Hydrogen bubble fiotation of fine minerals containing calcium

One characteristic of electro-flotation is the presence of micro bubbles that are well known for improving the flotation performance of fine particles. An electro-flotation method was studied with fine scheelite and fluorite particles sized into three different fractions. Experiments were performed in a modified Hallimond tube. We investigated the effects of gas holdup, particle size, and different mesh electrode apertures on mineral recovery. Flotation results show that two size fractions show increased flotation recovery as the gas holdup increases. For the sized scheelite and fluorite, the flotation effect is diverse for different sizes of the cathode aperture. Pictures of the bubbles taken by a high speed CCD were used to determine the hydrogen bubble size distribution generated as a function of collector, current density, and electrode size. The diameters of the hydrogen bubbles ranged from 12 to 117μm in alkaline conditions.

岩土孔隙率表征单元体及其分形近似判据

RVE(representative volume element)/REV(representative elementary volume)的存在性及其确定是尺度效应研究领域的一个基本科学问题.从复合材料微细观力学、岩土力学与工程领域分别分析了代表性体积单元(RVE)和表征单元体(REV)的异同,以后者为主要研究对象给出岩土介质REV研究的三层次分类.进一步以第三层次分类中的孔隙率、孔隙大小及分布分形维数为约束,引入分形几何理论描述岩土介质复杂孔隙结构,通过理论公式推演及与已有文献研究结果对比,提出了一种孔隙大小分布满足分形幂律特征条件下岩土介质孔隙率表征单元体(P-REV)尺度确定的近似判据,即岩土介质选择其内部最大孔隙孔径5倍的立方体单元即可作为微细观尺度孔隙结构(孔隙率)研究的REV.后续通过低阶概率函数等统计分析方法进行了验证,结果表明,以该近似判据确定的砂岩、泡沫混凝土等岩土试样P-REV与其他方法确定的结果基本吻合,可以给出具有代表性意义的统计结果,并在表征精度与计算效率之间提供合理的平衡点.