Effect of Different Forming Regimes on Retention Aid Programs (PPJ Studies)

Abstract

A new design of equipment called the Positive Pulse Jar (PPJ) was introduced in this study in order to compare the responses of different retention aid systems to hydrodynamic shear forces resulting from different idealized forming regimes. The major advantage of this equipment for this kind of study is the ability to simulate different forming regimes such as simple filtration, pulsation at different frequencies and amplitudes, uniform-shear forming, and a procedure corresponding to the Britt Jar method. Results showed that pulsations could increase the uniformity of paper, not only in the x-y direction, but also in some cases in the z direction as well. Under the conditions that were used for testing, a dual-polymer bridging system showed the greatest improvement in fine particle retention but this effect could be reduced by the application of hydrodynamic shear before dewatering. Following the application of high level of hydrodynamic shear, charge neutralization didn't show fully reversibility, and it was the least effective retention aid system compared with the other systems. Effects of new-designed cone rotor were also studied; making it possible to explore effects due to a well characterized average shear stress throughout the sample volume. For future studies, suggestions have been made to increase the usefulness of the PPJ as a tool in predicting the performance of new retention aid system under different forming conditions.