Agitating – Having specified feed means – Material introduced so as to cause rotary motion in mixing...
Reexamination Certificate
2000-02-16
2001-04-10
Cooley, Charles E. (Department: 1723)
Agitating
Having specified feed means
Material introduced so as to cause rotary motion in mixing...
C366S171100, C366S172100, C366S304000
Reexamination Certificate
active
06213632
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for treating an aqueous working medium, preferably a pulp suspension, and in particular a paper pulp suspension, with at least one treating fluid. In this connection, the expression aqueous working medium is intended to mean clean liquids, solutions, and suspensions, such as fiber suspensions. In this description the utilization of the present invention for treating pulp suspensions will primarily be described, since this invention has its principal application in this field, but it must be emphasized that it in no way is limited to this technical field.
BACKGROUND OF THE INVENTION
To provide paper pulp with its desired properties, such as proper brightness, the paper pulp is treated with one or more different treating fluids, for instance chlorine gas or oxygen. The pulp is therefore continuously conducted into a treatment device, in which the treatment fluid or fluids are brought into contact with the pulp fibers. In order to achieve optimal treatment results it is important that the fibers contact the treatment fluid as uniformly as possible, and for that reason fibers should be spread out to the greatest possible extent, and the treatment fluid should be homogeneously distributed in the suspension.
In prior so called low intensity devices the concentration of the treatment fluid of the pulp has been medium low to low in order to achieve the desired even quality of the fully treated pulp. These low intensity treatment devices have, to an ever increasing extent, been replaced by high intensity treating devices with a high concentration of the treatment fluid in relation to those previous types. Current devices of this latter type, however, unfortunately suffer from the drawback that the treatment zone, where the working medium undergoes shearing in order to mix the fibers and is subjected to the treatment fluid, does not show a completely homogenous shearing field. As a consequence, either (1) a part of the suspension will be incompletely treated, or (2) a part of the suspension will be “overtreated.”
The treatment according to (1) results in a homogeneously treated final product, whereas a treatment according to (2) means that too much treating fluid must be supplied to the suspension and/or that unnecessarily high energy needs to be supplied to the pulp suspension.
Both of these alternatives add to the costs.
A treatment device of this type for treating pulp suspensions is disclosed in Swedish Patent No. 8001970-6, corresponding to U.S. Pat. No. 4,416,548. This device comprises an axial inlet for the pulp suspension, which opens into a mixing chamber, in which a rotor is arranged. The pulp is fed through and is sheared in an annular slot, which is delimited by a stator ring and the rotor. The supply fluid is conducted through an axial inlet to the plane end surface of the rotor and thereafter flows radially along this surface up to and into the shearing slot where it is mixed with the suspension. Thereafter, the treated pulp flows out through a tangential outlet arranged after the slot. As shown in FIGS. 7 and 8 of this Swedish publication, the shearing area may be divided into several annular shearing slots having the same radial extension formed by several rotor connected rotor rings, which are inserted between interconnected stator rings. Since the present invention to a substantial extent is based on this known technique, reference is made to this publication for a more detailed description of the principal construction. However, it should be noted that this known solution suffers from the above stated shortcomings with respect to inhomogeneous shearing fields.
The object of the present invention is to provide a method and apparatus of the above kind to treat a working medium by a treatment fluid, which provide a treatment zone with a shearing field which allows a substantially homogenous treatment of the working medium at a lower price than has heretofore been possible.
SUMMARY OF THE INVENTION
In accordance with the present invention, this and other objects have now been realized by the invention of apparatus for treating an aqueous working medium with at least one treatment fluid, comprising a housing forming a treatment chamber, in which the aqueous working medium is to be treated with the at least one treatment fluid in a treatment zone, a rotatable rotor arranged in the treatment chamber to rotate about an axis, the rotatable rotor including a plurality of rotor rings carried by the rotatable rotor and coaxially arranged at the periphery of the rotatable rotor, a plurality of stationary stator rings coaxially inserted between the plurality of rotor rings, thereby forming a plurality of annular axial treatment slots having a radial size between the rotor rings and the stationary stator rings, the radial size of the annular axial treatment slots increasing with increasing distance from the axis of the rotatable rotor, inlet means for delivering the aqueous working medium and the at least one treatment fluid to one side of the annular axial treatment slots, and outlet means for the treated aqueous working media disposed at the other side of the annular axial treatment slots, whereby the aqueous working medium is sheared in the annular axial treatment slots during operation so that a substantially homogenous shearing velocity is achieved in each of the annular axial treatment slots. In a preferred embodiment, the radial size of each of the plurality of annular axial treatment slots is directly proportional to the radius of the surface of the one of the rotor rings defining each of the plurality of annular axial treatment slots.
In accordance with one embodiment of the apparatus of the present invention, the inlet means includes an inlet housing connected to the housing, the inlet housing including a cylindrical inlet chamber and having a tangential working medium inlet whereby the aqueous working medium forms a swirl in the cylindrical inlet chamber before it enters the treatment chamber.
In accordance with another embodiment of the apparatus of the present invention, the inlet means includes a treatment fluid inlet member, and the apparatus includes distribution means associated with the rotatable rotor, the treatment fluid inlet member including an opening spaced from the distribution means whereby the distribution means distributes the at least one treatment fluid radially towards the annular axial treatment slots. In a preferred embodiment, the distribution means comprises a substantially annular disc. In another embodiment, the opening in the treatment fluid inlet member is axially adjustable relative to the distribution means.
In accordance with another embodiment of the apparatus of the present invention, the apparatus includes throttling means for the aqueous working medium arranged between the inlet means for the aqueous working medium and the treatment chamber, whereby the aqueous working medium is provided with a turbulent flow before it enters the treatment chamber.
In accordance with another embodiment of the apparatus of the present invention, the housing includes a further treatment zone for further treatment of the aqueous working medium with a further treatment fluid arranged in the flow path of the aqueous working medium in the treatment chamber. Preferably, the inlet means includes a first treatment fluid inlet member and a second treatment fluid inlet member for supplying a further treatment fluid to the treatment zone, one of the first and second treatment fluid inlet members being arranged within the other of the first and second treatment fluid inlet members. In a preferred embodiment, both of the first and second treatment fluid inlet members are axially adjustable independently of each other.
In accordance with another embodiment of the apparatus of the present invention, the inlet means includes a treatment fluid inlet member for the further treatment fluid and the apparatus includes first and second distribution means associated with the rotatable rotor, the tre
Danielsson Magnus
Forslund Kjell
Kristrom Klas
Cooley Charles E.
Lerner David Littenberg Krumholz & Mentlik LLP
Valmet Fibertech Aktiebolag
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