CONTROL OF AN INDUSTRIAL DRUM FILTER BY USING ADAPTIVE MODELS

Abstract

Vacuum filters are often used to dry and wash lime mud before calcining it in the lime kiln of a sulphate pulp mill. The control of the kiln itself is quite problematic because of long time delays and complicated burning reactions. To avoid many kiln's control problems and to achieve energy savings in the kiln, the mud filter should operate steadily and produce dry mud. Here, based on a systematic study of the process, a self-tuning type two-variable control scheme is proposed for the filter. First, adaptive process models are specified based on mill experiments. The self-tuning control scheme is then developed for the drum filter. The proposed control method consists of a twovariable parameter adaptive control algorithm which includes compensation for filter efficiency and some other disturbances. Optimization of the blowing and scraping intervals is also possible. The controller is directly applicable to mud filters provided that they are controllable and the process model is identified. Energy savings of about 10 % can be achieved using this method. The method provides a general approach for drum filter control. In the end the general applicability of the methods and the results are also discussed.