Patent ID: 8747613

Claim:
A pressure diffuser for washing pulp, comprising: a generally upright, liquid-tight, pressurized vessel having a first interior volume defined therein for containing pulp to be treated under pressure; the vessel having a pulp inlet defined therein; the vessel having a pulp outlet defined therein, the vessel having only one elongate annular interior volume defined between an inwardly-facing pressure-vessel wall and an outwardly-facing surface of the screen body, the screen body standing up within the vessel in the first interior volume, the annular interior volume being conical-shaped; the vessel having a generally vertical pulp-flow disposed between the pulp inlet and the pulp outlet through the annular interior volume; the annular interior volume containing pulp and having upper and lower ends of different cross-sectional area, the pulp-flow being only flowable through the elongate annular interior volume; the inwardly-facing pressure-vessel wall having a plurality of headers disposed therein, the headers being in fluid communication with a wash fluid source and having nozzle means for introducing a wash liquid radially inwardly through the pulp-flow flowing in the elongate annular interior volume and into the hollow screen body; extraction means for withdrawing a liquid (FL) from the pulp-flow through the hollow screen body, a hydraulic cylinder, disposed above the vessel, having a connecting rod extending centrally through a top end of the vessel to the hollow screen body, the hydraulic cylinder having moving means for vertically moving the hollow screen body via the connecting rod in a first slow stroke concurrent with the pulp-flow and at a pulp-flow speed and moving the hollow screen body in a second fast stroke countercurrent to the pulp-flow; the pulp inlet being located at a bottom of the vessel, the hydraulic cylinder, having a movable piston inside the hydraulic cylinder, being located at a top of the vessel, the movable piston being connected to the screen via the connecting rod, the connecting rod having a first end connected to the movable piston and a second opposite end connected to the screen, the hydraulic cylinder having a ring-shaped bottom hydraulic chamber defined therein penetrated by the connecting rod, the ring-shaped bottom hydraulic chamber being located below the movable piston; and the hydraulic cylinder having a top hydraulic chamber defined therein not penetrated by any connecting rod, the top hydraulic chamber being located above the movable piston.