CN212204595U - A collaborative denitrification system for partial gasification of pulverized coal - Google Patents

Abstract

The utility model provides a pulverized coal partial gasification synergistic denitrification system, which has the advantages of simple structure, reasonable design, convenient transformation, ultra-low emission of nitrogen oxides from a power station boiler without ammonia injection, and high technical economy. The pulverized coal partial gasification synergistic denitration system includes a coal bunker, a coal mill, a boiler, a cyclone separator, a gasifier and a filter; the coal outlet of the coal bunker is connected to the coal mill inlet, and the coal pulverized coal outlet of the coal mill The inlet of the cyclone separator and the burner nozzle set in the main combustion area of the boiler are respectively connected, and the pulverized coal outlet of the coal mill is connected to the primary air duct; the fine pulverized coal outlet of the cyclone separator is connected to the burner nozzle, and the coarse pulverized coal outlet is connected to the gasification Furnace inlet; the gas outlet of the gasifier is divided into two paths, one is connected to the folded flame area of the boiler through the reburning nozzle, the other is connected to the tail flue after passing through the filter, and the tail flue is connected to the air through the spray gun. The tail flue at the tail of the preheater is provided with a catalyst layer downstream of the spray gun in the tail flue.

Description

A collaborative denitrification system for partial gasification of pulverized coal

technical field

The utility model relates to a flue gas denitration technology in thermal power plants, in particular to a coal powder partial gasification synergistic denitration system.

Background technique

Nitrogen oxide emissions from coal-fired power plants are one of the main causes of environmental problems such as acid rain and photochemical pollution. In recent years, nitrogen oxide emission standards have become more and more stringent, and some require that the nitrogen oxide emission concentration should not exceed 30 mg/m ³ .

The NOx emission reduction technologies commonly used in coal-fired power plants include low NOx combustion technology, non-selective catalytic reduction (SNCR) and selective catalytic reduction (SCR). Both SNCR and SCR technologies use ammonia as a denitration reducing agent. In order to ensure a higher denitration efficiency, a higher ammonia-nitrogen molar ratio is used in actual operation. However, the excessive injection of ammonia has a great impact on the economics of denitrification technology, and the annual consumption of ammonia alone for a 600MW unit has reached several million yuan. In addition, for thermal power units burning high-sulfur coal, the blockage of the air preheater caused by excessive ammonia injection has seriously affected the safety of the unit.

In order to reduce the ammonia consumption of the denitrification system, it is necessary to further explore the denitration potential of the low-nitrogen combustion technology. Low-nitrogen combustion technologies such as air classification and deep air classification are widely used, but further reducing the excess air coefficient in the main combustion area will cause problems such as a decrease in boiler combustion efficiency and high-temperature CO corrosion. In recent years, related technologies have begun to use fuel grading to reduce NOx emissions in the combustion process. For example, a dual-chamber pulverized coal gasification low-nitrogen combustion industrial boiler disclosed in patent CN201610745593 uses pulverized coal gasification and combustion technology to reduce NOx emissions, and uses auxiliary furnaces to reduce NOx emissions. The unburned CO and pulverized coal are burned again, and the double furnace structure is adopted to make the pulverized coal combustion have sufficient gasification space and burnout space. Another example is a low-NOx combustion method and device using pulverized coal pyrolysis gas reburning disclosed in patent CN200910201223. The pulverized coal pyrolysis gas is used as a gas reburning fuel, and is sent to the reburning zone of a pulverized coal boiler to efficiently reduce NOx, and the pulverized coal pyrolysis produces The semi-coke is carried by the primary air and enters the main combustion area of the pulverized coal boiler to complete the combustion. However, all the pyrolysis or gasification of pulverized coal requires a large amount of pyrolysis or gasification equipment, and the initial investment is large, which is not suitable for the renovation of existing coal-fired units; and CO is burned and gasified in the main combustion area, which The formation of CO in the main combustion zone is easy to form high temperature corrosion and reduce the service life of the equipment.

Utility model content

Aiming at the problems existing in the prior art, the utility model provides a pulverized coal partial gasification synergistic denitrification system, which has a simple structure, a reasonable design, and is easy to transform, and can realize ultra-low emission of nitrogen oxides from a power plant boiler without ammonia injection. , high technical economy.

The utility model is realized through the following technical solutions:

A pulverized coal partial gasification synergistic denitration system, comprising a coal bunker, a coal mill, a boiler, a cyclone, a gasifier and a filter;

The coal outlet of the coal bunker is connected to the coal mill inlet, the coal powder outlet of the coal mill is respectively connected to the cyclone separator inlet and the burner nozzle set in the main combustion area of the boiler, and the coal powder outlet of the coal mill is connected to the primary air duct;

The fine coal powder outlet of the cyclone separator is connected to the burner nozzle, and the coarse coal powder outlet is connected to the gasifier inlet;

The gas outlet of the gasifier is divided into two paths, one is connected to the folded flame area of the boiler through the reburning nozzle, the other is connected to the tail flue after passing through the filter, and the tail flue is connected to the tail of the air preheater through the spray gun Flue; a catalyst layer is arranged downstream of the spray gun in the tail flue.

Preferably, a primary air damping door is provided on the inlet connection pipeline of the cyclone separator.

Preferably, the gasifier is provided with a water cooling wall, and the output end of the water cooling wall is connected to the water supply port of the boiler.

Preferably, the reburning nozzle is arranged in the lower part of the SOFA wind in the boiler.

Preferably, the filter is a ceramic filter.

Preferably, the catalyst layer adopts Cu-Mn/Al ₂ O ₃ catalyst.

Compared with the prior art, the utility model has the following beneficial technical effects:

The utility model utilizes CO and _H2 produced by pulverized coal gasification to reduce nitrogen oxides in boiler flue gas, realizes ultra-low emission of nitrogen oxides from power plant boilers without ammonia injection, and solves the problem of ammonia consumption in ammonia injection denitrification. high volume and high ammonia slip. The reducing agent CO for the first-stage high-temperature reduction comes from pulverized coal, and there is no additional material consumption. After the first-stage reduction, non-precious metal catalysts can be used for the second-stage reduction under low temperature conditions, and the technology is economical. Through the synergistic effect of partial gasification of pulverized coal, high temperature reduction of CO, and low temperature catalytic reduction of CO, the concentration of nitrogen oxides is gradually reduced. The NOx concentration in the high temperature reduction stage is controlled within 150mg/ ^m3 , and the NOx concentration in the low temperature reduction stage is controlled within 50mg /m ³ or less. The gasifier can be combined with the existing coal-fired boilers to complete the low-nitrogen combustion transformation of the existing thermal power units.

The pulverized coal is separated into coarse and fine in the cyclone, and the coarse pulverized coal enters the gasifier, which can improve the CO yield in the gas; the fine pulverized coal enters the boiler for combustion, which can improve the ignition stability. The gas generated by gasification is mainly sent to the re-burning zone of the boiler for combustion, which produces the effect of synergistic denitrification while ensuring that the CO is burnt out.

Since the NOx produced in the combustion stage has been significantly reduced, the catalyst volume can be reduced, and the catalyst and lance can be arranged in the tail flue without the need for an external flue, which further reduces the complexity of the system and can be used in existing coal combustion Boiler flue gas denitration transformation.

Description of drawings

Fig. 1 is a schematic structural diagram of the pulverized coal partial gasification synergistic denitrification system according to the present invention.

In the picture: 1. Coal bunker, 2. Coal mill, 3. Primary air duct, 4. Burner nozzle, 5. Boiler, 6. Cyclone separator, 7. Gasifier, 8. Gas outlet, 9. Reburn Nozzle, 10. Filter, 11. Spray gun, 12. Catalyst layer, 13. Tail flue.

Detailed ways

The present utility model will be further described in detail below with reference to specific embodiments, which are to explain rather than limit the present utility model.

The utility model is a pulverized coal partial gasification synergistic denitrification system, which utilizes the CO produced by pulverized coal gasification to reduce the nitrogen oxides in the boiler flue gas economically and efficiently, which is completely different from the ammonia commonly used in the flue gas denitrification of thermal power plants at present. The reducing agent avoids the problems of high ammonia consumption and high ammonia slip caused by excessive ammonia injection.

Among them, the denitration system as shown in Figure 1 includes a coal bunker 1, a coal mill 2, a boiler 5, a cyclone separator 6, a gasifier 7 and a filter 10; the coal outlet of the coal bunker 1 is connected to the inlet of the coal mill 2 , the pulverized coal outlet of the coal mill 2 is respectively connected to the inlet of the cyclone separator 6 and the burner nozzle 4 set in the main combustion area of the boiler 5, and the pulverized coal outlet of the coal mill 2 is connected to the primary air duct 3, which is used to pass the connected The primary air transports the pulverized coal; the cyclone separator 6 is used to separate the coarse and fine pulverized coal, the fine pulverized coal outlet is connected to the burner nozzle 4 to send the fine pulverized coal into the boiler 5 for combustion, and the coarse pulverized coal outlet is connected to the gasifier 7 At the inlet, the coarse pulverized coal is gasified in the gasifier 7 to generate gas; the gas outlet 8 of the gasifier 7 is divided into two paths, one of which is connected to the folded flame area of the boiler 5 through the reburning nozzle 9, and the other through the filter 10. After filtering out the ash, it is connected to the tail flue 13. The tail flue 13 connects the gas to the tail flue 13 through the spray gun. The catalyst layer 12 is arranged in the tail flue 13 downstream of the spray gun.

In this preferred example, the filter 10 adopts a ceramic filter; the temperature of the tail flue 13 at the end of the air preheater is 120-140° C.; the catalyst layer 12 adopts a Cu-Mn/Al ₂ O ₃ catalyst.

When the collaborative denitration system of the utility model is used.

1) The raw coal in the coal bunker 1 becomes pulverized coal after being ground by the coal mill 2, and is carried by the primary air introduced by the primary air duct 3 into the boiler 5 and the gasifier 7. The pulverized coal accounts for 10-20%, and the pulverized coal entering the boiler 5 accounts for 80-90% as an example. If the volatile content of pulverized coal is high (such as lignite and bituminous coal), the proportion of pulverized coal entering the gasifier will be reduced; if the volatile content of pulverized coal is low (such as anthracite), the proportion of pulverized coal entering the gasifier will be increased. The amount of pulverized coal entering the gasifier is controlled by the primary air damper.

2) Coal powder is separated into coarse and fine in cyclone separator 6, fine coal powder is sent to boiler 5 for combustion through burner nozzle 4, and coarse coal powder enters gasifier 7 for gasification to generate coal gas. The main components of coal gas are CO, H ₂ , CO ₂ and N ₂ . The gasification furnace 7 adopts an entrained flow bed method, the gasification agent is air, and the heat required for the gasification of pulverized coal comes from the combustion of coke, and no heat needs to be introduced from the boiler. The gasifier is provided with a water cooling wall, which absorbs the heat released by the gasification and combustion of pulverized coal, and heats the boiler feed water, thereby improving the thermal efficiency of the boiler.

3) The gas is fed into the boiler 5 for combustion through the reburning nozzle 9, and the reburning nozzle 9 is located at the lower part of the SOFA wind in the boiler 5. CO burns out to generate CO ₂ and release heat. At the same time, CO and H ₂ in the gas will reduce the nitrogen oxides in the flue gas under the catalytic action of the boiler wall and the metal oxides in the flue gas fly ash to generate N ₂ and H ₂ O.

4) After the gas is filtered out of the ash in the filter 10, it is sent into the tail flue 13 through the spray gun 11. Under the action of the catalyst layer 12, it reacts with the nitrogen oxides in the flue gas to generate N ₂ and H ₂ O, thereby Reduce boiler NOx emissions. The CO flow in the spray gun 11 is adjusted according to the detection value of nitrogen oxides, which is generally in the order of ppm.

The unreacted CO in step 3) can participate in the denitration reaction in the tail flue catalyst layer, thereby reducing CO escape. Both the lance 11 and the catalyst layer 12 are arranged in the tail flue 13 . The catalyst layer 12 adopts Cu-Mn/Al ₂ O ₃ catalyst, which can achieve a denitration efficiency of 70% in the temperature range of 120-140°C. Different from the prior art, the catalyst layer 12 is arranged at the end of the air preheater, and the flue gas temperature ranges from 120 to 140°C.

Claims (6)

1. A pulverized coal partial gasification synergistic denitration system, characterized in that it comprises a coal bunker (1), a coal mill (2), a boiler (5), a cyclone (6), a gasifier (7) and filter(10); The coal outlet of the coal bunker (1) is connected to the inlet of the coal mill (2), and the pulverized coal outlet of the coal mill (2) is respectively connected to the inlet of the cyclone separator (6) and the combustion provided in the main combustion area of the boiler (5). The nozzle (4) of the pulverizer, the pulverized coal outlet of the pulverizer (2) is connected to the primary air duct (3); The fine coal powder outlet of the cyclone separator (6) is connected to the burner nozzle (4), and the coarse coal powder outlet is connected to the inlet of the gasifier (7); The gas outlet (8) of the gasifier (7) is divided into two paths, one path is connected to the folded flame angle area of the boiler (5) through the reburning nozzle (9), and the other path is connected to the tail smoke after passing through the filter (10). (13), the tail flue (13) connects the gas to the tail flue (13) at the tail of the air preheater through the spray gun (11); a catalyst layer (13) is provided downstream of the spray gun (11) in the tail flue (13). 12). 2. The pulverized coal partial gasification synergistic denitrification system according to claim 1, characterized in that, a primary air regulating door is provided on the inlet connection pipeline of the cyclone separator (6). 3. A pulverized coal partial gasification synergistic denitration system according to claim 1, wherein the gasifier (7) is provided with a water cooling wall, and the output end of the water cooling wall is connected to the water supply port of the boiler. 4. A pulverized coal partial gasification synergistic denitration system according to claim 1, characterized in that the reburning nozzle (9) is arranged at the lower part of the SOFA wind in the boiler (5). 5. The pulverized coal partial gasification synergistic denitration system according to claim 1, wherein the filter (10) adopts a ceramic filter. 6 . The pulverized coal partial gasification synergistic denitration system according to claim 1 , wherein the catalyst layer ( 12 ) adopts a Cu-Mn/Al ₂ O ₃ catalyst. 7 .

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