CN102553425A - Wet flue gas denitrifying system for coal fired power plant boiler - Google Patents

Abstract

The invention discloses a wet flue gas desulfurization system for a coal-fired power plant boiler, which includes an inlet flue, an outlet flue, an _SO2 absorption tower and a chimney, and the inlet flue communicates with the lower part of the _SO2 absorption tower , one end of the outlet flue communicates with the upper part of the _SO2 absorption tower, and the other end communicates with the chimney. The desulfurization system also includes a mortar pool, which is made of fly ash after the combustion of low-sulfur coal. fly ash slurry, the top of the _SO2 absorption tower is provided with at least one layer of shotcrete layer pipelines for conveying fly ash slurry, and a plurality of spiral nozzles are installed on the shotcrete layer pipeline, and the fly ash slurry is pumped through the pump After entering the spray layer pipeline, it is sprayed from the spiral nozzle in the form of mist, and the _SO2 gas in the boiler flue gas is removed by absorption. The desulfurization system uses fly ash after low-sulfur coal combustion to make slurry as a desulfurization absorbent. The equipment is simple and reliable, and can greatly reduce the investment and operation costs of the desulfurization system.

Description

A wet flue gas desulfurization system for coal-fired power plant boilers

technical field

The invention relates to the field of flue gas desulfurization and purification of coal-fired power plant boilers, in particular to a wet flue gas desulfurization system for coal-fired power plant boilers.

Background technique

China is a country where coal is the main energy source. The main fuel of coal-fired power stations is raw coal. The SO ₂ emitted by coal-fired air pollution is very serious and has become an important factor restricting the sustainable development of China's national economy. Therefore, Desulfurization of flue gas from coal-fired power plant boilers to control _SO2 pollution has become the most urgent task in the field of air pollution control in China.

The characteristic of wet flue gas desulfurization technology is that the entire desulfurization system is located at the back end of the flue. After the dust collector, the desulfurization process is carried out in the absorbent solution. Both the desulfurization agent and the desulfurization products are in a wet state. Therefore, wet flue gas desulfurization The process is a gas-liquid reaction, the desulfurization reaction speed is fast, and the desulfurization efficiency is high, which is suitable for flue gas desulfurization of coal-fired power plant boilers.

At present, the wet flue gas desulfurization technologies that have been developed in the world mainly include limestone washing method, double alkali method, Wellman-Lord method, magnesium oxide method and ammonia method, etc. Wet method desulfurization accounts for the total number of installed flue gas desulfurization units in the world. Different wet flue gas desulfurization technologies have their own advantages and disadvantages. At the same time, the wet desulfurization technologies used in domestic thermal power plants still have scaling, corrosion, huge investment, large power consumption, and poor operation. high cost issues. my country has a vast territory, and the sulfur content of coal-fired coal varies greatly. Therefore, there is no wet flue gas desulfurization technology that can be generally applied to the flue gas desulfurization of coal-fired power plant boilers in my country. Therefore, it is urgent to develop a technology suitable for my country's coal quality conditions. Wet desulfurization technology and process.

Fly ash is a solid combustion product discharged after the combustion of pulverized coal boilers. Its surface is loose and porous, with a large surface area and certain active groups. In addition, fly ash is mainly composed of silicon dioxide SiO ₂ , aluminum oxide Al ₂ O ₃ , ferric oxide Fe ₂ O ₃ and calcium oxide CaO. In addition, there are a small amount of magnesium, titanium, Oxides and rare oxides of potassium, sodium, phosphorus, etc. Among them, the mass percentages of the main components in each group are SiO ₂ : 40%-58%; Al ₂ O ₃ : 12%-29%; Fe ₂ O ₃ : 4%-18%; CaO: 4%- 7%; C: 1%-10%, because fly ash contains a large amount of porous amorphous SiO ₂ and Al ₂ O ₃ , which can adsorb acid gas SO ₂ , and the adsorption function includes physical adsorption and chemical adsorption. The chemical adsorption capacity of fly ash mainly depends on the Si-O and Al-O active groups in fly ash, which can combine with the chemical chain or ion of the adsorbate to generate adsorption.

The reserves of low-sulfur raw coal in northern China are relatively large, and the fly ash produced after burning low-sulfur coal has the characteristics of ^high alkalinity. The content of alkaline substances such as ²⁺ is high, the pH value is high, and it has a strong absorption capacity for _SO2 in the flue gas. For power plant boilers burning low-sulfur raw coal, due to the low _SO2 content in the flue gas, using low-sulfur coal fly ash slurry as an absorbent for desulfurization can meet environmental protection requirements, and will greatly reduce wet flue gas. The investment and operation cost of gas desulfurization system.

Contents of the invention

The purpose of the present invention is to provide a wet flue gas desulfurization system for coal-fired power plant boilers. The desulfurization system uses fly ash after low-sulfur coal combustion to make slurry as a desulfurization absorbent. The equipment is simple and reliable and can greatly reduce Investment and operating costs of the desulfurization system.

The purpose of the present invention is achieved by the following technical solutions: a wet flue gas desulfurization system for coal-fired power plant boilers, including inlet flue, outlet flue, _SO Absorption tower and chimney, the inlet flue It communicates with the bottom of the _SO2 absorption tower, one end of the outlet flue communicates with the top of the _SO2 absorption tower, and the other end communicates with the chimney. It is characterized in that: the desulfurization system also includes a mortar pool, and the mortar Fly ash slurry made from fly ash after combustion of low-sulfur coal is filled in the pool, and the upper part of the _SO2 absorption tower is provided with at least one layer of spraying layer pipelines for transporting the fly ash slurry, and the pipeline is provided with a mortar pump. One end of the mortar pipeline is connected to the shotcrete layer pipeline, and the other end is connected to the mortar pool. Multiple spiral nozzles are installed on the shotcrete layer pipeline. It is ejected and contacts with the boiler flue gas flowing upwards into the _SO2 absorption tower in a countercurrent manner to remove _SO2 gas in the boiler flue gas by absorption, and the desulfurized boiler flue gas enters the chimney through the outlet flue back out.

The desulfurization system of the present invention adds a mortar tank, and the fly ash slurry made of fly ash after low-sulfur coal combustion is filled in the mortar tank, and the slurry is made of fly ash after low-sulfur coal combustion as a desulfurization absorbent for boiler flue gas. It can greatly reduce the investment and operation cost of the desulfurization system.

In the present invention, the shotcrete layer pipelines are three-layered, and the three-layer shotcrete layer pipelines are arranged at equal intervals up and down in a parallel manner, and the three-layer shotcrete layer pipelines are all connected to the mortar pipelines.

The present invention can be improved as follows: the _SO2 absorption tower is also provided with at least one layer of mist eliminator on the upper part of the shotcrete layer pipeline to remove the slurry droplets carried in the boiler flue gas. The demister is two layers, arranged up and down.

The present invention can also be improved as follows: the desulfurization system is also provided with a cleaning water pipeline between the two layers of demisters, and the cleaning water pipeline is provided with a plurality of cleaning nozzles to flush the demisters regularly to prevent The demister is fouled and clogged.

In the present invention, the mortar tank is also connected to the boiler sewage pipeline and the process water pipeline respectively, and the boiler sewage and process water are sent to the mortar tank to replenish water after passing through the boiler sewage pipeline and the process water pipeline respectively.

The present invention can also be further improved as follows: the desulfurization system also includes a sedimentation tank, the sedimentation tank is arranged at the bottom of the _SO2 absorption tower, is integrated with the _SO2 absorption tower, and communicates with the _SO2 absorption tower, the The sedimentation tank and the mortar tank are connected through a sedimentation wastewater pipeline, and a water pump is arranged on the sedimentation wastewater pipeline, and the wastewater precipitated after sedimentation in the sedimentation tank is sent into the mortar tank for reuse through the water pump.

The sedimentation tank is also connected with a sedimentation ash delivery pipeline, and the sedimentation ash delivery pipeline is provided with an ash pump, and the fly ash slurry that has completed the desulfurization process flows into the sedimentation tank for precipitation, and the sedimentation ash generated after precipitation is pumped by the ash delivery pump. It is output through the sediment ash conveying pipeline.

In the present invention, both the inlet flue and the outlet flue are provided with flue baffles.

In the present invention, a stirrer is arranged in the mortar pool to stir the fly ash slurry evenly.

Compared with prior art, the present invention has following remarkable effect:

(1) The desulfurization system of the present invention uses fly ash after low-sulfur coal combustion to make slurry as a desulfurization absorbent for boiler flue gas. Because fly ash is cheap and easy to obtain, the cost of wet flue gas desulfurization system will be greatly reduced. Operating costs.

(2) The fly ash in the desulfurization system of the present invention can be discarded in use, that is, the fly ash slurry completes desulfurization, and after precipitation, the precipitated ash can be sent to the ash yard through the ash transport pump, and the precipitated waste water is then The water pump is sent to the mortar pool through the sedimentation wastewater pipeline, and will participate in the preparation of fly ash slurry again to realize waste utilization.

(3) The desulfurization system of the present invention uses the desulfurization absorbent made of fly ash after burning low-sulfur coal, which can solve the ubiquitous fouling problem in wet desulfurization systems. For systems that use limestone or lime alone as a desulfurizer, limestone, slaked lime (calcium hydroxide) and desulfurization products calcium sulfite and calcium sulfate have low solubility in water, so they are easy to precipitate or crystallize on the wall or pool to generate scaling. At the same time, the pH value of the desulfurizing agent slurry in the system using limestone alone as the desulfurizing agent is 5-6 during operation, which is easy to corrode the metal wall. The desulfurization absorbent made of fly ash after burning low-sulfur coal has a pH value of the desulfurizer slurry greater than 7 during operation, which will greatly reduce the corrosion problem. Self-produced, so the discarding method can be used. The desulfurization product is mixed in the fly ash slurry, and after precipitation, the desulfurization product mixed in the precipitated ash can be sent to the ash yard through the ash conveying pump, and the precipitated wastewater is pumped through the sedimentation wastewater. The pipes are sent into the mortar tank, which will re-participate in the preparation of fly ash slurry, so there will be no scaling problem on the wall or in the tank.

(4) The desulfurization system of the present invention is in the SO2 absorption tower, and the fly ash slurry and the boiler flue gas are in gas-liquid contact in a countercurrent manner, so as to ensure the full contact of the _SO2 gas in the fly ash slurry and the boiler smoke, with the best absorption effect.

(5) The mortar pool in the desulfurization system of the present invention is also connected with the boiler sewage pipeline and the process water pipeline respectively, and the boiler sewage and process water are sent into the mortar pool through the pipeline, and the waste water is also utilized while replenishing water to the mortar pool.

(6) The equipment of the desulfurization system of the present invention is simple and reliable, and the operating cost and operating cost of the equipment are relatively low.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Figure 1 is a schematic diagram of the overall structure of the desulfurization system of the present invention.

In the figure: 1. Inlet flue; 2. Bypass flue baffle; 3. SO ₂ absorption tower; 4. Inlet flue baffle; 5. Spiral nozzle; 6. Demister; 7. Ash pump; 8. Sedimentation ash pipeline; 9. Sedimentation tank; 10. Mortar tank; 11. Sedimentation wastewater pipeline; 12. Water pump; 13. Agitator; 14. Fly ash pipeline; 15. Boiler sewage pipeline; 16. Process water Pipeline; 17. Mortar pipeline; 18. Mortar pump; 19. Shotcrete layer pipeline; 20. Cleaning water pipeline; 21. Cleaning nozzle; 22. Exit flue; 23. Exit flue baffle; 24. Bypass flue 25. chimney

Detailed ways

As shown in Figure 1, a wet flue gas desulfurization system for coal-fired power plant boilers, the desulfurization system includes an inlet flue 1, a bypass flue baffle 2, an _SO2 absorption tower 3, and an inlet flue baffle 4. Spiral nozzle 5, demister 6, ash delivery pump 7, sedimentation ash delivery pipeline 8, sedimentation tank 9, mortar tank 10, sedimentation wastewater pipeline 11, water pump 12, agitator 13, fly ash pipeline 14, boiler exhaust Sewage pipeline 15, process water pipeline 16, mortar pipeline 17, mortar pump 18, shotcrete layer pipeline 19, cleaning water pipeline 20, cleaning nozzle 21, outlet flue 22, outlet flue baffle 23, bypass flue 24, Chimney 25. Sedimentation pond 9 of the present invention is arranged on _SO2 the bottom of absorption tower 3, is connected with _SO2 absorption tower 3, and is connected with _SO2 absorption tower 3, and sedimentation pond 9 is communicated with mortar pond 10 by sedimentation waste water pipeline 11, The sedimentation waste water pipeline 11 is provided with a water pump 12, and the separated waste water after the sedimentation tank 9 settles is sent to the mortar tank 10 for reuse through the water pump 12. The sedimentation tank 9 is also connected with a sedimentation ash delivery pipeline 8, and the sedimentation ash delivery pipeline 8 is provided with an ash delivery pump 7, and the fly ash slurry that has completed the desulfurization process flows into the sedimentation tank 9 for sedimentation, and the sedimentation ash generated after precipitation passes through the ash delivery After the pump 7 is pumped, it is output through the precipitated ash delivery pipeline 8 .

The inlet flue 1 of the present invention is provided with the inlet flue baffle 4, and the outlet flue 22 is provided with the outlet flue baffle 23, and the inlet flue 1 is connected with the bottom of the _SO absorption tower 3, and the outlet flue of the boiler One end of the road 22 is connected with the top of the _SO absorption tower 3, and the other end is connected with the chimney 25 through the outlet flue baffle plate 23, and the two sides of the bypass flue 24 with the bypass flue baffle plate 2 are installed. The ends communicate with the inlet flue 1 and the outlet flue 22 respectively.

The fly ash slurry that the fly ash after the fly ash after adornment low-sulfur coal combustion of the present invention is filled in the mortar pool 10 of the present invention is provided with agitator 13 in the mortar pool 10, so that the fly ash slurry is stirred evenly, SO The absorption tower ₃ The upper part is provided with a three-layer shotcrete layer pipeline 19 for transporting fly ash slurry, and one end of the mortar pipeline 17 with a mortar pump 18 communicates with the shotcrete layer pipeline 19, and the other end communicates with the mortar pool 10, and the shotcrete layer pipeline 19 A plurality of spiral nozzles 5 are installed on it, and the fly ash slurry is pumped into the shotcrete layer pipeline 19 by pump pressure, and then sprayed out from the spiral nozzles 5 in a mist form, together with the upwardly flowing boiler flue gas entering the _SO2 absorption tower 3 Countercurrent gas-liquid contact removes SO ₂ gas in the boiler flue gas by absorption, and the desulfurized boiler flue gas enters the chimney 25 through the outlet flue 22 and is discharged.

The three-layer shotcrete layer pipes 19 in the present invention are arranged at equal intervals up and down in a parallel manner, and the three-layer shotcrete layer pipes 19 are all communicated with the mortar pipes 17 .

SO among the present invention Absorption _tower 3 is also provided with two-layer mist eliminator 6 at the upper part of spraying layer pipeline 19, and two-layer mist eliminator 6 is arranged up and down, and mist eliminator 6 is set to remove carried in the boiler flue gas Serum droplets. A cleaning water pipeline 20 is also arranged between the two layers of demisters 6 , and a plurality of cleaning nozzles 21 are arranged on the cleaning water pipeline 20 to regularly flush the demisters 6 to prevent fouling of the demisters 6 from clogging.

The mortar tank 10 of the present invention is also communicated with the boiler sewage pipeline 23 and the process water pipeline 24 respectively, and the boiler sewage and process water are sent to the mortar tank 10 to replenish water after passing through the boiler sewage pipeline 23 and the process water pipeline 24 respectively.

When the desulfurization system of the present invention is in operation, the fly ash slurry prepared in the mortar tank 10 passes through the mortar pipeline 17, and is sent into the shotcrete pipeline 19 by the mortar pump 18, and is carried out by the spiral nozzle 5 installed on the shotcrete pipeline 19. After atomization, it is sprayed downwards into the _SO2 absorption tower 3. The flue gas from the boiler enters the _SO2 absorption tower 3 through the inlet flue 1 and the flue gas inlet baffle 4 and flows upward, and is washed by the atomized fly ash slurry droplets flowing downward in a countercurrent manner , the gas and the slurry are fully contacted, and the SO ₂ gas is removed by absorption. The flue gas that has been removed from the fly ash slurry flows through the two _- layer mist eliminator 6 located on the upper part of the grouting pipe 19, where the slurry droplets carried in the flue gas are removed, and then the flue gas passes through the outlet flue gas. Road 22 and outlet flue baffle plate 23 are sent into the atmosphere through the anti-corrosion treated chimney 25. In order to prevent fouling and clogging of the demister 6 , the process water fed through the cleaning water pipeline 20 regularly flushes the demister through the cleaning nozzle 21 .

In the _SO2 absorption tower 3, the fly ash slurry that has completed the desulfurization process directly flows into the sedimentation tank 9 located at the lower part of the _SO2 absorption tower 3, and through the sedimentation process, the precipitated ash is sent to the ash by the ash delivery pump 7 through the precipitated ash delivery pipeline 8. field. The wastewater precipitated by the sedimentation process is sent to the mortar tank 10 through the sedimentation wastewater pipeline 11 by the water pump 12 to participate in the preparation of the fly ash slurry again to realize waste utilization.

Since the inlet flue gas temperature is usually above 110°C, part of the moisture in the fly ash slurry in the _SO2 absorption tower 3 will evaporate, and the boiler blowdown water and process water are sent through the blowdown pipe 23 and the process water pipe 24 respectively. into the mortar pool 10 for compensation, while replenishing water to the mortar pool, waste water utilization is also realized.

Claims (10)

1. a wet method fume desulfurizing system that is used for coal-fired power station boiler comprises inlet flue duct (1), exhaust pass (22), SO ₂Absorption tower (3) and chimney (25), said inlet flue duct (1) and SO ₂The bottom on absorption tower (3) is connected, an end and the SO of said exhaust pass (22) ₂The top on absorption tower (3) is connected, and the other end is connected with chimney (25), it is characterized in that: said desulphurization system also comprises mortar pool (10), the pulverized fuel ash slurry that the flyash after the interior splendid attire low-sulfur coal burning of said mortar pool (10) is processed, said SO ₂The top on absorption tower (3) is provided with the gunite layer pipeline (19) of one deck conveying pulverized fuel ash slurry at least; The end that pipeline is provided with the dust piping (17) of slurry pump (18) is communicated with gunite layer pipeline (19); The other end is communicated with mortar pool (10); A plurality of spiral nozzles (5) are installed on the gunite layer pipeline (19), pulverized fuel ash slurry after pump pressure pumps into gunite layer pipeline (19) from spiral nozzle (5) with vaporific ejection, and get into SO ₂The boiler smoke that upwards flows in the absorption tower (3) is removed the SO in the boiler smoke with the contact of reflux type gas-liquid with the mode that absorbs ₂Gas, the boiler smoke after the desulfurization is discharged after exhaust pass (22) gets into chimney (25).

2. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 1; It is characterized in that: described gunite layer pipeline (19) is three layers; Three layers of gunite layer pipeline (19) are with spaced set about the parallel way, and three layers of gunite layer pipeline (19) all are communicated with described dust piping (17).

3. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 1 is characterized in that: said SO ₂Absorption tower (3) also is provided with one deck demister (6) at least being positioned at gunite layer pipeline (19) top, to remove slurries droplet entrained in the boiler smoke.

4. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 3 is characterized in that: described demister (6) is provided with up and down for two-layer.

5. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 4; It is characterized in that: said desulphurization system also is provided with rinse water pipeline (20) between two-layer demister (6); Said rinse water pipeline (20) is provided with a plurality of washer jets (21); Regularly demister (6) is washed, stop up to prevent demister (6) fouling.

6. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 1; It is characterized in that: said mortar pool (10) also is communicated with boiler blow-off waterpipe (23) and fresh water (FW) pipeline (24) respectively, and boiler blowdown water and fresh water (FW) are sent into moisturizing in the mortar pool (10) after passing through boiler blow-off waterpipe (23) and fresh water (FW) pipeline (24) respectively.

7. according to each described wet method fume desulfurizing system that is used for coal-fired power station boiler of claim 1 to 6, it is characterized in that: said desulphurization system also comprises sedimentation basin (9), and said sedimentation basin (9) is arranged on SO ₂The bottom on absorption tower (3) is with SO ₂Absorption tower (3) fuses, and and SO ₂Absorption tower (3) is connected; Said sedimentation basin (9) is communicated with through deposition waste pipe (11) with mortar pool (10); Deposition waste pipe (11) is provided with water pump (12), and the waste water that sedimentation basin (9) post precipitation is separated out is sent in the mortar pool (10) through water pump (12) and utilized again.

8. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 7; It is characterized in that: said sedimentation basin (9) also is connected with deposition grey conveyance conduit (8); Precipitate grey conveyance conduit (8) and be provided with defeated grey pump (7); The pulverized fuel ash slurry of accomplishing sulfur removal technology flows into deposition in the sedimentation basin (9), the deposition ash that generates through post precipitation through defeated grey pump (7) pump pressure after precipitate grey conveyance conduit (8) and export.

9. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 1 is characterized in that: said inlet flue duct (1), exhaust pass are provided with damper on (22).

10. the wet method fume desulfurizing system that is used for coal-fired power station boiler according to claim 1 is characterized in that: be provided with agitator (13) in the said mortar pool (10), so that pulverized fuel ash slurry is stirred.

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