Influence of particle size range on coal fly ash triboelectrostatic separation

Abstract

ABSTRACT Triboelectrostatic beneficiation, a dry separation technology recurred to electrification properties between carbon and ash, is employed to remove unburned carbon from coal fly ash effectively. Previous works showed that the efficiency of triboelectrostatic separation was influenced by particle size of fly ash. However, the effect of specific particle size range on triboelectric separation efficiency has not received appropriate academic attention. In this paper, a model of charge-to-mass ratio (CMR) which varied with particle sizes was established by Engineering Discrete Element Method (EDEM); on this basis, the effect of particle size range on triboelectric separation of fly ash was studied via screening before and after separation. Based on the Change rule of high loss-on-ignition (LOI), yield, CMR, LOI decrease rate of clean ash (LDC) and LOI increase rate of tailing (LIT), the results were obtained and shown as follows: carbon and ash can be separated efficiently when the particle size is between 38 ~ 74 μm; separation effect is deficient when the particle size is smaller than 38 μm due to insufficient depolymerization of the particles and CMR decrease. This indicates that the separation effect of triboelectric separation is not negatively correlated with particle size. Instead, there is an appropriate optimal separation range. Triboelectrostatic separation efficiency can be improved by screening fly ash in the narrow particle size under 74 μm, and the separation effect of narrow size grain samples obtained after screening is better than the full-size grain ones. Therefore, the fly ash should be screened properly before separation.