A high-strength high-purity chemical pulp pulping process and application

Abstract

The present application relates to pulping technology field, the present application provides a kind of high-strength high-cleanliness chemical pulp's pulping process, with bamboo willow edge scrap as fiber raw material, after 1 stage pre-steaming, chip washing, dehydration, 2 stage pre-steaming;The wood chip material after 2 stage pre-steaming is 1 stage extrusion and is dissolved, 1 stage chemical liquid pre-impregnation, 2 stage extrusion and is dissolved, 2 stage chemical liquid pre-impregnation;1 stage chemical liquid pre-impregnation uses sodium hydroxide solution and does not use hydrogen peroxide, the chemical reagent of 2 stage chemical liquid pre-impregnation process is sodium hydroxide, hydrogen peroxide and sodium silicate;Material after 2 stage chemical liquid pre-impregnation is 1 stage refining, separation, cooling, 1 stage high-concentration bleaching, 1 stage dehydration, 2 stage high-concentration bleaching, 2 stage dehydration;Pulp after 2 stage dehydration is latent, refining etc., and the finished product is prepared.This application process can produce high-strength, high-cleanliness chemical pulp, and the pulp cost is lower, and the pulp quality is better, and it is beneficial to high-end cultural paper etc. application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pulping, in particular to a pulping process of high-strength and high-cleanliness chemi-mechanical pulp and application. BACKGROUND

[0002] At present, the requirement of paper breaking length of domestic cultural paper teaching materials and light-coated paper products is generally above 4.0 km, and the requirement of paper breaking length of industrial laminated paper is above 7.0 km. However, the breaking length of most domestic chemi-mechanical pulp (hereinafter referred to as CMP) is about 3.0 km, and the tearing index is below 3.0 mN.m / g, which seriously affects the blending ratio of CMP in the above paper. 2

[0003] In wood resources, bamboo willow, also known as fast-growing bamboo willow, is a tree species mainly planted in Hunan and Hubei regions of China, and is mainly concentrated in the building decoration industry. The bamboo willow has light wood color and lower density than poplar, so it is very suitable as a fiber raw material for CMP. However, the strength and other qualities of the pulp made of bamboo willow fiber raw material still need to be further improved. SUMMARY

[0004] Therefore, the present application provides a pulping process of high-strength and high-cleanliness CMP and application. The present application can produce high-strength and high-cleanliness CMP, has lower pulping cost, better pulp quality, and is beneficial to the production of high-end cultural paper.

[0005] The present application provides a pulping process of high-strength and high-cleanliness CMP, which comprises the following steps:

[0006] The bamboo willow edge material is used as a fiber raw material, and is subjected to 1-stage pre-steaming, wood chip washing, dehydration, and 2-stage pre-steaming.

[0007] The wood chip material after 2-stage pre-steaming is subjected to 1-stage extrusion and defibration, 1-stage chemical liquid pre-soaking, 2-stage extrusion and defibration, and 2-stage chemical liquid pre-soaking. The 1-stage chemical liquid pre-soaking uses sodium hydroxide solution without using hydrogen peroxide, and the chemical reagent in the 2-stage chemical liquid pre-soaking process is sodium hydroxide, hydrogen peroxide and sodium silicate.

[0008] The material subjected to 2-stage chemical liquid pre-soaking is subjected to 1-stage grinding, separation, cooling, 1-stage high-concentration hydrogen peroxide bleaching, 1-stage dehydration, 2-stage high-concentration hydrogen peroxide bleaching, and 2-stage dehydration.

[0009] ​The 2nd dehydrated pulp is subjected to latent elimination, refining, screening and concentration to obtain the chemical mechanical finished pulp, with dust content of not more than 50 mm 2 / k, and a tear index greater than 3.5 mN.m 2 / g.

[0010] Preferably, the wood chip washing water temperature is 70-80 DEG C, and white water of a paper machine can also be introduced for washing.

[0011] Preferably, the exhaust temperature of the 1st pre-steaming and the 2nd pre-steaming is independently 80-90 DEG C.

[0012] Preferably, the 1st and 2nd extrusion disintegration are both high-load MSD extrusion, with a speed of not higher than 50 rpm.

[0013] Preferably, in the 1st chemical liquor pre-impregnation process, the absolute dry pulp consumption of sodium hydroxide is 0.1-0.5%, and the exhaust temperature is 70-90 DEG C.

[0014] In the 2nd chemical liquor pre-impregnation process, the absolute dry pulp consumption of sodium hydroxide is 3.0-4.0%, the absolute dry pulp consumption of hydrogen peroxide is 0.7-0.9%, and the absolute dry pulp consumption of sodium silicate is 1.5-2.0%.

[0015] Preferably, in the 1st hydrogen peroxide high-concentration bleaching process, the absolute dry pulp consumption of NaOH is 0.5-1.5%, and the absolute dry pulp consumption of hydrogen peroxide is 2.0-3.0%.

[0016] In the 2nd hydrogen peroxide high-concentration bleaching process, the absolute dry pulp consumption of NaOH is 0.2-0.5%, and the absolute dry pulp consumption of hydrogen peroxide is 0.2-0.4%.

[0017] Preferably, the 1st and 2nd hydrogen peroxide high-concentration bleaching processes both use sodium silicate, and do not use magnesium sulfate; and the bleaching temperature is independently 80-96 DEG C.

[0018] Preferably, the 1st and 2nd dehydrations are independently spiral press dehydrations.

[0019] Preferably, the chemical mechanical finished pulp has a tear index of 4.0-4.2 mN.m 2 / g, a brightness of 80-85% ISO, a freeness of 130-310 mL, and a cationic demand of 520 mu eq / L.

[0020] The application provides application of the pulp obtained by the pulping process as described above in papermaking.

[0021] The main innovation points and advantages of the pulp production process of the application include: using edge and corner bamboo willow raw materials for pulp production, breaking the dependence of traditional chemical pulp on poplar, responding to the national policy of using forestry three leftovers, and realizing the transformation of raw materials from resource type to waste utilization type; the application uses edge and corner bamboo willow in the APMP process, does not use H2O2 in the first stage of pre-soaking, and changes the traditional single-stage hydrogen peroxide bleaching to two-stage bleaching, which reduces the consumption of chemicals and improves the stability of whiteness. The application solves the problem of easy cutting of chemical pulp by technical optimization, effectively retains fiber strength, and has good bulkiness, which significantly improves the effect of chemical pulp ratio. Through in-depth research and innovation, the application is the first in China to use bamboo willow as raw material to produce high-strength chemical pulp, and the dust index of the pulp is good. The technology uses the edge and corner leftovers of bamboo willow in the furniture board industry as raw materials, and develops process technology and process parameters according to the characteristics of the raw materials, breaks the dependence of traditional chemical pulp on poplar and eucalyptus, effectively broadens the raw material resources of chemical pulp, alleviates the pressure of insufficient raw material supply, and can better improve the quality of chemical pulp, reduce production costs, and fully meet the production requirements of high-grade cultural paper and the like. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The production process flowchart of some embodiments of the application. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0024] The application provides a pulp production process of high-strength and high-cleanliness chemical pulp, which uses bamboo willow edge and corner materials as fiber raw materials, and the process steps include: first through 1-stage pre-steaming, wood chip washing, dehydration, 2-stage pre-steaming; the wood chip material after 2-stage pre-steaming is subjected to 1-stage extrusion and defibration, 1-stage chemical liquid pre-soaking, 2-stage extrusion and defibration, and 2-stage chemical liquid pre-soaking; the 1-stage chemical liquid pre-soaking uses sodium hydroxide solution and does not use hydrogen peroxide, and the chemical reagent in the 2-stage chemical liquid pre-soaking process is sodium hydroxide, hydrogen peroxide and sodium silicate; the material after 2-stage chemical liquid pre-soaking is subjected to 1-stage refining, separation, cooling, 1-stage high-concentration hydrogen peroxide bleaching, 1-stage dehydration, 2-stage high-concentration hydrogen peroxide bleaching and 2-stage dehydration; the pulp after 2-stage dehydration is subjected to latent heat elimination, refining, screening and concentration to obtain the chemical mechanical finished pulp, the dust degree of which is not more than 50 mm 2 / k, and the tear index is greater than 3.5 mN.m 2 / g.

[0025] In view of the deficiencies of the prior art, the present application studies a high-quality chemi-mechanical pulp with low raw material price, low chemical consumption and high strength, which is beneficial to large-scale popularization and application.

[0026] Referring to Figure 1 , Figure 1 The present application is a production process flowchart for some embodiments. The prepared edge and corner bamboo willow wood chips are screened first, and then are conveyed to a wood chip bin for production use. The present application breaks the dependence of traditional chemi-mechanical pulp on poplar, eucalyptus and acacia, and responds to the national policy of using forestry three leftovers. The wood chips used in the present application are bamboo willow edge and corner wood chips (or edge and corner bamboo willow wood chips). Bamboo willow has a relatively small density, and the main material is mainly used as a frame board for high-grade home furnishing and a board for high-grade decoration material (the trunk of bamboo willow is first peeled and the outer layer is cut off by a machine, and the tree core is reserved, and according to the needs of furniture, some are cut into squares and some are cut into circles). The present application uses the leftover materials of bamboo willow in the home furnishing industry for pulping and papermaking. The bamboo willow board waste and leftover materials are mainly leftover materials after peeling and other processes of the main material rotary cutting, which is usually a small part of the trunk close to the phloem part, and has less bark impurities. The leftover materials are sent to a biomass power plant for fuel before, and the present application is the first to use bamboo willow leftover materials as raw materials to produce high-strength and high-quality chemi-mechanical pulp.

[0027] The characteristics of the pulping fiber raw material in the specific embodiments of the present application include that the wood chip proportion is 100% bamboo willow leftover material, the wood chip specification is that the wood chip length is 19-25 mm, the thickness is 4.0±1 mm, the wood chip qualified rate is >=80% (mass percentage), and the bark rate is <=0.5%. If the bark rate exceeds 0.5%, the bark dust cannot be removed during the pulping process, and there are many black spots on the paper surface. The wood chip moisture content is >=38%. The subsequent process flow is briefly described as follows: wood chip bin→1# pre-steaming bin→wood chip washing→2# pre-steaming bin.

[0028] For the 1st pre-steaming and the 2nd pre-steaming, the corresponding wood chip pre-steaming bins are provided with metering screws, and the material level can be 40-60%. The exhaust port temperature is independently 80-90℃. A wood chip washing machine is used between 1# and 2# pre-steaming. The wood chip washing after the 1st pre-steaming is washed, and the washing water temperature is preferably 70-80℃. Then the wood chips are pumped to a single screw dewatering machine through a wood chip mixing tank. The present application uses bamboo willow leftover material for pulping, which can increase the wood chip washing water temperature, strengthen the water absorption and swelling of the wood chip washing process, improve the moisture content of the wood chip, and facilitate subsequent processing. In addition, white water of a paper machine can be introduced into the workshop to realize the step-by-step forward movement of the white water, and the water at the frontmost step is used for wood chip washing.

[0029] The wood chip material after two-stage pre-steaming is subjected to one-stage extrusion and defibration by a first wood chip extruder, and then is subjected to one-stage chemical liquor pre-steaming in a first pre-steamer and a reaction bin, and then is subjected to two-stage extrusion and defibration and two-stage chemical liquor pre-steaming after a discharge screw, to obtain pre-steamed material. The pre-steamer is a liquor adding point.

[0030] In the embodiment of the present application, the speed of the first wood chip extruder (MSD) is not higher than 50 rpm, the torque is 60-100 kN.m, the power is 600-700 kw, and the torque control is prior. The liquid level of the first pre-steamer can be 20-30%. The present application is different from the conventional process in that H2O2 is not used in the one-stage pre-steaming, and the use amount of NaOH to the absolutely dry pulp is preferably controlled to be 0.1-0.5%, and more preferably 0.5%. The material level of the first reaction bin is 20-30%, and the steam discharge temperature is 70-90℃. As preferred, the speed of the second wood chip extruder (MSD) in the embodiment of the present application is not higher than 50 rpm, the torque is 45-80 kN.m, the power is 500-700 kw, and the torque control is prior. The motor and filter plate of the two MSDs are optimized in the embodiment of the present application. The first MSD mainly extrudes and splits the wood chips, and the second MSD extrudes the wood chips into small strips, and can quickly and effectively dewater under high load.

[0031] Meanwhile, the liquid level of the second pre-steamer can be 20-30%, the use amount of NaOH to the absolutely dry pulp is preferably controlled to be 3.0-4.0%, the use amount of H2O2 to the absolutely dry pulp is 0.7-0.9%, and more preferably 0.8%, and the use amount of Na2SiO3 to the absolutely dry pulp is 1.5-2.0%. The process does not use Mg(OH)2 and MgSO4. The material level of the second reaction bin is 60-80%, and the steam discharge temperature is 70-90℃. According to the relatively small density of bamboo and willow, the pre-steaming effect is improved to improve the extrusion effect, which is beneficial to improve the grinding quality and reduce the grinding energy consumption.

[0032] After the completion of the second pre-steaming reaction, the obtained material can be subjected to a second discharge screw, a third discharge screw, a horizontal conveying screw, and a first side feeding screw, so as to enter the grinding, bleaching and other processes. The process flow is mainly as follows: one-stage high-concentration grinding (3# bleaching liquor adding point)→a first cyclone separator→a cooling screw→a first high-concentration bleaching tower→a first dewatering thickener→a heating screw (4# bleaching liquor adding point)→a second high-concentration bleaching tower→a second dewatering thickener.

[0033] In view of the soft material quality and easy penetration of bamboo and willow edge scraps, the embodiment of the present application preferably adopts only one high-concentration grinding equipment for conventional grinding before bleaching, and the grinding blade selection can also be optimized to prolong the residence time in the grinding machine and improve the splitting effect. The embodiment of the present application promotes the splitting of wood chips instead of cutting, and fully retains the strength.

[0034] The embodiment of the present application is based on previous use of poplar APMP pulping, and the traditional single-stage high-concentration bleaching with alkaline hydrogen peroxide is changed to two-stage bleaching, which can reduce chemical consumption while improving the stability of whiteness. A set of screw press equipment is added before each pulp tower to increase the concentration of the tower and reduce chemical consumption. In addition, no chelating agents such as Mg(OH)2, MgSO4, EDTA, etc. are used in the whole process.

[0035] Specifically, the process conditions of the 1st bleaching stage include: the chemical liquid adding point is the 1st disc mill spray pipe, the NaOH dosage for absolute dry pulp is preferably 0.5-1.5%, the H2O2 dosage for absolute dry pulp is preferably 2.0-3.0%, and the Na2SiO3 dosage for absolute dry pulp can be 0.5-2.0%; the bleaching concentration can be 25-40%, the bleaching temperature is preferably 90-96℃, and the material level control is 35-60%. The 2nd bleaching stage: the chemical liquid adding point is the heating screw, the NaOH dosage for absolute dry pulp is preferably 0.2-0.5%, the H2O2 dosage for absolute dry pulp is preferably 0.2-0.4%, and the Na2SiO3 dosage for absolute dry 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 control is 60-80%. For example, for one ton of pulp, 1000kg*2% = 20kg, 20-30kg of hydrogen peroxide can be added in the 1st bleaching stage, and the amount of chemicals added is relative to the weight of absolute dry pulp. In combination with the above pre-soaking process, the present embodiment can significantly reduce the consumption of other chemicals by appropriately increasing the alkali retention strength. Moreover, in the case of the same bleaching endpoint whiteness, the present embodiment can increase the whiteness by adding a certain amount of hydrogen peroxide at multiple points in a step-by-step manner, and the bleaching chemical consumption is significantly reduced.

[0036] As a preferred, the 1st dewatering and the 2nd dewatering are both in the way of screw press dewatering, that is, the 1st dewatering (concentration) and the 2nd dewatering (concentration) are respectively 1st screw press dewatering and 2nd screw press dewatering. In the preferred embodiment of the present application, the two-stage high-load MSD extrusion combined with the two-stage screw press extrusion process can efficiently discharge organic extractives from wood chips and high-density extrusion of alkali extractives, thereby reducing the burden of bleaching, etc. For example, the waste liquid of the upper stage of the two-stage screw press extrusion makes the bleaching agent more effective. The process realizes 2-stage extrusion, 1-stage grinding, and 2-stage screw press extrusion, effectively removing aromatic substances, triglycerides, pentosan, etc. from wood chips.

[0037] 2 stage hydrogen peroxide high concentration bleaching, 2 stage dewatering, the production process of the embodiment of the application can be: latent pool → 1# conical mill → 2# conical mill → 3# double disc mill → intermediate pulp pool → multi-stage pressure screen → good pulp pool → multi-disc thickener → medium concentration storage tower (pH is adjusted to 7-7.5 by sulfuric acid). The process conditions specifically include: the concentration of the 1# 2# 3# low concentration mill of the second stage is 4.5-5.5%, the grinding power is 600-1500kw, and the unit energy consumption is 20-60kw / admt. The operating conditions of the 1-3# pressure screen: the pressure screen gap is 0.25mm; the inlet pulp concentration is 1.2-1.8%; the inlet pressure is 2.5-4.0bar; the inlet and outlet pressure difference (Pout-Pin) is not more than 50kPa; the residue pulp / good pulp flow ratio can be 35-40%; the operating load is 40-50%; the good pulp flow ratio of the 2# / 1# pressure screen is 28-40%.

[0038] The embodiment of the application effectively broadens the pulp raw material resources, innovatively optimizes the pulp production process according to the unique properties of bamboo and willow, has lower pulp production cost, and has better pulp quality. The application uses a process of 2-stage MSD extrusion + 2-stage screw press + 2-stage bleaching, so that the pulp raw material cost is lower; the produced chemi-mechanical pulp ensures high strength, and the remaining indexes meet the needs of cultural paper, while having a lower cost advantage.

[0039] The embodiment of the application mainly tracks the physical strength indexes such as breaking length (tensile index) and tearing index according to the characteristics of bamboo and willow fibers and fully analyzes the characteristics of bamboo and willow edge scraps, wherein the tearing index is greater than 3.5mN.m 2 / g, and the beating degree of the final pulp is adjusted (such as the freeness is preferably controlled at 130-310ml), so that the pulp quality is better and the energy consumption is lower. Moreover, the dust index of the finished pulp obtained by the embodiment of the application is very good, the dust degree is 0-50mm 2 / k, which can be said to be "zero black point" dust, while other wood chip pulping often has small black point dust of tree bark on the paper surface due to incomplete removal of the tree bark. The application mainly uses low-cost bamboo and willow edge scraps to replace high-cost poplar which is limited by environmental protection, and 100% of the forestry three remaining materials are used to produce high-strength and high-cleanliness pulp, and the quality characteristics can be consistent with the traditional poplar APMP standard.

[0040] In the specific embodiment of the application, the tearing index of the chemi-mechanical finished pulp is 4.0-4.2mN.m 2 / g, the brightness is 80-85%ISO, the freeness can be 130-310mL, and the cationic demand is 520μeq / L. In addition, the tensile index of the finished pulp can reach 35-47N·m / g; the bulkiness is 2.55-2.93cm 3Fiber length 0.79-0.86mm, dust degree 0-50mm 2 / k.

[0041] From the pulp quality, the indexes of the embodiment of the application are greatly improved on the basis of the original process, especially the demand of positive charge, dust, and tear index, that is, the requirements of high strength and high cleanliness, which is beneficial to the high-end cultural paper and the like. Therefore, the application also provides application of the pulp obtained by the pulping process as described above in papermaking.

[0042] In order to better understand the technical content of the application, the following specific examples are provided to further illustrate the application. Unless otherwise specified, the proportions in the application are mass proportions.

[0043] Example 1

[0044] The application first screens the beaten corner bamboo willow wood chips, and then sends them for production.

[0045] (1) The characteristics of the pulping fiber raw material: the proportion of wood chips is 100% corner bamboo willow; the wood chip specifications include: wood chip length 19-25mm, thickness 4.0±1mm, wood chip qualified rate ≧80%(mass percentage), bark rate ≦0.5%, and wood chip moisture ≧38%.

[0046] (2) Referring to Figure 1 The production process thereof is briefly described as follows: raw material wood chips → wood chip screen → wood chip bin → 1# pre-steaming bin → wood chip washing → 2# pre-steaming bin → 1st stage extrusion → 1# pre-soaking device (1# pre-soaking liquor is added) → 2nd stage extrusion → 2# pre-soaking device (2# pre-soaking liquor is added) → 1st stage refining (3# bleaching liquor is added) → 1# cyclone separator → cooling screw → 1st stage high-concentration bleaching tower → 1# dehydration thickener → heating screw (4# bleaching liquor is added) → 2nd stage high-concentration bleaching tower → 2# dehydration thickener → latent pool → 1# conical mill → 2# conical mill → 3# double-disc mill → intermediate pool → pressure screen → good pulp pool → multi-disc → medium-concentration storage tower (pH is adjusted to 7-7.5 by sulfuric acid).

[0047] (3) Main production process technical conditions: (A) Wood chip pre-steaming bin level 40-60%, exhaust port temperature 80-90°C; wood chip washing water temperature 70-80°C; 1# wood chip extruder (MSD): speed 40-45 rpm, torque 60-100 kN.m, power 600-700 kw, torque control priority; 1# pre-soaker: liquid level 20-30%, NaOH dosage to absolute dry pulp 0.5%, 1# reaction bin level 20-30%, exhaust temperature 70-90°C; (B) 2# wood chip extruder (MSD): speed 40-45 rpm, torque 45-80 kN.m, power 500-700 kw, torque control priority; 2# pre-soaker: liquid level 20-30%, NaOH dosage to absolute dry pulp 3.0-4.0%, H2O2 dosage to absolute dry pulp 0.8%, Na2SiO3 dosage to absolute dry pulp 1.5-2.0%, 2# reaction bin level 60-80%, exhaust temperature 70-90°C; (C) Conventional 1-stage high consistency refining; 1-stage bleaching: chemical addition point is 1# disc refiner spray pipe, NaOH dosage to absolute dry pulp: 0.5-1.5%, H2O2 dosage to absolute dry pulp: 2.0-3.0%, Na2SiO3 dosage to absolute dry pulp: 0.5-2.0%, bleaching consistency: 25-40%, bleaching temperature: 90-96°C, level control: 35-60%; (D) 2-stage bleaching: chemical addition point is heating screw, NaOH dosage to absolute dry pulp: 0.2-0.5%, H2O2 dosage to absolute dry pulp: 0.2-0.4%, Na2SiO3 dosage to absolute dry pulp: 0.4-1.0%, bleaching consistency: 25-35%, bleaching temperature: 80-90°C, level control: 60-80%; (E) Two-stage 1# 2# 3# low consistency refining, refining consistency 4.5-5.5%, refining power 600-1500 kw, unit energy consumption 20-60 kw / admt; (F) 1-3# pressure screen operating conditions: pressure screen screen gap 0.25 mm, inlet consistency 1.2-1.8%; inlet pressure 2.5-4.0 bar; inlet and outlet pressure difference (Pout-Pin) no more than 50 kPa; slurry / good pulp flow ratio 35-40%; operating load 40-50%; 2# / 1# pressure screen good pulp flow ratio 28-40%.

[0048] (4) Pulp quality characteristics after bleaching and comparison:

[0049] The pulp whiteness is 80-85% ISO, freeness is 130-310 ml, breaking length is 3.55-4.74 km (tensile index is 35-47 N.m / g), and the breaking length of general chemical pulp is below 3.0 km;

[0050] The pulp bulkiness of the present application is 2.55-2.93 cm 3 / g, fiber length is 0.79-0.86 mm, and the fiber length of general hardwood chemical pulp is about 0.6 mm;

[0051] The pulp slurry of the present application has a dust content of 0-50mm 2 / kg, fiber bundle content of 0-0.2%, and a tear index of 4.0-4.2mN.m 2 / g; the general chemical pulp has a tear index of 3.0mN.m 2 / g or below;

[0052] The pulp slurry of the present application has a positive charge demand (PCD) of 520μeq / L, and the general hardwood chemical pulp has a PCD of about 2000μeq / L.

[0053] The finished pulp is analyzed in terms of beating degree, fiber condition and strength in the present embodiment, including screening, fiber analyzer and special instrument detection, and the results are as follows.

[0054] Table 1: Screening results of the pulp slurry

[0055]

[0056]

[0057] Table 2: Fiber condition of the pulp slurry

[0058]

[0059] Table 3: Strength index of the pulp slurry

[0060]

[0061] The beating degree of the pulp slurry can be converted into freeness according to the conversion table; the beating degree is an index of the drainage performance of the pulp properties, and different comprehensive production control is performed according to different paper machines and production paper requirements, other indexes, etc. As can be seen from the above, the present application solves the problem of easy cutting of the chemical pulp, effectively retains the fiber strength, and has the advantage of good bulkiness, which is very significant for improving the effect of chemical pulp ratio. The pulp-making process of the present application breaks the dependence of traditional chemical pulp on poplar and eucalyptus, effectively broadens the raw material resources of chemical pulp, and relieves the pressure of insufficient raw material supply.

[0062] Compared with the original process, the present application greatly improves the production process, updates the process, reduces the cost (for example, 200 degrees of electricity can be saved per ton of pulp, chemical consumption is reduced), and has better pulp-making quality characteristics, which can meet the requirements of high-strength and high-cleanliness chemical pulp, can be used for high-end cultural paper, etc., and is the first in China.

[0063] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea. The above description is only the preferred implementation manner of the present application, and it should be noted that, due to the limited expression of the text, there are objectively infinite specific structures, and for ordinary skilled persons in the technical field, some improvements, refinements or changes can be made without departing from the principles of the present application, and the above technical features can also be combined in an appropriate manner; the improvements, refinements, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, shall be regarded as the protection scope of the present application.

Claims

1. A pulping process for high-strength, high- cleanliness chemi-mechanical pulp, characterized in that, It comprises the following steps: The bamboo willow edge scraps are used as the fiber raw material, and are subjected to 1st pre-steaming, wood chip washing, dehydration, 2nd pre-steaming; The wood chip washing is performed at a water temperature of 70-80℃, and white water of a paper machine is introduced for washing; The wood chip material after the 2nd pre-steaming is subjected to 1st extrusion defibration, 1st chemical liquor pre-dipping, 2nd extrusion defibration, and 2nd chemical liquor pre-dipping; the 1st chemical liquor pre-dipping uses sodium hydroxide solution and does not use hydrogen peroxide, and the chemical reagents in the 2nd chemical liquor pre-dipping process are sodium hydroxide, hydrogen peroxide and sodium silicate; in the 1st chemical liquor pre-dipping process, the absolute dry pulp consumption of sodium hydroxide is 0.1-0.5%; in the 2nd chemical liquor pre-dipping process, the absolute dry pulp consumption of sodium hydroxide is 3.0-4.0%, and the absolute dry pulp consumption of hydrogen peroxide is 0.7-0.9%; the 1st extrusion defibration and the 2nd extrusion defibration are both high-load MSD extrusion, and the speeds are both not higher than 50rpm; The material after the 2nd chemical liquor pre-dipping is subjected to 1st refining, separation, cooling, 1st high-concentration hydrogen peroxide bleaching, 1st dehydration, 2nd high-concentration hydrogen peroxide bleaching, and 2nd dehydration; The 2nd dehydrated slurry is treated by eliminating, grinding, screening and concentrating to obtain the chemical mechanical finished pulp with dust content not more than 50 mm 2 / k, and the tear index is greater than 3.5 mN.m 2 / g; the whole process does not use Mg(OH)2, MgSO4 and EDTA chelating agent; In the 1st high-concentration hydrogen peroxide bleaching process, the absolute dry pulp consumption of NaOH is 0.5-1.5%, the absolute dry pulp consumption of hydrogen peroxide is 2.0-3.0%, and the absolute dry pulp consumption of Na2SiO3 is 0.5-2.0%; In the 2nd high-concentration hydrogen peroxide bleaching process, the absolute dry pulp consumption of NaOH is 0.2-0.5%, the absolute dry pulp consumption of hydrogen peroxide is 0.2-0.4%, and the absolute dry pulp consumption of Na2SiO3 is 0.4-1.0%.

2. The pulping process according to claim 1, characterized in that, The exhaust steam temperatures of the 1st pre-steaming and the 2nd pre-steaming are independently 80-90℃.

3. The pulping process according to claim 1, characterized in that, In the 1st chemical liquor pre-dipping process, the exhaust steam temperature is 70-90℃; In the 2nd chemical liquor pre-dipping process, the absolute dry pulp consumption of sodium silicate is 1.5-2.0%.

4. The pulping process according to claim 3, characterized in that, Both the 1st high-concentration hydrogen peroxide bleaching and the 2nd high-concentration hydrogen peroxide bleaching use sodium silicate and do not use magnesium sulfate; the bleaching temperatures are independently 80-96℃.

5. The pulping process according to claim 4, characterized in that, Both the 1st dehydration and the 2nd dehydration are independently the screw press dewatering mode.

6. The pulping process according to any one of claims 1-5, characterized in that, The chemical mechanical finished pulp has a tear index of 4.0-4.2 mN.m 2 / g, a brightness of 80-85% ISO, a freeness of 130-310 mL, and a positive charge demand of 520 μeq / L.

7. Application of the pulp obtained by the pulping process according to any one of claims 1-6 in papermaking.

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