WO2014185769A2

WO2014185769A2 - Method, apparatus and system for digestion and pressing of oil palm fruit

Info

Publication number: WO2014185769A2
Application number: PCT/MY2014/000073
Authority: WO
Inventors: Sulaiman BIN SHIAFI; Nik Suhaimi BIN MAT HASSAN; Yosri BIN MOHD SIRAN; Ahmad Jaril ASIS; Shawaluddin Tahiruddin
Original assignee: Sime Darby Malaysia Berhad
Priority date: 2013-05-13
Filing date: 2014-04-24
Publication date: 2014-11-20
Also published as: WO2014185769A3; MY165646A

Abstract

The present invention relates to a method for the digestion and pressing of oil palm fruit in a palm oil milling process. The method comprises controllably feeding a pretreated oil palm fruit into a digester having rotating means, injecting a predetermined amount of water at a temperature of 80°C to 100°C into and at bottom side of the digester to remove crude palm oil from the oil palm fruit and to dilute the crude palm oil, collecting the crude palm oil removed from the oil palm fruit through a perforated base plate provided within the digester; and discharging the digested oil palm fruit from the digester. The present invention also relates to a system and apparatus for carrying out the method of the invention.

Description

METHOD, APPARATUS AND SYSTEM FOR DIGESTION AND PRESSING OF OIL

PALM FRUIT

FIELD OF THE INVENTION

The present invention relates to a method, apparatus and system for digestion and pressing of oil palm fruits. More particularly, the present invention relates to a method, apparatus and system for digestion and pressing of oil palm fruits in palm oil milling process by injecting hot water into a digester.

BACKGROUND OF THE INVENTION In a typical palm oil milling process, several operations are involved in extracting palm oil from fresh oil palm fruit bunches. The major components of an oil palm fruit are the oil bearing tissue called mesocarp and the nut which contains the kernel. In a palm oil milling process, two major products obtained include crude palm oil and kernel. The operations involved in extracting crude palm oil from fresh oil palm fruit bunches include, sterilization, stripping, digestion and pressing, clarification, purification, drying and storage.

In a typical palm oil milling process, the fresh oil palm fruit brunches are first sterilized to inactivate the lipolytic enzymes, loosen the fruit on the brunches, soften the fruit, condition the kernels to minimize kernel breakage and cause protein to coagulate. The sterilized fruit is then stripped or separated from the brunches before the fruit is fed into a digester where the fruit is reheated to loosen the pericarp.

The digester used in a typical palm oil milling process is typically a cylindrical vessel that is heated and maintained at a temperature of 90°C to 100°C. The digester has rotating shafts which are fitted with beater arms that break up the fruit as the fruit rotates within the vessel. The digester is usually kept full and as the digested fruit is drawn out through perforations provided in the digester, freshly stripped fruit is fed into the digester. In principle, during the digestion process, two actions occur. Firstly, due to the weakening of cell membrane, there is an intensive release of virgin crude palm oil corresponds to about 15% to 20% of the weight of the fruit bunches, drawn out through the perforations of the digester. Secondly, there is a rupture of oil cell due to stirring action on the fruit mass.

After the fruit in the digester is loosen or digested, the digested mass of the oil palm fruit is then discharged from the digester and fed continuously to a pressing machine in which the fruit is pressed to produce a liquid stream consisting of oil, water, press cake or fibre and nuts. The liquid stream is then delivered to a clarification tank. In the conventional process, separation of the oil from the rest of the liquid is achieved by using settling tank based on gravity. In the settling tank, the mixture containing the crude palm oil is diluted with hot water to reduce the viscosity of the crude palm oil. This dilution of the crude palm oil is important as it makes it easier for the crude palm oil to be separated from the rest of the liquid in the settling tank. The oil mixture is then heated to about 85°C to 90°C and allowed to separate in the settling tank.

The oil recuperated from the settling tank then passes through a clarifier and dried under vacuum before the oil is sent to storage.

In the conventional dilution process described hereinabove, hot water is normally fed to crude oil gutter to dilute the pressed oil after the pressing operation. In this process, about up to 5.5% wet basis or up to 8.5% dry basis of the oil still remains in the pressed fibre after the extraction process. This means that the same amount of oil is not extracted from the palm fruit and this resulted in losses of the same amount of oil in the extraction process.

Some methods have been developed in the past to minimize the loss of oil in the extraction process, particularly in the digestion and pressing process. Some of the methods known in art include increasing the press cone pressure of the screw press so that more force can be exerted on the palm fruit to extract the oil. This method however often causes more breakages of kernels and nuts during the pressing process.

2 Another method that has been employed is to control the level of mash/oil palm fruit in the digester to ensure that complete digestion occurs within the digester. In this method, the level of the mash/oil palm fruit in the digester is monitored by a mechanical level indicator. When the level indicator shows that the level of the mash/oil palm fruit in the digester is low, more oil palm fruit will be fed into the digester. This method however is not very efficient as the feeding of the oil palm fruit into the digester is carried out manually. This causes a delay in adding more oil palm fruit into the digester when needed. Furthermore, the level of the contents in the digester is often not consistent. The level indicator may show readings that fluctuate between high and low at short intervals. By the time more oil palm fruit is ready to be fed into the digester manually, the level indicator may show a reading that does not require more oil palm fruit to be added. This results in poor digestion of the oil palm fruit as the oil palm fruit may not be added at appropriate time. For the purpose of palm oil milling, as much as possible of the oil content present in the palm fruit should be extracted, while at the same time minimizing oil losses.

Consequently, there is a need to provide a method, an apparatus and a system that seek to address at least one of the problems described hereinabove, or at least to provide an alternative.

SUMMARY OF THE INVENTION The above and other problems are solved and an advance in the art is made by a method, apparatus and system for digestion and pressing of oil palm fruit in a palm oil milling process in accordance with this invention. It is an advantage of a method, apparatus and system in accordance with this invention that the method, apparatus and system is able to reduce/remove oil content in mash/oil palm fruit during digestion process and this in turns reduces oil losses as some of the crude palm oil in the fruit is extracted out during the digestion process in the digester without affecting the quality of the crude palm oil obtained (i.e. increasing oil extraction and reducing oil losses). Therefore, oil losses/wastage due to oil contained in the pressed fiber that is to be disposed after the pressing process is reduced. A second advantage of this invention is that the method, apparatus and system is able to reduce (or at least

3 maintain) breakage of nuts and kernels of the oil palm fruit during the palm oil milling process. This is because high pressure of pressing of the oil palm fruit is not necessary since some of the oil present in the fruit has been extracted during the digestion process. A third advantage of this invention is that the method, apparatus and system allow the level of the mash/oil palm fruit in the digester to be detected more accurately and oil palm fruit to be fed into the digester automatically at appropriate time. A fourth advantage of this invention is that the system is integrated or linked to a digester level controller with hot water injection and to an on/off press machine operation. Furthermore, the crude palm oil can be easily collected from the digester through an efficient drainage system.

In accordance with an embodiment of this invention, a method for the digestion and pressing of oil palm fruit in a palm oil milling process is provided. The method comprises the controllably feeding a pretreated oil palm fruit into a digester having rotating means; controllably injecting a predetermined amount of water at a temperature of 80°C to 100°C into and at bottom side of the digester to remove crude palm oil from the oil palm fruit and to dilute the crude palm oil; collecting the crude palm oil removed from the oil palm fruit through a perforated base plate provided at the bottom of the digester; and discharging digested oil palm fruit from the digester.

In accordance with one embodiment of this invention, the method further comprises detecting level of contents in the digester prior to controllably feeding the pretreated oil palm fruit into the digester using an automated level detecting means. In accordance with the embodiment of this invention, the method further comprises maintaining a dilution ratio of water to crude palm oil to about 1 :1 using an automated controller system. Preferably, the water is in the range of about 25% to about 35%, and the crude palm oil is in the range of about 25% to about 35%. In other embodiment of this invention, the predetermined amount of water is controllably injected into and at the bottom side of the digester continuously using an automatic controller system.

In accordance with the embodiment of this invention, the oil palm fruit is pretreated by sterilizing and stripping the oil palm fruit from bunches. In accordance with another embodiment of this invention, a system for the digestion and pressing of oil palm fruit in a palm oil milling process is provided. The system comprises a digester having an inlet, an outlet and a perforated base plate provided at bottom of the digester for discharging crude palm oil removed from the digester; an automated level detecting means for detecting level of contents in the digester and controllably feeding a pretreated oil palm fruit into the digester; a water tank; a pipe in fluid communication with the water tank at one end and in fluid communication with the digester at another end, for delivering water from the water tank to the digester; and an automated controller system for controllably injecting the water from the water tank at a temperature of 80°C to 100°C into and at bottom side of the digester.

In accordance with one embodiment of this invention, the system further comprises a live steam injection having a valve for delivering steam to the digester for maintaining temperature of the digester within a predetermined range.

In accordance with one embodiment of this invention, the system further comprises a bottom plate proximate the perforated based plate for collecting crude palm oil discharged from the digester through the perforated base plate.

In accordance with one embodiment of this invention, the system further comprises a funnel proximate the perforated base plate for channeling the crude palm oil discharged from the digester through the perforated base plate to oil gutter.

In accordance with one embodiment of this invention, the system further comprises a digester chute proximate the bottom side of the digester for discharging digested oil palm fruit from the digester. In accordance with one embodiment of this invention, the system further comprises a pressing means for pressing digested oil palm fruit discharged from the digester chute.

In accordance with yet another embodiment of this invention, a digester for the digestion of oil palm fruit in palm oil milling process is provided. The digester

5 comprises a cylindrical housing having an inlet and an outlet; an automated level detecting means for detecting level of contents in the cylindrical housing and controllably feeding a pretreated oil palm fruit into the digester; a rotating means in the housing for rotating and urging the pretreated oil palm fruit received from the inlet through the housing in a direction towards the outlet; a pipe connected to the housing at one end for delivering water at a temperature of 80°C to 100°C into and at bottom side of the housing; and a perforated base plate at the bottom of the housing for discharging crude palm oil from the housing. In accordance with some embodiments of this invention, the perforated base plate having through holes with a diameter in a range of 4 mm to 6 mm. In some of these embodiments, the through holes are evenly spaced apart. In other embodiments, the through holes are arranged in a random manner. In some embodiments, a bottom plate is provided proximate the perforated base plate for collecting crude palm oil discharged from the digester through the perforated base plate.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other features and advantages of the present invention will more clearly understood from the following detailed description taken in conjunction with the accompanying drawings:

Figure 1 is a plan view of the digester system in accordance with the invention.

Figure 2A shows the minimum reading (see Table 1) of the emulsion layer of the crude palm oil obtained in accordance with the method of the present invention.

Figure 2B shows the average reading (see Table 1 ) of the emulsion layer of the crude palm oil obtained in accordance with the method of the present invention.

Figure 2C shows the maximum reading (see Table 1) of the emulsion layer of the crude palm oil obtained in accordance with the method of the present invention.

6 Figure 3A shows the minimum reading (see Table 3) of the emulsion layer of the crude palm oil obtained in accordance with the conventional method of injecting hot water into oil gutter to dilute the crude palm oil. Figure 3B shows the average reading (see Table 3) of the emulsion layer of the crude palm oil obtained in accordance with the conventional method of injecting hot water into oil gutter to dilute the crude palm oil.

Figure 3C shows the maximum reading (see Table 3) of the emulsion layer of the crude palm oil obtained in accordance with the conventional method of injecting hot water into oil gutter to dilute the crude palm oil.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a method, apparatus and system for the digestion and pressing of oil palm fruit in a palm oil milling process, in order to break up pericarps of the oil palm fruit and to extract oil from the oil palm fruit.

The method in accordance with the present invention comprises feeding pretreated oil palm fruit into a digester having rotating means. The oil palm fruit is rotated within the digester, causing the pericarps to loosen from nuts of the oil palm fruit. While the oil palm fruit is rotated within the digester, hot water at a temperate of about 80°C to about 100°C, preferably about 90°C to about 100°C is injected into and at bottom side of the digester to remove crude palm oil from the oil palm fruit and to dilute the crude palm oil.

The crude palm oil that is removed from the oil palm fruit is collected through a perforated base plate provided within the digester, preferably proximate the bottom of the digester. The digested oil palm fruit is removed and discharged from the digester through a digester chute, and delivered to a pressing machine, e.g. screw press. The removal of the crude palm oil in the digestion process results in less oil going into the pressing machine. This maximizes extraction of crude palm oil from the oil palm fruit as some amount of the crude palm oil is removed or extracted and collected from the digester before the oil palm fruit undergoes pressing process, which may result in some losses of oil during the pressing process. The amount of hot water to be injected into the digester is dependent on the amount of water and oil palm fruit present in the digester. Preferably, the amount of hot water to be injected is sufficient for maintaining about 1 : 1 dilution ratio of water to crude palm oil after the pressing process. Preferably, the water is within the range of about 25% to about 35% of the total mixture in the pressed liquor, and the crude palm oil is within the range of about 25% to about 35% of the total mixture in the pressed liquor. In one embodiment of the invention, the water is controllably injected into and at the bottom side of the digester continuously at a predetermined amount using an automated controller system.

In the method of the present invention, the oil palm fruit is pretreated by undergoing typical sterilization and stripping processes known in the art, before the oil palm fruit is fed into the digester.

The amount of pretreated oil palm fruit to be fed into the digester is determined by the level of contents present in the digester. The level of contents is monitored by an automated level detecting means, e.g. a sensor. During the digestion process, the digester is preferably maintained at about three quarter full. When the level of contents in the digester falls beyond the required level, more oil palm fruit will automatically and controllably be fed into the digester in a desired amount and at appropriate time when required. This automatic level detecting and feeding system is efficient as there will be no delay in feeding more oil palm fruit into the digester when needed. The system also helps to ensure that complete and effective digestion occurs within the digester.

In order to carry out the method as described hereinabove, use is made according to the invention of a system and apparatus represented diagrammatically by way of example, in the accompanying drawing. It is understood that other solutions which would be based on a similar principle form part of the present invention.

Referring to Figure 1 , a system for the digestion of oil palm fruit in a palm oil milling process according to the invention is provided. The system comprises a digester 10 having an inlet and an outlet, and a perforated base plate 14 provided at bottom of the digester for discharging crude palm oil removed from the digester; an

8 automated level detecting means 12 for detecting level of contents in the digester and controllably feeding a pretreated oil palm fruit into the digester; a water tank 16; a pipe 18 in fluid communication with the water tank 16 at one end and in fluid communication with the digester 10 at another end for delivering water from the water tank 16 to the digester 10; and an automated controller system 20 for controllably injecting the water at a temperature of about 80°C to about 100°C into and at the bottom of the digester.

In one embodiment of the invention, the water tank 16 is preferably an over- head process water tank that is in fluid communication with one end of the pipe 18 for supplying water to the pipe 18. Water is fed from the overhead process water tank 16 to the digester 10 via a hot water flow meter 30 by gravitational piping. The flow of the water from the water tank 16 to the digester 10 is controlled by the automated controller system 20 (or valve) which is activated to open as long as the press machine 24 is in operation. The automated controller system 20 controls the amount of hot water to be injected into and at the bottom of the digester for maintaining a preferred dilution ratio of water to crude palm oil in the digester to achieve the desired dilution of the crude palm oil. The system of the present invention further comprises a live steam injection 26 having valve 28 for delivering steam to the digester 10 for maintaining the temperature of the digester 10 within a certain range for softening the oil palm fruit in the digester 10. The temperature of the digester is preferably maintained within the range from about 80°C to about 100°C. One skilled in the art will recognise that other means may be employed to maintain the temperature of the digester within the said range.

The system may further comprise a bottom plate 32 for collecting the crude palm oil discharged from the digester 10 through the perforated base plate 14. The bottom plate 32 can be an integrated part of the digester or it can be a unit separable from the digester.

In one embodiment of the invention, the system may further comprise a funnel 34 proximate the perforated base plate 14 for channeling crude palm oil collected from the digester 10 to an oil gutter 36. In a preferred embodiment, the funnel 34 is positioned proximate the bottom plate 32 (as shown in Figure 1 ) if bottom plate 32 is used to collect the crude palm oil discharged from the digester 10 through the perforated base plate 14. Preferably, the funnel 34 is of the same size and/or shape as the bottom of the digester or the bottom plate 32. However, one skilled in the art will recognize that the funnel may take on other shapes and sizes without departing from this invention, as long as the funnel is of a size and shape sufficient to channel the oil collected from the digester 10 to the oil gutter 36.

The digested oil palm fruit is discharged from the digester 10 through a digester chute 22 after digestion is completed. The digested oil palm fruit is then delivered to a press machine 24 in which the digested oil palm fruit is pressed to produce a liquid stream consisting of oil, water, press cake or fibre and nuts. The liquid stream then passes through vibrating screens for removal of any fine solids before the liquid stream is delivered to a clarification tank (not shown) and dried under vacuum in any suitable conventional ways before the oil is sent to storage.

Referring to Figure 1 , the apparatus or digester in accordance with the present invention comprises a cylindrical housing having an inlet and an outlet; an automated level detecting means 12 for detecting level of contents in the cylindrical housing and controllably feeding a pretreated oil palm fruit into the cylindrical housing; a rotating means (not shown) for rotating and urging the oil palm fruit received from the inlet through the housing in a direction towards the outlet; a pipe 18 connected to the housing at one end for delivering hot water at a temperature of about 80°C to about 100°C into and at bottom side of the housing; and a perforated base plate 14 provided at the bottom of the housing for discharging crude palm oil removed from the oil palm fruit.

In one embodiment of the invention, the perforated base plate 14 has a plurality of through holes with each though hole having a diameter in a range of 4 mm to 6 mm, to provide better drainage of the crude palm oil from the digester. The through holes may be evenly spaced apart or they may be arranged randomly. The size of the through holes, the number of through holes provided on the base plate and the manner in which the through holes are arranged should be sufficient to allow the crude palm oil to be discharged from the digester efficiently. The perforated base plate may be made of a suitable steel or steel alloy. The automated level detecting means helps to monitor the level of contents in the digester to ensure that the digester is about three quarter full of oil palm fruit during the digestion process, and to control the amount of pretreated oil palm fruit to be fed into the digester. When the digester is less than three quarter full of oil palm fruit, more oil palm fruit will automatically and controllably be fed into the digester. This is to ensure that sufficient retention time is provided for complete digestion of the oil palm fruit to take place within the digester. This is to maximize the removal/extraction of crude palm oil from the oil palm fruit before the oil palm fruit undergoes pressing process.

The retention time for complete digestion of the oil palm fruit in the digester varies according to the size of pressed machine employed in the method. In one embodiment of the invention, the oil palm fruit is retained in the digester for about 15 to 20 minutes.

In a preferred embodiment of the invention, the automated level detecting means 12 is provided at the top portion of the digester 10. However, one skilled in the art will recognize that the automated level detecting means may be provided at any part of the digester without departing from this invention, as long as the automated level detecting means is able to monitor the level of contents in the digester accurately and control the amount of pretreated oil palm fruit to be fed into the digester.

As described hereinabove, a bottom plate 32 may be provided and may form part of the digester. The bottom plate 32 is preferably positioned proximate the perforated base plate 14 for collecting the crude palm oil discharged from the digester through the perforated base plate 14. The bottom plate 32 may be made of any suitable material including, but is not limited to, steel or steel alloy.

From the above description of the invention, it can be understood that method, apparatus and system of the present invention has several advantages over those known in the prior art. For example, the method, apparatus and system of the present invention introduce hot water injection at the bottom side of the digester. The digester has perforated base plate that provides improved drainage of the oil from the system and an automated level detecting means that controls the level of contents in the digester. The method, apparatus and system of the invention are able to reduce oil

11 losses in pressed fibre significantly, to about less than 4.5% wet basis. On average, about 1.0% wet basis of oil can be recovered by employing the method, apparatus and system of the invention. Instead of focusing at optimizing the press machine, the present invention focuses on introducing hot water injection into the digester to dilute and remove oil from the bottom of the digester at a first instance. This helps to reduce losses in oil which otherwise will occur during the pressing operation.

The quality of the recovered oil is not affected or compromised in any ways by using the method, apparatus and system of the present invention. The quality of the recovered oil is considered as normal diluted crude oil with no significant effect on the emulsion layer formation and no solid carried over to the next step in palm oil processing. The method, apparatus and system of the invention not only reduces oil loss in press cake, it also reduces nut breakages in the press cake as lower pressure needs to be applied to press the oil palm fruit to extract the oil.

The method employed in accordance with the invention does not change the rate of water dilution in palm oil milling process. The difference between the conventional digestion method and the method of the present invention is that in the present invention, water is added to the digester (before pressing process) while in the conventional method, water is added after the pressing operation.

The following examples are provided to further illustrate and describe particular specific embodiments of the present invention, and are in no way to be construed to limit the invention to the specific procedures, conditions or compositions described therein.

EXAMPLES

EXAMPLE 1

An experiment was carried out to illustrate the formation of emulsion when hot water is injected into and at the bottom of the digester and at the same time dilute the crude palm oil, in accordance with the method of the present invention.

12 36 samples containing crude palm oil were prepared in accordance with the method of the present invention. A spin test using a centrifuge equipment to spin the samples was carried out to determine the composition of the crude palm oil obtained by the method of the invention, which mainly consists of oil layer, emulsion layer, water layer and non-oil solid (NOS) layer, and to evaluate the emulsion layer formed by using the method, apparatus and system of the invention as compared to the conventional method used in the prior art to dilute crude palm oil. A good dilution or process is determined by maintaining a dilution ratio of water to crude palm oil to about 1 :1 (preferably, the water is in the range of about 25% to about 35%, and the crude palm oil is in the range of about 25% to about 35%) with no or less emulsion layer. If more emulsions are formed, it will reduce the efficiency of the clarification process and this will contribute to high oil loss in clarifier underflow.

After the spin test, thickness of the emulsion layer formed by each sample was measured. The minimum, average and maximum values of the measurements of the samples were obtained, and as shown in Table 1 and Figures 2A to 2C. Other measurements of the compositions of the crude palm oil were also taken and as shown in Table 2. Table 1 : Emulsion formation - Hot Water Injection into Digester

Table 2: Hot Water Injection into Digester

^*n - number of samples

13 EXAMPLE 2

An experiment was carried out to illustrate the formation of emulsion when hot water is injected into oil gutter to dilute the crude palm oil, in accordance with the conventional method.

40 samples containing crude palm oil were prepared in accordance with the conventional method of injecting hot water into oil gutter (after digestion and pressing process) to dilute the crude palm oil. Similar spin test was carried out to determine the composition of the crude palm oil obtained by the conventional method and to evaluate the emulsion layer formed by the method.

After the spin test, thickness of the emulsion layer formed by each sample was measured. The minimum, average and maximum values of the measurements of the samples were obtained, and as shown in Table 3 and Figures 3A to 3C. Other measurements of the compositions of the crude palm oil were also taken and as shown in Table 4.

Table 3: Emulsion formation - Hot Water Injection into Oil Gutter

Table 4: Hot Water Injection into Oil Gutter

^*n - number of samples Table 5: Statistical Analysis

- not significant, S - significant

Based on the data collected in Examples 1 and 2, it is clear that there is no significant difference on the emulsion layers formed between the method of the present invention and the conventional method known in the art as the measurements taken on the emulsion layers do not differ much in both Examples (see Tables 1 and 3). This means that the method of the present invention is effective and does not affect the concept of dilution of crude palm oil.

Table 2 shows the measurements of the compositions of the crude palm oils obtained in accordance with the method of the present invention when hot water was injected into the digester. Table 4 shows the measurements of the compositions of the crude palm oils obtained in accordance with the conventional method when hot water was injected into the oil gutter.

Based on the data collected and as shown in Tables 2 and 4, it is clear that there is no significant difference on the compositions of the crude palm oils obtained by the method of the present invention and the conventional dilution method known in the art as the readings on the compositions of the crude palm oils recorded in both methods do not differ much (see Tables 2 and 4).

In particular, Table 5 shows the statistical analysis results of comparison between the results obtained using the method of the present invention (Table 2) and the results obtained using the conventional method (Table 4). t-test is usually used to compare the significant difference between two results. When the t-value is less than the t-critical value, it means that there is no significant effect between the two methods. From Table 5, we can see that all the t-values are less than the respective t-critical values. This confirmed the findings that there is no significant difference on the compositions of the crude palm oils obtained by the method of the present invention and the conventional dilution method.

EXAMPLE 3

An experiment was carried out to evaluate the loss of crude palm oil in pressed fibre of crude palm fruit with and without injecting hot water into the digester.

In this experiment, hot water at a temperature of about 90°C to about 100°C was introduced into and at the bottom side of the digester. Hot water was supplied from an overhead process water tank by gravitational piping. The digester was maintained at three quarter full to ensure that there was an effective displacement of hot water in the digester. Samples of pressed fibre were taken hourly from the digester and analyzed for oil losses. In total, 66 samples were taken and the results obtained were as shown in Table 6. The readings in Table 7 were taken from samples obtained using the conventional method of introducing hot water into the oil gutter.

Table 6: Hot Water Injection into Digester

Table 7: Hot Water Injection into Oil Gutter

^*n - number of samples The results in Tables 6 and 7 show that there is a reduction in percentage of oil loss wet basis (OLWB) in the pressed fibre (about 5.13% to 4.11%) using the method of the present invention.

Table 8 Statistical Analysis

* NS - not significant, S - significant

Based on the data collected in this test, it is clear that there is a significant difference on the reduction of oil loss in the pressed fibre using the method of the present invention as compared to the conventional dilution method known in the art.

In particular, Table 6 shows the results of pressed fibre analysis obtained during the experiment when hot water was injected into the digester in accordance with the method of the present invention. Table 7 shows the results of pressed fibre analysis obtained during the experiment when hot water was injected into the oil gutter in accordance with the conventional method known in the art. Table 8 shows the statistical analysis results of comparison between the results obtained in accordance with the method of the present invention (Table 6) and the results obtained in accordance with the conventional method (Table 7). Similar t-test was used to compare the significant difference between the results obtained in the two methods. When the t-value is less than the t-critical value, it means that there is no significant difference between the two methods.

From table 8, we can see that the t-value for %OLWB (percentage of oil loss wet basis) is greater than the t-critical value. This means that there is a significant difference in terms of reduction in the oil loss in the pressed fibre using the method of the present invention as compared to the conventional dilution method. In other words, it means that by using the method of the present invention, oil loss in pressed fibre is reduced. The t-value for %VM (Moisture) and %Broken Nuts are less than the t-critical value. This means that there are no significant differences in terms of the moisture and broken nuts present in the pressed fibre using the method of the present invention as compared to the conventional dilution method.

EXAMPLE 4

This experiment was carried out to determine if there is any possible impact on oil clarification and oil recovery in sludge using the method of the invention.

Samples of clarifier underflow were taken hourly from the clarifier and analyzed for oil losses. The results obtained were as shown in Table 9. The readings in Table 10 were taken from samples obtained using the conventional method of introducing hot water into the oil gutter.

Table 9: Hot Water Injection into Digester

^*n - number of samples

Table 10: Hot Water Injection into Oil Gutter

Table 1 1 Statistical Analysis

- not significant, S - significant Based on the data collected in this Example, it is clear that there is no significant effect on the oil loss in clarifier underflow between the method of the present invention and the conventional dilution method known in the art.

In particular, Table 9 shows the results of oil loss in clarifier underflow which were obtained during the experiment when hot water was injected into the digester. Table 10 shows the results of oil loss in clarifier underflow which were obtained during the experiment when hot water was injected into the oil gutter. Table 11 shows the statistical analysis results of comparison between the results obtained in accordance with the method of the present invention (Table 9) and the results obtained in accordance with the conventional method (Table 10). Similar t-test was used to compare the significant difference between the results obtained in the two methods. When the t-value is less than the t-critical value, it means that there is no significant difference between the two methods.

From table 11 , we can see that all the t-values are less than the respective t- critical values. This means that there is no significant difference in the reduction of oil loss in clarifier underflow using the method of the present invention as compared to the conventional dilution method.

The above is a description of the subject matter the inventor regards as the invention and is believed that others can and will design alternative systems that include this invention based on the above disclosure.

19

Claims

1. A method for the digestion and pressing of oil palm fruit in a palm oil milling process, the method comprising:

controilably feeding a pretreated oil palm fruit into a digester having rotating means;

controilably injecting a predetermined amount of water at a temperature of 80°C to 100°C into and at bottom side of the digester to remove crude palm oil from the oil palm fruit and to dilute the crude palm oil;

collecting the crude palm oil removed from the oil palm fruit through a perforated base plate provided at the bottom of the digester; and

discharging digested oil palm fruit from the digester.

2. The method according to claim 1 , further comprising:

detecting level of contents in the digester prior to controilably feeding the pretreated oil palm fruit into the digester using an automated level detecting means.

3. The method according to claim 1 , further comprising:

maintaining a dilution ratio of water to crude palm oil to about 1 :1 using an automated controller system.

4. The method according to claim 3, wherein the water is in the range of about 25% to about 35%.

5. The method according to claim 3, wherein the crude palm oil is in the range of about 25% to about 35%.

6. The method according to claim 1 , wherein the predetermined amount of water is controilably injected into and at the bottom side of the digester continuously using an automated controller system.

7. The method according to claim 1 , wherein the oil palm fruit is pretreated by sterilizing and stripping the oil palm fruit from bunches.

20

8. A system for the digestion and pressing of oil palm fruit in a palm oil milling process, the system comprising:

a digester having an inlet, an outlet, and a perforated base plate provided at bottom of the digester for discharging crude palm oil removed from the oil palm fruit; an automated level detecting means for detecting level of contents in the digester and controllably feeding a pretreated oil palm fruit into the digester;

a water tank;

a pipe in fluid communication with the water tank at one end and in fluid communication with the digester at another end, for delivering water from the water tank to the digester; and

an automated controller system for controllably injecting the water from the water tank at a temperature of 80°C to 100°C into and at bottom side of the digester.

9. The system according to claim 8, further comprising:

a live steam injection having a valve for delivering steam to the digester for maintaining temperature of the digester within a predetermined range.

10. The system according to claim 8, further comprising:

a bottom plate proximate the perforated base plate for collecting crude palm oil discharged from the digester through the perforated base plate.

1 1. The system according to claim 8, further comprising:

a funnel proximate the perforated base plate for channeling the crude palm oil discharged from the digester through the perforated base plate to an oil gutter.

12. The system according to claim 8, further comprising:

a digester chute proximate the bottom side of the digester for discharging the digested oil palm fruit from the digester.

13. The system according to claim 12, further comprising:

a pressing means for pressing the digested oil palm fruit discharged from the digester chute.

14. A digester for the digestion of oil palm fruit in a palm oil milling process, the digester comprising: a cylindrical housing having an inlet and an outlet;

an automated level detecting means for detecting level of contents in the cylindrical housing and controllably feeding a pretreated oil palm fruit into the digester; a rotating means in the housing for rotating and urging the pretreated oil palm fruit received from the inlet through the housing in a direction towards the outlet;

a pipe connected to the housing at one end for delivering water at a temperature of 80°C to 100°C into and at bottom side of the housing; and

a perforated base plate at the bottom of the housing for discharging crude palm oil from the housing.

15. The method according to claim 1 , the system according to claim 8 and the digester according to claim 14, wherein the perforated base plate having through holes with a diameter in a range of 4 mm to 6 mm.

16. The method, the system and the digester according to claim 15, wherein the through holes are evenly spaced apart.

17. The method, the system and the digester according to claim 15, wherein the through holes are arranged in a random manner.

18. The digester according to claim 14, further comprising: