Near-infrared spectroscopy for on-line analysis of white and green liquors

Near-infrared (NIR) spectroscopy was investigated as an on-line method for measuring the composition of kraft white and green liquors. The results sho w that this approach can accurately predict concentrations of the three pri ncipal components in mill liquors: sodium hydroxide, sodium sulfide, and so dium carbonate. Effects of temperature on predicted composition can be quan tified using any one of three suggested methods. The presence of trace comp onents in mill liquors also contributes to prediction errors, but these eff ects can be quantified as offsets to adjust the model predictions. The feas ibility of NIR spectroscopy as an on-line tool for analyzing white and gree n liquors from three mills. Over long periods of on-line operation, occasio nal lab tests of liquor composition would be required to adjust the model o ffsets for gradual shifts for liquor composition.