Improving the chemistry control of paper-making furnishes with multiphase modelling

This paper presents a nearly ten years history of multiphase modelling of pH and calcium chemistry in neutral papermaking. Initially the multiphase modelling was focused on pulp acidification and pH buffering concepts, and the unit operation models were used to define the dosages of acidification chemicals and buffering aids at certain stages of the process. Multiphase chemistry calculation can be appended to process simulation, thus enabling the monitoring of chemistry of large-scale processes. Recently a pioneering chemistry simulation of a process integrate consisting of two paper machine lines with both mechanical and deinked feed stocks was performed. In this integrate difficulties were often experienced when the dosage of bleaching chemicals was increased while maintaining the high brightness target of the paper product. The simulation of the large integrate could be used to quantify the calcium carbonate losses at selected process units and to improve understanding of the bleaching practices in neutral papermaking.