Modelling and Control of an Evaporation Process

Model-based design is in many ways seen as a potential instrument in process industries due to the close link between the process and the model. In Växjö, the process industry of Lantmännen Reppe AB produces syrup. The syrup goes through an evaporation process in order to raise the sugar concentration. If the concentration gets to high the syrup turns solid, which can make the process a bit tricky to control. In this master’s thesis the goal is to model this process in the MathWorks environment Simulink in order to gain understandings about different aspects of the process and eventually bring forward and evaluate different control strategies. Information about the real process has been obtained by visits at the factory and mail correspondence with the process engineer of the plant. Important advices along the project have been given by supervisors at the Department of Automatic Control and at Combine Control Systems AB. The modelling is founded on approximations regarding no temperature or pressure dependencies, but only mass and energy balances. The model has been adjusted and tuned along the project in order to match the given process dynamics. The model verification has been conducted by comparisons of model simulations and process data. The model has in many ways proven to capture the fundamental behaviors of the process. A number of different control strategies have been tested in the model and the results have been compared. It has been shown that the present feed forward controller improves the system control but also that new feed forward controllers and a new sensor can improve the system control furthermore. The greatest improvements have been seen when introducing an additional sensor in the model.