Patent ID: 7452444
Filing Date: 2008-11-18
Classification: D21C

Abstract:
1. A method for washing wood chips in digester for the separation of wood fibers from their bonded state, the digester having a substantially vertical centerline, a substantially circular cross-section, and a wash zone adjacent the bottom end thereof and a plurality of individual wash screens disposed about the inner wall of the digester for the withdrawal of co-current downflow liquor from the wash zone, comprising the steps of: dynamically withdrawing substantially equal volumes of co-current downflow liquor from the wash zone through individual ones of the wash screens, said dynamic withdrawal including independent monitoring of the flow rate of co-current downflow liquor exiting the digester through individual ones of the wash screens, employing the monitored flow rate from an individual screen to increase or decrease the flow rate from said individual wash screen to a value substantially equal to the flow rate of liquor from the digester through each of the other individual ones of the plurality of wash screens, whereby the total volume of liquor exiting the digester through the plurality of wash screens is divided into equal volumes flowing from the wash zone of the digester through each of the individual ones of the wash screens, said equal volumes being extracted substantially simultaneously in a flow direction substantially radially of the digester about substantially the entire circumference of the digester and within a plane disposed substantially perpendicular to the vertical axis of the digester.