KR20080089284A - Pulp cleaner, method for manufacturing pulp, and method for cleaning pulp - Google Patents

Abstract

A pulp cleaner, a method for preparing pulp, and a method for cleaning pulp by using the pulp cleaner are provided to improve the extracting efficiency of lignin from pulp. A pulp cleaner comprises a chelating compound; and a water-soluble polymer. Preferably the chelating compound is at least one selected from the group consisting of EDTA, DTPA, HEDTA, EDDS, TTHA, HEDP, NTMP and PBTC; and the water-soluble polymer is at least one selected from the group consisting of an acrylic polymer and a maleic acid-based polymer.

Description

Pulp cleaner, pulp manufacturing method, and pulp cleaning method {PULP CLEANER, METHOD FOR MANUFACTURING PULP, AND METHOD FOR CLEANING PULP}

The present invention relates to a pulp cleaner for cleaning pulp, a method for producing washed pulp, and a method for cleaning pulp.

The process for producing pulp includes a cooking step of cooking wood chips to obtain pulp, a washing step of separating the pulp and black liquor containing lignin and washing the separated pulp, and bleaching the washed pulp. It includes the bleaching step to do (for example, refer patent document 1). The bleached pulp thus produced is used for papermaking and the like.

Background Art Conventionally, in so-called delignification in which lignin is removed from a cooking liquid in a washing step, a technique of using oxygen is widely used in view of environmental protection. However, this technique has a problem in that, when heavy metals (for example, iron and manganese) are present in the cooking liquor, reactive oxygen species produced by the heavy metals promote pulp damage.

Then, the technique which adds a predetermined organic chelating agent to a cooking liquid in order to block a heavy metal is disclosed (refer patent document 2). According to this technique, pulp damage can be suppressed while delignification using oxygen is performed.

(Patent Document 1) Japanese Patent Publication No. 48-39763

(Patent Document 2) Japanese Patent Application Laid-Open No. 5-93385

However, the lignin may not be extracted sufficiently even by the technique shown in Patent Literature 2. Here, a technique of further adding an organic chelating agent after delignification is also proposed, but the degree of lignin extraction is still insufficient.

In order to improve the cleanliness of the pulp, it is conceivable to increase the amount of washing water used in the washing step. However, since the black liquor recovered with the increase of the amount of washing water is diluted, when black liquor is used as the sodium hydroxide source, enormous energy is required for the concentration of the black liquor (ie, removal of water by evaporation).

Moreover, when lignin extraction becomes inadequate, it is necessary to use a large amount of bleaching agent in order to reduce coloring by lignin, and it is unpreferable from a viewpoint of environmental protection.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a pulp cleaning agent, a pulp manufacturing method, and a pulp cleaning method which can sufficiently extract lignin from a pulp raw material.

The present inventors have found that the presence of calcium, an alkaline earth metal, is the main factor that inhibits lignin extraction, and have completed the present invention. Specifically, the present invention provides the following.

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

(2) The chelating compound is EDTA (ethylenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), HEDTA (hydroxyethylenediaminetetraacetic acid), EDDS (ethylenediaminesuccinic acid), TTHA (triethylenetetraamine The pulp cleaning agent according to (1), which is at least one member selected from the group consisting of hexaacetic acid), HEDP (hydroxyethane phosphonic acid), NTMP (nitrilotrismethylenephosphonic acid), and PBTC (phosphonobutane tricarboxylic acid).

(3) The pulp cleaning agent according to (1) or (2), wherein the water-soluble polymer is at least one member selected from the group consisting of acrylic acid polymers and maleic acid polymers.

(4) a pulp manufacturing method comprising a cooking step of cooking pulp by cooking a pulp material in a cooking part, a washing step of washing the pulp in a pulp cleaning system, and a bleaching step of bleaching the washed pulp in a bleaching part,

And a adding step of adding at least one selected from the group consisting of a chelating compound and a water-soluble polymer to the pulp cleaning system.

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

(6) The pulp production method according to (4) or (5), wherein the water-soluble polymer is at least one member selected from the group consisting of acrylic acid polymers and maleic acid polymers.

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

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

(9) The pulp production 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 of the site to be added is equal to or greater than the second predetermined value.

(10) A pulp cleaning method in which a pulp obtained by cooking a pulp material is washed in a pulp cleaning system.

And a adding step of adding at least one selected from the group consisting of a chelating compound and 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 equal to or less than the first predetermined value.

(12) The pulp cleaning 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 greater than the second predetermined value.

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

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not specifically limited to this.

<Pulp production system, pulp manufacturing method>

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 cooking washing system 20, a pulp washing unit 30, and a bleaching unit in order from the upstream.

The cooking washing system 20 is equipped with a cooking pot 21, and the cooking pot 21 is used to cook and preliminarily wash the pulp material. Specifically, in the cooking zone 211 of the cooking kiln 21, a solution containing wood chips, sodium hydroxide, etc., which are pulp materials, is mixed and pressurized to dissolve the non-fiber component in the wood chips, and the cooking kiln 21 It is preliminarily cleaned in the cleaning zone 212 of. The pulp slurry in which the black liquor in which the non-fiber component is dissolved and the pulp are mixed via the washing zone 212 is transferred to the next pulp washing unit 30 via a blow tank (not shown). The cooking section of the present invention consists of cooking zone 211, and the cooking step constituting the pulp making method of the present invention refers to operations upstream of the cleaning zone 212.

The pulp cleaning unit 30 separates and cleans pulp from the pulp slurry. Specifically, the pulp slurry transferred from the cooking kiln 21 is introduced into a diffusion washing apparatus 31, subjected to countercurrent washing, and then transferred to a knotter 32. After the undiluted matter remaining in the notifier 32 is removed, the cooking liquid is replaced and cleaned by the first pre-drum cleaning device 33 and the second pre-drum cleaning device 34. As a result, black liquor containing lignin is recovered. Sodium hydroxide may be separated and reused from the recovered black liquor.

Subsequently, the pulp after the black liquor removal is supplied with steam from the steam mixer 35 and warmed to a predetermined temperature, and then stored in a pre-storage tank (not shown). The pulp stored in the pre-tank is introduced into the oxygen reactor 36 after being supplied with oxygen, and further delignification is performed in the oxygen reactor 36. The pulp discharged from the oxygen reactor 36 is transferred to the blow tank 37 and introduced into the first post drum cleaning device 38 and the second post drum cleaning device 39. In these 1st post drum washing apparatus 38 and the 2nd post drum washing apparatus 39, pulp is further wash | cleaned and lignin etc. are removed. The pulp from the second post drum cleaning device 39 is stored in a post reservoir (not shown) and then transferred to the bleaching unit. The pulp cleaning system of the present invention is composed of a washing zone 212 and a pulp washing unit 30, and the washing step constituting the pulp manufacturing method of the present invention indicates the operation from the above washing zone 212 upstream of the bleaching unit. .

Subsequently, the pulp is bleached in the bleaching section, thereby producing a good pulp that is preferably used for papermaking. The bleaching part and the bleaching agent used are possible as long as it is well known. The above is an example of the bleaching step constituting the pulp production method of the present 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 lignin extraction is inhibited by the calcium. The concentration corresponds to 10 to 100 times the amount of heavy metals.

On the other hand, since the amount of chelating compounds required to block calcium is about 70 mg / L of EDTA to 10 mg / L of calcium, when the amount of calcium is about 20 mg / L, the amount of EDTA added is too large and not practical.

The pulp manufacturing method of the present invention solves the above problems by adding an addition step of adding the pulp cleaner of the present invention to the washing zone 212 and the pulp cleaner 30 in addition to the cooking step, the washing step, and the bleaching step. do. Therefore, the pulp cleaner used in the present invention will be described below. The pulp cleaning method of the present invention also includes an addition step in addition to the cleaning step.

<Pulp cleaner>

The pulp cleaner of the present invention contains an effective amount of a chelating compound and a water-soluble polymer. Here, an "effective amount" means the amount which affects lignin extraction, is set suitably according to the added condition, and 0 is included.

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 of the site to be added. Generally, since the upstream side of the washing | cleaning zone 212 and the pulp washing | cleaning part 30 has a higher calcium concentration than downstream, a chelate compound is applied in the upstream of the washing | cleaning zone 212 and the pulp washing | cleaning part 30. The addition amount ratio of the water-soluble polymer to the resin becomes large.

Specifically, the pulp cleaner of the present invention usually contains both a chelating compound and a water-soluble polymer when added in a liquid having a calcium concentration greater than 10 mg / L and less than 60 mg / L. On the other hand, when calcium concentration is 10 mg / L (an example of a 1st predetermined value) or less, it is preferable to contain only a chelating compound, and when calcium concentration is 60 mg / L (an example of a 2nd predetermined value) or more, a water-soluble polymer It is preferable to contain only. In addition, the calcium concentration is usually 80 to 150 mg / L in the cooking liquid introduced into the diffusion washing device 31, 40 to 80 mg / L in the liquid stored in the pre-treatment tank, and 5 to 5 in the liquid stored in the post-treatment tank. 40 mg / L. Since the calcium concentration described herein may vary depending on various conditions such as the temperature at the portion where the pulp cleaner is added, it may be appropriately set according to the conditions. In addition, although such adjustment may be performed manually, a concentration detecting means for detecting calcium concentration and a control means for controlling the addition amount ratio based on the detected value may be provided and may be automatically controlled by these means.

The addition amount of the pulp cleaner of the present invention is usually 0.1 to 1.5 kg / pulp t (" pulp " as used herein refers to dry pulp). The addition amount of this range is also practical in cost. In addition, the pulp cleaner may be added to one or a plurality of parts of the cleaning zone 212 and the pulp cleaner 30, and may be added to the same or different parts by components such as chelating compounds and water-soluble polymers. .

Chelating compounds refer to compounds having the action of complexing metals. Although it does not specifically limit as a chelating compound which can be used, For example, EDTA (ethylenediamine tetraacetic acid), DTPA (diethylenetriamine pentaacetic acid), HEDTA (hydroxyethylenediamine tetraacetic acid), EDDS (ethylenediamine succinic acid) ), TTHA (triethylenetetraamine hexaacetic acid), HEDP (hydroxyethane phosphonic acid), NTMP (nitrilotrismethylenephosphonic acid) and PBTC (phosphonobutane tricarboxylic acid) may be at least one selected from the group consisting of . That is, a chelating compound may be used individually by 1 type, and may be used together in multiple types.

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

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

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

(Example)

The pulp cleaning agent of each composition was used in the pulp manufacturing system 10 mentioned above. The composition, quantity, and addition part of the added pulp cleaner are as showing in Tables 1-5. The calcium concentration was 10 mg / L in the second post drum cleaner 39, 50 mg / L in the first post drum cleaner 38 and 80 mg / L in the second pre drum cleaning device 34. In addition, abbreviation notation in Tables 1-5 is as above-mentioned.

Six hours after the addition, the pulp was recovered at the outlets of the added washing units 34, 38 and 39. The recovered pulp was measured by kappa value (Kα) according to the method described in "JIS P 8211." The results are shown together in Tables 1 to 5. The kappa value is an index of the amount of lignin in the pulp, and the kappa value. The less this indicates, the more sufficient lignin is extracted.

※ AA: "Aquaric DL40S" (made by Nippon Shokubai Corporation)

※ AA: "Aquaric DL40S" (made by Nippon Shokubai Corporation)

※ AA: "Aquaric DL40S" (made by Nippon Shokubai Corporation)

※ Sulfonic acid system: "PolythiPSS1900" (made by Lion)

AA: "Aquaric DL40S" (made by Nippon Shokubai Co., Ltd.)

AA / HAPS: "Aquaric GL386" (made by Nippon Shokubai Corporation)

AA / MA: "Aquaric TL37" (made by Nippon Shokubai)

MA: "Bellcllen 200" (made by BWA)

As shown in Table 1, the addition amount (treatment density | concentration) of the pulp cleaning agent turned out that many can extract more lignin in the range below 1.5 kg / pulp t. In addition, at a calcium concentration of 10 mg / L, lignin extraction could be further improved by reducing the addition ratio of the water-soluble polymer to the chelating compound, and lignin extraction was most improved when only the chelating compound was added.

In addition, it was found that all the chelating compounds shown in Table 2 can improve lignin extraction. Accordingly, the pulp production method of the present invention can be used using various chelating compounds, suggesting that it is excellent in versatility.

As shown in Table 3, under the calcium concentration of 50 mg / L, lignin extraction is improved with either the chelating compound or the water-soluble polymer, but the lignin extraction can be further improved by using the chelating compound and the water-soluble polymer together. I could see that.

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

As shown in Table 5, it was found that any water-soluble polymer can improve lignin extraction. Accordingly, it has been suggested that the pulp production method of the present invention can be used using various water-soluble polymers, and has excellent versatility. In addition, it was also found that among the water-soluble polymers, acrylic acid polymers (Examples 26 to 29) can further improve lignin extraction.

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.

* Explanation of symbols for the main parts of the drawings

10: pulp manufacturing system

20: cooking washing system

211: cooking area

30: pulp cleaning part

36: oxygen reactor

Claims (12)

A pulp cleaner containing an effective amount of a chelating compound and a water-soluble polymer. The method of claim 1, The chelating compound is at least one pulp cleaner selected from the group consisting of EDTA, DTPA, HEDTA, EDDS, TTHA, HEDP, NTMP, and PBTC. The method of claim 1, The water-soluble polymer is at least one pulp cleaner selected from the group consisting of acrylic acid polymer and maleic acid polymer. In a pulp manufacturing method comprising a cooking step of cooking the pulp by cooking the pulp material in the cooking unit, a washing step of washing the pulp in a pulp cleaning system, and a bleaching step of bleaching the washed pulp in the bleaching unit, And a adding step of adding at least one selected from the group consisting of a chelating compound and a water-soluble polymer to the pulp cleaning system. The method of claim 4, wherein The chelating compound is at least one pulp production method selected from the group consisting of EDTA, DTPA, HEDTA, EDDS, TTHA, HEDP, NTMP and PBTC. The method of claim 4, wherein And the water-soluble polymer is at least one selected from the group consisting of acrylic acid polymers and maleic acid polymers. The method of claim 4, wherein The pulp manufacturing method which increases the addition amount ratio of the said water-soluble polymer with respect to the said chelating compound in accordance with the increase of the calcium concentration contained in the liquid of the site | part added. The method of claim 4, wherein The pulp manufacturing method 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 method of claim 4, wherein The pulp manufacturing method which adds only the said water-soluble polymer, when the calcium concentration contained in the liquid of the site | part added is more than a 2nd predetermined value. In the pulp washing method of washing the pulp obtained by cooking the pulp material in a pulp washing system, A pulp cleaning method comprising the step of adding one selected from the group consisting of a chelating compound and a water-soluble polymer to the pulp cleaning system. The method of claim 10, The pulp washing method which adds only the said chelating compound, when the calcium concentration contained in the liquid of the site | part added is below 1st predetermined value. The method of claim 10, The pulp washing method which adds only the said water-soluble polymer, when the calcium concentration contained in the liquid of the site | part added is more than a 2nd predetermined value.

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