Green metallurgical processing of chromite

A new green metallurgical process for chromite ore has been proposed and developed to solve the serious environmental problem in the traditional production process of chromate. In the new process, the oxidation of chromite ore is carried out in sub-molten potassium hydroxide at 300 °C. Compared with the traditional roasting process in a rotary kiln at 1200 °C, the oxidation and mass transfer are greatly intensified in the new process. Chemical conversion of chromium is above 99% and the recovery of chromium is raised by more than 20% while the reaction temperature is dropped by 900 °C. Thus the energy consumption is decreased. Furthermore, as no limestone or dolomite additives are required, the amount of chromium-containing residue is decreased from 2.5 tonnes to 0.5 tonnes with the production of 1.0 tonne of product in the new process. As all reactions and separating operations are performed in liquid media, pollution due to toxic dust is prevented.With the change of reaction medium, the new process achieves higher resource and energy utilization efficiency. At the same time, the new process also changes the physical and chemical properties of other components co-existing in the chromite ore. The process provides the possibility for virtually complete utilization of chromite and zero emission of residue. Thus, the clean production of chromate can be realized.