CN201866755U - Flue gas waste heat recovery system for boiler in thermal power plant - Google Patents

Abstract

The utility model discloses a boiler flue gas waste heat recovery and utilization system in a thermal power plant, that is, a first heat exchanger is connected in parallel at the flue gas input and output ends of the flue gas channel air preheater of the boiler, and the heat exchange of the first heat exchanger The input and output ends of the medium are respectively connected to the input and output ends of any high-pressure condensate water heater through the flow control valve, and the condensate water passing through the high-pressure condensate water heater is heated; this system effectively improves the efficiency of boiler flue gas waste heat recovery and utilization, and improves the The heat transfer effect of the heat exchanger and the efficiency of the boiler and steam turbine.

Description

Thermal power plant boiler flue gas waste heat recovery and utilization system

technical field

The utility model relates to a system for recovering and utilizing waste heat of boiler flue gas in a thermal power plant.

Background technique

The air preheater of a thermal power plant is a heat exchanger. The high-temperature flue gas discharged from the boiler economizer exchanges heat with the cold air before entering the boiler, but the air flow rate is smaller than the flue gas flow rate. The air side of the air preheater The heat exchange with the flue gas side is asymmetrical, and the waste heat of high-grade flue gas is not fully utilized and discharged from the chimney; under the background of vigorously promoting energy conservation and emission reduction, how to reduce the flue gas for coal-fired boilers such as thermal power plants? It is of great significance to save energy and protect the environment by reducing heat energy loss. Flue gas heat energy loss during boiler operation is the most important heat energy loss. If the boiler flue gas heat can be recovered to the maximum extent and utilized in the generator set, the boiler operating efficiency and economic benefits can be improved.

As shown in Figure 1, the air from the boiler 10 is usually input after passing through the fan 11 and the air preheater 12, and the air preheater 12 heats the air to improve boiler efficiency and reduce energy consumption; Heater 12, dust collector 13, induced draft fan 14, booster fan 15, and desulfurization tower 16 are then discharged to the chimney 17. Obviously, the heat energy in the boiler flue gas is emptied, resulting in heat energy loss; the steam from the boiler 10 is output to the steam turbine 20 and then driven The generator 21 generates electricity, and the steam turbine 20 returns the steam after working to the boiler 10 through the heat recovery system 22; Between the head-end condensate heater of the recuperation system 22, the tail-end condensate heater is connected to the boiler 10, and each condensate heater is also respectively connected to the steam extraction end of the steam turbine 20. The front-end condensate heater of the recuperation system 22 is The low-pressure condensed water heater 25, and the tail-end condensed water heater is a high-pressure condensed water heater 24.

In order to avoid the loss of flue gas heat energy, the methods for recovery and utilization of boiler flue gas heat in the past are mainly as follows:

Multiple heat exchangers are connected in series in the boiler flue gas channel, and the heat obtained by heat exchange is used to heat the boiler feed water of the heat recovery system, thereby reducing steam extraction, generating more power, or heating the air entering the boiler, and improving boiler efficiency. Or heat the flue gas entering the chimney, which is beneficial to environmental protection. The input and output ends of the heat exchange medium of the heat exchanger used to heat the boiler feed water of the heat recovery system can be connected in series or in parallel to the condensate heater of the heat recovery system, and other heat exchangers can be connected in series after that, because the boiler flue gas The flue gas temperature in the channel decreases step by step, and if the boiler flue gas temperature is low, the heat exchange effect of each heat exchanger connected in series in the boiler flue gas channel will be significantly reduced, and the due performance of each heat exchanger will not be achieved. effect.

In addition, in order to prevent corrosion at the cold end of the air preheater in thermal power plants, especially for cold regions, a heater is installed in the cold air channel in front of the air preheater. Air, that is, the steam-air heat exchanger is arranged in the cold air passage. In this case, although the temperature of the cold air is increased, the temperature of the air entering the boiler is increased, thereby improving the efficiency of the boiler, but because the high-grade steam extraction of the steam turbine is used, the power generation capacity is reduced, and the economic benefits are reduced comprehensively.

Contents of the invention

The technical problem to be solved by the utility model is to provide a thermal power plant boiler flue gas waste heat recovery and utilization system. efficiency.

In order to solve the above technical problems, especially the asymmetry of heat exchange between the air side and the flue gas side of the air preheater, the boiler flue gas waste heat recovery and utilization system in thermal power plants includes boilers, fans, air preheaters, dust collectors, induced draft fans, A booster fan, a desulfurization tower, a chimney, a steam turbine and a heat recovery system, the heat recovery system includes a condenser, several high-pressure condensate heaters and low-pressure condensate heaters connected in series, and the steam output end of the boiler is connected to the The steam input end of the steam turbine, the condensed water output end of the steam turbine is connected to the input end of the recuperation system, the output end of the regenerating system is connected to the condensed water input end of the boiler, the output end of the fan, the air input end of the air preheater and the The output ends are connected in series to the boiler air input end, and the flue gas input and output ends of the air preheater, dust collector, induced draft fan, booster fan and desulfurization tower are connected in series to the boiler flue gas output end respectively and the flue gas input end of the chimney, the system also includes a first heat exchanger, a first flow control valve and a second flow control valve, the flue gas input end of the first heat exchanger is connected to the flue gas of the air preheater The gas input end of the first heat exchanger, the flue gas output end of the first heat exchanger is connected to the flue gas output end of the air preheater, and the heat exchange medium input and output ends of the first heat exchanger respectively pass through the first The flow control valve and the second flow control valve are connected to the input and output ends of any one of the high-pressure condensate heaters.

Further, in order to improve the heat exchange effect, the system also includes a feed water heat exchanger and a first circulation pump, and the input and output ends of the heat exchange medium of the first heat exchanger are connected to the feed water heat exchange through the first circulation pump. The input and output ends of the heat exchange medium of the feed water heat exchanger are respectively connected to the input and output ends of any high-pressure condensate heater through the first flow control valve and the second flow control valve. output.

Further, the system also includes a second heat exchanger, a third flow control valve and a fourth flow control valve, the flue gas input and output ends of the second heat exchanger are connected in series to the output end of the induced draft fan and the booster fan Between the input ends, the heat exchange medium input end of the second heat exchanger is connected to the input end of any low-pressure condensate heater through the third flow control valve, and the heat exchange medium input end of the second heat exchanger The medium output end is connected to the output end of any one of the low-pressure condensate heaters through the fourth flow control valve.

Further, the system also includes a third heat exchanger, an air heater and a second circulation pump, the flue gas input and output ends of the third heat exchanger are connected in series between the output end of the booster fan and the input end of the desulfurization tower Between, the air input and output ends of the air heater are connected in series between the fan output end and the air preheater air input end, and the heat exchange medium output end of the third heat exchanger passes through the second circulation The pump is connected to the heat exchange medium input end of the air heater, and the heat exchange medium output end of the air heater is connected to the heat exchange medium input end of the third heat exchanger.

Further, the system also includes a fourth heat exchanger, a flue gas heater and a third circulating pump, the flue gas input and output ends of the fourth heat exchanger are connected in series with the flue gas output ends of the third heat exchanger Between the flue gas input end of the desulfurization tower, the flue gas input and output ends of the flue gas heater are connected in series between the flue gas output end of the desulfurization tower and the flue gas input end of the chimney, and the fourth heat exchange The heat exchange medium output end of the gas heater is connected to the heat exchange medium input end of the flue gas heater through the third circulation pump, and the heat exchange medium output end of the flue gas heater is connected to the heat exchange medium of the fourth heat exchanger media input.

Further, in order to improve the controllability of the system, a flue gas bypass is provided between the flue gas input and output ends of the second heat exchanger through three air valves, and two of the three air valves are respectively set at At the flue gas input end and output end of the second heat exchanger, one of the three air valves is arranged on the flue gas bypass.

A cold air bypass is provided between the air input and output ends of the above-mentioned air heater through three air valves, and two of the three air valves are respectively arranged at the air input end and the output end of the air heater. One of the air valves is set on the cold air bypass, and the flue gas bypasses are respectively set through three air valves between the flue gas input and output ends of the first heat exchanger and the third heat exchanger, and the three air valves are respectively provided with flue gas bypasses. Two of the three air valves are respectively arranged at the flue gas input and output ends of the first heat exchanger and the third heat exchanger, and one of the three air valves is respectively arranged at the above-mentioned flue gas on the bypass.

A flue gas bypass is provided between the flue gas input and output ends of the fourth heat exchanger and the flue gas heater respectively through three dampers, and two of the three dampers are respectively set at the fourth The flue gas input end and output end of the heat exchanger, the flue gas heater, and one of the three air valves are respectively arranged on each of the above flue gas bypasses.

For the convenience of connection and installation, the flue gas input and output ends of the above-mentioned first heat exchanger can be connected in series in the flue of the boiler and the air preheater.

The flue gas input and output ends of the above-mentioned second heat exchanger can be connected to the flue gas output end of the air preheater and the input end of the dust collector.

The flue gas input and output ports of the fourth heat exchanger may be connected to the flue gas output port of the second heat exchanger and the flue gas input port of the booster fan.

In order to facilitate the control of the heat exchange effect of the system, the heat change of the above-mentioned air heater can be realized by the second circulation pump by adjusting the flow change of the circulating medium.

The heat change of the above-mentioned flue gas heater can be realized by adjusting the flow change of the circulating medium by the third circulation pump.

Since the utility model thermal power plant boiler flue gas waste heat recovery and utilization system adopts the above-mentioned technical scheme, that is, the flue gas input and output ends of the flue gas channel air preheater of the boiler are connected in parallel with the first heat exchanger, and the first heat exchanger The input and output ends of the heat exchange medium are respectively connected to the input and output ends of any high-pressure condensate water heater through the flow control valve, and the condensate water passing through the high-pressure condensate water heater is heated; this system effectively improves the recovery and utilization efficiency of boiler flue gas waste heat, The heat exchange effect of the heat exchanger and the efficiency of the boiler and the steam turbine are improved.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail:

Figure 1 is a schematic diagram of the connection of boiler flue gas exhaust in a thermal power plant.

Fig. 2 is the connection schematic diagram of the utility model thermal power plant boiler flue gas waste heat recovery and utilization system,

Figure 3 is a schematic diagram of the connection of the system with a feed water heat exchanger.

Figure 4 is a schematic diagram of the connection of this system with other heat exchangers,

Figure 5 is a schematic diagram of the connection of the system adding cold air bypass and flue gas bypass.

Detailed ways

As shown in Figure 2, the utility model thermal power plant boiler flue gas waste heat recovery and utilization system includes a boiler 10, a fan 11, an air preheater 12, a dust collector 13, an induced draft fan 14, a booster fan 15, a desulfurization tower 16, and a chimney 17 , a steam turbine 20 and a heat recovery system 22, the heat recovery system 22 includes a condenser 23, several high-pressure condensate heaters 24 and low-pressure condensate heaters 25 connected in series, and the steam output end of the boiler 10 is connected to the The steam input end of the steam turbine 20, the condensed water output end of the steam turbine 20 is connected to the input end of the heat recovery system 22, the output end of the heat recovery system 22 is connected to the condensed water input end of the boiler 10, the output end of the fan 11, the air preheating The air input end and output end of the device 12 are connected in series in sequence to the air input end of the boiler 10, the flue gas input and output ends of the air preheater 12, the dust collector 13, the induced draft fan 14, the booster fan 15 and the desulfurization tower 16 After being connected in series, the flue gas output end of the boiler 10 and the flue gas input end of the chimney 17 are respectively connected. The system also includes a first heat exchanger 5, a first flow control valve 51 and a second flow control valve 52. The first The flue gas input end of the heat exchanger 5 is connected to the flue gas input end of the air preheater 12, the flue gas output end of the first heat exchanger 5 is connected to the flue gas output end of the air preheater 12, The input and output ends of the heat exchange medium of the first heat exchanger 5 are respectively connected to the input and output ends of any high-pressure condensate heater 24 through the first flow control valve 51 and the second flow control valve 52 .

As shown in Figure 3, further, in order to improve the heat exchange effect, this system also includes a feed water heat exchanger 7 and a first circulation pump 71, the input and output ends of the heat exchange medium of the first heat exchanger 5 pass through the first A circulating pump 71 is connected to the heat exchange medium input and output ends of the feed water heat exchanger 7, and the feed water input and output ends of the feed water heat exchanger 7 pass through the first flow control valve 51 and the second flow control valve respectively. 52 is connected to the input and output ends of any one of the high-pressure condensate heaters 24 .

As shown in Figure 4, further, the system further includes a second heat exchanger 3, a third flow control valve 31 and a fourth flow control valve 32, the flue gas input and output ends of the second heat exchanger 3 are connected in series Between the output end of the induced draft fan 14 and the input end of the booster fan 15, the heat exchange medium input end of the second heat exchanger 3 is connected to any of the low-pressure condensate heaters through the third flow control valve 31 25 , the output end of the heat exchange medium of the second heat exchanger 3 is connected to the output end of any low-pressure condensate heater 25 through the fourth flow control valve 32 .

As shown in Figure 4, further, this system also includes a third heat exchanger 4, an air heater 6 and a second circulation pump 61, the flue gas input and output ends of the third heat exchanger 4 are connected in series to the increasing Between the output end of the compressor 15 and the input end of the desulfurization tower 16, the air input and output ends of the air heater 6 are connected in series between the output end of the fan 11 and the air input end of the air preheater 12, and the third The heat exchange medium output end of the heat exchanger 4 is connected to the heat exchange medium input end of the air heater 6 through the second circulation pump 61, and the heat exchange medium output end of the air heater 6 is connected to the third exchange medium. The input end of the heat exchange medium of the heat exchanger 4.

As shown in Figure 4, further, the system further includes a fourth heat exchanger 81, a flue gas heater 82 and a third circulation pump 83, and the flue gas input and output ends of the fourth heat exchanger 81 are connected in series to the Between the flue gas output end of the third heat exchanger 4 and the flue gas input end of the desulfurization tower 16, the flue gas input and output ends of the flue gas heater 82 are connected in series between the flue gas output end of the desulfurization tower 17 and the flue gas output end of the desulfurization tower 17. Between the flue gas input ends of the chimney 17, the heat exchange medium output end of the fourth heat exchanger 81 is connected to the heat exchange medium input end of the flue gas heater 82 through the third circulation pump 83, and the flue gas heats The heat exchange medium output end of the heat exchanger 82 is connected to the heat exchange medium input end of the fourth heat exchanger 81 .

As shown in Figure 5, further, in order to improve the controllability of the system, a flue gas bypass 92 is provided between the flue gas input and output ends of the second heat exchanger 3 respectively through three air valves 9, and the three air valves Two of the valves 9 are respectively arranged at the flue gas input end and the output end of the second heat exchanger 3 , and one of the three dampers 9 is arranged on the flue gas bypass 92 .

As shown in Figure 5, a cold wind bypass 91 is provided between the air input and output ends of the above-mentioned air heater 6 through three air valves 9, and two air valves in the three air valves 9 are respectively arranged on the air heater 6. The air input and output ends of the three air valves 9 are arranged on the cold air bypass 91, between the flue gas input and output ends of the first heat exchanger 5 and the third heat exchanger 4 A flue gas bypass 92 is respectively provided through three air valves 9, and two of the three air valves 9 are respectively arranged at the flue gas input ends of the first heat exchanger 5 and the third heat exchanger 4 and the output end, one of the three air valves 9 is set on each of the above-mentioned flue gas bypasses 92 .

As shown in Fig. 5, between the flue gas input and output ends of the fourth heat exchanger 81 and the flue gas heater 82, a flue gas bypass 92 is respectively provided through three dampers 9, and among the three dampers 9 Two air valves are respectively arranged at the flue gas input end and output end of the fourth heat exchanger 81 and the flue gas heater 82, and one air valve among the three air valves 9 is respectively arranged at each of the above-mentioned flue gas bypasses 92 on.

For the convenience of connection and installation, the flue gas input and output ends of the above-mentioned first heat exchanger 5 can be connected in series in the flue of the boiler 10 and the air preheater 12 .

The flue gas input and output ends of the above-mentioned second heat exchanger 3 can be connected to the flue gas output end of the air preheater 12 and the input end of the dust collector 13 .

The flue gas input and output ports of the fourth heat exchanger 81 may be connected to the flue gas output port of the second heat exchanger 3 and the flue gas input port of the booster fan 15 .

In order to facilitate the control of the heat exchange effect of the system, the heat change of the above-mentioned air heater 6 can be realized by the second circulation pump 61 by adjusting the flow change of the circulating medium.

The heat change of the above-mentioned flue gas heater 82 can be realized by the third circulating pump 83 by adjusting the flow change of the circulating medium.

Since the temperature of the flue gas in the flue gas channel of the boiler decreases step by step, the second heat exchanger and the third heat exchanger connected in series at the rear end of the flue gas channel are respectively connected to the low-pressure condensate heater and the air heater to heat the boiler at a relatively high temperature. Lower low-pressure condensate and air entering the boiler to improve the efficiency of the steam turbine and boiler, and reduce the steam extraction of the steam turbine by the low-pressure condensate heater; at the same time, the third heat exchanger is connected to the air heater to heat the air entering the boiler to avoid Corrosion of the cold end of the air preheater improves the service life of the air preheater; the fourth heat exchanger and flue gas heater are used to heat the temperature of the flue gas entering the chimney, which increases the smoke exhaust height of the chimney, which is beneficial to Environmental protection, while reducing the corrosion of the flue gas on the chimney; connect the first heat exchanger in parallel to the flue gas input and output ends of the air preheater, and connect the high-pressure condensate heater through the flow control valve, the first heat exchanger It is installed in the first section of the flue gas channel of the boiler, and the temperature of the flue gas obtained by it is relatively high, so it can be used to heat the high-pressure condensate water and reduce the steam extraction of the steam turbine by the high-pressure condensate water heater, and the steam turbine steam used by the high-pressure condensate water heater Both are high-quality steam, and reducing the extraction of high-quality steam further improves the efficiency of the steam turbine. This system effectively recycles and utilizes the waste heat of boiler flue gas, improves the working efficiency of boilers and steam turbines, and obtains good economic and social benefits.

Claims (11)

1. A thermal power plant boiler flue gas waste heat recovery and utilization system, comprising a boiler, fan, air preheater, dust collector, induced draft fan, booster fan, desulfurization tower, chimney, steam turbine and a heat recovery system, the heat recovery system It includes a condenser, several series-connected high-pressure condensate heaters and low-pressure condensate heaters, the steam output end of the boiler is connected to the steam input end of the steam turbine, and the condensate output end of the steam turbine is connected to the input end of the recuperation system. The output end of the heat recovery system is connected to the condensate input end of the boiler, the output end of the fan, the air input end and the output end of the air preheater are sequentially connected in series and then connected to the air input end of the boiler, the air preheater, The flue gas input and output ends of the dust collector, the induced draft fan, the booster fan and the desulfurization tower are connected in series in sequence and respectively connected to the boiler flue gas output end and the chimney flue gas input end. It is characterized in that: it also includes a first heat exchanger, a second heat exchanger A flow control valve and a second flow control valve, the flue gas input end of the first heat exchanger is connected to the flue gas input end of the air preheater, and the flue gas output end of the first heat exchanger is connected to the The flue gas output end of the air preheater, the heat exchange medium input and output ends of the first heat exchanger are respectively connected to any one of the high-pressure condensate heating through the first flow control valve and the second flow control valve The input and output terminals of the device. 2. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 1, characterized in that: the system also includes a feed water heat exchanger and a first circulation pump, the heat exchange medium input of the first heat exchanger, The output end is connected to the input and output ends of the heat exchange medium of the feed water heat exchanger through the first circulation pump, and the feed water input and output ends of the feed water heat exchanger pass through the first flow control valve and the second flow rate respectively. The control valve is connected to the input and output ends of any one of the high-pressure condensate heaters. 3. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 1, characterized in that: the system also includes a second heat exchanger, a third flow control valve and a fourth flow control valve, the second heat exchanger The flue gas input and output ends of the heat exchanger are connected in series between the output end of the induced draft fan and the input end of the booster fan, and the heat exchange medium input end of the second heat exchanger is connected to the The input end of any low-pressure condensate heater, the output end of the heat exchange medium of the second heat exchanger is connected to the output end of any low-pressure condensate heater through the fourth flow control valve. 4. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 1, characterized in that: the system also includes a third heat exchanger, an air heater and a second circulation pump, the third heat exchanger The flue gas input and output ends are connected in series between the booster fan output end and the desulfurization tower input end, and the air input and output ends of the air heater are connected in series between the fan output end and the air input end of the air preheater Between, the heat exchange medium output end of the third heat exchanger is connected to the heat exchange medium input end of the air heater through the second circulation pump, and the heat exchange medium output end of the air heater is connected to the The heat exchange medium input end of the third heat exchanger. 5. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 4, characterized in that: the system also includes a fourth heat exchanger, a flue gas heater and a third circulating pump, and the fourth heat exchanger The flue gas input and output end of the flue gas heater is connected in series between the flue gas output end of the third heat exchanger and the flue gas input end of the desulfurization tower, and the flue gas input and output end of the flue gas heater is connected in series with the desulfurization tower. Between the flue gas output end of the tower and the flue gas input end of the chimney, the heat exchange medium output end of the fourth heat exchanger is connected to the heat exchange medium input end of the flue gas heater through the third circulation pump, and the The heat exchange medium output end of the flue gas heater is connected to the heat exchange medium input end of the fourth heat exchanger. 6. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 3, characterized in that: flue gas bypasses are respectively provided between the flue gas input and output ends of the second heat exchanger through three air valves , two of the three air valves are respectively arranged at the flue gas input end and the output end of the second heat exchanger, and one of the three air valves is arranged on the above-mentioned flue gas bypass. 7. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 4, characterized in that: a cold air bypass is provided between the air input and output ends of the air heater through three air valves, and the three Two of the air valves are respectively arranged at the air input end and the output end of the air heater, one of the three air valves is arranged on the cold air bypass, and the first heat exchanger and the third heat exchanger A flue gas bypass is provided between the flue gas input and output terminals respectively through three air valves, and two of the three air valves are respectively set at the flue gas of the first heat exchanger and the third heat exchanger. The gas input end and the output end, and one of the three air valves is respectively set on each of the above-mentioned flue gas bypasses. 8. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 5, characterized in that: the fourth heat exchanger and the flue gas input and output ends of the flue gas heater are respectively provided with three air valves. There is a flue gas bypass, and two of the three air valves are respectively set at the flue gas input and output ends of the fourth heat exchanger and the flue gas heater, and one of the three air valves is The valves are respectively arranged on the above-mentioned flue gas bypasses. 9. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 1, characterized in that: the flue gas input and output ends of the first heat exchanger are connected in series in the flue of the boiler and the air preheater . 10. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 3, characterized in that: the flue gas input and output ends of the second heat exchanger are connected to the flue gas output ends of the air preheater and input to the dust collector. 11. The thermal power plant boiler flue gas waste heat recovery and utilization system according to claim 5, characterized in that: the flue gas input and output ends of the fourth heat exchanger are connected to the flue gas output ends of the second heat exchanger and The flue gas input end of the booster fan.

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