Abstract: In a causticizing process for separating at least white liquor and lime sludge out of the process, filters in the form of discs or drums are arranged. The filtrations take place under positive pressure and the filters are arranged in a closed system. Such a pressure filter can also be arranged for the separation of sludge.

Abstract: A filter for continuous filtering of suspension under pressure includes a pressure vessel, a shaft rotatably journalled in the pressure vessell and disc filters elements arranged on the shaft. The filter elements are composed of sectors and inlet filtrate channels in each sector are connected to axially extending channels in the shaft, one axial channel for each sector. The axial channels are connected to a filtrate valve formed to divide the filtering cycle corresponding to one rotation revolution for the filter elements in a number of filtering zones, at least one in liquid phase and one in gaseous phase. A separate filtrate outlet from the pressure vessel is connected to each filtering zone and means is controlling the difference pressure over the filtering zones independent of each other.

Abstract: In a rotating disc filter for dewatering a suspension comprising filter discs (3) divided into a plurality of disc sectors (4), the discharge of filtrate from each disc sector takes place through an axial filtrate channel (7). Each filtrate channel is at the side wall of the filter connected to a fall pipe (8) which rotates with the channel and extends in radial direction relative to the filter shaft (6). Preferably each of said filtrate channels is at said side wall provided with a pre-filtrate outlet (10).

Abstract: A rotating disc filter consists of disc sectors of preferably rustfree or acidproof steel about a filter shaft (9). Saddles (12) of a folded plate (1) form sector deck and support for filter cloth (4), and the troughs (13) of the folded plate together with the filter cloth abutting the saddles (12) form internal filtrate channels (11) extending from the outer periphery of the sector towards the filter shaft (9). Such a construction renders it possible to obtain sectors combining the requirements of large open filter cloth area, small internal volume affording for the filter operation an advantageously great ratio between filter surface and internal filtrate volume, high stability against lateral forces, and simple manufacture.