Control of a roasting process for the recovery of vanadium

Rotary Kilns or Multiple Hearth Roasters are commonly used for the extraction of Vanadium from steelworks slag. The process is long known but the requirement for efficient operation makes it difficult for the operator to handle the roaster in an optimal way. It is inevitable to hold a given process temperature profile and to provide the correct chemical environment for an efficient operation mode and to avoid undesired process behavior. Therefore, in this article a control concept is introduced which enables a high degree of automatization for a roasting process in a Multiple Hearth Furnace. The control concept is based on a temperature controller and a chemistry controller. An additional overhead controller is introduced that calculates desired values for the sub-controllers according an optimization criterion and under consideration of keeping the roaster within a desired scope of operation. The controller design is mainly model-based, in case of the chemistry controller, where it might sometimes be elaborate to provide a sufficient model, optionally a knowledge based fuzzy controller is used. In the design of the described control concept industrial applicability was given a high degree of importance.