celsius steam. In this way, multi-stage thermal energy cascade utilization and flexible supply of the hot water output by the gas cooler 2 can be achieved. For example, the first hot water provides a stable high-temperature heat source for the atmospheric-vacuum distillation process in the petroleum industry. For another example, the water vapor is used for heat tracing and pipeline cleaning in the petroleum industry.

[0028] In some embodiments, the flash component can comprise a pressure reducing valve 10 and a flash tank 11. The pressure reducing valve 10 can be connected to the gas cooler 2 through a pipeline. The pressure reducing valve 10 can also be connected to the flash tank 11 through a pipeline. The flash tank 11 can be connected to the second water supply valve 8 and the steam supply valve 9 through pipelines respectively. The pressure reducing valve 10 can reduce the pressure of the first hot water output by the gas cooler 2 to flash the first hot water. The flash tank 11, also known as an expansion tank or a gas-liquid separator, is used to flash the first hot water to obtain the second hot water and steam. The flash tank 11 can also store the second hot water and steam flashed out. The second water supply valve 8 can provide the second hot water flashed out by the flash tank 11 to the outside. The steam supply valve 9 can provide the water vapor flashed out by the flash tank 11 to the outside.

[0029] In some embodiments, the gas cooler 2 may include a water inlet and a water outlet. The water inlet of the gas cooler 2 may be connected to the water pump 1 through a pipeline. The water outlet of the gas cooler 2 may be connected to the first water supply valve 7 and the pressure reducing valve 10 through a pipeline. The gas cooler 2 may also include a carbon dioxide inlet and a carbon dioxide outlet. The carbon dioxide inlet of the gas cooler 2 may be connected to the carbon dioxide outlet of the compressor 5 through a pipeline. The carbon dioxide outlet of the gas cooler 2 may be connected to the carbon dioxide inlet of the throttle valve 6 through a pipeline. The carbon dioxide outlet of the throttle valve 6 may be connected to the carbon dioxide inlet of the air source evaporator 31 through a pipeline. Thus, the working liquids on both sides of the gas cooler 2 are carbon dioxide and water, respectively. The two working liquids realize heat exchange in the gas cooler 2.

[0030] In some embodiments, the waste heat superheater 4 may include a waste heat resource inlet 401 and a waste heat resource outlet 402. The waste heat resource inlet 401 may be connected to a waste heat resource supply device via a pipeline. The waste heat resource supply device may provide waste heat resources to the waste heat superheater 4. The waste heat resource outlet 402 may be connected to a waste heat resource processing device via a pipeline. The waste heat resources after heat exchange may enter the waste heat resource processing device through the waste heat resource outlet 402. The waste heat resource processing device may process the waste heat resources after heat exchange. For example, the waste heat resource processing device may include sewage treatment equipment.

[0031] The waste heat superheater 4 may also include a carbon dioxide inlet and a carbon dioxide outlet. The carbon dioxide inlet of the waste heat superheater 4 may be connected to the carbon dioxide outlet of the air source evaporator 31 via a pipeline. The carbon dioxide outlet of the waste heat superheater 4 may also be connected to the carbon dioxide inlet of the compressor 5 via a pipeline. Thus, the working fluids on both sides of the waste heat superheater 4 are carbon dioxide and waste heat resources, respectively. These two working fluids exchange heat within the waste heat superheater 4.

[0032] In some embodiments, the circulatory system may further include a controller. The controller may include a microcontroller unit (MCU). Of course, the controller may also include other devices capable of controlling functions. For example, the controller may include a computer device such as a desktop computer or a laptop computer.

[0033] See also Figure 2 The embodiments of this specification also provide a control method for a transcritical carbon dioxide circulation system capable of achieving high-temperature heating of 120 degrees Celsius in petroleum processes. The control method may be executed by a controller and may specifically include the following steps.

[0034] Step 201: Control the water pump to provide water to be heated to the gas cooler.

[0035] Step 202: Control the gas cooler to exchange heat between the supercritical carbon dioxide working medium and the water to be heated.

[0036] Step 203: Control the air source evaporation component to exchange heat between the external environment and the carbon dioxide working medium output by the gas cooler.

[0037] Step 204: Control the waste heat superheater to exchange heat between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component.

[0038] Step 205: Control the compressor to compress the carbon dioxide working medium output by the waste heat superheater to obtain the supercritical carbon dioxide working medium.

[0039] In some embodiments, the controller can send instructions to the water pump, so that the water pump can pump the water to be heated into the gas cooler. The controller can also send instructions to the gas cooler, so that the gas cooler exchanges heat between the inflowing supercritical carbon dioxide working medium and the inflowing water to be heated. The temperature of the supercritical carbon dioxide working medium is relatively high, which can reach 140-150 degrees Celsius. Through the gas cooler, the heat of the supercritical carbon dioxide working medium can be exchanged to the pressurized water, thereby increasing the temperature of the water, for example, the temperature of the water can be increased to 120 degrees Celsius. The controller can also send instructions to the air source evaporation component, so that the air source evaporation component exchanges heat between the inflowing carbon dioxide working medium and the air environment. The carbon dioxide working medium evaporates in the air source evaporation component. Through evaporation, the heat of the air environment can be absorbed, and the temperature is increased. The controller can also send instructions to the waste heat superheater, so that the waste heat superheater exchanges heat between the inflowing carbon dioxide working medium and the inflowing waste heat resource. The carbon dioxide working medium further absorbs the heat of the waste heat resource in the waste heat superheater, and the temperature is further increased. The controller can also send control instructions to the compressor, so that the compressor can compress the inflowing carbon dioxide working medium to obtain the supercritical carbon dioxide working medium in a high-temperature and high-pressure state.

[0040] For example, the controller can send start-up instructions to the water pump, the gas cooler, the air source evaporation component, the waste heat superheater, and the compressor, respectively. The water pump can pump the water to be heated into the gas cooler after receiving the start-up instruction. The gas cooler can exchange heat between the inflowing supercritical carbon dioxide working medium and the inflowing water to be heated after receiving the start-up instruction. The air source evaporation component can exchange heat between the inflowing carbon dioxide working medium and the air environment after receiving the start-up instruction. The waste heat superheater can exchange heat between the inflowing carbon dioxide working medium and the inflowing waste heat resource after receiving the start-up instruction. The compressor can compress the inflowing carbon dioxide working medium to obtain the supercritical carbon dioxide working medium after receiving the start-up instruction.

[0041] In some embodiments, the temperature and flow of the waste heat resource tend to be not constant, but there are large fluctuations. Therefore, a first fluctuation degree of the temperature of the waste heat resource and a second fluctuation degree of the flow can be determined; it can be determined whether the first fluctuation degree is greater than or equal to a first fluctuation threshold; it can be determined whether the second fluctuation degree is greater than or equal to a second fluctuation threshold; when the first fluctuation degree reaches the first fluctuation threshold or the second fluctuation degree reaches the second fluctuation threshold, the waste heat superheater can be controlled to stop heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component. For example, the controller can send a stop instruction to the waste heat superheater, so that the waste heat superheater stops heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component. In this way, when the temperature and / or flow of the waste heat resource fluctuate greatly, the waste heat superheater can stop heat exchange. In this way, the fluctuation of the exhaust temperature and the exhaust pressure of the compressor can be avoided, thereby affecting the stability of the water temperature output by the gas cooler. In this way, the temperature of the carbon dioxide working medium flowing into the waste heat superheater can be approximately equal to the temperature of the carbon dioxide working medium flowing out of the waste heat superheater. Therefore, only the air source evaporation component can exchange heat with the incoming carbon dioxide working medium and the air environment to increase the temperature of the carbon dioxide working medium. The first fluctuation threshold and the second fluctuation threshold can be preset.

[0042] For example, a temperature sensor and a flow sensor can be arranged at the waste heat resource inlet of the waste heat superheater. The temperature of the waste heat resource can be detected by the temperature sensor. The flow of the waste heat resource can be detected by the flow sensor. A plurality of temperatures and a plurality of flows detected within a set time interval can be obtained. A first fluctuation index of the plurality of temperatures can be calculated. The first fluctuation index can include a range, a variance, a standard deviation, etc., for characterizing the first fluctuation degree of the temperature of the waste heat resource. A second fluctuation index of the plurality of flows can be calculated. The second fluctuation index can include a range, a variance, a standard deviation, etc., for characterizing the second fluctuation degree of the flow of the waste heat resource.

[0043] In some embodiments, a first temperature of the waste heat resource can be obtained. It can be determined whether the first temperature is less than or equal to a first temperature threshold; when the first temperature is less than or equal to the first temperature threshold, it indicates that the temperature of the waste heat resource is too low, and the speed of the fan in the air source evaporation component can be increased. By increasing the number of revolutions of the fan, the amount of gas flowing to the air source evaporator can be increased, so that the carbon dioxide working medium can absorb heat from more air, thereby further increasing the temperature of the carbon dioxide working medium. In this way, stable operation under complex environment can be achieved through multi-source collaborative control, and the heat exchange of the air source and the waste heat resource can be intelligently balanced, thereby ensuring that the gas cooler can still stably output 120-degree high-temperature water under extreme environmental conditions.

[0044] The first temperature threshold value can be preset. For example, a first functional relationship between a temperature difference and an increase in the number of revolutions of the fan can be preset. A temperature difference between the first temperature and the first temperature threshold value can be calculated; the temperature difference can be substituted into the first functional relationship to calculate the increase in the number of revolutions; and the number of revolutions of the fan can be increased by the increase, thereby increasing the number of revolutions of the fan.

[0045] In some embodiments, a second temperature of an external environment can be obtained. For example, the temperature of an external air environment can be detected by a temperature sensor as the second temperature. It can be determined whether the second temperature is less than or equal to a second temperature threshold value; when the second temperature is less than or equal to the second temperature threshold value, it indicates that the temperature of the external air is too low, and the heat exchange capacity of the waste heat superheater can be increased. By increasing the heat exchange capacity of the waste heat superheater, the temperature of the carbon dioxide working medium can be increased. In this way, stable operation under complex environments can be achieved through multi-source collaborative control, and the heat exchange of air sources and waste heat resources can be intelligently balanced, thereby ensuring that the gas cooler can still stably output 120-degree high-temperature water under extreme environmental conditions.

[0046] For example, the heat exchange capacity of the waste heat superheater can be increased by increasing the flow rate of the waste heat resource and reducing the flow rate of the carbon dioxide working medium. This allows the carbon dioxide working medium to absorb heat from more waste heat resources to further increase the temperature.

[0047] The second temperature threshold value can be preset. For example, a second functional relationship between a temperature difference and a flow ratio can be preset. A temperature difference between the second temperature and the second temperature threshold value can be calculated; the temperature difference can be substituted into the second functional relationship to calculate the corresponding flow ratio. The flow ratio is the ratio of the flow rate of the waste heat resource to the flow rate of the carbon dioxide working medium. The flow rate of the carbon dioxide working medium and the flow rate of the waste heat resource in the waste heat superheater can be determined according to the flow ratio to control the heat exchange capacity of the waste heat superheater.

[0048] In some embodiments, the exhaust temperature of the compressor can be obtained; the exhaust pressure of the compressor can be increased when the exhaust temperature is less than a third temperature threshold value; and the exhaust pressure of the compressor can be controlled to remain unchanged when the exhaust pressure of the compressor reaches a pressure threshold value, and the rotational speed of the fan in the air source evaporation component can be reduced to reduce the suction pressure of the compressor.

[0049] A first temperature of the waste heat resource and a second temperature of the external environment can be obtained. When the first temperature is greater than a certain temperature threshold and the second temperature is less than another temperature threshold, it indicates that the current environment is high temperature and the waste heat is insufficient, and the discharge temperature of the compressor can be low. Therefore, the discharge temperature of the compressor can be obtained. The discharge temperature can be compared with a third temperature threshold to determine whether the discharge temperature is less than the third temperature threshold. A temperature sensor can be arranged at the carbon dioxide outlet of the compressor. The discharge temperature of the compressor can be obtained by the temperature sensor. The discharge temperature of the compressor can refer to the temperature of the supercritical carbon dioxide working medium output by the compressor.

[0050] When the discharge temperature is less than the third temperature threshold, the discharge pressure of the compressor can be increased. The discharge temperature of the compressor is related to the compression ratio of the compressor. The compression ratio can be, for example, the ratio of the discharge pressure of the compressor to the suction pressure of the compressor. By increasing the discharge pressure of the compressor, the compression ratio of the compressor is increased, so that the discharge temperature of the compressor is increased.

[0051] However, the discharge pressure of the compressor has an upper limit. When the discharge pressure of the compressor reaches a pressure threshold, in order to ensure safety, the discharge pressure of the compressor cannot continue to increase. Therefore, the discharge pressure of the compressor can be controlled to remain unchanged, and the rotation speed of the fan in the air source evaporation component can be reduced. By reducing the number of rotations of the fan, the evaporation temperature of the carbon dioxide working medium in the air source evaporator is reduced, and the evaporation pressure is also reduced, so that the pressure of the carbon dioxide working medium output by the air source evaporator is reduced. Correspondingly, the suction pressure of the compressor is also reduced. Since the discharge temperature of the compressor is related to the compression ratio of the compressor, by reducing the suction pressure under the condition that the discharge pressure remains unchanged, the compression ratio is also increased accordingly, so that the discharge temperature of the compressor is forced to increase. In this way, when the discharge pressure of the compressor reaches the pressure threshold, by reducing the rotation speed of the fan in the air source evaporation component, the suction pressure of the compressor is reduced, and the discharge temperature of the compressor is forced to increase.

[0052] To this end, a correlation between a discharge temperature of the compressor and a compression ratio of the compressor can be obtained; the compression ratio of the compressor can be calculated according to the correlation and the discharge temperature of the compressor (e.g., 140 degrees Celsius to 150 degrees Celsius). A current suction pressure of the compressor can be obtained; a target discharge pressure of the compressor can be calculated according to the current suction pressure and the calculated compression ratio. When the target discharge pressure is less than a pressure threshold, the current discharge pressure of the compressor can be increased to the target discharge pressure. In this way, the compression ratio of the compressor can be increased by increasing the discharge pressure of the compressor, so that the discharge temperature of the compressor is increased. When the target discharge pressure is greater than the pressure threshold, the current discharge pressure of the compressor can be increased to the pressure threshold. A target suction pressure of the compressor can be calculated according to the pressure threshold and the compression ratio. The suction temperature of the compressor can be calculated according to the target suction pressure and the pressure threshold by using a formula Pd=k1xTs+k2xPs+C; the number of revolutions of the fan can be calculated according to the suction temperature of the compressor. Wherein, Pd represents the discharge pressure of the compressor, Ts represents the suction temperature of the compressor, Ps represents the suction pressure of the compressor, k1, k2, C are coefficients. For example, a third functional relationship between the suction temperature and the number of revolutions of the fan can be obtained in advance. The suction temperature can be substituted into the third functional relationship to calculate the number of revolutions of the fan. The controller can control the fan to reach the number of revolutions. In this way, when the discharge pressure of the compressor reaches the pressure threshold, the suction pressure of the compressor is reduced by reducing the number of revolutions of the fan in the air source evaporation component, and then the discharge temperature of the compressor is forced to increase.

[0053] Therefore, the embodiment can dynamically realize the cooperative control of pressure and temperature.

[0054] The control method of the embodiment of the present specification can control the water pump to provide the water to be heated to the gas cooler; can control the gas cooler to exchange heat between the supercritical carbon dioxide working medium and the water to be heated; can control the air source evaporation component to exchange heat between the external environment and the carbon dioxide working medium output by the gas cooler; can control the waste heat superheater to exchange heat between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component; can control the compressor to compress the carbon dioxide working medium output by the waste heat superheater to obtain the supercritical carbon dioxide working medium. In this way, the control of the transcritical carbon dioxide cycle system which can realize the 120 degrees Celsius high temperature heat tracing of the petroleum process can be realized.

[0055] The control method of the embodiment of the present specification improves the temperature of the carbon dioxide working medium by recovering waste heat resources through the waste heat superheater, and realizes that the exhaust temperature of the compressor is stably 140-150 DEG C by combining the coordinated control of dynamic pressure and temperature. The heat source mode can also be intelligently switched according to the waste heat conditions, and through the intelligent switching mechanism and the multi-energy complementary strategy, the limitation of single heat source is broken through, and the waste heat recovery technology covering all scenes and all processes is provided for the petroleum industry, helping the industry to realize energy saving and emission reduction and sustainable development.

[0056] Please refer to Figure 3 The embodiment of the present specification also provides a control device applied to a transcritical carbon dioxide cycle system capable of realizing 120 DEG C high-temperature heat tracing of petroleum processes. The control device can include the following units.

[0057] The first control unit 301 is configured to control the water pump to provide the water to be heated to the gas cooler; The second control unit 302 is configured to control the gas cooler to exchange heat between the supercritical carbon dioxide working medium and the water to be heated; The third control unit 303 is configured to control the air source evaporation component to exchange heat between the external environment and the carbon dioxide working medium output by the gas cooler; The fourth control unit 304 is configured to control the waste heat superheater to exchange heat between the waste heat resources and the carbon dioxide working medium output by the air source evaporation component; The fifth control unit 305 is configured to control the compressor to compress the carbon dioxide working medium output by the waste heat superheater to obtain the supercritical carbon dioxide working medium.

[0058] The embodiment of the present specification also provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the above control method when executing the computer program.

[0059] The embodiment of the present specification also provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to implement the above control method.

[0060] The embodiment of the present specification also provides a computer program product, which includes a computer program, and the computer program is executed by a processor to implement the above control method.

[0061] Those skilled in the art will appreciate that the specification can provide for a method, a system or a computer program product. Accordingly, the specification can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware. Furthermore, the specification can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer-readable program code.

[0062] The specification is described with reference to flow diagrams and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the specification. It will be understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams and / or block diagrams, can be implemented by computer program instructions. The computer can be a personal computer, a laptop computer, a cellular telephone, a camera telephone, a smart phone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or a combination of any of these devices.

[0063] The various functional units in the embodiments of the specification can be integrated in one processing unit, or exist separately, or two or more functional units can be integrated in one processing unit.

[0064] Those skilled in the art will appreciate that the specification describes each of the embodiments with a certain degree of particularity. As those skilled in the art will readily appreciate, parts, elements and / or materials not described in detail can be present in each embodiment. Additionally, it will be appreciated that the specification is not limited in scope to the embodiments described in the specification, but rather the specification provides support for various combinations and permutations of the parts, elements and / or materials described in the specification.

[0065] Although the specification is illustrated through the embodiments, those skilled in the art know that the above embodiments are only used to help understand the core idea of the specification. Those skilled in the art will appreciate that the specification has many variations and changes. It is intended that the appended claims encompass these variations and changes without departing from the spirit of the specification.

Claims

1. A transcritical carbon dioxide circulation system capable of achieving high-temperature heating of 120 degrees Celsius in petroleum processes, characterized in that: The transcritical carbon dioxide circulation system includes a water pump, a gas cooler, an air source evaporation component, a waste heat superheater and a compressor; the gas cooler, the air source evaporation component, the waste heat superheater and the compressor are connected in sequence, and the water pump is connected to the gas cooler; The water pump is used to provide water to be heated to the gas cooler; The gas cooler is used for heat exchange between the supercritical carbon dioxide working medium and the water to be heated; The air source evaporation component is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler; The waste heat superheater is used for heat exchange between waste heat resources and the carbon dioxide working medium output by the air source evaporation component; The compressor is used to compress the carbon dioxide working medium output by the waste heat superheater to obtain supercritical carbon dioxide working medium.

2. The system according to claim 1, wherein: The air source evaporation component includes an air source evaporator and a fan; the air source evaporator is used for heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler; the fan is used to drive the external environment air to flow through the air source evaporator.

3. The system according to claim 1, wherein: The system further includes a first water supply valve; the gas cooler is connected to the first water supply valve; the first water supply valve is used to provide first hot water output by the gas cooler.

4. The system according to claim 1, wherein: The system also includes a flash evaporation component, a second water supply valve and a steam supply valve; the gas cooler is connected to the flash evaporation component, and the flash evaporation component is connected to the second water supply valve and the steam supply valve; the flash evaporation component is used to reduce the pressure of the first hot water output by the gas cooler to flash out second hot water and steam; the second water supply valve is used to provide the second hot water; and the steam supply valve is used to provide the steam.

5. The system according to claim 1, wherein: The waste heat resource includes at least one of waste hot water and waste hot flue gas.

6. A control method, applied to a transcritical carbon dioxide circulation system capable of achieving high-temperature heating of 120 degrees Celsius in a petroleum process according to any one of claims 1 to 5, characterized in that: The method comprises: Control the water pump to provide heated water to the gas cooler; controlling the gas cooler to perform heat exchange between the supercritical carbon dioxide working medium and the water to be heated; Controlling the air source evaporation component to perform heat exchange between the external environment and the carbon dioxide working medium output by the gas cooler; controlling the waste heat superheater to perform heat exchange between the waste heat resource and the carbon dioxide working fluid output by the air source evaporation component; The compressor is controlled to compress the carbon dioxide working medium outputted from the waste heat superheater to obtain supercritical carbon dioxide working medium.

7. The method according to claim 6, characterized in that The method further comprises: determining a first degree of fluctuation in the temperature of the waste heat resource and a second degree of fluctuation in the flow rate; When the first fluctuation degree reaches a first fluctuation threshold or the second fluctuation degree reaches a second fluctuation threshold, the waste heat superheater is controlled to stop heat exchange between the waste heat resource and the carbon dioxide working medium output by the air source evaporation component.

8. The method according to claim 6, characterized in that The method further comprises: Obtaining the first temperature of the waste heat resource; When the first temperature is lower than a first temperature threshold, the rotation speed of the fan in the air source evaporation component is increased.

9. The method according to claim 6, characterized in that The method further comprises: Obtaining a second temperature of the external environment; When the second temperature is lower than a second temperature threshold, the heat exchange capacity of the waste heat superheater is increased.

10. The method according to claim 6, characterized in that The method further comprises: Get the exhaust temperature of the compressor; When the exhaust temperature is lower than a third temperature threshold, increasing the exhaust pressure of the compressor; When the exhaust pressure of the compressor reaches a pressure threshold, the exhaust pressure of the compressor is controlled to remain unchanged, and the speed of the fan in the air source evaporation component is reduced to reduce the suction pressure of the compressor.

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