胜利褐煤外热式气流床温和气化建模研究:模型的求解及应用

摘要

The solution process and application of the one dimensional entrained flow bed gasification model proposed early were studied.It was found that the predicted values were in good agreement with the experimental values,with the error of less than 20％ for 92％ predicted values and less than 10％ for 75％ predicted values,which indicated proper dynamic equations and solving method for obtaining the values of unknown parameters were chosen.The model could also be used to predict well the gasification process under different temperature,atmosphere,residence time and particle diameter.The prediction results showed that,firstly,as the residence time increased,lignite conversion,H2 & CO2 content increased sharply and then slowly,CO content increased and then decreased,especially under high steam concentration and temperature.Secondly,ignite burning time is less than 0.5 seconds in 1％ O2 atmosphere at 800 ℃,significantly less than the gasification time,which proved the suppose that gasification process occurred after combustion process was reasonable.Thirdly,the sum content of CO,H2 in large size lignite gasification gas was higher than that in small size lignite gasification gas,which was consistent with the experimental results and may caused by the micro structure of different diameter char.Lastly,for initial carbon content of lignite particles in unit volume (Г),gas solid effective contact (collision) area in unit volume (∧),CO and CO2 partition coefficient in combustion process (α),sensitivities of coal conversion to them were at the same level,while sensitivities of the sum content of CO,H2 in gas to them were different significantly with the order from strong to weak,as α,∧,Г.%针对建立的一维气流床温和气化模型,研究了其求解过程、对实验结果预测的准确性、对不同条件下气化结果的预测及对参数敏感性的分析.结果发现,92％预测值误差小于20％,75％预测值误差小于10％.模型预测不同条件下的气化结果,与前人的理论研究和实验/工业化实践吻合.预测结果显示,随停留时间延长,褐煤转化率、H2和CO2含量先快速增加后缓慢增加,CO先增加后减小,尤其在较高水蒸气浓度和温度下;在1％O2气氛下,褐煤燃尽时间小于0.5s,明显小于气化反应时间;大粒径褐煤气化煤气中CO+H2含量较高,可能与不同粒径半焦的孔隙结构和反应性有关.氧化反应CO和CO2分配系数α,单位反应体积内褐煤颗粒的初始含碳质量Г及气固相有效接触(碰撞)面积∧,3个参数的物理意义可以很好地解释参数变化时褐煤转化率和煤气组成的变化,褐煤转化率对参数Г,∧,α的的敏感性相同,CO+H2含量对α的敏感性最强,∧次之,Г最弱.