冲击载荷下煤颗粒细观结构的非线性演化特征及对宏观粉碎特性影响的研究

One of the most important steps in the thermal utilization process of coal is comminution. In this study, coal particle structure will be comprehensively measured by some advanced equipments such as XRT and NMR from micro-level. Several non-linear theories such as fractal theory will be used to describe inner/surface defects of particles. The three dimension microstructure model would be constructed with the help of Monte Carlo method and be modified based on verification process between DEM/FEM simulation results and experimental data. Evolution processes of microsturcture at different stress strain stages caused by impact load are studied by statistical theory. At the same time, heterogenic and non-linear deformation characteristics and coupling effect of coal particle will be analyzed by experimental measurement. Therefore, impact of microstructure on micromechanical could be discussed. Under complex conditions, for example, high temperature, high humidity and cyclic loading, evolution modes of microstructure and their impact on micromechanics are analyzed. Space correlation rule of mechanical parameters could be decided by the distribution characteristics of micro-defect. A non-linear dynamic comminution model for coal particle will be established when microstructure characteristics are considered in the macroscopic constitution relationship. It will provide fundamental theory and propose retrofit directions to make the operation system of coal comminution process with higher efficiency and lower pollution.

煤的粉碎过程是决定其高效清洁热利用的重要环节之一。本课题利用XRT(同步辐射X射线)、NMR等仪器从细观层面对煤颗粒结构进行多角度测定，借助分形等非线性理论定量表征颗粒表面及内部缺陷；基于Monte Carlo等方法构建颗粒三维细观结构模型并采用DEM或FEM方法模拟修正；运用统计学方法确定冲击荷载等条件下细观结构在不同应力应变阶段的变化特征，研究煤颗粒的各向异性及非线性变形特征以及耦联效应，探讨细观结构对颗粒力学特性的影响规律；研究水份、湿度、往复荷载等复杂条件对颗粒细观结构的改变及与力学特性之间的相互耦联作用；基于细观缺陷的分布特点确定力学参数的空间相关性原则，将颗粒细观特征回归到宏观本构关系中并最终建立煤颗粒非线性动态粉碎力学模型，为煤制粉系统的高效、环保运行提供理论基础以及技术改进的方向。

提高煤粉碎效率不仅可以降低电厂能耗，还有助于煤炭的充分燃烧并降低NOx排放。前人通常在宏观层面对煤破碎能耗理论提出假说，但是从细观力学层面对煤的破碎过程研究还较少。本课题充分考虑到煤破碎过程中不同影响因素，基于单轴压力测试仪等开展力学实验，通过SEM、高速摄像、BET、压汞仪等进行细观形态分析，采用分形理论定量描述煤块表面孔隙结构及内部缺陷，运用统计学方法确定荷载等条件下细观结构在不同应力应变阶段的变化特征，研究煤块的各向异性及非线性变形特征以及耦联效应，采用以上方法对不同温度、不同湿度和循环载荷等不同条件下的煤破碎过程进行研究，从而探究多煤种在复杂条件下的力学特性变化规律，并对力学特性和细观结构之间关系进行拟合。采用Monte Carlo方法，结合Extrude方法构建实际孔隙分布的煤块三维细观结构模型，对不同条件下的煤破碎过程进行建模仿真分析，通过探究载荷作用下煤块内部的应力分布，确定最优的煤破碎条件参数，为将来工业技术开发提供理论基础。项目负责人2019年获国家科技进步二等奖1项（排名第二），2018年获湖北省科技进步一等奖1项（排名第二），项目共发表高水平论文14篇，其中SCI收录12篇，EI收录2篇，申请发明专利9个，其中授权6个，参加国际国内会议8次，培养研究生5人，其中3人获得出国交流机会；培养本科毕业生1人，获湖北省优秀学士学位论文称号。申请人在项目执行期获教育部新世纪人才称号。