Classifying – separating – and assorting solids – Fluid suspension – Liquid
Patent
1990-04-30
1992-07-21
Hajec, Donald T.
Classifying, separating, and assorting solids
Fluid suspension
Liquid
209208, 209211, 2103601, 2105121, B03D 0000
Patent
active
051315440
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a device for selectively separating particles in a liquid, in particular in a suspension. The invention is particularly suitable for the paper industry, in particular the cleaning of particulate suspensions, for example fibrous suspensions. The invention may, however, find other applications in separation or centrifugal fractioning techniques, in the recovery of immiscible liquids of differing densities, etc.
BACKGROUND OF THE INVENTION
There currently exists in the paper industry a large number of apparatuses intended for the cleaning or separation of fibrous suspensions.
In the document EP-B-0,037,347 of the Applicant (corresponding to U.S. Pat. No. 4,443,331), a free vortex device has been proposed, in which the suspension to be cleaned is supplied to a chamber of revolution rotating about its axis, of the type comprising:
fixed means for supplying the suspension, arranged along the longitudinal axis of said chamber of revolution, extended by movable means for deviating the suspension current towards the periphery of the chamber;
means for driving said chamber in rotation about its longitudinal axis;
fixed means for discharging the cleaned suspension and various separated fractions, arranged along the longitudinal axis of said chamber, preceded by movable deviating means and in which the means for discharging the lightest components is arranged along the longitudinal axis of rotation (2) on the same side as the supply means,
the movable deviating means preceding the fixed outlet means intercept most of the throughput of the suspension in the region of the periphery of the chamber, then deviate it towards the longitudinal axis of rotation, so as to recover most of the kinetic energy of rotation;
and wherein the main outlet means are situated at the opposite end to that of the chamber comprising the supply means and are arranged at the periphery of this chamber, so that a large central centrifugal zone is available.
This device provides excellent results as regards efficiency, reject rate and energy consumption, in particular for outputs less than about three hundred cubic meters per hour of diluted pulp (concentration of the order of 1%). In order to treat effectively higher outputs, i.e. throughputs greater than 300 cubic meters per hour of diluted pulp, it becomes necessary to increase the volume of the apparatus and hence its diameter. These large apparatus with a high cleaning capacity thus have various drawbacks depending on the conditions of their use.
Thus, if diluted pulp is being treated, there is first of all an increase in the pressure drop in the region of the bearings and the inlet/outlet ends, as well as in the peripheral cleaning zone, on account of the need to maintain sufficient turbulence with a high throughput. Furthermore, again in the case of diluted pulp, it becomes necessary, on account of the larger diameter, to increase the counterpressure at the outlet in order to extract the rejects intercepted along the axis of the central zone of the vortex, or alternatively to intercept it at the periphery of this zone: there is thus formed along the axis of the apparatus an air core which, having no fixed geometry, moves inside the suspension and generates vibrations throughout the body of the apparatus.
If treating pulp with a higher concentration (up to about (3)% (sic), the problems which arise are different. First of all, owing to the centrifugal force effect, the pulp tends to accumulate against the walls, thus also resulting in the risks of vibrations due to imbalances and clogging of the apparatus by very concentrated pulp. Furthermore, in order to individualize the movement of the fibers, it is necessary to maintain a high degree of turbulence and, for this reason, a big difference in peripheral/wall flow speeds, thus resulting in high pressure losses. Moreover, control of the flow at the periphery of the vortex, by the geometry of the ends, and that of the body of the apparatus essentially for small diameters, is fairly delicate a
REFERENCES:
patent: 2748668 (1956-06-01), Hornbostel
patent: 4332350 (1982-06-01), McGlellan
patent: 4443331 (1984-04-01), Julien Saint Amand
patent: 4533468 (1985-08-01), Ensor et al.
Julien Saint Amand Francois
Serres Alain
Centre Technique de l'Industrie des Papiers, Cartons et Cellulos
E. et M. Lamort
Hajec Donald T.
Kaufman Joseph A.
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