FR2748685A1 - PROCESS AND INSTALLATION FOR THE CONTINUOUS EXTRACTION OF A LIQUID CONTAINED IN A RAW MATERIAL - Google Patents

Abstract

The invention discloses a method for continuous extraction of a liquid contained in a raw material, characterised in that in a first section A of an extruding machine (1), the raw material is introduced and the following operations are carried out: a first mixing and a first heating operation, at least one pressing and one filtering operation on the material, at least one compression and one shearing operation, at least a second mixing and a second heating operation, and in a second section B of the said extruding machine (1), at least one pressing and one filtering operation on the material, and in a third section C of the said extruding machine (1), the dry residue of the said material is compressed and extruded. The invention also features a continuous extracting installation for implementing the method.

Description

 The present invention relates to a method and an installation for continuous extraction of a liquid contained in a raw material.

 The present invention applies for example to the extraction of oil from a oleaginous or oléoprotéagineuse raw material, algae, plants or citrus fruits.

 Currently, the extraction of the liquid contained in this kind of raw material is carried out by kneading or trituration, and then pressing in large units with a capacity ranging for example from 150,000 to 300,000 tons / year.

 In these units, the raw material first undergoes a so-called thermomechanical preparation phase, followed by a pressing phase carried out in flat presses or in single-screw filters so as to collect more or less dry residues.

 However, these residues resulting from the solid-liquid separation still have a residual liquid content, for example oil, of at least about 20% by weight, which is high and requires subsequent extraction treatment.

 For this purpose, the residues are treated in a solvent extraction unit, typically n-hexane, which finally gives a residue having a residual liquid content ranging from 1 to 3% by weight.

 However, this solvent extraction treatment is expensive and presents risks.

 These traditional equipment that have not changed for many years, are more bulky and consume high power and require relatively long processing times.

 In addition, we are witnessing an evolution of oilseed varieties, with the advent of new seeds, such as rapeseed 00, whose pressing is more delicate.

 To overcome this problem, it has been proposed to use an expander, but this solution is not entirely satisfactory.

 These problems encountered in solid-liquid separation are not specific to oilseeds and the agri-food industry in general requires the use of processes allowing the selective extraction of certain products from a varied raw material.

 The invention aims to provide a method of extracting a liquid contained in a raw material, which can significantly reduce the time required for the extraction of the liquid and thus the energy consumption.

The subject of the invention is therefore a process for the continuous extraction of a liquid contained in a raw material, such as for example an oleaginous or oléoprotéagineuse material, characterized in that
in a first part of an extrusion machine comprising two co-rotating and co-rotating screws driven in rotation about parallel axes inside a first sheath provided with intersecting bores, the raw material is introduced and we perform:
a first kneading and a first firing of the material,
at least one pressing and a filtration of the material to recover a part of the liquid contained in said material,
at least one compression and shearing of the material,
a second mixing and a second cooking of the material,
in a second part of the extrusion machine comprising two co-rotating mono-screws carried by parallel axes integral with the axes of the screws of the first part and driven in rotation inside a second elongated sheath provided with independent bores and not communicating with each other a light, at least one pressing and a filtration is performed to recover the liquid from the material leaving the first part of the extrusion machine,
and in a third part of said extrusion machine, the dry residue of said material is compressed and extruded.

According to other features of the invention
the first and the second firing are carried out at a temperature of between 90 and 1500.degree.
the residual liquid content in the dry residue leaving the extrusion machine is less than 15%.

The invention also relates to an installation for continuous extraction of a liquid contained in a raw material, characterized in that it comprises an extrusion machine comprising
a first part formed of two corotating and co-penetrating screws driven in rotation about parallel axes inside a first elongated sheath and provided with secant bores and determining:
an area of introduction and transport of the material,
a first zone for kneading and cooking the material,
at least one pressing and filtration zone for recovering part of the liquid contained in said material,
at least one zone of compression and shear of the material,
a second zone for kneading and cooking the material,
a second part formed of two co-rotating mono-screws carried by parallel axes integral with the axes of the screws of the first part and driven in rotation inside a second elongate sheath provided with independent bores and communicating with one another by a light and determining at least one pressing and filtering zone for recovering the liquid from the material leaving the first part of the extrusion machine,
and a third part determining a zone of compression and extrusion of the dry residue of said material.

According to other features of the invention
- The screws of the first part have, in the transport zones, kneading and cooking and pressing and filtration, a variable pitch,
the first sheath comprises, in said pressing and filtration zone, a filtering surface based on holes distributed over a portion of the periphery of said sheath,
the screws of the first part are provided, in the zone of compression and shearing of threads with not reversed with respect to the direction of transport of the material and provided with openings for the passage downstream of a controlled flow of material ,
each mono-screw, in the pressing and filtering zone of the second part, has a compression ratio of less than 8 and preferably of between 1.1 and 4,
the pitch of the mono-screws is constant in the pressing and filter zone of the second part and the diameter of the axis of each of said single-screws increases in the flow direction of the material,
in the pressing and filtering zone of the second part, the pitch of the mono-screws is gradually tightened in the flow direction of the material and the diameter of the axis of each of said single-screw is constant,
the second sleeve comprises, in said pressing and filtration zone, a filtering surface formed by holes distributed over a portion of the periphery of said sleeve,
the filtering surface has a transparency of between 3 and 50% and preferably between 5 and 20%,
- The compression zone and extrusion of the third part is formed by a die comprising at least one longitudinally displaceable insert and determining with the end of each single-screw, an adjustable air gap.

Other features and advantages of the invention will become apparent from the following description, made with reference to the accompanying drawings, in which:
FIG. 1 is a schematic sectional view in a vertical plane passing through the axis of a screw of an extraction installation according to the invention,
FIG. 2 is a schematic cross-sectional view of the extraction plant according to the invention,
FIG. 3 is a sectional view along the line 3-3 of FIG. 2
FIG. 4 is a sectional view along the line 4-4 of FIG. 2.

 FIGS. 1 and 2 diagrammatically show an installation for the continuous extraction of a liquid contained in a raw material, such as for example an oleaginous or oléoprotéagineuse material and in particular citrus fruits, vegetables or algae.

 This extraction installation consists of an extrusion machine generally designated by the reference 1 and which comprises three parts, respectively A, B and C.

 The extrusion machine 1 is fed at its upstream end of raw material through an orifice 2 connected to a feed hopper 3 which itself is fed with raw material through a storage hopper. 4 and a metering device 5, of the weight or volumetric type.

 The first part A of the extrusion machine 1 comprises two co-rotating and co-penetrating screws, respectively 10a and lob, driven in rotation about parallel axes, respectively 11a and 11b, inside a first sheath 12.

 The screws 10a and lob are rotated by an assembly, not shown, consisting of a motor, a geared motor and a gearbox.

 As shown in Figs. 1 and 2, the screws 10a and 10b are provided with helical threads that mesh with each other, and the inner wall of the sleeve 12 has two intersecting bores, respectively 12a and 12b, of inner diameter slightly greater than the outer diameter of the threads of the screw 10a and 10b.

 These threads are nested within each other and the two screws 10a and 10b are driven at the same rotational speed and in the same direction so that the two screws 10a and 10b are identical, the threads being simply offset by compared to others.

 As shown in FIG. 3, the screws 10a and 10b are advantageously constituted by splined shafts, respectively 13a and 13b, on which sections of screws are mounted.

 The inner bore of each of these sections is provided with splines corresponding to those of the spline shaft and the outer portion is provided with helical threads whose pitch differs according to the section considered for the transport and treatment of the raw material.

 As a result, it is possible to have a large number of sections making it possible to vary the pitch, the depth, the number of threads and the length of each treatment zone.

 Thus, the first part A of the extrusion machine 1 consists of several successive zones each corresponding to a particular phase of the extraction process according to the invention.

As shown in Figs. 1 and 2, the first part A of the extrusion machine 1 comprises:
an area A1 for introducing and transporting the material,
a first zone A2 for mixing and cooking the material,
at least one pressing and filtration zone A3 for recovering part of the liquid contained in said material,
at least one zone A4 for compressing and shearing the material,
and a zone A5 for kneading and cooking said material.

 In the first zone A1 for introducing and transporting the material, the screws 10a and 10b comprise threads 20 with a large pitch so as to ensure the transfer of the material introduced through the opening 2, which opens widely on both screw 10a and 10b for distributing said material in the threads 20.

 This material is therefore immediately transported downstream of the extrusion machine 1.

 In the zone A2 of the first part A of the extrusion machine 1, the screws 10a and 10b are provided with threads 21 with a wide pitch to ensure kneading of the material.

 In this zone A2, the sleeve 12 is provided with heating means 14 constituted by a circulation circuit for a heat transfer fluid or by an electric heating element, for example by induction.

 These heating means 14 make it possible to bake the material at a temperature of between 90 and 1500.degree.

 In the zone A3 for pressing and filtration, the screws 10a and 10b are provided with threads 22 with a tight pitch in order to carry out a pressing of the material to recover the liquid contained in this material.

 For this purpose, the sheath 12 is provided with a filtering surface formed with holes 15 distributed over a portion of the periphery of said sheath 12, as shown in FIG. 3.

 In the zone A4 of compressing and shearing the material, the screws 10a and 10b are provided with counter-threads 23, that is to say of threads with inverted pitch which comprise openings 24 extending radially from the axis of the screw to the periphery of the net and regularly distributed around the axis.

 In this way, it controls the passage of a controlled flow of material downstream which determines a braking at the area A4 and, therefore, a compression in the upstream part of the extrusion machine.

 This results in an effect of mixing and intense shearing of the material.

 Finally, in the zone As, the screws 10a and 10b are provided with threads 25 with tight pitch and against threads 26, that is, threads with an inverted pitch having openings 27 extending radially from the axis of the screw to the periphery of the net and distributed regularly around the axis.

 In this zone A5, the sleeve 12 is provided with heating means 16 constituted by a circulation circuit of a heat transfer fluid or by an electric heating element, for example by induction.

 These heating means 16 allow, in the zone A5, to achieve a firing of the material at a temperature between 90 and 1500C.

 As shown in the figures, the second part B of the extrusion machine 1 is formed of two co-rotating mono-screws, respectively 30a and 30b, carried by parallel axes, respectively 31a and 3lob, integral axes lla and ilb screws 10a and 10b of the first part A of the extrusion machine 1.

 The screws 30a and 30b are rotated inside a second elongated sheath 40 provided with bores, 40a and 40b respectively, for each of the screws 30a and 30b.

 These bores 40a and 40b are independent and communicate with each other by a slot 32 allowing the material to pass between the two bores 40a and 40b of the sleeve 40.

 In the second part B of the extrusion machine 1, the screws 30a and 30b determine at least one zone B1 and B2 for pressing and filtration to recover the liquid from the material leaving the first part A of said extrusion machine 1.

 In the exemplary embodiment shown in FIGS. 1 and 2, this zone is formed of a first zone B1 in which the screws 30a and 30b are provided with nets 33 with a wide pitch and a zone B2 in which the screws 30a and 30b are provided with threads 34 with a tight pitch.

 Thus, in the pressing and filtering zones B1 and B2, each single-screw 30a and 30b has a compression ratio of less than 8 and preferably of between 1.1 and 4.

 According to a first embodiment shown in Figs. 1 and 2, in the areas B1 and B2 of pressing and filtration, the pitch of the single-screw 30a and 30b is tightened in the direction of flow of the material and the diameter of the axis 31a and 31b of each of said single-screw is constant.

 According to a variant, in the zones B1 and B2 of pressing and filtration, the pitch of the single-screws 30a and 30b is constant while the diameter of the axis 31a and 31b of each of said single-screws increases in the direction of flow of the material.

 In this zone, the second sleeve 40 has a filtering surface formed by holes 41 distributed over a portion of the periphery of said sleeve 40.

 Preferably, the pressing and filtering zone comprises a first series of holes 41 with a diameter of 0.5rem over a length of 55mm, a second series of holes with a diameter of 0.6mm over a length of 70mn and a third series of holes. 41 holes diameter of 0.8mn over a length of 90mm.

 Each of these series of holes 41 is characterized by its percentage of transparency.

 This transparency is defined as the ratio of the area generated by the holes to the total internal surface of a bore.

 In the present case, there is a transparency respectively of 10.7, 7.6 and 9% for a bore diameter of 45.5mm.

 Finally, the third part C of the extrusion machine 1 determines a zone C1 for compressing and extruding the dry residue of said material.

 This zone C1 is formed by a die 50 which comprises an insert 51 cooperating with the tip of each mono-screw 30a and 30b and determining an air gap 52 and an outlet channel 53 of the dry residue.

 The air gap 52 is adjustable by the insert 51 which is mounted displaceable longitudinally by appropriate means, not shown.

In the first part A of the extrusion machine 1, one performs
a first kneading and a first firing of the material,
at least one pressing and a filtration of the material to recover a part of the liquid contained in said material,
at least one compression and shearing of the material,
and a second kneading and a second firing of this material.

 In the second part B of the extrusion machine 1, at least one pressing and a filtration is carried out to recover the liquid still contained in the material leaving the first part A and in the third part C of said extrusion machine 1 the dry residue of the material is compressed and extruded.

 The residual liquid content in the dry residue leaving the extrusion machine is less than 15%.

 The operating parameters of implementation of the extrusion machine 1 according to the invention vary depending on the type of the material.

 These parameters determine the effectiveness of the solid / liquid separation, ie the efficiency of the extraction of the liquid.

 As a parameter, it is possible to retain the feed rate of the material, the configuration of the screws, the rotational speed of the screws, the configuration of the die, the filtering surfaces provided in the sleeves and the temperature of the heating means.

 the feed rate of the material affects the fill rate of the screws and this flow rate is controlled, for example, by the weight or volumetric feeder.

 Moreover, the configuration of the screws determines the state of transformation of the material and consequently the physical and physicochemical characteristics of the product during the different phases of treatment.

 Especially in the pressing and filtration zones, the configuration of the mono-screws influences the pressing dynamics and the compression ratio.

 Thus, with the rotation of the screws, the configuration of these screws sets the pressing ratio which is equal to the ratio of the amount of material to be pressed contained in a thread on the time required to perform a complete rotation of this step.

 The rotational speed of the screws determines, for a given flow rate, the residence time of the material within the zone considered which contributes to the conditioning of this material at the inlet of the pressing and filtration zone.

 On the other hand, the configuration of the die is transcribed by three elements, the gap, the insert and the taper of the tips of the single-screw.

 The air gap makes it possible to create a more or less important material retention at the level of the die.

 The air gap therefore acts on the residence time of the material and the insert allows to recreate a material retention downstream of this gap.

 To change the flow of the material at the outlet of the die, it is possible to vary the taper of the tips of the single-screw, the diameter and / or the length of the discharge channel of the insert.

 This element therefore makes it possible to act on the residence time of the material, but also on the pressing time of this material within the gap and on its degree of crushing.

 The conicity of the points of the mono-screws makes it possible to modify the flow in the air gap and to modify the pressure in the die.

 The pressing and filtering zone, by its geometric characteristics, influences the quantities of liquid extracted and the liquid content of the dry residue at the outlet of the extrusion machine.

 The temperature of the heating means makes it possible to regulate the heat losses or to heat the material, also causing a change in the flow within the extrusion machine, as well as within the die.

 Various tests have been carried out with an installation according to the invention and the results of these tests are given below, by way of illustration and in no way limiting.

 Example.

 Tests have been carried out on rapeseed and pure almonds of rapeseed.

The extrusion machine has the following configuration, for a bore diameter of 55.5mm in the first part A provided with co-rotating and co-penetrating screws and a bore diameter of 45.5mn in the second part B provided with mono-screw.

<tb><SEP> PART <SEP> A <SEP> PART <SEP> B <SEP>
<tb><SEP> ZONES <SEP> A1-A2 <SEP> A3 <SEP> A4 <SEP> A5 <SEP> B1 <SEP> B2 <SEP>
<tb> LONG <SEP> JR <SEP> 600 <SEP> 100 <SEP> 100 <SEP> 50 <SEP> 50 <SEP> 100 <SEP> 250
<tb> DES <SEP> VIS
<tb><SEP> NOT <SEP><SEP> 50 <SEP> 35 <SEP> CF <SEP> 25 <SEP> CF <SEP> 35 <SEP> 25
<tb> VIS
<Tb>

TABLE 1
The operating parameters are as follows:
- feed rate: 70 kg / h
- speed of rotation of the screws: 35 rpm
- gap: 1.2mm
- dimensions of the insert
diameter of the evacuation channel: 16mm
length of drain channel: 6mm
- conicity of the points of single-screw: 1200
temperature of the heating means: 1500C
- not counter-nets (CF): 15mm
- the mechanical and thermal powers
consumed are each about 25kW / t.

 The extraction yields are between 81 and 85%.

 The solids content in the oil collected is less than 10%.

 The residual oil content in the cake is about 12%.

 SxeXple 2.

 Trials were carried out on dietary sunflower seeds.

The extrusion machine has the configuration shown in the table below for a bore diameter of 55.5mm in zone A with co-rotating and co-penetrating screws and a bore diameter of 45 mm. , 5mn in part B with mono-screws.

<Tb>

<SEP> PART <SEP> A <SEP> PART <SEP> B
<tb><SEP> ZONES <SEP> A1-A2 <SEP> A3 <SEP> A4 <SEP> As <SEP> B1 <SEP> B2 <SEP>
<tb><SEP> LENGTH <SEP> 600 <SEP> 100 <SEP> 50 <SEP> 50 <SEP> 50 <SEP> 100 <SEP> 250
<tb><SEP> OF <SEP> SCREWS
<tb> NOT <SEP><SEP> 50 <SEP> 35 <SEP> CF <SEP> 25 <SEP> CF <SEP> 35 <SEP> 25
<tb><SEP> VIS
<Tb>
TABLE 2
The operating parameters are as follows:
- feed rate: 70kg / h
- speed of rotation of the screws: 40 rpm
- air gap: 1, lmm
- dimensions of the insert
diameter of the evacuation channel: 6mm
length of drain channel: 6mm
- conicity of the points of single-screw: 1200
- temperature of the heating means: 1200C
- the mechanical and thermal powers
consumed are respectively 5kW / t and
20kW / t.

 The extraction yields are between 85 and 90%.

 The solids content in the oil collected is less than 10%.

 The residual oil content in the cake is about 15%.

Example3
Extraction tests were carried out on shelled castor beans.

The extrusion machine has the configuration indicated in the table below, the other parameters being identical to those of Example 1.

<Tb>

<SEP> PART <SEP> A <SEP> PART <SEP> B
<tb><SEP> ZONES <SEP> A1-A2 <SEP> A3 <SEP> A4 <SEP> A5 <SEP> B1 <SEP> B2
<tb> LENGTH <SEP> 600 <SEP> 100 <SEP> 50 <SEP> 150 <SEP> 100 <SEP> 250
<tb> DES <SEP> VIS
<tb><SEP> NOT <SEP><SEP> 50 <SEP> 35 <SEP> CF <SEP> 25 <SEP> 35 <SEP> 25
<tb><SEP> VIS
<Tb>
TABLE 3
The operating parameters are as follows: - feed rate 15kg / h - speed of rotation of the screws 30tr / min - air gap: mm - dimensions of the insert:
diameter of the evacuation channel: ltrrn
evacuation channel length: 6mm - taper of single-screw tips: 600 - temperature of heating means: 900C - mechanical and thermal powers
consumed are approximately
35kW / t and 15kW / t.

The extraction yields are between 85 and 90%.

 The solids content in the oil collected is about 10%.

 The residual oil content in the cake is less than 15%.

 The extrusion machine according to the invention may comprise intermediate introductions of raw material in order to introduce fresh raw material, or additives or adjuvants, for example water.

 Furthermore, the extrusion machine according to the invention can be used alone, in single pressure processes or upstream of a solvent extraction unit or in pre-pressure processes.

 The single pressure can be applied in the case of marginal crops such as castor or flax which requires relatively low pressing capacity, and for which the establishment of solvent extraction unit is not always desirable given its cost.

 Under these conditions, this extrusion machine can be installed to replace all traditional equipment either in small decentralized units or in large pressing units for specific work.

 In pre-pressure, the extrusion machine can be installed in large pressing units, only equipment, upstream of the solvent extraction unit.

 Tests carried out with an extraction plant according to the invention on oleaginous seeds, on algae, on citrus fruit, on plants show that the extrusion machine can be used as a single pressing tool, allowing the solid separation. liquid.

 The extrusion machine according to the invention offers multiple advantages.

 These include energy and material savings, thanks to the integration into a single machine of several thermomechanical transformation processes.

 For the same capacity of units and replacing traditional equipment, the extrusion machine saves energy consumption up to 50%.

 Another advantage lies in the integration within the same equipment functions of mixing, grinding, cooking and pressing.

 This gives the extrusion machine a simplicity of installation and operation, which reduces costs.

 The total control of the extrusion machine can be manual or computer assisted. The modifications of the operating parameters are made with very short response times.

 Thus, when changing the characteristics of the raw material, one can very quickly obtain high extraction performance.

 Although very compact, the extrusion machine is a modular and versatile equipment. It allows, by an easy disassembly of its constituent elements, to modify at will the configuration of the screws and other elements. This allows the treatment of different types of materials with short time of modification of the equipment and without that it induces very important investments, nor long time of imnobi- lisation.

 With regard to the products obtained at the exit of the extrusion machine, ie the liquid like oil or a solution in aqueous suspension and the solid comne the cake, the analyzes show that they are of good quality.

 The cake is produced in the form of pellets and exhibits good percolation ability in a subsequent solvent extraction phase.

 Thus, in addition to other equipment, the extrusion machine can also replace the use of expanders on certain production lines.

 The cake can be used directly on the production site itself.

Claims (12)

CLAIMS.  1. A method for continuously extracting a liquid contained in a raw material, such as an oleaginous or oléoprotéagineuse material, characterized in that  in a first part A of an extrusion machine (1) comprising two co-rotating and co-penetrating screws (10a, 10b) driven in rotation about parallel axes (11a, 11b) inside a first elongate sheath (12) provided with secant bores (12a, 12b), the raw material is introduced and  a first kneading and a first firing of the material,  at least one pressing and a filtration of the material to recover a part of the liquid contained in said material,  at least one compression and shearing of the material,  a second mixing and a second cooking of the material,  in a second part B of said extrusion machine (1) comprising two corotative single screws (30a, 30b) carried by parallel axes (31a, 31b) integral with the axes (11a, 11b) of the screws (lova, lOb); ) of the first part A and driven in rotation inside a second elongated sheath (40) provided with bores (40a, 40b) independent and communicating with one another by a light (32), at least one pressing is carried out and a filtration for recovering the liquid from the material leaving the first part A of the extrusion machine (1),  and in a third part C of said extrusion machine (1), the dry residue of the material is compressed and extruded.  2. Method according to claim 1, characterized in that the first and second firing are carried out at a temperature between 90 and 1500C.  3. Method according to claim 1, characterized in that the residual liquid content in the dry residue exiting the extrusion machine (1) is less than 15%.  4. Installation for continuously extracting a liquid contained in a raw material, for carrying out the method according to any one of claims 1 to 3, characterized in that it comprises an extrusion machine (1 ) with  a first part A formed of two co-rotating and co-penetrating screws (10a, 10b) driven in rotation about parallel axes (11a, 11b) inside a first elongate sheath (12) provided with bores (12a, 12b) intersecting and determining  an area A1 for introducing and transporting the material,  a first zone A2 for mixing and cooking the material,  at least one pressing and filtering zone A3 for recovering part of the liquid contained in said material,  at least one zone A4 for compressing and shearing the material,  a zone A5 for mixing and cooking the material,  a second part B formed of two co-rotating single-screw coils (30a, 30b) borne by parallel axes (31a, 31b) integral with the axes (11a, 11b) of the screws (10a, 10b) of the first part A and driven by rotation inside a second elongated sleeve (40) provided with bores (40a, 40b) independent and communicating with each other by a light (32) and determining at least one zone B1 and B2 for pressing and filtering to recover the liquid of the material leaving the first part A of the extrusion machine (1),  and a third portion C determining a zone C1 for compressing and extruding the dry residue of said material.  5. Installation according to claim 4, characterized in that the screws (lova, lOb) of the first part A have, in the transport zones, kneading and cooking and pressing and filtration, a variable pitch.  6. Installation according to claim 4, characterized in that the first sleeve (12) comprises, in said pressing and filtering zone, a filtering surface formed with holes (15) distributed over a portion of the periphery of said sleeve (12). .  8. Installation according to claim 4, characterized in that each single screw (30a, 30b) in the pressing and filtering zone of the second part B has a compression ratio of less than 8 and preferably of between 1.1 and 4.  9. Installation according to claims 4 or 8, characterized in that, in the pressing zone and a filtration of the second part B, the pitch of the single-screw (30a, 30b) is constant and the diameter of the axis ( 31a, 31b) of each of said single screws (30a, 30b) increases in the direction of flow of the material.  10. Installation according to claim 4 or 8, characterized in that, in the pressing and filtering zone of the second part B, the pitch of the single-screw (30a, 30b) tapers progressively in the flow direction of the material and the diameter of the axis (31a, 31b) of each of said single-screw (30a, 30b) is constant.  11. Installation according to claim 4, characterized in that the second sleeve (40) comprises, in said pressing and filtering zone, a filtering surface formed with holes (41) distributed over a portion of the periphery of said sleeve.  12. Installation according to claim 11, characterized in that the filtering surface has a transparency of between 3 and 50% and preferably between 5 and 20%.  13. Installation according to claim 4, characterized in that the area of compression and extrusion of the third part C is formed by a die (50) comprising at least one insert (51) movable longitudinally and determining with the end of each mono-screw (30a, 30b) an air gap (52) adjustable.