阅读说明：本技术 一种造纸浆改性为莱赛尔纤维专用浆粕的制备方法 (Preparation method for modifying papermaking pulp into pulp special for lyocell fibers ) 是由 王培荣 于 2021-01-07 设计创作，主要内容包括：一种造纸浆改性为莱赛尔纤维专用浆粕的制备方法,属于浆粕制浆制作技术领域。含有以下步骤：水力碎浆备料步骤、压榨脱水提浓步骤、反应塔水解步骤、第一多段洗涤步骤、碱塔精制步骤、压榨脱碱步骤、第二多段洗涤步骤、反应塔降聚步骤、第三多段洗涤步骤、酸化及络合处理步骤、第四多段洗涤步骤及抄造成形步骤。本发明的优点是：没有碱性蒸煮过程,不会产生高COD含量的蒸煮黑液或者红液,生产过程中的废水COD≤500,易于处理。在碱精制后的碱液可以经过膜处理,碱液可以循环使用,废物可以提取半纤维素及木质素等附加物。(A preparation method for modifying papermaking pulp into pulp special for lyocell fibers belongs to the technical field of pulp pulping. Comprises the following steps: the method comprises the steps of hydraulic pulping and material preparation, squeezing, dewatering and concentrating, reaction tower hydrolysis, a first multi-section washing step, alkali tower refining, squeezing and dealkalization, a second multi-section washing step, reaction tower polymerization reduction, a third multi-section washing step, acidification and complexation treatment, a fourth multi-section washing step and paper making and forming. The invention has the advantages that: the alkaline cooking process is not needed, the cooking black liquor or red liquor with high COD content is not generated, the COD of the wastewater in the production process is less than or equal to 500, and the treatment is easy. The alkali liquor after alkali refining can be subjected to membrane treatment, the alkali liquor can be recycled, and the waste can be used for extracting additives such as hemicellulose, lignin and the like.)

1. A preparation method for modifying papermaking pulp into pulp special for lyocell fibers is characterized by comprising the following steps: the method comprises the steps of hydraulic pulping and material preparation, squeezing, dewatering and concentrating, reaction tower hydrolysis, a first multi-section washing step, alkali tower refining, squeezing and dealkalization, a second multi-section washing step, reaction tower polymerization reduction, a third multi-section washing step, acidification and complexation treatment, a fourth multi-section washing step and paper making and forming.

2. The method for preparing the pulp special for the modification of the papermaking pulp into the lyocell fiber according to claim 1, wherein the hydraulic pulp crushing preparation step comprises: putting a platy paper-making wood pulp bag on a chain plate conveyor by using a bag clamping vehicle, manually shearing, extracting and removing packaging iron wires, conveying the wood pulp bag into a hydraulic pulper by using the chain plate conveyor, adding a certain amount of water in advance, and enabling the pulp plate to collide with a blade by using a centrifugal force generated by strong rotation of a rotor of the hydraulic pulper and be thrown to the edge of a groove body to form a horizontal vortex; and the pulp rises along the edge and falls back to the turntable, then a negative pressure area is formed in the center of the groove body, and the circulation forms a vertical vortex, so that the pulp and the like are contacted with the blade back and forth and are continuously disintegrated, and the pulp is broken into pulp porridge with the concentration of about 5 percent so as to be convenient for pumping.

3. The method for preparing the pulp special for the modification of the papermaking pulp into the lyocell fiber according to claim 1, wherein the step of press dewatering and concentration comprises the following steps: the slurry porridge with the concentration of about 5 percent is pumped to a mesh belt type dehydrator or a roller type pulp extruder by a low-concentration slurry pump, is strongly dehydrated to the dryness of about 30 percent by mechanical squeezing and is sent to a hydrolysis reaction tower;

a hydrolysis step of a reaction tower: the reaction tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the reaction tower, slurry is fed in and discharged out from the upper part, the hydrolysis tower is used for intermittent production, namely, the feeding is stopped after the slurry is fully fed in, the hydrolysis is carried out, and the discharged material is discharged and emptied to enter the next cycle after the hydrolysis is finished; during hydrolysis reaction, hydrolysate is pumped from the middle part and the bottom part of the hydrolysis tower and pumped from the upper part of the hydrolysis tower to realize strong circulation; the hydrolysate can be desalted water, or hydrochloric acid and inorganic acid of sulfuric acid; and hydrolyzing with desalted water at 150-175 ℃ for 30-180 min.

4. The method for preparing the pulp special for the modified lyocell fiber of the papermaking pulp according to claim 1, wherein the first multi-stage washing step comprises: the hydrolyzed pulp is pumped into a mesh belt type high-speed pulp washer or a roller type pulp extruder to realize mechanical dehydration, water addition replacement and multiple cycles.

5. The method for preparing the pulp special for the modification of the papermaking pulp into the lyocell fiber according to claim 1, wherein the alkali tower refining step comprises: the alkali tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the alkali tower, slurry enters from the top and exits from the bottom, the alkali tower is produced continuously, a certain liquid level is reserved, and the slurry enters and exits simultaneously; caustic soda solution for alkali refining, wherein the alkali content is 60-120 mg/L; temperature: 30-70 ℃; alkali refining time: 30-120 min; concentrating the pulp: 8 to 12 percent; oxygen can be added for strengthening in the alkali refining process.

6. The method for preparing the pulp special for the modification of the papermaking pulp into the lyocell fiber according to claim 1, wherein the pressing and dealkalizing steps are as follows: the hydrolyzed slurry is pumped into a double-mesh belt type or double-roll type squeezer, alkali liquor is extracted through mechanical extrusion, and the extracted alkali liquor can be recycled after being treated by a membrane removal treatment system.

7. The method for preparing the pulp special for the modified lyocell fiber of the papermaking pulp according to claim 1, wherein the second multi-stage washing step comprises: similar to the multi-stage washing after hydrolysis, the dealkalized pulp is diluted by adding water to be pulp congee with the concentration of about 5 percent and is sent into a mesh belt type high-speed pulp washer or a roller type pulp extruder by a pump to realize mechanical dehydration, water addition replacement and multiple cycles, thereby realizing the pulp washing mode of combining strong dehydration and replacement, and having high extraction rate and high washing factor.

8. The method for preparing the pulp special for the modified lyocell fiber of the papermaking pulp according to claim 1, wherein the step of reducing polymerization in the reaction tower comprises: the reaction tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the reaction tower, slurry enters from the lower part and flows out from the upper part, continuous production is carried out, and the reaction liquid medicine is hypochlorite or hydrogen peroxide; before the pump is sent into the reaction tower, a mixer is arranged in front of the pump, and reaction liquid medicine, steam, alkali liquor and the like are added; during the polymerization reduction reaction, the slurry is concentrated: 8% -12%, PH: 9-14, wherein the dosage of the hydrogen peroxide is 0.5% -5%; the temperature is 40-100 ℃, and the time is 30-180 min; a small amount of chelating agent aid may be added during the precipitation stage.

9. The method for preparing the pulp special for the modified lyocell fiber of the papermaking pulp according to claim 1, wherein the third multi-stage washing step comprises: adding water into the slurry after the precipitation to dilute the slurry to about 5 percent of concentration, pumping the slurry into a mesh belt type high-speed pulp washer or a roller type pulp extruder by a pump to realize mechanical dehydration, water addition replacement and multiple circulation, and realizing a pulp washing mode of combining strong dehydration and replacement.

10. The method for preparing the pulp special for the modified lyocell fiber of the papermaking pulp according to claim 1, wherein the acidification and complexation treatment steps are as follows: acidifying the slurry in an acidification tank or tower with inorganic acid sulfuric acid or hydrochloric acid; upon acidification, PH: 1-2, the temperature is 30-50 ℃, the time is 30-60 min, and a chelating agent or a complexing agent auxiliary agent is added after acidification;

a fourth multi-stage washing step: sending the acidified pulp into a mesh belt type high-speed pulp washer or a roller type pulp extruder through a pump to realize mechanical dehydration, water addition replacement and multiple cycles, and realizing a pulp washing mode of combining strong dehydration and replacement;

a papermaking forming step: the washed semi-finished pulp passes through a long net or a wet part of a clamping net, is distributed and formed in a low-concentration state, is dehydrated through a net part in a vacuum area, is mechanically pressed and dehydrated in a large roller area to form a pulp board with 50% dryness, is dried into a formed pulp board with 90% dryness through a plurality of drying cylinders or an air cushion type dryer, is cut into plate-shaped pulp with 800x600 specification through a paper cutter, and is packed and bundled into a finished product to be packaged and put in storage; and (5) drying the finished product.

Technical Field

The invention belongs to the technical field of pulp making, and relates to a preparation method for modifying papermaking pulp into pulp special for lyocell fibers.

Background

Lyocell fiber (Lyocell) is commonly called as "velveteen", is made from natural plant fiber as a raw material, is known in the middle of the 90 s of the 20 th century, and is known as the most valuable product in artificial fiber history in the last half century. The Lyocell fiber has various excellent performances of natural fiber and synthetic fiber, Lyocell is green fiber, raw materials of Lyocell are inexhaustible cellulose in nature, a production process has no chemical reaction, a used solvent is nontoxic, the recovery rate of the solvent can reach more than 99%, and the production process is green and environment-friendly, so the Lyocell fiber is called as '21 st century green fiber'.

The lyocell fiber industry has monopoly status, the production technology is basically monopolized in foreign companies, the productivity is small, in recent years, along with further digestion and absorption of the lyocell fiber production technology by domestic enterprises, the lyocell fiber production technology slowly becomes a relatively mature solvent method regenerated cellulose fiber industrialized production technology, the single-line production capacity of a new project in China is further improved, the lyocell industry in China is steadily developed, and the capacity of 100 million tons of productivity is expected to be reached in the coming years.

The raw material for producing the special pulp for the lyocell fiber is wood, and because the market demand is low, the production factory is mainly in the states of America, south Africa and the like at present, the productivity is low, and the total yield is low; no manufacturers for producing the pulp special for the lyocell fiber exist in China. The domestic wood pulp is mainly dissolving pulp for making paper pulp and common viscose fiber.

1. Present production technology for making paper pulp by wood

Peeling raw wood, slicing by a slicer, putting the wood chips into a boiler, reacting with caustic soda or sulfate cooking liquor at a certain temperature and under a certain pressure to prepare coarse pulp, washing and screening the coarse pulp for multiple times, then putting the coarse pulp into a bleaching section, reacting with alkaline and neutral bleaching agents (the bleaching agents comprise alkaline hydrogen peroxide, hypochlorite, chlorine dioxide, oxygen, ozone and the like) for multiple times to prepare bleached pulp, washing and screening for multiple times, removing impurities, papermaking, forming, drying, slitting to prepare platy wood pulp, and packaging with a certain specification and weight, wherein the commercial pulp is called paper pulp.

2. Production technology of dissolving pulp for viscose fiber at present

Peeling raw wood, slicing by a slicer, allowing the wood chips to enter a No. 1 digester, performing high-temperature prehydrolysis, extracting polysaccharide, allowing the raw wood to enter a No. 2 digester again, reacting with caustic soda and sulfate cooking liquor at a certain temperature and under a certain pressure to obtain coarse pulp, washing and screening the coarse pulp for multiple times, allowing the coarse pulp to enter a bleaching section, allowing the coarse pulp to react with alkaline and neutral bleaching agents (such as alkaline hydrogen peroxide, hypochlorite, chlorine dioxide, oxygen, ozone and the like) for multiple times to obtain bleached pulp, washing and screening for multiple times, removing impurities, papermaking, forming, drying, and cutting to obtain the platy dissolved pulp.

3. Production technology of current foreign lyocell fiber special pulp

Peeling raw wood, slicing by a slicer, putting the wood chips into a digester, reacting with sulfite cooking liquor at a certain temperature and under a certain pressure to prepare coarse pulp, washing and screening the coarse pulp for multiple times, then putting the coarse pulp into a bleaching section, reacting with alkaline and neutral bleaching agents (the bleaching agents comprise alkaline hydrogen peroxide, chlorine dioxide, oxygen, ozone and the like) for multiple times, performing acid treatment or complexing treatment to prepare bleached pulp, washing and screening for multiple times, removing impurities, papermaking, forming, drying and slitting to prepare platy wood pulp which is special pulp for lyocell fibers.

The pulping method produces a large amount of malodorous gas and polluted wastewater in the production process, particularly in the high-temperature cooking stage, and has high chroma and heavy pollution.

The papermaking wood pulp can not be used for the production of lyocell fibers due to the low content of methyl cellulose, higher viscosity, high polymerization degree, and high content of hemicellulose, various ash contents and metal ions. The dissolving pulp for viscose fiber cannot be directly used for the production of lyocell fiber because of high metal ions and high polysaccharide content.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method for modifying papermaking pulp into special pulp for lyocell fibers.

A preparation method for modifying papermaking pulp into pulp special for lyocell fibers comprises the following steps: the method comprises the steps of hydraulic pulping and material preparation, squeezing, dewatering and concentrating, reaction tower hydrolysis, a first multi-section washing step, alkali tower refining, squeezing and dealkalization, a second multi-section washing step, reaction tower polymerization reduction, a third multi-section washing step, acidification and complexation treatment, a fourth multi-section washing step and paper making and forming.

The invention has the advantages that:

(1) provides a new method for producing the pulp special for the lyocell fiber;

(2) in the production process, an alkaline cooking process is not adopted, the cooking black liquor or red liquor with high COD content is not generated, the COD of the wastewater in the production process is less than or equal to 500, and the wastewater is easy to treat.

(3) The alkali liquor after alkali refining can be subjected to membrane treatment, the alkali liquor can be recycled, and the waste can be used for extracting additives such as hemicellulose, lignin and the like.

(4) The quality indexes of the pulp special for the lyocell fiber are as follows:

polymerization degree: 450-600, alpha cellulose is more than or equal to 90%, R10 is more than or equal to 90%, R18 is more than or equal to 93%, ash content is less than or equal to 0.1%, Fe is less than or equal to 2.0ppm, Ca is less than or equal to 50ppm, Mg is less than or equal to 50ppm, and whiteness is more than or equal to 92%.

Detailed Description

It will be apparent that those skilled in the art can make many modifications and variations based on the spirit of the present invention.

As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It will be understood that when an element, component or section is referred to as being "connected" to another element, component or section, it can be directly connected to the other element or section or intervening elements or sections may also be present. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art.

The following examples are further illustrative in order to facilitate the understanding of the embodiments, and the present invention is not limited to the examples.

Example 1:

a preparation method for modifying papermaking pulp into pulp special for lyocell fibers widens the production method of the pulp special for the lyocell fibers, reduces the investment scale of equipment and reduces the pollution load in the production of wood pulp.

A preparation method for modifying papermaking pulp into pulp special for lyocell fibers comprises the following steps:

hydraulic pulp crushing and material preparation: a platy paper-making-grade wood pulp bag (800x600x850, 220Kg) is placed on a chain plate conveyor by a bag clamping vehicle, package iron wires (steel belts) are removed by manual shearing and extraction, then the chain plate conveyor is conveyed into a hydraulic pulper (a certain amount of water is added in advance), and a pulp plate collides with a blade and is thrown to the edge of a groove body to form a horizontal vortex by the centrifugal force generated by the strong rotation of a rotor of the hydraulic pulper. And the pulp rises along the edge and falls back to the turntable, then a negative pressure area is formed in the center of the groove body, and the circulation forms a vertical vortex, so that the pulp and the like are contacted with the blade back and forth and are continuously disintegrated, and the pulp is broken into pulp porridge with the concentration of about 5 percent so as to be convenient for pumping.

Squeezing, dewatering and concentrating: the slurry gruel with the concentration of about 5 percent is pumped to a mesh belt type dehydrator or a roller type pulp extruder by a low-concentration slurry pump, is strongly dehydrated to the dryness of about 30 percent by mechanical squeezing, and is sent to a hydrolysis reaction tower.

A hydrolysis step of a reaction tower: the reaction tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the reaction tower, slurry is fed in and discharged out from the upper part, the hydrolysis tower is used for batch production, namely, the feeding is stopped after the slurry is fully fed in, the hydrolysis is carried out, and the discharged material is discharged and emptied into the next cycle after the hydrolysis is finished. During hydrolysis reaction, hydrolysate is pumped from the middle part and the bottom part of the hydrolysis tower and pumped from the upper part of the hydrolysis tower to realize strong circulation; the hydrolysate can be desalted water, or hydrochloric acid and inorganic sulfuric acid. Hydrolyzing with desalted water at 150-175 ℃ for 30-180 min;

a multi-stage washing step: the hydrolyzed pulp is pumped into a mesh belt type high-speed pulp washer or a roller type pulp extruder to realize mechanical dehydration, water addition replacement and multiple cycles, so that a pulp washing mode of combining powerful dehydration and replacement is realized, the extraction rate is high, and the washing factor is high;

alkali tower refining: the alkali tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the alkali tower, slurry enters from the top and exits from the bottom, and the alkali tower is produced continuously, keeps a certain liquid level and enters while exiting. Caustic soda solution for alkali refining, wherein the alkali content is 60-120 mg/L; temperature: 30 to 70 ℃. Alkali refining time: 30-120 min; concentrating the pulp: 8 to 12 percent; oxygen can be added for strengthening in the alkali refining process.

And (3) squeezing and dealkalizing: the hydrolyzed slurry is pumped into a double-mesh belt type or double-roll type squeezer, alkali liquor is extracted through mechanical extrusion, and the extracted alkali liquor can be recycled after being treated by a membrane removal treatment system.

A multi-stage washing step: similar to the multi-section washing after hydrolysis, the dealkalized pulp is diluted by adding water to be pulp congee with the concentration of about 5 percent, and is sent into a mesh belt type high-speed pulp washer or a roller type pulp extruder by a pump to realize mechanical dehydration, water addition replacement and multiple cycles, thereby realizing the pulp washing mode of combining strong dehydration and replacement, and having high extraction rate and high washing factor;

a step of descending polymerization of a reaction tower: the reaction tower is a vertical stainless steel tower, a spiral stirrer is arranged at the lower part of the reaction tower, slurry enters from the lower part and flows out from the upper part, continuous production is carried out, and the reaction liquid medicine is hypochlorite or hydrogen peroxide. Before the pump is sent into the reaction tower, a mixer is arranged in front of the pump, and reaction liquid medicine, steam, alkali liquor and the like are added. During the polymerization reduction reaction, the slurry is concentrated: 8% -12%, PH: 9-14, wherein the dosage of the hydrogen peroxide is 0.5% -5%; the temperature is 40-100 ℃, and the time is 30-180 min; a small amount of chelating agent aid may be added during the precipitation stage.

A multi-stage washing step: adding water into the slurry after the precipitation to dilute the slurry to about 5 percent of concentration, pumping the slurry into a mesh belt type high-speed pulp washer or a roller type pulp extruder by a pump to realize mechanical dehydration, water addition replacement and multiple circulation, and realizing a pulp washing mode of combining strong dehydration and replacement.

Acidifying and complexing treatment: the slurry acidification is carried out in an acidification tank or tower, and inorganic acid sulfuric acid or hydrochloric acid is used for acidification. Upon acidification, PH: 1-2, the temperature is 30-50 ℃, the time is 30-60 min, and a chelating agent or a complexing agent auxiliary agent is added after acidification.

A multi-stage washing step: the acidified pulp is pumped into a mesh belt type high-speed pulp washer or a roller type pulp extruder to realize mechanical dehydration, water addition replacement and multiple cycles, and a pulp washing mode of combining powerful dehydration and replacement is realized.

A papermaking forming step: the washed semi-finished pulp passes through a long net or a wet part of a clamping net, is distributed and formed in a low-concentration state, is dehydrated through a net part in a vacuum area, is mechanically pressed and dehydrated in a large roller area to form a pulp board with 50% dryness, is dried into a formed pulp board with 90% dryness through a plurality of drying cylinders or an air cushion type dryer, is cut into plate-shaped pulp with 800x600 specification through a paper cutter, and is packed and bundled into a finished product to be packaged and put in storage.

And (5) drying the finished product.

Example 2:

a preparation method for modifying papermaking pulp into pulp special for lyocell fibers comprises the following steps:

step 1), preparing materials: removing packaging iron wires (steel belts) of the paper-making wood pulp bag, and crushing the paper-making wood pulp bag into paste with the concentration of about 5% by a hydraulic pulper;

step 2), squeezing, dewatering and conveying: the pulp gruel with the concentration of about 5 percent is pressed mechanically and dehydrated to the dryness of about 30 percent, and then is sent into a hydrolysis reaction tower.

Step 3), hydrolysis of a reaction tower: the reaction tower is a vertical stainless steel tower, the upper part is fed in and the lower part is discharged out, the batch production is carried out, and the hydrolysate can be circulated strongly; the hydrolysate can be desalted water, or hydrochloric acid and inorganic sulfuric acid. Hydrolyzing with desalted water at 150-175 ℃ for 30-180 min;

step 4), washing with multi-section washing equipment, strongly dewatering and replacing are combined with each other, the extraction rate is high, and the washing factor is high;

step 5), refining in an alkali tower: the alkali tower is a vertical stainless steel tower, caustic soda is used for alkali refining, and the alkali content is 60-120 mg/L; temperature: 30 to 70 ℃. Alkali refining time: 30-120 min; concentrating the pulp: 8 to 12 percent; oxygen can be added for strengthening in the alkali refining process.

Step 6), squeezing and dealkalizing: the squeezed alkali liquor can be recycled after being treated by a membrane removing treatment system.

Step 7), reducing polymerization and adjusting viscosity: the reaction tower is a vertical stainless steel tower, and the reaction liquid medicine is hypochlorite or hydrogen peroxide.

Concentrating the pulp: 8% -12%, PH: 9-14, wherein the dosage of the hydrogen peroxide is 0.5% -5%; the temperature is 40-100 ℃, and the time is 30-180 min; a small amount of chelating agent aid may be added during the precipitation stage.

Step 8), acidification and complexation treatment: inorganic acid sulfuric acid or hydrochloric acid is used for acidification. Upon acidification, PH: 1-2, the temperature is 30-50 ℃, the time is 30-60 min, and a chelating agent or a complexing agent auxiliary agent is added after acidification.

And step 9), after the pulp is washed by multiple sections again, manufacturing and slitting forming are carried out by a long-mesh multi-cylinder paper machine or a mesh-sandwiched air cushion pulp machine. The finished pulp is 800x600 specification or roll pulp.

Example 3:

the preparation method for modifying papermaking pulp into the pulp special for the lyocell fibers as described in the embodiment 1 and the embodiment 2 comprises the following parameters and process conditions:

1. raw materials: sulfate bleached softwood pulp, wherein DP: 950, alpha cellulose: 86 percent, 89 percent of whiteness, 0.3 percent of ash and 25ppm of Fe.

2. The hydraulic pulper is pulped by desalted water, and the concentration is 4.5 percent.

3. And (4) squeezing and dewatering by a single-screw squeezer, wherein the dryness is 32%.

4. Hydrolysis in a hydrolysis tower: introducing saturated steam, and heating to 160 deg.C for 90 min.

5. Extruding, dehydrating and washing by a double-screw pulp extruder, feeding into a refining tower, concentrating pulp: 10%, temperature 35 ℃, alkali content 80mg/L, time 60 min.

6. Dealkalizing the extruder of the double-net pulp press, pressing the extruder to 25 percent of dryness, removing a membrane by using an alkali liquor system, adjusting the concentration of the slurry and feeding the slurry into a reaction tower.

7. Polymerization reduction reaction tower: the pulp concentration is 10%, the hydrogen peroxide dosage is 1%, the temperature is 55 ℃, the time is 60min, and the chelating agent auxiliary agent EDTA dosage is 0.1%.

8. And extruding, dehydrating and washing by a double-screw extruder.

9. Acidification and complexation treatment: concentrating the pulp: 4.5%, hydrochloric acid for acidification, PH: 1-2 ℃, the temperature is 40 ℃, the dosage of the chelating agent auxiliary agent EDTA is 0.1%, and the time is 60 min.

10. And extruding, dehydrating and washing by a double-screw extruder.

11. Low concentration flow, concentration 2%, mesh forming, air cushion drying, and rolling into pulp.

Example 4: the preparation method for modifying papermaking pulp into the pulp special for the lyocell fibers as described in the embodiment 1 and the embodiment 2 comprises the following parameters and process conditions:

1. raw materials: sulfate bleached eucalyptus pulp, wherein DP: 850, alpha cellulose: 91.5 percent, whiteness of 91 percent, ash content of 0.3 percent and Fe content of 25 ppm.

2. The hydraulic pulper is pulped by desalted water, and the concentration is 4.5 percent.

3. And (4) squeezing and dewatering by a single-screw squeezer, wherein the dryness is 32%.

4. Hydrolysis in a hydrolysis tower: introducing saturated steam, and heating to 160 deg.C for 90 min.

5. Extruding, dehydrating and washing by a double-screw pulp extruder, feeding into a refining tower, concentrating pulp: 10 percent, the temperature is 35 ℃, the alkali content is 85mg/L, and the time is 60 min.

6. Dealkalizing the extruder of the double-net pulp press, pressing the extruder to 25 percent of dryness, removing a membrane by using an alkali liquor system, adjusting the concentration of the slurry and feeding the slurry into a reaction tower.

7. Polymerization reduction reaction tower: the pulp concentration is 10%, the hydrogen peroxide dosage is 1%, the temperature is 55 ℃, the time is 50min, and the chelating agent auxiliary agent EDTA dosage is 0.1%.

8. And extruding, dehydrating and washing by a double-screw extruder.

9. Acidification and complexation treatment: concentrating the pulp: 4.5%, hydrochloric acid for acidification, PH: 1-2 ℃, the temperature is 40 ℃, the dosage of the chelating agent auxiliary agent EDTA is 0.1%, and the time is 60 min.

10. And extruding, dehydrating and washing by a double-screw extruder.

11. Low concentration flow, concentration 2%, mesh forming, air cushion drying, and rolling into pulp.

As described above, although the embodiments of the present invention have been described in detail, it will be apparent to those skilled in the art that many modifications are possible without substantially departing from the spirit and scope of the present invention. Therefore, such modifications are also all included in the scope of protection of the present invention.