A. Ahlstrom Corporation

Kamyr, Inc.

Mika P Makela

Toivo J Niskanen

Kaj Henricson

Olavi E Pikka

Vesa J Vikman

Kari Peltonen

Brian F Greenwood

Stephen J Dunn

Method and apparatus for mixing a first medium to a second medium and a

A method and mixer are provided for mixing chemical (such as a gas like chlorine or oxygen) with a slurry (such as paper pulp having a consistency of about 1-16%) in such a way that separation of gas from the slurry at the discharge from the mixer is avoided. Where the mixer housing has a radial discharge, the leading and trailing walls of the discharge (in the direction of circular and tangential movement of slurry within the main body housing of the mixer) present curved configurations to transition the slurry from circular/tangential movement to radial movement. The curvature of the configurations (which may be provided by inserts) does not exceed an angle of about 10 degrees at any point along them until radial flow is established. Alternatively, the discharge may allow the tangential movement of the pulp in the main housing to continue by cutting off the original radial pulp discharge outlet, and welding or otherwise attaching a retrofit new discharge outlet to the main housing body similar to a pump volute with a gradually increasing cross-section.

Minimizing gas separation in a mixer outlet

In the inventive method and apparatus for the continuous discharge of water and fine particles from a suspension, particularly fibrous pulp, the pulp or suspension is thickened without forcing the removal of water through a relatively thick, uncontrollably gathered fiber mat. In the method, the suspension to be thickened is fed into a filtering chamber, the suspension is continuously mixed for equalizing consistency differences, the liquid is continuously removed from the suspension through a filter and the thickness of a fiber mat which forms on the filter surface is controlled by subjecting the mat to shear stresses. In a thickening apparatus for practicing this method, at least one of co-operating surfaces--i.e. the filtering surface (8) and its counter-surface (10)--is provided with loosening members (12) for non-mechanically limiting the thickness of a fiber mat forming on the filtering surface and thereby preventing the uncontrolled formation of such a mat on the filtering surface (8).

Method and apparatus for thickening a fiber suspension and removing fine

The present invention relates to a method and apparatus for the continuous discharge of water from suspension, especially from fibrous pulp, whereby pulp is caused to thicken without having the water to be removed through a thick uncontrollably gathered fiber mat. In accordance with the invention the suspension to be thickened is fed into a filtering chamber, the suspension is formed as a layer that is continuously being mixed for equalizing the consistency differences, the liquid is continuously removed from the suspension and the thickness of the fiber mat being formed on the filter surface is controlled by subjecting said mat to shear stresses. The above described method is realized by an apparatus, in which at least one of the co-operating surfaces, the filtering surface (8) and its counter surface (10), is provided with means (12) for non-mechanically limiting the thickness of a fiber mat on the filtering surface, whereby a uncontrolled formation of a fiber mat on the filtering surface (8) is prevented.

Method and apparatus for thickening fiber suspension

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Karhula, Finland

Mika P Makela