Surface Modification of Coal With Carbon Dioxide and Its Application to Advanced Coal Cleaning

本研究使用了来自不同地区的4种煤（大同、万多、伊利诺斯和神木）。采用100-200目煤进行浸没时间测定，评价煤表面润湿性。分别引入空气、氮气和二氧化碳气体进行浮选试验。将气体喷入煤浆后，对煤浆进行化学分析。浮选和化学分析采用细煤（平均粒径约为30mum）。部分煤在实验前用0.6kgf/cm^2的二氧化碳气体处理。大同煤和神木煤采用煤油捕集，其他煤采用重油A捕集。四种煤经二氧化碳处理后的疏水性均略高于未处理煤。当注入二氧化碳气体时，大同煤和宛宛煤的钙、镁溶解量最高，煤中玄武岩和方解石含量同时降低。用二氧化碳浮选，经二氧化碳处理的煤比未处理的煤产率最高。以含方解石和白云石的神木煤为例，随着ph的降低，可燃物与矿物的分离效率越高。在合适的操作条件下，得到了平均粒径为2mum的磨粉产品。磨矿介质和容器的磨损与煤中嵌布的石英、黄铁矿和氧化铁等硬矿物的含量密切相关。

Four coals from different localities (Datong, Wandoan, Illinois and Shenmu) were used in this study. Immersion time measurements were carried out to assess wettability of coal surface using 100-200 mesh coals. Flotation tests were conducted by introducing air, nitrogen and carbon dioxide gases, respectively. After sparging the gases into coal slurries, the slurries were chemically analyzed. For flotation and chemical analysis fine coals (mean particle size : about 30mum) were used. Some of the coals were treated with 0.6kgf/cm^2 of carbon dioxide gas prior to the experiments. The collectors used were kerosene for Datong and Shenmu coal, and heavy oil A for the other coals.The hydrophobicity of four coals treated with carbon dioxide became slightly higher than that of untreated coal. When sparging carbon dioxide gas, the highest amounts of calcium and magnesium were dissolved from Datong and Wandoan coals and the amounts of bassanite and calcite in the coals were simultaneously decreased. By flotation with carbon dioxide, the maximum yield was obtained for the coals treated with carbon dioxide than the untreated coals. In the case of Shenmu coal containing calcite and dolomite, separation efficiency of combustibles from mineral matters became higher with decreasing pH.Fine grinding of four coals were investigated. The ground product with a mean size of 2mum was obtained at a suitable operating conditions for all coals. The wear loss of the grinding media and vessel depended strongly on the amount of the hard minerals disseminated in coal, such as quartz, pyrite and iron oxide.