Abstract: A processing system including a pressurized blow tank for receiving the high pressure discharge from a wood pulp digester and utilizing the digester steam in evaporators or other heat recovery units. The blow tank which receives the treated cellulose, cooking liquor and high pressure steam from the digester also provides some additional fiber conditioning since the cellulose remains under significant pressure and temperature during the interval before it is discharged from the blow tank. A valve is provided in the blow tank for withdrawing high pressure steam separately from the cooking liquid and treated cellulose, and the valve is operated by a controller responding to pressure sensed in the blow tank. Cold cooking liquor is pumped into the blow tank in response to temperatures measured in the blow tank and the temperature of the cold liquor itself. Alternately the flow of additional cooking liquor can be controlled in response to levels sensed in the blow tank.