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The aim of this study is to diagnose and optimize a closed multistage gold ore flotation circuit in an operational industrial plant. Linear circuit analysis (LCA), a partition-based model, and a mass balance model using flotation first-order kinetics are employed to diagnose the current process. The result shows that the current circuit operates with high recovery but the gold grade of the final concentrate is low owing to the low buoyancy ratio. Hence, several alternative circuits with different streamlines and cell arrangements are proposed and simulated using LCA and a mass balance model. The result suggests that if the current process is changed to an alternative circuit in which the floated product stream of the rougher bank is changed, then the gold grade of the concentrate can be improved by 128%. Finally, the current circuit is optimized by changing it to an alternative circuit. This study provides a methodology for adapting the simulation of optimization for the flotation circuit of an industrial plant via LCA and mass balance simulation. [ABSTRACT FROM AUTHOR]

• A simulation of a grinding/classification process of gold ore was conducted. • The process was analyzed to identify the problem and propose a layout rearrangement. • Throughput can be increased about 69% by switching ball mill in the process. • This study showed simulation can be used to predict the effect of layout rearrangement. In this study, a simulation of layout rearrangement in grinding/classification process was conducted to increase the throughput of an industrial plant processing 5.9 t/h of gold ore in Jeollanamdo province, Korea. The layout was rearranged to maintain the final product particle size while restoring the loss of throughput that has resulted from recent developments in mines. The process is composed of two-stage circuit, the first stage is an open circuit of the first ball mill and spiral classifier, and the second stage is a closed circuit of the second ball mill and hydrocyclone. Particle size distributions of each streams were predicted through simulation, using the population balance (PBM), Stokes' and Plitt's models for the ball mill, spiral classifier, and hydrocyclone, respectively. Lab-scale parameters for PBM were obtained by conducting batch grinding tests. The obtained lab-scale parameters were scaled-up using an empirical scale-up equation based on the industrial plant conditions. Using the obtained particle size distributions, the reduction ratio based on the 80% passing size was calculated to be 80.5 for the first ball mill, while it was only 1.19 for the second ball mill. To solve the process imbalance problem, a layout rearrangement that involves the switching of the first and second ball mills in the process was proposed. The final product was finer, with the 50% passing size reducing from 35 μ m to 31 μ m. The throughput of the industrial plant can therefore be increased by approximately 36% to 8 t/h. This study provides the guideline of the methodology which can help in adapting the simulation of layout rearrangement in the grinding/classification process for an industrial plant. [ABSTRACT FROM AUTHOR]