THROUGH DRYING OF PAPER .1. SUCTION DRUM DESIGN FROM CONSTANT AIR-FLOW RATE DATA

For investigation of through drying of paper tissue it is convenient t o use laboratory-scale apparatus which operates batch-wise. Since comm ercial suction drums show a constant pressure difference across the pa per along the perimeter of the drum, it would be desirable to realize this constant pressure difference in the batch apparatus also. However , an apparatus with constant air flow rate is much simpler. It is show n that data obtained under constant air flow rate can be used for a sc ale-up to suction drums, which operate under constant pressure differe nce. Also, it is indicated that vacuum dewatering chambers upstream of the drum, which mechanically remove liquid water from the paper, have to be taken into account when predicting the air flow rate.