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author：EBICO 2020-01-13
Low nitrogen combustion technology
I. fractional combustion of air
Air stage combustion science is one of the low NOx combustion technologies extensively used at domestic and abroad.Shanxi blue sky environmental safety equipment co., LTD.
1. Basic principle: the air required for fuel combustion is divided into two or extra tiers and sent into the furnace, so that the coal combustion procedure can be executed in ranges on the foundation of maintaining the average excess air coefficient unchanged:
1) * segment is fuel-rich combustion, in which, < 1, 70-80% of the complete air required for combustion is despatched from the most important combustion zone, so as to make certain fuel combustion beneath hypoxia conditions, build a reducing atmosphere, and inhibit the era of fuel-type NOx;
2) the 2nd stage is oxygen-rich combustion. The residual air (burnout wind) is sent to the furnace from the burnout zone above the primary combustion zone to whole the burnout process of pulverized coal.Although there is a giant amount of air in the burnt-out area, a phase of NOx will be generated again, however overall the production of NOx in the furnace is reduced.
2. Factors affecting NOx reduction impact of fractional combustion of air:
1) excess air coefficient distribution of two-stage combustion;
2) combustion temperature;
3) remain time, etc.;
Air staged combustion shall forestall slagging and corrosion in the fuel-rich combustion zone
Second, smoke recirculation
1. Principle: section of the flue fuel after combustion is extracted from the air preheater and at once fed into the furnace, or is first fed into the bellows and blended with warm air and then fed into the furnace, so as to minimize the combustion temperature and oxygen concentration, thus decreasing the production of NOx;
Gas recirculation rate = (recirculation fume volume)/(fume volume besides recirculation) ×100%
2. The impact of fuel recirculation on decreasing NOx is related to gas varieties and recirculation rate, and the discount charge of NOx will increase with the enlarge of recirculation rate.
3. When the recirculation rate is 15-25%, the NOx emission attention of pulverized coal furnace can be reduced by way of ~ 25%.
4. The standard recycling charge should be round 10 ~ 20%;
5. The greater the combustion temperature (such as liquid slag discharge furnace), the greater the have an effect on of recirculation charge on NOx reduction;
※ the use of flue fuel recirculation requires the installation of recirculation fan and flue, etc., which increases the funding and the system is greater complex, so technical and monetary assessment is required.
Three, gas classification combustion
1. Fractional combustion of fuel, additionally acknowledged as reburning technology, frequently USES the precept of lowering and destroying NOx by means of hydrocarbons. The entire combustion division is divided into three parts.
1) main combustion zone: burning and generating NOx;
2) reburning zone: the remaining 15 ~ 20% of the fuel is sent to the secondary combustion zone at the upper part of the main combustion zone to form a strong reducing atmosphere to reduce NOx to N2.
3) burndown zone: positioned above the reburning zone, the burndown wind is despatched to make the incomplete combustion products burn out
2. The factors affecting NOx reduction in the reburning zone are:
1) kinds of secondary fuels;
2) proportion of secondary fuel;
3) extra air coefficient in the reburning zone;
4) reburning area temperature;
5) residence time of flue gas in the reburning zone, etc.
※ the adoption of reburning technology requires thinking about the universal top of the boiler to make sure the burnout price of the fuel in the reburning zone.
In addition, the modern-day worldwide mainstream low nitrogen combustion technology also includes: thick mild combustion, low essential combustion area excess air, low NOx burner and so on,