FR2511894A1 - IMPROVED APPARATUS FOR WASHING AND GRANULOMETRIC SEPARATION OF SUSPENDED SOLID MATERIALS - Google Patents

Abstract

PERFECTED EQUIPMENT, INTENDED TO ALLOW OPERATIONS FOR WASHING SOLID MATERIALS IN SUSPENSION IN A LIQUID PHASE TO REMOVE SOLUBILIZED MATERIALS AND OR TO CARRY OUT PRECISE GRANULOMETRIC SEPARATIONS OF SOLID MATERIALS IN SUSPENSION IN SUSPENSION IN A PHASE, IN ORDER TO REMOVE SOLUBILIZED MATERIALS AND OR TO CARRY OUT PRECISE GRANULOMETRIC SEPARATIONS OF SOLID MATERIALS IN SUSPENSION OF SUSPENSION IN THE SUSPENSION COMPONENT, IN THE SUSPENSION COMPONENT, IN THE SUSPENSION COMPONENT IN SUSPENSION, IN THE SUSPENSION SUSPENSION PLACES OF HORIZONTAL PERFORATED TRAYS, SUSPENSION SUPPLY MEANS TO BE TREATED AND TREATMENT AND EXTRACTION LIQUID OF THE TREATED SUSPENSION AS WELL AS A PULSATORY DEVICE, CHARACTERIZED IN THAT, FOR AN IMPORTING COLUMN TO BE TREATED, AND THE TREATMENT AND EXTRACTION LIQUID OF THE TREATED SUSPENSION AS WELL AS A PULSATORY DEVICE, CHARACTERIZED IN THAT, FOR AN IMPORTING COLUMN, REPLATELY EACH HAVING A SURFACE S, A PERFORATION COEFFICIENT HAS A VALUE AT LEAST 10 AND PREFERABLY BETWEEN 20 AND 300.

Description

11894

  PERFECTIN APPARATUS FOR IAVAGE AND SEPAMATIGN

  GRANUIOMETRIC OF SUSPENDED SOLID MATERIALS

  The invention relates to a new apparatus for washing solid materials suspended in a liquid phase to remove the materials

  solubilized and / or intended for carrying out a granulametri-

  as specified by said materials, said apparatus being in the form of a pulsating liquid treatment column, provided with perforated plates. For a long time already, the specialized literature has described numerous apparatuses, some of which were particularly suitable for washing solids in aqueous suspension, while the others were more oriented towards the classification operations of solid materials in suspension

in a liquid phase.

  However, apparatus having the double possibility of allowing the washing of aqueous suspensions of solid materials and their classification

  have been proposed to those skilled in the art.

  It is in this spirit that the French patent N O 1 281 826 described a pulsating liquid column allowing continuous washing to be carried out.

  of an aqueous suspension of solid materials, in which the li-

  which is an aqueous liquor containing dissolved materials in solution

  lized, during the attack of an ore for example, liquor which must be replaced, during the washing operation, by the water introduced for this purpose.

  According to this document, the apparatus making it possible to carry out such an operation

  tion of washing, and which can allow the settling of an ore, suspended in a liquid phase, is formed of a vertical column, inside which are arranged perforated plates, or other

  obstacles, extending horizontally across the column, and spa-

  vertically relative to each other, means for intro

  to draw off solids or a suspension at one end of said column, and other means for introducing a treatment liquid into said column in the vicinity of the other end, means making it possible to extract a liquid phase or a suspension from the first end mentioned, as well as means for extracting solids suspended in the treatment liquid by the other end, finally, means for creating a pulsation in the contents of the column so as to force the solid materials and the liquid phase to cross the perforations of the plates extending horizontally across the column.

  Thus, according to such an apparatus, it is possible to carry out, for example

  ple, the washing of an aqueous suspension resulting from the attack on a mine-

  rai, by intimate contact between solid materials which move from the top to the bottom of the said column and an ascending treatment liquid,

introduced at the foot of the column.

  The presence of perforated plates, or other obstacles, distributed in the

  column at judicious intermediate distances, causes a fracture

  operation of the suspension between the plates constituting stages of

  treatment as well as a forced displacement of said suspension, this pheno-

  leads being favored by a pulsating effect caused by the introduction

  treatment fluid at spaced time intervals.

  Thus, according to this apparatus and according to the process which is associated with it, it appears possible to extract, discontinuously, from the bottom of the column, the suspension of washed solids containing no more than a small part of the materials in solution, by introducing discontinuously

  from the bottom of the column, and in a pulsating manner, the liquid from the

  a part of which leaves with the extracted suspension while the other part rises to the top of the column from which it emerges by overflow with the feed liquid and with almost all of the materials

  solution and materials to be disposed of.

  However, despite all the precautions that a person skilled in the art could take, in particular by requiring the reproduction of the material described in the aforementioned document and compliance with the conditions of application of said process,

  it appeared to the plaintiff that the results obtained were disappointing

  In fact, the efficiency of the washing obtained, evaluated according to the conventional rules of backwashing, was found to be much lower than the

  theoretical value that a person skilled in the art could calculate.

  On the strength of this observation, the plaintiff, continuing its research, has found and developed an improved column technology, mentioned above, leading to very efficient results, very close

  of those that can be expected by theory.

  According to the invention, the improved apparatus, intended to allow washing operations of solid materials suspended in a liquid phase to remove the solubilized materials and / or perform precise particle size separations of solid materials suspended in said phase, consists of a vertical column in which horizontal perforated trays are placed, means for supplying suspension or to be treated and for extracting the treated suspension and treatment liquid, as well as a pulsating device, is characterized in that that, for a column comprising N perforated trays actually implanted, each having an area S, a perforation coefficient p,

  ratio between the total area of the perforations and the area of said area

  teau, the pulsating device delivering the summation V of the volumes transferred alternately upwards and downwards per unit of time, the liquid used for washing or particle size separation having a density dn while the liquid leaving by overflow has a density do and that the solid materials in suspension have a density ds, g being the acceleration of gravity, we choose a diameter 0 of the perforations and a distance

  average 1 between these perforations in such a way that a coef-

  ficient K 1 associating the technical characteristics of said column, defined by the relation: 1 = V 1 ddn do K 1 ES * l do dn * d

  at a value at least equal to 10 and preferably between 20 and 300.

  According to the invention, the improved device comprises a vertical column

  treatment, intended to allow very intimate contact between ma-

  solid materials moving from the top to the bottom of said column, and

a liquid treatment phase.

  The solid materials to be treated are generally introduced in the form

  of an aqueous and / or organic suspension in which materials may

  may be in solution, while the liquid treatment phase may be

  water, an aqueous solution and / or a liquid of organic origin,

  in the form of a mixture or emulsion.

  The vertical treatment column can be cylindrical over its entire

  height But, the area of said column containing the trays is pre-

  preferentially of hyperbolic form, or constituted by the combination

  cylinders and / or truncated cones enveloping a theoretical hyperbola.

  This theoretical hyperbola is such that, v being the kinematic viscosity of the liquid phase at the level of a plate having the surface S, we have

  over the entire height of said zone the constant S / v ratio.

  According to a first arrangement, the vertical column consists, in its upper part, of a cylindrical collecting zone, in its middle part, of a cylindrical zone of sufficient height to receive the N plates and of diameter less than or equal to that of the upper cylindrical zone, the upper and middle zones being connected together by an inverted truncated cone whose large base is integral with the upper cylindrical zone, finally, in its lower part, of a zone

  conical, the base of which is connected to the cylindrical middle zone.

  According to a second arrangement, the vertical column comprises, in its upper part, a cylindrical collection zone, in its middle part,

  a hyperbolic zone of reverse revolution, the large base of which is shortened

  strung to the previous cylindrical zone and, including the small base, turned

  downwards, is extended by a cylindrical zone forming the inner part

  of said column which ends with an inverted cone of revolution.

  According to another arrangement, the vertical column is also provided in its upper part with a cylindrical zone, in its middle part, with a

  inverted truncated cone, the large base of which is integral with the cylin-

  upper dike of the same diameter, and the small base of which is situated towards the bottom of the said column, finally, in its lower part, of a cylindrical zone, the diameter of which is identical to that of the small base of the abovementioned truncated cone , which is extended by a cone of revolution

  the base of which is connected to the lower cylindrical zone.

  Finally, according to a final arrangement, the vertical column is made up,

  in the upper, middle and lower parts, by cylindrical zones

  successive risks of decreasing diameters, each zone being connected to the previous one by planar junction rings, or inverted cone trunks, the lower cylindrical zone extending downwards by a

inverted cone of revolution.

  Inside the vertical column is created a treatment zone

  situated between the above-mentioned upper and lower cylindrical parts.

  This treatment area is provided with perforated trays placed horizontally

  Likewise and at equal distance from each other Said perforated plates, can also form groups each comprising one or more equidistant plates, the distance existing between each group being

  generally higher than that existing between the shelves.

  One end of the column is equipped with means allowing the

  production of the suspension to be washed and / or elutrier, and evacuation means

  cuation of the liquid phase loaded with solubilized materials and / or elutriated materials, while the other end of said column is equipped with means for extracting the washed and / or sorted solid materials

  and means for introducing the liquid washing and / or elutria-

tion.

  Finally, placed on the lower cylindrical zone of said column is a pulsating device intended to create in the enclosure a movement of

  raising and lowering of the suspension through the perforated plates

in the treatment area.

  By increasing its research and by carrying out its experiments to develop the apparatus according to the invention, the applicant has been led to note and establish that the various technical parameters of a column intended for washing and precise particle size separation of suspended materials as well as the numerous parameters attached to the various treated and treating media were associated in relations defining two coefficients K 1 and K 2 This is how, for a column

  vertical comprising N perforated trays actually implanted, having each

  cun a surface S, a perforation coefficient p and provided with a pulsation mnyen delivering the soundmm V of the volumes transferred alternately upwards and downwards per unit of time, the washing liquid having a density dn and the outgoing liquid in overflow by the upper part of the vertical column a density do sufficiently different from dn, and

  solid materials in suspension a density ds, we choose a diameter

  be 0 for the perforations and an average distance 1 between said perforations

  holes in such a way that a coefficient K 1 is adjusted by the above-mentioned relation: 2 v N 2 dn do (1) 1 LPS Lg do dn

  at a value at least equal to 10 and preferably between 20 and 300.

  In the case where the densities dn of the washing liquid and do of the liquid

  both in overflow, have a relative deviation of less than 2%, a coefficient K 2 defined by the relation

K = (2)

  2 p S * v in which v is the kinematic viscosity of the liquor at the level of a surface tray S, with perforation diameter 0 and coefficient of

  perforation p, the coefficient K 2 must be associated with the coefficient K 1 pre-

  cited, this coefficient K 2 having a care value equal to 100 and pre-

  ference between 300 and 5000.

  In these two relationships, the plaintiff was led to find experience

  mentally that the coefficient of perforation p, ratio between the total surface of the perforations of a tray and the surface of this tray, must be understood between the limits 0.001 and 0.25 and, preferably, between 0, 005 and 0.1 . All the parameters characterizing the values to be given to K 1 and K 2 must

  be caught up in a coherent system of unity.

  Furthermore, all of these parameters are well known to those skilled in the art and

  can be easily defined by him in each case.

  Thus, the settling surface S, also known as the surface of the

  plateau, is defined according to the classic and well-known rules of the

  cantation to ensure a desired production tonnage.

  Likewise, the volume V transferred alternately up and down the vertical column per unit of time, is fixed at a value at least

  equal to the volume required to transfer the suspended solids

  from one floor to another, and on the basis of a given hourly production.

  This volume V is moved in a discontinuous and pulsating manner by the bottom of the column by virtue of the presence of means provided for ensuring said pulsation, so that the washing liquid is evacuated in part with the suspension washed and extracted while the other part goes back to

11894

  the top of the column from which it emerges by overflow with the liquid of a-

  feeding and with almost all the materials in solution.

  The Applicant has found that the effectiveness of the treatment is all the better when the instantaneous flow of suspension produced by the pulsations in each direction approaches a continuous flow during each fraction.

  of the cycle, that is to say during each forced displacement of said suspension

up and down.

  The number of trays N theoretically necessary is obviously determined by a person skilled in the art as a function of the degree of washing or of classification

  desired, according to the rules of art.

  The number N of trays actually set up is always less than twice the number N of trays theoretically necessary in the vertical column.

  In addition, the diameter 0 of the perforations in each tray is generally

  ral, greater than six times the diameter of the largest particles present

  in the suspension to be treated, and the distance between two plates must

  be at least equal to the average distance 1 between the perforations.

  As for the coefficients K 1 and K 2, they have been defined experimentally and the limits between which they can be situated are those for which tests have been carried out both with suspensions

  only with solutions free of solid phase.

  The invention will be better understood thanks to the description of the apparatus.

  shown in vertical section according to Figures 1 to 4.

  According to Figure 1, the vertical treatment column, intended for washing

  and the selective particle size separation of solid materials in addition to

  board, has a cylindrical central zone (1) for treatment surmounted by an upper cylindrical zone (2) provided with an overflow (3), the median (1) and upper (2) zones being connected together by the frustoconical surface inverted (4), then a lower cylindrical zone (5) is

  extending by a conical surface of revolution (8).

11894

  At the upper end of the column, that is to say in the zone (2), there is a supply line (10) through which the suspension to be treated is introduced into the column The treatment liquid enters

  in the lower cylindrical zone (5) via the cana-

  reading (7) under the action, for example, of a pump (not shown). In the central treatment zone (1), the N trays (16) are provided with perforations (17) spaced apart from each other by a length

  mean 1 The median treatment zone (1), of appreciable vertical extent

  ciable, is intended to allow a very intimate contact between the liquid phases to be treated and treatment and the solid phase of the materials to elutrier The suspension in a liquid phase of the solid materials to be treated being introduced by the pipe (10), a mechanical means pulsation (6), placed in the lower cylindrical zone (5) of the column ensures the upward and downward movement of the material contained in said column A fraction of the treatment liquid introduced by the pipe (7) moves from the bottom to the top of the column, coming into intimate contact with the solid materials being treated, by virtue of a circulation against the current with respect to said materials. This fraction of the treatment liquid is then discharged by the overflow (3) into the cylindrical zone. (2) of the Solid materials column which,

  during treatment, move down the column, are evacuated

  with the other fraction of the treatment liquid through

  of the pipeline (9), called the column underflow.

  According to the other figures, the median processing zone is a hyperbolic surface of revolution (12) in the case of FIG. 2, the small section of which faces downwards, while in the case of FIG. 3 this median zone of treatment consists of an inverted frustoconical surface (13) and that, in the case of FIG. 4, said median treatment zone is formed of successive cylindrical zones (14) of decreasing diameter from the top to the bottom of said column, each cylindrical area

  being connected to the next by an inverted frustoconical surface (15).

  As for the separation by elutriation of the solid materials suspended in the liquid phase, it is carried out by transfer of said materials, from one plate to another, under the action of the volume of the suspension displaced by the pulsations, then by the resuspension of said materials between each tray constituting a treatment stage, the fraction of the finest solids migrating up the column, while the fraction of the gravest soles moving down from said

  column Thus, each processing stage defined by the interval

  caught between two plates constitutes a hydroseparator supplied by the as-

  sociation of the flow rates of suspension of solid materials, coming from the immediately higher stage when the pulsation propagates downwards and coming from the immediately lower stage when the pulsation propagates upwards Therefore, this stage produces a suspension of grainy solid materials when the pulsation propagates down the column and a suspension of fine solid materials when the pulsation propagates up the said column The solid materials arriving at the underflow (9) of the column are therefore passed successively into a series of hydroseparators in which they have been resuspended and redecanted and consequently, are increasingly depleted in

fine solid materials.

  Therefore, the efficiency of the separation of solid materials in two

  fractions, one grainy and the other fine by means of the N + 1 stages of hy-

  droseparation is much higher than that obtained with a water separator

classic.

  Consequently, the apparatus according to the invention proves to be very effective not only for washing a suspension of a solid material

  in a liquid phase, but also to carry out serious separations

  very precise solid flow gauges according to two classes, one fine leaving with the overflow, the other grainy being extracted by

the base of the column.

EXAMPLE 1

  This example illustrates an attempt to wash and classify alumina trihydrate, suspended in a sodium liquor of density 1.28, at a temperature of 540 C, of average particle size 60-65 P, in Royen of

  pilot column produced according to the data of the prior art.

  Said column was of a cylindro-conical type, with a total height of 4 meters, comprising from top to bottom: a first cylindrical collection and overflow zone of diameter 01 = 2.25 m, connected by means of a truncated cone with a second cylindrical zone with a height of 0.5 meters and a diameter 02 = 1.67 m, containing 10 plates spaced 40 millimeters apart, pierced with holes 9 millimeters in diameter, arranged in a square mesh of millimeters per side, corresponding to a percentage of perforation p = 3.5%, said zone being connected by means of a truncated cone to a third cylindrical zone with a height of 1 meter and a diameter of 03 = 1.05 m, provided with 20 trays spaced 40 millimeters apart, drilled with 11 il millimeter holes in a square mesh of 40 millimeters

  side, corresponding to a percentage of perforation of 6.26%.

  This third zone was extended by a cylindrical part of the same diameter and height 0.5 m, which was provided with a pneumatic blower and an inlet pipe for the washing water. This third zone

  ended with a cone opening onto the underflow opening.

  The column was supplied by the first cylindrical zone by means of

  7.1 m 3 / h of an aqueous suspension containing 5 tonnes of aluminum trihydrate

mine.

  At the same time, said column received in the lower cylindrical zone

  5.5 m 3 / h of washing water of which 2.8 m 3 / h were transferred to the overflow The total pulsation flow in both directions representing

13.4 m 3 / h.

  A suspension containing 2.4 tonnes was extracted from the column 3.7 m 3 / h

of solids by the underflow.

  The respective densities of the liquid and solid phases were: column overflow: do = 1.2 washing water: dn = l solid: ds = 2.4

  The concentration ratio of dissolved salts in the liquid phases of a-

  the feed and underflow was only 7.5, a result which should have been obtained with a theoretical number of plates N = 3, whereas

trays were installed.

  Simultaneously with the washing operation, the classification of

alumina hydrate grains.

  The effectiveness of the classification was defined by the "sharing curve" method known as "TREIP CURVE", referenced TROMP K F "Neue Wege fur die Beurte-ilung der Aufbereitung von Steinkohlen

  Gluckauf 73 (1937) 125/131 151/156, which gave ad 50, diameter of par-

  ticles with a probability 0.5 of going out under, equal to 67 mi-

  crons, and an imperfection of the partition curve ("imperfection Index") I d 75 d 25 =

1 = -0.25

  The above-mentioned construction and operating data of the column

  led to a coefficient K 1 = 0.65.

EXAMPLE 2

  This example illustrates the improved apparatus according to the invention with

  which were washed and classified as trihy alumina

  dratée suspended in a sodium liquor of density 1.09, at room temperature

  stripping of 520 C, average particle size 60-65 y, by means of a column

  pilot carried out according to the data of the invention.

  Said column was of a cylindro-conical type, with a total height of 4 meters, comprising from top to bottom: a first cylindrical collection and overflow zone of diameter 1 = 1.60 m, connected by means of a truncated cone with a second cylindrical zone with a height of 0.5 meters and a diameter 02 = 1.07 m containing 10 plates spaced 40 millimeters apart, pierced with holes 6 millimeters in diameter, arranged in a square mesh of millimeters on the side, corresponding to a percentage of perforation p = 1.8%, said zone being connected to the core of a truncated cone to a third cylindrical zone with a height of 1 meter and a diameter of 03 = 0.97 m , provided with 17 trays spaced 40 millimeters apart, drilled with 9 millimeter holes in a square mesh 40 millimeters in side,

  corresponding to a percentage of perforation of 4%.

  This third zone was extended by a cylindrical part of the same diameter.

  meter and height 0.5 m, which was equipped with a pneumatic blower and an inlet pipe for washing water This third zone is

  ended with a cone opening onto the underflow opening.

  The column was supplied by the first cylindrical zone by means of

  11.3 m / h of an aqueous suspension containing 6 tonnes of a- trihydrate

  lumine. At the same time, said column received in the lower cylindrical zone 6-

3 3

  3.1 m 3 / h of washing water, 1.6 m of which was transferred to the surface

  pours The total pulsation flow in both directions was

14.9 m 3 / h.

  2.3 m / h were extracted from the column from a suspension containing 1.9 tonnes

solids by underflow.

  The respective densities of the liquid and solid phases were: column overflow: do = 1.09 washing water: dn = 1 solid: ds = 2.4

  The concentration ratio of dissolved salts in the liquid phases of

  mentation and underflow was only 103, which would result

  had to obtain with a theoretical number of trays N = 15.5 while 27 plates

teaux were installed.

  Simultaneously with the washing operation, the classification of

alumina hydrate grains.

  The efficiency of the classification was defined by the method of the "partition curve" which gave an d 50, diameter of particles having a

  0.5 probability of going out underwater, equal to 73 microns, and an imper-

  division curve division ("imperfection Index) I 75 d 25 2 d 50 0.15 The aforementioned construction and operating data of the column

  led to a coefficient K 1 = 10.

EXAMPLE 3

  This example illustrates the improved apparatus according to the invention with

  which were washed and classified as trihy alumina

  dratée suspended in a sodium liquor of density 1.09, at the temp-

  52 C temperature, average particle size 60-65 i, by means of a column

  pilot carried out according to the data of the invention.

  Said column was of a cylindro-conical type, with a total height of 4 meters, comprising from top to bottom: a first cylindrical collection and overflow zone of diameter t = 1.60 m, connected by means of a truncated cone with a second cylindrical zone with a height of 0.5 meters and diameter 0 = 1.07 m, containing 10 plates spaced 40 millimeters apart, pierced with holes 5 millimeters in diameter, arranged in a square mesh of millimeters on the side, corresponding to a percentage of perforation p = 1.2%, said zone being connected by means of a truncated cone to a third cylindrical zone with a height of 1 meter and diameter 03 = 0.97 m , provided with 17 trays spaced 40 millimeters apart, drilled with holes of 6.5 millimeters in a square mesh of 40 millimeters

  side, corresponding to a percentage of perforation of 2.1%.

  This third zone was extended by a cylindrical part of the same diameter.

  meter and height 0.5 m, which was equipped with a pneumatic blower and an inlet pipe for washing water This third zone is

  ended with a cone opening onto the underflow opening.

  The column was supplied by the first cylindrical zone by means of

  11 m 3 / h of an aqueous suspension containing 5.8 tonnes of aluminum trihydrate

mine.

  At the same time, said column received in the lower cylindrical zone

  less than 2.7 m 3 / h of washing water, of which 1.1 m 3 / h was transferred to the surface

  erse The total pulsation flow in both directions represented

14.1 me / h.

  2.4 m 3 / h were extracted from the column from a suspension containing 2 tonnes of

solid by the underflow.

  The respective densities of the liquid and solid phases were: column overflow: do = 1.09 washing water: dn = 1 solid: ds = 2.4

  The concentration ratio of dissolved salts in the liquid phases of a-

  the feed and underflow was only 220, a result which should have been obtained with a theoretical number of trays N = 23 while

27 trays were installed.

  Simultaneously with the washing operation, the classification of

alumina hydrate grains.

  The efficiency of the classification was defined by the method of the "partition curve" which gave an d 50, diameter of particles having a

  0.5 probability of going out underwater, equal to 75 microns, and an inper-

  division of the imperfection index d 25 2 d 50 The aforementioned construction and operating data of the column

  led to a coefficient K 1 = 30.

Claims (3)

CLAIMS / Improved apparatus, intended to allow washing operations of solid materials suspended in a liquid phase to remove the solubilized materials and / or perform precise granulometric separations of solid materials suspended in said phase, consisting a vertical column in which are placed horizontal perforated trays, supply means for suspension to be treated and for liquid for treatment and extraction of the treated suspension, as well as a pulsating device, characterized in that , for a column comprising N perforated trays actually implanted, each having an area S, a perforation coefficient p, ratio between the total area of the perforations and the surface of said tray, the pulsating device delivering the sum V of the volumes transferred alternately upwards and downwards per unit of time, the liquid used for washing or for particle size separation having a nsity dn while the liquid leaving by overflow has a density do and the solid materials in suspension have a density ds, g being the acceleration of gravity, we choose a diameter 0 of the perforations and an average distance 1 between these perforations such that a coefficient K 1 is associated with the technical characteristics of the said column, defined by the relation: K_l V 2 N dn dod K 1 = p S lg do dn do with a value at least equal to 10 and preferably between 20 and 300. 2 / Improved apparatus according to claim 1, characterized in that, when the densities dn of the washing liquid and do of the liquid leaving the overflow have a relative difference of less than 2%, the coefficient is associated with the coefficient K 1 a coefficient K 2 defined defined by the relation v K 2 î in which v is the kinematic viscosity of the liquor at the level of a tray, which is adjusted to a value at least equal to 100 and preferably between 300 and 5000. / Apparatus p finished according to claim 1 or 2, characterized in that the perforation coefficient p, ratio between the total area of the perforations of a tray and the area of this tray, is between the limits 0.001 l and 0.25 and, preferably between 0.005 and 0.1.   4 / improved apparatus according to claims 1 and 2, charac-   that the N perforated trays actually implanted in the   column are in a cylindrical area of said column.    / Improved apparatus according to claims 1 and 2, charac-   in that the N perforated trays actually implanted in the   column are in a hyperbolic area of said column.   / Improved apparatus according to claims 1 and 2, charac-   terized in that the N perforated trays actually implanted in the column are in an area formed by the combination of several   coaxial cylindrical-conical shapes of said column.   7 / improved apparatus according to claim 6, characterized in that the area formed by the combination of several coaxial cylindroconical shapes of said column is the outer envelope of a hyperbolic form.   8 / improved apparatus according to claims 5 and 7, characterized   in that, v being the kinematic viscosity of the liquid phase at the level of a plate having the surface S, we have over the entire height of the zone of   hyperbolic form the constant S / v ratio.