Characterisation and beneficiation studies of charge chrome slag

Abstract

Background: The slag generated at Indian charge chrome plants is associated with various amounts of charge chrome values. It has been established that charge chromes present in the slag are magnetic in nature. Hence, investigations have been carried out to recover these values lost in the slag in order to enhance and improve the productivity of the charge chrome plant. Methods: A low-to medium-intensity magnetic separator has been adopted in the process to recover the charge chrome values. The effects of different variables such as particle size, moisture content and magnetic intensity have been studied. Large-scale magnetic separation studies at a feed rate of 100-120 kg/h have also been carried out to confirm the bench-scale studies. Detailed mineralogical studies have been carried out by using different techniques. Results and conclusion: Mineralogical studies reveal that the slag essentially consists of spinel, olivine, chromite, metallic phase and glassy matrix. The metallic phases are very fine grained and present within the spinel grains. The textural pattern of the metallic phases indicated that complete recovery of chrome values from this slag is extremely difficult. The beneficiation study involving magnetic separation techniques indicated the possibility of recovering a product containing 57% Cr2O3 with a yield of 1.5% using 2-stage magnetic separation route. The product obtained by this magnetic separation route can be reused in the charge chrome furnace or blended with high-grade materials to improve the economics of the plant.