Comprehensive utilization system for waste heat of power plant

Abstract

The utility model discloses a power plant waste heat comprehensive utilization system, and relates to the technical field of energy conservation and environmental protection. According to the technical key points, the system comprises a warm air blower connected with an indirect air cooling system, and the warm air blower is installed on the inlet side of a first induced draft fan; an air outlet of the first induced draft fan is connected with one end of the air side of the air preheater, and the other end of the air side of the air preheater is connected with the boiler; one end of the smoke side of the air preheater is connected with a flue at the tail of the boiler, and the other end of the smoke side of the air preheater is connected with an air inlet of the low-pressure economizer; a gas outlet of the low-pressure economizer is connected with the tail gas treatment module. According to the scheme, the exhaust steam waste heat of the steam turbine and the exhaust smoke waste heat of the boiler are comprehensively utilized at the same time, so that the two parts of waste heat are utilized to the greatest extent, the coal consumption of a power plant is reduced, and meanwhile, the heat pollution to the environment can be reduced.

Description

Technical Field

[0001] This application relates to the field of energy conservation and environmental protection technology, and in particular to a comprehensive utilization system for waste heat from power plants. Background Technology

[0002] Thermal power plants generate electricity through heat-work conversion based on the Rankine cycle. According to the heat method analysis, the main heat losses in power plants are caused by heat losses from turbine exhaust and boiler flue gas. Discharging this heat through air or cooling water inevitably leads to significant energy waste. This is especially true for large units, where the main sources of waste heat are the heat carried away by the turbine exhaust cooling water and the heat carried by the boiler exhaust. Taking boiler flue gas as an example, the exhaust temperature of power plant boilers is typically 120–150°C. If this heat is directly discharged into the air, the corresponding heat loss is equivalent to 5%–12% of the fuel's heat. Therefore, there is an urgent need to provide a new approach to comprehensively utilize the preheating of turbine exhaust and the waste heat from boiler flue gas generated during power plant operation to improve the overall efficiency of the thermal power unit and reduce coal consumption. Utility Model Content

[0003] This application provides a power plant waste heat comprehensive utilization system, which can comprehensively utilize the preheating of steam turbine exhaust and the waste heat of boiler flue gas generated during the operation of the power plant to improve the overall efficiency of the heat engine and reduce the coal consumption of the power plant.

[0004] The above-mentioned objective of this application is achieved through the following technical solution:

[0005] A power plant waste heat comprehensive utilization system includes a warm air blower connected to an indirect air-cooling system via a pipeline system, and the warm air blower is installed on the inlet side of a first induced draft fan. The warm air blower can heat the cold air before it enters the first induced draft fan by obtaining heat from the indirect air-cooling system.

[0006] The air outlet of the first induced draft fan is connected to one end of the air preheater via a piping system, and the other end of the air preheater is connected to the boiler via a piping system.

[0007] One end of the air preheater on the flue gas side is connected to the flue at the tail of the boiler through a pipeline system, and the other end of the air preheater on the flue gas side is connected to the air inlet of the low-pressure economizer through a pipeline system.

[0008] The outlet of the low-pressure economizer is connected to the tail gas treatment module, which is used to remove dust and desulfurize the flue gas discharged from the outlet of the low-pressure economizer.

[0009] Furthermore, the warm air blower is a hot water warm air blower, and a circulating water pipe is connected to the hot water warm air blower on the circulating water pipe between the condenser and the intercooling tower in the indirect air cooling system.

[0010] Furthermore, the inlet and outlet ends of the heat exchanger in the hot water heater are connected to the water supply header and return header in the circulating water pipe between the condenser and the intercooler tower via water supply pipe and water outlet pipe, respectively.

[0011] Furthermore, a heat transfer fluid booster pump is installed on the water supply pipe.

[0012] Furthermore, there are two heat transfer water booster pumps, and the two heat transfer water booster pumps are installed in parallel on the water supply pipe.

[0013] Furthermore, a side pipe is added to the water supply pipe downstream of the heat transfer water booster pump, and a heat transfer water heat exchanger is installed on the side pipe.

[0014] Furthermore, a return water branch pipe is connected between the water supply pipe and the water outlet pipe and the connection end of the circulating water pipe between the condenser and the intercooler tower.

[0015] Furthermore, the exhaust gas treatment module includes an electrostatic precipitator. The air inlet of the electrostatic precipitator is connected to the air outlet of the low-pressure economizer through an air transmission pipeline. The air outlet of the electrostatic precipitator is connected to the air inlet side of the second induced draft fan through an air transmission pipeline. The air outlet side of the second induced draft fan is connected to the desulfurization absorption tower through an air transmission pipeline.

[0016] In summary, this application includes at least one of the following beneficial technical effects:

[0017] The waste heat coupling utilization scheme adopted in this application combines the waste heat from both the turbine exhaust and the boiler flue gas, thereby maximizing the utilization of both types of waste heat. Specifically, the waste heat from the turbine exhaust generated in the indirect air-cooling system is piped to the air heater. This heats the cold air at the inlet of the first induced draft fan to a certain temperature, reducing the amount of flue gas heat required for the air preheater to heat the boiler intake air. Besides sharing the waste heat from the turbine exhaust with the boiler flue gas to heat the cold air entering the first induced draft fan at the air preheater, the heat saved from utilizing the turbine exhaust in the boiler exhaust is piped to the low-temperature economizer to heat the condensate, thus replacing the waste heat with high-quality heat and returning it to the thermal system, achieving the goal of reducing unit heat consumption. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of this application;

[0020] Figure 2 yes Figure 1 A schematic diagram of the specific structure within the rectangular frame.

[0021] Attached reference numerals: 1. Warm air blower; 2. First induced draft fan; 3. Air preheater; 4. Boiler; 5. Low-pressure economizer; 6. Tail gas treatment module; 61. Electrostatic precipitator; 62. Second induced draft fan; 63. Desulfurization absorption tower; 7. Water supply pipe; 8. Water outlet pipe; 9. Heat medium water booster pump; 10. Side pipe; 11. Heat medium water heat exchanger; 12. Return water branch pipe. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0023] like Figure 1 and Figure 2 As shown, this application discloses a power plant waste heat comprehensive utilization system, which includes a warm air blower 1 connected by a pipeline system and an indirect air cooling system. The warm air blower 1 is installed on the inlet side of the first induced draft fan 2. The warm air blower 1 can heat the cold air before it enters the first induced draft fan 2 by obtaining heat from the indirect air cooling system.

[0024] The air outlet of the first induced draft fan 2 is connected to one end of the air side of the air preheater 3 through a pipeline system, and the other end of the air side of the air preheater 3 is connected to the boiler 4 through a pipeline system.

[0025] One end of the air preheater 3 on the flue gas side is connected to the flue at the tail of the boiler 4 through a pipeline system, and the other end of the air preheater 3 on the flue gas side is connected to the air inlet of the low-pressure economizer 5 through a pipeline system.

[0026] The outlet of the low-pressure economizer 5 is connected to the exhaust gas treatment module 6, which is used to remove dust and desulfurize the flue gas discharged from the outlet of the low-pressure economizer 5.

[0027] In the above embodiments, the boiler 4 of the power plant usually needs to introduce air into it during operation. However, if cold air from the environment is directly sent into the boiler 4 through the first induced draft fan 2, it will affect the thermal efficiency of the boiler 4. Therefore, an air preheater 3 is usually added between the first induced draft fan 2 and the boiler 4. The existing air preheater 3 directly obtains heat energy from the flue gas in the tail flue of the boiler 4 to heat the air flowing into the boiler 4, so as to reduce the energy consumption of the boiler 4.

[0028] This application adopts a combined waste heat utilization scheme, that is, simultaneously utilizing the waste heat from the turbine exhaust and the waste heat from the boiler 4 flue gas, thereby maximizing the utilization of both types of waste heat. Specifically, the waste heat from the turbine exhaust generated in the indirect air-cooling system is piped to the air heater 1. This heats the cold air at the inlet of the first induced draft fan 2 to a certain temperature, reducing the amount of heat required from the flue gas for the air preheater 3 to heat the air entering the boiler 4. Besides sharing the waste heat from the turbine exhaust with the boiler 4 flue gas to heat the cold air entering the first induced draft fan 2 at the air preheater 3, the heat saved from utilizing the turbine exhaust in the boiler 4 flue gas is piped to the low-temperature economizer to heat the condensate, thus displacing high-quality heat and returning it to the thermal system. This waste heat utilization system effectively improves the overall efficiency of the power plant's thermal power unit and reduces energy consumption.

[0029] Furthermore, such as Figure 1 and Figure 2 As shown, the warm air heater 1 is a hot water warm air heater 1. A circulating water pipe is connected to the hot water warm air heater 1 on the circulating water pipe between the condenser and the indirect air cooling tower in the indirect air cooling system.

[0030] In the above embodiments, the indirect air-cooled system includes equipment such as a condenser, a circulating water pump, an indirect cooling tower, and radiators. Circulating water flows inside the circulating water pipe between the condenser and the indirect cooling tower. This circulating water absorbs heat from the exhaust steam discharged from the turbine in the condenser. After absorbing the heat from the exhaust steam, the circulating water is sent to the indirect cooling tower for cooling through the circulating water pipe. The air in the indirect cooling tower exchanges heat with the circulating water, and the cooled circulating water returns to the condenser through the circulating water pipe to continue cooling the exhaust steam, forming a closed-loop system. The purpose of connecting a circulating water line to the circulating water pipe in this application is to utilize the circulating water that has absorbed the heat from the exhaust steam. The heat energy in the circulating water is used to work together with the flue gas from the boiler 4 to act on the air preheater 3. This not only utilizes some of the heat energy in the circulating water but also reduces the workload of the indirect cooling tower.

[0031] Furthermore, such as Figure 2As shown, the inlet and outlet ends of the heat exchanger in the hot water heater 1 are connected to the water supply header and return header in the circulating water pipe between the condenser and the intercooler through the water supply pipe 7 and the water outlet pipe 8, respectively.

[0032] In the above embodiments, the water supply header in the indirect air-cooling system refers to the pipe section that transports the circulating water that has absorbed the turbine exhaust steam at the condenser to the intercooling tower. The return header is the pipe section that returns the circulating water to the condenser after it has been cooled in the intercooling tower. The main purpose of the hot water heater 1 is to use hot water to heat the air. Since the circulating water flowing in the water supply header absorbs heat from the turbine exhaust steam, the temperature of the circulating water in the water supply pipe is higher than that in the return pipe. Therefore, this application connects the inlet of the heat exchanger in the hot water heater 1 to the water supply header through the water supply pipe 7. In this way, the circulating water tributary carrying heat energy will enter the hot water heater 1 to heat the cold air that is about to enter the first induced draft fan 2. When the circulating water is discharged from the outlet of the heat exchanger of the hot water heater 1 after use, it is in a cooled state after its internal heat energy has been utilized. Therefore, this application guides it directly to the return header through the outlet pipe 8 so that it can return to the condenser to recover the heat energy of the turbine exhaust steam.

[0033] Furthermore, such as Figure 2 As shown, a heat transfer water booster pump 9 is installed on the water supply pipe 7.

[0034] In the above embodiments, the heat transfer water booster pump 9 can provide sufficient power for the circulating water introduced from the circulating water pipe of the indirect air cooling system to circulate in equipment such as the water supply pipe 7, the water outlet pipe 8, and the hot water heater 1.

[0035] Furthermore, such as Figure 2 As shown, there are two hot water booster pumps 9, and the two hot water booster pumps 9 are installed in parallel on the water supply pipe 7.

[0036] In the above embodiments, the purpose of setting two hot water booster pumps 9 in parallel on the water supply pipe 7 is that if one of the hot water booster pumps 9 malfunctions, it can be quickly switched to the other hot water booster pump 9 to ensure that the circulating water circuit flowing to the hot water heater 1 operates normally.

[0037] Furthermore, such as Figure 2 As shown, a side pipe 10 is added to the water supply pipe 7 downstream of the heat medium water booster pump 9, and a heat medium water heat exchanger 11 is installed on the side pipe 10.

[0038] In the above embodiments, due to the low temperature of the circulating water in the indirect air-cooling system during winter, the temperature rise of the hot water heater 1 on the air inlet side of the first induced draft fan 2 is limited, resulting in the final air temperature not reaching the air inlet temperature required by the boiler 4. Therefore, this application adds a heat transfer medium water heat exchanger 11 (specifically, a steam / circulating water heat exchanger) to the water supply pipe 7. By introducing auxiliary steam or hot water into the heat transfer medium water heat exchanger 11, it can be used to auxiliary heat the circulating water in the water supply pipe 7 during winter, so as to ensure that the hot water heater 1 provides sufficient heat source for the air about to enter the first induced draft fan 2.

[0039] Furthermore, such as Figure 2 As shown, a return water branch pipe 12 is connected between the water supply pipe 7 and the water outlet pipe 8 and the connection end of the circulating water pipe between the condenser and the intercooler tower.

[0040] In the above embodiments, valves are installed at the inlet end of the water supply pipe 7, the outlet end of the water outlet pipe 8, and the upper side of the return water branch pipe 12. (In addition, valves can be added at important nodes such as the heat medium water booster pump 9 and the heat medium water heat exchanger 11, which can improve the safety and stability of the entire system operation.) At the same time, a temperature sensor is installed upstream of the connection between the return water branch pipe 12 and the outlet pipe 8 to detect the temperature in the outlet pipe 8. When the circulating water in the outlet pipe 8 still has usable residual heat after passing through the hot water heater 1, the valves on the water supply pipe 7 and the outlet pipe 8 can be closed, and the valve on the return water branch pipe 12 can be opened, so that the circulating water flows back to the hot water heater 1 for reuse. This can effectively improve the utilization efficiency of the heat energy in the circulating water and reduce unnecessary heat energy waste.

[0041] Furthermore, such as Figure 1 As shown, the exhaust gas treatment module 6 includes an electrostatic precipitator 61. The air inlet of the electrostatic precipitator 61 is connected to the air outlet of the low-pressure economizer 5 through an air transmission pipeline. The air outlet of the electrostatic precipitator 61 is connected to the air inlet side of the second induced draft fan 62 through an air transmission pipeline. The air outlet side of the second induced draft fan 62 is connected to the desulfurization absorption tower 63 through an air transmission pipeline.

[0042] In the above embodiments, after the flue gas from boiler 4 passes through the low-pressure economizer 5, its flue gas temperature can be reduced. With the reduced flue gas temperature, the resistivity of the dust particles in the flue gas will also decrease accordingly. Thus, when the flue gas passes through the electrostatic precipitator 61, the secondary voltage of the precipitator can be effectively increased, fully utilizing the electrostatic precipitator's charge collection efficiency and improving its overall efficiency. After being treated by the electrostatic precipitator 61 of this application, the particulate matter in the flue gas can be effectively removed, thereby significantly reducing the amount of dust emitted into the atmosphere. This application provides a second induced draft fan 62 at the outlet of the electrostatic precipitator 61 to provide power for the flow of flue gas. The outlet side of the second induced draft fan 62 is connected to the desulfurization absorption tower 63 via a gas transmission pipe. Thus, before being discharged into the air, the flue gas undergoes desulfurization treatment (i.e., removal of sulfur dioxide) in the desulfurization absorption tower 63, thereby reducing pollution and protecting the environment.

[0043] The implementation principle of this embodiment is as follows: The water supply pipe 7 of this application can directly obtain some of the circulating water that has absorbed the heat of the turbine exhaust steam from the water supply pipe of the indirect air-cooling system to the hot water heater 1. The circulating water can preheat the cold air drawn in by the first induced draft fan 2 at the hot water heater 1. Then, after the circulating water releases heat energy due to heating the cold air, it will flow from the outlet pipe 8 to the return water header in the indirect air-cooling system. Together with the circulating water in the return water header, it will flow to the condenser to reabsorb the heat of the turbine exhaust steam. The first induced draft fan 2 continues to deliver the air heated by the hot water heater 1 to the air preheater 3. In the air preheater 3, its flue gas side is connected to the tail flue of the boiler 4. The flue gas of the boiler 4 will use part of its heat in the air preheater 3 to further heat the air heated by the hot water heater 1, so as to ensure that the temperature of the air entering the boiler 4 meets the production process requirements. Compared with simply using the flue gas of the boiler 4 to heat the cold air that needs to enter the boiler 4, this can reduce the energy loss of the flue gas of the boiler 4 at the air preheater 3. As a result, the flue gas of the boiler 4 has more heat energy to heat the condensate when it flows to the low-pressure economizer 5, thereby replacing the high-quality heat and returning it to the heat system, achieving the purpose of reducing the heat consumption of the unit. After passing through the low-pressure economizer 5, the flue gas of the boiler 4 will continue to pass through the electrostatic precipitator 61 and the desulfurization absorption tower 63 in sequence under the action of the second induced draft fan 62, to ensure its safety and environmental protection when it is finally discharged into the environment. This application integrates the waste heat from the turbine exhaust and the waste heat from the boiler flue gas, maximizing the utilization of these two types of waste heat in power plant production and thereby reducing the unit's heat consumption.

[0044] Furthermore, the hot water heater 1 of this application, after obtaining circulating water from the water supply pipe of the indirect air-cooling system, fully utilizes the heat inside while also sharing some of the burden of the indirect cooling tower (because this part of the circulating water originally needed to be cooled by the indirect cooling tower). Taking a 2×1000MW coal-fired unit as an example, the circulating water volume that the indirect cooling tower of each unit needs to handle can be reduced by about 2100t / h, and the corresponding air-cooled radiator area can be reduced by about 3% during construction, with this part of the cost being about 67,800 m². 2 The diameter of the cooling tower can be reduced by approximately 4 meters, and the tower height can be reduced by approximately 2 meters. The initial investment in the air-cooled tower radiator can be reduced by approximately 3.86 million yuan, and the civil engineering cost of the cooling tower can be reduced by approximately 1.39 million yuan, resulting in an overall reduction of initial investment of 5.15 million yuan. After the waste heat comprehensive utilization system of this application is used in a 2×1000MW coal-fired unit, the standard coal consumption for power generation of a single unit will be reduced by 2.257g / kW.h, and the annual coal cost savings can reach approximately 5.56 million yuan (based on an annual utilization of 5500 hours and a standard coal price of 447.76 yuan / ton).

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A comprehensive waste heat utilization system for power plants, characterized in that: The system includes a heater (1) connected by a piping system and an indirect air-cooling system, and the heater (1) is installed on the inlet side of the first induced draft fan (2). The heater (1) can heat the cold air before it enters the first induced draft fan (2) by obtaining heat from the indirect air-cooling system. The air outlet of the first induced draft fan (2) is connected to one end of the air side of the air preheater (3) through a pipeline system, and the other end of the air side of the air preheater (3) is connected to the boiler (4) through a pipeline system. One end of the air preheater (3) on the flue gas side is connected to the flue at the tail of the boiler (4) through a pipeline system, and the other end of the air preheater (3) on the flue gas side is connected to the air inlet of the low-pressure economizer (5) through a pipeline system. The outlet of the low-pressure economizer (5) is connected to the tail gas treatment module (6), which is used to perform dust removal and desulfurization treatment on the flue gas discharged from the outlet of the low-pressure economizer (5).

2. The power plant waste heat comprehensive utilization system according to claim 1, characterized in that: The heater (1) is a hot water heater (1). A circulating water pipe is connected to the hot water heater (1) on the circulating water pipe between the condenser and the intercooling tower in the indirect air-cooling system.

3. The power plant waste heat comprehensive utilization system according to claim 2, characterized in that: The inlet and outlet ends of the heat exchanger in the hot water heater (1) are connected to the water supply header and return header in the circulating water pipe between the condenser and the intercooler via the water supply pipe (7) and the water outlet pipe (8), respectively.

4. The power plant waste heat comprehensive utilization system according to claim 3, characterized in that: A heat transfer water booster pump (9) is installed on the water supply pipe (7).

5. The power plant waste heat comprehensive utilization system according to claim 4, characterized in that: The number of the heat medium water booster pumps (9) is two, and the two heat medium water booster pumps (9) are installed in parallel on the water supply pipe (7).

6. The power plant waste heat comprehensive utilization system according to claim 4 or 5, characterized in that: A side pipe (10) is added to the water supply pipe (7) downstream of the heat medium water booster pump (9), and a heat medium water heat exchanger (11) is installed on the side pipe (10).

7. The power plant waste heat comprehensive utilization system according to claim 6, characterized in that: A return water branch pipe (12) is connected between the water supply pipe (7) and the water outlet pipe (8) and the connection end of the circulating water pipe between the condenser and the intercooler tower.

8. The power plant waste heat comprehensive utilization system according to claim 1, characterized in that: The exhaust gas treatment module (6) includes an electrostatic precipitator (61). The air inlet of the electrostatic precipitator (61) is connected to the air outlet of the low-pressure economizer (5) through an air transmission pipeline. The air outlet of the electrostatic precipitator (61) is connected to the air inlet side of the second induced draft fan (62) through an air transmission pipeline. The air outlet side of the second induced draft fan (62) is connected to the desulfurization absorption tower (63) through an air transmission pipeline.

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