An efficient method of preparing Si-Fe-Al-Ca alloy from coal gasification fine slag via plasma smelting and alternating current magnetic field.

It is of great significance to solve the environmental problems caused by the unreasonable treatment of coal gasification slag. This study successfully produced Si-Fe-Al-Ca alloy from low-carbon fine slag with petroleum coke as reducing agent in a plasma furnace with an alternating current magnetic field, which solved the problem of the high reactivity requirement of carbon reductant for plasma smelting. The optimum carbon content of the mixed low-carbon fine slag and petroleum coke is 105% of the theoretical value. As the strength of the alternating current magnetic field increased (from 0% to 100% of the maximum power), the yield of the alloy (from 25.46% to 58.19%) and the recovery ratios of each element (Si, Fe, Al, Ca, Ti) increased. In addition, as the magnetic field strength increased, the pores inside the alloy became smaller, the composition of the alloy became more homogeneous, and a better separation of the alloy from the slag was observed. The main composition of the alloy at the strongest alternating current magnetic field is Si: 51.14 wt%, Fe: 28.41 wt%, Al: 9.14 wt%, Ca: 7.15 wt%, Ti: 2.03 wt%. We attribute the enhanced smelting effect of the alternating current magnetic field to the resistive heat and Lorentz force produced by the induced current. In addition, the skin effect concentrated the induced current on the surface of the oxide particles and carbon particles, which increased the temperature of the reaction interface and promoted the carbothermal reduction reaction.

Preparation of Al-Si alloys with silicon cutting waste from diamond wire sawing process.

Large amounts of silicon cutting waste (SCW) are generated during Si wafers producing process. In this paper, SCW was mixed with Al powder to prepare Al-Si alloys by a one-step smelting process in corundum crucibles. The influences of smelting temperature (1000 °C, 1200 °C and 1500 °C) on the products of each zone (surface layer zone, loose granular zone and blocky products zone) were investigated. Al-Si alloys in the form of granular and blocky were prepared and the blocky Al-Si alloys mainly concentrated in the blocky products zone. The increase of smelting temperature can promote the aggregation of Al-Si alloy particles. The yields of Al-Si alloy blocks obtained at 1000 °C, 1200 °C and 1500 °C were 0%, 58% and 69%, respectively. The Si contents of Al-Si alloy blocks at 1200 °C and 1500 °C were 15.8 wt% and 17.1 wt% respectively. After compacting the raw materials, the yields of the blocky Al-Si alloys obtained at 1000 °C, 1200 °C and 1500 °C were increased to 65%, 72% and 79% and the corresponding Si contents of the blocky Al-Si alloys were increased to 16.0 wt%, 16.5 wt% and 17.3 wt% respectively. The reaction mechanism of the alloying process was also investigated.