难浮煤颗粒-气泡间液膜的薄化破裂机理研究

Flotation is one of the most effective methods for coal cleaning. However, low-rank coal, oxidized coal, and low ash middling are difficult to be captured by bubbles because of the low surface hydrophobicity of these particles. The drainage rate of a thin liquid film between the bubble and these particles is slow and is sometimes equal to zero. Thus, typical representative difficult-to-float coal samples will be selected. X-ray photoelectron spectroscopy will be used to scan the surface molecular structure and composition (aliphatic hydrocarbon chain, oxygen functional groups, benzene). Statistical analysis will be used to study surface hydrophobic properties. Bubble–particle force variation measurements will be performed with an atomic force microscope. In addition, thin film apparatus will be used to measure the spatial and temporal profile of the film thinning between bubble and particle, and the calculation of surface force will be obtained through the numerical analysis of fluid. Based on results, a joint collector will be used to intensify and restore the hydrophobicity of difficult-to-float particles through the synergy bonding interaction between collector and coal surface molecules. Bubble–particle interaction force and liquid film thinning and rupture dynamics behavior will be tested and verified after joint collector modification from the aspect of interface force and nanometer scale. The mechanism of film thinning and rupture will be revealed. Therefore, this project will provide a guiding significance for high efficiency flotation of coal and non-coal minerals.

浮选是细粒煤洁净加工最有效的方法之一，但低阶煤、氧化煤、中低灰的中煤连生体等难浮煤表面疏水性差，浮选过程中颗粒-气泡间液膜薄化破裂速度慢、甚至不破裂，煤粒难以被气泡捕获。针对这一浮选难题，选取代表性难浮煤进行样品制备及性质测试，利用光电子能谱（XPS）扫描其表面分子结构组成（脂肪烃链、含氧官能团、苯环），统计分析样品表面的疏水位点分布；在难浮煤颗粒-气泡接触过程中，利用原子力显微镜（AFM）测试颗粒-气泡相互作用力的变化规律，利用液膜分析系统（TFA）观测煤与气泡间液膜的薄化以及破裂过程，并且通过流体数值分析，计算表面作用力。在此基础上，通过复配捕收剂分子与煤表面分子的键合协同，强化难浮煤颗粒的表面疏水性，进一步测试并相互验证复配捕收剂改性后的难浮煤颗粒-气泡相互作用力及其液膜的薄化破裂动力学行为。难浮煤颗粒-气泡间液膜薄化破裂机理的揭示，有望为煤及非煤矿物的高效浮选回收提供借鉴。

我国低阶/氧化煤等难浮煤储量大（40%左右），表面丰富的含氧基团和发达的孔隙结构导致其疏水性差，水分子极易在煤粒表面形成牢固的水化膜，阻碍捕收剂分子吸附以及气泡粘附，致使浮选回收难，亟需以浮选颗粒气泡间、气泡间相互作用为着重点进行基础分析，旨在为难浮煤高效提质提供理论借鉴。. 项目利用浮选液膜分析仪探索颗粒气泡、气泡间液膜的薄化破裂行为，借助SRYL方程分析了液膜的临界破裂厚度、薄化速率以及界面力学信息。亲水性颗粒气泡间的最终平衡膜始终保持稳定状态，气泡接近速度决定了颗粒气泡间液膜的轮廓，从而影响颗粒排水过程的动力学，在排液初期，气泡快速“逼近”颗粒表面，使得距离颗粒表面最近的中心点排液速度放缓。粗糙的亲水颗粒-气泡间液膜稳定，而粗糙的疏水颗粒气泡的粘附作用强。疏水力是诱发气泡间液膜薄化破裂的根本原因，NaCl和SDS的加入均减缓了液膜排液速率。气泡尺寸增加致使体系Laplace驱动力减小，导致气泡间平衡膜厚度增加；随着气泡接近速度增加，流体阻力诱发气液界面开始出现“浅凹”形变，但对气泡间最终平衡膜厚度的影响不大。. 利用AFM直接测试颗粒气泡以及气泡间相互作用力，借助SRYL模型拟合试验测试值，以揭示难浮煤颗粒气泡以及气泡间液膜稳定性机理。疏水玻璃与气泡间的疏水力以3.50 nm的衰减长度按单指数模型衰减，液膜在32.96 nm临界破裂厚度处破裂。该疏水力倾向于一种短程力，源自界面的水分子重排熵效应。SDS存在体系下气泡间相互作用力一直表现为斥力作用，SDS实现了气泡间疏水引力的有效屏蔽。气泡间排斥力随着接近速度的增加而增加，通过增加AFM Setpoint仍无法有效触发液膜破裂。. 基于以上难浮煤颗粒气泡排液及颗粒气泡间相互作用力学机制的研究，提出了基于界面调控的难浮煤高效分选技术，开发了适用于难浮煤浮选的极性复合捕收剂，形成了基于复合药剂和荷电微泡联合的难浮煤浮选界面调控技术。