Method and apparatus for washing pulp by means of intensified suction

A method and an apparatus for washing a solids-containing suspension by means of a suction drum washer comprising a drum provided with a filtration surface, a main vacuum source such as a drop leg and washing tubes connected to the frame of the suction drum washer. A washing liquid stream is introduced by a first washing tube is directed to contact the pulp layer on the surface of the drum in a point below 10 degrees after the surface of the suspension and a vacuum of at least 0.1 bar greater than the main vacuum source, i.e. intensified suction is applied by means of a separate vacuum source to filtering surface at the contacting point of the first liquid stream and the pulp layer or maximum of 10 degrees before the contacting point. The intensified suction may be utilized also for boosting end of filtration stage (II) and drying stage (IV). Filtrate from the drying stage (IV) can be used at the same washer as a washing liquid at the first or the second washing tube.