A method for treating and reusing papermaking white water

Abstract

The present application belongs to the technical field of papermaking white water treatment, especially a papermaking white water treatment and reuse method. In view of the problems of low fiber and filler recovery efficiency, poor quality of reused materials, lack of cooperation among various treatment units, and unstable system operation in the existing papermaking white water treatment and reuse process, the following scheme is proposed, which includes the following steps: S1: online monitoring and characteristic analysis of papermaking white water; S2: gradient targeted flocculation pretreatment of white water; S3: pumping the pretreated white water into a partition-optimized multi-disc filter for dynamic filtration. The present application realizes multi-unit intelligent linkage and self-adaptive optimization of the whole process of white water treatment by constructing a closed-loop control system from online monitoring, intelligent decision-making to precise execution, significantly improves the recovery efficiency of fiber and filler and the quality of papermaking, realizes efficient hierarchical reuse of water resources and source reduction of pollutants, and achieves the unity of economic, environmental and social benefits.

Description

Technical Field

[0001] This invention relates to the field of papermaking white water treatment technology, and in particular to a method for treating and reusing papermaking white water. Background Technology

[0002] In the waste paper manufacturing process, to achieve water conservation and "zero discharge" goals, white water systems generally adopt highly closed-loop circulation. This leads to the continuous accumulation of dissolved organic matter, colloidal substances, and fine fibers in the water system, causing a series of production problems such as deterioration of pulp filtration, increased paper machine breakage rate, decreased paper strength, and microbial growth. Existing treatment technologies, such as traditional air flotation or single / multi-disc filtration, mainly focus on the preliminary separation of solids, and have problems such as low recovery efficiency of fine components, unstable operation, and poor quality of recovered materials (direct reuse affects paper strength).

[0003] In the existing technology, the treatment and reuse of papermaking white water suffers from problems such as low fiber and filler recovery efficiency, poor quality of recycled materials, and lack of coordination among treatment units leading to unstable system operation. To address these issues, we propose a method for treating and reusing papermaking white water. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies in the treatment and reuse of papermaking white water, such as low fiber and filler recovery efficiency, poor quality of reused materials, and instability in system operation due to lack of coordination among processing units. Therefore, this invention proposes a method for treating and reusing papermaking white water.

[0005] The papermaking white water treatment and reuse method provided in this application adopts the following technical solution: A method for treating and reusing white water from papermaking includes the following steps: S1: Online monitoring and characteristic analysis of papermaking white water; S2: Pre-treat white water by step-by-step targeted flocculation; S3: Pump the pretreated white water into a zoned optimized multi-disc filter for dynamic filtration; S4: Collect and reuse the filtered filtrate in multiple stages to ensure its quality. S5: The recycled fiber filler is subjected to efficient dehydration and surface activation modification; S6: The modified filler is compounded and homogenized with the paper pulp online; S7: High-frequency vibrating inclined screen is used for deep interception and fiber recovery of end-of-pipe wastewater; S8: Dynamically optimize process parameters.

[0006] Furthermore, in step S1, an integrated online water quality analysis instrument is installed on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity, and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. Based on the built-in expert model, the system dynamically analyzes and provides early warnings on the concentration, charge characteristics, and changing trends of the fine / colloidal components in the white water.

[0007] Furthermore, in step S2, based on the real-time analysis results, precise stepwise flocculation is performed on the white water in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 5-15 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring.

[0008] Furthermore, in S2, in the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (8 million to 15 million) is added to the system. The dosage is finely adjusted to 2-10 mg / L based on turbidity feedback. Under low shear conditions, this promotes further bridging and growth of the flocs, forming dense and uniform filterable flocs.

[0009] Furthermore, in step S3, the pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high-precision zone, mesh size ≥ 150 mesh) and an outer zone (standard-precision zone, mesh size ≥ 100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree, and backwash pressure, are applied to the filter to achieve selective and efficient retention and stripping of flocs of different particle sizes.

[0010] Furthermore, in step S4, the filtrate produced by the multi-disc filter is classified into three levels according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which have the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system.

[0011] Furthermore, in step S5, the slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 25%-35%. Subsequently, the dewatered slurry is transported to a modified reactor equipped with a temperature-controlled jacket and a high-speed disperser. Under a temperature of 55-65°C and continuous mechanical shearing, cationic starch (added at 1.0%-3.0% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, an alkenyl succinic anhydride derivative (added at 0.5%-1.5% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface.

[0012] Furthermore, in step S6, the obtained modified filler slurry is continuously and stably injected into the main slurry pipe of the papermaking flow system at a ratio of 1%-5% of the total main slurry on an absolute dry basis using a high-precision metering pump. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network.

[0013] Furthermore, in step S7, the collected shallow turbid filtrate and other low-concentration white water are gathered and evenly distributed onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with a homogenizing and energy dissipation device. The vibration frequency of the inclined screen is controlled at 15-25Hz and the amplitude is controlled at 1-2mm. Under these conditions, the residual microfibers in the water are efficiently intercepted, and the intercepted fiber residue is dewatered by a spiral and then reused.

[0014] Furthermore, in S8, online water quality data, operating status data of each device, and data from the final paper basis weight and strength online testing instrument are integrated, collected, and analyzed. Based on the fuzzy-PID composite control algorithm, the flocculant addition curve is dynamically optimized according to water quality changes. Based on the ash content detection results of the recycled pulp, the modifier addition amount is adjusted in reverse. Based on the real-time signal of paper smoothness, the compounding ratio is finely adjusted.

[0015] In summary, this application includes at least one of the following beneficial technical effects: 1. This solution dynamically adjusts the flocculation process based on real-time water quality data (such as colloidal charge and turbidity), adjusts the zoned operation parameters of the multi-disc filter according to changes in white water load, and fine-tunes the front-end modification and compounding process based on the final paper quality signal. This effectively overcomes the problems of independent operation of each unit and poor resistance to shock loads in traditional methods. 2. This solution forms dense flocs with a better particle size distribution through a precisely controlled flocculation process, creating ideal conditions for subsequent filtration; while the physically separated and zoned multi-disc filter plates can selectively retain and efficiently strip flocs of different sizes, avoiding the problems of fine particle run-off or clogging that exist in traditional single-zone filtration. 3. This solution fundamentally improves the surface properties of the recycled fiber filler by performing targeted charge modification and hydrophobic grafting treatment, thereby enhancing its affinity and bonding strength with pulp fibers. Subsequently, online homogenization technology combining turbulent injection and static mixing is used to ensure the uniform distribution of the modified filler in the paper web.

[0016] This invention constructs a closed-loop control system from online monitoring and intelligent decision-making to precise execution, realizing intelligent linkage and adaptive optimization of multiple units throughout the entire white water treatment process. While significantly improving the recovery efficiency of fiber fillers and the quality of paper, it also achieves efficient graded reuse of water resources and source reduction of pollutants, thus achieving a unity of economic, environmental and social benefits. Attached Figure Description

[0017] Figure 1 This is a flowchart of a method for treating and reusing white water from papermaking, as proposed in this invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of 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 1 A method for treating and reusing white water from papermaking includes the following steps: S1: Install an integrated online water quality analysis instrument on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. The system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of fine / colloidal components in the white water based on the built-in expert model. S2: Based on real-time analysis results, precise stepwise flocculation is implemented in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 5 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring. In the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (8 million) is added to the system. The dosage is finely adjusted to 2 mg / L according to turbidity feedback. Under low shear conditions, the flocs are further bridged and grown to form dense, uniform, and filterable flocs. S3: The pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high precision zone, mesh size ≥150 mesh) and an outer zone (standard precision zone, mesh size ≥100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree and backwash pressure, are applied to the filter to achieve selective and efficient interception and stripping of flocs of different particle sizes. S4: The filtrate produced by the multi-disc filter is classified into three grades according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which has the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system. S5: The slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 25%. Then, the dewatered slurry is transported to a modified reactor with a temperature control jacket and a high-speed disperser. Under the temperature of 55°C and continuous mechanical shear, cationic starch (1.0% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, alkenyl succinic anhydride derivative (0.5% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface. S6: The modified filler slurry obtained is continuously and stably injected into the main slurry pipe of the papermaking flow system through a high-precision metering pump at a ratio of 1% of the total main slurry on an absolute dry basis. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network. S7: Collect the shallow turbid filtrate and other low-concentration white water, and evenly distribute it onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. Control the vibration frequency of the inclined screen at 15Hz and the amplitude at 1mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The intercepted fiber residue is then dewatered by a spiral and reused. S8: Integrates and analyzes online water quality data, operating status data of various equipment, and data from the final paper basis weight and strength online testing instrument. Based on the fuzzy-PID composite control algorithm, it dynamically optimizes the flocculant addition curve according to water quality changes, adjusts the modifier addition amount in reverse according to the ash content test results of the recycled pulp, and fine-tunes the compounding ratio according to the real-time signal of paper smoothness.

[0020] Example 2 The difference between this embodiment and Embodiment 1 is that: (Refer to...) Figure 1 A method for treating and reusing white water from papermaking includes the following steps: S1: Install an integrated online water quality analysis instrument on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. The system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of fine / colloidal components in the white water based on the built-in expert model. S2: Based on real-time analysis results, precise stepwise flocculation is implemented in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 8 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring. In the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (10 million) is added to the system. The dosage is finely adjusted to 4 mg / L according to turbidity feedback. Under low shear conditions, the flocs are further bridged and grown to form dense, uniform, and filterable flocs. S3: The pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high precision zone, mesh size ≥150 mesh) and an outer zone (standard precision zone, mesh size ≥100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree and backwash pressure, are applied to the filter to achieve selective and efficient interception and stripping of flocs of different particle sizes. S4: The filtrate produced by the multi-disc filter is classified into three grades according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which has the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system. S5: The slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 28%. Then, the dewatered slurry is transported to a modified reactor with a temperature control jacket and a high-speed disperser. Under the temperature of 58°C and continuous mechanical shear, cationic starch (1.5% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, alkenyl succinic anhydride derivative (0.8% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface. S6: The modified filler slurry obtained is continuously and stably injected into the main slurry pipe of the papermaking flow system through a high-precision metering pump at a ratio of 2% of the total main slurry on an absolute dry basis. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network. S7: Collect the shallow turbid filtrate and other low-concentration white water, and evenly distribute it onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. Control the vibration frequency of the inclined screen at 18Hz and the amplitude at 1.2mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The intercepted fiber residue is then dewatered by a spiral and reused. S8: Integrates and analyzes online water quality data, operating status data of various equipment, and data from the final paper basis weight and strength online testing instrument. Based on the fuzzy-PID composite control algorithm, it dynamically optimizes the flocculant addition curve according to water quality changes, adjusts the modifier addition amount in reverse according to the ash content test results of the recycled pulp, and fine-tunes the compounding ratio according to the real-time signal of paper smoothness.

[0021] Example 3 The difference between this embodiment and Embodiment 1 is that: (Refer to...) Figure 1 A method for treating and reusing white water from papermaking includes the following steps: S1: Install an integrated online water quality analysis instrument on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. The system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of fine / colloidal components in the white water based on the built-in expert model. S2: Based on real-time analysis results, precise stepwise flocculation is implemented in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 10 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring. In the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (12 million) is added to the system. The dosage is finely adjusted to 6 mg / L according to turbidity feedback. Under low shear conditions, the flocs are further bridged and grown to form dense, uniform, and filterable flocs. S3: The pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high precision zone, mesh size ≥150 mesh) and an outer zone (standard precision zone, mesh size ≥100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree and backwash pressure, are applied to the filter to achieve selective and efficient interception and stripping of flocs of different particle sizes. S4: The filtrate produced by the multi-disc filter is classified into three grades according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which has the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system. S5: The slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 30%. Then, the dewatered slurry is transported to a modified reactor with a temperature control jacket and a high-speed disperser. Under the temperature of 60°C and continuous mechanical shear, cationic starch (addition amount of 2.0% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, alkenyl succinic anhydride derivative (addition amount of 1% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface. S6: The modified filler slurry obtained is continuously and stably injected into the main slurry pipe of the papermaking flow system through a high-precision metering pump at a ratio of 3% of the total main slurry on an absolute dry basis. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network. S7: Collect the shallow turbid filtrate and other low-concentration white water, and evenly distribute it onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. Control the vibration frequency of the inclined screen at 20Hz and the amplitude at 1.5mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The fiber residue obtained by interception is dewatered by a spiral and then reused. S8: Integrates and analyzes online water quality data, operating status data of various equipment, and data from the final paper basis weight and strength online testing instrument. Based on the fuzzy-PID composite control algorithm, it dynamically optimizes the flocculant addition curve according to water quality changes, adjusts the modifier addition amount in reverse according to the ash content test results of the recycled pulp, and fine-tunes the compounding ratio according to the real-time signal of paper smoothness.

[0022] Example 4 The difference between this embodiment and Embodiment 1 is that: (Refer to...) Figure 1 A method for treating and reusing white water from papermaking includes the following steps: S1: Install an integrated online water quality analysis instrument on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. The system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of fine / colloidal components in the white water based on the built-in expert model. S2: Based on real-time analysis results, precise stepwise flocculation is implemented in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 12 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring. In the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (14 million) is added to the system. The dosage is finely adjusted to 8 mg / L according to turbidity feedback. Under low shear conditions, the flocs are further bridged and grown to form dense, uniform, and filterable flocs. S3: The pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high precision zone, mesh size ≥150 mesh) and an outer zone (standard precision zone, mesh size ≥100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree and backwash pressure, are applied to the filter to achieve selective and efficient interception and stripping of flocs of different particle sizes. S4: The filtrate produced by the multi-disc filter is classified into three grades according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which has the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system. S5: The slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 32%. Then, the dewatered slurry is transported to a modified reactor equipped with a temperature control jacket and a high-speed disperser. Under the temperature of 62°C and continuous mechanical shear, cationic starch (addition amount of 2.5% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, alkenyl succinic anhydride derivative (addition amount of 1.2% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface. S6: The modified filler slurry obtained is continuously and stably injected into the main slurry pipe of the papermaking flow system through a high-precision metering pump at a ratio of 4% of the total main slurry on an absolute dry basis. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network. S7: Collect the shallow turbid filtrate and other low-concentration white water, and evenly distribute it onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. Control the vibration frequency of the inclined screen at 22Hz and the amplitude at 1.6mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The intercepted fiber residue is then dewatered by a spiral and reused. S8: Integrates and analyzes online water quality data, operating status data of various equipment, and data from the final paper basis weight and strength online testing instrument. Based on the fuzzy-PID composite control algorithm, it dynamically optimizes the flocculant addition curve according to water quality changes, adjusts the modifier addition amount in reverse according to the ash content test results of the recycled pulp, and fine-tunes the compounding ratio according to the real-time signal of paper smoothness.

[0023] Example 5 The difference between this embodiment and Embodiment 1 is that: (Refer to...) Figure 1 A method for treating and reusing white water from papermaking includes the following steps: S1: Install an integrated online water quality analysis instrument on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. The system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of fine / colloidal components in the white water based on the built-in expert model. S2: Based on real-time analysis results, precise stepwise flocculation is implemented in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 15 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring. In the second stage of the reactor, a cationic polyacrylamide solution with a specific molecular weight (15 million) is added to the system. The dosage is finely adjusted to 10 mg / L according to turbidity feedback. Under low shear conditions, the flocs are further bridged and grown to form dense, uniform, and filterable flocs. S3: The pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone (high precision zone, mesh size ≥150 mesh) and an outer zone (standard precision zone, mesh size ≥100 mesh). The operating parameters set by the central control system based on the white water flow rate and TS concentration, including spindle speed, zone vacuum degree and backwash pressure, are applied to the filter to achieve selective and efficient interception and stripping of flocs of different particle sizes. S4: The filtrate produced by the multi-disc filter is classified into three grades according to its solid content and clarity: the ultra-clear filtrate (solid content ≤30mg / L) is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which has the highest requirements for water purity; the clear filtrate (solid content ≤80mg / L) is collected and reused in the intermediate stages of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate (solid content ≤150mg / L) is collected and used as the feed water for the subsequent inclined wire deep treatment system. S5: The slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 35%. Then, the dewatered slurry is transported to a modified reactor equipped with a temperature control jacket and a high-speed disperser. Under the temperature of 65°C and continuous mechanical shear, cationic starch (addition amount of 3.0% of the oven-dry solids) is first added to the system and reacted for 10 minutes. Then, alkenyl succinic anhydride derivative (addition amount of 1.5% of the oven-dry solids) is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface. S6: The modified filler slurry obtained is continuously and stably injected into the main slurry pipe of the papermaking flow system through a high-precision metering pump at a ratio of 5% of the total main slurry on an absolute dry basis. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network. S7: Collect the shallow turbid filtrate and other low-concentration white water, and evenly distribute it onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. Control the vibration frequency of the inclined screen at 25Hz and the amplitude at 2mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The intercepted fiber residue is then dewatered by a spiral and reused. S8: Integrates and analyzes online water quality data, operating status data of various equipment, and data from the final paper basis weight and strength online testing instrument. Based on the fuzzy-PID composite control algorithm, it dynamically optimizes the flocculant addition curve according to water quality changes, adjusts the modifier addition amount in reverse according to the ash content test results of the recycled pulp, and fine-tunes the compounding ratio according to the real-time signal of paper smoothness.

[0024] Experimental Example I. Experimental Objective The superiority of the method of the present invention over traditional methods is verified in terms of fiber and filler recovery efficiency, recycled water quality, paper quality after application of recycled materials (fillers), and system operation stability. II. Experimental Materials and Equipment Experimental water sample: taken from the white water pool of a waste paper mill, mixed evenly and then packaged separately to ensure that the initial conditions of the comparative experiment were consistent; Traditional method equipment includes: dissolved air flotation (DAF) device, ordinary multi-disc filter (with a uniform filter mesh size of 100 mesh), and corresponding dosing and reclaimed water tanks; The method and equipment of this invention: Integrated online monitoring system (simulating or actually installing pH, conductivity, turbidity, and colloidal charge meters); Two-stage flocculation reactor (with adjustable stirrer); Partition-optimized multi-disc filter (simulating 150 mesh inner zone and 100 mesh outer zone); Three-stage filtrate collection tank; Belt dehydrator and surface activation modification reactor (with temperature control and shear); High-frequency vibrating inclined screen; Central control system (simulating or using PLC + host computer to realize dynamic parameter adjustment logic); Online static mixer, high-precision metering pump; Analytical and testing instruments: COD analyzer, total suspended solids (TSS) analyzer, laser particle size analyzer, zeta potential meter, paper former, paper strength tester, ash content analyzer, etc. III. Experimental Methods 1. Experimental setup: Control group: A "traditional air flotation + ordinary multi-disc filtration" process was used. Flocculants (PAC, CPAM) were added at a fixed empirical dosage. The air flotation effluent entered the multi-disc filtration system; part of the filtered water was reused, and the recovered slurry was directly recycled back to the slurry system. Experimental group: The entire process from S1 to S8 was strictly performed according to the instructions of this invention (based on the parameters of Example 3). Online monitoring data drove the dynamic addition of flocculant, the filtrate was recycled in three stages, and the recovered packing material was added to the main slurry through an online compounding system after surface activation modification. 2. Operation and Monitoring: The two sets of experiments were run in parallel, treating the same flow rate of white water, and running continuously for 72 hours to simulate fluctuations in actual production (which can be achieved by slightly changing the quality of the influent manually). Monitoring points and frequency: Influent / effluent water quality: TSS, COD, and turbidity are measured every 2 hours; Key unit efficiency: Fiber retention rate and packing retention rate of the air flotation / multi-disc unit are measured / calculated every 4 hours; Characteristics of the recovered material: Samples of the recovered slurry were taken every 8 hours to analyze its particle size distribution and zeta potential; the contact angle of the modified filler slurry was measured (to assess hydrophobicity). Paper quality: Every 12 hours, two sets of systems reused water and recycled materials (the control group reused directly, and the experimental group reused after modification) were used to make paper sheets with the same basis weight under a fixed ratio, and their tensile strength, bursting strength and ash content were measured. System stability: Record whether manual intervention (such as cleaning or adjustment) was required for the air flotation skimming tank and multi-disc filter screen in the control group during the entire operation period, and the number of times and effects of dynamic optimization based on S8 in the experimental group; Comparison of Expected Data Evaluation indicators unit Traditional method (air flotation + ordinary multi-plate) The method of this invention (step-by-step targeted flocculation - intelligent filtration - modification and reuse) 1. Solids recovery efficiency Fiber recovery rate % 85-90 ≥95 Packing material (ash) recovery rate % 70-80 ≥90 2. Effluent water quality Multi-disk / main unit water-cooled TSS mg / L 80-150 ≤30 (ultra-clear filtrate) / ≤80 (clear filtrate) Average COD of final system discharge / reclaimed water mg / L Reduce by 30-40% Reduce by 50-65% 3. Recycled materials and paper quality Recycled fillers can be directly applied to the tensile index of paper. N·m / g Decrease of 5-10% Increase by 3-8% Paper ash content uniformity (coefficient of variation) % High (>15%) Significantly reduced (<10%) 4. System Operation and Resource Utilization Water replenishment rate % Based on the quality of the reclaimed water, it is relatively high. Reduce by 20-30% Flocculant consumption per unit output kg / ton of paper Fixed or empirical values, with large fluctuations. Reduce by 10-20% System resistance to shock loads - Poor quality, requires frequent manual adjustments. Strong, the central system automatically adjusts parameters 5. Long-term operational stability Cleaning frequency of critical equipment (such as multi-disc) Next / week 2-3 0.5-1 Experimental conclusions The table above shows that the recycling efficiency is comprehensively improved: the recovery rate of microfibers and fillers is higher, reducing resource waste; water quality is optimized for differentiated reuse: different qualities of recycled water are produced, achieving "high-quality and high-use", significantly improving the water reuse rate and reducing clean water consumption; the value of recycled materials is enhanced: through surface activation modification of recycled fillers, they are transformed from "harmful impurities" into "functional additives", which not only do not affect but can even improve the strength of paper; the system operates intelligently and stably: through closed-loop control of "online monitoring - intelligent decision-making - precise execution", the system's resistance to shock loads is significantly enhanced, chemical and energy consumption is reduced, and stable and efficient operation is achieved.

[0025] 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 method for treating and reusing white water from papermaking, characterized in that: Includes the following steps: S1: Online monitoring and characteristic analysis of papermaking white water; S2: Pre-treat white water by step-by-step targeted flocculation; S3: Pump the pretreated white water into a zoned optimized multi-disc filter for dynamic filtration; S4: Collect and reuse the filtered filtrate in multiple stages to ensure its quality. S5: The recycled fiber filler is subjected to efficient dehydration and surface activation modification; S6: The modified filler is compounded and homogenized with the paper pulp online; S7: High-frequency vibrating inclined screen is used for deep interception and fiber recovery of end-of-pipe wastewater; S8: Dynamically optimize process parameters.

2. The method for treating and reusing papermaking white water according to claim 1, characterized in that: In step S1, an integrated online water quality analysis instrument is installed on the outlet pipeline of the white water pool in the papermaking workshop to continuously monitor the chemical oxygen demand, total suspended solids, colloidal charge, conductivity and pH value of the white water in real time. The monitoring data is transmitted to the central control system in real time. Based on the built-in expert model, the system dynamically analyzes and provides early warnings on the concentration, charge characteristics and changing trends of the fine / colloidal components in the white water.

3. The method for treating and reusing papermaking white water according to claim 2, characterized in that: In step S2, based on real-time analysis results, precise stepwise flocculation is performed on the white water in the white water pretreatment reactor. Polyaluminum chloride flocculant is added to the first stage of the reactor, and its dosage is dynamically adjusted according to the online colloidal charge signal. The control range is 5-15 mg / L for every 1 mV decrease in zeta potential. Colloidal destabilization and initial micro-floc formation are completed under high shear stirring.

4. The method for treating and reusing papermaking white water according to claim 3, characterized in that: In step S2, in the second stage of the reactor, a cationic polyacrylamide solution of a specific molecular weight is added to the system. The dosage is finely adjusted to 2-10 mg / L based on turbidity feedback. Under low shear conditions, this promotes further bridging and growth of the flocs, forming dense and uniform filterable flocs.

5. A method for treating and reusing papermaking white water according to claim 4, characterized in that: In step S3, the pretreated white water is transported to a multi-disc filter with an improved structure. Each fan-shaped filter disc is physically separated radially to form two independent filtration and stripping units: an inner zone and an outer zone. The operating parameters set by the central control system based on the white water flow rate and TS concentration, including the spindle speed, zone vacuum degree, and backwash pressure, are applied to the filter to achieve selective and efficient retention and stripping of flocs of different particle sizes.

6. A method for treating and reusing papermaking white water according to claim 5, characterized in that: In step S4, the filtrate produced by the multi-disc filter is classified into three levels according to its solid content and clarity: the ultra-clear filtrate is collected and directly reused in the high-pressure spraying of the paper machine wire section and the coating preparation process, which have the highest requirements for water purity; the clear filtrate is collected and reused in the intermediate process of pulp dilution and pulp pump sealing water production; and the shallow turbid filtrate is collected and used as the feed water for the subsequent inclined wire deep treatment system.

7. A method for treating and reusing papermaking white water according to claim 6, characterized in that: In step S5, the slurry rich in fiber and filler recovered by the multi-disc filter is mechanically dewatered by a belt dewatering machine to increase its dryness to 25%-35%. Then, the dewatered slurry is transported to a modified reactor equipped with a temperature control jacket and a high-speed disperser. Under a temperature of 55-65°C and continuous mechanical shearing, cationic starch is first added to the system and reacted for 10 minutes. Then, an alkenyl succinic anhydride derivative is added and the reaction continues for 20 minutes to complete the charge modification and hydrophobic grafting of the filler particle surface.

8. A method for treating and reusing papermaking white water according to claim 7, characterized in that: In step S6, the modified filler slurry is continuously and stably injected into the main slurry pipe of the papermaking flow system at a ratio of 1%-5% of the total main slurry on an absolute dry basis using a high-precision metering pump. The injection point is selected in a pipe section with turbulent flow, and the fluid kinetic energy is used to achieve initial dispersion. Subsequently, an online static mixer is installed after the slurry pump to perform forced homogenization treatment on the mixed slurry to ensure that the modified filler is evenly distributed in the fiber network.

9. A method for treating and reusing papermaking white water according to claim 8, characterized in that: In step S7, the collected shallow turbid filtrate and other low-concentration white water are gathered and evenly distributed onto the screen surface of a high-frequency micro-amplitude vibrating inclined screen through a water distribution system equipped with homogenization and energy dissipation devices. The vibration frequency of the inclined screen is controlled at 15-25Hz and the amplitude is controlled at 1-2mm. Under these conditions, the residual fine fibers in the water are efficiently intercepted. The intercepted fiber residue is then dewatered by a spiral and reused.

10. A method for treating and reusing papermaking white water according to claim 9, characterized in that: In step S8, online water quality data, operating status data of various devices, and data from the final paper basis weight and strength online testing instrument are integrated, collected, and analyzed. Based on the fuzzy-PID composite control algorithm, the flocculant addition curve is dynamically optimized according to water quality changes. Based on the ash content test results of the recycled pulp, the amount of modifier added is adjusted in reverse. Based on the real-time signal of paper smoothness, the compounding ratio is finely adjusted.

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