基于界面调控的粉煤灰中未燃炭脱除机理研究

Froth flotation is an important and frequently-used method to remove unburned carbon from coal fly ash. The existence of unburned carbon in coal fly ash is harmful to its use in construction area. After burning in a high temperature, however, great changes about physic-chemical characteristics take place in the interface of unburned carbon, e.g., multi-porous surfaces, high oxidation surfaces, deposition of some hard-to-float minerals fused in combustion process on the surfaces of unburned carbon. In addition, solution chemistry of the pulp in flotation system also presents diverse characteristics. These changes result in the instability of froth flotation system and the difficulty of the flotation removal of unburned carbon. In this project, the interfaces of unburned carbon will be characterized by the measurements of physic-chemical properties, and adsorption kinetics model of collector on the interface of unburned carbon will be set. Froth stability mechanism of unburned carbon flotation system will be determined by froth stability measurements based on solution chemistry regulation. Combining pore characteristic of unburned carbon and researches on fluid dynamics of pipe flow of flotation column, dissolving out mechanism of free gas in the pore of unburned carbon will be also investigated. On the basement of the above studies, the interface-control and froth stability mechanism of hard-to-float unburned carbon flotation will be established, and relationship between froth stability and flotation performance will be modeled. Therefore, in addition to the important theoretical value on the interface-control and high efficiency mineralization of hard-to-float particles, this project also has significant practical value for the high efficient removal of unburned carbon in coal fly ash and even efficient development of the low quality hard-to-float coal.

粉煤灰浮选脱碳是粉煤灰综合利用的重要途径，但由于经过高温燃烧之后，未燃炭的表面物理化学特征发生较大变化，表面疏松多孔，同时由于其部分难浮矿物融熔后沉积在未燃炭表面，浮选泡沫体系极不稳定，未燃炭脱除困难。本项目通过未燃炭表面物理化学性质的测试及表征，建立捕收剂在其表面的吸附动力学模型；通过多种手段调整浮选体系的溶液化学环境，进行泡沫稳定性的测试及未燃炭表面改性研究，探明粉煤灰浮选脱炭体系的泡沫稳定机制；结合未燃炭表面的孔隙特征，采用流场测试技术和数值模拟手段研究浮选柱管流场下未燃炭毛细孔自由气体的析出机理。通过以上研究建立难浮未燃炭浮选脱除的界面调控和泡沫稳定机制，建立泡沫稳定性和浮选脱碳行为之间的关系模型。因而本项目在关于难浮选颗粒界面调控及高效矿化方面的研究不仅具有重要的理论价值，而且对于粉煤灰未燃炭的高效脱除乃至低品质难选煤的高效开发具有普遍的指导意义。

从矿物组成、表观形貌、界面可浮性和体系泡沫行为的角度，系统分析了粉煤灰的矿物组成特点、界面特征和浮选体系特征。粉煤灰中的颗粒组成中以非晶质的玻璃体为主，颗粒形貌大多以球状体、棱角分明的不规则体、多孔体等为主。未燃炭的接触角仅为35.9°，可浮性较差，与燃前原煤相比，未燃炭中的C、H元素含量明显下降。上述因素是导致未燃炭难浮的根本原因。.分析了泡沫结构要素内的物理化学过程与泡沫衰变之间的关系，形成了“泡沫的结构要素稳定，则泡沫稳定”的重要认识：泡沫的衰变过程其实就是泡沫内液膜的兼并和破裂过程，泡沫内的排液过程导致液膜的薄化，从而加速液膜的兼并和破裂，这是泡沫衰变的根本原因。.结合Laplace定律、DLVO理论和扩展的DLVO理论，探讨了泡沫液膜的热力学排液机理和泡沫Plateau通道内的重力排液过程。对于液膜排液过程：毛细压作用越大，液膜内液体的排出越快；分离压作用越大，液膜内液体的排出越慢；对于Plateau通道内的排液过程：泡沫内的含水量越大，排液速度越快；泡沫内的液体粘度越大，排液越缓慢；泡沫内的液相表面张力越小，排液越缓慢。.从液相性质调控的角度研究了起泡剂溶液的表面张力和气液界面弹性、增粘剂的液相粘度、无机盐离子在水基两相气泡及泡沫形成过程中的作用。以无烟煤煤泥、肥煤煤泥和未燃炭三种疏水性程度不同的炭质颗粒为研究对象，考察了颗粒的可浮性和粒度对泡沫稳定性的影响。研究表明：颗粒体系的泡沫稳定性随着颗粒疏水性的增大而提高，随着颗粒粒度的增大而降低。.研究了未燃炭的孔隙特征和射流条件下的空化效应，采用金、聚氯乙烯、铅和玻璃四种材质的基地进行空化试验。研究表面：颗粒表面的疏水性越强，在其上附着的亚微米气泡越多。对于疏水性不同的四种材质的基底，在气泡发生器喷嘴射流速度分别为26.52m/s和36.36m/s时，疏水性不同的基底上吸附的气泡数目和大小不同，随着喷嘴水流速度增高，基底上附着的气泡数目增多，这说明在射流气泡发生器中，空化效应对气泡大小和数目起着决定性作用。.以韶关发电厂的湿排粉煤灰为试验用样，进行了基于泡沫稳定性调节的浮选药剂筛选试验。优选出捕收能力较强的柴油为捕收剂、起泡能力和浮选效果较好的FMH为起泡剂、兼有增粘作用和表面活性的聚乙二醇为增粘剂。