FR2522586A1 - MULTI-STAGE SCREW PRESS FILTER FOR EXTRACTING AND FILTERING SOLUBLE MATERIALS CONTAINED IN PLANT MATERIALS - Google Patents

Abstract

MULTI-STAGE SCREW FILTER PRESS FOR THE EXTRACTION OF JUICES FROM PROTEIN PLANTS AND CARBON PLANTS, INCLUDING AT LEAST THREE PRESS BODIES OF DIFFERENT DESIGN, IN SERIES, IN WHICH SIMPLE ADJUSTMENT OF THE ROTATION SPEED OF THE SCREWS IN EACH BODY AND ONE IN RELATION TO THE OTHER ALLOWS TO APPROACH THE OPTIMAL CONDITIONS OF SEPARATION, SO AS TO OBTAIN A SOLID PHASE OF SICCITY GREATER THAN 45-50 AND A JUICE CONTAINING LESS THAN 1 TO 2 OF DRY MATTER IN SUSPENSION, WHATEVER THE MATERIAL TREATED.

Description

Screw press filter to extract the soluble matter contained

in vegetable matter.

  The present invention relates to a method 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 juices, by the use of a poly- screw press

  valente. 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 in grates or dumplings for plant materials such as roots,

  tubers, fruits; or summarily broken down by use

  of devices with rotor 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 allow to obtain a production of juice containing little insoluble matter in suspension. pushed raw materials, fibrous or not, leads, with the use of conventional helical screw presses, 'an extrusion of part of the raw material

through the filter 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 a

  part of the extractable juices contained.

  These presses generally have a screw, or two parallel screws, or two successive screws, the first of which has a function

of force-feeding screws.

  The near-object filter of the present invention makes it possible to extract juice containing a minimum of insoluble matter, from finely ground raw materials, and by obtaining cake of much higher dryness than that obtained with presses. usual, and this for 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 Z respectively

and about 3 Z.

  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 higher than 50 Z of dry matter and juices containing less than 2 Z of dry matter

in suspension.

  The raw materials are, before introduction into the

  press, crushed very finely by devices ensuring the

  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 choppers

  preconditioners, flatteners, ball mills).

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

current rod section.

  Depending on the raw materials to be treated and the destination of the products, these may or may not receive a thermal and chemical pretreatment after possible incorporation of fibrous materials, all of these possible pretreatments having the object of further improving the yield of the separation. liquid and solid phases and to obtain maximum purity of the juices (presence

  insoluble or coagulable matter).

  The physico-chemical pretreatment of carbohydrate plants is the subject of the patent application filed on the same day as the present application under No. 82 The filter press according to the invention makes it possible to adapt the time and pressure parameters to products to be treated in a variety of ways, to avoid in particular that a premature or too high pressure causes a partial extrusion of the solid material through the filter. This is achieved by breaking down the filtration and pressure phases, performing 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 endless part of the last body

  only being 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 tone of the end portion of the latter body (which can be modified by replacing this part) we can approach, for a given raw material flow rate, 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 thus act on

  pressure levels at the inlet of each screw body.

  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.

  Figure I shows 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 body

  press 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 in

  according to 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 the juices flow into this part without increasing pressure by the screw of the body 1, but by the action of the intake pressure of

raw materials.

  FIG. 5 expresses the evolution of the pressures P existing in each of the sections, in the particular case of a material

  2 C first determined and the apparatuses and adjustments of Figures 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, to obtain a dryness

  maximum oil cake associated with the highest purity of the juices.

  The press according to the invention is shown diagrammatically in FIG. I 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 loaded liquids, according to the sparrow pump principle This device introduces the raw material through the orifice II into the first press body; a first press body 1 consisting of 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

  reduced pre-spinning of the material (section 15).

  the filter grid 12 is shown in FIG. 2 and is made up of non-clogging longitudinal bars 123, 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, c 6 slightly higher outer tee, in order to avoid possible jamming of products in the slots; the rotating inner screw V 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 115 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 the part 15 with solid 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 in

extension of it.

  It performs the first pressure function which allows a first spin of the material, following the pre-spin performed 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 rotary screw V 2 inside the grid 21 comprises: 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 creates a cylindrical surface forming a clearance with respect to the surface inside of the filter grid from I to 2 mm in addition to the thickness of the irons

dishes or bars.

  The speed of the screw V 2 is adjustable so as to

  allow optimum adjustment of differential speeds-

  them between the screws V and V 2, and thus ensure an adjustable and controlled progressiveness of the juice extraction speed between the downstream end part of V 1 and the inlet zone of V 2 A third press body 3 , arranged in series downstream of the second press body, ie below the second press body

  press, or as an extension of it.

  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 substances soluble at this stage in the material.

  The entry zone is a closed cylindrical body located upstream of the last filtering part Its volute

  is suitable for the migration time of the water,

  LEMENT ADDED Any water is added by injectors placed on a circular ramp at the periphery of the cylindrical body, and introduced under pressure. The central rotating cylindrical rotor is integral with the screw V 3 It is equipped with elements of inclined arms ensuring the regular advancement of the material the cylindrical filter grid 3 is of identical design to the grid 21, but it comprises, at its end downstream, a portion 32 protruding from the end of the screw turns and ensuring a wiping finish

  at high material pressure.

  The rotary screw V 3 inside the grid comprises an entry zone into the possible water injection part, described above; a conical zone of design similar to the screw V 2,

  with weaker taper 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 differential speed 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, for 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 efficiency of separation of the solid and liquid phases, very different raw materials,

  without replacing any of the constituent elements.

Claims (9)

R E V E N D I C A T I O N S   1 Multi-stage screw filter press for extracting juices from protein and carbohydrate plants,   characterized in that it comprises at least three press press bodies   different concept, placed in series, the number of bodies and the layout of the section variations of the different bodies being determined in such a way that, by simply adjusting the speed of rotation of the screws in each press body and one with respect to the other, after having fixed, as a function of the raw material, the admission pressure of the latter and the taper of the interchangeable end part of the last body, one approaches the optimal separation conditions and obtains a solid phase of dryness greater than 45-50% and a juice containing less than I to 2% of dry matter in suspension, whatever the raw material treated, and   without the need to replace one or more screws.   2 filter press according to claim 1, characterized in that one or more of the last press body includes means for injecting water directly into the product   pressed, without concomitant introduction of air.   3 filter press according to one of claims I 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 full turns, rotating at adjustable speed in a cylindrical filter grid with non-clogging longitudinal bars   having an internal slit 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 internal diameter of the bars from 2 to 10 mm. n O   Filter press according to one of Claims I to 4,   characterized in that the first body is supplied with adjustable pressure.   6 filter press according to one of claims I to 5   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 screen similar to that of the first body, the play between the diameter of the cylinder generated by the rotating screw and the inside diameter of the   bars of the grid being from I 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 I to 7,   characterized in that in the last part of the last press body; the conical rotor is equipped with a coilless extension 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 I to 8,   characterized in that the filter grid is provided with a device   allowing it to vibrate at low frequency.   Filter press according to one of Claims 1 to 9,   characterized in that the last screw body may include local variations in the pitch of the screw or in the cross section of   the screw which generate a variation of the pressure by successive peaks.   Il Filter press according to one of Claims I to 10,   characterized in that the juices are discharged 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.   12 Filter press according to one of claims I 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 for homogenizing the product by fixed circular ramp, and arm   turning solidly with the rotor of the screw.