JP2008248454A - Pulp washing agent, method for producing pulp, and method for washing pulp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pulp washing agent more sufficiently extracting lignin from a pulp raw material, to provide a method for producing pulp, and to provide a method for washing the pulp. <P>SOLUTION: The pulp washing agent contains effective amounts of a chelating compound and a water-soluble polymer. The lignin extraction is improved by adding the pulp washing agent to a washing zone 212 and a pulp washing part 30. Furthermore, the ratio of the amount of the added water-soluble polymer to the chelating compound is preferably increased as the pulp washing agent is added on the upstream side of the washing zone 212 and the pulp washing part 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pulp cleaning agent for cleaning pulp, a method for producing a cleaned pulp, and a method for cleaning a pulp.

  The pulp manufacturing process includes cooking procedures for cooking wood chips to obtain pulp, a cleaning procedure for separating the pulp and black liquor containing lignin, washing the separated pulp, and bleaching the washed pulp. Bleaching procedure (see, for example, Patent Document 1). The bleached pulp produced in this way is used for papermaking and the like.

  Conventionally, in so-called delignification, in which lignin is removed from cooking liquor by a washing procedure, a technique using oxygen is frequently used from the viewpoint of environmental protection. However, this technique has a problem that when heavy metals (for example, iron, manganese) are present in the cooking liquid, active oxygen species generated by the heavy metals promote damage to the pulp.

Then, the technique of adding a predetermined | prescribed organic chelating agent to cooking liquid in order to seal a heavy metal is disclosed (refer patent document 2). According to this technique, damage to pulp can be suppressed while delignification using oxygen is performed.
Japanese Patent Publication No. 48-39963 JP-A-5-93385

  However, even with the technique disclosed in Patent Document 2, lignin may not be sufficiently extracted. Here, a technique of adding an organic chelating agent after delignification has also been proposed, but the degree of lignin extraction is still insufficient.

  It is conceivable to increase the amount of washing water used in the washing procedure in order to improve the cleanliness of the pulp. However, since the black liquor recovered as the amount of washing water increases is diluted, when black liquor is used as a sodium hydroxide source, a large amount of energy is required for concentration of black liquor (ie, removal of water by evaporation). Cost.

  Moreover, when lignin extraction becomes insufficient, it is necessary to use a large amount of bleaching agent in order to reduce coloring by lignin, which is not preferable from the viewpoint of environmental protection.

  This invention is made | formed in view of the above situation, and it aims at providing the pulp washing | cleaning agent which can extract lignin more fully from a pulp raw material, a pulp manufacturing method, and a pulp washing method.

  The present inventor has found that the presence of calcium, an alkaline earth metal, is a major factor that inhibits lignin extraction, and has completed the present invention. Specifically, the present invention provides the following.

  (1) A pulp cleaning agent containing an effective amount of a chelating compound and a water-soluble polymer.

  (2) The chelating compound includes EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (hydroxyethylenediaminetetraacetic acid), EDDS (ethylenediaminesuccinic acid), TTHA (triethylenetetraaminehexaacetic acid), HEDP ( The pulp cleaner according to (1), which is at least one selected from the group consisting of hydroxyethanephosphonic acid), NTMP (nitrilotrismethylenephosphonic acid), and PBTC (phosphonobutanetricarboxylic acid).

  (3) The pulp cleaning agent according to (1) or (2), wherein the water-soluble polymer is an acrylic acid polymer and / or a maleic acid polymer.

(4) Pulp production having a cooking procedure in which pulp material is digested in the cooking section to obtain pulp, a washing procedure in which the pulp is washed in a pulp washing system, and a bleaching procedure in which the washed pulp is bleached in the bleaching section A method,
The pulp manufacturing method which further has the addition procedure which adds a chelating compound and / or a water-soluble polymer to the said pulp washing system.

  (5) The chelating compound includes EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (hydroxyethylenediaminetetraacetic acid), EDDS (ethylenediaminesuccinic acid), TTHA (triethylenetetraaminehexaacetic acid), HEDP ( The pulp production method according to (4), which is at least one selected from the group consisting of hydroxyethanephosphonic acid), NTMP (nitrilotrismethylenephosphonic acid), and PBTC (phosphonobutanetricarboxylic acid).

  (6) The pulp manufacturing method according to (4) or (5), wherein the water-soluble polymer is an acrylic acid polymer and / or a maleic acid polymer.

  (7) The pulp manufacturing method according to any one of (4) to (6), wherein the ratio of the water-soluble polymer to the chelating compound is increased according to an increase in the concentration of calcium contained in the liquid at the site to be added. .

  (8) The pulp manufacturing method according to any one of (4) to (7), wherein only the chelating compound is added when the calcium concentration contained in the liquid at the site to be added is equal to or less than the first predetermined value.

  (9) The pulp manufacturing method according to any one of (4) to (7), wherein only the water-soluble polymer is added when the calcium concentration contained in the liquid at the site to be added is equal to or higher than a second predetermined value.

(10) A pulp cleaning method for cleaning pulp obtained by digesting pulp material in a pulp cleaning system,
A pulp cleaning method comprising an addition procedure of adding a chelating compound and / or a water-soluble polymer to the pulp cleaning system.

  (11) The pulp cleaning method according to (10), wherein only the chelating compound is added when the calcium concentration contained in the liquid at the site to be added is not more than a first predetermined value.

  (12) The pulp washing method according to (10), wherein only the water-soluble polymer is added when the calcium concentration contained in the liquid at the site to be added is equal to or higher than the second predetermined value.

  According to the present invention, since an effective amount of the chelating compound and / or water-soluble polymer is added, the degree of lignin extraction is synergistically improved, and lignin can be extracted more sufficiently from the pulp raw material.

  Hereinafter, although embodiment of this invention is described, this invention is not specifically limited to this.

<Pulp manufacturing system and pulp manufacturing method>
FIG. 1 is a block diagram showing an example of a pulp production system to which a cleaning agent according to the present invention is applied. The pulp manufacturing system 10 includes a digestion cleaning system 20, a pulp cleaning unit 30, and a bleaching unit in order from the upstream.

  The digester cleaning system 20 has a digester 21 in which the pulp material is digested and preliminarily cleaned. Specifically, in the cooking zone 211 of the digester 21, the non-fiber components in the wood chips are dissolved by mixing wood chips that are pulp materials and a solution containing sodium hydroxide or the like, and steaming under pressure. Then, preliminary cleaning is performed in the cleaning zone 212 of the digester 21. The pulp slurry obtained through the washing zone 212 and mixed with the black liquor in which the non-fiber components are dissolved and the pulp is transferred to the next pulp washing unit 30 through a blow tank (not shown). The cooking section of the present invention is constituted by the cooking zone 211, and the cooking procedure constituting the pulp manufacturing method of the present invention refers to the work up to the upstream of the washing zone 212.

  The pulp cleaning unit 30 separates and cleans the pulp from the pulp slurry. Specifically, the pulp slurry transferred from the digester 21 is introduced into the diffusion cleaning device 31, subjected to countercurrent cleaning, and then transferred to the knotter 32. The cooking liquor is subjected to replacement washing in the first pre-drum washing device 33 and the second pre-drum washing device 34 after the undistilled material remaining in the knotter 32 is removed. Thereby, the black liquor containing lignin is collect | recovered. Sodium hydroxide may be separated from the recovered black liquor and reused.

  Subsequently, the pulp after the black liquor is removed is heated to a predetermined temperature by being supplied with steam by the steam mixer 35 and then stored in a front storage tank (not shown). The pulp stored in the pre-storage tank is supplied with oxygen and then introduced into the oxygen reactor 36 where further delignification is performed. The pulp discharged from the oxygen reactor 36 is transferred to a blow tank 37 and introduced into a first rear drum cleaning device 38 and a second rear drum cleaning device 39. In the first post-drum cleaning device 38 and the second post-drum cleaning device 39, the pulp is further cleaned and lignin and the like are removed. Pulp from the second post-drum cleaning device 39 is stored in a post-storage tank (not shown) and then transferred to the bleaching section. The pulp washing system of the present invention is constituted by the washing zone 212 and the pulp washing unit 30, and the washing procedure constituting the pulp manufacturing method of the present invention refers to the operation from the washing zone 212 to the upstream of the bleaching unit.

  Subsequently, the pulp is bleached in the bleaching section to produce a high-quality pulp that is preferably used for papermaking. A bleaching part and the bleaching agent used may be a conventionally well-known thing. The above is an example of the bleaching procedure which comprises the pulp manufacturing method of this invention.

  As described above, a large amount of calcium is present in the liquid flowing through the washing zone 212 and the pulp washing unit 30, and the lignin extraction is inhibited by this calcium. The concentration corresponds to 10 to 100 times the amount of heavy metal.

  On the other hand, the amount of chelate compound necessary to seal calcium is about 70 mg / L EDTA with respect to 10 mg / L calcium. Therefore, when the amount of calcium is about 20 mg / L, the amount of EDTA added becomes extremely large. Is not practical.

  The pulp production method of the present invention has the above-mentioned problems by further including an addition procedure for adding the pulp cleaning agent of the present invention to the washing zone 212 and the pulp washing section 30 in addition to the cooking procedure, the washing procedure, and the bleaching procedure. Resolve. Then, the pulp cleaning agent used by this invention is demonstrated below. Moreover, the pulp washing | cleaning method of this invention has an addition procedure in addition to a washing procedure.

<Pulp cleaning agent>
The pulp cleaning agent of the present invention contains an effective amount of a chelating compound and a water-soluble polymer. Here, the “effective amount” means an amount that affects lignin extraction, and is appropriately set according to the conditions to be added, including zero.

  Specifically, it is preferable to increase the addition amount ratio of the water-soluble polymer to the chelating compound in accordance with the increase in the calcium concentration contained in the liquid at the site to be added. In general, the upstream of the washing zone 212 and the pulp washing section 30 has a higher calcium concentration than the downstream, and therefore the amount of the water-soluble polymer added to the chelating compound as it is applied upstream of the washing zone 212 and the pulp washing section 30. The ratio increases.

  Specifically, the pulp detergent of the present invention usually contains both a chelating compound and a water-soluble polymer when added to a liquid having a calcium concentration in the range of more than 10 mg / L and less than 60 mg / L. It is preferable. On the other hand, when the calcium concentration is 10 mg / L (an example of the first predetermined value) or less, it is preferably only a chelating compound, and when the calcium concentration is 60 mg / L (an example of the second predetermined value) or more, it is water-soluble. It is preferable that it is only a polymer. Normally, the calcium concentration is 80 to 150 mg / L in the cooking liquid introduced into the diffusion cleaning device 31, and 40 to 80 mg / L in the liquid stored in the front storage tank, and stored in the rear storage tank. 5 to 40 mg / L in the liquid to be prepared. The calcium concentration described here may vary depending on various conditions such as the temperature in the portion to which the pulp detergent is added, and may be appropriately set according to the conditions. Further, such adjustment may be performed manually, but is provided with a concentration detection means for detecting the calcium concentration and a control means for controlling the addition amount ratio based on the detection value, and these means automatically It may be controlled.

  The addition amount of the pulp cleaning agent of the present invention is usually 0.1 to 1.5 kg / pulp t (here, “pulp” refers to dry pulp). The addition amount in this range is practical in terms of cost. In addition, the pulp cleaning agent may be added to one or a plurality of locations of the cleaning zone 212 and the pulp cleaning unit 30, or may be added to the same location or a separate location for each component such as a chelating compound and a water-soluble polymer. .

  A chelating compound refers to a compound having an effect of complexing a metal. Although it does not specifically limit as a chelating compound which can be used, For example, EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (hydroxyethylenediaminetetraacetic acid), EDDS (ethylenediaminesuccinic acid), TTHA (triethylenetetraamine) It may be at least one selected from the group consisting of hexaacetic acid), HEDP (hydroxyethanephosphonic acid), NTMP (nitrilotrismethylenephosphonic acid), and PBTC (phosphonobutanetricarboxylic acid). That is, the chelating compound may be used alone or in combination of two or more.

  Although it does not specifically limit as a water-soluble polymer, For example, an acrylic acid type polymer and a maleic acid type polymer can be used. In addition, a water-soluble polymer may be used individually by 1 type, and may be used together with multiple types. However, the monomer ratio of acrylic acid and / or maleic acid is preferably 30% or more.

  Examples of the acrylic polymer include polyacrylic acid (AA), a copolymer of acrylic acid and 2-hydroxy-3-allyloxy-1-propanesulfonic acid (AA / HAPS), and a copolymer of acrylic acid and methyl acrylate. Examples thereof include one or more of a polymer (AA / MA), a copolymer of methyl acrylate and isobutylene (MA / IB), and a copolymer of methyl acrylate, acrylic acid, and vinyl acetate.

  As the maleic acid polymer, various conventionally known polymers can be used.

  In the pulp production system 10 described above, pulp cleaning agents having various compositions were used. Tables 1 to 5 show the composition and amount of the added pulp cleaning agent and the added part. The calcium concentration was 10 mg / L in the second rear drum cleaning device 39, 50 mg / L in the first rear drum cleaning device 38, and 80 mg / L in the second front drum cleaning device 34. The abbreviations in Tables 1 to 5 are as described above.

  Six hours after the addition, the pulp was recovered at the outlet of each of the added cleaning devices 34, 38, 39. The recovered pulp was measured for kappa number (Kα) according to the method described in “JIS P 8211”. The results are also shown in Tables 1-5. The kappa number is an indicator of the amount of lignin in the pulp, and the smaller the kappa number, the more extracted the lignin.

※ＡＡ：「アクアリックＤＬ４０Ｓ」（日本触媒社製）

* AA: “Aquaric DL40S” (manufactured by Nippon Shokubai Co., Ltd.)

※ＡＡ：「アクアリックＤＬ４０Ｓ」（日本触媒社製）

* AA: “Aquaric DL40S” (manufactured by Nippon Shokubai Co., Ltd.)

※ＡＡ：「アクアリックＤＬ４０Ｓ」（日本触媒社製）

* AA: “Aquaric DL40S” (manufactured by Nippon Shokubai Co., Ltd.)

※スルホン酸系：「ポリティＰＳ１９００」（ライオン社製）
ＡＡ：「アクアリックＤＬ４０Ｓ」（日本触媒社製）
ＡＡ／ＨＡＰＳ：「アクアリックＧＬ３８６」（日本触媒社製）
ＡＡ／ＭＡ：「アクアリックＴＬ３７」（日本触媒社製）
ＭＡ：「ベルクレン２００」（ＢＷＡ社製）

* Sulphonic acid series: “POLITY PS1900” (manufactured by Lion)
AA: “Aquaric DL40S” (manufactured by Nippon Shokubai Co., Ltd.)
AA / HAPS: “AQUALIC GL386” (manufactured by Nippon Shokubai Co., Ltd.)
AA / MA: “AQUALIC TL37” (manufactured by Nippon Shokubai Co., Ltd.)
MA: “Berglen 200” (manufactured by BWA)

  As shown in Table 1, it was found that the amount of pulp detergent added (treatment concentration) can be extracted more when the amount is higher than 1.5 kg / pulp t. Moreover, under the condition of a calcium concentration of 10 mg / L, lignin extraction can be further improved by reducing the ratio of the amount of the water-soluble polymer added to the chelating compound, and the lignin extraction can be most improved when only the chelating compound is added. It was.

  Moreover, it turned out that all the chelating compounds shown in Table 2 can improve lignin extraction. Thereby, it was suggested that the pulp manufacturing method of this invention can be used using various chelating compounds, and is excellent in versatility.

  As shown in Table 3, under the condition of a calcium concentration of 50 mg / L, lignin extraction is improved by either the chelating compound or the water-soluble polymer, but by using the chelating compound and the water-soluble polymer in combination, It was found that lignin extraction can be improved further.

  As shown in Table 4, under the condition of a calcium concentration of 80 mg / L, the lignin extraction can be further improved by increasing the ratio of the addition amount of the water-soluble polymer to the chelating compound, and when only the water-soluble polymer is added. The lignin extraction could be improved most.

  As shown in Table 5, it was found that any water-soluble polymer can improve lignin extraction. Thereby, it was suggested that the pulp manufacturing method of this invention can be used using various water-soluble polymers, and is excellent in versatility. Moreover, it turned out that an acrylic acid type polymer (Examples 26-29) can further improve lignin extraction among water-soluble polymers.

It is a block diagram which shows an example of the pulp manufacturing system with which the cleaning agent which concerns on this invention is applied.

Explanation of symbols

10 Pulp production system 20 Cooking cleaning system 211 Cooking zone (cooking part)
30 Pulp washing section 36 Oxygen reactor

Claims (12)

  A pulp cleaning agent containing an effective amount of a chelating compound and a water-soluble polymer.   The pulp cleaning agent according to claim 1, wherein the chelating compound is at least one selected from the group consisting of EDTA, DTPA, HEDTA, EDDS, TTHA, HEDP, NTMP, and PBTC.   The pulp cleaning agent according to claim 1 or 2, wherein the water-soluble polymer is an acrylic acid polymer and / or a maleic acid polymer. A pulp production method comprising: a cooking procedure for cooking pulp material in a cooking section to obtain pulp; a washing procedure for washing the pulp in a pulp washing system; and a bleaching procedure for bleaching the washed pulp in a bleaching section. And
The pulp manufacturing method which further has the addition procedure which adds a chelating compound and / or a water-soluble polymer to the said pulp washing system.   The pulp manufacturing method according to claim 4, wherein the chelating compound is at least one selected from the group consisting of EDTA, DTPA, HEDTA, EDDS, TTHA, HEDP, NTMP, and PBTC.   The pulp manufacturing method according to claim 4 or 5, wherein the water-soluble polymer is an acrylic acid polymer and / or a maleic acid polymer.   The pulp manufacturing method according to any one of claims 4 to 6, wherein an addition ratio of the water-soluble polymer to the chelating compound is increased in accordance with an increase in a calcium concentration contained in a liquid at a site to be added.   The pulp manufacturing method according to any one of claims 4 to 7, wherein only the chelating compound is added when the calcium concentration contained in the liquid of the part to be added is not more than a first predetermined value.   The pulp manufacturing method according to any one of claims 4 to 7, wherein only the water-soluble polymer is added when the calcium concentration contained in the liquid at the site to be added is equal to or higher than a second predetermined value. A pulp washing method for washing pulp obtained by digesting pulp material in a pulp washing system,
A pulp cleaning method comprising an addition procedure of adding a chelating compound and / or a water-soluble polymer to the pulp cleaning system.   The pulp washing | cleaning method of Claim 10 which adds only the said chelating compound when the calcium concentration contained in the liquid of the site | part added is below a 1st predetermined value. The pulp washing | cleaning method of Claim 10 which adds only the said water-soluble polymer, when the calcium concentration contained in the liquid of the site | part added is 2nd predetermined value or more.

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