On-Line Estimation of Initial Wood Chip Moisture in Kraft Pulping, 1997 Pulping Conference Proceedings

Pulping quality greatly depends on the capacity to achieve a desired final lignin content in the pulp or kappa number. The final kappa number is a complex function of several variables. Some of these variables are unmeasured, therefore the estimation of the final kappa number and its control become complex. The initial wood chip moisture is not directly available in a batch-to-batch basis and its uncertainty varies the chemical concentration. Moisture changes can depend on the wood structure, the time that wood has been left in the wood yard, and weather conditions.

A methodology to estimate the initial moisture of wood chips and the preliminary results are presented. This estimation is accomplished by analyzing the on-line effective alkali measurements obtained by a calibrated toroidal conductivity meter, along with the modeling of physical phenomena occurring at the beginning of batch cooks. The proper estimation of this variable should aid in taking corrective actions to account for changes in moisture content.