Abstract: A central screen element being located substantially parallel with the vertical axis of a pulp digester is provided. In the vertical direction, the screen element comprises at least one zone including one screen segment for removing a liquid stream from the digester and at least one outlet for introducing a liquid stream to the digester. The zones may be adjacent or separated and liquid streams may be independently removed and introduced, as required by the properties and the stage of the cooking process. A screen element may be used in both continuous and batch digesters.

Abstract: A bar screen is primarily intended for use in draining liquid from wood chips and pulp without blocking the bar screen. The area of use is especially a process area, in which cooking and circulation liquid is removed from a pressure vessel when making chemical pulp and paper pulp by continuous method. This type of bar screen is characterized in that behind the filtering gap of the screen bars, there is a flow space in which the liquid flows towards a discharge outlet. By adjusting the flow space, a flow rate of liquid which stops blocking due to accumulation is maintained in the background. The sturdiness of the screen structure is improved by adjustable support taps.

Abstract: An arrangement for mounting a screen (20) in a continuous digester used for making chemical pulp or paper pulp. Such a digester includes a substantially cylindrical pressure vessel arranged in an upright position, the pressure vessel having a smaller diameter at the top end of the digester than at the bottom end of the digester, the diameter of the digester being changed at regionally defined areas by one or more conical sections (4). The screens are mounted at these conical sections to remove liquid from chips or pulp in the digester. In the present arrangement an upper edge (21) of the screen (20), which, in the operating position, is located higher, is arranged in the region of the conical section (4). In particular, the screen extends substantially to the section of the conical section, which has the smallest diameter.

Abstract: A mechanically cleanable screen for separating liquid from chips and pulp without the screen getting blocked, particularly in the process area where cooking and circulation liquids are removed from a pressure vessel during the production of chemical pulp and paper pulp by a continuous method. The screen has two screens: a primary screen and a secondary screen which are attached to a common body one after another in the direction of the liquid to be filtered so that they form a cassette. The blades of the secondary screen generate shear and push forces that clean the slots of the primary screen.