FIELD OF THE INVENTION The present invention relates generally to arrangement for drying oil palm lumbers. More particularly, the present invention relates to an improved method and system for fast drying an oil palm lumber that requires less drying time and energy, inexpensive and demonstrates almost free of drying defects. BACKGROUND OF THE INVENTION

Oil palm wood derived from oil palm (Elaeis guineensis) is a relatively new material that is rapidly gaining popularity as a versatile and strategic alternative to wood materials. It can be obtained from oil palm trunk which could be turned into lumber through appropriate sawn as well as air drying and kiln drying processes, be it conventionally or with some modifications at the process parameters.

Oil palm lumber has its own idiosyncrasies and monocotyledonous nature that reflects in a great variation of properties compared to the traditional woods. It has a very high moisture content that varies between 100% to 500% as opposed to woods depends on the part of the trunk where the wood is taken. Based on depth of the trunk, the highest moisture content was reached at the center of trunk and a gradual decrease to the outer part of trunk. Although kiln drying is commonly used for drying of oil palm lumber, it is however completely different than kiln drying other timber, particularly due to high moisture variation.

One problem with the kiln drying in the conventional system is that it takes a much longer time to dry usually in time periods up to 35 days or more, and often requiring intervention in order to finish the drying process. Another problem is that the conventional kiln drying for oil palm lumber which takes place in a dry kiln would have caused the wood to have sustained substantial drying defects. The drying defects include warp, cracks, end checks, internal check, surface checks and cell collapse. Furthermore, this type of drying process has high financial, operational and energy costs, requiring specialized equipment including appropriate driers. The problems however have never been addressed sufficiently by prior attempts and consequently, there still exists a need for an improved method and system for drying an oil palm lumber. Although there are methods and systems for the same in the prior art, for many practical purposes, there is still considerable room for improvement.

SUM MARY OF THE INVENTION The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.

Accordingly, the present invention provides a method of drying an oil palm lumber. The method can be characterized by the steps of determining a thickness of the oil palm lumber; selectively forming a plurality of holes in a predefined pattern based on the thickness of the oil palm lumber, wherein the plurality of holes extends in a direction of the thickness; pressing and heating the oil palm lumber with the plurality of holes formed thereon using hot plates at a predefined set of temperature, time and compression level; and subjecting, after the pressing and heating, the oil palm lumber into a kiln drying for reducing to a target moisture content.

Preferably, the method further comprises comparing the thickness of the oil palm lumber against a thickness threshold; and assigning, based on the thickness, the oil palm lumber to the hole-forming. Preferably, the method further comprises determining an initial moisture content, a density and a lumber position in respect of oil palm trunk of the oil palm lumber; comparing the initial moisture content, the density and the lumber position against a moisture content threshold, a density threshold and a lumber position lookup chart, respectively; and assigning, based on the initial moisture content, the density, the lumber position or any combination thereof, the oil palm lumber to either a one-stage pressing and heating or a two-stage pressing and heating to achieve an intermediate moisture content.

It is preferred that the one-stage pressing and heating comprises a first predefined set of temperature, time and compression level.

It is preferred that the two-stage pressing and heating comprises a first stage having the first predefined set and a second stage having a second predefined set of temperature, time and compression level that is different than that of the first stage.

Preferably, the step of selectively forming a plurality of holes comprises machining the plurality of holes to a diameter along the thickness of the oil palm lumber to form through holes, blind holes or any combination thereof.

Preferably, at the step of subjecting the oil palm lumber into a kiln drying, the target moisture content of the oil palm lumber is reduced from an intermediate moisture content resulted from the pressing and heating. In accordance with another aspect of the present invention, there is provided a system for drying an oil palm lumber.

The system can be characterized by a segregation unit configured for monitoring a thickness, an initial moisture content, a density and a lumber position in respect of oil palm trunk of the oil palm lumber and for comparing the same against respective thresholds; a hole-forming unit configured for selectively forming a plurality of holes in a predefined pattern based on the thickness of the oil palm lumber; a first drying unit comprising a one-stage pressing and heating and a two-stage pressing and heating configured for hot-pressing the oil palm lumber with the plurality of holes formed thereon to an intermediate moisture content based on the initial moisture content, the density, the lumber position or any combination thereof, wherein the one-stage pressing and heating comprises a first predefined set of temperature, time and compression level, wherein the two- stage pressing and heating comprises a first stage having the first predefined set and a second stage having a second predefined set of temperature, time and compression level that is different than that of the first stage; and a second drying unit configured for kiln-drying the oil palm lumber having the intermediate moisture content to a target moisture content. Preferably, the segregation unit comprises a thickness segregation unit and a moisture content, density and lumber position segregation unit.

Preferably, the plurality of holes extends in a direction of the thickness of the oil palm lumber.

Preferably, the plurality of holes, in the predefined pattern, are arranged in longitudinal, transversal and diagonal directions.

Preferably, the plurality of holes are through holes, blind holes or any combination thereof.

Preferably, the second drying unit is positioned after the first drying unit.

Preferably, the respective thresholds include a moisture content threshold, a density threshold and a lumber position lookup chart.

It is therefore an advantage of the present invention that significantly shortens the drying time of the oil palm lumber from days to hours, free of drying defects and reduces financial, operational and energy costs.

It is therefore another advantage of the present invention that the method and system can be easily employed for drying of the oil palm lumber and maintained in a highly specific and compact, cost-effective, quick and simple manner, without the use of complicated and sophisticated components.

The foregoing and other objects, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

Figure 1 is a flow diagram depicting a method of drying an oil palm lumber according to one embodiment of the present invention;

Figure 2 illustrates a plurality of holes formed on the oil palm lumber that is arranged in a predefined pattern according to one embodiment of the present invention; Figure 3 illustrates a cross-sectional view of the oil palm lumber showing a blind hole and a through hole according to one embodiment of the present invention;

Figure 4 is a plot of moisture content and time taken for drying showing comparison between the conventional kiln drying and the present invention according to one embodiment of the present invention; and

Figure 5 is a plot of moisture content and time taken for drying showing comparison on the hot pressing between two oil palm lumbers having two different initial moisture contents according to embodiment of the present invention.

Figure 7 shows the device for dissipating impact energy according to another preferred embodiment of the present invention; and

Figure 8 shows the device for dissipating impact energy mounted to the structure according to another exemplary embodiment of the present invention;

It is noted that the drawings may not be to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numberings represent like elements between the drawings. DETAILED DESCRIPTION OF THE INVENTION

It is an object of the present invention to provide an improved method and system for drying an oil palm lumber that can significantly shorten the drying time of the oil palm lumber from weeks to hours, that has minimal or free of drying defects and that can reduce financial, operational and energy costs involved thereof. It is further an object of the present invention to allow deployment and maintenance of the method and system thereof in a highly specific and compact, cost-effective, quick and simple manner, without the use of complicated and sophisticated components.

According to one preferred embodiment of the present invention, the method of drying an oil palm lumber comprises a number of steps as shown in Figure 1. The oil palm lumber which can be prepared from either the outer and inner parts of oil palm trunk will be physically examined to determine its thickness as in step 100. The length of the oil palm lumber, on the other hand, can vary and is not necessarily limited to any size magnitude.

In step 100a, once the thickness of the oil palm lumber has been determined, the detected thickness of the oil palm lumber will be compared against a thickness threshold. Preferably, the thickness threshold is defined at an earlier stage. At this thickness segregation, the oil palm lumber will be basically categorized or assigned into one of at least two groups having two different ranges of thickness as divided by the aforesaid thickness threshold. For instance, let the thickness threshold be at 1 cm, any oil palm lumber with thickness less than 1 cm will be assigned to a first group and the rest will be assigned to a second group having lumber of thickness more than or equal to 1 cm. At this instance, the maximum thickness of the oil palm lumber is preferably set to about 3 cm. Depends upon the number of thresholds set up therefor, the number of groups of different ranges of thickness will increase proportionally.

Subsequently, at least one of the groups of different ranges of thickness will be selected and the oil palm lumber which falls within the said group will be assigned to the next step which is hole-forming. This is in accordance with step 100b whereby the oil palm lumber is assigned to the hole-forming based on its thickness measured thereof.

To facilitate monitoring the thickness of the oil palm lumber and segregating the oil palm lumber, the present invention provides a suitable segregation unit 200, namely a thickness segregation unit 200a in accordance with one preferred embodiment.

The oil palm lumber obtained from conventional oil palm sawing patterns can be used and employed in the present invention. However, an oil palm lumber obtained from quality polygon sawing patterns and cant sawing patterns is preferred to be used.

Following step 100b, the method executes the step of selectively forming a plurality of holes 300 (see step 101 ). In this respect, the plurality of holes 300 will be formed on the oil palm lumber selected from the preceding step, preferably in a predefined pattern. Of the predefined pattern, the plurality of holes 300 is arranged in longitudinal, transversal and diagonal directions as shown by Figure 2.

According to one exemplary embodiment of the present invention, the plurality of holes 300 are arranged with diagonal holing arrangement at 30 mm diagonal distance, diameter of 5-9 mm depending upon the initial moisture content of the oil palm lumber. For any sample with an initial moisture content of less than 200%, the hole diameter will be about 5-8 mm and any sample with an initial moisture content of more than or equal to 200%, the hole diameter will be about 6- 9 mm.

The plurality of holes 300 can extend in a direction of the thickness of the oil palm lumber thereof. In step 101 a, machining tool such as drillers can be used to machine the plurality of holes 300 to a certain diameter along the thickness of the oil palm lumber to form through holes, blind holes or any combination thereof. An example of a blind hole and a through hole is shown by a cross-sectional view of the oil palm lumber in Figure 3. A blind hole refers to a hole that is reamed, drilled or milled to a specified depth without breaking through to the other side of the oil palm lumber. The depth of holing can be made within a range of 30-70% of the thickness of the oil palm lumber, which depends on the initial moisture content of the same. Any sample with an initial moisture content of less than 200% (those from the outer part of trunk) should have holing 50-70% of the original thickness, and any sample with an initial moisture content of more than or equal to 200% (those from the inner part of trunk) should have holing 30-50% of the original thickness. A through hole, on the hand, refers to a hole that is reamed, drilled or milled completely through the oil palm lumber. The through hole gives faster drying and more stable final product, while the blind hole gives one surface clear with a slightly longer drying time compared to the through hole. The plurality of holes 300 are drilled into the oil palm lumber to quicken the evaporation. With regards to the plurality of holes 300, the hole diameter can range from 0.5-0.9 cm with the distance between holes set at 2-3 cm.

This above step 101 is preferably executed by a hole-forming unit 201 that can be configured to selectively form a plurality of holes in a predefined pattern based in the thickness of the oil palm lumber.

Once the plurality of holes 300 is formed on the oil palm lumber, the step 102 of pressing and heating the said oil palm lumber using hot plates will commence. The pressing and heating or simply the hot-pressing is preferably conducted at a predefined set of temperature, time and compression level, which can be executed by a first drying unit 202 applying modified direct contact drying using a hot press. During this step, the first drying unit 202 will create compressed surface layers which provide additional strength to the oil palm lumber in addition to its main function of preventing or reducing drying defects.

The first drying unit 202 comprises a one-stage pressing and heating 202a and a two-stage pressing and heating 202b. The one-stage pressing and heating 202a comprises a first predefined set of temperature, time and compression level. The two-stage pressing and heating 202b, on the other hand, comprises a first stage 202b' having the first predefined set and a second stage 202b" having a second predefined set of temperature, time and compression level that is different than that of the first stage 202b'. According to one exemplary embodiment of the present invention, the one- stage pressing and heating 202a has a first predefined set of about 180°C temperature, 40 minutes time and 10-20% compression level as well as cyclic to achieve of about 20-40% of intermediate moisture content. The plates should be opened at least two times to release the buildup steam within the first 10 minutes. The two-stage pressing and heating 202b, in addition to the above first predefined set as its first stage 202b', comprises a second predefined set of about 180°C, 40 minutes time and 20-60% compression level as well as cyclic for its second stage 202b". Similar to the one-stage pressing and heating 202a, the plates should also be opened at least two times to release the buildup steam within the first 10 minutes when dealing with the two-stage pressing and heating 202b. At the two- stage pressing and heating 202b, the first stage 202b' is followed immediately by the second stage 202b" until about 20-40% of intermediate moisture content is achieved. In this regard, the oil palm lumber will next be segregated according to its moisture content, density, lumber position in respect of oil palm trunk or any combination thereof in the following step 104, where an initial moisture content, a density and a lumber position in respect of oil palm trunk of the oil palm lumber is determined. The initial moisture content will be compared against a moisture content threshold in step 104a. Similarly, in this step, the density and the lumber position will also be compared against a density threshold and a lumber position lookup chart, respectively. Subsequently, in step 104b, based on the initial moisture content, the density, the lumber position or any combination thereof, the oil palm lumber will be assigned to either the one-stage pressing and heating 202a or the two-stage pressing and heating 202b so as to suitably achieve an intermediate moisture content.

At the moisture content segregation, for example, the oil palm lumber will be basically categorized or assigned into one of at least two groups having two different ranges of moisture content as divided by the aforesaid moisture content threshold. For instance, let the moisture content threshold be at 200%, any oil palm lumber with moisture content less than 200% will be assigned to a first group and the rest will be assigned to a second group having lumber of moisture content more than or equal to 200%. Depending upon the number of thresholds set up therefor, the number of groups of different ranges of moisture content will increase proportionally.

In another example, at the density segregation, the oil palm lumber will be categorized into one of at least two groups having two different ranges of density as divided by the aforesaid density threshold. For instance, let the density threshold be at 0.3 gram per cubic centimeter (g/cm ³ ), any oil palm lumber with density less than 0.3 g/cm ³ will be assigned to a first group and the rest will be assigned to a second group having lumber of density more than or equal to 0.3 g/cm ³ . Depending upon the number of thresholds set up therefor, the number of groups of different ranges of density will increase proportionally.

With regards to the lumber position, an oil palm lumber may be extracted from any portion of oil palm trunk along its radius. To ease understanding, divide a cross-section of the oil palm trunk into three distinct ring layers along the surface, be it equally or proportionally and consider the outer most ring layer as Lumber Position 1 and the two inner most layers from the inner portion of the oil palm trunk as Lumber Position 2. These positions, i.e. Lumber Position 1 and Lumber Position 2, will be referred to as the lumber position lookup chart. Subsequently, any oil palm lumber falls within Lumber Position 1 will be assigned to a first group and the rest will be assigned to a second group having lumber obtained from Lumber Position 2. Depending upon the number of thresholds set up therefor, the number of groups of different ranges of density will increase proportionally.

Subsequently, at least one of the groups of different ranges of moisture content, density and lumber position will be selected and the oil palm lumber which falls within the said group will be assigned to the next step which is the hot- pressing. This is in accordance with step 102 whereby the oil palm lumber is assigned to the hot-pressing based on its moisture content detected thereof. It is further possible that the lumber is segregated based on any combination thereof. This includes a preferred combination of moisture content and density, moisture content and lumber position, density and lumber position, and a combination of all of them, which is moisture content, density and lumber position.

To facilitate monitoring the moisture content of the oil palm lumber and segregating the oil palm lumber, the present invention provides another suitable segregation unit 200, namely a moisture content, density and lumber position segregation unit 200b in accordance with one preferred embodiment.

The final step involves drying the oil palm lumber in a kiln of a second drying unit 203 at high temperature of between about 90°C and 1 10°C to reduce the intermediate moisture content to a target moisture content, as shown in step 103. The oil palm lumber, after heating and pressing, will be subject to a kiln drying for reducing to the target moisture content. The target moisture content is preferably 5-10%. The second drying unit 203 is preferably positioned immediately after the first drying unit 202. Figure 4 provides a comparison of drying rate of the conventional kiln drying and the present invention (represented by I and I I of two different initial moisture contents). From the plot, it can be seen that the conventional kiln drying requires about 5 weeks in order to complete the drying process, i.e. to achieving the target moisture content, while the present invention requires only 3 hours to achieving the same. Figure 5 provides more details on a comparison of compression level between two samples of oil palm lumber of the present invention (represented by I and I I of two different initial moisture contents).

As can be appreciated, the oil palm lumber produced thereof can be used in substantially the same way wood is used. It can be used as, for example but not limited to, a decorative piece, furniture, handicrafts and interior design parts as well as structure of boards.

The terms "a" and "an," as used herein, are defined as one or more than one. The term "plurality," as used herein, is defined as two or more than two. The term "another," as used herein, is defined as at least a second or more. The terms "including" and/or "having," as used herein, are defined as comprising (i.e., open language). While this invention has been particularly shown and described with reference to the exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.