Improved extraction of vanadium from a Chinese vanadium‐bearing stone coal using a modified roast‐leach process

Abstract

AbstractVanadium is a rare metal mainly used in the steel industry. Vanadium‐bearing stone coal is an important source of vanadium in China. The common process used to extract vanadium from the stone coals is roast‐leach, which has the disadvantages of low vanadium recovery and significant pollution. This work presents a modified roast‐leach process in order to improve the efficiency of the extraction. The modifications include a two‐step leaching process: first water leach, followed by an acid leach of the water‐leaching residue in a dilute HCl solution. In addition, the precipitate was recycled from the acid‐leaching solution to the oxidation roast for use as a roasting agent, and low dosages of sodium salts (Na2CO3 and Na2SO4) were included in the oxidation roast to reduce the volume of HCl and Cl2 exhaust gases and environmental pollution. The study was performed on a typical vanadium‐bearing stone coal from the Xiushui mine in Jiangxi province, China. The results show that the modified process achieved a vanadium recovery of 85% from the stone coal, much higher than that from a one‐step leach process (water leach or acid leach alone). Also, it has been found that optimum values of the roast temperature and time in the preroast (750 °C and 30 min) and oxidation roast (780 °C and 90 min) were required in order to obtain the maximum vanadium recovery from stone coal. It is shown that the modified roast‐leach process is an economic and effective process for the recovery of vanadium from stone coals. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.