Effect of fibres on fluidized bed expansion parameters

Abstract

Better ways to protect water resources and the environment must be implemented in the papermaking industry to help Canada achieve its strategic target in maintaining a healthy environment and ecosystems. Closing down paper machine whitewater systems is the only way to reach that goal. However, under such conditions, a build-up of dissolved and colloidal substances in whitewater occurs. This results in lower paper quality and paper machine runnability problems. A fluidized bed reactor with modified solid sorbents is proposed to remove contaminants from paper machine whitewater prior to recycling. However, the whitewater fibre content significantly modifies bed expansion creating a major impact on the terminal particle velocity and the Richardson and Zaki expansion coefficient. Fibre flocculation was identified as a key characteristic that must be included in the classical equations describing fluidization. A modification for Newton's terminal velocity law and a new model for the expansion coefficient have been developed.