FR2619516A1 - PROCESS AND APPARATUS FOR EXTRACTING SOLUBLE COMPONENTS FROM PLANTS, ESPECIALLY MARITIME PLANTS - Google Patents

Abstract

An apparatus for extracting soluble phytocomponents comprises a septum 10 supporting a batch 56 of solid-liquid mixture; a chamber 20 having an open face adjacent to this septum; means 32, 18 establishing and suppressing the tightness of said open face with respect to said septum; means 32, 42 pressing said batch 56 against said septum 10, inside the chamber 20, to express a liquid 71 through said septum 10; and means 12 - 15, 16 releasing said septum 10 from said chamber 20, for removing successive batches 76 from the solid fraction of said mixture.

Description

1i 2619516

  METHOD AND APPARATUS FOR EXTRACTING COMPONENTS

  PLANT SOLUBLES, ESPECIALLY MARITIME PLANTS

  The present invention relates to a method of extracting

  tion of soluble components from plants, in particular

  to bind maritime plants, as well as to an expression device which can be used in particular, inter alia, for the

implementation of such a method.

  It has so far been proposed to extract compounds

  soluble health such as mucilaginous substances (for example carrageenan, agar, furcellaran and substances

  similar) from a variety of plants, in particular

  bottom of maritime plants, by heating these plants in an excess aqueous alkaline solution, then by carrying out a filtration, as described for example in the patents

  US-A-3,094,517 (Stanley), US-A-3,176,003 (Stancioff), US-A-

  3,236,833 (Gordon et al), US-A-3,476,741 (Jonas) and US-A 3,907,770 (Strong). In such methods, a large excess quantity of liquid is used and / or the mucilaginous component is degraded. Consequently, the desired product can be obtained, either in a degraded form, or in a substantially non-degraded form (i.e. with minimal degradation), only after

  that a large amount of liquid has been removed from the solution

  diluted filtered tion. Removing excess liquid, for example water, makes the product considerably more expensive

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  and lengthens the time necessary for the implementation of the method.

  It has also been proposed to express a liquid from solid-liquid mixtures, by subjecting the mixture to pressure against a sieve or a "septum", as for example in a cider press. The apparatus used to carry out the expression operations ranges from simple low-cost presses operating in batches, of the box type, trays, crucibles, troughs and cages, to screw presses, rolling mills and ribbon presses , of elaborate design and operating continuously. Although a continuous expression apparatus is advantageous from the point of view of labor savings, it is not currently applicable to solid-liquid mixtures having a low internal tension, since the latter tend to be crushed at away from the walls or organs of compression and beyond their limits, rather than through the septum

  porous. It has also been proposed to overcome this difficulty.

  cultivated by adding, to the mixture, pressing aids in the form of wood fibers, rice glumes and the like, which increases the total cost of

  operation and requires disposal of auxiliary waste

  pressing res. Continuous presses, and in particular ribbon presses, also give expressed products

  which contain substantial percentages of solids

  and are, therefore, of reduced purity.

  An expression apparatus of the batch operating type, using the concept generally known under the name "confined expression", can be used for liquid-solid mixtures having a low internal tension, but

  accuses the inconvenience of claiming a large sum of labor

  vail. It is moreover common in practice to dilute

  with excess water the liquid-solid mixtures obtained-

  naked, of a viscous viscosity, by heating in a solution

  alkaline aqueous plants containing so-

  mucilaginous lubles, in particular maritime plants containing carrageenan, before separating the liquid from the solid. Dilution allows the liquid to be separated by

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  conventional filtration or centrifugation equipment, but greatly increases the amount of liquid which must

  be eliminated to obtain a dry product.

  The application of the present invention makes it possible to obtain

  define the rapid separation of a liquid from liquid-solid mixtures in which the weight ratio of the liquid

  and solid does not exceed 6: 1, and in which the concentration

  mucilage (for example alginates, carra-

  geenan, agar, locust bean gum, acacia gum, tragacanth gum, pectin,

  chocolate, etc.) is greater than 2% by weight and is

  preferably between 3% and 10% by weight.

  The present invention provides a method for obtaining a high level of expression of liquids with liquid-solid mixtures, in particular those containing low concentrations of liquid, with reduced operating costs and by reducing or eliminating, in the same time, the need to add pressing aids to mixtures with low internal tension. It is well known that the average percentage of expression, from a liquid-solid mixture, can be increased by increasing the pressure exerted, or by decreasing the thickness of the

  layer of liquid-solid mixture deposited on the septum.

  The effect of increased pressure quickly fades as the pressure increases, and

  it is not very advantageous to use, in the process of the pre-

  invention, expression pressures greater than

  about 4.2 MPa. The thickness of the layer can be almost

  sée, during each stroke of the machine, depends on the ma-

  pressed, the nature of the cake produced and the

  exercised. When the solid substances making up the cake are compressible (as in most cases involving expression), increasing the pressure does not have linear effects on the average expression rate, and an increase in the pressure at infinity gives

  a small advantage. One can obtain, with min-

  these, such a large rate of expression, per unit of over-

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  face, which it seems not very beneficial to exercise, in the cham-

  bre of expression, pressures exceeding 4.2 MPa, although

  this order of magnitude is in no way limiting. For example-

  ple, when this pressure is applied to express pasta containing carrageenan lambda, with viscosities -

  of expressed products greater than 100,000 centi-

  poises, final cake thicknesses of 0.3 mm are used and expression rates of 1 kg / s per square meter of filtration septum can be reached during pressurization (in terms of product expressed). The time interval, during which an effective pressurization of the chamber is maintained during each operating cycle, can be only 0.05 seconds and does not necessarily have to exceed approximately 0.5 seconds. In most cases it is of little benefit to use pressure times

  longer, although it is worth examining indi-

  each case in order to optimize the overall flows.

  Consequently, in one of its aspects, the present invention relates to the expression carried out from a mass of plants such as maritime plants containing, in aqueous solution, at least one solubilized component, which consists in subjecting a layer of said plants, on a

  porous septum, at a pressure of at least 2 MPa exerted con-

  be this septum, for a period of approximately 9.05 se-

  after 0.5 seconds, in order to express said solution through

  towards said septum and allowing a deposit of plant residues whose thickness is between approximately 0.3 mm and 2 mm to remain on this septum. Such a process results, without the addition of a pressing aid or a solid filling substance, by the expression of a quantity of liquid solution which represents at least 80% by weight of the mass of plants treated, which is a very satisfactory result, in particular in the case of a solution of carrageenan lambda expressed from maritime plants subjected to

alkaline treatment.

  The present invention therefore relates to a pro-

  yielded to extract solu components from plants

  wheat, preferably under a. substantially non-degraded form, by heating the plants in contact with an aqueous alkaline medium to dissolve the components and form a mixture of liquid and solid; by depositing, on a porous septum, successive batches of the mixture spaced from each other; by successively pressing each batch against the septum to express the liquid through this septum, while retaining the residue of the solid on the septum; and eliminating,

  of this septum, each batch of residue.

  The invention also relates to an apparatus for expressing

  sea a liquid with a mixture of solid and liquid, this apparatus comprising a porous septum for supporting a layer of the mixture to be expressed; a chamber with an open face adjacent to the septum; means for establishing and eliminating the seal of the open face with respect to the septum; means for pressing said layer of mixture against said septum, inside said chamber in sealed condition with respect to this septum, for expressing liquid with the mixture, through the septum; and means for extracting the septum away from the face of the

  chamber, while the sealing of this chamber is removed

  mé, so as to evacuate from said chamber, successive portions of the solid fraction of the mixing layer

after the expression of liquid.

  -The septum used in the present invention is of the type which does not clog, that is to say being not obstructed.

  by a solid substance in case of prolonged use.

  Lightweight classic fabrics and felts, woven with multifilament yarn, tend to clog

  very quickly and require excessive washing to recover

  ver their permeability, which implies a loss of product.

  The best results are obtained by using, as a septum, fine sieves which are braided in a weave

  twill, from nylon monofilaments or poly-

  ester, and have a nominal pore diameter or

  vertures between 0.6 micrometer and 6 micrometers, as well as filament diameters between 20 micrometers

6 C2619516

  and 50 micrometers. Appropriate septa presenting the

  specified characteristics are available in the trade

  this. The use of such a septum makes it possible to separate the so-

  residual liquids from this septum after the expression of the liquid, simply by scraping; modest, if any, washing is required to restore permeability. Liquids such as aqueous mucilage solutions, having a viscosity greater than 1000 cP, can be easily separated from solid plant residues, using

such a septum.

  The invention will now be described in more detail.

  by way of non-limiting examples, with regard to the

  attached sins in which: Figure 1 is a side elevation with partial section, illustrating one of the embodiments of the apparatus of the present invention;

  FIG. 2 is a fragmentary section on an enlarged scale

  die, showing a second embodiment of the apparatus; Figure 3 is a fragmentary section of one of the embodiments of the chamber sealing system; Figure 4 is a fragmentary section of a second form of the chamber sealing system; Figure 5 is a fragmentary section of a third form of the chamber sealing system; FIG. 6 is a fragmentary section, showing another form of sealing system used in the present invention; and

  Figure 7 is a side elevation with section through

  tial, observed at right angles to the view in FIG. 1, showing a third embodiment of the

present invention.

  As illustrated in the drawings, the form of realization

  tion of Figure 1 has a porous septum 10 is present

  both as a continuous band passing around pulleys 12, 13, 14, 15 and driven intermittently, in the direction

  marked with arrows, using a drive mechanism

  16 with motor and belt. A cylinder 18, installed above

  above the strip 10, has an open underside which forms a chamber 20 with the septum. This cylinder 18 is supported by tie rods 22 subject to a support piece 24, which is in turn mounted on a piston 26 housed, with sliding ability, in a hydraulic cylinder.

  lique 28 supported by a profile 30 in I. A hydraulic fluid

  Lique is delivered to the cylinder 28 and is evacuated by suitable means (not shown), so that the piston 26 and, therefore, the cylinder 18 can be moved up and down so as to press, with tight contact, the lower edge of the cylinder 18 against

septum 10.

  A means of pressurizing the chamber 20, housed inside the cylinder 18, takes the form of a piston 32 provided with a flat and perforated underside 34. The piston 32 is supported by a pilot piston 36 performing a reciprocating motion in a second hydraulic cylinder 38, the latter being independently supported by profiles 40

  in I and being equipped with means (not shown) for intro

  draw off and evacuate a hydraulic fluid, so as to

  ner the piston 36 and to drive the piston 32 for the

  pressurization or depressurization of the chamber 20.

  A permeable anvil 42, installed below the septum and the cylinder 18, has multiple support bars spaced 44 directly below the open face of the cylinder 18. A perforated metal screen 46 is mounted on these bars and is crowned directly at the - below the septum

  , by a sieve 48 made of fine mesh metal wires (fig.

  gures 2 and 3). The anvil 42 is rigidly supported on I-shaped sections 50 which, in turn, rest on a frame of

  support 52. A funnel 54 protrudes from the bottom of the anvil 42.

  A supply device is installed above the septum 10, in the direct vicinity of the cylinder 18, in order to deposit successive batches 56 of a liquid-solid mixture on the

  face of septum 10, before it is placed above

  below the open face of cylinder 18. The device

  feed comprises a hopper 58 associated with a comp

  integral material 60 batch metering device and a delivery nozzle 62, as well as a delivery piston 64 actuated by a jack

  drive hydraulic 66, all of these parts being

  tees on a support frame 68. Similar to cylinders 28 and 38, the hydraulic cylinder 66 is equipped with a system

  (not shown) to supply hydraulic fluid

  in order to deliver, at synchronized intervals, metered batches of the liquid-solid mixture coming from the hopper 58. The hydraulic systems for controlling the jacks 28, 38 and 66,

  as well as the motorized drive 16 of the septum 10, are coordinated

  given by conventional means for operation

  at the desired pace, as set out below.

  A conveyor belt 70, located below the end

  open lower half of funnel 54, is led by a

  classic drive mechanism 72 with motor and belt.

  A scraper 74 is installed in the immediate vicinity of the downstream strand of the septum 10, so as to eliminate therefrom lots 76 of solid residues carried by this sep um coming from the zone underlying the cylinder 18, and a receptacle 78 serves to collect the solid residues. A spray nozzle is also mounted in the direct vicinity of the septum 10 below the scraper 74, in order to rid this septum, by washing, of any solid residue continuing to adhere;

  washing wastes are collected by a receptacle 82.

  During operation of the embodiment illustrated in FIG. 1, the feed device is actuated to deposit, on the surface of the septum 10, a metered batch of liquid-solid mixture coming from the metering compartment 60, that is to say when the septum 10 is immobile, either when it progresses. To allow this septum to advance, the piston 26 and the pilot piston 36 are both actuated in their respective hydraulic chambers,

  to pull the cylinder 18 away from the septum 10 (removing

  thus mant the sealing of the chamber 20), and also to extract the piston 32 (which causes depressurization

  from room 20). Then, the septum set in motion completes

  mines lot 56 to a location inside the

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  limits of the lower edge of cylinder 18, after which this sep-

  tum is stopped, then the piston 26 is actuated to push the lower edge of the cylinder 18 against the septum 10, around the lot 56, which establishes the tightness of the open face of the cylinder 18 relative to said septum which is supported,

  below, by the anvil 42, the screen 46 and the screen 48.

  The pressure prevailing between the lower edge of the cylinder 18 and the septum 10 must be greater, preferably at least 0.6 MPa, than the pressure subsequently exerted on the batch 56, inside the chamber 20, in order to maintain the desired seal. The narrow width of the bottom edge

  of cylinder 18 promotes the development of a strong pressure

  sion between this edge and the septum 10, against the anvil 42.

  The pilot piston 36 is then actuated to impart a downward movement to the piston 32, then pressurizing the chamber 20 and compressing the batch 56 against the septum in order to express the liquid, through this septum, into the funnel 54 to from which it is directed onto the surface of the conveyor belt 70. The liquid 71, having a high viscosity, remains collected near the center of the surface of the belt 70 and it is conveyed, by this

  last, to a delivery station for a

later.

  At the end of the expression step, the piston 32 is raised to depressurize the chamber 20 and the cylinder 18 is moved towards this raised piston, so as to remove the sealing of its lower edge against the septum 10. This septum 10 is then advanced to the left as illustrated in FIG. 1, carrying, on its surface, the residual solids from lot 56. The immediately successive lot 56 is

  simultaneously introduced into chamber 20, within the limits

  tes from the bottom edge of cylinder 18, then the cycle is repeated. When each successive batch 76 of solid residue reaches the scraper 74, it is scraped off and falls into the receptacle 78 from the surface of the septum, which is then rinsed or washed by an outgoing spray

  nozzle 80. As shown in this embodiment

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  tion, septum 10 is a continuous band and is reused

  repeatedly for successive batches.

  A second embodiment is illustrated on

  Figure 2 of the drawings, in which the corresponding parts

  generally correspond to those of FIG. 1. It is distinguished, from the embodiment of FIG. 1, by the

  the fact that the piston 32 is provided with an intake tube or pipe

  sion 84 connected to a circulation channel 86, which extends vertically through the piston and opens, on the bottom 34 thereof, into the chamber 20. The lower outlet of the channel 86 is provided with a valve 88 to spherical shutter, used to allow a downward flow which traverses the

  channel 86, but prohibiting a flow in the opposite direction.

  The free upper end of the tube 84 is connected to the

  nozzle 62 of a supply device such as that illus-

  very in Figure 1. In this embodiment, the

  synchronization of the various drive mechanisms is re-

  frozen so that a fresh batch of liquid mixture-

  solid is introduced into the chamber 20, through the channel 86, after the tightness of the cylinder 18 has been established with respect to the septum 10, and before the piston 32 has been

  actuated to pressurize chamber 20.

  Figures 3 to 5 of the drawings show alternative embodiments of the lower edge of the cylinder 18, as well as

  anvil 42 associated with its support screen and sieve.

  In the structure according to FIG. 3, the lower edge of the cylinder 18 is provided with a front lining 90 made of a compressible elastomer and the edge of the mesh screen 48 is also provided with a coating 92 in one

  compressible elastomer which faces the lining 90.

  When the cylinder 18 is pressed against the anvil 42, the

  elements 90 and 92 made of elastomers serve to ensure the tightness

  the edge of this cylinder 18 against the septum 10. In FIG. 4, another embodiment is seen in which the lower internal edge of the cylinder 18 is detached, at 94, to receive an O-ring 96 made of an elastomer which replaces the front trim 90, the structure being, for ll

  the rest, identical to that shown in FIG. 3.

  FIG. 5 illustrates another embodiment,

  in which the internal and external edges 98 of the edge

  bottom of the cylinder 18 are bevelled or rounded and in which the front lining 90 is removed, the seal being imparted by the pressure exerted on the coating 92 of elastomer installed on the screen 48 with a metal mesh. In FIG. 6, we still see another embodiment which is identical to that of the

  Figure 4, with the exception that it is devoid of the coating

  rubber housing placed on the edge of the sieve 48 at mail-

  metal thread, sealing being ensured by compression of the O-ring 96 against the upper face of the septum. An appropriate choice of the components of training

  makes it easy to reach an overall cycle time of

  less than 3 seconds, and an overall hourly rate of

  1200 kg / h per square meter of filtration septum

  can be obtained in the example of an aqueous solution

  closing carrageenan lambda and having a viscosity -20 thick. For a contained part of carrageenan representing 4%, this translates into a final yield of 48 kg / h per square meter of dry equivalent of lambda carrageenan. In the considered example of lambda carrageenan, obtaining this average flow rate, using conventional equipment (for example plate and frame filter presses), would require the dilution of the base material in l water, so that its part contained in lambda carrageenan is approximately 0.5% by weight in order to reduce the viscosity

  up to around 500 cP, and would require a wire surface

  200 square meter tration. In addition, additions

  of a filtration aid would be born

  to prevent blockage of the fabric filters.

  In the embodiment illustrated in the figure

  7 of the drawings, the general design of the septum and the

  anvil corresponds to that of Figure 1 and the feeding device introduces the batch of liquid-solid mixture

  directly in room 20, through an admission

12 1951

  sion 84 as in the embodiment of Figure 2; however, the piston 32 remains fixed during the expression of the liquid through the septum, the pressure necessary to express this liquid through the septum, being generated by the hydraulic cylinder 66 of the supply device. As illustrated in FIG. 7, the piston 32 is supported from a frame 110, resting on profiles 112 in I to which the anvil 42 is connected. The support takes the form of articulated rods 122 and 123, the first of which is pivotally mounted on the frame 110 and the second of which is

  fixed to piston 32, with the possibility of pivoting through the

  median of a pin joint 124. The rods are pivotally articulated, one on the other and on one of the ends of a drawbar or control rod 126, the other end of this drawbar being connected to a crank 128 mounted on one side

  of the frame 110, and actuated by a reversible hydraulic cylinder

ble 130.

  In this embodiment, the piston 32 is also

  also provided with outwardly projecting arms or wings 132 which cover a cylinder 134 and attached wings 136

  to this cylinder and extending outward. A solidarity

  loose position is established, between the piston 32 and the cylinder 134, in the form of bolts 138 fixed to the wings 136 and crossing the wings 132, compression springs 140 being interposed between the wings to push the latter away from the each other. Guide pins 142, secured to the anvil 42, have stops to limit the movement of the cylinder 134 towards this anvil. An elastic O-ring 144, embedded in the

  bottom of cylinder 134, serves as a seal.

  Inserting or removing shims 146,

  between the piston 32 and the trunnion seal 124, makes it possible to adjust

  ter at will the vertical dimension of the chamber 20, tan-

  say that the sealing pressure, between the bottom edge

  of cylinder 134 and septum 10, can be adjusted by inserting

  rant or by removing shims 148. In this way, the apparatus can be easily adjusted to be used with a wide range of liquid-solid base mixtures, as well

  that with various septa of thickness or permeability will

  reliable. As in the other embodiments, means

  conventional synchronization systems can be provided for

  order the operating sequence and rhythm of the hydraulic cylinders

  lines 66 and 130, as well as the advance of septum 10 below

piston 32 and cylinder 134.

  In service, when the desired section of the septum 10 is below the cylinder 134, the hydraulic cylinder is actuated to push the drawbar 126 to the left, considering FIG. 7; in this way, the

  rods 122 and 123 are brought into alignment and the

  tone 32 is moved down from a position

  towed, to a locked stationary position in which it forms the upper wall of the chamber 20, as shown in FIG. 7. This chamber 20 is a chamber of fixed dimensions when the piston 32 occupies its locked position. During the downward movement of this piston 32, the cylinder 134 is also pushed down by the

  compression springs 140, until it comes to rest

  quer against the guide pins (limiting stops) 142, the O-ring 144 being compressed against the septum

  10, with which it seals. The hydraulic cylinder 66 is then actuated to forcefully insert the mete

  liquid-solid base swath in chamber 20, via

  inlet tube 84, the pressure being sufficient

  strong to express liquid through the septum 10

  while the piston 32 remains locked in its position.

  This pressure is maintained until the flow of liquid passing through the septum 10 approaches zero, consequently forming a mass or a cake of solids.

  waste inside Room 20. The length of time required

  the formation of the residual solid mass is

  same order of magnitude as that required when

  that a movement of the piston 32, in the embodiment

1 4 2619516

14 ool

  of Figure 1, is used to exert pressure, that is

  that is, it is in the range of 0.05 seconds to 0.5 seconds.

  The hydraulic cylinder 130 is then actuated to retract the piston 32 which, after a slight delay, drives the cylinder 134 with it via the bolts

138 of loose joining.

  The time delay involved in the withdrawal of the

  cylinder 134 allows it to block the septum against the anvil

  me 42, and promotes the release of the underside of the piston 32 from the mass of residual solids. The rest of the operating cycle is the same as that of the forms of

realization of Figures 1 and 2.

* Optionally, the gap between the scraper 74 and the septum 10 (Figure 1) can be adjusted to eliminate

  only a part of the deposits of residual solid material

  re, i.e. the least dense fraction, for recycling purposes. The remaining fraction, of higher density,

  can then be removed by a second scraper (not shown

  felt), as in the embodiment of Figure 1.

  If desired, the septum 10 can be supplemented with additional sheet material, such as paper or filter cloth deposited on the top of the septum 10; this additional sheet material can be disposable if desired. In fact, all of septum 10 can be disposable

if costs allow.

  It goes without saying that many modifications can

  be made to the invention as described and shown

without departing from its framework.

to I 2619516

Claims (10)

  1. Method for extracting soluble components from plants, process characterized in that it consists in heating said plants in contact with an aqueous alkaline medium, in order to dissolve said components and to form a mixture of liquid and solid; to place,   on a porous septum, successive batches of said space mixture   from each other; successively pressing each of said batches against said septum to express said liquid through this septum, while retaining a residue of said sol.   on said septum; and to remove from this septum each of the- so-called waste lots.   2. Method according to claim 1, characterized in that it includes the step of advancing the septum intermittently opposite an expression station; and by the fact that the pressing step is carried out at said station, the elimination step being carried out after this post has been crossed.   3. Method according to claim 2, characterized in that the step of depositing the batches is carried out before   the septum is routed to the aforementioned station.   4. Method according to claim 2, characterized in that the step of depositing the batches is carried out at the aforementioned station, the elimination step being carried out after the septum has left this position.   5. Method according to claim 1, characterized in that the plants are maritime plants containing   carrageenan, the expressed liquid containing carragee-   nan in an amount of at least 3% by weight.   6. Apparatus for expressing a liquid with a mixture of solid and liquid, apparatus characterized in that it comprises a porous septum (10) for supporting a layer or batch (56) of said mixture to be expressed; a chamber (20) provided with an open face adjacent to said septum (10); means (32, 18; 134) for establishing and removing   the tightness of said open face with respect to said sep-   tum (10); means (32, 42) for pressing said batch (56) 16 Z619516   of mixing against said septum (10), inside the   said chamber (20) in sealed condition, for expressing liquid (71) from said mixture, through said septum (10); and means (12 - 15, 16) for pulling said septum (10) away from the face of said chamber (20), while the sealing of this chamber is removed, so as to evacuate from said chamber (20), successive portions (76) of the solid fraction of said batch (56) of mixture after said expression of liquid (71).   7. Apparatus according to claim 6, characterized in that the septum takes the form of a strip (10) projecting beyond the abovementioned open face; and by the fact that this apparatus comprises a permeable anvil (42) which is opposite to said open face and is situated on the side of said septum (10) facing away from the chamber (20), as well as a means ( 16) to advance said septum (10) across said open face when the sealing of said chamber (20) is deleted.   8. Apparatus according to claim 7, characterized by   the fact that the means to establish and remove the seal-   tee have means (26, 28, 36, 38) for moving the chamber (20) and the anvil (42) towards and away from each other, in order to wedge the septum (10) Between   the anvil and the edges of the abovementioned open face.   9. Apparatus according to claim 6, 7 or 8, character-   laughed at by the fact that the pressing means comprise a piston (32) sealingly housed inside the chamber (20), as well as means (26, 28, 36, 38) for moving said piston (32) towards and away from the septum (10), in order to compress the mixture against said septum and release the latter.   10. Apparatus according to claim 6, 7 or 8, character-   laughed at by the fact that the pressing means comprise a device (58, 60, 62, 64, 66) for introducing the mixture (56) of solid and liquid into the chamber (20) under a   hydraulic pressure, while keeping the dimensions fixed sions of this room (20).