10kg/h下行床褐煤低氧气化及半焦反应特性

摘要

A pilot-plant downdraft gasifier with a feeding rate of 10 kg/h was developed for lignite gasification.Contrast with the lab-scale gasifier,then the effects of different reactor dimension on characteristics of lignite low-oxygen gasification were investigated.The pore structure and alkalis retention of semi-coke were respectively studied by physical adsorption and inductively coupled plasma spectrometer (ICP-OES),and the semi-coke specific reactivity was studied by thermogravimetric analysis(TGA).The results show that the gas components of 10 kg/h have the same trend as the lab-scale gasifier without baffle structure.But the baffle structure of 10 kg/hgasifier can extend gas residence time,thus promote the secondary reaction and the cracking degree of macromolecules,and achieve relative high volume fraction of CH4.The increases of oxygen volume fraction can promote the semi-coke pore cracking and collapsing,resulting in semi-coke pore transforming into mesoporous/macropores.The partial "heating effect" and baffle structure of 10 kg/h gasifier can promote alkalis evaporation,resulting in decreases of alkalis retention in semi-coke.The specific reactivity of semi-coke from 10 kg/h gasifier is much lower than that of the lab-scale gasifier and it is directly attribute to the reducing of active sites and weaken of alkalis catalyst.%利用进料量10 kg/h的下行床反应器对褐煤进行气化实验.与前期相同类型的小型气化炉进行比较,对比考察反应器尺度对褐煤低氧气化特性的影响.通过物理吸附手段和等离子体发射光谱仪(ICP-OES)分别研究气化半焦的孔隙结构和碱金属滞留,并应用热重分析仪(TGA)研究半焦的反应性.结果表明:10 kg/h气化炉的煤气变化趋势尽管与小型气化炉的煤气变化趋势一致,但10 kg/h气化炉特有的折流结构能增加煤气的停留时间,促进二次反应和大分子裂解;煤气组成中CH4的体积分数偏高.随着气化剂中氧气体积分数的增加,10 kg/h气化炉气化半焦的孔隙破裂、坍塌程度增大,半焦孔隙趋向介孔/大孔过渡.10 kg/h气化炉的局部“热效应”及特有的折流结构可促进碱金属挥发,使生成半焦的碱金属滞留量减少.10 kg/h气化炉气化半焦的反应性比小型气化炉半焦的反应性更低,半焦孔隙过渡所导致的反应活性位减少及半焦中碱金属滞留量减少所导致的催化作用减弱是半焦反应性更低的原因.