CN111780095A - Combustion system, control method thereof and preheating equipment - Google Patents
Combustion system, control method thereof and preheating equipment Download PDFInfo
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- CN111780095A CN111780095A CN202010588775.0A CN202010588775A CN111780095A CN 111780095 A CN111780095 A CN 111780095A CN 202010588775 A CN202010588775 A CN 202010588775A CN 111780095 A CN111780095 A CN 111780095A
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- 238000002485 combustion reaction Methods 0.000 title claims abstract description 100
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000000446 fuel Substances 0.000 claims abstract description 89
- 239000004449 solid propellant Substances 0.000 claims abstract description 75
- 239000007787 solid Substances 0.000 claims abstract description 65
- 239000000463 material Substances 0.000 claims abstract description 11
- 239000000571 coke Substances 0.000 claims description 58
- 230000009467 reduction Effects 0.000 claims description 23
- 239000003034 coal gas Substances 0.000 claims description 17
- 230000003647 oxidation Effects 0.000 claims description 9
- 238000007254 oxidation reaction Methods 0.000 claims description 9
- 230000001154 acute effect Effects 0.000 claims description 3
- 239000007789 gas Substances 0.000 description 44
- 239000003245 coal Substances 0.000 description 31
- 238000006722 reduction reaction Methods 0.000 description 23
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000000843 powder Substances 0.000 description 9
- RHZUVFJBSILHOK-UHFFFAOYSA-N anthracen-1-ylmethanolate Chemical compound C1=CC=C2C=C3C(C[O-])=CC=CC3=CC2=C1 RHZUVFJBSILHOK-UHFFFAOYSA-N 0.000 description 7
- 239000003830 anthracite Substances 0.000 description 7
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- MWUXSHHQAYIFBG-UHFFFAOYSA-N Nitric oxide Chemical compound O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 6
- 239000002956 ash Substances 0.000 description 6
- 239000002802 bituminous coal Substances 0.000 description 6
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 229910021529 ammonia Inorganic materials 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 239000002817 coal dust Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000003077 lignite Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000011343 solid material Substances 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000010882 bottom ash Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002309 gasification Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229930195733 hydrocarbon Natural products 0.000 description 1
- 150000002430 hydrocarbons Chemical class 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
- F23C7/02—Disposition of air supply not passing through burner
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C6/00—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion
- F23C6/04—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection
- F23C6/042—Combustion apparatus characterised by the combination of two or more combustion chambers or combustion zones, e.g. for staged combustion in series connection with fuel supply in stages
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C7/00—Combustion apparatus characterised by arrangements for air supply
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
Abstract
The invention relates to a combustion system comprising: the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs; the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part; and the furnace is provided with a solid fuel inlet and a gas fuel inlet, the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction. The invention also relates to a preheating device and a control method of a combustion system.
Description
Technical Field
The embodiment of the invention relates to the field of preheating combustion, in particular to a combustion system and a control method thereof, and preheating equipment.
Background
China is a country with coal as a main energy source, the coal combustion consumption is about 24 hundred million tons every year, and the NOx discharged by coal combustion is largeAn important cause of haze. The NOx emission of the boiler burning the bituminous coal and the lignite is more than 200mg/m3Above, the ultra-low NOx emission level is achieved through a non-selective catalytic reduction (SNCR) and Selective Catalytic Reduction (SCR) combined denitration measure (the SNCR and the SCR are post-combustion removal technologies), and the original NOx emission of the boiler burning anthracite is more than 600mg/m3Above, even by SNCR and SCR combined denitration measures can not reach 50mg/m3The following ultra-low NOx emission levels. In addition, during the combined denitration process of SNCR and SCR, the secondary pollution problem caused by ammonia escape can be brought. Therefore, the great reduction of NOx emission in the pulverized coal combustion process is an important direction and industry requirement for the development of clean coal combustion technology and coal-fired boilers.
The preheating combustion is a mode of preheating coal powder and then combusting the coal powder, the preheating temperature of the coal powder is higher than 800 ℃, and not only fuel modification is realized in the preheating process, but also the nitrogen of the coal is converted into N2Can reach more than 40 percent, and the preheating creates conditions for the efficient combustion and low NOx emission of coal, especially low volatile coal.
However, in the pulverized coal preheating combustion, the preheating fuel enters the hearth completely at one time, which is not beneficial to the efficient reduction of NOx generated by the combustion of the preheating fuel.
Disclosure of Invention
The present invention has been made to mitigate or solve at least one aspect or at least one point of the above-mentioned problems.
In the invention, the strong reducing gas such as high-temperature coal gas can be used for realizing the reduction of NOx, the NOx emission level of the preheating combustion of the coal dust can be greatly reduced, and the ultralow NOx emission of the preheating combustion of the coal dust is favorably realized.
According to an aspect of an embodiment of the present invention, there is provided a combustion system including:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs;
the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part;
and the furnace is provided with a solid fuel inlet and a gas fuel inlet, the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction.
According to another aspect of an embodiment of the present invention, there is provided a control method of the above combustion system, the furnace being provided with a tertiary air inlet between the solid fuel inlet and the gaseous fuel inlet in a height direction, the method including the steps of: the solid fuel and the gas fuel from the second gas-solid separator are combusted in different regions.
According to still another aspect of an embodiment of the present invention, there is provided a preheating apparatus including:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs; and
and the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part.
Drawings
FIG. 1 is a schematic illustration of a combustion system according to an exemplary embodiment of the present disclosure;
FIG. 2 is a schematic diagram illustrating a division of a combustion zone of the combustion system of FIG. 1;
FIG. 3 is a schematic illustration of a combustion system according to another exemplary embodiment of the present disclosure;
FIG. 4 is a schematic illustration of a combustion system according to yet another exemplary embodiment of the invention.
Detailed Description
The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention. In the drawings, the same reference numerals are used to designate the same or similar components.
As shown in fig. 1, a boiler (corresponding to a combustion system) according to an exemplary embodiment of the present invention mainly includes a preheater 1, a gas-solid separator 2, and a furnace 3.
In one embodiment, the preheater 1 is a circulating fluidized bed, and primary air conveys pulverized coal into the preheater, wherein the pulverized coal is preheated to a temperature above 800 ℃. The coal powder is preheated and then converted into a preheating fuel containing high-temperature coal gas and high-temperature coke.
As shown in fig. 1, the preheater 1 includes a preheating chamber 10, the preheating chamber 10 providing a space for preheating fuel, and on the preheating chamber, although not shown, there may be provided: a fuel inlet, provided at the lower part or bottom of the preheating chamber 10, adapted to introduce fuel, such as coal, into the preheating chamber; and the preheating air inlet is arranged at the bottom of the preheating chamber 10 and is suitable for introducing preheating air into the preheating chamber, and the preheating air is used for fluidizing the solid materials in the preheating chamber 10 and providing oxygen required by partial combustion of fuel. The bottom of the preheating chamber 10 can be provided with an air distribution device matched with the preheating air inlet for uniformly introducing preheating air into the preheating chamber.
As shown in fig. 1, the preheater further comprises a first gas-solid separator 12, which may be a cyclone separator, although not shown, may comprise: the upper part of the separator 12 is communicated with the upper part of the preheating chamber 10 and is suitable for separating the high-temperature fuel preheated in the preheating chamber; a central cylinder is arranged on the top plate, and high-temperature fuel (comprising high-temperature coal gas and high-temperature coke) meeting the requirements after preheating leaves the first gas-solid separator 12 from the central cylinder; the lower part of the conical section is provided with a blanking pipe, and the high-temperature solid fuel and bed materials collected by the separator enter the blanking pipe. The barrel section corresponds to the separation chamber of the first gas-solid separator.
As shown in fig. 1, the preheater further comprises a material returning device 13, wherein the material returning device 13 is communicated with the lower part of the feed pipe of the first gas-solid separator 12 and the lower part of the preheating chamber 10 and is suitable for returning the high-temperature solid fuel and the bed material in the feed pipe to the preheating chamber 10.
The gas-solid separator 2 is a second gas-solid separator and comprises an inlet, a gas outlet and a solid outlet. Which may be a cyclone or an inertial separator, may have the same structure as the first gas-solid separator, i.e. with a cyclone and a down pipe 21 (corresponding to the solids outlet) and an upper outlet (corresponding to the gas outlet). The inlet of the first gas-solid separator is communicated with the outlet of the central cylinder of the first gas-solid separator 12, the gas outlet of the second gas-solid separator is communicated with the hearth, and the solid outlet is communicated with the hearth through another position. High-temperature fuel (high-temperature coal gas carrying high-temperature coke) from the central barrel of the first gas-solid separator 12 flows into the gas-solid separator 2, and under the separation action of the second gas-solid separator, solid particles (high-temperature coke) enter a boiler from a separator discharge pipe 21 through a high-temperature solid fuel nozzle for combustion; the gas carries a small portion of coke which is not separated to enter the hearth through an upper outlet 22 at a position different from the position of the high-temperature solid fuel.
As shown in fig. 1, the furnace walls of the furnace comprise shoulders a, which make the cross-sectional area of the lower part of the furnace larger than that of the upper part of the furnace, said shoulders a making an obtuse angle with the vertical direction (in the figure, it is assumed that the furnace walls above the shoulders of the furnace are vertical walls, thus corresponding to the vertical direction), the shoulders a defining together with the other furnace walls the inner space of the furnace; and the high-temperature solid fuel separated by the second separator enters the hearth from the position of the shoulder, and the shoulder is provided with a high-temperature solid fuel nozzle. The hot gas fuel nozzles 22 are arranged on the vertical wall of the furnace. Over the high temperature gas fuel nozzle 22, an over-fire air 33 is also provided.
The space of the hearth is divided into a lower space and an upper space by a horizontal plane at the intersection of the shoulder A of the hearth and the vertical wall surface of the hearth. More specifically, the front wall and the rear wall at the lower part of the hearth 3 are inclined outwards (the inclined part forms a shoulder A) compared with the upper part, the space at the lower part of the hearth is large, the hearth 3 comprises an even secondary air distribution device 31 positioned at the bottom of the hearth, secondary air is evenly supplied from the bottom of the hearth, preheating fuel is sprayed into the hearth from the shoulder part in an inclined way downwards and then undergoes a combustion reaction with the secondary air from the bottom of the hearth, slag blocks formed in the combustion process of high-temperature coke at the bottom of the hearth can be discharged from the bottom of a boiler, tertiary air is sprayed from the adjacent part of the space at the lower part of the hearth and the space at the. Controlling the amount of the secondary air to ensure that a region (positioned in the lower space of the hearth) between the secondary air and the tertiary air nozzle 32 is a high-temperature coke reduction region, and burning the high-temperature coke in a reducing atmosphere; the area between the tertiary air nozzle 32 and the high-temperature gas fuel nozzle 22 (in the upper space of the hearth) is an oxidation area of high-temperature coke, the area between the high-temperature gas fuel nozzle 22 and the over-fire air 33 is a high-temperature coal gas reduction area, and the over-fire air 33 is an over-fire area. The above high temperature coke reducing zone, high temperature coke oxidizing zone, high temperature gas reducing zone and burnout zone are exemplarily shown in fig. 2.
Therefore, in the embodiment shown in fig. 1, the high-temperature gas-solid mixed fuel containing high-temperature coal gas and high-temperature coke generated after the pulverized coal is preheated is not directly injected into the furnace chamber, but the combustion of the high-temperature coke and the high-temperature coal gas is realized by the gas-solid separator 2, so that the combustion of the furnace chamber can be divided into four control areas of a high-temperature coke reduction area, a high-temperature coke oxidation area, a high-temperature coal gas reduction area and a burnout area.
The following illustrates the specific operation and principles of the embodiment of fig. 1.
The primary air conveys the pulverized coal into the preheater 1, the preheater can be a circulating fluidized bed, the primary air quantity accounts for 15-30% of the theoretical combustion air quantity of the pulverized coal, namely the air-fuel equivalent ratio of the primary air is 0.15-0.30, the circulating fluidized bed can be of a heat insulation type, and can also be internally provided with a water-cooling heating surface, the preheating temperature of the pulverized coal is 800-. During the preheating process of the bituminous coal powder in the preheater, the separated volatile components, part of coke and the like are subjected to combustion and gasification reaction with primary air, so that the heat balance is maintained, meanwhile, the volatile components and part of the coke are converted into high-temperature coal gas, and solid materials which do not react with the primary air are converted into high-temperature coke. After the coal powder is preheated by the circulating fluidized bed, the inner holes of the coke become rich, the activity is enhanced, the combustion and the burnout of the coke are facilitated, and partial steam can be introduced into the preheater to play a coke activation effect in order to promote the modification effect of the coke. During the preheating process of the coal powder in the circulating fluidized bed, the bed is in strong reducing atmosphere, and the coal nitrogen separated out during the preheating process is easy to be converted into N2Conversion occurs, which creates conditions for ultra-low NOx emissions from coal combustion.
After the preheated fuel enters the separator 2, gas-solid separation can be realized, solid namely high-temperature coke flows into the lower part of the boiler hearth, and the high-temperature coke is ignited because the temperature of the high-temperature coke exceeds 800 ℃, so that the high-temperature coke is sprayed into the hearth and meets secondary air uniformly flowing from the bottom of the hearth to generate space combustion reaction. The secondary air at the bottom of the hearth plays a role in supporting combustion and supporting bottom air, so that pulverized coal particles are prevented from directly rushing into an ash bucket area at the lowest part of the hearth, and the combustion loss is reduced.
The area between the secondary air and the tertiary air at the lower part of the hearth is a high-temperature coke reducing area, because the high-temperature coke and the secondary air are fully mixed, the local oxygen concentration is low, the temperature of the reducing area is high, the temperature of the reducing area can be controlled below an ash melting point, such as 1200 ℃, so that the slagging and contamination tendency of ash can be reduced, the stable operation of a boiler is facilitated, and on the other hand, under the temperature range, especially when the temperature of the hearth is higher than 1000 ℃, the reduction reaction of the coke and the nitrogen oxide has a high speed, the nitrogen oxide can be effectively reduced, and meanwhile, the generation of thermal NOx can be better avoided.
The area between the tertiary air nozzle 32 and the hot gas fuel nozzle 22 is a hot coke oxidation area where the hot coke is burned out, and the combustion temperature is 1100 ℃, for example, because most of the N in the hot coke is precipitated in the reduction area and the conversion to N occurs2In the oxidation zone, the content of N in the high-temperature coke is low, N in the coke is separated from the surface, a part of the N is converted into NOx, and a part of the N is converted into N2。
NOx formed by N in the high-temperature coke upwards enters the high-temperature coal gas reduction zone along with the gas flow again, and the high-temperature gas fuel contains CH4、H2And CO, and NOx formed from high-temperature coke is easily reduced to N2Conversion, at the same time, of part of HCN and NH in the gas3Etc. also undergo reduction reactions.
Finally, the gas of the high-temperature solid fuel and the high-temperature gas fuel enters a burnout zone, and unreacted gas or a small part of coke particles are mixed with over-fire air and are burnt out.
The gas-solid separator 2 is arranged at the outlet of the preheater, so that the layered and zoned combustion of the high-temperature coke and the high-temperature coal gas is realized, the combustion reaction time of the high-temperature coke is effectively prolonged, and different control methods aiming at the migration and conversion of coke nitrogen, volatile nitrogen and the like are realized, namely, the coke nitrogen is mainly subjected to out-of-phase reduction with the coke after being separated out at the lower part of the hearth, and the volatile nitrogen is subjected to reduction reaction with generated NOx and reduction reaction of hydrocarbon gas or CO in a high-temperature coal gas reduction zone. In the process of preheating and burning the pulverized coal, the burning temperature can be controlled to be lower than the ash melting point, the slagging and corrosion tendency of a hearth is reduced, and the stable and safe operation of a boiler is facilitated.
In a more specific exemplary embodiment, primary air carries bituminous coal into the preheater, the equivalence ratio of the primary air is 0.2-0.3, the working temperature of the preheater is 800-900 ℃, the outflow speed of preheated fuel from a nozzle is 20-30m/s, and the preheated fuel flows into the gas-solid separator 2 to realize the separation of high-temperature coal gas and high-temperature coke. The high-temperature coke is sprayed into the high-temperature coke reduction zone from the lower part at the speed of 3-8m/s, and the high-temperature coal gas is sprayed into the upper part of the hearth at the speed of 20-35 m/s. The equivalent ratio of secondary air is 0.3-0.5, the average temperature of high-temperature coke combustion is 1100 ℃, the equivalent ratio of tertiary air is 0.2-0.4, the equivalent ratio of overfire air is 0.1-0.3, and the NOx emission of the preheating combustion of bituminous coal powder is about 30-50mg/m3。
In another more specific exemplary embodiment, the primary air carries the anthracite coal into the preheater, the primary air equivalence ratio is 0.1-0.2, the working temperature of the preheater is 900-. The high-temperature coke is sprayed into the high-temperature coke reduction zone from the lower part at the speed of 3-8m/s, and the high-temperature coal gas is sprayed into the upper part of the hearth at the speed of 20-35 m/s. The equivalent ratio of secondary air is 0.3-0.5, the average temperature of high-temperature coke combustion is 1100 ℃, the equivalent ratio of tertiary air is 0.2-0.4, the equivalent ratio of overfire air is 0.1-0.3, and the NOx emission of the preheated and combusted anthracite powder is about 50-80mg/m3。
In the structure shown in fig. 1-2 and subsequently mentioned fig. 3 and 4, the overfire air supplies the overfire air from the bottom of the furnace in a vertically upward direction, which is both combustion air and bottom supporting air, so that the risk of the preheated fuel or solid fuel directly rushing into the bottom ash hopper area can be reduced.
In an alternative embodiment, although not shown, overfire air ports may also be provided in the inclined side walls of the lower portion of the furnace as shown in FIGS. 1-4, to provide overfire air in an obliquely upward direction. In a further alternative embodiment, the angle formed between the outlet direction of the secondary air port and the direction of the solid fuel entering the furnace is an acute angle larger than 30 degrees.
Further, in an alternative embodiment, although not shown, the direction in which the overfire air is also provided by the overfire air ports is not limited to being obliquely upward, but may be substantially horizontal as long as it facilitates the lifting of the solid fuel.
In fig. 1-2, the lower portion of the firebox is enlarged by the presence of the shoulder a, but the present invention is not limited thereto. FIG. 3 is a schematic view of a combustion system in accordance with another exemplary embodiment of the invention, wherein the overall cross-sectional shape of the furnace combustion zone above the preheating fuel jets may be maintained constant. As will be appreciated by those skilled in the art, the term "substantially unchanged" is also intended to include substantially unchanged cases.
As shown in fig. 3, the furnace is provided with a fuel inlet channel B which communicates with the hot solid fuel nozzle, and as shown in fig. 3, the fuel inlet channel extends obliquely downward, and the solid fuel outlet of the second separator 2 communicates with the fuel inlet channel a.
As shown in fig. 3, the fuel inlet passage B includes an end portion B1, the end face of which is at an obtuse angle with respect to the vertical direction, and the solid fuel outlet of the second separator 2 communicates with the fuel inlet passage B at the end face.
In fig. 1-3, two sets of preheating devices and second separators are provided at opposite furnace vertical walls of the furnace, but the present invention is not limited thereto, and it is also possible to provide one set of preheating devices and one second separator at only one furnace vertical wall of the furnace, as shown in fig. 4.
In the invention, the high-temperature gas-solid mixed fuel containing high-temperature gas (namely high-temperature gas fuel) and high-temperature coke (namely high-temperature solid fuel) generated after the pulverized coal is preheated realizes the separation of the high-temperature gas and the high-temperature coke by a gas-solid separator, the high-temperature coke enters from the lower part of a hearth, the high-temperature gas enters from the upper part of the hearth, and a combustion area of the hearth can be divided into the reducing and oxidizing alternating atmosphere of a high-temperature coke reduction area, a high-temperature coke oxidation area, a high-temperature gas reduction area and a burnout area, thereby realizing the subarea control of the high-temperature coke combustion and the high-temperature gas combustion and achieving the effect of.
By adopting the scheme of the invention, the pulverized coal preheating combustion ultra-low NOx boiler can be realized, and the low (ultra-low) NOx emission of bituminous coal, lignite and anthracite can be realized. For example, the raw NOx emissions from bituminous coal combustion may be less than 50mg/m3And an ammonia spraying facility is not needed any more, secondary pollution caused by ammonia escape is reduced, the technical problem of secondary treatment of the catalyst is solved, and economic and environmental benefits are improved. As another example, the initial NOx emissions for anthracite combustion may be less than 100mg/m3Or directly reaches 50mg/m3In the following, by combining SNCR measures, the ultralow NOx emission of anthracite combustion can be realized, and the technical problem that the ultralow NOx emission cannot be met by anthracite combustion is solved.
By adopting the scheme of the invention, the combustion temperature of the pulverized coal can be lower than the ash melting point, the risk of slag bonding of the boiler is reduced, and the safe and stable operation is facilitated.
By adopting the scheme of the invention, the secondary air at the bottom of the boiler hearth is combustion-supporting air and also serves as bottom supporting air, so that the risk that preheated fuel directly rushes into the ash bucket area at the bottom of the boiler is reduced, and volume combustion of high-temperature coke at the bottom of the hearth is realized through uniform arrangement of the secondary air.
In the present invention, the structure formed by the preheating device and the second separator may form a preheating apparatus, which is not limited to be used in the preheating system or the boiler combustion system shown in fig. 1 to 4, but may be used alone or together with other devices than the pulverized coal boiler.
It is to be noted that, in the present invention, each numerical range, except when explicitly indicated as not including the end points, can be either the end points or the median of each numerical range, and all fall within the scope of the present invention.
Based on the above, the invention provides the following technical scheme:
1. a combustion system, comprising:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs;
the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part;
and the furnace is provided with a solid fuel inlet and a gas fuel inlet, the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction.
2. The combustion system of claim 1, wherein:
the hearth is provided with a secondary air inlet, and the secondary air inlet is lower than the solid fuel inlet in the height direction.
3. The combustion system of claim 2, wherein:
the secondary air from the secondary air inlet is vertical secondary air; or
The secondary air from the secondary air inlet is transverse or obliquely upward secondary air.
4. The combustion system of claim 2, wherein:
the secondary air inlet is arranged on the inclined side wall of the lower part of the hearth, and an acute angle of more than 30 degrees is formed between the air outlet direction of the secondary air inlet and the direction of the solid fuel entering the hearth.
5. The combustion system of any of claims 1-4, wherein:
the hearth is provided with a tertiary air inlet, and the tertiary air inlet is positioned between the solid fuel inlet and the gas fuel inlet in the height direction.
6. The combustion system of any one of claims 1-5, wherein:
the hearth is provided with an overfire air inlet which is higher than a gas fuel inlet.
7. The combustion system of claim 1, wherein:
the first gas-solid separator and the second gas-solid separator are cyclone separators.
8. The combustion system of claim 1, wherein:
and the two opposite furnace walls of the furnace are respectively provided with a preheating device and a second gas-solid separator.
9. The combustion system of claim 1, wherein:
the fuel solid is coke generated by the preheating device, and the gas fuel is coal gas generated by the preheating device.
10. The combustion system of any one of claims 1-9, wherein:
the hearth wall of the hearth comprises a shoulder, the shoulder forms an obtuse angle with the outside in the vertical direction of 90-180 degrees, and the shoulder defines a part of the inner space of the hearth; and is
The solid fuel inlet is disposed at the shoulder.
11. The combustion system of any one of claims 1-9, wherein:
the hearth is provided with a fuel inlet channel, the fuel inlet channel is communicated with the solid fuel inlet, the fuel inlet channel extends obliquely downwards, and the solid fuel outlet is communicated with the fuel inlet channel.
12. The combustion system of claim 11, wherein:
the fuel inlet channel comprises an end part, the end face of the end part and the outer included angle in the vertical direction are obtuse angles between 90 degrees and 180 degrees, and the solid fuel outlet is communicated with the fuel inlet channel through the end face.
13. The combustion system of claim 12, wherein:
the overall cross-sectional shape of the hearth with the solid fuel inlet upward remains unchanged.
14. A control method of a combustion system according to claim 5, the method comprising the steps of:
the solid fuel and the gas fuel from the second gas-solid separator are combusted in different regions.
15. According to the method of 14, the combustion system is the combustion system according to 5, primary air and solid fuel are introduced into the preheating chamber, the hearth is provided with a secondary air inlet, a tertiary air inlet and an over-fire air inlet, and the method comprises the following steps:
make the combustion area in the furnace be solid fuel reduction zone, solid fuel oxidation zone, gaseous fuel reduction zone, burn out zone in proper order in the direction of height, wherein: a solid fuel reduction area is arranged between the secondary air inlet and the tertiary air inlet, a solid fuel oxidation area is arranged between the tertiary air inlet and the gas fuel inlet, a gas fuel reduction area is arranged between the gas fuel inlet and the overfire air inlet, and the overfire area is arranged above the overfire air inlet.
16. The method of claim 15, wherein:
the air volume of the primary air accounts for 15-30% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the air volume of the secondary air accounts for 25-70% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the air volume of the tertiary air accounts for 20-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, and the air volume of the over-fire air accounts for 10-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber.
17. A preheating apparatus comprising:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs;
and the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part.
Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments and combinations of elements without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
Claims (17)
1. A combustion system, comprising:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs;
the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part;
and the furnace is provided with a solid fuel inlet and a gas fuel inlet, the solid fuel outlet is communicated with the solid fuel inlet, the gas fuel outlet is communicated with the gas fuel inlet, and the gas fuel inlet is higher than the solid fuel inlet in the height direction.
2. The combustion system of claim 1, wherein:
the hearth is provided with a secondary air inlet, and the secondary air inlet is lower than the solid fuel inlet in the height direction.
3. The combustion system of claim 2, wherein:
the secondary air from the secondary air inlet is vertical secondary air; or
The secondary air from the secondary air inlet is transverse or obliquely upward secondary air.
4. The combustion system of claim 2, wherein:
the secondary air inlet is arranged on the inclined side wall of the lower part of the hearth, and an acute angle of more than 30 degrees is formed between the air outlet direction of the secondary air inlet and the direction of the solid fuel entering the hearth.
5. The combustion system of any of claims 1-4, wherein:
the hearth is provided with a tertiary air inlet, and the tertiary air inlet is positioned between the solid fuel inlet and the gas fuel inlet in the height direction.
6. The combustion system of any of claims 1-5, wherein:
the hearth is provided with an overfire air inlet which is higher than a gas fuel inlet.
7. The combustion system of claim 1, wherein:
the first gas-solid separator and the second gas-solid separator are cyclone separators.
8. The combustion system of claim 1, wherein:
and the two opposite furnace walls of the furnace are respectively provided with a preheating device and a second gas-solid separator.
9. The combustion system of claim 1, wherein:
the fuel solid is coke generated by the preheating device, and the gas fuel is coal gas generated by the preheating device.
10. The combustion system of any of claims 1-9, wherein:
the hearth wall of the hearth comprises a shoulder, an included angle between the shoulder and the outer part of the vertical direction is an obtuse angle, and the shoulder limits one part of the inner space of the hearth; and is
The solid fuel inlet is disposed at the shoulder.
11. The combustion system of any of claims 1-9, wherein:
the hearth is provided with a fuel inlet channel, the fuel inlet channel is communicated with the solid fuel inlet, the fuel inlet channel extends obliquely downwards, and the solid fuel outlet is communicated with the fuel inlet channel.
12. The combustion system of claim 11, wherein:
the fuel inlet channel comprises an end part, the end face of the end part and the outer included angle in the vertical direction are obtuse angles, and the solid fuel outlet is communicated with the fuel inlet channel through the end face.
13. The combustion system of claim 12, wherein:
the overall cross-sectional shape of the hearth with the solid fuel inlet upward remains unchanged.
14. A control method of a combustion system according to claim 5, the method comprising the steps of:
the solid fuel and the gas fuel from the second gas-solid separator are combusted in different regions.
15. The method as claimed in claim 14, wherein the combustion system is a combustion system as claimed in claim 5, the preheating chamber is filled with primary air and solid fuel, and the furnace chamber is provided with a secondary air inlet, a tertiary air inlet and an over-fire air inlet, and the method comprises the following steps:
make the combustion area in the furnace be solid fuel reduction zone, solid fuel oxidation zone, gaseous fuel reduction zone, burn out zone in proper order in the direction of height, wherein: a solid fuel reduction area is arranged between the secondary air inlet and the tertiary air inlet, a solid fuel oxidation area is arranged between the tertiary air inlet and the gas fuel inlet, a gas fuel reduction area is arranged between the gas fuel inlet and the overfire air inlet, and the overfire area is arranged above the overfire air inlet.
16. The method of claim 15, wherein:
the air volume of the primary air accounts for 15-30% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the air volume of the secondary air accounts for 25-70% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, the air volume of the tertiary air accounts for 20-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber, and the air volume of the over-fire air accounts for 10-40% of the theoretical combustion air volume of the solid fuel entering the preheating chamber.
17. A preheating apparatus comprising:
the preheating device comprises a preheating chamber, a first gas-solid separator and a material returning device which are communicated in pairs;
and the upper outlet of the first gas-solid separator is communicated with the inlet of the second gas-solid separator, and the second gas-solid separator is provided with a gas fuel outlet positioned at the upper part and a solid fuel outlet positioned at the lower part.
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