Liquid purification or separation – Filter – Movable medium
Patent
1992-12-07
1995-09-26
Spear, Frank
Liquid purification or separation
Filter
Movable medium
210511, B01D 1104
Patent
active
054531926
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a centrifugal extractor comprising several superimposed stages in which two normally immiscible liquids are brought together in order to ensure the treatment of a first of the liquids by a second one of the liquids.
It should be noted that at least one of the two liquids brought together within the extractor can also contain suspended solid particles.
Centrifugal extractors are apparatuses producing an emulsion of a liquid to be treated and a treatment liquid, which are normally immiscible, with a view to aiding the treatment and then ensuring the separation of the two liquids by centrifuging. The liquid to be treated can in particular be constituted by a heavy aqueous phase, whereas the treatment liquid is a light, organic phase.
In practice, it is usually necessary to repeat these two operations a certain number of times in order to optimize the treatment. For this purpose, use is normally made of centrifugal extractors having several superimposed stages. In these centrifugal extractors the heavy aqueous phase to be treated circulates from top to bottom which is from the upper stage to the lower stage, whereas the light organic phase ensuring the treatment circulates from bottom to top which is from the lower stage to the upper stage of the apparatus.
Among the existing centrifugal extractors with superimposed stages, reference is made to the centrifugal extractors of type LX marketed by ROBATEL SLPI. Within a fixed enclosure, these centrifugal extractors comprise a bowl which can be rotated at high speed around a vertical axis and which defines internally several superimposed separating compartments. The rotary bowl is in turn placed coaxjelly around a fixed, central, tubular barrel or shaft, which extends towards the inside each of the separating compartments.
In the bottom of each of the separating compartments, the rotary bowl has a mixing chamber, which is separately penetrated by the heavy phase from the stage located immediately above, and the light phase from the stage located immediately below. A stirring disk, integral with the fixed central shaft or barrel, cooperates with the walls of the mixing chamber rotating at high speed in order to bring about an extremely fine emulsion of the light and heavy phases. Moreover, the assembly constituted by the mixing chamber, as well as the channels for introducing and discharging the two phases into and out of said chamber, together with the stirring disk, form a pump permitting the suction of the two phases from the adjacent stages.
The two phases of the emulsion created in this way are then separated by centrifugal force in the separating compartment of the corresponding stage. The relatively light phase is admitted into the mixing chamber of the stage immediately above it by a passage located in the vicinity of the fixed, central shaft. The relatively heavy phase redascends towards the mixing chamber of the stage immediately below it by channels located on the outer periphery of the rotary bowl.
Centrifugal extractors having several superimposed stages and constructed in this way are essentially satisfactory, but suffer from two significant disadvantages.
The first of these disadvantages results from the circulation of the heavy phase from a given stage to the stage immediately below it by channels formed in the rotary bowl on the periphery thereof. In view of the fact that the bowl rotates at very high speeds and which can, for example, reach approximately 20 to 30 m/s, the solid particles generally present in the heavy phase tend to agglomerate under the effect of the centrifugal force, which leads to clogging actions necessitating the stopping of the apparatus. Moreover, the high density of the agglomerated solid materials, due to the centrifugal force, makes the unclogging operations long and difficult.
A second disadvantage of centrifugal extractors with several superimposed stages of the type described hereinbefore is due to the air present within the apparatus. During the rotation of the bow
REFERENCES:
patent: 2776193 (1957-01-01), Habicht
patent: 3459368 (1969-08-01), Dollfus
SGN Societe Generale pour les Techniques Nouvelles
Spear Frank
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