Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Patent
1992-08-31
1994-11-08
Hruskoci, Peter A.
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
210791, 210106, 210112, 210143, 210407, B01D 2532
Patent
active
053624033
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method and device for a discharge of a filter cake, loosened from filtration elements, out of a filter vessel of a filter apparatus, more particularly, out of a high pressure continuous filter device.
2. Description of the Related Art
Such a method and device is known, in which a loosened filter cake is discharged from an over-pressured filter vessel by means of two conveyor screws which adjoining each other at an angle of 90 degrees. The second conveyor screw, which debouches out of the filter vessel, along with the more or less compressed filter cake forms a closure between the inner-side and the outer-side of the filter vessel while under pressure, so that only the filter cake will be transported outside by the second conveyor screw and no pressure-loss will occur in the filter vessel itself.
This known method has the drawback that, with certain types of cake compositions, the cake in the second conveyor screw no longer is transported outside, but starts to turn along with the conveyor screw.
Also in this known method and device, certain types of cake composition generate an inadmissibly high wearing of the blades of the conveyor screws, causing the necessity to replace them quickly and repeatedly.
The invention aims to obviate the drawbacks of the known method and apparatus for discharge of a filter cake, loosened from filter elements, out of a filter vessel of a filter apparatus, more particularly, out of a high pressure continuous filter apparatus.
SUMMARY OF THE INVENTION
The method according to the invention is characterized in that the filter cake is conveyed towards a discharge shaft, to fall down into it, and when the cake reaches a certain height within the shaft, the shaft is opened near or at the bottom end, and the filter cake is pushed or blown out of the shaft by the over-pressure in the filter vessel.
By applying the method according to the invention, the filter cake is continuously conveyed out of the filter vessel towards the discharge shaft, the shaft opens and closes periodically to periodically press or blow away the cake, collected within the shaft, out of the shaft.
The pressing or blowing away of the filter cake out of the shaft may take place completely without any disturbances and, by the expansion of gas or air, present within the space between the cake elements in the shaft during the pressing or blowing away of the cake from out of the shaft, the cake elements are caused to be loosened from each other and from the wall of the shaft in a favourable manner.
The filter cake loosened from the filter elements may be conveyed towards the discharge shaft in various ways.
According to a characteristic of the method according to the invention, the filter cake is conveyed towards the shaft by means of a conveyor screw.
During the pressing or blowing away of the cake from out of the shaft it is inevitable, that along with the cake a part of the air- or gas-content of the filter vessel is discharged along with the filter cake to the outside and causing the occurrence of a certain pressure-loss within the filter vessel.
In order to reduce this pressure-loss to a minimum during the pressing or blowing away of the filter cake from out of the discharge shaft, the method according to the invention is further characterized in that the cake is sealed with a powder-shaped or viscous means, e.g. a viscous oil, before the cake is pressed or blown away out of the shaft.
The sealing means may be put into the shaft in various ways. Thus, the sealing means may be pressed into the shaft by means of a plunger.
The periodical opening and closing of the discharge of the shaft may take place in various ways.
In a favourable way according to a further characteristic of the method according to the invention, the opening and closing of the discharge of the shaft takes place automatically, and more in particular under the control of one or more sensors, placed within the shaft.
Thus, a high level sensor may be present, which m
REFERENCES:
patent: 3230865 (1966-01-01), Hibbel et al.
patent: 3943033 (1976-03-01), Wallen
patent: 4287058 (1981-09-01), Larsen
patent: 4810373 (1989-03-01), Rice
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