Evaluation of Soap Recovery Efficiency from Black Liquor – Analytical Tools

ABSTRACT
Soap skimmings (“soap”) are typically recovered from black liquor in kraft mills that process a high percentage of
softwood. In many mills, the recovery of soap is inefficient, negatively impacting performance of evaporators and
recovery boilers and resulting in loss of potential revenue. A thorough evaluation of soap recovery performance in a
kraft mill requires measurement of soap content in black liquor at various sampling locations, especially around the
soap skimmer. The standard laboratory method for evaluating soap content in black liquor is a complex, multi-step
process that relies on solvent extraction and titration; most mills send these samples to an outside lab for this
analysis. In this study, ~ 100 black liquor samples, with a wide range of soap concentrations, were tested by the
standard solvent extraction method. After additional dilution, each sample was also tested with a surface tension
meter. The results were found to correlate very closely with the solvent extraction tests results. This alternate
method, using surface tension measurements of diluted black liquor samples, produces rapid results and can be
easily implemented in most Kraft mills, which would facilitate much more frequent in-house evaluations of soap
recovery performance.

Keywords
Firing liquor, droplet trajectories, visual analysis, recovery boiler

TAPPI conference proceedings and presentations, technical papers, and publication articles provide technical and management data and solutions on topics covering the Pulp, Paper, Tissue, Corrugated Packaging, Flexible Packaging, Nanotechnology and Converting Industries.

Simply select the quantity, add to your cart and your conference paper, presentation or article will be available for immediate download.