Method and apparatus for thickening a suspension
AssigneeA. Ahlstrom Corporation
InventorKaj O. Henricson
Life of this patent
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Abstract
A method and apparatus for thickening a pulp, in particular a pulp containing fibres. The pulp is thickened hydraulically while it flows through a space between two screen surfaces. Thickening on alternate screen surfaces is prevented for cleaning by closing the valves in the outlets. Pulp is removed from the screen surfaces by vanes.
Claims17
A method for thickening a suspension, in particular a pulp containing fibres, comprising thickening the pulp while it flows through a space between two screen surfaces by maintaining a pressure difference, which is required by the thickening, over the screen surfaces causing filtrate to flow through the screen surfaces, and intermittently preventing the pulp from thickening on alternate screen surfaces including by removing pulp thickened on each such alternate screen surface when no filtrate flows through such alternate screen surface.
Apparatus for thickening a suspension, in particular a pulp containing fibers, the apparatus comprising a closed pressure-proof vessel provided with a pulp inlet, an outlet for the thickened pulp, and at least two filtrate outlets equipped with closing devices;
- and at least two opposite screen surfaces disposed inside the vessel the space between which constitutes a pulp thickening zone and on the other side of which filtrate spaces are formed;
- said filtrate spaces lying in communication with waid filtrate outlets, respectively, and being at lower pressure when said closing devices are open to create a pressure difference across the screen to enable filtrate to flow through the screens;
- wherein at least one of the screen surfaces is stationary and the opposite screen surface rotates around a shaft;
- and means for intermittently preventing the pulp from thickening on alternate screen surfaces including at least one vane disposed in the thickening zone between the stationary and the rotating screen surfaces at a short distance from the screen surfaces for alternate relative movement in relation to the stationary and to the rotating screen surfaces;
- and means enabling the closing devices disposed in the filtrate outlets to be intermittently closed to prevent flow of filtrate through the associated screen surface sufficient for pulp thickened on such surface to be removed by relative movement of said one vane and such surface.
A method for thickening a suspension, in particular a pulp containing fibers, comprising the steps of:
- (a) flowing pulp to be thickened through a space between first and second screen surfaces;
- (b) providing a pressure difference across the screen surfaces causing filtrate to flow through the screen surfaces;
- (c) preventing pulp from thickening on the first screen surface by preventing flow of filtrate through the first screen surface and removing pulp therefrom;
- (d) subsequently preventing pulp from thickening on the second screen surface by preventing flow of filtrate through the second screen surface and removing pulp therefrom;
- and
- (e) thereafter, from time to time, intermittently repeating steps (c) and (d) in that order.
Dependencies are inferred from the claim text.