Abstract: A mass tower for medium or high consistency fiber suspension includes a vertically elongated circumferential side wall defining a space for receiving the fiber suspension. The bottom portion of the mass tower is filled with a material in an amount and of sufficient strength, preferably sand, gravel or concrete, to support the weight of the fiber suspension above the filling material. The filling material forms a bottom surface in contact with the fiber suspension and has an opening therein. Within the filling material is formed a flow channel in communication with the opening and extending through the filling material towards the side of the bottom portion for allowing the fiber suspension to be discharged from the mass tower. A method of manufacturing a mass tower and a method of converting an existing mass tower is also disclosed.

Abstract: A method and apparatus for controlling the flow of a fiber suspension having a direction of flow and a consistency from 5-25% including a treatment chamber having an axis extending in the direction of flow of the fiber suspension, a suspension inlet and a suspension outlet opposite the suspension inlet, the suspension inlet and outlet having the same diameter and an axis in alignment with the axis of said treatment chamber;a fluidizing rotor within the chamber for fluidizing the fiber suspension, the fluidizing rotor having an axis of rotation transverse to the axis of the treatment chamber; anda throttling arrangement disposed between the rotor and the suspension outlet for throttling the suspension flow.

Abstract: A thermal system includes a plurality of heat exchangers in series and the same number of flash tanks in series is interposed between two subsequent effects of a multiple effect evaporating system for sulfate black liquor. The liquor is indirectly heated in the heat exchangers by vapor produced by step-by-step expansion of the same liquor in the flash tanks and additionally by steam from an external source. To decrease the viscosity of the black liquor it is heated to a temperature of 190.degree.-200.degree. C. and retained in a reactor vessel for 10-20 minutes.Preferably the flash tanks and the heat exchange elements are positioned on top of each other within a shell to form an integral construction in which the vapor compartment of each flash tank is directly connected to the vapor compartment of a corresponding one of the heat exchange elements.