表面酸洗对低阶煤分级浮选的影响

The Effect of Surface Pickling on the Classified Flotation of Low-rank Coal

我国低阶煤煤炭资源储量大,但由于其表面含氧官能团丰富、孔隙发达及表面粗糙度大,其浮选工艺一直未实现工业应用。为提高低阶煤煤泥可浮性,对低灰粒级煤样进行盐酸酸洗处理后进行浮选试验。结果表明,在2 mol/L酸洗浓度下,500~250μm、250~125μm和125~74μm粒度级的浮选精煤产率达到最大,分别为97.87%、98.95%和97.22%;随后随酸洗浓度继续增加,浮选精煤产率降到最低,分别为93.51%、90.70%和89.43%。而-74μm粒度级的浮选精煤产率由94.10%持续降低到48.18%。结合Zeta电位测试和扫描电镜(SEM)分析结果可知:较低的酸洗浓度(2 mol/L)能有效脱除负电性强的含氧官能团,从而改善低阶煤表面的可浮性;而较高酸洗浓度(4~10 mol/L)使得低阶煤表面孔隙明显增多,浮选过程中,新增加的孔隙会被水分子填充并形成水化膜,从而降低了煤表面的疏水性,进而使浮选精煤产率降低。

China has a large resource reserve of low-rank coal. However, due to the rich surface oxygen-containing functional groups, developed pores and large surface roughness, the low-rank coal flotation process has not been industrially applied. In order to improve the floatability of low-rank coal slime, the low-ash coal sample was subjected to hydrochloric acid pickling treatment and then flotation test was carried out. The results shows that at a pickling concentration of 2 mol/L, the yields of flotation clean coal with particle sizes of 500~250 μm, 250~125 μm and 125~74 μm reach the maximum, which are 97.87%, 98.95% and 97.22%, respectively. Subsequently, as the pickling concentration continues to increase, the yield of flotation clean coal drops to the lowest level, respectively 93.51%, 90.70% and 89.43%. The yield of flotation clean coal with particle sizes of-74 μm continuously reduced from 94.10% to 48.18%. Combining the Zeta potential test and scanning electron microscope(SEM) analysis results, it can be seen that a lower pickling concentration(2 mol/L) can effectively remove the oxygen-containing functional groups with strong negative charge, thereby improving the floatability of the low-rank coal surface. Higher pickling concentration(4~10 mol/L) significantly increases the surface pores of low-rank coal. During the flotation process, the newly added pores will be filled with water molecules and form a hydration film, thereby reducing the hydrophobicity of the coal surface and further reducing the yield of flotation clean coal.