低阶煤颗粒-气泡诱导时间测试及表面改性

Low-rank coal particle-bubble induction time test and surface modification

低阶煤由于表面含有大量极性含氧官能团,孔隙发达,导致浮选效率低。通过表面改性提高煤表面的疏水性是改善浮选性能的关键。采用扫描电子显微镜分析了低阶煤的表面形貌,通过改变煤样表面粗糙度以及使用酸碱溶液浸泡对煤样进行改性,并采用接触角测试表征煤样改性后表面润湿性的变化,借助诱导时间测量装置研究了煤样改性后颗粒-气泡粘附特性,通过浮选试验验证改性后煤样表面可浮性的变化。结果表明,低阶煤表面粗糙,孔隙和裂隙较发达,有较多细小颗粒附着在表面。改变煤样表面粗糙度并测量诱导时间发现,煤片的接触角越大,煤样-气泡间诱导时间越小。采用pH=1的盐酸对煤样进行改性,随着浸泡时间的增加,煤样-气泡间诱导时间逐渐减小。将煤样置于不同pH值溶液中浸泡,随着溶液pH值的增加,在酸性溶液中煤样接触角逐渐增加,诱导时间逐渐减小;在碱性溶液中,煤样接触角先增加后减小,诱导时间呈现先减小后增加的趋势。不同pH值溶液对煤样改性后浮选试验结果与诱导时间测试结果一致,表明酸溶液以及适当浓度的碱溶液改性可以提高煤样疏水性,提高精煤可燃体回收率,改善浮选性能。

Because the surface of low-rank coal contains a large number of polar oxygen-containing functional groups and developed pores,the flotation efficiency is low.Improving hydrophobicity of coal by surface modification is the key to improve flotation performance.In this paper,the surface morphology of low rank coal was analyzed by scanning electron microscopy.The surface roughness of the coal sample was changed and the coal sample was modified by acid and alkali solution soaking.The surface wettability of the coal sample after modification was characterized by contact angle test.The particle-bubble attachment after coal sample modification was studied by means of induction time measuring device.The change of surface floatability of modified coal sample was verified by flotation test.The results show that the surface of low rank coal is rough,the pores and cracks are more developed,and there are more fine particles attached to the surface.By changing the surface roughness of coal sample and measuring the induction time,it is found that the larger the contact angle of coal is,the smaller the induction time between coal sample and bubble is.Hydrochloric acid solution with pH=1 was used to modify the coal sample.As the soaking time increased,the induction time between coal sample and bubble gradually decreased.The coal samples were soaked in solutions with different pH values.As the pH value of the solution increased,the contact angle of the coal samples in acidic solution gradually increased,and the induction time gradually decreased.In alkaline solution,the contact angle of coal sample first increases and then decreases,and the induction time shows a trend of first decreasing and then increasing.The results of flotation test after modification of coal samples with different pH values are consistent with the test results of induction time,indicating that modification of acid solution and alkali solution with appropriate concentration can improve the hydrophobicity of coal samples,improve combustible recovery and flotation performance.