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Model development for real oxygen delignification processes, TAPPI Journal October 2024
ABSTRACT: Previous extensive work has been done on modeling the oxygen delignification process, based on how the basic parameters, i.e., temperature, kappa number, concentration of alkali, and concentration of oxygen, affect the delignification rate. However, these models are not used extensively to evaluate the performance of real processes, primarily because they have not been able to properly consider all the essential issues affecting delignification in practice. Such issues include the mass transfer and consumption of oxygen, which defines the concentration of dissolved oxygen in the process, and the effect of that concentration on the delignification rate. In this paper, a new way to model the oxygen delignification process is used in which these parameters, among other smaller matters, are taken into account. The basic model and its parameters were defined by the information obtained from the literature, delignification made in the laboratory tests, and mill processes and mill tests. An essential aspect of these studies was the information obtained from the oxygen concentration measured in the residual gas obtained from the top of the reactor. With the aid of this measurement, it was possible to define more accurately the consumption of oxygen and partial pressure of oxygen that define the concentration of dissolved oxygen in the reactor. Using mill experiments, a model was formed that predicts the operation of the oxygen delignification process. The model was used to show how much the process could be improved by optimizing the charge of the oxygen. The mill experiments also confirmed that mass transfer of oxygen is modeled correctly enough, except when the charge of oxygen is very low and/or the mixing is not efficient enough. In that case, there is variation in the concentration of oxygen in the process that should be taken into account in the modeling.
Journal articles
Magazine articles
Colloid chemical aspects of paper formation in the presence of nanofibrillated cellulose and cationic starch, TAPPI Journal September 2024
ABSTRACT: A series of experimental tests were carried out to examine colloidal-scale consequences of optionally treating nanofibrillated cellulose (NFC) with cationic starches of different charge density and dosage (0.5% or 2.0% by weight), adding that material to a furnish prepared from 100% recycled copy paper, and then subjecting the mixture to very different levels of hydrodynamic shear. Tests included optical microscopy, sediment volume tests, sediment velocity tests, and “percent fines” assessment by means of a fiber quality analyzer (FQA). In addition, the zeta potential and charge demand of the studied materials were evaluated. Optical imaging revealed that cationic starch treatment of the NFC tended to agglomerate it into multiparticle clusters, which sometimes could be mostly redispersed by hydrodynamic shear. Subsequent addition of the starch-treated NFC to the default furnish resulted in much of the colloidal material becoming attached to fibers. Subsequent shearing of the mixtures was at least partly effective in separating the clusters of NFC from the fiber surface, resulting in essentially a two-component mixture. Multiparticle NFC clusters coexisted with the fiber suspension, sometimes attached and sometimes not, depending on the details of treatments. Sediment volume tests showed that systems containing cationic starch-treated NFC tended to have a higher density after settling in comparison to untreated NFC; these findings are consistent with the cationic starch acting as a stabilizer on the solid surfaces, allowing them to slide past each other during the settling process. Application of intense hydrodynamic shear tended to result in denser sediment. Results of tests with the sediment velocity messurement and the FQA percent fines assessment did not correlate well with changes in test conditions considered in this study.
Journal articles
Cavitation-jet deinking: A new technology for deinking of recovered paper, TAPPI JOURNAL September 2014
Cavitation-jet deinking: A new technology for deinking of recovered paper, TAPPI JOURNAL September 2014
Journal articles
Editorial: TAPPI JOURNAL 2014 Best Research Paper Award highlights potential of cavitation-jet deinking, TAPPI JOURNAL April 2015
Editorial: TAPPI JOURNAL 2014 Best Research Paper Award highlights potential of cavitation-jet deinking, TAPPI JOURNAL April 2015
Journal articles
Organic material dissolved during oxygen-alkali pulping of hot water-extracted birch sawdust 15APR237
Organic material dissolved during oxygen-alkali pulping of hot water-extracted birch sawdust, TAPPI JOURNAL April 2015
Journal articles
Magazine articles
Editorial: In praise of challenging papers
Editorial: In praise of challenging papers, and those who review them, TAPPI JOURNAL August 2015
Journal articles
Systematic screening of biorefinery technologies at the early stage of design, TAPPI JOURNAL October 2012
Systematic screening of biorefinery technologies at the early stage of design, TAPPI JOURNAL October 2012
Journal articles
Semi-bleached paper and fermentation products from a larch biorefinery, TAPPI JOURNAL October 2012
Semi-bleached paper and fermentation products from a larch biorefinery, TAPPI JOURNAL October 2012
Journal articles
Effect of commercial xylanases applied at extreme conditions in a eucalyptus pulp mill, TAPPI JOURNAL October 2012
Effect of commercial xylanases applied at extreme conditions in a eucalyptus pulp mill, TAPPI JOURNAL October 2012
Journal articles
Magazine articles
Generlized stead-state model for chlorine dioxide brightning
Generlized stead-state model for chlorine dioxide brightning of hardwood kraft pulps, TAPPI JOURNAL May 2017