Modelling and optimization of carbon-in-pulp gold recovery processes

The paper presents a mixed-integer nonlinear programming approach to construction and operational optimization of carbon-in-pulp (CIP) processes related to hydrometallurgical gold recovery plants. In this plant section, gold in the form of aurocyanide complex ions is adsorbed on the active sites of carbon particles. This takes place in a series of agitated tanks where carbon is countercurrently transferred with respect to the pulp. Three basic process operating modes are reported and analysed: namely carousel, continuous, and sequential. The mathematical model of the CIP process is developed for each one of the operating modes examined. Economic evaluation is carried out proposing the sum of annual gold loss to the tailings plus the total annual cost as a minimization object subject to constraints dictated by the process model. The original problem is suitably decomposed into a series of nonlinear programming problems and solved with successive quadratic programming techniques. A characteristic case study is presented to demonstrate the effectiveness of the proposed method.