CN111473325A - O-shaped catalyst2/H2Low NO for brown coal and gasified carbon residue of O combustion boilerxSystem and method for co-firing - Google Patents

Abstract

The invention discloses a system and a method for low _NOx mixed combustion of lignite and gasification residual carbon in an O ₂ /H ₂ O combustion boiler. The invention utilizes the dried lignite and coal-water slurry gasification residual carbon to carry out O ₂ /H ₂ O co-combustion in the power station boiler, and further optimizes the air distribution mode in the furnace, which can not only reduce the _NOx emission at the boiler outlet, but also It can effectively use lignite and coal-water slurry gasification residues with high moisture content and difficult to use directly. Utilize LNG gasification to provide cold energy for cryogenic air separation equipment, and then produce oxygen. High temperature flue gas is used to heat lignite and coal-water slurry gasification residual carbon and dry water into steam, and O ₂ /H ₂ O combustion is carried out in the furnace. The dried gasification residue is preheated by flue gas to strengthen its combustion in the furnace. The cold energy in the gasification of oxygen and nitrogen in the cryogenic air separation system is used to collect the moisture in the flue gas, and then heat it to steam for use in the system, which not only improves the energy utilization efficiency of the system, but also eliminates the white visual pollution in the flue gas. .

Description

A system and method for low NOx blending of lignite and gasification residual carbon in an O2/H2O combustion boiler

technical field

The invention belongs to the technical field of power generation by pulverized coal boilers in power stations, and particularly relates to a system and method for low- _NOx blending of lignite and gasification residual carbon in an O ₂ /H ₂ O combustion boiler.

Background technique

At present, the proven lignite reserves in my country exceed 100 billion tons. However, due to its high moisture content, lignite is difficult to be directly burned and utilized in boilers. Therefore, the current utilization of lignite is first dried and then put into the boiler for combustion. Coal-water slurry gasification residual carbon is a by-product of coal-water slurry gasifier, and it is a solid waste with great application prospects. With the continuous development of the coal chemical industry, its output is getting higher and higher. Coal water slurry gasification residual carbon has high moisture content and high carbon content, but low volatile content, and it is difficult to directly burn in the boiler, so it can be burned and used in the boiler after drying. The nitrogen content of lignite is low but the volatile content is high. It is an important way to realize the clean and efficient utilization of lignite and the reuse of solid waste to be mixed with coal-water slurry gasification residual carbon in power station boilers.

O ₂ /H ₂ O oxygen-enriched combustion, compared with traditional O ₂ /CO ₂ oxygen-enriched combustion, reduces the flue gas circulation system and reduces the complexity of the system; during the O ₂ /H ₂ O combustion process, there is no smoke Gas recirculation process, thus reducing the generation of impurity gases such as NO _x and SO _x , and the main products after combustion are H ₂ O and CO ₂ , which are all beneficial to the purification process of CO ₂ . In addition, in the O ₂ /H ₂ O combustion process, since there is no nitrogen, no thermal NO _x is generated, only fuel NO _x is generated, which has far-reaching significance for reducing NO _x emissions from coal-fired power plant boilers.

O ₂ /H ₂ O combustion of lignite and coal-water slurry gasification residual carbon in coal-fired power plant boilers, combined with the characteristics of lignite's low nitrogen content and high volatile content, can not only realize the combustion of coal-water slurry gasification residual carbon The utilization of solid wastes such as carbon can also further reduce _NOx emissions from coal-fired boilers. It is beneficial to realize the cascade utilization of coal in my country and the efficient and clean utilization of solid waste with high water content.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a system and method for low _NOx blending of lignite and gasification residual carbon in an O ₂ /H ₂ O combustion boiler. The invention utilizes the dried lignite and coal-water slurry gasification residual carbon to carry out O ₂ /H ₂ O co-combustion in the power station boiler, and further optimizes the air distribution mode in the furnace, which can not only reduce the _NOx emission at the boiler outlet, but also It can effectively use lignite and coal-water slurry gasification residues with high moisture content and difficult to use directly. Utilize LNG gasification to provide cold energy for cryogenic air separation equipment, and then produce oxygen. High temperature flue gas is used to heat lignite and coal-water slurry gasification residual carbon and dry water into steam, and O ₂ /H ₂ O combustion is carried out in the furnace. The dried gasification residue is preheated by flue gas to strengthen its combustion in the furnace. The cold energy in the gasification of oxygen and nitrogen in the cryogenic air separation system is used to collect the moisture in the flue gas, and then heat it to a steam state for use in the system, which not only improves the energy utilization efficiency of the system, but also eliminates the white vision in the flue gas. Pollution. Coupling LNG equipment, lignite drying system and energy and material in power station boilers not only utilizes the flame retardant fuel, but also improves the efficiency of industrial production.

The present invention adopts following technical scheme to realize:

An O ₂ /H ₂ O combustion boiler lignite and gasification residual carbon low _NOx blending system, including LNG gasification station, cryogenic air separation plant, first flue gas condenser, first water collector, first Coal bunker, coal mill, first drying header, second coal bunker, second drying header, tubular preheater, burnout fan, primary fan, secondary fan, first induced draft fan, second induced draft fan , the second flue gas condenser, the second water collector and the boiler body, and the ignition zone, the main combustion zone and the burnout zone arranged on the boiler body from bottom to top; wherein,

The side wall of the boiler body in the ignition zone is provided with a first lignite inlet, a gasification residue char inlet and a second lignite inlet from bottom to top, a hot air inlet is arranged on the side wall of the boiler body in the main combustion zone, and the boiler body in the burnout zone A burn-out air inlet is arranged on the side wall; the first air preheater and the second air preheater are arranged in the tail flue of the boiler body from the inside to the outside, and the oxygen-enriched primary air and secondary air pass through the first induced draft fan. It is preheated by the first air preheater, and then the primary air and secondary air enter the ignition zone and the main combustion zone through the first lignite inlet, the gasification residue char inlet, the second lignite inlet and the hot air inlet; After the second induced draft fan, the second air preheater is used to preheat, and then the pure oxygen burnout air enters the burnout zone through the burnout air inlet;

The liquefied natural gas gasification of the LNG gasification station provides cold energy for the cryogenic air separation plant to produce pure oxygen, and then uses the cold energy during the gasification of liquid nitrogen and liquid oxygen to condense and dry the lignite and coal-water slurry gasification of the residual carbon and the flue gas. The moisture in the tail flue gas forms an O ₂ /H ₂ O combustion atmosphere in the boiler body. The lignite enters the coal mill from the first coal bunker, is ground into powder, and then enters the first drying header, and the coal-water slurry gas The carbonization residue enters the second drying header from the second coal bunker; the lignite and coal-water slurry gasification residue are dried in the first drying header and the second drying header respectively by the tail flue gas, and the dried gasification residue The carbon is preheated in the tubular preheater and then passed into the boiler to strengthen its combustion; the cold energy of liquid oxygen and liquid nitrogen are used to condense in the first flue gas condenser and the second flue gas condenser respectively. The flue gas from the tubular preheater and the flue gas before the flue gas dust collector, the condensed water is collected in the first water collector and the second water collector respectively, and finally collected into the first water collector, using high temperature smoke The gas heats the water in the first water collector to a steam state, and combines with the gasified pure oxygen to form oxygen-enriched primary air, secondary air and pure oxygen burnout air, which are respectively driven by the primary fan, the secondary fan and the combustion air. As much as possible the fan is led out and sent to the boiler, and the air distribution mode is optimized to reduce the _NOx generation in the furnace.

A further improvement of the present invention is that it also includes a flue gas dust collector and a chimney, and the condensed flue gas is dedusted in the flue gas dust collector (25), and finally discharged from the chimney.

The method for burning lignite and gasification residual carbon O ₂ /H ₂ O, including:

(1) Use tail flue gas to dry lignite and coal-water slurry gasification residual carbon, collect the moisture after drying, and form O ₂ /H ₂ O combustion atmosphere in the furnace;

(2) Use the cold energy of liquid nitrogen and liquid oxygen to condense and collect the moisture in the flue gas;

(3) Use the tail flue gas to preheat the gasification residual carbon to strengthen its combustion process;

(4) The gasification residue carbon inlet is arranged between the first lignite inlet and the second lignite inlet, and the high volatile characteristics of lignite are used to support the combustion of the gasification residue to strengthen the combustion process in the ignition area;

(5) The high temperature flue gas is used to heat the water in the first water collector into a steam state, and then mixed with pure oxygen and sent into the furnace for combustion, which optimizes the air distribution method.

A method for co-firing gasification residual carbon with low _NOx combustion of lignite in power station boilers, including:

(1) O ₂ /H ₂ O combustion is formed in the boiler, which reduces the _NOx emission of the boiler;

(2) Using pure oxygen and water vapor to mix into oxygen-enriched primary air, secondary air and pure oxygen burnout air, while strengthening the combustion of fuel in the boiler, it will also reduce the _NOx emission at the boiler outlet;

(3) Preheating the oxygen-enriched primary air, secondary air and pure oxygen burnout air in the first air preheater and the second air preheater to improve the combustion efficiency of the boiler;

(4) The oxygen ratio in the oxygen-enriched primary air and the secondary air can be adjusted as needed, and the furnace temperature can also be adjusted while the low _{NOx is} burned.

The system and method for coupling lignite and gasification residual carbon O ₂ /H ₂ O low _NOx co-combustion provided by the present invention have the following beneficial technical effects:

(1) O ₂ /H ₂ O combustion in the furnace is realized by using lignite and coal-water slurry gasification residual carbon drying water and tail flue gas condensing water, which is beneficial to reduce _NOx emissions;

(2) Utilize high volatile lignite and coal-water slurry gasification residual carbon for co-combustion, and use flue gas for preheating before gasification residual carbon enters the furnace, which is conducive to its combustion;

(3) Oxygen-enriched primary air, secondary air and pure oxygen-burning exhaust air are formed by pure oxygen and water vapor, which optimizes the air distribution method, which is conducive to the ignition and combustion of lignite and gasification residual carbon, and is also conducive to reducing _NOx emissions from boilers quantity;

(4) Using the cold energy of LNG gasification to produce liquid oxygen and liquid nitrogen in cryogenic air separation equipment, the efficiency and energy utilization rate of industrial production are improved;

(5) Using the cold energy of liquid oxygen and liquid nitrogen to condense and collect the moisture in the flue gas, not only can the collected water be sent to the furnace for O ₂ /H ₂ O combustion and utilization, but also can eliminate white visual pollution.

Description of drawings

Fig. 1 is a schematic diagram of a system of the present invention for mixing lignite and gasification residual carbon with low _NOx in an O ₂ /H ₂ O combustion boiler.

Description of reference numbers:

1 is the LNG gasification station, 2 is the cryogenic air separation plant, 3 is the first flue gas condenser, 4 is the first water collector, 5 is the first coal bunker, 6 is the coal mill, and 7 is the first dryer Header, 8 is the second coal bunker, 9 is the second drying header, 10 is the tubular preheater, 11 is the burnout fan, 12 is the primary fan, 13 is the secondary fan, 14 is the first lignite inlet, 15 is the gasification residual carbon inlet, 16 is the second lignite inlet, 17 is the hot air inlet, 18 is the exhaust air inlet, 19 is the first air preheater, 20 is the second air preheater, and 21 is the first air inlet. Fan, 22 is the second induced draft fan, 23 is the second flue gas condenser, 24 is the second water collector, 25 is the flue gas dust collector, 26 is the chimney, and 27 is the boiler body.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

Referring to Fig. 1, the present invention provides an O ₂ /H ₂ O combustion boiler lignite and gasification residual carbon low _NOx blending system, including LNG gasification station 1, cryogenic air separation plant 2, first flue gas condensation 3, the first water collector 4, the first coal bunker 5, the coal mill 6, the first drying header 7, the second coal bunker 8, the second drying header 9, the tubular preheater 10, the burnout Fan 11, primary fan 12, secondary fan 13, first lignite inlet 14, gasification residual char inlet 15, second lignite inlet 16, hot air inlet 17, burnout air inlet 18, first air preheater 19, Two air preheaters 20, a first induced draft fan 21, a second induced draft fan 22, a second flue gas condenser 23, a second water collector 24, a flue gas dust collector 25, a chimney 26 and a boiler body 27, and the bottom The boiler ignition area, main combustion area and burnout area arranged above; among them,

The liquefied natural gas is gasified by the LNG gasification station 1 to provide cold energy for the production of pure oxygen in the cryogenic air separation plant 2, and then the cold energy during the gasification of liquid nitrogen and liquid oxygen is used to condense and dry the preheated lignite and coal-water slurry gasification residual carbon. The moisture in the flue gas and the tail flue gas forms an O ₂ /H ₂ O combustion atmosphere in the boiler body 27, and the dried gasification residual carbon is preheated in the tubular preheater 10 and then passed into the boiler, intensifies its combustion.

Further, the lignite enters the coal mill 6 from the first coal bunker 5, is ground into powder, and then enters the first drying header 7, and the coal-water slurry gasification residual carbon enters the second drying header from the second coal bunker 8 9. The tail flue gas is used to dry the lignite and coal-water slurry gasification residual carbon in the first drying header 7 and the second drying header 9 respectively, and the dried flue gas is then passed into the tubular preheater 10 for preheating of the gasification residual carbon. heat to intensify the combustion process in its furnace.

Further, the flue gas and flue gas dust remover 25 coming out of the tubular preheater 10 are condensed in the first flue gas condenser 3 and the second flue gas condenser 23 by using the cold energy of liquid oxygen and liquid nitrogen respectively. The former flue gas and condensed water are collected in the first water collector 4 and the second water collector 24 respectively, and finally collected into the first water collector 4 .

Further, the high-temperature flue gas is used to heat the water in the first water collector 4 to a steam state, and combined with the gasified pure oxygen to form oxygen-enriched primary air, secondary air and pure oxygen burn-out air, which are respectively composed of primary air. The fan 12, the secondary fan 13 and the burn-out fan 11 are led out and sent to the boiler, and the optimized air distribution reduces the _NOx generation in the furnace. Finally, the condensed flue gas is dedusted in the flue gas dust collector 25, and finally by the chimney 26 discharge.

Further, in the boiler, the gasification residual carbon inlet 15 is arranged between the first lignite inlet 14 and the second lignite inlet 16, and the high volatile characteristics of lignite are used to assist the gasification of the residual carbon to strengthen the combustion process in the ignition area.

Further, the oxygen-enriched primary air and secondary air are preheated by the first air preheater 19, and then the primary air and the secondary air pass through the first lignite inlet 14, the gasification residue char inlet 15, the second lignite inlet 16 and the hot air The inlet 17 enters the ignition zone and the main combustion zone; the second air preheater 20 preheats the pure oxygen burnout air, and the pure oxygen burnout air enters the burnout zone through the burnout air inlet 18 .

Further, high-temperature flue gas from the first water collector 4 is condensed by using liquid nitrogen to produce cold energy during nitrogen gasification, and the collected moisture is used for O ₂ /H ₂ O combustion, and high-purity nitrogen is simultaneously produced for industrial use. Production.

Referring to FIG. 1 , the method for burning lignite and gasification residual carbon O ₂ /H ₂ O provided by the present invention includes:

(1) Use tail flue gas to dry lignite and coal-water slurry gasification residual carbon, collect the moisture after drying, and form O ₂ /H ₂ O combustion atmosphere in the furnace;

(2) Use the cold energy of liquid nitrogen and liquid oxygen to condense and collect the moisture in the flue gas;

(3) Use the dried flue gas to preheat the gasification residual carbon to strengthen its combustion process;

(4) The gasification residue carbon inlet 15 is arranged between the first lignite inlet 14 and the second lignite inlet 16, and utilizes the characteristics of high volatile content of lignite to support the gasification of the gasification residue to strengthen the combustion process in the ignition zone;

(5) The high-temperature flue gas is used to heat the water in the first water collector 4 into a steam state, which is then mixed with pure oxygen and sent into the furnace for combustion, thereby optimizing the air distribution method.

Referring to FIG. 1 , the method for coupling low- _NOx combustion of lignite in a power station boiler with mixed combustion of gasification residual carbon provided by the present invention includes:

(1) O ₂ /H ₂ O combustion is formed in the boiler, which can effectively reduce the _NOx emission of the boiler;

(2) Using pure oxygen and water vapor to mix into oxygen-enriched primary air, secondary air and pure oxygen burnout air, while strengthening the combustion of fuel in the boiler, it will also reduce the _NOx emission at the boiler outlet;

(3) Preheating the oxygen-enriched primary air, secondary air and pure oxygen burnout air in the first air preheater 19 and the second air preheater 20 to improve the combustion efficiency of the boiler;

(4) The oxygen ratio in the oxygen-enriched primary air and the secondary air can be adjusted according to the needs, and the furnace temperature can also be adjusted while the low _{NOx is} burned.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Other modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention, as long as they do not depart from the technology of the present invention. The spirit and scope of the solution should be included in the scope of the claims of the present invention.

Claims (4)

1. O-shaped catalyst₂/H₂Low NO for brown coal and gasified carbon residue of O combustion boiler_xThe mixed combustion system is characterized by comprising an L NG gasification station (1), a cryogenic air separation plant (2), a first flue gas condenser (3), a first water collector (4) and a first water collectorThe system comprises a coal bunker (5), a coal mill (6), a first drying header (7), a second coal bunker (8), a second drying header (9), a tubular preheater (10), a burnout fan (11), a primary fan (12), a secondary fan (13), a first induced draft fan (21), a second induced draft fan (22), a second flue gas condenser (23), a second water collector (24) and a boiler body (27), as well as a fire striking zone, a main burning zone and a burnout zone which are arranged on the boiler body (27) from bottom to top; wherein,

a first brown coal inlet (14), a gasification carbon residue inlet (15) and a second brown coal inlet (16) are arranged on the side wall of the boiler body (27) in the ignition zone from bottom to top, a hot air inlet (17) is arranged on the side wall of the boiler body (27) in the main combustion zone, and an over-fire air inlet (18) is arranged on the side wall of the boiler body (27) in the over-fire zone; the first air preheater (19) and the second air preheater (20) are arranged in a tail flue of the boiler body (27) from inside to outside, oxygen-enriched primary air and secondary air are preheated by the first air preheater (19) after passing through a first induced draft fan (21), and then the primary air and the secondary air enter an ignition area and a main combustion area through a first lignite inlet (14), a gasification carbon residue inlet (15), a second lignite inlet (16) and a hot air inlet (17); the pure oxygen over-fire air is preheated by a second air preheater (20) after passing through a second induced draft fan (22), and then enters the over-fire area through an over-fire air inlet (18);

the method comprises the steps of gasifying liquefied natural gas of an L NG gasification station (1) to provide cold energy for producing pure oxygen for a cryogenic air separation plant (2), condensing and drying smoke generated after lignite and coal water slurry gasified carbon residue and moisture in tail smoke by utilizing liquid nitrogen and the cold energy generated in liquid oxygen gasification, and forming O in a boiler body (27)₂/H₂In the O combustion atmosphere, lignite enters a coal mill (6) from a first coal bunker (5), is ground into powder, then enters a first drying collection box (7), and coal water slurry gasification carbon residue enters a second drying collection box (9) from a second coal bunker (8); the tail flue gas is used for drying lignite and coal water slurry gasified residual carbon in a first drying header (7) and a second drying header (9) respectively, and the dried gasified residual carbon is preheated in a tubular preheater (10) and then is introduced into a boiler to strengthen the combustion; the cold energy generated when the liquid oxygen and the liquid nitrogen are gasified is respectively utilized to condense the smoke and the smoke coming out of the tubular preheater (10) in the first smoke condenser (3) and the second smoke condenser (23)Flue gas in front of the dust remover (25), condensed water is collected in the first water collector (4) and the second water collector (24) respectively and finally collected to the first water collector (4), high-temperature flue gas is used for supplying heat to a steam state for water in the first water collector (4), and the condensed water is combined with gasified pure oxygen to form oxygen-enriched primary air, secondary air and pure oxygen over-fire air, the oxygen-enriched primary air, the secondary air and the pure oxygen over-fire air are led out by the primary air fan (12), the secondary air (13) and the over-fire air fan (11) respectively and sent into a boiler, and the air distribution mode is optimized, so that NO in the boiler_xThe amount of production.

2. O according to claim 1₂/H₂Low NO for brown coal and gasified carbon residue of O combustion boiler_xThe mixed combustion system is characterized by also comprising a flue gas dust remover (25) and a chimney (26), wherein the condensed flue gas is subjected to dust removal in the flue gas dust remover (25) and is finally discharged from the chimney (26).

3. O according to claim 1 or 2₂/H₂Low NO for brown coal and gasified carbon residue of O combustion boiler_xLignite and gasified carbon residue O of co-combustion system₂/H₂A method of O-combustion, comprising:

(1) drying lignite and coal water slurry gasified carbon residue by utilizing tail flue gas, collecting dried water, and forming O in a furnace₂/H₂O combustion atmosphere;

(2) condensing and collecting moisture in the flue gas by using cold energy generated during gasification of liquid nitrogen and liquid oxygen;

(3) preheating gasified carbon residue by utilizing tail flue gas to strengthen the combustion process;

(4) the gasification carbon residue inlet (15) is arranged between the first lignite inlet (14) and the second lignite inlet (16), and the gasification carbon residue is assisted by utilizing the characteristic of high volatile components of lignite to combust gas, so that the combustion process of an ignition area is strengthened;

(5) the water in the first water collector (4) is heated to be in a steam state by using high-temperature flue gas, and then is mixed with pure oxygen and sent into the furnace for combustion, so that the air distribution mode is optimized.

4. O according to claim 1 or 2₂/H₂Low NO for brown coal and gasified carbon residue of O combustion boiler_xPower station boiler brown coal blending combustion gasification carbon residue coupling low NO of blending combustion system_xA method of combustion, comprising:

(1) formation of O in a boiler₂/H₂O combustion, reduced NO in boiler_xDischarging;

(2) the pure oxygen and the water vapor are mixed into oxygen-enriched primary air, secondary air and pure oxygen over-fire air, so that the combustion of fuel in the boiler is enhanced, and NO at the outlet of the boiler is reduced_xDischarging;

(3) oxygen-enriched primary air, secondary air and pure oxygen over-fire air are preheated in a first air preheater (19) and a second air preheater (20), so that the combustion efficiency of the boiler is improved;

(4) the oxygen proportion in the oxygen-enriched primary air and the secondary air is adjusted according to the requirement, and the low NO is_xThe temperature of the hearth can be adjusted while the combustion is carried out.

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