Fiber screening and recycling process for backflow glue solution in surface sizing

Abstract

The invention belongs to the technical field of papermaking, and particularly relates to a fiber screening and recycling process for a backflow glue solution in surface sizing. The process comprises the following steps: feeding materials to a spraying cavity through a sizing feeding groove, and transferring the materials to paper after the sizing amount is controlled by a sizing upper roller, a sizing lower roller and a metering rod. And the redundant sizing material and the new sizing material are scraped by the metering rod and flow into the reflux tank. And after the backflow glue solution is subjected to pumping and centrifugal separation pretreatment by a slag separator, heavy slag is treated by a circular vibrating screen, and the recycled glue solution is reused in a backflow tank. And the accepted pulp enters the square vibration sieve, is distributed to the stepped sieve plate through the porous sieve spraying cavity, and is respectively collected to the 1 # or 2 # collecting tank. And the 1 # collecting tank is connected with a slag separator. And concentrating and screening residues treated by the circular vibrating screen and the square vibrating screen, feeding impurities to a waste paper line pulper for recycling, and blending accepted pulp into a core layer for papermaking. According to the fiber screening and recycling process for the backflow glue solution in surface sizing, the material loss is small, the recycling rate is high, energy is saved, consumption is reduced, and zero emission of waste in papermaking is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a fiber screening and recovery process of reflux glue solution in surface sizing. Background Art

[0002] In the field of pulp and paper, the surface sizing process, as a key link to improve paper quality and performance, has been widely used at home and abroad. In particular, the rapid development of film transfer sizing technology has not only significantly increased the speed of the machine, but also effectively improved the sizing effect and surface performance of the paper. However, with the continuous advancement of papermaking technology and the increasing production demand, the surface sizing process is also facing new challenges and problems.

[0003] First, although the increase in vehicle speed has brought about a significant increase in production efficiency, it has also exacerbated the problem of fine fiber peeling on the paper surface. As the vehicle speed increases, the peeling force on the fine fibers on the paper surface also increases, and the viscosity and permeability of the glue itself further exacerbate the fiber peeling phenomenon. This not only affects the strength and uniformity of the paper, but also increases the fiber loss and glue waste during the production process.

[0004] Secondly, while pursuing efficient production, large domestic papermaking companies have also begun to gradually equip themselves with self-made chemical mechanical pulp or chemical pulping lines. However, the pipeline wet pulp produced by these pulping lines is often not fully heat-dissipated, resulting in a large amount of fiber fragments. After entering the sizing system, these fiber fragments will seriously affect the stability of the glue and the sizing effect. In addition, some companies that use waste paper for pulping are also facing the problem of unstable waste paper quality. Excessive ash content in waste paper will carry a large amount of inorganic matter into the sizing system, further affecting paper quality and production stability.

[0005] In view of the above problems, the prior art proposes a surface sizing starch glue purification system and its application method. The system purifies the slurry by combining a pressure screen, a slag remover, a square vibrating screen and other equipment. However, the purification system still has some shortcomings in practical applications. For example, the slag remover can only remove part of the heavy slag by adjusting the pressure difference, and due to the adhesion of the rubber, these heavy slags often carry a large amount of fiber rubber loss. In addition, the mesh aperture of the square vibrating screen is large (100-120 mesh), and the bottom of the screen plate is directly connected to the feed trough, which easily leads to screen blockage and rubber loss. At the same time, the impurities after removal are directly discharged into the wastewater, which not only causes a waste of resources, but also increases the difficulty and cost of water treatment. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a fiber screening and recovery process for the reflux glue solution in surface sizing, which has small material loss, high recovery rate, energy saving and consumption reduction, and achieves zero waste discharge in papermaking.

[0007] The fiber screening and recovery process of the reflowing glue solution in the surface sizing of the present invention comprises the following steps: (1) The glue feeding trough feeds the glue spray chamber, and the spray chamber sprays on the surface of the upper and lower glue rollers. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper. The upper and lower glue rollers circulate, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux trough. The mass of the reflux accounts for 90-95% of the amount of material fed; (2) The glue liquid in the reflux tank is pumped to the cleaner for centrifugal separation to pre-treat heavy impurities; (3) The heavy residue at the bottom of the slag remover enters the circular vibrating screen to treat the heavy residue, and the recovered glue is reused in the reflux tank, forming a short circulation process; (4) The square vibrating screen receives the good pulp from the slag remover, enters the porous square screen spray chamber for distribution, and enters the sieve plate area. The four sieve plates, 1# sieve plate, 2# sieve plate, 3# sieve plate, and 4# sieve plate, are laid flat in a stepped manner with an angle of 1-3°. The 1# sieve plate corresponds to the 1# sieve plate collection chamber, which is connected to the 1# collection tank. The rubber material in the 1# collection tank is returned to the good pulp outlet of the slag remover. The 2# sieve plate, 3# sieve plate, and 4# sieve plate correspond to the 2# / 3# / 4# sieve plate collection chamber, which is connected to the 2# collection tank. The 2# collection tank is connected to the upper trough for further reuse. (5) The slag after being processed by the circular vibrating screen and the square vibrating screen is connected to the recovery slag tank. After concentration and screening, the screened impurities are transported to the waste paper line pulper for reuse, and the screened good pulp is added to the core layer papermaking.

[0008] The inlet pressure of the slag remover in step (2) is controlled at 250-300 kPa, and the inlet and outlet pressure difference is controlled at 150-180 kPa.

[0009] The mesh size of the circular vibrating screen in step (3) is 200 meshes.

[0010] The concentration of the vibrating slag after the circular vibrating sieving treatment in step (3) is ≥1.5%, and the ash content is ≥1%.

[0011] The hole diameter of the porous square screen spray chamber in step (4) is 2-3 cm.

[0012] The mesh number of the 1# sieve plate in step (4) is 60-80 mesh, and the rubber material in the 1# collecting tank is returned to the good pulp outlet of the slag remover. The reflux flow rate is measured and controlled to be 15-20% of the inlet square vibrating screen flow rate.

[0013] The mesh sizes of the 2# sieve plate, the 3# sieve plate, and the 4# sieve plate in step (4) are set to 120 mesh, 100 mesh, and 80 mesh, respectively.

[0014] The 2# collecting tank and the 1# collecting tank in step (4) are configured as a one-way overflow structure.

[0015] The square vibrating screen in step (4) is equipped with a movable spray water pipe, the water temperature of the spray water pipe is 60-70°C, the moving speed is 0.01-0.1m / s, and the spray pressure is 3-6kPa.

[0016] The pulp concentration after concentration in step (5) is 2.5-3.5%.

[0017] The screening in step (5) uses a first-stage three-stage pressure screen.

[0018] Specifically, the fiber screening and recovery process of the reflowing glue solution in the surface sizing comprises the following steps: (1) The glue feeding trough feeds the glue spray chamber, and the spray chamber sprays glue on the surface of the upper and lower glue rollers. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper. The upper and lower glue rollers circulate back, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux trough. The mass of the reflux accounts for 90-95% of the amount of material fed. If the ratio is less than this, there will be coating leaks.

[0019] (2) The glue liquid in the reflux tank is pumped to the cleaner for centrifugal separation and pretreatment of heavy impurities. The inlet pressure of the cleaner is controlled at 250-300 kPa, and the inlet and outlet pressure difference is controlled at 150-180 kPa.

[0020] (3) The heavy residue at the bottom of the slag remover enters a 200-mesh circular vibrating screen for treatment, and heavy impurities are removed. The recovered rubber liquid is pumped to the reflux tank, forming a short-circuit process and multi-stage treatment to reduce rubber loss. The circular vibrating screen residue is recovered to the recovery residue tank. The concentration of the vibrating screen residue is ≥1.5%, and the ash content is ≥1%.

[0021] (4) The square vibrating screen receives the good slurry from the slag remover and enters the sieve plate area through the 2-3 cm porous tube steady pressure distribution of the porous square screen spray chamber. The four sieve plates, 1# sieve plate, 2# sieve plate, 3# sieve plate and 4# sieve plate, are laid flat in a step-by-step manner with an angle of 1-3°. The 1# sieve plate corresponds to the 1# sieve plate collection chamber, which is connected to the 1# collection tank. The mesh number of the sieve plate is 60-80 to prevent the rubber from coming out of the main pipe from blocking the screen. The rubber from the 1# collection tank is returned to the good slurry outlet of the slag remover. A flow meter is installed on the return pipeline to display the reflux flow rate. The reflux flow rate is controlled to be 15-20% of the inflow square vibrating screen flow rate to avoid the feed flow rate Fluctuation; the mesh numbers of 2# sieve plate, 3# sieve plate and 4# sieve plate are set to 120 mesh, 100 mesh and 80 mesh respectively, 2# sieve plate, 3# sieve plate and 4# sieve plate correspond to 2# / 3# / 4# sieve plate collecting material chamber, 2# / 3# / 4# sieve plate collecting material chamber is connected to 2# collecting tank, 2# collecting tank is connected to feeding tank for continuous reuse, one-way overflow tank is set on the top of 2# collecting tank and 1# collecting tank, which is convenient for disassembly and replacement of a certain sieve plate, and can be continuously processed. The square vibrating screen is equipped with a spray water pipe, which is movable. The movable spray water temperature is 60-70℃, the moving speed is 0.01-0.1m / s, and the spray pressure is 3-6kPa.

[0022] (5) The slag after being processed by the circular vibrating screen and the square vibrating screen is connected to the recovery slag tank. After being concentrated to a concentration of 2.5-3.5% by the round screen, it enters the first-level three-stage pressure screen for screening. The screened impurities are transported to the waste paper line pulper for reuse, and the screened good pulp is added to the core layer papermaking. Because the recycled material in the slag tank contains enzyme-converted starch, the strength of the damaged pulp can be improved.

[0023] Compared with the prior art, the present invention has the following beneficial effects: After the fiber screening and recovery process of the returned glue solution in the surface sizing of the present invention is implemented, the papermaking sizing section no longer discharges waste glue solution, the monthly sizing starch consumption is reduced by 6-10 tons, and the fiber consumption per ton of paper is reduced by 1-2kg / t; the sizing residue content of the sizing solution is reduced from 6500ppm to 4368-4953ppm, the cleanliness of the glue solution is improved by 21.91%-27.2%, and the amount of defective products returned due to downgrading of sizing streaks is reduced by 48-54 tons per month; the COD content of the wastewater received by the water plant from the paper machine is reduced from 7000ppm to 5883-6627ppm, the suspended matter content is reduced from 624ppm to 408-603ppm, and the TDS content is reduced from 2230ppm to 1410-1896ppm. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the fiber screening and recovery process of the reflowing glue solution in the surface sizing of the present invention.

[0025] Figure 2Schematic diagram of a square vibrating screen.

[0026] Figure 1 Middle: 1. Glue application upper roller; 2. Glue application lower roller; 3. Feeding trough; 4. 2# collecting trough; 5. 1# collecting trough; 6. Square vibrating screen; 7. Reflux trough; 8. Deslagging device; 9. Circular vibrating screen; 10. Residue recovery trough; 11. Round screen; 12. Pressure screen; 13. Broken paper trough; 14. Paper; Figure 2 Middle: 15, good pulp inlet; 16, porous square screen spray chamber; 17, 1# sieve plate; 18, 2# sieve plate; 19, 3# sieve plate; 20, 4# sieve plate; 21, spray water pipe; 22, spray water bracket; 23, 1# sieve plate collecting chamber; 24, 2# / 3# / 4# sieve plate collecting chamber. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with specific embodiments.

[0028] The % described in the present invention is a mass percentage.

[0029] The fiber screening and recovery process of the reflowing glue solution in the surface sizing of the present invention is as follows Figure 1-2 As shown, the working steps are: (1) The glue feeding trough 3 feeds glue to the glue spray chamber, which sprays glue on the surface of the upper glue roller 1 and the lower glue roller 2. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper 14. The upper glue roller 1 and the lower glue roller 2 circulate back, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux groove 7. The mass of the reflux accounts for 90-95% of the feeding amount.

[0030] (2) The glue liquid in the reflux tank 7 is pumped to the cleaner 8 for centrifugal separation to pre-treat heavy impurities. The inlet pressure of the cleaner 8 is controlled at 250-300 kPa, and the inlet and outlet pressure difference is controlled at 150-180 kPa.

[0031] (3) The heavy residue at the bottom of the slag remover 8 enters the 200-mesh circular vibrating screen 9 for treatment, and the heavy impurities are removed. The recovered rubber liquid is pumped to the reflux tank 7, forming a short circulation process and multi-stage treatment to reduce the loss of rubber. The residue of the circular vibrating screen 9 is recovered to the recovery residue tank 10. The concentration of the vibrating screen residue is ≥1.5%, and the ash content is ≥1%.

[0032] (4) The square vibrating screen 6 receives the good pulp from the slag remover 8, enters the porous square screen spray chamber 16 from the good pulp inlet 15, and enters the sieve plate area through a 2-3 cm porous tube pressure distribution. The four sieve plates, 1# sieve plate 17, 2# sieve plate 18, 3# sieve plate 19, and 4# sieve plate 20, are laid flat in a stepped manner with an angle of 1-3°. The 1# sieve plate 17 corresponds to the 1# sieve plate collecting chamber 23, which is connected to the 1# collecting tank 5. The mesh number of the sieve plate is 60-80 to prevent the rubber from coming out of the main pipe from blocking the screen. The rubber from the 1# collecting tank 5 is returned to the good pulp outlet of the slag remover 8. A flow meter is installed on the return pipeline to display the reflux flow rate. The reflux flow rate is controlled to be 15-20% of the flow into the square vibrating screen 6 to avoid fluctuations in the feed flow rate; The mesh numbers of sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 are set to 120 mesh, 100 mesh, and 80 mesh respectively. 2# sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 correspond to 2# / 3# / 4# sieve plate collecting chambers 24. 2# / 3# / 4# sieve plate collecting chambers 24 are connected to 2# collecting tank 4, and 2# collecting tank 4 is connected to feeding tank 3, and the material liquid continues to be reused. A one-way overflow structure is set between 2# collecting tank 4 and 1# collecting tank 5, which is convenient for disassembly and replacement of a certain sieve plate, and can be continuously processed. A spray water pipe 21 is equipped on the square vibrating screen 6, and the spray water pipe 21 is fixed on the spray water bracket 22 and is movable. The spray water temperature is 60-70°C, the moving speed is 0.01-0.1m / s, and the spray pressure is 3-6kPa.

[0033] (5) The slag processed by the circular vibrating screen 9 and the square vibrating screen 6 is connected to the recovery slag tank 10, and after being concentrated to a concentration of 2.5-3.5% by the round screen 11, it enters the first-stage three-stage pressure screen 12 for screening. The screened impurities are transported to the waste paper line pulper for reuse. After screening, the good pulp enters the broken paper tank 13 for the core layer papermaking.

[0034] Example 1 The fiber screening and recovery process of the reflowing glue solution in the surface sizing comprises the following steps: (1) The glue feeding trough 3 feeds glue to the glue spray chamber, which sprays glue on the surface of the upper glue roller 1 and the lower glue roller 2. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper 14. The upper glue roller 1 and the lower glue roller 2 circulate back, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux groove 7. The mass of the reflux accounts for 90% of the feeding amount.

[0035] (2) The glue liquid in the reflux tank 7 is pumped to the cleaner 8 for centrifugal separation to pre-treat heavy impurities. The inlet pressure of the cleaner 8 is controlled at 250 kPa, and the inlet and outlet pressure difference is controlled at 150 kPa.

[0036] (3) The heavy residue at the bottom of the slag remover 8 enters the 200-mesh circular vibrating screen 9 for treatment, and the heavy impurities are removed. The recovered rubber liquid is pumped to the reflux tank 7, forming a short circulation process and multi-stage treatment to reduce the loss of rubber. The residue of the circular vibrating screen 9 is recovered to the recovery residue tank 10. The concentration of the vibrating screen residue is 1.5% and the ash content is 1.2%.

[0037] (4) The square vibrating screen 6 receives the good pulp from the slag remover 8, enters the porous square screen spray chamber 16 from the good pulp inlet 15, and enters the sieve plate area through a 2-3 cm porous tube pressure distribution. The four sieve plates, 1# sieve plate 17, 2# sieve plate 18, 3# sieve plate 19, and 4# sieve plate 20, are laid flat in a stepped manner with an angle of 1°. The 1# sieve plate 17 corresponds to the 1# sieve plate collecting chamber 23, which is connected to the 1# collecting tank 5. The mesh number of the sieve plate is 60 to prevent the rubber from coming out of the main pipe from blocking the screen. The rubber from the 1# collecting tank 5 is returned to the good pulp outlet of the slag remover 8. A flow meter is installed on the return pipeline to display the reflux flow rate. The reflux flow rate is controlled to be 15% of the flow into the square vibrating screen 6 to avoid fluctuations in the feed flow rate; The mesh numbers of sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 are set to 120 mesh, 100 mesh, and 80 mesh respectively. 2# sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 correspond to 2# / 3# / 4# sieve plate collecting chambers 24. 2# / 3# / 4# sieve plate collecting chambers 24 are connected to 2# collecting tank 4, and 2# collecting tank 4 is connected to feeding tank 3, and the material liquid continues to be reused. A one-way overflow structure is set between 2# collecting tank 4 and 1# collecting tank 5, which is convenient for disassembly and replacement of a certain sieve plate, and can be continuously processed. A spray water pipe 21 is equipped on the square vibrating screen 6, and the spray water pipe 21 is fixed on the spray water bracket 22 and is movable. The spray water temperature is 60°C, the moving speed is 0.01m / s, and the spray pressure is 3kPa.

[0038] (5) The slag processed by the circular vibrating screen 9 and the square vibrating screen 6 is connected to the recovery slag tank 10, and after being concentrated to a concentration of 2.5% by the round screen 11, it enters the first-level three-stage pressure screen 12 for screening. The screened impurities are transported to the waste paper line pulper for reuse. After screening, the good pulp enters the damaged paper tank 13 for the core layer papermaking.

[0039] After the implementation of the fiber screening and recovery process of the returned glue liquid in the above surface sizing, the papermaking sizing section no longer discharges waste glue liquid, the monthly sizing starch consumption is reduced by 6 tons, and the fiber consumption per ton of paper is reduced by 1kg / t; the sizing liquid residue content is 4953ppm, the cleanliness of the glue liquid is improved by 22.45%, and the amount of defective products returned due to downgrading of sizing streaks is reduced by 54 tons per month; the COD content of paper machine wastewater received by the water plant is 5883ppm, the suspended solid content is 408ppm, and the TDS content is 1410ppm.

[0040] Example 2 The fiber screening and recovery process of the reflowing glue solution in the surface sizing comprises the following steps: (1) The glue feeding trough 3 feeds glue to the glue spray chamber, which sprays glue on the surface of the upper glue roller 1 and the lower glue roller 2. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper 14. The upper glue roller 1 and the lower glue roller 2 circulate back, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux groove 7. The mass of the reflux accounts for 92% of the feeding amount.

[0041] (2) The glue liquid in the reflux tank 7 is pumped to the cleaner 8 for centrifugal separation to pre-treat heavy impurities. The inlet pressure of the cleaner 8 is controlled at 280 kPa, and the inlet and outlet pressure difference is controlled at 165 kPa.

[0042] (3) The heavy residue at the bottom of the slag remover 8 enters the 200-mesh circular vibrating screen 9 for treatment, and the heavy impurities are removed. The recovered rubber liquid is pumped to the reflux tank 7, forming a short circulation process and multi-stage treatment to reduce the loss of rubber. The residue of the circular vibrating screen 9 is recovered to the recovery residue tank 10. The concentration of the vibrating screen residue is 1.7% and the ash content is 1.5%.

[0043] (4) The square vibrating screen 6 receives the good pulp from the slag remover 8, enters the porous square screen spray chamber 16 from the good pulp inlet 15, and enters the sieve plate area through a 2-3 cm porous tube pressure distribution. The four sieve plates, 1# sieve plate 17, 2# sieve plate 18, 3# sieve plate 19, and 4# sieve plate 20, are laid flat in a stepped manner with an angle of 2°. The 1# sieve plate 17 corresponds to the 1# sieve plate collecting chamber 23, which is connected to the 1# collecting tank 5. The mesh number of the sieve plate is 70 to prevent the rubber from coming out of the main pipe from blocking the screen. The rubber from the 1# collecting tank 5 is returned to the good pulp outlet of the slag remover 8. A flow meter is installed on the return pipeline to display the reflux flow rate. The reflux flow rate is controlled to be 15% of the flow into the square vibrating screen 6 to avoid fluctuations in the feed flow rate; The mesh numbers of sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 are set to 120 mesh, 100 mesh, and 80 mesh respectively. 2# sieve plates 18, 3# sieve plates 19, and 4# sieve plates 20 correspond to 2# / 3# / 4# sieve plate collecting chambers 24. 2# / 3# / 4# sieve plate collecting chambers 24 are connected to 2# collecting tank 4, and 2# collecting tank 4 is connected to feeding tank 3, and the material liquid continues to be reused. A one-way overflow structure is set between 2# collecting tank 4 and 1# collecting tank 5, which is convenient for disassembly and replacement of a certain sieve plate, and can be continuously processed. A spray water pipe 21 is equipped on the square vibrating screen 6, and the spray water pipe 21 is fixed on the spray water bracket 22 and is movable. The spray water temperature is 65°C, the moving speed is 0.05m / s, and the spray pressure is 5kPa.

[0044] (5) The slag processed by the circular vibrating screen 9 and the square vibrating screen 6 is connected to the recovery slag tank 10, and after being concentrated to a concentration of 3.0% by the round screen 11, it enters the first-level three-stage pressure screen 12 for screening. The screened impurities are transported to the waste paper line pulper for reuse. After screening, the good pulp enters the broken paper tank 13 for the core layer papermaking.

[0045] After the implementation of the fiber screening and recovery process of the returned glue liquid in the above surface sizing, the papermaking sizing section no longer discharges waste glue liquid, the monthly sizing starch consumption is reduced by 8 tons, and the fiber consumption per ton of paper is reduced by 1.4kg / t; the sizing liquid residue content is 4683ppm, the cleanliness of the glue liquid is improved by 21.95%, and the amount of defective products returned due to downgrading of sizing streaks is reduced by 48 tons per month; the COD content of paper machine wastewater received by the water plant is 6416ppm, the content of suspended solids is 468ppm, and the TDS content is 1710ppm.

[0046] Example 3 The fiber screening and recovery process of the reflowing glue solution in the surface sizing comprises the following steps: (1) The glue feeding trough 3 feeds glue to the glue spray chamber, which sprays glue on the surface of the upper glue roller 1 and the lower glue roller 2. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper 14. The upper glue roller 1 and the lower glue roller 2 circulate back, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux groove 7. The mass of the reflux accounts for 95% of the feeding amount.

[0047] (2) The glue liquid in the reflux tank 7 is pumped to the cleaner 8 for centrifugal separation to pre-treat heavy impurities. The inlet pressure of the cleaner 8 is controlled at 300 kPa, and the inlet and outlet pressure difference is controlled at 180 kPa.

[0048] (3) The heavy residue at the bottom of the slag remover 8 enters the 200-mesh circular vibrating screen 9 for treatment, and the heavy impurities are removed. The recovered rubber liquid is pumped to the reflux tank 7, forming a short circulation process and multi-stage treatment to reduce the loss of rubber. The residue of the circular vibrating screen 9 is recovered to the recovery residue tank 10. The concentration of the vibrating screen residue is 1.8%, and the ash content is 1.8%.

[0049] (4) The square vibrating screen 6 receives the good pulp from the slag remover 8, enters the porous square screen spray chamber 16 from the good pulp inlet 15, and enters the screen plate area through a 2-3 cm porous tube pressure distribution. The four sieve plates, 1# sieve plate 17, 2# sieve plate 18, 3# sieve plate 19, and 4# sieve plate 20, are laid flat in a stepped manner with an angle of 3°. The 1# sieve plate 17 corresponds to the 1# sieve plate collecting chamber 23, which is connected to the 1# collecting tank 5. The mesh number of the sieve plate is 80 to prevent the rubber from coming out of the main pipe from blocking the screen. The rubber from the 1# collecting tank 5 is returned to the good pulp outlet of the slag remover 8. A flow meter is installed on the return pipeline to display the reflux flow rate. The reflux flow rate is controlled to be 20% of the flow into the square vibrating screen 6 to avoid fluctuations in the feed flow rate; 2 The mesh numbers of #sieve plate 18, 3#sieve plate 19 and 4#sieve plate 20 are set to 120 mesh, 100 mesh and 80 mesh respectively. 2#sieve plate 18, 3#sieve plate 19 and 4#sieve plate 20 correspond to 2# / 3# / 4#sieve plate collecting chamber 24. 2# / 3# / 4#sieve plate collecting chamber 24 is connected to 2#collecting tank 4, 2#collecting tank 4 is connected to feeding tank 3, and the material liquid is continuously reused. 2#collecting tank 4 and 1#collecting tank 5 are provided with a one-way overflow structure, which is convenient for disassembly and replacement of a certain sieve plate, and can be continuously processed. The square vibrating screen 6 is equipped with a spray water pipe 21, which is fixed on the spray water bracket 22 and is movable. The spray water temperature is 70°C, the moving speed is 0.1m / s, and the spray pressure is 6kPa.

[0050] (5) The slag processed by the circular vibrating screen 9 and the square vibrating screen 6 is connected to the recovery slag tank 10, and after being concentrated to a concentration of 3.5% by the round screen 11, it enters the first-level three-stage pressure screen 12 for screening. The screened impurities are transported to the waste paper line pulper for reuse. After screening, the good pulp enters the broken paper tank 13 for the core layer papermaking.

[0051] After the implementation of the fiber screening and recovery process of the returned glue liquid in the above surface sizing, the papermaking sizing section no longer discharges waste glue liquid, the monthly sizing starch consumption is reduced by 10 tons, and the fiber consumption per ton of paper is reduced by 2kg / t; the sizing liquid screen residue content is 4368ppm, the glue liquid cleanliness is improved to 27.2%, and the amount of defective products returned due to downgrading of sizing streaks is reduced by 52 tons per month; the COD content of paper machine wastewater received by the water plant is 6627ppm, the suspended matter content is 603ppm, and the TDS content is 1896ppm.

Claims

1. A fiber screening and recovery process of the reflowing glue solution in surface sizing, characterized in that: The following steps are involved: (1) The glue feeding trough feeds the glue spray chamber, and the spray chamber sprays on the surface of the upper and lower glue rollers. The metering rod controls the amount of glue on the surface through pressure, and then transfers it to the paper. The upper and lower glue rollers circulate, and the excess glue on the surface and the newly sprayed glue are scraped off by the metering rod again and flow into the reflux trough. The mass of the reflux accounts for 90-95% of the amount of material fed; (2) The glue liquid in the reflux tank is pumped to the cleaner for centrifugal separation to pre-treat heavy impurities; (3) The heavy residue at the bottom of the slag remover enters the circular vibrating screen to treat the heavy residue, and the recovered glue is reused in the reflux tank, forming a short circulation process; (4) The square vibrating screen receives the good pulp from the slag remover, enters the porous square screen spray chamber for distribution, and enters the sieve plate area. The four sieve plates, 1# sieve plate, 2# sieve plate, 3# sieve plate, and 4# sieve plate, are laid flat in a stepped manner with an angle of 1-3°. The 1# sieve plate corresponds to the 1# sieve plate collection chamber, which is connected to the 1# collection tank. The rubber material in the 1# collection tank is returned to the good pulp outlet of the slag remover. The 2# sieve plate, 3# sieve plate, and 4# sieve plate correspond to the 2# / 3# / 4# sieve plate collection chamber, which is connected to the 2# collection tank. The 2# collection tank is connected to the upper trough for further reuse. (5) The slag after being processed by the circular vibrating screen and the square vibrating screen is connected to the recovery slag tank. After concentration and screening, the screened impurities are transported to the waste paper line pulper for reuse, and the screened good pulp is added to the core layer papermaking.

2. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The inlet pressure of the slag remover in step (2) is controlled at 250-300 kPa, and the inlet and outlet pressure difference is controlled at 150-180 kPa.

3. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The mesh size of the circular vibrating screen in step (3) is 200 meshes.

4. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The concentration of the vibrating slag after the circular vibrating sieving treatment in step (3) is ≥1.5%, and the ash content is ≥1%.

5. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The hole diameter of the porous square screen spray chamber in step (4) is 2-3 cm.

6. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The mesh number of the 1# sieve plate in step (4) is 60-80 mesh, and the rubber material in the 1# collecting tank is returned to the good pulp outlet of the slag remover. The reflux flow rate is measured and controlled to be 15-20% of the inlet square vibrating screen flow rate.

7. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The mesh sizes of the 2# sieve plate, the 3# sieve plate and the 4# sieve plate in step (4) are set to 120 mesh, 100 mesh and 80 mesh respectively; the 2# collecting tank and the 1# collecting tank in step (4) are set to a one-way overflow structure.

8. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The square vibrating screen in step (4) is equipped with a movable spray water pipe, the water temperature of the spray water pipe is 60-70°C, the moving speed is 0.01-0.1m / s, and the spray pressure is 3-6kPa.

9. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The pulp concentration after concentration in step (5) is 2.5-3.5%.

10. The fiber screening and recovery process of the reflowing glue solution in surface sizing according to claim 1, characterized in that: The screening in step (5) uses a first-stage three-stage pressure screen.

Images