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Journal articles
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Open Access
The solubility of calcium carbonate in green liquor handling systems, TAPPI Journal October 2019

ABSTRACT: The formation of hard calcite (CaCO3) scale in green liquor handling systems is a persistent problem in many kraft pulp mills. CaCO3 precipitates when its concentration in the green liquor exceeds its solubility. While the solubility of CaCO3 in water is well known, it is not so in the highly alkaline green liquor environment. A systematic study was conducted to determine the solubility of CaCO3 in green liquor as a function of temperature, total titratable alkali (TTA), causticity, and sulfidity. The results show that the solubility increases with increased temperature, increased TTA, decreased causticity, and decreased sulfidity. The new solubility data was incorporated into OLI (a thermodynamic simulation program for aqueous salt systems) to generate a series of CaCO3 solubility curves for various green liquor conditions. The results help explain how calcite scale forms in green liquor handling systems.

Journal articles
Open Access
Editor's Note: A Meeting of Minds, TAPPI JOURNAL April 2009

Editor's Note: A Meeting of Minds, TAPPI JOURNAL April 2009

Journal articles
Open Access
Eucalyptus Wood Quality and Its Impact on Kraft Pulp Production and Use, TAPPI JOURNAL August 2009

Eucalyptus Wood Quality and Its Impact on Kraft Pulp Production and Use, TAPPI JOURNAL August 2009

Journal articles
Magazine articles
Open Access
How to use total dissolved solids measurements to evaluate the performance of diffuser washers—A mill study, TAPPI Journal April 2020

ABSTRACT: Various types of pulp washing equipment are available. Each washing device has a unique mechanical construction, and the washing principle is often a combination of dilution, thickening, and displacement washing. In this work, the performance of the pressure diffuser washer is studied. In stepwise trials, the effect of the feed and discharge consistencies on the performance of the diffuser was studied. The effect of the downward velocity of the screen on the pressure diffuser’s washing efficiency was also studied. The measurement of total dissolved solids (TDS) by a process refractometer was used as a wash loss measurement unit and the refractometer’s results were used in the calculations of standardized Nordén efficiency (E10) values. The chemical oxygen demand (COD) and conductivity values were also measured and their results compared to the TDS results.The results indicated that feed consistency has a significant effect on the performance and effectiveness of the diffuser washers in the mill. It can also be stated that when the downward velocity of the screen is adjusted to too high a level, the washing efficiency of the pressure diffuser decreases. As a conclusion from the mill tests, it can be stated that even small process parameter changes can provide enhanced diffuser washing at the beginning of the washing line, which has a direct effect on the performance of post-oxygen washing.

Journal articles
Magazine articles
Open Access
Mill experience of calcium carbonate scale formation in green liquor pipelines, TAPPI Journal August 2020

ABSTRACT: Experience of hard calcite (CaCO3) scale formation in green liquor pipelines at four kraft pulp mills was systematically investigated to determine if there is any correlation between the severity of the scaling problem at each mill and the design and operating conditions of its causticizing plant. The results show that the high degree of supersaturation of calcium ions (Ca2+) in the liquor is the main contributing factor. Mills that operate at a lower green liquor total titratable alkali (TTA), higher causticity, and a larger liquor temperature drop are more likely to produce a green liquor that is supersaturated with Ca2+, and thus experience more severe scaling problems. In order to minimize CaCO3 scaling, the green liquor handling equipment should be operated as steady as possible to avoid conditions that allow Ca2+ to be supersaturated. The strategies include minimizing variations in liquor TTA, insulating the green liquor pipelines to reduce temperature gradients, and adding lime mud to weak wash to provide seeds for precipitation to occur on mud particles instead of on metal substrate.

Journal articles
Open Access
An introduction to optimizing supplemental nutrients at pulp and paper wastewater treatment plants, TAPPI JOURNAL November 2014

An introduction to optimizing supplemental nutrients at pulp and paper wastewater treatment plants, TAPPI JOURNAL November 2014

Journal articles
Open Access
Fundamental study on developing wood powder as an additive of paperboard, TAPPI JOURNAL November 2014

Fundamental study on developing wood powder as an additive of paperboard, TAPPI JOURNAL November 2014

Journal articles
Open Access
Calcium carbonate in the paper industry â?¢ blessing for coated papermaking and curse for recycling processes, TAPPI JOURNAL November 2014

Calcium carbonate in the paper industry • blessing for coated papermaking and curse for recycling processes, TAPPI JOURNAL November 2014

Journal articles
Open Access
Chip size distribution for an ultra-high-yield sulfite process

Over the Wire, Paper360º November/December 2014

Journal articles
Open Access
Agenda 2020: Next Generation Chemical Pulping

Agenda 2020: Next Generation Chemical Pulping, TAPPI JOURNAL October 2014

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