A novel method for the determination of black liquor viscosity by multiple headspace extraction gas chromatography

• A GC method was developed to detect the viscosity of concentrated black liquors.
• Methanol is used as the tracer and its release profile is measured by MHE-GC.
• Two correlation approaches were established for the calibration method.
• The presented method is simple and practical for black liquor viscosity testing.

This work demonstrates a novel method for the determination of viscosity in the concentrated black liquors from pulp mill recovery process. The method is based on the kinetic release of methanol (a vapor tracer) to the headspace in a sample closed vial by a multiple headspace extraction gas chromatographic technique. Both theoretical and empirical models were proposed for establishing the correlation with the reference method. The results showed that the correlation using either of the models is excellent for the tested black liquor samples (at 110 °C). The presented method is simple and practical and can be a valuable tool for black liquor viscosity related research and applications.