[0024] The present invention will be further described in detail below in conjunction with the drawings.
[0025] The traditional waste heat recovery system based on organic Rankine cycle consists of five main components, namely pump, evaporator, expander, condenser and generator. The system configuration is as follows figure 1 Shown. In the traditional waste heat recovery system based on the organic Rankine cycle, the liquid organic working fluid (state point 1) from the outlet of the condenser is pressurized by the pump and then sent to the evaporator (state point 2); the liquid working fluid is in the evaporator Constant pressure heating, from the supercooled liquid to the saturated liquid state and the gas-liquid two-phase state, and finally into the saturated vapor state (or superheated vapor state), that is, state point 3; the saturated vapor (or superheated vapor) is sent to the expander To expand and do work to output mechanical energy, the generator converts the mechanical energy into electrical output, and the expander exhaust steam (state point 4) is sent to the condenser, where it is condensed by cold water into a liquid working fluid (state point 1) to complete The entire cycle. In the above process, the waste heat medium is cooled from state point 5 to state point 6, and cold water is heated from state point 7 to state point 8. When the traditional organic Rankine cycle waste heat recovery system achieves the highest system efficiency, the net electric power output of the system is very small, resulting in poor recovery and utilization of waste heat energy by the system. In addition, when the organic working fluid exchanges heat with the waste heat source in the system evaporator, the temperature in the evaporation section remains unchanged, resulting in a large heat transfer temperature difference between the waste heat source and the waste heat source, resulting in obvious irreversible loss of effective energy.
[0026] The traditional waste heat recovery system based on organic flash cycle is composed of eight main components, namely pump, heater, flash tank, expander, throttle valve, mixer, condenser and generator. The system configuration is as follows figure 2 Shown. The liquid organic working fluid (state point 1) from the outlet of the condenser is pressurized by the pump and then sent to the heater (state point 2), where it is heated at a constant pressure to become a saturated liquid working fluid (state point 3); after the liquid is saturated It is sent to the flash tank, where it flashes into a vapor-liquid two-phase mixture (state point 4), in which saturated steam (state point 4") is sent to the expander to expand and perform work, and saturated liquid (state point 4') ) Is then sent to the mixer to mix with the exhaust steam of the expander (state point 5) after the pressure is reduced by the throttle valve (state point 6); finally, the mixture (state point 7) is sent to the condenser, where it is condensed by cold water It becomes a liquid working fluid (state point 1) to complete the entire cycle. In the above process, the waste heat medium is cooled from state point 8 to state point 9, and cold water is heated from state point 10 to state point 11. Traditional organic flash evaporation Although the cycle reduces the irreversible effective energy loss of the working fluid in the evaporator due to the large heat transfer temperature difference in the organic Rankine cycle, its additional throttling process introduces additional irreversible effective energy loss.
[0027] See image 3 , The present invention proposes a waste heat recovery system based on organic Rankine cycle and organic flash cycle, which couples the basic organic Rankine cycle and organic flash cycle into one system. Cooling medium and organic working fluid are introduced into condenser J. The organic working fluid outlet of condenser J is connected to the inlet of low-pressure pump A through a pipeline, and the outlet of low-pressure pump A is connected to the organic working fluid inlet of heater B through a pipeline for heating. The waste heat working fluid is introduced into the device B, and the waste heat working fluid obtains a saturated liquid working fluid through heat exchange with the organic working fluid. The organic working fluid outlet of the heater B is connected to the inlet of the flash tank C through a pipeline, and the flash tank C The outlet of the liquid working medium is connected to the inlet of the high-pressure pump D through the pipeline, and the outlet of the high-pressure pump D is connected to the organic working medium inlet of the evaporator E through the pipeline. Perform heat exchange to obtain superheated steam or saturated steam. The steam outlet of evaporator E is connected to the steam inlet of high-pressure expander F through a pipeline, and the steam outlet of high-pressure expander F is connected to mixer K through a pipeline, and the saturated steam of flash tank C is The outlet is directly connected to the mixer K through a pipeline, the steam outlet of the mixer K is connected to the steam inlet of the low-pressure expander H through a pipeline, and the steam outlet of the low-pressure expander H is connected to the organic working fluid inlet of the condenser J through a pipeline. Both the expander F and the low-pressure expander H are connected with a generator I.
[0028] As a preferred embodiment, a common preheater can be provided on the pipeline between the low-pressure pump A and the heater B, and between the low-pressure expander H and the condenser J, and the low-pressure expansion is respectively introduced into the preheater. The exhaust steam of engine H and the liquid organic working fluid pressurized by the low-pressure pump A, the liquid organic working fluid is heated by the exhaust steam of the low-pressure expander H in the preheater and then sent to the heater B, and the low-pressure expander H The exhaust steam is cooled by the pumped liquid in the preheater and sent to the condenser J.
[0029] As another preferred embodiment, the waste heat recovery system based on the organic Rankine cycle and the organic flash cycle of the present invention can be provided with a reheater on the pipeline between the high-pressure expander F and the mixer K, and the high-pressure expander F The exhaust steam is sent to the reheater and then heated by the waste heat working fluid, the heated steam is sent to the mixer K, and the cooled waste heat working fluid is sent to the evaporator E.
[0030] In the above embodiments, the organic circulating working fluid can be a pure organic working fluid with isentropic fluid or dry fluid characteristics, or a mixed organic working fluid formed by mixing two or more pure organic working fluids.
[0031] In the above embodiment, the high-pressure expander F and the low-pressure expander H can use the same type of expander (including various speed expanders and volumetric expanders, such as centrifugal expanders, turbo expanders, screw type expanders, etc. Expanders, reciprocating expanders, scroll expanders, rolling rotor expanders, sliding vane expanders, etc.), two different types of expanders can also be used.
[0032] In the waste heat recovery system and method based on the organic Rankine cycle and the organic flash cycle of the present invention, the liquid organic working fluid at the outlet of the condenser J (state point 1) is pressurized by the low-pressure pump A and then sent to the heater B (state point) 2), recover a part of the residual heat energy into saturated liquid (state point 3); then the saturated liquid is sent to flash tank C, and flashed in the flash tank into a vapor-liquid two-phase mixture (state point 4), where the liquid The working fluid (state point 4') is pressurized by the high-pressure pump D and then sent to the evaporator E (state point 5) for further recovery of waste heat energy, while the saturated steam (state point 4") is sent to the mixer K; evaporator E The outlet superheated steam (or saturated steam, state point 6) enters the high-pressure expander F to expand and perform work, and then the exhaust steam of the high-pressure expander F (state point 7) is sent to the mixer K and the saturated steam from the flash tank C Mixing; the mixed steam (state point 8) is sent to the low-pressure expander H to expand and do work, the exhaust steam of the low-pressure expander H (state point 9) is sent to the condenser J, and is condensed by cold water into a liquid working fluid ( State point 1) completes the entire cycle. In the above process, the waste heat medium flows from state point 10 through evaporator E and heater B and then is cooled to state point 12, and cold water is heated from state point 13 to state point 14 .
[0033] See Figure 4 Obviously, the waste heat recovery system of the present invention couples the basic organic Rankine cycle and the organic flash cycle together, eliminating the liquid working fluid in the basic organic flash cycle after the flash tank through the throttle valve to reduce pressure and throttling The irreversible energy loss caused. In addition, due to the presence of a low-pressure pump and a high-pressure pump in the system, the evaporation pressure of the organic Rankine cycle in the coupled system is increased, and the latent heat of vaporization required for the evaporation process of saturated liquid is reduced, making the organic working fluid in the vapor-liquid two-phase region The resulting evaporative heat exchange process is shortened, the heat exchange temperature difference curve between the organic working fluid and the waste heat medium is improved, and the irreversible energy loss of the organic working fluid in the evaporative heat exchange process is reduced. Finally, in the coupled system, the waste heat medium flows through the two heat exchangers of the evaporator and the heater in turn, while the organic working fluid flows through the two expanders of the high-pressure expander and the low-pressure expander in turn, which improves the system’s energy The recycling capacity of the system increases the net electric power output of the system. According to the above-mentioned design system of the present invention, the energy utilization efficiency of the system, the net electric power output and the waste heat energy recovery and utilization capacity of the system can be improved.
[0034] The foregoing descriptions are merely preferred embodiments of the present invention, and are not used to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principle of the present invention, the technical solution is still Several simple modifications and substitutions can be made, and these modifications and substitutions also fall within the protection scope defined by the submitted claims.
