A heat recovery system for low-grade heat sources

Abstract

The present application discloses a low-grade heat source heat recovery system, comprising an evaporator, a compressor, a condenser and a throttling expansion valve or a hydraulic turbine connected in sequence, wherein the throttling expansion valve or the hydraulic turbine is also connected to the evaporator to form a circulation loop between the evaporator, the compressor, the condenser and the throttling expansion valve or the hydraulic turbine, wherein the circulation loop is used to circulate a heat transfer medium, wherein the heat transfer medium evaporates through heat exchange with a low-grade heat source through the evaporator, and the heat transfer medium releases heat through the condenser. The low-grade heat source heat recovery system recovers the heat of the low-grade heat source while avoiding the resource consumption of cooling the low-grade heat source, reducing equipment investment and device land occupation; at the same time, the heat of the low-grade heat source is used to produce a heating medium, reducing the consumption of coal and the like for generating the heating medium, and reducing environmental pollution, operating costs and energy consumption.

Description

Technical Field

[0001] The present application belongs to the field of petrochemical thermal management technology, and in particular, relates to a low-grade heat source heat recovery system and method. Background Art

[0002] In petrochemical plants, there are many low-grade heat sources that are difficult to use. These low-grade heat sources are generally discarded due to their low temperature and low energy density. In some cases, in order to reduce their temperature, a large amount of circulating cooling water or air coolers are required to cool them down. This not only wastes the energy in these low-grade heat sources, but also increases the additional cooling water consumption and electricity consumption, and increases the equipment investment and device area.

[0003] At the same time, there are still a large number of situations in petrochemical plants that require the use of high-grade heat sources. For example, using steam / saturated steam as a heating medium requires consuming a large amount of coal to burn to generate steam / saturated steam. On the one hand, the process of burning coal to generate steam / saturated steam will emit a large amount of carbon dioxide, causing environmental pollution; on the other hand, the consumption of steam / saturated steam will increase the operating costs and energy consumption of the device.

[0004] How to utilize the low-grade heat sources of petrochemical plants, reduce heat source waste, avoid the extra cost consumption of low-grade heat sources, and at the same time reduce the energy consumption, operating costs and environmental pollution caused by generating high-quality heat sources is an urgent problem to be solved in this field.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] The present application aims to at least to some extent solve the technical problem that low-grade heat sources in petrochemical plants cannot be utilized, resulting in waste of heat sources or extra cost consumption in processing low-grade heat sources. To this end, the present application provides a low-grade heat source heat recovery system.

[0007] An embodiment of the present application provides a low-grade heat source heat recovery system, which includes an evaporator, a compressor, a condenser, and a throttling expansion valve or a hydraulic turbine connected in sequence, and the throttling expansion valve or the hydraulic turbine is also connected to the evaporator to form a circulation loop between the evaporator, the compressor, the condenser, and the throttling expansion valve or the hydraulic turbine, and the circulation loop is used to circulate a heat transfer medium, wherein the heat transfer medium evaporates through heat exchange with the low-grade heat source through the evaporator, and the heat transfer medium releases heat through the condenser; the saturation temperature of the heat transfer medium at the inlet of the compressor is 20°C to 90°C, the saturation temperature of the heat transfer medium at the outlet of the compressor is 80°C to 200°C, and the temperature of the low-grade heat source is 20°C to 90°C.

[0008] In some embodiments, a discharge buffer tank is provided between the condenser and the throttling expansion valve or the hydraulic turbine.

[0009] In some embodiments, a suction buffer tank is provided between the evaporator and the compressor.

[0010] In some embodiments, a superheater is provided between the suction buffer tank and the compressor.

[0011] In some embodiments, the superheater allows the superheat temperature of the heat transfer medium to be 5°C to 20°C.

[0012] In some embodiments, a gas-liquid separator is provided between the condenser or the discharge buffer tank and the throttling expansion valve, or a gas-liquid separator is provided between the hydraulic turbine and the evaporator;

[0013] The gas outlet of the gas-liquid separator is connected to any one of the inlet of the suction buffer tank, the inlet of the superheater, and the air inlet end of the compressor;

[0014] The liquid outlet of the gas-liquid separator is communicated with the inlet of the throttling expansion valve or the inlet of the evaporator.

[0015] In some embodiments, the compressor has 2 to 5 sections, and the gas outlet of the gas-liquid separator is connected to the inlet of any one of the second to fifth sections of the compressor.

[0016] In some embodiments, the hydraulic turbine also provides mechanical driving force into or outside the low-grade heat recovery system.

[0017] In some embodiments, in the low-grade heat source heat recovery system, the evaporator, the compressor, and the condenser can be one or more respectively; when there are multiple evaporators, the multiple evaporators are arranged in series or in parallel; when there are multiple compressors, the multiple compressors are arranged in series or in parallel; when there are multiple condensers, the multiple condensers are arranged in series or in parallel.

[0018] In some embodiments, the heat medium is selected from substituted or unsubstituted alkanes, heteroalkanes, olefins or heteroolefins having 3 to 6 carbon atoms.

[0019] The embodiments of the present application have at least the following beneficial effects:

[0020] In the above-mentioned low-grade heat source heat recovery system, the heat transfer medium is heated and vaporized by the low-grade heat source in the evaporator to absorb the heat of the low-grade heat source. The vaporized heat transfer medium is passed through the compressor to increase the pressure and temperature, thereby increasing the saturation temperature of the heat transfer medium. Then, the heat transfer medium is converted into a condensed heat transfer medium through heat exchange with the heated medium through the condenser, thereby realizing the conversion of the low-grade heat source into a high-grade heat source for the generation of the heating medium. Afterwards, the heat transfer medium is depressurized and cooled by a throttling expansion valve so that it can be circulated to the evaporator to further absorb heat and recover heat from the low-grade heat source; or the residual pressure of the heat transfer medium is recovered and reused by the hydraulic turbine to realize the cooling and pressure reduction and then circulated to the evaporator to further absorb heat and recover heat from the low-grade heat source. During the heat transfer process from the low-grade heat source to the high-grade heat source, the heat transfer medium can utilize the phase change of the heat transfer medium to absorb more latent heat of phase change, and during the evaporation heat exchange process, the corresponding heat transfer medium can be selected according to the temperature of the low-grade heat source, thereby improving the heat absorption efficiency of the heat transfer medium and reducing the temperature requirement for the low-grade heat source. While recovering the heat of the low-grade heat source, it also avoids the resource consumption of cooling the low-grade heat source, reduces equipment investment and device floor space; at the same time, the heat of the low-grade heat source is used to produce the heating medium, reducing the consumption of coal and the like for generating the heating medium, and reducing environmental pollution, operating costs and energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 The schematic diagram of the structure of the heat recovery system of the low-grade heat source in the first embodiment of the present application is shown;

[0023] Figure 2The schematic diagram of the structure of the heat recovery system of the low-grade heat source in the second embodiment of the present application is shown;

[0024] Figure 3 The schematic diagram of the structure of the heat recovery system of the low-grade heat source in the third embodiment of the present application is shown;

[0025] Figure 4 The schematic diagram of the structure of the heat recovery system of the low-grade heat source in the fourth embodiment of the present application is shown;

[0026] Figure 5 A schematic structural diagram of a heat recovery system for a low-grade heat source in Embodiment 5 of the present application is shown.

[0027] Reference numerals:

[0028] 100. Evaporator; 200. Suction buffer tank; 300. Superheater; 400. Compressor; 410. First stage of compressor; 420. Second stage of compressor; 500. Condenser; 600. Discharge buffer tank; 700. Throttling expansion valve; 710. First throttling expansion valve; 720. Second throttling expansion valve; 800. Hydraulic turbine; 900. Gas-liquid separator; 1000. Valve. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0030] In addition, the present application may repeat reference numbers and / or reference letters in different examples, and such repetition is for the purpose of simplicity and clarity, and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides various specific examples of processes and materials, but those of ordinary skill in the art may recognize the application of other processes and / or the use of other materials.

[0031] The present application is described below with reference to the accompanying drawings and specific embodiments:

[0032] This application provides a low-grade heat source heat recovery system, such as Figure 1 and Figure 2As shown, the low-grade heat source heat recovery system includes an evaporator 100, a compressor 400, a condenser 500 and a throttling expansion valve 700 or a hydraulic turbine 800 which are connected in sequence. The throttling expansion valve 700 or the hydraulic turbine 800 is also connected to the evaporator 100 to form a circulation loop among the evaporator 100, the compressor 400, the condenser 500 and the throttling expansion valve 700 or the hydraulic turbine 800. The circulation loop is used to circulate a heat transfer medium, wherein the heat transfer medium evaporates by heat exchange with the low-grade heat source through the evaporator 100, and the heat transfer medium releases heat through the condenser 500; the saturated temperature of the heat transfer medium at the inlet of the compressor 400 is 20°C to 90°C, the saturated temperature of the heat transfer medium at the outlet of the compressor 400 is 80°C to 200°C, and the temperature of the low-grade heat source is 20°C to 90°C.

[0033] In the above-mentioned low-grade heat source heat recovery system, the heat transfer medium is heated and vaporized by the low-grade heat source in the evaporator 100 to absorb the heat of the low-grade heat source. The vaporized heat transfer medium passes through the compressor 400 to increase the pressure and temperature, thereby increasing the saturation temperature of the heat transfer medium, and then the heat transfer medium releases heat through the condenser 500, that is, the heat transfer medium can directly heat the material to be heated through the condenser 500, or the heat transfer medium can heat the material to be heated through the heated medium after exchanging heat with the heated medium through the condenser 500, so as to achieve the purpose of converting the low-grade heat source into a high-grade heat source for heating. Afterwards, the heat transfer medium can be depressurized and cooled by the throttling expansion valve 700 so as to circulate to the evaporator 100 to further absorb heat and recover heat from the low-grade heat source; or the residual pressure of the heat transfer medium can be recovered and reused by the hydraulic turbine 800 to achieve depressurization and pressure reduction and then circulate to the evaporator 100 to further absorb heat and recover heat from the low-grade heat source.

[0034] During the heat transfer process from the low-grade heat source to the high-grade heat source, the heat transfer medium can utilize the phase change of the heat transfer medium to absorb more phase change latent heat, and during the evaporation heat exchange process, the corresponding heat transfer medium can be selected according to the temperature of the low-grade heat source, thereby improving the heat absorption efficiency of the heat transfer medium and reducing the temperature requirement for the low-grade heat source. While recovering the heat of the low-grade heat source, it also avoids the resource consumption of cooling the low-grade heat source, reducing equipment investment and device floor space; at the same time, the heat of the low-grade heat source is used to replace steam / saturated steam heating or generate steam / saturated steam heating, reducing the energy consumption of generating steam / saturated steam coal, etc., and reducing environmental pollution, operating costs and energy consumption.

[0035] In this embodiment, the low-grade heat source can be low-temperature water. In the field of petrochemical industry, the temperature range of low-temperature water is generally 30°C to 90°C. For example, the temperature of low-temperature water can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, etc. Low-temperature water in this temperature range cannot be used in some cases of petrochemical industry. Direct discharge will cause more heat waste. In some cases, it is necessary to cool this low-temperature water before it can be discharged. This application is based on the inventive concept of converting the low-temperature heat energy contained in these low-temperature waters into high-temperature heat energy that can be used. By making the saturated temperature of the heat transfer medium at the inlet of the compressor 400 20°C to 90°C and the saturated temperature at the outlet of the compressor 400 80°C to 200°C, the heat transfer medium is matched with the low-grade heat source at any temperature in the temperature range of 20°C to 90°C, so that the heat transfer medium can fully absorb the heat energy contained in the low-grade heat source when it is gasified.

[0036] Furthermore, the residual pressure of the heat transfer medium after heat exchange and cooling in the condenser 500 is further utilized through the hydraulic turbine 800, that is, the residual energy of the heat transfer medium after condensation and heat exchange is utilized, the utilization efficiency of energy recovered in the cycle is improved, and the energy consumption is further reduced; and the energy carried by the heat transfer medium after heat exchange and cooling in the condenser 500 is absorbed and converted through the hydraulic turbine 800, which further reduces the thermal energy of the heat transfer medium, and is more conducive to the re-circulation of the heat transfer medium to the evaporator 100 to improve the absorption efficiency of the heat of the low-grade heat source.

[0037] In the present application, the heat transfer medium and the low-grade heat source enter different flow channels of the evaporator 100 for heat exchange respectively, and the heat transfer medium absorbs energy from the low-grade heat source in the evaporator 100 and vaporizes.

[0038] In the present application, the superheated gas phase heat transfer medium enters the compressor 400, and the compressor 400 performs work to achieve an increase in the pressure and temperature of the heat transfer medium.

[0039] In the present application, the heat transfer medium condenses in the condenser 500 / user heat exchanger to absorb heat and cool down, and then transfers the heat out. The heat transfer medium releases heat through the condenser 500. When the substance to be heated is a fluid, the heat transfer medium can be directly heat-exchanged with the substance to be heated through the condenser 500 to achieve the purpose of utilizing the heat carried by the heat transfer medium; when the substance to be heated is a non-fluid or is not suitable for entering the condenser 500, the heat transfer medium can be heat-exchanged with a heating medium such as water / steam through the condenser 500, and then the substance to be heated is heated by the heating medium.

[0040] In the present application, optionally, the condensed liquid phase heat transfer medium is decompressed to a suitable pressure through the throttling expansion valve 700, and partially vaporized, and the pressure after decompression should be greater than the pressure before entering the evaporator 100. Alternatively, the condensed heat transfer medium can be decompressed to a suitable pressure through the hydraulic turbine 800, partially vaporized and perform work externally, and the hydraulic turbine 800 is the preferred pressure reduction means to replace the throttling expansion valve 700, which can further reduce energy consumption.

[0041] As an optional implementation, Figure 1 and Figure 2 As shown, a discharge buffer tank 600 is provided between the condenser 500 and the throttling expansion valve 700 or the hydraulic turbine 800 .

[0042] The discharge buffer tank 600 is arranged between the condenser 500 and the throttling expansion valve 700 or between the condenser 500 and the hydraulic turbine 800, which can buffer the pressure fluctuation of the low-grade heat source heat recovery system, reduce the flow unevenness of the pipeline between the condenser 500 and the throttling expansion valve 700 or the hydraulic turbine 800, avoid the generation of excessive flow, and make the pipeline pressure between the condenser 500 and the throttling expansion valve 700 or the hydraulic turbine 800 more stable, which is beneficial to the operation of the expansion valve or the hydraulic turbine 800, and makes the low-grade heat source heat recovery system work more smoothly.

[0043] As an optional implementation, Figure 1 and Figure 2 As shown, a suction buffer tank 200 is provided between the evaporator 100 and the compressor 400 .

[0044] The suction buffer tank 200 is arranged between the evaporator 100 and the compressor 400, and can buffer the pressure of the gas phase heat transfer medium sucked into the suction end of the compressor 400 by the evaporator 100, reduce the flow unevenness of the pipeline between the evaporator 100 and the compressor 400, reduce inertia loss, and improve the suction performance of the compressor 400.

[0045] As an optional implementation, Figure 1 and Figure 2 As shown, a superheater 300 is provided between the suction buffer tank 200 and the inlet of the compressor 400 .

[0046] After the heat transfer medium exchanges heat with the low-grade heat source through the evaporator 100, it will be converted from liquid to gas phase. However, it is inevitable that the conversion is incomplete or the gas phase heat transfer medium entrains part of the liquid heat transfer medium. In order to avoid the liquid heat transfer medium entering the suction end of the compressor 400 and causing liquid hammer, the superheater is arranged between the evaporator 100 and the compressor 400, so that the heat transfer medium after absorbing heat in the evaporator 100 passes through the superheater first, and the heat transfer medium before entering the compressor 400 is superheated by the superheater, so that the heat transfer medium is superheated and fully vaporized before entering the suction end of the compressor 400, so as to avoid the heat transfer medium carrying liquid into the compressor 400 and causing damage to the compressor 400, thereby ensuring the safe operation of the compressor 400. In the specific implementation process, the superheat temperature of the heat transfer medium can be adjusted as needed, preferably, the heat transfer medium is superheated by 5°C to 20°C. While fully vaporizing the heat transfer medium through superheating, the superheat temperature of the superheater is reduced as much as possible to reduce the energy consumption of the superheater, that is, to reduce the overall energy consumption of the low-grade heat source heat recovery system, reduce operating costs, and improve the economic benefits of low-grade heat source heat recovery.

[0047] As an optional implementation, Figures 1 to 3 As shown, a gas-liquid separator 900 is provided between the condenser 500 or the discharge buffer tank 600 and the throttling expansion valve 700, or a gas-liquid separator 900 is provided between the hydraulic turbine 800 and the evaporator 100;

[0048] The gas outlet of the gas-liquid separator 900 is connected to any one of the inlet of the suction buffer tank 200, the inlet of the superheater 300, and the air inlet end of the compressor 400;

[0049] The liquid outlet of the gas-liquid separator 900 is communicated with the inlet of the throttling expansion valve 700 or the inlet of the evaporator 100 .

[0050] The function of the gas-liquid separator 900 is to separate the partially vaporized heat transfer medium into gas and liquid. By connecting the gas outlet of the gas-liquid separator 900 with any one of the inlet of the suction buffer tank 200, the inlet of the superheater 300, and the air inlet of the compressor 400, the separated gas phase heat transfer medium bypasses the evaporator 100 and directly enters the suction buffer tank 200, the superheater 300 or the compressor 400, thereby preventing the gas phase heat transfer medium from entering the evaporator 100 and affecting the heat exchange between the liquid heat transfer medium and the low-grade heat source in the evaporator 100.

[0051] As an optional implementation, Figure 4 and Figure 5As shown, the compressor 400 has 2 to 5 sections, and the gas outlet of the gas-liquid separator 900 is connected to the inlet of any one of the second to fifth sections of the compressor 400. In this embodiment, after the heat transfer medium is separated by the gas-liquid separator 900, the separated gas-phase heat transfer medium is counted into the second to fifth sections of the compressor 400, so that the gas-phase heat transfer medium separated by the gas-liquid separator 900 bypasses the evaporator, the buffer suction tank, the first section of the compressor and other devices, which can reduce the energy consumption of the gas-phase heat transfer medium in these devices, and reduce the flow of the gas-phase heat transfer medium through the occupied channels in these devices, which can further reduce the energy consumed by the operation of the low-grade heat source heat recovery system and further improve the energy efficiency of the system.

[0052] As an optional implementation, the hydraulic turbine also provides mechanical driving force to the low-grade heat recovery system or outside the low-grade heat recovery system. In this embodiment, the hydraulic turbine not only has the function of a throttling expansion valve, but also can replace the throttling expansion valve to achieve the cooling and pressure reduction of the heat transfer medium, and can also convert part of the static pressure energy of the heat transfer medium in the system into mechanical energy, and can output the mechanical energy to a device that needs mechanical energy inside or outside the system.

[0053] For example, in the low-grade heat source outside the low-grade heat source heat recovery system, a pump is provided to drive the low-grade heat source to continuously flow so as to exchange heat with the heat transfer medium. The hydraulic turbine in the low-grade heat source heat recovery system can output mechanical energy to the rotating equipment such as the pump that drives the low-grade heat source, that is, to improve the energy utilization efficiency of the heat transfer medium in each cycle, and also to reduce the energy consumption used to drive the low-grade heat source.

[0054] As an optional implementation, in the low-grade heat source heat recovery system, the evaporator 100, the compressor 400, and the condenser 500 can be one or more, respectively; when there are multiple evaporators 100, multiple evaporators 100 are arranged in series or in parallel; when there are multiple compressors 400, multiple compressors 400 are arranged in series or in parallel; when there are multiple condensers 500, multiple condensers 500 are arranged in series or in parallel. Further optionally, in the low-grade heat source heat recovery system, there can be one or more superheaters, and multiple superheaters can be arranged in series or in parallel.

[0055] In this embodiment, by connecting multiple evaporators 100 in series, the heat exchange process surface between the heat transfer medium and the low-grade heat source can be extended, the degree of heat absorption of the heat transfer medium to the low-grade heat source can be deepened, the temperature of the low-grade heat source can be further reduced, and the heat recovery of the low-grade heat source can be increased. Similarly, by connecting multiple condensers 500 in series, the heat exchange process surface between the heat transfer medium and the substance to be heated or the heating medium can be extended, the degree of heating of the substance to be heated or the heating medium by the heat transfer medium can be deepened, the heating temperature can be further increased, and the utilization rate of the heat carried by the heat transfer medium can be improved. By connecting multiple compressors 400 in series, the heat transfer medium can be pressurized in multiple stages, the temperature and pressure of the heat transfer medium can be further increased, and the pressure of the heat transfer medium can meet the requirements of different heating temperatures. By connecting multiple superheaters in series, the superheating temperature of the heat transfer medium can be increased, so that the heat transfer medium remains in a gas phase and does not carry liquid heat transfer medium, avoiding liquid hammer phenomenon in the compressor 400.

[0056] In this embodiment, the heat exchange rate of the heat transfer medium can be increased by arranging multiple evaporators 100 in parallel and / or multiple condensers 500 in parallel; the compression rate of multiple heat transfer media can be increased by arranging multiple compressors 400 in parallel, thereby improving the overall heat recovery efficiency of the low-grade heat source heat recovery system. In addition, by arranging multiple evaporators 100 in parallel or multiple condensers 500 in parallel, it is also possible to utilize low-grade heat sources from different sources or provide high-grade heat for different heat uses.

[0057] As an optional embodiment, the heat transfer medium is selected from substituted or unsubstituted alkanes, heteroalkanes, olefins or heteroolefins having carbon atoms of 3 to 5. In this embodiment, the heteroalkanes contain at least one heteroatom different from carbon or hydrogen, and the heteroolefins contain at least one heteroatom different from carbon or hydrogen, and the heteroatom is preferably selected from halogen elements.

[0058] In the present application, the heat transfer medium can be a single-component substance or a multi-component mixture. Optionally, the heat transfer medium can be selected from alkanes, heteroalkanes, olefins or heteroolefins of C3, C4, C5, and C6. In the specific implementation process, a suitable heat transfer medium can be selected according to the temperature of the low-grade heat source, so that the heat transfer medium can be gasified after heat exchange with the low-grade heat source through the evaporator 100, so as to absorb more heat through the phase conversion of the heat carrier. For example, in the following embodiments of the present application, the heat transfer medium can be any one or more of propane, trichlorobutane, cyclobutane, n-pentane, n-pentene, trifluoropentene, and n-hexane.

[0059] In the field of petrochemical devices, the temperature of a general low-grade heat source is between 30°C and 90°C. In order to utilize the low-grade heat source in this temperature range, the heat transfer medium is made gaseous at 30°C to 90°C, so that the heat transfer medium can be vaporized during the heating process of the low-grade heat source at 30°C to 90°C to absorb the heat of the low-grade heat source. Furthermore, low-grade heat sources with a temperature higher than 60°C can be utilized in petrochemical devices, while low-grade heat sources with a temperature of 30°C to 60°C are difficult to utilize in petrochemical devices. In the present application, the heat transfer medium is made gaseous at 30°C to 90°C, preferably at 30°C to 60°C, so that the heat transfer medium can produce a gasification phase change when absorbing the temperature of the low-grade heat source, so that a large amount of heat can be absorbed from the low-grade heat source as phase change latent heat, so as to improve the recovery rate of the low-grade heat source.

[0060] In the low-grade heat source recovery system, the selection of heat transfer medium needs to be optimized and compared according to the temperature of the low-grade heat source. In the embodiment, when the temperature of the low-grade heat source is 40℃~70℃, the above-mentioned heat transfer medium of this application is selected. When recovering about 20MW of low-grade heat source, only 5MW of steam or electricity is needed, which can save 270,000 tons of steam consumption and 10.46 million tons of cooling water consumption per year, reduce carbon emissions by 84,000 tons, and reduce operating costs by 14.36 million yuan. When the temperature of the low-grade heat source is 20℃~40℃, the above-mentioned heat transfer medium of this application is selected. When recovering about 80MW of low-grade waste heat, only about 20MW of steam or electricity is needed, which can save 1.06 million tons of steam consumption, save 46.67 million tons of cooling water, reduce carbon emissions by 388,000 tons, and reduce operating costs by 59.65 million yuan.

[0061] As an optional implementation, at the outlet of the compressor 400, the temperature of the heat transfer medium is 80°C to 200°C.

[0062] In the field of petrochemical devices, the heating temperature generally required is above 80°C. In this embodiment, the temperature of the heat transfer medium reaches 80°C to 200°C through the heating and temperature raising treatment of the compressor 400, so that when the heat transfer medium releases the temperature through the condenser 500, the external heating temperature of the heat transfer medium can reach 80°C to 200°C to meet the heating temperature requirements of the petrochemical device. In the specific implementation process, the temperature of the heat transfer medium after being treated by the compressor 400 can be adjusted according to the heating temperature requirements of downstream users to achieve the purpose of providing different heating temperatures.

[0063] Embodiment 1

[0064] like Figure 1As shown, the low-grade heat source heat recovery system includes an evaporator 100, an intake buffer tank 200, a superheater 300, a compressor 400, a condenser 500, a discharge buffer tank 600 and a throttling expansion valve 700. The evaporator 100, the intake buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600 and the throttling expansion valve 700 are connected end to end in sequence, and the outlet of the discharge buffer tank 600 is also connected to the inlet of the intake buffer tank 200. A circulation loop is formed among the evaporator 100, the suction buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600 and the throttling expansion valve 700, in which a heat transfer medium circulates. At the same time, a heat source flow channel is provided in the evaporator 100 to circulate a low-grade heat source, and a heating flow channel is provided in the condenser 500 to circulate a heat exchange medium, so as to achieve the purpose of transferring heat in the low-grade heat source to the heat exchange medium, so that the temperature of the heat exchange medium reaches a preset use temperature.

[0065] Figure 1The arrow direction in the figure shows the flow direction of the heat transfer medium. The liquid phase heat transfer medium initially fed enters the evaporator 100. The liquid phase heat transfer medium exchanges heat with the low-grade heat source in the evaporator 100. The liquid phase heat transfer medium absorbs heat and vaporizes to generate gas phase heat transfer medium. The gas phase heat transfer medium carries a large amount of latent heat of phase change. The gas phase heat transfer medium enters the suction buffer tank 200, and the pressure of the gas phase heat transfer medium is buffered by the suction buffer tank 200. The gas phase heat transfer medium buffered by the suction buffer tank 200 enters the superheater, and is superheated by 5°C to 20°C in the superheater to ensure that the heat transfer medium is completely vaporized and enters the compressor 400 in a completely different form. The overheated gas phase heat transfer medium enters the compressor 400. Under the pressure-boosting effect of the compressor 400, the pressure and temperature of the gas phase heat transfer medium are increased to a suitable pressure and temperature according to the needs of the downstream heat exchange user, generating a high-temperature and high-pressure gas phase heat transfer medium. Here, the high temperature and high pressure refer to the gas phase heat transfer medium before entering the compressor 400. There is no specific pressure and temperature limit. The specific pressure and temperature can be adjusted according to the needs of the downstream heat exchange user. The high-temperature and high-pressure gas phase heat transfer medium enters the condenser 500 (user heat exchanger) to condense and release heat, and transfers the heat to the material or heating medium that needs to be heated. After the high-temperature and high-pressure gas phase heat transfer medium is heat exchanged in the condenser 500, it generates a liquid phase heat transfer medium or a liquid phase and gas phase mixed heat transfer medium, thereby replacing the original steam / saturated steam with the heat transfer medium as the heat medium of the condenser 500 (for the heat exchanger), reducing the consumption of steam / saturated steam by the petrochemical device. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 enters the discharge buffer tank 600, and the flow and pressure are balanced under the action of the discharge buffer tank 600. The heat transfer medium after passing through the discharge buffer tank 600 enters the throttling expansion valve 700 for decompression and partial vaporization, and then the partially vaporized liquid phase heat transfer medium after decompression enters the evaporator 100 to absorb heat and vaporize, forming a cycle; at the same time, when the gas content in the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 is relatively high, part of the heat transfer medium after passing through the discharge buffer tank 600 can also bypass the throttling expansion valve 700 and the evaporator 100 and directly enter the suction tank for the next cycle.

[0066] Embodiment 2

[0067] like Figure 2 As shown, the low-grade heat source heat recovery system includes an evaporator 100, a suction buffer tank 200, a superheater 300, a compressor 400, a condenser 500, a discharge buffer tank 600, a hydraulic turbine 800 and a gas-liquid separator 900.

[0068] The evaporator 100, the suction buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600, the hydraulic turbine 800 and the gas-liquid separator 900 are connected end to end in sequence, and the gas outlet of the gas-liquid separator 900 is also connected to the inlet of the superheater, and a circulation loop is formed among the evaporator 100, the suction buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600, the hydraulic turbine 800 and the gas-liquid separator 900, and a heat transfer medium circulates in the circulation loop. At the same time, a heat source flow channel is provided in the evaporator 100 to circulate a low-grade heat source, and a heating flow channel is provided in the condenser 500 to circulate a heating medium.

[0069] Figure 2The arrow direction in the figure shows the flow direction of the heat transfer medium. The liquid phase heat transfer medium initially fed enters the evaporator 100. The liquid phase heat transfer medium exchanges heat with the low-grade heat source in the evaporator 100. The liquid phase heat transfer medium absorbs heat and vaporizes to generate a gas phase heat transfer medium. The gas phase heat transfer medium carries a large amount of latent heat of phase change. The gas phase heat transfer medium enters the suction buffer tank 200, and the pressure of the gas phase heat transfer medium is buffered by the suction buffer tank 200. The gas phase heat transfer medium buffered by the suction buffer tank 200 enters the superheater, and is superheated by 5°C to 20°C in the superheater to ensure that the heat transfer medium is completely vaporized and enters the compressor 400 in a completely different form. The superheated gas phase heat transfer medium enters the compressor 400. Under the pressure-boosting effect of the compressor 400, the pressure and temperature of the gas phase heat transfer medium are increased to a suitable pressure and a suitable temperature according to the needs of the downstream heat exchange user, and a high temperature and high pressure gas phase heat transfer medium is generated. Here, the high temperature and high pressure are relative to the gas phase heat transfer medium before entering the compressor 400, and there is no specific pressure and temperature limit. The high-temperature, high-pressure gaseous heat transfer medium enters the condenser 500 (user heat exchanger) to condense and release heat, and transfers the heat to the substance or heating medium that needs to be heated. The high-temperature, high-pressure heat transfer medium generates a liquid heat transfer medium or a liquid-gas mixed heat transfer medium, thereby replacing the original steam / saturated steam with the heat transfer medium as the heat medium of the condenser 500 (for the heat exchanger), reducing the consumption of steam / saturated steam in the petrochemical plant. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 enters the hydraulic turbine 800, so that the hydraulic turbine 800 converts the residual pressure of the liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium into mechanical energy to perform external work, thereby reducing the vaporization rate of the heat transfer medium and reducing the energy consumption of the device, and can be further converted into electricity for utilization, thereby further saving energy and reducing consumption; the liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the hydraulic turbine 800 enters the gas-liquid separator 900, and is separated into gas and liquid by the gas-liquid separator 900, so that the liquid phase heat transfer medium enters the evaporator 100 to absorb heat and vaporize, thus forming a cycle; at the same time, the gas phase heat transfer medium after the gas-liquid separation by the gas-liquid separator 900 bypasses the evaporator 100 and directly enters the superheater for the next cycle.

[0070] Embodiment 3

[0071] like Figure 3As shown, the low-grade heat source heat recovery system includes an evaporator 100, an intake buffer tank 200, a superheater 300, a compressor 400, a condenser 500, a discharge buffer tank 600, a hydraulic turbine 800, a gas-liquid separator 900 and a throttling expansion valve 700. The evaporator 100, the intake buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600, the hydraulic turbine 800 and the throttling expansion valve 700 are connected end to end in sequence, and the inlet, liquid outlet and gas outlet of the gas-liquid separator 900 are respectively connected to the hydraulic turbine 800, the throttling expansion valve 700 and the intake buffer tank 200. A circulation loop is formed between the evaporator 100, the suction buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600, the hydraulic turbine 800 and the throttling expansion valve 700. A heat transfer medium flows in the circulation loop, and the gas phase heat transfer medium is diverted to the suction buffer tank 200 through the gas-liquid separator 900. At the same time, a heat source flow channel is provided in the evaporator 100 to circulate a low-grade heat source, and a heating flow channel is provided in the condenser 500 to circulate a heated medium, so as to achieve the purpose of transferring heat in the low-grade heat source to the heated medium, so that the temperature of the heated medium reaches a preset use temperature.

[0072] Figure 3The arrow direction in the figure shows the flow direction of the heat transfer medium. The liquid phase heat transfer medium initially fed enters the evaporator 100. The liquid phase heat transfer medium exchanges heat with the low-grade heat source in the evaporator 100. The liquid phase heat transfer medium absorbs heat and vaporizes to generate gas phase heat transfer medium. The gas phase heat transfer medium carries a large amount of latent heat of phase change. The gas phase heat transfer medium enters the suction buffer tank 200, and the pressure of the gas phase heat transfer medium is buffered by the suction buffer tank 200. The gas phase heat transfer medium buffered by the suction buffer tank 200 enters the superheater, and is superheated by 5°C to 20°C in the superheater to ensure that the heat transfer medium is completely vaporized and enters the compressor 400 in a completely different form. The overheated gas phase heat transfer medium enters the compressor 400. Under the pressure-boosting effect of the compressor 400, the pressure and temperature of the gas phase heat transfer medium are increased to a suitable pressure and temperature according to the needs of the downstream heat exchange user, generating a high-temperature and high-pressure gas phase heat transfer medium. Here, the high temperature and high pressure refer to the gas phase heat transfer medium before entering the compressor 400. There is no specific pressure and temperature limit. The specific pressure and temperature can be adjusted according to the needs of the downstream heat exchange user. The high-temperature and high-pressure gas phase heat transfer medium enters the condenser 500 (user heat exchanger) to condense and release heat, and transfers the heat to the material or heating medium that needs to be heated. After the high-temperature and high-pressure gas phase heat transfer medium is heat exchanged in the condenser 500, it generates a liquid phase heat transfer medium or a liquid phase and gas phase mixed heat transfer medium, thereby replacing the original steam / saturated steam with the heat transfer medium as the heat medium of the condenser 500 (for the heat exchanger), reducing the consumption of steam / saturated steam by the petrochemical device. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 enters the discharge buffer tank 600, and the flow and pressure are balanced under the action of the discharge buffer tank 600. The heat transfer medium after passing through the discharge buffer tank 600 enters the energy-saving turbine 800, so that the hydraulic turbine 800 converts the residual pressure of the liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium into mechanical energy to do external work, thereby reducing the vaporization rate of the heat transfer medium and reducing the energy consumption of the device. It can also be further converted into electricity for utilization, thereby further saving energy and reducing consumption. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the hydraulic turbine 800 enters the gas-liquid separator 900, and is separated into gas and liquid by the gas-liquid separator 900, so that the liquid phase heat transfer medium enters the evaporator 100 to absorb heat and vaporize, thus forming a cycle. At the same time, the gas phase heat transfer medium after the gas-liquid separation by the gas-liquid separator 900 bypasses the evaporator 100 and directly enters the suction buffer tank for the next cycle.

[0073] Embodiment 4

[0074] like Figure 4 As shown, the low-grade heat source heat recovery system of Example 4 is different from that of Example 3 in that the compressor 400 includes two sections, the first section 410 of the compressor and the second section 420 of the compressor are connected in sequence, and the outlet of the gas-liquid separator 900 is connected to the inlet of the second section 420 of the compressor.

[0075] Figure 4 The arrow direction in the figure shows the flow direction of the heat transfer medium. The liquid phase heat transfer medium initially fed enters the evaporator 100. The liquid phase heat transfer medium exchanges heat with the low-grade heat source in the evaporator 100. The liquid phase heat transfer medium absorbs heat and vaporizes to generate gas phase heat transfer medium. The gas phase heat transfer medium carries a large amount of latent heat of phase change. The gas phase heat transfer medium enters the suction buffer tank 200, and the pressure of the gas phase heat transfer medium is buffered by the suction buffer tank 200. The gas phase heat transfer medium buffered by the suction buffer tank 200 enters the superheater, and is superheated by 5°C to 20°C in the superheater to ensure that the heat transfer medium is completely vaporized and enters the compressor 400 in a completely different form. The overheated gas phase heat transfer medium enters the compressor 400. Under the pressure-boosting effect of the compressor 400, the pressure and temperature of the gas phase heat transfer medium are increased to a suitable pressure and temperature according to the needs of the downstream heat exchange user, generating a high-temperature and high-pressure gas phase heat transfer medium. Here, the high temperature and high pressure refer to the gas phase heat transfer medium before entering the compressor 400. There is no specific pressure and temperature limit. The specific pressure and temperature can be adjusted according to the needs of the downstream heat exchange user. The high-temperature and high-pressure gas phase heat transfer medium enters the condenser 500 (user heat exchanger) to condense and release heat, and transfers the heat to the material or heating medium that needs to be heated. After the high-temperature and high-pressure gas phase heat transfer medium is heat exchanged in the condenser 500, it generates a liquid phase heat transfer medium or a liquid phase and gas phase mixed heat transfer medium, thereby replacing the original steam / saturated steam with the heat transfer medium as the heat medium of the condenser 500 (for the heat exchanger), reducing the consumption of steam / saturated steam by the petrochemical device. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 enters the discharge buffer tank 600, and the flow and pressure are balanced under the action of the discharge buffer tank 600. The heat transfer medium after passing through the discharge buffer tank 600 enters the hydraulic turbine 800, so that the hydraulic turbine 800 converts the residual pressure of the liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium into mechanical energy to do external work, thereby reducing the gasification rate of the heat transfer medium, reducing the energy consumption of the device, and can be further converted into electricity for use, further Energy saving and consumption reduction; after passing through the hydraulic turbine 800, the liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium enters the gas-liquid separator 900, and is separated into gas and liquid by the gas-liquid separator 900, so that the liquid phase heat transfer medium enters the evaporator 100 to absorb heat and vaporize, thus forming a cycle; at the same time, the gas phase heat transfer medium after gas-liquid separation by the gas-liquid separator 900 bypasses the evaporator 100, the suction buffer tank 200, the superheater 300 and the first stage 410 of the compressor, and directly enters the second stage 420 of the compressor to enter the next cycle.

[0076] Embodiment 5

[0077] like Figure 5As shown, the low-grade heat source heat recovery system includes an evaporator 100, an intake buffer tank 200, a superheater 300, a first section 410 of a compressor, a second section 420 of a compressor, a condenser 500, a discharge buffer tank 600, a second throttling expansion valve 710, a second throttling expansion valve 720 and a gas-liquid separator 900. The evaporator 100, the intake buffer tank 200, the superheater 300, the first section 410 of a compressor, the second section 420 of a compressor, the condenser 500, the discharge buffer tank 600, the first throttling expansion valve 710 and the second throttling expansion valve 720 are connected end to end in sequence, and the inlet, the liquid outlet and the gas outlet of the gas-liquid separator 900 are connected to the second throttling expansion valve, the first throttling expansion valve and the compressor, respectively. The second section of the compressor is connected, and a circulation loop is formed among the evaporator 100, the suction buffer tank 200, the superheater 300, the first section 410 of the compressor, the second section 420 of the compressor, the condenser 500, the discharge buffer tank 600, the second throttling expansion valve 720 and the first throttling expansion valve 710. A heat transfer medium flows in the circulation loop, and the gas phase heat transfer medium is diverted to the second section 420 of the compressor through the gas-liquid separator 900. At the same time, a heat source flow channel is provided in the evaporator 100 to circulate a low-grade heat source, and a heating flow channel is provided in the condenser 500 to circulate a heated medium, so as to achieve the purpose of transferring heat in the low-grade heat source to the heated medium, so that the temperature of the heated medium reaches a preset use temperature. At the same time, the outlet of the discharge buffer tank 600 is also connected to the inlet of the suction buffer tank 200, forming a circulation loop among the evaporator 100, the suction buffer tank 200, the superheater 300, the compressor 400, the condenser 500, the discharge buffer tank 600 and the throttling expansion valve 700. A heat transfer medium circulates in the circulation loop. At the same time, a heat source flow channel is provided in the evaporator 100 to circulate a low-grade heat source, and a heating flow channel is provided in the condenser 500 to circulate a heat exchange medium, so as to achieve the purpose of transferring heat in the low-grade heat source to the heat exchange medium, so that the temperature of the heat exchange medium reaches a preset use temperature.

[0078] Figure 1The arrow direction in the figure shows the flow direction of the heat transfer medium. The liquid phase heat transfer medium initially fed enters the evaporator 100. The liquid phase heat transfer medium exchanges heat with the low-grade heat source in the evaporator 100. The liquid phase heat transfer medium absorbs heat and vaporizes to generate gas phase heat transfer medium. The gas phase heat transfer medium carries a large amount of latent heat of phase change. The gas phase heat transfer medium enters the suction buffer tank 200, and the pressure of the gas phase heat transfer medium is buffered by the suction buffer tank 200. The gas phase heat transfer medium buffered by the suction buffer tank 200 enters the superheater, and is superheated by 5°C to 20°C in the superheater to ensure that the heat transfer medium is completely vaporized and enters the compressor 400 in a completely different form. The overheated gas phase heat transfer medium enters the compressor 400. Under the pressure-boosting effect of the compressor 400, the pressure and temperature of the gas phase heat transfer medium are increased to a suitable pressure and temperature according to the needs of the downstream heat exchange user, generating a high-temperature and high-pressure gas phase heat transfer medium. Here, the high temperature and high pressure refer to the gas phase heat transfer medium before entering the compressor 400. There is no specific pressure and temperature limit. The specific pressure and temperature can be adjusted according to the needs of the downstream heat exchange user. The high-temperature and high-pressure gas phase heat transfer medium enters the condenser 500 (user heat exchanger) to condense and release heat, and transfers the heat to the material or heating medium that needs to be heated. After the high-temperature and high-pressure gas phase heat transfer medium is heat exchanged in the condenser 500, it generates a liquid phase heat transfer medium or a liquid phase and gas phase mixed heat transfer medium, thereby replacing the original steam / saturated steam with the heat transfer medium as the heat medium of the condenser 500 (for the heat exchanger), reducing the consumption of steam / saturated steam by the petrochemical device. The liquid phase heat transfer medium or the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 enters the discharge buffer tank 600, and the flow and pressure are balanced under the action of the discharge buffer tank 600. The heat transfer medium after passing through the discharge buffer tank 600 enters the throttling expansion valve 700 for decompression and partial vaporization, and then the partially vaporized liquid phase heat transfer medium after decompression enters the evaporator 100 to absorb heat and vaporize, forming a cycle; at the same time, when the gas content in the liquid phase and gas phase mixed heat transfer medium after passing through the condenser 500 is relatively high, part of the heat transfer medium after passing through the discharge buffer tank 600 can also bypass the throttling expansion valve 700 and the evaporator 100 and directly enter the suction tank for the next cycle.

[0079] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0080] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0081] It should be noted that all directional indications in the embodiments of the present application are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0082] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0083] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0084] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0085] In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0086] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A low-grade heat source heat recovery system, characterized in that: The low-grade heat source heat recovery system comprises an evaporator, a compressor, a condenser and a throttling expansion valve or a hydraulic turbine which are connected in sequence, and the throttling expansion valve or the hydraulic turbine is also connected to the evaporator to form a circulation loop between the evaporator, the compressor, the condenser and the throttling expansion valve or the hydraulic turbine, and the circulation loop is used to circulate a heat transfer medium, wherein the heat transfer medium evaporates by heat exchange with the low-grade heat source through the evaporator, and the heat transfer medium releases heat through the condenser; the saturation temperature of the heat transfer medium at the inlet of the compressor is 20°C~90°C, the saturation temperature of the heat transfer medium at the outlet of the compressor is 80°C~200°C, and the temperature of the low-grade heat source is 30°C~90°C; the low-grade heat The source is low-temperature water produced in the petrochemical industry; a discharge buffer tank is provided between the condenser and the throttling expansion valve or the hydraulic turbine; a suction buffer tank is provided between the evaporator and the compressor; a superheater is provided between the suction buffer tank and the inlet of the compressor, and the superheater makes the superheat temperature of the heat transfer medium 5°C~20°C; a gas-liquid separator is provided between the condenser or the discharge buffer tank and the throttling expansion valve, or a gas-liquid separator is provided between the hydraulic turbine and the evaporator; the gas outlet of the gas-liquid separator is connected to any one of the inlet of the suction buffer tank, the inlet of the superheater, and the air inlet end of the compressor; the liquid outlet of the gas-liquid separator is connected to the inlet of the throttling expansion valve or the inlet of the evaporator.

2. The low-grade heat source heat recovery system according to claim 1, characterized in that: The compressor has 2 to 5 sections, and the gas outlet of the gas-liquid separator is communicated with the inlet of any one of the second to fifth sections of the compressor.

3. The low-grade heat source heat recovery system according to claim 1, characterized in that: The hydraulic turbine also provides mechanical driving force into or outside the low-grade heat recovery system.

4. The low-grade heat source heat recovery system according to claim 1, characterized in that: In the low-grade heat source heat recovery system, the evaporator, the compressor, and the condenser can be one or more respectively; when there are multiple evaporators, the multiple evaporators are arranged in series or in parallel; when there are multiple compressors, the multiple compressors are arranged in series or in parallel; when there are multiple condensers, the multiple condensers are arranged in series or in parallel.

5. The low-grade heat source heat recovery system according to any one of claims 1 to 4, characterized in that: The heat transfer medium is selected from substituted or unsubstituted alkanes, heteroalkanes, olefins or heteroolefins having 3 to 6 carbon atoms.

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