燃煤化学链气化中铁基复合载氧体与焦油相互作用机理研究

To solve the problems that exist in the current coal gasification technology of coal-based synthetic natural gas process, such as the low H2/CO ratio，the complicated process and high carbon emission to produce the H2/CO ratio syngas that meet the requirement of methanation, a novel chemical-looping gasification technology is proposed in this project to achieve the produced syngas with H2/CO ratio maintained at 3 and simultaneously capture the CO2 by using one-step method. However, the tar components derived from the coal pyrolysis process of the reduction period could result in the carbon deposited on the iron-based oxygen carrier particles , which would show a significant impact on the reactivity and reduction degree of iron-based oxygen carrier. With the aim of improving the performance of tar removal and resistance to carbon deposition for iron-based oxygen carrier, the deep reduction mechanism of iron-based oxygen carrier will be investigated by the theoretical and experimental studies in this project. Based on the analyses of carbon deposition and tar cracking pathways of iron-based oxygen carrier at the molecular level, the modification mechanism and method will be studied to explore the iron-based composite oxygen carrier with the functions of deep reduction, tar removal and resistance to carbon deposition, eventually obtaining the coupling regulatory mechanism of deep reduction with the tar removal and resistance to carbon deposition for iron-based composite oxygen carrier. The investigation in this project will preliminarily establish a theoretical screening basis of iron-based oxygen carrier for this novel coal-based chemical-looping gasification process with high H2/CO ratio syngas production.

新型燃煤化学链气化技术可以一步实现合成气中H2/CO比为3并协同捕集CO2的目标，能够解决煤制天然气工艺中现有煤气化技术存在H2/CO比低、达到符合甲烷化H2/CO比要求所需工艺复杂、碳排放高等问题。然而，还原阶段煤热解过程产生的焦油组分易于造成铁基载氧体积碳，严重影响了铁基载氧体的活性及其还原深度。本项目从改善铁基载氧体脱焦油、抗积碳的性能角度出发，拟通过理论分析和实验研究揭示焦油作用下铁基载氧体的深度还原机制，基于分子层面上对铁基载氧体焦油裂解途径及积碳形成路径的解析，探索具备“深度还原-脱焦油-抗积碳”铁基复合载氧体的改性机制及方法，获得铁基复合载氧体深度还原协同脱焦油、抗积碳的耦合调控机制，初步建立新型燃煤化学链气化制备高H2/CO比合成气的铁基载氧体筛选理论基础。

项目提出的新型燃煤化学链气化工艺可以通过更短的工艺链产生满足后续甲烷化过程所需的H2/CO比合成气，并实现CO2协同捕集，但还原阶段煤热解过程产生的焦油组分易于造成铁基载氧体积炭，严重影响铁基载氧体活性及其还原深度等问题，研究了典型煤焦油模型化合物在铁基载氧体逐级还原过程中的转化机理、积炭形成机制以及铁基载氧体不同还原阶段的氧传递机制，并与镍基和铜基载氧体进行了比较，发现萘的转化过程与载氧体类型无关，但与载氧体中的晶格氧含量密切相关，随着载氧体还原程度加深，晶格氧传递愈加困难，萘转化率逐级下降，导致积炭含量增加；对苯和萘作用下四种载氧体（铁基载氧体和负载NiO、CuO、CoO活性组分的三种铁基复合载氧体）的积炭行为研究表明，四种载氧体深度还原状态下均更易生成积炭，但添加活性组分后有利于提高铁基载氧体抗积炭性能，反应温度的升高也有利于提高载氧体反应活性、降低积炭含量，但高温状态时对于含碳量高的萘会降低铁基复合载氧体抗积碳性能。结合铁基载氧体还原阶段的氧传递量子模拟研究及载氧体物理结构表征分析，证实了载氧体中的晶格氧传递特性是决定其深度还原、脱焦油、抗积炭性能的关键因素，具有更快的氧迁移传递速率和更低的氧空位形成能的载氧体具有更好的深度还原性能和脱焦油、抗积炭能力。在此基础上，基于量子模拟、实验研究和表征分析筛选出了高活性铁基复合载氧体的活性组分，合成了理化性能稳定、氧迁移速率快的铁基复合载氧体，探索了活性组分提升铁基载氧体还原性能的作用机制，在具备脱焦油、抗积炭性能的基础上实现了铁基载氧体的深度还原。项目的研究成果对于新型燃煤化学链气化工艺的进一步发展提供了基础数据和理论指导。