Organic Rankine-flash coupling cascade cycle multi-temperature-zone waste heat co-processing system

Abstract

The invention provides an organic Rankine-flash coupling cascade cycle multi-temperature-zone waste heat cooperative treatment system, belongs to the technical field of efficient waste heat recycling, and solves the problems of resource waste, excessive carbon emission and the like caused by direct emission of industrial waste heat. The system comprises an organic Rankine sub-circulation system and an organic flash evaporation sub-circulation system, and a cycle working medium is octamethyltrisiloxane. The energy source of the organic Rankine sub-circulation system is high-temperature industrial waste heat of more than 500K, and the energy source of the organic flash evaporation sub-circulation system is medium-low-temperature industrial waste heat of 300-500K. High-temperature dead steam in the organic Rankine sub-circulation system is mixed with flash steam in the organic flash sub-circulation system and then expands in a cascade mode to do work, the heat load of a condenser is reduced while the work yield is increased, saturated liquid after flash preheats condensate, and the heat absorption capacity of a coupling system and irreversible loss of an organic evaporator are reduced. The power output characteristic of the whole scheme is realized by controlling the cycle working medium ratio of the sub-cycle system and the flash evaporation pressure of the system.

Description

Technical Field

[0001] This invention belongs to the field of efficient waste heat reuse technology, and in particular relates to a multi-temperature zone waste heat synergistic treatment system with organic Rankine-flash evaporation coupled cascade cycle. Background Technology

[0002] The industrial energy consumption generated by a fossil fuel-dominated energy structure is the core driver of carbon emissions, meaning that a large amount of high-energy, low-grade heat energy is emitted into the environment as waste heat. The organic Rankine cycle system is one of the core devices for waste heat recovery and reuse, utilizing the phase change characteristics of organic working fluids to achieve combined heat and power (CHP) and realize energy grade conversion. However, the basic organic Rankine cycle system suffers from high system heat loss and low efficiency due to the increased irreversibility of the evaporator caused by the phase change. Furthermore, condenser structure optimization contradicts system thermodynamic performance optimization, as lower condensing temperatures help improve system thermal efficiency but increase the heat load on the condenser and evaporator. Therefore, improving the configuration of the organic Rankine cycle system is a necessary measure.

[0003] Flash circulation systems are a reliable alternative to reduce evaporator heat loss. They are based on three-phase circulation systems, utilizing a turbine instead of a two-phase expander. This retains the advantage of no phase change in the heater of a three-phase circulation system, obtaining steam through rapid pressure reduction, while avoiding the manufacturing difficulties of two-phase expanders. However, considering the limitations of flash circulation systems in low-heat-source applications and the negative effects of low-energy expansion, this invention aims to combine the advantages of organic Rankine cycles and flash circulation systems to form an organic Rankine-flash coupled cascade circulation system, thereby achieving efficient synergistic treatment of waste heat in multiple temperature zones. Summary of the Invention

[0004] In view of this, in order to solve the problems of resource waste and excessive carbon emissions caused by direct discharge of industrial waste heat, this invention proposes a multi-temperature zone waste heat co-treatment system with organic Rankine-flash coupling cascade cycle. By introducing an organic flash sub-cycle system, the drawbacks of the Rankine cycle system, such as high irreversibility, are improved, thus forming an organic Rankine-flash coupling cascade cycle scheme to achieve the goal of efficient recovery and reuse of industrial waste heat in different temperature zones.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a multi-temperature zone waste heat synergistic treatment system with organic Rankine-flash coupling cascade cycle, comprising an organic Rankine sub-cycle system and an organic flash sub-cycle system. The organic Rankine sub-cycle system includes an organic evaporator, a high-temperature organic turbine, an organic condenser, and a liquid working fluid mixing tank. The organic flash sub-cycle system includes an organic preheater, an organic flash tank, a gas working fluid mixing tank, and a low-temperature organic turbine. The outlet of the organic preheater is connected to the inlet of the organic evaporator and the inlet of the organic flash tank, respectively. The outlet of the organic evaporator is connected to the inlet of the high-temperature organic turbine. The outlet of the high-temperature organic turbine and the steam outlet of the organic flash tank are both connected to the inlet of the gas working fluid mixing box. The outlet of the gas working fluid mixing box is connected to the inlet of the low-temperature organic turbine, and the outlet of the low-temperature organic turbine is connected to the inlet of the organic condenser. The saturated liquid outlet of the organic flash evaporator and the outlet of the organic condenser are connected to the liquid working fluid mixing tank. The energy of the saturated liquid after flash evaporation is used to preheat the condensate. The outlet of the liquid working fluid mixing tank is connected to the inlet of the organic preheater.

[0006] Furthermore, a throttling valve is installed between the organic preheater and the organic flash tank for the circulating working fluid, and a circulating working fluid pump is installed between the liquid working fluid mixing tank and the organic preheater.

[0007] Furthermore, the organic flash sub-circulation system is a single-stage flash system.

[0008] Furthermore, the energy source of the organic Rankine sub-cycle system is high-temperature industrial waste heat, with a thermal energy of ≥500 K, and the energy source of the organic flash sub-cycle system is medium-low temperature industrial waste heat, with a thermal energy of 300~500 K.

[0009] Furthermore, the working fluid in both the organic Rankine sub-cycle system and the organic flash sub-cycle system is octamethyltrisiloxane.

[0010] Furthermore, both the high-temperature organic turbine and the low-temperature organic turbine are radial flow type.

[0011] Furthermore, the organic preheater is a single-phase heat exchanger with a fixed tube sheet structure.

[0012] Furthermore, the organic evaporator is a phase change heat exchanger with a U-tube heat exchanger structure, where the phase change side is on the tube side.

[0013] Furthermore, the organic condenser is a phase change heat exchanger with a fixed tube sheet structure, where the phase change side is on the tube side.

[0014] Furthermore, the waste heat coolant in the organic condenser is water.

[0015] Compared with existing technologies, the beneficial effects of the multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle described in this invention are: 1. This invention integrates an organic flash sub-cycle system into an organic Rankine cycle system. On the one hand, it performs secondary expansion of high-temperature exhaust steam to improve work gain, while the high-temperature exhaust steam can increase the temperature of flash steam, further improving the expansion work of the low-temperature turbine. On the other hand, it utilizes the flash saturated liquid to preheat the condensate, reducing the heat absorption, thereby improving the thermal performance of the coupled system.

[0016] 2. This invention reduces the irreversibility of the organic Rankine sub-circulation system and the organic flash sub-circulation system by preheating the condensate and removing the flash saturated liquid through a throttling process, thereby improving the efficiency of the coupled system.

[0017] 3. The circulating working fluid of this invention is octamethyltrisiloxane (MDM). This working fluid has a wide operating range and a peak temperature of over 600K. It can be matched with medium-low temperature and high-temperature waste heat to achieve synergistic treatment of waste heat in multiple temperature zones.

[0018] 4. The present invention is flexible in operation. The coupled system can operate in conjunction or independently, without being constrained by the coupling components or the form of the energy source. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This invention relates to a multi-temperature zone waste heat synergistic treatment system based on an organic Rankine-flash coupled cascade cycle.

[0020] In the diagram: 1-Organic preheater, 2-Organic evaporator, 3-High-temperature organic turbine, 4-Gas working fluid mixing tank, 5-Low-temperature organic turbine, 6-Organic condenser, 7-Liquid working fluid mixing tank, 8-Circulating working fluid pump, 9-Throttle valve, 10-Organic flash tank. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0022] See Figure 1 This embodiment describes a multi-temperature zone waste heat co-treatment system with an organic Rankine-flash coupled cascade cycle, comprising an organic Rankine sub-cycle system and an organic flash sub-cycle system. The organic Rankine sub-cycle system is a basic type (the simplest Rankine cycle structure), and the organic flash sub-cycle system is a single-stage flash system.

[0023] The energy source for the organic Rankine sub-cycle system is high-temperature industrial waste heat (≥500 K), and the energy source for the organic flash sub-cycle system is medium-low temperature industrial waste heat (300~500 K).

[0024] The organic Rankine sub-circulation system includes an organic evaporator 2, a high-temperature organic turbine 3, an organic condenser 6, a liquid working fluid mixing tank 7, and a circulating working fluid pump 8; the organic flash sub-circulation system includes an organic preheater 1, a throttling valve 9, an organic flash tank 10, a gas working fluid mixing tank 4, and a low-temperature organic turbine 5.

[0025] The outlet of the organic preheater 1 is connected to the organic evaporator 2 and the throttling valve 9, respectively. The outlet of the throttling valve 9 is connected to the organic flash tank 10. The outlet of the organic evaporator 2 is connected to the high-temperature organic turbine 3. The outlet of the high-temperature organic turbine 3 and the steam outlet of the organic flash tank 10 are both connected to the gas working fluid mixing box 4. The high-temperature exhaust steam enters the organic flash sub-circulation system to achieve energy cascade utilization.

[0026] The outlet of the gas working fluid mixing tank 4 is connected to the cryogenic organic turbine 5, and the outlet of the cryogenic organic turbine 5 is connected to the organic condenser 6. The cryogenic exhaust gas returns to the organic Rankine sub-circulation system, realizing the coupled operation of the system.

[0027] The saturated liquid outlet of the organic flash evaporator 10 and the outlet of the organic condenser 6 are connected to the liquid working fluid mixing tank 7. The energy of the saturated liquid after flash evaporation is used to preheat the condensate.

[0028] The liquid working fluid mixing tank 7 is connected to the circulating working fluid pump 8, and the outlet of the circulating working fluid pump 8 is connected to the organic preheater 1.

[0029] The circulating working fluid in both the organic Rankine subcycle system and the organic flash subcycle system is octamethyltrisiloxane (MDM).

[0030] The organic preheater 1 is a single-phase heat exchanger, and its structure is also a fixed tube sheet heat exchanger.

[0031] The organic evaporator 2 and the organic condenser 6 are phase change heat exchangers, with structures of a U-tube heat exchanger and a fixed tube sheet heat exchanger, respectively. The phase change side is in the tube side, and the waste heat coolant in the organic condenser 6 is water.

[0032] Both the high-temperature organic turbine 3 and the low-temperature organic turbine 5 are radial flow type.

[0033] The circulating working fluid is divided into two streams at the outlet of the organic preheater 1. One stream enters the organic flash sub-circulation system through the throttling valve 9, and the other stream enters the organic Rankine sub-circulation system through the organic evaporator 2.

[0034] The circulating working fluid of the organic flash sub-circulation system contains saturated vapor and saturated liquid at the outlet of the organic flash tank 10. The circulating working fluid of the organic Rankine sub-circulation system and the saturated vapor are combined in the gaseous working fluid mixing tank 4, and all circulating working fluids are combined in the liquid working fluid mixing tank 7.

[0035] The power output characteristics of the design scheme are controlled by the ratio of the circulating working fluid at the outlet of the organic preheater 1 and the flash pressure of the organic flash tank 10.

[0036] The following is in conjunction with the appendix Figure 1 Detailed workflow description of the multi-temperature zone waste heat co-treatment system with organic Rankine-flash coupling cascade cycle: The low-temperature, low-pressure circulating working fluid MDM enters the organic preheater 1 and is heated to saturated liquid. It is then divided into two streams. One stream of circulating working fluid enters the organic flash evaporation sub-circulation system through the throttle valve 9. It undergoes a pressure reduction flash evaporation process in the flash tank 10 to obtain saturated steam and saturated liquid. The saturated steam enters the gas working fluid mixing tank 4, and the saturated liquid enters the liquid working fluid mixing tank 7.

[0037] Another circulating working fluid is used in the organic Rankine cycle system to absorb heat at equal pressure to saturated steam in the organic evaporator 2, and then enters the high-temperature organic turbine 3. The resulting high-temperature exhaust steam also enters the gas working fluid mixing tank 4. Then, in the low-temperature organic turbine 5, the high-temperature exhaust steam undergoes stepped expansion. The low-temperature exhaust steam passes through the organic condenser 6, and the low-temperature waste heat is carried away by circulating cooling water. The condensate and flash saturated liquid are mixed in the liquid working fluid mixing tank 7 to increase the condensate temperature. The condensate is then returned to the organic preheater 1 via the circulating working fluid pump 8 to complete the entire cycle. The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A multi-temperature zone waste heat synergistic treatment system with organic Rankine-flash coupling cascade cycle, characterized in that: The system includes an organic Rankine sub-circulation system and an organic flash sub-circulation system. The organic Rankine sub-circulation system includes an organic evaporator (2), a high-temperature organic turbine (3), an organic condenser (6), and a liquid working fluid mixing tank (7). The organic flash sub-circulation system includes an organic preheater (1), an organic flash tank (10), a gas working fluid mixing tank (4), and a low-temperature organic turbine (5). The outlet of the organic preheater (1) is connected to the inlet of the organic evaporator (2) and the inlet of the organic flash tank (10), respectively. The outlet of the organic evaporator (2) is connected to the inlet of the high-temperature organic turbine (3). The outlet of the high-temperature organic turbine (3) and the steam outlet of the organic flash tank (10) are both connected to the inlet of the gas working fluid mixing box (4). The outlet of the gas working fluid mixing box (4) is connected to the inlet of the low-temperature organic turbine (5), and the outlet of the low-temperature organic turbine (5) is connected to the inlet of the organic condenser (6). The saturated liquid outlet of the organic flash evaporator (10) and the outlet of the organic condenser (6) are connected to the liquid working fluid mixing tank (7). The energy of the saturated liquid after flash evaporation is used to preheat the condensate. The outlet of the liquid working fluid mixing tank (7) is connected to the inlet of the organic preheater (1).

2. The multi-temperature zone waste heat synergistic treatment system according to claim 4, characterized in that: A throttling valve (9) is installed between the organic preheater (1) and the organic flash tank (10) for the circulating working fluid, and a circulating working fluid pump (8) is installed between the liquid working fluid mixing tank (7) and the organic preheater (1).

3. The multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle according to claim 1, characterized in that: The organic flash evaporation sub-circulation system is a single-stage flash evaporation system.

4. The multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle according to claim 1, characterized in that: The energy source of the organic Rankine sub-cycle system is high-temperature industrial waste heat, with a thermal energy of ≥500 K. The energy source of the organic flash sub-cycle system is medium-low temperature industrial waste heat, with a thermal energy of 300~500 K.

5. The multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle according to claim 1, characterized in that: The circulating working fluid in both the organic Rankine sub-cycle system and the organic flash sub-cycle system is octamethyltrisiloxane.

6. The multi-temperature zone waste heat synergistic treatment system according to claim 1, characterized in that: Both the high-temperature organic turbine (3) and the low-temperature organic turbine (5) are radial flow type.

7. The multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle according to claim 1, characterized in that: The organic preheater (1) is a single-phase heat exchanger with a fixed tube sheet structure.

8. The multi-temperature zone waste heat synergistic treatment system according to claim 1, characterized in that: The organic evaporator (2) is a phase change heat exchanger with a U-shaped tube heat exchanger structure, and the phase change side is in the tube side.

9. The multi-temperature zone waste heat synergistic treatment system of organic Rankine-flash coupled cascade cycle according to claim 1, characterized in that: The organic condenser (6) is a phase change heat exchanger with a fixed tube sheet structure, and the phase change side is on the tube side.

10. The multi-temperature zone waste heat synergistic treatment system according to claim 9, characterized in that: The waste heat coolant in the organic condenser (6) is water.

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