Paper making and fiber liberation – Apparatus – Digester
Patent
1996-05-22
1998-05-05
Czaja, Donald E.
Paper making and fiber liberation
Apparatus
Digester
162248, 366302, 366307, B01F 500
Patent
active
057468907
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for admixing a processing agent into a pulp suspension in a vessel. More, particularly, the present invention relates to such a device in which the processing agent can consist of liquids and chemicals, substantially in a fluid state, which can be used for dilution or other types of processing.
BACKGROUND OF THE INVENTION
It is of decisive importance to obtain persistently uniform and proportional admixture of the processing agent with the pulp if one wishes to achieve acceptable results in various types of pulp processing.
In those arrangements which are presently utilized, the processing agent is mixed together in the lower portion of a pulp vessel. The pulp concentration in the pulp vessel is normally between about 10 and 20%, which must be lowered to about 2.5 and 8% in order to make it possible to pump the pulp suspension out of the vessel. When the pulp vessel is used as a bleaching tower, it is then necessary to supply a dilution fluid through a number of nozzles in a restricted lower portion of the tower. The bottom zone of the tower in such a case is restricted by a cylindrical cone in order to guide the processing agent in a circular manner.
The use of a high pulp concentration, for example, of about 12%, in the vessel renders it problematic to achieve a uniform admixture. In order to reduce this problem, the size of the vessel has generally been reduced. However, such an arrangement nevertheless requires considerable energy, due to incomplete admixture techniques and to an unsuitable configuration of the bottom of the vessel.
SUMMARY OF THE INVENTION
In accordance with the present invention, these and other problems have now been overcome, and the supply and central distribution of the processing agent, as well as the flow of the suspension, has been improved. Thus, improved mixing results can now be achieved while, at the same time, energy consumption can be lowered to a minimum value.
In accordance with the present invention, this is accomplished by the discovery of a mixing device for mixing a processing agent with a suspension comprising a mixing vessel having an inner surface and including a lower cylindrical portion having a diameter, an agitator mounted with respect to the inner surface of the mixing vessel for creating a flow of the pulp suspension across the mixing vessel, processing agent supply means for supplying the processing agent to the flow of the pulp suspension across the mixing vessel, and a flow divider mounted with respect to the inner surface of the mixing vessel at a location substantially opposite the location of the agitator, the flow divider comprising a substantially vertical front distribution edge spaced from the inner surface of the mixing vessel and a pair of arcuate front surfaces extending from the front distribution edge to the inner surface of the mixing vessel on opposite sides of the front distribution edge.
In accordance with a preferred embodiment, the pair of arcuate front surfaces are substantially vertical.
In accordance with one embodiment of the mixing device of the present invention, the suspension comprises a pulp suspension. In a preferred embodiment, the pair of arcuate front surfaces extend to the inner surface of the mixing vessel substantially tangentially.
In accordance with another embodiment of the mixing device of the present invention, the front distribution edge is directly opposite the agitator. In a preferred embodiment, the front distribution edge is located on a diameter of the mixing vessel, and the pair of arcuate front surfaces comprise cylindrical surfaces having a predetermined radius. In a preferred embodiment, the predetermined radius is between about 20 and 25% of the diameter of the mixing vessel.
In accordance with another embodiment of the mixing device of the present invention, the pair of arcuate front surfaces include an upper surface defining an inclined plane with respect to the inner surface of the mixing vessel. Preferably, the front distribution
REFERENCES:
patent: 2139430 (1938-12-01), Witham, Jr.
patent: 5118199 (1992-06-01), Howk
Patent Abstracts of Japan, vol. 10, No. 269, C-372, abstract ofJP, A, 61-93819 (Teikoku Denki Seisakusho K.K.), 12 May 1986.
Czaja Donald E.
Leavitt Steven B.
Sunds Defibrator Industries AB
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