EP0088687A1 - Screw filtering press for extracting soluble matter contained in vegetal matter and vegetal soggy by-products - Google Patents

Abstract

Screw filtering press with multiple stages for the extraction of juice from protein-containing plants, and carbohydrate-containing plants, comprising at least three press bodies of different design in series and in which simple adjustment of the speed of rotation of the screws in each body relative to one another makes it possible for near optimum separation conditions to be achieved, so as to obtain a solid phase whose dryness is greater than 45-50% and a juice containing less than 1 to 2% of dry material in suspension, irrespective of the material treated. <IMAGE>

Description

The present invention relates to a process for continuously expressing most of the water of constitution and soluble matter of different wet plant products, while minimizing the proportion of insoluble matter passing through the juice, by using a versatile screw press.

The usual helical screw presses are generally designed to operate on a single type of raw material, for example protein plants such as alfalfa or carbohydrate plants such as beets or fruits. In addition, the processed raw materials are generally not very ground, rather reduced to shreds or husks for plant materials such as roots, tubers, fruits; or exploded summarily by the use of rotor devices rotating at high speed. This conditioning, which can be assimilated to a reduction in small strands or small pieces, is carried out in order to obtain a production of juice containing little insoluble matter in suspension. In fact, a thorough grinding of the raw materials, fibrous or not, entails, with the use of the usual helical screw presses, an extrusion of part of the raw material through the filtering grid.

These screw presses therefore do a job of extracting the juice through the material, associated with a laceration causing a partial destructuring of the material and an extraction of part of the extractable juices contained.

These presses generally comprise a screw, or two parallel screws, or two successive screws, the first of which has the function of a force-feeding screw.

The filter press object of the present invention allows the extraction of juice containing a minimum of insoluble matter, from finely ground raw materials, and by obtaining cake with a much higher dryness than that obtained with the presses. usual, and this for materials raw materials with very different characteristics such as protein plants and carbohydrate plants, the latter having an insoluble dry matter content which can be approximately 10% and approximately 3% respectively, and plant by-products from the food industry containing 60 to 95% water.

The filter press according to the invention makes it possible to obtain, from protein plants, oil cakes whose dryness is greater than 45% of dry matter and juices containing less than 1% of dry matter in suspension, and from carbohydrate plants, oil cakes with a dryness of more than 50% dry matter and juices containing less than 2% dry matter in suspension.

The raw materials are, before introduction into the press, very finely ground by devices ensuring the bursting of most of the cells, by convex surfaces under pressure between which the material passes, with or without impact contact between the convex surfaces (use of preconditioning choppers, flatteners, ball mills ...).

Fragile components such as leaves, young stems for protein plants or roots or tubers, can be destructured to the level of the constituent cell, harder components, such as less young stems or parts of fibrous plants can be destructured to at strands of length less than one or two centimeters for a current section of stem.

Depending on the raw materials to be treated and the destination of the products, these may or may not receive thermal and chemical and / or enzymatic pretreatment after possible incorporation of fibrous materials, all of these possible pretreatments having the object of further improving the yield of the separation of the liquid and solid phases and of obtaining maximum purity of the juices (minimum nrssence of insoluble or coagulable materials).

The filter press according to the invention makes it possible to adapt the time and pressure parameters to very diverse products to be treated, in order to avoid in particular that a premature or too high pressure causes a partial extrusion of the solid material through the filter.

This result is obtained by breaking down the filtration and pressure phases, by carrying out the operation in three (or more) successive filtration and pressure screws.

The apparatus according to the invention is therefore a multi-stage screw filter press with at least three bodies of different design, placed in series, the pressed material passing successively from one to the other, and the speed of screw rotation being adjustable in each press body.

The number of press bodies and the layout of the section variations of the different press bodies are determined, according to the different products to be treated, so that it is not necessary to replace one or more screws to treat a given product , the terminal portion without a turn of the last press body being the only interchangeable.

The rotational speeds of the screws are adjusted each and with respect to each other, so that, taking into account the pressure level at the inlet of the raw material and the taper of the terminal part of the latter body (which can be modified by replacing this part), we can approach, for a given raw material flow, the optimal conditions for separation of the liquid and solid phases. The adjustments are made, for a determined flow rate of raw material introduced into the first press body, by progressive reduction of each of the rotational speeds of the screws of the different bodies, ensuring relative flow rates between two successive bodies so that the downstream screw acts as a brake on the upstream body and so that one can act on the pressure levels at the inlet of each screw body.

• La figure 1 représente un filtre-presse selon l'invention comportant trois corps de presse 1, 2 et 3 et une partie terminale sans spire 32.
• La figure 2 représente une coupe transversale d'un corps de presse montrant la grille filtrante.
• La figure 3 donne un exemple de l'évolution des sections transversales S des parties filtrantes de trois corps de vis en fonction de leurs longueurs 1 considérées mises bout à bout.
• La figure 4 traduit, pour l'exemple de la figure 3 et pour des vitesses de rotation déterminées, la variation du débit volumique D engendré pour chaque section filtrante, compte tenu du fait que la matière a une consistance liquide sur la première partie du corps 1 et que les jus s'écoulent dans cette partie sans augmentation de pression par la vis du corps 1, mais par l'action de la pression d'admission de la matière première.
• La figure 5 exprime l'évolution des pressions P existant dans chacune des sections, dans le cas particulier d'une matière première déterminée et des appareils et réglages des figures 3 et 4.
• La figure 6 représente, pour un produit déterminé, la courbe d'évolution idéale du volume V du produit restant dans la vis, en fonction de sa position dans le filtre-presse, pour obtenir une siccité de tourteau maximum associée à la plus grande pureté des jus.

In the case of carbohydrate plants, the efficiency of extracting carbohydrates from juices can be increased by the fact that one or more of the latter press bodies include means for injecting cold or hot water directly, without introducing air at the same time.

• FIG. 1 represents a filter press according to the invention comprising three press bodies 1, 2 and 3 and an end portion without a coil 32.
• Figure 2 shows a cross section of a press body showing the filter grid.
• FIG. 3 gives an example of the evolution of the cross sections S of the filtering parts of three screw bodies as a function of their lengths 1 considered placed end to end.
• FIG. 4 translates, for the example of FIG. 3 and for determined rotational speeds, the variation in the volume flow rate D generated for each filtering section, taking into account the fact that the material has a liquid consistency on the first part of the body 1 and that the juices flow into this part without increasing pressure by the screw of the body 1, but by the action of the inlet pressure of the raw material.
• FIG. 5 expresses the evolution of the pressures P existing in each of the sections, in the particular case of a determined raw material and of the apparatuses and adjustments of FIGS. 3 and 4.
• FIG. 6 represents, for a given product, the ideal evolution curve of the volume V of the product remaining in the screw, as a function of its position in the filter press, in order to obtain a maximum cake dryness associated with the highest purity juices.

• . un dispositif d'alimentation sous pression réglable et constante du premier corps de la presse. Ce dispositif est constitué par une pompe à vis et membrane, volumétrique, pour liquides chargés, selon principe de la pompe moineau. Ce dispositif introduit la matière première par l'orifice II dans le premier corps de presse ;
• . un premier corps de presse 1 constitué par une grille filtrante cylindrique 12 et nn corps de vis intérieur tournant 13. Ce premier corps de presse réalise la fonction de filtration primaire (section 14) des jus libérés dans la matière première broyée et un préessorage réduit de la matière (section 15).
  • - la grille filtrante 12 est représentée dans la figure 2 et est constituée de barreaux 123 longitudinaux non colmatants, de section transversale polygonale, avec largeur des fentes 121 côté intérieur de 0,1 à 0,5 mm et une largeur de fente 122, côté extérieur légèrement supérieur, afin d'éviter le coincement éventuel de produits dans les fentes ;
  • - la vis intérieure tournante V₁ comprend une première partie 14 sous forme de rubans, afin que la matière se répartisse régulièrement sur l'ensemble de la surface filtrante correspondante et que l'efficacité de filtration soit maximum sur cette surface, sous une pression donnée ;
  • - la deuxième partie 15 de la vis comprend une spire pleine partant du tube central ;
  • - selon les débits des presses et les produits à traiter le jeu 125 entre grille et vis est fixé entre 2 et 10 mm ;
  • - la grille comprend, dans la partie 15 avec vis à filet plein, des fers plats 124 servant à guider la matière et à s'opposer à sa rotation avec la vis ;
  • - la grille 12 peut être soumise ou non, selon la nature des produits, à une vibration à faible fréquence permettant d'augmenter très sensiblement le débit spécifique de la grille ;
  • - la vitesse de la vis V₁ est réglable.
• . Un deuxième corps de presse 2 disposé en série en aval du premier corps de presse, soit en dessous du premier corps, soit en prolongement de celui-ci.

The press according to the invention is shown diagrammatically in FIG. 1 and comprises the following main members:

• . a device for supplying adjustable and constant pressure to the first body of the press. This device consists of a screw and diaphragm pump, volumetric, for charged liquids, according to the sparrow pump principle. This device introduces the raw material through orifice II into the first press body;
• . a first press body 1 constituted by a cylindrical filter grid 12 and a rotating internal screw body 13. This first press body performs the primary filtration function (section 14) of the juices released into the ground raw material and a reduced pre-spin of the material (section 15).
  • - the filter grid 12 is shown in FIG. 2 and is made up of longitudinal bars 123 non-clogging, of polygonal cross-section, with width of the slots 121 on the inner side from 0.1 to 0.5 mm and a width of the slot 122, slightly higher on the outer side, in order to avoid possible jamming of products in the slots;
  • the rotating internal screw V ₁ comprises a first part 14 in the form of tapes, so that the material is distributed evenly over the whole of the corresponding filtering surface and that the filtration efficiency is maximum on this surface, under a given pressure ;
  • - The second part 15 of the screw comprises a full turn starting from the central tube;
  • - depending on the flow rates of the presses and the products to be treated, the clearance 125 between grid and screw is fixed between 2 and 10 mm;
  • - The grid comprises, in part 15 with full thread screws, flat irons 124 serving to guide the material and to oppose its rotation with the screw;
  • - the grid 12 may or may not be subjected, depending on the nature of the products, to a low frequency vibration making it possible to very significantly increase the specific flow rate of the grid;
  • - the speed of the screw V ₁ is adjustable.
• . A second press body 2 arranged in series downstream of the first press body, either below the first body, or as an extension of the latter.

• - la grille cylindrique 21 filtrante en périphérie, est de même conception générale que la grille filtrante 12, avec une largeur de fente de 0,1 à 0,2 mm, et la présence de fers plats sur la totalité de la longueur de la grille, à raison d'un nombre variable selon le diamètre de la grille et égal à 4 au minimum ;
• - la vis tournante V₂ à l'intérieur de la grille 21 comprend :
  • . un axe conique de diamètre croissant de l'entrée vers la sortie, déterminant une variation de section transversale débitante adaptée à la moyenne des caractéristiques des produits à traiter ;
  • . une spire pleine enroulée sur l'axe conique, ayant un pas compris entre 0,2 et 0,4 fois le diamètre extérieur du cylindre engendré par la vis. L'extérieur de la spire engendre une surface cylindrique formant un jeu par rapport à la surface intérieure de la grille filtrante de 1 à 2 mm en plus de l'épaisseur des fers plats ou barrettes.
  • . La vitesse de la vis V_z est réglable de façon a permettre le réglage optimum des vitesses différentielles entre les vis V₁ et V₂₉ et ainsi assurer une progressivité réglable et maîtrisée de la vitesse d'extraction des jus entre la partie d'extrémité aval de V₁ et la zone d'entrée de V₂.

It performs the first pressure function which makes it possible to carry out a first spin of the material, following the pre-spin carried out in the end part of the first press body.

• - the cylindrical filter grid 21 at the periphery, is of the same general design as the filter grid 12, with a slit width of 0.1 to 0.2 mm, and the presence of flat bars over the entire length of the grid , at the rate of a variable number depending on the diameter of the grid and equal to at least 4;
• - the rotating screw V ₂ inside the grid 21 includes:
  • . a conical axis of increasing diameter from the inlet to the outlet, determining a variation in flow cross section adapted to the average of the characteristics of the products to be treated;
  • . a full turn wound on the conical axis, having a pitch of between 0.2 and 0.4 times the outside diameter of the cylinder generated by the screw. The outside of the turn generates a cylindrical surface forming a clearance with respect to the inside surface of the filter grid by 1 to 2 mm in addition to the thickness of the flat bars or bars.
  • . The speed of the screw V _z is adjustable so as to allow optimum adjustment of the differential speeds between the screws V ₁ and V ₂₉ and thus ensuring an adjustable and controlled progressiveness of the speed of extraction of the juices between the downstream end part of V ₁ and the input area of V ₂ .

A third press body 3, arranged in series downstream of the second press body, either below the second press body, or in extension thereof.

• - La zone d'entrée est un corps cylindrique fermé situé en amont de la dernière partie filtrante. Son volume est approprié au temps de migration de l'eau éventuellement ajoutée. L'eau éventuelle est ajoutée par injecteurs disposés sur une rampe circulaire à la périphérie du corps cylindrique, et introduite sons pression.

It performs the second pressure function, which ensures a second spin of the material and has an inlet zone 31 allowing a possible injection of hot water in order to improve the extraction of soluble substances at this stage in the matter.

• - The inlet zone is a closed cylindrical body located upstream of the last filtering part. Its volume is appropriate for the migration time of any water added. Any water is added by injectors placed on a circular ramp at the periphery of the cylindrical body, and introduced under pressure.

• - la grille filtrante cylindrique 3 est de conception identique à la grille 21, mais elle comporte, à son extrémité aval, une partie 32 dépassant l'extrémité des spires de vis et assurant une finition d'essorage à pression élevée de la matière.
• - La vis tournante V à l'intérieur de la grille comprend :
  • . une zone d'entrée dans la partie d'injection éventuelle d'eau, décrite ci-avant ;
  • . une zone conique de conception similaire à la vis V₂, avec conicité plus faible que celle de V₂. La dernière partie 32 de ce cône est sans spire, de façon à assurer la formation d'un bouchon de produit effectuant une répartition régulière de la pression exercée par le produit sur le pourtour de la partie terminale du troisième corps de presse. L'épaisseur de produit entre le rotor et la grille filtrante est, dans cette partie, inférieure à 5 cm.
  • . La vitesse de rotation de la vis V₃ est réglable de façon à permettre le réglage optimum de la vitesse , différentielle par rapport à V₂, et ainsi assurer la maîtrise de la progressivité d'extraction des jus dans la dernière phase de pression.

The central rotating cylindrical rotor is integral with the screw V ₃ . It is equipped with inclined arm elements ensuring the regular advancement of the subject;

• - The cylindrical filter grid 3 is of identical design to the grid 21, but it comprises, at its downstream end, a part 32 protruding from the end of the screw turns and ensuring a wiping finish at high pressure of the material.
• - The rotating screw V inside the grid includes:
  • . an entry zone into the possible water injection part, described above;
  • . a conical zone similar in design to the screw V ₂ , with a smaller conicity than that of V ₂ . The last part 32 of this cone is without a turn, so as to ensure the formation of a product plug effecting a regular distribution of the pressure exerted by the product on the periphery of the terminal part of the third press body. The thickness of product between the rotor and the filter grid is, in this part, less than 5 cm.
  • . The speed of rotation of the screw V ₃ is adjustable so as to allow optimum adjustment of the speed, differential with respect to V ₂ , and thus ensuring control of the progressiveness of juice extraction in the last pressure phase.

According to a variant of the filter press according to the invention, the last body of the screw may have local variations in the pitch of the screw or in the cross section of the screw, which generate a variation in the pressure by successive peaks, making it possible to improve the speed of juice extraction.

The juices are evacuated outside the press by gravity flow and collected separately for each press body, with a view to possible treatment different from all or part of these.

The filter press according to the invention thus makes it possible to process consecutively, with the maximum separation efficiency. solid and liquid phases, very different raw materials, without replacing any of the constituent elements.

Claims (12)

1. Multi-stage screw filter press for extracting juices from protein and carbohydrate plants, and plant by-products containing 60 to 95% of water, characterized in that it comprises at least three press body con- tion that different ^p, placed in series, the number of bodies and tracédæ section of variations of different body being determined so that, by simple adjustment of the rotational speed of the screw in each press body and one with respect to the other, after having fixed, as a function of the raw material, the inlet pressure thereof and the conicity of the interchangeable end part of the last body, we approach the optimal conditions of separation and obtains a solid phase of dryness greater than 45-50% and a juice containing less than 1 to 2% of dry matter in suspension, whatever the raw material treated, and without the need to replace one or more screw. 2. Filter press according to claim 1, characterized in that one or more of the last press bodies comprises means making it possible to inject water directly into the pressed product, without concomitant introduction of air. 3. Filter press according to one of claims 1 and 2, characterized in that the first press body, ensuring primary filtration of the juices released by the finely ground raw material and a pre-spinning of the material, comprises a rotor of which the first part is a ribbon screw and the second a screw with full turns, rotating at adjustable speed in a cylindrical filtering grid with non-clogging longitudinal bars having an internal slot width of 0.1 to 0.5 mm. 4. Filter press according to claim 3, characterized in that the grid is equipped with bars opposing the rotation of the product. With the screw, the clearance to the radius between the cylinder generated by the rotating screw and the inside diameter of the bars being from 2 to 10 mm. 5. Filter press according to one of claims 1 to 4, characterized in that the first body is supplied under adjustable pressure. 6. Filter press according to one of claims 1 to 6, characterized in that it comprises, after the first body, at least two other pressing bodies in series, of similar design, with conical screw with adjustable speed for each body, and filter grid similar to that of the first body, the clearance between the diameter of the cylinder generated by the rotating screw and the internal diameter of the bars of the grid being 1 to 2 mm. 7. Filter press according to claim 6, characterized in that in each of the bodies the coil wound around the conical rotor has a pitch equal to 0.2 - 0.4 times the diameter of the outer cylinder generated by the rotation of the screw . 8. Filter press according to one of claims 1 to 7, characterized in that, in the last part of the last press body, the conical rotor is equipped with an extension without turns ensuring the formation of a product plug whose thickness between the rotor and the filter grid is less than 5 cm. 9. Filter press according to one of claims 1 to 8, characterized in that the filter grid is provided with a device for making it vibrate at low frequency. 10. Filter press according to one of claims 1 to 9, characterized in that the last body of the screw may comprise local variations in the pitch of the screw or in the cross section of the screw which generate a variation in the pressure by peaks successive. 11. Filter press according to one of claims 1 to 10, characterized in that the juices are discharged outside the press by gravity flow and collected separately for each press body, for possible treatments different from all or part of these. 12. Filter press according to one of claims 1 and 2, characterized in that the water injection zone in one of the last press bodies is equipped with a device for incorporating water and homogenization of the product by fixed circular ramp, and arm rotating integrally with the rotor of the screw.

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