Cellulose (2025) 32:1835–1850 https://doi.org/10.1007/s10570-024-06344-3
ORIGINAL RESEARCH
Experimental investigation of pulp dewatering by high vacuum suction boxes Mahlohonono Mafela · Tobias Louw · Johann Görgens · Garreth Saunders · Michael Garces de Gois · Johannes P. Kotze · Wian Van der Westhuizen · Luvuyo Tyhoda
Received: 11 July 2024 / Accepted: 14 December 2024 / Published online: 26 December 2024 © The Author(s) 2024
Abstract Reducing energy consumption by indus- trial processes has become imperative because of rising energy costs and efforts toward decarboni- sation. The continuous manufacturing of paper is energy intensive due in part to the water removal process required to convert pulp slurries to valuable paper products. This necessitates the development of energy conservation techniques, while simultane- ously ensuring the quality of the product. A pilot- scale test unit was developed to quantify the effects of dwell time, vacuum pressure, and refining energy on the achievable pulp concentration or dryness level of three pulp types utilised in paper machines. Pulp dr y matter was investigated as a means of gauging
vacuum consumption and hence energy utilisation i n paper machines, which could potentially reduce utility consumption of the overall drying process. A novel approach to simulate the pulsating high vacuum zone in t he for ming section of a paper machine was implemented, allowing the development of statistical correlations to explore vacuum dewatering conditions that may lead to energy efficiency. Bleached hard- wood, mechanical/groundwood and recycled pulp were characterised to determine the effects of refin- ing energy o n fibre morphology and their drainage behaviour i n pulp slur r ies. A dr yness level of 21.8% at − 55 kPa gauge was achieved for bleached hard- wood, whereas lower values of 19.8 and 18.3% were observed for recycled and mechanical pulps, respec- tively. This behaviour was attributed to the differ- ences in drainability and morphology of the pulps due to their respective unique properties, further exagger- ated by refining. Keywords Vacuum dewatering · Pulp refining · Pulp characterisation Introduction Th e pulp dewatering process in paper machines is energy-intensive (Ramaswamy 2003; Laurijssen et al. 2013; Rezk et al. 2013; Sjöstrand 2020). Fil- trate removal occurs in three distinct stages, each with varying levels of energy utilisation (Ramaswamy
M. Mafela · T. Louw · J. Görgens ( * ) Department of Chemical Engineering, University of Stellenbosch, Pr ivate Ba gX1 , Matieland, Stellenbosch 7602, South Africa e-mail: jgorgens@sun.ac.za
G. Saunders · M. G. de Gois · J. P. Kotze TF Design (Pty) Ltd, Unit 1, Devon Valley Industrial Park, Devon Valley Road, Stellenbosch 7600, South Africa W. Van der Westhuizen Mpact, Innovation Research and Development, The Vineyard Office Park cnr Adam Tas and Devon Valley Road, Stellenbosch 7600, South Africa L. Tyhoda Department of Forest and Wood Science, University of Stellenbosch, Private Bag X1, Stellenbosch 7602, South Africa
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