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Magazine articles
Causes of poor dregs settling in a green liquor clarifier, TAPPI Journal August 2022
ABSTRACT: A study was conducted to examine the most likely parameters responsible for poor dregs settling at a kraft mill over a 2.5-year period, using multivariate data analysis (MVDA) and machine learning (ML) techniques. The dregs settling behavior seems to be seasonally influenced, implying that wood quality variation can be a factor. The results from the MVDA/ML analysis show that poor dregs settling is correlated to incomplete combustion and/or low load conditions in the recovery boiler, low sulfidity in the causticizing plant, and high flow in the green liquor•weak wash cycle. Compositions of dregs and black liquor were also examined to identify correlations with impaired dregs settling. The results show that poor dregs settling strongly correlates with high silicon (Si) content in dregs and moderately correlates with high iron (Fe) and high aluminum (Al) contents, and with low bulk density in dregs. For mills that experience dregs settling or green liquor filtering issues, regular compositional analyses of dregs, green liquor, weak wash, and black liquor are recommended in order to monitor the dynamics of silicon and other constituents in the recovery cycle.
Journal articles
Magazine articles
Utilization of kraft pulp mill residuals, TAPPI Journal February 2022
ABSTRACT: Kraft pulp mills produce on average about 100 kg of solid residuals per metric ton of pulp produced. The main types of mill waste are sludge from wastewater treatment plants, ash from hog fuel boilers, dregs, grits, and lime mud from causticizing plants and lime dust from lime kilns. Of these, about half is disposed of in landfills, which highlights the need and potential for waste recycling and utilization. Sludge is either incinerated in hog fuel boilers to generate steam and power or used in various forms of land application, including land spreading, composting, or as an additive for landfill or mine waste covers. The majority of hog fuel boiler ash and causticizing plant residues is landfilled. Alkaline residuals can be conditioned for use in land application, manufacture of construction materials, and production of aggregates for road work. This technical review summarizes residuals utilization methods that have been applied in pulp and paper mills at demonstration- or full-scale, and therefore may act as a guide for mill managers and operators whose goal is to diminish the costs and the environmental impact of waste management.
Journal articles
Magazine articles
Preparing prehydrolyzed kraft dissolving pulp via phosphotungstic acid prehydrolysis from grape branches, TAPPI Journal January 2022
ABSTRACT: Dissolving pulp was successful prepared via phosphotungstic acid (PTA) prehydrolysis kraft (PHK) cooking followed by an elementary chlorine-free (ECF) bleaching process from grape branches. The effects of prehydrolysis temperature, reaction time, and PTA concentration that potentially affect the quality of dissolving pulp product on chemical components of pulp were studied via an orthogonal experiment. The structure of lignin was activated during the PTA prehydrolysis phase, and lignin was easily removed during the following cooking process. Thus, relatively mild conditions (140°C, 100 min) can be used in the cooking process. During the prehydrolysis phase, temperature exhibited the most significant influence on the cellulose purity of the obtained pulp fiber, followed by reaction time and PTA concentration. The optimized prehydrolysis conditions were as follows: prehydrolysis temperature, 145°C; reaction time, 75 min; and PTA concentration, 1 wt%. Whether the excessively high prehydrolysis temperature or prolonging the reaction time did not favor the retention of long chain cellulose, the delignification selectivity for the cooking process could not be further improved by excessive PTA loading. Under these prehydrolysis conditions, 94.1% and 29.0% for a-cellulose content and total yield could be achieved after the given cooking and bleaching conditions, respectively. Moreover, the chemical structure and crystal form of cellulose were scarcely changed after PTA prehydrolysis, which could be confirmed by results from Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). PTA prehydrolysis could be considered as an alternative method for preparing PHK dissolving pulp under relatively mild cooking conditions.
Journal articles
Amine boranes as new reductive bleaching chemicals on softwood pulp single stage and multistage processes, TAPPI JOURNAL, February 1999, Vol. 82(2)
Amine boranes as new reductive bleaching chemicals on softwood pulp single stage and multistage processes, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
A cradle-to-gate life cycle assessment of straw pulp incorporation into telephone directory-grade paper, TAPPI JOURNAL, February 1999, Vol. 82(2)
A cradle-to-gate life cycle assessment of straw pulp incorporation into telephone directory-grade paper, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
Factors affecting the partitioning of methanol vapor-liquid phases in black liquors, TAPPI JOURNAL, February 1999, Vol. 82(2)
Factors affecting the partitioning of methanol vapor-liquid phases in black liquors, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
Investigation of chemical recovery unit floor tube overheat failures, TAPPI JOURNAL, February 1999, Vol. 82(2)
Investigation of chemical recovery unit floor tube overheat failures, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
Closure of a nine-acre industrial landfill using pulp and paper mill residuals, TAPPI JOURNAL, February 1999, Vol. 82(2)
Closure of a nine-acre industrial landfill using pulp and paper mill residuals, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
Fractionation of softwood fiber (tmp) using a rotating cone, TAPPI JOURNAL, February 1999, Vol. 82(2)
Fractionation of softwood fiber (tmp) using a rotating cone, TAPPI JOURNAL, February 1999, Vol. 82(2)
Journal articles
Mechanical pulp fines: effect of particle size and shape, TAPPI JOURNAL, February 1999, Vol. 82(2)
Mechanical pulp fines: effect of particle size and shape, TAPPI JOURNAL, February 1999, Vol. 82(2)