恒温下玉米芯焦与煤混燃动力学研究

KINETIC CHARACTERISTICS OF TORREFIED CORNCOB AND COAL CO-FIRING UNDER ISOTHERMAL CONDITION

利用自制恒温热重实验系统,研究煤种、生物质焦掺混比例、生物质焦碳化温度及温度等对玉米芯焦与煤混燃特性的影响,并通过随机孔模型求解燃烧反应活化能。结果表明:玉米芯焦与不同煤种混燃时,均可降低燃烧反应表观活化能,加快燃烧过程;且随所选煤的灰分含量的增加或挥发分含量的减小,玉米芯焦对混合样品燃烧过程的改善程度更加明显。混合样品中玉米芯焦掺混比例增大,燃烧反应表观活化能降低,样品燃烧失重过程加快,燃烧速率增大。制备玉米芯焦的碳化温度升高,掺混试样燃烧过程的改善程度呈现出先增大后减小的变化规律。不同实验温度下的动力学计算结果表明,低温段(800~950℃)的燃烧反应表观活化能明显大于高温段(950~1100℃)。

In this study,the combustion behavior of torrefied corncob and their blends with coal was investigated by using a modified constant temperature thermogravimetric apparatus.The effects of coal ranks,biochar blending ratio,pyrolysis temperature and experimental temperature on the co-firing characteristics were studied.Kinetic parameters of combustion were calculated by random pore model.The results show that the kinetic activation energy of the combustion can be reduced and the combustion process can be accelerated when torrefied corncob is blended with coal with different ranks.As the ash content of the selected coal increases or the volatile content decreases,the improvement of the biochar on the combustion process of the blended sample becomes more obvious.With the increase of biochar blending ratio,the activation energy of the combustion reaction decreases,the weight loss process of the blended sample is accelerated,and the burning rate increases.As the pyrolysis temperature of corncob increases,the improvement degree of the combustion process of the blended sample increases first and then decreases.The kinetic calculation results at different experimental temperatures show that the activation energy of the combustion reaction in the low temperature section(800-950℃)is significantly larger than that in the high temperature section(950-1100°C).