Approach for Online Characterization of Bubbles in Liquid by Image Analysis: Application to Oxygen Delignification Process

Abstract

Tiny gas bubbles are used in a number of industrial processes for separating solids from liquids and for facilitating heat and mass transfer between separate phases. Bubble size is known to be one of the important factors affecting the performance of these processes, so it would be useful to be able to monitor its behavior. In this paper, a novel methodology for automated characterization of oxygen dispersion bubbles is presented. The approach is based on analyzing digital images produced by an industrial CMOS camera which is attached to the process by a borescope. The developed methodology for analyzing images offers robustness and fastness which are significant advantages when it comes to online use of the method in real industrial environments. The approach is demonstrated in an oxygen delignification process, which is an important stage of chemical pulping and widely used for lignin removal before bleaching pulp. The results show that online monitoring of oxygen bubble size is possible using the method.