Method of monitoring the digestion of lignocelluloses with the aid of FTIR spectroscopy

摘要

In contrast to the current process control systems in the pulp industry, in which cooking parameters such as temperature, cooking time and/or consumption of chemicals are determined and used to calculate a prediction of the endpoint of cooking, FTIR-spectroscopic control observes the progress of cooking by direct and simultaneous determination of the concentration of the substances dissolved out of the lignocelluloses and of the cooking chemicals. In this method, an IR data set determined from the absorption of the digestion solution in the near and/or middle IR range is linked with the analytical data of the cooked pulps, for example the residual lignin content, by means of mathematical/statistical evaluation methods, for example multiple regression analyses. The statistical relevance of the correlation equations is continuously improved by using the latest cooking results each time. This method allows digestions to be controlled in such a way that the values of the cooked pulps agree with the prescribed values with greater accuracy than when using hitherto conventional methods.