Electrical properties of fly ash and its decarbonization by electrostatic separation

The basic principle of fly ash triboelectrification is analysed. The mineral electrical index and test method are introduced. The electric difference of different mineral composition of fly ash is discussed by analysis of chemical and mineral composition of fly ash in Xinwen power plant. The dielectric constant and charge–mass ratio of carbon and ash of fly ash are tested. Combined with the experimental study on rotary triboelectrostatic separation, the charged characteristic of fly ash particles with different size is gained. The results show that the dielectric constant of fly ash with different grain size decreased with the decrease of particle size, which lead to the poor electrical conductivity. Thus it can be seen that particle size plays a leading role in conductivity. The charge of carbon and ash with each size increased with the decreased of particle size; and the charge–mass ratio between carbon and ash with the same size larger with the decrease of size, which indicated that the finer particle size, the more favorable for triboelectrification separation. In the same conditions, the best decarburization effect is realized when the particle size ranges from 0.038 to 0.074 mm, whose decarbonization rate and efficiency index reached 38.93% and 120.83% respectively.