The Benefication of Ultrafine Coal by Using the LM, Modified LM, and Conventional Flotation Cell

This article describes modification of the LM cell developed by Cheng Xinghua and using it to clean ultrafine coal. The major modifications involve replacing the column in a standard LM cell with a hydrocyclone and giving air into the system through a porous material. Thus, centrifugal forces are also incorporated into the system and a higher coal recovery is obtained. In addition, such important design and operating parameters as the apex diameter, gas flow rate, wash water rate, reagent dosage, and solid ratio were optimized, which affect the performance of the modified LM cell. Next, flotation experiments were carried out using the standard LM cell and conventional mechanical cell and the results were compared with those obtained from the flotation with the modified LM cell. It was established that the modified LM cell is an effective one for cleaning ultrafine coal and has a considerably high capacity. In fact, following the flotation of merely 60 sec, coals with an ash content of 46% yielded clean coals having a 10-15% ash content with 70-75% combustible recovery. The conventional flotation cell, on the other hand, produced a poor selectivity and lower coal yield. The separation efficiency of the modified LM cell was in the 55-60% range, whereas that of the conventional cell varied between 50-55%.