煤泥干粉在流化床中燃烧特性的实验研究

Combustion characteristics of dry coal slime powders in a fluidized bed

为了探索煤泥燃烧利用的新途径,首先研究了煤泥干粉的燃烧动力学,然后在高2 000 mm、内径100 mm实验室规模的流化床中系统研究了其燃烧特性。结果表明,煤泥干粉燃烧为一级反应。在床温900℃、床料为40目石英砂的条件下,当u/umf>6,即操作气速过高时,由于煤泥干粉粒径较细,煤泥在床内停留时间较短,燃烧不充分,炉内轴向温度与烟气中CO,SO2,NOx等污染物浓度波动大;当u/umf<2时,由于气速过低,流化质量差,密相区物料出现沉积,导致炉内煤粉出现'爆燃';在u/umf为2~6之间,随着流化气速增加,CO,SO2,NOx等烟气组分均明显增加。当以相同Ca/S摩尔比加入石灰石后,随流化气速降低,气体停留时间增加,SO2和石灰石的气固接触改善,炉内脱硫效率提高。

Aiming at exploring new techniques for coal slime combustion,the combustion kinetics of Dry Coal Slime Powders(DCSP)was firstly investigated by a thermogravimetric analyzer.Then,the combustion characteristics of the DCSP was further measured in a fluidized bed with a height of 2 000 mm and an inside diameter of 100 mm.The results showed that the combustion of DCSP can be well correlated by a first-order reaction kinetics.At the bed temperature 900℃with 40 mesh quartz sand as the bed material,the axial temperature profile and the CO,SO2,NOx concentrations fluctuate significantly when u/umf>6,because the residence time of DCSP in the bed is too short to allow the complete combustion to be achieved at higher gas velocities.At lower gas velocities(u/umf<2)the fluidization quality is poor,the flammable fine coal slime powders accumulated in bed bottom lead to sudden and explosive combustions,causing the bed temperature to rise sharply.When u/umf is between 2 and 6,the CO,SO2,NOx all increase with the increase of u/umf.Experimental data also revealed that at the same Ca/S molar ratio,the SO2 removal efficiency by in-bed limestone increase with the decrease of gas velocity,which is resulted from the increased residence time at lower gas velocities.