CN115559145A - Pulping process and application of high-strength high-cleanliness chemi-mechanical pulp - Google Patents

Pulping process and application of high-strength high-cleanliness chemi-mechanical pulp Download PDF

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Publication number
CN115559145A
CN115559145A CN202211411971.6A CN202211411971A CN115559145A CN 115559145 A CN115559145 A CN 115559145A CN 202211411971 A CN202211411971 A CN 202211411971A CN 115559145 A CN115559145 A CN 115559145A
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China
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stage
pulp
section
hydrogen peroxide
chemical liquid
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Chinese (zh)
Inventor
洪嘉远
董超
赵靖
徐燕
史梦华
胡成
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Yueyang Paper Co ltd
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Yueyang Paper Co ltd
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21B—FIBROUS RAW MATERIALS OR THEIR MECHANICAL TREATMENT
    • D21B1/00—Fibrous raw materials or their mechanical treatment
    • D21B1/04—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres
    • D21B1/12—Fibrous raw materials or their mechanical treatment by dividing raw materials into small particles, e.g. fibres by wet methods, by the use of steam
    • D21B1/14—Disintegrating in mills
    • D21B1/16—Disintegrating in mills in the presence of chemical agents
    • 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
    • D21C1/00—Pretreatment of the finely-divided materials before digesting
    • D21C1/06—Pretreatment of the finely-divided materials before digesting with alkaline reacting compounds
    • 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
    • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
    • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
    • D21H11/02—Chemical or chemomechanical or chemothermomechanical pulp
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/64—Paper recycling

Abstract

The invention relates to the technical field of pulping, and provides a pulping process of high-strength high-cleanliness chemi-mechanical pulp, which takes bamboo willow leftover materials as fiber raw materials and comprises the steps of 1-stage presteaming, wood chip washing, dehydration and 2-stage presteaming; carrying out 1-section extrusion fluffing, 1-section chemical liquid pre-soaking, 2-section extrusion fluffing and 2-section chemical liquid pre-soaking on the 2-section pre-steamed wood sheet material; the 1-section chemical liquid presoaking process adopts sodium hydroxide solution without using hydrogen peroxide, and the chemical reagents of the 2-section chemical liquid presoaking process are sodium hydroxide, hydrogen peroxide and sodium silicate; 1-stage grinding, separating, cooling, 1-stage high-concentration bleaching, 1-stage dehydrating, 2-stage high-concentration bleaching and 2-stage dehydrating are carried out on the material presoaked by the 2-stage chemical liquid; and (3) performing latency elimination, pulp grinding and the like on the pulp dehydrated in the 2 sections to obtain the finished pulp. The process can produce high-strength and high-cleanliness chemi-mechanical pulp, has lower pulping cost and better pulp quality, and is beneficial to the application of preparing high-end cultural paper and the like.

Description

Pulping process and application of high-strength high-cleanliness chemi-mechanical pulp
Technical Field
The invention relates to the technical field of pulping, in particular to a pulping process and application of high-strength high-cleanliness chemi-mechanical pulp.
Background
At present, the requirements of auxiliary paper and light-coated paper products for cultural paper teaching materials in China on the paper breaking length are generally more than 4.0km, and the requirements of the industrial laminating paper on the paper breaking length are more than 7.0 km. While the domestic chemi-mechanical pulp (chemical mechanical pulp for short) mostly takes poplar, eucalyptus and acacia wood as main fiber raw materials, the fracture length is basically about 3.0km under the knocking degree of 45-500SR, and the tear index is 3.0mN.m 2 Below/g, the blending ratio of the chemi-mechanical pulp in the above paper types is seriously influenced. Some enterprises in the industry mix a small amount of pine in raw materials to try to improve the strength of the pulp, but the pine is expensive and the chemical-mechanical pulp of the pine is difficult to bleach, so that the production cost such as the use of chemicals is increased and the pulp is not paid.
In wood resources, bamboo willow is called fast-growing bamboo willow, is a great number of tree species planted in the Hunan and the North of China, and is mainly and intensively used in the building decoration industry. The bamboo willow wood has lighter color and slightly lower density than poplar wood, so the bamboo willow wood is very suitable for being used as a chemical-mechanical pulp raw material. However, the pulp prepared by using bamboo willow as fiber raw material still needs to be further improved in quality such as strength.
Disclosure of Invention
In view of the above, the invention aims to provide a pulping process and application of high-strength high-cleanliness chemi-mechanical pulp, which can produce high-strength high-cleanliness chemi-mechanical pulp, and is lower in pulping cost, better in pulp quality, and beneficial to preparing high-end cultural paper and the like.
The invention provides a pulping process of high-strength high-cleanliness chemi-mechanical pulp, which comprises the following steps:
bamboo willow leftover materials are used as fiber raw materials and are subjected to presteaming for 1 section, wood chip washing, dehydration and presteaming for 2 sections;
2 sections of the steamed wood sheet material are subjected to 1 section of extrusion fluffing, 1 section of chemical liquid presoaking, 2 sections of extrusion fluffing and 2 sections of chemical liquid presoaking; the 1-section chemical liquid presoaking process adopts sodium hydroxide solution without using hydrogen peroxide, and the chemical reagents of the 2-section chemical liquid presoaking process are sodium hydroxide, hydrogen peroxide and sodium silicate;
1-section pulping, separating and cooling the material presoaked by the 2 sections of chemical liquid medicines, 1-section high-concentration hydrogen peroxide bleaching, 1-section dehydration, 2-section high-concentration hydrogen peroxide bleaching and 2-section dehydration;
the pulp after 2 sections of dehydration is processed by latency elimination, pulp grinding, screening and concentration to obtain the chemical mechanical finished pulp with the dust degree not exceeding 50mm 2 K, and tear index of more than 3.5mN.m 2 /g。
Preferably, the temperature of the water for washing the wood chips is 70-80 ℃, and paper machine white water can be introduced for washing.
Preferably, the exhaust temperature of the 1-stage presteaming and the 2-stage presteaming is independently 80-90 ℃.
Preferably, the 1-stage extrusion fluffing and the 2-stage extrusion fluffing are both high-load MSD extrusion, and the speed is not higher than 50rpm.
Preferably, in the 1-section chemical liquid preimpregnation process, the dosage of sodium hydroxide to oven dry pulp is 0.1-0.5%, and the steam exhaust temperature is 70-90 ℃;
in the 2-stage chemical liquid pre-dipping process, the dosage of sodium hydroxide to the oven dry pulp is 3.0-4.0%, the dosage of hydrogen peroxide to the oven dry pulp is 0.7-0.9%, and the dosage of sodium silicate to the oven dry pulp is 1.5-2.0%.
Preferably, in the 1-stage high-concentration hydrogen peroxide bleaching process, the dosage of NaOH to oven dry pulp is 0.5-1.5%, and the dosage of hydrogen peroxide to oven dry pulp is 2.0-3.0%;
in the 2-stage high-concentration hydrogen peroxide bleaching process, the dosage of NaOH to oven dry pulp is 0.2-0.5%, and the dosage of hydrogen peroxide to oven dry pulp is 0.2-0.4%.
Preferably, sodium silicate is adopted in both the 1-stage high-concentration hydrogen peroxide bleaching and the 2-stage high-concentration hydrogen peroxide bleaching, and magnesium sulfate is not used; the bleaching temperature is independently 80-96 ℃.
Preferably, the 1-stage dehydration and the 2-stage dehydration are independently a screw press dehydration mode.
Preferably, the chemi-mechanical finished pulp has a tear index of 4.0-4.2mN.m 2 (ii)/g, whiteness 80-85% ISO, freeness 130-310mL, and positive charge requirement 520 μ eq/L.
The present invention provides the use of the pulp obtained from the pulping process as described hereinbefore in papermaking.
The main innovation points and advantages of the pulping process of the invention comprise: the leftover bamboo willow raw material is adopted for pulping, the dependence of traditional chemi-mechanical pulp on poplar is broken, three forestry residues are used by all trees in response to national policies, and the raw material realizes the conversion from a resource type to a waste utilization type; the invention uses the bamboo willow in the APMP process, and uses H instead of one section of presoaking 2 O 2 And the traditional single-stage hydrogen peroxide bleaching is changed into 2-stage bleaching, so that the consumption of chemicals is reduced, and the stability of whiteness is improved. The invention solves the problem of easy cutting of the chemi-mechanical pulp through technical optimization, effectively maintains the fiber strength, simultaneously maintains the advantages of good bulk and the like, and has obvious effect of improving the proportioning of the chemi-mechanical pulp. The invention has been innovated and studied deeply, the bamboo willow is the raw material to produce the high-strength chemi-mechanical pulp for the first time in China, and the dust index of the pulp is better. The technology adopts the leftover bits and pieces of bamboo willows in the furniture board industry as raw materials, researches and develops the technological process and technological parameters according to the characteristics of the raw materials, breaks the dependence of the traditional chemi-mechanical pulp on poplar and eucalyptus, effectively widens the chemi-mechanical pulp raw material resources, relieves the pressure of insufficient raw material supply, can improve the quality of the chemi-mechanical pulp, reduces the production cost, and can completely meet the production requirements of high-grade cultural paper and the like.
Drawings
FIG. 1 is a schematic flow diagram of a production process according to some embodiments of the present invention.
Detailed Description
The technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
The invention provides a pulping process of high-strength high-cleanliness chemi-mechanical pulp, which takes bamboo willow leftover materials as fiber raw materials and comprises the following process steps: firstly, pre-steaming at 1 section, washing wood chips, dehydrating and pre-steaming at 2 sections; carrying out 1-section extrusion fluffing, 1-section chemical liquid pre-soaking, 2-section extrusion fluffing and 2-section chemical liquid pre-soaking on the 2-section pre-steamed wood sheet material; the 1-section chemical liquid presoaking process adopts a sodium hydroxide solution without using hydrogen peroxide, and the chemical reagents of the 2-section chemical liquid presoaking process are sodium hydroxide, hydrogen peroxide and sodium silicate; carrying out 1-stage pulping, separation and cooling on the material presoaked by the 2-stage chemical liquid, 1-stage high-concentration bleaching of hydrogen peroxide, 1-stage dehydration, 2-stage high-concentration bleaching of hydrogen peroxide and 2-stage dehydration on the material; the pulp after 2 sections of dehydration is processed by latency elimination, pulp grinding, screening and concentration to obtain the chemical mechanical finished pulp with the dust degree not exceeding 50mm 2 K, and tear index of more than 3.5mN.m 2 /g。
Aiming at the defects of the prior art, the high-quality chemi-mechanical pulp with low raw material price, low chemical consumption, high strength and the like is researched, and the large-scale popularization and application are facilitated.
Referring to fig. 1, fig. 1 is a schematic flow diagram of a manufacturing process according to some embodiments of the present invention. In the embodiment of the invention, the punched bamboo willow wood chips are screened and then conveyed to a wood chip bin for production and use. The technology breaks the dependence of the traditional chemi-mechanical pulp on poplar, eucalyptus and acacia wood, responds to national policies and completely uses three forestry residues, and the wood chip used in the invention is a bamboo willow corner wood chip (or called corner bamboo willow wood chip). The bamboo willow has relatively low density, the main material is mainly used as a frame plate of high-grade home and a plate of high-grade decorative material (bark of a trunk of the bamboo willow is firstly stripped, an outer layer of the trunk of the bamboo willow is cut off by a machine, a tree core is reserved, and the trunk of the bamboo willow is cut into square shapes and round shapes according to furniture requirements). The leftover bits and pieces are sent to a biomass power plant before being used as fuel, and the application is the first domestic creation of producing high-strength and other-quality chemical-mechanical pulp by taking bamboo willow leftover bits and pieces as raw materials.
The pulping fiber raw material in the embodiment of the invention is characterized by comprising the following components: the wood chip proportion is 100 percent of bamboo willow leftover materials; the specification of the wood chip is that the length of the wood chip is 19-25 mm, the thickness is 4.0 +/-1 mm, the qualification rate of the wood chip is equal to or greater than 80% (mass percent), the bark rate is equal to or less than 0.5% (for example, more than 0.5%, bark dust cannot be removed in the pulping process, a plurality of black spots exist on a paper surface), and the water content of the wood chip is equal to or greater than 38%. The following process flow is briefly described: wood chip bin → 1# pre-steaming bin → wood chip washing → 2# pre-steaming bin.
For the 1-section presteaming and the 2-section presteaming, the corresponding wood chip presteaming bins are provided with metering screws, the material level can be 40-60%, and the temperature of an exhaust port is 80-90 ℃ independently. And (3) washing the wood chips subjected to the 1-stage presteaming by using a wood chip washing machine between the 1# and the 2# presteaming, wherein the temperature of washing water is preferably 70-80 ℃, and then the wood chips enter a wood chip mixing tank and are pumped to a single-screw dehydrator. The invention adopts the raw materials of the corner bamboo willow for pulping, can improve the temperature of the washing water of the wood chips, strengthen the water absorption swelling in the washing process of the wood chips, improve the moisture content of the wood chips and facilitate the subsequent processing. In addition, white water of a paper machine can be introduced into a workshop, the white water can move forward section by section, and the water at the forefront section can be used for washing wood chips.
In the embodiment of the invention, 2 sections of pre-steamed wood sheet materials are extruded and defibered for 1 section by a No. 1 wood chip extruder, then 1 section of chemical liquid medicine is presoaked in a No. 1 presoaking device, a reaction bin and the like, and 2 sections of extrusion defibering and 2 sections of chemical liquid medicine presoaking can be carried out by a discharge screw to obtain presoaked materials. Wherein the prepreg is a liquid medicine adding point.
In the examples of the invention, the speed of the No. 1 wood chip extruder (MSD) is not higher than 50rpm, the torque is 60-100kN.m, the power is 600-700kw, and the torque control is preferred. Moreover, the liquid level of the No. 1 prepreg can be 20-30%, and the invention is different from the traditional process in that H is not used in one-section prepreg 2 O 2 Preferably, the dosage of NaOH to the oven dry pulp is controlled to be 0.1-0.5 percent, and more preferably 0.5 percent; the material level of the No. 1 reaction bin is 20-30%, and the exhaust temperature is 70-90 ℃. Preferably, the speed of the 2# wood chip extruder (MSD) in the embodiment of the invention is not higher than 50rpm, torque of 45-80kN.m, power of 500-700 kw, and priority of torque control. The embodiment of the invention optimizes the motors and filter plates of 2 MSDs, wherein the first MSD section mainly extrudes wood chips to crack, and the second MSD section extrudes the wood chips to small strips, so that the water can be quickly and effectively dehydrated under high-load extrusion.
Meanwhile, the liquid level of the No. 2 prepreg can be 20-30%, the dosage of NaOH to absolute dry pulp is preferably controlled to be 3.0-4.0%, and H is preferably controlled to be 2 O 2 The amount of Na to be used is 0.7 to 0.9%, preferably 0.8%, based on the amount of oven-dried pulp 2 SiO 3 The dosage of the oven-dry pulp is 1.5 to 2.0 percent, and Mg (OH) is not used in the process 2 And MgSO 2 4 (ii) a The material level of the No. 2 reaction bin is 60-80%, and the exhaust temperature is 70-90 ℃. According to the embodiment of the invention, according to the characteristic that the bamboo willow is relatively low in density, the extrusion effect is improved by improving the pre-soaking effect, the pulping quality is favorably improved, and the pulping energy consumption is reduced.
After the 2# pre-dipping reaction is finished, the obtained material can pass through the 2# discharging screw, the 3# discharging screw, the horizontal conveying screw and the 1# side feeding screw, and then enters the processes of grinding, bleaching and the like. The process flow mainly comprises the following steps: 1-stage high consistency refining (addition point of #3 bleach liquor) → 1# cyclone → cooling screw → 1-stage high consistency bleaching tower → 1# dewatering thickener → heating screw (addition point of # 4 bleach liquor) → 2# high consistency bleaching tower → 2# dewatering thickener.
The embodiment of the invention preferably adopts only one high-concentration pulping device for conventional pulping before bleaching, and can also optimize the selection of grinding discs, prolong the retention time in the grinding mill and improve the devillicating and brooming effects aiming at the problems that the bamboo willow leftover materials are soft and the pulping is easy to permeate; the embodiments of the present invention promote devillicating, rather than cutting, of the wood chips, with sufficient retention of strength.
On the basis of the prior poplar APMP pulping, the embodiment of the invention changes the traditional single-stage alkaline hydrogen peroxide high-concentration bleaching into two-stage bleaching, thereby reducing the consumption of chemicals and improving the stability of whiteness. Before each pulp tower enters the tower, a set of spiral squeezing equipment is added, so that the concentration of pulp entering the tower is improved, and the consumption of chemicals is reduced. In addition, the whole process does not use Mg (OH) 2 、MgSO 4 Chelating agents such as EDTA。
Specifically, the 1-stage bleaching process conditions comprise: the addition point of the liquid medicine is a No. 1 disc mill blow-off pipe, the dosage of NaOH to the absolute dry pulp is preferably 0.5 to 1.5 percent, and H is 2 O 2 The preferable dosage of the oven-dried pulp is 2.0-3.0 percent, na 2 SiO 3 The dosage of the oven-dried pulp can be 0.5 to 2.0 percent; the bleaching concentration can be 25-40%, the bleaching temperature is preferably 90-96 ℃, and the material level is controlled to be 35-60%. 2, bleaching: the liquid medicine adding point is a heating spiral part, the dosage of NaOH to oven-dried pulp is preferably 0.2-0.5%, H 2 O 2 The preferable dosage of the oven-dried pulp is 0.2-0.4 percent, na 2 SiO 3 The dosage of the oven-dried pulp can be 0.4-1.0%; the bleaching concentration can be 25-35%, the bleaching temperature is preferably 80-90 ℃, and the material level is controlled to be 60-80%. For example, one ton of pulp, 1000kg x 2% =20kg, 20-30 kg of hydrogen peroxide can be added in 1 stage of bleaching, and the addition amount of the medicine is relative to the weight of the absolutely dry pulp. In combination with the above pre-dipping process, the embodiments of the present invention can greatly reduce the consumption of other chemicals by properly increasing the alkali retention strength. In addition, under the condition of the same bleaching end point whiteness, the whiteness is improved in a stepped manner by adding a certain amount of hydrogen peroxide at multiple points, and the dosage of bleaching chemicals is obviously reduced.
Preferably, the 1-stage dewatering and the 2-stage dewatering are both screw press dewatering, that is, the 1-stage dewatering (concentrating) and the 2-stage dewatering (concentrating) are respectively the 1# screw press dewatering and the 2# screw press dewatering. In the preferred embodiment of the invention, two-stage high-load MSD extrusion is combined with two-stage screw press extrusion process, so that organic extract in the wood chips can be efficiently discharged, alkali extract can be efficiently extruded and discharged at high density, further bleaching burden is reduced, and the like, for example, bleaching agent effect is more remarkable due to waste liquid in the upper stage of the two-stage screw press extrusion. 2-stage extrusion, 1-stage grinding and 2-stage screw extrusion are realized in the process, and aromatic substances, triglyceride, pentosan and the like in the wood chips are effectively removed.
After 2 stages of high-concentration hydrogen peroxide bleaching and 2 stages of dehydration, the production process flow of the embodiment of the invention can be as follows: the submergence eliminating tank → 1# conical mill → 2# conical mill → 3# double disc mill → middle pulp tank → multistage pressure screen → good pulp tank → multi disc thickener → middle concentrated pulp tower (pH is adjusted 7-7.5 by sulphuric acid). The process conditions specifically include: the concentration of the second-stage No. 1#2#3 low-consistency mill pulp grinding is 4.5-5.5%, the pulp grinding power is 600-1500 kw, and the unit energy consumption is 20-60 kw/admt. The operating conditions of the No. 1-3 pressure screen are as follows: the sieve gap of the pressure sieve is 0.25mm; the pulp inlet concentration is 1.2-1.8%; the slurry inlet pressure is 2.5-4.0 bar; the pressure difference between the inlet and the outlet (P out-P in) is not more than 50kPa; the flow ratio of the slag pulp to the good pulp can be 35-40 percent; the operation load is 40-50%; the ratio of the good pulp flow rate of the No. 2/No. 1 pressure screen is 28-40%.
The embodiment of the invention effectively widens the pulping raw material resources, innovatively optimizes the pulping process flow according to the unique properties of the bamboo willow, and has lower pulping cost and better pulp quality. The invention adopts the processes of 2-stage MSD extrusion, 2-stage screw extrusion and 2-stage bleaching, so that the cost of the pulping raw material is lower; the produced chemi-mechanical pulp ensures higher strength, other indexes meet the requirements of the cultural paper, and meanwhile, the chemi-mechanical pulp has the advantage of lower cost.
The embodiment of the invention mainly fully analyzes the characteristics of the bamboo willow leftover materials according to the characteristics of the bamboo willow fibers, and completely tracks physical strength indexes such as core parameter fracture length (tensile index) and tearing index, wherein the tearing index is more than 3.5mN.m 2 The concentration/g is adjusted according to the control of the beating degree of the final slurry (if the freeness is preferably controlled according to 130-310 ml), the slurry quality is better, and the energy consumption is lower. In addition, the dust index of the finished product slurry obtained in the embodiment of the invention is very good, and the dust degree is 0-50mm 2 And/k, namely dust of zero black spots, and the other wood chip pulping often has the phenomenon that after barks are not removed completely, bark type small black spot dust appears on the paper surface. The invention mainly uses the low-price bamboo willow leftover materials to replace high-price poplar wood which is limited by environmental protection, 100 percent of the forestry three-leftover bamboo willow leftover materials are used for pulping, high-strength and high-cleanliness pulp is produced, and the quality characteristics of the pulp can be consistent with the traditional poplar APMP standard.
In a specific embodiment of the invention, said chemi-mechanical pulp has a tear index of 4.0-4.2mN.m 2 Per g, whiteness 80-85% ISO, freeness 130-310mL, positive charge requirement 520 μ eq/L. In addition, the tensile index of the finished pulp can reach 35-47 N.m/g; bulk of2.55-2.93cm 3 (iv) g; the fiber length is 0.79-0.86mm, and the dust degree is 0-50mm 2 /k。
From the aspect of the pulp quality, all indexes of the embodiment of the invention are greatly improved on the basis of the original process, and particularly, the positive charge demand, dust and tearing index meet the requirements of high strength and high cleanliness, so that the method is beneficial to preparing high-end cultural paper and the like. The invention therefore also provides the use of the pulp obtained from the pulping process as hereinbefore described in papermaking.
In order that the technical contents of the invention may be better understood, specific examples are provided below to further illustrate the invention. Unless otherwise specified, the mass ratio is used in the present invention.
Example 1
The invention firstly screens the well-punched bamboo willow wood chips and then sends the chips to production for use.
(1) The pulping fiber raw material is characterized in that: the wood chip proportion is 100 percent of corner bamboo willow; the chip specifications include: the length of the wood chip is 19-25 mm, the thickness is 4.0 +/-1 mm, the qualification rate of the wood chip is equal to or greater than 80% (mass percent), the bark rate is equal to or less than 0.5%, and the water content of the wood chip is equal to or greater than 38%.
(2) Referring to fig. 1, the production process flow is briefly described as follows: the preparation of the raw materials comes from wood chips → a wood chip screen → a wood chip bin → a No. 1 pre-steaming bin → wood chip washing → a No. 2 pre-steaming bin → 1 segment extrusion → a No. 1 presoaking device (No. 1 presoaking liquid medicine is added) → 2 segment extrusion → 2# presoaking device (No. 2 presoaking liquid medicine is added) → 1 segment refining (No. 3 bleaching liquid adding point) → 1# cyclone separator → cooling screw → 1 segment high consistency bleaching tower → 1# dehydration thickener → heating screw (No. 4 bleaching liquid adding point) → 2# high consistency bleaching tower → 2# dehydration thickener → latent elimination tank → 1# conical mill → 2# conical mill → 3# double disc mill → intermediate tank → pressure screen → good pulp tank → multi-disc → medium consistency pulp storage tower (pH 7-7.5 is adjusted by sulfuric acid).
(3) The main production process technical conditions are as follows: (A) The wood chip pre-steaming bin material level is 40-60%, and the steam outlet temperature is 80-90 ℃; the temperature of the wood chip washing water is 70-80 ℃; chip extruder # 1 (MSD): the speed is 40-45rpm, the torque is 60-100kN.m, the power is 600-700kw, and the torque control is prior; 1# prepreg: the liquid level is 20-30%, the dosage of NaOH to absolute dry pulp is 0.5%, the material level of the No. 1 reaction bin is 20-30%, and the exhaust temperature is 70-90 ℃; (B) 2# WoodSheet press (MSD): the speed is 40-45rpm, the torque is 45-80kN.m, the power is 500-700 kw, and the torque control is prior; 2# prepreg: liquid level 20-30%, naOH consumption 3.0-4.0%, H 2 O 2 0.8% of oven-dried pulp and Na 2 SiO 3 The dosage of the oven dry pulp is 1.5 to 2.0 percent, the material level of the No. 2 reaction bin is 60 to 80 percent, and the exhaust temperature is 70 to 90 ℃; (C) conventional 1-stage high-consistency refining; bleaching in the 1 stage: the liquid medicine adding point is a 1# disc mill blowing pipe, and the dosage of NaOH to the oven dry pulp is as follows: 0.5-1.5%, H 2 O 2 The dosage of oven-dried pulp is as follows: 2.0 to 3.0 percent of Na 2 SiO 3 The dosage of oven-dried pulp is as follows: 0.5-2.0%, bleaching concentration: 25-40%, bleaching temperature: 90-96 ℃, and material level control: 35 to 60 percent; (D) 2-stage bleaching: the liquid medicine adding point is a heating screw, and the dosage of NaOH to oven-dried pulp is as follows: 0.2-0.5%, H 2 O 2 The dosage of oven-dried pulp is as follows: 0.2 to 0.4 percent of Na 2 SiO 3 The dosage of oven-dried pulp is as follows: 0.4-1.0%, bleaching concentration: 25-35%, bleaching temperature: 80-90 ℃, and material level control: 60 to 80 percent; (E) The concentration of the second-stage No. 1#2#3 low-consistency grinding is 4.5-5.5%, the grinding power is 600-1500 kw, and the unit energy consumption is 20-60 kw/admt; (F) 1-3 # pressure screen operating conditions: the screen gap of the pressure screen is 0.25mm, and the pulp inlet concentration is 1.2-1.8%; the pulp inlet pressure is 2.5-4.0 bar; the pressure difference between the inlet and the outlet (P outlet-P inlet) is not more than 50kPa; the flow ratio of the slag pulp to the good pulp is 35 to 40 percent; the running load is 40-50%; the ratio of the number 2/1 pressure screen to the good pulp flow is 28-40%.
(4) Quality characteristics and comparison of bleached pulp:
the slurry has a whiteness of 80-85 ISO, a freeness of 130-310ml, a breaking length of 3.55-4.74km (tensile index of 35-47 N.m/g), and a breaking length of less than 3.0km for a generalized mechanical slurry;
the bulk density of the sizing agent is 2.55-2.93 cm 3 The fiber length is 0.79-0.86mm, and the common hardwood chemi-mechanical pulp is about 0.6 mm;
the dust degree of the sizing agent is 0-50mm 2 Per kg, fiber bundle content 0-0.2%, tear index 4.0-4.2mN.m 2 (iv) g; the generalized chemi-mechanical pulp is 3.0mN.m 2 The ratio of the total carbon content to the total carbon content is below g;
the Positive Charge Demand (PCD) of the slurry is 520 mu eq/L, and the common hardwood chemi-mechanical slurry is about 2000 mu eq/L.
The present embodiment specifically analyzes the beating degree, fiber condition and strength of the finished pulp, including sieving, fiber analyzer and special instrument detection, and the results are as follows.
TABLE 1 sizing results
Figure BDA0003939027060000081
Figure BDA0003939027060000091
TABLE 2 pulp fiber conditions
Figure BDA0003939027060000092
TABLE 3 slurry Strength index
Figure BDA0003939027060000093
The beating degree of the slurry can be converted into the freeness according to a comparison table; the beating degree is the beating degree, is an index of the water filtering performance in the paper pulp property, and is used for carrying out different comprehensive production regulation and control according to different paper machines, the requirements of paper production, other indexes and the like. Therefore, the method solves the problem that the chemi-mechanical pulp is easy to cut off, effectively maintains the fiber strength, simultaneously maintains the advantage of good bulk, and has very obvious effect of improving the proportioning of the chemi-mechanical pulp. The pulping process breaks the dependence of the traditional chemi-mechanical pulp on poplar and eucalyptus, effectively widens the raw material resources of the chemi-mechanical pulp, and relieves the pressure of insufficient raw material supply.
Compared with the original process, the invention greatly improves the production process, has updated flow, lower cost (for example, electricity can be saved by 200 ℃ per ton of pulp, the consumption of chemicals is reduced), better pulping quality characteristics, can meet the requirements of high-strength high-cleanliness chemi-mechanical pulp, can be used for preparing high-end cultural paper and the like, and belongs to the domestic initiative.
The principles and embodiments of the present invention have been described herein using specific examples, which are presented only to assist in understanding the method and its core concepts of the present invention. It should be noted that there are no specific structures but rather a few limitations to the preferred embodiments of the present invention, and that many modifications, adaptations, and variations are possible and can be made by one skilled in the art without departing from the principles of the present invention; such modifications, variations, or combinations, or other applications of the inventive concepts and solutions as may be employed without such modifications, are intended to be included within the scope of the present invention.

Claims (10)

1. A pulping process of high-strength high-cleanliness chemi-mechanical pulp is characterized by comprising the following steps:
bamboo willow leftover materials are used as fiber raw materials and are subjected to presteaming for 1 section, wood chip washing, dehydration and presteaming for 2 sections;
carrying out 1-section extrusion fluffing, 1-section chemical liquid pre-soaking, 2-section extrusion fluffing and 2-section chemical liquid pre-soaking on the 2-section pre-steamed wood sheet material; the 1-section chemical liquid presoaking process adopts sodium hydroxide solution without using hydrogen peroxide, and the chemical reagents of the 2-section chemical liquid presoaking process are sodium hydroxide, hydrogen peroxide and sodium silicate;
carrying out 1-stage pulping, separation and cooling on the material presoaked by the 2-stage chemical liquid, 1-stage high-concentration bleaching of hydrogen peroxide, 1-stage dehydration, 2-stage high-concentration bleaching of hydrogen peroxide and 2-stage dehydration on the material;
performing latency elimination, pulp grinding, screening and concentration on the pulp after 2 sections of dehydration to prepare the chemical mechanical finished pulp, wherein the dust degree is not more than 50mm 2 K, and tear index greater than 3.5mN.m 2 /g。
2. A pulping process according to claim 1, characterized in that the wood chips are washed with water at a temperature of 70-80 ℃ and optionally with paper machine white water.
3. A pulping process according to claim 2, characterized in that the exhaust temperatures of the 1-stage presteaming and the 2-stage presteaming are independently 80-90 ℃.
4. The pulping process of claim 1, wherein the 1 stage extrusion fluffing and the 2 stage extrusion fluffing are both high load MSD extrusions, and the speed is not higher than 50rpm.
5. The pulping process according to claim 4, wherein in the 1-stage chemical liquid preimpregnation process, the dosage of sodium hydroxide to absolute dry pulp is 0.1-0.5%, and the steam exhaust temperature is 70-90 ℃;
in the 2-stage chemical liquid pre-dipping process, the dosage of sodium hydroxide to the oven dry pulp is 3.0-4.0%, the dosage of hydrogen peroxide to the oven dry pulp is 0.7-0.9%, and the dosage of sodium silicate to the oven dry pulp is 1.5-2.0%.
6. The pulping process according to claim 5, wherein in the 1-stage high-concentration hydrogen peroxide bleaching process, the dosage of NaOH to the oven dry pulp is 0.5-1.5%, and the dosage of hydrogen peroxide to the oven dry pulp is 2.0-3.0%;
in the 2-stage high-concentration hydrogen peroxide bleaching process, the dosage of NaOH to oven dry pulp is 0.2-0.5%, and the dosage of hydrogen peroxide to oven dry pulp is 0.2-0.4%.
7. The pulping process of claim 6, wherein the 1-stage and 2-stage high-intensity hydrogen peroxide bleaching both employ sodium silicate and do not employ magnesium sulfate; the bleaching temperature is independently 80-96 ℃.
8. A pulping process according to claim 7, wherein the 1-stage dewatering and the 2-stage dewatering are independently screw press dewatering.
9. Pulping process according to any of claims 1-8, characterized in thatCharacterized in that the chemi-mechanical end product pulp has a tear index of 4.0-4.2mN.m 2 (ii)/g, whiteness 80-85% ISO, freeness 130-310mL, and positive charge requirement 520 μ eq/L.
10. Use of a pulp obtained from a pulping process according to any of claims 1 to 9 for papermaking.
CN202211411971.6A 2022-11-11 2022-11-11 Pulping process and application of high-strength high-cleanliness chemi-mechanical pulp Pending CN115559145A (en)

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