Apparatus for the recovery of oil from oil-bearing vegetable matter

Apparatus for recovering oil, especially edible oils, from oil-containing fruit and seed in which immediately upon cleaning the fruit and seed, this oil-bearing material is subjected to cold pressing without prior heat treatment to recover a portion of the oil and the residue is thereupon extracted. The apparatus comprises a worm press formed with a perforated cylinder and a worm rotatable in said cylinder, said worm and said cylinder are subdivided along their lengths into a plurality of sections by respective shear gaps and throttles. The depth of the helical groove between flights progressively decreases toward the shear gaps and, in general, along the worm. The thread depth can range between 2 and 12% of the outer diameter of the worm which is preferably constant over the entire length thereof. Each flight may have a progressively decreasing pitch angle toward the outlet side and can be between 7.5 and 15.

FIELD OF THE INVENTION 
Our present invention relates to an apparatus for the recovery of oil, 
especially edible oil, from vegetable matter, namely, oil-bearing fruits 
and oil-bearing seed. 
BACKGROUND OF THE INVENTION 
Oil-bearing vegetable matter, especially oil fruits such as olive meat or 
flesh, and oil-bearing seed such as sesame seed, sunflower seed and soy 
beans can be cleaned, treated mechanically and thermally, prepressed and 
finally extracted to recover a large portion of the material oils (edible 
oils) therefrom. 
The mechanical and thermal treatments, known as conditioning are generally 
carried out in two separate steps. In a first step a precomminution is 
effected so that the cellular matter which contains the oil is broken 
down. The apparatus used for this purpose can include fluted or grooved 
drums or rollers and flaking drums. 
The second step follows the mechanical conditioning and involves a thermal 
treatment in which the vegetable matter is moistened as required, 
preheated and dried in conditioning drums or heating trays. Only 
thereafter is the oil-bearing seed or meat prepressed to remove part of 
the oil, the balance being recovered by the solvent extraction thereafter. 
The earlier system not only has the disadvantage that the comminuting 
devices are subjected to a high degree of wear and in many instances are 
detrimental to an effective oil recovery, but also that the numerous 
successive steps require a large transport path for the vegetable matter 
which in itself may cause deterioration of the product. 
Furthermore, the heating devices usually require agitators or turners for 
the vegetable matter which consume energy and must be continuously 
monitored so that the plant occupies considerable space and requires 
attendance of a large staff for effective monitoring. 
There have been attempts to overcome these disadvantages. For example, in 
German patent documents (Printed Application-Auslegeschrift) DE-AS No. 
2,335,385 (see U.S. Pat. No. 4,024,168) there is described a process in 
which the oil-bearing fruit and oil-bearing seed is conditioned in the 
absence of air thermally and mechanically in a single process step. 
For this purpose, a worm or screw press is utilized. Although this system 
affords a significant energy saving, the overall energy consumption of oil 
recovery by this process is still excessive, particularly in these days of 
significant concern for energy conservation. 
It has already been proposed to provide direct extraction of the vegetable 
matter. For example, in German patent document (Open 
Application-Offenlegungsschrift) DE-OS No. 24 53 911, a prepressing of the 
oil-bearing material is omitted although, to reach a high degree of oil 
recovery and a minimal oil content in the residue after extraction, it is 
necessary to transform the vegetable matter into especially fine flakes. 
For example, for sunflower seed the subdivision must be three times 
greater than is otherwise the case. The intermediate products frequently 
must be moistened and dried during their movement through the system. 
Furthermore the larger amount of oil increases the subsequent distillation 
costs and requires a three-fold larger apparatus with three times the 
energy requirement. 
OBJECTS OF THE INVENTION 
It is thus the principal object of the present invention to provide an 
improved apparatus of recovering oil from oil-bearing vegetable matter, 
e.g. the vegetable matter described in the aforementioned publications, 
with significantly less energy than heretofore and with a substantially 
simpler apparatus. 
A more specific object of the invention is an apparatus for oil recovery 
which will yield an especially high quality product and residue. 
Yet another object of the invention is to provide a low cost, simply 
operating, economical and easily monitored apparatus for the recovery oil 
from oil-bearing vegetable materials. 
SUMMARY OF THE INVENTION 
These objects and others which will become apparent hereinafer are 
attained, in accordance with the present invention, in a method of and an 
apparatus for the recovery of oil in a manner which has low energy 
consumption and which can use a simple and reliable device to obtain 
maximum oil recovery and a high quality residue. 
According to the invention, the oil-bearing vegetable matter, directly 
after cleaning (and without any heating or thermal conditioning) is 
directly prepressed to expel a portion of the trapped oil with the residue 
being thereafter extracted by solvent extraction techniques. It has been 
found to be important to the invention that the cold prepressing of the 
oil-bearing vegetable matter be carried out at a temperature of about 
20.degree. C. using a screw-type press. The oil obtained in the pressing 
operation has a temperature of 30.degree. to 50.degree. C. 
Since the system of the invention eliminates completely the mechanical and 
thermal conditioning heretofore required before pressing, the system has 
been found to be especially energy conserving and to involve low capital 
cost. 
According to the apparatus aspects of the invention, the prepressing is 
carried out in a sieve-type worm or screw press, i.e. a screw press in 
which the worm rotates in a perforated or open work barrel or cylinder, 
preferably formed by rods or bars extending parallel to the axis of the 
worm. According to this aspect to the invention, at least one throttle 
location is provided at which the passage between the worm and the wall of 
the cylinder is constricted inwardly and each of the throttles forms a 
shear gap between the worm and the cylinder wall. 
According to a feature of the invention, the throttles can be formed from 
inwardly extending shoulders or annular portions formed on the wall of the 
cylinder so that the shear gap is provided between the shaft and the 
annular inward projection directly between flights of the worm to either 
side of this portion of the shaft. 
The depth of the helical groove between flights can progressively decrease 
toward the shear gaps and, in general along the worm, this decrease in 
thread depth and hence cross section may be discontinuous. The thread 
depth can range between 2 and 12% of the outer diameter of the worm which 
is preferably constant over the entire length thereof and each flight or 
thread may have a progressively decreasing pitch angle toward the outlet 
side. Alternatively successive flights, separated by shear gaps, may have 
pitch angles which are less in the direction of the outlet. The pitch 
angle can be between 7.5.degree. and 15.degree.. 
According to another feature of the invention, the widths of the shear gaps 
can decrease successively toward the output side of the press, the ratio 
between the depth of the preceding flight or thread to the succeeding 
width of the shear gap ranging between 3 and 15. 
Stripping fingers may project from the wall of the cylinder and the grooves 
between the threads and the flights themselves can be interrupted at these 
locations. Furthermore, it has been found to be advantageous to provide 
longitudinal grooves at least over the first flight which decreases in 
depth in the direction of movement of the material.

SPECIFIC DESCRIPTION 
The invention, as will be apparent from the specific example, comprises 
cold pressing the oil-bearing seed or fruit (oil-bearing vegetable matter) 
in an initial step without previous mechanical or thermal conditioning and 
thereafter subjecting the residue to a solvent extraction. 
The prepressing can be carried out in a press of the type illustrated in 
the drawing and comprising a worm 13 rotating in a perforated cylinder 2 
and provided with threads or flights 1. 
Along the passage formed by the cylinder 2 these are provided throttles 3, 
4 and 5 which subdivide the passage into worm passages 6, 7 and 8. The 
throttles 3, 4 and 5 define shear gaps 9, 10 and 11 between the 
cylindrical wall and outwardly flaring bosses of the worm. Each shear gap 
9, 10 and 11 has a cross section which is smaller than the cross section 
of the worm passage 6, 7 or 8 upstream thereof in the direction of 
movement of the material. The pressed oil passes through the openings in 
the wall of the cylinder (see U.S. Pat. No. 4,024,168) while the residue 
is discharged axially at the right-hand end for solvent extraction. The 
throttles 3 through 5 subdivide the length of the worm press into three 
sections a, b and c which differ in geometry as follows: 
In section a the pitch angle of the worm is 15.degree., the flight height 
(thread depth) h.sub.1 is 12% of the worm diameter D and the ratio of the 
length of section a to the diameter D is 4.5:1. 
The throttle 3 following section a forms a shear gap 9 whose width (radial 
dimension) is such that it is 1/4.6 of the cross section of flow between 
successive turns of the flight (having the depth h.sub.1). 
In section b the pitch angle of the worm is 7.5.degree., the ratio of the 
section length to the worm diameter is 2.3:1 and these relationships are 
the same for section c. However, in section c the root diameter of the 
shaft is greater so that the cross section h.sub.2 in section b is only 
10% of the worm diameter D and in section c the depth h.sub.3 is 5% of the 
diameter D. 
The throttles 4 and 5 form shear gaps whose radial width is 1/5.75 and 1/6 
of the values h.sub.2 and h.sub.3 of the preceding worm passages 7 and 8, 
respectively. The worm press ends in an outlet 11 formed by the 
corresponding shear gap and the throttle 5. 
In the region of each throttle 3, 4 or 5 the flight of the worm is either 
throughgoing or interrupted (the latter being illustrated) and the worm 
flight can be interrupted at locations at which stripping fingers 17 
penetrate radially into the space between turns of the flight. The 
stripping fingers 17 increase the displacement capacity of the worm by 
reducing the tendency of the material to be recirculated within a zone by 
the worm. 
The stripping fingers can also be so dimensioned as to further comminute 
the material. 
While the throttles in FIG. 1 are formed by enlargements on the worm, the 
worm shaft 13' (FIG. 2) can have a constant diameter or, in any event, a 
smaller diameter, with each throttle gap 16 being formed by an inward 
projection 15 from the cylinder wall 2'. In this case, the flank of the 
inwardly projecting shoulder 15 converges frustoconically inwardly. 
FIG. 3 shows that the stripping fingers project radially into the cylinder 
at 17 while FIG. 4 shows an advantageous embodiment in which the region of 
the funnel inlet 13 of the cylinder 2 can be formed with a polygonal 
profile defined by grooves 18 which are angularly equispaced and increase 
progressively in depth in the direction of movement of the material to the 
right. 
SPECIFIC EXAMPLE 
The press shown in FIG. 1 was used with throughputs of 300 to 500 kg in 
succession of rape, linseed and sunflower seed and produces press cakes an 
oil content of 13 to 25% by weight. The residue is extracted as press cake 
in an extractor for 50, 100 and 150 minutes (see the aforementioned U.S. 
patent) and the results are compared with a conventional method involving 
breaking, rolling, thermal conditioning, prepressing and extraction using 
identical quantities of seed. 
Table 1 shows the quality evaluation of the oil recovered from rape seed. 
TABLE 1 
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Quality Oil produced by 
Process of 
Characteristics 
Conventional Process 
the Invention 
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Peroxide value 
1 0.4 
Anisidine value 
1.1 0.7 
Total Phosphorous in 
crude oil 175 ppm 71 ppm 
Phosphorus content 
in deslimed oil 
145 ppm 59 ppm 
Chlorophyll 17 ppm 7 ppm 
Color according 
to Lovibond 175 155 
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From this table it can be seen that the oil of the invention is of much 
higher quality than that which results from the conventional process. 
Table 2 shows the residual oil content of the press cake as a function of 
extraction time with the system of the invention and the conventional 
process. 
TABLE 2 
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Process 
Known Process of the Invention 
Residual Oil Content Reffered to Dry Substance 
Weight % Weight % 
Extraction Sun- Sun- 
Time (min.) 
Rape Linseed flower 
Rape Linseed 
flower 
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50 2.1 -- 2.2 1.2 0.7 1.5 
100 1.4 -- 1.5 0.85 0.4 0.9 
150 1.2 -- 1.3 0.7 0.3 0.6 
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Table 3 below shows other advantages of the invention apart from the lesser 
investment cost, e.g. by illustrating the energy consumption for the 
various process steps of the earlier system and that of the invention. The 
mechanical pressing utilizes approximately the same amount of electricity 
and substantially less steam energy than heretofore. The middle columns of 
the table show a direct extraction without prepressing after rolling and 
conditioning. 
TABLE 3 
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Conventional Process of the 
Process Direct Extraction 
Invention 
Electri- Electri- Electri- 
cal Steam cal Steam cal Steam 
Process 
Energy 
Comsump- 
Energy 
Consump- 
Energy 
Consump- 
Step Consump. 
tion Consump. 
tion Consump. 
tion 
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Rolling 
20 -- 80 -- -- -- 
Heating 
Structur- 
ing 5 60 5 82 -- -- 
Prepres- 
sing 20 -- -- -- 50 -- 
Extrac- 
tion/Dis- 
tillation 
1 50 1 150 1 50 
Total 
46 110 86 232 51 50 
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