ABSTRACT:

Little attention has been paid during process development studies to possible changes in cost of metal production when a process plant is exposed to varying degrees of metal grades emanating from a sea nodules mining area. Study of these aspects requires process optimization. An approach for optimization of a process technology at a given throughput of nodules has been developed. This uses a robust multi-objective process optimization technique coupled with process simulation and indicative cost economics. A case study illustrates the approach; minimization of process chemical cost with simultaneous maximization of metal values produced is considered. The approach may easily be extended to include other objectives, including energy, for any process technology.

INTRODUCTION

The multi-metal deep sea nodules as a resource has been compared to terrestrial nickel laterite ores which can be processed via pyrometallurgical or hydrometallurgical means. Although the process development strategies for sea nodules could be drawn from processing of similar terrestrial ores, the exploration, mining and transportation costs are greater than laterite ores. Thus, researchers who had embarked upon newer routes have been drawn into the manganese recovery option to work out a viable route for recovery of all metals. The manganese recovery option is not necessarily connected to the market situation; for recovery of three metals, stability of the manganese containing residue becomes an important consideration, specifically for environmental considerations. The polymetallic nodules resources can thus be compared to low grade manganese ores with higher investment risks where, additional income from copper and nickel recovery is expected to balance the extra costs for exploration, mining and transportation. Current research efforts globally have realized the importance of manganese recovery, although, these have scarcely been directed towards flow sheet development and subsequent testing for commercial viability.

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