IITs Madras, Kanpur find way to recycle waste material from iron ore mining

Iron ore waste known as slime could be better used than discarded, say researchers

Researchers at the Indian Institutes of Technology Madras and Kanpur have developed a process to convert waste produced from iron ore mining into an environment-friendly material that can be reused by industry.

The researchers collaborated with NMDC and JSW Steel to transform slime into iron-rich materials suitable for blast furnace charging through a microwave-assisted beneficiation process. The process is economical as the microwave selectively interacts with iron oxides or carbon mix, leaving out other impurities (like silica, alumina, phosphorus oxides) while also rapidly heating the material compared to conventional routes, saving a significant amount of energy and emissions.

This project is of importance to India as while processing iron ore, particles smaller than 0.15 mm generated and are discarded as waste known as slime. Slime generated during mining is about 20-25 per cent of the total iron ore feed and it is dumped between iron-bearing mountain ranges.

 

Over years of mining, this has resulted in huge slime ponds holding several million tonnes of locked iron content. The slime, besides lying unproductively, may damage the land and environment. Currently, these slimes are partly exported as low-grade iron ore.

"This project has led to the creation of a lab with high-temperature facilities at IIT Madras, which was renamed as Centre for Pyrometallurgy, comprising equipment and facilities created by IMPRINT INDIA funds to perform lab-scale investigations of high-temperature processes involving reduction roasting or smelting," said Ajay Kumar Shukla, associate professor and head, centre for pyrometallurgy, department of metallurgical and materials engineering, IIT Madras.

"The project resulted in a significant breakthrough towards the development of technology to process lean quality fine iron ores on a large scale in a cost-effective and environmentally friendly manner," said Anish Upadhyaya, Department of Materials Science and Engineering, IIT Kanpur.

IITs Madras and Kanpur undertook a project under IMPRINT INDIA (Impacting Research Innovation and Technology), an initiative of the union education ministry. The researchers also published their findings in a reputed peer-reviewed journal with research scholars Soumya Ranjan Mohanty and Sunil Yadav.

"This work demonstrates an innovative, cost-effective, and energy-efficient way which may be upscaled further towards the development of a technology to beneficiate the lean quality iron ores," said Vibuti Roshan, deputy general manager (research and development) at NMDC.

Ramehwar Sah, Head (R&D), JSW Steel, noted, "Considering the upcoming challenges on the raw material front by steel industries in India, research and development in the area of iron ore beneficiation is the need of the hour. Such work exhibits an excellent and successful example of industry-academia interaction."