Liquid purification or separation – Filter – Movable medium
Patent
1993-03-26
1995-08-22
Dawson, Robert A.
Liquid purification or separation
Filter
Movable medium
210381, 210393, 210404, 210412, 209303, 209497, B01D 3306
Patent
active
054437377
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for separating suspensions, preferably containing fibre pulp, comprising a housing, a filter body with a wall of filter material situated in the housing, spray means adapted to spray jets of a suspension to be separated directly onto one side of said wall of filter material, and means for displacing the filter body relative to said spray means. During operation the suspension is separated into a fine fraction, which passes through the filter material and which contains fine particles, and a coarse fraction, which does not pass through the filter material and which contains coarse particles and some fine particles.
In a known separation device of this kind according to SE 462 597, the filter body is arranged rotatably about a horizontal axis, the wall of the filter body being constituted by an annular vertical disc, which is coaxial with said horizontal axis. In order to enable the largest part as possible of the filter material of the known separation device to be utilized for the separation, the jets of suspension from the spray means have to hit the filter material at various distances from the centre of the annular disc. This means that the velocity of the filter material relative to said jets of suspension decreases the closer the centre of the annular disc the jets of suspension hit the filter material. In consequence the separation result will be different at different radial portions of the filter material, which is a drawback.
Another drawback with the known separation device is that coarse fraction created where jets of suspension hit upper portions of the filter material will flow downwards on the filter material disturbing the jets of suspension hitting lower situated portions of the filter material, with the result that the intended separation is deteriorated. It is true that the known separation device is provided with guide means intended to guide created coarse fraction away from the filter material. However, said guide means has proved to be inefficient, since it must be arranged stationary and spaced from the filter material. Thus, some coarse fraction can pass through the formed gap between the stationary guide means and the moving filter material and still disturb lower jets of suspension.
Yet another drawback with the known separation device is that its flow capacity is limited because of that it must be possible to check the condition of the filter material and the function of the spray means during operation. Thus, not more than two annular discs can be arranged coaxially with each other to enable a safe inspection of them and of the function of the spray means during operation. Such an inspection may be performed with the aid of inspection doors in the housing at mutual sides of the disc pair. The flow capacity of the known separation device may certainly be increased by increasing the diameter of the discs, but from practical reasons the diameter of the discs is limited to a maximum of about 4 meters. Nor would it be practical to increase the distance between adjacent discs to enable inspection between the discs during operation, whereby more than two discs could be installed, since in this case the space demand for the known separation device would substantially increase. The object of the present invention is to provide a separation device of the kind here present, which does not suffer from the above described drawbacks of the known separation device.
This object is obtained by means of a separation device of the kind mentioned initially, which primarily is characterized in that the filter body forms a substantially circular cylindrical drum with a vertical centre axis, the circumferential wall of the drum comprising said wall of filter material, and that said displacement means is adapted to turn said cylindrical drum about said vertical centre axis during operation.
Hereby the advantage is obtained that the entire filter material will have substantially constant velocity relative to the jets of suspension from the spray means during ope
REFERENCES:
patent: 1926402 (1933-09-01), Pearce
patent: 2165807 (1939-07-01), Muphree et al.
patent: 2186836 (1940-01-01), McLaughlin
patent: 3451550 (1969-06-01), Cox
patent: 4210539 (1980-07-01), Shiban
patent: 4563273 (1986-01-01), Gessler
patent: 5008010 (1991-04-01), Langner
patent: 5124029 (1992-06-01), Fjallstrom et al.
Atkeison Charles
Fjallstrom Roland
Frykhult Rune
Celleco Hedemora AB
Dawson Robert A.
Walker W. L.
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