低阶煤极性基团调控及压力梯度脱水机制研究

Rich oxygen polar groups in low rank coal profoundly affected the moisture adsorption and occurrence mode，thus, affects the energy consumption of drying process, spontaneous combustion tendency and moisture absorption behavior. Evaporation drying wastes a lot of latent heat of evaporation in drying process, and it is difficult to solve the negative impact of polar group，however the non-evaporation drying technology has remarkable energy-saving advantages. The innovation of this project lies in: (1) Put forward the mechanism of polar group regulation， which combines the modification of surface infiltration with directional decomposition by microwave，The essence of synergy is that energy can be focused on the polar group，so that it could realize the deep directional control of the polar groups. The change of hydrophilic/hydrophobic characteristic in inner pore, is expected to achieve a dehydration technology with lower energy consumption; (2) Put forward the mechanism of pressure gradient of dehydration through the coordination of mechanical and thermal action. Its essence is to achieve synergy of mechanical and thermal stress gradient moisture migration effects, give full play to both of the strengths. The idea is: remove the weakly combined free water and physically bounded water based on centrifugal field; remove the strongly combined chemical adsorbed water and physically bounded water conditioned by channel connectivity based on pressure gradient which comes from internal moisture evaporation. Related research results can provide theoretical guidance for the development of ideal drying method of low energy consumption.

低阶煤中丰富的含氧极性基团深刻影响了水分的吸附和赋存形态，并进而影响干燥过程能耗、自燃倾向及水分复吸行为。蒸发干燥浪费了大量的潜热，且难以较好解决极性基团的负面影响，非蒸发干燥则具有显著节能优势。本项目创新之处在于：（1）提出了表面渗透改性与微波定向分解协同的极性基团调控机制，其协同的本质在于使能量可集中作用于极性基团，实现对极性基团的定向深度调控。孔隙内部亲疏水特性的改变，可望实现更低能耗的脱水；（2）提出了机械与热力作用协同的压力梯度脱水机制。本质在于实现机械与热力两种压力梯度湿分迁移作用的协同，可充分发挥两者的长处。其构想是采用基于离心力场的压力梯度脱水方法脱除结合能较低的自由水和物理束缚水，采用基于内部水分蒸发的压力梯度脱水方法脱除结合能较高的化学吸附水以及受孔道连通性制约的物理束缚水。相关研究成果可为开发理想的低能耗干燥方法提供理论指导。

低阶煤中丰富的含氧极性基团深刻影响了水分的吸附和赋存形态，利用基于压力梯度的湿分迁移是实现快速、高强度干燥的关键。基于极性基团调控和压力梯度脱水过程，本项目取得以下研究进展：.（1）发展了基于水热作用的低阶煤加压渗透提质及极性基团调控。在高温高压下对低阶煤进行水热加压渗透，同步实现水分非蒸发脱除和含氧极性基团的高效分解；以褐煤自身水分为反应介质获得良好煤质改性和极性基团脱除效果；通过改变煤水布置方式实现饱和蒸汽水热提质处理并获得良好脱水提质效果；探究了水分形态对极性基团脱除的影响机制。.（2）发展了低阶煤微波干燥特性及动力学研究。实验发现增大功率和粒径、减小质量对增强微波干燥效果具有正向促进作用；验证Midilli-Kucuk模型在描述微波干燥过程中的有效性，并通过动力学计算获得褐煤微波干燥活化能；微波干燥后样品复吸行为得到明显抑制，干燥气氛中水蒸气对极性基团脱除具有积极促进效果。.（3）从实验角度验证低阶煤极性基团微波调控中的非热效应。针对性设计单变量微波辐照实验，证实微波制热效应对极性基团的脱除具有重要影响；通过同升温对比及近常温调控实验，证实微波辐照在极性基团调控过程中存在非热效应，脱除量与微波功率、辐照时间呈现正相关关系。.（4）建立低阶煤双尺度干燥模型和薄层褐煤微波理论模型。通过修正扩散系数和引入吸附脱附速率，依据能量守恒定律和质量守恒定律建立了无蒸发界面褐煤干燥模型；采用多尺度方法，建立了褐煤干燥双尺度模型；基于麦克斯韦方程组、能量守恒方程、扩散方程，建立了描述薄层褐煤微波干燥过程的理论模型，模拟了微波干燥过程中电磁场及温度分布。