Automatisering av spraytorkningsprocess

Sammanfattning: ABB Surge Arrestors in Ludvika have for a long time had a problem to keep the moisture at a steady state in the production of their ZnO-powder, that is used to produce varistors. Some black-box models of the spray drying process have been designed and evaluated to find a solution for the problem. After evaluating the collected data it has been found that variations in the supply voltage causes control difficulties for the operator. A cascade control system was designed, consisting of three PI control loops designed with lambda tuning. The disturbance in the supply voltagewas used as a feed forward in the control system. At the end of the project the control system was installed, and tests were made to verify the functionality of the regulator. It was shown that most of the variations in the moisture of the powder could be eliminated using small resources, through purchase of a process controller and four power meters. The standard deviation in the moisture was decreased from a level of 0.32%, measured when the process was manually controlled, down to 0.07% measured when the control system was used. This also solved the given problem.