FI74623C - MOTSTROEMSEXTRAKTIONSANORDNING. - Google Patents

Description

74623

Vastavirtauuttolaite

The present invention relates to an improved countercurrent extraction apparatus comprising a screw conveyor and an improved process for co-extracting soluble or dispersable substances from a substrate using such an extraction apparatus.

Countercurrent extraction equipment is known in the food processing industry for the continuous extraction of liquids, solutes and fines from their associated solids. Such extractors (diffuser path) generally comprise a pair of parallel, counter-rotating screw conveyors mounted in a inclined or vertical elongate housing having the shape of a hook or a completely closed tube. The material to be processed, such as the chopped sugar, is fed to the lower end of the housing and is moved upwards by rotating the screw while: ·· the extraction liquid (usually water) is fed to the upper end of the housing and flows downwards by gravity. Single-screw countercurrent extractors are also known, but have been found to be relatively inefficient because the solid tends to accumulate on one side of the housing while the broth tends to flow relatively unobstructed! down along the other side. A similar problem may occur in double screws, but to a lesser extent, because the opposite rotation promotes a more even distribution of solids in the width of the screws. ". Del 1 e.

A: Single screw 11a is transported 11a has the important advantage of simplicity and affordability compared to twin screw countercurrent extraction-Sii and efforts have been made to improve such single screw extraction equipment. It has surprisingly been found that the operating efficiency of countercurrent extraction devices can be considerably improved by means of a relatively simple means from time to time by reversing the direction of rotation of the screw conveyor. Reversing the direction of rotation of the screw conveyor causes the relatively compressed raw material mass to be extracted to open to allow the extraction liquid to penetrate the mass, the duttones being thus squeezed out of the mass as the screw conveyor takes its original direction of rotation.

The present invention comprises a countercurrent extraction device comprising an elongate tubular or trough-shaped housing having an inlet at one end or near one end and an outlet at the other end or near the other end, the longitudinal axis of the housing being inclined upwards from one end to the other, a screw float placed in the housing ti n having at least one substantially helical vane and rotatable about its longitudinal axis in the housing si, means for conveying the extractable substance introduced from said one end of the housing to said other end of the housing, means for introducing the extracting liquid into said housing so that the introduced liquid flows downwards in the housing at one end opposite to the substance to be extracted, the means for rotating the screw conveyor, and the invention is characterized in that the means periodically reverses the direction of rotation of the screw conveyor and at the same time that the device has means for removing the extracting liquid from the housing at or near one end of the housing, means for heating the removed liquid and returning the heated liquid to the housing so that the returned heated liquid comes into contact with the substance to be extracted.

Another aspect of the present invention comprises an improvement in the process for extracting soluble or dispersible substances from a substrate by a countercurrent extraction device, the method comprising periodically reversing the direction of rotation of the screw conveyor of the extraction device.

Although the present invention will now be described with reference to countercurrent extraction devices using a single screw conveyor, it is to be understood that the present invention can be used in countercurrent extraction devices having multiple screw conveyors. In addition, the following treatment is limited to screw extractors intended for extracting components from a vegetable raw material or the like, when in practice the extractor can also be used for what can be called reverse extraction, i. for impregnating solids with a broth and such applications are also considered to be within the scope of this invention.

In a particularly preferred embodiment of the present invention, the side of the screw conveyor blade which is not active when moving said raw material towards said other end of the housing is provided with a plurality of substantially radially spaced ribs spaced along the length of the screw conveyor. The purpose of these fins is to adhere to the relatively compressed mass of solid substrate material in the extractor and to help break it to allow free percolation of the extraction liquid into the mass of solid material. If desired, such fins can also be provided on the surface of the wing that is active in transferring solids from one end of the housing to the other end.

It is preferred that the sieve means be used to filter the extracted liquid before it is removed from one end of the housing. The strainer means preferably includes a plate extending transversely across the housing at or near one end thereof and through which the drive shaft of the screw conveyor extends. The plate is provided with at least one opening through which the extraction liquid can pass and the filter plate is placed in close parallel with the plate on its side further from said other end of the housing and arranged to rotate with the screw conveyor drive shaft past said opening or openings in the plate and thus self-cleaning.

The apparatus is preferably provided with means for recirculating the extraction liquid from said one end of the housing, heating it to the desired temperature and returning it to the housing at a point between the ends of the housing. A suitable portion of the extraction liquid exiting the bottom of the housing is recommended to be passed through an independent heat exchanger where it is heated and recirculated to the housing above one of the ends mentioned at one point. Since the purpose is to provide rapid heating of the material at an early stage of the process, the recyclable broth must be introduced into the lower half of the housing, preferably at a point about 1/20 to 1/4 of the length of the housing from said one end.

In another embodiment, the extraction device is also provided with means for ensuring a predetermined level of extraction liquid in the lower parts of the housing, as it has been found that solid / liquid contact is improved if the extraction liquid is allowed to accumulate in a controlled manner near the solids loading site. For example, suitable control means senses the liquid level and compensates for changes in the extraction liquid by automatic control of the outlet flow and / or inlet flow rate.

The housing of the extractor is preferably provided with a jacket through which the liquid can be passed. In this way, the temperature of the housing and to some extent the temperature of its contents can be adjusted.

The actuators of the extractor can be any reversible actuator. It is preferred that the drive device is an electric motor or a hydraulic motor whose direction of rotation can be reversed. In an alternative embodiment, the reversible gearbox may be located between the motor and the screw conveyor.

As with extractors operated with a continuous forward screw movement, the performance of the extractors used according to the principles outlined above is affected by many factors such as the nature of the charge, charge temperature, broth flow rate, screw inclination, screw rotation speed and screw helix angle and individual

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74623 users modify these factors to meet certain requirements. Nevertheless, one feature of the present invention is to find that for maximum efficiency, there is an optimal ratio between the time the screw (s) are driven forward and the time the drive (s) are driven backwards. In general, this means that preferably the net time in the forward operation of the screw should not exceed 75%, more preferably not 50% and most preferably it should not exceed 25%.

In the present invention, the net forward time is defined as: x 100

TF + TR

where TF = total operating time of the screw in forward motion TR = total operating time of the screw in reverse motion.

The intake of recovered soluble solids has been found to increase as the net forward time decreases, but clearly the associated decrease in flow rate must be taken into account when determining the optimal economic operating conditions.

The extraction liquid is often water, but other liquids, including organic liquids or aqueous solutions of organic substances, may be used. The process can be used to extract a soluble or dispersible substance from a fruit or vegetable raw material such as sugar beet, sweet millet, grapes, grape lees, tea, citrus fruits, citrus peels, apples, pears and animal raw materials such as fish heads. Residues such as apple peels and hearts, citrus peels and grape lees can also be exhaustively extracted to recover the valuable soluble components that are normally discarded with these wastes * 6 74623. Soluble sugars recovered from the peel and hearts of an apple or pear can be used to make preservative syrup or can be used as an alcohol. Other residue-containing substances, such as perfume dyes or particularly useful substances, such as pectins, can be recovered. For satisfactory extraction, it is preferred that the raw materials be in particulate form, the particle shape being such that the extraction path for casting the solute out of the particles is short in at least one direction.

The extracted substrate material is removed from the housing through an outlet from said other end of the housing. The outlet is preferably located in the side wall of the housing above the level of the screw conveyor. Preferably, an outlet conveyor is used to transfer the extracted substrate material horizontally and upwardly from the housing to the outlet. In a particularly preferred embodiment of the invention, the discharge conveyor at its lower end runs around a roller mounted on an extension of the longitudinal axis of the screw conveyor and motor means are used to drive the discharge conveyor independently of the screw conveyor.

A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically shows a countercurrent extraction device according to the present invention.

Figure 2 is a semi-schematic view of a countercurrent extraction apparatus according to the present invention.

Figure 3 shows a section of the housing along the line III-III in Figure 2.

Figure 4 shows a longitudinal section of the lower end of the housing and screw of the extractor of Figure 2.

Fig. 5 is a graph showing the effect of intermittent reversal of the direction of rotation of the screw conveyor of the countercurrent extraction device according to the present invention.

Il 7 74623

Fig. 6 is a graph comparing liquid levels in the housing of a countercurrent extractor when the screw conveyor is continuously rotated in one direction and when the direction is periodically reversed.

Fig. 7 is a graph illustrating the improved contact efficiency of a countercurrent extraction apparatus according to the present invention.

Fig. 8 is a graph illustrating the effect of back and forth rotation time on the intake of solids soluble in a screw conveyor in a countercurrent extraction apparatus according to the present invention.

Figure 9 shows a section along the line IX-IX in Figure 2.

As can be seen in Figure 1, the countercurrent extraction device 10 comprises an elongate trough-shaped housing 11 in which a screw conveyor 12 is arranged, which is arranged to rotate about its longitudinal axis by drive means 13. The housing 11 is provided with an inlet hopper 14 for introducing extractable material. The funnel 14 is located above the lower end of the screw, which screw is slightly inclined upwards towards the outlet 15 of the treated solids. The device is provided with an outlet line 16 for discharging the extraction liquid which is charged into the housing 11 via the charge line 17. A heat exchanger 18 is located in the bypass line 19 to heat the removed liquid and return it through the nozzle 21 to the lower end of the housing 11 to heat the material to be treated.

The means for reversing the direction of rotation 22 are interposed between the drive means 13 and the screw conveyor 12 to periodically reverse the direction of rotation of the screw conveyor 12.

Figures 2, 3 and 4 show a countercurrent extraction device similar to the extraction device of Figure 1, and in these figures the same reference numerals are used to indicate similar parts.

The extraction device 10 comprises a trough-like housing 11 in which a screw conveyor 12 is arranged, which is arranged to rotate about its longitudinal axis in the housing 11. The motor 13 is arranged to drive a screw conveyor 12 and includes turning means for periodically reversing the direction of screw rotation. The motor 13 is operatively connected to the spindle 23 of the screw conveyor 12 by two aligned wheels 24 and 25 and a chain 26, the aspect ratio of the wheels 24 and 25 being selected so that the spindle 23 and the screw conveyor 12 rotate about 1 rpm when the motor 13 rotates at a suitable operating speed. The mandrel 23 is supported on bearings 27 and 28 located at both ends of the housing 11.

The screw conveyor 12 includes a helical vane 29 positioned around the mandrel 23. The wing 29 is provided with circumferentially directed slots 30 and a plurality of radially oriented ribs 31 located on the side of the wing 29 which is not involved in transferring the material to be extracted from the inlet end of the housing 11 to its outlet end.

The material to be extracted is charged into the housing 11 via an inlet funnel 14. The extracted material is removed through the outlet 15. The discharge conveyor 50, which includes two continuous chains 51 with transport slats 52, is positioned to convey the extracted material from the bottom of the housing 11 up its side wall 53 to the outlet 15. The chains 51 are supported by three sets of toothed wheels. One set of wheels 54 is mounted on the shaft 22 of the screw conveyor 12 and rotates freely thereon. The other two sets of wheels 55 and 56 are mounted on axles parallel to the axle 22. An electric motor 57 including speed control means is arranged to drive the wheels 55 via a belt 58. In this way, the substance can be removed at a constant speed regardless of the rotational speed and direction of rotation of the shaft 22.

The lower end of the housing 11 has a strainer for sieving the extracted liquid before it is removed from the housing 11. The strainer comprises

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74623 an end plate 34 provided with openings 35. A screw 36 and a back plate 37 are located behind the end plate 34 and connected to a spindle 23, and arranged to be rotatable by this spindle. The sieved extracted liquid is discharged through an outlet line 16 to a heat exchanger 18, where it first passes through an exchanger plate 38 where it flows countercurrently with the feed water of line 17 and then through an exchanger plate 39 where it flows countercurrently with the cooling water of line 41. The now cooled product is then removed from the extractor via line 16. A portion of the extracted juice in line 16 is turned to line 19, passed through an exchanger plate 42 where it is heated as it flows countercurrently with hot water from line 43 and removed back to housing 11 to heat fresh, introduced, extractable material. The line 19, heated with recycled liquids, is discharged into the housing 11 between one-tenth and four-quarters along the housing 11.

The supply water line 17, after passing through the exchange plate 38, passes to the exchange plate 44, where it flows countercurrently with the hot water of the line 45. The wire discharges into the housing 11 at its upper end.

The housing 11 is provided with an insulated hot water jacket 46. Hot water passes through the conduits 47 and out of the jacket through the conduits 48.

In use, the extractable material is introduced into the lower end of the housing 11 and a screw conveyor 12 is rotated to start the movement of the material along the housing 11. Heated feed water is fed to the housing 11 via line 17 and feed water, together with free flowing juice and extracted matter and fines. to the housing 11 via line 19.

As the material to be extracted advances along the housing 11, it becomes compressed by a wing 29 to form a compact mass of partially extracted material. When the direction of rotation of the screw conveyor 12 is reversed, the fins 31 bite into the compact mass, forcing it to open and release fresh feed water. When the conveyor 12 is turned in its original direction of rotation, the material to be extracted becomes recompressed and the feed water, together with more extracted material, becomes extruded. This opening of the compressed mass of extractable feedstock significantly enhances the performance of the extractor and results in improved yields of extracted material.

The results described in the graphical representation of Figure 5 were obtained using a single-screw extractor (length 2 m, diameter 20 cm, helix angle 150, slope 3.50). Initially, charged with a sliced apple, the screw was driven continuously forward at a speed of 1 rpm; when equilibrium was reached (determined by effluent analysis), the screw was operated for a period during which forward travel was stopped every 15 seconds and the screw was driven back 1/20 turn. Finally, the screw rotated continuously again. It can be seen from Figure 5 that immediately after the introduction of the turning operation, there was an increase in the broth outlet rate, indicating that the opening of the apple pulp allowed the liquid to escape from the pulp at the top of the screw. Returning to continuous similar rotation, the broth output ceased for some time when the extraction water did not flow freely through the apple pulp but became trapped in the tissue. A significant increase in sugar concentration (° Brix) in the effluent during reciprocating rotation was also observed.

The data shown in Figures 6-8 were obtained using similar equipment, but the movement of the screw was automatically controlled so that the reciprocating periods consisted of series of alternating 100 seconds forward and 70 seconds reverse. 352 g of sliced 11,746 3 apples were fed to the extractor every 5 minutes and water (65 ° C) was fed at a rate of 77.3 g / minute to the top of the screw. Mass flow readings and broth and solids concentrations at removal were determined periodically.

The test runs were performed with a continuous forward and backward movement of the screw. At the end of each run, when the system was in equilibrium, the retention of free fluid and the retention of solids in the screw were determined. The inclusion of the opposite movement increased the yield of soluble solids obtained in the art as well as the concentration at which they were recovered.

Figure 6 illustrates an easier flow path for the broth through the apple pulp when reciprocating.

The solids / liquids contact efficiency was also found to be improved because the concentrations of extracted soluble solids, measured in ° Brix units, were higher when the screw was reciprocating (Fig. 7).

The effect of variation in the forward / backward movement of the screw on the intake of soluble solids was studied by feeding Shiraz grapes and the results are shown in Figure 8.

The following are examples of the process of the present invention.

Example I

Gordo-type grapes, which are known to be difficult to press due to their slippery nature, were taken from the end of a winemaking dryer and fed at a rate of 600 kg / h through an extraction apparatus equipped with a 4.5 m screw with a diameter of 0.5 m.

The yield data for the extractor and the conventional winemaking press are shown in the following table.

74623

Winery Countercurrent Screw Extractor____

English Translation:

Component Supply Deletion Supply Deletion

Fixed tot. % 28.56 40.05 29.94 29.04

Water% 71.44 59.95 70.06 70.96

Soluble solids,% 15.20 13.90 18.60 10.70

Insoluble solids,% 13.36 26.15 11.34 18.34

Soluble / soluble ratio 1.14 0.53 1.64 0.58

Recovery,%

Soluble in dried grapes from solid 53.5 to 64.6

In the second experiment, 4250 kg of Shiraz grapes were extracted and the recovery of soluble solids was 82%. The mass data are listed in the following table.

Component Feed Solid Removal Juice

Soluble solids% 25.9 14.2 20.0 Amount, kg 4250 1290 4,500

Soluble solids tot. kg 1100 183 900

Example II

The traditional process of making lime juice in the West Indies takes about 30 days. However, by using a countercurrent extraction process to extract sliced fruit, the production time of lime juice can be reduced to 1 1/2 hours.

In one case, the yield of lime juice was equal to the weight of the lime fed. This "juice" was an excellent lime juice beverage when diluted with 4 volumes of water and the appropriate amount of sugar was added to balance the taste.

11.

13 74623

Example III

Using a procedure similar to that for lime (tti) fruit, 100 kg of lemon produced a "juice" which, extended to 400 kg by adding water and 32 kg of sugar, produced an excellent chip drink.

It will be apparent to those skilled in the art that numerous variations and modifications may be made to the invention as described above without departing from the scope of the generally described invention.

Claims (6)

74623 A countercurrent extraction device (10) comprising an elongate tubular or trough-shaped housing (11) having an inlet (14) at one end or near one end and an outlet (15) at or near the other end, wherein the longitudinal axis of the housing (11) is inclined upwards from one end to the other, a screw conveyor (12) housed in the housing (11) having at least one substantially helical vane (29) rotatable about its longitudinal axis for conveying the extractable material introduced from the housing (11) into said housing from one end of the housing at one end, means (17) for introducing an extracting liquid into said other end of the housing (11) so that the introduced liquid flows downwards in the housing (11) at one end opposite to the substance to be extracted, drive means (13, 22) for rotating the screw conveyor, characterized in that the drive means from time to time reverse the direction of rotation of the screw conveyor and at the same time cause extraction the net movement of the substance forward from one end to the other and that the device (10) has means (16) for removing the extracting liquid from the housing (11) at or near one end, means (18) for heating the removed liquid and returning the heated liquid to the housing (11); that the returned heated liquid comes into contact with the substance to be extracted. Countercurrent extraction device according to claim 1, characterized in that the side of the wing (29) of the screw conveyor (12) which does not participate in conveying material towards said other end of the housing is provided with a plurality of substantially radially spaced ribs (31) at spaced points along the screw conveyor. length. Countercurrent extraction device according to claim 1 or 2, characterized in that it is provided with sieve means for filtering the extracted liquid before it is removed from said one end of the housing. Countercurrent extraction device according to claim 3, characterized in that the sieving means comprise closing means (34) with an opening or openings (35) extending across one end of the housing or adjacent to this end and through which the shaft (23) of the screw conveyor (12) extends and that the strainer member (37) is located close to the opening or openings (35) of the closure means on the side of said means remote from said other end of the housing and the strainer member is arranged to rotate continuously past the opening or openings so as to be self-cleaning. Countercurrent extraction device according to Claim 1, characterized in that the means for circulating the liquid are arranged such that the recycled liquid returns to the housing (11) at a position (21) at a distance of 1/20 to 1/4 of the length of the housing. Countercurrent extraction device according to one of the preceding claims, characterized in that it has means for ensuring a predetermined extraction liquid height at one end of the housing (11) when the extraction device is in operation. 16 74623