Improving flotation decarbonization efficiency of coal gasification fly ash by mechanically breaking pore: An experimental and molecular dynamics simulation study

Abstract

The high unburned carbon content of solid waste coal gasification fly ash is the main reason that it cannot be used in the construction material industry, which leads to serious waste of resources and environmental pollution. Currently, decarburization flotation has been a dominating method for coal gasification fly ash resource utilization. However, the flotation process has low efficiency and high reagent consumption because of the rich surface porosity of unburned carbon. Herein, we innovatively developed a mechanical grinding strategy to break the pore distribution on the surface of unburned carbon, significantly reducing the pore size, increasing hydrophobic functional groups and improving the flotation efficiency. The removal rate of unburned carbon is more than 95% in flotation tailings with a mechanical grinding intensity of 120 rpm and grinding time of 30 min. Furthermore, the adsorption of water on porous unburned carbon surface was studied by molecular dynamics simulation for the first time, and the results show that decreasing the particle surface porosity of unburned carbon can accelerate the diffusion rate of water molecules on the unburned carbon surface, improve the wettability of the particle surface and increase the adhesion probability between the unburned carbon particles and bubbles and remarkably improve the its floatability. This work is the first application of mechanically breaking pore to the flotation separation of unburned carbon and ash from coal gasification fly ash and provides valuable inspiration for the design of porous particles flotation, not limited to the separation of gasification fly ash.