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Journal articles
Open Access
Bleaching and brightness stability of aspen biomechanical pulps, TAPPI JOURNAL, November 1993, Vol. 76(11)

Bleaching and brightness stability of aspen biomechanical pulps, TAPPI JOURNAL, November 1993, Vol. 76(11)

Journal articles
Open Access
Steam drying and fluidized-bed calcination of lime and mud, TAPPI JOURNAL, November 1993, Vol. 76(11)

Steam drying and fluidized-bed calcination of lime and mud, TAPPI JOURNAL, November 1993, Vol. 76(11)

Journal articles
Open Access
Formation of polychlorinated phenolic compounds during high chlorine dioxide substitution bleaching: part 1: laboratory investigation, TAPPI JOURNAL, August 1994, Vol. 77(8)

Formation of polychlorinated phenolic compounds during high chlorine dioxide substitution bleaching: part 1: laboratory investigation, TAPPI JOURNAL, August 1994, Vol. 77(8)

Journal articles
Magazine articles
Open Access
Eucalyptus black liquor properties in a lignin extraction process: density, dry solids, viscosity, inorganic, and organic content, TAPPI Journal March 2023

ABSTRACT: Extracting lignin from black liquor is becoming more common, although only a few research papers discuss the impact of the process on the liquor’s primary properties. This work aims to determine the changes in black liquor properties as it undergoes a lignin extraction process using carbon dioxide (CO2). A diluted eucalyptus black liquor sample (DBL) was acidified with CO2 to a final pH of 8.5. After filtration, the kraft lignin was removed, and the filtrated lignin lean black liquor (LLBL) was collected. Five acidified black liquors (ABL) samples were collected during acidification at pH 10.5; 10.0; 9.5; 9.0; and 8.5. The samples were analyzed regarding lignin content in solution, sodium carbonate (Na2CO3), sodium sulfate (Na2SO4), density, dry solids content, and viscosity. While Na2SO4 remained almost constant, Na2CO3 presented an enormous increase in its concentration when comparing DBL with LLBL. As pH decreased, the lignin content in the solution was also reduced due to lignin precipitation. The results showed similar behavior for dry solids, density, and viscosity of the supernatant, but an increase in density was observed around pH 9.00. In light of this, the density of LLBL turns out to be closer to the one in the initial DBL. The significant increase in carbonate content could explain this behavior during acidification with CO2 once the inorganic content significantly influences the property. The viscosity was determined from 10 s-1 to 2000 s-1. We observed a Newtonian behavior for all samples. The increase in carbonate content in the sample is crucial information to the recovery cycle, especially for calculating the mass and energy balance when targeting the use of the LLBL.

Journal articles
Magazine articles
Open Access
On the diagnosis of a fouling condition in a kraft recovery boiler: combining process knowledge and data-based insights, TAPPI Journal March 2023

ABSTRACT: Fouling is still a major challenge for the operation of kraft recovery boilers. This problem is caused by accumulation of ash deposits on the surfaces of heat exchangers in the upper part of the boiler over time. The first consequence is the reduction of steam production due to loss of heat transfer and, finally, the shutdown of the boiler due to clogging. The present work investigated the operational condition of a modern kraft boiler under a critical fouling condition. This boiler had even faced a manual cleaning due to a clogging event. This analysis combined process knowledge, plant team experience, and a data-driven approach, given the complexity of the process. In this sense, historical data covering this critical period of operation were collected. After a cleaning procedure, they were used to obtain a predictive neural network model for the flue gas pressure drop in the boiler bank, which is an indirect measure of ash deposit accumulation. Once validated, it was used for sensitivity analysis, with the aim of quantifying the effects of the model inputs. Five variables out of eighteen accounted for nearly 60% of the total effect on pressure drop. Namely, primary air temperature (21.6% of the total effect) and flow rate (11.1%), black liquor flow rate (9.9%) and temperature (8.4%), and white liquor sulfidity (8.6%). The analysis of these results mainly suggested an excess of carryover, which composes the ash deposits. Recommended actions to mitigate the fouling condition involved adjustments to the primary air system before the more drastic solution of reducing the boiler load.

Journal articles
Magazine articles
Open Access
Techno-economic analysis of hydrothermal carbonization of pulp mill biosludge, TAPPI Journal March 2023

ABSTRACT: For many mills, the biosludge from wastewater treatment is difficult to recycle or dispose of. This makes it a challenging side stream and an important issue for chemical pulping. It often ends up being burned in the recovery or biomass boiler, although the moisture and non-process element (NPE) contents make it a problematic fuel. Biosludge has proven resistant to attempts to reduce its moisture. When incinerated in the biomass boiler, the heat from dry matter combustion is often insufficient to yield positive net heat. Mixing the sludge with black liquor in the evaporator plant for incineration in the recovery boiler is more energy efficient, but is still an additional load on the evaporator plant, as well as introducing NPEs to the liquor. In this study, treating the biosludge by hydrother-mal carbonization (HTC), a mild thermochemical conversion technology, is investigated. The HTC process has some notable advantages for biosludge treatment; taking place in water, it is well suited for sludge, and the hydrochar product is much easier to dewater than untreated sludge. In this study, two HTC plant designs are simulated using IPSEpro process simulation software, followed by economic analysis. Low temperature levels are used to minimize investment costs and steam consumption. The results show that if the sludge is incinerated in a biomass boiler, payback periods could be short at likely electricity prices. The HTC treatment before mixing the sludge with black liquor in the evaporator plant is profitable only if the freed evaporator capacity can be used to increase the firing liquor dry solids content.

Journal articles
Open Access
Characterization of refined papermaking pulps using hydrodynamic parameters from filtration analysis, TAPPI JOURNAL May 2015

Characterization of refined papermaking pulps using hydrodynamic parameters from filtration analysis, TAPPI JOURNAL May 2015

Journal articles
Open Access
Dimensional stability of mechanical pulps - drying shrinkage and hygroexpansivity, TAPPI JOURNAL, June 1993, Vol. 76(6)

Dimensional stability of mechanical pulps - drying shrinkage and hygroexpansivity, TAPPI JOURNAL, June 1993, Vol. 76(6)

Journal articles
Open Access
Polyelectrolyte interactions with papermaking fibers: the mechanism of surface-charge decay, TAPPI JOURNAL, December 1993, Vol. 76(12)

Polyelectrolyte interactions with papermaking fibers: the mechanism of surface-charge decay, TAPPI JOURNAL, December 1993, Vol. 76(12)

Journal articles
Open Access
ISO 9000 requirements for pulp and paper testing equipment maintenance, TAPPI JOURNAL, February 1993, Vol. 76(2)

ISO 9000 requirements for pulp and paper testing equipment maintenance, TAPPI JOURNAL, February 1993, Vol. 76(2)

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