Two stage smelting process for recovery of manganese from low manganese bearing material

Abstract

Marine manganese nodules or sea nodules are considered to be an important source of strategic metals like copper, nickel and cobalt and several processes for recovery of these metals have been developed round the world. During the hydrometallurgical treatment of manganese nodules to recover these metals, a considerable amount of residue is generated which mainly constitute manganese, iron and silica along with lime, magnesia, alumina etc. The overall processing economy lies with the recovery of manganese from the leach residue and hence a process to recover manganese in the form of silicomanganese alloy from the leach sea nodules residue has been developed at NML, Jamshedpur. Owing to low Mn/Fe ratio in the leach residue, a new process comprising two stage carbothermic reduction smelting of residue in a submerged electric arc furnace has been adopted. In the first stage the iron is selectively reduced and an iron rich alloy with slag of high Mn/Fe ratio is produced. The slag of first stage is resmelted in the second stage to produce silicomanganese alloy. After establishing the process parameters on bench scale, a pilot plant to process the residue on 350 Kg/ day scale has been set up and trails on pilot scale have been carried out. So far, standard grade silicomanganese alloy with 71% manganese recovery has been achieved in the pilot scale trials.