Research On Desulfurization Of Metallurgical Slag With Sulfu By Oxidizing Roasting

Slag is one of the main solid wastes in the metallurgical industry. The annual emission of slag is greater than200million tons in China. Such a huge amount of new slag was accumulated year by year and it has posed a severe challenge to the sustainable development of steel industry. It is important to improve the comprehensive utilization of slag for the national low-carbon economic development requirements and the implementation of national energy-saving and emission reduction targets. The accumulation of sulfur in the recycling process of sulfur-containing slag limits the utilization of slag. It is effective to increase utilization of slag by reach on desulfuration of slag with sulfur.The occurrence state of sulfur in slag was defined by research in the present paper. Based on this, controlled roasting on CaS powers was taken by high-temperature simultaneous differential thermal analysis and high-temperature controlled atmosphere furnace. It provided a theoretical basis for desulphurizing roasting of slag with sulfur. Research conclusions are as follows:(1) Sulfur in slag exists separately as CaS phase, or partly replaces CaO in calcium aluminate to form complex phase Ca12Al14O32S.(2) Calcination of CaS in oxidative atmosphere showed different reaction characteristics. CaS was oxidized to CaSO4firstly between700℃and900℃, and then CaSO4occured Solid-Solid reaction with residual CaS to generate CaO between900℃and1100℃.(3) Calcination reaction was affected mostly by temperature, particle size of CaS and oxygen partial pressure. With temperature and oxygen partial pressure increasing, the conversion rate of calcination reaction rised. The Solid-Solid reaction rate of CaSO4and CaS increased with temperature rising.(4) Optimal calcination method is that when CaS calcined under high oxidative atmosphere for a certain time converted partially to CaSO4solid-solid reaction between CaSO4and residual CaS took place to get CaO, and sulfur was removed in the form of gas phase. Specific parameters were as follows:roasting60minutes under oxygen concentration of21%at900℃; Then roasting40minutes under inert atmosphere at1100℃. And roast it once more. Mass fraction of CaO in calcination product was85%.(5) As the solution degree of sulfur in industrial slag is very high, combined with the affect of raw material particle size, desulfurization effect of industrial slag calcined following the aforementioned calcination method was somewhat poor, but sulfur content of slag still decreased by60%after calcined.