Analysis of the effects of pressure profile, furnish, and microfibrillated cellulose on the dewatering of papermaking furnishes

In this paper, we present an improved experimental method for studying the initial dewatering process in papermaking. We studied the effects of the dewatering pressure profile, the furnish type, and microfibrillated cellulose (MFC) on the development of flow resistance and the final solids content of the filtered sheet. The major difference from the previous studies is the possibility to control the dewatering pressure profile during filtration. The filtration process is monitored by measuring the pressure drop over the filtrated sheet and the flow rate through the filtered sheet as a function of time. In the end, the final solids content is measured. Our results indicate that the sheet solids content after the initial dewatering depends on the magnitude and the shape of the pressure profile used during the filtration and that this dependency remains after wet pressing. Laboratory scale measurements are repeated in pilot scale using a papermaking research environment, with comparable results. Surprisingly, we found that the addition of MFC increases the solids content. This was verified in laboratory and pilot scale studies. Overall, this study shows that laboratory scale measurements can be useful in determining the optimal dewatering conditions for different furnish types.