Steam-water dual heat source waste heat power generation split-flow system and thermal economic optimization design method

Abstract

The application discloses a steam-water double-heat-source waste heat power generation shunt system and a thermal economic optimization design method. The steam-water double-heat-source waste heat power generation shunt system comprises a high-pressure loop and a low-pressure loop. A hot water input end of the high-pressure loop and a hot water input end of the low-pressure loop are simultaneously connected with an external hot water pipe. The high-pressure loop and the low-pressure loop are respectively provided with a first generator. The first generator / the second generator is used for generating power according to high-temperature and high-pressure organic steam generated in the high-pressure loop / the low-pressure loop to push a first expander / ORC expander to generate power. The application can shunt the hot water heat source, thereby maximizing the utilization of the hot water waste heat. In addition, more net output power can be output at the minimum power generation cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste heat power generation, in particular to a steam-water dual heat source waste heat power generation split-flow system and a thermal economic optimization design method. BACKGROUND

[0002] In order to reduce carbon emissions and achieve carbon neutrality, the organic Rankine cycle (ORC) as a very promising waste heat recovery technology has been widely studied. Through the ORC, renewable energy such as solar energy, geothermal energy or waste heat energy in industrial production can be recovered, and at the same time, electric energy can be obtained. A simple ORC system can output power through four parts: evaporator, condenser, expander and working fluid pump. The whole system has high safety, simple structure and good thermodynamic performance, which is conducive to energy saving and emission reduction. In the practical application of waste heat recovery, it is challenging to recover heat from different heat sources at the same time. Many industrial processes, such as chemical manufacturing and steel smelting, produce a large amount of waste heat in the form of steam and water. In the above cases, steam may come from combustion and chemical processes, and hot water may come from process cooling processes. Therefore, it is common for steam heat sources and hot water heat sources to coexist. By recovering waste heat from steam and water, energy consumption and costs can be reduced, and the overall efficiency of industrial processes can be improved. There is little research on the structural design of an ORC system using steam and hot water as a combined heat source. SUMMARY

[0003] The purpose of the present application is to provide a steam-water dual heat source waste heat power generation split-flow system and a thermal economic optimization design method, which can on the one hand split the hot water heat source to maximize the use of hot water waste heat, and on the other hand output more net output power at the minimum power generation cost.

[0004] The technical solution of the present application to solve the above technical problems is as follows:

[0005] The present application provides a steam-water dual heat source waste heat power generation split-flow system, which comprises a high-pressure loop and a low-pressure loop, a hot water input end of the high-pressure loop and a hot water input end of the low-pressure loop are simultaneously connected to an external hot water pipe, the high-pressure loop and the low-pressure loop are respectively provided with a first generator and a second generator, and the first generator / second generator is used to generate power according to the high-temperature and high-pressure organic steam generated by hot water in the high-pressure loop / low-pressure loop to drive a first expander / ORC expander.

[0006] Alternatively, the high-pressure loop further comprises a first evaporator, a first preheater, a second preheater, a first working fluid pump, a first condenser, a third generator and a second expander.

[0007] The outlet of the first expander is communicated with the steam inlet of the first evaporator to form a b passage;

[0008] The steam outlet of the first evaporator is communicated with the steam inlet of the second preheater to form a c passage;

[0009] The steam outlet of the second preheater is communicated with the external hot water pipe to form a d passage;

[0010] The liquid outlet of the first evaporator is communicated with the inlet of the second expander to form a 1 passage;

[0011] The outlet of the second expander is communicated with the gas inlet of the first condenser to form a 2 passage;

[0012] The gas outlet of the first condenser is communicated with the inlet of the first working medium pump to form a 3 passage;

[0013] The outlet of the first working medium pump is communicated with the condensate inlet of the first preheater to form a 4 passage;

[0014] The condensate outlet of the first preheater is communicated with the condensate inlet of the second preheater to form a 5 passage;

[0015] The condensate outlet of the second preheater is communicated with the raw liquid inlet of the first evaporator to form a 6 passage;

[0016] The water source inlet of the first preheater is communicated with the outlet of the external hot water pipe as the hot water input end of the high-pressure loop to form an a" passage, and the water source outlet is communicated with the inlet of the external hot water pipe to form a b" passage, the hot water source enters the first preheater through the a" passage, and after being heated by the first preheater, enters the external hot water pipe through the b" passage;

[0017] The input of the first expander is a high-pressure saturated steam heat source, which generates a first power source through the first expander and generates electricity through a first generator; and the high-pressure saturated steam heat source is reduced in pressure to wet steam through the work of the steam expander, the wet steam enters the first evaporator through the b passage to evaporate the organic working medium in the first evaporator from a saturated liquid state to a saturated gaseous state, the saturated gaseous state enters the ORC expander through the 1 passage to drive the ORC expander to work and generate electricity and change the saturated steam into low-temperature and low-pressure organic exhaust steam, the organic exhaust steam enters the first condenser through the 2 passage and is condensed into organic condensate in the first condenser, the organic condensate enters the first working medium pump through the 3 passage, is pressurized by the first working medium pump and enters the first preheater through the 4 passage to absorb the heat of the hot water heat source to form the organic working medium, the organic working medium enters the second preheater through the 5 passage, and the steam heat source at the steam outlet of the evaporator enters the second preheater through the c passage to enable the steam waste heat in the second preheater to process the organic working medium, and the processed steam forms hot water which enters the external hot water pipe through the d passage.

[0018] Alternatively, the high-pressure loop further comprises a first cold water pump and a first cooling tower, the output end of the first cold water pump is communicated with the cold water input end of the first condenser to form an m' passage, the cold water output end of the first condenser is communicated with the input end of the first cooling tower to form an n passage, and the output end of the first cooling tower is communicated with the input end of the first cold water pump to form an m passage;

[0019] The cold water in the first cooling tower enters the first cold water pump through the m passage, is pressurized by the first cold water pump and then enters the first condenser through the m' passage to provide a water cooling source for the first condenser, and the water-cooled liquid enters the first cooling tower through the n passage.

[0020] Alternatively, the low-pressure loop comprises a third preheater, a second evaporator, an ORC expander, a second condenser, a second cold water pump and a second working medium pump;

[0021] The water source inlet of the second evaporator is communicated with the outlet of the external hot water pipe as a hot water input end of the low-pressure loop to form an a' passage, and the water source outlet is communicated with the water source inlet of the third preheater to form a b' passage;

[0022] The water source outlet of the third preheater is communicated with the inlet of the external hot water pipe to form a c' passage;

[0023] The complete liquid outlet of the second evaporator is communicated with the inlet of the ORC expander to form a 1' passage;

[0024] The outlet of the ORC expander is communicated with the gas inlet of the second condenser to form a 2' passage;

[0025] The gas outlet of the second condenser is connected to the inlet of the second working medium pump to form a 3' passage;

[0026] The outlet of the second working medium pump is connected to the condensate inlet of the third preheater to form a 4' passage;

[0027] The condensate outlet of the third preheater is connected to the raw material liquid inlet of the second evaporator to form a 5' passage;

[0028] The hot water heat source enters the second evaporator through an a' passage, so that the saturated liquid organic working medium in the second evaporator absorbs heat of the hot water heat source and becomes saturated gas; the hot water outlet of the second evaporator enters the third preheater through a b' passage, and the subcooled organic working medium in the third preheater absorbs heat of the hot water heat source, and the water source outlet of the third preheater enters the external hot water pipe through a c' passage;

[0029] The saturated gas enters the ORC expander through a 1' passage to drive the ORC expander to work and generate the second power source and generate electricity through the second generator, and the saturated gas becomes the low-temperature and low-pressure second organic exhaust steam, which enters the second condenser through a 2' passage and is condensed into the second organic condensate in the second condenser, the second organic condensate enters the second working medium pump through a 3' passage, the second working medium pump pressurizes the second organic condensate to generate the second subcooled organic working medium, which enters the third preheater through a 4' passage, and the second subcooled organic working medium absorbs heat of the hot water heat source in the third preheater to become the second organic working medium and enters the second evaporator through a 5' passage.

[0030] Optionally, the low-pressure loop further comprises a second cold water pump and a second cooling tower, the output end of the second cold water pump is connected to the cold water input end of the second condenser to form a m1' passage, the cold water output end of the second condenser is connected to the input end of the second cooling tower to form a n1 passage, and the output end of the second cooling tower is connected to the input end of the second cold water pump to form a m1 passage;

[0031] The cold water in the second cooling tower enters the second cold water pump through the m1 passage, is pressurized by the second cold water pump and then enters the second condenser through the m1' passage to provide a water cooling source for the second condenser, and the water-cooled liquid enters the second cooling tower through the n1 passage.

[0032] The application also provides a thermal economic optimization design method based on the steam-water dual-heat-source waste heat power generation split-flow system.

[0033] S1: According to the known parameters and boundary conditions in the steam-water dual heat source waste heat power generation shunt system, the hot water shunt ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low pressure loop evaporator outlet hot water temperature range are determined;

[0034] S2: According to the hot water shunt ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low pressure loop evaporator outlet hot water temperature range, the first maximum net output power of the steam-water dual heat source waste heat power generation shunt system and the first maximum net output power corresponding first power generation cost and its corresponding high pressure loop part first steam heat source outlet parameter and first hot water heat source outlet parameter, and the low pressure loop first evaporator outlet hot water temperature are determined by using the particle swarm algorithm;

[0035] S3: According to the hot water shunt ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low pressure loop evaporator outlet hot water temperature range, the optimal net output power of the steam-water dual heat source waste heat power generation shunt system and the optimal power generation cost corresponding high pressure loop part second steam heat source outlet parameter and second hot water heat source outlet parameter, and the low pressure loop second evaporator outlet hot water temperature are determined by using the second generation non-dominated sorting genetic algorithm;

[0036] S4: According to the known parameters, boundary conditions, high pressure loop part first / second steam heat source outlet parameters and first / second hot water heat source outlet parameters, and low pressure loop first / second evaporator outlet hot water temperatures, the parameters of each device in the steam-water dual heat source waste heat power generation shunt system are determined.

[0037] Optionally, the S2 comprises:

[0038] S21: According to the hot water shunt ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low pressure loop evaporator outlet hot water temperature range, all initial particles of the particle swarm algorithm are obtained;

[0039] S22: The fitness value of all particles is determined by the objective function, and the fitness value is the net output power corresponding to each particle output;

[0040] S23: According to the hot water shunt ratio range, the high pressure loop part steam heat source outlet parameter range, the hot water heat source outlet parameter range, the low pressure loop evaporator outlet hot water temperature range and the fitness value of the particle, the optimal fitness value and the particle vector corresponding to the optimal fitness value are determined, wherein the particle vector comprises the hot water shunt ratio, the high pressure loop part steam heat source outlet parameter, the hot water heat source outlet parameter and the low pressure loop evaporator outlet hot water temperature;

[0041] S24: outputting the optimal adaptation value as a first maximum net output power, and determining a first power generation cost corresponding to the first maximum net output power according to the first maximum net output power;

[0042] S25: outputting a particle vector corresponding to the optimal adaptation value as high-pressure loop part first steam heat source outlet parameters and first hot water heat source outlet parameters, and low-pressure loop first evaporator outlet hot water temperature.

[0043] Optionally, the objective function comprises:

[0044] t pin = min{ (t c -t evap ), (t d -t5), (t a′ -t5), (t b″ -t4)}

[0045] t pin = min{ (t c -t evap ), (t d -t5), (t a′ -t5), (t a′mid -t evap ), (t b′ -t4)}

[0046] Wherein, t pin represents a pinch point temperature, t c represents a first evaporator steam outlet temperature, t evap represents an evaporation temperature, t d represents a second preheater steam outlet temperature, t5 represents a first preheater condensate outlet temperature, t a′ represents a hot water heat source inlet temperature, t b″ represents a first preheater water source outlet temperature, t4 represents a first working medium pump outlet temperature, t a′mid represents a first preheater working medium saturated liquid state corresponding hot water temperature, t b′ represents a first evaporator water source outlet temperature.

[0047] The known parameters comprise: steam inlet parameters and hot water inlet parameters, and the hot water inlet parameters comprise hot water inlet flow rate;

[0048] S23 comprises:

[0049] According to the hot water shunt ratio range and the hot water inlet flow rate, a hot water flow rate range entering the high-pressure loop and a hot water flow rate range entering the low-pressure loop are obtained;

[0050] According to the high-pressure loop part steam heat source outlet parameter range and hot water heat source outlet parameter range, the relationship between the evaporation temperature and the working medium flow rate is determined by using the first law of thermodynamics;

[0051] According to the high-low of the total heat exchange amount of hot water, the position of the pinch temperature difference is determined;

[0052] According to the position of the pinch temperature difference and the objective function, the evaporation temperature and the working medium flow rate of the high-pressure loop are determined;

[0053] According to the evaporation temperature and the working medium flow rate of the high-pressure loop, the net output power and the power generation cost of the high-pressure loop are determined;

[0054] According to the pinch temperature difference and the hot water temperature range at the outlet of the evaporator in the low-pressure loop, the evaporation temperature of the low-pressure loop is obtained;

[0055] According to the evaporation temperature of the low-pressure loop, the net output power and the power generation cost of the low-pressure loop are determined;

[0056] Net output power W net is expressed as:

[0057] W net =f(t d ,P d ,r sp ,t b″ ,t b′ )

[0058] The power generation cost EPC is expressed as:

[0059] EPC=f(t d ,P d ,r sp ,t b″ ,t b′ )

[0060] Wherein, t d represents the steam outlet temperature of the second preheater, P d represents the steam outlet pressure of the second preheater, r sp represents the hot water diversion ratio, t b″ represents the water source outlet temperature of the first preheater, t b′ represents the first evaporator water source outlet temperature.

[0061] Alternatively, the S3 comprises:

[0062] S31: According to the high-pressure saturated steam heat source outlet parameter range and the hot water heat source outlet parameter range, the Pareto frontier curve with the horizontal and vertical coordinates being the net output power and the power generation cost of the steam-water dual heat source waste heat power generation diversion system is obtained by using the second generation non-dominated sorting genetic algorithm;

[0063] S32: using a multi-objective optimization decision method to obtain an optimal net output power and an optimal power generation cost, and high-pressure loop part second steam heat source outlet parameters and second hot water heat source outlet parameters corresponding to the optimal net output power and the optimal power generation cost, and a low-pressure loop second evaporator outlet hot water temperature corresponding to the optimal net output power and the optimal power generation cost.

[0064] Optionally, the S31 comprises:

[0065] According to the hot water diversion ratio range, the high-pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low-pressure loop evaporator outlet hot water temperature range, the design parameters of the second generation non-dominated sorting genetic algorithm are determined.

[0066] According to the design parameters of the second generation non-dominated sorting genetic algorithm, N initial populations are created.

[0067] The N parent individuals in the N initial populations are subjected to a simulated binary crossover operation, a mutation polynomial operation and a tournament selection operation to obtain N offspring individuals; wherein the individual represents the hot water diversion ratio range, the high-pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low-pressure loop evaporator outlet hot water temperature range.

[0068] The N offspring individuals and the N parent individuals are combined to form 2N individuals.

[0069] All solutions corresponding to the 2N individuals are generated.

[0070] The Pareto level of all solutions is determined by using an elitist strategy, and the Pareto level of all solutions is sorted.

[0071] The boundary individual in each set of the sorting result is set to have infinite crowding degree, and the crowding degree of other individuals is calculated.

[0072] The better new individual is determined by using the crowding degree and is put into the parent population until the parent population is filled.

[0073] It is judged whether the current iteration meets the maximum iteration number, if yes, a Pareto frontier curve with steam-water dual heat source waste heat power generation diversion system net output power and power generation cost as horizontal and vertical coordinates is obtained according to the individuals in the current parent population, otherwise, the iteration is continued.

[0074] The present application has the following beneficial effects:

[0075] On one hand, the present application can split the hot water heat source, so as to maximize the utilization of the hot water waste heat; on the other hand, the present application can optimize the design of the waste heat power generation split system under different steam-water heat source conditions, reasonably allocate the heat exchange amount of the heat source in each loop, so as to realize the maximum net output power by utilizing the existing waste heat, and also optimize the net output power and economy of the system, so as to output more net output power under the minimum power generation cost. BRIEF DESCRIPTION OF DRAWINGS

[0076] Figure 1 Fig. 1 is a structural schematic diagram of a steam-water dual heat source waste heat power generation split system of the present application;

[0077] Figure 2 Fig. 4 is a flow chart of the heat economy optimization design method of the present application;

[0078] Figure 3 Fig. 5 is a specific expansion flow chart of S23;

[0079] Figure 4 Fig. 6 is a schematic diagram of the particle swarm algorithm result;

[0080] Figure 5 Fig. 7 is a schematic diagram of the Pareto frontier curve obtained by the NSGA-II algorithm optimization.

[0081] BRIEF DESCRIPTION OF DRAWINGS

[0082] 10-first expander; 11-first generator; 12-first preheater; 13-second preheater; 14-first evaporator; 15-second expander; 16-third generator; 17-first condenser; 18-first working medium pump; 19-first cold water pump; 20-first cooling tower; 21-third preheater; 22-second evaporator; 23-ORC expander; 24-second generator; 25-second condenser; 26-second working medium pump; 27-second cooling tower; 28-second cold water pump. DETAILED DESCRIPTION

[0083] The principles and characteristics of the present application are described below in combination with the drawings, and the examples are only used to explain the present application, and are not used to limit the scope of the present application.

[0084] Example 1

[0085] The present application provides a steam-water dual heat source waste heat power generation split system, as shown in Fig. 1, which comprises a first expander 10, a first generator 11, a first preheater 12, a second preheater 13, a first evaporator 14, a second expander 15, a third generator 16, a first condenser 17, a first working medium pump 18, a first cold water pump 19, a first cooling tower 20, a third preheater 21, a second evaporator 22, an ORC expander 23, a second generator 24, a second condenser 25, a second working medium pump 26, a second cooling tower 27, and a second cold water pump 28. Figure 1As shown, the steam-water dual heat source waste heat power generation split-flow system comprises a high-pressure loop and a low-pressure loop, a hot water input end of the high-pressure loop and a hot water input end of the low-pressure loop are simultaneously communicated with an external hot water pipe, the high-pressure loop and the low-pressure loop are respectively provided with a first generator 11 and a second generator 24, the first generator 11 / second generator 24 is used to generate power according to the high-temperature and high-pressure organic steam generated in the high-pressure loop / low-pressure loop to drive a first expander 10 / ORC expander 23.

[0086] Alternatively, the high-pressure loop further comprises a first evaporator 14, a first preheater 12, a second preheater 13, a first working medium pump 18, a first condenser 17, a third generator 16 and a second expander 15;

[0087] The outlet of the first expander 10 is communicated with the steam inlet of the first evaporator 14 to form a b passage;

[0088] The steam outlet of the first evaporator 14 is communicated with the steam inlet of the second preheater 13 to form a c passage;

[0089] The steam outlet of the second preheater 13 is communicated with the external hot water pipe to form a d passage;

[0090] The liquid outlet of the first evaporator 14 is communicated with the inlet of the second expander 15 to form a 1 passage;

[0091] The outlet of the second expander 15 is communicated with the gas inlet of the first condenser 17 to form a 2 passage;

[0092] The gas outlet of the first condenser 17 is communicated with the inlet of the first working medium pump 18 to form a 3 passage;

[0093] The outlet of the first working medium pump 18 is communicated with the condensate inlet of the first preheater 12 to form a 4 passage;

[0094] The condensate outlet of the first preheater 12 is communicated with the condensate inlet of the second preheater 13 to form a 5 passage;

[0095] The condensate outlet of the second preheater 13 is communicated with the raw liquid inlet of the first evaporator 14 to form a 6 passage;

[0096] The water source inlet of the first preheater 12 is communicated with the outlet of the external hot water pipe as the hot water input end of the high-pressure loop to form an a" passage, and the water source outlet is communicated with the inlet of the external hot water pipe to form a b" passage, the hot water source enters the first preheater 12 through the a" passage, and enters the external hot water pipe through the b" passage after being heated by the first preheater 12;

[0097] The input of the first expander 10 is a high-pressure saturated steam heat source, which generates a first power source through the work of the first expander 10 and generates electricity through the first generator 11; and the high-pressure saturated steam heat source is reduced in pressure to wet steam after working through the steam expander, the wet steam enters the first evaporator 14 through the b passage to evaporate the organic working medium in the first evaporator 14 from a saturated liquid state to a saturated gaseous state, the saturated gaseous state enters the ORC expander 23 through the 1 passage to drive the ORC expander 23 to work and generate electricity and change the saturated steam into low-temperature and low-pressure organic exhaust steam, the organic exhaust steam enters the first condenser 17 through the 2 passage and is condensed into organic condensate in the first condenser 17, the organic condensate enters the first working medium pump 18 through the 3 passage, is pressurized by the first working medium pump 18 and enters the first preheater 12 through the 4 passage to absorb the heat of the hot water heat source to form the organic working medium, the organic working medium enters the second preheater 13 through the 5 passage, and the steam heat source at the steam outlet of the evaporator enters the second preheater 13 through the c passage to enable the steam waste heat in the second preheater 13 to process the organic working medium, and the processed steam forms hot water which enters the external hot water pipe through the d passage.

[0098] Alternatively, the high-pressure loop further comprises a first cold water pump 19 and a first cooling tower 20, the output end of the first cold water pump 19 is communicated with the cold water input end of the first condenser 17 to form an m' passage, the cold water output end of the first condenser 17 is communicated with the input end of the first cooling tower 20 to form an n passage, and the output end of the first cooling tower 20 is communicated with the input end of the first cold water pump 19 to form an m passage;

[0099] The cold water in the first cooling tower 20 enters the first cold water pump 19 through the m passage, is pressurized by the first cold water pump 19 and then enters the first condenser 17 through the m' passage to provide a water cooling source for the first condenser 17, and the water-cooled liquid enters the first cooling tower 20 through the n passage.

[0100] Alternatively, the low-pressure loop comprises a third preheater 21, a second evaporator 22, an ORC expander 23, a second condenser 25, a second cold water pump 28 and a second working medium pump 26.

[0101] The water source inlet of the second evaporator 22 is communicated with the outlet of the external hot water pipe as a hot water input end of the low-pressure loop to form an a' passage, and the water source outlet is communicated with the water source inlet of the third preheater 21 to form a b' passage;

[0102] The water source outlet of the third preheater 21 is communicated with the inlet of the external hot water pipe to form a c' passage;

[0103] The outlet of the second evaporator 22 is connected to the inlet of the ORC expander 23 to form a 1' path;

[0104] The outlet of the ORC expander 23 is connected to the gas inlet of the second condenser 25 to form a 2' path;

[0105] The gas outlet of the second condenser 25 is connected to the inlet of the second working medium pump 26 to form a 3' path;

[0106] The outlet of the second working medium pump 26 is connected to the condensate inlet of the third preheater 21 to form a 4' path;

[0107] The condensate outlet of the third preheater 21 is connected to the raw material liquid inlet of the second evaporator 22 to form a 5' path;

[0108] The hot water heat source enters the second evaporator 22 through an a' path, so that the saturated liquid organic working medium in the second evaporator 22 absorbs the heat of the hot water heat source and becomes a saturated gas state; the hot water at the outlet of the second evaporator 22 enters the third preheater 21 through a b' path, and the subcooled organic working medium in the third preheater 21 absorbs the heat of the hot water heat source, and the water source at the outlet of the third preheater 21 enters the external hot water pipe through a c' path;

[0109] The saturated gas enters the ORC expander 23 through a 1' path to drive the ORC expander 23 to work and generate a second power source and generate electricity through a second generator 24, and at the same time, the saturated gas becomes a low-temperature and low-pressure second organic exhaust steam, the second organic exhaust steam enters the second condenser 25 through a 2' path, and is condensed into a second organic condensate in the second condenser 25, the second organic condensate enters the second working medium pump 26 through a 3' path, the second working medium pump 26 pressurizes the second organic condensate to generate a second subcooled organic working medium, and the second subcooled organic working medium enters the third preheater 21 through a 4' path, and the second subcooled organic working medium absorbs the heat of the hot water heat source in the third preheater 21 to become a second organic working medium and enters the second evaporator 22 through a 5' path.

[0110] Optionally, the low-pressure loop further comprises a second cold water pump 28 and a second cooling tower 27, the output end of the second cold water pump 28 is connected to the cold water input end of the second condenser 25 to form a m1' path, the cold water output end of the second condenser 25 is connected to the input end of the second cooling tower 27 to form a n1 path, and the output end of the second cooling tower 27 is connected to the input end of the second cold water pump 28 to form a m1 path;

[0111] The cold water in the second cooling tower 27 enters the second cold water pump 28 through the m1 passage, is pressurized by the second cold water pump 28, and then enters the second condenser 25 through the m1' passage to provide a water cooling source for the second condenser 25, and the water-cooled liquid enters the second cooling tower 27 through the n1 passage.

[0112] The application also provides a thermal economic optimization design method of the steam-water dual-heat-source waste heat power generation split-flow system. Figure 2 As shown in the figure, the thermal economic optimization method comprises:

[0113] S1: According to the known parameters and boundary conditions in the steam-water dual-heat-source waste heat power generation split-flow system, the hot water split-flow ratio range, the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low-pressure loop evaporator outlet hot water temperature range are determined; the known parameters include: steam inlet parameters and hot water inlet parameters, and the hot water inlet parameters include hot water inlet flow rate;

[0114] A certain coal-to-oil process, and the ORC circulating working medium is R245fa. The known design parameters and boundary conditions are shown in Table 1. The condenser adopts a water-cooled counterflow heat exchanger. The evaporator adopts a counterflow heat exchanger. The expander adopts a screw expander. The cold water pump and the working medium pump adopt screw pumps.

[0115] Table 1 Known design parameters and boundary conditions

[0116]

[0117]

[0118] Taking the heat source parameters in Table 1 as an example, a thermodynamic model, a heat exchanger heat transfer model, and a system economic model are established and calculated. The above process is calculated by matlab, and the refprop function is called to obtain the property parameters of water and R245fa working medium.

[0119] S2: According to the hot water split-flow ratio range, the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low-pressure loop evaporator outlet hot water temperature range, the first maximum net output power and the first power generation cost of the steam-water dual-heat-source waste heat power generation split-flow system are determined by using the particle swarm algorithm. The first steam heat source outlet parameter and the first hot water heat source outlet parameter of the high-pressure loop part, and the first evaporator 14 outlet hot water temperature in the low-pressure loop are determined.

[0120] Alternatively, the S2 comprises:

[0121] S21: Based on the hot water split ratio range, the range of steam heat source outlet parameters in the high-pressure loop, the range of hot water heat source outlet parameters, and the range of hot water temperature at the evaporator outlet in the low-pressure loop, all initial particles of the particle swarm algorithm are obtained.

[0122] S22: Determine the fitness value of all particles using the objective function. The fitness value is the net output work of each particle.

[0123] Alternatively, the objective function may include:

[0124] t pin =min{(t c -t evap ),(t d -t5),(t a′ -t5),(t b″ -t4)}

[0125] t pin =min{(t c -t evap ),(t d -t5),(t a′ -t5),(t a′mid -t evap ),(t b′ -t4)}

[0126] Among them, t pin The pinch point temperature, t c The temperature at the steam outlet of the first evaporator 14 is represented by t. evap t represents the evaporation temperature. d t5 represents the steam outlet temperature of the second preheater 13, and t5 represents the condensate outlet temperature of the first preheater 12. a′ Indicates the inlet temperature of the hot water heat source and t a′ =t a” , t b″ t4 represents the water source outlet temperature of the first preheater 12, and t4 represents the outlet temperature of the first working fluid pump 18. a′mid This represents the hot water temperature (t) when the working fluid in the first preheater 12 is in a saturated liquid state. b′ This indicates the water source outlet temperature of the first evaporator 14.

[0127] S23: Based on the hot water split ratio range, the range of steam heat source outlet parameters in the high-pressure loop, the range of hot water heat source outlet parameters, the range of hot water temperature at the evaporator outlet in the low-pressure loop, and the fitness value of the particles, determine the optimal fitness value and the particle vector corresponding to the optimal fitness value, wherein the particle vector includes the hot water split ratio, the steam heat source outlet parameters in the high-pressure loop, the hot water heat source outlet parameters, and the hot water temperature at the evaporator outlet in the low-pressure loop;

[0128] The process of determining the optimal fitness value is as follows:

[0129] The fitness of each particle is traversed, and the fitness of each particle is compared with the value of the historical maximum net output power. If the fitness of the particle i is greater than the historical maximum net output power, the vector of the particle i is replaced with the vector of the historical maximum net output power Pbest i ; otherwise, the vector Pbest i is not replaced.

[0130] The fitness of each particle is traversed, and the maximum net output power obtained by all particles is screened. The fitness of each particle is compared with the maximum net output power. If the fitness of the particle i is greater than the maximum net output power, the vector of the particle i is replaced with the vector of the population maximum net output power Gbest; otherwise, the vector Gbest is not replaced.

[0131] The new particle (i+1) is calculated according to the speed vector iteration formula and the position vector iteration formula of the particle i:

[0132] v i (t+1)=v i (t)+c1r1(pbest i (t)-x i (t))+c2r2(gbest i (t)-x i (t))

[0133] x i (t+1)=x i (t)+v i (t+1)

[0134] Wherein, subscript i is a positive integer, indexing each particle in the particle swarm; v is the speed vector of the particle; x is the position vector of the particle; t is the iteration number; c1 and c2 are learning factors, set to 2; r1 and r2 are random numbers between 0 and 1, Pbest is the best position vector of the particle i in the population, and Gbest is the best position vector of the particle i in history.

[0135] It is judged whether the new particle (t+1) obtained satisfies the iteration number. If yes, the position vector X i+1 of the new particle (t+1) is used to find the corresponding optimal hot water shunt ratio, optimal high-pressure loop partial steam heat source outlet parameter, optimal hot water heat source outlet parameter and optimal low-pressure loop evaporator outlet hot water temperature.

[0136] Otherwise, the fitness value of new particle (t+1) is calculated and iteration is carried out until the optimal hot water split ratio, the optimal high-pressure loop partial steam heat source outlet parameter, the optimal hot water heat source outlet parameter and the optimal low-pressure loop evaporator outlet hot water temperature are obtained;

[0137] According to the optimal hot water split ratio, the optimal high-pressure loop partial steam heat source outlet parameter, the optimal hot water heat source outlet parameter and the optimal low-pressure loop evaporator outlet hot water temperature, the optimal fitness value is obtained.

[0138] In addition, the known parameters of the present application include: steam inlet parameters and hot water inlet parameters, the hot water inlet parameters including hot water inlet flow and hot water inlet temperature, and the steam inlet parameters including steam inlet pressure and steam inlet flow.

[0139] With reference to the specific embodiments of the present application, Figure 3 As shown in S23, S23 includes:

[0140] According to the hot water split ratio range and the hot water inlet flow, the hot water flow range entering the high-pressure loop and the hot water flow range entering the low-pressure loop are obtained;

[0141] Specifically, the split ratio r sp is calculated by the following formula:

[0142]

[0143] m hw and m hw′ are the hot water flow entering the high-pressure loop and the hot water flow entering the low-pressure loop, kg / s.

[0144] According to the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, the relationship between the evaporating temperature and the working medium flow is determined by using the first law of thermodynamics;

[0145] According to the high and low of the total hot water heat exchange amount, the position of the pinch temperature difference is determined;

[0146] According to the high and low of the total hot water heat exchange amount, the working medium at the outlet of the first preheater 12 can be in two-phase or subcooled state, if the working medium at the outlet of the first preheater 12 is in subcooled state, the second preheater 13 undertakes the remaining part of the working medium subcooled section heat exchange amount, and the evaporator undertakes the whole working medium two-phase heat exchange amount, at this time, the position of the pinch temperature difference is determined by the formula t pin = min{(t c -t evap ), (t d -t5), (t a′ -t5), (t b″t4) is calculated; if the working medium at the outlet of the first preheater 12 is in a two-phase state, the first preheater 12 bears all the working medium subcooling heat exchange and part of the working medium two-phase heat exchange, the second preheater 13 and the evaporator bear the remaining working medium two-phase heat exchange, and the pinch point temperature difference position is determined by the formula t pin = min{(t c -t evap ),(t d -t5),(t a′ -t5),(t a′mid -t evap ),(t b′ -t4)}.

[0147] According to the position of the pinch point temperature difference and the objective function, the evaporation temperature and the working medium flow rate of the high-pressure loop are determined;

[0148] According to the evaporation temperature and the working medium flow rate of the high-pressure loop, the net output power and the power generation cost of the high-pressure loop are determined;

[0149] According to the pinch point temperature difference and the hot water temperature range at the outlet of the evaporator in the low-pressure loop, the evaporation temperature of the low-pressure loop is obtained;

[0150] According to the evaporation temperature of the low-pressure loop, the net output power and the power generation cost of the low-pressure loop are determined.

[0151] The net output power W net is expressed as:

[0152] W net = f(t d ,P d ,r sp ,t b″ ,t b′ )

[0153] The power generation cost EPC is expressed as:

[0154] EPC = f(t d ,P d ,r sp ,t b″ ,t b′ )

[0155] Where t d represents the steam outlet temperature of the second preheater 13 (steam condensate outlet temperature), P d represents the steam outlet pressure of the second preheater 13 (steam heat source outlet pressure), r sp represents the hot water diversion ratio, t b″ represents the water source outlet temperature of the first preheater 12 (high-pressure loop hot water outlet temperature), and t b′represents the first evaporator 14 water source outlet temperature (low pressure loop evaporator outlet hot water temperature).

[0156] S24: outputting the optimal adaptation value as the first maximum net output power, and determining the first power generation cost corresponding to the first maximum net output power according to the first maximum net output power;

[0157] S25: outputting the particle vector corresponding to the optimal adaptation value as the high-pressure loop portion first steam heat source outlet parameter and the first hot water heat source outlet parameter, and the low-pressure loop first evaporator outlet hot water temperature.

[0158] In the particle swarm algorithm, "particles" are each independent variable set, i.e. (steam condensate outlet temperature t d , steam heat source outlet pressure P d , hot water diversion ratio r sp , high-pressure loop hot water outlet temperature t b″ , low-pressure loop evaporator outlet hot water temperature t b′ ). The particles update themselves by tracking two "extremes", the first "extreme" is the optimal value found by the particles themselves, and the particle parameters are called historical best position vectors, and the second "extreme" is the optimal solution currently found by the entire population, and the particle parameters are called global best position vectors. These two optimal variable vectors make all particles approach these directions, while changing their own positions and speeds, until the maximum net output power W net is found. The particle swarm design parameters in Table 2 are used for optimization calculation. The results are as follows Figure 4 , the maximum net output power under different particle numbers can converge after 50 iterations.

[0159] Table 2 Particle swarm algorithm design parameters

[0160]

[0161] S3: according to the hot water diversion ratio range, the high-pressure loop portion steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the low-pressure loop evaporator outlet hot water temperature range, using the second generation non-dominated sorting genetic algorithm, determining the high-pressure loop portion second steam heat source outlet parameter and the second hot water heat source outlet parameter corresponding to the optimal net output power and the optimal power generation cost of the steam-water dual heat source waste heat power generation diversion system, and the low-pressure loop second evaporator 22 outlet hot water temperature;

[0162] Optionally, the S3 comprises:

[0163] S31: obtaining a Pareto frontier curve with horizontal and vertical coordinates being net output power and power generation cost of the steam-water dual heat source waste heat power generation split-flow system according to the high pressure saturated steam heat source outlet parameter range and the hot water heat source outlet parameter range by using the second generation non-dominated sorting genetic algorithm;

[0164] Optionally, the S31 comprises:

[0165] determining design parameters of the second generation non-dominated sorting genetic algorithm according to the hot water split-flow ratio range, the high pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low pressure loop;

[0166] creating N initial populations according to the design parameters of the second generation non-dominated sorting genetic algorithm;

[0167] applying a simulated binary crossover operation, a mutation polynomial operation and a tournament selection operation to N parent individuals in the N initial populations to obtain N offspring individuals; wherein the individual represents the hot water split-flow ratio range, the high pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low pressure loop;

[0168] composing 2N individuals by combining the N offspring individuals and the N parent individuals;

[0169] generating all solutions corresponding to the 2N individuals;

[0170] determining Pareto levels of all solutions by using an elitist strategy and sorting the Pareto levels of all solutions;

[0171] namely, storing all individuals with n(i)=0 into a set F(1); for each individual j in the current set F(1), examining a set S(j) of individuals dominated by the individual j, subtracting 1 from n(k) of each individual k in the set S(j) and storing the individual k into a set H; taking the set F(1) as a first level non-dominated individual set and assigning the same non-dominated order i to individuals in the set, then continuing to perform hierarchical operation on the set H and assigning corresponding non-dominated orders until all individuals are hierarchized;

[0172] setting an infinite value for crowding distance of boundary individuals in each set of the sorting result and calculating the crowding distance i d of other individuals;

[0173]

[0174] wherein i d represents the crowding distance of the i-th point, represents the j-th objective function value of the i+1-th point, The jth objective function value of the i-1th point.

[0175] The new individual with better crowding degree is put into the parent population until the parent population is filled;

[0176] It is judged whether the current iteration meets the maximum iteration number, if yes, the Pareto front curve of the horizontal and vertical coordinates being the net output power and the power generation cost of the steam-water dual heat source waste heat power generation split-flow system is obtained according to the individuals in the current parent population, otherwise, the iteration is continued.

[0177] After sorting and crowding degree calculation, each individual in the population obtains two attributes, i.e. non-dominated sorting and crowding degree, and the selection order is defined as follows: if the non-dominated sorting of two individuals is different, the individual with smaller sorting number (i.e. the individual separated out first in the allocation set) is taken; if the two individuals are in the same level, the individual with less surrounding crowding (i.e. the individual with larger crowding degree) is taken until the number of selected individuals reaches N, thereby filling the parent population.

[0178] The input second-generation non-dominated sorting genetic algorithm (NSGA-II) design parameters are shown in Table 3, wherein each individual represents a set of independent variables, i.e. (steam condensate outlet temperature t d , steam heat source outlet pressure P d , hot water split-flow ratio r sp , high-pressure loop hot water outlet temperature t b” , low-pressure loop evaporator outlet hot water temperature t b’ ). The optimization result obtained by the NSGA-II algorithm is a Pareto front curve composed of the net output power and the power generation cost calculated after all individuals are iterated by the maximum genetic generation number. As shown in Figure 5 , each optimization result on the Pareto front curve is taken as an evaluation object, i.e. (net output power W net , power generation cost EPC), and a decision needs to be made to obtain the optimal solution of multi-objective optimization.

[0179] Table 3 NSGA-II algorithm design parameters

[0180]

[0181] S32: An optimal decision is made on the Pareto front curve by using a decision method of multi-objective optimization, to obtain an optimal net output power and an optimal power generation cost, and high-pressure loop part second steam heat source outlet parameters and second hot water heat source outlet parameters corresponding to the optimal net output power and the optimal power generation cost, and a low-pressure loop second evaporator 22 outlet hot water temperature.

[0182] The decision method of multi-objective optimization includes:

[0183] A1: weights are assigned to the net output work and power generation cost indicators using an entropy weight method;

[0184] The weight w in the entropy weight method j is:

[0185]

[0186] where e j represents the information entropy of the jth indicator and K is a constant and K = 1 / ln(m), y ij is the proportion of the jth indicator of the ith number and F ij represents the normalized matrix element of the individual in the Pareto frontier curve.

[0187] A2: the distance of the evaluation object from the optimal solution and the worst solution is sorted using an approximation ideal solution sorting method, to obtain a sorting result;

[0188] The distance d i+ of the evaluation object from the optimal solution is:

[0189]

[0190] The distance d i- of the evaluation object from the worst solution is:

[0191]

[0192] where w j represents the weight and e j represents the information entropy of the jth indicator and K is a constant and K = 1 / ln(m), y ij is the proportion of the jth indicator of the ith number and F ij represents the normalized matrix element of the individual in the Pareto frontier curve, is the optimal value, is the worst value.

[0193] A3: the proximity of the optimization result to the ideal value is calculated according to the sorting result.

[0194] The proximity C i of the optimization result to the ideal value is:

[0195]

[0196] where d i+ represents the distance of the evaluation object from the optimal solution and d i-represents the distance of the evaluation object from the worst solution and w j represents the weight and e j represents the information entropy of the jth index and K is a constant and K = 1 / ln(m), y ij is the proportion of the ith number and the jth index and F ij represents the normalized matrix element of the individual in the Pareto front curve, is the optimal value, is the worst value.

[0197] Through the NSGA-II algorithm, the optimization results under different individual numbers and genetic generations are shown in Table 4. It is found that after decision-making by the entropy weight method, the deviation of optimizing net output power is within 0.9%, and the deviation of optimizing power generation cost is within 1.3%. In addition, the optimization results will have certain deviations when the ranges of selected independent variables are different.

[0198] Table 4 Multi-objective optimization results

[0199]

[0200]

[0201] S4: According to the known parameters, boundary conditions, high-pressure loop part first / second steam heat source outlet parameters and first / second hot water heat source outlet parameters, and low-pressure loop first / second evaporator 22 outlet hot water temperature, the parameters of each device in the steam-water dual heat source waste heat power generation split system are determined.

[0202] Example 2

[0203] Assuming that the steam-hot water working condition is shown in Table 5, by fixing other heat source parameters, changing one heat source parameter, the single-objective and multi-objective optimization results of ORC system under different heat source conditions are analyzed.

[0204] Table 5 Heat source change of dual heat source ORC system

[0205]

[0206] Through the above method, the optimization design results of the steam-water dual heat source waste heat power generation split system are shown in Tables 6-9.

[0207] Table 6 Optimization results under different steam inlet pressures

[0208]

[0209] Table 7 Optimization results under different steam flow rates

[0210]

[0211]

[0212] Table 8 Optimization results under different hot water temperatures

[0213]

[0214]

[0215] Table 9 Optimization results under different hot water flow rates

[0216]

[0217]

[0218] From the optimization results under different heat source parameters, in order to improve the economic performance, the steam-water dual heat source waste heat power generation split system will appropriately increase the hot water temperature at the outlet of the high-pressure preheater and the hot water split ratio in the independent parameters. Through multi-objective optimization, the net output power of a part will be reduced, but the power generation cost of the system will be reduced and the power generation efficiency of the system will be improved. Under the same heat source, the net output power of the multi-objective optimization is averagely 2.5% lower than that of the single-objective optimization result, the power generation cost is averagely 9.3% lower than that of the single-objective optimization result, and the power generation efficiency is averagely improved by 0.41%.

[0219] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for thermoeconomic optimization design of a steam-water dual heat source waste heat power generation split-flow system, characterized in that, The thermal economy optimization method comprises: S1: according to the known parameters and boundary conditions of the steam-water dual heat source waste heat power generation shunt system, the hot water shunt ratio range, the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low-pressure loop are determined; S2: according to the hot water shunt ratio range, the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low-pressure loop, the first maximum net output power of the steam-water dual heat source waste heat power generation shunt system and the first maximum net output power corresponding to the first power generation cost and the corresponding high-pressure loop partial first steam heat source outlet parameter and first hot water heat source outlet parameter and the first evaporator outlet hot water temperature in the low-pressure loop are determined by using a particle swarm algorithm; The S2 comprises: S21: all initial particles of the particle swarm algorithm are obtained according to the hot water shunt ratio range, the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low-pressure loop; S22: the fitness value of all particles is determined by a target function, and the fitness value is the net output power corresponding to each particle; In the S22, the target function comprises: wherein, represents the pinch temperature, represents the steam outlet temperature of the first evaporator, represents the evaporation temperature, represents the steam outlet temperature of the second preheater, represents the condensate outlet temperature of the first preheater, represents the hot water source inlet temperature, represents the water source outlet temperature of the first preheater, represents the outlet temperature of the first working medium pump, represents the hot water temperature corresponding to the saturated liquid state of the working medium in the first preheater, represents the water source outlet temperature of the first evaporator; The known parameters comprise a steam inlet parameter and a hot water inlet parameter, and the hot water inlet parameter comprises a hot water inlet flow rate; S23: according to the hot water shunt ratio range, the high-pressure loop partial steam heat source outlet parameter range, the hot water heat source outlet parameter range, the evaporator outlet hot water temperature range in the low-pressure loop and the fitness value of the particle, the optimal fitness value and the particle vector corresponding to the optimal fitness value are determined, wherein the particle vector comprises the hot water shunt ratio, the high-pressure loop partial steam heat source outlet parameter, the hot water heat source outlet parameter and the evaporator outlet hot water temperature in the low-pressure loop; S23 comprises: According to the hot water shunt ratio range and the hot water inlet flow rate, the hot water flow rate range entering the high-pressure loop and the hot water flow rate range entering the low-pressure loop are obtained; According to the high-pressure loop partial steam heat source outlet parameter range and the hot water heat source outlet parameter range, the relationship between the evaporation temperature and the working medium flow rate is determined by using the first law of thermodynamics; According to the high and low of the total heat exchange amount of hot water, the position of the pinch temperature difference is determined, comprising: According to the total heat exchange amount of the hot water, the working medium at the outlet of the first preheater can be in a two-phase or sub-cooled state. If the working medium at the outlet of the first preheater is in a sub-cooled state, the second preheater bears the remaining working medium sub-cooled heat exchange amount, and the evaporator bears all working medium two-phase heat exchange amount. At this time, the location of the pinch point temperature difference is calculated by the formula If the working medium at the outlet of the first preheater is in a two-phase state, the first preheater bears all working medium sub-cooled heat exchange amount and part of working medium two-phase heat exchange amount, and the second preheater and the evaporator jointly bear the remaining working medium two-phase heat exchange amount. At this time, the location of the pinch point temperature difference is determined by the formula ​ According to the position of the pinch temperature difference, the evaporation temperature and the working medium flow rate of the high-pressure loop are determined; According to the evaporation temperature and the working medium flow rate of the high-pressure loop, the net output power and the power generation cost of the high-pressure loop are determined; According to the pinch temperature difference and the evaporator outlet hot water temperature range in the low-pressure loop, the evaporation temperature of the low-pressure loop is obtained; According to the evaporation temperature of the low-pressure loop, the net output power and the power generation cost of the low-pressure loop are determined; Net output power is represented as: Generation cost is represented as: wherein, represents the steam outlet temperature of the second preheater, represents the steam outlet pressure of the second preheater, represents the hot water split ratio, represents the water source outlet temperature of the first preheater, represents the first evaporator water source outlet temperature; S24: the optimal fitness value is output as the first maximum net output power, and the first power generation cost corresponding to the first maximum net output power is determined; S25: the particle vector corresponding to the optimal fitness value is output as the high-pressure loop partial first steam heat source outlet parameter and the first hot water heat source outlet parameter, and the first evaporator outlet hot water temperature in the low-pressure loop; S3: determining the second steam heat source outlet parameter and the second hot water heat source outlet parameter of the high pressure loop part, the second evaporator outlet hot water temperature in the low pressure loop, and the optimal net output power and the optimal power generation cost corresponding to the optimal net output power and the optimal power generation cost of the steam-water dual heat source waste heat power generation split-flow system by using the second generation non-dominated sorting genetic algorithm according to the hot water split-flow ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low pressure loop; The S3 comprises: S31: obtaining a Pareto frontier curve with the horizontal and vertical coordinates being the net output power and the power generation cost of the steam-water dual heat source waste heat power generation split-flow system by using the second generation non-dominated sorting genetic algorithm according to the high pressure saturated steam heat source outlet parameter range and the hot water heat source outlet parameter range; S32: obtaining the optimal net output power and the optimal power generation cost, and the second steam heat source outlet parameter and the second hot water heat source outlet parameter of the high pressure loop part, the second evaporator outlet hot water temperature in the low pressure loop corresponding to the optimal net output power and the optimal power generation cost by using a multi-objective optimization decision method to make an optimal solution to the Pareto frontier curve; The multi-objective optimization decision method comprises: A1: assigning weights to the net output power and the power generation cost index by using an entropy weight method; The entropy weight method in which the weight value is: wherein, represents the information entropy of the j th indicator and , K is a constant and , is the proportion of the i th number of the j th indicator and , represents the normalized matrix element of the individual in the Pareto frontier curve; A2: sorting the distances of the evaluation objects from the optimal solution and the worst solution by using an approximation ideal solution sorting method to obtain a sorting result; the distance of the evaluation object from the optimal solution is: The distance of the evaluation object from the worst solution is: wherein is the optimal value, is the worst value; A3: calculating the closeness of the optimization result to the ideal value according to the sorting result; the closeness of the optimization result to an ideal value is: S4: determining the parameters of each device in the steam-water dual heat source waste heat power generation split-flow system according to the known parameters, the boundary conditions, the first / second steam heat source outlet parameter and the first / second hot water heat source outlet parameter of the high pressure loop part, and the first / second evaporator outlet hot water temperature in the low pressure loop.

2. The thermally economic design optimization method of claim 1, wherein, The S31 comprises: determining the design parameters of the second generation non-dominated sorting genetic algorithm according to the hot water split-flow ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low pressure loop; creating N initial populations according to the design parameters of the second generation non-dominated sorting genetic algorithm; performing cross operation, mutation polynomial operation and tournament selection operation on N parent individuals in the N initial populations by using a simulated binary mating method to obtain N child individuals; wherein the individual represents the hot water split-flow ratio range, the high pressure loop part steam heat source outlet parameter range and the hot water heat source outlet parameter range, and the evaporator outlet hot water temperature range in the low pressure loop; combining the N child individuals and the N parent individuals to form 2N individuals; generating all solutions corresponding to the 2N individuals; determining the Pareto levels of all solutions by using an elite strategy, and sorting the Pareto levels of all solutions; setting the boundary individual crowding degree in each set of the sorting result to be infinite, and calculating the crowding degree of other individuals; putting the better new individuals into the parent population by using the crowding degree until the parent population is filled up; If yes, the Pareto front curve of the horizontal and vertical coordinates of the net output power and the power generation cost of the steam-water dual heat source waste heat power generation split-flow system is obtained according to the individuals in the current parent population, otherwise, the iteration is continued.

3. The thermally economic design optimization method of claim 1, wherein, The steam-water dual heat source waste heat power generation split-flow system comprises a high-pressure loop and a low-pressure loop, a hot water input end of the high-pressure loop and a hot water input end of the low-pressure loop are simultaneously connected to an external hot water pipe, the high-pressure loop and the low-pressure loop are respectively provided with a first generator and a second generator, and the first generator / second generator is used to generate power according to high-temperature and high-pressure organic steam in the high-pressure loop / low-pressure loop to drive a first expander / ORC expander.

4. The thermoeconomic design optimization method of claim 3, wherein, The high-pressure loop further comprises a first evaporator, a first preheater, a second preheater, a first working medium pump, a first condenser, a third generator and a second expander; An outlet of the first expander is connected to a steam inlet of the first evaporator to form a b passage; A steam outlet of the first evaporator is connected to a steam inlet of the second preheater to form a c passage; A steam outlet of the second preheater is connected to the external hot water pipe to form a d passage; A liquid outlet of the first evaporator is connected to an inlet of the second expander to form a 1 passage; An outlet of the second expander is connected to a gas inlet of the first condenser to form a 2 passage; A gas outlet of the first condenser is connected to an inlet of the first working medium pump to form a 3 passage; An outlet of the first working medium pump is connected to a condensate inlet of the first preheater to form a 4 passage; A condensate outlet of the first preheater is connected to a condensate inlet of the second preheater to form a 5 passage; A condensate outlet of the second preheater is connected to a raw material liquid inlet of the first evaporator to form a 6 passage; A water source inlet of the first preheater is connected to an outlet of the external hot water pipe as the hot water input end of the high-pressure loop to form an a'' passage, and a water source outlet thereof is connected to an inlet of the external hot water pipe to form a b'' passage, hot water enters the first preheater through the a'' passage, and after being heated by the first preheater, the hot water enters the external hot water pipe through the b'' passage; The input of the first expander is a high-pressure saturated steam heat source, which generates a first power source through the first expander and generates electricity through a first generator; and the high-pressure saturated steam heat source is reduced in pressure to wet steam through work of the steam expander, the wet steam enters the first evaporator through the b passage to evaporate the organic working medium in the first evaporator from a saturated liquid state to a saturated gaseous state, the saturated gaseous state enters the second expander through the 1 passage to drive the second expander to generate electricity and change the saturated steam into low-temperature and low-pressure organic exhaust steam, the organic exhaust steam enters the first condenser through the 2 passage and is condensed into organic condensate in the first condenser, the organic condensate enters the first working medium pump through the 3 passage, is pressurized by the first working medium pump and enters the first preheater through the 4 passage to absorb heat of the hot water heat source to form the organic working medium, the organic working medium enters the second preheater through the 5 passage, and the steam heat source at the steam outlet of the evaporator enters the second preheater through the c passage to enable the steam waste heat in the second preheater to process the organic working medium, and the processed steam forms hot water which enters an external hot water pipe through the d passage.

5. The thermally economic design optimization method of claim 4, wherein, The high-pressure loop further comprises a first cold water pump and a first cooling tower, an output end of the first cold water pump being communicated with a cold water input end of the first condenser to form an m' passage, a cold water output end of the first condenser being communicated with an input end of the first cooling tower to form an n passage, and an output end of the first cooling tower being communicated with an input end of the first cold water pump to form an m passage; The cold water in the first cooling tower enters the first cold water pump through the m passage, is pressurized by the first cold water pump and then enters the first condenser through the m' passage to provide a water cooling source for the first condenser, and the water-cooled liquid enters the first cooling tower through the n passage.

6. The thermally economic design optimization method of claim 3, wherein, The low-pressure loop comprises a third preheater, a second evaporator, an ORC expander, a second condenser, a second cold water pump and a second working medium pump; A water source inlet of the second evaporator is communicated with an outlet of the external hot water pipe as a hot water input end of the low-pressure loop to form an a' passage, and a water source outlet thereof is communicated with a water source inlet of the third preheater to form a b' passage; A water source outlet of the third preheater is communicated with an inlet of the external hot water pipe to form a c' passage; A complete liquid outlet of the second evaporator is communicated with an inlet of the ORC expander to form a 1' passage; An outlet of the ORC expander is communicated with a gas inlet of the second condenser to form a 2' passage; A gas outlet of the second condenser is communicated with an inlet of the second working medium pump to form a 3' passage; An outlet of the second working medium pump is communicated with a condensate inlet of the third preheater to form a 4' passage; A condensate outlet of the third preheater is communicated with a raw material liquid inlet of the second evaporator to form a 5' passage; The hot water heat source enters the second evaporator through a' passage to make the saturated liquid organic working medium in the second evaporator absorb heat of the hot water heat source to become saturated gas; The saturated gas enters the ORC expander through 1' passage to drive the ORC expander to work and generate the second power source and generate electricity through the second generator, and at the same time, the saturated gas becomes the low-temperature and low-pressure second organic exhaust steam, the second organic exhaust steam enters the second condenser through 2' passage, and is condensed into the second organic condensate in the second condenser, the second organic condensate enters the second working medium pump through 3' passage, the second working medium pump pressurizes the second organic condensate to generate the second cold organic working medium, and the second cold organic working medium enters the third preheater through 4' passage, the second cold organic working medium absorbs heat of the hot water heat source in the third preheater to become the second organic working medium and enters the second evaporator through 5' passage.

7. The thermally economic design optimization method of claim 6, wherein, The low-pressure loop further comprises a second cold water pump and a second cooling tower, an output end of the second cold water pump is communicated with a cold water input end of the second condenser to form m1' passage, a cold water output end of the second condenser is communicated with an input end of the second cooling tower to form n1 passage, and an output end of the second cooling tower is communicated with an input end of the second cold water pump to form m1 passage; The cold water in the second cooling tower enters the second cold water pump through m1 passage, is pressurized by the second cold water pump, and enters the second condenser through m1' passage to provide a water cooling source for the second condenser, and the water-cooled liquid enters the second cooling tower through n1 passage.

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