ABB has applied the Expert Optimizer solution to the zinc flotation circuits of Boliden’s Garpenberg plant in Sweden. ABB and Boliden agreed to collaborate on a project to achieve a successful application of Model Predictive Control (MPC) to a complete flotation circuit. The aims were to stabilize the process in spite of external disturbances, such as ore quality changes, and to maximize the zinc revenue through zinc recovery and concentrate grade. Successfully optimizing the circuit required that three criteria be met. The behavior of the process had to be predicted using a reliable dynamic model of the flotation circuit. Then cost functions and finally operating constraints were incorporated in order to produce a robust MPC application. In order to achieve certainty regarding the controller benefits, a measurement campaign was started at the end of 2008 and finished in the middle of 2009. The results showed that concentrator efficiency (directly corresponding to revenue) was at least one percentage unit higher when MPC was used, compared with the existing manual control strategy. In addition, the zinc concentrate grade has been higher and more consistent, while the recovery has remained at the same level.
ABB Switzerland Ltd, Zürich (CH),
Tel.: +41 58-586-8832, www.abb.com