The Effect of Process Variables in Chlorine Dioxide Prebleaching of Birch Kraft Pulp. Part 1. Inorganic Chlorine Compounds, Kappa Number, Lignin, and Hexenuronic Acid Content.

ABSTRACT This study investigated the effects of temperature, chlorine dioxide dosage, and filtrate circulation on various filtrate and pulp properties in chlorine dioxide prebleaching of birch kraft pulp. Also the effect of a preceding A-stage was examined. Kappa number, delignification, and hexenuronic acid removal were unaffected by the used dilution media and temperature. Increasing ClO2 charge resulted in a lower…

Towards complete impregnation of wood chips with aqueous solutions. Part I. A retrospective and critical evaluation of the penetration process.

ABSTRACT This paper evaluates the process of liquid penetration into wood chips from the retrospective viewpoint of industrial development and research and provides a summary of currently available knowledge in this area. During the past few decades, researchers have been dealing mainly with pulping chemistry and the back-end of pulping processes, while less attention has been paid to the front-end…

A Model for Chlorine Dioxide Delignification of Chemical Pulp.

ABSTRACT A phenomenon based model for chlorine dioxide delignification of chemical pulp is introduced. The pulp suspension environment is modeled using the concept of two liquid phases, one inside and the other external to the fiber wall. Physico-chemical processes taking place during delignification are implemented with thermodynamic, mass transfer and reaction kinetic models. A broad library of chemical reactions is…

Specific Permeability of Wood to Water. Part 1: Longitudinal Specific Permeability of Steamed, Impregnated, and Kraft-Cooked Wood.

ABSTRACT Two apparatuses for measuring the specific permeability of wood specimens are presented. The developed method was used to measure specific permeability to water in the longitudinal direction (of the log) for three wood species, pine (Pinus sylvestris), birch (Betula pendula), and eucalyptus (Eucalyptus grandis). The wood species were cooked to a certain degree under kraft cooking conditions. The effect…

Kinetics of Aldehyde Oxidation by Chlorous Acid.

ABSTRACT Chlorous acid is known to react with aldehydes. This study investigated the oxidation kinetics of different aldehydes by chlorous acid. Reaction rates with chlorous acid at 25 °C were obtained for formaldehyde (11.0 M−1 s−1), vanillin (0.59 M−1 s−1), veratraldehyde (1.00 M−1 s−1), benzaldehyde (5.6 M−1 s−1), glucose (3.39 × 10−3 M−1 s−1), glycolaldehyde (39.0 M−1 s−1), and 5-formyl-2-furancarboxylic…

Reactions of aldehydes with chlorous acid and chlorite in chlorine dioxide bleaching.

ABSTRACT The role of chlorine (III) compounds, i.e. chlorous acid (HClO(2)) and chlorite (ClO(2)(-)), in chlorine dioxide bleaching were investigated by treating different pulps with Cl(III). It was discovered that in addition to its fully inorganic reactions, chlorous acid is consumed by organic structures present in the pulp. These structures were assumed to be aldehydes. The aldehydes might exist already…

Specific Permeability of Wood to Water. Part 2: Perpendicular Specific Permeability of Steamed, Impregnated, and Kraft-Cooked Wood.

ABSTRACT A method for measuring the perpendicular specific permeability of wood specimens to water is presented, which is a modification of the method presented in part 1 of this work. The specific permeability in the perpendicular direction of the log of three wood species, pine (Pinus sylvestris), birch (Betula pendula), and eucalyptus (Eucalyptus grandis), was measured from kraft-cooked wood of…

Lignin oxidation mechanisms under oxygen delignification conditions. Part 3. Reaction pathways and modeling

ABSTRACT A detailed kinetic model for the lignin oxidation chemistry is presented. It is based mainly on the mechanisms and kinetics presented in the literature. Parameters that could not be found in the literature were regressed against the experimental data obtained from oxidation experiments with softwood kraft lignin. In addition to the detailed model for the chemistry, acid-base equilibrium reactions…

Modeling chlorine dioxide bleaching of chemical pulp (Aalto University)

ABSTRACT This doctoral thesis deals with the phenomenon-based modeling of pulp bleaching. Previous bleaching models typically utilize one or two empirical correlations to predict the kinetics in kappa number development. Empirical correlations are simple to develop, but their parameters are often tied to the validation system. A major benefit of physico-chemical phenomenon models is that they are valid regardless of…