Medium-temperature waste heat recovery system combining resident heating and cascade organic Rankine cycle and operation method

Abstract

The invention discloses a medium-temperature waste heat recovery system combining resident heating and cascade organic Rankine cycle and an operation method. The system comprises a medium-temperature waste heat distribution unit, a heating unit, a first-stage organic Rankine cycle power generation unit, a second-stage organic Rankine cycle power generation unit and a wetland restoration system. Medium-temperature waste heat resources are divided into two parts to be recycled, one part is used for supplying heat to residents by heating heating water, and the other part serves as a heat source to drive a cascade organic Rankine cycle system to generate power. The maximum cycle heat efficiency and # imgabs0 # efficiency of the cascade organic Rankine cycle can be realized by optimizing the running parameters of the circulating organic working medium; heating return water is used for preheating the organic Rankine cycle system in combination with heating parameters of residents in China, so that the comprehensive energy efficiency of the system is further improved; the cooling water flow of the organic Rankine cycle system is optimized in combination with heat using scenes such as wetland restoration, the proper cooling water outlet temperature is obtained, and the waste heat recovery of the system is maximized.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste heat recovery and utilization, and specifically relates to a medium-temperature waste heat recovery system and an operation method combining residential heating with a cascade organic Rankine cycle. Background Art

[0002] With the increase in energy demand, how to efficiently utilize energy, especially the recovery of waste heat in industrial processes, has become increasingly important. Waste heat utilization technology is an effective means to improve power generation efficiency and reduce operating energy consumption. At the same time, the waste heat recovery system is also an important part of the integrated flue gas pollutant treatment system. Therefore, vigorously developing waste heat utilization technology is of great significance to improving energy utilization efficiency and reducing energy costs. At present, the waste heat recovery system based on the organic Rankine cycle has the problem of a small coverage temperature range and the inability to effectively recover and utilize waste heat in the medium and low temperature sections; and the medium and low temperature waste heat resources are mostly recovered and utilized as heat sources for power generation, and are rarely recovered in combination with low-temperature heat scenarios such as residential heating; the waste heat recovery means are single, and it is not possible to effectively form a cascade utilization of waste heat resources. Summary of the invention

[0003] In order to solve the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a medium-temperature waste heat recovery system and operation method combining residential heating and cascade organic Rankine cycle, so as to improve the utilization of waste heat in different temperature ranges, thereby enhancing the comprehensiveness of waste heat utilization and providing possibility for large-scale development of waste heat recovery and utilization.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A medium-temperature waste heat recovery system combining residential heating and a cascade organic Rankine cycle, characterized in that it includes a medium-temperature waste heat distribution unit, a heating unit, a first-stage organic Rankine cycle power generation unit, a second-stage organic Rankine cycle power generation unit and a wetland restoration system; the outlet end of the medium-temperature waste heat distribution unit is respectively connected to the waste heat inlet end of the heating water heater of the heating unit and to the waste heat inlet end of the first evaporator of the first-stage organic Rankine cycle power generation unit; the wetland restoration system is respectively connected to the first condenser of the first-stage organic Rankine cycle power generation unit and the second condenser of the second-stage organic Rankine cycle power generation unit.

[0006] The heating unit includes a heating return water collector, a heating water heater and a residential heating system; the cold water passing through the heating return water collector exchanges heat with the waste heat from the medium-temperature waste heat distribution unit through the heating water heater, and then enters the residential heating system to realize heating, and the heating return water with a certain temperature enters the first-stage organic Rankine cycle power generation unit and the second-stage organic Rankine cycle power generation unit respectively to preheat the organic working fluid, and then returns to the heating return water collector.

[0007] Preferably, the heating water heater is a plate heater.

[0008] Preferably, the first-stage organic Rankine cycle power generation unit includes a first evaporator, a first expander, a first condenser, a first liquid storage tank, a first circulating working fluid pump, a first preheater, and a first generator; the cold side of the first evaporator, the first expander, the hot side of the first condenser, the first liquid storage tank, the first circulating working fluid pump and the cold side of the first preheater are connected in sequence to form a first-stage organic working fluid circulation loop; the first expander is connected to the first generator through a shaft connector to form a first expander generator set, the waste heat energy side inlet of the first evaporator is connected to the medium-temperature waste heat distribution unit, the low-temperature fluid side of the first condenser is externally connected to the tap water supply end, and the heated cooling water is connected to the wetland restoration system.

[0009] Preferably, the second-stage organic Rankine cycle power generation unit includes a second evaporator, a second expander, a second condenser, a second liquid storage tank, a second circulating working fluid pump, a second preheater, and a second generator; the second evaporator cold side, the second expander, the second condenser hot side, the second liquid storage tank, the second circulating working fluid pump and the second preheater cold side are connected in sequence to form a second-stage organic working fluid circulation loop; the second expander is connected to the second generator through a shaft connector to form a second expander generator set, the second evaporator waste heat energy side inlet is connected to the first evaporator hot side of the first-stage organic Rankine cycle power generation unit, the second condenser low-temperature fluid side is externally connected to the tap water supply end, and the heated cooling water is connected to the wetland restoration system.

[0010] Further preferably, the first-stage organic Rankine cycle power generation unit uses propane as the circulating working fluid; the second-stage organic Rankine cycle power generation unit uses R134a as the circulating working fluid; the first evaporator, the first preheater, the second evaporator, and the second preheater all use plate heaters; the first expander and the second expander both use screw expanders.

[0011] The present invention also discloses an operating method of a medium-temperature waste heat recovery system combining residential heating and a cascade organic Rankine cycle based on the above-mentioned method. After the waste heat energy is distributed in the medium-temperature waste heat distribution unit, one stream of waste heat energy enters the heating unit to realize residential heating; another stream of waste heat energy enters the hot side of the first evaporator of the first-stage organic Rankine cycle power generation unit to heat the organic working fluid to realize power generation, and the waste heat energy at the outlet of the hot side of the first evaporator enters the hot side of the second evaporator of the second-stage organic Rankine cycle power generation unit to heat the organic working fluid to realize power generation; the heating return water at the outlet of the residential heating system in the heating unit respectively enters the hot side of the first preheater of the first-stage organic Rankine cycle power generation unit and the hot side of the second preheater of the second-stage organic Rankine cycle power generation unit to preheat the organic working fluid; the cooling water via the first condenser and the second condenser is connected to the wetland restoration system to realize energy cascade utilization.

[0012] Preferably, the medium-temperature waste heat temperature ranges from 150 to 200°C; the outlet heating water temperature of the heating water heater is 60 to 80°C; the inlet temperature of the heating return water of the first preheater and the second preheater is 40 to 60°C; the inlet temperature of the waste heat energy of the second evaporator is 100 to 130°C. The outlet cooling water temperature of the first condenser and the second condenser is 30 to 35°C.

[0013] The advantages of the above system and operation method of the present invention are: first, the cascade organic Rankine cycle can be used to recycle waste heat at different temperatures, ensuring efficient recovery of waste heat. Second, waste heat energy can be distributed in a timely manner according to the difference between heating demand and power generation demand, achieving a better cogeneration ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the structure of a medium-temperature waste heat recovery system combining residential heating and a cascade organic Rankine cycle provided by the present invention.

[0015] In the figure: 1. Medium-temperature waste heat distribution unit; 2. Heating unit; 201. Heating return water collector; 202. Heating water heater; 203. and residential heating system; 3. First-stage organic Rankine cycle power generation unit; 301. First evaporator; 302. First expander; 303. First condenser; 304. First liquid storage tank; 305. First circulating working fluid pump; 306. First preheater; 307. First generator; 4. Second-stage organic Rankine cycle power generation unit; 401. Second evaporator; 402. Second expander; 403. Second condenser; 404. Second liquid storage tank; 405. Second circulating working fluid pump; 406. Second preheater; 407. Second generator; 5. Wetland restoration system. DETAILED DESCRIPTION

[0016] Combination Figure 1 The present invention discloses a medium-temperature waste heat recovery system combining residential heating with a cascade organic Rankine cycle, comprising five subsystems: a medium-temperature waste heat distribution unit 1, a heating unit 2, a first-stage organic Rankine cycle power generation unit 3, a second-stage organic Rankine cycle power generation unit 4, and a wetland restoration system 5. The outlet end of the medium-temperature waste heat distribution unit 1 is respectively connected to the waste heat inlet end of the heating water heater 202 of the heating unit 2 and to the waste heat inlet end of the first evaporator 301 of the first-stage organic Rankine cycle power generation unit 3; the wetland restoration system 5 is respectively connected to the first condenser 303 of the first-stage organic Rankine cycle power generation unit 3 and the second condenser 403 of the second-stage organic Rankine cycle power generation unit 4.

[0017] The heating unit 2 includes a heating return water collector 201, a heating water heater 202 and a residential heating system 203; the cold water passing through the heating return water collector 201 exchanges heat with the waste heat from the medium-temperature waste heat distribution unit 1 through the heating water heater 202, and then enters the residential heating system 203 to achieve heating, and the heating return water containing a certain temperature enters the first-stage organic Rankine cycle power generation unit 3 and the second-stage organic Rankine cycle power generation unit 4 respectively to preheat the organic working medium, and then returns to the heating return water collector 201.

[0018] The heating water heater 202 adopts a plate heater. The plate heat exchanger has the characteristics of compact structure and high heat transfer efficiency, and is suitable for small heat exchange scenarios such as ORC power generation systems.

[0019] The first-stage organic Rankine cycle power generation unit 3 includes a first evaporator 301, a first expander 302, a first condenser 303, a first liquid storage tank 304, a first circulating working fluid pump 305, a first preheater 306, and a first generator 307; the cold side of the first evaporator 301, the first expander 302, the hot side of the first condenser 303, the first liquid storage tank 304, the first circulating working fluid pump 305 and the cold side of the first preheater 306 are connected in sequence to form a first-stage organic working fluid circulation loop; the first expander 302 is connected to the first generator 307 through a shaft connector to form a first expander generator set, the waste heat energy side inlet of the first evaporator 301 is connected to the medium-temperature waste heat distribution unit 1, the low-temperature fluid side of the first condenser 303 is externally connected to the tap water supply end, and the heated cooling water is connected to the wetland restoration system 5, so that the low-temperature thermal energy is applied to the ecological and environmental protection industry, realizing the cascade utilization of low-temperature thermal energy and enriching the heat use scenario.

[0020] The second-stage organic Rankine cycle power generation unit 4 includes a second evaporator 401, a second expander 402, a second condenser 403, a second liquid storage tank 404, a second circulating working fluid pump 405, a second preheater 406, and a second generator 407; the second evaporator 408 cold side, the second expander 402, the second condenser 403 hot side, the second liquid storage tank 404, the second circulating working fluid pump 405 and the second preheater 406 cold side are connected in sequence to form a second-stage organic working fluid circulation loop; the second expander 402 is connected to the second generator 407 through a shaft connector to form a second expander generator set, the waste heat energy side inlet of the second evaporator 401 is connected to the hot side of the first evaporator 301 of the first-stage organic Rankine cycle power generation unit 3, the low-temperature fluid side of the second condenser 403 is externally connected to the tap water supply end, and the heated cooling water is connected to the wetland restoration system 5, so that the low-temperature thermal energy is applied to the ecological and environmental protection industry, realizing the cascade utilization of low-temperature thermal energy and enriching the heat use scenario.

[0021] The first-stage organic Rankine cycle power generation unit 3 uses propane as the circulating working fluid. Propane has good thermodynamic properties, moderate latent heat of vaporization, low boiling point, ideal critical temperature and pressure, and can achieve efficient energy conversion in the organic Rankine cycle; and propane has good environmental characteristics, low raw material cost, and reasonable operating cost. The second-stage organic Rankine cycle power generation unit 4 uses R134a as the circulating working fluid. R134a is friendly to the ecological environment, with a critical temperature of 101.1℃, and is suitable for low-temperature heat source power generation systems; it has good thermal conductivity and specific heat capacity, which is conducive to improving the efficiency of the entire heat exchange system; it has high chemical stability, good compatibility with common materials, and will not cause metal corrosion and other phenomena; R134a is a non-flammable refrigerant with low toxicity and good safety. The first evaporator 301, the first preheater 306, the second evaporator 401, and the second preheater 406 all use plate heaters. The plate heat exchanger has the characteristics of compact structure and high heat transfer efficiency, and is suitable for small heat exchange scenarios such as ORC power generation systems. The first expander 302 and the second expander 402 are both screw expanders. The screw expander is simple and compact, has high operational reliability, is adaptable to a variety of working fluids and working conditions, has an isentropic efficiency that can usually reach 60%-80%, and is easy to maintain and overhaul.

[0022] The present invention discloses an operation method of a medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle. In combination with the demand for combined heat and power generation, the medium-temperature waste heat distribution unit 1 distributes waste heat energy of 150-200°C. One waste heat energy enters the heating unit 2 to heat the heating water to 60-80°C to achieve heating for residents; the other waste heat energy enters the first-stage evaporator 301 of the first-stage organic Rankine cycle power generation unit 3 to heat the organic working fluid, realize heat-work conversion and generate electricity, and the waste heat energy after heat exchange is reduced to 100-130 ℃, connected to the hot side of the second-stage evaporator 401 of the second-stage organic Rankine cycle power generation unit 4, to heat the organic working medium to generate electricity; the heating return water in the heating unit 2 is respectively connected to the hot sides of the first-stage preheater 306 of the first-stage organic Rankine cycle power generation unit 3 and the second-stage preheater 406 of the second-stage organic Rankine cycle power generation unit 4, so as to preheat the organic working medium; the outlet cooling water of the first condenser 303 and the second-stage condenser 403 is connected to the wetland restoration system 5, which is used in heat-using scenarios such as wetland restoration to realize energy cascade utilization.

[0023] The medium-temperature waste heat temperature ranges from 150 to 200°C; the outlet heating water temperature of the heating water heater 202 is 60 to 80°C; the inlet temperature of the heating return water of the first preheater 306 and the second preheater 406 is 40 to 60°C; the inlet temperature of the waste heat energy of the second evaporator 401 is 100 to 130°C. The outlet cooling water temperature of the first condenser 303 and the second condenser 403 is 30 to 35°C. The water source at this temperature can be used for low-temperature heat use scenarios such as wetland restoration, realizing the cascade recovery and utilization of energy, and enriching the heat use scenarios under low-temperature conditions.

[0024] The present invention divides the medium-temperature waste heat resources into two parts for recycling. One part is used to heat the heating water for heating the residents, and the other part is used as a heat source to drive the cascade organic Rankine cycle system to generate electricity. By optimizing the operating parameters of the circulating organic working fluid, the maximum cycle thermal efficiency and efficiency; combined with my country's residential heating parameters, the organic Rankine cycle system is preheated with heating return water to further improve the system's overall energy efficiency; combined with heat use scenarios such as wetland restoration, the cooling water flow of the organic Rankine cycle system is optimized to obtain a suitable cooling water outlet temperature and maximize the system's waste heat recovery.

Claims

1. A medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle, characterized in that: The invention comprises a medium-temperature waste heat distribution unit (1), a heating unit (2), a first-stage organic Rankine cycle power generation unit (3), a second-stage organic Rankine cycle power generation unit (4) and a wetland restoration system (5); the outlet end of the medium-temperature waste heat distribution unit (1) is respectively connected to the waste heat inlet end of the heating water heater (202) of the heating unit (2) and the waste heat inlet end of the first evaporator (301) of the first-stage organic Rankine cycle power generation unit (3); the wetland restoration system (5) is respectively connected to the first condenser (303) of the first-stage organic Rankine cycle power generation unit (3) and the second condenser (403) of the second-stage organic Rankine cycle power generation unit (4).

2. A medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle according to claim 1, characterized in that: The heating unit (2) comprises a heating return water collector (201), a heating water heater (202) and a residential heating system (203); cold water passing through the heating return water collector (201) exchanges heat with waste heat energy from a medium-temperature waste heat distribution unit (1) through the heating water heater (202), and then enters the residential heating system (203) to achieve heating; the heating return water containing a certain temperature enters the first-stage organic Rankine cycle power generation unit (3) and the second-stage organic Rankine cycle power generation unit (4) respectively to preheat the organic working medium, and then returns to the heating return water collector (201).

3. A medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle according to claim 2, characterized in that: The heating water heater (202) is a plate-type heater.

4. The medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle according to claim 1, characterized in that: The first-stage organic Rankine cycle power generation unit (3) comprises a first evaporator (301), a first expander (302), a first condenser (303), a first liquid storage tank (304), a first circulating working fluid pump (305), a first preheater (306) and a first generator (307); the cold side of the first evaporator (301), the first expander (302), the hot side of the first condenser (303), the first liquid storage tank (304), the first circulating working fluid pump (305) and the cold side of the first preheater (306) are sequentially connected to form a first-stage organic working fluid circulation loop; the first expander (302) is connected to the first generator (307) via a shaft connector to form a first expander generator set, the waste heat energy side inlet of the first evaporator (301) is connected to the medium-temperature waste heat distribution unit (1), the low-temperature fluid side of the first condenser (303) is externally connected to a tap water supply end, and the heated cooling water is connected to the wetland restoration system (5).

5. The medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle according to claim 1, characterized in that: The second-stage organic Rankine cycle power generation unit (4) comprises a second evaporator (401), a second expander (402), a second condenser (403), a second liquid storage tank (404), a second circulating working fluid pump (405), a second preheater (406) and a second generator (407); the second evaporator (401) cold side, the second expander (402), the second condenser (403) hot side, the second liquid storage tank (404), the second circulating working fluid pump (405) and the second preheater (406) cold side are sequentially connected to form a second-stage organic working fluid circulation loop; the second expander (402) is connected to the second generator (407) via a shaft connector to form a second expander generator set; the waste heat energy side inlet of the second evaporator (401) is connected to the hot side of the first evaporator (301) of the first-stage organic Rankine cycle power generation unit (3); the low-temperature fluid side of the second condenser (403) is externally connected to a tap water supply end, and the heated cooling water is connected to the wetland restoration system (5).

6. A medium-temperature waste heat recovery system combining residential heating and cascade organic Rankine cycle according to claim 5, characterized in that: The first-stage organic Rankine cycle power generation unit (3) uses propane as a circulating working fluid; the second-stage organic Rankine cycle power generation unit (4) uses R134a as a circulating working fluid; the first evaporator (301), the first preheater (306), the second evaporator (401), and the second preheater (406) all use plate heaters; and the first expander (302) and the second expander (402) both use screw expanders.

7. The method for operating a medium-temperature waste heat recovery system combining residential heating and a cascade organic Rankine cycle according to any one of claims 1 to 6, characterized in that: After the waste heat energy is distributed in the medium-temperature waste heat distribution unit (1), one stream of waste heat energy enters the heating unit (2) to heat the heating water to provide heating for residents; another stream of waste heat energy enters the hot side of the first evaporator (301) of the first-stage organic Rankine cycle power generation unit (3) to heat the organic working fluid to generate electricity; the waste heat energy at the hot side outlet of the first evaporator (301) enters the hot side of the second evaporator (01) of the second-stage organic Rankine cycle power generation unit (4) to heat the organic working fluid to generate electricity; the heating return water at the outlet of the residential heating system (203) in the heating unit (2) respectively enters the first-stage organic Rankine cycle power generation unit (3) and the second-stage organic Rankine cycle power generation unit (4) to preheat the organic working fluid; the cooling water via the first condenser (303) and the second condenser (403) is connected to the wetland restoration system (5) to achieve cascaded energy utilization.

8. The method for operating a medium-temperature waste heat recovery system combining residential heating and a cascade organic Rankine cycle according to claim 7, characterized in that: The medium-temperature waste heat has a temperature range of 150-200°C; the outlet heating water temperature of the heating water heater (202) is 60-80°C; the inlet heating return water temperature of the first preheater (306) and the second preheater (406) is 40-60°C; The waste heat energy inlet temperature of the second evaporator (401) is 100-130° C. The outlet cooling water temperature of the first condenser (303) and the second condenser (403) is 30-35° C.

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