Abstract

A screen assembly particularly adapted to be used in a continuous or batch digester in the production of cellulose (chemical) pulp utilizes a particular screen plate construction that enhances productivity while minimizing blockage of the screen slots (and subsequent non-uniformities in the pulp produced when the screen is blocked). A screen plate having a convex outer surface and concave inner surface (substantially an arc of between 20-60 degrees) is pivotally connected for movement about a vertical axis on one side edge to frame mounted in the digester. The screen plate has a plurality of slots (e.g. 2-13 mm wide) machined in it, and the screen plate is positioned in the digester so that the inclination angle of the slots relative to the horizontal or vertical is between 30-60 (e.g. about 45) degrees. A plurality of land areas are provided between regions of the slots in screen plate. A plurality of support pins may be connected (e.g. welded) to the screen plate outer surface and extend outwardly from it. The support pins in different land areas are offset from each other and may be disposed in an imaginary straight line that make an angle substantially the same as the angle of the slots with respect to the horizontal or vertical. Preferably the slots taper outwardly at the outer surface at an angle of between about 10-60 (e.g. about 30) degrees.