JP2006104631A - Method for digesting lignocellulose material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for digesting lignocellulose material to give pulp of low kappa number in high yield. <P>SOLUTION: The method for digesting lignocellulose material to give pulp of low kappa number in high yield comprises treating the lignocellulose material in a permeation step at 110-140°C using a digesting liquid containing 1-10 wt.%, based on bone-dry lignocellulose material, of an active alkali and 0.001-1.5 wt.%, based on bone-dry lignocellulose material, of a quinone compound. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for cooking lignocellulosic materials. More specifically, the present invention relates to a pulp production method that effectively performs an alkaline cooking method using quinone compounds.

  The main production method of chemical pulp that has been industrially used so far is the alkaline cooking method of lignocellulosic materials such as wood, and many kraft methods using an alkaline cooking solution mainly composed of sodium hydroxide and sodium sulfide. A so-called quinone compound cooking method in which quinone compounds are added to this alkaline cooking solution is also widely known.

  In the quinone compound cooking method, the added quinone compounds oxidize and stabilize the terminal aldehyde groups of cellulose and hemicellulose, thereby preventing the peeling reaction and suppressing the elution reaction of cellulose and hemicellulose. On the other hand, the quinone compounds that have become hydroquinone type act on lignin to reduce and dissolve lignin, which itself becomes quinone type. In this way, quinone compounds stabilize cellulose and hemicellulose through their own redox cycle and promote delignification, so that when the pulp kappa number is compared under the same conditions, the yield improves. It is said that the effect of reducing the amount of active alkali necessary for cooking is brought about.

The kraft method has also been improved in recent years, and a method called the modified kraft cooking, which is characterized by adding the cooking liquor by dividing it at the beginning and in the middle of cooking, has appeared. An improvement is seen. (For example, Patent Document 1)
It is also known to use quinone compounds for this modified kraft cooking (for example, Patent Documents 2 to 4), and the quinone compounds penetrate into the lignocellulosic material together with the alkaline cooking liquid as described above to exhibit the effect. Therefore, it can be easily predicted that a certain effect can be obtained by adding quinone compounds to these methods as in the conventional kraft method. However, these methods are active in the middle to late stages of cooking because the active alkali addition rate contained in the cooking liquid added first, that is, the cooking liquid supplied to the infiltration process accounts for 50 to 90% of the total cooking liquid. There is a high possibility that the alkali will be insufficient, and the organic solids and quinone compounds react with each other because the organic solids that have been eluted in the cooking solution are permeated at a high concentration even in the initial stage of cooking. However, during the subsequent extraction of black liquor, many quinone compounds are extracted together with the organic solid content, and there is a problem that the effect of the quinone compound is reduced, but neither patent specifically mentions this problem .

Furthermore, with regard to modified craft cooking, by extracting cooking black liquor from several places in the cooking kettle and supplying a portion of the cooking black liquor during the cooking process, the concentration of organic solids in the black liquor in the system is reduced, Several improved methods for improving delignin selectivity and strength have been known (for example, Patent Documents 5 and 6). In these improved methods, it is considered effective to add quinone compounds. ing. (For example, Patent Documents 7 to 9) Since the quinone compounds permeate into the lignocellulosic material together with the alkaline cooking liquid as described above to express the effect, the quinone compounds are added to these cooking methods as in the conventional kraft method. When added, it can be easily predicted that a certain effect can be obtained. However, in these cooking methods, a considerable amount of cooking black liquor is extracted at the initial stage of cooking, so that there is a lack of active alkali in the subsequent cooking process, and the redox cycle function of quinone compounds is reduced, resulting in There is a problem that delignification efficiency is lowered, but neither patent specifically mentions this problem.
Japanese Patent Laid-Open No. 5-156583 Japanese Patent Laid-Open No. 4-119184 JP-A-4-209833 Japanese Patent Laid-Open No. 4-20984 Special table hei 10-504614 Special table 2002-523640 JP 2000-129586 Special table 2003-301392 Special table 2004-522873

  The problem to be solved by the present inventors is to provide an effective method of using quinone compounds in these modified kraft cooking methods and subsequent improvements, and in particular, maximize the effect of adding quinone compounds. The purpose is to provide optimum processing conditions in the so-called permeation process at the initial stage of cooking in order to achieve the limit. The present inventors have developed a cooking experiment apparatus in which cooking liquid can be arbitrarily added / extracted during cooking so as to be able to correspond to a method adapted to these modified kraft cooking, and by proceeding with examination, a specific cooking The present inventors have completed the present invention by finding a clear effect improvement by adding quinone compounds depending on conditions.

  That is, the present invention is (1) a method of cooking lignocellulosic material through a permeation step and a cooking step using a cooking solution containing an alkaline metal hydroxide, and the cooking is performed for each step of the permeation step and the cooking step. In the cooking method in which the liquid is added to at least one place, the cooking liquid for treating the lignocellulosic material in the permeation step contains 1 to 10% by weight of the active alkali with respect to the weight of the absolutely dry lignocellulosic material, and quinone compounds. A digestion method for lignocellulosic material, characterized in that it is a digestion liquid containing 0.001 to 1.5% by weight based on the weight of the absolutely dry lignocellulose material.

  In the method of (1), the present invention includes (2) the treatment temperature of the lignocellulosic material in the infiltration step being in the range of 110 to 140 ° C., and (3) digestion in which the lignocellulosic material is processed in the infiltration step. The liquid is 5 to 50% of the total cooking liquid used for cooking the lignocellulosic material, and (4) the liquid ratio of the cooking liquor treating the lignocellulosic material in the infiltration step to the weight of the absolutely dry lignocellulosic material is 2 to 2. It is 6 L / kg, and (5) the method of cooking lignocellulosic material, characterized in that a part of the cooking solution in the infiltration step is extracted as black liquor in the infiltration step.

  Further, in the method of (5), the present invention is such that (6) the extraction temperature of black liquor in the infiltration step is in the range of 110 to 140 ° C., and (7) the black liquor extraction rate in the infiltration step is The method of cooking lignocellulosic material is characterized by being 10% or more of the cooking liquor used for the treatment of lignocellulosic material.

  Furthermore, the present invention provides the method (1) to (7), wherein (8) the maximum cooking temperature at which the lignocellulosic material is treated in the cooking step following the infiltration step is greater than or equal to the maximum temperature in the infiltration step. (9) The lignocellulosic material characterized in that the active alkali addition rate of the cooking liquor for treating the lignocellulosic material in the cooking step following the infiltration step is equal to or higher than the active alkali addition rate in the infiltration step. Lignocellulose characterized in that the quinone compounds used in the cooking method and the methods (1) to (9) are one or more compounds selected from quinone compounds, hydroquinone compounds and precursors thereof. It is based on the cooking method of the material.

  By adopting the method of the present invention, quinone compounds rapidly permeated into the lignocellulosic material by adding quinone compounds under these conditions that normally fall short of alkali and increase the kappa number. Covers the shortage of alkali at the beginning of cooking, the redox cycle of quinone compounds functions effectively through accelerated cooking, and the redox cycle of quinone compounds functions effectively due to the presence of relatively much alkali in the cooking process. Thus, the promotion of delignification can be continued, and as a result, effects such as reduction of the kappa number and increase of the pulp yield are obtained.

  In the present invention, compared with the conventional technique, the organic alkali content eluted in the black liquor is obtained by extracting the cooking waste liquid prior to the cooking process in which the main delignification occurs, with a low active alkali addition rate. It is presumed that the quinone compounds extracted together with the quinone compounds can be minimized, and the effect of the quinone compounds appears effectively in the subsequent cooking step. In the present invention, most of the remaining active alkali can be allocated to the cooking step after the infiltration step, that is, from the middle stage to the latter stage of cooking, which is the main place for delignification, so that further delignification is promoted. In addition, since the active alkali addition rate in the infiltration process at the initial stage of cooking is low, the frequency of cellulose cleavage reaction (peeling reaction) can be suppressed, and it is estimated that the pulp yield is further increased.

  As a lignocellulosic material cooking method to which the present invention can be suitably applied, a cooking method generally having an infiltration step and a cooking step can be mentioned. A continuous cooking method having an infiltration step and a cooking step is preferable, but other cooking methods such as a so-called batch cooking method may be used as long as an effect equivalent to the present invention is obtained. Here, the infiltration step is a step in which the liquor cellulose material is infiltrated into the lignocellulosic material prior to the cooking step, and a part of the delignification reaction proceeds. In the cooking step, the delignification reaction of the lignocellulosic material by the cooking liquid is substantially performed. It is a process that progresses automatically. As a cooking apparatus for continuously digesting lignocellulosic material to which the present invention can be suitably applied, a one-bessel type cooking apparatus in which a tower top zone, an upper cooking zone, a lower cooking zone, etc. are provided inside the cooking tank, or cooking A two-vessel cooking apparatus in which an osmotic vessel is installed in front of the kettle is mentioned. Usually, in a one-vessel type cooking apparatus, the top zone is responsible for the osmosis process, and in the two-vessel cooking apparatus, the osmosis vessel is responsible for the osmosis process.

  Even if any of these digesters or other digesters is used, there are mainly a permeation process in which the liquor is permeated into the lignocellulosic material and a digestion process in which a substantial cooking reaction is performed. It has been practiced to appropriately divide the total cooking liquid used in the cooking system that combines the process and the cooking process, and to supply and add the cooking liquid to at least one location for each of the permeation process and the cooking process. Furthermore, in the cooking process, it is widely performed to divide the cooking zone into a plurality of parts, and to add the cooking liquid separately to each cooking zone and extract the black liquor. Also in the infiltration process, the infiltration of the 2 vessel cooking apparatus In some cases, the cooking liquor is added to the middle stage of the vessel and added in two or more portions.

  The cooking liquor used in the present invention contains an alkaline metal hydroxide and refers to what is called white liquor or black liquor used in so-called pulp mills. In addition, those obtained by modifying some of these components may be used. Examples of the modified cooking liquor include polysulfide cooking liquor obtained by oxidizing white liquor.

The sulfidity of the total cooking solution used in the entire cooking system including the infiltration step and the cooking step is preferably 5 to 50%, and the active alkali addition rate is preferably 10 to 30% based on the weight of the absolutely dry lignocellulose material. . Here, the active alkali means a weight of sodium sulfide (Na ₂ S) and sodium hydroxide (NaOH) converted to sodium oxide (Na ₂ O) in so-called kraft cooking liquor. The degree of sulfidization refers to the content of sodium sulfide (all converted to Na ₂ O) with respect to the active alkali in the cooking liquor. In addition, about the modified cooking liquids, such as a polysulfide cooking liquid, the value of the cooking liquid before a modification | reformation is used.

  In this invention, a cooking liquid is added to at least 1 place for every process of an osmosis | permeation process and a cooking process. Usually, the above-mentioned cooking liquor is divided into a predetermined ratio and supplied and added for each step, but at that time, operations such as dilution, concentration or component adjustment may be performed as necessary.

  The lignocellulosic material used in the present invention is preferably a wood chip such as conifer or hardwood, but may be called non-wood such as bagasse or straw and is not particularly limited. Examples of wood types include Douglas fir, spruce, pine, and cedar as conifers, and beech, oak, eucalyptus, aspen, and hippo as hardwoods.

  In the present invention, the lignocellulosic material and the cooking liquor are supplied to and added to the infiltration step, and the cooking liquor is infiltrated into the lignocellulosic material. There are no particular restrictions on the method and order of supply and addition of the lignocellulosic material and cooking liquor to the infiltration step, and they may be supplied simultaneously to the infiltration step, or may be supplied and added separately. In the present invention, it is useful to contain a quinone compound in the cooking liquid at that time. There is no restriction | limiting in the method of making a quinone compound contain in a cooking liquid, Arbitrary methods, such as the method of mixing with a cooking liquid previously and supplying and adding to an osmosis | permeation process, the method of supplying and adding to an osmosis | permeation process separately, are employable.

  The active alkali in the cooking liquor for treating the lignocellulosic material in the infiltration step is preferably 1 to 10% by weight based on the weight of the absolutely dry lignocellulosic material. If it is less than 1% by weight, the alkali becomes insufficient, the function of the redox cycle of the quinone compounds is lowered, and as a result, the delignification efficiency is also lowered. If it exceeds 10% by weight, the redox cycle of the quinone compounds will not be different from the condition in which the cooking liquor is added all at once, and the function of the redox cycle of the quinone compounds will be reduced due to insufficient active alkali in the cooking process. Since delignification efficiency may also decrease, it is not preferable. 2 to 7% by weight is more preferable.

  In this invention, it is preferable that the processing temperature of what is called an osmosis | permeation process after a cooking start is 110 to 140 degreeC. Temperature conditions within this range are preferable because the penetration of the cooking liquor into the lignocellulosic material and the initial delignification reaction proceed gently. More preferably, it is 120-130 degreeC. When the temperature is 110 ° C. or lower, it is not preferable because the cooking liquor penetrates into the lignocellulosic material and the initial delignification reaction is difficult to proceed. If the temperature exceeds 140 ° C., the cooking reaction such as delignification reaction is activated and the alkali becomes insufficient, and the kappa number increases. The temperature may be constant or may be changed by gradually raising the temperature within this temperature range.

  In the present invention, the treatment time in the so-called infiltration step after the start of cooking is preferably 10 minutes or more. If it is less than 10 minutes, the cooking liquor hardly penetrates into the lignocellulose material, which is not preferable. The upper limit is limited by the structure of the kettle, the amount of lignocellulosic material supplied, and the like.

  In the present invention, the split ratio of the cooking liquor supplied to the permeation process and the cooking process, that is, the split ratio to each process of the total cooking liquid used for the lignocellulosic material cooking in the cooking system that combines the permeation process and the cooking process. Preferably supplies 5 to 50% of the total cooking liquor to the infiltration step, particularly preferably 10 to 45% of the total cooking liquor is supplied to the infiltration step. Specifically, it is determined by the liquid ratio and the active alkali addition rate in each step. For example, when the liquid ratio is 3 L / kg as a whole and the active alkali addition rate is in the range of 14 to 18% by weight, the infiltration step The cooking liquor for treating the lignocellulosic material is preferably 20-40% of the total cooking liquor.

  In the cooking method to which the method of the present invention is applied, the lignocellulosic material that has been subjected to the infiltration treatment of the cooking liquor in the infiltration step is continuously sent to the cooking step, and in the cooking step, the cooking reaction mainly consisting of delignification reaction by the cooking liquor. Progresses. As the cooking temperature in the cooking process, a temperature condition higher than the temperature in the infiltration process is generally selected, but it is not necessarily a constant temperature condition. That is, as the maximum temperature of the cooking temperature at which the lignocellulosic material is processed in the cooking step, a temperature that is preferably equal to or higher than the maximum temperature in the treatment of the infiltration step, more preferably a temperature higher than the maximum temperature in the processing of the infiltration step is selected. Specifically, the maximum temperature of the cooking step is selected from a temperature range of 120 to 180 ° C., preferably 140 to 170 ° C., but as the cooking step, the temperature is appropriately increased within these temperature ranges, The lignocellulosic material can be cooked under a temperature operation such as a temperature drop or under a constant temperature condition.

  In the present invention, the active alkali addition ratio of the cooking liquor used in the cooking step to the lignocellulosic material is preferably equal to or higher than the active alkali addition rate of the cooking liquor used in the infiltration step, and particularly preferably used in the infiltration step. Set higher than the active alkali addition rate of the cooking liquor. In this cooking process, it becomes the main delignification reaction field, so if it is lower than the active alkali addition rate of the cooking liquor used in the infiltration process, the alkali becomes insufficient and the redox cycle function of quinone compounds deteriorates. Since delignification efficiency also falls, it is not preferable. As a method of supplying the cooking liquid used in this cooking process to the cooking process, in addition to the method of adding to the first part of the cooking process, a method of dividing the cooking liquid and adding it to each part of the cooking process may be used. . The cooking liquor used in the cooking process may contain quinone compounds as in the permeation process. For other operations not specifically mentioned, the usual cooking operation is adopted. be able to.

  In the present invention, the volume ratio (liquid ratio) of the cooking liquid to the weight of the absolutely dry lignocellulosic material in the infiltration process at the initial stage of cooking is preferably 2 to 6 L / kg. More preferably, it is 2.5-4 L / kg. Here, the liquid ratio represents the amount of liquid per weight of the absolutely dry chip. If the liquid ratio is less than 2 L / kg, the cooking liquor does not sufficiently permeate the lignocellulosic material, which may reduce the effect. If the liquid ratio exceeds 6 L / kg, not only the penetration efficiency of the quinone compounds into the lignocellulosic material is lowered, but also the effect of reducing the amount of chemical solution used is lowered, which is not preferable. The liquid ratio does not need to be constant during the permeation process and the cooking process, and the liquid ratio may be changed by adding the cooking liquid and extracting the cooking waste liquid, but it is preferable to be within the above range as an average. .

  In the present invention, for the purpose of reducing the organic solid content in the cooking system in the infiltration process, it is preferable to perform an operation of extracting a part of the cooking liquid in the infiltration process out of the system as black liquor. Extraction of the cooking liquor in the infiltration process may be in the middle of the infiltration process or at the end of the infiltration process, but from the viewpoint of efficiency, extraction is preferably performed at the end of the infiltration process. It is good also as completion | finish of an infiltration process with extraction. On the other hand, when extracting the cooking liquid in the middle of the infiltration process, it is preferable to add the cooking liquid and continue the infiltration operation. The extraction amount of the cooking liquor in the infiltration process is 10% or more, preferably 50% or more with respect to the cooking liquid in the infiltration process, although it depends on the ratio of the cooking liquid and the timing of extraction. Unless otherwise specified, it is particularly preferable to extract the entire extractable cooking liquor. Specifically, for example, when the liquid ratio is 2.5 L / kg or less, 10% or more of the cooking liquid added to the infiltration step is preferable, and when the liquid ratio is 4 L / kg or more, 50% or more is preferable. If the extraction amount is small, a large amount of organic solids remain in the digester, and the organic solids react with the quinone compounds, reducing the effects of improving the yield and reducing the active alkali due to the quinone compounds. This is not preferable. The cooking waste liquid (black liquor) extracted during the infiltration process can be recycled as a part of the cooking liquid.

  In the present invention, the addition ratio of the quinone compounds used together with the cooking liquor in the infiltration step includes the quinone compounds in the cooking liquid so as to be 0.001 to 1.5% by weight per weight of the absolutely dry lignocellulose material. It is preferable to do so. More preferably, it is 0.01 to 0.5% by weight. If it is less than 0.001% by weight, the effect of adding quinone compounds cannot be sufficiently obtained, which is not preferable. On the other hand, if it exceeds 1.5% by weight, the effect of addition in proportion to the increased amount cannot be obtained, which is economically undesirable.

  The quinone compounds used in the present invention include not only quinone compounds but also compounds selected from hydroquinone compounds and their precursors, and known compounds can be used as cooking aids. For example, anthraquinone, dihydroanthraquinone (eg, 1,4-dihydroanthraquinone), tetrahydroanthraquinone (eg, 1,4,4a, 9a-tetrahydroanthraquinone, 1,2,3,4-tetrahydroanthraquinone), methylanthraquinone (eg, 1-methylanthraquinone, 2-methylanthraquinone), methyldihydroanthraquinone (eg, 2-methyl-1,4-dihydroanthraquinone), methyltetrahydroanthraquinone (eg, 1-methyl-1,4,4a, 9a-tetrahydroanthraquinone, Quinone compounds such as 2-methyl-1,4,4a, 9a-tetrahydroanthraquinone), anthrahydroquinone (generally 9,10-dihydroxyanthracene), methylanthrahydroquino (For example, 2-methylanthrahydroquinone), dihydroanthrahydroanthraquinone (for example, 1,4-dihydro-9,10-dihydroxyanthracene) or an alkali metal salt thereof (for example, disodium salt of anthrahydroquinone, 1,4- Dihydro-9,10-dihydroxyanthracene disodium salt) and the like, and precursors such as anthrone, anthranol, methylanthrone, and methylanthranol are listed.

  In the quinone compounds used in the present invention, it is important that the quinone compounds added to the permeation step are uniformly diffused in the alkali cooking liquid and permeate into the chip. Therefore, it is preferable to add as a liquid mixture containing the quinone compounds. For example, the above-mentioned quinone compounds such as tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene) alkaline aqueous solution, 9,10-anthraquinone hydroquinone alkaline aqueous solution, 9,10-anthraquinone, etc. The slurry liquid etc. are mentioned. The particle size of the quinone compounds in the liquid mixture is preferably 5 μm or less, and more preferably 1 μm or less on average in order to rapidly penetrate into the lignocellulose material and exhibit the effect. Furthermore, those existing in the form of a solution such as an alkali aqueous solution of tetrahydroanthraquinone or an alkaline aqueous solution of anthrahydroquinone are more preferable because they can penetrate more rapidly into the lignocellulose material.

  The effects of the quinone compounds in the present invention include not only the reduction of the kappa number and the increase of the pulp yield, but also the reduction of the amount of chemicals used, the increase of the pulp viscosity, the reduction of the cooking temperature and the like. These effects vary depending on the type of quinone compounds, the type of lignocellulose material, cooking conditions, etc., and are not indicated by absolute values, but the present invention has found conditions that can be improved relatively. .

In the present invention, it is preferable that the quinone compounds are allowed to act on the lignocellulosic material together with the cooking liquor in the infiltration step at the start of cooking, but the supply and addition methods are not particularly limited as described above. Of course, even if quinone compounds are added together with cooking liquor in the cooking process following the infiltration process, the effect will be manifested, but adding the entire amount of quinone compounds together with the cooking liquid in the infiltration process will infiltrate the lignocellulose material. Is preferable because it is performed quickly and sufficiently.
"Example"

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, it cannot be overemphasized that this invention is not limited to these Examples.
"Test equipment and operation overview"
The following examination was performed using a laboratory cooking experiment apparatus developed by our company. A flow chart of the apparatus is shown in FIG. Here, the outline of the apparatus and the operation will be described with reference to FIG. 1. A predetermined amount of lignocellulosic material and cooking liquor are charged into a digester (1) equipped with a heating device and a stirring device (not shown), and a circulation pump, etc. The cooking liquor was circulated through the cooking liquor circulation line (5) by the circulation device (4). After the permeation operation of the cooking liquor into the lignocellulosic material under predetermined conditions, the cooking liquor was drawn out to the cooking liquor (black liquor) receiver (3) through the cooking liquor (black liquor) draw line (7). Subsequently, the cooking liquor in the cooking liquor feeder (2) was fed into the cooking system through the cooking liquor supply line (6), and the lignocellulosic material was cooked. In addition, the operation of supplying and extracting the cooking liquor was performed by a pressure operation (a pressure adjusting system, a valve and the like are not shown).
"Test method"
The yield of the unbleached pulp obtained was determined by measuring the yield of the carefully selected pulp from which the koji was removed. The kappa number of unbleached pulp was determined according to TAPPI test method T236hm-85.
“Comparative Example 1”

Eucalyptus chips (hereinafter also simply referred to as chips) (83.6 g as an absolute dry weight) were used as the lignocellulose material. The composition of the alkali cooking solution is NaOH: Na ₂ S: Na ₂ CO ₃ = 103.7: 41.4: 32.7 (Na ₂ O conversion), and the active alkali addition rate is 16.5% by weight (contrast) It was adjusted to terms of Na ₂ O); dry chips. The first cooking liquid added at the start of cooking (corresponding to the cooking liquid in the infiltration process; the same applies hereinafter) and the second cooking liquid added during cooking (corresponding to the cooking liquid in the cooking process; the same applies hereinafter). In order to divide the cooking liquor split ratio into 10:90, the following preparation was performed.

The first cooking liquor is 10% by volume (active alkali addition rate is 1.7% by weight) of the prepared cooking solution with an active alkali addition rate of 16.5% by weight (vs. dry chip; converted to Na ₂ O). Equivalent) was taken out, and the water was brought into the tip and distilled water was added if necessary so that the liquid ratio was 2.7 L / kg with respect to the absolutely dry tip. The second cooking liquor has the remaining 90 vol% (active alkalinity equivalent to 14.8 wt%) and the water content brought into the chip so that the liquid ratio is 2.7 L / kg with respect to the absolutely dry chip. And distilled water as necessary.

The chips were put in a digester and heated to 100 ° C., and the first cooking solution heated to 100 ° C. in another container was added to the digester, and cooking was started. The temperature was raised from 100 ° C. at a rate of 1 ° C./min, and when the temperature reached 120 ° C., 100 cc of black liquor was extracted from the digester. Immediately after that, the second cooking liquor previously heated to 120 ° C. is added to the digester and the temperature rise is resumed at 1 ° C./min. The maximum temperature is maintained at 155 ° C., and thereafter the maximum temperature is maintained. However, cooking was performed until the H factor reached about 500. Table 1 shows the yield and kappa number of the unbleached pulp obtained.
“Comparative Example 2”

The experiment was performed in the same manner as in Comparative Example 1 except that the splitting ratio of the first cooking liquid and the second cooking liquid was set to 25:75 (the active alkali addition ratio of the first cooking liquid was 4.1 wt. %). The results are shown in Table 1.
“Comparative Example 3”

The experiment was performed in the same manner as in Comparative Example 1 except that the splitting ratio of the first cooking liquid and the second cooking liquid was 40:60 (the active alkali addition ratio of the first cooking liquid was 6.6 wt. %). The results are shown in Table 1.
“Comparative Example 4”

The experiment was performed in the same manner as in Comparative Example 1 except that the splitting ratio of the first cooking liquid and the second cooking liquid was 50:50 (the active alkali addition ratio of the first cooking liquid was 8.3 wt. %). The results are shown in Table 1.
“Comparative Example 5”

The experiment was performed in the same manner as in Comparative Example 1 except that the splitting ratio of the first cooking liquid and the second cooking liquid was set to 5:95 (the active alkali addition ratio of the first cooking liquid was 0.8 weight). %). The results are shown in Table 1.
“Comparative Example 6”

  The experiment was performed in the same manner as in Comparative Example 1 except that the splitting ratio of the first cooking liquid and the second cooking liquid was set to 70:30 (the active alkali addition ratio of the first cooking liquid was 11.6 wt. %). The results are shown in Table 1.

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 1 (the active alkali addition rate of the first cooking liquor was 1.7% by weight). The results are shown in Table 1.

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 2 (the active alkali addition rate of the first cooking liquor was 4.1% by weight). The results are shown in Table 1.

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 3 (the active alkali addition rate of the first cooking liquor was 6.6% by weight). The results are shown in Table 1.

As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 4 (the active alkali addition rate of the first cooking liquor was 8.3% by weight). The results are shown in Table 1.
“Comparative Example 7”

As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 5 (the active alkali addition rate of the first cooking liquor was 0.8% by weight). The results are shown in Table 1.
“Comparative Example 8”

As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 6 (the active alkali addition ratio of the first cooking liquor was 11.6% by weight). The results are shown in Table 1.
"Comparative Example 9"

Experiment was performed in the same manner as in Comparative Example 1 except that the time when the second cooking liquor was added was when the cooking temperature was 110 ° C., and the splitting ratio of the first cooking liquor and the second cooking liquor was set to 25:75. (The active alkali addition rate of the first cooking liquor was 4.1% by weight). The results are shown in Table 2.
"Comparative Example 10"

The experiment was performed in the same manner as in Comparative Example 9 except that the time when the second cooking liquid was added was set at a cooking temperature of 130 ° C. The results are shown in Table 2.
“Comparative Example 11”

The experiment was performed in the same manner as in Comparative Example 9 except that the time when the second cooking liquid was added was set at a cooking temperature of 140 ° C. The results are shown in Table 2.
“Comparative Example 12”

The experiment was performed in the same manner as in Comparative Example 9 except that the time when the second cooking liquid was added was set at a cooking temperature of 80 ° C. The results are shown in Table 2.
"Comparative Example 13"

  The experiment was performed in the same manner as in Comparative Example 9 except that the time when the second cooking liquid was added was set at a cooking temperature of 150 ° C. The results are shown in Table 2.

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 9. The results are shown in Table 2.

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 10. The results are shown in Table 2.

As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 11. The results are shown in Table 2.
“Comparative Example 14”

As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 12. The results are shown in Table 2.
"Comparative Example 15"

  As a quinone compound, except that tetrahydroanthraquinone (1,4-dihydro-9,10-dihydroxyanthracene disodium) is added only to the first cooking solution so as to be 0.05% by weight based on the absolutely dry chip. The experiment was conducted in the same manner as in Comparative Example 13. The results are shown in Table 2.

Summarizing the above results and comparing the effects of quinone compounds under the same cooking conditions, the active alkali addition rate of the first cooking liquor is in the range of 1 to 10% per Na dry lignocellulose material weight (Na ₂ O conversion), It is clear that the effect of the quinone compounds is improved when the initial conditions for treating the lignocellulosic material using the same are the conditions in which the temperature is 110 ° C. to 140 ° C.

  According to the present invention, in the alkali cooking method performed in the presence of quinone compounds, the effect of quinone compounds, that is, the pulp yield is further improved by pulping within a specific active alkali addition rate and temperature range. The relationship between the kappa number and the pulp yield can be further improved. That is, the effects of reducing the kappa number at the same active alkali addition rate and improving the pulp yield at the same kappa number are achieved.

It is a schematic diagram which shows the flow of the laboratory cooking experiment apparatus for obtaining the Example and comparative example of this invention.

Explanation of symbols

  1 .... digester kettle, 2 .... cooking liquor feeder, 3 .... cooking liquor (black liquor) receiver, 4 .... circulation device, 5 .... cooking liquor circulation line, 6 .... cooking liquor supply line, 7. -Cooking liquid (black liquor) extraction line

Claims (10)

  A method of cooking lignocellulosic material through a permeation step and a cooking step using a cooking solution containing an alkaline metal hydroxide, wherein the cooking liquor is added to at least one place for each step of the permeation step and the cooking step. In the solution, the cooking liquor for treating the lignocellulose material in the permeation step contains 1 to 10% by weight of active alkali with respect to the weight of the absolutely dry lignocellulose material, and 0% of the quinone compounds with respect to the weight of the absolutely dry lignocellulose material. A cooking method for lignocellulosic material, characterized by being a cooking solution containing 0.001 to 1.5% by weight.   The method for digesting a lignocellulosic material according to claim 1, wherein the treatment temperature of the lignocellulosic material in the infiltration step is in the range of 110 to 140 ° C.   The cooking method for lignocellulosic material according to claim 1, wherein the cooking liquor for treating the lignocellulosic material in the infiltration step is 5 to 50% of the total cooking liquor used for cooking the lignocellulose material.   The method for cooking lignocellulosic material according to claim 1, wherein the ratio of the cooking liquor for treating the lignocellulosic material in the infiltration step to the weight of the absolutely dry lignocellulosic material is 2 to 6 L / kg.   The method for cooking lignocellulosic material according to claim 1, wherein a part of the cooking liquid in the infiltration step is extracted as black liquor in the infiltration step.   6. The method for cooking lignocellulosic material according to claim 5, wherein the extraction temperature of black liquor in the infiltration step is in the range of 110 to 140 ° C.   6. The method of cooking lignocellulose material according to claim 5, wherein the extraction rate of black liquor in the infiltration step is 10% or more with respect to the cooking liquor used for the treatment of lignocellulose material in the infiltration step.   The maximum temperature of the cooking temperature at which the lignocellulosic material is processed in the cooking process following the infiltration process is a temperature equal to or higher than the maximum temperature in the processing of the infiltration process. Cooking method of lignocellulosic material.   The active alkali addition rate of the cooking liquid which processes a lignocellulose material in the cooking process following an osmosis | permeation process is more than the active alkali addition rate in an osmosis | permeation process, The any one of Claim 1 thru | or 7 characterized by the above-mentioned. Cooking method of lignocellulosic material. The method for cooking lignocellulosic materials according to any one of claims 1 to 9, wherein the quinone compounds are one or more compounds selected from quinone compounds, hydroquinone compounds and precursors thereof. .

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