Distillation method

Abstract

The present invention discloses a cooking method in which partially digested wood-cellulosic feedstock is compressed during cooking to provide high molecular weight xylan, lignin and pulp.

Description

[Technical Field]

[0001] The present disclosure relates to a cooking method for the combined production of high-yield high molecular weight (HMW) xylan, HMW lignin, sulfite, and dissolving pulp from a cellulosic fiber source, and to a digester (digester) system in which the cooking method can be used. The pulp produced according to this method is useful for producing paper-grade pulp, dissolving cellulose products, and cellulose derivatives. [Background technology]

[0002] Pulp, also known as paper pulp or dissolving cellulose, is a bleached wood pulp with a high cellulose content that is chemically produced from wood using the soda process or the kraft process. The kraft and soda processes are commonly used pulping methods. In the traditional kraft process, wood is treated with an aqueous mixture of sodium hydroxide and sodium sulfide. In the soda process, wood is treated with sodium hydroxide. This treatment decomposes and solubilizes the lignin, defibrating the wood fibers.

[0003] Generally, wood pulp containing high levels of alpha cellulose is known in the art as dissolving pulp and is used to produce cellulose derivatives and products for a variety of applications. Other terms synonymous with dissolving pulp are chemical cellulose and special high alpha pulp. Two processes are commonly used to produce dissolving pulp: 1) The acid sulfite process, the development of which began around the beginning of this century (Rydholm, SA, Pulping Processes, p. 280, Interscience Publishers, New York-London-Sydney 1965); and 2) Preliminary hydrolysis - the Kraft process, the development of which began in 1929 (Rydholm, supra - p. 281).

[0004] The latter process utilizes an acidic pretreatment ("pre-hydrolysis") step to remove hemicellulose before the alkaline pulping (delignification) step. South African Patent No. 88 / 4037 discloses a pre-hydrolysis - neutral sulfite - anthraquinone process (PH-NS-AO) for the production of "hemicellulose hydrolysis and special pulp" (high alpha grade). This pre-hydrolysis step essentially performs the same function as the pre-hydrolysis step that precedes the Kraft (sulfate) pulping process to produce dissolving-grade pulp. On the other hand, the neutral sulfite-anthraquinone delignification step is essentially the same as the process also known as the semi-alkaline sulfite-anthraquinone (SAS-AQ) method, which was first reported by Raubenheimer, S. and Eggers, S.H. (both researchers employed by SAPPI LIMITED, the applicant of this application) at a technical conference in 1979, namely the 11th European ESPRA Congress held in Maastricht, The Netherlands, in May 1979.

[0005] Furthermore, conventional paper and dissolving pulp production using the Kraft or soda processes, which include a prehydrolysis step, suffers from the disadvantage of low yields because the hemicellulose and cellulose in wood are decomposed during the process, primarily in the prehydrolysis step, and are transferred to acid condensates as low-molecular-weight hemicellulose, monosaccharides, and hemicellulose degradation products. The soda process also suffers from the disadvantage of low yields because the cooking time is very long, resulting in the decomposition of the hemicellulose and cellulose in wood during the cooking process. Because it is difficult to extract these degradation products from the digester, the decomposed material is at best used for energy production by evaporating and burning the components, or simply discarded as waste.

[0006] WO99 / 47733 discloses a method for producing cellulose fibers, the degree of polymerization of which can be adjusted by acid hydrolysis and oxidative degradation. However, the kraft pulp obtained by this process has a large amount of residual hemicellulose, which makes the obtained pulp less useful for producing regenerated cellulose for use in textile applications, for example. Because these residual compounds have a negative effect on the process behavior and, as a result, on the mechanical properties of the textile fibers produced therefrom.

[0007] US2009 / 0312536 discloses a process for producing dissolving pulp suitable for textile applications from cellulosic starting materials using the Kraft process combined with a cold caustic extraction (CCE) type refining step.

[0008] Both WO2011 / 138633 and WO2011 / 138634 disclose pulp processing methods that include a cold caustic soda extraction step, but the disclosed methods describe procedures that result in low overall yields of dissolving pulp and are expensive. Summary of the Invention [Problem to be solved by the invention]

[0009] It is therefore an object of the present disclosure to provide an improved industrial-scale cooking process for producing high-yield dissolving pulp with low hemicellulose content, which can be easily delignified and bleached to the required brightness and viscosity levels.

[0010] It is another object to provide a cooking system for woody cellulosic feedstocks (wood-based cellulosic feedstocks) that provides pulp, high molecular weight xylan and high molecular weight lignin without sulfur compounds. [Means for solving the problem]

[0011] At least some of the above and other objects can be achieved by the present invention as defined in the independent claims. The present invention is advantageous in that it allows for the production of value-added products, such as HMW hemicellulose, HMW xylan and HMW lignin, from lignocellulosic feedstocks used in pulping. Furthermore, the present invention uses less energy in the production of dissolving pulp or paper-grade pulp than conventional pulping processes.

[0012] The present invention also allows for reduced processing and / or cooking times. A further advantage is that the process provides a higher overall yield of paper-grade pulp and dissolving pulp than can be achieved using conventional prehydrolyzed soda, prehydrolyzed kraft, or sulfite processes to produce paper-grade or dissolving-grade pulp. The embodiments described below provide further advantages.

[0013] According to a first embodiment, the following is provided: 1. A cooking method comprising: a) providing a wood-based cellulose feedstock (wood-based cellulose feedstock) including chips, pin chips, shavings, sawdust, or a combination thereof; b) pretreating the wood-based cellulose feedstock by exposing it to steam to provide a pretreated material; c) optionally pre-hydrolyzing the pre-treated material with steam or water to provide a pre-hydrolyzed material; d) optionally grinding and compressing the pre-treated and / or pre-hydrolyzed material to release HMW xylan from the pre-treated and / or pre-hydrolyzed material into a hydrolysate, and recovering the hydrolysate containing HMW xylan; e) neutralizing with sodium hydroxide or sodium hydroxide containing sulfur or replacing with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid; f) cooking in a cooking liquor containing sulfur-containing sodium hydroxide or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid to provide a cooked cellulosic material in spent cooking liquor; g) comminuting and compressing the cooked cellulosic material to release HMW lignin from the cooked cellulosic material into the spent cooking liquor, thereby providing an HMW lignin fraction in black liquor and a compressed cellulose fraction; h) replacing the spent cooking liquor with a replacement liquor containing 1 to 40% available alkali as NaOH or an acid sulfite cooking liquor, or with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid; i) recovering the HMW lignin from the HMW lignin fraction in the black liquor and from the displacement liquor; and j) recovering a dissolving pulp from said compressed cellulose fraction. A cooking method comprising:

[0014] The present cooking method is advantageous in that it can provide the combined production of HMW hemicellulose, HMW xylan, HMW lignin, and dissolving pulp. In particular, HMW xylan can be produced in this method by pre-hydrolysis to open the structure of the fiber cell walls, followed by compression to extrude the HMW xylan from the fiber cell walls.

[0015] The method improves xylan yield, lignin yield, and / or cellulose yield, while reducing wood consumption, cooking time, and the amount of water in the lignin-containing fraction. These effects have the advantage of reducing energy consumption during evaporation. Furthermore, the method allows for the recovery of high-value products, HMW xylan and HMW lignin, during pulping.

[0016] According to a second embodiment, there is provided a HMW xylan fraction obtainable using the method.

[0017] As shown in the examples, compared to prior art cooking processes, the present method provides xylan with higher molecular weight, higher xylan yield, and higher xylan concentration in the HMW xylan fraction.

[0018] According to a third aspect, there is provided a HMW lignin fraction obtainable using the method.

[0019] Using this method, HMW lignin fractions can be obtained with better lignin yields and higher consistency. The HMW lignin also has an increased molecular weight compared to that produced according to conventional processes, such as those disclosed in PCT / FI2011 / 050651.

[0020] According to a fourth aspect, there is provided a pulp obtained by using the present method. The pulp obtained according to the method of the present invention has higher brightness and requires less wet pressing and lower steam consumption during drying compared to pulp produced according to prior art methods. Furthermore, the dissolving pulp may have a lower hemicellulose content compared to pulp produced by conventional methods.

[0021] Embodiments of the present disclosure offer certain advantages. Depending on the embodiment, one or several of the following advantages can be achieved: reduced consumption of chemicals, water, cellulose fiber sources, and energy; improved yield of cellulose, and increased molecular weight of xylan and lignin. [Brief explanation of the drawings]

[0022] [Figure 1] Figure 1 shows a schematic diagram of one embodiment of the present digestion method, which includes pre-steaming and pre-hydrolysis of wood-based cellulosic feedstock, and a digestion (digestion) system for grinding and / or compressing the condensate from the wood chips after pre-hydrolysis. The process parameters mentioned in Figure 1 are exemplary only, and other process parameters can be used, as described in this disclosure.

[0023] [Figure 2] Figure 2 shows a schematic diagram of one embodiment of a digester (cooking) system for compressing cooking liquor from wood chips in a prehydrolyzed kraft or soda cooker. The process parameters mentioned in Figure 2 are exemplary only, and other process parameters can be used, as described in this disclosure.

[0024] [Figure 3] Figure 3 shows one embodiment of a general process for compressing wood chips and extruding cooking liquor. The process parameters mentioned in Figure 3 are exemplary only, and other process parameters can be used as described in this disclosure.

[0025] [Figure 4] Figure 4 shows a schematic representation of one embodiment of a process for displacing spent liquor from compressed wood chips. The process parameters mentioned in Figure 4 are exemplary only, and other process parameters can be used, as described in this disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0026] Detailed Description As used herein, the term "comprising" encompasses the broader terms "including," "containing," and "comprehending," as well as the narrower terms "consisting of" and "consisting only of."

[0027] In one embodiment, the process steps are performed in the order specified in any aspect, embodiment, or claim. In another embodiment, any process step specified to be performed on a product or intermediate obtained in a preceding process step is performed directly on said product, i.e., without additional, optional, or auxiliary processing steps that may chemically or physically alter the product between said two steps.

[0028] In one embodiment, the wood-based cellulose feedstock used in the present cooking process is in the form of chips, pin chips, shavings, or sawdust, or a combination thereof. It is preferred to use wood chips, and more preferred to use softwood (coniferous) or hardwood (hardwood) chips, such as eucalyptus, pine, or spruce chips. However, when wood chips are used as the primary feedstock, the feedstock may contain lesser amounts of, for example, pin chips and / or sawdust.

[0029] Unless otherwise stated, all percentage values ​​refer to % dry weight.

[0030] The process is suitable for use in a plant or mill, i.e. industrial (large) scale process.

[0031] Referring to Figure 1, in one embodiment, pretreatment includes steaming the chips, which can be carried out in a silo by supplying steam at 3.5 bar for 30 minutes. In one embodiment, prehydrolysis can be carried out at 175°C for 20 minutes. In one embodiment, cooking can be carried out in cooking liquor at 155°C for 50-70 minutes.

[0032] Referring to Figure 2, in one embodiment, cooking is carried out for 50-70 minutes in a digester vessel operated at 155°C, compaction is carried out at 155°C for 50-70 minutes, and displacement is carried out at 90°C.

[0033] Referring to Figure 3, in one embodiment, chips from the cooking step are fed to a milling and pressing step at 155°C and a kappa number of 100-2, where they are removed through a 7mm gap.

[0034] Referring to Figure 4, in one embodiment, a column of chips is compressed at 1 bar in the presence of a 90°C liquor containing 1-15 g / L of effective alkali, which allows for the collection of high molecular weight spent liquor (including HMW lignin) and cellulose.

[0035] In one embodiment, the woody cellulose feedstock has a xylan content of 4% or more by weight.

[0036] The term high molecular weight xylan (HMW xylan) refers to xylans with a weight average molecular weight (MW) of 45000 g / mol or greater for hardwoods (broadleaf trees) and softwoods (conifers).

[0037] The term high molecular weight lignin (HMW lignin) refers to lignin with a weight average molecular weight (MW) of 4580 g / mol or greater for hardwoods and 4980 g / mol or greater for softwoods.

[0038] In one embodiment, molecular weight is measured by size exclusion chromatography and is expressed as average molecular weight (MW).

[0039] Hemicellulose may be recovered from the hydrolysate in step d.

[0040] According to one embodiment, pre-treatment by steaming is preferred to achieve air evacuation from the wood chips to improve penetration of the liquid into the porous wood. The preliminary steaming can be carried out in a separate steaming vessel or a chip silo. The steaming can be carried out by using low-pressure steam at a pressure of about 3.5 bar for at least 10 minutes, preferably more than 20 minutes. In one embodiment, the preliminary steaming comprises pre-steaming with low-pressure steam at 1 to 4 bar for 1 to 100 minutes to provide a pre-treated material.

[0041] The temperature used in the pretreatment (preliminary treatment) is preferably selected from the range of 80 to 120°C, more preferably from the range of 100 to 120°C, and even more preferably from the range of 110 to 120°C.

[0042] In one embodiment, the prehydrolysis is carried out with steam or water at a temperature selected from the range of 150-220° C. In one embodiment, the prehydrolysis step comprises prehydrolysis with steam at 8-15 bar for 1-150 minutes at a temperature selected from the range of 150-220° C.

[0043] Wood chips typically have a roughly rectangular shape with a height, length, and width. However, the geometry of a wood chip can vary, for example, depending on its manufacturing process. The length (longest dimension) and width (second-longest dimension) of the chip can be considered to determine the chip's general "flat side," and its thickness is the chip's smallest dimension. In the case of pin chips, the width and thickness can be close to each other, thereby forming an elongated object like a match. The exact dimensions of the chip can vary.

[0044] In one embodiment, the cellulose feedstock serving as the fiber source for the wood-based cellulose feedstock comprises or consists of wood chips, and grinding and compression are applied until the surface area of ​​the wood chips is maximized. Preferably, the grinding and compression is performed at a rate of 250 to 2000 kg / m to release HMW xylan and / or HMW lignin. 3 , preferably 350 to 1525 kg / m 3 The grinding and compaction are performed to achieve a density of 0.01 mm. Grinding and compaction to a maximum surface area can be achieved by using a gap that allows the smallest dimension, or "side," of the chips to enter first. Devices used for this purpose can be segmented plates, feed screws with blades that decrease in distance, plug feed screws that feed against rotating segment plates, rotors and stators with segmented plates, modified pumps with segmented plates that allow the pump's stator and rotor to pressurize and feed, drum presses with gaps and segmented surfaces, and modified stator and rotor systems. The solution to the problem is not limited to the above and can be adapted by those skilled in the art.

[0045] In a preferred embodiment, the chip is forced into the gap such that the flat side of the chip with the largest surface area does not enter the gap first, which can be achieved by pre-orienting the chip into the gap where it will not fit onto its flat side.

[0046] In one embodiment, the grinding and compacting is carried out by drawing the material through a gap at cooking conditions and releasing the HMW lignin into the spent liquor, thereby providing an HMW lignin fraction in the black liquor.

[0047] In one embodiment, the conditions of a previous step, such as an optional pre-hydrolysis or cooking step, are maintained when removing the material through the gap in the next step, for example to release xylan or lignin.

[0048] In one embodiment, the grinding and compaction is carried out to a consistency of more than 10%, preferably more than 20%, or more preferably more than 30%, preferably more than 65%. The consistency can be measured using the standard TAPPI T240 Consistency of Pulp Suspension or the corresponding ISO 4119 standard.

[0049] In one embodiment, the method comprises steps c) and d), wherein the grinding and compacting in step d) is carried out at the prehydrolysis temperature used in step c) to a consistency of at least 10% by weight.

[0050] In one embodiment, the grinding and compression is carried out by removing the wood chips through a gap in the range of 50 mm to 8 mm, resulting in a reduction in the porosity of the wood within the gap of at least 20%, 30%, 40%, 50%, 60%, 70% or more and the release of HMW lignin. Correspondingly, when the method comprises an optional prehydrolysis step followed immediately by an optional grinding and compression step, HMW xylan may be released.

[0051] In one embodiment, the grinding and compacting is carried out by drawing pin tips through gaps in the range of 35 mm to 6 mm, resulting in a reduction in wood porosity within the gaps of at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, or more than 70% and the release of HMW lignin. Correspondingly, when the method comprises an optional prehydrolysis step and an optional grinding and compacting step immediately following the prehydrolysis step, HMW xylan may be released.

[0052] In one embodiment, the grinding and compacting is carried out by drawing sawdust through a gap in the range of 20 mm to 4 mm, resulting in a reduction in wood porosity within the gap of at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, or more than 70% and the release of HMW lignin. Correspondingly, HMW xylan may be released when the method comprises an optional prehydrolysis step followed immediately by an optional grinding and compacting step.

[0053] In one embodiment, the grinding and compacting is carried out by pressing the prehydrolyzed and / or cooked cellulosic material through a gap, and The size of this gap is chosen as follows: The gap between the wood chips is selected from the range of 50mm to 8mm. The gap for the pin tip is selected from the range of 35 mm to 6 mm, The gap for the sawdust is selected from the range of 20 mm to 4 mm.

[0054] The porosity of wood materials is expressed as 1 - the amount of wood in the pores (kg / m 3 ) / 1500kg / m 3 It is calculated as follows.

[0055] The term black liquor in the present invention means used cooking liquor, i.e., spent liquor or used cooking liquor.

[0056] In one embodiment, the black liquor or spent liquor is replaced with a replacement liquor containing 1-40% effective alkali as NaOH or NaOH cooking liquor, or a replacement liquor containing an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid. The replacement liquor thus replaces or transforms the black liquor (spent cooking liquor), and after the replacement step, the cooked and pressed cellulose-containing material (the cellulose fraction from which HMW xylans and HMW lignins have been removed in the previous step) remains in the replacement liquor.

[0057] In one embodiment, HMW lignin is recovered from the HMW lignin fraction in the spent liquor and from the displacement liquor, for example, by evaporating the water in the black liquor and recovering the lignin.

[0058] As the HMW xylan is extruded from the cell wall, a liquid fraction containing the HMW xylan fraction and a solid fraction containing the compacted material are formed.

[0059] In one embodiment, the milling and compaction in step d) begins before the wood chips reach a porosity level of 0.66-0.9, preferably 0.67-0.9, more preferably 0.7-0.85. The porosity level is determined by the following formula: 1 - (mass of dry material / density of cellulose (1500 kg / m 3 )) can be calculated as

[0060] In one embodiment, the method comprises steps c) and d), wherein the compression in step d) is 350 kg / m 3 ~2000kg / m 3 , preferably 350 kg / m 3 ~1525kg / m 3 This is carried out until a density selected from the range of

[0061] In one embodiment, the cooking method comprises a pre-hydrolysis step c) and a grinding and compacting step d).

[0062] In one embodiment, the neutralization in step e) is carried out using white liquor having a sulfidity of 1 to 45%, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid.

[0063] In one embodiment, steps d) and g) are performed to increase the porosity of the cell walls of the fibers.

[0064] Total alkali, active alkali, and effective alkali mean the measured values ​​of soda, white liquor, and green liquor by standard method SCAN-N 30:85 or corresponding TAPPI or ISO standards.

[0065] In one embodiment, neutralization is carried out using NaOH with a sulfidity of 1-45%, an alkaline solution containing 1-45% effective alkali as NaOH solution (measured by method SCAN-N 30:85 or corresponding TAPPI or ISO standard), or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid. When an organic acid is used, the chemical loading can be selected from the range of 1-100 g / kg organic acid. The chemical loading is calculated from the initial dry wood mass (kg) as the mass of the selected chemical. The ratio of cooking liquor to biomaterial can be selected from 2-10 mass kg.

[0066] In one embodiment, the neutralization is carried out using sodium hydroxide having a sulfidity.

[0067] In one embodiment, the neutralization is carried out using NaOH solution.

[0068] In one embodiment, the neutralization liquor contains NaOH having a sulfidity of 1-45%, 1-45% effective alkali as the NaOH cooking liquor, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid to provide a digested cellulosic material in spent liquor. The chemical loading is calculated from the initial dry wood mass (kg) as the mass of the selected chemical.

[0069] The mass ratio of the neutralizing liquid to the wood cellulose material can be selected from the range of 2 to 10 in terms of the dry mass of the wood cellulose material.

[0070] In one embodiment, the hydrolysate is recovered with HMW xylan and subsequently neutralized. Under these conditions, the present invention is able to extrude xylan from the cell walls and keep xylan from degrading, since most of the xylan is removed before entering the high alkaline concentration in the neutralization step.

[0071] In one embodiment, the neutralization is carried out at a temperature of at least 120°C, preferably greater than 150°C, or more preferably greater than 170°C.

[0072] Weight percent refers to dry weight, such as the dry weight of wood in wood-based cellulosic feedstocks (wood-based cellulosic feedstocks).

[0073] The HMW xylan of the present invention can be collected immediately after prehydrolysis because the xylan does not come into contact with the alkali used in the cooking step. Thus, the yield and molecular weight of the xylan are maximized. The hydrolyzate can also be replaced with a neutralization liquor. However, some of the xylan is subsequently decomposed by the alkali in the neutralization liquor, resulting in a decrease in xylan yield. In the prior art document PCT / FI2011 / 050651, pressure and shearing were initiated only after the lignin, hemicellulose, and cellulose reached their softening points after the cooking step, resulting in chemically and physically different products.

[0074] According to one embodiment of the neutralization step, an alkali load of 10%, 15%, 20%, 25%, 30%, 35% or 70% w / w (% by weight) effective alkali as NaOH or pure NaOH is used for neutralization. Preferably, an alkali load of about 20% w / w is used. In one embodiment, the neutralization step is carried out by contacting the cellulosic material with the neutralization liquid by pumping the neutralization liquid through the compacted material.

[0075] The term cooking liquor refers to white liquor, black liquor, soda, or a mixture thereof commonly used in chemical pulping during the cooking stage. White liquor is a strongly alkaline solution containing sodium hydroxide and sodium sulfide in water, resulting in an opaque white color. White liquor may contain small amounts of sodium carbonate, sodium sulfate, sodium thiosulfate, sodium chloride, calcium carbonate, and other accumulated salts. Soda contains sodium hydroxide and trace amounts of compounds found in wood.

[0076] In one embodiment, cooking is carried out in an alkaline cooking liquor containing 1-45% effective alkali as NaOH having a sulfidity of 1-45%, or with NaOH, or with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid to provide a cooked cellulosic material in spent liquor.

[0077] The mass ratio of the cooking liquor to the woody cellulose material can be selected from the range of 2 to 10 in terms of the dry mass of the raw material.

[0078] According to one embodiment, cooking is carried out in a cooking liquor at a temperature of at least 120°C, preferably above 150°C, more preferably above 170°C.

[0079] During cooking, at least 5% by weight, for example 5-10% by weight, preferably more than 10% by weight, of dry wood raw material is used.

[0080] During cooking, more than 10% by weight of cooking liquor is used relative to the total weight.

[0081] The cooked cellulosic material in the cooking liquor may have an alpha cellulose content of greater than 60% by weight, preferably greater than 70% by weight, and even more preferably greater than 80% by weight.

[0082] According to one embodiment, cooking is continued until a final kappa number is reached, followed by compaction and / or grinding through a gap of 50 mm to 8 mm for wood chips, or a gap of 35 mm to 6 mm for pin chips, and a gap of 20 mm to 4 mm for sawdust.

[0083] The kappa number can be selected between 120 and 1 in the cooking step. More specifically, for dissolving pulp, the desired kappa number can be selected between 1 and 15, and for paper-grade pulp, the kappa number can be between 15 and 50. The cooking temperature can be selected from the range of 120°C to 180°C. The temperature can be selected by those skilled in the art depending on the desired kappa number.

[0084] In one embodiment, when producing pulp for dissolving pulp, cooking is continued until a kappa number selected between 100 and 1 is reached.

[0085] In one embodiment, when producing paper grade pulp, cooking is continued until a kappa number selected between 50 and 15 is reached.

[0086] In one embodiment, the method comprises steps c) and d), wherein the grinding and compressing in step d) is carried out until a consistency of at least 60% by weight is reached.

[0087] In one embodiment, the cooking in step f) is continued at a cooking temperature selected from the range of 120-180°C until a kappa number selected from the range of 100-3 is reached.

[0088] According to one embodiment, in step g) the comminution and compaction of the wood chips is carried out by forcing the wood chips into interstices under the conditions of the cooking step as described above, releasing the HMW lignin into the cooking liquor, thereby forming a liquid HMW lignin fraction and a solid fraction comprising the compacted material.

[0089] In one embodiment, the grinding and compacting in step g) can begin before the wood chips reach a porosity level of 0.65-0.9, preferably 0.66-0.9, more preferably 0.7-0.85.

[0090] The compressed cellulose fraction has an alpha cellulose content of greater than 85%, more preferably greater than 90%, more preferably greater than 95%.

[0091] In one embodiment, the cooked cellulosic material is compressed in black liquor at a pressure selected from the range of 1 to 250 kPa to form a solid column having a consistency of at least 5% by weight. Non-limiting examples of suitable pressures to reach a selected target consistency value include 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa, 10 kPa, 20 kPa, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa, 110 kPa, 120 kPa, 130 kPa, 140 kPa, 150 kPa, 160 kPa, 170 kPa, 180 kPa, 190 kPa, 200 kPa, 210 kPa, 220 kPa, 230 kPa, 240 kPa, and 250 kPa. Non-limiting examples of suitable consistency values ​​include 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 5-50%, 5-40%, 5-30%, and 5-20% by weight.

[0092] In step h), the black liquor is preferably replaced with a replacement liquor having a lower lignin content than the black liquor. At the end of step g), the compacted column of material may be replaced by diluting to a consistency selected from the range of 2-35% by weight, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 2-30%, 2-25%, 2-20%, 2-10%, or 2-5% by weight.

[0093] In one embodiment, in step i), the HMW lignin fraction is recovered from both the black liquor and the displacement liquor.

[0094] In one embodiment, in step j) a cellulose fraction or a dissolving pulp is recovered.

[0095] In one embodiment, step g) is carried out at the cooking temperature used in step f) until a consistency of at least 10% by weight is reached.

[0096] In one embodiment, the method comprises steps c) and d), wherein in step d) the compression pressure is selected from the range of 35 kPa to 1000 kPa.

[0097] In one embodiment, step g) comprises pressing at a pressure selected from the range of 1 kPa to 250 kPa to form a column having a consistency of at least 5 wt. %, and wherein the displacement step h) is carried out by displacing the black liquor with a second displacement liquor having a lower lignin content than the lignin content in the black liquor.

[0098] In one embodiment, the displacement liquid has an alkali loading selected from the range of 1% to 40% effective alkali per dry weight of the cellulosic material, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid.

[0099] In one embodiment, the substitution step h) is carried out at a temperature selected from the range of 70°C to 200°C.

[0100] In one embodiment, after step j), the dissolving pulp is dewatered to remove 90% or more of the alkali, lignin, and dissolved xylan, and other organic and inorganic matter as a liquid stream from the pulp to provide a dewatered pulp.

[0101] In one embodiment, the method comprises delignifying the dewatered pulp with oxygen to provide a delignified pulp, optionally followed by washing and pressing.

[0102] In one embodiment, at least a HMW lignin fraction and at least a HMW xylan fraction are recovered from the spent liquor and the second displacement liquor. Optionally, a lignin fraction and / or a xylan fraction comprising smaller molecular weight species is also recovered.

[0103] The method improves xylan, lignin and cellulose yields, reduces wood consumption, cooking time and increases the amount of recovered lignin and xylan-containing liquor. [Example]

[0104] The effects that can be obtained by embodiments of the method of the present invention are demonstrated by the following experiments, which should not be considered as limiting the scope of the present invention. The abbreviation REF (reference) refers to the prior art method, i.e., the cooking method without the compaction step according to the present invention. Cooking conditions can be selected by those skilled in the art to obtain a target kappa number at the end of the cooking stage.

[0105] Example 1 In this example, an increase in xylan molecular weight was observed when the method according to the present invention, which includes a prehydrolysis step and a grinding and compression step, was performed. Eucalyptus chips and pine chips were processed according to both the present method and the reference method (REF), i.e., the method set forth in EP 0 442 806 A1. The wood chips were pretreated with steam at 115°C for 5 minutes to remove air from the chips. Prehydrolysis was carried out using water at 175°C for 25 minutes. The chips were then ground with a rotor and compressed against the wall of a pressure vessel to feed through a narrow gap. The hydrolyzed material from the source was then compressed to a material consistency of greater than 65%. HMW xylan was recovered from the hydrolyzate. The prehydrolyzed material was then neutralized with alkali having an effective alkali loading of 6 mol / kg as NaOH in soda cooking and a sulfidity of 28% in prehydrolyzed kraft cooking. The temperature was 150°C. The neutralization time was 17 minutes, after which the neutralization liquor was replaced with cooking liquor using a cooking liquor to wood ratio of 4. The effective alkali loading as NaOH was 2.5 mol / kg, and the sulfidity of the prehydrolyzed kraft cook was 28%. The cooking temperature was 156°C, and after cooking with an H-factor of 25, the chips were fed through a narrow gap where they were crushed by a rotor and compressed against the wall of the pressure vessel, causing crushing and compaction, and the spent liquor containing HWM lignin was replaced with wash filtrate. The cooking results for the prehydrolyzed soda and prehydrolyzed kraft cooks are shown in Table 1.

[0106] [Table 1]

[0107] According to Table 1, when cooking is done according to the present invention, the Mw molecular weight of xylan and lignin increases and the cooking time decreases.

[0108] Example 2 This example presents the xylan yield and consistency obtained using the present invention and compares it with conventional cooking methods. In these samples, wood chips were crushed and prehydrolyzed at 15 MPa pressure, then compressed through a 50 mm to 8 mm gap, and the hydrolysate collected for xylan analysis. In the prior art, marked REF, crushing and compression were not used.

[0109] [Table 2]

[0110] According to Table 2, the xylan yield (%) is increased when cooking is done according to the present invention.

[0111] These results confirm that the present method improves yields from both feedstocks, reduces cooking times, and provides different kappa numbers.

[0112] The foregoing description provides a complete and informative description of the best modes presently contemplated by the inventors for carrying out the invention, as non-limiting examples of specific implementations and embodiments of the invention. However, it will be apparent to those skilled in the art that the invention is not limited to the details of the foregoing embodiments, and that it may be practiced in other embodiments using equivalent means, or in different combinations of embodiments, without departing from the characteristics of the invention.

[0113] Moreover, some of the features of the above-described embodiments of the invention can be used to advantage without the corresponding use of other features. Accordingly, the foregoing description should be considered as merely illustrative of the principles of the invention, and not in limitation thereof. The scope of the invention is therefore limited only by the appended claims. Aspects or embodiments that may be included in the present invention are summarized as follows. [1]. 1. A cooking method comprising: a) providing a wood-based cellulose feedstock comprising chips, pin chips, shavings, sawdust, or a combination thereof; b) pretreating the wood-based cellulose feedstock by exposing it to steam to provide a pretreated material; c) optionally pre-hydrolyzing the pre-treated material with steam or water to provide a pre-hydrolyzed material; d) optionally grinding and compressing the pre-hydrolyzed material to release HMW xylan from the pre-hydrolyzed material into a hydrolysate, and recovering the hydrolysate together with the HMW xylan; e) neutralizing with sodium hydroxide or sodium hydroxide containing sulfur or replacing with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid; f) cooking in a cooking liquor containing sulfur-containing sodium hydroxide or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid to provide a cooked cellulosic material in spent cooking liquor; g) comminuting and compressing the cooked cellulosic material to release HMW lignin from the cooked cellulosic material into the spent cooking liquor, thereby providing an HMW lignin fraction in black liquor and a compressed cellulose fraction; h) replacing the black liquor with a replacement liquor or acidic sulfite cooking liquor containing 1 to 40% available alkali as NaOH, or with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid; i) recovering the HMW lignin from the HMW lignin fraction in the black liquor and from the displacement liquor; and j) recovering a dissolving pulp from said compressed cellulose fraction. A cooking method comprising: [2]. The method according to item 1, comprising steps c) and d), wherein the grinding and compacting are carried out at the prehydrolysis temperature used in step c) to a consistency of at least 10% by weight. [3]. The method according to item 1 or 2, comprising steps c) and d), wherein the grinding and compression in step d) is carried out to a consistency of at least 60% by weight. [4]. The steps c) and d) are included, and the compression in step d) is 350 kg / m 3 ~2000kg / m 3 a density selected from the range of 350 kg / m 3 ~1525kg / m 3 The method according to any one of items 1 to 3, wherein the method is carried out until a density selected from the range of [5]. 5. The method according to any one of items 1 to 4, comprising steps c) and d), wherein in step d) the compression pressure is selected from the range of 35 kPa to 1000 kPa. [6]. 6. The method according to any one of items 1 to 5, wherein the cooking in step f) is continued at a cooking temperature selected from the range of 120 to 180°C until the kappa number is selected from the range of 100 to 3. [7]. the grinding and compacting is carried out by pressing the prehydrolyzed material and / or the digested cellulosic material through a gap; and The size of this gap is chosen as follows: The gap between the wood chips is selected from the range of 50mm to 8mm. The gap for the pin tip is selected from the range of 35 mm to 6 mm, The gap for sawdust is selected from the range of 20 mm to 4 mm. The method according to any one of items 1 to 6 above. [8]. 8. The method according to any one of items 1 to 7, wherein step g) is carried out at the cooking temperature used in step f) to a consistency of at least 10% by weight. [9]. 9. The method according to any one of items 1 to 8, wherein the neutralization in step e) is carried out using white liquor having a sulfidity of 1 to 45%, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid.

[10] . 10. The method according to any one of items 1 to 9, wherein the optional steps d) and g) are carried out to increase the porosity of the cell walls of the fibers.

[11] . 11. The method according to any one of items 1 to 10, wherein the step g) comprises pressurizing at a pressure selected from the range of 1 kPa to 250 kPa to form a column having a consistency of at least 5 wt %, and the replacement step h) is carried out by replacing the black liquor with a second replacement liquor having a lignin content lower than the lignin content in the black liquor.

[12] . 12. The method according to any one of items 1 to 11, wherein the displacement liquid has an alkali loading selected from the range of 1% to 40% as effective alkali per dry weight of the cellulose material, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid.

[13] . 13. The method according to any one of the above items 1 to 12, wherein the substitution step h) is carried out at a temperature selected from the range of 70°C to 200°C.

[14] . 14. The method according to any one of items 1 to 13, wherein after step j), the dissolving pulp is dewatered to remove 90% or more of the alkali, lignin and dissolved xylan and other organic and inorganic matter as a liquid stream from the dissolving pulp to provide a dewatered pulp.

[15] . 15. The method according to any one of the preceding items 1 to 14, comprising delignifying the dewatered pulp with oxygen to provide a delignified pulp, optionally followed by washing and pressing.

[16] . A high-molecular-weight xylan fraction obtained by the method according to any one of items 1 to 15 above.

[17] . A high-molecular-weight lignin fraction obtained by the method according to any one of items 1 to 15 above.

[18] . Pulp obtained by the method according to any one of items 1 to 15 above.

Claims

1. 1. A cooking method comprising: a) providing a woody cellulose feedstock comprising chips, pin chips, shavings, sawdust, or a combination thereof; b) pretreating the wood-based cellulose feedstock by exposing it to steam to provide a pretreated material; c) pre-hydrolyzing the pre-treated material with steam or water to provide a pre-hydrolyzed material; d) grinding and compressing the prehydrolyzed material to release HMW xylan from the prehydrolyzed material into a hydrolysate, and recovering the hydrolysate together with the HMW xylan; e) neutralizing with sodium hydroxide or sodium hydroxide containing sulfur or replacing with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid; f) cooking in a cooking liquor containing sulfur-containing sodium hydroxide or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid to provide a cooked cellulosic material in spent cooking liquor; g) comminuting and compressing the cooked cellulosic material to release HMW lignin from the cooked cellulosic material into the spent cooking liquor, thereby providing an HMW lignin fraction in black liquor and a compressed cellulose fraction; h) displacing the black liquor with a displacing liquor or acid sulfite cooking liquor containing 1 to 40% available alkali as NaOH, or with an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid, and malic acid; i) recovering the HMW lignin from the HMW lignin fraction in the black liquor and from the displacement liquor; and 1. A cooking method comprising recovering a dissolving pulp from the compressed cellulose fraction, j) A cooking method wherein said grinding and compacting is carried out at the prehydrolysis temperature used in step c) to a consistency of at least 10% by weight.

2. 2. The method of claim 1, wherein the grinding and compacting in step d) is carried out to a consistency of at least 60% by weight.

3. The compression in step d) is 350 kg / m ３ ~2000 kg / m ３ 3. The method of claim 1 or 2, wherein the density is selected from the range of

4. 4. The method according to any one of claims 1 to 3, wherein in step d) the pressure of said compression is selected from the range of 35 kPa to 1000 kPa.

5. 5. The method according to any one of claims 1 to 4, wherein the cooking in step f) is continued at a cooking temperature selected from the range of 120 to 180°C until a kappa number selected from the range of 100 to 3 is reached.

6. the grinding and compacting is carried out by pressing the prehydrolyzed material and / or the digested cellulosic material through a gap; and The size of this gap is chosen as follows: The gap between the wood chips is selected from the range of 50 mm to 8 mm; The gap for the pin tip is selected from the range of 35 mm to 6 mm; The gap for sawdust is selected from the range of 20 mm to 4 mm; The method according to any one of claims 1 to 5.

7. 7. The method according to any one of claims 1 to 6, wherein step g) is carried out at the cooking temperature used in step f) to a consistency of at least 10% by weight.

8. 8. The method according to claim 1, wherein the neutralization in step e) is carried out using white liquor having a sulfidity of 1 to 45%, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid.

9. The method of any one of claims 1 to 8, wherein optional steps d) and g) are performed to increase the porosity of the fiber cell walls.

10. 10. The method of claim 1, wherein step g) comprises pressurizing at a pressure selected from the range of 1 kPa to 250 kPa to form a column having a consistency of at least 5 wt. %; and wherein the displacement step h) is carried out by displacing the black liquor with a second displacement liquor having a lignin content lower than the lignin content in the black liquor.

11. 11. The method of any one of claims 1 to 10, wherein the displacement liquid has an alkali loading selected from the range of 1% to 40% effective alkali per dry weight of cellulosic material, or sodium hydroxide, or an organic acid selected from lactic acid, acetic acid, formic acid, citric acid, oxalic acid, uric acid and malic acid.

12. 12. The method of any one of claims 1 to 11, wherein said substitution step h) is carried out at a temperature selected from the range of 70°C to 200°C.

13. 13. The method of any one of claims 1 to 12, wherein after step j), the dissolving pulp is dewatered to remove at least 90% of the alkali, lignin and dissolved xylan and other organic and inorganic matter as a liquid stream from the dissolving pulp to provide a dewatered pulp.

14. 14. The method of claim 13, comprising delignifying the dewatered pulp with oxygen to provide a delignified pulp, optionally followed by washing and pressing.

15. A high molecular weight xylan fraction obtainable using the method according to any one of claims 1 to 14, having a weight average molecular weight (MW) of 45,000 g / mol or more.

16. A high molecular weight lignin fraction obtained from hardwood using the method of any one of claims 1 to 14, having a weight average molecular weight (MW) of 4580 g / mol or more.

17. A high molecular weight lignin fraction obtained from softwood using the method of any one of claims 1 to 14, and having a weight average molecular weight (MW) of 4980 g / mol or greater.

18. Pulp obtainable using the method according to any one of claims 1 to 14.

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