Mechanism of vessel separation with hydrocyclone. I. Vessel separation with Centri-Cleaner.

Abstract

Experimental study with Centri-Cleaner to separate vessel elements from wood fibers was carried out using several bleached kraft pulps produced from some tropical and other hardwoods. Vessel separation efficiencies of pulp were examined in detail. It became clear firstly that vessel elements having larger projected area and lower L/D ratio (ratio of longer side length(L) to shorter one(D) of projected vessel element) were separated more effectively into reject side of hydrocyclone. Secondly, separation efficiency varied with pulp species. It was considered that one of the main reasons was the differences of shape(L/D) and size(projected area) of vessel elements. The pulp containing many slender(high L/D ratio) vessel elements had low separation efficiency. Furthermore, the separation efficiency decreased with an increase in pulp consistency for Centri-Cleaner treatment. This is probably due to the development of fiber network in a Centri-Cleaner at high pulp consistency, which would hinder the settling of vessel elements.