(438f) Sub-Molten Salt Environmentally Benign Technology

In China, mineral processing contributes greatly to the environment pollution. With the objective of improving the resource utilization efficiency and eliminating environmental pollution at the source, an emerging technology called Sub-Molten Salt (SMS) cleaner technology has been developed by the Institute of Process Engineering, Chinese Academy of Sciences. The SMS medium is defined as a controllable ionized medium with high alkali concentration. The fundamental results show that, the SMS medium has high mean ion activity coefficient and is capable of providing highly active oxygen anion, which enables to effectively facilitate the mass transfer of the oxygen anion in the mineral surface, greatly enhance the abnormal change of the mineral surface structure due to the surface energy increased, essentially intensify the decomposition of oxide bearing ore, and remarkably increase the chemical conversion to theoretical value. In addition, the low vapour pressure and high boiling point of the SMS medium makes it possible to operate at low pressure and temperature with low energy consumption. Main valuable components can be obtained in the SMS technology by salt-out separation method. The SMS technology has been applied in processing chromite ore. The Cr yield is increased from 75% in the traditional technology to as high as 99%, and the residue can be used as desulphurization agent or as the raw material in the steel and cement plants, thus to eliminate the pollution of toxic chromium-containing residue at the source. It was also found that, the SMS technology is suitable for processing other special minerals similar to chromite, including bauxite, ilmenite, and niobate-tantalate mineral.