烟煤焦在H2O和CO2气氛下的结构演变与气化反应性关联

本研究以烟煤在1000 ℃热解所制得的焦样为研究对象，考察了其在H₂O、CO₂及两者混合气氛下的结构演变，以及气化反应性的影响。为了探究焦样在气化过程中的结构演变，利用氮吸附、SEM和拉曼光谱等表征手段分析不同碳转化率下的焦样结构。结果表明，H₂O气氛对焦样结构的演变明显不同于CO₂气氛，揭示了焦样在两种气氛下的反应路径不同。因结构演变的不同，随碳转化率的增加，焦样在两种气氛下表现出不同的气化反应性能。在CO₂气氛下，焦样的气化反应速率随碳转化率的增加而逐渐降低，与H₂O气氛存在下变化趋势相反。在H₂O和CO₂共气化条件下，煤焦在H₂O和CO₂混合气氛下的反应速率高于单气氛下的反应速率的计算值，表现出一定的协同作用。这是因为焦样与H₂O反应能够产生较大的比表面积，为焦样与CO₂反应提供更多的反应场所，促进了焦样与CO₂的反应。

Structural evolution of a bituminous coal char related to its synchronized gasification behavior with H2O and/or CO2

This work aims to investigate the structural evolution of the char during gasification under a single or mixed atmosphere of H₂O and/or CO₂ with the synchronized investigation of the effect of the varying char structure on the gasification reactivity. The experimental char was prepared from a bituminous coal at 1000°C. The changes of the char structure along with the progress of the carbon conversion during gasification were characterized using N₂ adsorption, SEM, and Raman spectroscopy. The results revealed that H₂O showed a more dramatically change on the char structure than CO₂ and two reactants had different reaction pathways. The different pathways of reactants affected the evolution manners of the char structure and different gasification reactivity of char was related to structural evolution. The specific reaction rate between the char and CO₂ decreased monotonously with increasing carbon conversion. However, the opposite trends are observed when H₂O exist, either H₂O alone or the mixtures of H₂O and CO₂. The char gasification reactivity was under the common effect of physical and chemical structure. In terms of the mixture of H₂O and CO₂, the significant specific surface area caused by H₂O provided more active sites for CO₂. The interactions between H₂O and CO₂ promoted reaction between C and CO₂ (C + CO₂ → CO) in mixtures of H₂O and CO₂, leading to higher amount of CO and higher specific reaction rate than calculated.