Comprehensive energy utilization system and method based on waste heat utilization of combined cycle units

Abstract

The present invention discloses a comprehensive energy utilization system and method based on waste heat utilization of a combined cycle unit, the system comprising a power generation module, a seawater desalination module, a hot and cold water unit and a central air conditioning system; the power generation module comprises a gas turbine, a compressor, a waste heat boiler, a steam turbine and a generator; the seawater desalination module comprises a flash evaporation device and a low-temperature multi-effect seawater desalination device; the flash evaporation device in the seawater desalination module utilizes the waste heat generated by the power generation module to generate low-pressure steam; the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate seawater; the low-temperature water generated by the flash evaporation device is mixed with the condensate generated by the low-temperature multi-effect seawater desalination device and then enters the hot and cold water unit for heat exchange, so as to realize the refrigeration or heating of the central air conditioning system. The system can utilize the waste heat of flue gas for desalination and water production, and the mixed water generated in the seawater desalination process can participate in the refrigeration or heating of the indoor central air conditioning system, realizing the efficient cascade utilization of the energy of the combined cycle unit.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive energy utilization, and in particular to a comprehensive energy utilization system and method based on waste heat utilization of a combined cycle unit. Background Art

[0002] Desalination is a technology that uses energy to obtain fresh water resources. According to the different forms of energy in the desalination process, desalination can be divided into multi-stage flash evaporation and multi-effect distillation thermal technologies that mainly consume heat energy and reverse osmosis membrane technologies that mainly consume electricity, commonly known as thermal methods and membrane methods. However, due to the shortcomings of the membrane method, such as large footprint, large chemical consumption, and performance being greatly affected by seawater temperature, its application prospects are lower than those of the thermal method. At present, low-temperature multi-effect seawater desalination devices are widely used in thermal processes. The heat source requirement of this device is mainly slightly superheated or saturated steam not higher than 75°C.

[0003] At present, the tail flue gas of the waste heat boiler of most combined cycle power generation units is directly discharged into the atmosphere at a temperature of 80℃~110℃. The waste heat energy of this flue gas is not fully utilized, which reduces the thermal efficiency of the whole plant and affects the economic efficiency of the combined cycle unit operation.

[0004] In addition, with the development of the global economy, energy and environmental protection situation, and the vigorous development of new energy, power generation companies are currently facing more stringent environmental protection requirements and severe market operating conditions. Power generation companies are exploring new development or transformation directions. One of the directions is for power generation companies to transform from pure power generation companies to comprehensive energy supply bases including electricity, heat, steam, gas, cold, water, etc.

[0005] In view of this, for some combined cycle units built in coastal areas, the present invention proposes a water-electricity-cooling integrated energy system based on waste heat utilization of combined cycle units to achieve efficient cascade utilization of energy of combined cycle units. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a comprehensive energy utilization system and method based on the waste heat utilization of a combined cycle unit; the system utilizes the waste heat of the flue gas at the tail of the waste heat boiler of the combined cycle unit to provide the required heat source for the low-temperature multi-effect seawater desalination device to desalinate and produce water; at the same time, the mixed water generated in the seawater desalination process flows back to the hot and cold water unit to participate in the cooling or heating of the indoor central air-conditioning system, thereby realizing efficient cascade utilization of the energy of the combined cycle unit.

[0007] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0008] A comprehensive energy utilization system based on waste heat utilization of a combined cycle unit, comprising a power generation module, a seawater desalination module, a hot and cold water unit and a central air conditioning system;

[0009] The power generation module includes a gas turbine, a compressor, a waste heat boiler, a steam turbine, and a generator; the waste heat boiler includes a steam generation system and a smoke-water heat exchanger; the seawater desalination module includes a flash evaporation device and a low-temperature multi-effect seawater desalination device; the hot and cold water unit includes a condenser, a compressor, and an evaporator;

[0010] The gas turbine, the compressor and the steam turbine jointly drive the generator to generate electricity; the flash evaporation device in the seawater desalination module utilizes the waste heat generated by the power generation module to generate low-pressure steam; the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater; the low-temperature water generated by the flash evaporation device is mixed with the condensate generated by the low-temperature multi-effect seawater desalination device and then enters the hot and cold water unit for heat exchange; the refrigerant in the hot and cold water unit absorbs heat in the evaporator to provide chilled water for cooling the central air-conditioning system; or the refrigerant in the hot and cold water unit releases heat in the condenser to provide heated water for heating the central air-conditioning system.

[0011] Furthermore, the flue gas outlet of the gas turbine is connected to the waste heat boiler; the flue gas is discharged after passing through the steam generation system and the flue gas-water heat exchanger in sequence; the steam generation system, the steam turbine and the condenser form a loop.

[0012] Furthermore, the water outlet of the smoke-water heat exchanger is connected to the flash evaporation device.

[0013] Furthermore, the low-pressure steam outlet of the flash evaporation device is connected to the heat source inlet of the low-temperature multi-effect seawater desalination device through a first electric valve.

[0014] Furthermore, the low-temperature water outlet of the flash evaporation device is connected to a low-temperature water outlet pipeline, which is connected to the hot and cold water unit through a first low-temperature water pipeline and a second low-temperature water pipeline in parallel; a second electric valve is provided on the first low-temperature water pipeline, and a third electric valve is provided on the second low-temperature water pipeline.

[0015] Furthermore, the evaporator, compressor and condenser in the hot and cold water unit are connected in sequence to form a refrigerant circuit.

[0016] Furthermore, the water inlet of the condenser is connected to the first low-temperature water pipeline, the water outlet of the condenser is connected to the water inlet of the smoke-water heat exchanger through the first water circulation pipeline, and the first water circulation pipeline is provided with a fourth electric valve; the water outlet of the evaporator is connected to the water inlet of the central air-conditioning system through the chilled water inlet, and the chilled water inlet is provided with a fifth electric valve; the water outlet of the central air-conditioning system is connected to the water inlet of the evaporator through the chilled water circuit; and a sixth electric valve is provided on the chilled water pipeline.

[0017] Furthermore, the water inlet of the evaporator is connected to the second low-temperature water pipeline; the water outlet of the evaporator is connected to the water inlet of the smoke-water heat exchanger through the second water circulation pipeline, and the second water circulation pipeline is provided with a seventh electric valve; the water outlet of the condenser is connected to the water inlet of the central air-conditioning system through the hot water inlet, and the hot water inlet is provided with an eighth electric valve; the water outlet of the central air-conditioning system is connected to the water inlet of the condenser through the hot water circuit, and the hot water circuit is provided with a ninth electric valve.

[0018] Furthermore, the low-temperature water outlet pipeline is also connected to the water inlet of the smoke-water heat exchanger through a low-temperature water circuit; and a tenth electric valve is provided on the low-temperature water circuit.

[0019] Furthermore, the low-temperature water outlet pipeline is also connected to the second water circulation pipeline through a low-temperature water circuit; and a tenth electric valve is provided on the low-temperature water circuit.

[0020] Based on the above system, the present invention further provides a comprehensive energy utilization method based on waste heat utilization of a combined cycle unit, specifically:

[0021] When the central air conditioning system is cooling:

[0022] Close the third electric valve, the tenth electric valve, the ninth electric valve, the seventh electric valve, and the eighth electric valve, and open the second electric valve, the sixth electric valve, the fifth electric valve, and the fourth electric valve; use the flue gas heat exchanger to recover the waste heat of the tail flue gas of the waste heat boiler, and after the heat exchange, the hot water enters the flash evaporation device to generate low-pressure steam, and the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater; the generated fresh water enters the fresh water user; the condensed water generated by the low-temperature multi-effect seawater desalination device is mixed with the low-temperature water generated by the flash evaporation device and then enters the condenser in the hot and cold water unit through the first low-temperature water pipeline to exchange heat with the compressed refrigerant, and after the heat exchange, the condensed water re-enters the flue gas water heat exchanger through the first water circulation pipeline to absorb heat; the refrigerant in the hot and cold water unit evaporates and absorbs heat in the evaporator, and the chilled water output by the central air-conditioning system is cooled, and the chilled water after cooling enters the central air-conditioning system through the chilled water inlet for refrigeration;

[0023] When the central air conditioning system is heating:

[0024] The third electric valve, the tenth electric valve, the ninth electric valve, the seventh electric valve and the eighth electric valve are opened, and the second electric valve, the sixth electric valve, the fifth electric valve and the fourth electric valve are closed; the waste heat of the tail flue gas of the waste heat boiler is recovered by using the flue gas-water heat exchanger, and the hot water after heat exchange enters the flash evaporation device to generate low-pressure steam, and the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater, and the generated fresh water enters the fresh water user; the condensed water generated by the low-temperature multi-effect seawater desalination device is mixed with the low-temperature water generated by the flash evaporation device; a part of the mixed water enters the evaporator in the hot and cold water unit through the second low-temperature water pipeline for further cooling to generate condensed water; the other part of the mixed water passes through the tenth electric valve, and then mixes with the condensed water output by the evaporator and enters the flue gas-water heat exchanger to absorb heat; the refrigerant in the hot and cold water unit condenses and releases heat in the condenser, and the air-conditioning water output by the central air-conditioning system is heated, and the heated air-conditioning water enters the central air-conditioning system through the hot water inlet and the eighth electric valve for heating.

[0025] The beneficial effects of the present invention are:

[0026] The present invention installs a flue gas-water heat exchanger in the tail area of ​​the waste heat boiler in the combined cycle unit, and utilizes the heat generated by the heat exchange between the tail flue gas and water in the flue gas-water heat exchanger to drive a low-temperature multi-effect seawater desalination device to produce fresh water. At the same time, the low-temperature water generated in the seawater desalination process is mixed with condensed water and enters the hot and cold water unit to participate in the cooling / heating of the indoor central air-conditioning system, thereby meeting the normal working and living needs of indoor personnel.

[0027] On the one hand, the present invention not only realizes the waste heat utilization of the flue gas at the tail of the waste heat boiler of the combined cycle unit, thereby improving the thermal efficiency of the entire plant of the combined cycle unit, but also, on the other hand, constructs the industrial layout of the hydropower and cooling integrated energy system, realizes the efficient cascade utilization of energy, and enhances the survival and sustainable development capabilities of power generation enterprises under the new situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of an integrated energy utilization system based on waste heat utilization of a combined cycle unit according to Example 1 of the present invention.

[0029] Figure 2 This is a schematic diagram of an integrated energy utilization system based on waste heat utilization of a combined cycle unit according to Example 2 of the present invention.

[0030] In the figure, 1: gas turbine; 2: compressor; 3: waste heat boiler, 301: steam generation system, 302: smoke-water heat exchanger; 4: steam turbine; 5: generator; 6: flash evaporation device; 7: low-temperature multi-effect seawater desalination device; 8: hot and cold water unit, 801: condenser, 802: compressor, 803: evaporator; 9: condenser; 10: low-pressure steam pipeline; 11: first electric valve; 12: central air conditioning system; 13: low-temperature water outlet pipeline; 14: first low-temperature water pipeline; 15: second low-temperature water pipeline; 16: first Second electric valve; 17: third electric valve; 18: first water circulation pipeline; 19: fourth electric valve; 20: chilled water inlet; 21: fifth electric valve; 22: chilled water circuit; 23: sixth electric valve; 24: second water circulation pipeline; 25: seventh electric valve; 26: hot water inlet; 27: eighth electric valve; 28: hot water circuit; 29: ninth electric valve; 30: low-temperature water circuit; 31: tenth electric valve; 32: condensate pipeline; 33: eleventh electric valve; 34: fresh water user; 35: twelfth electric valve. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0032] Example 1

[0033] like Figure 1 A comprehensive energy utilization system based on waste heat utilization of a combined cycle unit is shown, which includes a power generation module, a seawater desalination module, a hot and cold water unit and a central air-conditioning system.

[0034] The power generation module includes a gas turbine 1, a compressor 2, a waste heat boiler 3, a steam turbine 4, and a generator 5; the waste heat boiler 3 includes a steam generation system 301 and a smoke-water heat exchanger 302; the seawater desalination module includes a flash evaporation device 6 and a low-temperature multi-effect seawater desalination device 7; the hot and cold water unit 8 includes a condenser 801, a compressor 802, and an evaporator 803.

[0035] The flue gas outlet of the gas turbine 1 is connected to the waste heat boiler 3; the flue gas passes through the steam generation system 301 and the flue gas water heat exchanger 302 in sequence and is then discharged; the steam generation system 301, the steam turbine 4 and the condenser 9 form a loop.

[0036] In this embodiment, the rotating shafts of the gas turbine 1, the compressor 2, and the steam turbine 4 are coaxially connected; the compressor inhales air from the surrounding atmosphere, pressurizes it, and supplies it to the combustion chamber of the gas turbine; the internal energy of the high-pressure gas ejected from the combustion chamber is converted into mechanical energy to drive the generator 5 to generate electricity; the high-temperature gas discharged from the gas turbine 1 enters the waste heat boiler 3, and the waste heat boiler 3 heats water into steam through the steam generation system 301 to drive the steam turbine 4, which drives the generator 5 to generate electricity. The exhaust steam of the steam turbine 4 is condensed by the condenser 9 and then enters the waste heat boiler 3, and the steam generation system 301 generates steam, which enters the steam turbine 4 to form a steam-water cycle.

[0037] The flash evaporation device 6 in the desalination module generates low-pressure steam using the waste heat generated by the power generation module. Specifically, the water outlet of the flue gas-water heat exchanger 302 is connected to the water inlet of the flash evaporation device 6. The low-pressure steam outlet of the flash evaporation device 6 is connected to the heat source inlet of the low-temperature multi-effect desalination device 7 through the low-pressure steam pipeline 10. A first electric valve 11 is provided on the low-pressure steam pipeline 10. The flue gas waste heat at the tail of the waste heat boiler 3 is recovered by the flue gas-water heat exchanger 302, and the hot water after heat exchange enters the flash evaporation device 6 to generate low-pressure steam. The low-pressure steam enters the low-temperature multi-effect desalination device 7 to desalinate the seawater; the low-temperature water generated by the flash evaporation device 6 is mixed with the condensate generated by the low-temperature multi-effect desalination device 7 and then enters the hot and cold water unit 8 for heat exchange.

[0038] The refrigerant in the hot and cold water unit 8 absorbs heat in the evaporator 803 to provide chilled water for cooling the central air-conditioning system 12; or the refrigerant in the hot and cold water unit 8 releases heat in the condenser 801 to provide heated water for heating the central air-conditioning system 12.

[0039] Specifically, the low-temperature water outlet of the flash device 6 is connected to a low-temperature water outlet pipeline 13, and a twelfth electric valve 35 is provided on the low-temperature water outlet pipeline. The low-temperature water outlet pipeline 13 is connected to the cold and hot water unit 8 through a first low-temperature water pipeline 14 and a second low-temperature water pipeline 15 connected in parallel; a second electric valve 16 is provided on the first low-temperature water pipeline 14, and a third electric valve 17 is provided on the second low-temperature water pipeline 15.

[0040] The evaporator 803, the compressor 802 and the condenser 801 in the hot and cold water unit 8 are connected in sequence to form a refrigerant circuit.

[0041] The water inlet of the condenser 801 is connected to the first low-temperature water pipeline 14, and the water outlet of the condenser 801 is connected to the water inlet of the smoke-water heat exchanger 302 through the first water circulation pipeline 18, and the first water circulation pipeline 18 is provided with a fourth electric valve 19; the water outlet of the evaporator 803 is connected to the water inlet of the central air-conditioning system 12 through the chilled water inlet 20, and the chilled water inlet 20 is provided with a fifth electric valve 21; the water outlet of the central air-conditioning system 12 is connected to the water inlet of the evaporator 803 through the chilled water circuit 22; the chilled water circuit 22 is provided with a sixth electric valve 23.

[0042] The water inlet of the evaporator 803 is also connected to the second low-temperature water pipeline 15; the water outlet of the evaporator 803 is connected to the water inlet of the smoke-water heat exchanger 302 through the second water circulation pipeline 24, and the second water circulation pipeline 24 is provided with a seventh electric valve 25; the water outlet of the condenser 801 is connected to the water inlet of the central air-conditioning system 12 through the hot water inlet 26, and the hot water inlet 26 is provided with an eighth electric valve 27; the water outlet of the central air-conditioning system 12 is connected to the water inlet of the condenser 801 through the hot water circuit 28, and the hot water circuit 28 is provided with a ninth electric valve 29.

[0043] The low-temperature water outlet pipeline 13 is also connected to the second water circulation pipeline 24 through a low-temperature water circuit 30 ; a tenth electric valve 31 is provided on the low-temperature water circuit 30 .

[0044] Furthermore, the condensate outlet of the low-temperature multi-effect seawater desalination device 7 is connected to the low-temperature water outlet pipeline 13 through a condensate pipeline 32; an eleventh electric valve 33 is provided on the condensate pipeline 32. The condensate output by the low-temperature multi-effect seawater desalination device 7 can be mixed with the low-temperature water output by the flash evaporation device 6.

[0045] In this system, the first electric valve 11 regulates and controls the amount of low-pressure steam entering the low-temperature multi-effect seawater desalination device 7; the twelfth electric valve 35 regulates and controls the low-temperature water flow of the flash evaporation device 6; and the eleventh electric valve 33 regulates and controls the condensate flow of the low-temperature multi-effect seawater desalination device 7.

[0046] The energy utilization process of the comprehensive energy utilization system is as follows:

[0047] When the central air conditioning system is cooling:

[0048] Close the third electric valve 17, the tenth electric valve 31, the ninth electric valve 29, the seventh electric valve 25, and the eighth electric valve 27, and open the second electric valve 16, the sixth electric valve 23, the fifth electric valve 21, and the fourth electric valve 19. The flue gas waste heat of the waste heat boiler 3 is recovered by the flue gas water heat exchanger 302. After the heat exchange, the hot water enters the flash evaporation device 6 to generate low-pressure steam, and the low-pressure steam enters the low-temperature multi-effect seawater desalination device 7 to desalinate the seawater; the generated fresh water enters the fresh water user 34 to meet the user's needs. The condensed water produced by the low-temperature multi-effect seawater desalination device 7 is mixed with the low-temperature water produced by the flash evaporation device 6 and enters the condenser 801 in the hot and cold water unit 8 through the first low-temperature water pipeline 14 to exchange heat with the compressed refrigerant. After the heat exchange, the condensed water re-enters the smoke-water heat exchanger 302 through the first water circulation pipeline 18 to absorb heat; the refrigerant in the hot and cold water unit 8 evaporates and absorbs heat in the evaporator 803, and the chilled water coming out of the central air-conditioning system 12 is cooled. After cooling, the chilled water enters the central air-conditioning system 12 through the chilled water inlet 20 for refrigeration.

[0049] When the central air conditioning system is heating:

[0050] The third electric valve 17, the tenth electric valve 31, the ninth electric valve 29, the seventh electric valve 25, and the eighth electric valve 27 are opened, and the second electric valve 16, the sixth electric valve 23, the fifth electric valve 21, and the fourth electric valve 19 are closed. The flue gas waste heat of the waste heat boiler 3 is recovered by the flue gas water heat exchanger 302. After the heat exchange, the hot water enters the flash evaporation device 6 to generate low-pressure steam. The low-pressure steam enters the low-temperature multi-effect seawater desalination device 7 to desalinate the seawater. The generated fresh water enters the fresh water user 34 to meet the user's needs. The condensed water generated by the low-temperature multi-effect seawater desalination device 7 is mixed with the low-temperature water generated by the flash evaporation device 6; a part of the mixed water enters the evaporator 803 in the cold and hot water unit 8 through the second low-temperature water pipeline 15 to further cool down and generate condensed water; the other part of the mixed water passes through the tenth electric valve 31, and then mixes with the condensed water output by the evaporator 803 and enters the flue gas water heat exchanger 302 to absorb heat. The refrigerant in the hot and cold water unit 8 condenses and releases heat in the condenser 801, heating the air-conditioned water coming out of the central air-conditioning system 12. The heated air-conditioned water enters the central air-conditioning system 12 through the hot water inlet 26 and the eighth electric valve 27 for heating.

[0051] Example 2

[0052] like Figure 2 The comprehensive energy utilization system based on waste heat utilization of combined cycle units shown in the figure is different from the embodiment 1 in that the gas turbine and the steam turbine are arranged in separate shafts. The system working mode of the embodiment 2 is the same as that of the embodiment 1.

[0053] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A comprehensive energy utilization system based on waste heat utilization of combined cycle units, characterized in that: It includes power generation module, seawater desalination module, hot and cold water units and central air conditioning system; The power generation module includes a gas turbine, a compressor, a waste heat boiler, a steam turbine, and a generator; the waste heat boiler includes a steam generation system and a smoke-water heat exchanger; the seawater desalination module includes a flash evaporation device and a low-temperature multi-effect seawater desalination device; the hot and cold water unit includes a condenser, a compressor, and an evaporator; The gas turbine, the compressor and the steam turbine jointly drive the generator to generate electricity; the flash evaporation device in the seawater desalination module utilizes the waste heat generated by the power generation module to generate low-pressure steam; the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater; the low-temperature water generated by the flash evaporation device is mixed with the condensate generated by the low-temperature multi-effect seawater desalination device and then enters the hot and cold water unit for heat exchange; the refrigerant in the hot and cold water unit absorbs heat in the evaporator to provide chilled water for cooling the central air-conditioning system; or the refrigerant in the hot and cold water unit releases heat in the condenser to provide heated water for heating the central air-conditioning system.

2. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 1 is characterized in that: The flue gas outlet of the gas turbine is connected to the waste heat boiler; the flue gas is discharged after passing through the steam generation system and the flue gas-water heat exchanger in sequence; the steam generation system, the steam turbine and the condenser form a loop.

3. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 1 is characterized in that: The water outlet of the smoke-water heat exchanger is connected to the flash evaporation device; the low-pressure steam outlet of the flash evaporation device is connected to the heat source inlet of the low-temperature multi-effect seawater desalination device through a first electric valve.

4. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 3 is characterized in that: The low-temperature water outlet of the flash evaporation device is connected to a low-temperature water outlet pipeline, which is connected to the hot and cold water unit through a first low-temperature water pipeline and a second low-temperature water pipeline connected in parallel; a second electric valve is provided on the first low-temperature water pipeline, and a third electric valve is provided on the second low-temperature water pipeline.

5. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 4 is characterized in that: The evaporator, compressor and condenser in the hot and cold water unit are connected in sequence to form a refrigerant circuit.

6. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 5, characterized in that: The water inlet of the condenser is connected to the first low-temperature water pipeline, the water outlet of the condenser is connected to the water inlet of the smoke-water heat exchanger through the first water circulation pipeline, and a fourth electric valve is provided on the first water circulation pipeline; the water outlet of the evaporator is connected to the water inlet of the central air-conditioning system through the chilled water inlet, and a fifth electric valve is provided on the chilled water inlet; the water outlet of the central air-conditioning system is connected to the water inlet of the evaporator through the chilled water circuit; a sixth electric valve is provided on the chilled water pipeline.

7. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 6 is characterized in that: The water inlet of the evaporator is connected to the second low-temperature water pipeline; the water outlet of the evaporator is connected to the water inlet of the smoke-water heat exchanger through the second water circulation pipeline, and the second water circulation pipeline is provided with a seventh electric valve; the water outlet of the condenser is connected to the water inlet of the central air-conditioning system through the hot water inlet, and the hot water inlet is provided with an eighth electric valve; the water outlet of the central air-conditioning system is connected to the water inlet of the condenser through the hot water circuit, and the hot water circuit is provided with a ninth electric valve.

8. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 7 is characterized in that: The low-temperature water outlet pipeline is also connected to the second water circulation pipeline through a low-temperature water loop; a tenth electric valve is provided on the low-temperature water loop.

9. The comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 8, characterized in that: The condensate outlet of the low-temperature multi-effect seawater desalination device is connected to the low-temperature water outlet pipeline through a condensate pipeline; an eleventh electric valve is arranged on the condensate pipeline.

10. A comprehensive energy utilization method of the comprehensive energy utilization system based on waste heat utilization of combined cycle units according to claim 9, characterized in that: When the central air conditioning system is cooling: Close the third electric valve, the tenth electric valve, the ninth electric valve, the seventh electric valve, and the eighth electric valve, and open the second electric valve, the sixth electric valve, the fifth electric valve, and the fourth electric valve; use the flue gas heat exchanger to recover the waste heat of the tail flue gas of the waste heat boiler, and after the heat exchange, the hot water enters the flash evaporation device to generate low-pressure steam, and the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater; the generated fresh water enters the fresh water user; the condensed water generated by the low-temperature multi-effect seawater desalination device is mixed with the low-temperature water generated by the flash evaporation device and then enters the condenser in the hot and cold water unit through the first low-temperature water pipeline to exchange heat with the compressed refrigerant, and after the heat exchange, the condensed water re-enters the flue gas water heat exchanger through the first water circulation pipeline to absorb heat; the refrigerant in the hot and cold water unit evaporates and absorbs heat in the evaporator, and the chilled water output by the central air-conditioning system is cooled, and the chilled water after cooling enters the central air-conditioning system through the chilled water inlet for refrigeration; When the central air conditioning system is heating: The third electric valve, the tenth electric valve, the ninth electric valve, the seventh electric valve and the eighth electric valve are opened, and the second electric valve, the sixth electric valve, the fifth electric valve and the fourth electric valve are closed; the waste heat of the tail flue gas of the waste heat boiler is recovered by using the flue gas-water heat exchanger, and the hot water after heat exchange enters the flash evaporation device to generate low-pressure steam, and the low-pressure steam enters the low-temperature multi-effect seawater desalination device to desalinate the seawater, and the generated fresh water enters the fresh water user; the condensed water generated by the low-temperature multi-effect seawater desalination device is mixed with the low-temperature water generated by the flash evaporation device; a part of the mixed water enters the evaporator in the hot and cold water unit through the second low-temperature water pipeline for further cooling to generate condensed water; the other part of the mixed water passes through the tenth electric valve, and then mixes with the condensed water output by the evaporator and enters the flue gas-water heat exchanger to absorb heat; the refrigerant in the hot and cold water unit condenses and releases heat in the condenser, and the air-conditioning water output by the central air-conditioning system is heated, and the heated air-conditioning water enters the central air-conditioning system through the hot water inlet and the eighth electric valve for heating.

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