Processes for treating non-wood raw materials

Abstract

Methods for pretreating non-wood raw materials, particularly empty fruit bunch (EFB)5 raw materials, and pulps obtained using these methods are described.

Description

[Technical field]

[0001] The present invention provides a method for pre-treating non-wood raw materials, in particular empty fruit bunch (EFB) raw materials, which are waste products formed after the extraction of palm oil, for subsequent use in the manufacture of paper or textile grade pulp for applications in industries such as printing and writing paper, tissue paper, paperboard and fashion clothing. [Background technology]

[0002] The growing emphasis on environmental sustainability coupled with the global shortage of wood raw materials for the pulp and paper industry has meant that the focus has shifted to finding alternative non-wood raw material sources. The same is true for the textile industry, where there is a trend towards using renewable raw materials in fibre production.

[0003] Examples of non-wood raw materials that offer interesting alternatives to wood raw materials include oil palm empty fruit bunch (EFB) fiber, bamboo, kenaf, wheat / rice straw, coconut coir and bagasse.

[0004] Oil palm (elaeis guineensus), typically grown in Southeast Asian countries such as Indonesia, Malaysia, and Thailand, is an important source of vegetable oil, specifically palm oil. Various biomasses are generated during palm oil extraction. One of the most abundant biomasses generated is the empty fruit bunch (EFB) fiber, which is generated by the first step of the oil extraction process, where the fruit and nuts are removed from the bunch. EFB generation has been increasing year by year, with more than 30 million tons generated in Indonesia alone in 2015 alone. This presents an environmental problem in itself, since often this waste is simply left to rot, attracting rodents.

[0005] EFB has several properties that make it interesting as a raw material for pulp - it has a high cellulose fiber content and a low lignin content, which is similar to hardwood fibers, and can be used to provide high quality paper and regenerated cellulose. Processes are known that use EFB as a raw material, which is then subjected to cooking to produce a chemical pulp from which it is then possible to produce paper and regenerated cellulose, such as viscose, modal, lyocell and other man-made cellulose (MMC) fibers.

[0006] Although EFB and other non-woods are promising alternatives to wood in both the paper and textile industries, a problem that arises with these feedstocks is the presence of impurities that cause problems either with processing and / or with the quality of the final product. This means that when EFB and other non-woods are used as feedstocks, the cooking process must be adapted to include a pretreatment step to remove these impurities. Impurities of particular concern include oil (in the form of fatty acids), silica, ash, and other non-process element (NPE) content. Although it has been possible to develop processes to effectively remove oil, ash residues, and NPEs, removal of silica has proven difficult.

[0007] Although difficult for non-wood feedstocks in general, the removal of silica from EFB feedstocks is particularly challenging. Studies of EFBs have revealed that they have a specific structure consisting of silica agglomerates embedded in the fibers (see Figure 1), and it is these silica agglomerates that are believed to contribute to the strength and stiffness of the EFB (see also Law et al., (2007) Bioresources 2(3), 351-362). However, as mentioned above, the presence of silica in pulp mills is undesirable for several reasons, in particular due to recovery problems, poor product quality, and damage to machinery as a result of silica deposition during processing. Therefore, methods of pretreating EFB feedstocks to remove silica are being investigated. To date, pretreatment methods have included physical, chemical and biological treatments, such as washing with water, treatment with acid, ultrasonic treatment, fungal / enzyme treatment, and treatment with alkali (Agusta et al., (2018) Journal of Japan Tappo 6, 641-49; Tye et al. (2013) Procedia Environmental Sciences 20, 328-335; Farah et al., 2014, BioResource 9(1), 938-951; Nik et al., (208), MCRJ Special Issue 4(2), 117-128; Zawati et al., (2015) Wood Research 60(1), 157-166; Harsono et al., (2015), Journal of Wood Science 62, 55-73; Rusdan (2002) Oil Palm Bulletin 44, 19-24), Rusdan et al., (2018) Journal of Tropical Forest Science 19(3), 121-126, Bahrin et al., (2012) Biorescources 7(2), 1784-1801, and Isroi et al., Molecules 17(12), 14995-15002).

[0008] For any pretreatment process, it is necessary to balance the removal of impurities, in this case silica agglomerates, with the damage caused to the EFB feedstock by the pretreatment process. Most of these pretreatments have been described in the context of producing sugars, either for bioethanol production, furfural production, or chemical pulp production. In contrast, the present invention is primarily concerned with processes for producing man-made cellulose fibers (regenerated cellulose), such as viscose, for the textile industry, which are highly sensitive not only to the presence of silica, but also to any fiber damage suffered during previous processing steps. Thus, even if known processes can remove enough silica for its intended end use, the remaining silica levels are still too high to be acceptable in the textile industry for regenerated cellulose fibers.

[0009] It is therefore apparent that a pretreatment process is needed for non-wood raw materials that will ultimately be used in fiber manufacturing, which removes high levels of silica without damaging the non-wood raw materials. Summary of the Invention

[0010] Against this background, the present inventors have identified a pretreatment process that is effective in removing silica agglomerates from non-wood feedstocks while avoiding causing significant damage to the cellulosic components of the feedstock.

[0011] More particularly, the present invention provides a method for pretreating a non-wood material, comprising the steps of: (a) Washing non-wood raw materials; (b) contacting the washed non-wood raw material with an acid solution; and (c) contacting the washed non-wood raw material with an alkaline solution; wherein the method comprises an additional washing step (d) between steps (b) and (c).

[0012] Advantageously, the inventors have found that by carrying out steps (a), (b), (c) and (d), the pretreatment process results in a feedstock that is substantially free of silica while preserving its structural integrity and minimizing damage to the cellulosic components of the feedstock. Specifically, the inventors have surprisingly found that by combining a series of steps, each carried out under conditions sufficiently mild to avoid undesirable structural damage, it is possible to effectively remove problematic silica agglomerates from the feedstock fibers. This is particularly surprising given the industry's previous understanding that extreme and / or harsh conditions are required to remove these silica agglomerates.

[0013] Moreover, the pretreatment method of the present invention can be easily integrated into existing wood flour / shredded chip mills, organosolv and soda or kraft pulp mills. It is particularly advantageous for use in integrated pulp mills, i.e., mills where the entire process is carried out from raw material to final product, because reactants from later stages of the process can be recycled into the pretreatment method, particularly step (b). This improves efficiency and minimizes waste.

[0014] The present invention further provides dissolving pulp (DP) from non-woody raw materials, particularly from non-woody empty fruit bunch (EFB) raw materials, having a silica content of less than about 80 ppm. Advantageously, the low level of silica present in the DP means that it can subsequently be processed into regenerated cellulose fibers for the textile industry to produce high quality products. In particular, if silica is still present in the DP, problems with cellulose dissolution will occur and the spinnerets used to subsequently draw fibers from the DP will become clogged.

[0015] The present invention further provides kraft pulp (KP) from non-wood raw materials, particularly from non-wood empty fruit bunch (EFB) raw materials, having a silica content of less than about 600 ppm. Advantageously, the low level of silica present in KP means that it can be subsequently processed into paper products without damaging the digester used. In particular, if silica is still present in the KP, it can lead to its deposition in the digester (i.e., sand deposits), which can not only damage the machinery but also lead to holes in the final product. The KP produced by the method described herein does not suffer from these problems.

[0016] The inventors have found that the DP and KP obtained from feedstock pretreated according to the method of the present invention are of equivalent or better quality than the DP and KP obtained using conventional wood feedstock, and can be obtained in comparable yields. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The pretreatment method of the present invention may be used with a variety of non-wood raw materials. In this regard, the term "non-wood raw material" is used herein to denote any raw material that is plant-based but not derived from a wood source. Examples of suitable non-wood raw materials include oil palm empty fruit bunches (EFB), bamboo, bagasse, kenaf, coconut coir, and wheat / rice straw. Preferably, the non-wood raw material is an EFB raw material, or a bamboo raw material. Most preferably, the wood raw material is an EFB raw material.

[0018] The term "non-process elements (NPEs)" is used herein to refer to undesirable inorganic impurities other than silica and ash, such as metals including iron and calcium.

[0019] The first step of the pretreatment process of the present invention is step (a) of washing the non-wood raw material. This washing step is included initially for the purpose of removing residual oil from the non-wood raw material. Washing can be carried out using either water and / or steam. Preferably, washing step (a) is carried out at a temperature in the range of 80°C to 100°C. It will be appreciated that if water is used in washing step (a) at the lower end of this temperature range, a mixture of water and steam will be present, while at the higher end of the temperature range, steam will be present. During step (a) of the method of the present invention, it is preferred that the non-wood raw material is mechanically agitated, preferably by gentle mechanical agitation. It is preferred that only a small degree of agitation is provided to the non-wood raw material, such as may be achieved by passing the non-wood raw material through a screw-type conveyor. One skilled in the art will be familiar with screw-type conveyors, an example of which is shown in FIG. 11.

[0020] Prior to step (a) of the method of the present invention, the non-wood raw material may be subjected to process steps that are standard in the industry, such as shredding. When the non-wood raw material is shredded, the resulting fibres preferably have a length in the range of about 5 mm to about 100 mm.

[0021] After the initial washing step (a), the washed non-wood raw material is contacted with an acid solution in step (b) of the method. Contacting the non-wood raw material with acid reduces the content of any remaining metal impurities. In particular, it is effective in removing iron and calcium residues from the raw material. Furthermore, without wishing to be bound by theory, it is believed that this acid treatment step is also crucial in the process of removing silica from the feedstock. As mentioned above, non-wood raw materials, particularly EFB raw materials, have a structure in which silica agglomerates are embedded on the surface of the fibers. Contacting the fibers with acid causes them to shrink, which in turn initiates the process of eliminating the silica agglomerates.

[0022] The acid solution comprises acid and water. Any acid may be used to form the acid solution. Preferably, the acid used is selected from the group consisting of sulfuric acid, hydrochloric acid, an aqueous solution of chlorine dioxide, and mixtures thereof. As will be described later, pulp mills typically include a bleaching step. An advantage of the pretreatment method of the present invention is that the acid used in step (b) of the pretreatment method can be provided by the acid used in the bleaching step that is directly recycled to step (b) of the pretreatment method, which can result in improved efficiency and minimized waste and cost generation.

[0023] The acid solution of step (b) contains an acid at a concentration in the range of about 0.2-5.0%, which ensures that the acid solution is concentrated enough to shrink the fibers of the non-wood feedstock to facilitate removal of silica impurities, yet dilute enough to minimize undesirable damage to the feedstock, particularly the cellulose therein.

[0024] Preferably, step (b) is carried out at a pH in the range of 1-3.

[0025] Step (b) is generally carried out at a temperature ranging from about 80° C. to about 100° C. It is preferred to carry out step (b) at an elevated temperature because this increases the rate at which step (b) proceeds and improves the efficiency of the process.

[0026] If the non-wood feedstock from step (a) has been washed at elevated temperatures as described above, then by similarly carrying out step (b) at elevated temperatures (i.e., at a temperature in the range of about 80 to about 100° C.), the overall process efficiency is improved by avoiding the need to include a step of cooling the washed non-wood feedstock prior to step (b).

[0027] Step (b) is carried out for a time sufficient to cause shrinkage of the fibers. Preferably, step (b) has a duration in the range of about 30 to about 60 minutes. The extent to which step (b) has progressed can be monitored by measuring the content of the impurities to be removed, in particular ash residue, NPEs and silica. At the end of step (b), typically, the silica content will have been reduced by a small amount, while the ash residue and NPEs will have been almost completely removed. Those skilled in the art will be familiar with suitable quality measurements.

[0028] In step (c) of the method of the present invention, the washed non-wood raw material is contacted with an alkaline solution. Contacting the raw material with an alkaline solution further helps to remove silica impurities. More specifically, contacting the raw material with an alkaline solution causes fiber swelling that contributes to the removal of silica from the raw material.

[0029] Step (c) is carried out after step (a), but may be carried out either before or after step (b). In one method according to the invention, step (c) is carried out before step (b). In an alternative method according to the invention, step (c) is carried out after step (b). Preferably, step (c) is carried out after step (b). This is advantageous because, after pretreatment, the non-woody raw material is cooked to form a pulp, as will be described in more detail below. The preferred cooking step is carried out under alkaline conditions, so that when the pretreatment method ends with an alkaline step, it is already at a suitable pH for the cooking step, thus avoiding the need for an additional neutralization step.

[0030] It is the combination of steps (b) and (c), which respectively shrink and expand the non-wood raw material, that leads to the effective removal of silica impurities.

[0031] The alkaline solution used in step (c) comprises an alkali and water. Any alkali may be used to form the alkaline solution, but preferably the alkali is sodium hydroxide. Sodium hydroxide is preferred because it is also used in the subsequent cooking step immediately after pretreatment, as described above. By using the same alkali in step (c), the overall process efficiency is improved.

[0032] The alkaline solution of step (c) contains an alkali in a concentration ranging from about 0.2 to about 5.0%, which ensures that the alkaline solution is concentrated enough to swell the fibers of the non-wood feedstock to facilitate removal of silica impurities, yet dilute enough to minimize undesirable damage to the feedstock, particularly the cellulose therein.

[0033] Preferably, step (c) is carried out at a pH in the range of 12-14.

[0034] Step (c) is generally carried out at a temperature ranging from about 80° C. to about 100° C. It is preferred to carry out step (c) at an elevated temperature because this increases the rate at which step (b) proceeds and improves the efficiency of the process.

[0035] If the non-wood feedstock from step (a) has been washed at elevated temperatures as described above, then by similarly carrying out step (c) at elevated temperatures (i.e., at a temperature in the range of about 80 to about 100° C.), the overall process efficiency is improved by avoiding the need to include a step of cooling the washed non-wood feedstock prior to step (c).

[0036] Step (c) is carried out for a time sufficient to result in expansion of the fibers. Preferably, step (c) has a duration in the range of about 30 to about 60 minutes. The extent to which step (c) has progressed can be monitored by measuring the silica content remaining in the feedstock. At the end of step (c), there will typically be a significant reduction in silica content. Those skilled in the art will be familiar with suitable quality measurements.

[0037] Regardless of the order in which steps (b) and (c) are performed, the pretreatment method of the present invention includes a further washing step, step (d), between steps (b) and (c). This washing step is included for the primary purpose of removing metal and silica (typically fine silica) impurities that have been dislodged from the non-wood fibres as a result of the earlier steps performed. The washing of step (d) can be carried out using either water and / or steam. Preferably, washing step (d) is carried out at a temperature in the range of 80°C to 100°C. It will be appreciated that if water is used in washing step (d) at the lower end of this temperature range, a mixture of water and steam will be present, whereas at the higher end of the temperature range, steam will be present. During step (a) of the method of the present invention, it is preferred that the non-wood raw material is mechanically agitated, preferably by gentle mechanical agitation. It is preferred that only a small degree of agitation is provided to the non-wood raw material, such as may be achieved by passing the non-wood raw material through a screw-type conveyor. One of the screw-type conveyors, an example of which is shown in FIG. 11, will be familiar to those skilled in the art.

[0038] The process of the present invention may include a further washing step (e) after step (b) or step (c), whichever is the last performed. This additional washing step, when present, is included for the primary purpose of removing silica impurities. Washing step (e) may be carried out using either water and / or steam. Preferably, washing step (e) is carried out at a temperature in the range of 80°C to 100°C. It will be appreciated that if water is used in washing step (e) at the lower end of this temperature range, a mixture of water and steam will be present, while at the higher end of the temperature range, steam will be present. During step (a) of the process of the present invention, it is preferred that the non-wood raw material is mechanically agitated, preferably by gentle mechanical agitation. It is preferred that only a small degree of agitation is provided to the non-wood raw material, such as may be achieved by passing the non-wood raw material through a screw-type conveyor. One skilled in the art will be familiar with screw-type conveyors, an example of which is shown in FIG. 11.

[0039] The non-wood raw materials once subjected to the pretreatment method of the present invention are suitable for further processing to form pulp, which in turn can then serve as a raw material for paper or as a raw material in the production of regenerated cellulose, e.g., viscose, modal, lyocell or other MMC fibers.

[0040] The method of the present invention can be carried out using standard equipment found in a standard pulp mill, with which one of ordinary skill in the art would be familiar. In particular, the pretreatment method of the present invention is useful in integrated pulp mills, so that materials, such as acids used in the bleaching process, can be reused in the pretreatment method of the present invention.

[0041] The non-wood raw materials may be formed into bales prior to further processing, or alternatively, the non-wood raw materials may be pelletized prior to further processing.

[0042] Those skilled in the art will be familiar with suitable methods for converting pretreated non-woody raw materials into pulp. In particular, there are two common methods used to cook the raw materials, specifically the sulfate (Kraft) process and the prehydrolysis (PH) Kraft process.

[0043] In the Kraft process, the pretreated non-woody raw material is mixed with a hot mixture known as "white liquor" that contains water, sodium hydroxide, and sodium sulfite. Anthraquinone may be included as an accelerator to improve yield. During this process, the lignin present in the raw material is decomposed and dissolved in the alkali. The remaining solid pulp, known as "brown stock", can be recovered ready for further processing steps. The mixed liquor ("black liquor"), which contains a lignin fraction, a small fraction of carbohydrates, sodium sulfate, sodium carbonate, and other inorganic salts, can be removed and then incinerated to provide energy that is fed back into the cooking process.

[0044] The "brown pulp" obtained from the kraft process is typically bleached to provide a pulp with high brightness. There are several different bleaching processes that can be used, which will be familiar to those skilled in the art. One example of a suitable bleaching process is chlorine-free (ECF) bleaching, in which the brown pulp is contacted sequentially with monopersulfuric acid (which can be produced by mixing sulfuric acid with hydrogen peroxide), chlorine dioxide, hydrogen peroxide, and chlorine dioxide. Another example of a suitable bleaching process is totally chlorine-free (TCF) bleaching, in which the brown pulp is subjected to bleaching with ozone and hydrogen peroxide. In particular, TCF typically includes four or five different stages, both of which include treatment with chelating agents, as well as several bleaching stages, such as bleaching with oxygen, alkaline extraction with hydrogen peroxide addition, peracetic acid bleaching, and / or hydrogen peroxide bleaching with or without oxygen. TCF bleaching has the advantage that it does not use any chlorine and therefore does not produce any chlorine-containing by-products. The quality of the pretreated non-wood feedstock obtained by the process of the present invention means that less energy is required in the bleaching process.

[0045] An advantage of the pretreatment method of the present invention is that the acid used in such bleaching step can be recycled back to step (b) of the pretreatment method, therefore reducing the amount of acid required for the overall process and reducing waste.

[0046] In the PH Kraft process, the non-woody raw material is first subjected to an aqueous autohydrolysis process that removes hemicellulose and some lignin. It is then cooked under alkaline conditions (Kraft cooking) to remove most of the lignin and a small fraction of the remaining hemicellulose. A final multi-stage bleaching step (e.g., ECF or TCF bleaching) is performed to improve the brightness of the final pulp. Anthraquinone may be included as an accelerator to improve yields in the PH Kraft process.

[0047] Preferably, the pretreated non-wood feedstock resulting from the method of the present invention is cooked using a PH Kraft process.

[0048] In both cooking methods, the quality of the pulp obtained can be controlled by varying several parameters, in particular the H-factor, P-factor, Kappa number and the % effective alkali. In particular, by controlling these parameters it is possible to control whether the pulp obtained is a dissolving pulp (DP) or a kraft pulp (KP).

[0049] Dissolving pulp (DP) is a high-grade pure cellulose pulp that has a high level of brightness, uniform molecular weight distribution and an open pore structure, which makes it highly reactive. DP is typically used in the production of regenerated cellulose.

[0050] Kraft pulp (KP) is a pulp that contains both cellulose and hemicellulose. KP is typically used in the production of paper.

[0051] As one skilled in the art would recognize, these parameters have standard definitions. H-factor is a kinetic model of the rate of delignification and is dependent on both temperature and time. P-factor is dependent on time and temperature in aqueous media. Kappa number is a measure of the completeness of the process and gives an indication of the amount of lignin remaining in the pulp; it is measured as the amount of standard potassium permanganate solution that the pulp will consume. % Effective Alkali is the total concentration of alkaline components other than carbonate present in the reaction, measured by titrating a sample of white liquor with strong acid according to the procedure set out in SCAN-N-30.

[0052] Examples of suitable parameter ranges for obtaining DP and KP are shown in Table 1 below. [Table 1]

[0053] As a result of the pretreatment method of the present invention subjected to non-woody raw materials, the present invention provides DP and KP having very low impurity contents.

[0054] Surprisingly, it was also found that shorter cooking times were required when the non-woody raw materials were treated according to the method of the present invention prior to cooking, meaning that less energy was required for the cooking process. Furthermore, it was found that the non-woody raw materials treated according to the method of the present invention required less bleaching. Moreover, as can be seen in Figure 10, the post-bleaching of the non-woody raw materials treated according to the method of the present invention required significantly less bleaching chemicals, especially when the non-woody raw materials are EFB raw materials, with almost half the chemical consumption.

[0055] In particular, the DP and KP obtained using the pretreatment method of the present invention meet the specifications shown in Table 2 below. [Table 2]

[0056] The low silica content of the DP obtained using the process of the present invention is particularly surprising in view of the problems previously encountered in attempting to remove silica from non-wood feedstocks, especially when the non-wood feedstock is an EFB feedstock.

[0057] In this regard, the present invention provides a dissolving pulp derived from non-wood sources having a silica content of less than about 80 ppm.

[0058] The silica content can be determined according to the method set out in standard Tappi T211-om-07.

[0059] Alternatively, or in addition, the dissolving pulp derived from non-wood feedstock has an Fe content of about 10 ppm or less.

[0060] The iron (Fe) content can be determined according to the method set out in standard Tappi T618-cm-01.

[0061] Alternatively, or in addition, the dissolving pulp derived from non-wood sources has a Ca content of about 75 ppm or less.

[0062] The calcium content can be determined according to the method set out in standard Tappi T618-cm-01.

[0063] The presence of Fe and / or Ca impurities in DP is undesirable as it affects the downstream processes of dissolving cellulose and ultimately leads to the need to increase the amounts of chemicals used in such processes.

[0064] Alternatively, or in addition, the dissolving pulp derived from non-wood sources has an ash content of about 0.12% by weight or less.

[0065] The ash content can be determined according to the method set out in standard Tappi T322-om-07.

[0066] The present invention further provides a kraft pulp derived from non-wood sources having a silica content of less than about 600 ppm.

[0067] Alternatively, or in addition, the kraft pulp derived from non-wood sources has an ash content of about 0.35% or less.

[0068] In particular, the present invention provides a dissolving pulp derived from non-wood empty fruit bunches (EFB) having a silica content of less than about 80 ppm.

[0069] Alternatively, or in addition, the dissolving pulp derived from the non-wood EFB has an Fe content of about 10 ppm or less.

[0070] Alternatively, or in addition, the dissolving pulp derived from the non-wood EFB has a Ca content of about 75 ppm or less.

[0071] Alternatively, or in addition, the dissolving pulp derived from the non-wood EFB has an ash content of about 0.12% or less.

[0072] The present invention further provides a non-wood empty fruit bunch (EFB) derived kraft pulp having a silica content of less than about 600 ppm.

[0073] Alternatively, or in addition, the non-woody empty fruit bunch (EFB) derived kraft pulp has an ash content of about 0.35% or less.

[0074] The DP of the present invention has high brightness. Brightness is a measure of the amount of incident light reflected from the pulp under specified conditions, as measured by the method presented in the standard Tappi T525-om-06. The DP of the present invention preferably has a brightness (ISO) of about 90% or more.

[0075] The KP of the present invention has a high brightness. Brightness is a measure of the amount of incident light reflected from the pulp under specified conditions, as measured by the method presented in the standard Tappi T525-om-06. The KP of the present invention preferably has a brightness (ISO) of about 90% or more.

[0076] The dissolving pulp obtained by the method of the present invention may be further processed to provide regenerated cellulose. The term "regenerated cellulose" is used herein to describe a class of materials produced by converting natural cellulose from non-woody raw materials into soluble cellulose derivatives, followed by regeneration, typically to form either fibers or films. Those skilled in the art will be familiar with techniques for processing dissolving pulp to form regenerated cellulose. In this further processing, the first step is typically to convert the dissolving pulp into a cellulose dope. If the final product is a viscose textile fiber, the next step is typically to subject the cellulose dope to sulfurization in the presence of CS2 and sodium hydroxide. If the final product is a lyocell textile fiber, the cellulose dope is typically to an N-methylmorpholine N-oxide (NMMO) reaction. In either case, the product of the subsequent step may be extruded through a spinneret and regenerated to form the desired man-made fiber, such as viscose and / or lyocell textile fiber. It is also possible to produce other man-made cellulose (MMC) fibers, which is an attractive option in the textile industry. Because it can be manufactured using significantly less water compared to, for example, cotton, the resulting material is highly breathable.

[0077] The kraft pulp obtained by the method of the present invention can be further processed to produce paper products. Those skilled in the art will be familiar with techniques for forming paper products from pulp. In particular, the process typically involves suspending the pulp in water, followed by mechanical flattening, drying and cutting to form sheets and rolls.

[0078] The present invention will now be described in more detail with reference to the following figures and examples, which are not intended in any way to limit the scope of the claims. [Brief description of the drawings]

[0079] [Figure 1]FIG. 1 is a diagram of the location of silica agglomerates in an EFB fiber. [Diagram 2] FIG. 2 is a block diagram illustrating the pre-processing method of the present invention. [Figure 3(a)] FIG. 3(a) shows the silica content of non-wood EFB feedstock before and after pretreatment according to the method of the present invention compared to the prior art. [Figure 3(b)] FIG. 3(b) shows the silica content of non-wood bamboo feedstock before and after pretreatment with the method of the present invention compared to the prior art. [Figure 4(a)] FIG. 4(a) shows the ash content of non-wood EFB feedstocks before and after pretreatment according to the method of the present invention compared to the prior art. [Figure 4(b)] FIG. 4(b) shows the ash content of non-wood bamboo feedstock before and after pretreatment according to the method of the present invention compared to the prior art. [Diagram 5] FIG. 5 shows the silica content of non-wood EFB feedstock and non-wood bamboo feedstock before and after the pretreatment method of the present invention. [Figure 6] FIG. 6 is an image of a non-wood EFB KP produced by the method of the present invention. [Figure 7] FIG. 7 is an image of a non-wood EFB DP produced by the method of the present invention. [Figure 8] FIG. 8 is a block diagram illustrating a process for making paper products that includes the pretreatment method of the present invention. [Figure 9(a)] FIG. 9(a) is a block diagram illustrating a process for producing viscose, including the pretreatment of the present invention. [Figure 9(b)] FIG. 9(b) is a block diagram illustrating a process for producing lyocell, including the pretreatment of the present invention. [Figure 10] FIG. 10 shows the chlorine dioxide (ClO2) consumption during an ECF bleaching process carried out on EFB feedstock treated according to the method of the present invention versus hardwood, specifically acacia crassicarpa (ACRA), Eucalyptus pellita (EPEL), and Eucalyptus hybrid (EHYB). [Figure 11] FIG. 11 illustrates a screw-type conveyor that may be used to move non-wood raw materials from one stage to another in the process of the present invention. [Figure 12] FIG. 12 shows the date and time when the feedstock was changed from standard wood feedstock to mixed EFB / wood feedstock in Example 3. [Figure 13] FIG. 13 shows the productivity (H-factor) of a mill that changed its feedstock from wood chips to mixed EFB / wood chips during the trial described in Example 3. [Figure 14] FIG. 14 shows the oxygen charge consumed during bleaching in the mill described in Example 3. [Figure 15] FIG. 15 shows the alkali charge consumed during bleaching in the mill described in Example 3. [Figure 16] FIG. 16 shows the silica content of bleached kraft pulp obtained from the mixed feedstock described in Example 3. [Figure 17] FIG. 17 shows the stain / count of bleached kraft pulp obtained from the mixed stock described in Example 3. EXAMPLES

[0080] Example 1 - Non-wood EFB raw materials Approximately 100 kg of non-wood EFB, processed to be free of kernels, palm seeds and mud, was obtained from Asian Agri (RGE Palm Oil Business) and passed through a shredder and washer to obtain EFB feedstock with fiber lengths ranging from 5 to 100 mm.

[0081] The silica and ash residue contents of the non-wood EFB were measured according to Tappi T618-cm-01, and the results are shown in Figures 3(a) and 4(a).

[0082] The non-wood EFB material was then washed in a drum washer using a mixture of water and steam at a temperature ranging from 80-100°C. The EFB material was moved to the next processing step by a screw conveyor (which provides a small degree of mechanical agitation). The washing step was carried out for a duration of 30-60 minutes. The washed EFB material was then passed through a vessel containing an acid solution at a temperature ranging from 80-100°C and with a sufficient liquor ratio (7-10) having a pH ranging from 1-3. After 30-60 minutes, the EFB material was removed from the vessel containing the acid and passed through a drum washer where it was washed using a mixture of water and steam at a temperature ranging from 80-100°C. After 30-60 minutes, the washed and acid treated EFB material was passed through a vessel containing an alkaline solution at a temperature ranging from 80-100°C and with a sufficient liquor ratio (7-10) having a pH ranging from 12-14. After 30-60 minutes, the EFB was removed from the alkali-containing vessel and passed through a drum washer which washed it using a mixture of water and steam at temperatures ranging from 80-100° C. The pretreated EFB material was moved to the next step by a screw conveyor (which provides a small degree of mechanical agitation).

[0083] The silica and ash residual content of the pretreated EFB feedstock was measured according to Tappi T618-cm-01 and is shown in Figures 3(a) and 4(b).

[0084] The pretreated EFB stock was then cooked under prehydrolyzed Kraft (P factor 1000-1300) / Kraft for both DP and KP. Available alkali was used in amounts ranging from 15-20% and H-factors ranged from about 100-300 (see Table 1). Target specifications for chemical pulps (DP and KP), presented in Table 2, were achieved.

[0085] Example 2 - Non-wood bamboo raw materials Approximately 5 kg of non-wood bamboo skin was shredded and passed through a mesh sieve of size 7–13 mm to form bamboo chips of standard particle size.

[0086] The silica and ash residue contents of non-wood bamboo were measured according to Tappi T618-cm-01, and the results are shown in Figure 3(b) and Figure 4(b).

[0087] The non-wood bamboo raw material was then washed in a drum washer using a mixture of water and steam at a temperature ranging from 80 to 100°C. The bamboo raw material was moved to the next processing step by a conveyor belt. The washing step was carried out for a duration of 30 to 60 minutes. The washed bamboo raw material was then passed through a vessel containing an acid solution at a temperature ranging from 80 to 100°C and with a sufficient liquor ratio (4 to 7) having a pH range of 1 to 3. After 30 to 60 minutes, the bamboo raw material was removed from the vessel containing the acid and passed through a drum washer where it was washed using a mixture of water and steam at a temperature ranging from 80 to 100°C. After 30 to 60 minutes, the washed and acid treated bamboo raw material was passed through a vessel containing an alkaline solution at a temperature ranging from 80 to 100°C and with a sufficient liquor ratio (4 to 7) having a pH range of 12 to 14. After 30-60 minutes, the bamboo material was removed from the alkali container and passed through a drum washer, which washed it using a mixture of water and steam at temperatures ranging from 80-100°C. The pre-treated bamboo material was moved to the next step by a conveyor belt.

[0088] The silica and ash residue contents of the pretreated bamboo feedstock were measured according to Tappi T618-cm-01 and are shown in Figure 3(b) and Figure 4(b).

[0089] The pretreated bamboo feedstock was then cooked under prehydrolyzed Kraft (P factor 500-800) / Kraft for both DP and KP. Available alkali was used in amounts ranging from 15-20% and H factor ranged from about 500-700. The target specifications for chemical pulps (DP and KP), presented in Table 2 above, were achieved.

[0090] Example 3 - EFB raw material factory test In an operational mill processing 35 tons of feedstock per day, standard wood feedstock was replaced with a mixed wood feedstock containing 5-10% by weight EFB feedstock. Various products were monitored as summarized below. The process to which the mixed EFB feedstock was subjected included the pretreatment method of the present invention.

[0091] Figure 12 shows when the feedstock was changed to contain 5-10 wt% EFB feedstock. It is clear from Figure 13 that higher cooking productivity (as evidenced by lower H-factor) was observed at the same level of alkali loading and kappa number when the feed was changed to mixed EFB feedstock. With reference to Figures 14 and 15, it is also clear that the consumption of chemicals in the bleaching process was reduced - both oxygen and alkali loadings were reduced, and the total loading of ClO2 was also reduced (47.3 kg for pure wood feedstock vs. 46.2 kg for mixed EFB / wood feedstock).

[0092] In addition to these reductions in both chemical consumption and energy requirements, it has been found that the quality of the final bleached pulp was advantageously maintained. In particular, the resulting pulp had the following properties: [Table 3]

[0093] The final product in the mill trial described in Example 3 was a paper product. When the raw material was changed from pure wood to a mixture of EFB and wood and the process included the pretreatment method of the present invention, it was surprising to see that the final paper product had superior properties, specifically, a tensile strength of 70 Nm / g and a yield strength of 1.39 cm. 3 The paper was found to have a bulk density of 1000 g / g. The paper also demonstrated high performance in both drainage and runnability.

[0094] Overall, by replacing the wood feedstock with the mixed EFB / wood feedstock and including the pretreatment method of the present invention, it was possible to produce a product with the required superior properties while reducing energy consumption by approximately 10%.

[0095] Exemplary embodiments The present invention is further described by reference to the following numbered exemplary embodiments.

[0096] 1. A method for pretreating non-wood raw materials, comprising the steps of: (a) washing the non-wood raw materials; (b) contacting the washed non-wood feedstock with an acid solution; and (c) contacting the washed non-wood material with an alkaline solution. wherein the method comprises an additional washing step (d) between steps (b) and (c).

[0097] 2. The method of embodiment 1, wherein step (b) is performed before step (c).

[0098] 3. The method of embodiment 1, wherein step (c) is performed before step (b).

[0099] 4. The method of any preceding embodiment, wherein in step (a), the non-wood feedstock is washed using water and / or water steam.

[0100] 5. The method of any preceding embodiment, wherein step (a) is carried out at a temperature in the range of 80 to 100 °C.

[0101] 6. The method of any preceding embodiment, wherein in step (a), the non-wood feedstock is passed through a screw-type conveyor.

[0102] 7. The method of any preceding embodiment, wherein in step (b), the washed non-wood feedstock is contacted with the acid solution at a temperature in the range of 80-100° C. for a duration of 30-60 minutes.

[0103] 8. The method of any preceding embodiment, wherein in step (b), the pH is in the range of 1 to 3.

[0104] 9. The method of any preceding embodiment, wherein in step (b), the acid solution comprises an acid selected from the group consisting of sulfuric acid, hydrochloric acid, an aqueous solution of chlorine dioxide, and mixtures thereof.

[0105] 10. The method of any preceding embodiment, wherein in step (b), the acid solution comprises an acid at a concentration of about 0.2 to about 5%.

[0106] 11. The method of any one of the preceding embodiments, wherein in step (b), the acid solution comprises recycled acid solution from a process for bleaching dissolving pulp (DP) and / or kraft pulp (KP).

[0107] 12. The method of embodiment 11, wherein in step (b), the acid solution comprises recycled acid at a concentration of about 0.2 to about 5%.

[0108] 13. The method of any preceding embodiment, wherein in step (d), the non-wood feedstock is washed using water and / or water steam.

[0109] 14. The method of any preceding embodiment, wherein step (d) is carried out at a temperature in the range of 80 to 100 °C.

[0110] 15. The method of any preceding embodiment, wherein in step (d), the non-wood feedstock is passed through a screw-type conveyor.

[0111] 16. The method of any preceding embodiment, wherein in step (c), the washed non-wood feedstock is contacted with the alkaline solution at a temperature in the range of 80-100° C. for a duration of 30-60 minutes.

[0112] 17. The method of any preceding embodiment, wherein in step (c), the pH is in the range of 12 to 14.

[0113] 18. The method of any preceding embodiment, wherein in step (c), the alkaline solution comprises sodium hydroxide.

[0114] 19. The method of embodiment 18, wherein in step (c), the alkaline solution comprises sodium hydroxide at a concentration of about 0.2 to about 5%.

[0115] 20. (e) Washing the product obtained after steps (a) to (d). 4. The method of any preceding embodiment, further comprising:

[0116] 21. The method of embodiment 20, wherein in step (e), the product is washed with water and / or water steam.

[0117] 22. The method of embodiment 20 or embodiment 21, wherein step (e) is carried out at a temperature in the range of 80 to 100°C.

[0118] 23. The method according to any one of embodiments 20 to 22, wherein in step (e), the non-wood feedstock is passed through a screw-type conveyor.

[0119] 24. The method of any preceding embodiment, wherein the non-wood feedstock is non-wood empty fruit bunches (EFB).

[0120] 25. A method for producing dissolving pulp (DP) from non-wood raw materials, comprising: (i) pretreating the non-wood raw material using the method according to any one of embodiments 1 to 24; and (ii) steaming the pretreated non-wood material to produce DP; The method comprising:

[0121] 26. A method for producing kraft pulp (KP) from non-wood raw materials, comprising: (i) pretreating the non-wood raw material using the method according to any one of embodiments 1 to 24; and (ii) steaming the pretreated non-woody material to produce kraft pulp; The method comprising:

[0122] 27. The method of embodiment 25 or embodiment 26, wherein the non-wood raw material is non-wood empty fruit bunch (EFB).

[0123] 28. The method of embodiment 25 or embodiment 27, comprising the further step of bleaching the DP obtained in step (ii).

[0124] 29. The method of embodiment 26 or embodiment 27, comprising the further step of bleaching the KP obtained in step (ii).

[0125] 30. The method of embodiment 28 or embodiment 29, wherein the bleaching process is a chlorine-free (ECF) bleaching process.

[0126] 31. The bleaching step comprises: (iii) sequentially treating the DP with peroxymonosulfuric acid, chlorine dioxide, hydrogen peroxide, and chlorine dioxide; 31. The method of embodiment 30, comprising:

[0127] 32. The method of embodiment 28 or embodiment 29, wherein the bleaching process is a totally chlorine-free (TCF) bleaching process.

[0128] 33. The method of any one of embodiments 28-32, wherein acid from the bleaching step is recycled to step (b) of the pretreatment step (i).

[0129] 34. The method of embodiment 26, 27, or 29-33, wherein the KP is converted into a paper product.

[0130] 35. The method of embodiment 25, 27, 28 or 30-33, wherein the DP is converted into regenerated cellulose.

[0131] 36. The method of embodiment 35, wherein the regenerated cellulose is selected from the group consisting of viscose fibers, modal fibers, lyocell and MCC fibers.

[0132] 37. A dissolving pulp obtainable by the method according to any one of embodiments 25, 27, 28 or 30 to 33.

[0133] 38. Kraft pulp obtainable by the method according to any one of embodiments 26, 27 or 29 to 33.

[0134] 39. Dissolving pulp derived from non-wood sources having a silica content of less than about 80 ppm.

[0135] 40. The dissolving pulp of embodiment 37 or embodiment 39, having an Fe content of about 10 ppm or less.

[0136] 41. The dissolving pulp of any one of embodiments 37, 39 or 40, having a Ca content of about 75 ppm or less.

[0137] 42. The dissolving pulp of embodiment 37 or any one of embodiments 39-41, having an ash content of about 0.12% or less.

[0138] 43. The dissolving pulp of embodiment 37 or any one of embodiments 39-42, which is derived from a non-wood EFB.

[0139] 44. Kraft pulp derived from non-wood sources having a silica content of less than about 600 ppm.

[0140] 45. The kraft pulp of embodiment 38 or embodiment 44 having an ash content of about 0.35% or less.

[0141] 46. ​​The kraft pulp of any one of embodiments 38, 44 or 45, derived from a non-wood EFB.

[0142] 47. Use of a dissolving pulp (DP) according to embodiment 37 or embodiments 39 to 43 in the manufacture of cellulose fibers.

[0143] 48. Use of the kraft pulp (KP) according to embodiment 38 or embodiments 44 to 46 in the manufacture of paper.

Claims

1. 1. A method for pretreating non-wood empty fruit bunch (EFB) material, comprising: (a) washing the non-wood empty fruit bunch (EFB) material; (b) contacting the washed non-wood empty fruit bunch (EFB) material with an acid solution at a temperature in the range of 80-100° C. for a duration of 30-60 minutes; and (c) contacting the washed non-wood empty fruit bunch (EFB) material with an alkaline solution at a temperature in the range of 80-100° C. for a duration of 30-60 minutes. Including, the method comprises an additional washing step (d) between steps (b) and (c); Step (b) is carried out before step (c); The method.

2. 2. The method of claim 1, wherein in step (a), the non-wood empty fruit bunch (EFB) material is washed using water and / or steam.

3. 2. The method of claim 1, wherein in step (d), the non-wood empty fruit bunch (EFB) material is washed using water and / or steam.

4. (e) washing the product obtained after steps (a) to (d). The method of claim 1 further comprising:

5. 1. A process for producing dissolving pulp (DP) from non-wood empty fruit bunch (EFB) material, comprising: (i) pretreating the non-wood empty fruit bunch (EFB) material using the method of any one of claims 1 to 4; and (ii) steaming the pretreated non-wood empty fruit bunch (EFB) material to produce DP. The method comprising:

6. 1. A method for producing kraft pulp (KP) from non-wood empty fruit bunch (EFB) materials, comprising: (i) pretreating the non-wood empty fruit bunch (EFB) material using the method of any one of claims 1 to 4; and (ii) steaming the pretreated non-wood empty fruit bunch (EFB) material to produce KP. The method comprising:

7. A dissolving pulp derived from non-wood empty fruit bunch (EFB) materials having a silica content of less than about 80 ppm.

8. 8. The dissolving pulp of claim 7 having an Fe content of about 10 ppm or less.

9. 9. The dissolving pulp of claim 7 or 8 having a Ca content of about 75 ppm or less.

10. 9. The dissolving pulp of claim 7 or 8 having an ash content of about 0.12% or less.

11. Kraft pulp derived from non-woody empty fruit bunch (EFB) sources having a silica content of less than about 600 ppm.

12. 12. The kraft pulp of claim 11 having an ash content of about 0.35% by weight or less.

13. 9. Use of the dissolving pulp (DP) according to claim 7 or 8 in the manufacture of cellulose fibres.

14. 13. Use of the kraft pulp (KP) according to claim 11 or claim 12 in the manufacture of paper.

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