注入热活化过硫酸钠溶液增透松软低渗煤层的试验研究

煤层注水具有防突降尘、预防煤层自燃和冲击地压等作用,为提高煤层低压注水综合消突作用,增大煤层透气性,以河南省耿村煤矿13230综放工作面为工程背景,选取局部区域注50℃过硫酸钠(SPS)溶液进行化学增透后测定煤层透气性和瓦斯抽采纯量。使用Kruss DSA25光学测量仪测量煤样表面接触角θ,以考察SPS溶液质量分数、活化温度对煤样润湿性的影响,优选50℃作为SPS溶液的最佳活化温度;采用等温吸附实验测定煤样吸附常数a,b值,使用压汞实验测试孔隙特性并用分形理论计算孔隙粗糙度,采用扫描电子显微镜观察煤样表面形貌变化,采用TOC分析仪对返排液进行总有机碳(TOC)测试。分析结果表明:升温可有效活化SPS产生具有强氧化性能的硫酸根自由基(SO4-·)、并氧化水生成羟基自由基(·OH),质量分数为1%的50℃活化SPS溶液可将耿村煤样的接触角θ由106.80°降低至45.05°,接触角下降57.82%,显著改善煤样的润湿性,增强煤表面与注水溶液的作用;耿村矿13230工作面注活化过硫酸钠溶液后煤样对瓦斯的吸附能力显著降低,吸附常数a值下降17.27%,吸附常数b值下降37.39%,煤样总孔容增加57.74%,孔隙率增加70.35%,中大孔孔容及孔容占比增大,微小孔的孔容及孔容占比减小,煤样的渗透容积增加、吸附容积减小;活化SPS溶液能将煤中占据或封堵孔道的部分小分子相物质氧化溶出,使得孔裂隙得到延伸和疏通,同时使煤表面出现新的微裂纹,改善煤体内孔隙连通性。耿村矿13230工作面在注活化SPS溶液后其单孔瓦斯抽采纯量提高137.14%,达到8.3 L/min;瓦斯体积分数及煤层透气性系数分别提高220%,1650%,达到32%,0.1015 m2/(MPa2·d);钻孔瓦斯流量衰减系数降低83.48%,低至0.0115 d-1,煤层瓦斯抽放难易程度由较难抽放水平提升为可以抽放水平,增透效果显著。

Comparison of deep desulfurization methods in alumina production process

Several methods of deep desulfurization in alumina production process were studied, and the costs of these methods were compared. It is found that most of the S2- in sodium aluminate solution can be removed by adding sodium nitrate or hydrogen peroxide in digestion process, and in this way the effect of S2- on alumina product quality is eliminated. However, the removal efficiency of 2?32OS in sodium aluminate solution is very low by this method. Both S2- and 2?32OS in sodium aluminate solution can be removed completely by wet oxidation method in digestion process. The cost of desulfurization by wet oxidation is lower than by adding sodium nitrate or hydrogen peroxide. The results of this research reveal that wet oxidation is an economical and feasible method for the removal of sulfur in alumina production process to improve alumina quality, and provide valuable guidelines for alumina production by high-sulfur bauxite.