CN215411846U - Ultralow NOx combustion system of opposed firing boiler - Google Patents
Ultralow NOx combustion system of opposed firing boiler Download PDFInfo
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- CN215411846U CN215411846U CN202120142128.7U CN202120142128U CN215411846U CN 215411846 U CN215411846 U CN 215411846U CN 202120142128 U CN202120142128 U CN 202120142128U CN 215411846 U CN215411846 U CN 215411846U
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Abstract
The utility model discloses an ultra-low NOx combustion system of a hedging combustion boiler, which comprises: the multi-row burners are arranged along the water-cooled wall of the hearth of the boiler at intervals in the vertical direction, and each row of burners comprises a plurality of burners; the first over-fire air nozzles are oppositely arranged on the front water-cooled wall and the rear water-cooled wall of the hearth above the combustor and are communicated with a hot secondary air supply pipeline; and each pair of second overfire air nozzles are oppositely arranged on the front and rear water-cooled walls of the hearth above the first overfire air nozzles and are communicated with the hot primary air supply pipeline. The utility model has the advantages that the overfire air is distributed in a shunting and layering way, so that the mixture is sufficient in the later combustion stage, and the NOx content at the SCR inlet is reduced.
Description
Technical Field
The utility model relates to the field of opposed firing equipment. More particularly, the present invention relates to an ultra-low NOx combustion system for opposed firing boilers.
Background
With the increasing national environmental protection requirements and the increasing emission pressure of thermal power plants, the storage unit is modified to meet the ultra-low NOx emission requirement, and the newly-built unit requires that the NOx at the SCR inlet is lower than 150mg/Nm3(conversion to O)26%) to reduce the operating cost of the SCR. For the better bituminous coals and with tangential firing, it is generally easier to achieve or meet SCR inlet NOx of less than 150mg/Nm3The requirements of (1); however, for opposed firing boilers, the best level at present can only reach 200-250 mg/Nm3According to the current opposed-flow combustion technology, the NOx at the SCR inlet is required to be lower than 150mg/Nm3It is difficult or even impossible. The main reasons are: the opposed firing boiler features good mixing in the early stage of firing and poor mixing in the later stage, which is not favorable for controlling the CO concentration to a lower level, thereby limiting the air classification degree in the height direction, and thus the NOx concentration is higher than that of tangential firing technology.
In a conventional opposed firing mode boiler, a burner is a cyclone burner, a SOFA nozzle adopts a double-wind-zone nozzle with central direct current and outer ring cyclone, the structure is complex, and the resistance is relatively large. The opposed combustion mode boiler is characterized by that the mixing of boiler in the early combustion period is good, and the mixing in the later combustion period is poor. The secondary air and SOFA (over-fire air) of the hedging combustion boiler are both from secondary air, the air speed is about 40m/s, the ratio of the secondary air to tangential combustion is poor in rigidity and penetrating power, and later-period mixing is poor, so that the chemical equivalent of a main combustion area of the hedging combustion boiler cannot be too low, otherwise, the economical efficiency of the boiler is influenced due to the fact that the CO concentration is too high due to poor later-period mixing, and the main reason that the NOx emission concentration of the hedging combustion boiler is higher than that of the tangential combustion boiler is.
Therefore, aiming at the condition of the existing opposed firing boiler, if measures can be taken, the later-stage mixing of the opposed firing boiler is enhanced, the CO concentration at the outlet of the hearth can be effectively controlled, favorable conditions can be created for the depth classification of the main combustion area, the NOx concentration at the SCR inlet of the opposed firing boiler is controlled to the level equivalent to tangential firing, and meanwhile, the boiler can be ensured to have higher efficiency.
SUMMERY OF THE UTILITY MODEL
An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.
It is still another object of the present invention to provide an ultra-low NOx combustion system for opposed firing boilers, which reduces the NOx content at the SCR inlet by distributing the overfire air in a split and layered arrangement to achieve sufficient mixing at the later stage of combustion.
To achieve these objects and other advantages in accordance with the purpose of the utility model, there is provided an ultra low NOx combustion system of a opposed firing boiler, comprising:
the multi-row burners are arranged along the water-cooled wall of the hearth of the boiler at intervals in the vertical direction, and each row of burners comprises a plurality of burners;
the first over-fire air nozzles are oppositely arranged on the front water-cooled wall and the rear water-cooled wall of the hearth above the combustor and are communicated with a hot secondary air supply pipeline;
and each pair of second overfire air nozzles are oppositely arranged on the front and rear water-cooled walls of the hearth above the first overfire air nozzles and are communicated with the hot primary air supply pipeline.
Preferably, the first over-fire air nozzles are located 3.5-7 m above the uppermost layer of the burner, and the second over-fire air nozzles are located 1-4 m below the smoke-folding angle in the hearth.
Preferably, the first over-fire air nozzles are double-air-zone nozzles with central direct current and outer ring rotational flow, the second over-fire air nozzles are direct current nozzles, and the first over-fire air nozzles and the second over-fire air nozzles are arranged in staggered mode.
Preferably, an air volume measuring device and an air volume adjusting device are arranged on the hot secondary air supply pipeline communicated with the first over-fire air nozzle and the hot primary air supply pipeline communicated with the second over-fire air nozzle.
Preferably, the number of rows of the burners is 2-4, and the number of burners in each row is 4-8.
Preferably, the furnace also comprises a plurality of rows of close-wall air nozzles, the plurality of rows of close-wall air nozzles are vertically arranged along the front water wall and the rear water wall of the furnace at intervals, are higher than the lower row of burners and lower than the first over-fire air nozzle, and are communicated with the hot primary air supply pipeline.
Preferably, each row of adherent air nozzles is provided with at least two pairs of adherent air nozzles, the airflow directions of the two pairs of adherent air nozzles respectively face to the left water-cooled wall and the right water-cooled wall of the hearth, and each pair of adherent air nozzles are arranged in a staggered mode in the vertical direction.
Preferably, the furnace further comprises an anti-corrosion spraying layer which is laid on the left water-cooled wall and the right water-cooled wall of the furnace.
The utility model at least comprises the following beneficial effects:
first, overfire air (SOFA) is arranged above the upper burner and divides the overfire air SOFA into two parts: one part of the hot secondary air is led out and arranged on the front wall and the rear wall of the hearth above the upper burner and is a first over-fire air nozzle; the other part of the hot primary air is introduced and arranged on the front wall and the rear wall of the hearth above the first overfire air nozzle and is a second overfire air nozzle, and the second overfire air nozzle is arranged in a shunting and layering way, so that the mixture in the later combustion period can be fully mixed, and the CO concentration at the outlet of the hearth can be controlled to be lower (horizontal), and the NOx content at the inlet of the SCR can be reduced.
Secondly, hot primary air is used as an adherent air source, so that the rigidity of adherent air is increased, the range is farther, the coverage surface is wider, a layer of protective gas film is formed at the position close to the walls of the left and right water-cooled walls, and the high-temperature corrosion of the water-cooled walls at the two sides of the main combustion area can be effectively prevented.
Thirdly, due to the characteristics of the opposed combustion of the front wall and the rear wall of the opposed combustion boiler, the flame scours the left and the right water cooling walls, if unburned coal powder exists in the flame, the flame can be combusted on the left and the right water cooling walls, and thus a strong reducing atmosphere (namely high CO concentration and low O) is formed2Concentration). When the sulfur content in the coal is higher, S in the coal is easy to generate highly corrosive H under the action of reducing atmosphere2S, thereby having adverse effects on the left and right water-cooled wall pipes, forming high-temperature reductive sulfur corrosion, and reducing the left and right water-cooled wall pipesThe problem that the boiler needs to be replaced in a large area is solved, and the safe and economic operation of the boiler is seriously influenced. The anticorrosive spraying layer is laid on the left and right water-cooled walls, so that the protection of the left and right walls of the hearth can be enhanced, and the corrosion is prevented.
Additional advantages, objects, and features of the utility model will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the utility model.
Drawings
FIG. 1 is a schematic side view of the combustion boiler according to one embodiment of the present invention;
FIG. 2 is a layout diagram of a front water wall of a furnace according to one embodiment of the present invention.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the utility model by referring to the description text.
It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials, if not otherwise specified, are commercially available; in the description of the present invention, the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings only for the convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
As shown in fig. 1 to 2, the present invention provides an ultra-low NOx combustion system of a opposed firing boiler, comprising:
the boiler comprises a plurality of rows of burners 3, wherein the plurality of rows of burners 3 are vertically arranged along a water-cooled wall of a hearth 2 of the boiler 1 at intervals, and each row of burners 3 comprises a plurality of burners 3;
at least one pair of first over-fire air nozzles 4, wherein each pair of first over-fire air nozzles 4 is oppositely arranged on the front and rear water-cooled walls of the hearth 2 above the combustor 3 and is communicated with a hot secondary air supply pipeline;
and each pair of second overfire air nozzles 5 is oppositely arranged on the front and rear water-cooled walls of the hearth 2 above the first overfire air nozzles 4 and is communicated with the hot primary air supply pipeline.
In the above technical solution, the overfire air (SOFA) is arranged above the upper burner 3 and divides the overfire air SOFA into two parts: one part of the hot secondary air is induced, the air rate of the hot secondary air can be 17-30%, the hot secondary air is arranged on the front wall and the rear wall of the hearth 2 above the upper-layer combustor 3 and is a first over-fire air nozzle 4(SOFA1, the air rate is selected according to the coal quality characteristics for over-fire, if the over-fire coal quality is used, the air rate is low, and the air of the first over-fire air nozzle 4 is divided into two stages to be arranged, namely SOFA11 and SOFA 12); the other part of the hot primary air is introduced, the air rate of the hot primary air can be 8-15%, the hot primary air is arranged on the front wall and the rear wall of the hearth 2 above the first overfire air nozzle 4 and serves as a second overfire air nozzle 5(SOFA2), and the total air rate of the overfire air is increased to 25-38%. Through the shunting layering arrangement, the combustion later period can be fully mixed, so that the CO concentration at the outlet of the hearth 2 can be controlled to a lower (100ppm) level, the combustion efficiency of the boiler 1 is not reduced while NOx is reduced, and the CO concentration is reduced to a lower (100ppm) level.
In another technical scheme, the first over-fire air nozzles 4 are located 3.5-7 m above the uppermost burner 3, and the second over-fire air nozzles 5 are located 1-4 m below a smoke-folding angle in the hearth 2. The height difference is set, so that the mixture in the later combustion period can be fully mixed, and the concentration of NOx at the outlet of the hearth 2 can be reduced. The burner 3 may be a cyclone burner.
In another technical scheme, the first over-fire air nozzles 4 are double-air-zone nozzles with central direct current and outer ring rotational flow, the second over-fire air nozzles 5 are direct current nozzles, and the first over-fire air nozzles 4 and the second over-fire air nozzles 5 are arranged in a staggered manner. The staggered arrangement can further promote mixing in the later period of combustion to reduce the NOx content at the outlet of the hearth 2.
In another technical scheme, an air quantity measuring device and an air quantity adjusting device are arranged on a hot secondary air supply pipeline communicated with the first over-fire air nozzle 4 and a hot primary air supply pipeline communicated with the second over-fire air nozzle 5. Different air rates can be adjusted according to the coal quality characteristics, so that the coal-fired application range of the opposed firing boiler 1 is enlarged.
In another technical scheme, the rows of the burners 3 are 2-4, and the number of the burners 3 in each row is 4-8. The number of burners 3 described above can substantially satisfy a wide range of coal-fired ranges.
In another technical scheme, the furnace also comprises a plurality of rows of wall-attached air nozzles 6, wherein the wall-attached air nozzles 6 are vertically arranged along the front water wall and the rear water wall of the furnace 2 at intervals, are higher than the lower row of burners 3 and lower than the first over-fire air nozzles 4, and the wall-attached air nozzles 6 are communicated with a hot primary air supply pipeline. Hot primary air is used as an adherent air source, so that the rigidity of adherent air is increased, the range is farther, the coverage surface is wider, a protective gas film is formed at the position close to the walls of the left and right water-cooled walls, and the high-temperature corrosion of the water-cooled walls at the two sides of the main combustion area can be effectively prevented.
In another technical scheme, each row of adherent air nozzles 6 is provided with at least two pairs of adherent air nozzles 6, the airflow directions of the two pairs of adherent air nozzles 6 respectively face to the left water-cooled wall and the right water-cooled wall of the hearth 2, and each pair of adherent air nozzles 6 are arranged in a staggered mode in the vertical direction. The staggered arrangement can increase the airflow protection area of the adherence air nozzle 6, thereby enhancing the air film protection capability.
In another technical scheme, the furnace also comprises an anti-corrosion spraying layer which is laid on the left water-cooled wall and the right water-cooled wall of the hearth 2.
Due to the characteristics of the opposed combustion of the front wall and the rear wall of the opposed combustion boiler 1, flame scours the left and the right water cooling walls, if unburned coal dust exists in the flame, the flame can be combusted on the left and the right water cooling walls, and thus a strong reducing atmosphere (namely high CO concentration and low O) is formed2Concentration). When the sulfur content in the coal is higher, S in the coal is easy to generate highly corrosive H under the action of reducing atmosphere2S, thereby having adverse effect on the left and right water-cooled wall pipes, forming high-temperature reductive sulfur corrosion, causing the problem that the left and right water-cooled wall pipes are seriously thinned and need to be changed in large area, and seriously affecting the safe and economic operation of the boiler 1. An anticorrosive spray coating is arranged on the surface of the substrate, canFurther enhancing the protection of the left and right water-cooled walls of the hearth 2.
While embodiments of the utility model have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the utility model pertains, and further modifications may readily be made by those skilled in the art, it being understood that the utility model is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (8)
1. An ultra-low NOx combustion system for opposed firing boilers, comprising:
the multi-row burners are arranged along the water-cooled wall of the hearth of the boiler at intervals in the vertical direction, and each row of burners comprises a plurality of burners;
the first over-fire air nozzles are oppositely arranged on the front water-cooled wall and the rear water-cooled wall of the hearth above the combustor and are communicated with a hot secondary air supply pipeline;
and each pair of second overfire air nozzles are oppositely arranged on the front and rear water-cooled walls of the hearth above the first overfire air nozzles and are communicated with the hot primary air supply pipeline.
2. The ultra-low NOx combustion system of opposed firing boiler of claim 1, wherein said first overfire air port is located 3.5-7 m above the uppermost burner and said second overfire air port is located 1-4 m below the dog-ear in the furnace.
3. The ultra-low NOx combustion system of opposed-flow fired boiler according to claim 1 wherein said first over-fire air ports are dual-air zone ports with a central straight flow, outer ring swirl flow, said second over-fire air ports are straight flow ports, and said first over-fire air ports are staggered from said second over-fire air ports.
4. The ultra-low NOx combustion system of an opposed firing boiler as set forth in claim 1, wherein an air volume measuring device and an air volume adjusting device are provided on the hot overfire air supply duct communicating with said first overfire air port and on the hot primary air supply duct communicating with said second overfire air port.
5. The ultra-low NOx combustion system of opposed firing boiler of claim 1, wherein the number of rows of burners is 2 to 4, and the number of burners per row is 4 to 8.
6. The ultra-low NOx combustion system of an opposed firing boiler as set forth in claim 1, further comprising a plurality of rows of close-wall air ports vertically spaced along the front and rear water walls of the furnace, and above the lower row of burners and below the first overfire air port, said close-wall air ports communicating with the hot primary air supply duct.
7. The ultra-low NOx combustion system of claim 1, wherein each row of wall-attached air nozzles has at least two pairs of wall-attached air nozzles, the air flow directions of the two pairs of wall-attached air nozzles are respectively towards the left water-cooled wall and the right water-cooled wall of the furnace chamber, and each pair of wall-attached air nozzles are arranged in a vertically staggered manner.
8. The ultra-low NOx combustion system of opposed firing boiler of claim 1, further comprising a corrosion protection coating applied to the left and right waterwalls of the furnace.
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| CN202120142128.7U CN215411846U (en) | 2021-01-19 | 2021-01-19 | Ultralow NOx combustion system of opposed firing boiler |
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| CN202120142128.7U CN215411846U (en) | 2021-01-19 | 2021-01-19 | Ultralow NOx combustion system of opposed firing boiler |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117091143A (en) * | 2023-08-16 | 2023-11-21 | 河北怀燃科技有限公司 | Secondary air supply device and incineration system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117091143A (en) * | 2023-08-16 | 2023-11-21 | 河北怀燃科技有限公司 | Secondary air supply device and incineration system |
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