| 1. |
- Sjöstrand, Björn, 1987-, et al.
(författare)
-
Dewatering of Softwood Kraft Pulp with Additives of Microfibrillated Cellulose and Dialcohol Cellulose
- 2019
-
Ingår i: BioResources. - : North Carolina State University. - 1930-2126 .- 1930-2126. ; 14:3, s. 6370-6383
-
Tidskriftsartikel (refereegranskat)abstract
- The addition of nano-and micro-fibrillated cellulose to conventional softwood Kraft pulps can enhance the product performance by increasing the strength properties and enabling the use of less raw material for a given product performance. However, dewatering is a major problem when implementing these materials to conventional paper grades because of their high water retention capacity. This study investigated how vacuum dewatering is affected by different types of additives. The hypothesis was that different types of pulp additions behave differently during a process like vacuum suction, even when the different additions have the same water retention value. One reference pulp and three additives were used in a laboratory-scaled experimental study of high vacuum suction box dewatering. The results suggested that there was a linear relationship between the water retention value and how much water that could be removed with vacuum dewatering. However, the linear relationship was dependent upon the pulp type and the additives. Additions of micro-fibrillated cellulose and dialcohol cellulose to the stock led to dewatering behaviors that suggested their addition in existing full-scale production plants can be accomplished without a major redesign of the wire or high vacuum section.
|
|
| 2. |
- Sjöstrand, Björn, 1987-, et al.
(författare)
-
Numerical model of water removal and air penetration during vacuum dewatering
- 2021
-
Ingår i: Drying Technology. - : Taylor & Francis. - 0737-3937 .- 1532-2300. ; 39:10, s. 1349-1358
-
Tidskriftsartikel (refereegranskat)abstract
- Dewatering and air flow in high vacuum suction boxes was examined. The work was mainly numerical and was based on, and compared with, previously published experimental results of vacuum dewatering from laboratory equipment and from a pilot paper machine. A previously published numerical model for wet pressing is used as the basis for this work. The aims of this study were to find new fitting parameters that allows the previous model to be used for vacuum dewatering instead of pressing, and to examine two extensions to the original model. The results indicate that the new vacuum dewatering model for moisture can predict the dewatering behavior for several different experimental data series both from laboratory equipment and a pilot paper machine using the same set of fitting parameters. Two different numerical models for air flow through the paper sheet, during vacuum dewatering, were developed based on postulating that the decrease in moisture permeability is accompanied by a simultaneous increase in air permeability. The models for air flow can also be fitted to experimental data and predict the magnitudes of air flow during vacuum dewatering. The data sets for air flow exhibit a certain degree of operator dependence though, so that one set of fitting parameters is not enough for obtaining good agreement with all data sets.
|
|
| 3. |
- Sjöstrand, Björn, 1987-
(författare)
-
Vacuum Dewatering of Cellulosic Materials : New insights into transport phenomena in the papermaking process
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Working towards sustainable development within the forest industry, the dewatering of pulp and paper must be fully understood along with the dewatering of other cellulose-based materials. Huge amounts of energy are used during paper manufacturing so there is a potential for making the processes more energy-efficient. This thesis attempts to gain understanding of vacuum dewatering in the forming section of the conventional papermaking process and its connection with energy consumption in order to suggest actions that may be taken not only to improve energy efficiency but also facilitate the introduction of new materials into existing processes. The main objective of this thesis is to develop a deeper understanding of the vacuum dewatering of forest-based cellulosic materials in existing paper manufacturing processes. Aspects of how rewetting, the structure of the forming fabric and additives of cellulosic materials affect vacuum dewatering are discussed in detail throughout. There is also a large section discussing the use of numerical models and software simulations of dewatering in the forming section of a papermaking machine. A brief background of the papermaking process is presented, along with useful numerical models used previously in that particular context. Three sets of experiments, including rewetting, forming fabrics and additions of cellulosic materials, compose the bulk of the thesis’ method along with two sets of simulations regarding fabrics and additives. This thesis shows how rewetting is both rapid and substantial after high vacuum suction boxes, the way in which the structure of the forming fabrics affects vacuum dewatering and how additions of micro-fibrillated cellulose and dialcohol cellulose affect vacuum dewatering. The results of the simulations and numerical models show how they can be used to explore ways of saving energy in the process as well as to facilitate the introduction of cellulosic additives into existing papermaking processes.
|
|
