An improved process for the preparation of Si-Fe-Al-Ca alloy from coal gasification fine slag via three-phase plasma smelting

With the rapid development of coal gasification as a method of clean coal utilization, how to recycle its solid waste coal gasification fine slag (CGFS) is a hot research issue due to the serious environmental pollution problems caused by landfill disposal of CGFS in industry. The preparation of alloys from CGFS by high-temperature carbothermal reduction is a clean and effective method for synergistically utilizing the carbon and ash fractions in CGFS, however, the current method still needs to be improved for future large-scale industrial production. In this study, a three-phase plasma furnace with AC power was used to prepare Si-Fe-Al-Ca alloy from CGFS. The alloy yield increased from 58.19 % to 69.66 %, and the recovery ratios of Si, Al, and Ca elements also increased. The generation and reaction of SiO is key reason why achieving 100 % silicon recovery is difficult. The semi-molten slag shells covering the top of the reaction zone during the smelting process have a positive effect on increasing the Si, K, Mg elemental recoveries. This study improves the previous recycling method of CGFS via a laboratory-scale DC plasma furnace and provides ideas for the large-scale industrial application of CGFS high-temperature carbothermal reduction for the preparation of Si-Fe-Al-Ca alloy.