The Role of Gas Dispersion in the Oxygen Delignification Process, 19PEERS

Oxygen delignification is an essential part of the pulp production process. Delignification occurs with the aid of an alkali and dissolved oxygen. Dissolved oxygen is obtained by dispersing oxygen gas into the pulp suspension by using efficient mixers. Little is known about the state of oxygen gas dispersion and its effect on oxygen delignification kinetics and efficiency. This paper will present results about the effect of gas bubble size dispersion on the performance of oxygen delignification. The results are based mainly on the detailed studies made in a Finnish hardwood mill where the oxygen bubble size distribution could be altered in the feed of the reactor.  An essential part of these studies was the use of a new continuous in-line gas bubble size measurement systems to simultaneously determine the bubble size distribution in the feed and top of the reactor. Information in regard to oxygen consumption in the reactor could be obtained. Accordingly, these studies quantified the effect of oxygen bubble size on the kappa reduction. The effect of different operational factors on the oxygen bubble size will also be reviewed. 

Finally, a relationship between the gas bubble size and the liquid phase oxygen mass transfer coefficient (kLa) is presented. This connects the bubble size to the kappa reduction rate. Based on the presented modelling approach and evaluation of practical factors, which are not taken into account in the modelling, it was concluded, that the volumetric average oxygen bubble size should preferably be smaller than 0.2 mm in practice. 

The new bubble size measurement, information which has and will be obtained from the processes, and a presented modelling approach give a very new base to understand, monitor, adjust and design oxygen delignification processes. 

TAPPI conference proceedings and presentations, technical papers, and publication articles provide technical and management data and solutions on topics covering the Pulp, Paper, Tissue, Corrugated Packaging, Flexible Packaging, Nanotechnology and Converting Industries.

Simply select the quantity, add to your cart and your conference paper, presentation or article will be available for immediate download.