Insight into the mechanism of gasification fine slag enhanced flotation with selective dispersion flocculation

Coal gasification fine slag (CGFS) produced in the coal chemical industry has caused severe environmental pollution and resource waste. To realize the utilization of CGFS, we have to efficiently separate unburned carbon (UC) in CGFS. In this work, based on the discovery of the covering between CGFS particles, the selective dispersion flocculation flotation method is proposed to improve the efficient separation of UC from CGFS. The mechanism of selective dispersion flocculation is revealed through adsorption mode, interaction force between particles, and the particle size distribution of floc under different reagent conditions. Results show that a hy-drophilic layer is formed on the surface of ash particles, which hinders the adsorption of PAM and ash particles due to the chemical adsorption of SHMP with ash particles. However, carbon particles are not affected by SHMP and can be directly adsorbed with PAM. This selective adsorption dominates the interaction force of adsorbed particles, and then controls the agglomeration of particles. After selective dispersion flocculation, the original carbon-ash selective agglomeration state is changed to the carbon-carbon selective agglomeration state. D90 of fine carbon particles changed from 110.21 mu m to 356.84 mu m. Compared with the traditional flotation process, the combustible recovery rate of foam products is increased by 10.4 % and loss on ignition (LOI) is increased by approximately 5 %. This work is conducive to fundamentally understanding the mechanism of selective dispersion flocculation. It is helpful to guide the separation of carbon and ash from gasification slag in industry.

Automated summary

Coal gasification fine slag (CGFS) generated in the coal chemical industry poses serious environmental pollution and resource wastage. By studying the phenomenon of covering between CGFS particles, this study proposes a selective dispersion flocculation flotation method to efficiently separate unburned carbon (UC) from CGFS. The mechanism of selective dispersion flocculation is revealed through the analysis of adsorption mode, interaction force between particles, and particle size distribution. Results show that selective adsorption controls the agglomeration of particles, transforming the original carbon-ash selective agglomeration state to carbon-carbon selective agglomeration state. This work improves the recovery rate of combustible materials and provides guidance for the separation of carbon and ash from gasification slag in industry.