Computer simulation of a molybdenite leaching process using dilute nitric acid

Abstract

A computer model has been developed to simulate the major part of a proposed hydrometallurgical process for the leaching of molybdenite concentrates. The leaching is achieved with dilute nitric acid (1–6 M) under conditions that permit precipitation of high-purity MoO 3 · 1 2 H 2O from filtered leach solutions. Because the leaching rate is low under these conditions, unleached molybdenite is recycled in a circulating load, after regrinding and reflotation. The leach takes place in several cocurrent stages at a pulp density enhanced by the circulating load, and overall recovery of the order of 98% is predicted, based on losses in the reflotation step rather than on poor extraction in the leach. The computer model is based on a set of material balances and incorporates data obtained from batch leaching and grinding tests to characterize the major kinetic phenomena. Input variables include: (a) nitric acid flow rates, (b) leach-solution strength, (c) solids input rate, (d) leach tank volumes, (e) number of cocurrent leaching stages and (f) degree of bypass of recycle solids around reflotation. The primary output variable is the ratio of recycle to new solids in the feed, and the model also predicts the value of strategic variables such as overall recovery and daily production rate of purified molybdic oxide.