Metallurgical processing of polymetallic Ocean nodules

Abstract

During the last five decades metallurgical processing of polymetallic nodule is of global interest-as well as a challenge-for researchers, and industries. This has generated a vast knowledge base, but till now there is no commercial operation. Some of the main reasons are: (1) lack of a techno-economically feasible mining operation, (2) poor economics of metal extraction, in comparison with similar terrestrial resources, and (3) environmental impact of mining as well as metal extraction. For metallurgists, the processing of polymetallic nodules becomes more challenging with passage of time because the environmental and processing norms keep changing for lean resources like polymetallic nodules. Considering the processes developed for nodule, and the current trend, the authors feel (1) production of alloy pig iron for use in series 200 stainless steel, and (2) aqueous reduction processes based on sulphuric acid, HCl/Cl2, or ammonia under atmospheric conditions hold good promise for a cost-effective, low capex, and environmentally accepted process.