Dynamic drainage simulation

Drainage interacts with formation and ultimately with machine output and product quality. But, traditional methods of drainage measurement which focus on gravity drainage and which do not take shear into account cannot simulate the mechanisms which control drainage in the papermaking process. This paper describes a dynamic drainage tester which can give far more information than traditional methods. It can show clearly the effect of furnish morphology, on the drainage dynamics in stocks of equivalent freeness levels, and, the effects of fibre type, length and degree of fibrillation can be studied. The aim is to use the tester to imitate the forming dwell times on a full size former. The effects of refining and chemical additives could then be assessed before conducting full scale trials. It is also intended to develop a standardised method for drainage measurement.