Phase evolution of tin, iron and calcium oxides roasted in a simulative sintering atmosphere

Detoxication and recycling of chromium slag and C-bearing dust via composite agglomeration process (CAP)-blast furnace method

The utilization of virulent chromium slag has always been a worldwide problem, and lots of C-bearing dust produced in steel industry has not been utilized efficiently. Sintering is a potential method to treat these two kinds of solid wastes, but it is limited by small treatment capacity, incomplete detoxification of Cr(Ⅵ) when they were directly added into sintering process. In this study, an innovative technology of co-processing chromium slag and C-bearing dust via composite agglomeration process (CAP)-blast furnace method was put forward and systematically investigated. In the CAP, the chromium slag and C-bearing dust were first made into composite pellets and added into the matrix feed for co-sintering. The results showed that, 20% chromium slag and 5% C-bearing dust could be co-disposed by the CAP without destroying the quality of the sinters. Cr(VI) was completely reduced to Cr(III) or metal Cr. 12.83% Cr existed as metal Cr, and the rest of Cr existed in spinel as (Mg, Fe)(Cr, Al)2O4 or in silico-ferrite of calcium and alumina as Cr(Ⅲ). After blast furnace smelting, 90.22% Cr in sinters entered stainless mother liquor to be recycled.

A value-added multistage utilization process for the gradient-recovery tin, iron and preparing composite phase change materials (C-PCMs) from tailings

Tin-, iron-bearing tailing is a typically hazardous solid waste in China, which contains plenty of valuable tin, iron elements and is not utilized effectively. In this study, a multistage utilization process was put forward to get the utmost out of the valuable elements (tin and iron) from the tailings, and a gradient-recovery method with three procedures was demonstrated: (1) An activated roasting followed by magnetic separation process was conducted under CO-CO2 atmosphere, tin and iron were efficiently separated during magnetic separation process, and 90.8 wt% iron was enriched in magnetic materials while tin entered into non-magnetic materials; (2) The tin-enriched non-magnetic materials were briquetted with CaCl2 and anthracite and roasted, then tin-rich dusts were collected during the chloridizing roasting process; (3) The roasted briquettes were infiltrated in melting NaNO3 to prepare NaNO3/C-PCMs by a infiltration method. Three kinds of products were obtained from the tailings by the novel process: magnetic concentrates containing 64.53 wt.% TFe, tin-rich dusts containg 52.4 wt.% TSn and NaNO3/C-PCMs for high temperature heat storage. Such a comprehensive and clean utilization method for tin-, iron-bearing tailings produced no secondary hazardous solid wastes, and had great potential for practical application.