水蒸气对褐煤原位气化半焦反应性能及微观结构的影响

为了揭示水蒸气对半焦反应性和微观结构的影响,在自制两段新型反应器上依次进行了褐煤干燥、热解及"热"焦的水蒸气原位气化研究。利用TGA、BET和Raman光谱仪,对原位气化半焦进行反应性和微观结构解析。结果表明,在反应温度为600 ℃时,水蒸气对半焦转化率、反应性及微观结构影响很小。温度达到700~900 ℃,在半焦与水蒸气接触的前2 min,虽然半焦转化率变化不大,但其反应性、小环(3~5个芳环)与大环(≥6个环)体系之比及含氧官能团却急剧降低;大于2 min,半焦转化率逐渐增大,反应性、小环与大环之比及含氧官能团缓慢降低;而半焦孔结构在2 min 前后却具有基本一致的变化趋势。半焦与水蒸气接触的前2 min,小环与大环之比和含氧官能团急剧降低是导致反应性显著降低的重要因素,大于2 min,芳环体系的变化是导致反应性进一步降低的原因。

Effects of steam on the reactivity and microstructure of char from in-situ gasification of brown coal

To examine the effects of steam on the char reactivity and its microstructure, experiments of drying and pyrolysis of brown coal as well as the in-situ gasification of "hot" char were carried out in a newly-designed two-stage reactor. The reactivity and microstructure of in-situ gasification char were characterized by TGA, BET and Raman spectroscopy respectively. The results show that at low temperature of 600 ℃, the steam has little effect on the conversion, reactivity and microstructure of char. When it reaches 700~900 ℃, there are different change trends before and after 2 min of reaction between char and steam. In the first 2 min, the reactivity, the ratio of small aromatic ring systems (3~5 rings) to the large fused rings (≥6 rings) and O-containing functional groups decrease dramatically although the char conversion varies little; after 2 min, however, char conversion increases gradually, char reactivity, the ratio of small to big aromatic ring systems and O-containing functional groups decrease slowly. In addition, the pore structure of char follows almost the same variation before and after 2 min. During the first 2 min, a sharp decrease of the ratio of small to big aromatic ring systems and O-containing functional groups are the important factors leading to the decrease of char reactivity; while after 2 min, the change of aromatic ring systems results in the further decrease of char reactivity.