Method for screening and a screening apparatus
AssigneeRed Wire Oy
InventorJouko Hautala
Life of this patent
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Abstract
The present invention is directed to methods and apparatus for screening a pulp suspension where the pulp suspension is directed to a screening space, where a part of the fibres in the pulp is screened using a drum-type rotor. The residual pulp suspension is then directed to a dilution space where it is mixed with recirculated pulp flow and the pulp suspension in the dilution space will be screened. Resulting preliminary reject flow is directed to a mixing space where it mixes with a dilution flow. The recirculated pulp flow is then directed back to the dilution space.
Claims13
A method for screening a pulp suspension, the method comprising:
- directing a pulp suspension to a screening space between a filtering screen and a rotating drum-type rotor;
- screening a part of the fibres in the pulp suspension in the screening space through the screen;
- directing at least a part of the flow passing through the screen to at least one accept outlet;
- directing a reject flow to at least one reject outlet;
- directing a residual pulp flow from the screening space to a dilution space, the dilution space being bordered at least partly by the filtering screen;
- mixing the residual pulp flow with a recirculated pulp flow at least partly in the dilution space;
- screening a part of the fibres in the pulp suspension in the dilution space through the filtering screen;
- directing at least a part of a dilution flow to a reject space where it mixes with a preliminary reject flow;
- and
- directing the recirculated pulp flow to the dilution space.
A screening apparatus for screening a pulp suspension, the apparatus comprising:
- at least one inlet port for an incoming pulp suspension flow;
- at least one inlet port for a dilution flow;
- at least one outlet port for an accept flow;
- at least one outlet port for a reject flow;
- a filtering screen;
- a drum-type rotor inside the filtering screen;
- a screening space between the filtering screen and the rotor;
- a reject space where at least a part of the dilution flow can mix with at least a part of a preliminary reject flow forming a recirculated pulp flow;
- and
- a dilution space arranged to receive a residual pulp flow from the screening space and the recirculated pulp flow from the reject space,
- wherein the filtering screen is extended to border, at least partly, the dilution space.
Dependencies are inferred from the claim text.