Device for dehydrating and washing suspensions of fibrous material

A device for dewatering and washing fiber stock suspensions, comprising:

• a housing;
• two adjacent rolls situated in the housing for counter-rotation about a respective two rotation axes which lie on a horizontal plane, whereby the rolls have outer surfaces which define a dewatering gap therebetween, through which a filter mat formed on each roll is dewatered;
• a headbox for each roll, each headbox situated for introducing fiber stock suspension onto the outer surface at the lower half of each roll;
• means adjacent the outer surface of each roll, following each headbox in the rotation direction, for applying pressure on the suspension against the outer surface of the roll to partially dewater the suspension and thereby form a filter mat in advance of said gap;
• discharge means beneath said gap for removing the filter mat from the rolls and discharging the mat from the housing;
• wherein the surface of each roll has openings, each roll has a filtrate drain channel below the outer surface, and the drain channels are fluidly connected to the roll outer surface by inlets which define a filtrate flow path that is oriented from the channels to the roll surface, in a direction against the sense of rotation of the respective roll.