Dynamic Control and Simulation of Conveyor-Belt Dryers: Model-Based Control of Moisture in Fishfeed

Abstract

The removal of moisture from solids is an important and often necessary part of the production process withinseveral different industries. This especially includes the food industry, since almost all food products are dried at least once during the production process. Drying is primarily applied to either ease the handling of the product, extend its storage life, increase its quality or all of the above.In this thesis, a mathematical model of a conveyor-belt dryer is developed. The model consists of four partialdifferential equations (PDE), including the calculations of dew point temperatures. The PDEs are solved numericallyby way of finite difference and simulated graphically. The model is verified using experimental data from a dryer applied in the production of fish feed. Furthermore, a basic control solution (PID) and amodel-based control solution (MPC) are developed. The simulation results shows the feasibility and stability of both the non-linear model and a linearized version of the model. In addition, simulations of both the basic and the model-based controller show that the moisture content can be controlled automatically and smoothly, and furthermore, that the model-based control solution outperforms the basic control solution.