Dewatering properties of low grammage handsheets of softwood kraft pulps modified to minimize the need for refining

Abstract

Previous paper (Rahman et al. 2017) showed that the yield of softwood kraft pulp increased by the addition of either polysulfide or sodium borohydride because of higher hemicellulose retention. An increase in hemicellulose content can make dewatering more difficult as WRV of the pulp increases, but instead, an overall increase in pulp yield could improve dewatering as a sheet of a certain weight will contain fewer fibres, giving a more open sheet structure. It was therefore of interest to measure the dewatering properties of low grammage handsheets (20 g/m2) under conditions mimicking the tissue paper machine dewatering processes, and sheet strength properties, WRV, °SR and fibre dimensions were also studied. The results showed that the positive influence of overall yield increase dominated over the negative influence of an increase in hemicellulose content on the dewatering properties, particularly at lower refining energy levels. Moreover, higher yield and higher hemicellulose content pulps had a higher tensile index at the same dryness. A given tensile index was achieved with less refining energy. The results indicate that increased yield and hemicellulose content by modification of the kraft pulping process will result in a pulp with a potential to improve tissue paper quality.

Method for studying water removal and air penetration during through air drying of tissue in laboratory scale

“…5. The typical shape of the diminishing returns of the dewatering curve is consistent with both previous data from the same laboratory equipment (Sjöstrand et al 2016(Sjöstrand et al , 2017(Sjöstrand et al , 2019Rahman et al 2018;Sjöstrand and Brolinson 2022), and with laboratory and pilot data from other publications of vacuum dewatering (Attwood 1962;Neun 1994Neun , 1996Räisänen et al 1996;Ramaswamy 2003;Pujara et al 2008). The shape of the dewatering curve shows the well-known dewatering mechanism for vacuum dewatering where water between the fibers is removed first, to an initial high dewatering rate, and as the water becomes increasingly less accessible the dewatering rate levels out, and gradually goes to zero.…”

Improved vacuum dewatering of grease-proof paper utilizing a multi-slit vacuum suction box in laboratory scale

“…In accordance with the previously mentioned expected dryness curves, the dryness of the grease-proof paper over dwell time reached a plateau (Attwood 1962;Neun 1994;Räisänen et al 1996;Baldwin 1997;Räisänen 2000;Ramaswamy 2003;Granevald et al 2004;Pujara et al 2008;Rahman et al 2018;Sjöstrand et al 2019;Hubbe et al 2020;Sjöstrand and Brolinson 2022;Sjöstrand 2023). Each of the four series, for both paper basis weights, representing a new set of slits with increased vacuum throughout, is plotted in Figs.…”

“…These asymptotes would thereby be overcome by utilizing a higher degree of vacuum by the time these asymptotes have been reached in order to reach a higher degree of dryness, with a lesser energy expenditure (Attwood 1962;Neun 1994;Räisänen et al 1996;Baldwin 1997;Räisänen 2000;Ramaswamy 2003;Granevald et al 2004;Pujara et al 2008;Rahman et al 2018;Sjöstrand et al 2019Sjöstrand et al , 2023Hubbe et al 2020;Sjöstrand and Brolinson 2022). Common commercial paper machines utilize dwell times in terms of milliseconds (Ramaswamy 2003).…”

Enhancing Through Air Drying process efficiency: Investigating laboratory-to-pilot scale correspondence and impact of process variables on tissue paper manufacturing

“…The air volumes are directly connected to the pump energy in the vacuum section and thus connected to energy consumption of the process (Sjöstrand 2023). The dewatering behavior for the forming fabric was expected and in line with previous observations of vacuum dewatering and penetrated air volume (Attwood 1962;Neun 1994Neun , 1996Räisänen et al 1996;Ramaswamy 2003;Pujara et al 2008;Sjöstrand et al 2016Sjöstrand et al , 2017Rahman et al 2018;Sjöstrand and Brolinson 2022;Sjöstrand et al 2023;Sjöstrand 2023). According to the laboratory results of solids content development for TAD fabrics (Fig.…”