the cellulosic material in the vessel to a pulp and discharging the pulp from the batch digester vessel before restarting the transporting of the slurry into the digester vessel application_number US 201113177841 A description fig1 is a schematic diagram of a chip feed system 10 and a batch digester vessel 12 for chemically processing cellulosic fibrous material the batch digester vessel 12 operates in a repeating sequence of filling cooking and discharge during the filling step chips from the chip feed system flow into a top inlet 46 of the vessel cooking liquor 14 or transport liquor 60 flows with the chips into the vessel cooking liquor may also be added separately to the vessel during the filling step in addition steam 20 may be added via conduit 40 to the vessel during the filling step the flow of chips into the vessel ceases at the end of the filling step the cooking step follows the filling step after the top inlet is capped e g sealed the cooking step involves impregnating the chips in the vessel with the cooking liquor maintaining the chips under conditions e g 5 to 10 kilogram centimeter squared kg cm 2 and at elevated temperatures.