燃用褐煤六角切圆670 t/h炉低NOx煤粉燃烧技术的研究

某厂燃用褐煤六角切圆670t／h炉为降低NOx排放，进行了如下改造：将原有燃烧器全部改造为水平浓淡风煤粉燃烧器，由于水平浓淡两股一次风煤粉气流各自远离燃料的化学当量比，可有效减少NOx的生成；在燃烧器顶部增设燃尽风喷口，使下部主燃烧区域处于氧浓度较低的气氛，可有效减少NOx的生成；将上、中层燃烧器的下二次风射流轴线向水冷壁偏转一定角度，加大上排燃烧器的二次风切圆直径，推迟二次风与一次风风粉混合物的混合，减少着火阶段的供氧量，可有效减少NOx的生成。试验结果证明，额定负荷下NOx排放量显著降低到315．4mg／m^3(O2=6％，干烟气)，远低于排放标准，锅炉效率可达91．85％，比原设计值高1．32％。

A Study of the Low NOx Emission-based Pulverized Coal Combustion Technology for a Hexagonal and Tangential-fired 670 t/h Boiler Operating on Lignite

A series of modifications have been carried out with a view to reducing NO x emissions for a hexagonal and tangential fired 670 t/h boiler operating on lignite. They include, among others, the following. All of the original burners were retrofitted to become horizontal type dense and dilute air pulverized coal burners. As the two streams of primary air pulverized coal flow of horizontal dense and dilute air respectively deviates considerably from a stoichiometric ratio, this can effectively reduce the generation of NO x . At the top of the burners a burn off air spray nozzle was added, creating at the lower portion of the main combustion zone an atmosphere with a relatively low oxygen concentration, and thereby effectively lessening the generation of NO x . The axis of the lower secondary air jet flow of the upper and lower layer of burners was made to deflect a certain angle relative to a water wall, and the tangential diameter of the secondary air at the upper row burners was enlarged. As a result, the mixing of the secondary and primary air pulverized coal mixture is postponed, thus decreasing the oxygen supply at the ignition stage and effectively reducing the generation of NO x . The test results have demonstrated that at a rated load the NO x emissions can be significanly reduced to 315.4 mg/m 3 (O 2 = 6%, dry flue gas), far lower than the emission standards. Meanwhile, a boiler efficiency of 91.85% can be attained, which is higher than the original design value by 1.32%.