半焦空气分级燃烧排放试验研究 - -

半焦是低阶煤经低温热解后的产物,其中半焦粉与煤粉工业锅炉常用煤种烟煤相比价格低廉。若能将半焦粉用作煤粉工业锅炉的燃料,既可拓宽煤粉工业锅炉的适用燃料范围,又可增强煤粉工业锅炉的市场竞争力。由于半焦挥发分低、固定碳高,实现其着火和稳定燃烧需要更高的温度,同时,降低NO_x初始排放也是一个技术难题。为了实现半焦在煤粉工业锅炉中的稳定燃烧及NO_x排放的降低,采用两段式滴管炉开展半焦空气分级燃烧NO_x排放规律研究。笔者对半焦空气不分级燃烧NO_x排放规律进行了研究,主要探究了主燃区温度(1 000～1 400℃)及过量空气系数的影响,为后续空气分级燃烧降低NO_x的效果提供对比依据。半焦空气分级燃烧试验主要研究了主燃区温度(1 000～1 400℃)及二次风比例(0.4～0.8)的影响,并从燃尽率、NO_x减少比例、灰样微观孔隙和形貌等方面进行论证,试验结果表明,在空气不分级燃烧条件下,即燃尽风配风比例为0时,随着主燃区温度升高,NO_x排放浓度随之迅速升高;随着过量空气系数增加,NO_x浓度先迅速增加,过量空气系数大于1.15时,NO_x浓度增速变缓;在空气分级燃烧中,相同主燃区温度条件下,二次风比例由高到低变化时,NO_x排放呈先迅速下降后缓慢回升的变化趋势,燃尽率先快速升高而后趋于平缓。二次风比例为0.56时(即燃尽风率为0.39),燃尽率达90%,NO_x排放浓度降至最低,为120 mg/m3以下,此时是试验条件下的最佳二次风比例。 Semi-coke is the product of low-rank coal pyrolysis at low temperature. The price of pulverized semi-coke is lower than that of bituminous coal which is the commonly used in industrial pulverized coal boiler. If semi-coke can be used as the fuel of industrial pulverized coal boiler,the applicable fuel range of the coal-fired industrial boiler will be widen. Besides,the market competitiveness of coal-fired industrial boiler can be enhanced. Because of the low volatile content and a high fixed carbon content,semi-coke needs a higher temperature for ignition and steady combusiton. What's more,the decrease of NO_xemission is a also a technical problem. The NO_x emission properties of semi-coke air-staged combustion was studied in two-stage drop-tube furnace to realize steady combustion in pulverized coal industrial boiler and low NO_xemission of semi-coke. In this paper,the NO_xemission law of semi coke air non-staged combustion was studied.The influence of fuel-rich zone temperature( 1 000-1 400 ℃) and excess air coefficient( 1.0-1.3) were explored to give a comparison with the following air-staged combustion experiment. In semi-coke air-staged combustion experiment,the influence of the fuel-rich zone temperature( 1 000-1 400 ℃) and the ratio of secondary air( 0.4-0.8) were explored. Besides,the burn-out rate,NO_x decrement rate and microscopic pore structure and morphology of air-graded combustion ash were analyzed to reach a comprehensive conclusion. It can be concluded from the non-staged combustion experiment that under the condition of air non staged combustion,and when the ratio of exhaust air to air distribution is 0,the NO_xemission increases rapidly with the fuel-rich zone temperature increasing. When the excess air coefficient increases,the NO_xemission increases rapidly first,and then the increase becomes slowly when excess air coefficient is over 1.15.It can be concluded from the air-staged combustion experiment that when the