Prediction of important sulphite pulp properties from near infrared spectra: a feasibility study and comparison of methods

Sammendrag

In the pulp and paper industry there is a need to replace some of the time consuming, expensive pulp analyses in use today. These methods should be replaced by rapid, non-destructive analyses. Near infrared spectroscopy has proven to be an important tool in that context, and has been used for several purposes in the sulphate industry. Very little work has however been published for the sulphite industry, as is the theme in this case. In this work calibration models have been made to predict Kappa No. and viscosity in unbleached pulp. Since these pulp analyses are impossible to perform during processing, the NIR spectra have been measured on the cooking liquor instead. In other words NIR has been measured on cooking liquor and used to create calibration models for pulp contents. In order to find models with good predictive abilities, four different preprocessing methods of the NIR spectra have been tested, along with four different calibration methods. The results from this work confirm the idea that NIR on cooking liquor can be used to predict pulp, and based on the validation results, the recommended model is PLS on the 1st derivative of the spectra.