The optimization of an improved method of fine coal dewatering

Abstract

An improved method of dewatering fine coal (−500 μm) by vacuum filtration was developed and optimized. Tests on a bench scale vacuum filter showed that when a filter cake was deliberately damaged, causing the airflow through the cake to increase and the applied vacuum to decrease, a lower final moisture content could be achieved as well as a higher rate of dewatering. This method was optimized, taking into account the optimum time to inflict the damage to the filter cake during a single dewatering cycle. The amount and character of the inflicted damage to the filter cake was also investigated. It was found that the optimum time to inflict the damage was as soon as possible after the point of 100% saturation, decreasing the final moisture percentage from 29% to 24%. The configuration of the damage had no significant influence to the final moisture content of the filter cake. This led to believe that the air flow through the cake during dewatering is mainly hindered by a layer of ultra fine coal that will form at the top of a filter cake. Further investigation showed this layer to be approximately a third from the top of the filter cake, relating to a particle size of between 120 and 130 μm.