Generation of aqueous foams and fiber foams in a stirred tank

Generation of fiber foams with surface aeration was studied by simultaneous mixing of pulp fibers, surfactant, air and water in a lab-scale tank. The mixing took place in either transient or turbulent conditions. The effect of impeller type (RT-6 and BT-6), mixing speed, mixing power, and surfactant dosage on air content, bubble size and half-life time of the foam was investigated. Air content increased with increasing agitation power saturating to 50?75% depending on the SDS dosage. The dependence of bubble size on power was a power law with an exponent typical for processes where coalescence plays an important role. The relation between the half-life time and air content was well described by a power law. Power number of the BT-6 impeller was almost constant, and similar to that of pure water in turbulent conditions. The power number of the RT-6 impeller varied and was similarly to gas-liquid stirred tanks, in many cases clearly below that of water. The variability of the power number of RT-6 could be explained with the variation of the mixing Reynolds number. ? 2021 The Authors. Published by Elsevier B.V. on behalf of Institution of Chemical Engineers. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The generation of fiber foams with surface aeration was studied by simultaneously mixing pulp fibers, surfactant, air, and water in a lab-scale tank under transient or turbulent conditions. The air content and bubble size were found to be influenced by mixing power and surfactant dosage, with the half-life time of the foam related to air content. The impeller type and mixing Reynolds number were identified as factors affecting the power number during mixing.