WO2021024026A1

WO2021024026A1 - A method for preparing empty fruit bunch fiber in a paper and/or pulp production process

Info

Publication number: WO2021024026A1
Application number: PCT/IB2019/056745
Authority: WO
Inventors: Chalerm KOKANUTAPORN
Original assignee: Thai Eastern Pulp And Paper Co., Ltd.
Priority date: 2019-08-08
Filing date: 2019-08-08
Publication date: 2021-02-11

Abstract

An embodiment of the current invention provides a method for preparing empty fruit bunch (EFB) fibers in a paper and/or pulp production process. The method comprises the following steps: EFB fibers are delivered and/or loaded into a hopper. Steam is injected into the hopper in order to steam the EFB fibers. The EFB fibers are released from the hopper into a chain of downstream process containers. The chain of downstream processing containers are configured to wash lignin out from the steamed EFB fibers and to perform a NaOH treatment on the steamed and washed EFB fibers.

Description

A Method For Preparing Empty Fruit Bunch Fiber in a Paper and/or Pulp Production

Process

Embodiments of the present invention refer to a method for preparing empty fruit bunch fiber in a paper and/or pulp production process. Further embodiments refer to a method for removing lignin from the empty fruit bunch fiber.

Empty fruit bunch (EFB) fibers, i.e., oil palm empty fruit bunches resulting from processing fresh oil palm fruit bunches, may be treated or used for pulp generation. The fiber wall of an EFB fiber is made up with a number of layers. The fibril orientation in the layers is important for the fiber stiffness and the fiber strength of a pulp and/or paper. Lignin is also contained between the layers, in particularly in the so-called middle lamella area.

If the amount of lignin is too high, the EFB fibers may still be or remain in bundles, and not individual EFB fibers. This affects the strength properties expressed as tensile index and tear index.

Physical characterization of handsheets was made for an assessment of paper making per formance. Table 1 shows the result of testing laboratory handsheets with a grammage of 125 g/m² prepared from pulp without laboratory refining and after laboratory refining. The laboratory refining, with 4000 revolutions, took place in a PFI refining mill.

For the results see Table 1 below.

Table 1

Strength properties, expressed as tensile and/or tear index, remain low or are low even after laboratory refining, which indicates that the EFB fibers have poor bonding ability regarding high lignin contained and/or bundled EFB fibers, and may require further refining for exposing EFB fiber surfaces with better bonding ability.

In a conventional production plant EFB fiber pulp may be produced without heat, in a so- called cold soda process. Before selling a pulp dried sheet, improving the quality, for exam ple by removing lignin and oil excess out of the EFB fiber, was tested for many years.

There is a need for an effective and low cost approach to remove lignin from the EFB fibers without destroying the EFB fibers, which is easy to maintain and uses less harmful chemi cals, in order to improve the pulp quality.

This objective is solved by the subject matter of the independent claims.

An embodiment of the current invention provides a method for preparing empty fruit bunch (EFB) fibers in a paper and/or pulp production process. The method comprises the following steps:

EFB fibers are delivered and/or loaded into a hopper.

Steam is injected into the hopper in order to steam the EFB fibers.

The EFB fibers are released from the hopper into a chain of downstream process containers.

The chain of downstream processing containers are configured to wash lignin out from the steamed EFB fibers and to perform a NaOFI treatment on the steamed and washed EFB fibers.

In other words, EFB fibers are loaded into a hopper, are steamed in the hopper by the injected steam and are released from the hopper into a chain of downstream processing containers in order to prepare the EFB fibers for further processing, e.g., before washing lignin out from the steamed EFB fibers and before the NaOFI treatment of the steamed and washed EFB fibers.

The method for preparing EFB fibers is performed in a hopper or in a TEPP fiber sterilizer, which is configured to steam long EFB fibers in order to remove lignin. The process is using steam to open the surface of the EFB fibers, in particularly the middle lamella area, in order to remove lignin without destroying the EFB fibers and to use less harmful chemicals in order to avoid water treatment costs and to protect the environment.

The long EFB fibers are delivered and/or loaded into a hopper, for example for 800 kg bone dry (BD), containing around 0% of moisture, of each batch. Steam, for example about 3.5 tons of steam with a temperature of about 150°C and a pressure about 3.5 bars, is injected into the hopper to increase the temperature, for example up to 150° C for about five minutes. For example, after about five minutes, the hopper gate opens and the long EFB fibers are released into the next processing container, for example into a pulper tank, where the pulp production continues.

According to embodiments (see for example claim 2), washing out lignin comprises mixing the steamed EFB fibers with water in a pulper tank and releasing water with lignin from the pulper tank.

As a result of the steaming, the surface of the EFB fiber opens up, in particular the middle lamella area. After the steamed fiber is loaded into the pulper tank, the rotor of the pulper tank starts to mix the EFB fiber with, for example, 20 m³ of water contained in the pulper tank, for, for example, 20 minutes, to be the first stage of EFB fiber cleaning before deliver ing the EFB fibers to the NaOFI tank. Mixing with water may result in washing out lignin from the middle lamella area and washing out sand, small pieces of palm shells, and excessive oil contained by the EFB fiber. The lignin, sand, palm shell and excessive oil is removed easily, by releasing them with the water from the pulper tank.

According to embodiments (see for example claim 3), the method further comprises draining out used water and spraying new water into the washed and steamed EFB fibers once or several times before the NaOFI treatment.

In some cases the EFB fibers may be washed once more or several times before the NaOFI treatment. Further washing may comprise draining out used water and spraying new water into the washed and steamed EFB fibers. The used water released from the pulper tank and/or from the further washing may be recycled, e. g. it may be delivered to an Equalizer pond (EQ) and/or to an oil-tap pond to treat used water and to send or deliver the water back into the process or back into the pulper tank. According to further embodiments (see for example claim 4), the draining out used water and spraying new water is performed in one or more washer machines.

Further washing the EFB fibers in separate tanks or washer machines may result in speed ing up the pulp/paper production process by chunking up the washing process into smaller steps which may be conducted parallel, within similar time frames.

Furthermore, using separate tanks or containers for the process steps makes it easier to reuse or recycle water. Using one chemical chest for the entire pulp production process makes it more difficult to reuse water, regarding this water may contain lignin, sand, palm shell, excessive oil and NaOFI, which makes it difficult to separate waste and chemical agents.

In a preferred embodiment (see for example claim 5), the mass mixing ratio of EFB fibers to water is within a range of 1 :40 to 1 :60, preferably about 1 :50 within the pulper tank.

In an optimal situation, 800 kg of steamed EFB fiber is mixed with 20 m³ of water. This translates to a mass mixing ratio of 1 :50. In other cases the mass mixing ratio may be within a range of 1 :40 to 1 :60. Choosing the right mass mixing ratio may result in washing out a maximum amount of lignin with a minimum amount of water usage.

In a preferred embodiment (see for example claim 6), the mixing in the pulper tank is per formed for about 15 to 25 minutes, preferably about 20 minutes.

After the steamed EFB fiber is loaded, the rotor may start to mix EFB fiber with water for 20 minutes to be the first stage of EFB fiber cleaning before delivering the EFB fiber to the NaOFI tank.

An optimal mixing time may result in using less amount of water while washing the same amount or more lignin out of the EFB fiber and/or may result in speeding up the process with the same amount of lignin washed out.

In a preferred embodiment (see for example claim 7), the steamed EFB fibers are mixed with a quantity of 20 m³ water in the pulper tank. After conducting steaming on the EFB fiber, the surface of the EFB fiber, or especially the middle lamella area, opens. The steamed EFB fibers are mixed with about 20 m³ water in order to wash the lignin out from the middle lamella area of the EFB fiber.

According to embodiments (see for example claim 8), the EFB fibers are longer than 2 cm.

Using long EFB fibers, such as more than 2 cm long, in the pulp/paper production process may be more energy efficient by not cutting EFB fibers into small pieces, for example smaller than 2 cm.

Furthermore, using long EFB fibers may result in a pulp/paper with a higher tearing re sistance and/or a higher tensile strength.

According to further embodiments (see for example claim 9), injecting the steam into the hopper increases the temperature of the EFB fibers in the hopper to a range of 60-150 °C.

The temperature increase of the EFB fibers to a range of 60-150 °C, preferably 150 °C, may open the surface of the EFB fiber, in particular the middle lamella area.

As lignin is contained in the middle lamella area, more lignin may be removed and/or re leased from the EFB fibers resulting more individual, less bundled EFB fibers and/or a re duced NaOFI consumption in the pulp/paper production. For example, in a conventional, usual process about 62.5 kg NaOFI/1 ton of EFB fiber is used, while in the present process, after advanced stream treatment, about 50 kg NaOFI /1 ton of EFB fiber is used. In the inventive process less NaOFI is consumed because the EFB fiber surface or the middle lamella is opened and it is easy for the EFB fiber to absorb NaOFI.

According to further embodiments (see for example claim 10), the steam is injected into the hopper for a time period of 5-20 minutes.

Injecting the steam into the hopper for a time period of 5-20 minutes, preferably 5 minutes may be sufficient enough to increase the temperature of the EFB fibers to a range of 60- 150 °C and/or to open the surface of the EFB fibers, especially the middle lamella area. This allows washing more lignin out from the EFB fiber and/or an easy NaOFI absorption in a further process step. According to further embodiments (see for example claim 11 ), the steam is injected into the hopper for about 5 minutes and the temperature of the EFB fibers is increased to about 150 °C.

Increasing the temperature of the EFB fibers to about 150 °C within 5 minutes may result in an effective process, wherein a maximum opening of the EFB fiber surface may be reached with the high temperature, while keeping the production fast by steaming the EFB fibers just for 5 minutes.

According to further embodiments (see for example claim 12), the pressure of the steam injected into the hopper is around 3.5 bars.

The steaming process in the hopper uses dry steam or slightly super-heated, saturated steam to avoid possible condensation problems. For example, the about 3 tons of steam used in the steaming process may have a temperature of 150 °C and a pressure of 3.5 bars.

According to further embodiments (see for example claim 13), an injection ratio of steam to EFB fibers is within a range of 3:1 to 4.5:1 , preferably about 3.75:1 .

Choosing an optimal injection ratio which may be within a range of 3:1 to 4.5:1 , preferably about 3.75:1 , may be energy efficient, because injecting steam into the hopper full of EFB fibers may use less power than heating up a mixture of EFB fibers and water further down in the production process.

Furthermore, an optimal injection ratio serves to open the surface of all of the EFB fibers in the hopper with a minimum amount of steam.

According to further embodiments (see for example claim 14), a batch of 800 kg BD EFB fiber is loaded into the hopper and steam by a quantity of 3 tons of steam.

Choosing an optimal injection ratio, which may mean injecting a quantity of about 3 tons of steam into 800 kg of BD EFB fibers, may be energy efficient, because injecting steam into the hopper full of EFB fibers may use less power than heating up a mixture of EFB fibers and water further down in the production process. Furthermore, an optimal injection ratio serves to open the surface of all of the EFB fibers in the hopper with a minimum amount of steam.

Embodiments of the present invention will be discussed referring to the enclosed figures, wherein:

Fig.1 shows a flowchart of a method for steaming EFB fibers in a hopper;

Fig.2 shows an embodiment of a hopper, configured to steam the EFB fibers;

Fig.3 shows an embodiment of a system configured to prepare and/or pre-process EFB fibers in a pulp/paper production process;

Fig.4 shows a schematic representation of the EFB fiber structure;

Fig.5 shows schematic representations of the inside steam pipes used in the hopper; Fig.6 shows a schematic representation of the cross-section of the hopper;

Fig.7 shows a diagram with the saturation curve of a steam;

Fig.8 shows a design of a system comprising an EFB fiber depot, conveyer belts, hoppers and pulper tanks.

Embodiments of the present invention will subsequently be discussed referring to the en closed figures. Flere, identical reference numbers are provided to elements having identical or similar functions, so that the description is mutually applicable and interchangeable.

It is noted that any embodiments as defined by the claims may be supplemented by any of the details, features and functionalities described herein. Also, the embodiments described herein may be used individually, and may also optionally be supplemented by any of the details, features and functionalities, including the claims. Also, it is noted that the individual aspects described herein may be used individually or in combination. Thus, details may be added to each of said individual aspects without adding details to another one of said as pects.

The present invention is understood more fully from the detailed description given below, and from the accompanying drawings of embodiments of the present invention which, how ever, are not to be taken to limit the present invention to the specific embodiments de scribed, but are for explanation and understanding only.

Fig. 1 shows an embodiment of a flow chart of a method 100 according to the present invention for preparing empty fruit bunch (EFB) fibers in a paper and/or pulp production process. The method 100 comprises the steps of loading EFB fibers into a hopper 110, injecting steam into the hopper in order to steam the EFB fibers 120 and releasing the EFB fibers into a chain of downstream processing containers 130.

The chain of downstream processing containers is further configured to wash lignin out from the steamed EFB fibers and to perform a NaOFI treatment of the steamed and washed EFB fibers.

The method 100 improves the pulp and/or paper quality by preparing the EFB fibers for removing lignin from the EFB fiber. Long EFB fibers are delivered and loaded 110 into the hopper, for example a batch of 800 kg BD EFB fibers.

As a next step steam is injected 120, for example for 5 minutes, into the hopper to increase the temperature of the EFB fibers in the hopper up to 150 °C. Due to the steaming 120 the surface of the EFB fibers, especially the middle lamella area, is opened, making sure that the lignin in the EFB fiber, or in the middle lamella area, may be washed out in one of the containers of the chain of downstream processing containers.

As a final step, the EFB fibers are released 130 into a chain of downstream processing containers which may include a container to wash lignin out from the steamed EFB fibers and an another containers to perform a NaOFI treatment of the steamed and washed EFB fibers.

Fig. 2 shows an embodiment of a hopper 200, in which the method 100 in Fig. 1 may be conducted. The hopper 200 comprises an upper wall 210, side walls 220, inside steam pipes 250, outside steam pipes 260 and a lower wall 230. The upper wall 210 comprises an inlet 240, configured to load the EFB fibers into the hopper 200.

One of the side walls 220 of the hopper 200 comprises an outlet 270, which is formed in a lower portion of the one of the side walls 220 and is configured to release the steamed EFB fibers into a chain of downstream containers. The inlet 240 and/or the outlet 270 of the hopper 200 is closable.

The lower wall 230 is inclined towards the outlet 270 of the hopper 200, wherein the incli nation of the lower wall 230 is within a range of 40° to 60°, preferably about 50°. The inside steam pipes 250 are triangle pipes arranged in one or more corners of the hopper 200, wherein two sides of each triangle pipe 250 extend parallel to the side walls 220, or in some cases parallel to the one of the side walls 220 and the lower wall 230, forming the corner.

The third side of the triangle comprises holes 255, facing in the direction of the interior of the hopper 200, configured to inject steam into the hopper 200.

At least one inside steam pipe 250 comprises a first portion and a second portion, wherein the first portion extending in a corner between adjacent side walls 220 of the hopper 200 and the second portion extending in a corner between one of the side walls 220 and the lower wall 230 of the hopper 200.

The inside steam pipes 250 are supplied with steam by a main steam inlet 280 over the one or more outside steam pipes 260. The main steam inlet 280 is the connecting point from a steam pipe outside the factory in order to inject steam into the inside steam pipes 260 in the hopper 200, over the outside steam pipes 260.

The hopper 200 is made of a non-corrosive material, for example of a stainless steel mate rial, and may optionally be supported by an outer frame 290.

The method 100 in Fig. 1 is executed in the hopper 200. The EFB fibers are loaded into the hopper 200 through the inlet 240. The closable outlet 270 is closed during the loading and/or the steaming process. After the loading the inlet 240 may be closed as well.

As a next step, the outside steam pipes 260 are supplying the inside steam pipes 250 with steam from the main steam pipe inlet 280. As the inside steam pipes 250 are filling up with steam from the outside steam pipe 260 the inside steam pipes 250 are releasing steam through the holes 255 into the hopper 200.

The about 3 tons of steam used in the steaming process has a temperature of about 150 °C and a pressure of about 3.5 bars. Approximately 800 kg BD EFB fibers in the hopper 200 are steamed for about a time period between 5 to 20 minutes, preferably 5 minutes. Due to the steaming process, the temperature of the long EFB fibers in the hopper 200 is increased to a range of 60-150 °C, preferably 150 °C. Furthermore, the surface of the EFB fibers is opening up, particularly the middle lamella area, in which lignin is contained. Opening the surface of the middle lamella area makes it easier to wash lignin out from the EFB fiber in a further downstream process step.

Furthermore, injecting steam into the hopper 200 consumes less power than injecting the steam into a tank, wherein additional water temperature is also increased. The opened mid dle lamella surface makes it easier for the EFB fiber to absorb NaOFI, resulting in a less NaOFI consumption. A further benefit of the steaming process and/or the hopper 200 is that the hopper 200 is not a complicated equipment, the maintenance cost of the hopper 200 is low.

After the steaming process, the closable outlet 270 of the hopper 200 is opened and the steamed EFB fiber is released into a chain of downstream processing containers, wherein the chain of downstream processing containers is configured to wash lignin out from the steamed EFB fibers and to perform a NaOFI treatment of the steamed and washed EFB fibers.

Fig. 3 shows an embodiment of a system 300 for preparing and/or pre-processing EFB fibers in a pulp/paper production process. The system 300 comprises a TEPP fiber sterilizer or hopper 200, described in Fig. 2, and a chain of downstream processing containers 310.

The hopper 200 releases steamed EFB fiber into the chain of downstream processing con tainers 310, which comprises a pulper tank 320 and a NaOFI tank 330. Furthermore, the chain of downstream processing containers may comprise an optional washer machine 340 between the pulper tank 320 and the NaOFI tank 330.

Long EFB fibers are delivered and loaded into the hopper 200, which may contain an 800 kg batch of BD EFB fibers. Steam is injected into the hopper 200 to increase the tempera ture in the hopper 200 up to about 150 °C for about 5 minutes.

For example, after the 5 minutes, the hopper gate or the closable outlet opens and the steamed long EFB fiber is released into the chain of downstream processing containers 310, in particular into a pulper tank 320, for further processing in the pulp/paper production. The pulper tank may contain about 20 m³ of water. After the steamed EFB fiber is loaded into the pulper tank 320, the rotor of the pulper tank 320 starts to mix the EFB fiber with the water for about 20 minutes to be the first stage of the EFB fiber cleaning before delivering it to the NaOFI tank 330, wherein a digestion takes place. Regarding an EFB fiber is a hollow fiber, and a batch of EFB fiber contains or is contami nated with sand, small pieces of palm shell and excessive oil, naturally, it is better to heat up at the hopper 200. Steamed EFB fibers are released into the pulper tank 320, and the pulper tank 320 is mixing the steamed EFB fibers with about 20 m³ of water, so lignin, sand, palm shell and excessive oil may be removed easily.

Used water of the pulper tank 320 and/or the washer machine 340 is delivered to an EQ and/or to an oil-tap pond to treat used water and to send or deliver the water back into the process or into the pulper tank, in order to recycle the water.

After the pulper tank working or mixing for 20 minutes, the mixture of EFB fiber and water may be delivered to the washer machine. The washer machine may separate the EFB fibers from dirty water and may deliver the EFB fibers to the NaOFI tank. The used water may be released to the EQ and/or the oil-tap pond.

After about 20 minutes of mixing, the steamed and washed EFB fiber is optionally delivered to a washer machine 340. The washer machine 340 drains out used water and sprays new water into the EFB fiber before sending the EFB fiber to the NaOFI tank 330. Draining out used water and spraying new water into the EFB fibers may be conducted once or several times in one or more washer machines 340.

The steamed and washed EFB fibers are delivered into a NaOFI tank 330, wherein the digestion takes place. The digestion in the NaOFI tank 330 after the inventive steaming method 100 in Fig. 1 is different from a usual, conventional process.

The inventive method 100 in Fig. 1 allows removing more lignin out of the EFB fibers. EFB fibers of the pulp/paper are more individual and less bundled as in a conventional process. Furthermore, the NaOFI consumption may be reduced as well. For example, in a usual, conventional process about 62.5 kg NaOFI /1 ton of EFB fiber is used, while in the inventive process, after applying the steaming method 100 in Fig. 1 , about 50 kg NaOFI /1 ton of EFB fiber is used.

Fig. 4 shows a schematic representation of the structure of an EFB fiber 400, which may be prepared and/or pre-processed in the method 100 in Fig. 1. EFB fiber 400 is a hollow fiber with a lumen 410 in the middle. The lumen 410 is surrounded by a fiber wall, which is made up with a number of layers: S₃, S₂, Si, P. The thickest layer of the EFB fiber wall is the S₂ layer. The fibril orientation in the layers is important for the fiber stiffness and the fiber strength. The outer layer of the EFB fiber is the middle lamella area 420. Lignin is contained in the middle lamella 420.

The method 100 in Fig. 1 uses long EFB fibers, longer than 2 cm. Short EFB fibers, 2-4 mm, and waste EFB fibers, that is shorter than 2 mm, are rejected. If the EFB fiber is longer than 4 mm, a screening machine is separating the fiber and delivering back to the process to refine again.

The steaming method 100 in Fig. 1 opens the surface of the EFB fibers 400 and makes it easier to remove the lignin from the middle lamella area 420.

Microscopic pictures of an EFB pulp produced in a conventional pulp production show that the pulp consists of a large portion of EFB fiber bundles together with individual EFB fibers 400 and many minor elements. Strength properties of the EFB fiber pulp expressed as ten sile index and/or tear index are low, which indicates that the EFB fibers 400 have poor bonding ability regarding the high lignin contained in the middle lamella area 420 in Fig. 4.

The method 100 in Fig. 1 offers a way to remove lignin without destroying the EFB fibers 400 in Fig. 4 and allows to use less harmful chemicals in order to avoid water treatment costs and to protect the environment.

Fig. 5 shows schematic representations of the inside steam pipes 250 used in the hopper 200. The inside steam pipes 250 are configured to hold a pressure of at least 3 bars or at least of a pressure of 3.5 bars.

Fig. 5a shows a schematic side-view of one of the inside steam pipes 250. The inside steam pipe 250 have a triangle shape and one side of the triangle shaped pipe 250 comprises small holes 255 in order to release steam into the hopper. A distance between neighboring holes 255 is within a range of 8 to 12 cm, preferably about 10 cm.

Fig. 5b shows a schematic cross-section of the inside steam pipe 250, wherein the holes 255 of the inside steam pipes 250 are punched in a flow direction of the steam out of the holes, such that the holes have a shield protecting the hole 255 from the EFB fibers clog ging. According to the method 100 in Fig. 1 , after loading the EFB fibers into the hopper, steam is injected into the inside steam pipes 250. The inside steam pipes release steam into the hopper through the holes 255, facing in the direction of the interior of the hopper. After the steaming process, the closable outlet of the hopper is opened and the steamed EFB fiber is released into a chain of downstream processing containers.

Fig. 6 shows a cross-section of the hopper 200. The hopper 200 comprises an upper wall 210 comprising an inlet 240, side walls 220, and a lower wall 230. One of the side walls 220 comprises an outlet 270, which is formed in a lower portion of the side wall 220. The outlet 270 is closable with a door or hopper gate 610.

The lower wall is inclined towards the closable outlet 270, wherein the inclination of the lower wall is within a range of 40° to 60°, preferably about 50°.

The cross-section of the hopper 200 further shows an inside steam pipe 250, which com prises a first portion and a second portion, wherein the first portion extending in a corner between adjacent sides walls 220 of the hopper 200 and a second portion extending in a corner between one of the side walls 220 and the lower wall 230 of the hopper 200. The inside steam pipe 250 further comprises holes 255, through which the steam is injected into the hopper 200.

Fig. 6 shows a cross-section of the hopper 200, in which a method 100 in Fig. 1 may be performed. The EFB fiber is loaded into the hopper through the inlet 240 of the hopper 200 while the hopper gate 610 is closed. The EFB fiber is steamed in the hopper 200, wherein the steam is injected through the holes 255 of the inside steam pipes 250 for about 5 minutes. After the steaming process the hopper gate 610 opens and the steamed EFB fibers are released into a chain of downstream containers through the closable outlet 270.

Fig. 7 shows a diagram with a steam saturation curve, wherein the steam may be used in the method 100 in Fig. 1. The saturation curve shows the equilibrium point between the steam and the heated water.

The dashed lines are representing the pressure value and the temperature value of the steam used in the method 100 in Fig. 1 : 3.5 bars and 150 °C. The used steam is a dry steam, a slightly super-heated steam, which may be used in order to avoid possible con densation problems in the pipes and/or in the hopper. Fig. 8 shows a design of a system 800 comprising an EFB fiber depot 810, conveyer belts 820, hoppers 200, described in Fig. 2, and pulper tanks 320.

The EFB fibers are stored in the fiber depot 810. The fiber depot 810 is connected to the inlet of the hopper 200 over the conveyer belts 820. The steaming method 100 is executed in the hoppers 200. The outlet of the hopper 200 may release its content into a pulper tank 320.

The EFB fibers are taken from the EFB fiber depot 810 and loaded into the hopper 200 with the help of the conveyer belts 820. The EFB fibers are steamed in the hopper 200 for about 5 minutes. After 5 minutes, the steamed EFB fibers are released from the hopper into the pulper tanks 320. In the pulper tanks the steamed EFB fibers are mixed with water for about 20 minutes in order to release lignin with the used water. After about 20 minutes, the steamed and washed EFB fibers are delivered into a chain of downstream processing con tainers.

Although some aspects have been described as features in the context of an apparatus it is clear that such a description may also be regarded as a description of corresponding features of a method. Although some aspects have been described as features in the con text of a method, it is clear that such a description may also be regarded as a description of corresponding features concerning the functionality of an apparatus.

In the Detailed Description, it can be seen that various features are grouped together in examples for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed examples require more fea tures than are expressly recited in each claim. Rather, as the following claims reflect, in ventive subject matter may lie in less than all features of a single disclosed example.

Thus, the following claims are hereby incorporated into the Detailed Description, where each claim may stand on its own as a separate example. While each claim may stand on its own as a separate example, it is to be noted that, although a dependent claim may re fer in the claims to a specific combination with one or more other claims, other examples may also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of each feature with other dependent or inde pendent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended to include also features of a claim to any other independent claim even if this claim is not directly made dependent to the in dependent claim.

The above described examples are merely illustrative for the principles of the present dis- closure. It is understood that modifications and variations of the arrangements and the de tails described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the patent claims and not by the specific details presented by way of description and explanation of the examples herein.

Claims

1. A method (100) for preparing empty fruit bunch fiber (400) in a paper and/or pulp production process, comprising the steps of: delivering and/or loading (110) empty fruit bunch fibers into a hopper (200); injecting steam (120) into the hopper in order to steam the empty fruit bunch fibers; releasing (130) the empty fruit bunch fibers from the hopper into a chain of down stream processing containers (310), wherein the chain of downstream processing containers is configured to wash lignin out from the steamed empty fruit bunch fibers and to perform an NaOH treatment of the steamed and washed empty fruit bunch fibers.

2. The method according to claim 1 , wherein washing out lignin comprises mixing the steamed empty fruit bunch fibers with water in a pulper tank (320) and releasing water and lignin from the pulper tank.

3. The method according to claim 2, comprising draining out used water and spraying new water into the washed and steamed empty fruit bunch fibers once or several times before the NaOH treatment.

4. The method according to claim 3, wherein the draining out used water and spraying new water is performed in one or more washer machines (340).

5. The method according to one of the claims 2 to 4, wherein a mass mixing ratio of empty fruit bunch fibers to water within the pulper tank is in a range of 1 :40 to 1 :60, preferably about 1 :50.

6. The method according to one of the claims 2 to 5, wherein mixing in the pulper tank is performed for about 15 to 25 minutes, preferably about 20 minutes.

7. The method according to one of the preceding claims, wherein the steamed empty fruit bunch fibers is mixed with a quantity of 20 m³ water in the pulper tank.

8. The method according to one of the previous, wherein the empty fruit bunch fibers are longer than 2 cm.

9. The method according to one of the previous claims, wherein the injecting the steam into the hopper increases the temperature of the empty fruit bunch fibers in the hopper to a range of 60 - 150 °C.

10. The method according to one of the previous claims, wherein the steam is injected into the hopper for a time period of 5 - 20 minutes.

11. The method according to one of the previous claims, wherein the steam is injected into the hopper for about 5 minutes and wherein the temperature of the empty fruit bunch fibers is increased to about 150°C.

12. The method according to one of the previous claims, wherein the pressure of the steam injected into the hopper is around 3.5 bars.

13. The method according to one of the previous claims, wherein an injection ratio of steam to empty fruit bunch fibers is within a range of 3:1 to 4.5 :1 , preferably about 3.75 :1 .

14. The method according to one of the preceding claims, wherein a batch of 800 kg empty fruit bunch fibers is load into the hopper and steamed by a quantity of 3 tons of steam.