低阶煤颗粒-气泡粘附过程的界面化学特性及其液膜失稳机制研究

With the rapidly increasing yield of low rank coal in China, the problems of fine particle flotation have been a technical bottleneck， restricting its clean and efficient utilization. Aiming at the characteristic of flotation of low rank coal and beginning with the surface reactivity and interfacial chemistry, the present research work closely revolves with the core process of mineralization between bubbles and particles, which involves in the bubble-particle interaction, instability, rupture of wetting film and the formation of three-phase contact line (TPCL). The advanced analysis methods, such as reflection interference contrast microscopy (RICM), atomic force microscope (AFM), wetting film analysis system (TFA), high speed micro dynamic system, the interdisciplinary theories of mineral processing, colloid and interface chemistry, thermodynamics and process dynamics are employed. By applying these methods and theories, the surface activity and reactivity of low rank coal are firstly studied in both mesoscopic and microscopic scale. In addition, the mechanism of origin and function of long-range hydrophobic forces based on nano-bubble bridging is explored to grasp the variation law of hydrophobic interaction force between different types of low rank coal particles and bubbles. Furthermore, the critical thickness，instability conditions and thinning dynamics of wetting film are investigated to reveal the mechanism of wetting film instability and attachment between particles and bubbles and to find appropriate methods of controlling wetting film thinning. As a result, the theory of coal slime flotation is further enriched and the theoretical and technical support for improving mineralization efficiency and flotation effectiveness of low rank coal is provided.

随着我国低阶煤资源开发量的不断增加，细粒低阶煤的浮选问题已成为制约低阶煤高效清洁利用的瓶颈问题。本项目针对低阶煤浮选的特点，从表面反应性和界面化学入手，围绕粘附过程中颗粒-气泡间作用力、液膜的失稳与破裂以及三相接触周边的铺展这些矿化核心环节展开研究工作。利用反射干涉对比显微镜（RICM）、原子力显微镜(AFM)、液膜分析系统（TFA）、高速显微动态系统等先进分析测试手段，综合运用矿物加工学、界面化学、热力学和动力学等多学科的交叉方法，从介观和微观尺度上，研究低阶煤表面活性及其反应性；探索基于纳米气泡桥接的长程疏水力形成与作用机制，掌握不同类型低阶煤颗粒-气泡间疏水作用力的变化规律；研究颗粒-气泡间液膜临界厚度、失稳条件及其薄化动力学行为，揭示颗粒-气泡间的液膜失稳机理和粘附机制，并找到合适的调控途径和方法。从而可进一步丰富煤泥浮选理论，为改善低阶煤的矿化效率和浮选效果提供理论和技术支撑。

细粒低阶煤的浮选问题严重制约着低阶煤的清洁高效利用，是煤炭行业迫切需要解决的重大技术难题。本项目从低阶煤表面反应性和界面化学入手，围绕粘附过程中颗粒-气泡间作用力、液膜的失稳与破裂以及三相接触周边的铺展这些浮选矿化核心环节展开研究工作。.根据研究计划，开展了低阶煤的表面特征、表面润湿热力学行为及表面水化特性研究，研究了低阶煤表面水化作用的影响因素，探究了不同疏水性表面之间水化膜的薄化特征；进行了颗粒-气泡间疏水作用力的理论计算与测试分析，系统揭示了长程、短程疏水力的起源机制；开展了液膜失稳及排液动力学研究，探讨了表面力和流体阻力对液膜时空演化的驱动机制，明晰了低阶煤-气泡间液膜失稳与破灭的机理；开展了低阶煤颗粒-气泡捕获时三相接触周边扩展行为研究，揭示了三相接触周边形成扩展机制；开展了超声空化预处理和不同浆体溶液环境下低阶煤浮选过程工艺条件的研究，建立了关于浮选溶液化学环境的浮选可燃体回收率模型，初步掌握了液膜薄化过程的调控途径和方法。研究表明，疏水引力是驱动低阶煤颗粒-气/油泡粘附矿化的决定性因素，短程疏水力来源于疏水表面水分子的排空区，克服短程内的范德华斥力，诱发液膜失稳；疏水体系下的长程疏水力来源于亚稳态液膜的空化现象，加速液膜的薄化过程，二者协同触发液膜的破裂。颗粒-气/油泡间粘附过程的可视化研究佐证了这一结论，增强的疏水引力使水化膜在28 ms内完成薄化、破裂过程，在42 ms内完成粘附过程；建立了关于浮选溶液化学环境的可燃体回收率模型，找到了低阶煤浮选的最佳工艺条件，使粘附所需诱导时间降低了30%以上，可燃体回收率提高了66%。.本项目按计划完成了全部研究内容，并达到预期目标。发表SCI论文12篇，EI论文6篇，培养博士3名，硕士5名，其中1人荣获江苏省优秀博士学位论文。项目研究成果进一步丰富了煤泥浮选理论，为低阶煤浮选工业应用提供了重要理论依据和技术支撑。