Sedimentation of refined cellulosic pulp fines in the suspension during physical agglomeration

Abstract

A physical coagulator of fines was employed to separate suspensions comprising refined sulphate cellulose and waste paper, where no reagents were required. The physical coagulator was a porous cylinder with a rotating disk placed in its cavity. Using the MorFi Neo fibre analyser and the Hitachi SU 3500 digital microscope, a dispersed size distribution of well-developed fines in a suspension derived from softwood and hardwood pulp was obtained. The kinetics of fine sedimentation in the suspension was studied. The sedimentation rate of both individual agglomerates and a mass of them, as well as the magnitude of mass concentration in a cleared liquid, was determined. A relationship between the concentration of fines in the suspension and the structure of the pulp during their sedimentation was established. To intensify the fines sedimentation process, it was proposed to return a part of the sediment to the suspension passing into the physical coagulator. Process parameters for the sedimentation process and the construction of the sedimentation tank were obtained. The unit designed for collecting fines from the suspension is shown schematically. Use of this unit reduced the fibre sedimentation time, decreased the loads in wastewaters, and retained the consumer value of the pulp fibres.

Unraveling the Rheology of Nanocellulose Aqueous Suspensions: A Comprehensive Study on Biomass-Derived Nanofibrillated Cellulose

“…The dispersion state of NFC in water depends on its structure, surface groups, nanofibrillation degree, and solid concentration. For example, for the <0.2 wt% NFC aqueous suspension prepared by nanofibrillation of the wood cellulose pulps using a high-intensity ultrasonicator, the NFC may precipitate at the bottom of the beaker after the suspension has been standing for a period [19]. In contrast, TEMPOoxidized NFC aqueous dispersion is very stable.…”

Wood fibre recapture from process water during wet-forming of fiberboard: Process modelling with environmental and economic assessment

“…At the stage of moulding and forming a wood fibre mat, a certain amount of fine fraction leaves the sieve filter section and enters the wastewater, thus reducing the quality of the wastewater, further contaminating machine parts, forming slime, etc. (Yablochkin et al 2004;Hebert-Ouellet et al 2017;Vititnev et al 2021a;Voinov et al 2022).…”

“…One method to recover wood fibre and reuse it in the core production of fibreboards, paper, and cardboard is by recapturing it directly from white water (Michanickl 1996;Miao et al 2013;DaCunha et al 2016;Grossmann and Zelm 2016;Viger-Gravel et al 2017;Ihnat et al 2018Ihnat et al , 2020Zeng et al 2018;Hernandez et al 2021).The most widely used methods of recapturing fibre from wastewater involve sedimentation flotation with subsequent dehydration by various methods (Hubbe et al 2016;Voinov et al 2022).…”