On-line  Quality  Control

In general two types of control strategies canbe distinguished .The first strategy is focused on maintaining constant values of process conditions ,such as temperatures ,flow and pressures .The idea is that constant process conditions will result in constant product quality .A more recent second control strategy is based on indirect or direct contol of the desired product quality parameters .In this case the setpoints of the process conditions are determined by mathematical models which describe  the interactions between process and product properties.At present ,the models used are black box models with little or no physico-chemical background ,In section 3.1 a case is presented using these black box models for feed-forwarding  control of evaporators and spray dryers .

In the very near future ,it is expacted that physico-chemical predictive models will also be applied to model -based control.An example of a research project in this area is given in Section 3.2