CN103062754B - Power station machine furnace integrated cold end comprehensive optimization system - Google Patents

Abstract

The invention discloses an integrated cold-end comprehensive optimization system for a power station machine and furnace, which belongs to the field of power station energy saving. The system mainly includes a steam turbine, a main economizer, a main flue, a bypass flue, a combined flue, and main air preheating device, smoke-water heat exchanger, high and low pressure heater, deaerator, flue gas-air heater and extraction condensing air preheater. The extraction and condensing air preheater is arranged in series in multiple stages, and part of the exhaust steam of the steam turbine and the corresponding low-pressure stage extraction are sequentially extracted to preheat the cold air step by step; the first, second and third stage smoke-water heat exchangers are set up to heat the feed water and condensate, replacing the higher pressure extraction of the steam turbine. As a result, the cold end comprehensive optimization system of machine-furnace integration uses high-efficiency waste heat and uses low-pressure extraction steam to heat air to save high-pressure extraction steam for heat recovery, thereby significantly increasing unit output and realizing deep energy saving and reduction of coal-fired generating units. consumption; and reduce the problem of low-temperature corrosion of the heating surface by waste heat utilization, and the economic benefits are remarkable.

Description

Comprehensive optimization system for the cold end of power plant machine furnace integration

technical field

The invention belongs to the field of energy saving and emission reduction, and particularly relates to a comprehensive optimization system for the integrated cold end of a power station machine and furnace, specifically: (1) on the air side, steam turbine exhaust and low-pressure steam extraction are used to preheat the cold air step by step, The preheated air enters the main air preheater and is further heated to the required temperature; (2) The flue gas at the outlet of the boiler economizer enters the main air preheater and the first and second stage flue gas of the bypass flue at the same time. Water heat exchanger, the outlet flue gas enters the third-stage flue-water heat exchanger after being merged at the boiler tail, and then enters the dust removal and desulfurization device; (3) The first-stage flue-water heat exchanger can be used to heat the turbine feed water, replace Partial high-pressure steam extraction, the second and third-stage smoke-water heat exchangers can also be used to heat higher-temperature condensed water and replace higher-pressure steam extraction; etc., flexibly design different flue gas waste heat utilization methods and connection methods between the flue gas heat exchangers at all levels and the steam turbine steam water system.

Background technique

Energy conservation and emission reduction of large thermal power units is an important energy strategy in China. In China, coal-fired power plants consume nearly half of the country's coal production, and the boiler exhaust temperature of general coal-fired units is around 120-140°C, resulting in a large amount of low-grade energy being directly discharged to the environment, resulting in a huge waste of waste heat resources. With the continuous rise of coal energy prices in recent years and the increasing cost of coal-based power generation, thermal power plants are facing huge energy-saving pressures, constantly seeking new application technologies for reducing coal consumption and saving energy, and increasing related Capital investment.

The effective use of flue gas waste heat is the main way to save energy for coal-fired power plant boilers. Utilizing the waste heat of flue gas at the tail of the boiler to heat condensed water can not only effectively reduce the exhaust gas temperature of the boiler and improve boiler efficiency, but also input heat into the heat system through the waste heat exchanger. The heat can displace part of the regenerative extraction steam of the steam turbine. When the amount of steam entering the turbine remains unchanged, the displacement and extraction steam returns to the steam turbine to continue to expand and do work. The higher the extraction level of displacement, the more work the extraction steam does. However, low-level steam extraction is used to preheat cold air, and high-temperature flue gas is replaced to heat condensed water, which can squeeze out high-level steam extraction and continue to work. Therefore, in the case of constant fuel input, the output power of the steam turbine can be increased, and the thermal efficiency and economy of the unit can be improved.

In order to recover and utilize high-temperature flue gas waste heat, increase the inlet temperature of condensed water, and replace steam extraction with a higher energy level turbine in Niederaussem Power Plant in Germany, the bypass flue technology is integrated in the flue gas waste heat utilization system. Part of the gas enters the air preheater, and the other part enters the bypass flue to heat the high-pressure feed water in the high-temperature heat exchanger and the condensed water in the low-temperature heat exchanger. A cold air preheater is arranged after the parallel flue to recover the flue gas. Waste heat with lower smoke temperature levels.

The waste heat recovery system of the Niederaussem power plant in Germany can save about 7g/kWh of standard coal consumption for power generation. However, since German power plants generally use lignite as fuel, the exhaust gas temperature is generally high, even as high as 160 °C. Therefore, the tail gas waste heat of German coal-fired power plants very high. However, China's coal-fired power plants use ordinary anthracite and bituminous coal as fuel, and the flue gas temperature is relatively low, generally around 120-140°C, which is quite different from the actual situation in German power plants. Such as SO ₂ , SO ₃ , NO _x and other corrosive gases, when the wall surface temperature drops below the acid dew point, the low-temperature pipe wall is prone to strong low-temperature flue gas corrosion, and at the same time forms with the fly ash in the flue gas, mainly calcium sulfate The cement-like substance increases the ventilation resistance of the flue gas side, increases the power consumption of the fan, and intensifies the corrosion of the tube wall, seriously affecting the safe and economical operation of the boiler. Therefore, the waste heat recovery system of Niederaussem power plant in Germany is not suitable for coal-fired power plants in China.

The present invention proposes a comprehensive optimization system for the integrated cold end of the power station machine and furnace, which solves the shortcomings of the above-mentioned technologies. The energy counterparts and cascades use the tail flue gas energy, and use the low-pressure cylinder of the steam turbine to extract steam and the flue gas at the boiler tail to preheat the air. systems and methods. This new idea of energy utilization is to use the bypass flue and low-level extraction to recover higher-quality flue gas heat and heat higher-level condensate without changing the flue gas temperature at the outlet of the air preheater. Instead of the higher-level steam extraction, the reduced heat absorption of the air preheater is compensated by the condensation heat release of the low-pressure cylinder of the steam turbine and the waste heat of the flue gas at the tail of the boiler, which can comprehensively prevent low-temperature corrosion caused by too low flue gas temperature. It is a new technology that is really suitable for energy saving and emission reduction of coal-fired power plants in China.

Contents of the invention

The object of the present invention is to propose a comprehensive optimization system for the integrated cold end of the power station machine furnace, which mainly includes the high-pressure cylinder of the steam turbine, the medium-pressure cylinder of the steam turbine and the low-pressure cylinder of the steam turbine in series, the main economizer of the boiler, the main flue, the bypass Road flue, combined flue, main air preheater, smoke-water heat exchanger, high-pressure heater, deaerator, low-pressure heater, flue gas-air heater and extraction condensing air preheater; its characteristics It is: after the main flue 2 and the bypass flue 3 are connected in parallel, the upper end is connected with the main economizer 1, and the lower end is connected with the confluent flue 22, and the first-stage smoke-water heat exchanger 5 and the The second-stage smoke-water heat exchanger 6 and the third-stage smoke-water heat exchanger 16 are arranged in the confluent flue 22; the main air preheater 4 is respectively connected to the confluent flue 22, the main flue 2 and the fourth-stage steam extraction Condensing air preheater 27, wherein the fourth stage extraction condensing air preheater 27, the third stage extraction air preheater 26, the second stage extraction condensing air preheater 25 and the first stage Extraction condensing air preheaters 24 are connected in series; the outlet of confluence flue 22 is connected to the desulfurization device after passing through dust collector 23, and the inlet of first-stage smoke-water heat exchanger 5 is connected to No. 3 high pressure through No. 28 valve and No. 29 valve On both sides of the heater 9, the outlet of the first-stage smoke-water heat exchanger 5 is connected to both sides of the No. 1 high-pressure heater 7 through the 30th and 31st valves, and the two sides of the No. 2 high-pressure heater 8 are respectively connected to the 29th valve and the 31st valve Connection; No. 1 to No. 3 high-pressure heaters are respectively connected to the high-pressure cylinder 17 of the steam turbine and the medium-pressure cylinder 18 of the steam turbine; the outlet 6 of the second-stage smoke-water heat exchanger is connected to the side of the No. 5 low-pressure heater 11 through the 33rd valve, and the No. The inlet of the second-stage smoke-water heat exchanger 6 is connected to the other side of No. 5 low-pressure heater 11 through the 33rd valve, and the inlet and outlet of the third-stage smoke-water heat exchanger 16 are connected to No. 6 through the 34th and 35th valves On both sides of the low-pressure heater 12, the second-stage smoke-water heat exchanger 6 and the third-stage smoke-water heat exchanger 16 are directly connected through the 36th valve, No. 5 low-pressure heater 11, No. 6 low-pressure heater 12, No. 7 low-pressure heater 13 and No. 8 low-pressure heater 14 form a series structure through condensed water and water supply pipelines; and are respectively connected with the exhaust port of steam turbine low-pressure cylinder 19; the exhaust port of steam turbine low-pressure cylinder 19 is also connected with condenser 20 No. 8 low-pressure heater 14 inlet connection.

The flue gas-air heater 15 is bridged in the confluent flue 22 and the flue connecting the fourth-stage extraction condensing air preheater 27 and the main air preheater 4 to replace the third-stage smoke-water heat exchanger 16 .

The first stage, the second stage and the third stage arranged in the main flue 2, the bypass flue 3 and the combined flue 22 and connected with No. 5 to No. 8 low-pressure heaters and No. 1 to No. 3 high-pressure heaters The first-stage flue-water heat exchanger recovers the waste heat of the flue gas to heat the condensate water or feed water of the steam turbine.

On the air preheating side: the first stage to the fourth stage extraction condensing air preheater preheats the cold air step by step, and the condensed water after the extraction steam of each stage releases heat in the extraction condensing air preheater flows into the In the return pipe of the low-pressure heater corresponding to this level of steam extraction.

On the flue gas waste heat utilization side: most of the flue gas at the outlet of the economizer 1 still enters the main air preheater 4 from the main flue 2, and the other part enters the bypass flue 3, and passes through the first-stage flue-water heat exchanger 5 in turn After the second-stage smoke-water heat exchanger 6, the two streams of flue gas enter the combined flue 22, pass through the third-stage smoke-water heat exchanger 16 and dust collector 23, and then enter the desulfurization unit for final discharge.

On the condensed water heating side: the condensed water is extracted from the inlet of a high-pressure heater of a certain stage, heated by the first-stage smoke-water heat exchanger 5 and then returned to the outlet of a higher-level high-pressure heater, and the condensed water is extracted from the inlet of a certain-stage low-pressure heater through the second After being heated by the first-level smoke-water heat exchanger 6, it returns to the outlet of the higher-level low-pressure heater.

The beneficial effect of the present invention is that the integrated cold end comprehensive optimization system of the power plant machine furnace provided has the following characteristics:

1. The steam extraction condensing air preheater is arranged in series in multiple stages to preheat the cold air step by step, and the heat exchange loss is small; the steam extraction condensing air preheater extracts the low-pressure steam of the steam turbine, and the temperature and pressure are very low. It has low working ability in the steam turbine, which is beneficial to energy saving. The heat exchange method of steam in the extraction and condensing air preheater is the heat exchange method of steam condensation phase change heat, which releases a large amount of latent heat, and the heating object is non-corrosive air. There is no corrosion problem in the heat exchanger, and the air Can be preheated to over 100 degrees Celsius.

2. The arrangement of the main heat exchangers on the flue gas side forms a series-parallel structure, which is conducive to utilizing the waste heat of the flue gas to the greatest extent.

3. The use of the three-stage smoke-water heat exchanger is relatively flexible, and can be flexibly adjusted through the valve. The smoke-water heat exchanger and the heater are arranged in parallel, and the water side resistance reduced by the condensed water not flowing through the heater is sufficient to compensate for its flow. Through the increased resistance of the smoke-water heat exchanger, it does not need to add a water pump, which is more conducive to the transformation on the basis of the thermal system of the original power plant.

4. The system is flexible and open. According to the needs, the extraction condensing air preheater can be removed, and the flue gas-air heat exchanger can be used to release heat directly to the air.

5. Set up a steam extraction condensing air preheater and use the waste heat of the exhaust steam of the steam turbine to preheat the cold air, which can heat the cold air to 8-20°C, which can effectively avoid the problem of freezing in winter, and at the same time use waste heat to save a lot of low-temperature heat energy. Save circulating water; at the same time, the extraction condensing air preheater is also suitable for air-cooled units. Generally, air-cooling units have relatively high exhaust pressure and high exhaust parameters. The introduction of extraction condensing air preheaters can increase the air temperature to 15-40°C.

6. The system may not be equipped with a third-stage flue-water heat exchanger, which can reduce the flue gas resistance, further reduce the transformation investment, and maintain a high exhaust gas temperature, basically solving the problem caused by the low flue gas temperature at the boiler tail during the waste heat utilization process. low temperature corrosion problems. According to calculations, this integrated system can reduce the standard coal consumption of power generation by 6-11g/KWh, and the economic benefits are remarkable.

Description of drawings

Figure 1 is a schematic diagram of the comprehensive optimization system of the integrated cold end of the power plant machine and furnace

Figure 2 is a schematic diagram of the comprehensive optimization system for the integrated cold end of the power station machine and furnace with flue gas-air preheater

Implementation

The invention proposes a comprehensive optimization system for the integrated cold end of a power station machine and furnace. The following will be described in conjunction with the accompanying drawings and examples.

In the schematic diagram of the comprehensive optimization system for the integrated cold end of the power station machine and furnace as shown in Figure 1, the integrated cold end integrated optimization system for the power plant mainly includes the high pressure cylinder of the steam turbine, the medium pressure cylinder of the steam turbine and the low pressure cylinder of the steam turbine in series, and the main coal-saving boiler flue, main flue, bypass flue, combined flue, main air preheater, smoke-water heat exchanger, high-pressure heater, deaerator, low-pressure heater, flue gas-air heater and extraction condensing Air preheater; after the main flue 2 and bypass flue 3 are connected in parallel, the upper end is connected to the main economizer 1, the lower end is connected to the confluent flue 22, and the first-stage smoke-water exchange is arranged in the bypass flue 3 in sequence The heat exchanger 5, the second-stage smoke-water heat exchanger 6, and the third-stage smoke-water heat exchanger 16 are arranged in the confluent flue 22; the main air preheater 4 is respectively connected to the confluent flue 22, the main flue 2 and the second Four-stage steam extraction condensing air preheater 27, of which the fourth stage steam extraction condensing air preheater 27, the third stage steam extraction condensing air preheater 26, the second stage steam extraction condensing air preheater 25 is connected in series with the first-stage steam extraction condensing air preheater 24; the outlet of the confluence flue 22 passes through the dust collector 23 and then is connected to the desulfurization device, and the inlet of the first-stage smoke-water heat exchanger 5 passes through the 28th valve and the 29th valve Connected to both sides of No. 3 high-pressure heater 9, the outlet of first-stage smoke-water heat exchanger 5 is connected to both sides of No. 1 high-pressure heater 7 through No. 30 valve and No. 31 valve, and both sides of No. 2 high-pressure heater 8 are connected to No. 29 The valve is connected to the No. 31 valve; No. 1 to No. 3 high-pressure heaters are respectively connected to the high-pressure cylinder 17 of the steam turbine and the medium-pressure cylinder 18 of the steam turbine; the outlet 6 of the second-stage smoke-water heat exchanger is connected to the No. 5 low-pressure heater through the No. 33 valve On one side of 11, the inlet of the second-stage smoke-water heat exchanger 6 is connected to the other side of No. 5 low-pressure heater 11 through the 33rd valve, and the inlet and outlet of the third-stage smoke-water heat exchanger 16 pass through the 34th valve and the 35th valve. The valves are connected to both sides of the No. 6 low-pressure heater 12. The second-stage smoke-water heat exchanger 6 and the third-stage smoke-water heat exchanger 16 are directly connected through the No. 36 valve. No. 5 low-pressure heater 11 and No. 6 Low-pressure heater 12, No. 7 low-pressure heater 13 and No. 8 low-pressure heater 14 form a series structure through condensed water and water supply pipeline; Connect with No. 8 low-pressure heater 14 inlet through condenser 20.

As shown in Figure 2, a flue gas-air heater 15 can be installed at the outlet of the extraction air preheater 26, and the flue gas-air heat exchanger 15 can be used to directly release heat to the air, and the waste heat of the flue gas can be recovered for further preheating Air; as shown in Figure 1, the flue gas-air heater 15 may not be provided, but the third-stage flue-water heat exchanger 16 is used to heat the condensed water or feed water. At this time, higher-level extraction steam can be extracted for further Preheat the air. The system is flexible and open, and the fourth-stage steam extraction condensing air preheater 27 can be removed as required, as shown in Figure 2, the comprehensive optimization system for the integrated cold end of the power station machine and furnace; the second stage can be completely omitted The three-stage smoke-water heat exchanger 16 can reduce the smoke resistance and reduce the transformation investment. At this time, the flue gas temperature at the tail of the boiler is 120-150°C, and there is no low-temperature flue gas corrosion on the heating surface of the tail, so no special anti-corrosion materials are needed, which can further reduce the transformation investment.

The principle is as follows: on the air side, part of the exhaust steam of the steam turbine and the low-level extraction steam are sequentially extracted, and pass through the first-stage extraction condensing air preheater 24, the second-stage extraction condensing air preheater 25, and the third-stage steam extraction respectively. The extraction condensing air preheater 26 and the fourth-stage extraction condensing air preheater 27 preheat the cold air step by step, and the condensate after the extraction steam releases heat in the extraction condensing air preheater flows into the extraction The steam corresponds to the return pipe of the next stage low-pressure heater.

On the flue gas side, the flue gas at 350-450°C at the outlet of the economizer 1 is divided into two paths: one path is connected to the main air preheater 4, and the other path passes through the bypass flue 3 and passes through the first-stage flue-water heat exchanger 5 in turn and the second-stage smoke-water heat exchanger 6, depending on the parameters of the unit, the condensed water extracted from the inlet of a certain high-pressure heater is heated by the first-stage smoke-water heat exchanger 5 and then returned to the outlet of a higher-level high-pressure heater. The condensed water extracted from the inlet of the first-stage low-pressure heater is heated by the second-stage smoke-water heat exchanger 6 and then returned to the outlet of the higher-stage low-pressure heater.

The present invention rationally utilizes the residual heat of flue gas at the tail of the boiler based on the principles of energy counterpart and cascade utilization, and proposes for the first time the method of using steam extraction from the low-pressure cylinder of the steam turbine and flue gas at the tail of the boiler to preheat the air step by step, which correspondingly reduces the suction of the air preheater Heat, which can recover high-quality flue gas waste heat to heat the condensed water of higher-level heaters and discharge higher-level extraction steam, and at the same time effectively reduce the heat caused by the temperature of the flue gas at the tail of the boiler being lower than the acid dew point in the process of waste heat utilization. According to calculations, the system can reduce the standard coal consumption of power generation by 6-11g/KWh, and the economic benefits are remarkable.

Claims (6)

1. A comprehensive optimization system for the integrated cold end of a power station machine and furnace, the system mainly includes a steam turbine, a boiler main economizer, a main flue, a bypass flue, a confluent flue, a main air preheater, and smoke-water heat exchange heater, high-pressure heater, deaerator, low-pressure heater, flue gas-air heater and extraction condensing air preheater; it is characterized in that: after the main flue (2) and the bypass flue (3) are connected in parallel , the upper end is connected to the main economizer (1), the lower end is connected to the confluent flue (22), and the first-stage smoke-water heat exchanger (5) and the second-stage smoke-water heat exchanger (5) are arranged in the bypass flue (3) in sequence The heater (6) and the third-stage smoke-water heat exchanger (16) are set in the confluent flue (22); the main air preheater (4) is respectively connected to the confluent flue (22) and the main flue (2) And the fourth stage extraction condensing air preheater (27), wherein the fourth extraction condensing air preheater (27), the third extraction condensing air preheater (26), the second The extraction condensing air preheater (25) and the first stage extraction condensing air preheater (24) are connected in series; the outlet of the combined flue (22) is connected to the desulfurization device after passing through the dust collector (23), the first stage The inlet of the smoke-water heat exchanger (5) is connected to both sides of the No. 3 high-pressure heater (9) through the 28th and 29th valves, and the outlet of the first-stage smoke-water heat The valves are connected to both sides of No. 1 high-pressure heater (7), and No. 2 high-pressure heater (8) is respectively connected to No. 29 valve and No. 31 valve; No. 1 to No. 3 high-pressure heaters are respectively connected to the steam turbine high-pressure cylinder (17), The medium-pressure cylinder (18) of the steam turbine is connected; the outlet of the second-stage smoke-water heat exchanger (6) is connected to the side of the No. 5 low-pressure heater (11) through the 33rd valve, and the inlet of the second-stage smoke-water heat exchanger (6) Connect to the other side of No. 5 low-pressure heater (11) through No. 32 valve, and the inlet and outlet of the third-stage smoke-water heat exchanger (16) are connected to No. 6 low-pressure heater (12) through No. 34 and No. 35 valves ), where the second-stage smoke-water heat exchanger (6) and the third-stage smoke-water heat exchanger (16) are directly connected through the No. 36 valve, No. 5 low-pressure heater (11), and No. 6 low-pressure heater (12), No. 7 low-pressure heater (13) and No. 8 low-pressure heater (14) form a series structure through condensed water and water supply pipelines; they are respectively connected to the exhaust port of the low-pressure cylinder (19) of the steam turbine; the low-pressure cylinder of the steam turbine (19) The exhaust port is also connected with the inlet of No. 8 low-pressure heater (14) through the condenser (20). 2. A comprehensive cold-end comprehensive optimization system for power plant furnace integration according to claim 1, characterized in that, between the confluent flue (22) and the fourth stage extraction condensing air preheater (27) and the main The flue gas-air heater (15) is bridged in the flue connected to the air preheater (4), replacing the third-stage smoke-water heat exchanger (16). 3. A comprehensive cold-end comprehensive optimization system for power station machine furnace integration according to claim 1, characterized in that the combined and No. 5 to No. The first-stage, second-stage, and third-stage flue-water heat exchangers connected to No. 1 low-pressure heater and No. 1 to No. 3 high-pressure heaters recover waste heat from the flue gas to heat the condensate water or feed water of the steam turbine. 4. A comprehensive cold-end comprehensive optimization system for power plant furnace integration according to claim 1, characterized in that, on the air preheating side: the first to fourth extraction condensing air preheaters are preheated step by step Hot and cold air, the condensed water after each level of extraction steam releases heat in the extraction condensing air preheater flows into the return pipe of the low-pressure heater corresponding to the level of extraction respectively. 5. A comprehensive cold-end comprehensive optimization system for power plant furnace integration according to claim 1, characterized in that, on the flue gas waste heat utilization side: most of the flue gas at the outlet of the economizer (1) is still passed through the main flue ( 2) It enters the main air preheater (4), and the other part enters the bypass flue (3), and passes through the first-stage smoke-water heat exchanger (5) and the second-stage smoke-water heat exchanger (6) in turn, and then , the two streams of flue gas enter the confluent flue (22), pass through the third-stage flue-water heat exchanger (16) and dust collector (23), then enter the desulfurization unit, and finally discharge. 6. A comprehensive cold-end comprehensive optimization system for power plant furnace integration according to claim 1, characterized in that, on the condensate heating side: condensate is extracted from the inlet of a high-pressure heater of a certain stage and exchanged with smoke and water at the first stage After being heated by the device (5), it returns to the outlet of the higher-level high-pressure heater, and the condensed water extracted from the inlet of a certain-level low-pressure heater is heated by the second-level smoke-water heat exchanger (6) and then returned to the outlet of the higher-level low-pressure heater.