Controlling the solid content of product black - liquor in an evaporation plant - using predictive algorithm based on the mix of feedforward and feedback control

The Paper presents a scheme of the solid content control of a black - liquor evaporation. The scheme which results in better linearity and stability of plant model is different from conventional practice in that we use the flow rate of input black - liquor to regulate the concentration of final product. To overcome the severe time delay and sluggish response of the plant, a predictive control algorithm based on the mix of feedforward and feedback is introduced. The control system proves to be satisfactory in accuracy and stability.