PL182263B1 - System for reducing NOx emissions in power boilers with a front burner system - Google Patents

Abstract

A system for reducing NOK emissions in power boilers with a front-/'"-s burner system, constituting connections of individual coal mills of a mill assembly with specific lower burners of the power boiler with dust ducts for a compacted dust-air mixture and with specific upper burners with dust ducts for a diluted dust-air mixture, comprising devices for concentrating dust in the dust-air mixture and dividing the stream into a compacted and diluted dust-air mixture, installed axially in the outlet heads of the coal mills of the mill assembly, characterized in that two or four dust ducts (11) of the diluted dust-air mixture are led out from the upper part of the devices (6) for concentrating dust in the dust-air mixture and dividing the stream into a compacted and diluted mixture of the mill assembly (MW1), (MW2), (MW3), (MW4) and are connected to two or four burners in the upper part (III) or (IV) row, and three dust ducts (12) of the compacted dust-air mixture are led out from the devices (6) for concentrating dust in the dust-air mixture and dividing the stream into a compacted and diluted mixture and are connected to three burners (I) or (II) row so that the mill (MW1) is connected by three dust ducts (12) of the compacted dust-air mixture to the burners (1) of the first, third, fifth (I) row, and two dust ducts (11) of the diluted dust-air mixture is connected to the middle burners (1) of the third and fourth (IV) row, the mill (MW2) is connected by three dust ducts (12) of the compacted dust-air mixture to the burners (2) of the second, fourth, sixth (I) row, and dust ducts (U) of the diluted dust-air mixture is connected to the burners (2) of the first, the second, fifth, sixth (IV) order, the mill (MW3) is connected by three dust ducts (12) for the compacted dust-air mixture to the burners (3) of the first, third, fifth (II) order, and by four dust ducts (U) for the diluted mixture to the burners (3) of the first, second, fifth, sixth (III) order, the mill (MW4) is connected by three dust ducts (12) for the compacted dust-air mixture to the burners (4) of the second, fourth, sixth (II) order,

Description

The present invention relates to a system for reducing emissions of _NOx in power boilers with the front circuit pulverized coal burners disposed on a wall of the furnace in rows situated one above the other, where the mixture dust-air is produced in coal mills with a device for the concentration of dust in the mixture and separation of the stream on thickened and thin mixture.

Power boilers with a front pulverized burner system are known, where each of the mills supplies one horizontal row of burners. Depending on the demand for steam, combustion takes place in the burners in all rows when the steam demand is high, or in some rows with reduced demand. The idea is to always obtain steam of the same temperature and pressure with varying amounts of steam produced.

It was noticed that depending on which row of burners is active, the NO _x content in the exhaust gas changes. It has been found that when the lowest row of burners is in operation, the percentage of NO _X in the flue gas is 30-40% lower in relation to the percentage of NO _X in the flue gas when all rows of burners are in operation. During the operation of the highest row of burners, the percentage of NO _X in the exhaust gas is higher than the average. Due to the NO _x content in the flue gas, with reduced steam production, it would be expedient to use the lower rows of burners, but it turns out that it then becomes difficult to obtain the desired steam temperature and pressure due to underheating of the steam superheaters. This makes it necessary to use in these cases the operation of higher rows of burners, which, however, worsens the composition of the exhaust gases, because the percentage of NO _x content in them increases.

From the application of the invention no. P-302596, a system for feeding a dust-gas mixture to burners of power boilers is known, having a separating-mixing device located upstream of the burner inlet, connected on one side with at least one coal mill by means of dust-gas mixture lines that are tangentially led to the device, and on the other hand, with cables installed in one end face of this device. It is connected to at least two dust nozzles located in the lower part of the burner, excluding the dust nozzle located in the upper part of the burner. The released upper part of the burner is preferably connected to an additional air supply above the region of the actual burner belt.

From the patent application no. P-302597 a system for feeding a dust-gas mixture to burners of power boilers is known, characterized in that the pipes of at least three mills operating in any configuration are connected with at least two dust nozzles located in the lower part of the burner, excluding the nozzle dust located at the top of the burner. The released upper part of the burner is preferably connected to the supply of additional air above the area of the actual burner belt.

From the application to the European Patent Office No. 0225157, a device for reducing nitrogen oxide emissions from power coal-fired boilers is known.

Polish patent no. 171 108 describes a system for reducing the content of NO _X in the flue gas, which is a combination of coal mills with burners in an industrial boiler fired with a fuel-air mixture made of coal dust, which burners are located on the wall of the furnace in the front arrangement, where individual coal mills they are connected to pairs of burners, where in each pair of burners one of the burners is located in the higher row and the other of the burners is located in the lower row and the burners lie in one and the same vertical row, i.e. they lie one above the other.

The aim of the invention is to develop a system for reducing NO _X emissions in power boilers with a front burner system, ensuring a constant level of steam and flue gas temperatures downstream of the boiler and a significant reduction of NO _X emissions in the flue gas, regardless of whether all mills connected to specific boiler burners are in operation.

A system for reducing NO _X emissions in power boilers with a front burner system, which is a connection of individual coal mills of the mill unit with specific lower burners of the power boiler through dust-air condensed mixture lines and with specific upper burners with thin dust-air mixture lines

182 263 dust-air mixture, containing devices for dust concentration in the dust-air mixture and separation of the stream into a dust-air-thickened mixture and a dust-air diluted mixture built axially in the outlet heads of the coal mills of the mill set according to the invention, characterized in that two or four the dust ducts of the diluted dust-air mixture are led out of the upper part of the devices for dust concentration in the dust-air mixture and the separation of the stream into a thickened mixture! thinned group of mills and are connected with two or four burners in the upper third or fourth row, and three dust lines of the concentrated dust-air mixture are led out of the devices for dust concentration in the dust-air mixture and separation of the stream into a thickened and diluted mixture and are connected with three burners of the first and second row. The first mill is connected with the first, third and fifth row burners with the three dust-air condensed lines, and the two dust-air condensed mixing lines with the middle third and fourth row burners. The second mill is connected through three dust-air conduits to the second, fourth, sixth-first row burners, and the thin dust-air mixture is connected to the first, second, fifth, sixth-fourth row burners through the thin dust-air conduit. The third mill is connected with the first, third, fifth and second row burners by means of three dust pipes of the compacted dust-air mixture, and the four dust pipes of the diluted dust-air mixture are connected to the burners of the first, second, fifth, sixth row of the third order. The fourth mill is connected with the second, fourth, sixth and second order dust-ducts of the compacted dust-air mixture, and the two dust ducts of the diluted dust-air mixture are connected to the third, fourth and third row burners.

Devices for the concentration of dust in the dust-air mixture and the separation of the stream into a dust-air mixture, thickened and diluted, have centrally located on the coal chute pipe of individual mills of the mill unit, spreading the stream of the dust-air mixture, and cones over the cones, concentrically built on the discharge pipe, through bushings for flow of the diluted dust-air mixture and parallel passage chambers coaxially with them of the thickened dust-air mixture.

Two or four dust pipes of the diluted dust-air mixture are led out of the sleeve from the upper part of the devices for dust concentration in the dust-air mixture and the separation of the stream into a thickened mixture! sparse group of mills. The three dust pipes of the condensed dust-air mixture are led out of the passage chambers of the devices for dust concentration in the dust-air mixture and the separation of the stream into a thickened and thin mixture of the mill group.

The system according to the invention enables the feeding of 70-80% of the dust to the lower burners of the first and second row, and the remaining 20-30% of the dust to the upper burners of the third and fourth row, independently of the configuration of the operating mill units. Superheating of fresh and secondary steam and the emission level of nitrogen oxides do not depend on the configuration of operating mill units. The system allows accurate as a result of mixing of the combustion products in the combustion zone to reduce emissions of nitrogen oxides NO _x to levels below that required in the entire operating range of the boiler from the minimum downforce, regardless of the number of operating mills. The boiler efficiency is increased, the flue gas temperature is lowered downstream of the boiler and the boiler technical minimum is reduced without the need to support combustion with oil burners. The content of combustible parts in the ash is reduced. The devices installed in the outlet heads of the mills enable the concentration of dust in the dust-air mixture coming from the mills and the separation of the concentrated dust-air mixture and thin air-dust mixture into streams.

The system according to the invention allows for a significant reduction of the NO _x content in the flue gas with minimal costs of furnace reconstruction. It can be used in mills from which the outgoing streams of dust-air mixture are both swirled and not swirled.

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The subject of the invention has been shown in the embodiment in the drawing, where Fig. 1 shows the system of connection of the individual mills of the mill unit with the dust-conduits of the thickened and diluted mixture with individual burners of certain rows of burners of the power boiler, Fig. 2 - vertical section through the device for dust concentration in the dust-mixture air and stream separation into a thickened mixture! sparse, built into the outlet head of each of the mills.

The system for reducing the emission of nitrogen oxides NO _X in power boilers with a front burner system consists of a system for connecting individual MW1, MW2, MW3, MW4 coal mills to specific burners 1,2,3,4, rows I, II, III, IV of the boiler power system with 12 dust-air mixture condensed from the mill unit MW1, MW2, MW3, MW4 to the lower burners of the power boiler and dust pipes with 11 diluted dust-air mixture supplied from the mill unit MW1, MW2, MW3, MW4 to the upper burners of the power boiler, shown in Fig. 1, and includes devices 6 for concentration of the dust-air mixture and separation of the stream into a thickened and diluted mixture, built axially in the outlet heads 5 of individual mills of the milling unit MW1, MW2, MW3, MW4, shown in Fig. 2.

The burners 1 of the power boiler are connected to the MW1 mill. The burners 2 are connected to the MW2 mill. The burners 3 are connected to the MW3 mill. 4 burners are connected to the MW4 mill.

The dust lines 11 of the thin air / dust mixture are connected to two or four burners in the top row III or IV. The dust lines 12 of the dust-air condensed mixture are connected to three burners of the 1st or 2nd row.

Referring to Fig. 1, the MW1 mill is connected by three dust-air compacted dust lines 12 to first, third, and fifth-row burners 1 and two dust-air thinned-air burners 11 to middle third and fourth row burners 1. The MW2 mill is connected by three dust lines 12 of a dust-air condensed mixture to burners 2 of the second, fourth, and sixth row, and dust ducts 11 of a diluted dust-air mixture to burners 2 of the first, second, fifth and sixth row. The MW3 mill is connected by three dust-lines 12 of the dust-air condensed mixture with burners 3 of the first, third, fifth and second order and four dust-pipes 11 of the diluted dust-air mixture with burners 3 of the first, second, fifth, sixth row III. The MW4 mill is connected by three dust-air conduits 12 to the second, fourth, and sixth row burners 4 and two dust conduits 11 of the diluted dust-air mixture to burners 4 of the third, fourth and third row.

According to Fig. 2, the device 6 for concentrating the dust in the dust-air mixture and separating the stream into a dust-air mixture, thickened and thinned, is axially built in the outlet head 5 of each of the mills MW1, MW2, MW3, MW4, centrically on the chute pipe 8 coal to a specific mill. It includes a cone 7 located centrally on the chute 8, dividing the stream of the dust-air mixture leaving the mill MW1, MW2, MW3, MW4, and a cone 7 over the cone 7, built concentrically on the discharge pipe 8, and a through sleeve 9 for the flow of the diluted dust-air mixture and a concentric parallel with it a passage chamber 10 for a compacted dust-air mixture. The sleeve 9 leads from the upper part of the devices 6 for dust concentration in the dust-air mixture and the separation of the stream into a dust-air mixture, thickened and diluted into two or four dust ducts 11 of the thinned dust-air mixture, and three dust ducts 12 of the compacted mixture lead out of the passage chambers 10. dust-air mixture.

In accordance with the embodiment, the swirled streams of the dust-air mixture leaving the mills MW1, MW2, MW3, MW4 enter the outlet heads 5 of individual mills, in which devices 6 for concentration of dust in the dust-air mixture and for the separation of the stream into a thickened and diluted mixture are installed. The streams of the dust-air mixture are diffused on the cones 7 and change the direction of the flow. As a result, streams of compacted dust-air mixture flow outside the outlet heads 5.

182 263

Gases and smaller amounts of particles change the flow direction behind the cones 7 towards the axis of the outlet heads 5. The concentrated mixture streams enter the through-chambers 10 from which the dust ducts 12 of the dust-air mixture are led to specific burners of the 1st or 2nd row of the power boiler. Streams of the thinned mixture enter the sleeves 9, from which the dust lines 11 of the thinned dust-air mixture are led to certain 3rd and 4th row burners.

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FIG. 2

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FIG 4

Publishing Department of the Polish Patent Office. Circulation of 60 copies. Price PLN 2.00.

Claims (4)

Patent claims 1. System for reducing NO _X emissions in power boilers with a front burner system, constituting connections of individual coal mills of the mill unit with specific lower burners of the power boiler with dust-air condensed mixture lines and with specific upper burners with dust-air diluted mixture lines, including concentration devices of dust in the dust-air mixture and the separation of the stream into a thickened and diluted dust-air mixture built axially in the outlet heads of the coal mills of the mill unit, characterized in that two or four dust ducts (11) of the diluted dust-air mixture are led out of the upper part of the devices ( 6) for dust concentration in the dust-air mixture and separation of the stream into a thickened mixture! diluted from the mill set (MW1), (MW2), (MW3), (MW4) and are connected with two or four burners in the upper (III) or (IV) row, and three dust ducts (12) of the compacted dust-air mixture are led out from devices (6) for dust concentration in the dust-air mixture and separation of the stream into a thickened and diluted mixture, and are connected to three burners (I) or (II) of the row so that the mill (MW1) with three dust lines (12) of the thickened dust mixture is connected to the burners (1) of the first, third, fifth (I) row, and through two dust pipes (11) of the dilute dust-air mixture is connected to the middle burners (1) of the third and fourth (IV) row, mill (MW2) three the dust pipes (12) of the concentrated dust-air mixture are connected to the burners (2) of the second, fourth, sixth row (I), and the dust pipes (11) of the diluted dust-air mixture are connected to the burners (2) of the first, second, fifth, sixth row. (IV) row, a mill (MW3) with three dust pipes The ami (12) of the concentrated dust-air mixture is connected to the burners (3) of the first, third, fifth (II) row, and the four dust pipes (11) of the thinned mixture are connected to the burners (3) of the first, second, fifth, sixth (III) ), the mill (MW4) is connected with three dust-air conduits (12) to the second, fourth, sixth (II) row burners (4), and the two dust conduits (11) of the thin dust-air mixture are connected to the burners ( 4) third, fourth (III) order. 2. The system according to claim The method of claim 1, characterized in that the devices (6) for dust concentration in the dust-air mixture and the separation of the stream into a thickened and diluted dust-air mixture have centrally located on the coal discharge pipe (8) of individual mills of the mill unit (MW1), (MW2) , (MW3), (MW4) cones (7) spreading the stream of the dust-air mixture, and over the cones (7) there are concentrically mounted on the chute pipe (8) through sleeves (9) for the flow of the diluted dust-air mixture and concentrically parallel with them the passage chambers (10) of the compacted dust-air mixture. 3. The system according to p. The method of claim 1, characterized in that two or four dust pipes (11) of the thinned dust-air mixture are led out of the sleeve (9) from the upper part of the devices (6) for dust concentration in the dust-air mixture and separation of the stream into a thickened and diluted mixture from the mill set ( MW1), (MW2), (MW3), (MW4). 4. The system according to p. The method of claim 1, characterized in that the three dust pipes (12) of the compacted dust-air mixture are led out of the passage chambers (10) of the devices (6) for dust concentration in the dust-air mixture for the separation of the stream into a thickened and thin mixture of the mill unit (ΜΛ ¥ 1), (MW2), (MW3), (MW4). 182 263