Date of Award


Degree Name

Bachelor of Science


Paper Science and Engineering


This project began with an observation of a coating make-down tank at a nearby paper mill. The make down tank, a cowles dissolver, was being used to disperse and mix pigment and other common coating ingredients. Because the tank was unbaffled, the circulating suspension climbed the walls of the vessel, and could only be half filled to prevent overflowing.

There is a view held by some people that good dispersion cannot be obtained when baffles are used in these tanks. This paper mill obviously held this view.

The basic motivation for this thesis was the fact that the paper industry is currently using various numbers of baffles in the agitated vessels used for coating makedown. This must stem from a difference in opinion as to optimum number of baffles to use.

The purpose of this thesis was to investigate and make conclusions on how the number of baffles affects the efficiency of open impeller mixers to disperse pigments.