Development of Low-cost Smelting Reduction Process Using Cupola Furnace for Efficient Use of Inferior Grade Manganese Ores and Rejects

Consumption of manganese ores is increasing day by day mainly due to increased demand of steel products. Low-grade manganese ores and rejects are generated during mining of high-grade resources for production of manganese alloys. These low-grade resources hold significant portion of manganese values as well as creating problems of storage and mining space for mine owners. This study has been carried out to develop a low-cost process to recover values from these kinds of ores using a conventional cupola furnace. Different types of ore blends of 0.5-ton quantity composed of low-grade Mn ore, dolomite, quartz, cast iron and coke were smelted in pilot scale cupola furnace to produce high MnO slag and pig iron. Attempts were made to improve Fe-reduction and separation from MnO-bearing slag by controlling the air flow rate, burden composition, ore agglomeration, pre-reduction, use of different reductants, etc. It was found that developed process is capable to produce slag with MnO: > 35% and Fe (t) < 5% using low-grade Mn ores (Mn: 27.36%; Fe (t): 22.36%; SiO2: 6.75%; Al2O3: 12.36%). The process can achieve Fe reduction between 50 and 70% of total input Fe. Low reduction efficiency is mainly due to low retention time (1-2 h) of liquid slag in the furnace and additional gangue materials contributed by low-grade coke and furnace lining dilutes MnO level in slag. Cupola furnace uses coke (0.3-0.5 ton/ton of ore) as a source of energy and reducing agent which is relatively cheaper than electricity. It is easy to operate and need less capex than the competing technologies to process low-grade ores and rejects to produce synthetic MnO-enriched product which can be used as a cheaper raw material for ferroalloy, battery, and chemical industry. So, the process has shown potential to be further explored using suitably designed cupola (hot blast, etc.) and specifically designed agglomerates to achieve further MnO-enriched products.