CN109945677A - A high-efficiency flue gas waste heat recovery tower with desulfurization function - Google Patents

Abstract

A high-efficiency flue gas waste heat recovery tower with desulfurization function belongs to the technical field of waste heat recovery and utilization of boiler flue gas in thermal power plants. The flue gas from the dust collector is subjected to waste heat recovery and desulfurization treatment. The high-temperature flue gas enters the tower from the bottom of the flue gas waste heat recovery tower, and passes through the packing layer, the circulating water spray layer, the mist eliminator and the mist eliminator from bottom to top. The cleaning system is in direct contact with the spray circulating water for countercurrent heat exchange. In the process, the residual heat of the flue gas, SO ₂ and dust particles in the flue gas are absorbed by the circulating water and enter the bottom of the tower. After being neutralized by NaOH, part of the circulating water continues to participate in the circulation along the circulating pipeline. Gas waste heat is recycled. The flue gas waste heat recovery tower in the present invention adopts the direct contact heat exchange technology between flue gas and water, which improves the heat and mass transfer effect, enhances the heat exchange capacity, and has both desulfurization capability, which can realize the integration of flue gas waste heat recovery and desulfurization It reduces the initial investment of the power plant and realizes further purification of the flue gas.

Description

A high-efficiency flue gas waste heat recovery tower with desulfurization function

technical field

The invention belongs to the technical field of flue gas purification and flue gas waste heat recovery and utilization in coal-fired thermal power plants and coal-fired boiler rooms, and in particular relates to a high-efficiency flue gas waste heat recovery that uses flue gas waste heat for central heating and has desulfurization functions at the same time tower.

Background technique

The design value of the exhaust gas temperature of the coal-fired boiler in the thermal power plant is usually set at 120~140℃, and the heat it carries accounts for about 3%~8% of the input heat of the boiler. This part of the heat is often wasted in vain, which is the main reason for the low thermal efficiency of the boiler. one. The pollution caused by the emission of coal-fired boilers is also one of the reasons for the frequent occurrence of smog in the heating season. Therefore, it is necessary to specially develop flue gas waste heat recovery and flue gas purification technologies for coal-fired boilers.

At present, the recovery and utilization of waste heat from flue gas is mainly aimed at sensible heat recovery of high-temperature flue gas. However, sensible heat recovery only accounts for a small part of total heat recovery. Low-temperature flue gas contains a large amount of latent heat of condensation, and the potential for waste heat recovery is huge. If a flue gas waste heat recovery device with an indirect contact heat exchanger as the main body is used to recover low-temperature flue gas waste heat, there are problems such as large required heat exchange area and low-temperature corrosion, and the economy is poor. The flue gas waste heat recovery tower with direct contact heat exchanger as the main body sprays and condenses the low-temperature flue gas, so that the flue gas and low-temperature water are in direct contact for heat exchange, which can increase the heat transfer area and improve the heat transfer efficiency at the same time. Play the effect of flue gas purification. On the other hand, the wet desulfurization process commonly used in thermal power plants adopts the form of countercurrent spraying of desulfurization slurry and flue gas. After the high-temperature flue gas passes through the spray system of the desulfurization tower, the temperature decreases, and part of the sensible heat has been dissipated with the desulfurization process. Environment. If the waste heat recovery device and the desulfurization system are set up independently, not only the waste heat recovery effect is not good, but also the power plant investment is increased, and the waste heat in the low-temperature and high-humidity flue gas from the desulfurization tower is directly recovered, which is technically difficult.

In view of the above problems, designing a high-efficiency flue gas waste heat recovery tower with both desulfurization functions and combining the desulfurization system with the flue gas waste heat recovery system is an effective means to achieve energy conservation and emission reduction in thermal power plants.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a high-efficiency flue gas waste heat recovery tower with desulfurization function for coal-fired boilers, in order to solve the problems of low waste heat recovery efficiency and poor economy of flue gas recovery and utilization systems in the prior art. At the same time, the waste heat recovery tower in the present invention has both desulfurization capability, which can meet the desulfurization requirements of thermal power plants, and can also be used to further reduce pollutant emissions and improve the environmental benefits of power plants. In order to achieve the above-mentioned goals, the technical scheme of the present invention:

A high-efficiency flue gas waste heat recovery tower with desulfurization function, including a mist eliminator 2, a mist eliminator cleaning system 3, a circulating water spray layer 4, a packing layer 5, a desulfurizing agent inlet 6, a waste heat circulating water pump 7, and desulfurizing agent conveying Pump 8, condensate collection system 9, flue gas inlet valve 10, flue gas bypass pipeline valve 11, check valve 12, supporting flue, pipeline and various valves;

The interior of the high-efficiency flue gas waste heat recovery tower is sequentially provided with a packing layer 5, a circulating water spray layer 4, a demister cleaning system 3 and a demister 2 from bottom to top;

The high-temperature flue gas generated by the boiler room enters the flue gas waste heat recovery tower 1 along the pipeline through the flue gas inlet valve 10 after being dedusted and filtered. The spray device sprays from top to bottom, and the high-temperature flue gas passes through the packing layer 5 and the spray water is fully contacted with the gas-liquid two-phase to achieve the effect of heat and mass transfer, so that the system exhaust gas is cooled to below the dew point temperature, and the water in the flue gas The steam condenses and releases heat, and the low-humidity flue gas after heat exchange is removed by the mist eliminator 2 to remove the water mist. The clean dry flue gas is discharged from the flue gas outlet section at the top of the high-efficiency flue gas waste heat recovery tower and enters the chimney, where the waste heat of the flue gas is absorbed by the circulating water. ;

The mist eliminators 2 are arranged in parallel with wave-shaped plates, and parallel airflow passages of flue gas can be formed between adjacent wave-shaped plates. be separated;

The mist eliminator 2 is equipped with a mist eliminator cleaning system 3, which is washed with a layer of process water, and the process water enters the mist eliminator 2 through valve control;

The circulating water spray layer 4 is mainly composed of a spray main pipe 101, a plurality of branch pipes, a nozzle connecting pipe 108, a nozzle 105 and a support seat 106. The circulating water spray layer 4 is fixed on the tower body 107 of the desulfurization tower through the support seat 106. On the upper side, a plurality of annular branch pipes are fixedly installed on the support base 106, and the spray main pipe 101 is communicated with each branch pipe; the nozzles 105 are evenly arranged on the branch pipes through the nozzle connecting pipe 108 to ensure that the nozzle has no spray on the entire cross-sectional area. Blind shower area; the circulating water after the heat exchange and cooling from the heat exchanger enters the spray main pipe 101 through the external circulation pipe section 100, and flows through the nozzles 105 on each branch pipe to achieve uniform spraying and exchange heat with the flue gas;

The nozzle 105 is made of silicon carbide.

The filler layer 5 is filled with plastic porous balls, which provides sufficient contact surface for the gas and liquid phases, and improves the heat and mass transfer effect between the flue gas and the spray circulating water;

The desulfurizing agent solution is fed into the high-efficiency flue gas waste heat recovery tower from the desulfurizing agent inlet 6 at the bottom of the high-efficiency flue gas waste heat recovery tower through the valve and the check valve 12 along the pipeline through the desulfurizing agent delivery pump 8, and the heat and mass exchange with the spray circulating water is completed. , the SO gas in the _flue gas will be dissolved in the circulating water, the water vapor in the flue gas will exothermic and condense at the same time, and the condensed water will react with the desulfurizer at the bottom of the high-efficiency flue gas waste heat recovery tower to achieve partial desulfurization. The remaining fine particles in the flue gas will also stay in the high-efficiency flue gas waste heat recovery tower under the flushing of the water flow to further purify the flue gas;

Part of the treated condensed water at the bottom of the high-efficiency flue gas waste heat recovery tower will continue to participate in the circulation as circulating water, and the rest will eventually enter the condensate collection system 9 from the bottom of the high-efficiency flue gas waste heat recovery tower through valve control, and the recovered condensed water will be used as water in the plant , so as to achieve the purpose of water saving;

The high-temperature circulating water after heat exchange with flue gas and water treatment is sent from the bottom of the high-efficiency flue gas waste heat recovery tower by the waste heat circulating pump through the valve, the waste heat circulating pump 7 and the valve in turn to the water-water plate heat exchanger and the return water of the heat network. Heat exchange; the low-temperature waste heat circulating water cooled by heat exchange returns to the high-efficiency flue gas waste heat recovery tower along the pipeline to continue spraying heat exchange with the flue gas;

When the high-efficiency flue gas waste heat recovery tower needs to be repaired, close the inlet valve 10 of the flue gas section, and open the flue gas bypass pipeline valve 11 set between the pipeline leading to the chimney and the dust collector. The gas is directly discharged from the chimney;

When the waste heat circulating water pump 7 is overhauled, the high-temperature circulating water from the high-efficiency flue gas waste heat recovery tower directly enters the circulating water spray layer 4 through the valve control, and circulates spray heat exchange;

A valve is installed between the inlet and outlet pipes of the heat exchanger. When the anti-corrosion and high-efficiency water-to-water plate heat exchanger is repaired, the high-temperature circulating water from the high-efficiency flue gas waste heat recovery tower directly enters the circulating water spray layer through the valve. 4. Circulating spray heat exchange.

Beneficial effects of the present invention: The present invention adopts the direct contact waste heat recovery technology of flue gas and water, and combines high-efficiency water-water plate heat exchangers to realize the recovery and utilization of low-temperature flue gas waste heat. The gas waste heat recovery tower adopts an optimized packing layer, which makes the flue gas flow velocity distribution in the tower more uniform, increases the contact area and contact time of the flue gas waste heat spray water, and improves the transmission of flue gas and water. Heat and mass transfer, enhanced heat transfer capacity. The flue gas waste heat recovery tower in the present invention can also effectively reduce the content of SO ₂ and fine particulate matter in the flue gas, effectively reduce PM2.5 emission, and has a desulfurization function. The technology integrating waste heat recovery and flue gas desulfurization and dust removal saves the initial investment of the power plant. In the heating season, the waste heat of flue gas can be used to heat the return water of the heating network through the water-water plate heat exchanger, which enhances the heating capacity of the thermal power plant, improves the energy utilization efficiency, reduces the environmental impact of the thermal power plant, and has both economic benefits. and environmental benefits.

Description of drawings

Fig. 1 is the schematic diagram of the high-efficiency flue gas waste heat recovery tower with desulfurization function of the present invention.

Figure 2 is a schematic diagram of the arrangement of spray layer nozzles in the flue gas waste heat recovery tower.

In the figure: 1 flue gas waste heat recovery tower; 2 demister; 3 demister cleaning system; 4 circulating water spray layer; 5 packing layer; 6 desulfurizer inlet; 7 waste heat circulating water pump; 8 desulfurizer delivery pump; 9 Condensate collection system; 10 flue gas inlet section valve; 11 flue gas bypass pipe valve; 12 check valve; 13-20 valve; 100 external circulation pipe section; 101 spray main pipe; 102 outer annular branch pipe; 103 middle annular branch Pipe; 104 inner annular branch pipe; 105 nozzle; 106 support seat; 107 desulfurization tower body.

Detailed ways

The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

As shown in Figure 1, the high-temperature flue gas generated by the boiler room enters the flue gas waste heat recovery tower 1 through the flue gas inlet valve 10 along the pipeline after being dedusted and filtered. The flue gas flows from bottom to top, and the circulating water is sprayed by the circulating water. The spray device in the spray layer 4 sprays from top to bottom, and the flue gas is fully contacted with the spray water through the packing layer 5 in gas-liquid two-phase to achieve the effect of heat and mass transfer, so that the system exhaust gas is cooled to below the dew point temperature, and the smoke The water vapor in the gas condenses and releases heat, and the low-humidity flue gas after heat exchange is removed by the demister cleaning system 3 and demister 2 to remove the water mist, and the clean dry flue gas is discharged from the top of the waste heat recovery tower and enters the chimney. Absorbed by spray circulating water;

The prepared desulfurizer solution is sent to the flue gas waste heat recovery tower 1 from the desulfurizer inlet 6 by the desulfurizer delivery pump 8 along the pipeline through the valve 19 and the check valve 12 . After completing the heat and mass exchange with the spray circulating water, the S0 gas in the _flue gas will be dissolved in the circulating water, the water vapor in the flue gas will be exothermic and condensed at the same time, and the condensed water will react with the desulfurizer at the bottom of the waste heat recovery tower to achieve partial For the purpose of desulfurization, the remaining fine particles in the flue gas will also stay in the recovery tower under the flushing of water flow, further purifying the flue gas;

During the heating period, when the return water temperature T _h of the heat network is low and the outlet water temperature T _tc of the recovery tower is high, and T _tc >T _h , when the temperature difference between the two meets the minimum temperature difference required by the heat exchanger, the temperature is T The return water of the heat network of _h enters the subsequent anti-corrosion and high-efficiency water-water plate heat exchanger, and exchanges heat with the high-temperature circulating water from the flue gas waste heat recovery tower 1, absorbs the flue gas waste heat, and the temperature rises ΔT ₁ . (T _h +ΔT ₁ )≥T _g , then the heat of the heating system is completely supplied by the waste heat of flue gas; if (T _h +ΔT ₁ )<T _g at this time, the return water of the heating network passes through the anti-corrosion and high-efficiency water—water After the plate heat exchanger is heated, it enters the heating network heater and is further heated until it reaches the water supply temperature T _g that meets the operating requirements and then sends it to the heating network, but the heating amount only needs to meet the temperature rise T _g -(T _h +ΔT ₁ ), namely Yes, so it can greatly reduce the steam extraction of the heating network heater;

Figure 2 shows the layout of spray layer nozzles in the flue gas waste heat recovery tower. In the figure: external circulation pipe section 100, main pipe 101, outer annular branch pipe 102, middle annular branch pipe 103, inner annular branch pipe 104, nozzle 105 , the support base 106 and the tower body 107 of the desulfurization tower;

The spray circulating water is sent into the main pipe 101 from the external circulation pipe section 100, and is sent to the nozzle 105 by the nozzle connecting pipe 108 through each annular branch pipe connected to the main pipe 101 in turn, the outer annular branch pipe 102, the middle annular branch The pipes 103 and the inner annular branch pipes 104 are arranged at equal intervals along the inner diameter of the cross section of the tower body, so that the nozzles 105 can be evenly distributed on the entire cross section of the tower body 107 of the desulfurization tower, so that the spray water and the flue gas can be fully contacted, and there is no spray blind area. , improve heat exchange and desulfurization efficiency. The nozzle connecting pipe 103 extends vertically downward from the branch pipe. The support base 106 is disposed under the spray pipeline, which can improve the stability of the spray device.

The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, some improvements can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims (10)

1. a high-efficiency flue gas waste heat recovery tower with desulfurization function, is characterized in that, described high-efficiency flue gas waste heat recovery tower comprises mist eliminator (2), mist eliminator cleaning system (3), circulating water spray layer (4), packing layer (5), desulfurizer inlet (6), waste heat circulating water pump (7), desulfurizer delivery pump (8), condensate collection system (9), flue gas inlet valve (10), smoke Gas bypass pipeline valve (11), check valve (12), supporting flue, pipeline and various valves; A packing layer (5), a circulating water spray layer (4), a mist eliminator cleaning system (3) and a mist eliminator (2) are sequentially arranged inside the high-efficiency flue gas waste heat recovery tower from bottom to top; The high-temperature flue gas generated by the boiler room enters the flue gas waste heat recovery tower 1 through the flue gas inlet valve (10) along the pipeline after being dedusted and filtered. 4) The spray device inside sprays from top to bottom, and the high-temperature flue gas passes through the packing layer (5) and the spray water is fully contacted with the gas-liquid two-phase to achieve the effect of heat and mass transfer, so that the system exhaust gas is cooled to below the dew point temperature , the water vapor in the flue gas condenses and releases heat, the low-humidity flue gas after heat exchange is removed by the mist eliminator (2), and the clean dry flue gas is discharged from the flue gas outlet section at the top of the high-efficiency flue gas waste heat recovery tower and enters the chimney , the waste heat of flue gas is absorbed by circulating water; The mist eliminators (2) are arranged in parallel with wave-shaped plates, and parallel airflow passages of the flue gas can be formed between adjacent wave-shaped plates. separated from above; The mist eliminator (2) is equipped with a mist eliminator cleaning system (3), which is washed with a layer of process water, and the process water enters the mist eliminator (2) through valve control; The circulating water spray layer (4) is mainly composed of a spray main pipe (101), a plurality of branch pipes, a nozzle connecting pipe (108), a nozzle (105) and a support seat (106). ) is fixed on the tower body (107) of the desulfurization tower through the support seat (106), the multiple annular branch pipes are fixedly installed on the support seat (106), and the spray main pipe (101) is communicated with each branch pipe; the nozzle (105) The nozzle connecting pipes (108) are evenly arranged on the branch pipes to ensure that the nozzles have no spray blind area in the entire cross-sectional area; the circulating water after the heat exchange and cooling from the heat exchanger enters the spray through the external circulating pipe section (100). The main pipe (101) flows through the nozzles (105) on each branch pipe to achieve uniform spraying and exchange heat with the flue gas; The desulfurizing agent solution is fed into the high-efficiency flue gas waste heat recovery tower from the desulfurizing agent inlet (6) at the bottom of the high-efficiency flue gas waste heat recovery tower through the valve and the check valve (12) along the pipeline through the desulfurizing agent conveying pump (8), and is circulated with the spray. After the water completes the heat and mass exchange, the SO gas in the _flue gas will be dissolved in the circulating water, and the water vapor in the flue gas will release heat and condense at the same time, and the condensed water will react with the desulfurizer at the bottom of the high-efficiency flue gas waste heat recovery tower to achieve partial For the purpose of desulfurization, the remaining fine particles in the flue gas will also stay in the high-efficiency flue gas waste heat recovery tower under the flushing of water flow to further purify the flue gas; Part of the treated condensed water at the bottom of the high-efficiency flue gas waste heat recovery tower will continue to participate in the circulation as circulating water, and the rest will eventually enter the condensate collection system (9) from the bottom of the high-efficiency flue gas waste heat recovery tower through valve control, and the recovered condensed water will be used as the plant Internal water use, so as to achieve the purpose of water saving; The high-temperature circulating water after heat exchange with flue gas and water treatment is sent from the bottom of the high-efficiency flue gas waste heat recovery tower to the water-water plate heat exchanger and the heat network return pump through the valve, the waste heat circulating pump (7), and the valve in turn. The water is used for heat exchange; the low-temperature waste heat circulating water cooled by the heat exchange is returned to the high-efficiency flue gas waste heat recovery tower along the pipeline to continue spraying heat exchange with the flue gas. 2. the high-efficiency flue gas waste heat recovery tower according to claim 1, is characterized in that, when the high-efficiency flue gas waste heat recovery tower needs to be overhauled, the inlet valve (10) of the flue gas section is closed, and the opening is arranged on the chimney and the dust collector. The flue gas bypass pipe valve (11) between the outgoing pipes, the flue gas coming out of the dust collector is directly discharged from the chimney. 3. The high-efficiency flue gas waste heat recovery tower according to claim 1 and 2, is characterized in that, when the waste heat circulating water pump (7) is overhauled, the high-temperature circulating water that comes out in the high-efficiency flue gas waste heat recovery tower is directly controlled by a valve Entering the circulating water spray layer (4), circulating spray heat exchange. 4. The high-efficiency flue gas waste heat recovery tower according to claim 1 and 2 is characterized in that, a valve is arranged between the inlet and outlet pipelines of the heat exchanger, and when the anti-corrosion and high-efficiency water-water plate heat exchanger is overhauled, The high-temperature circulating water from the high-efficiency flue gas waste heat recovery tower directly enters the circulating water spray layer (4) through the valve, and circulates spray heat exchange. 5. The high-efficiency flue gas waste heat recovery tower according to claim 3 is characterized in that, a valve is arranged between the inlet and outlet pipelines of the heat exchanger, and when the anti-corrosion and high-efficiency water-water plate heat exchanger is repaired, the high-efficiency The high temperature circulating water coming out of the flue gas waste heat recovery tower directly enters the circulating water spray layer (4) through the valve, and circulates spray heat exchange. 6. The high-efficiency flue gas waste heat recovery tower according to claim 1, 2 or 5, wherein the nozzle (105) is made of silicon carbide. 7 . The high-efficiency flue gas waste heat recovery tower according to claim 3 , wherein the nozzle ( 105 ) is made of silicon carbide. 8 . 8. The high-efficiency flue gas waste heat recovery tower according to claim 4, wherein the nozzle (105) is made of silicon carbide. 9. The high-efficiency flue gas waste heat recovery tower according to claim 1, 2, 5, 7 or 8, wherein the packing layer (5) is filled with plastic porous balls to provide sufficient gas and liquid two phases. The contact surface improves the heat and mass transfer effect between the flue gas and the spray circulating water. 10. The high-efficiency flue gas waste heat recovery tower according to claim 6, characterized in that, the packing layer (5) is filled with plastic porous balls to provide sufficient contact surface for gas and liquid two phases, so as to improve flue gas and spray. The heat and mass transfer effect between the shower and circulating water.