A pulping process based on the synergistic optimization of pulp mill sludge and sewage fibers
Patent Information
- Application Number
- CN202610927950.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-06-25
- Publication Date
- 2026-10-27
Smart Images
Figure CN122980273A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of papermaking and pulping technology, and in particular to a pulping process based on the synergistic optimization of pulp residue and wastewater fiber from packaging paper mills. Background Technology
[0002] With the continuous improvement of waste paper recycling rates, secondary fibers have become a major raw material source for packaging paper production. Packaging paper mills inevitably generate a large amount of pulp residue during the waste paper pulping process. Studies have shown that the useful fiber content in pulp residue can reach over 80%, with a high proportion of long fibers. At the same time, papermaking white water and wastewater treatment systems also carry a large amount of fine fibers. The fibers in both types of waste have high recycling value, but current technologies for their recycling are significantly inadequate.
[0003] Regarding pulp residue treatment, current technologies typically involve collecting the pulp residue and simply mixing it for reuse in the papermaking system, without classifying the recovered fibers by length. This results in the waste of the reinforcing effect of long fibers and the underutilization of the filling effect of short and fine fibers. In terms of wastewater fiber recovery, the fine fibers in papermaking white water have a large specific surface area and slow settling velocity, limiting the recovery efficiency of conventional flocculation processes. More importantly, currently, pulp residue treatment systems and wastewater treatment systems in packaging paper mills usually operate independently, lacking a synergistic mechanism at the material flow level.
[0004] To address the aforementioned problems, this invention provides a pulping process based on the synergistic optimization of packaging paper mill pulp residue and wastewater fiber. Summary of the Invention
[0005] The purpose of this invention is to address the shortcomings of existing technologies, such as the high reuse value of fibers in waste materials, but significant deficiencies in their recycling methods. This invention proposes a pulping process based on the synergistic optimization of pulp residue from packaging paper mills and wastewater fibers.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: Design a pulping process based on the synergistic optimization of pulp residue and wastewater fiber from packaging paper mills, including the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
[0007] Furthermore, the grading sieve system in step one includes a primary grading sieve and a secondary grading sieve. The sieve slot width or sieve aperture diameter of the primary grading sieve is 0.8-1.2 mm, and the sieve slot width of the secondary grading sieve is 0.4-0.6 mm. After grading, the fiber length of the long fiber component is ≥1.2 mm, the fiber length of the medium-long fiber component is 0.5 mm ≤ L < 1.2 mm, and the short fiber component is a mixture of short fibers and fine fibers, wherein the fiber length of the short fibers is 0.1 mm ≤ L < 0.5 mm, and the fiber length of the fine fibers is L < 0.1 mm.
[0008] Furthermore, in step one, the ratio of one part to another of the long fiber component is (10-30):(70-90); in step two, the amount of long fiber component added as a coagulant carrier is 5%-15% of the total suspended solids in the wastewater.
[0009] Furthermore, before the long fiber component mentioned in step two is added as a coagulation aid, it is first subjected to a high-speed shear dispersion treatment for 30-60 seconds, with a shear rate of 3000-5000 rpm.
[0010] Furthermore, the flocculation recovery described in step two adopts a three-stage cascade flocculation process: the first stage adds an inorganic coagulant and stirs rapidly for 1-3 minutes at a stirring speed of 150-250 rpm; the second stage adds a long-fiber coagulation aid carrier and stirs at a medium speed for 5-10 minutes at a stirring speed of 60-100 rpm; the third stage adds an organic flocculant and stirs slowly for 10-30 minutes at a stirring speed of 20-40 rpm.
[0011] Furthermore, in step two, the inorganic coagulant is selected from at least one of polyaluminum chloride and aluminum sulfate, and the addition amount is 50-200 mg / L of wastewater; the organic flocculant is selected from anionic polyacrylamide or nonionic polyacrylamide, and the addition amount is 2-10 mg / L of wastewater.
[0012] Furthermore, the directional slurry preparation mentioned in step three is as follows: Bottom layer pulp preparation: long fiber components are mixed with virgin softwood pulp at a mass ratio of (60-80):(20-40), and pulped to a freeness of 28-35°SR; Core layer pulping: The medium-length fiber component and the recycled fiber pulp are mixed at a mass ratio of (50-70):(30-50) and pulped to a freeness of 30-38°SR; Surface layer pulp preparation: The short fiber component is concentrated and used alone or mixed with virgin pulp at a mass ratio of (70-90):(10-30), and pulped to a freeness of 35-45°SR.
[0013] Furthermore, instead of using the short fiber component mentioned in step three for the surface layer slurry, it is mixed with the surface sizing starch at a mass ratio of (10-30):(70-90), and after homogenization, it is used as a surface sizing reinforcing filler.
[0014] Furthermore, before the wastewater described in step two undergoes flocculation and recovery, its pH is adjusted to 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
[0015] Furthermore, before the wastewater described in step two undergoes flocculation and recovery, its pH is adjusted to 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
[0016] The present invention proposes a pulping process based on the synergistic optimization of pulp residue and wastewater fiber from packaging paper mills. The beneficial effects are as follows: The present invention performs two-stage classification and screening of pulp residue fiber, and directs the long fiber, medium-long fiber and short fiber components for recycling into the bottom layer, core layer and top layer of packaging paper respectively. This achieves the tiered utilization effect of long fiber reinforcement, medium fiber filling and short fiber membrane composition, and significantly improves the comprehensive utilization value of recycled fiber. Secondly, this invention uses the graded long fiber components as a coagulation aid carrier for the recovery of wastewater microfiber flocculation. By utilizing the skeletal structure and surface active groups of the long fibers, it provides a core carrier for microfiber flocculation, effectively improving the flocculation and sedimentation efficiency of microfibers, with a recovery rate of over 88%. Furthermore, this invention constructs a complete material cycle chain of pulp residue classification, long fiber coagulation aid, wastewater fiber recovery, and synergistic pulp preparation, realizing deep coupling and synergistic effect between pulp residue treatment and wastewater treatment. The process is simple, the equipment modification cost is low, and it is easy to promote industrialization. Attached Figure Description
[0017] Figure 1 This is a flowchart of the present invention. Detailed Implementation
[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0019] Example 1 Reference Figure 1As one embodiment of the present invention, a pulping process based on the synergistic optimization of packaging paper mill pulp residue and wastewater fiber is disclosed. Specifically, the process includes the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. Specifically, approximately 5 tons / day of pulp residue discharged from the pulping section, measured by oven-dry weight, is transported to the grading and screening system. The primary grading screen uses a slotted screen with a slot width of 1.0 mm. The undersize material consists of short fibers with a fiber length less than 0.5 mm, accounting for approximately 35% of the oven-dry pulp residue. The oversize material is then sent to the secondary grading screen. The secondary grading screen also uses a slotted screen with a slot width of 0.5 mm. The oversize material consists of long fibers with a fiber length ≥ 1.2 mm, accounting for approximately 25% of the oven-dry pulp residue. The undersize material consists of medium-long fibers with a fiber length of 0.5 mm ≤ L < 1.2 mm, accounting for approximately 40% of the oven-dry pulp residue.
[0020] The graded long fiber components are allocated in a 20:80 ratio. 20% (approximately 0.25 tons / day) is sent to the wastewater flocculation and recovery unit as a coagulation aid, and 80% (approximately 1.0 ton / day) is sent to the bottom layer slurry system. The medium and long fiber components (approximately 2.0 tons / day) are sent to the core layer slurry system. The short fiber components (approximately 1.75 tons / day) are concentrated and then sent to the surface layer slurry system.
[0021] Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Specifically, approximately 8,000 tons / day of mixed wastewater generated from each process section, with a suspended solids content of approximately 800~1200 mg / L, is introduced into an equalization tank, and after the pH is adjusted to 7.0, it is sent to a flocculation reaction tank.
[0022] 0.25 tons / day of the long fiber component obtained in step one was added to the flocculation reactor as a coagulant carrier, with the addition amount being 10% of the total suspended solids in the wastewater. Before addition, the long fiber component was subjected to high-speed shear dispersion treatment for 45 seconds, with a shear rate of 4000 rpm.
[0023] The flocculation recovery adopts a three-stage flocculation process: the first stage adds polyaluminum chloride at a dosage of 120 mg / L of wastewater, and stirs rapidly for 2 minutes at a stirring speed of 200 rpm; the second stage adds long-fiber coagulant carrier, and stirs at a medium speed for 8 minutes at a stirring speed of 80 rpm; the third stage adds anionic polyacrylamide at a dosage of 5 mg / L of wastewater, and stirs slowly for 20 minutes at a stirring speed of 30 rpm.
[0024] The total flocculation reaction time is 30 minutes. After the reaction is completed, the mixture is sent to a sedimentation tank for solid-liquid separation. The surface loading of the sedimentation tank is 0.8 m³ / (m²·h). The concentration of the recovered fiber slurry obtained from the separation is approximately 5%, with an oven-dry yield of approximately 6.5 tons / day. The supernatant is reused in the production system.
[0025] Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Specifically, the fiber pulp recovered in step two and the fiber components obtained from grading in step one are respectively blended according to the quality requirements of each layer of packaging paper: Bottom layer pulping: The second part of the long fiber component, 1.0 ton / day, is mixed with virgin softwood pulp at a mass ratio of 70:30 and beaten to a freeness of 32°SR. It is used for the bottom layer of packaging paper making to provide the paper with ring crush strength and burst strength. Core layer pulping: 2.0 tons / day of medium and long fiber components are mixed with 3.0 tons / day of fiber pulp recovered in step 2 at a mass ratio of 60:40 and beaten to a freeness of 35°SR. This mixture is used for the core layer of packaging paper to provide the paper with bulk and stiffness. Surface layer pulping: 1.75 tons / day of short fiber component is concentrated and mixed with virgin pulp at a mass ratio of 85:15, and beaten to a freeness of 40°SR. It is used for the surface layer of packaging paper to provide the paper with smoothness and surface strength.
[0026] Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
[0027] Specifically, the top layer slurry, core layer slurry, and bottom layer slurry prepared in step three are fed into the top layer headbox, core layer headbox, and bottom layer headbox of a multilayer paper machine, respectively. After multilayer forming, lamination, pressing, drying, calendering, and winding, the finished corrugated base paper is obtained.
[0028] Example 2 As another embodiment of the present invention, it discloses a pulping process based on the synergistic optimization of packaging paper mill pulp residue and wastewater fiber, including the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. The grading sieve system includes a primary grading sieve and a secondary grading sieve. The sieve slot width or sieve aperture diameter of the primary grading sieve is 0.8 mm, and the sieve slot width of the secondary grading sieve is 0.4 mm. After grading, the fiber length of the long fiber component is ≥1.2 mm, the fiber length of the medium-long fiber component is 0.5 mm ≤ L < 1.2 mm, and the short fiber component is a mixture of short fibers and fine fibers, wherein the fiber length of the short fibers is 0.1 mm ≤ L < 0.5 mm, and the fiber length of the fine fibers is L < 0.1 mm. The ratio of one part to the other of the long fiber component is 10:70; the amount of the long fiber component added as a coagulant in step two is 5% of the total suspended solids in the wastewater; Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Before being added as a coagulation aid, the long fiber component undergoes a high-speed shear dispersion treatment for 30 seconds, with a shear rate of 3000 rpm. In addition, the flocculation recovery adopts a three-stage cascade flocculation process: the first stage adds an inorganic coagulant and stirs rapidly for 1 minute at a stirring speed of 150 rpm; the second stage adds a long-fiber coagulation aid carrier and stirs at a medium speed for 5 minutes at a stirring speed of 60 rpm; the third stage adds an organic flocculant and stirs slowly for 10 minutes at a stirring speed of 20 rpm. The inorganic coagulant is selected from at least one of polyaluminum chloride and aluminum sulfate, and is added at a rate of 50 mg / L wastewater; the organic flocculant is selected from anionic polyacrylamide or nonionic polyacrylamide, and is added at a rate of 2 mg / L wastewater. Before flocculation and recovery, the wastewater is first adjusted to pH 6.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system. Before flocculation and recovery, the wastewater is first adjusted to pH 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
[0029] Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Wherein, the directional slurry preparation is: Bottom layer pulping: Long fiber components are mixed with virgin softwood pulp at a mass ratio of 60:20 and pulped to a freeness of 28°SR; Core layer pulping: The medium-length fiber component and recycled fiber pulp are mixed at a mass ratio of 50:30 and pulped to a freeness of 30°SR; Surface layer pulp preparation: The short fiber component is concentrated and used alone or mixed with virgin pulp at a mass ratio of 70:10, and pulped to a freeness of 35°SR; In addition, the short fiber component is not used for the surface layer slurry, but is mixed with the surface sizing starch at a mass ratio of 10:70, and after homogenization, it is used as a surface sizing reinforcing filler. Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
[0030] Example 3 As another embodiment of the present invention, it discloses a pulping process based on the synergistic optimization of packaging paper mill pulp residue and wastewater fiber, including the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. The grading sieve system includes a primary grading sieve and a secondary grading sieve. The primary grading sieve has a sieve slot width or sieve aperture diameter of 1.0 mm, and the secondary grading sieve has a sieve slot width of 0.5 mm. After grading, the long fiber component has a fiber length ≥ 1.2 mm, the medium-long fiber component has a fiber length of 0.5 mm ≤ L < 1.2 mm, and the short fiber component is a mixture of short fibers and fine fibers, wherein the short fiber has a fiber length of 0.1 mm ≤ L < 0.5 mm, and the fine fiber has a fiber length of L < 0.1 mm. The ratio of one part to the other of the long fiber component is 20:80; in step two, the amount of the long fiber component added as a coagulant carrier is 10% of the total suspended solids in the wastewater. Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Before being added as a coagulation aid, the long fiber component undergoes a high-speed shear dispersion treatment for 45 seconds, with a shear rate of 4000 rpm. In addition, the flocculation recovery adopts a three-stage flocculation process: the first stage adds an inorganic coagulant and stirs rapidly for 2 minutes at a stirring speed of 200 rpm; the second stage adds a long-fiber coagulation aid carrier and stirs at a medium speed for 7.5 minutes at a stirring speed of 80 rpm; the third stage adds an organic flocculant and stirs slowly for 20 minutes at a stirring speed of 30 rpm. The inorganic coagulant is selected from at least one of polyaluminum chloride and aluminum sulfate, and the addition amount is 125 mg / L of wastewater; the organic flocculant is selected from anionic polyacrylamide or nonionic polyacrylamide, and the addition amount is 6 mg / L of wastewater. Before flocculation and recovery, the wastewater is first adjusted to pH 7 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
[0031] Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Wherein, the directional slurry preparation is: Bottom layer pulping: The long fiber component is mixed with virgin softwood pulp at a mass ratio of 70:30 and pulped to a freeness of 31.5°SR; Core layer pulping: The medium-length fiber component and recycled fiber pulp are mixed at a mass ratio of 60:40 and pulped to a freeness of 34°SR; Surface layer pulping: The short fiber component is concentrated and used alone or mixed with virgin pulp at a mass ratio of 80:20, and pulped to a freeness of 40°SR; In addition, the short fiber component is not used for the surface layer slurry, but is mixed with the surface sizing starch at a mass ratio of 20:80, and after homogenization, it is used as a surface sizing reinforcing filler. Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
[0032] Example 4 As another embodiment of the present invention, it discloses a pulping process based on the synergistic optimization of packaging paper mill pulp residue and wastewater fiber, including the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. The grading sieve system includes a primary grading sieve and a secondary grading sieve. The primary grading sieve has a sieve slot width or sieve aperture diameter of 1.2 mm, and the secondary grading sieve has a sieve slot width of 0.6 mm. After grading, the long fiber component has a fiber length ≥ 1.2 mm, the medium-long fiber component has a fiber length of 0.5 mm ≤ L < 1.2 mm, and the short fiber component is a mixture of short fibers and fine fibers, wherein the short fiber has a fiber length of 0.1 mm ≤ L < 0.5 mm, and the fine fiber has a fiber length of L < 0.1 mm. The ratio of one part to the other of the long fiber component is 30:90; the amount of the long fiber component added as a coagulant in step two is 15% of the total suspended solids in the wastewater; Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Before being added as a coagulation aid, the long fiber component undergoes a high-speed shear dispersion treatment for 60 seconds, with a shear rate of 5000 rpm. In addition, the flocculation recovery adopts a three-stage flocculation process: the first stage adds an inorganic coagulant and stirs rapidly for 3 minutes at a stirring speed of 250 rpm; the second stage adds a long-fiber coagulation aid carrier and stirs at a medium speed for 10 minutes at a stirring speed of 100 rpm; the third stage adds an organic flocculant and stirs slowly for 30 minutes at a stirring speed of 40 rpm. The inorganic coagulant is selected from at least one of polyaluminum chloride and aluminum sulfate, and the addition amount is 200 mg / L of wastewater; the organic flocculant is selected from anionic polyacrylamide or nonionic polyacrylamide, and the addition amount is 10 mg / L of wastewater. Before flocculation and recovery, the wastewater is first adjusted to pH 7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system. Before flocculation and recovery, the wastewater is first adjusted to pH 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
[0033] Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Wherein, the directional slurry preparation is: Bottom layer pulping: Long fiber components are mixed with virgin softwood pulp at a mass ratio of 80:40 and pulped to a freeness of 35°SR; Core layer pulping: The medium-length fiber component and recycled fiber pulp are mixed at a mass ratio of 70:50 and pulped to a freeness of 38°SR; Surface layer pulping: The short fiber component is concentrated and used alone or mixed with virgin pulp at a mass ratio of 90:30, and pulped to a freeness of 45°SR; In addition, the short fiber component is used instead of the surface layer slurry, and is mixed with the surface sizing starch at a mass ratio of 30:90, and after homogenization, it is used as a surface sizing reinforcing filler; Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
[0034] Specifically, this invention performs two-stage grading and screening of pulp residue fibers, and repurposes long fibers, medium-length fibers and short fibers into the bottom layer, core layer and top layer of packaging paper, respectively. This achieves a tiered utilization effect of long fiber reinforcement, medium fiber filling and short fiber membrane composition, significantly improving the comprehensive utilization value of recycled fibers. Secondly, this invention uses the graded long fiber components as a coagulation aid carrier for the recovery of wastewater microfiber flocculation. By utilizing the skeletal structure and surface active groups of the long fibers, it provides a core carrier for microfiber flocculation, effectively improving the flocculation and sedimentation efficiency of microfibers, with a recovery rate of over 88%.
[0035] Furthermore, this invention constructs a complete material cycle chain of pulp residue classification, long fiber coagulation aid, wastewater fiber recovery, and synergistic pulp preparation, realizing deep coupling and synergistic effect between pulp residue treatment and wastewater treatment. The process is simple, the equipment modification cost is low, and it is easy to promote industrialization.
[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A pulping process based on the synergistic optimization of pulp residue and wastewater fiber from packaging paper mills, characterized in that, Includes the following steps: Step 1: The pulp residue discharged from the pulping section of the packaging paper mill is screened and graded by a grading sieve system to obtain long fiber components, medium-long fiber components and short fiber components respectively. Step 2: A portion of the long fiber component obtained from the grading is used as a coagulation aid carrier and added to the flocculation and recovery unit of the wastewater from the packaging paper mill. It is used in conjunction with inorganic coagulants and organic flocculants to flocculate and recover the fine fibers in the wastewater, thereby obtaining recovered fiber pulp. Step 3: The other part of the long fiber component obtained from grading, the medium and long fiber component, the short fiber component, and the recycled fiber pulp obtained in Step 2 are respectively oriented and mixed according to the quality requirements of the packaging paper surface layer, core layer, and bottom layer. Step 4: The prepared pulp layers are fed into a multi-layer paper machine for forming to obtain the finished packaging paper.
2. The pulping process according to claim 1, characterized in that, The grading sieve system described in step one includes a primary grading sieve and a secondary grading sieve. The sieve slot width or sieve aperture diameter of the primary grading sieve is 0.8-1.2 mm, and the sieve slot width of the secondary grading sieve is 0.4-0.6 mm. After grading, the fiber length of the long fiber component is ≥1.2 mm, the fiber length of the medium-long fiber component is 0.5 mm ≤ L < 1.2 mm, and the short fiber component is a mixture of short fibers and fine fibers, wherein the fiber length of the short fibers is 0.1 mm ≤ L < 0.5 mm, and the fiber length of the fine fibers is L < 0.1 mm.
3. The pulping process according to claim 1, characterized in that, In step one, the ratio of one part to another of the long fiber component is (10-30):(70-90); in step two, the amount of long fiber component added as a coagulant carrier is 5%-15% of the total suspended solids in the wastewater.
4. The pulping process according to claim 1, characterized in that, Before the long fiber component mentioned in step two is added as a coagulation aid, it is first subjected to a high-speed shear dispersion treatment for 30-60 seconds, with a shear rate of 3000-5000 rpm.
5. The pulping process according to claim 1, characterized in that, The flocculation recovery described in step two adopts a three-stage cascade flocculation process: In the first stage, an inorganic coagulant is added and stirred rapidly for 1-3 minutes at a stirring speed of 150-250 rpm; in the second stage, a long-fiber coagulation aid carrier is added and stirred at a medium speed for 5-10 minutes at a stirring speed of 60-100 rpm; in the third stage, an organic flocculant is added and stirred slowly for 10-30 minutes at a stirring speed of 20-40 rpm.
6. The pulping process according to claim 1, characterized in that, The inorganic coagulant in step two is selected from at least one of polyaluminum chloride and aluminum sulfate, and the addition amount is 50-200 mg / L of wastewater; the organic flocculant is selected from anionic polyacrylamide or nonionic polyacrylamide, and the addition amount is 2-10 mg / L of wastewater.
7. The pulping process according to claim 1, characterized in that, The directional slurry preparation mentioned in step three is as follows: Bottom layer pulp preparation: long fiber components are mixed with virgin softwood pulp at a mass ratio of (60-80):(20-40), and pulped to a freeness of 28-35°SR; Core layer pulping: The medium-length fiber component and the recycled fiber pulp are mixed at a mass ratio of (50-70):(30-50) and pulped to a freeness of 30-38°SR; Surface layer pulp preparation: The short fiber component is concentrated and used alone or mixed with virgin pulp at a mass ratio of (70-90):(10-30), and pulped to a freeness of 35-45°SR.
8. The pulping process according to claim 1, characterized in that, The short fiber component mentioned in step three is not used for the surface layer slurry. Instead, it is mixed with the surface sizing starch at a mass ratio of (10-30):(70-90), and after homogenization, it is used as a surface sizing reinforcing filler.
9. The pulping process according to claim 1, characterized in that, Before flocculation and recovery, the wastewater described in step two is first adjusted to pH 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.
10. The pulping process according to claim 1, characterized in that, Before flocculation and recovery, the wastewater described in step two is first adjusted to pH 6.5-7.5 in an equalization tank; the wastewater includes at least one of the following: white water from the pulping section, white water from the papermaking machine, and mixed wastewater from the wastewater treatment system.