Apparatus for use in Palm Oil Extraction

Technical Field

The present invention relates to an apparatus for use in palm oil extraction. In particular, the apparatus is for use in the sterilization of oil palm fruit.

Background

Sterilization is an important process in the extraction and production of palm oil from oil palm fruit bunches as it affects many properties of the oil palm fruit. In particular, downstream milling problems may be avoided if proper and adequate sterilization of the fruits has taken place. Sterilization aids in cooking the fruit pericarp, therefore facilitating the de-oiling during the pressing stage where oil is pressed out from the cooked and digested fruit. Furthermore, the lipolytic enzymes present in the pericarp are inactivated during the sterilization and are prevented from producing excessive free fatty acids in the oil. Sterilization also loosens the fruits from the stalk of the fruit bunch, which facilitates subsequent processing of the oil palm fruits. The nuts of the oil palm fruits are also preconditioned through loosening of the kernels inside the nuts. This minimises the kernel breakage during the subsequent kernel recovery process.

The sterilization process is generally carried out in a pressure vessel such as a cylindrical vessel filled with steam of certain physical properties. For example, the vessel may be of a horizontal or vertical design. In the case of horizontal sterilizers, open-top perforated steel cages filled with oil palm fruit are pushed on rail tracks into the sterilizer for sterilization. Multiple cages would be required, together with equipment such as overhead cranes/tippers, transfer carriages, cantilever trolleys, indexers, capstans/hydraulic winches, wheel loaders/skid loaders, etc. Skilled labour would be required for the operation and maintenance of such equipment. Further, much capital will be required to procure the equipment and provide a marshalling yard with rail tracks. Although relatively good sterilization can be achieved in a horizontal sterilizer since the fruit bunches are uniformly spread across the length of the vessel, the disadvantages include a significant amount of steam being wasted in the repeated heating of the relatively extensive volumes of air surrounding the fruit cages. Oil losses also occur due to the dripping of condensate from the sterilized fruit bunches during the transport of the cages for further processing of the fruit bunches after sterilization.

Although the above problems associated with horizontal sterilizers may not be experienced in vertical sterilizers, vertical sterilizers of a large capacity have several disadvantages. For example, when fruit bunches are loaded into the sterilizer, the impact of the fruit bunches falling through a distance from the top opening to the base of the sterilizer sometimes deforms and damages the base of the sterilizer. Further, after the fruits have been loaded into the sterilizer, the excessive compaction of the fruit bunches in the bottom half of the sterilizer due to the weight of the bunches above may prevent steam from being evenly distributed in the sterilizer. This may result in over-sterilization of the fruit bunches at or near the top of the sterilizer, and under-sterilization of the fruit bunches in the centre and at the bottom of the sterilizer. Another problem that may be encountered is that steam condensate may accumulate in the pockets of space within the compacted fruit bunches resulting in ineffective removal of air during a venting stage of the sterilization process. If the air is not removed effectively, a longer period of sterilization may be required at any given sterilization pressure as the overall temperature of the vessel would be lower due to the presence of the resulting steam-air mixture as compared to if only steam was present in the vessel. Further, due to the compaction of fruit bunches near the bottom of the sterilizer, sterilized fruit bunches lying further down along the length of the sterilizer tend to get congested at the exit of the outlet, resist gravity movement of fruit bunches lying above them and then form a blockage, preventing the smooth discharge of the sterilized fruit from the bottom of the sterilizer. This phenomenon is more generally referred to as the arching effect.

Summary

According to a first aspect, there is provided an apparatus for sterilizing oil palm fruit comprising a container having a wall, the container comprising: at least one steam inlet; and at least two manifolds inside the container in fluid communication with the at least one steam inlet, the at least two manifolds being attached to an inner surface of the wall and being spaced from each other, wherein the at least two manifolds each comprises a plurality of steam outlets for distributing steam inside the container.

The container may further comprise an inlet for receiving fruits and an outlet for discharging the sterilized fruits. The inlet and/or outlet may comprise a door operated manually or hydraulically.

Each of the at least two manifolds may have a trapezoidal cross-section. In particular, the manifold may have a trapezoidal cross-section with one side attached to the inner surface of the wall of the container and with the steam outlets provided on the other three sides of the manifold for effective distribution of the steam into the container. In particular, the upper portion of the manifold may be sloped downwards to aid in the discharge of the sterilized fruit.

Any suitable number of manifolds may be used in the container. For example, the container may comprise two, three, four or more manifolds. The manifolds may be distributed across the longitudinal axis of the container. The vertical distance between adjacent manifolds may be approximately equal. In particular, there may be three manifolds that are substantially equally spaced along a central longitudinal axis of the container.

The manifold may further comprise at least one channel extending between and across the manifold to form at least two segments of the manifold. The segments formed may be of the same or different size. For example, the manifold may comprise a channel extending between and across the manifold, through the centre of the manifold to form two equal segments.

The channel may comprise at least one steam outlet. In particular, the at least one steam outlet may be in the middle section of the channel. The channel may comprise a first portion having an inverted "V" profile.

The at least one channel of adjacent manifolds may be offset from each other. For example, when there are two or more manifolds, and at least two manifolds comprise a channel extending between and across the manifold, the orientation of the channels may be offset from one manifold to the next.

The container may further comprise at least one projection projecting from the inner surface of the wall of the container, wherein the at least one projection is inclined relative to the longitudinal axis of the container. The projection may be in the form of an inclined plate with one end attached to the inner surface of the wall of the container. The at least one projection may be inclined relative to the longitudinal axis of the container both

circumferentially and radially. The at least one projection may be circumferentially projecting from the inner surface of the wall of the container. The at least one projection may be longitudinally adjacent to the at least two manifolds. In particular, the container may comprise a plurality of projections spaced along the longitudinal axis of the container with each of the plurality of projections being offset from each other and adjacent projections inclining circumferentially in opposite directions.

The container may further comprise discharging means to discharge the sterilized fruit from the container after the sterilization process has been completed. The discharging means may be adjacent to the outlet for discharging sterilized fruit. The discharging means may comprise an inclined plate inclining towards the outlet for discharging sterilized fruit and an arm. The arm may be a retractable arm. The retractable arm may be operated by electrical or hydraulic means. For example, the retractable arm may be a retractable auger.

The container may further comprise a desuperheater for desuperheating steam in the container. The desuperheater may comprise a pipe for running water. The pipe may be in fluid communication with at least one water inlet. A substantial portion of the pipe may be within the container and extending downwards and adjacent to the discharging means. The pipe may comprise a plurality of apertures. The apertures may be distributed across the entire length of the pipe.

According to a particular aspect, there is provided an apparatus for sterilizing oil palm fruit comprising a container having a wall, the container comprising: at least one inlet for receiving fruit; at least one outlet for discharging fruit; at least one water inlet adjacent to the inlet for receiving fruit for the entry of water into the container for steam desuperheating; at least one air outlet for venting air from the container; at least one steam exhaust outlet adjacent to the inlet for receiving fruit; at least one steam condensate outlet for discharging condensate and steam-air mixture from the container; and at least twelve steam inlets for the entry of steam into the container, with four steam inlets for each of three manifolds attached horizontally to the circumference of the inner surface of the wall of the container.

Brief Description of the Drawings

In order that the invention may be fully understood and readily put into practical effect there shall now be described by way of non-limitative example only preferred embodiments of the present invention, the description being with reference to the accompanying illustrative drawings. In the drawings:

Figure 1 is a vertical cross-sectional view of an apparatus according to a first preferred embodiment;

Figure 2 is a sectional view (B-B) of part of the apparatus of Figure 1 ; Figure 3 is a sectional view (C-C) of part of the apparatus of Figure 1 ; Figure 4 is a sectional view (D-D) of part of Figure 2; and Figure 5 is a sectional view (E-E) of part of Figure 3.

Detailed Description of Exemplary Embodiments

Referring to Figure 1 , there is a sterilizer 10 comprising a hydraulically-operated loading door 4 adjacent to the top portion 1 of sterilizer 10 which can be opened to load bunches of fruit into sterilizer 10. A hydraulically-operated discharging door 5 adjacent to lower portion

3 of sterilizer 10 allows sterilized fruit to be removed after the sterilization process. An inclined plate 16 fixed to the inner surface 24 of the wall of sterilizer 10 near lower portion 3 of sterilizer 10 and inclining towards discharging door 5 assists in discharging the fruit bunches. A retractable auger 20 driven by a hydraulic or electric motor 19 aids in the discharge of sterilized fruit through discharging door 5.

Sterilizer 10 may be of any suitable shape. For example, the horizontal cross-section of sterilizer 10 may be cylindrical. Figure 1 shows a substantially cylindrical sterilizer 10, the longitudinal axis of sterilizer 10 positioned vertically, with loading door 4 for receiving fruit at top portion 1 of sterilizer 10 and discharging door 5 for discharging sterilized fruit at lower portion 3 of sterilizer 10.

Steam inlet valves 11 allow steam to be injected into sterilizer 10. Steam inlet valves 11 are in fluid communication with manifolds 12. Manifolds 12 are attached to the inner surface 24 of the wall surrounding the hollow interior 2 of sterilizer 10. Each manifold 12 comprises a plurality of steam outlets 12a spaced around the circumference of manifold 12 for the discharge of steam through steam outlets 12a into hollow interior 2.

Manifold 12 may be of any suitable shape. Manifold 12 may take the shape of the horizontal cross-section of sterilizer 10 and be attached to the inner surface 24 of the wall of sterilizer 10. For example, manifold 12 may be in the form of a circular or elliptical ring. Manifold 12 as shown in Figures 2 and 3 is in the form of a circular ring. Figure 5 shows a sectional view E-E of manifold 12. In particular, the trapezoidal cross-section of manifold 12 is shown in Figure 5. As seen in Figure 5, the upper portion 25 of the trapezoidal cross- section of manifold 12 slopes towards lower portion 3 of sterilizer 10, assisting the discharge of fruit bunches from sterilizer 10.

A steam exhaust valve 8 and an air-vent valve 7 adjacent to top portion 1 of sterilizer 10 discharge steam and air, respectively, from sterilizer 10. A blow-down valve 9 and a bleed- off bypass valve 18 discharge steam condensate and steam-air mixture from sterilizer 10. A steam desuperheater 14 is in fluid communication with a water control valve 6 external to but adjacent to the top portion 1 of sterilizer 10. Desuperheater 14 extends into sterilizer 10 down to and adjacent to inclined plate 16. Desuperheater 14 has a plurality of apertures (not shown) along the length of desuperheater 14. Water running through desuperheater 14 may exit desuperheater 14 at these apertures and accordingly, water may be distributed at various heights of sterilizer 10 for desuperheating of steam within sterilizer 10.

A pressure-equalization pipe 15 is also located in sterilizer 10 to substantially eliminate the pressure differential that would otherwise exist between top portion 1 and lower portion 3 of sterilizer 10 due to the impedance to the free movement of steam caused by wet and compacted fruit bunches within sterilizer 10. If the pressure is not equalised, the initial discharge of condensate would lower the pressure at lower portion 3 of the sterilizer 10 and consequently reduce subsequent flow of condensate from sterilizer 10. Accordingly, pressure-equalization pipe 15 facilitates the discharge of steam-air mixture and condensate formed due to condensation of steam inside sterilizer 10, from lower portion 3 of sterilizer 10. Pressure-equalization pipe 15 extends longitudinally inside sterilizer 10, from adjacent to and below top portion 1 of sterilizer 10, to and through inclined plate 16.

Projections 17 project from the inner surface 24 of the wall of sterilizer 10 and are longitudinally adjacent to manifold 12. Projections 17 extend radially inwards from inner surface 24 of the wall of sterilizer 10. Projections 17 are inclined relative to the longitudinal

axis of sterilizer 10 towards the centre of sterilizer 10 to assist in reducing the arching effect of masses of fruit bunches inside sterilizer 10, and may also ease the discharge of fruit bunches close to the inner surface 24 of the wall of sterilizer 10. Projections 17 are substantially equally spaced along the longitudinal axis of sterilizer 10 with longitudinally adjacent projections 17 offset from each other.

Figures 2 and 3 show sectional views B-B and C-C, respectively, of sterilizer 10. It can be seen from Figures 2 and 3 that manifold 12 comprises a plurality of steam outlets 12a spaced along the circumference of manifold 12. Manifold 12 also has a channel 13 extending between and across manifold 12 to form at least two segments. Channel 13 may extend through the radial centre of manifold 12 to form two equal segments. Channel 13 may break the fall of fruit bunches when fruit bunches are loaded into sterilizer 10 for sterilization. Channels 13 reduce the impact of fruit bunches falling to lower portion 3 of sterilizer 10, thereby protecting lower portion 3 of sterilizer 10. Channels 13 may also aid in reducing the arching effect. Channels 13 of two adjacent manifolds 12 may be offset from one manifold 12 to the next in order to increase the probability of fruit bunches landing on channels 13.

A sectional view D-D of channel 13 is shown in Figure 4. Figure 4 shows that the upper part 26 of channel 13 has an inverted "V" profile. Such a profile is advantageous in reducing the arching effect of the masses of fruit bunches in sterilizer 10.

Channel 13 has steam outlets 13a at approximately in the centre portion of channel 13. Steam outlets 13a on channel 13 distribute the steam exiting steam outlets 13a into the middle section of the hollow interior 2 of sterilizer 10.

Figures 2 and 3 also show the direction in which projections 17 incline (indicated by arrows) relative to the longitudinal axis of sterilizer 10. Therefore, fruit bunches adjacent to projections 17 during discharge from sterilizer 10 will slide along projections 17 towards lower portion 3 of sterilizer 10.

Before fresh oil palm fruit bunches are loaded into sterilizer 10, loading door 4 is opened while discharging door 5 and all the other valves except for air-vent valve 7 are closed. Fresh fruit bunches are conveyed via a series of cnain conveyors from their storage area in

the palm oil mill loading ramps (not shown) and are transferred to a distributing conveyor 21 above sterilizer 10. From distributing conveyor 21, the fruit bunches are discharged through a chute 22 into sterilizer 10 through loading door 4 until sterilizer 10 is almost full. Distributing conveyor 21 is then stopped and loading door 4 is closed and locked.

After sterilizer 10 is loaded with fruit bunches, steam inlet valves 11 are opened to inject low pressure steam, for example at about 3 bars gauge pressure, into sterilizer 10. The steam from steam inlet valves 11 enters sterilizer 10 via manifold 12 and steam outlets 12a, as well as channel 13 and steam outlets 13a, into hollow interior 2 of sterilizer 10. If the source of steam is exhaust steam from a turbine, the exhaust steam may have been kept superheated to avoid condensation and consequent erosion of the turbine blades and connected pipework. Water control valve 6 serves to control the release of water under pressure into sterilizer 10 via steam desuperheater 14 in order to optimally desuperheat the steam entering hollow interior 2 of sterilizer 10 via steam outlets 12a and steam outlets 13a. The water flow rate required for desuperheating is electronically computed from signals detected by sensors (not shown) monitoring the condition and flow rate of the incoming steam. Upon desuperheating, the efficiency of the sterilization process is improved, as the heat transfer coefficient of the desuperheated steam increases dramatically and the temperature at which the desuperheated steam condenses back into water remains relatively constant. Air vent valve 7 is still kept open to allow the air which is displaced by steam in the top portion 1 of sterilizer 10 to escape. Blow-down valve 9 and bleed-off bypass valve 18 are opened in order to discharge the steam that condenses on the fruit bunches and on the inner surface 24 of the wall of sterilizer 10. Some uncondensed steam and displaced air from the fruit bunches are also discharged together with the steam condensate.

After a few minutes, air vent valve 7 and blow-down valve 9 are closed in order to start building up the pressure within sterilizer 10. Bleed-off bypass valve 18, however, is kept partially open to allow a continuous small flow of condensate together with a steam-air mixture from sterilizer 10. When the pressure inside sterilizer 10 has risen from zero to a peak pressure of about 3 bars gauge pressure, steam inlet valves 11 and bleed-off bypass valve 18 are closed and a holding period is commenced to allow the sterilization of the fruit bunches in sterilizer 10. During this period, the steam pressure inside sterilizer' 10 drops steadily due to condensation of steam. At the end of the holding

period, which may be of approximately thirty minutes, blow-down valve 9 is opened followed by steam exhaust valve 8 to discharge the condensate and residual steam, respectively. As a result, sterilizer 10 is depressurised.

If a single peak sterilization method is used, this would signal the end of the sterilization process. In the case of a multiple peak sterilization process, however, when the steam pressure in sterilizer 10 has dropped significantly due to condensation after reaching the peak pressure, blow-down valve 9 and steam exhaust valve 8 are opened, as in the case of single peak sterilization, to discharge the condensate and steam-air mixture from sterilizer 10. Steam exhaust valve 8 is then closed and steam inlet valves 11 are opened to inject steam once again into sterilizer 10. After venting for a few minutes, blow-down valve 9 is closed and the steam pressure inside sterilizer 10 rises steadily once again to the peak pressure. This cycle of alternate venting and building up of steam pressure in sterilizer 10 is repeated a number of times depending on the number of peaks desired. Only at the final peak does the holding period begin. At the end of the holding period, blow- down valve 9 and steam exhaust valve 8 are opened, as done for the single peak sterilization method, to discharge the condensate and residual steam, respectively, and to depressurize sterilizer 10.

Once sterilizer 10 has been depressurized, loading door 4 is unlocked and opened followed by discharging door 5. Retractable auger 20 driven by a hydraulic or electric motor 19 is operated to aid in the discharge of the sterilized fruit bunches from sterilizer 10 and onto a chain conveyor 23 adjacent to discharging door 5 of sterilizer 10 for further processing. The orientation of the upper plate of manifold 12, channels 13 and projections 17 assist in reducing the arching effect of masses of the compacted sterilized fruit bunches inside sterilizer 10, as explained above. Inclined plate 16 further aids the discharge of the fruit bunches from sterilizer 10. When the discharge of fruit bunches is smooth, auger 20 may be retracted using hydraulic or electric power to provide additional space for the fruit bunches to exit sterilizer 10 unimpeded.

Whilst there has been described in the foregoing description preferred embodiments of the present invention, it will be understood by those skilled in the technology concerned that many variations in details of design, construction and/or operation may be made without departing from the present invention.