CN203323116U - Low nitrogen oxide direct-flow pulverized coal combustion device suitable for lean coal-fired boiler - Google Patents

Abstract

The utility model relates to a low nitrogen oxide direct-flow pulverized coal combustion device suitable for a lean coal-fired boiler, which can realize stable and efficient combustion, enable nitrogen oxide emission to be on low level and promote low-nitrogen combustion transformation technology of the lean coal-fired boiler. The combustion device comprises main burner groups which are distributed at the four corners of a lean coal-fired boiler furnace in a quadrangularly tangential firing mode, have the same structures and are matched with a high-temperature corrosion resisting water wall system of the boiler furnace; each main burner group comprises pulverized coal burners and secondary air nozzles, which are arranged at intervals, an over-fire air separation unit is arranged at the upper part of each main burner group correspondingly, a layer of precombustion chamber backflow burners are arranged at the interval of n layers of the pulverized coal burners, the jet flow rotating direction of each main burner group is counter-clockwise, and the rotating direction of jet flows at the secondary air port next to the upper part of the precombustion chamber backflow burner is clockwise; furthermore, the hypothetical tangent circle diameter of the secondary air port is more than that of the main burner; the over-fire air separation unit is divided into an upper unit and a lower unit, wherein the jet flow of the lower unit is in a large hypothetical tangent circle mode, and the upper unit is in an opposed firing mode.

Description

A kind of low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler

Technical field

The utility model relates to a kind of direct-flow pulverized coal combustion device, relates in particular to a kind of low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler.

Background technology

Nitrogen oxide (NOx) is a kind of being detrimental to health, and destroys the pollutant of atmospheric environment.Wherein coal-fired power plant is topmost emission source, account for 67% of NOx discharge capacity, and along with increasing proportion, the fired power generating unit installed capacity can increase, for controlling the NOx pollutant emission level of China's coal fired thermal power plant, the more strict fossil-fuel power plant atmospheric pollutant emission standard that country promulgates in succession, more strict discharged nitrous oxides level has been proposed, and do not remake various criterion for coal, that is to say no matter be bituminous coal fired boiler or meager coal, or even anthracite-fired boiler all will be carried out unified discharge standard, and the pulverized-coal fired boiler that China went into operation before 2004 has adopted relatively backward low nitrogen burning technology abroad, discharged nitrous oxides concentration is higher, in these boilers, adopt the boiler of the direct-flow pulverized coal combustion mode of tangential firing to be in the great majority, boiler capacity is with 135MW, 300MW and 600MW are main, the NOx concentration of emission of these boilers is higher, wherein bituminous coal fired boiler NOx concentration of emission is at 500-800mg/Nm ³, Lean Coal-fired Boiler is at 650-1100mg/Nm ³the NOx concentration of emission of anthracite-fired boiler is higher, the discharged nitrous oxides concentration of these boilers is far above the emission request of " fossil-fuel power plant atmospheric pollutant emission standard " nitrogen oxide of the new promulgation of national environmental protection section, in order to respond national environmental standard, and consider technological transformation cost and operating cost, it is burner reconstruction low NO that current thermal power plant mostly adopts first, then in flue, adopts selective catalytic reduction (SCR) to carry out flue-gas denitrification.Carry out at present the #1-#4 boiler of the low nitrogen burning transformation of a large amount of fired power generating unit as the Pump of Zhou County Power Plant ' of magnificent electric group both at home and abroad, the #3 of Zhangqiu power plant, the #4 boiler, the #4 of the Laiwu power plant of Huaneng Group group and #5 boiler, the #1 of Peng Lai power plant and the #2 boiler of state electricity group, the #7 of Zhangjiakou power plant boiler of Datang group etc., these boilers are all the direct current pulverized-coal fired boilers of tangential firing, in these transformation cases, correctional effect is all bituminous coal or boiler using brown coal preferably, the Lean Coal-fired Boiler correctional effect is all undesirable, #3 stove as China certain power plant of electricity, subcritical boiler for 1000t/h, fire coal is meager coal, pulverized coal preparation system is that Ball Mill is direct-firing, after carrying out the low nitrogen burning transformation, when using meager coal, the concentration of emission of NOx is 534mg/Nm ³the time, boiler flyash carbon content is 8.8%, and boiler efficiency is only 85.5%, and after mixing deified coal (deifying coal is high-volatile bituminous coal), the concentration of emission of NOx will be 410mg/Nm ³, boiler flyash carbon content reduces to 3.5%, the #2 of power plant of magnificent electric group stove and for example, the superpressure boiler that boiler is 435t/h, fire coal is meager coal, pulverized coal preparation system is storage formula in Ball Mill, after carrying out the low nitrogen burning transformation, also occur that the NOx concentration of emission is high, unburned carbon in flue dust raises, the situation of putting out a fire several times, appear in low-load combustion-stabilizing characteristic variation when 75%BMCR (maximum continuous rating of Boiler Maximum Continuous Load boiler).By comprehensive investigation, find, at present domestic and international low nitrogen burning is transformed comparatively successful story and is all carried out on bituminous coal or boiler using brown coal, successful experience without comparison also on Lean Coal-fired Boiler, this is because the coal characteristic of meager coal has been compared relatively big difference with bituminous coal, and Lean Coal-fired Boiler also has larger difference on structural design, therefore some are applicable to the low nitrogen modification Experience of bituminous coal fired boiler and can not be adapted to Lean Coal-fired Boiler fully, through many Lean Coal-fired Boilers that carry out the low nitrogen burning transformation are analyzed to discovery, all exist the NOx concentration of emission to descend few, unburned carbon in flue dust raises and causes the boiler economy to reduce, high temperature corrosion appears in water-cooling wall, the problem that the low-load combustion-stabilizing effect reduces.

Due to the understanding of the basic principle of the mechanism of production of nitrogen oxide and low nitrogen burning technology comparative maturity all at present, by literature search, find, document about the low nitrogen burning technical elements mainly concentrates on this two aspects at present, be based on the one hand introduction or the numerical computations of the various low nitrogen burning technology of low nitrogen burning know-why aspect, Hua Qing how, Zhu Yue, Pan Zhiqiang etc., " Summary of Low NOx Combustion Technology " " boiler manufacture " 2000 (4): 34-38; Liu Zhichao. the experiment of coal-fired boiler NOx discharge concentration affects factor and analysis [J]. electric power station system engineering, 2005,21 (5): 30-34; Vasquez E, Sears R " Combustion control techniques achieve0.15lb/BBBtu NOx without SCR " " Power Engineering ", 2003,107 (1): 39-42; Wang Chunlin, Zhou Hao, " the low NOx combustion optimization based on genetic algorithm and SVMs " " Proceedings of the CSEE " 2007 (11): 40-44; Song Yaqiang, " the numerical experimentation research of pulverized-coal fired boiler low NOx combusting technology " Southeast China University's Master's thesis, 2005; Above these documents belong to be introduced the low nitrogen burning technology or adopts some low nitrogen burning technology of method validation of numerical simulation not relate to a certain concrete low NO, especially is not designed into the low NO that is adapted to meager coal and how when guaranteeing the boiler low nitrogen burning, prevents and treats high temperature corrosion etc.That the application document of low NO is as Liu Wen, " application of low nitrogen burning technology on the 420t/h of Wang Long power plant coal-burning boiler " " boiler manufacture ", 2011,7 (4): 26-29 on the other hand; Yu Qingming, Zhang Bo, Zhu Xianran etc. " low NO transformation and operation method of adjustment are inquired into " " North China power technology " 2012 (7) 35-38; Xiao Yanhua, Chenfeng, " the low nitrogen burning technology is in the practical application of Rui Ming power plant " " energy project " 2008 (1): 55-59 etc.The described successful case of these documents is all carried out on bituminous coal fired boiler, in poor flammability coal, as meager coal, anthracite etc., does not substantially have.Nie Qihong, Sun Shaozeng, Wu Shaohua etc., " application study of the deep or light low-NOx pulverized coal burner of Novel horizontal on Lean Coal-fired Boiler ", " Proceedings of the CSEE ", 2002,22 (7): 155-159, at this piece of Introduction of Literatures the early stage application of flap type shade type low NO on the 300MW Lean Coal-fired Boiler: the minimum concentration of emission of NOx is 631mg/m ³In the situation that the stable minimum steady load that fires of oil of not throwing of ature of coal is for 140MW, the steady combustion characteristic that can find out this burner is better, but the NOx concentration of emission is too high, do not met new national environmental standard, and the high temperature corrosion situation of Lean Coal-fired Boiler is more serious, do not clearly state the effective measures of control high temperature corrosion in document yet.

The patent that finds that there is correlation by patent retrieval is as follows:

Patent 89109301.X reduces combustion method and the device thereof of formation of nitrogen oxides, the basic principle of this device is that the air that the gas by introducing flue gas or other reproducibilities is sneaked into burning use reduces the oxygen amount in combustion air, and then reduces combustion zone and generate nitrogen oxide.This method is applicable to small-sized burner and is not suitable for large-sized station boiler, because the burning of large-sized boiler needs large quantity of air, thereby the exhaust gas volumn extracted is also very large, the normal operation of the heat transmission equipment of extraction point back will be had a strong impact on, and contain a large amount of dusts and corrosive gas in flue gas, and need to consider dedusting and anticorrosion when extracting flue gas, the flue gas of also mentioning extraction in Patent right requirement is cooling, this part heat can not utilize, and can reduce boiler efficiency again.

The burner of patent 95224587.6 strengthening coal dust firings and reduction nitrogen oxide, the ejector action that this patent utilization adds a high-speed jet (velocity ratio V1/V2=0-17) generation in a wind makes the spout coal dust produce concentrated phase and dilute phase, this patent is because flow type pump with injection can entrainment the exchange that high-temperature flue gas is strengthened caloic and heat, for strengthening coal dust firing, be favourable, effect not explanation in patent as for the concentrated phase produced and dilute phase, and only depending on the deep or light low oxygen combustion that do not adopt, the effect that reduces nitrogen oxide can be not clearly.A bit that this patent is implementing larger difficulty in addition, install wear-resisting and resistant to elevated temperatures induction tunnel difficulty additional larger in a wind snout, adopt in addition any medium to be difficult to select as flow type pump with injection, and flow type pump with injection is difficult to realize higher velocity ratio, at the normal primary air velocity in service of boiler at 20-28m/s, even the velocity ratio of 5 times, the flow velocity of flow type pump with injection is also wanted 100-140m/s, produce such flow type pump with injection and acquire a certain degree of difficulty in power plant, so also do not have so far the data introduction to adopt the burner of this technology in station boiler.

200510047662.5 1 kinds of combustion technology for removing low NOx by using superfine powdered coal in re-combustion zone of patent, this patent principle is exactly to utilize the combustion again of microfine coal to form reduced zone, and the NOx that the territory, primary zone is generated is reduced into N ₂This method is mainly carried out at present in laboratory, for large-sized station boiler, be difficult to realize, at first be that superfine powdered coal is difficult to obtain, no matter that newly go into operation unit or retrofitted unit will obtain superfine powdered coal and must set up new production device for superfine pulverized coal, and the explosion proof ratings of production device for superfine pulverized coal is higher, the input of power plant is larger; Another reason needs special microfine coal spout, also needs other input; This patent is only mentioned the microfine coal fineness of bituminous coal in the claims, and other coals are not related to.

The combustion method of 200610090797.4 1 kinds of low-nitrogen oxide dischargings of patent, its principle is to utilize the Secondary Air of the high-temperature oxygen-enriched flue gas of recirculating fluidized bed as pulverized-coal fired boiler, and coal dust is burnt in the environment of high-temperature low-oxygen, reduces the generation of NOx.This method is difficult to realize for the power plant that there is no CFBB, for the power plant that CFBB is arranged, to adopt this method difficulty quite large, reason is that the exhaust gas volumn of large-sized boiler needs is large, and to consider high temperature, the problem such as in flue gas dust burdening is large, the input of equipment, design and construction is huge.

The oxygen-enriched combusting method of 200610123491.4 1 kinds of discharged nitrous oxides of patent, its principle is to utilize the carrier of oxygen volume concentrations to be less than 30% oxidant and fuel injects and forms flow type pump with injection from the coaxial sleeve tube burner noz(zle), reduces the generation of NOx by the speed difference of adjusting fuel and flow type pump with injection.At first this method will increase the equipment of the oxidant that the volumetric concentration that produces oxygen is 30%, but also needs dynamic equipment to make oxidant accelerate to certain speed, and equipment is comparatively complicated and explosion precaution will be arranged; This patent also requirement will be adjusted the generation that effluxvelocity reduces NOx, because each burner will be adjusted at any time, concerning the operations staff, the workload of operation is larger, the person, due to the primary air velocity of each burner, difference is arranged, and make the effluxvelocity adjusted design for automatically adjusting also more difficult realization; A bit that flame temperature is higher, the easy coking in combustion chamber due to jet and the at first oxygen-enriched combusting in combustion chamber that burns in addition.

The low nitrogen DC burner of the two classifications of patent 200620079010.X, its basic principle is separated to wind of part in overfire air port and forms two strands of coal dusts, reaches the fuel-staged combustion mode.Coal powder direct supplying burner independently, and is the high-abrasive material that wall is thicker, a part of coal dust be assigned in Secondary Air, and coal burner and Secondary Air air channel all will produce larger variation, manufactures and designs or construct all to be difficult to realize; Also have the wind-warm syndrome of Secondary Air up to arriving 350-400 ℃ and also fluctuation at any time of secondary wind pressure, coal dust is sneaked into to rear whole hot secondary air duct explosion danger.

200710071816.3 1 kinds of methods for the coal-burning boiler low nitrogen oxide burning of patent, this patent be also utilize the refinement coal dust fire again the discharge that principle reduces nitrogen oxide, proposed that the refinement coal dust is thinner and the ratio refinement coal dust is larger.This patent realize difficulty the same with patent 200510047662.5 no longer the narration.

200810085042.4 1 kinds of methods that adopt the pulverized-coal fired boiler reduction nitrogen oxide of internal combustion burner of patent, the principle of this patent is by plasma igniter or minim oil lighter, coal dust to be lighted in precombustion chamber, and then by reducing the generation of the excess air coefficient minimizing NOx in primary zone, its essence of this method still realizes reducing the generation of NOx by the oxygen amount that reduces primary zone, can save fuel oil at this internal combustion burner of several power plant application note aspect ignition of the boiler, and can play steady combustion effect when underload, but the easy coking of spout, scaling loss, if do not install additional and separate the after-flame wind snout for this burner upper furnace zone, DeGrain aspect reduction NOx, also have and easily to cause high temperature corrosion the wall-cooling surface reducibility gas of main combustion zone is more.

Patent 200810240478.6 and 200820233871.8 low nitrogen combustion apparatus and method, its principle is adopt pre-burning cell-type burner and install igniter additional, and then main combustion zone carries out anoxycausis, in upper boiler, introduces and separates after-flame wind and realize low nitrogen burning.The coking, the scaling loss that also very easily cause the coal dust spout of this patent, and produce high temperature corrosion at the wall-cooling surface that makes primary zone.

200910054141.0 1 kinds of low-nitrogen oxide discharging coal powder tangential combustion devices of patent, its basic principle is that wind and Secondary Air interval are arranged in primary zone, arrange the after-flame wind snout on the wall of the road of upper boiler burner hearth, and the imaginary circle diameter of after-flame wind is larger.This patent can obtain low nitrogen effect preferably on bituminous coal or boiler using brown coal, but be not suitable for the bad meager coal of fire behaviour, because unstable combustion can cause underload concerning Lean Coal-fired Boiler the time is arranged at the interval of wind and Secondary Air, and the anoxycausis in primary zone can make water-cooling wall produce high temperature corrosion.

Patent 201110033811.8 low-nitrogen oxide discharging coal powder decoupling burning devices and coal dust decoupling burning method, this patent Introduction a kind of burner solve the contradiction of unburned carbon in flue dust and low nitrogen burning by the deep or light separation in the two poles of the earth, this burner due to rich-lean ratio is large to a certain extent can overheavy firing and reduce the generation of NOx in primary zone, but this burner is owing to existing stronger recirculating zone non-adjustable very easily in the spout coking, and this patent does not solve the measure of water wall high temperature corrosion.

The many coal low-nitrogen direct-current coal dust combustions of patent 201110324431.X, the topmost characteristics of this combustion system are that overfire air port can horizontal and vertical swing; Fired wind and be divided into two groups of certain distance are arranged separating.The DC burner group generally all is designed to far to control vertical oscillation and is used for regulating reheat steam temperature at present, but this patent is designed to horizontal hunting (manually) by overfire air port, the wind of ratio of momentum due to Secondary Air is large like this, regulate the burning tangential circle diameter by the Level tune overfire air port, realize the burning of many coals.At first this mode is burnt by adjusting, and to adapt to coal type change side effect excursions many, that adapt to coal narrower and realize inconvenient for tangential circle diameter, the size of the burning circle of contact is all different to every kind of ature of coal of every boiler of adaptability of coal, there is no ready-made experience form the basis, to constantly grope, and the large steady combustion of burning tangential circle diameter is good but easily cause adherent burning and coking, during the little underload of the burning circle of contact, steady fuel efficiency fruit is bad.If adopt this burner to burn certain meager coal, at first to know that burning this meager coal needs the great burning circle of contact, owing to having no basis, can need constantly test could determine the size of the burning circle of contact, but it is very difficult that this regulative mode implements, be difficult to realize that horizontal and vertical all adopts executing agency's automatic swing because the boiler-burner regional space is limited, can only adopt at present vertical oscillation is that automatic swing and horizontal hunting adopt manual adjustments, need the on-the-spot pivot angle that carries out the manual adjustment Secondary Air, change the burning tangential circle diameter and adapt to coal type change, but adjusted according to the whole overfire air ports of field experience the time that at least needs three hours, also having a problem is that the larger circle of contact is favourable to steady combustion, but high temperature corrosion more easily occurs water-cooling wall, and this patent does not relate to the measure that prevents and treats high temperature corrosion.

Patent 201120044217.4 pulverized-coal fired boiler low-nitrogen direct-current combustion apparatus, this burner is mainly to have optimized existing low NO as the middle part Secondary Air is carried out to deflection, change wind snout of deep or light separation into adjustable dense and thin separate burner, the generation of changing reducing NOx through these is favourable.By the adherent atmosphere of the boiler water wall to the deflection Secondary Air is housed, measure, the deflection Secondary Air due to ratio and intensity less very limited to the effect that changes the adherent atmosphere of water-cooling wall, therefore this burner, for Lean Coal-fired Boiler, does not solve the problem of low-load combustion-stabilizing and water wall high temperature corrosion.

Also find that in retrieving some low nox swirling burners are as 200780017391.6 1 kinds of low nox swirling pulverized coal burners of patent; 201010145738.9 three layers of secondary air low nitrogen oxide swirling burner; 201120339568.8 turbulent burner low NOx low-load combustion-stabilizing devices etc., because this patent is direct-flow pulverized coal combustion device, do not have comparativity not do labor with cyclone burner.

According to above analysis, can find, it is relatively good that current low nitrogen straight-through pulverized coal burner is applicable to fire behaviour, the higher coal of fugitive constituent is as bituminous coal or brown coal, the coal poor for fire behaviour produces more negative effect as meetings such as meager coals, be mainly manifested in: (1), flying dust and boiler slag carbon content raise, and the boiler economy reduces.(2), boiler low load stable combustion reduction.(3), water-cooling wall wall reducing atmosphere is higher, high temperature corrosion easily occurs in water-cooling wall.These problems do not solve, and in low nitrogen burning when transformation of carrying out Lean Coal-fired Boiler, not only affect the low nitrogen correctional effect of boiler but also will have a strong impact on the safety and economic operation of boiler.

The utility model content

The purpose of this utility model is exactly for addressing the above problem, a kind of low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler is provided, the burning that can realize stabilizing the economy can make again discharged nitrous oxides be down to reduced levels, and the low nitrogen burning renovation technique of Lean Coal-fired Boiler is promoted.

For achieving the above object, the utility model adopts following technical scheme:

A kind of low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler, it comprises with Terms of Corner Tangential Combustion and is arranged in four jiaos, Lean Coal-fired Boiler burner hearth and main burner group that structure identical that coordinate with the water-cooling wall high temperature corrosion resistance system of burner hearth; Each main burner group comprises spaced coal burner and overfire air port; Main burner group top is provided with corresponding separation after-flame wind group; Every n layer coal burner, one deck precombustion chamber return flow burner is set, the jet rotary direction of main burner group is counterclockwise, but the overfiren air port jet rotary direction on next-door neighbour precombustion chamber return flow burner top is clockwise, and the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Separating after-flame wind component is upper group and lower group, and a lower group jet adopts large imaginary circle mode, and upper group adopts the opposed firing mode.

The top of described main burner group also is provided with the tertiary air spout, and spout adopts large bluff body, and the direction of rotation of tertiary air jet is that the imaginary circle diameter is greater than the anticlockwise imaginary circle diameter of main burner jet counterclockwise.

Described precombustion chamber return flow burner comprises precombustion chamber, and its front end is a wind snout, and rear end is for mixing bellows, and mixing bellows is wind regimes of the interior surrounding air spout of precombustion chamber upper inside wall; For the ball type pulverizer system, what mix bellows is by secondary hot-air, and tertiary air and natural cold wind provide wind regime, and tertiary air is from the part of tertiary air spout; For unit pulverized-coal system, what mix bellows is by secondary hot-air, and cold Secondary Air provides wind regime; Be provided with the wall temperature measurement device at the precombustion chamber outer wall.

Described wall temperature measurement device is the sheet thermal resistance be arranged on the precombustion chamber outer wall, by thermal resistance collection to temperature signal deliver to control system.

The height of described precombustion chamber is greater than 3 with the ratio of a wind snout high temperature.

Two groups of compact Layout up and down of described separation after-flame wind group or be separated by a distance layout, wherein descend component to account for total points from after-flame wind group and be less than 50% from the ratio of after-flame wind air quantity, on lower group throat area ratio, component is large from the after-flame wind snout, to guarantee that lower component is less than upper group of after-flame wind wind speed from the wind speed of after-flame wind, the same imaginary circle of organizing after-flame wind at present is than 1.6 times of main burner, to realize that lower component is from the low wind speed of after-flame wind, large tangential firing mode; Upper component accounts for total points from after-flame wind and is greater than 50% from the ratio of after-flame wind air quantity, upper group of area of injection orifice is less than component from after-flame wind snout area, with guarantee upper component from the wind speed of after-flame wind higher than group's after-flame wind wind speed, upper group of after-flame elegance arrange with diagonal, and the imaginary circle diameter of upper group after-flame wind is 0.

Described water-cooling wall high temperature corrosion resistance system comprises annular bellows, little bellows, contact bellows and ventilation slot, described annular bellows is that the hot Secondary Air of hot Secondary Air contact bellows is delivered to each little bellows and got in touch with bellows and then deliver to the ventilation slot on the water-cooling wall fin, at the water-cooling wall wall, forms oxidizing atmosphere; The bar shaped ventilating opening of described ventilation slot for opening on wall-cooling surface, hot Secondary Air contact bellows are provided with annular bellows blast control baffle plate with the connecting pipe of annular bellows, are used for regulating according to the reducing atmosphere situation on water-cooling wall surface the hot secondary air flow of introducing.

Described coal burner adopts the concentration coal burner of venetian blind type, and deep or light speed difference is in 15%.

The width of the steady combustion tooth of described tertiary air spout is 1/3～1/2 of tertiary air spout height.

The high temperature corrosion resistance low NOx direct-flow pulverized coal combustion device of adaptation meager coal of the present utility model has several key points when design, 1), the precombustion chamber size of precombustion chamber return flow burner and a wind snout height, according to the flammability of field position size and poor meager coal, determine, to guarantee the stability of burning.2), the upper auxiliary wind snout area near the precombustion chamber return flow burner will reduce to guarantee that auxiliary wind postpones to sneak into a wind and guarantees smooth combustion.3), lower component is from after-flame wind snout area, shared air quantity ratio, imaginary circle diameter and wind speed will determine according to ature of coal, boiler heating power parameter and fineness of pulverized coal.4), upper component, is determined in the factor that considers Temperature Deviation from relevant parameter component under determining of after-flame wind after the relevant parameter of after-flame wind.5), in the anti-locking system of water wall high temperature corrosion, position, size and the quantity of annular passage, ventilation slot will be determined according to high temperature corrosion situation and on-the-spot concrete structure occur in the past.

According to the NOx formation mechanism, the generation of NOx is with to destroy main and following factor relevant: (1) coal characteristic; (2) ignition temperature; (3) reaction zone flue gas atmosphere in burner hearth; (4) fuel and the combustion product time of staying in flame high-temperature region and burner hearth.Low NOx combusting technology, control above-mentioned key parameter by changing burning condition exactly, to suppress NOx, generates or decompose the NOx generated, and reaches the purpose of reduce NOx emission.The low nitrogen burning technology of domestic and international application adopts the technology that low oxygen combustion method and additive method combine at present, mainly adopts shade type burner (horizontal bias or vertical strong/weak)+biasing surrounding air (or adherent wind)+SOFA (Separated Over Fire air separates after-flame wind).Its principle of concentration coal burner is to utilize the interior shutter of nozzle body or helix fin that breeze airflow is divided into to deep or light two stocks not send into burner hearth, and the high required ignition heat of dense phase pulverized coal concentration is few, is beneficial to ignition and steady combustion; The light required air of later stage that supplements mutually, be beneficial to the after-flame of coal dust, and bias combustion has all departed from the generation that the chemical equivalent burning greatly reduces NOx simultaneously; Biasing surrounding air or adherent wind action are mainly the reducing atmospheres of avoiding that prevents adherent burning and alleviate water-cooling wall; Separate after-flame wind (SOFA) control combustion reaction equivalent, further reduce NOx, simultaneously in coke after-flame later stage delivery of supplemental oxygen amount, the combustible content in flying dust is reduced.These low nitrogen burning technology obtain reasonable effect on bituminous coal fired boiler, and the NOx discharge of most of boiler can be controlled at 300mg/Nm ³, some boiler can be controlled at 200mg/Nm ³, but in the application of Lean Coal-fired Boiler, effect is poor, and this is that main manifestations is that fugitive constituent is low because the coal characteristic of meager coal has been compared relatively big difference with the coal characteristic of bituminous coal, and fixed carbon and sulfur content are higher, make meager coal fire behaviour and burnout rate poor, in order to adapt to the coal characteristic of meager coal, the thermal parameter design comparison of Lean Coal-fired Boiler is high, as adopted higher volume heat load and section of burner hearth calorific intensity, and for the burnout rate that improves meager coal employing hyperoxia in service amount, the ignition temperature of burner hearth is also higher, these factors have all directly affected the effect of low nitrogen burning technology, and produce aforesaid many negative effects, for fear of these negative effects, the utility model adopts has surely combustion property strengthen combustion intensity of the better steady fuel efficiency fruit burning that the precombustion chamber return flow burner combines to improve primary combustion zone with common shade burner preferably, in the situation that being less than 1, excess air coefficient improves the ignition temperature in primary zone to realize, reduce the generation of NOx, reduce flying dust and boiler slag carbon content, adopt the Researched of Air Staging Combustion Burning Pulverized Coal mode to reduce the NOx concentration of emission, at burning-out zone because the after-flame wind facies is Cryogenic air for the inner flue gas of the stove temperature, entering of this part air can reduce the temperature in after-flame zone, but after the coke in these unburnt pulverized coal particles burns away, the temperature in after-flame zone can raise again, and the coke burn-off rate that simultaneously improves the after-flame zone in order to reduce as far as possible negative effect adopts upper and lower two groups of different wind rates, not synchronized and different imaginary circle diameters to separate after-flame wind and realize Researched of Air Staging Combustion Burning Pulverized Coal, because the meager coal sulfur content is higher, excess air coefficient in main combustion zone is less than 1 such combustion system and will inevitably makes boiler water wall generation high temperature corrosion simultaneously, so the oxidizing atmosphere that the auxiliary wind of the wall formula that adopts distributed, little wind rate, high wind speed strengthens the water-cooling wall wall is avoided high temperature corrosion, whole like this combustion process is able to comprehensive optimization, the burning that can realize stabilizing the economy can make again discharged nitrous oxides be down to reduced levels, and the low nitrogen burning renovation technique of Lean Coal-fired Boiler is promoted.

The beneficial effects of the utility model are:

1), in primary zone, ignition temperature and strength increase when excess air coefficient is less than 1, reduce the growing amount of the nitrogen oxide in primary zone, makes boiler slag carbon content and unburned carbon in flue dust decrease simultaneously.

2) component up and down by different wind rates and wind speed not only can reduce the generation of nitrogen oxide but also can effectively strengthen the coke granule burning from after-flame wind, reduces unburned carbon in flue dust, at the minimizing Temperature Deviation, certain effect is also arranged.

3) can effectively change the reducing atmosphere on water-cooling wall surface, by to examples measure, the oxygen amount minimum on water-cooling wall surface is 0.5%, and (transformation front face oxygen amount: be 0.7% to the maximum, more measuring point oxygen amount is 0 far above the wall oxygen amount before transformation to be 3% to the maximum.)

4) adopt one deck precombustion chamber return flow burner in the every n layer of primary combustion zone coal burner, improve combustion intensity and the steady combustion property of boiler.

5) the upper overfire air port area of precombustion chamber return flow burner reduces and the direction of rotation traditional method of indicating the pronunciation of a Chinese character, and adopts larger imaginary circle diameter, makes Secondary Air sneak into postponement, plays steady combustion effect.

6) the mixing bellows of the part tertiary air being introduced to the precombustion chamber return flow burner are used for temperature adjustment, and that has reduced tertiary air directly sends into air quantity, favourable to boiler combustion.

7) the tertiary air spout installs wider combustion stabilizing body additional, is used for strengthening burning.

8) the imaginary circle diameter of tertiary air jet is greater than the imaginary circle diameter of main burner jet, is also for steady combustion.

9) the large imaginary circle of lower group SOFA elegance, area of injection orifice strengthens simultaneously, and wind speed is reduced, and can realize that large coke granule that fractional combustion can make again to be thrown away by primary air obtains sufficient oxygen amount and burns away, favourable to the minimizing unburned combustible in fly ash.

10) opposed firing of jet for upper group SOFA elegance, area of injection orifice reduces simultaneously, and wind speed is improved, and promotes the penetrability of SOFA jet, favourable to reducing unburned combustible in fly ash.

The accompanying drawing explanation

Fig. 1 is the low NOx direct-flow pulverized coal combustion device structural representation for the unit pulverized-coal system Lean Coal-fired Boiler.

The side view that Fig. 1 a is Fig. 1.

Fig. 2 is the low NOx direct-flow pulverized coal combustion device structural representation for the ball type pulverizer system Lean Coal-fired Boiler.

The side view that Fig. 2 a is Fig. 2.

Fig. 3 is first kind precombustion chamber return flow burner structural representation front view.

Fig. 4 is Equations of The Second Kind precombustion chamber return flow burner structural representation front view.

Fig. 5 is two class precombustion chamber return flow burner structural representation side views.

Fig. 6 is that the high temperature corrosion resistance ventilation slot is arranged schematic diagram.

Fig. 7 is that the high temperature corrosion resistance annular bellows is arranged schematic diagram.

The connection diagram that Fig. 8 is high temperature corrosion resistance annular bellows and little bellows.

Each lip jet that Fig. 9 is main burner (except BC, EF layer overfire air port) flows to schematic diagram.

Figure 10 is that BC, EF layer overfire air port jet stream are to schematic diagram.

Figure 11 is that lower group of SOFA lip jet flows to schematic diagram.

Figure 12 is that upper group of SOFA lip jet flows to schematic diagram.

Figure 13 is that the tertiary air lip jet flows to schematic diagram.

In figure: A, B, C, D, E, F is coal burner, AA, AB, BC, CC, DD, DE, EF, FF1 and FF2 are overfire air port, G is the tertiary air spout, SOFA1, SOFA2, SOFA3, SOFA4 is four layers and separates the after-flame wind snout, 1, precombustion chamber, 2, secondary hot-air is controlled baffle plate, 3, secondary cold wind is controlled baffle plate, 4, mix bellows, 5, the sheet thermal resistance, 6, tertiary air is controlled baffle plate, 7, a wind snout, 8, temperature indicating device, 9, built-in surrounding air spout, 10, water screen tube, 11, ventilation slot, 12, annular bellows, 13, the annular bellows blast is controlled baffle plate, 14, little bellows, 15, the contact bellows, 16, hot Secondary Air contact bellows.

The specific embodiment

Below in conjunction with Figure of description and embodiment, the technical solution of the utility model is further elaborated.

The boiler that uses meager coal has two kinds of forms at present, and a kind of is the boiler that adopts the ball type pulverizer system, this boiler pulverized coal carried by hot air, and the weary gas of mill exhauster is sent in stove as tertiary air; The another kind of unit pulverized-coal system that adopts, pulverized coal preparation system is relatively simple, there is no the tertiary air spout in burner.Therefore embodiment of the present utility model has two classes, is respectively the boiler of embodiment 1 the ball type pulverizer system and the boiler of embodiment 2 unit pulverized-coal systems.To be described in detail respectively with reference to the accompanying drawings.

Embodiment 1

Subcritical, middle single reheat, controlled circulation drum boiler that the China #3 of power plant of electric group boiler is evaporation capacity 1025t/h, combustion system is Terms of Corner Tangential Combustion, there are six layers of coal burner at every angle, with the overfire air port interval, arrange, pulverized coal preparation system is the direct-firing of double-inlet and double-outlet steel ball coal mill, and using coal is meager coal.This boiler-burner has adopted the technology of early stage U.S. CE, and the concentration of emission of NOx is higher, and concentration of emission is at 750-900mg/Nm ³, unburned carbon in flue dust is at 5-6%.In order to reach the up-to-date thermal power plant's pollutant emission standard of country, the #3 boiler has been carried out to the low nitrogen burning transformation, adopted this low NOx direct-flow pulverized coal combustion device that is adapted to meager coal.

Fig. 1 is that the utility model is applied to the structural representation in embodiment 1, has 6 layers of coal burner and is respectively the A layer, B layer, C layer, D layer, E layer and F layer; Overfire air port is 9 layers and is respectively the AA layer, AB layer, BC layer, CC layer, DD layer, DE layer, EF layer, FF1 layer and FF2 layer; Separation after-flame wind is 4 layers and is respectively SOFA1, SOFA2, SOFA3, SOFA4.In 6 layers of coal burner, A, C, D and F grate firing burner are common shade burner, there is no specific (special) requirements, require rich-lean ratio more than 2, deep or light side speed difference is in 15%; B layer and E grate firing burner are the precombustion chamber return flow burner, and the structure of precombustion chamber return flow burner is shown in Fig. 3 and Fig. 5.The precombustion chamber return flow burner utilizes precombustion chamber 1 to make high temperature gases recirculating heat coal dust exactly, improve combustion intensity, reduce flying dust and boiler slag carbon content, because the backflow of high-temperature flue gas easily makes to catch fire in advance, easily cause precombustion chamber 1 coking, the precombustion chamber wall temperature is raise, the wall temperature of precombustion chamber is to be measured by sheet thermal resistance 5, show wall temperature by temperature indicating device 8, cooling by built-in surrounding air spout 9 in order to reduce the precombustion chamber wall temperature, mix bellows 4 built-in surrounding air is provided, provide wind regime by hot Secondary Air and cold secondary for mixing bellows, wind-warm syndrome in the mixing bellows is regulated by secondary hot-air control baffle plate 2 and secondary cold wind control baffle plate 3.

Fig. 6, Fig. 7 and Fig. 8 are the anti-locking system of water wall high temperature corrosion.At first according to the direction of rotation of tangential firing and the position of water screen tube 10 generation high temperature corrosions, determine the position of ventilation slot 11, then the annular bellows 12 that enters of drawing hot Secondary Air from secondary hot-air contact bellows 16 enters each little bellows 14, the blast of annular bellows 12 is controlled baffle plate 13 by the annular bellows blast and is carried out regulation and control, between little bellows 14, by contact bellows 15, couples together.

Fig. 9, Figure 10, the jet stream that Figure 11 and Figure 12 are each layer of spout is to schematic diagram, the size that has meaned the imaginary circle diameter of tangential firing, size and the direction of rotation of the imaginary circle diameter that wherein Fig. 9 is AA, A, AB, B, C, CC, DD, D, DE, E, F, FF1 and FF2 layer lip jet, Fig. 9 shows that the direction of rotation of main burner is counterclockwise rotation; Size and the direction of rotation of the imaginary circle diameter of the lip jet that Figure 10 is BC and EF layer, figure shows that this two-layer jet is for rotation clockwise, and the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Size and the direction of rotation of the imaginary circle diameter that Figure 11 is SOFA1 and SOFA2 layer jet, Figure 11 shows that the direction of rotation of SOFA1 and SOFA2 layer jet is for counterclockwise, the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Figure 12 be SOFA1 and SOFA2 layer jet stream to showing, this is two-layer is opposed firing, that is to say that the imaginary circle diameter is 0.

Below in conjunction with accompanying drawing, with regard to some key points in embodiment 1, describe: several size L1 in Fig. 1, L2, L3 and L4, need to determine according to ature of coal, boiler structure and test or experience, the precombustion chamber height that L1 is the precombustion chamber return flow burner, the precombustion chamber height has determined capacity of returns and the circulating flow strength of high-temperature flue gas, and L1 will determine according to the poorest ature of coal, as far as possible high in the selection of L1; L3 is the upper overfire air port near the precombustion chamber return flow burner, and at first this jet size is subject to the restriction of L1, and for the combustion intensity that guarantees that having of precombustion chamber return flow burner is enough, this layer of Secondary Air will postpone to sneak into breeze airflow, so L3 is as far as possible little; The distance that L2 is upper and lower two groups of burners, this distance is definite according to the pressure reduction of the number of coal burner and warm oneself in front of a fire side and back-fire side, and rule is that three layers of coal burner of coal are one group; The distance that L4 is upper and lower two groups of SOFA spouts, can determine according to the practical structures size of boiler and the discharged nitrous oxides concentration of requirement, is recommended as 0-2m; The size that L5 is lower group of SOFA spout, the size that L6 is upper group of SOFA spout, L5 is larger than L6, higher than upper group of SOFA vent wind speed to guarantee lower group of SOFA vent wind speed; The hot blast rate of the introducing in the high temperature corrosion resistance system require the boiler total blast volume 3% in, the position of air vent and quantity will be determined according to the position of easy generation high temperature corrosion and the direction of rotation of burner jet.

Embodiment 2

Subcritical, middle single reheat, controlled circulation drum boiler that the Huaneng Group #3 of power plant of group boiler is evaporation capacity 1025t/h, combustion system is Terms of Corner Tangential Combustion, there are six layers of coal burner at every angle, with auxiliary wind snout interval, arrange, pulverized coal preparation system is DTM350/600 shaped steel ball mill the ball type pulverizer system, pulverized coal carried by hot air, weary gas is sent into burner hearth as tertiary air, and using coal is Jinzhong City's meager coal.The concentration of emission of this boiler NOx is higher, and concentration of emission is at 800-950mg/m ³, unburned carbon in flue dust is at 3-6%.In order to reach the up-to-date thermal power plant's pollutant emission standard of country, the #3 boiler has been carried out to the low nitrogen burning transformation, also adopted this low NOx direct-flow pulverized coal combustion device that is adapted to meager coal.

Fig. 2 is that the utility model is applied to the structural representation in embodiment 2, has 6 layers of coal burner and is respectively the A layer, B layer, C layer, D layer, E layer and F layer; Overfire air port is 8 layers and is respectively the AA layer, AB layer, BC layer, CC layer, DD layer, DE layer, EF layer and FF1 layer; One deck tertiary air spout G layer, arrange surrounding air around the tertiary air spout and be used for cooled nozzle and install steady combustion tooth additional and be used for steady combustion; Separation after-flame wind is 4 layers and is respectively SOFA1, SOFA2, SOFA3, SOFA4.In 6 layers of coal burner, A, C, D and F grate firing burner are common shade burner, there is no specific (special) requirements, require rich-lean ratio more than 2, deep or light side speed difference is in 15%; B layer and E grate firing burner are the precombustion chamber return flow burner, and the structure of precombustion chamber return flow burner is shown in Fig. 4 and Fig. 5.The precombustion chamber return flow burner utilizes precombustion chamber 1 to make high temperature gases recirculating heat coal dust exactly, improve combustion intensity, reduce flying dust and boiler slag carbon content, because the backflow of high-temperature flue gas easily makes to catch fire in advance, easily cause precombustion chamber 1 coking, the precombustion chamber wall temperature is raise, the wall temperature of precombustion chamber is to be measured by sheet thermal resistance 5, show wall temperature by temperature indicating device 8, cooling by built-in surrounding air spout 9 in order to reduce the precombustion chamber wall temperature, mix bellows 4 built-in surrounding air is provided, by tertiary air, hot Secondary Air and cold secondary provide wind regime for mixing bellows, the wind-warm syndrome of mixing in bellows is controlled baffle plate 2 by secondary hot-air, tertiary air controls baffle plate 6 and secondary cold wind control baffle plate 3 is regulated, on control bellows wind-warm syndrome, the preferential tertiary air of selecting is controlled, can reduce like this air quantity of tertiary air spout G layer, to reducing tertiary air, to the disturbance of boiler combustion, be very favourable.In the research of other meager coal low nitrogen burnings being transformed to unsuccessful case, find, one of them key factor is that tertiary air is dealt with improperly, reduction and boiler combustion to nitrogen oxide have produced comparatively serious negative effect, in this embodiment, except using the part tertiary air as temperature adjustment wind, added at the tertiary air spout the steady fuel efficiency fruit that wider steady combustion tooth is used for strengthening tertiary air, also had the imaginary circle diameter of tertiary air jet is amplified further to strengthen burning and see Figure 13.

Fig. 6, Fig. 7 and Fig. 8 are the anti-locking system of water wall high temperature corrosion.At first according to the direction of rotation of tangential firing and the position of water screen tube 10 generation high temperature corrosions, determine the position of ventilation slot 11, then the annular bellows 12 that enters of drawing hot Secondary Air from secondary hot-air contact bellows 15 enters each little bellows 14, the blast of annular bellows 12 is controlled baffle plate 13 by the annular bellows blast and is carried out regulation and control, between little bellows 14, by contact bellows 15, couples together.

Fig. 9, Figure 10, Figure 11, the jet stream that Figure 12 and Figure 13 are each layer of spout is to schematic diagram, the size that has meaned the imaginary circle diameter of tangential firing, size and the direction of rotation of the imaginary circle diameter that wherein Fig. 9 is AA, A, AB, B, C, CC, DD, D, DE, E, F, FF1 and FF2 layer lip jet, Fig. 9 shows that the direction of rotation of main burner is counterclockwise rotation; Size and the direction of rotation of the imaginary circle diameter of the lip jet that Figure 10 is BC and EF layer, figure shows that this two-layer jet is for rotation clockwise, and the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Size and the direction of rotation of the imaginary circle diameter that Figure 11 is SOFA1 and SOFA2 layer jet, Figure 11 shows that the direction of rotation of SOFA1 and SOFA2 layer jet is for counterclockwise, the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Figure 12 be SOFA1 and SOFA2 layer jet stream to showing, this is two-layer is opposed firing, that is to say that the imaginary circle diameter is 0; Figure 13 shows that the direction of rotation of tertiary air jet is for counterclockwise, consistent with the direction of rotation of primary combustion zone, but the imaginary circle diameter of tertiary air jet is larger than the footpath of the imaginary circle of primary combustion zone jet.

Below in conjunction with accompanying drawing, with regard to some key points in embodiment 2, describe: several size L1 in Fig. 1, L2, L3 and L4, need to determine according to ature of coal, boiler structure and test or experience, the precombustion chamber height that L1 is the precombustion chamber return flow burner, the precombustion chamber height has determined capacity of returns and the circulating flow strength of high-temperature flue gas, and L1 will determine according to the poorest ature of coal, as far as possible high in the selection of L1; L3 is the upper overfire air port near the precombustion chamber return flow burner, and at first this jet size is subject to the restriction of L1, and for the combustion intensity that guarantees that having of precombustion chamber return flow burner is enough, this layer of Secondary Air will postpone to sneak into breeze airflow, so L3 is as far as possible little; The distance that L2 is upper and lower two groups of burners, this distance is definite according to the pressure reduction of the number of coal burner and warm oneself in front of a fire side and back-fire side, and rule is that three layers of coal burner of coal are one group; The distance that L4 is upper and lower two groups of SOFA spouts, can determine according to the practical structures size of boiler and the discharged nitrous oxides concentration of requirement, is recommended as 0-2m; The size that L5 is lower group of SOFA spout, the size that L6 is upper group of SOFA spout, L5 is larger than L6, higher than upper group of SOFA vent wind speed to guarantee lower group of SOFA vent wind speed; The hot blast rate of the introducing in the high temperature corrosion resistance system require the boiler total blast volume 3% in, the position of air vent and quantity will be determined according to the position of easy generation high temperature corrosion and the direction of rotation of burner jet; The width of the steady combustion tooth that L7 is the tertiary air spout, the recommendation of L7 is 1/3～1/2 of tertiary air spout height.

In these two embodiment that distinguish to some extent, the high temperature corrosion resistance low NOx direct-flow pulverized coal combustion device that adapts to meager coal is all obtained effect preferably, and when ature of coal approaches designing coal quality, the concentration of emission of NOx can be controlled at 350mg/Nm ³Below, the slag of boiler and fly ash combustible material obviously do not rise, and boiler efficiency approaches design load, and while boiler surely combustion property obviously improves.

Claims (9)

1. a low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler, it is characterized in that, it comprises with Terms of Corner Tangential Combustion and is arranged in four jiaos, Lean Coal-fired Boiler burner hearth and main burner group that structure identical that coordinate with the water-cooling wall high temperature corrosion resistance system of burner hearth; Each main burner group comprises spaced coal burner and overfire air port; Main burner group top is provided with corresponding separation after-flame wind group; Every n layer coal burner, one deck precombustion chamber return flow burner is set, the jet rotary direction of main burner group is counterclockwise, but the overfiren air port jet rotary direction on next-door neighbour precombustion chamber return flow burner top is clockwise, and the imaginary circle diameter is larger than the imaginary circle diameter of main burner; Separating after-flame wind component is upper group and lower group, and a lower group jet adopts large imaginary circle mode, and upper group adopts the opposed firing mode.

2. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 1, it is characterized in that, the top of described main burner group also is provided with the tertiary air spout, spout adopts large bluff body, the direction of rotation of tertiary air jet is that the imaginary circle diameter is greater than the anticlockwise imaginary circle diameter of main burner jet counterclockwise.

3. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 1 or 2, it is characterized in that, described precombustion chamber return flow burner comprises precombustion chamber, its front end is a wind snout, rear end is for mixing bellows, and mixing bellows is wind regimes of the interior surrounding air spout of precombustion chamber upper inside wall; For the ball type pulverizer system, what mix bellows is by secondary hot-air, and tertiary air and natural cold wind provide wind regime, and tertiary air is from the part of tertiary air spout; For unit pulverized-coal system, what mix bellows is by secondary hot-air, and cold Secondary Air provides wind regime; Be provided with the wall temperature measurement device at the precombustion chamber outer wall.

4. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 3, is characterized in that, described wall temperature measurement device is the sheet thermal resistance be arranged on the precombustion chamber outer wall, by thermal resistance collection to temperature signal deliver to control system.

5. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 3, is characterized in that, the height of described precombustion chamber is greater than 3 with the ratio of a wind snout high temperature.

6. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 1, it is characterized in that, two groups of compact Layout up and down of described separation after-flame wind group or be separated by a distance layout, wherein descend component to account for total points from after-flame wind group and be less than 50% from the ratio of after-flame wind air quantity, on lower group throat area ratio, component is large from the after-flame wind snout, to guarantee that lower component is less than upper group of after-flame wind wind speed from the wind speed of after-flame wind, with organizing the imaginary circle of after-flame wind than 1.6 times of main burner at present, to realize the low wind speed of lower component from after-flame wind, large tangential firing mode, upper component accounts for total points from after-flame wind and is greater than 50% from the ratio of after-flame wind air quantity, upper group of area of injection orifice is less than component from after-flame wind snout area, with guarantee upper component from the wind speed of after-flame wind higher than group's after-flame wind wind speed, upper group of after-flame elegance arrange with diagonal, and the imaginary circle diameter of upper group after-flame wind is 0.

7. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 1, it is characterized in that, described water-cooling wall high temperature corrosion resistance system comprises annular bellows, little bellows, contact bellows and ventilation slot, described annular bellows is that the hot Secondary Air of hot Secondary Air contact bellows is delivered to each little bellows and got in touch with bellows and then deliver to the ventilation slot on the water-cooling wall fin, at the water-cooling wall wall, forms oxidizing atmosphere; The bar shaped ventilating opening of described ventilation slot for opening on wall-cooling surface, hot Secondary Air contact bellows are provided with annular bellows blast control baffle plate with the connecting pipe of annular bellows, are used for regulating according to the reducing atmosphere situation on water-cooling wall surface the hot secondary air flow of introducing.

8. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 1, is characterized in that, described coal burner adopts the concentration coal burner of venetian blind type, and deep or light speed difference is in 15%.

9. the low NOx direct-flow pulverized coal combustion device that is adapted to Lean Coal-fired Boiler as claimed in claim 2, is characterized in that, the width of the steady combustion tooth of described tertiary air spout is 1/3～1/2 of tertiary air spout height.

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