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Fibre Loss in Recycle Paper Mills: A methodology to quantify in main reject streams and overall fibre balance, TAPPICon25

How to Manage Safety in Today’s Changed Work Environment, TAPPICon25

Validation of a continuous digester anodic protection system

Introduction to Fitness-For-Service applications for the Pulp & Paper Industry, TAPPICon25

Case study: Long-term solution for stopping and preventing stress corrosion cracking in two-vessel digester system, TAPPICon25

Unlocking the Power of Advanced Data Analytics: Techniques and Practical Strategies for Successful Implementations Panel Discussion, TAPPICon25

Beyond KPIs: Harnessing the Power of Data Obscurity, TAPPICon25

Functional Lignin-Based Barrier Coatings for Paper Packaging, TAPPICon25

Recycled Food and Beverage Cartons as a Replacement for Declining Traditional Feedstock in Molded Pulp Production, TAPPICon25

Effects of calcium on sodium salt scaling with the presence of resin acids and fatty acids, TAPPI Journal June 2026

ABSTRACT: Reintroducing tall oil soap or its related products into high dry solids black liquor has been found to reduce sodium salt scaling in falling film evaporators. Aside from resin acids and fatty acids, which are the likely scale inhibitors, calcium is reintroduced into black liquor because of the relatively high calcium content of tall oil soap. One concern is that this increase in calcium content might lead to the formation of additional calcium and sodium scales in evaporators. In this work, we investigated the relationship among trace amounts of calcium, sodium salts, resin acids, and fatty acids in a controlled system using a model salt solution and a benchtop setup. We studied the effects of the calcium carbonate addition and calcium carbonate scales on sodium salt scaling in the presence of resin acids and fatty acids. We found that some calcium carbonate is incorporated in the precipitated sodium crystals, and the suspended sodium crystals become larger and more compact with increasing calcium carbonate concentration. Experiments in the benchtop setup show that precipitating calcium carbonate scale on the heat exchanger does not lead to a higher rate of sodium salt scaling. The solubility of calcium carbonate is not affected by the addition of resin acids and fatty acids. These findings indicate that the reduction in sodium salt scaling through the addition of tall oil soap is primarily related to resin acids and fatty acids, rather than to calcium or to interactions between calcium and mixtures of resin and fatty acids.