CN112127193A - Production process for improving quality index of dissolving pulp by using bleaching process - Google Patents
Production process for improving quality index of dissolving pulp by using bleaching process Download PDFInfo
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- CN112127193A CN112127193A CN202011020653.8A CN202011020653A CN112127193A CN 112127193 A CN112127193 A CN 112127193A CN 202011020653 A CN202011020653 A CN 202011020653A CN 112127193 A CN112127193 A CN 112127193A
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- 238000004061 bleaching Methods 0.000 title claims abstract description 92
- 229920000875 Dissolving pulp Polymers 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 57
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 33
- OSVXSBDYLRYLIG-UHFFFAOYSA-N dioxidochlorine(.) Chemical compound O=Cl=O OSVXSBDYLRYLIG-UHFFFAOYSA-N 0.000 claims abstract description 56
- 239000004155 Chlorine dioxide Substances 0.000 claims abstract description 28
- 235000019398 chlorine dioxide Nutrition 0.000 claims abstract description 28
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000003513 alkali Substances 0.000 claims abstract description 18
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 claims abstract description 12
- 238000010306 acid treatment Methods 0.000 claims abstract description 11
- 239000002738 chelating agent Substances 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims description 28
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 20
- 239000002002 slurry Substances 0.000 claims description 15
- 239000001301 oxygen Substances 0.000 claims description 12
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- 238000003756 stirring Methods 0.000 claims description 12
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 11
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 239000007788 liquid Substances 0.000 claims description 9
- 239000007844 bleaching agent Substances 0.000 claims description 8
- 239000007864 aqueous solution Substances 0.000 claims description 7
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 3
- 239000000243 solution Substances 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims 1
- 239000002253 acid Substances 0.000 abstract description 8
- 229910021645 metal ion Inorganic materials 0.000 abstract description 8
- 239000012535 impurity Substances 0.000 abstract description 6
- 230000009257 reactivity Effects 0.000 abstract description 6
- 229920000433 Lyocell Polymers 0.000 abstract description 5
- 230000000694 effects Effects 0.000 abstract description 4
- 150000002500 ions Chemical class 0.000 abstract description 2
- 238000000746 purification Methods 0.000 abstract description 2
- 229920002678 cellulose Polymers 0.000 description 15
- 229920005610 lignin Polymers 0.000 description 15
- 239000001913 cellulose Substances 0.000 description 14
- 229920000297 Rayon Polymers 0.000 description 9
- 238000006116 polymerization reaction Methods 0.000 description 9
- 229920002488 Hemicellulose Polymers 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 239000000047 product Substances 0.000 description 5
- 235000008577 Pinus radiata Nutrition 0.000 description 4
- 241000218621 Pinus radiata Species 0.000 description 4
- 239000000835 fiber Substances 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- 229920001131 Pulp (paper) Polymers 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000010411 cooking Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- WQYVRQLZKVEZGA-UHFFFAOYSA-N hypochlorite Chemical compound Cl[O-] WQYVRQLZKVEZGA-UHFFFAOYSA-N 0.000 description 2
- 239000004627 regenerated cellulose Substances 0.000 description 2
- BDHFUVZGWQCTTF-UHFFFAOYSA-M sulfonate Chemical compound [O-]S(=O)=O BDHFUVZGWQCTTF-UHFFFAOYSA-M 0.000 description 2
- 101100410783 Arabidopsis thaliana PXG2 gene Proteins 0.000 description 1
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 description 1
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 229920003086 cellulose ether Polymers 0.000 description 1
- 238000001311 chemical methods and process Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000007380 fibre production Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 238000009897 hydrogen peroxide bleaching Methods 0.000 description 1
- -1 iron ion Chemical class 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008832 photodamage Effects 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 229910021655 trace metal ion Inorganic materials 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000004383 yellowing Methods 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/16—Bleaching ; Apparatus therefor with per compounds
- D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/147—Bleaching ; Apparatus therefor with oxygen or its allotropic modifications
Landscapes
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
Abstract
The invention discloses a production process for improving quality index of dissolving pulp by using a bleaching process, and a bleaching process D thereof0‑Eop‑D1‑AQThe method specifically comprises the following steps: (1) d0Bleaching with chlorine dioxide; (2) an Eop alkali treatment purification section; (3) d1Bleaching with chlorine dioxide; (4) stage A was acid treated and the chelating agent EDTA-2Na was added. The improved four-stage bleaching process is simple and smooth, the acid treatment A and the chelating agent adopt the easily available dilute sulfuric acid and EDTA-2Na, the effect of deeply removing ash and metal ion impurities is obvious, the quality of the dissolving pulp product is stable, and the dissolving pulp product meets the industrial standard. The invention can further reduce ash impurities, particularly F in the common-grade dissolving pulpe 3+The content of ions improves the quality of the dissolving pulp, and further improves the dissolvingThe reactivity of the pulp creates a precondition for producing tencel-level dissolving pulp.
Description
Technical Field
The invention relates to the technical field of pulping and papermaking, in particular to a production process for improving quality indexes of dissolving pulp by using a bleaching process.
Background
Dissolving pulp is derived cellulose prepared by a prehydrolysis-sulfate process (PHK process) or an acid sulfite process, belongs to the field of refined pulp, is mainly used for producing viscose fibers, cellulose ester, cellulose ether and other products, wherein the most used dissolving pulp is used for producing viscose fibers, and part of high-grade dissolving pulp is used for producing tencel Lyocell and the like.
Dissolving pulp requires low content of hemicellulose, ash and lignin, and the degree of polymerization is also specified.
In the preparation process of dissolving pulp, the main purpose of bleaching is 3, one is to improve whiteness, which is the most main purpose, the dissolving pulp has higher requirement on whiteness, and the whiteness of the dissolving pulp for viscose is generally required to be more than 80% ISO; the second purpose is to adjust the degree of polymerization, and the degree of polymerization of common viscose fibers is required to be 500 +/-20; the third purpose is to remove ash, which has a great influence on the reactivity of the dissolving pulp and is therefore removed as much as possible during the preparation process.
Bleaching is a process for further removing lignin and other impurities, and dissolving pulp is high-purity and high-whiteness pulp. Different from the pulp for common papermaking, the degree of polymerization, viscosity and reactivity of the dissolving pulp can be adjusted by different bleaching methods and process conditions while improving the purity and whiteness of the pulp in the bleaching process, so that the bleaching becomes a very important process in the production of the dissolving pulp. With the development of bleaching technology, new high-efficiency and low-pollution bleaching processes have been widely applied to dissolving pulp production. At present, oxygen delignification (O), chlorine dioxide bleaching (D), hypochlorite (H), hydrogen peroxide bleaching (P), and the like are commonly used as bleaching methods. The purposes of oxygen delignification are to remove lignin, reduce kappa number, control and adjust the viscosity of the pulp and the polymerization degree of cellulose, and create conditions for subsequent bleaching.
Chlorine dioxide (D) is an excellent bleaching agent, can selectively oxidize and degrade lignin to remove the lignin and improve whiteness, has light damage to cellulose, and becomes an important bleaching means in dissolving pulp production, and two-stage or three-stage bleaching is generally adopted. Studies have shown that CLO2 not only reduces the resin content, but more importantly improves the reactivity, viscosity and filtration properties of the dissolving pulp.
Hydrogen peroxide (P) bleaching is commonly used in the end stage to supplement bleaching and also to prevent yellowing of the pulp to stabilize pulp brightness.
The acid treatment (A) can not only improve and stabilize the whiteness of the bleached pulp, but also reduce the ash content and the metal ion content in the pulp. Ash and metal ions in the dissolving pulp have a negative influence on the production of regenerated cellulose or cellulose derivatives. If ash exists in dissolving pulp in viscose fiber production, the aging time and filtration are affected by SiO2 in the ash, the viscosity of viscose is increased, the dissolving capacity of cellulose sulfonate in alkali liquor is reduced, and the content of the cellulose sulfonate is controlled to be below 0.60 percent as much as possible; the presence of metal ions increases the viscosity of the viscose and can form insoluble salts (such as CaSO4, MgSO4) with acids, thereby reducing the transparency of the acid bath or clogging the spinneret; fe3+And the metal impurities can accelerate the degradation of the alkali cellulose, so that the process is unstable, and the strength and the color of the viscose fiber are influenced finally.
The dissolving pulp is easy to bleach to high whiteness, and 1-2 bleaching stages are required to be selected and allocated in the bleaching process to adjust the viscosity, so that the final polymerization degree is uniformly distributed as much as possible. The method is different from the method that ordinary chemical pulp always pursues high viscosity, and D0-E-D1-P, O-D-E-P, O-D0-E-D1-P, O-A-Zq-P and the like can be selected for common bleaching. Optimizing the production process of dissolving pulp is one of the important methods for improving the reaction performance of dissolving pulp. In order to avoid excessive damage to the cellulose during bleaching, the amount of bleaching agent, temperature, pH, etc. must be carefully controlled.
The dissolving pulp is essentially natural cellulose, and has high cellulose content, very low content of impurities such as hemicellulose, ash and the like, proper viscosity, uniform relative molecular mass distribution and good reaction performance. These properties have a significant impact on the production process of regenerated cellulose and cellulose derivatives and the quality of downstream products. Therefore, the production needs to be strictly controlled, and the quality of the dissolving pulp can be comprehensively improved only by starting from a plurality of links such as raw material selection, a cooking process, a bleaching process, chemical refining and the like.
Disclosure of Invention
The invention aims to provide a production process for improving quality index of dissolving pulp by using a bleaching processThe technical problem to be solved is to optimally upgrade the traditional ECF four-stage bleaching process by combining the practical experience of dissolving pulp production in the Qingshan paper industry for 8 years, and to prepare the Qingshan dissolving pulp into the original bleaching process flow D after the laboratory process research and experimental verification0-Eop-D1-P is improved to D0-Eop-D1-AQParticularly, the original P section is changed into an acid treatment section (A section) and a chelating agent EDTA (Q) is added, so that the purposes of simple preparation process, smooth flow, stable and improved product quality, accordance with the industrial standard and capability of meeting the requirements of users on higher-grade dissolving pulp and even tencel-grade dissolving pulp are achieved.
In order to achieve the technical purpose, the design scheme of the invention is as follows:
a production process for improving quality indexes of dissolving pulp by utilizing a bleaching process comprises the following four stages:
1)D0and (3) section bleaching: the first bleaching stage is bleaching agent of chlorine dioxide CLO2The aqueous solution is used for treating the fine slurry prepared by the PHK method by using the aqueous solution of chlorine dioxide, and is a stage for further removing lignin in the slurry and improving whiteness.
The factors influencing the bleaching by chlorine dioxide include the dosage of chlorine dioxide, bleaching time, pH value, bleaching temperature, pulp concentration and the like, and key production process parameters are in a controlled range.
2) And (3) bleaching in an Eop section: in the second bleaching stage, the bleaching agent is 32% of industrial liquid alkali, 27.5% of industrial hydrogen peroxide and 93% of oxygen. The alkali treatment section is used for further removing lignin and colored substances, and the difficultly soluble chlorinated lignin is dissolved and washed out to be the purification section.
Only a part of the chlorinated lignin is dissolved in acid liquor formed in chlorination and washed out through the bleaching process of chlorine dioxide, and along with the consumption of the chlorine dioxide, a part of the difficultly soluble chlorinated lignin is dissolved and washed out in subsequent alkali treatment, so that the alkali treatment section is connected after the bleaching section of the chlorine dioxide for further removing lignin and colored substances. During alkali treatment, the alkali treatment conditions are controlled to be strong, lignin can be dissolved out, hemicellulose can be effectively removed, and the content of alpha-cellulose and the average polymerization degree are improved. The influence factors of the alkali treatment section include alkali amount, treatment temperature, bleaching time, pulp concentration and the like, and key production process parameters are in a controlled range.
3)D1And (3) section bleaching: third stage bleaching, D1The purpose of bleaching is to increase the brightness of the pulp to the desired level and to keep the viscosity of the PHK slurry within a certain range. According to a typical procedure CEDED with chlorine dioxide bleaching, at D0The dosage of the chlorine dioxide is 0.5 to 2.0 percent, D1The consumption of chlorine dioxide in the section is 0.4-0.6%, and the whiteness can reach above 86.0% ISO.
4) Acid treatment A stage: the fourth stage bleaching and the chelating agent EDTA-2Na (disodium ethylenediaminetetraacetate) was added. The pulp is treated by acid, so that the hemicellulose is removed, the acid washing effect is achieved, and the ash content and the metal ion content of the pulp are reduced. Under the acidic condition, the alkali-resistant hemicellulose can be obviously removed, so that the alpha-cellulose content of the pulp is improved; thus, for PHK slurries, the residual hemicellulose is more stable to alkali, but can be removed by acid extraction (a). The chelating agent is used for combining with metal ions to form a stable ring structure, and preventing the metal ions from being absorbed by the paper pulp, thereby further reducing the content of trace metal ions, particularly Fe, in the pulp3+The content of ions.
Bleaching is a chemical process for improving whiteness and purity of pulp by removing lignin in pulp or changing the structure of chromophoric groups of lignin through the action of chemicals, and is an important process for producing dissolving pulp. The bleaching process has many chemical reactions, many influencing factors and complex operation. Bleaching of dissolving pulp is required for three purposes: improving the whiteness (brightness) of the cellulose; properly reducing the polymerization degree of cellulose and leading the molecular size to be uniform; further improves the purity, removes non-cellulose impurities such as grease, wax, lignin, ash content, iron and the like in the dissolving pulp, and further improves the reactivity of the dissolving pulp. Generally, the higher the whiteness, the better the reactivity without changing the spinning process.
The quality of dissolving pulp depends mainly on the nature of the raw materials and the production process of the dissolving pulp.
For dissolving pulp production, raw materials are basic, cooking is critical, bleaching is adjustment, and performance is the goal.
Further, said D0The process of the section bleaching comprises the following steps: adding the slurry and chlorine dioxide water solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 68-70 ℃ for 70-75min, wherein the reaction pH value is 2.5.
D0In the stage bleaching step, the concentration of the pulp is 10%, and the dosage of the chlorine dioxide is 12.0 Kg/ADT.
Further, the Eop section bleaching process comprises the following steps: will pass through D0Adding the pulp after the section bleaching and 32% of industrial liquid alkali, 27.5% of industrial hydrogen peroxide and 93% of oxygen into a reaction container, uniformly stirring, and reacting at 75-78 ℃ for 80-85min, wherein the reaction pH value is 11.0.
In the Eop section bleaching step, the dosage of the 32% industrial liquid alkali is 12Kg/ADT, the dosage of the 27.5% industrial hydrogen peroxide is 3.0Kg/ADT, and the dosage of the 93% oxygen is 5 Kg/ADT.
Further, said D1The process of the section bleaching comprises the following steps: adding the slurry bleached by the Eop section and chlorine dioxide aqueous solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 70-72 ℃ for 120-130min, wherein the reaction pH value is 3.5.
D1In the step of the stage bleaching, the dosage of the chlorine dioxide is 4.0-6.0 Kg/ADT.
The acid treatment A section process comprises the following steps: will pass through D1Adding the slurry after the stage bleaching, 5 percent of dilute sulfuric acid and EDTA-2Na into a reaction container, uniformly stirring, and reacting at 78-80 ℃ for 120-130min, wherein the reaction pH value is 5.5.
In the step of acid treatment A, the dosage of the 5% dilute sulfuric acid is 1.0Kg/ADT, and the dosage of the EDTA-2Na is 3.0 Kg/ADT.
By the improved four-stage bleaching process D of the invention0-Eop-D1-AQThe following effects can be achieved:
(1) the ash content of the PHK dissolving pulp quality index of the final product is 0.06 percent and is greatly lower than the ash content index of the common-grade dissolving pulp, and the production requirement of the high-grade dissolving pulp can be met.
(2) The quality index iron of the PHK dissolving pulp of the final product is 4.0ppm, and the PHK dissolving pulp meets the quality index requirement of the tencel-grade dissolving pulp.
(3) The medium used in the A section of the acid treatment section is dilute sulfuric acid, and the chelating agent uses EDTA-2Na, so that the effect of removing ash and metal ions is obvious, and the agent is economical and easy to obtain and has high performance-price ratio.
Detailed Description
A production process for improving quality index of dissolving pulp by using a bleaching process comprises the following steps:
1)D0and (3) section bleaching: adding the slurry and chlorine dioxide water solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 68-70 ℃ for 70-75min, wherein the reaction pH value is 2.5;
the concentration of the slurry is 10%, and the dosage of the chlorine dioxide is 12.0 Kg/ADT;
2) and (3) bleaching in an Eop section: will pass through D0Adding the pulp subjected to the stage bleaching and 32% of industrial liquid alkali, 27.5% of industrial hydrogen peroxide and 93% of oxygen into a reaction container, uniformly stirring, and reacting at 75-78 ℃ for 80-85min, wherein the reaction pH value is 11.0;
the dosage of the 32% industrial liquid caustic soda is 12Kg/ADT, the dosage of the 27.5% industrial hydrogen peroxide is 3.0Kg/ADT, and the dosage of the 93% oxygen is 5 Kg/ADT;
3)D1and (3) section bleaching: adding the slurry bleached by the Eop section and chlorine dioxide aqueous solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 70-72 ℃ for 120-130min, wherein the reaction pH value is 3.5;
the dosage of the chlorine dioxide is 4.0-6.0 Kg/ADT.
4) Acid treatment A stage: will pass through D1Adding the slurry after the stage bleaching, 5 percent of dilute sulfuric acid and EDTA-2Na into a reaction container, uniformly stirring, and reacting at 78-80 ℃ for 120-130min, wherein the reaction pH value is 5.5.
The dosage of the 5% dilute sulfuric acid is 1.0Kg/ADT, and the dosage of the EDTA-2Na is 3.0 Kg/ADT.
The present invention is illustrated by the following specific examples.
Example 1
The four-stage bleaching process technology D is adopted for 6 months, 10 days to 14 days in 20190-Eop-D1-AQTrial production of Tencel-grade dissolving pulp is carried out, and 1032 tons of radiata pine dissolving pulp with higher grade is produced smoothly and continuously in the process.
Radiata pine dissolving pulp D0-Eop-D1The control of key production process parameters of four-stage bleaching is shown in table 1:
TABLE 1 Pinus radiata dissolving pulp D0-Eop-D1-AQFour-stage bleaching process conditions
| Item | D0 | Eop | D1 | A+Q |
| Concentration of pulp/% | 10 | 10 | 10 | 10 |
| CLO2The dosage is Kg/ADT | 12.0 | — | 4.0 | — |
| The dosage of the liquid caustic soda is Kg/ADT | — | 12 | — | — |
| The dosage of the hydrogen peroxide is Kg/ADT | — | 3.0 | — | — |
| Oxygen O2 Kg/ADT | — | 5.0 | — | — |
| Dilute sulfuric acid Kg/ADT | — | — | — | 1.0 |
| Chelating agent EDTAKg/ADT | — | — | — | 3.0 |
| Bleaching pH | 2.5 | 11.9 | 3.5 | 5.5 |
| Reaction temperature/. degree.C | 68℃ | 75℃ | 70℃ | 78℃ |
| Reaction time/min | 70min | 80min | 120min | 120min |
Remarking: ADT is the code for air-dried tons, i.e. a pulp representing a dryness of 90%.
Oxygen being O2Compressed gas with a purity of more than 93.0% is generally at a pressure of 11.0 bar.
The quality of the dissolving pulp finished product prepared by the four-stage bleaching process route of the embodiment 1 of the invention is shown in table 2:
TABLE 2 Tencel level Radiata pine dissolving pulp finished product quality
As can be seen from Table 2, the average degree of polymerization of the finished dissolving pulp prepared in the embodiment 1 of the invention is 621DP, which completely meets the requirement of tencel-grade dissolving pulp; the iron ion content (4mg/kg) can meet the requirement of tencel-level dissolving pulp; the content and whiteness of the alpha-cellulose are respectively 92.2 percent and 86.86 percent, and the requirements of the common viscose grade dissolving pulp can be met.
In conclusion, the dissolving pulp with higher quality can be prepared by adopting the four-stage bleaching process technology.
The above-mentioned embodiments are only preferred embodiments of the present invention, and do not limit the technical scope of the present invention, so that the changes and modifications made by the claims and the specification of the present invention should fall within the scope of the present invention.
Claims (9)
1. A production process for improving quality indexes of dissolving pulp by utilizing a bleaching process is characterized by comprising the following steps of: which involves four stages of bleaching, i.e. D0Stage bleaching, Eop stage bleaching, D1Stage A of bleaching and acid treatment;
said D0The bleaching agent used in the stage bleaching is chlorine dioxide aqueous solution with the concentration of 8.0 g/L;
the bleaching agent used in the Eop section bleaching is a mixture of 32% of industrial liquid alkali, 27.5% of industrial hydrogen peroxide and 93% of oxygen;
said D1The bleaching agent used in the stage bleaching is chlorine dioxide aqueous solution with the concentration of 8.0 g/L;
the acid treatment section A takes 5% dilute sulfuric acid as a medium and EDTA-2Na as a chelating agent.
2. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process according to claim 1, which is characterized in that: said D0The process of the section bleaching comprises the following steps: adding the slurry and chlorine dioxide water solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 68-70 ℃ for 70-75min, wherein the reaction pH value is 2.5.
3. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process as claimed in claim 2, wherein the production process comprises the following steps: the concentration of the slurry is 10%, and the dosage of the chlorine dioxide is 12.0 Kg/ADT.
4. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process according to claim 1, which is characterized in that: the Eop section bleaching process comprises the following steps: will pass through D0Adding the pulp after the section bleaching and 32% of industrial liquid alkali, 27.5% of industrial hydrogen peroxide and 93% of oxygen into a reaction container, uniformly stirring, and reacting at 75-78 ℃ for 80-85min, wherein the reaction pH value is 11.0.
5. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process as claimed in claim 4, wherein the production process comprises the following steps: the dosage of the 32% industrial liquid caustic soda is 12Kg/ADT, the dosage of the 27.5% industrial hydrogen peroxide is 3.0Kg/ADT, and the dosage of the 93% oxygen is 5 Kg/ADT.
6. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process according to claim 1, which is characterized in that: said D1The process of the section bleaching comprises the following steps: adding the slurry bleached by the Eop section and chlorine dioxide aqueous solution with the concentration of 8.0g/L into a reaction vessel, uniformly stirring, and reacting at 70-72 ℃ for 120-130min, wherein the reaction pH value is 3.5.
7. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process as claimed in claim 6, wherein the production process comprises the following steps: the dosage of the chlorine dioxide is 4.0-6.0 Kg/ADT.
8. The production process for improving the quality index of dissolving pulp by utilizing the bleaching process according to claim 1, which is characterized in that: the acid treatment A section process comprises the following steps: will pass through D1Adding the slurry after the stage bleaching, 5 percent of dilute sulfuric acid and EDTA-2Na into a reaction container, uniformly stirring, and reacting at 78-80 ℃ for 120-130min, wherein the reaction pH value is 5.5.
9. The process of claim 8, wherein the bleaching step is performed to improve the quality index of the dissolving pulp, and the process comprises the following steps: the dosage of the 5% dilute sulfuric acid is 1.0Kg/ADT, and the dosage of the EDTA-2Na is 3.0 Kg/ADT.
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| CN115075033A (en) * | 2022-05-31 | 2022-09-20 | 中国制浆造纸研究院有限公司 | Method for preparing pulp by prehydrolysis sulfate pulp |
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