A transcritical CO2 circulation system capable of achieving 120℃ high-temperature heat tracing in petroleum processes and its control method.

Abstract

The present specification relates to the technical field of industrial heat pump, and particularly relates to a transcritical CO2 cycle system capable of realizing 120 DEG C high-temperature heat tracing of petroleum process and a control method thereof. The cycle system 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 sequentially connected, and the water pump is connected with the gas cooler; the water pump is used for providing water to be heated to the gas cooler; the gas cooler is used for heat exchange between supercritical carbon dioxide working medium and the water to be heated; the air source evaporation component is used for heat exchange between an external environment and carbon dioxide working medium output by the gas cooler; the waste heat superheater is used for heat exchange between waste heat resources and carbon dioxide working medium output by the air source evaporation component; and the compressor is used for compressing carbon dioxide working medium output by the waste heat superheater to obtain supercritical carbon dioxide working medium. The embodiment of the present specification can improve the temperature and stability of heat supply.

Description

Technical Field

[0001] This specification relates to the field of industrial heat pump technology, and in particular to a transcritical carbon dioxide cycle system and its control method that can achieve high-temperature heat tracing of 120 degrees Celsius in petroleum processes. Background Technology

[0002] Heat pump technology is a highly efficient energy transfer technology based on the reverse Carnot cycle. It achieves efficient transfer of heat energy from a low-temperature heat source to a high-temperature heat source through the phase change cycle of the working fluid. In related technologies, traditional heat pump systems typically rely on a single low-temperature heat source (such as geothermal energy). However, low-temperature heat sources exhibit temperature fluctuations, resulting in poor heating stability for heat pump systems using a single low-temperature heat source. Furthermore, heat pump systems using a single low-temperature heat source also have relatively low heating temperatures, typically struggling to exceed the 80-degree Celsius upper limit, thus failing to meet the process requirements of industries such as the petroleum industry, which require high-temperature heat sources (e.g., above 120 degrees Celsius). Summary of the Invention

[0003] This specification provides an embodiment of a transcritical carbon dioxide circulation system and its control method for achieving 120°C high-temperature heat tracing in petroleum processes, thereby improving the heating temperature and the stability of the heating supply.

[0004] This specification provides an embodiment of a transcritical carbon dioxide circulation system capable of achieving 120°C high-temperature heat tracing in petroleum processes. The transcritical carbon dioxide circulation system includes a water pump, a gas cooler, an air source evaporator, a waste heat superheater, and a compressor. The gas cooler, the air source evaporator, the waste heat superheater, and the compressor are connected in sequence, and the water pump is connected to the gas cooler.

[0005] The water pump is used to supply water to be heated to the gas cooler;

[0006] The gas cooler is used for heat exchange between the supercritical carbon dioxide working fluid and the water to be heated.

[0007] The air source evaporation component is used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler.

[0008] The waste heat superheater is used for heat exchange between waste heat resources and the carbon dioxide working fluid output by the air source evaporation component.

[0009] The compressor is used to compress the carbon dioxide working fluid output by the waste heat superheater to obtain supercritical carbon dioxide working fluid.

[0010] This specification also provides a control method for a transcritical carbon dioxide cycle system capable of achieving 120°C high-temperature heating in petroleum processes, the method comprising:

[0011] Control the water pump to supply heated water to the gas cooler;

[0012] The gas cooler is controlled to exchange heat between the supercritical carbon dioxide working fluid and the water to be heated;

[0013] The air source evaporation component is controlled to exchange heat with the external environment and the carbon dioxide working fluid output by the gas cooler;

[0014] The waste heat superheater is controlled to exchange heat between the waste heat resources and the carbon dioxide working fluid output by the air source evaporation component;

[0015] The compressor is controlled to compress the carbon dioxide working fluid output from the waste heat superheater to obtain supercritical carbon dioxide working fluid.

[0016] The transcritical carbon dioxide circulation system for achieving 120°C high-temperature heat tracing in petroleum processes, as described in this specification, includes a water circuit and a carbon dioxide working fluid circuit. The water circuit includes a water pump and a gas cooler. The carbon dioxide working fluid circuit includes a gas cooler, an air-source evaporator, a waste heat superheater, and a compressor. The working fluid of the gas cooler includes carbon dioxide and pressurized water. Heat exchange occurs between the two working fluids in the gas cooler. By exchanging heat from the supercritical carbon dioxide working fluid to the pressurized water, the gas cooler can output high-temperature hot water. In the carbon dioxide working fluid circuit, the air-source evaporator is used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler, while the waste heat superheater is used for heat exchange between waste heat resources and the carbon dioxide working fluid output by the air-source evaporator. Through the synergistic effect of the air-source evaporator and the waste heat superheater, the compressor's exhaust temperature can be increased, for example, to 120°C, thereby increasing the temperature of the hot water output by the gas cooler. Furthermore, through the synergistic effect of the air-source evaporator and the waste heat superheater, the fluctuation of compressor exhaust temperature can be reduced, thereby reducing the fluctuation of hot water output from the waste heat superheater and improving the stability of the circulating system's heating supply. Therefore, the transcritical carbon dioxide circulating system of this specification, capable of achieving 120°C high-temperature heat tracing in petroleum processes, is applicable to processes requiring high-temperature heat sources of 80°C to 100°C or higher, such as crude oil preheating and atmospheric and vacuum distillation, precisely matching the high-temperature heat source requirements of petroleum processes. In addition, the waste heat superheater is used for heat exchange between waste heat resources and the carbon dioxide working fluid output from the air-source evaporator, thereby enabling the recovery of industrial waste heat resources, avoiding waste, and reducing environmental burden. Furthermore, the carbon dioxide working fluid has physical characteristics such as low critical temperature and high critical pressure, with a GWP (Global Warming Potential) of 1 and an ODP (Ozone Depletion Potential) of 0, thus possessing excellent environmental attributes and meeting the green transformation needs of the petroleum industry. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. The drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the functional structure of a transcritical carbon dioxide circulation system that can achieve 120-degree Celsius high-temperature heating in petroleum processes, as described in the embodiments of this specification.

[0019] Figure 2 This is a schematic flowchart of a control method for a transcritical carbon dioxide circulation system that can achieve 120°C high-temperature heat tracing in petroleum processes, as described in the embodiments of this specification.

[0020] Figure 3 This is a schematic diagram of the control device for a transcritical carbon dioxide circulation system that can achieve 120-degree Celsius high-temperature heat tracing in petroleum processes, as described in the embodiments of this specification. Detailed Implementation

[0021] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. The specific embodiments described herein are only used to explain this disclosure, and not to limit this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure are within the scope of protection of this disclosure. In addition, relational 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 these entities or operations.

[0022] In energy-intensive industries such as petroleum and steel, the inefficient recovery of industrial waste heat has become a core challenge hindering green transformation. Statistics show that approximately 70% of waste heat generated in the industrial sector is directly emitted as hot flue gas and wastewater, with an overall recovery rate of less than 30%. Taking the petroleum industry as an example, its core processes, such as atmospheric and vacuum distillation, require a continuous supply of high-temperature heat sources of 80°C to 100°C or higher. However, current technologies still rely on traditional heating methods that are energy-intensive and polluting, such as electric heating or direct combustion of primary energy sources. These methods are not only costly to operate but also result in significant pollutant emissions. Furthermore, waste heat resources generated in petroleum processes, such as wastewater at 10°C to 15°C from low-temperature water desalination and pipeline cleaning, are not included in the recovery system, leading to waste. Additionally, heat pump technology, a highly efficient energy transfer technology based on the reverse Carnot cycle, achieves efficient transport of heat energy from low-temperature heat sources to high-temperature heat sources through the phase change cycle of the working fluid. Existing heat pump systems are still limited by a single heat source architecture, resulting in poor heating stability and low heating temperatures. For example, when the temperature of the single low-temperature heat source is below 40 degrees Celsius or fluctuates drastically, the heat pump system struggles to maintain stable heating, failing to meet the stringent temperature control requirements of petroleum processes. Furthermore, heat pump systems use traditional refrigerants such as R134a. These traditional refrigerants lead to relatively low energy efficiency at low temperatures and a high GWP (Global Warming Potential), resulting in significant carbon emissions.

[0023] Please see Figure 1 This specification provides an embodiment of a transcritical carbon dioxide circulation system capable of achieving 120°C high-temperature heat tracing in petroleum processes. The transcritical carbon dioxide circulation system capable of achieving 120°C high-temperature heat tracing in petroleum processes may include a water pump 1, a gas cooler 2, an air source evaporator 3, a waste heat superheater 4, and a compressor 5. The transcritical carbon dioxide circulation system capable of achieving 120°C high-temperature heat tracing in petroleum processes may include a water circuit and a carbon dioxide working fluid circuit. The water circuit may include the water pump 1 and the gas cooler 2. The carbon dioxide working fluid circuit may include the gas cooler 2, the air source evaporator 3, the waste heat superheater 4, and the compressor 5.

[0024] Water pump 1 is connected to gas cooler 2 via pipeline. Water pump 1 is used to supply water to be heated to gas cooler 2. Water pump 1 can be, for example, a centrifugal pump, plunger pump, magnetic pump, etc. The water to be heated can come from a water source such as surface water or groundwater. Water pump 1 can draw water to be heated from a water source; it can also pump high-pressure water into gas cooler 2 to drive the flow of water in the water circuit.

[0025] In the carbon dioxide working fluid loop, the carbon dioxide working fluid flows sequentially through the gas cooler 2, the air source evaporator 3 and the waste heat superheater 4 through the compression action of the compressor 5, and finally returns to the inlet of the compressor 5, repeating the above cycle.

[0026] Gas cooler 2 can be a heat exchanger used for heat exchange between supercritical carbon dioxide working fluid and water to be heated. Gas cooler 2 can be, for example, a microchannel heat exchanger, a shell-and-tube heat exchanger, or a plate heat exchanger. The working fluids of gas cooler 2 include carbon dioxide working fluid and pressurized water. These two working fluids exchange heat within gas cooler 2. Carbon dioxide is in a supercritical state when its temperature is above a certain critical temperature (e.g., 31.1 degrees Celsius) and its pressure is above a certain critical pressure (e.g., 7.38 MPa). Supercritical carbon dioxide has a high temperature, such as 140-150 degrees Celsius. Gas cooler 2 can exchange the heat from the supercritical carbon dioxide working fluid to the pressurized water, thereby raising the water temperature. Furthermore, the high pressure of the water to be heated within gas cooler 2 causes the boiling point of the water to rise accordingly. Therefore, gas cooler 2 can output high-temperature heated water.

[0027] After heat exchange occurs in the gas cooler 2, the carbon dioxide working fluid's temperature and / or pressure decreases, and its phase changes from supercritical to subcritical, for example, becoming a gas-liquid two-phase state. The gas cooler 2 is connected to the air source evaporator 3 via piping. The carbon dioxide working fluid output from the gas cooler 2 can enter the air source evaporator 3. The air source evaporator 3 can be used for heat exchange between the external environment and the carbon dioxide working fluid output from the gas cooler 2. The carbon dioxide working fluid evaporates within the air source evaporator 3. Through evaporation and absorption of ambient heat, the temperature and / or pressure increase, causing the carbon dioxide working fluid to become saturated.

[0028] The air-source evaporator 3 is connected to the waste heat superheater 4 via a pipeline. The carbon dioxide working fluid output from the air-source evaporator 3 can enter the waste heat superheater 4. The waste heat superheater 4 can be a heat exchanger used for heat exchange between the waste heat resource and the carbon dioxide working fluid output from the air-source evaporator 3. The waste heat superheater 4 can be, for example, a microchannel heat exchanger, a shell-and-tube heat exchanger, a plate heat exchanger, etc. Thus, after the carbon dioxide working fluid absorbs heat from the external environment in the air-source evaporator 3, it can further absorb heat from the waste heat resource in the waste heat superheater 4, and its temperature and / or pressure can be further increased, changing its phase state to a superheated state.

[0029] Compressor 5 can be connected to waste heat superheater 4 and gas cooler 2 via pipelines. The carbon dioxide working fluid output from waste heat superheater 4 can enter compressor 5. Compressor 5 compresses the carbon dioxide working fluid, reducing it to a high-temperature, high-pressure state, thus obtaining supercritical carbon dioxide. The supercritical carbon dioxide output from compressor 5 can enter gas cooler 2, exchanging heat with pressurized water to heat it. Therefore, the carbon dioxide working fluid forms a circuit with gas cooler 2, air source evaporator 3, waste heat superheater 4, and compressor 5. Through the phase change of the carbon dioxide working fluid, water can be heated, for example, to 120 degrees Celsius or higher.

[0030] The transcritical carbon dioxide circulation system provided in the embodiments of this specification, capable of achieving 120°C high-temperature heat tracing in petroleum processes, solves the problems of strong dependence on a single heat source, large heat supply fluctuations, and low resource recycling rates, significantly improving the flexibility of waste heat recovery. It provides the petroleum industry with waste heat recovery technology covering all scenarios and the entire process, helping the industry achieve energy conservation, emission reduction, and sustainable development. Details are as follows.

[0031] (1) The transcritical carbon dioxide circulation system for achieving 120°C high-temperature heat tracing in petroleum processes provided in the embodiments of this specification, in the carbon dioxide working fluid loop, the air source evaporator 3 is used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler 2, and the waste heat superheater 4 is used for heat exchange between the waste heat resources and the carbon dioxide working fluid output by the air source evaporator 3. Thus, by innovatively integrating the air source and waste heat resources, the suction temperature and / or suction pressure of the compressor 5 can be increased, so that the discharge temperature of the compressor 5 can reach 140°C to 150°C or above, thereby increasing the temperature of the hot water output by the gas cooler 2. In addition, by innovatively integrating the air source and waste heat resources, the defects of strong fluctuation and poor stability of a single low-temperature heat source can be overcome, the fluctuation of the discharge temperature of the compressor 5 can be reduced, thereby reducing the fluctuation of the hot water output by the gas cooler 2 and improving the stability of the circulation system's heating supply. Furthermore, by innovatively integrating air source and waste heat resources, the system can automatically switch to another normal low-temperature heat source when either the air source evaporator 3 or the waste heat superheater 4 fails, thus improving system operational stability. Therefore, the circulation system of this embodiment can achieve 120°C high-temperature heat tracing in petroleum processes, and is suitable for various scenarios such as crude oil preheating and heat tracing, thereby providing the petroleum industry with an efficient, stable, and environmentally friendly high-temperature thermal management solution.

[0032] The suction temperature of compressor 5 can refer to the temperature of the carbon dioxide working fluid entering compressor 5, for example, it can be equal to the temperature of the carbon dioxide working fluid output from waste heat superheater 4. The suction pressure of compressor 5 can refer to the pressure of the carbon dioxide working fluid entering compressor 5, for example, it can be equal to the pressure of the carbon dioxide working fluid output from waste heat superheater 4. The discharge pressure of compressor 5 can refer to the pressure of the supercritical carbon dioxide working fluid output by compressor 5. The discharge temperature of compressor 5 can refer to the temperature of the supercritical carbon dioxide working fluid output by compressor 5.

[0033] (2) The transcritical carbon dioxide circulation system provided in the embodiments of this specification can realize high-temperature heating of 120 degrees Celsius in petroleum processes. The waste heat superheater 4 is used for heat exchange between waste heat resources and the carbon dioxide working fluid output by the air source evaporation component 3. Thus, the circulation system can realize the recovery and utilization of industrial waste heat resources, avoid the waste of industrial waste heat resources, reduce the environmental burden, and improve the overall energy efficiency of the system.

[0034] (3) The transcritical carbon dioxide circulation system provided in the embodiments of this specification, which can realize high-temperature heating of 120 degrees Celsius in petroleum processes, uses carbon dioxide as the working fluid. Carbon dioxide working fluid has physical characteristics such as low critical temperature and high critical pressure. Its GWP (Global Warming Potential) is 1 and ODP (Ozone Depletion Potential) is 0, which has good environmental protection properties, no pollutant emissions, and is suitable for extreme environments, thus meeting the needs of green transformation of the petroleum industry. In addition, the carbon dioxide working fluid has a low critical temperature (30.98 degrees Celsius) and a high critical pressure (7.38 MPa). In the supercritical state, it can achieve heat transfer without phase change through countercurrent heat exchange, which can raise the temperature of the water to be heated to above 120 degrees Celsius, precisely matching the needs of petroleum processes for high-temperature heat sources.

[0035] In some embodiments, waste heat resources may include at least one of waste hot water and waste hot flue gas. Waste heat resources include industrial waste heat resources generated in industries such as petroleum and steel. For example, the waste heat resources may include wastewater (10-15 degrees Celsius) or low-temperature cooling water generated during processes such as low-temperature water desalination and pipeline cleaning. As another example, the waste heat resources may also include wastewater (50-60 degrees Celsius) obtained after separating the oil-water mixture extracted by the pumping unit during oil extraction in the petroleum industry.

[0036] In some embodiments, the air source evaporation component 3 includes 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 via piping. The air source evaporator 31 is used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler 2. The fan 32 is used to drive the external ambient air to flow through the air source evaporator 31. By driving the external ambient air to flow through the air source evaporator 31, the carbon dioxide working fluid air source evaporator 31 can absorb more heat.

[0037] In some embodiments, the carbon dioxide working fluid circuit may further include a throttling valve 6. The throttling valve 6 is connected via piping to both the gas cooler 2 and the air source evaporator 3 (e.g., air source evaporator 31). The throttling valve 6 can depressurize the carbon dioxide working fluid output from the gas cooler 2, reducing its pressure to the low pressure required by the air source evaporator 3. This causes the carbon dioxide working fluid to change from a gas-liquid phase to a gas-liquid phase. As the pressure decreases, the boiling point of the carbon dioxide working fluid also decreases. The two-phase carbon dioxide working fluid can absorb heat from the air environment and evaporate into gas in the air source evaporator 3, thus achieving an endothermic process. This results in the carbon dioxide working fluid changing to a saturated state. The throttling valve 6 may have a narrow flow channel. The carbon dioxide working fluid output from the gas cooler 2 can achieve rapid pressure reduction when passing through the narrow flow channel.

[0038] In some embodiments, the water path of the circulation system may further include a first water supply valve 7. The first water supply valve 7 can be connected to the gas cooler 2 via a pipeline. The first water supply valve 7 can supply the first hot water output from the gas cooler 2. The first water supply valve 7 may be provided with a first water inlet 701. The first water supply valve 7 can regulate the flow rate of the first water inlet 701.

[0039] In some embodiments, the water circuit of the circulation system may further include a flash evaporation component, a second water supply valve 8, and a steam supply valve 9. The gas cooler 2 is connected to the flash evaporation component via pipelines, and the flash evaporation component is connected to the second water supply valve 8 and the steam supply valve 9 via pipelines. The flash evaporation component is used to depressurize the first hot water output from the gas cooler 2 to flash out second hot water and steam. The second water supply valve 8 can provide the second hot water flashed out by the flash evaporation component. The second water supply valve 8 may be provided with a second water inlet 801. The second water supply valve 8 can regulate the flow rate of the second water inlet 801. The steam supply valve 9 can provide the steam flashed out by the flash evaporation component. The steam supply valve 9 may be provided with a steam outlet 901. The steam supply valve 9 can regulate the flow rate of the steam outlet 901. The temperature of the second hot water and steam is lower than the temperature of the first hot water. The pressure of the second hot water and steam is lower than the pressure of the first hot water. For example, the first hot water is high-temperature hot water, such as hot water at 120 degrees Celsius. The second hot water is medium-temperature hot water, such as hot water at 100 degrees Celsius to 110 degrees Celsius. The steam is medium-temperature steam, for example, steam at 100°C to 110°C. This allows for multi-stage, cascaded utilization and flexible supply of the hot water output from gas cooler 2. For example, the first hot water can provide a stable high-temperature heat source for atmospheric and vacuum distillation processes in the petroleum industry. Furthermore, steam can be used for heat tracing and insulation, and pipeline cleaning in the petroleum industry.

[0040] In some embodiments, the flash evaporation component may include a pressure reducing valve 10 and a flash tank 11. The pressure reducing valve 10 can be connected to the gas cooler 2 via a pipeline. The pressure reducing valve 10 can also be connected to the flash tank 11 via a pipeline. The flash tank 11 can be connected to a second water supply valve 8 and a steam supply valve 9 via pipelines, respectively. The pressure reducing valve 10 can reduce the pressure of the first hot water output from the gas cooler 2 to flash evaporate the first hot water. The flash tank 11, also known as an expansion tank or gas-liquid separator, is used to flash evaporate the first hot water to obtain second hot water and steam. The flash tank 11 can also store the flashed second hot water and steam. The second water supply valve 8 can supply the flashed second hot water from the flash tank 11. The steam supply valve 9 can supply the flashed steam from the flash tank 11.

[0041] In some embodiments, the gas cooler 2 may include a water inlet and a water outlet. The water inlet of the gas cooler 2 can be connected to the water pump 1 via a pipeline. The water outlet of the gas cooler 2 can be connected to the first water supply valve 7 and the pressure reducing valve 10 via 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 can be connected to the carbon dioxide outlet of the compressor 5 via a pipeline. The carbon dioxide outlet of the gas cooler 2 can be connected to the carbon dioxide inlet of the throttle valve 6 via a pipeline. The carbon dioxide outlet of the throttle valve 6 can be connected to the carbon dioxide inlet of the air source evaporator 31 via a pipeline. Thus, the working liquids on both sides of the gas cooler 2 are carbon dioxide and water, respectively. The two working liquids achieve heat exchange in the gas cooler 2.

[0042] 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 can be connected to a waste heat resource providing device via a pipeline. The waste heat resource providing device can provide waste heat resources to the waste heat superheater 4. The waste heat resource outlet 402 can be connected to a waste heat resource treatment device via a pipeline. The waste heat resources after heat exchange can enter the waste heat resource treatment device through the waste heat resource outlet 402. The waste heat resource treatment device can treat the waste heat resources after heat exchange. For example, the waste heat resource treatment device may include a wastewater treatment device.

[0043] 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 can 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 can 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. The two working fluids exchange heat in the waste heat superheater 4.

[0044] In some embodiments, the circulation 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 control functions. For example, the controller may include computer devices such as desktop computers and laptops.

[0045] Please see Figure 2 This specification also provides a corresponding control method for a transcritical carbon dioxide cycle system capable of achieving 120°C high-temperature heating in petroleum processes. The controller may be the implementing entity of the control method, and the method may specifically include the following steps.

[0046] Step 201: Control the water pump to supply the water to be heated to the gas cooler.

[0047] Step 202: Control the gas cooler to exchange heat between the supercritical carbon dioxide working fluid and the water to be heated.

[0048] Step 203: Control the air source evaporation component to exchange heat with the external environment and the carbon dioxide working fluid output by the gas cooler.

[0049] Step 204: Control the waste heat superheater to exchange heat between the waste heat resources and the carbon dioxide working fluid output by the air source evaporation component.

[0050] Step 205: Control the compressor to compress the carbon dioxide working fluid output from the waste heat superheater to obtain supercritical carbon dioxide working fluid.

[0051] In some embodiments, the controller can send instructions to the water pump to pump water to be heated into the gas cooler. The controller can also send instructions to the gas cooler to exchange heat between the incoming supercritical carbon dioxide working fluid and the incoming water to be heated. The supercritical carbon dioxide working fluid has a high temperature, such as 140°C to 150°C. Through the gas cooler, the heat from the supercritical carbon dioxide working fluid can be exchanged with the pressurized water, thereby raising the water temperature, for example, to 120°C. The controller can also send instructions to the air source evaporator to exchange heat between the incoming carbon dioxide working fluid and the surrounding air. The carbon dioxide working fluid evaporates within the air source evaporator. Through evaporation, it absorbs heat from the surrounding air, thus increasing its temperature. The controller can also send instructions to the waste heat superheater to exchange heat between the incoming carbon dioxide working fluid and the incoming waste heat resources. The carbon dioxide working fluid further absorbs heat from the waste heat resources in the waste heat superheater, further increasing its temperature. The controller can also send control commands to the compressor, enabling the compressor to compress the incoming carbon dioxide working fluid to obtain supercritical carbon dioxide working fluid under high temperature and high pressure.

[0052] For example, the controller can send start commands to the water pump, gas cooler, air source evaporator, waste heat superheater, and compressor respectively. Upon receiving the start command, the water pump can pump water to be heated into the gas cooler. Upon receiving the start command, the gas cooler can exchange heat between the incoming supercritical carbon dioxide working fluid and the incoming water to be heated. Upon receiving the start command, the air source evaporator can exchange heat between the incoming carbon dioxide working fluid and the surrounding air. Upon receiving the start command, the waste heat superheater can exchange heat between the incoming carbon dioxide working fluid and the incoming waste heat resources. Upon receiving the start command, the compressor can compress the incoming carbon dioxide working fluid to obtain supercritical carbon dioxide.

[0053] In some embodiments, the temperature and flow rate of the waste heat resource are often not constant but fluctuate significantly. Therefore, a first degree of temperature fluctuation and a second degree of flow rate fluctuation can be determined; it can be determined whether the first degree of fluctuation is greater than or equal to a first fluctuation threshold; it can be determined whether the second degree of fluctuation is greater than or equal to a second fluctuation threshold; when the first degree of fluctuation reaches the first fluctuation threshold or the second degree of fluctuation 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 fluid output by the air source evaporator. For example, the controller can send a stop command to the waste heat superheater, causing it to stop heat exchange between the waste heat resource and the carbon dioxide working fluid output by the air source evaporator. Thus, when there are significant fluctuations in the temperature and / or flow rate of the waste heat resource, the waste heat superheater can stop heat exchange. This avoids significant fluctuations in the compressor's exhaust temperature and pressure, thereby affecting the stability of the hot water temperature output by the gas cooler. In this way, the temperature of the carbon dioxide working fluid flowing into the waste heat superheater can be approximately equal to the temperature of the carbon dioxide working fluid flowing out of the waste heat superheater. Therefore, the temperature of the carbon dioxide working fluid can be increased by exchanging heat between the incoming carbon dioxide working fluid and the surrounding air using only the air-source evaporation component. The first and second fluctuation thresholds can be preset.

[0054] For example, a temperature sensor and a flow sensor can be installed at the waste heat resource inlet of the waste heat superheater. The temperature sensor can detect the temperature of the waste heat resource. The flow sensor can detect the flow rate of the waste heat resource. Multiple temperatures and multiple flow rates detected within a set time interval can be acquired. A first fluctuation index of the multiple temperatures can be calculated. The first fluctuation index may include range, variance, standard deviation, etc., to characterize the first degree of fluctuation in the waste heat resource temperature. A second fluctuation index of the multiple flow rates can be calculated. The second fluctuation index may include range, variance, standard deviation, etc., to characterize the second degree of fluctuation in the waste heat resource flow rate.

[0055] 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. If 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 rotational speed of the fan in the air-source evaporator can be increased. By increasing the fan speed, the amount of gas flowing to the air-source evaporator can be increased, allowing the carbon dioxide working fluid to absorb more heat from the air, thereby further increasing the temperature of the carbon dioxide working fluid. Thus, stable operation in complex environments can be achieved through multi-source coordinated control, intelligently balancing the heat exchange between the air source and the waste heat resource, thereby ensuring that the gas cooler can still stably output 120 degrees Celsius high-temperature water even under extreme environmental conditions.

[0056] The first temperature threshold can be preset. For example, a first functional relationship between the temperature difference and the increase in fan speed can be preset. The temperature difference between the first temperature and the first temperature threshold can be calculated; the temperature difference can be substituted into the first functional relationship to calculate the increase in speed; the fan speed can be increased by the increase, thereby increasing the fan speed.

[0057] In some embodiments, a second temperature of the external environment can be obtained. For example, the temperature of the 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; when the second temperature is less than or equal to the second temperature threshold, 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 fluid can be increased. Thus, stable operation in complex environments can be achieved through multi-source collaborative control, intelligently balancing the heat exchange of the air source and waste heat resources, thereby ensuring that the gas cooler can still stably output 120 degrees Celsius high-temperature water under extreme environmental conditions.

[0058] 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 decreasing the flow rate of the carbon dioxide working fluid. This allows the carbon dioxide working fluid to absorb more heat from the waste heat resource, thereby further increasing the temperature.

[0059] The second temperature threshold can be preset. For example, a second functional relationship between the temperature difference and the flow rate ratio can be preset. The temperature difference between the second temperature and the second temperature threshold can be calculated; the temperature difference can be substituted into the second functional relationship to calculate the corresponding flow rate ratio. This flow rate ratio is the ratio of the waste heat resource flow rate to the carbon dioxide working fluid flow rate. Based on the flow rate ratio, the flow rate of the carbon dioxide working fluid and the flow rate of the waste heat resource in the waste heat superheater can be determined to control the heat exchange of the waste heat superheater.

[0060] In some embodiments, the compressor's discharge temperature can be obtained; when the discharge temperature is less than a third temperature threshold, the compressor's discharge pressure can be increased; when the compressor's discharge pressure reaches a pressure threshold, the compressor's discharge pressure can be kept constant, and the fan speed in the air source evaporator component can be reduced to reduce the compressor's intake pressure.

[0061] The system can acquire a first temperature of the waste heat resource and a second temperature of the external environment. When the first temperature is greater than a certain temperature threshold and the second temperature is less than another temperature threshold, it indicates a high-temperature environment with insufficient waste heat, and the compressor's discharge temperature may be low. Therefore, the compressor's discharge temperature can be acquired. The discharge temperature can be compared with a third temperature threshold to determine if it is lower than the third threshold. A temperature sensor can be installed at the compressor's carbon dioxide outlet. The compressor's discharge temperature can be obtained through this sensor. The compressor's discharge temperature can refer to the temperature of the supercritical carbon dioxide working fluid output by the compressor.

[0062] When the exhaust temperature is below the third temperature threshold, the compressor's exhaust pressure can be increased. The compressor's exhaust temperature is related to its compression ratio. The compression ratio can be, for example, the ratio between the compressor's exhaust pressure and intake pressure. By increasing the compressor's exhaust pressure, the compressor's compression ratio increases, thereby increasing the compressor's exhaust temperature.

[0063] However, the compressor's discharge pressure has an upper limit. When the compressor's discharge pressure reaches the pressure threshold, it cannot be increased further to ensure safety. Therefore, the compressor's discharge pressure can be kept constant by reducing the fan speed in the air-source evaporator. By reducing the fan speed, the evaporation temperature and pressure of the carbon dioxide refrigerant in the air-source evaporator decrease, thus reducing the pressure of the carbon dioxide refrigerant output by the evaporator. Correspondingly, the compressor's intake pressure also decreases. Since the compressor's discharge temperature is related to its compression ratio, reducing the intake pressure while keeping the discharge pressure constant increases the compression ratio, forcing an increase in the compressor's discharge temperature. Thus, when the compressor's discharge pressure reaches the pressure threshold, reducing the fan speed in the air-source evaporator lowers the compressor's intake pressure, thereby forcibly increasing the compressor's discharge temperature.

[0064] Therefore, the correlation between the compressor's discharge temperature and its compression ratio can be obtained; the compressor's compression ratio can be calculated based on this correlation and the compressor's discharge temperature (e.g., 140°C to 150°C). The compressor's current intake pressure can be obtained; the target discharge pressure can be calculated based on the current intake pressure and the calculated compression ratio. When the target discharge pressure is less than a pressure threshold, the compressor's current discharge pressure can be increased to the target discharge pressure. Thus, by increasing the compressor's discharge pressure, the compressor's compression ratio increases, thereby increasing the compressor's discharge temperature. When the target discharge pressure is greater than a pressure threshold, the compressor's current discharge pressure can be increased to the pressure threshold. The compressor's target intake pressure can be calculated based on the pressure threshold and the compression ratio. The compressor's intake temperature can be calculated using the formula Pd = k1 × Ts + k2 × Ps + C based on the target intake pressure and the pressure threshold; the fan speed can be calculated based on the compressor's intake temperature. Where Pd represents the compressor's discharge pressure, Ts represents the compressor's intake temperature, Ps represents the compressor's intake pressure, and k1, k2, and C are coefficients. For example, a third functional relationship between the intake temperature and the fan speed can be obtained in advance. The intake temperature can be substituted into the third functional relationship to calculate the fan speed. The controller can control the fan to reach the specified speed. Thus, when the compressor's discharge pressure reaches the pressure threshold, the compressor's intake pressure is reduced by decreasing the fan speed in the air source evaporator, thereby forcibly increasing the compressor's discharge temperature.

[0065] Therefore, this embodiment can dynamically achieve coordinated control of pressure and temperature.

[0066] The control method described in this specification can control a water pump to supply water to a gas cooler; control the gas cooler to exchange heat between the supercritical carbon dioxide working fluid and the water to be heated; control the air source evaporator to exchange heat between the external environment and the carbon dioxide working fluid output from the gas cooler; control the waste heat superheater to exchange heat between waste heat resources and the carbon dioxide working fluid output from the air source evaporator; and control the compressor to compress the carbon dioxide working fluid output from the waste heat superheater to obtain supercritical carbon dioxide working fluid. This enables the control of a transcritical carbon dioxide circulation system capable of providing 120°C high-temperature heating in petroleum processes.

[0067] The control method described in this specification recovers waste heat resources through a waste heat superheater to increase the temperature of the carbon dioxide working fluid. Combined with dynamic pressure and temperature synergistic control, it achieves a stable compressor exhaust temperature of 140°C to 150°C. Furthermore, it can intelligently switch heat source modes based on waste heat conditions. Through intelligent switching mechanisms and multi-energy complementary strategies, it overcomes the limitations of a single heat source, providing the petroleum industry with waste heat recovery technology covering all scenarios and processes, thus helping the industry achieve energy conservation, emission reduction, and sustainable development.

[0068] Please see Figure 3 This specification also provides a control device for a transcritical carbon dioxide cycle system capable of achieving 120°C high-temperature heating in petroleum processes. The control device may include the following units.

[0069] The first control unit 301 is used to control the water pump to supply water to be heated to the gas cooler;

[0070] The second control unit 302 is used to control the gas cooler to exchange heat between the supercritical carbon dioxide working fluid and the water to be heated;

[0071] The third control unit 303 is used to control the air source evaporation component to exchange heat with the external environment and the carbon dioxide working fluid output by the gas cooler;

[0072] The fourth control unit 304 is used to control the waste heat superheater to exchange heat between the waste heat resources and the carbon dioxide working fluid output by the air source evaporation component;

[0073] The fifth control unit 305 is used to control the compressor to compress the carbon dioxide working fluid output from the waste heat superheater to obtain supercritical carbon dioxide working fluid.

[0074] This specification also provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the above-described control method.

[0075] This specification also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described control method.

[0076] This specification also provides a computer program product, which includes a computer program that, when executed by a processor, implements the above-described control method.

[0077] Those skilled in the art will understand that this specification can be provided as a method, system, or computer program product. Therefore, this specification may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware. Furthermore, this specification may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0078] This specification is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments thereof. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. The computer may be a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0079] The functional units in the embodiments of this specification can be integrated into one processing unit, or each functional unit can exist physically separately, or two or more functional units can be integrated into one processing unit.

[0080] Those skilled in the art will understand that the descriptions of the various embodiments in this specification have different focuses, and parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments. Furthermore, it is understood that those skilled in the art, after reading this specification, can conceive of any combination of some or all of the embodiments listed in this specification without creative effort, and such combinations are also within the scope of disclosure and protection of this specification.

[0081] Although this specification has been described through embodiments, those skilled in the art will understand that the above embodiments are merely illustrative of the core ideas of this specification. Those skilled in the art will appreciate that many variations and modifications are possible with this specification. It is intended that the appended claims encompass these variations and modifications without departing from the spirit of this specification.

Claims

1. A control method applied to a transcritical carbon dioxide cycle system capable of achieving 120°C high-temperature heating in petroleum processes, characterized in that, The method includes: Control the water pump to supply heated water to the gas cooler; The gas cooler is controlled to exchange heat between the supercritical carbon dioxide working fluid and the water to be heated; The air source evaporation component is controlled to exchange heat with the external environment and the carbon dioxide working fluid output by the gas cooler; The waste heat superheater is controlled to exchange heat between the waste heat resources and the carbon dioxide working fluid output by the air source evaporation component; The compressor is controlled to compress the carbon dioxide working fluid output from the waste heat superheater to obtain supercritical carbon dioxide working fluid; Determine the first degree of temperature fluctuation and the second degree of flow fluctuation of the waste heat resource; When the first fluctuation level reaches the first fluctuation threshold or the second fluctuation level reaches the second fluctuation threshold, the waste heat superheater is controlled to stop the heat exchange between the waste heat resource and the carbon dioxide working fluid output by the air source evaporation component. The first temperature for obtaining waste heat resources; When the first temperature is lower than the first temperature threshold, increase the speed of the fan in the air source evaporation component; The transcritical carbon dioxide cycle system includes a water pump, a gas cooler, an air source evaporator, a waste heat superheater, and a compressor. The gas cooler, the air source evaporator, 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 supply water to be heated to the gas cooler. The gas cooler is used for heat exchange between the supercritical carbon dioxide working fluid and the water to be heated. The air source evaporator is used for heat exchange between the external environment and the carbon dioxide working fluid output by the gas cooler. The waste heat superheater is used for heat exchange between waste heat resources and the carbon dioxide working fluid output by the air source evaporator. The compressor is used to compress the carbon dioxide working fluid output by the waste heat superheater to obtain supercritical carbon dioxide working fluid.

2. The method according to claim 1, characterized in that, The method further includes: To obtain a second temperature of the external environment; When the second temperature is less than the second temperature threshold, the heat exchange capacity of the waste heat superheater is increased.

3. The method according to claim 1, characterized in that, The method further includes: Obtain the compressor's discharge temperature; When the exhaust temperature is below the third temperature threshold, increase the compressor's exhaust pressure; When the compressor's discharge pressure reaches the pressure threshold, the compressor's discharge pressure is kept constant, and the fan speed in the air source evaporator is reduced to lower the compressor's intake pressure.

4. A transcritical carbon dioxide circulation system capable of achieving 120°C high-temperature heating in petroleum processes, characterized in that, The transcritical carbon dioxide cycle system is controlled using any one of the methods in claims 1-3.

5. The system according to claim 4, characterized in that, 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 fluid output by the gas cooler; the fan is used to drive the external ambient air to flow through the air source evaporator.

6. The system according to claim 4, characterized in that, The system also 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 the first hot water output by the gas cooler.

7. The system according to claim 4, characterized in that, The system further 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 depressurize the first hot water output from the gas cooler to flash evaporate the 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.

8. The system according to claim 4, characterized in that, The waste heat resources include at least one of waste hot water and waste heat flue gas.

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