A cogeneration waste heat utilization system

Abstract

This patent discloses a cogeneration waste heat utilization system, which includes an absorption heat pump heating subsystem, a compression heat pump heating subsystem and a pressure isolation station heat exchanger; the return water temperature of the absorption heat pump is 50°C, and the temperature difference between the outlet water and the return water is 30°C. The outlet water of the absorption heat pump passes through the intermediate heat exchanger, the secondary heat exchanger station heat exchanger, the pressure isolation station heat exchanger, and the exhaust steam heat exchanger in turn and then enters the absorption heat pump to form a hot water cycle. The first-station heating user pipeline and the secondary heat exchanger station heat exchanger form an absorption heat pump heating cycle; the compression heat pump obtains a low-temperature heat source from the pressure isolation station heat exchanger and is connected to the compression heat pump user pipeline to form a compression heat pump heating cycle; its advantages are: without increasing the steam extraction capacity of the thermal power plant turbine, it expands the heating capacity, improves the utilization rate of cogeneration waste heat, and enhances energy conservation and emission reduction efforts, with huge economic and social benefits.

Description

Technical Field

[0001] The invention patent relates to cogeneration, in particular to a cogeneration waste heat utilization system, and belongs to the field of waste heat utilization technology. Background Art

[0002] Compared with the traditional steam / water heat exchange station, the heat supply station established by the absorption heat pump in the cogeneration is significantly characterized in that the absorption heat pump, driven by high-temperature thermal energy (steam extraction from the turbine), raises the thermal energy of the low-temperature heat source (part of the exhaust steam discharged from the condenser to the air-cooling island) to medium temperature, thereby reducing the heating cost and improving the thermal energy utilization efficiency. The energy efficiency ratio (COP) of the absorption heat pump can reach 1.6 to 1.8.

[0003] The centralized heating system formed by combined heat and power with absorption heat pump as the first station (absorption heat pump heating system for short) has the economic and social benefits of energy saving, emission reduction and consumption reduction, and has broad development prospects. However, it has the following problems:

[0004] The heating load is limited by the steam extraction capacity of thermal power plants' steam turbines. With economic development, heating demand continues to increase. The contradiction between the growth rate of heat load in the heating area and the limited capacity of the heating source station is becoming increasingly prominent. Once the steam extraction capacity provided by the power plant is limited, it will be difficult to expand the capacity of the heating source station.

[0005] Low waste heat utilization. The exhaust heat from the condenser of a thermal power plant is 1.3 times the installed capacity of the generator. Flue gas losses account for approximately 3% to 5% of boiler heat losses. The steam released from the deaerator and flash steam from the boiler's fixed discharge constitute significant waste heat resources. However, waste heat from absorption heat pumps only accounts for 37.5% to 44% of heating capacity. Consequently, a significant amount of waste heat remains unrecovered in thermal power plants.

[0006] The energy efficiency ratio is affected by the return water temperature. When the extraction and exhaust steam thermal parameters are stable, the main factor affecting the COP value of the absorption heat pump is the return water temperature of the heating network. Its value is inversely proportional to the COP. That is, as the heat load decreases, the return water temperature of the heating network increases, and the COP value of the absorption heat pump decreases. During the heating season, when the outdoor temperature rises or the user takes measures to reduce the heat load (such as improving the insulation of the building enclosure and implementing temperature compensation control), the system return water temperature will increase, resulting in a decrease in the COP value of the absorption heat pump, thereby weakening the absorption heat pump's ability to absorb the waste heat of the exhaust steam. Summary of the Invention

[0007] In response to the above problems, the purpose of the present invention is to design a cogeneration waste heat utilization system that does not increase the steam extraction volume on the basis of the absorption heat pump heating system, improves the energy efficiency ratio of the heating system by recycling and utilizing more waste heat from the thermal power plant, expands the heating capacity by at least 1 times, and further improves the economic and social benefits of cogeneration.

[0008] The technical solution of the present invention is: a cogeneration waste heat utilization system, comprising an absorption heat pump heating subsystem, a compression heat pump heating subsystem and a pressure isolation station heat exchanger;

[0009] The absorption heat pump heating subsystem includes an absorption heat pump, an intermediate heat exchanger, an exhaust steam heat exchanger, a secondary heat exchange station heat exchanger and a first-station heating user. The absorption heat pump is driven by the steam extraction of the thermal power plant turbine to absorb the exhaust steam of the air-cooling island to form the first heating station. The return water temperature of the absorption heat pump is 50°C, and the temperature difference between the outlet water and the return water is 30°C. The outlet water of the absorption heat pump first enters the secondary side of the intermediate heat exchanger from the outlet of the absorption heat pump to absorb heat and increase the temperature by 10°C. Then, it enters the primary side of the heat exchanger of the secondary heat exchange station through the first-station water supply main pipe to release heat. The return water of the first station enters the primary side of the heat exchanger of the pressure isolation station through the first-station return water main pipe to release heat, and then enters the secondary side of the exhaust steam heat exchanger to absorb heat and increase the temperature to the absorption heat pump return water temperature before entering the absorption heat pump return water port to form an absorption heat pump hot water cycle.

[0010] The hot water circulation on the primary side of the intermediate heat exchanger is provided by a waste heat source, which is composed of any one or a combination of any two or all three of the flue gas from the thermal power plant boiler, the exhaust steam from the deaerator, and the flash steam from the boiler. The hot water generated by the waste heat source is used as the circulating hot water on the primary side of the intermediate heat exchanger. The exhaust steam from the air-cooling island enters the primary side of the exhaust steam heat exchanger. The heating user network at the first station is connected to the secondary side of the heat exchanger at the secondary heat exchange station to form an absorption heat pump heating cycle.

[0011] The compression heat pump heating subsystem includes an energy storage autocoupling unit, a compression heat pump, and a compression heat pump heating user. The compression heat pump uses the heat released by the return water from the first station in the pressure isolation station heat exchanger as a low-temperature heat source. The water outlet of the compression heat pump evaporator absorbs heat on the secondary side of the pressure isolation station heat exchanger and then adjusts the water temperature to the required temperature of the evaporator through the energy storage autocoupling unit before entering the evaporator, forming a low-temperature hot water cycle. The energy storage autocoupling unit is a device with heat storage, heat exchange and flow regulation functions, which can provide continuous and stable low-temperature hot water to the compression heat pump evaporator. The condenser end of the compression heat pump is connected to the compression heat pump user pipeline network to form a compression heat pump heating cycle.

[0012] The installed capacity of the compression heat pump heating subsystem is equal to or greater than the installed capacity of the absorption heat pump heating subsystem, and the heat released by the return water from the first station on the primary side of the heat exchanger in the pressure isolation station is greater than the demand for a low-temperature heat source by a compression heat pump of the same installed capacity as the absorption heat pump heating subsystem;

[0013] The exhaust steam heat exchanger is a heat exchange device installed on the exhaust steam pipeline leading out of the air-cooling island of the thermal power plant, and is a steam / water heat exchanger;

[0014] The pressure isolation station heat exchanger is a heat exchanger configured in the machine room of the absorption heat pump heating subsystem for maintaining and regulating the water supply pressure;

[0015] The first station return water main pipe is arranged at the same course as the first station water supply main pipe before entering the primary side water inlet of the pressure isolation station heat exchanger;

[0016] The water inlet temperature of the intermediate heat exchanger is 100°C and the water outlet temperature is 85°C; the exhaust steam inlet temperature of the exhaust steam heat exchanger on the primary side and the exhaust steam inlet temperature of the absorption heat pump are 54°C to 60°C, and the extraction steam inlet temperature of the absorption heat pump is 170°C to 280°C;

[0017] The outlet water temperature of the primary side of the heat exchanger in the secondary heat exchange station and the inlet water temperature of the primary side of the heat exchanger in the pressure isolation station are 60°C to 50°C; the outlet water temperature of the primary side of the heat exchanger in the pressure isolation station and the inlet water temperature of the secondary side of the exhaust steam heat exchanger are 30°C to 20°C, the outlet water temperature of the secondary side of the exhaust steam heat exchanger and the return water temperature of the absorption heat pump are 50°C, and the outlet water temperature of the absorption heat pump and the inlet water temperature of the secondary side of the intermediate heat exchanger are 10°C lower than the water supply temperature of the water supply main pipe of the first station;

[0018] The outlet water temperature of the compression heat pump evaporator and the inlet water temperature of the secondary side of the pressure isolation station heat exchanger are 25°C, the outlet water temperature of the secondary side of the pressure isolation station heat exchanger and the inlet water temperature of the energy storage autocoupling unit are 55°C to 45°C; the outlet water temperature of the energy storage autocoupling unit and the inlet water temperature of the compression heat pump evaporator are 30°C;

[0019] The temperature of the flue gas of the boiler is 160°C, and the waste heat is recovered in the flue gas waste heat recovery device to produce 100°C hot water; the temperature of the steam discharged from the deaerator is 151°C and the pressure is 0.14MPa, and the waste heat is recovered in the deaerator ejector to produce 100°C hot water; the temperature of the boiler fixed-row flash steam is 160°C and the pressure is 0.7-0.9MPa, and the waste heat is recovered in the fixed-row ejector to produce 100°C hot water;

[0020] The compression heat pump is a water / water heat pump composed of a screw compressor or a centrifugal compressor, and the absorption heat pump is a first-class absorption heat pump.

[0021] The advantages of this patent are:

[0022] 1) Without increasing the steam extraction capacity of the thermal power plant's steam turbine, the heating capacity is expanded, the utilization rate of cogeneration waste heat is improved, and energy conservation and emission reduction efforts are enhanced;

[0023] a. Further utilizes the waste heat from thermal power plants. The outlet water temperature of the absorption heat pump is 10°C lower than the design value. The water absorbs heat from the waste heat source through the intermediate heat exchanger to raise the temperature by 10°C. The return water of the absorption heat pump does not come directly from the return water of the secondary heat exchange station. Instead, it is the low-temperature return water of the secondary heat exchange station after releasing heat in the pressure isolation station heat exchanger. The return water absorbs heat in the exhaust steam heat exchanger and is heated to 50°C. On the basis of absorbing the exhaust steam for heating by the absorption heat pump, more waste heat from the power plant is recovered and utilized, including the waste heat from some exhaust steam from the air-cooling island, boiler flue gas or deaerator exhaust steam, and boiler flash steam. This further improves the recovery and utilization rate of waste heat from thermal power plants.

[0024] b. The return water of the absorption heat pump comes from the outlet water on the secondary side of the exhaust steam heat exchanger. Its temperature can be stabilized at 50°C by adjusting the exhaust steam volume on the primary side of the exhaust steam heat exchanger. It is not affected by the fluctuation of the heat load at the user end, thus ensuring the design energy efficiency ratio of the absorption heat pump and facilitating the recovery and utilization of the exhaust steam by the absorption heat pump.

[0025] c. The 55℃~45℃ / 25℃ hot water circulation formed on the secondary side of the pressure isolation station heat exchanger provides a continuous and stable low-temperature heat source for the compression heat pump evaporator through the energy storage autocoupling unit. Driven by a small amount of electricity, a compression heat pump heating subsystem is formed. Its heating load depends on the energy of the low-temperature heat source. The heat released by the outlet water on the primary side of the secondary heat exchanger heat exchanger in the pressure isolation station heat exchanger can meet or exceed the demand for low-temperature heat source of the compression heat pump with the same installed capacity as the absorption heat pump, thereby achieving the purpose of expanding the heating load by at least 1 times on the basis of the heating load of the absorption heat pump heating subsystem. The compression heat pump heating users are the new heat users beyond the heating users of the first station.

[0026] d. Although compression heat pumps require electricity to drive, they have the advantage of high energy efficiency (COP value is 5-6). 80%-83% of the heat energy in the compression heat pump heating load comes from low-temperature heat sources. The economic benefits of using the return water of the absorption heat pump heating subsystem as a low-temperature heat source are higher than the electricity consumed by the compression heat pump. In addition, the compression heat pump has a strong heating load adjustment capability, which can further reduce electricity consumption while ensuring the quality of heating.

[0027] 2) Improved heating quality: Since the return water main pipe of the first station is arranged at the same process as the water supply main pipe of the first station before entering the heat exchanger of the pressure isolation station, it is beneficial to the hydraulic balance of the large-scale heating network and the balanced heating temperature at the user end.

[0028] 3) Reduced initial investment; the heating system established by the present invention has a larger supply / return water temperature difference than the absorption heat pump heating system of the same capacity, and the actual supply / return water temperature difference can reach 60°C. According to the fluid pipe diameter design specifications, the diameter of the first station supply / return water main pipe can be reduced by one third; the outlet water temperature of the absorption heat pump of the present invention is 10°C lower than the design temperature. Under the same outlet / return water temperature difference and the same installed capacity, the cost of the absorption heat pump is reduced; the cost of a compression heat pump with the same heating capacity is lower than that of an absorption heat pump, and the machine room of the compression heat pump heating subsystem does not occupy the site of the first heating station. The area occupied by the station at the user end is equivalent to the secondary heat exchange station of the absorption heat pump heating subsystem. In summary, the initial investment can be reduced by 30%.

[0029] 4) It has huge economic and social benefits (see the embodiment examples for details). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : Schematic diagram of the structure of the waste heat utilization system according to an embodiment of the present invention;

[0031] Figure 2 : Schematic diagram of waste heat source structure;

[0032] Figure 3 : Schematic diagram of the energy storage autocoupling unit structure;

[0033] In the figure: 1-absorption heat pump heating subsystem; 11-absorption heat pump; 111-exhaust steam inlet; 112-exhaust steam condensate outlet; 113-extraction steam inlet; 114-extraction steam condensate outlet; 12-intermediate heat exchanger; 121-waste heat water inlet; 122-waste heat water outlet; 13-exhaust steam heat exchanger; 131-exhaust steam inlet; 132-exhaust steam condensate outlet; 14-first station return water main pipe; 15-secondary heat exchange station heat exchanger; 16-first station heating user; 17-first station water supply main pipe; 18-first station user-end circulating water pump; 19-first station circulating water pump;

[0034] 2-Compression heat pump heating subsystem; 21-Energy storage autocoupling unit; 211-Water outlet pipe; 212-Water outlet valve; 213-Phase change thermal storage material; 214-Water inlet pipe; 22-Compression heat pump; 221-Evaporator; 222-Compressor; 223-Condenser; 224-Compression heat pump user-end circulating water pump; 225-Expansion valve; 226-Cooling pump; 23-Compression heat pump heating user; 24-Water inlet main pipe; 25-Water outlet main pipe; 26-Secondary side water pump of pressure isolation station heat exchanger; 3-Pressure isolation station heat exchanger; 4-Flue gas waste heat recovery device; 5-Deaerator ejector pipe; 6-Fixed row ejector pipe; 7-Waste heat water supply pipe; 8-Waste heat return pipe. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] like Figure 1 As shown, the cogeneration waste heat utilization system described in this patent includes an absorption heat pump heating subsystem 1, a compression heat pump heating subsystem 2 and a pressure isolation station heat exchanger 3;

[0037] The absorption heat pump heating subsystem includes an absorption heat pump 11, an intermediate heat exchanger 12, an exhaust steam heat exchanger 13, a secondary heat exchange station heat exchanger 15 and a first-station heating user 16. The absorption heat pump 11 is a first-class absorption heat pump, which is also called a heat-increasing heat pump. It can use high-temperature thermal energy to drive the low-temperature thermal energy to medium temperature, thereby improving the thermal energy utilization efficiency. The absorption heat pump 11 is driven by the extraction steam of the steam turbine of the thermal power plant and absorbs part of the exhaust steam from the air-cooling island as the heat source on the primary side of the absorption heat pump 11. The low-temperature hot water absorbs heat on the secondary side of the absorption heat pump 11 and its temperature rises, thereby generating medium-temperature circulating hot water. The extraction steam and exhaust steam enter the absorption heat pump 11 from their respective pipelines. The extraction steam introduced from the steam turbine with a temperature of 170°C to 280°C enters the absorption heat pump 11 from the extraction steam inlet 113 of the absorption heat pump 11 and is discharged from the extraction steam condensate outlet 114 (entering the deaerator). The exhaust steam pipeline outlet introduced from the air-cooling island of the thermal power plant to the absorption heat pump 11 is connected to the exhaust steam inlet 111 of the absorption heat pump 11. The exhaust steam with a temperature of 54°C to 60°C enters the absorption heat pump 11 from the exhaust steam inlet 111 and is discharged from the absorption heat pump 11 from the exhaust steam condensate outlet 112 (discharged to the deaerator).

[0038] The flue gas from the boiler flue of a thermal power plant, the steam discharged from the deaerator, or the flash steam discharged from the boiler can be the waste heat source. It can be any one of the flue gas from the boiler flue, the steam discharged from the deaerator, or the flash steam discharged from the boiler. It can also be any two of the three combined as the waste heat source. It can also be all three as the waste heat source. The 160°C flue gas from the boiler flue is recovered in the flue gas waste heat recovery device 4 to produce 100°C hot water. The 0.14MPa, 151°C steam discharged from the deaerator is recovered in the deaerator ejector pipe 5 to produce 100°C hot water. The 0.7-0.9MPa, 160°C flash steam from the boiler discharge is recovered in the ejector pipe 6 to produce 100°C hot water. Figure 2The figure shows the situation where the flue gas from the boiler flue of a thermal power plant, the exhaust steam from the deaerator and the flash steam from the boiler are used as the waste heat sources. The hot water generated by the three waste heat sources is collected and used as waste heat water. The 100°C waste heat water enters the primary side of the intermediate heat exchanger 12 from the waste heat water inlet 121 through the waste heat water supply pipe 7. After the heat is released in the intermediate heat exchanger 12 and the temperature is reduced to 85°C, it is discharged from the waste heat water outlet 122. The 85°C hot water discharged from the waste heat water outlet 122 passes through the waste heat return pipe 8 and then enters the flue gas waste heat recovery device 4, the deaerator ejector pipe 5, the fixed exhaust ejector pipe 6 and the fixed exhaust ejector pipe 7. After absorbing heat and raising its temperature to 100°C, the heat then flows through waste heat supply pipe 7 into the primary side of intermediate heat exchanger 2, forming a heat exchange cycle and continuously providing a heat source for intermediate heat exchanger 12. Exhaust steam heat exchanger 13 is a steam / water heat exchanger installed on the exhaust steam pipeline leading from the thermal power plant's air-cooling island. Exhaust steam from the thermal power plant's air-cooling island, at a temperature of 54°C to 60°C, enters the primary side of exhaust steam heat exchanger 13 through exhaust steam inlet 131. There, it releases heat and becomes condensed water, which then returns to the deaerator through exhaust steam condensate outlet 132. Low-temperature hot water, at a temperature of 20°C to 30°C, from the return main pipe 14 at the first station receives heat on the secondary side of exhaust steam heat exchanger 13, raising its temperature to 50°C before entering the absorption heat pump 11.

[0039] The return water port of the absorption heat pump 11 is connected to the secondary side water outlet of the exhaust steam heat exchanger 13, the water outlet of the absorption heat pump 11 is connected to the secondary side water inlet of the intermediate heat exchanger 12, the secondary side water outlet of the intermediate heat exchanger 12 is connected to the primary side water inlet of the secondary heat exchange station 15 through the first station water supply main pipe 17, the primary side water outlet of the secondary heat exchange station 15 is connected to the primary side water inlet of the pressure isolation station 3 through the first station return water main pipe 14, the primary side water outlet of the pressure isolation station 3 is connected to the secondary side water inlet of the exhaust steam heat exchanger 13 The secondary water inlet of the exhaust steam heat exchanger 13 is connected, and the secondary water outlet of the exhaust steam heat exchanger 13 is connected with the return water port of the absorption heat pump 11, thereby forming an absorption heat pump hot water circulation loop. A first-station circulating water pump 19 is provided on the connecting pipe between the secondary water outlet of the exhaust steam heat exchanger 13 and the secondary return water port of the absorption heat pump 11. The first-station circulating water pump 19 provides power for the absorption heat pump hot water circulation; the pressure isolation station heat exchanger 3 is a heat exchanger configured in the machine room on the first-station return water main pipe 14 for adjusting the water supply pressure.

[0040] In this embodiment, the outlet water temperature of the absorption heat pump 11 is 80°C, and the temperature difference between the outlet water and the return water is 30°C; in order to improve the efficiency of the absorption heat pump 11, the return water temperature needs to be controlled at 50°C. After the temperature of the circulating hot water entering the absorption heat pump 11 is increased from 50°C to 10°C lower than the design temperature, that is, the outlet water temperature of the absorption heat pump 11 is set to 80°C, it is then drawn out from the outlet of the absorption heat pump 11 through a pipeline into the secondary side of the intermediate heat exchanger 12, absorbs heat from the primary side of the intermediate heat exchanger 12, and after the temperature is increased from 80°C to the design temperature of 90°C, it enters the first station water supply main pipe 17 from the secondary side outlet of the intermediate heat exchanger 12, and is supplied to the primary side of the secondary heat exchange station heat exchanger 15 through the first station water supply main pipe 17. The water outlet provides hot water, and the outlet water temperature of the secondary side of the intermediate heat exchanger 12, the inlet water temperature of the primary side of the secondary heat exchange station heat exchanger 15, and the water supply temperature of the first station water supply main pipe 17 are all 90°C; after the heat is released in the secondary heat exchange station heat exchanger 15 and the temperature drops to 60°C~50°C, it is led out from the primary side outlet of the secondary heat exchange station heat exchanger 15 to the first station return water main pipe 14, and then enters the pressure isolation station heat exchanger 3 through the first station return water main pipe 14 to release heat on the primary side and the temperature drops to 30°C~20°C (temperature difference is 30°C). This low-temperature return water at 30°C to 20°C is led from the primary side outlet of the pressure isolation station heat exchanger 3 to the secondary side inlet of the exhaust steam heat exchanger 13. After absorbing the heat of the exhaust steam in the exhaust steam heat exchanger 13, the temperature is raised to 50°C. The 50°C hot water led from the secondary side outlet of the exhaust steam heat exchanger 13 then enters the return water port of the absorption heat pump 11 through a pipeline to form a hot water circulation of the absorption heat pump 11.

[0041] There can be multiple first-station heating users 16 depending on the heating load and heating area. Each first-station heating user 16 represents an independent heating area. The water inlets of the heating branch pipes of multiple first-station heating users 16 are connected to the first-station water supply main pipe 17, and the water outlets of the heating branch pipes are connected to the first-station return water main pipe 14. The first-station return water main pipe 14 is arranged co-routed with the first-station water supply main pipe 17 before connecting to the pressure isolation station heat exchanger 3, which facilitates hydraulic balance in large-scale heating networks.

[0042] The secondary side water supply temperature of the secondary heat exchange station heat exchanger 15 is 60°C, and the return water temperature is 50°C, which is used for normal heating of users; the secondary side water inlet and outlet of the secondary heat exchange station heat exchanger 15 are respectively connected to the water outlet and water inlet of the first-station heating user 16 pipe network, forming a first-station user heating cycle, and a first-station user-end circulating water pump 18 is provided on the connecting pipe between the water outlet of the first-station heating user 16 pipe network and the secondary side water inlet of the secondary heat exchange station heat exchanger 15. The first-station user-end circulating water pump 18 is used to provide power for the first-station user heating cycle.

[0043] The absorption heat pump 11 is driven by the steam extraction from the thermal power plant's steam turbine to absorb part of the exhaust steam from the air-cooling island to form the first heating station. Furthermore, through the special design of absorbing the waste heat from the power plant with the outlet water and absorbing part of the exhaust steam from the air-cooling island with the return water, hot water reaching the design temperature is provided to the heat exchanger 15 of the secondary heat exchange station. The first-station heating user 16 obtains heat through the heat exchanger 15 of the secondary heat exchange station, forming the absorption heat pump heating subsystem 1.

[0044] The outlet water temperature of the absorption heat pump 11 in the absorption heat pump heating subsystem 1 described in this patent is 80°C, which is 10°C lower than the design value, that is, 10°C lower than the water supply temperature of the first station water supply main pipe 17 and the inlet water temperature of the secondary heat exchange station heat exchanger 15. It has the following advantages: 1) The outlet water of the absorption heat pump 11 absorbs the waste heat on the secondary side of the intermediate heat exchanger 12, and the temperature of the hot water is increased by 10°C before entering the first station water supply main pipe 17, providing heat source heating to the primary side of the secondary heat exchange station heat exchanger 15, which not only meets the demand of the secondary heat exchange station heat exchanger 15 for circulating hot water, but also further improves the waste heat utilization efficiency; 2) The cost of the absorption heat pump 11 is proportional to the outlet water temperature, which is conducive to reducing the initial investment of the absorption heat pump 11; 3) The outlet / return water temperature difference of the absorption heat pump 11 is within the design range, the outlet water temperature is reduced, and its energy efficiency ratio is improved.

[0045] The temperature design value of the return water in the return water main pipe 14 of the absorption heat pump heating subsystem 1 before entering the pressure isolation station heat exchanger 3 is 30℃ lower than the water supply temperature of the first station water supply main pipe 17. The specific temperature value is related to the heat load change of the first station heating user 16, which is generally 60-50℃. The return water in the return water main pipe 14 of the first station enters the pressure isolation station heat exchanger 3 on the primary side and releases 30℃ temperature difference heat, and the temperature drops to 30℃-20℃, which has the following advantages: 1) The heat energy of the first station heat source is fully utilized to provide a low-temperature heat source for the compression heat pump heating subsystem 2; 2) The low return water temperature of the first station is conducive to long-distance transportation, and the heat loss of the pipeline network is small. At the same time, due to the first station The temperature difference between the hot water in the water supply main pipe 17 and the first station return water main pipe 14 can reach 70°C to 60°C, which can reduce the diameter of the first station supply / return water main pipe and save the initial construction investment; 3) The return water at 30°C to 20°C in the first station return water main pipe 14 enters the exhaust steam heat exchanger 13 to absorb the exhaust steam waste heat. By controlling the exhaust steam amount of the exhaust steam inlet 131, the return water temperature of the absorption heat pump 11 can be controlled at 50°C, which is conducive to the stability of the energy efficiency ratio of the absorption heat pump 11, which is impossible for conventional absorption heat pump heating systems. Further, the recovery rate of the exhaust steam waste heat of the air-cooled island is improved. The energy efficiency ratio of the present invention can reach 2.75, which is 1.6 times higher than that of conventional absorption heat pump heating systems.

[0046] The compression heat pump heating subsystem 2 includes an energy storage autocoupling unit 21, a compression heat pump 22, and a compression heat pump heating user 23. The compression heat pump includes an evaporator 221, a compressor 222, a condenser 223, and an expansion valve 225. The working fluid inside the evaporator 221 absorbs heat from low-temperature hot water and vaporizes, which is then drawn into the compressor 222. The compressor 222 compresses the low-pressure working fluid gas into high-temperature, high-pressure gas, which is then fed into the condenser 223. Water, forcibly circulated by the compression heat pump user-side circulating water pump 224, also passes through the condenser 223, where it is heated by the working fluid and then fed to the user. The working fluid is cooled into a liquid, which is then throttled and cooled by the expansion valve 225 before flowing back into the evaporator 221, repeating this cycle. The compression heat pump 22 is a water / water heat pump composed of a screw compressor or a centrifugal compressor. Driven by electricity, the compression heat pump 22, the condenser, and the compression heat pump heating user 23 form a compression heat pump heating subsystem with an energy efficiency ratio of 5 to 6.

[0047] like Figure 3 As shown, the energy storage autocoupling unit 21 includes a water outlet pipe 211 and a water inlet pipe 214 provided on a closed box body, and a phase change thermal storage material 213 placed in the box body. An outlet valve 212 is provided on the water outlet pipe 211. The water inlet of the evaporator 221 is connected to the water outlet pipe 211 of the energy storage autocoupling unit 21, and the water outlet of the evaporator 221 is connected to the water outlet main pipe 25.

[0048] The low-temperature heat source of the compression heat pump heating subsystem 2 comes from the heat released by the return water of the absorption heat pump heating subsystem 1 at a temperature difference of 30°C on the primary side of the pressure isolation station heat exchanger 3. 82% of this heat can meet the demand for low-temperature heat source of the compression heat pump heating subsystem 2 with the same installed capacity as the absorption heat pump heating subsystem 1, so the installed capacity of the compression heat pump heating subsystem 2 can be equal to or greater than the installed capacity of the absorption heat pump heating subsystem 1.

[0049] The 55°C to 45°C hot water from the secondary side water outlet of the pressure isolation station heat exchanger 3 enters the water inlet pipe 214 of the energy storage autocoupling unit 21 through the water inlet main pipe 24, and enters the box of the energy storage autocoupling unit 21 through the water inlet pipe 214. The phase change heat storage material 213 has the function of absorbing, storing and releasing heat. The water temperature in its outlet pipe 211 is 30°C. The 30°C hot water enters the evaporator 221 through the outlet pipe 211 to release heat and the temperature drops to 25°C. The 25°C hot water is then drawn out from the outlet of the evaporator 221 and collected into the water outlet main pipe 25. Then, the water outlet main pipe 25 enters the secondary side of the heat exchanger 3 of the heat isolation station through the secondary side water inlet of the pressure isolation station heat exchanger 3 to form a low-temperature hot water circulation. A water outlet valve 212 is installed between the water outlet pipe 211 and the water inlet of the evaporator 221 to regulate the water flow to the evaporator 221. A cooling pump 226 is installed on the connecting pipe between the water outlet of the evaporator 221 and the main water outlet pipe 25. This cooling pump 226 is used to provide power for the low-temperature hot water circulation on the evaporator side. A secondary-side water pump 26 for the pressure isolation station heat exchanger is installed on the main water outlet pipe 25 to provide power for the secondary-side hot water circulation of the pressure isolation station heat exchanger 3.

[0050] The 25℃ low-temperature hot water from the outlet of the evaporator 221 of the compression heat pump 22 is collected in the outlet main pipe 25 and connected to the secondary side water inlet of the pressure isolation station heat exchanger 3. After the heat exchange temperature rises to 55℃~45℃, it is adjusted to 30℃ by the energy storage autocoupling unit 21 and then enters the evaporator 221 of the compression heat pump 22, providing a low-temperature heat source for the compression heat pump 22. The condenser 223 of the compression heat pump 22 is connected to the compression heat pump heating user 23 to form a compression heat pump heating cycle; the cooling of the compression heat pump 22 The outlet water temperature of the condenser 223 is 60°C, and the return water temperature is 50°C, which is used for normal heating of users; the water inlet and outlet of the condenser 223 of the compression heat pump 22 are respectively connected to the water outlet and water inlet of the compression heat pump heating user 23 pipe network, forming a compression heat pump heating circulation loop, and a compression heat pump user-end circulating water pump 224 is provided on the connecting pipe between the water inlet of the condenser 223 and the water outlet of the pipe network of the compression heat pump heating user 23 to provide power for the compression heat pump heating cycle.

[0051] The heating load and number of compression heat pump heating users 23 depend on the heat released by the return water of the absorption heat pump heating subsystem 1 in the pressure isolation station heat exchanger 3 and the heating area. The water inlet pipe 214 of the energy storage autocoupling unit 21 of each compression heat pump heating user 23 is connected to the water inlet mother pipe 24, and the water outlet pipe 211 of the energy storage autocoupling unit 21 of each compression heat pump heating user 23 is connected to the water inlet of the evaporator of each compression heat pump 22, and the water outlet of each evaporator 221 is connected to the water outlet mother pipe 25.

[0052] The heat released by the return water of the absorption heat pump heating subsystem 1 on the primary side of the pressure isolation station heat exchanger 3 is low-grade thermal energy with the same installed capacity as the absorption heat pump heating subsystem 1, and the low-grade thermal energy is greater than the demand for low-temperature heat source of the compression heat pump heating subsystem 2 with the same installed capacity as the absorption heat pump heating subsystem 1; since the heat released by the return water of the absorption heat pump heating subsystem 1 in the pressure isolation station heat exchanger 3 can meet the demand for low-temperature heat source of the compression heat pump heating subsystem 2 with an installed capacity greater than that of the absorption heat pump heating subsystem 1, the present invention achieves the purpose of at least doubling the heating capacity of the absorption heat pump heating subsystem 1.

[0053] The technical effects, economic and social benefits of the present invention are illustrated below with data from specific examples.

[0054] Example 1:

[0055] A thermal power plant in northern China can provide 22 t / h of three-stage steam extraction for its steam turbine (with an extraction pressure of 0.8 MPa to 1.3 MPa and a temperature of 180°C to 275°C). The heating area of the first heating station, user 16, is 1 million square meters, with a calculated heat load of 50 MW. Given the steam extraction capacity constraints, the installed capacity of absorption heat pump 11 at the first heating station is 25 MW, which can only meet the heating load of 500,000 square meters.

[0056] By adopting the technical solution of the present invention, on the basis of the installed capacity of 25MW of the absorption heat pump heating subsystem 1, the waste heat of the thermal power plant is recovered and utilized as a low-temperature heat source, and the compression heat pump heating subsystem 2 with a heating capacity of 25MW is expanded, increasing the heating area to 1 million square meters. The heat required for the newly added 25MW heating load comes from: 1) Recovery and utilization of waste heat from the thermal power plant: 25MWh / h, including 8.34MWh / h (30GJ / h) of waste heat from the power plant recovered by raising the temperature of the absorption heat pump outlet water from 80℃ to 90℃; the return water of the return water main pipe 14 of the first station is heated from 20℃~30℃ to 50℃ on the secondary side of the exhaust steam heat exchanger 13, and 16.7MWh / h (60.12GJ / h) of exhaust steam waste heat is recovered;

[0057] 2) The power consumption of the compression heat pump 22 is 4.55MWh / h (16.38GJ / h). Furthermore, 20.45MW of the absorbed waste heat can meet the low-temperature heat source demand of the 25MW compression heat pump. With the remaining 4.55MW as the low-temperature heat source, the installed capacity of the compression heat pump unit can be further increased by 5.83MW, that is, the installed capacity of the compression heat pump heating subsystem 2 can actually be increased to 30.83MW.

[0058] Example 2:

[0059] A northern enterprise and residential area has a heating area of 1 million square meters and a calculated heat load of 50 MW. It plans to build a 50 MW absorption heat pump heating station at a power plant located 4 kilometers from the heating area. The hot water temperature of the heating main pipe 17 at the first station and the inlet water temperature of the secondary heat exchanger 15 are both 90°C, and the outlet water temperature of the secondary heat exchanger 15 is 60°C. The investment in the absorption heat pump station is 31 million yuan. The heating season is 6 months, the steam price is 45 yuan / GJ, and the energy cost per unit area is 20.24 yuan / m 2 .

[0060] In the heating system established by the present invention, the installed capacity of the absorption heat pump heating subsystem 1 only needs 25MW, and the other 25MW heat load is borne by the compression heat pump heating subsystem 2.

[0061] Economic benefits: Compared with conventional absorption heat pump heating systems, this patented technology has the following advantages: 1) Saving investment: The absorption heat pump first station is reduced from 50MW to 25MW, saving half the cost; because the diameter of the first station heating main pipe 17 is reduced by one-third, the pipe network investment can be reduced by 20%, which offsets the cost of the increased compression heat pump heating subsystem 2, and the construction cost of the entire heating system can be reduced by 30%; 2) Reducing pipe network heat loss: The first station water supply main pipe 17 is short in length and the return water temperature of the first station return water main pipe 14 is low, and the pipe network heat loss can be reduced from 15% of the conventional absorption heat pump heating system to 5%; 3) The system energy efficiency ratio is improved to 2.75; 4) The energy consumption cost per unit area is 17.2 yuan / m 2 , which is 3.04 yuan / m lower than the conventional absorption heat pump heating system 2 Further economic benefits are reflected in the fact that the compression heat pump heating subsystem 2 has a more flexible load control capability and can also enjoy time-of-use electricity price dividends.

[0062] Social benefits: 1) The heating capacity can be expanded by 1.23 times without increasing the amount of steam extracted and with a small amount of electricity, which greatly alleviates the contradiction between the heating source and the heating demand; 2) The heat emission to the environment is reduced by 152,126 GJ; 3) Compared with the conventional absorption heat pump heating system, each heating season consumes about 6,431 tons of standard coal, reduces carbon emissions by 7,703 tons, reduces sulfide emissions by 61.5 tons, and reduces nitrogen oxide emissions by 54 tons.

Claims

1. A cogeneration waste heat utilization system, characterized by: It includes absorption heat pump heating subsystem, compression heat pump heating subsystem and pressure isolation station heat exchanger; The absorption heat pump heating subsystem includes an absorption heat pump, an intermediate heat exchanger, an exhaust steam heat exchanger, a secondary heat exchange station heat exchanger and a first-station heating user. The absorption heat pump is driven by the steam extraction of the thermal power plant turbine to absorb the exhaust steam of the air-cooling island to form the first heating station. The return water temperature of the absorption heat pump is 50°C, and the temperature difference between the outlet water and the return water is 30°C. The outlet water of the absorption heat pump first enters the secondary side of the intermediate heat exchanger from the outlet of the absorption heat pump to absorb heat and increase the temperature by 10°C. Then, it enters the primary side of the heat exchanger of the secondary heat exchange station through the first-station water supply main pipe to release heat. The return water of the first station enters the primary side of the heat exchanger of the pressure isolation station through the first-station return water main pipe to release heat, and then enters the secondary side of the exhaust steam heat exchanger to absorb heat and increase the temperature to the absorption heat pump return water temperature before entering the absorption heat pump return water port to form an absorption heat pump hot water cycle. The hot water circulation on the primary side of the intermediate heat exchanger is provided by a waste heat source, which is composed of any one or a combination of any two or all three of the flue gas from the thermal power plant boiler, the exhaust steam from the deaerator, and the flash steam from the boiler. The hot water generated by the waste heat source is used as the circulating hot water on the primary side of the intermediate heat exchanger. The exhaust steam from the air-cooling island enters the primary side of the exhaust steam heat exchanger. The heating user network at the first station is connected to the secondary side of the heat exchanger at the secondary heat exchange station to form an absorption heat pump heating cycle. The compression heat pump heating subsystem includes an energy storage autocoupling unit, a compression heat pump, and a compression heat pump heating user. The compression heat pump uses the heat released by the return water from the first station in the pressure isolation station heat exchanger as a low-temperature heat source. The water outlet of the compression heat pump evaporator absorbs heat on the secondary side of the pressure isolation station heat exchanger and then adjusts the water temperature to the required temperature of the evaporator through the energy storage autocoupling unit before entering the evaporator, forming a low-temperature hot water cycle. The energy storage autocoupling unit is a device with heat storage, heat exchange and flow regulation functions, which can provide continuous and stable low-temperature hot water to the compression heat pump evaporator. The compression heat pump condenser end is connected to the compression heat pump user pipeline network to form a compression heat pump heating cycle.

2. The cogeneration waste heat utilization system according to claim 1, characterized in that: The installed capacity of the compression heat pump heating subsystem is equal to or greater than the installed capacity of the absorption heat pump heating subsystem, and the heat released by the first station return water on the primary side of the pressure isolation station heat exchanger is greater than the demand for low-temperature heat source of the compression heat pump with the same installed capacity as the absorption heat pump heating subsystem.

3. The cogeneration waste heat utilization system according to claim 1, characterized in that: The exhaust steam heat exchanger is a heat exchange device arranged on the exhaust steam pipeline leading out of the air-cooling island of the thermal power plant, and is a steam / water heat exchanger.

4. The cogeneration waste heat utilization system according to claim 1, characterized in that: The pressure isolation station heat exchanger is a heat exchanger arranged in a machine room of an absorption heat pump heating subsystem for maintaining and regulating the water supply pressure.

5. The cogeneration waste heat utilization system according to claim 1, characterized in that: The first station return water main pipe is arranged at the same course as the first station water supply main pipe before entering the primary side water inlet of the pressure isolation station heat exchanger.

6. The cogeneration waste heat utilization system according to claim 1, characterized in that: The inlet water temperature of the intermediate heat exchanger measured once is 100°C, and the outlet water temperature is 85°C; the exhaust steam inlet temperature on the primary side of the exhaust steam heat exchanger and the exhaust steam inlet temperature of the absorption heat pump are 54°C to 60°C, and the extraction steam inlet temperature of the absorption heat pump is 170°C to 280°C.

7. The cogeneration waste heat utilization system according to claim 1, characterized in that: The outlet water temperature of the primary side of the heat exchanger of the secondary heat exchange station and the inlet water temperature of the primary side of the heat exchanger of the pressure isolation station are 60℃~50℃; the outlet water temperature of the primary side of the heat exchanger of the pressure isolation station and the inlet water temperature of the secondary side of the exhaust steam heat exchanger are 30℃~20℃, the outlet water temperature of the secondary side of the exhaust steam heat exchanger and the inlet water temperature of the absorption heat pump are 50℃, and the outlet water temperature of the absorption heat pump and the inlet water temperature of the secondary side of the intermediate heat exchanger are 10℃ lower than the water supply temperature of the water supply main pipe of the first station.

8. The cogeneration waste heat utilization system according to claim 1, characterized in that: The outlet water temperature of the compression heat pump evaporator and the inlet water temperature of the secondary side of the pressure isolation station heat exchanger are 25°C, the outlet water temperature of the secondary side of the pressure isolation station heat exchanger and the inlet water temperature of the energy storage autocoupling unit are 55°C to 45°C; the outlet water temperature of the energy storage autocoupling unit and the inlet water temperature of the compression heat pump evaporator are 30°C.

9. The cogeneration waste heat utilization system according to claim 1, characterized in that: The temperature of the flue gas of the boiler is 160°C, and the waste heat is recovered in the flue gas waste heat recovery device to produce 100°C hot water; the temperature of the steam discharged from the deaerator is 151°C, and the pressure is 0.14Mpa, and the waste heat is recovered in the deaerator ejector to produce 100°C hot water; the temperature of the boiler fixed-row flash steam is 160°C, and the pressure is 0.7-0.9Mpa, and the waste heat is recovered in the fixed-row ejector to produce 100°C hot water.

10. The cogeneration waste heat utilization system according to claim 1, characterized in that: The compression heat pump is a water / water heat pump composed of a screw compressor or a centrifugal compressor, and the absorption heat pump is a first-class absorption heat pump.

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