Background technology
The nitrogen oxide that coal dust firing produces is one of primary pollution source of atmosphere pollution, and it destroys ecological environment except forming acid rain, can also form photochemical fog, harm humans health.Coal powder recombustion low nitrogen oxide burning technology is the measure of the reduction nitrogen oxide of a kind of high nitric efficiency, low investment, low operating cost, the key of coal powder recombustion low nitrogen oxide burning technology is the reburning zone that forms reducing atmosphere, but the power coal ature of coal of China is generally relatively poor, with coal dust as reburning fuel, the reburning zone is difficult to form stablizes reducing atmosphere, and the nitrogen oxide percent reduction is lower; The after-flame of coal-fired powder is also relatively poor again; Adopt coal dust combustion technology again, the excess air coefficient in the primary zone of boiler is lower than conventional boiler, and the reburning zone is a reducing atmosphere, easily high temperature corrosion and slagging scorification; These problems have limited the coal dust application of combustion technology again.
Summary of the invention
The present invention uses the coal dust stable reducing atmosphere of the difficult formation in combustion technology reburning zone again in order to solve, and the nitrogen oxide percent reduction is lower, and the problem of slagging scorification and high temperature corrosion easily takes place for primary zone and reburning zone simultaneously.A kind of method that is used for the coal-burning boiler low nitrogen oxide burning is provided, the method that is used for the coal-burning boiler low nitrogen oxide burning realizes by following steps: the regular particle size coal dust that () will account for boiler oil caloric value 80%~85% is sent into the primary zone of boiler furnace bottom, at excess air coefficient is to burn with horizontal bias wind combustion technology under 0.8~1 the condition; (2) utilizing air, flue gas or flue gas and AIR MIXTURES is that 20~60 microns the boiler oil caloric value that accounts for is that 15%~20% coal dust is sprayed into by the top, primary zone as reburning fuel with particle mean size, form the reburning zone, the excess air coefficient of reburning zone outlet is controlled to be 0.85~0.95, reburning zone gas residence time 0.2 second~0.8 second, reburning fuel burns with horizontal bias combustion technology or straight flow combustion mode; (3) spray into after-flame wind to the top of reburning zone, form burning-out zone and burning-out zone is exported excess air coefficient and be controlled to be 1.15~1.2, the imperfect combustion product of reburning zone outlet can reach the purpose of low nitrogen oxide burning in the coal-burning boiler at the further after-flame of burning-out zone.The method that is used for the coal-burning boiler low nitrogen oxide burning among the present invention is a reburning fuel with the coal dust, is convenient to fire the low nitrogen oxide burning The Application of Technology again.The present invention will be more coal-fired powder carry out thinning processing, improve the reactivity of coal dust, help again catching fire and after-flame of coal-fired powder, help the reburning zone and form stable reducing atmosphere and reduce the nitrogen oxide that the primary zone generates.The coal tar surface area that its reaction generates after the coal-fired again powder refinement increases, and the ability of nitrogen oxides reduction also is improved, and helps the reduction of nitrogen oxide.Reburning fuel adopts the horizontal bias combustion technology, adopting the horizontal bias combustion technology to help reburning fuel surely fires, the horizontal bias combustion technology has postponed coal-fired powder again and has carried coal-fired again powder Air mixing process simultaneously, reduce the nitrogen oxide that the reburning fuel burning generates, increase also simultaneously that coal-fired again powder initial reaction stage produces can nitrogen oxides reduction the concentration of groups such as CHi, HCN, NHi, help the reduction of nitrogen oxide.High temperature corrosion and slagging scorification that reburning fuel horizontal bias mode is burnt and can also be alleviated the reburning zone.Adopt " horizontal bias wind " combustion system in the primary zone, it is the coal powder density height of a dense wind breeze airflow, help catching fire and steady combustion of breeze airflow, " horizontal bias wind " combustion system reduces the primary zone nitrogen oxide simultaneously and generates, a light wind breeze airflow coal powder density of back-fire side is lower, add the effect of side secondary air, can guarantee near the oxidizing atmosphere that water-cooling wall is, alleviate the slagging scorification and the high temperature corrosion in primary zone; The empty excess coefficient in primary zone can further suppress the generation of primary zone nitrogen oxide less than 1.Reburning zone of the present invention forms stable reducing atmosphere easily, and the high temperature corrosion and the slagging scorification that can obviously alleviate boiler, and common coal-burning boiler can reduce 50%~65% of discharged nitrous oxides.The present invention is main objective for implementation with coal-powder boiler, and initial outlay and operating cost are moderate, promptly can be applicable to newly constructed boiler, also is applicable to the improved use of active service coal-burning boiler unit.
The specific embodiment
The specific embodiment one: a kind of method that is used for the coal-burning boiler low nitrogen oxide burning realizes by following steps in the present embodiment: the regular particle size coal dust that () will account for boiler oil caloric value 80%~85% is sent into the primary zone of boiler furnace bottom, at excess air coefficient is to burn with horizontal bias wind combustion technology under 0.8~1.05 the condition; (2) utilizing air, flue gas or flue gas and AIR MIXTURES is that 20~60 microns the boiler oil caloric value that accounts for is that 15%~20% coal dust is sprayed into by the top, primary zone as reburning fuel with particle mean size, form the reburning zone, the excess air coefficient of reburning zone outlet is controlled to be 0.85~0.95, reburning zone gas residence time 0.2 second~0.8 second, reburning fuel burns with horizontal bias combustion technology or straight flow combustion mode; (3) spray into after-flame wind to the top of reburning zone, form burning-out zone and burning-out zone is exported excess air coefficient and be controlled to be 1.15~1.2, the imperfect combustion product of reburning zone outlet can reach the purpose of low nitrogen oxide burning in the coal-burning boiler at the further after-flame of burning-out zone.
The specific embodiment two: the regular particle size coal dust that the difference of the present embodiment and the specific embodiment one is will to account in the step () boiler oil caloric value 82%~84% is put into the primary zone of boiler furnace bottom.Other step is identical with the specific embodiment one.
The specific embodiment three: the regular particle size coal dust that the difference of the present embodiment and the specific embodiment one is will to account in the step () boiler oil caloric value 83% is put into the primary zone of boiler furnace bottom.Other step is identical with the specific embodiment one.
The specific embodiment four: the difference of the present embodiment and the specific embodiment one is that primary zone outlet excess air coefficient is 0.9~1.02 in the step ().Other step is identical with the specific embodiment one.
The specific embodiment five: the difference of the present embodiment and the specific embodiment one is that primary zone outlet excess air coefficient is 0.93~1 in the step ().Other step is identical with the specific embodiment one.
The specific embodiment six: the difference of the present embodiment and the specific embodiment one is that primary zone outlet excess air coefficient is 0.95 in the step ().Other step is identical with the specific embodiment one.
The specific embodiment seven: the difference of the present embodiment and the specific embodiment one is that primary zone outlet excess air coefficient is 0.9 in the step ().Other step is identical with the specific embodiment one.
The specific embodiment eight: the difference of the present embodiment and the specific embodiment one is in the step (two) with particle mean size to be that 25~40 microns the boiler oil caloric value that accounts for is that 16%~18% coal dust is sprayed into by the top, primary zone.Other step is identical with the specific embodiment one.
The specific embodiment nine: the difference of the present embodiment and the specific embodiment one is that the excess air coefficient that in the step (two) reburning zone is exported is controlled to be 0.88~0.92.Other step is identical with the specific embodiment one.
The specific embodiment ten: the difference of the present embodiment and the specific embodiment one is that the excess air coefficient that in the step (two) reburning zone is exported is controlled to be 0.9.Other step is identical with the specific embodiment one.
The specific embodiment 11: the difference of the present embodiment and the specific embodiment one is the middle reburning zone of step (two) gas residence time 0.3 second~0.6 second.Other step is identical with the specific embodiment one.
The specific embodiment 12: the difference of the present embodiment and the specific embodiment one be in the step (three) burning-out zone outlet excess air coefficient be the gas that under 1.18 the condition come out in the reburning zone from burning-out zone by and burning.Other step is identical with the specific embodiment one.
The specific embodiment 13: be implemented mode below in conjunction with Fig. 1 explanation, a kind of method that is used for the coal-burning boiler low nitrogen oxide burning realizes by following steps in the present embodiment: the regular particle size coal dust (1) that () will account for boiler oil caloric value 85% is sent into the primary zone (A) of boiler furnace bottom, at excess air coefficient is to burn with horizontal bias wind combustion technology under 0.95 the condition; (2) utilizing air, flue gas or flue gas and AIR MIXTURES is that 45 microns the boiler oil caloric value that accounts for is that 15% coal dust (2) is sprayed into by the top, primary zone as reburning fuel with particle mean size, form the reburning zone, the excess air coefficient of reburning zone outlet is controlled to be 0.9, and the reburning zone gas residence time is 0.4 second.Reburning fuel burns with the horizontal bias combustion technology; (3) spray into after-flame wind (3) to the top of reburning zone (B), form burning-out zone (C) and the outlet excess air coefficient of burning-out zone (C) is controlled to be 1.15, the imperfect combustion product of reburning zone outlet further after-flame during by burning-out zone reaches the purpose of low nitrogen oxide burning in the coal-burning boiler.