JP2016211087A - Method for cleaning deposit generated in dissolving pulp production process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of cleaning deposits in a dissolving pulp production process.SOLUTION: Provided is a method for cleaning deposits in a dissolving pulp production process containing a step where at least either sodium hydroxide or potassium hydroxide of 5,000 to 150,000 mg/L or lower and a hydrogen peroxide feed compound of 3,000 to 50,000 mg/L or lower expressed in terms of hydrogen peroxide are added to a dissolving pulp production process water system, and the dissolving pulp production process water system is cleaned.SELECTED DRAWING: None

Description

  The present disclosure relates to a method for cleaning deposits generated in a dissolving pulp manufacturing process, and a method for manufacturing a dissolving pulp including a cleaning process using the cleaning method.

  In the production of paper and pulp as its raw material, sludge-like dirt caused by virgin pulp or filler adheres or accumulates on pipes and wall materials in the process water system, causing various problems. For this reason, various methods for cleaning the process water system have been proposed, for example, a method using various surfactants, a method using caustic soda, a method using organic phosphonic acid, etc. (for example, Patent Document 1).

  In addition, in the production of pulp, cooking using alkali is performed, and since a large amount of alkali and water are used for this cooking, the alkali is recovered from the cooking waste liquid discharged in the cooking process and reused. . In the alkali recovery process, concentration of cooking waste liquid (black liquor) using an evaporator or the like is performed. However, there is a problem that scales adhere to the black liquor concentrator and piping, block the piping, or reduce productivity. is there. For this reason, for example, it has been proposed to wash the scale using a polybasic aminocarboxylic acid compound under alkaline conditions (for example, Patent Document 2).

JP-A-3-244698 JP 2007-63696 A

  Pulp is classified into papermaking pulp (PP) that is made into paper and used as paper, and dissolved pulp (DP) that is used as a raw material such as rayon or cellophane, when classified according to use. Papermaking pulp is produced so as to actively leave hemicellulose from the viewpoint of improving the yield of pulp, and contains cellulose and hemicellulose. On the other hand, dissolved pulp is desired to have a high purity of cellulose, so that it is produced by chemical refining to remove hemicellulose as much as possible to increase the purity of cellulose. The purity of cellulose in the pulp is usually 90%. %.

  That is, papermaking pulp and dissolving pulp differ not only in use but also in the production method and composition in pulping. There was a problem that deposits generated in the dissolving pulp manufacturing process could not be sufficiently washed by the conventional washing method.

  Therefore, the present disclosure provides, in one or a plurality of embodiments, a method capable of cleaning deposits in a dissolving pulp manufacturing process.

  In one or a plurality of embodiments, the present disclosure is a method for cleaning deposits in a dissolving pulp manufacturing process, wherein at least one of sodium hydroxide and potassium hydroxide is 5000 mg / L to 150,000 mg / L, hydrogen peroxide The present invention relates to a washing method including washing a dissolving pulp production process water system by adding 3000 mg / L or more and 50000 mg / L or less of a supply compound in terms of hydrogen peroxide to the dissolving pulp production process water system.

  In one or a plurality of embodiments, the present disclosure relates to a dissolving pulp manufacturing method including a step of cleaning a dissolving pulp manufacturing process system by the above-described cleaning method.

  According to the present disclosure, in one or a plurality of embodiments, deposits generated in a dissolving pulp manufacturing process can be washed.

Drawing 1 is a schematic diagram for explaining an example of a pulping process in melted kraft pulp. FIG. 2 is a schematic diagram for explaining an example of a black liquor concentration (chemical recovery) step in the dissolving pulp manufacturing step. FIG. 3 is a schematic diagram for explaining the apparatus used in the cleaning effect confirmation test used in the examples.

  The present disclosure uses at least one of sodium hydroxide and potassium hydroxide of 5000 mg / L to 150,000 mg / L and a hydrogen peroxide supply compound of 3000 mg / L to 50000 mg / L (in terms of hydrogen peroxide). Based on the knowledge that deposits in the dissolving pulp manufacturing process can be efficiently washed.

Dissolved pulp consists of dissolved sulfite pulp (DSP) produced by the SP method (sulfite method), which is cooked using calcium hydrogen sulfite (acid cooking solution), and a mixed solution of sodium hydroxide and sodium sulfide (alkaline cooking solution). ) And dissolved kraft pulp (DKP) produced by the KP method (craft method). As shown in FIG. 1, in the production of dissolved kraft pulp, prehydrolysis (PHV) 2 using acid is performed between chipping (chip pin) 1 and cooking 4. Dissolved pulp manufacturing process water-based deposits contain sulfur and are mainly organic. On the other hand, the deposits (sludge) in the papermaking pulp manufacturing process water system are mainly composed of inorganic substances. That is, as shown in the following table, the composition of the deposit is greatly different between the dissolving pulp manufacturing process water system and the papermaking pulp manufacturing process water system. From the difference in the composition of such deposits, it has been thought that the deposits in the dissolving pulp manufacturing process cannot be sufficiently washed by the conventional cleaning method in the pulp manufacturing process. Although the mechanism is unclear, the present inventors use at least one of sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound in combination with the above-mentioned predetermined concentration to remove deposits in the dissolving pulp manufacturing process water system. They found that they could be cleaned.

  According to the present disclosure, in one or a plurality of embodiments, the deposits of the dissolving pulp production process water system can be efficiently washed. In one or a plurality of embodiments, the deposits in the dissolving pulp production process water system include deposits adhered to a heat transfer surface (distributor) or the like. In one or a plurality of embodiments, the dissolved pulp manufacturing process water system deposits include piping, pumps, wall materials, evaporators and washers disposed in the chemical recovery device (black liquor concentrating device) constituting the dissolving pulp manufacturing process water system. And deposits adhered or deposited on a screen or the like. Therefore, according to the present disclosure, in one or a plurality of embodiments, it adheres to the blow pump (3 in FIG. 1) disposed between the pre-hydrolysis kettle (PHV) and the digester in the dissolved kraft pulp manufacturing process water system. Alternatively, the deposited deposit can be cleaned. According to the present disclosure, in one or a plurality of embodiments, it is possible to clean the deposit attached or deposited on the evaporator of the black liquor concentration process system.

  The “dissolving pulp manufacturing process” in the present disclosure refers to a process for manufacturing a dissolving pulp, and preferably refers to a pulping process in manufacturing a dissolving pulp. In the present disclosure, the dissolving pulp is obtained by the KP method (craft method) using a dissolved sulfite pulp (DSP) produced by the SP method (sulfite method) and a mixed solution (alkaline cooking solution) of sodium hydroxide and sodium sulfide. And dissolved kraft pulp (DKP) to be produced.

  In one or a plurality of embodiments, the deposits to be cleaned include deposits containing an ignition loss of 50% by weight or more and a sulfur content of 1% by weight or more. In the present disclosure, “ignition (ignition) loss” refers to the mass of a substance that volatilizes when the deposit is ignited. The ignition loss (ignition) represents the amount of organic matter contained in the deposit in one or more embodiments. The ignition loss (ignition) can be calculated from the mass reduction rate (mass ratio before and after heating) by the ignition loss test. The ignition loss (ignition) can be determined according to JISK0102: 2013. Specifically, it can be determined by the method described in the examples. In one or a plurality of embodiments, the loss of ignition (ignition) of the deposit to be cleaned is 50% by weight or more, or 99% by weight or less.

  In one or a plurality of embodiments, the deposit to be cleaned contains 1% by weight or more of a sulfur content. In the present disclosure, the “sulfur content” refers to various sulfur, inorganic sulfur compounds, and organic sulfur compounds contained in the deposit. In one or a plurality of embodiments, the deposit to be cleaned contains 1% by weight or more of a sulfur content. In one or a plurality of embodiments, the deposit to be cleaned contains a sulfur content of 50% by weight or less. The content of sulfur can be obtained as an oxide by the bulk FP method by performing fluorescent X-ray analysis of the incinerated product and ash obtained by ignition (ignition) reduction. Specifically, it can be determined by the method described in the examples.

[Washing method of dissolving pulp manufacturing process water system]
In one or more embodiments of the present disclosure, at least one of sodium hydroxide and potassium hydroxide is 5000 mg / L or more and 150,000 mg / L or less, and the hydrogen peroxide supply compound is 3000 mg / L or more and 50000 mg / L in terms of hydrogen peroxide. The present invention relates to a method for cleaning deposits in a dissolving pulp manufacturing process (hereinafter, also referred to as “cleaning method of the present disclosure”) including adding L to the dissolving pulp manufacturing process water system to wash the dissolving pulp manufacturing process water system. Therefore, in one or a plurality of embodiments, the cleaning method of the present disclosure includes at least one of sodium hydroxide and potassium hydroxide of 5000 mg / L to 150,000 mg / L and 3000 mg / L to 50000 mg / L (hydrogen peroxide And a dissolving pulp manufacturing process water system is washed with the hydrogen peroxide supply compound of (converted).

  The cleaning method of the present disclosure includes adding at least one of sodium hydroxide and potassium hydroxide to 5000 mg / L or more and 150,000 mg / L or less to a dissolving pulp manufacturing process water system. From the viewpoint of washing efficiency, in one or a plurality of embodiments, at least one of sodium hydroxide and potassium hydroxide is added at 10,000 mg / L or more, 20000 mg / L or more, 30000 mg / L or more, or 40000 mg / L or more. Including. From the viewpoint of processing costs, in one or a plurality of embodiments, at least one of sodium hydroxide and potassium hydroxide is added at 130,000 mg / L or less, 100000 mg / L or less, 60000 mg / L or less, or 50000 mg / L or less. including. In the present disclosure, the concentration (mg / L) of sodium hydroxide and potassium hydroxide refers to a concentration converted as 100% NaOH or 100% KOH.

  The cleaning method of the present disclosure includes adding a hydrogen peroxide supply compound in an amount of 3000 mg / L or more and 50000 mg / L or less in terms of hydrogen peroxide to a dissolving pulp manufacturing process water system. In terms of cleaning efficiency, in one or more embodiments, the method includes adding a hydrogen peroxide supply compound of 3500 mg / L or more, 4000 mg / L or more, 5000 mg / L or more, or 8000 mg / L or more. Moreover, from the point of processing cost, in one or some embodiment, it includes adding 45000 mg / L or less, 40000 mg / L or less, 15000 mg / L or less, or 10000 mg / L or less in hydrogen peroxide supply compound. In the present disclosure, the concentration (mg / L) of the hydrogen peroxide supply compound refers to a concentration converted to 100% hydrogen peroxide.

  Examples of the hydrogen peroxide supply compound include hydrogen peroxide and a compound capable of generating or supplying hydrogen peroxide. Examples of the compound capable of generating or supplying hydrogen peroxide include, in one or a plurality of embodiments, an inorganic peracid or a salt thereof, an organic peracid or a salt thereof, or a hydrogen peroxide adduct. Examples of the inorganic peracid include perboric acid, percarbonate, and peroxysulfuric acid in one or more embodiments. Examples of the organic peracid include peracetic acid and the like in one or more embodiments. Examples of the hydrogen peroxide adduct include urea and the like in one or more embodiments.

  In the cleaning method of the present disclosure, the ratio (A: B (weight ratio)) of at least one of sodium hydroxide and potassium hydroxide (A) to the hydrogen peroxide supply compound (B) is one from the viewpoint of the cleaning effect. Or in embodiments, 1: 11-500: 3, or 1: 10-100: 3. Moreover, it is 20: 80-99: 1, 40: 60-98: 2, 45: 55-97: 3, 50: 50-97: 3 or 52: 48-95: 5 from the same point. In the present disclosure, the ratio (A: B (weight ratio)) of at least one of sodium hydroxide and potassium hydroxide (A) to the hydrogen peroxide supply compound (B) is sodium hydroxide, potassium hydroxide, and peroxide. Each hydrogen supply compound is defined as 100% sodium hydroxide, potassium hydroxide or hydrogen peroxide, and the weight ratio after conversion.

  In the cleaning method of the present disclosure, cleaning is performed at a pH of 11 or more in one or more embodiments. From the viewpoint of cleaning efficiency, the pH is 12 or more or 13 or more in one or more embodiments.

  In one or a plurality of embodiments, the cleaning method of the present disclosure can clean deposits on an evaporator in a black liquor concentration process system (chemical recovery process system). In one or a plurality of embodiments, the cleaning method of the present disclosure can clean deposits of a blow pump disposed between a pre-hydrolysis tank and a digester. However, the deposits to be cleaned in the present disclosure are not limited to these. Therefore, in one or a plurality of embodiments, the cleaning method of the present disclosure includes adding at least one of sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound to the black liquor concentration process system. In one or more embodiments of the cleaning method of the present disclosure, at least one of sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound are added between the prehydrolysis kettle and the blow pump. including.

  In one or more embodiments, the cleaning method of the present disclosure may include adding a cleaning agent component other than at least one of sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound. Other detergent components include, in one or more embodiments, 1-hydroxyethane-1,1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), hexamethylenediamineetra (methylenephosphonic acid), diethylenetriaminepenta (methylene Phosphonic acid), nitrilotrimethylphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, tetrasodium salt of ethylenediaminetetraacetic acid, and the like. The addition amount of the other cleaning components is 1000 mg / L or more or 2000 mg / L or more in one or more embodiments. The addition amount of the other cleaning components is 100000 mg / L or less or 50000 mg / L or less in one or more embodiments.

  In one or a plurality of embodiments, the cleaning method of the present disclosure is a dissolved pulp manufacturing process water system as long as it is an adhering substance that includes a loss of ignition (ignition) of 50% by weight or more and a sulfur content of 1% by weight or more. Deposits other than the deposits adhering to can be washed. Therefore, as another aspect, the present disclosure provides an adhering material containing 50% by weight or more of ignition (ignition) loss and 1% by weight or more of sulfur, and at least one of sodium hydroxide and potassium hydroxide. The present invention relates to a method for cleaning using a hydrogen peroxide supply compound of from 5000 mg / L to 150,000 mg / L and from 3000 mg / L to 50000 mg / L in terms of hydrogen peroxide.

[Method for producing dissolving pulp]
In one or a plurality of embodiments, the present disclosure relates to a dissolving pulp manufacturing method including a step of cleaning a dissolving pulp manufacturing process system by the cleaning method of the present disclosure (hereinafter referred to as “dissolving pulp manufacturing method of the present disclosure”). Say). The manufacturing method of the dissolving pulp of this indication includes the process pulped by SP method (sulfite method) in one or some embodiment. The manufacturing method of the dissolving pulp of this indication includes the process of pulping by KP method (craft method) in one or some embodiment.

  In one or a plurality of embodiments, the manufacturing method of the dissolving pulp of the present disclosure includes a black liquor concentration step, and the cleaning step includes washing the deposits of the evaporator in the black liquor concentration step system.

[Washing soap]
In one or a plurality of embodiments, the present disclosure relates to a dissolving pulp manufacturing process water-based cleaning agent comprising at least one of sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound. The hydrogen peroxide supply compound is as described above.

[Cleaning kit]
In one or a plurality of embodiments, the present disclosure provides a cleaning of a dissolving pulp manufacturing process water system including a container filled with at least one of sodium hydroxide and potassium hydroxide, and a container filled with a hydrogen peroxide supply compound. Relates to the kit. The hydrogen peroxide supply compound is as described above.

The present disclosure may relate to one or more of the following embodiments;
[1] A method for cleaning deposits in a dissolving pulp manufacturing process,
Add at least one of sodium hydroxide and potassium hydroxide to 5000 mg / L or more and 150,000 mg / L or less, and add a hydrogen peroxide supply compound in terms of hydrogen peroxide to 3000 mg / L or more and 50000 mg / L or less to the dissolving pulp manufacturing process water system And washing the dissolving pulp production process water system.
[2] The cleaning method according to [1], wherein the deposits to be cleaned include deposits containing 50% by weight or more of loss of ignition (ignition) and 1% by weight or more of sulfur.
[3] The cleaning method according to [1] or [2], comprising adding at least one of the sodium hydroxide and potassium hydroxide and the hydrogen peroxide supply compound to the black liquor concentration step system.
[4] The cleaning method according to any one of [1] to [3], wherein the deposit to be cleaned is a deposit on an evaporator in a black liquor concentration process system.
[5] The method according to [1] or [2], comprising adding at least one of the sodium hydroxide and potassium hydroxide and the hydrogen peroxide supply compound between a prehydrolysis kettle and a blow pump. Cleaning method.
[6] The cleaning method according to [1], [2] or [5], wherein the deposit to be cleaned is a blow pump deposit disposed between the pre-hydrolysis tank and the digester.
[7] The hydrogen peroxide supply compound is selected from the group consisting of hydrogen peroxide, peracetic acid, perboric acid, percarbonate, peroxysulfuric acid, urea, and combinations thereof, any of [1] to [6] A cleaning method according to claim 1.
[8] A method for producing dissolved pulp, comprising a step of washing a dissolving pulp producing process aqueous system by the washing method according to any one of [1] to [7].

  Hereinafter, this indication is further explained using an example and a comparative example. However, the present disclosure is not construed as being limited to the following examples.

In a 50 ml glass container, No. Each drug shown in 1 to 5 was added to prepare 40 g of a cleaning solution. Each of the prepared cleaning solutions had a pH of 11 or higher. The following drugs were used.
NaOH: 50% sodium hydroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.)
H ₂ O ₂ : 35% hydrogen peroxide solution (Wako Pure Chemical Industries, Ltd.)
HEDP: 95% 1-hydroxyethylidene-1,1-diphosphonic acid (manufactured by Wako Pure Chemical Industries, Ltd.)
EDTA4Na: ethylenediaminetetraacetic acid tetrasodium salt (dihydrate) (manufactured by Kishida Chemical Co., Ltd.)

The confirmation test of the cleaning effect was performed using the apparatus shown in FIG. 300 mg of the deposit 13 collected by the evaporator in the chemical recovery (black liquor concentration) process of a paper mill that produces dissolving pulp by the SP method is placed in a 20-mesh cylindrical wire mesh 12 placed in the glass container 11, After adding 40 g of the prepared cleaning solution, the processing solution 15 was stirred with a stirrer 14 at 60 ° C. for 4 hours. The deposit 1 or deposit 2 shown in Table 3 below was used as the deposit. The pH of the treatment liquid at the time of treatment (at the time of stirring) was 11 or more. After completion of the stirring, the cylindrical wire mesh containing the deposit was taken out, washed with running water for 2 hours, dried at 70 ° C. for 4 hours, and the weight of the deposit was measured. No. The same procedure was performed for 6-9 drugs. The results are shown in Table 4 below together with the concentration of each component during processing. The removal rate (%) was calculated using the following formula.
Removal rate (%) = (weight of untreated deposit (300 mg) −weight of deposit after treatment) / 300 mg × 100

[Weight loss (burning)]
The loss on ignition (ignition) was measured as follows. That is, according to JISK0102: 2013, the evaporation residue of the deposit obtained by drying with a drier at 105 ° C. for 2 hours was placed in a crucible and heated in an electric furnace at 800 ° C. for 1 hour to obtain ashing.
[Composition of deposits]
The composition of the deposit was measured as follows. That is, fluorescent X-ray analysis of the incinerated product and ash obtained by reducing the amount of ignition (ignition) was performed, and the composition was determined as an oxide by the bulk FP method.

  As shown in Table 4, according to Examples 1-7, the removal rate was very high compared with Comparative Examples 1-5. Moreover, in Examples 1-7, compared with Comparative Examples 1-5, the deposit | attachment after completion | finish of agitation collapse | crumbled. From these results, according to the cleaning method using the cleaning agents of Examples 1 to 7, it is considered that the deposit in the dissolving pulp manufacturing process such as the deposit 1 or 2 in the dissolving pulp manufacturing process water system can be removed.

Claims (8)

A method for cleaning deposits in a dissolving pulp manufacturing process,
Add at least one of sodium hydroxide and potassium hydroxide to 5000 mg / L or more and 150,000 mg / L or less, and add a hydrogen peroxide supply compound in terms of hydrogen peroxide to 3000 mg / L or more and 50000 mg / L or less to the dissolving pulp manufacturing process water system And washing the dissolving pulp production process water system.   2. The cleaning method according to claim 1, wherein the deposits to be cleaned include deposits containing an ignition loss of 50% by weight or more and a sulfur content of 1% by weight or more.   The washing | cleaning method of Claim 1 or 2 including adding at least one of the said sodium hydroxide and potassium hydroxide and a hydrogen peroxide supply compound to a black liquor concentration process system.   The cleaning method according to any one of claims 1 to 3, wherein the deposit to be cleaned is a deposit on an evaporator in a black liquor concentration process system.   The washing | cleaning method of Claim 1 or 2 including adding at least one of the said sodium hydroxide and potassium hydroxide, and a hydrogen peroxide supply compound between a prehydrolysis kettle and a blow pump.   The cleaning method according to claim 1, 2, or 5, wherein the deposit to be cleaned is a deposit from a blow pump disposed between the prehydrolysis kettle and the digester.   The cleaning according to any one of claims 1 to 6, wherein the hydrogen peroxide supply compound is selected from the group consisting of hydrogen peroxide, peracetic acid, perboric acid, percarbonate, peroxysulfuric acid, urea, and combinations thereof. Method.   The manufacturing method of dissolving pulp including the process of wash | cleaning a dissolving pulp manufacturing process aqueous system with the washing | cleaning method in any one of Claim 1 to 7.

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