PAPER making! FROM THE PUBLISHERS OF PAPER TECHNOLOGY INTERNATIONAL FROM THE PUBLISHERS OF PAPER TE Volume 7, Number 1, 2021
Application of (super)cavitation for the recycling of process waters in paper producing industry Janez Kosel (a), Matej Š u š tar š i č (b), Martin Petkov š ek (c), Mojca Zupanc (c), Mija Se ž un (b) , Matevž Dular (c) In paper production industry, microbial contaminations of process waters are common and can cause damage to paper products and equipment as well as the occurrence of pathogens in the end products. Chlorine omission has led to the usage of costly reagents and products of lower mechanical quality. In this study, we have tested a rotation generator equipped with two sets of rotor and stator assemblies to generate developed cavitation (unsteady cloud shedding with pressure pulsations) or supercavitation (a steady cavity in chocked cavitation conditions) for the destruction of a persistent bacteria Bacillus subtilis. Our results showed that only supercavitation was effective and was further employed for the treatment of waters isolated from an enclosed water recycle system in a paper producing plant. The water quality was monitored and assessed according to the chemical (COD, redox potential and dissolved oxygen), physical (settleable solids, insolubles and colour intensity) and biological methods (yeasts, aerobic and anaerobic bacteria, bacterial spores and moulds). After one hour of treatment, a strong 4 logs reduction was achieved for the anaerobic sulphate reducing bacteria and for the yeasts; a 3 logs reduction for the aerobic bacteria; and a 1.3 logs reduction for the heat resistant bacterial spores. A 22% reduction in COD and an increase in the redox potential (37%) were observed. Sediments were reduced by 50% and the insoluble particles by 67%. For bacterial destruction in real industrial process waters, the rotation generator of supercavitation spent 4 times less electrical energy in comparison to the previously published cavitation treatments inside the Venturi
constriction design. Contact information: a Institute for the Protection of Cultural Heritage of Slovenia, Slovenia b Pulp and Paper Institute of Ljubljana, Slovenia c Faculty of Mechanical Engineering, University of Ljubljana, Slovenia
Ultrasonics - Sonochemistry 64 (2020) 105002 https://doi.org/10.1016/j.ultsonch.2020.105002 Creative Commons Attribution 4.0 International License
The Paper Industry Technical Association (PITA) is an independent organisation which operates for the general benefit of its members – both individual and corporate – dedicated to promoting and improving the technical and scientific knowledge of those working in the UK pulp and paper industry. Formed in 1960, it serves the Industry, both manufacturers and suppliers, by providing a forum for members to meet and network; it organises visits, conferences and training seminars that cover all aspects of papermaking science. It also publishes the prestigious journal Paper Technology International and the PITA Annual Review , both sent free to members, and a range of other technical publications which include conference proceedings and the acclaimed Essential Guide to Aqueous Coating .
Article 6 – Ultrasonication of Process Waters
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