脱水制浆耦合过程中煤结构的变化及对液化反应性的影响

Coal dewatering and coal swelling as pretreating method for coal liquefaction process have been studied extensively. There is, however, little attention paied to correlate the two processes. Partial liquefaction of coal at the low temperature and low pressure of 3-5MPa requires a better coal swelling by solvent for better coal dispersing and radical extinguishing. It was found that coal dewatering process led to a negative impact on coal swelling and its liquefaction reactivity. A new coal pretreating method with coupling of dewatering and slurry preperation was proposed. It helps keeping a loose structure for coal and improves coal's swelling property. This project aims to study the changes of hydrogen bonds and oxygen functional groups and the influence on the pore sturcture of coal in coupling processe of dewatering and slurry prepatration. By studying the changes of hydrogen bonds and oxygen functional groups and understanding the properties and interaction of water-solvent-coal mixture system, an attempt will made to understand the reason for the improvement of coal swelling in solvents during the coupling process of dewatering and slurry preparation. Based on the understanding for the coupling process, the correlation among dewatering/swelling/deoxygen-coal structure-liquefaction reactivity will be established. This study also aims to provide basic data for optimalizing the coupling process.

煤脱水和溶胀技术作为煤液化转化预处理工艺的研究有大量的文献报道，但关联这两种技术的研究鲜有报道。对于低压（3-5MPa）和较低温度下的煤加氢液化反应，要求溶剂对煤充分溶胀，以保证液化过程中对煤的充分分散和对自由基的及时熄灭。申请人前期研究发现煤直接脱水过程对煤结构及液化性能有很大负面影响，提出了脱水制浆耦合的新型煤预处理方案。该过程使煤在脱水过程中能够保持结构松散、并促进溶剂油对煤的溶胀。本项目拟对比研究煤直接脱水和脱水制浆耦合过程中非共价键（氢键）以及弱共价键（含氧官能团）的变化规律，及其对煤孔隙结构的影响；通过对煤中氢键及含氧键变化规律的研究，结合对不同条件下水-溶剂油-煤体系性质和相互作用关系的认识，理解脱水制浆耦合可促进溶剂对煤溶胀的主要原因；通过对脱水制浆耦合过程机理的理解，建立脱水/溶胀/脱氧-物理化学结构-液化反应性间的联系，为实现脱水和制浆过程的最佳配合提供科学依据。

对于低压（3-5MPa）和较低温度下的煤加氢液化反应，要求溶剂对煤充分溶胀，产生疏松煤结构的效果，促进煤的加氢液化。前期研究发现煤直接脱水过程对煤结构及液化性能有很大负面影响，提出了脱水制浆耦合的新型煤预处理工艺。本课题旨在通过研究煤在不同条件下脱水时的转化规律，认识煤脱水制浆耦合过程的内在优势，为新型煤预处理工艺的优化提供理论依据。. 本课题比较了单一脱水和脱水-制浆耦合两种处理方法对煤液化反应的影响，研究了不同油煤浆预处理条件下煤结构和液化产物组成的变化，引入了微波预处理技术。研究发现，油煤浆的微波预处理，对煤的化学结构影响较小，但可促进煤结构疏松、改善溶剂-煤间的互溶效果，进而使煤加氢液化转化率和油收率得到显著提高。通过对松木屑（富含氧）醇解过程机理的研究，以及对辽河稠油（富含沥青质）/煤焦油馏份油体系热生焦规律的研究，阐明了溶剂在含碳固体原料热解聚和热缩聚过程中的作用。饱和烃、单环芳烃和缩合四环芳烃呈现促进生焦的作用，双环芳烃、三环芳烃和缩合双环芳烃呈现抑制生焦的作用。基于不同分子结构中C-H键离解能和生成加氢反应中间体活化能的量子化学计算数据，分析了煤液化反应过程中，溶剂的最可几供氢路径：（1）煤热解自由基首先与供氢溶剂的α氢碰撞，形成过渡态；（2）α氢脱离主体后，形成α位溶剂自由基，引发β位C-H键能的大幅降低；（3）β氢脱离主体形成氢自由基。