Carbothermic reduction of chromite fluxed with aluminum spent potlining

Aluminum spent potlining (SPL) was employed as both the fluxing agent and a source of carbonaceous reductant for the carbothermic reduction of chromite, aiming to allow effective separation of alloy from the slag component. The experimental results show that the carbonaceous component of the SPL is more reactive towards chromite reduction compared to graphite. The formation of refractory spinel (MgAl2O4) on chromite particles hinders further reduction and alloy growth. The slag-making components of the SPL (e.g. nepheline and NaF) form molten slags at low temperatures (~1300℃) and partly dissolve the refractory spinel as well as the chromite. Destruction of the spinel layer with enhanced mass transfer greatly improves the alloy growth, which can be further promoted by reduction at a higher temperature (e.g. 1500℃). Ferrochrome alloy particles grow large enough at 1500℃ in the presence of SPL, allowing effective separation from the slag component using elutriation separation.

Thermal behaviors, combustion mechanisms,evolved gasses, and ash analysis of spent potlining for a hazardous waste management

An unavoidable but reusable waste so as to enhance a more circular waste utilization has been spent potlining(SPL) generated by the aluminum industry.The combustion mechanisms, evolved gasses, and ash properties of SPL were characterized dynamically in response to the elevated temperature and heating rates.Differential scanning calorimetric(DSC) results indicated an exothermic reaction behavior probably able to meet the energy needs of various industrial applications.The reaction mechanisms for the SPL combustion were best described using the 1.5-, 3-and 2.5-order reaction models.Fluoride volatilization rate of the flue gas was estimated at 2.24%.The SPL combustion emitted CO_(2), HNCO, NO, and NO_(2) but SO_(x).The joint optimization of remaining mass, derivative thermogravimetry, and derivative DSC was achieved with the optimal temperature and heating rate combination of 783.5 ℃, and 5 ℃/min, respectively.Interaction between temperature and heating rate exerted the strongest and weakest impact on DSC and remaining mass, respectively.The fluorine mainly as the formation of substantial NaF and CaF_(2) in the residual ash.Besides,the composition and effect of environment of residual solid were evaluated.The ash slagging tendency and its mineral deposition mechanisms were elucidated in terms of turning SPL waste into a benign input to a circular waste utilization.