A method for improving the quality stability of papermaking process reconstituted tobacco slurry

Abstract

The application discloses a method for improving the quality stability of papermaking method reconstituted tobacco slurry, mainly comprising the following steps: (1) material mixing and leaching; (2) solid-liquid separation; (3) solid dilution, stirring and mixing in a dilution slurry tank; (4) material conveying to a pre-beating slurry tank for stirring and mixing; (5) material conveying to a mill for beating treatment and then storing in a post-beating slurry tank. A flow metering device is arranged on a dilution water pipeline, a first concentration detection device and a first self-circulation pipeline are sequentially arranged on an outlet pipeline of the dilution slurry tank, a concentration-adjusting water pipeline, a second concentration detection device, a second self-circulation pipeline and a cleaning water pipeline are sequentially arranged on an outlet pipeline of the pre-beating slurry tank; the online automatic regulation and control of the dilution water amount of material head and tail material conveyed from the leaching process to the pulping process is realized, the mill start-stop machine process mode is improved, the slurry quality fluctuation caused by the mill start-stop machine is avoided, the unqualified slurry is avoided to be conveyed to subsequent production links, and the quality stability of the slurry is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of reconstituted tobacco production, and particularly relates to a method for improving the quality stability of pulp of papermaking reconstituted tobacco. TECHNICAL BACKGROUND

[0002] The pulping technology is a process of realizing a series of changes in longitudinal and transverse forms such as defibration, cutting and filament splitting of insoluble substances under the action of mechanical force by means of pulping equipment, and finally forming pulp for paper machine. The pulping process is a key process in the production of papermaking reconstituted tobacco, and the quality and stability of the pulp directly affect the quality of reconstituted tobacco base sheet and finished product.

[0003] After the tobacco stem and tobacco dust used for papermaking reconstituted tobacco production are mixed, leached and solid-liquid separated, the water-insoluble solid degree is about (36-40) %, and if a low-concentration pulping process is adopted, the water-insoluble solids delivered by the leaching process need to be diluted and thickened before pulping. In the existing process, the dilution water flow is calculated according to the water-insoluble solid degree delivered by the leaching process and the target concentration of the material after dilution, and the post operator will set a value for the dilution water flow before production operation. However, in the actual production process, when the solid-liquid separation equipment of the leaching process is started and stopped, the material plug inside the equipment is not fully formed, and the material at the head and tail has a low degree. If the dilution water flow is still set according to the original calculated flow, the concentration of this part of material at the head and tail after dilution is too low, and even if the concentration is adjusted again before pulping, it cannot be adjusted to the target concentration. In addition, the pulping equipment used in the pulping process is mostly a mill. In order to ensure a certain amount of pulp stock in the production line, the mill production pulp capacity is usually greater than the pulp consumption capacity of the subsequent process paper machine, so the mill will have a certain downtime every production shift. However, in the existing mode, the mill start-stop control is judged by the post operator according to experience, and the mill start-stop standards of each shift are not uniform, and the mill start-stop times and the amount of material at the head and tail cannot be accurately controlled. At the same time, when the mill is stopped, it needs to be flushed. Because there is a large amount of pulp that has not been completely treated in the mill chamber, the flushing water and pulp will be recovered to the pre-pulping storage tank, so that when the mill is started again, the concentration of the material in the pre-pulping storage tank is too low, usually from the target concentration (3.7-3.9) wt% to about 3.0 wt%, and the quality and stability of the pulp are seriously affected. Therefore, in the existing technology, whether it is the material at the head and tail of the leaching process or the start-stop of the mill in the pulping process, it will affect the quality and stability of the pulp prepared in the pulping process, and the delivery of this part of unqualified pulp to the next process will also cause the physical and chemical quality of the papermaking reconstituted tobacco base sheet and finished product to fluctuate.

[0004] CN113287776B discloses a papermaking method for reconstituted tobacco pulp concentration control system, which detects the moisture content and instantaneous flow of the water-insoluble solid after solid-liquid separation in the extraction process by designing an online moisture meter and a weighing meter screw, thereby regulating the dilution water quantity of the material after solid-liquid separation, and improving the stability of the pulp concentration after dilution. However, it does not realize automatic control of the mill start-stop according to the actual storage amount of the online pulp, does not realize hierarchical control of the target concentration of the material after dilution according to the mill operating condition, and the cleaning water after the mill stops causes the concentration of the material in the adjusting pulp tank to decrease rapidly, the adjusting pulp tank outlet concentration controller can only adjust the concentration of the material with slight fluctuation around the target concentration, and cannot adjust the material with concentration significantly lower than the target concentration. Therefore, when the mill starts again, the recovery of the concentration of the material in the adjusting pulp tank can only be realized by supplementing new material from the extraction process to gradually replace the low-concentration material, and the concentration recovery takes a long time. Meanwhile, the scheme has high cost investment and large occupied space, and some old factories do not have conditions for optimization and reconstruction, and it is difficult to calibrate and maintain the instruments and meters in a hot and humid environment. SUMMARY

[0005] The present application discloses a method for improving the quality stability of papermaking reconstituted tobacco pulp, which realizes online regulation of the dilution water quantity of the material head and tail delivered from the extraction process to the pulping process, realizes automatic control of the mill start-stop according to the online pulp storage amount, realizes hierarchical control of the target concentration of the material after dilution according to the mill operating condition, provides the material for pulping in a short time, guarantees the production continuity, avoids the fluctuation of the pulp quality caused by the mill start-stop, prevents the delivery of unqualified pulp to the subsequent production link, and improves the pulp quality and its stability. The present application has wide application range, low investment, and low maintenance cost, and has achieved good application effect.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] A method for improving the quality stability of papermaking reconstituted tobacco pulp, the process is as follows:

[0008] (1) mixing and extracting tobacco stems, tobacco fines and water in a mixing extraction tank according to a certain proportion;

[0009] (2) delivering the mixed material in step (1) to a wringer for solid-liquid separation to obtain extraction liquid and water-insoluble solids;

[0010] (3) storing the extraction liquid in step (2) in an extraction liquid storage tank, diluting the water-insoluble solids with dilution water, storing the diluted material in a dilution pulp tank, and continuously stirring and mixing; the concentration of the material at the outlet of the dilution pulp tank is set as a first target concentration, and a first concentration detection device and a first self-circulation pipeline are sequentially arranged on the outlet pipeline of the dilution pulp tank;

[0011] (4) The material diluted to the first target concentration in step (3) is transported to the pre-beating pulp tank and continuously stirred and mixed to adjust the material concentration to the second target concentration. A concentration-adjusting water pipeline, a second concentration detection device, a second self-circulation pipeline and a cleaning water pipeline are sequentially arranged on the outlet pipeline of the pre-beating pulp tank.

[0012] (5) The material adjusted to the second target concentration in step (4) is transported to the mill at a certain flow rate, the mill starts to run, and the pulp after beating treatment is stored in the post-beating pulp tank. A cleaning water recovery pipeline is arranged on the outlet pipeline of the mill and connected to the pre-beating pulp tank.

[0013] (6) When the actual pulp storage amount of the production line reaches 85% of the set storage amount, the mixing leaching tank stops transporting the material to the wringer, and when the liquid level of the dilution pulp tank is ≤60%, the transportation of the material to the pre-beating pulp tank is stopped, and the concentration of the material at the outlet of the dilution pulp tank is adjusted to the third target concentration.

[0014] (7) When the liquid level of the pre-beating pulp tank is ≤30%, clean water is used to clean the mill and the associated pipelines, and the cleaning water and the material in the mill chamber are recovered to the pre-beating pulp tank, and the mill stops running.

[0015] (8) When the actual pulp storage amount of the production line is less than 35% of the set storage amount, the material in the dilution pulp tank is used to adjust the concentration of the material in the pre-beating pulp tank, so that the material in the pre-beating pulp tank reaches the second target concentration.

[0016] (9) After the concentration adjustment of the material in the pre-beating pulp tank in step (8) is completed, the mill starts to run again, and the material reaching the second target concentration in step (8) is subjected to beating treatment, and the pulp after beating treatment is stored in the post-beating pulp tank.

[0017] Further, a dilution water flow metering device is arranged on the dilution water pipeline in step (3), and the running current of the wringer and the concentration of the material at the outlet of the dilution pulp tank are used as two-level feedback factors to adjust the dilution water flow in steps (3) and (6). The operating relationship between the running current of the wringer and the dilution water flow is shown in formula 1, and the operating relationship between the concentration of the material at the outlet of the dilution pulp tank and the dilution water flow is shown in formula 2. When the dilution water flow values calculated by formula 1 and formula 2 are different, the smaller one is taken to adjust the dilution water flow. The above formula 1 and formula 2 are as follows:

[0018]

[0019] In the formula:

[0020] Q'——dilution water flow, m 3 / h;

[0021] A'——running current of the wringer, real-time monitoring, unit: A;

[0022] Q - the required dilution water flow rate after the formation of the extruder plug, obtained by collecting past production data, a known quantity, unit: m 3 / h;

[0023] A - the stable running current of the extruder after the formation of the plug, obtained by collecting past production data, a known quantity, unit: A.

[0024]

[0025] In the formula:

[0026] Q' - dilution water flow rate, m 3 / h;

[0027] A' - the running current of the extruder, real-time monitoring, unit: A;

[0028] A - the stable running current of the extruder after the formation of the plug, obtained by collecting past production data, a known quantity, unit: A;

[0029] K - the absolute dry material quantity conveyed after the formation of the extruder plug, obtained by collecting past production data, a known quantity, unit: t / h;

[0030] L 稀 - actual liquid level of the dilution pulp pool, real-time monitoring, unit: %;

[0031] V 稀 - effective volume of the dilution pulp pool, unit: m 3 ;

[0032] C 稀 - actual concentration of the material at the outlet of the dilution pulp pool, real-time monitoring, unit: wt%;

[0033] C 稀目 - first target concentration of the dilution pulp pool, a known quantity, unit: wt%.

[0034] Further, the first target concentration, the second target concentration, and the third target concentration are respectively (4.0-4.4) wt%, (3.7-3.9) wt%, and (4.6-4.8) wt%.

[0035] Further, if the concentration of the material at the outlet of the dilution pulp pool in step (3) does not reach the numerical range of the first target concentration or the concentration of the material at the outlet of the dilution pulp pool in step (6) does not reach the numerical range of the third target concentration, the material in the dilution pulp pool is returned to the dilution pulp pool through the first self-circulation pipeline for continuous circulation and mixing.

[0036] Further, in the step (8), the dilution slurry pool material is returned to the dilution slurry pool through the first concentration detection device and the first self-circulation pipeline, the dilution slurry pool material is self-circulated for (2-4) min, during which the first concentration detection device collects the real-time concentration of the dilution slurry pool material every 2 s, when the self-circulation of the dilution slurry pool material is completed, the first concentration detection device calculates the average concentration of the dilution slurry pool material during the self-circulation, that is, the actual concentration of the dilution slurry pool material; the pre-beating slurry pool material is returned to the pre-beating slurry pool through the second concentration detection device and the second self-circulation pipeline, the pre-beating slurry pool material is self-circulated for (2-4) min, during which the second concentration detection device collects the real-time concentration of the pre-beating slurry pool material every 2 s, when the self-circulation of the pre-beating slurry pool material is completed, the second concentration detection device calculates the average concentration of the pre-beating slurry pool material during the self-circulation, that is, the actual concentration of the pre-beating slurry pool material; the amount of dilution slurry pool material needed to be supplemented to the pre-beating slurry pool is calculated according to the actual concentration of the dilution slurry pool material, the actual concentration of the pre-beating slurry pool material, the actual liquid level of the pre-beating slurry pool and the second target concentration, and the specific calculation is shown in formula 3, and the above formula 3 is as follows:

[0037]

[0038] In the formula:

[0039] V' 稀 The amount of dilution slurry pool material needed to be supplemented to the pre-beating slurry pool, unit: m 3 ;

[0040] L 叩 The actual liquid level of the pre-beating slurry pool, real-time monitoring quantity, unit: %

[0041] V 叩 The volume of the pre-beating slurry pool, known quantity, unit: m 3 ;

[0042] C 叩 The actual concentration of the material at the outlet of the pre-beating slurry pool, real-time monitoring quantity, unit: wt%

[0043] C 稀 The actual concentration of the material at the outlet of the dilution slurry pool, real-time monitoring quantity, unit: wt%

[0044] C 叩目 The second target concentration, known quantity, unit: wt%.

[0045] Further, in the step (1), the mass of the tobacco stems is (1-1.8) times the mass of the tobacco stems, the mass of the water is (5-8) times the sum of the mass of the tobacco stems and the mass of the tobacco stems, and the temperature of the water is (50-65)℃; in the step (2), the density of the leaching liquid is (1.048-1.057) g / cm 3 , and the dryness of the water-insoluble solid is (28-39) %.

[0046] Further, by regulating the dilution slurry pool outlet pump operating frequency, the dilution slurry pool material needing to be supplemented is transported to the pre-beating slurry pool within (5-7) min, so that the pre-beating slurry pool material concentration is quickly restored to the second target concentration.

[0047] Further, the actual slurry storage amount of the production line in steps (6) and (8) is obtained by real-time acquisition of the liquid levels of the slurry storage tanks, and then multiplying the liquid levels of the slurry storage tanks by the volumes of the slurry storage tanks, and the set slurry storage amount is obtained by adding the volumes of the slurry storage tanks of the production line.

[0048] The application provides a method for improving the quality stability of papermaking method reconstituted tobacco slurry, compared with the prior art, the application has a wider application range, and the following beneficial effects are achieved without increasing hardware facilities such as equipment and instruments:

[0049] (1) According to the dryness change of the water-insoluble solids at the head and tail of the material transported to the pulping process from the extraction process, the dilution water amount is regulated in real time, so that the pulping process is provided with performance stable material for beating treatment;

[0050] (2) The start-stop machine process mode of the pulping process mill is improved, automatic control of the start-stop machine of the mill is realized according to the online slurry storage amount, so that the start-stop machine times of the mill and the amount of the head and tail caused by the start-stop machine are uniformly and accurately controlled;

[0051] (3) The target concentration of the slurry in the dilution slurry pool is controlled in stages, before the mill is started again, the slurry with a higher concentration in the dilution slurry pool is used to balance the concentration of the slurry with a low concentration in the pre-beating slurry pool, so that the mill is started and operated again after the material in the pre-beating slurry pool reaches the target concentration in a short time, the concentration adjustment time of the material in the pre-beating slurry pool is reduced from (30-45) min in the prior art to (5-7) min, the production continuity is ensured, the invalid running time of the mill is reduced, the slurry quality and stability are improved, and good production application effect is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 It is a process flow schematic diagram of the application. DETAILED DESCRIPTION

[0053] The following implementation examples are given to explain the application in more detail, and it is necessary to point out that the following implementation examples cannot be understood as a limitation on the protection scope of the application, and some non-essential improvements and adjustments made by the skilled person in the art to the application according to the above application content shall still belong to the protection scope of the application.

[0054] Example 1

[0055] A method for improving the quality stability of papermaking method reconstituted tobacco slurry, like Figure 1As shown, the specific process is: 1200 kg of tobacco stems, 1800 kg of tobacco dust and 18 m 3 of water at 65℃ are mixed in a mixing leaching tank, and after solid-liquid separation by a squeezing machine, a leaching solution with a density of 1.055 g / cm 3 and water-insoluble solids with a dryness of 30% are obtained; the leaching solution is stored in a leaching solution storage tank, and the water-insoluble solids are diluted and stored in a dilution pulp pool, and continuously stirred and mixed, the stable running current after the formation of the squeezing machine plug is set to 75 A, the dilution water flow is 45 m 3 / h, the running current of the squeezing machine and the concentration of the material at the outlet of the dilution pulp pool are monitored in real time, for example, when the running current of the squeezing machine is 60 A and the concentration of the material at the outlet of the dilution pulp pool is 4.2 wt%, the dilution water flow is calculated to be 36.00 m 3 / h according to formula 1; when the running current of the squeezing machine is 60 A, the dry material amount transported after the formation of the squeezing machine plug is 2.1 t / h, the effective volume of the dilution pulp pool is 20 m 3 , the real-time liquid level of the dilution pulp pool is 40%, and the concentration of the material at the outlet of the dilution pulp pool is 4.2 wt%, the dilution water flow is calculated to be 36.14 m 3 / h according to formula 2, to avoid concentration overshoot, the smaller value of 36.00 m 3 / h is taken to control the amount of dilution water, so that the material at the outlet of the dilution pulp pool reaches the first target concentration of 4.4 wt% and is transported to the pre-beating pulp pool, if the concentration of the material at the outlet of the dilution pulp pool exceeds the range of (4.0-4.4) wt%, the material in the dilution pulp pool is returned to the dilution pulp pool through a first self-circulation pipeline for continuous circulation mixing to avoid the pulp that does not reach the first target concentration being transported to the pre-beating pulp pool; when the opening degree of the valve of the pre-beating pulp pool outlet concentration adjustment water pipeline is about 33%, the material at the outlet of the pre-beating pulp pool reaches the second target concentration of 3.8 wt%, which is then transported to the mill at a flow rate of 60 m 3 / h, the mill starts to run, and after beating treatment, the pulp is stored in the post-beating pulp pool, if the concentration of the material at the outlet of the pre-beating pulp pool exceeds the range of (3.7-3.9) wt%, the material in the pre-beating pulp pool is returned to the pre-beating pulp pool through a second self-circulation pipeline for continuous circulation mixing to avoid the pulp that does not reach the second target concentration being transported to the mill; when the actual amount of stored pulp in the production line reaches 85% of the set amount of stored pulp (153 m 3) the mixing leaching tank stops conveying material to the wringer, the dilution slurry tank stops conveying material to the pre-beating slurry tank, the dilution slurry tank material returns to the dilution slurry tank through the first self-circulation pipeline, the running current of the wringer gradually decreases from about 75 A, and the running current of the wringer and the concentration of the dilution slurry tank outlet material are monitored in real time; according to the smaller value in formula 1 and formula 2, the dilution water quantity is online and real-time regulated, so that the dilution slurry tank outlet material reaches the third target concentration of 4.8wt%; when the pre-beating slurry tank liquid level is less than or equal to 30%, clean water is used to clean the mill and associated pipelines, the cleaning water and the material in the mill chamber are recovered to the pre-beating slurry tank, and the mill stops running; when the actual slurry storage quantity of the production line is less than 35% (63m 3 ) of the set slurry storage quantity, the dilution slurry tank material returns to the dilution slurry tank through the first self-circulation pipeline for 4 minutes of self-circulation, during which the first concentration detection device collects the real-time concentration of the dilution slurry tank material every 2 seconds; when the self-circulation of the dilution slurry tank material is completed, the first concentration detection device calculates the average concentration of the dilution slurry tank material during self-circulation, that is, the actual concentration of the dilution slurry tank material is 4.80wt%; the pre-beating slurry tank material returns to the pre-beating slurry tank through the second self-circulation pipeline for 4 minutes of self-circulation, during which the second concentration detection device collects the real-time concentration of the pre-beating slurry tank material every 2 seconds; when the self-circulation of the pre-beating slurry tank material is completed, the second concentration detection device calculates the average concentration of the pre-beating slurry tank material during self-circulation, that is, the actual concentration of the pre-beating slurry tank material is 3.10wt%; at this time, the actual liquid level of the pre-beating slurry tank is 34%, the volume is 20m 3 , and the second target concentration of the pre-beating slurry tank material is 3.80wt%; according to formula 3, it is calculated that the dilution slurry tank material quantity needed to be supplemented to the pre-beating slurry tank is 4.76m 3 ; the running frequency of the dilution slurry tank outlet pump is regulated to 40Hz, so that the conveying flow rate reaches 50m 3 / h; within 6 minutes, 4.76m 3 of dilution slurry tank material is conveyed to the pre-beating slurry tank for concentration adjustment of the pre-beating slurry tank material; during this period, the pre-beating slurry tank material returns to the pre-beating slurry tank through the second concentration detection device and the second self-circulation pipeline for self-circulation and mixing; after the concentration adjustment of the pre-beating slurry tank material is completed, the mixing leaching tank resumes conveying material to the wringer, the dilution slurry tank resumes conveying material to the pre-beating slurry tank, and the pre-beating slurry tank material is conveyed to the mill at a flow rate of 60m 3 / h; the mill starts running again, and the pulp after beating treatment is stored in the post-beating slurry tank.

[0056] Comparative Example 1-1

[0057] The leaching liquid obtained after solid-liquid separation by the wringer is stored in a leaching liquid storage tank, and the water-insoluble solid is diluted and stored in the dilution slurry tank and continuously stirred and mixed; the dilution water flow rate is set to 45m 3 / h, the diluted slurry pool material is transported to the pre-beating slurry pool, the outlet concentration of the pre-beating slurry pool is adjusted by adjusting the valve opening degree of the thickening water pipeline, so that the outlet material of the pre-beating slurry pool reaches the second target concentration 3.80%, and then the pre-beating slurry pool is transported to the mill at a flow rate of 60 m 3 / h, the mill starts to run, and the pulp after beating is stored in the post-beating slurry pool; the post personnel real-time monitor the slurry storage of the production line, and when all the slurry storage tanks of the production line are full (180 m 3 ), the manual control of the mixed leaching tank stops the transportation of the material to the wringer, the dilution slurry pool stops the transportation of the material to the pre-beating slurry pool, the mill and the associated pipeline are cleaned with water, the cleaning water and the material in the mill chamber are recovered to the pre-beating slurry pool, and the mill stops running; when the slurry in all the slurry storage tanks of the production line is ≤100 m 3 , the manual control of the mixed leaching tank restores the transportation of the material to the wringer, the dilution slurry pool restores the transportation of the material to the pre-beating slurry pool, the material in the pre-beating slurry pool is returned to the pre-beating slurry pool through the second concentration detection device and the second self-circulation pipeline for self-circulation mixing, at this time, the concentration of the material in the pre-beating slurry pool is 3.00 wt%, the flow rate of the dilution water is gradually reduced manually, the concentration of the material in the dilution slurry pool is gradually increased, the material with a higher concentration in the dilution slurry pool is continuously supplemented to the pre-beating slurry pool, after 35 min, the concentration of the material in the pre-beating slurry pool reaches (3.70-3.90) wt%, the slurry pool pump continues to transport the material to the pre-beating slurry pool, and then the pre-beating slurry pool pump transports the material to the mill at a flow rate of 60 m 3 / h, and the mill starts to run.

[0058] The concentration of the material in the dilution slurry pool and the pre-beating slurry pool in Example 1 and Comparative Example 1-1 is tracked and monitored, and the relative standard deviation (RSD) value of the concentration of the material in the dilution slurry pool and the pre-beating slurry pool is calculated, and the results are shown in Table 1.

[0059] Table 1 Stability comparison of the concentration of the material in the dilution slurry pool and the pre-beating slurry pool

[0060]

[0061]

[0062] The comparison results in Table 1 show that, in the production process of the papermaking method reconstituted tobacco, by the method of the present application, the RSD value of the concentration of the material in the dilution slurry pool is reduced from 5.97% under the original process (Comparative Example 1-1) to 3.05%; by improving the start-stop mode of the mill and the concentration adjustment process of the pre-beating slurry pool, the RSD value of the concentration of the material in the pre-beating slurry pool is reduced from 8.68% under the original process (Comparative Example 1-1) to 2.20%, which provides the pulp-making process with stable quality material.

[0063] Comparative Example 1-2

[0064] The leaching liquor obtained after solid-liquid separation by the extruder is stored in a leaching liquor storage tank, the water-insoluble solids are weighed and metered by a screw conveyor, the moisture content is detected by an online infrared moisture meter, and after dilution, the water-insoluble solids are stored in an adjusted pulp tank. The instantaneous flow rate of the weighed and metered screw is 5600 kg / h, the moisture content of the water-insoluble solids is 64%, and the automatic adjustment of the dilution water flow rate is 47.45 m 3 / h, so that the concentration of the material at the outlet of the dilution pulp tank reaches (3.80±0.10) wt% and is delivered to the pre-beating pulp tank, and then the material is delivered to the mill at a flow rate of 60 m 3 / h by the pre-beating pulp tank pump. When the concentration of the material at the outlet of the adjusted pulp tank exceeds the range of (3.80±0.10) wt%, the material delivered by the adjusted pulp tank pump is returned to the adjusted pulp tank and is temporarily not delivered to the pre-beating pulp tank. If the concentration of the material at the outlet of the adjusted pulp tank is >3.9%, the opening of the concentration-adjusting water valve at the outlet of the adjusted pulp tank is adjusted to be larger, and if the concentration of the material at the outlet of the adjusted pulp tank is <3.7%, the opening of the concentration-adjusting water valve at the outlet of the adjusted pulp tank is adjusted to be smaller. The concentration of the material in the adjusted pulp tank is finely adjusted to reduce fluctuations, and when the concentration of the material at the outlet of the adjusted pulp tank reaches (3.80±0.10)%, the material is again delivered to the pre-beating pulp tank and the mill by the adjusted pulp tank pump. The post personnel real-time monitor the storage of the pulp in the production line, and when all the pulp storage tanks in the production line are full (180 m 3 ), the manual control of the mixed leaching tank is stopped to deliver material to the extruder, the adjusted pulp tank is stopped to deliver material to the pre-beating pulp tank, clean water is used to clean the mill and associated pipelines, the cleaning water and the material in the chamber of the mill are recovered to the adjusted pulp tank, and the mill is stopped. When the pulp in all the pulp storage tanks in the production line is ≤100 m 3 , the manual control of the mixed leaching tank is restored to deliver material to the extruder, and the adjusted pulp tank pump is used to return the material to the adjusted pulp tank and temporarily not deliver the material to the pre-beating pulp tank. At this time, the concentration of the material in the adjusted pulp tank is 3.10 wt%, the automatic control of the dilution water flow rate is removed, and the manual control mode is changed to manual control. The dilution water flow rate is gradually reduced manually, the adjusted pulp tank is continuously supplemented with fresh material with a higher concentration, and after 40 min, the concentration of the material at the outlet of the adjusted pulp tank reaches (3.80±0.10) wt%. The material is continuously delivered to the pre-beating pulp tank by the adjusted pulp tank pump, and then delivered to the mill by the pre-beating pulp tank pump. The mill is started.

[0065] When the mill needs to be started again after being stopped in Example 1 and Comparative Examples 1-2, the concentration of the material before beating at the same concentration adjustment time is tracked and counted, and the results are shown in Table 2.

[0066] Table 2: Concentration data of the material in the dilution pulp tank and the adjusted pulp tank

[0067]

[0068] The comparison results in Table 2 show that, in the production process of papermaking process reconstituted tobacco, by the method of the present application, when the mill needs to be started again after shutdown, the material concentration adjustment time before beating is reduced from 40 min (Comparative Examples 1-2) to 6 min, the concentration adjustment efficiency is obviously improved, the production continuity is ensured, the invalid running time of the mill is reduced, and the energy consumption cost is reduced.

[0069] Example 2

[0070] A method for improving the quality stability of papermaking process reconstituted tobacco slurry, as shown in Figure 1 , the specific process is: 1200 kg of tobacco stem, 1800 kg of tobacco dust and 18 m 3 of water at 65℃ are mixed and extracted in a mixing extraction tank, and after solid-liquid separation by a wringer, an extraction liquid with a density of 1.055 g / cm 3 and water-insoluble solids with a dryness of 37% are obtained; the extraction liquid is stored in an extraction liquid storage tank, and the water-insoluble solids are diluted and stored in a dilution pulp pool, and continuously stirred and mixed, the stable running current of the wringer after the formation of the plug is set to 75 A, the required dilution water flow is 45 m 3 / h, the running current of the wringer and the concentration of the material at the outlet of the dilution pulp pool are monitored in real time, for example, when the running current of the wringer is 65 A and the concentration of the material at the outlet of the dilution pulp pool is 4.2 wt%, the dilution water flow is calculated to be 39.00 m 3 / h according to Formula 1; when the running current of the wringer is 65 A, the dry material amount transported after the formation of the plug of the wringer is 2.1 t / h, the effective volume of the dilution pulp pool is 20 m 3 , the real-time liquid level of the dilution pulp pool is 40%, and the concentration of the material at the outlet of the dilution pulp pool is 4.2 wt%, the dilution water flow is calculated to be 39.18 m 3 / h according to Formula 2, to avoid concentration overshoot, the smaller value of 39.00 m 3 / h is taken as the dilution water amount control, so that the material at the outlet of the dilution pulp pool reaches the first target concentration of 4.4 wt% and is transported to the pre-beating pulp pool, if the concentration of the material at the outlet of the dilution pulp pool exceeds the range of (4.0-4.4) wt%, the material in the dilution pulp pool is returned to the dilution pulp pool through the first self-circulation pipeline for continuous circulation mixing, to avoid the slurry that does not reach the first target concentration being transported to the pre-beating pulp pool; when the valve opening degree of the pre-beating pulp pool outlet concentration adjustment water pipeline is about 33%, the material at the outlet of the pre-beating pulp pool reaches the second target concentration of 3.8 wt%, and then it is transported at a flow rate of 60 m 3A flow rate of / h is delivered to the mill, and the mill starts operation. After pulping, the slurry is stored in the post-impact slurry tank. If the material concentration at the outlet of the pre-impact slurry tank exceeds the range of (3.7~3.9) wt%, the material in the pre-impact slurry tank is returned to the pre-impact slurry tank through the second self-circulation pipeline for continuous circulation and mixing, preventing slurry that has not reached the second target concentration from being delivered to the mill. The process continues until the actual slurry storage in the production line reaches 85% (153m³) of the set storage capacity. 3 When the mixing and leaching tank stops feeding material to the extruder, and the dilution tank stops feeding material to the pre-extrusion tank, the material in the dilution tank returns to the dilution tank via the first self-circulation pipeline. The operating current of the extruder gradually decreases from about 75A. The amount of dilution water is adjusted online in real time according to the smaller value in Formula 1 and Formula 2, so that the material at the outlet of the dilution tank reaches the third target concentration of 4.6wt%. When the liquid level in the pre-extrusion tank is ≤30%, the mill and related pipelines are cleaned with clean water. The cleaning water and the material in the mill chamber are recovered to the pre-extrusion tank, and the mill stops running. When the actual slurry volume in the production line is less than 35% (63m³) of the set slurry volume, the mill stops running. 3 At this time, the material in the dilution slurry tank is returned to the dilution slurry tank via the first concentration detection device and the first self-circulation pipeline for 3 minutes of self-circulation. During this period, the first concentration detection device collects the real-time concentration of the material in the dilution slurry tank every 2 seconds. When the self-circulation of the material in the dilution slurry tank ends, the first concentration detection device calculates the average concentration of the material in the dilution slurry tank during the self-circulation period, that is, the actual concentration of the material in the dilution slurry tank is 4.6 wt%. The material in the pre-impact slurry tank is returned to the pre-impact slurry tank via the second concentration detection device and the second self-circulation pipeline for 3 minutes of self-circulation. During this period, the second concentration detection device collects the real-time concentration of the material in the pre-impact slurry tank every 2 seconds. When the self-circulation of the pre-impact slurry tank ends, the second concentration detection device calculates the average concentration of the material in the pre-impact slurry tank during the self-circulation period, that is, the actual concentration of the material in the pre-impact slurry tank is 3.2 wt%. At this time, the actual liquid level of the pre-impact slurry tank is 34%, and the volume is 20 m³. 3 The second target concentration of the material in the pre-aperture slurry tank is 3.8 wt%. Based on Formula 3, the amount of diluted slurry material that needs to be added to the pre-aperture slurry tank is calculated to be 5.1 m³. 3 5.1m 3 The material from the dilution tank is conveyed to the pre-aperture tank for concentration adjustment. During this process, the material from the pre-aperture tank is returned to the pre-aperture tank via a second concentration detection device and a second self-circulation pipeline for self-circulation mixing. After the concentration adjustment of the material in the pre-aperture tank is completed, the mixing and leaching tank resumes conveying material to the extruder, and the dilution tank resumes conveying material to the pre-aperture tank. The material from the pre-aperture tank is then conveyed at a rate of 60m... 3 A flow rate of / h is delivered to the mill, the mill starts up again, and the pulp is stored in the post-pulping tank after pulping.

[0071] Comparative Example 2

[0072] The leaching solution obtained after solid-liquid separation by the extruder is stored in a leaching solution storage tank, and the water-insoluble solids are diluted and stored in a dilution pulp pool, and continuous stirring and mixing are performed, and the dilution water flow is set to 45 m 3 / h, and the diluted material in the dilution pulp pool is transported to the pre-beating pulp pool, the valve opening degree of the thickening water pipeline at the outlet of the pre-beating pulp pool is adjusted to make the material at the outlet of the pre-beating pulp pool reach the second target concentration of 3.8 wt%, and then the material is transported to the mill at a flow rate of 60 m 3 / h, the mill starts to run, and the pulp after beating treatment is stored in the post-beating pulp pool; the post personnel real-time monitor the pulp storage condition of the production line, and when all the pulp storage tanks of the production line are full (180 m 3 ), the manual control of the mixed leaching tank is stopped to deliver material to the extruder, the dilution pulp pool is stopped to deliver material to the pre-beating pulp pool, clean water is used to clean the mill and the associated pipeline, the cleaning water and the material in the mill chamber are recovered to the pre-beating pulp pool, and the mill stops running; when the pulp in all the pulp storage tanks of the production line is ≤30 m 3 , the manual control of the mixed leaching tank is restored to deliver material to the extruder, the dilution pulp pool is restored to deliver material to the pre-beating pulp pool, the material in the pre-beating pulp pool is returned to the pre-beating pulp pool through the second concentration detection device and the second self-circulation pipeline for self-circulation mixing, at this time, the concentration of the material in the pre-beating pulp pool is 3.2 wt%, and by continuously supplementing the material with a higher concentration in the dilution pulp pool to the pre-beating pulp pool, the concentration of the material in the pre-beating pulp pool reaches the second target concentration of 3.8 wt%, and when the material in the pre-beating pulp pool reaches the second target concentration, the material in the pre-beating pulp pool is transported to the mill at a flow rate of 60 m 3 / h, the mill starts to run again, and the pulp after beating treatment is stored in the post-beating pulp pool.

[0073] The wet weight index of the paper-making process reconstituted tobacco pulp prepared in Example 2 and Comparative Example 2 was tracked and detected, and the relative standard deviation (RSD) value of the wet weight of the pulp was calculated, and the results are shown in Table 3.

[0074] Table 3 Comparison of wet weight stability of paper-making process reconstituted tobacco pulp

[0075]

[0076] The comparison results in Table 3 show that in the production process of paper-making process reconstituted tobacco, the RSD value of the wet weight of the paper-making process reconstituted tobacco pulp prepared by the method of the application is reduced from 18.54% under the original process (Comparative Example 2) to 10.33%, and the stability of the pulp quality is obviously improved.

Claims

1. A method for improving the quality stability of reconstituted tobacco pulp in papermaking, characterized in that, The process is as follows: (1) Mix and extract tobacco stems, tobacco dust, and water in a mixing and extraction tank in a certain proportion; (2) The mixture in step (1) is fed to a desqueezer for solid-liquid separation to obtain leachate and water-insoluble solids; (3) Store the leaching solution in step (2) into the leaching solution storage tank, add water-insoluble solids to dilute the solution, store the diluted material in the dilution slurry tank and continuously stir and mix it. Set the material concentration at the outlet of the dilution slurry tank as the first target concentration. The outlet pipeline of the dilution slurry tank is equipped with a first concentration detection device and a first self-circulation pipeline in sequence. (4) The material diluted to the first target concentration in step (3) is transported to the pre-stirring slurry tank and continuously stirred and mixed to adjust the material concentration to the second target concentration. The outlet pipe of the pre-stirring slurry tank is equipped with a concentration adjustment water pipeline, a second concentration detection device, a second self-circulation pipeline and a cleaning water pipeline in sequence. (5) The material adjusted to the second target concentration in step (4) is transported to the mill at a certain flow rate. The mill starts to run. After pulping, the slurry is stored in the post-pulping slurry tank. A cleaning water recovery pipeline is provided on the mill outlet pipeline and connected to the pre-pulping slurry tank. (6) When the actual slurry volume of the production line reaches 80-90% of the set slurry volume, the mixing and leaching tank stops conveying material to the extruder. When the liquid level of the dilution tank is ≤60%, the material is stopped conveying to the pre-dip slurry tank. The concentration of the material at the outlet of the dilution tank is adjusted to the third target concentration by adjusting the amount of dilution water. (7) When the liquid level in the pre-impact slurry tank is ≤30%, clean the mill and related pipelines with clean water. The cleaning water and the material in the mill chamber are recycled to the pre-impact slurry tank, and the mill stops running. (8) When the actual slurry volume in the production line is less than 35% of the set slurry volume, the concentration of the slurry material in the pre-tap slurry tank is adjusted by diluting the slurry tank material so that the slurry material in the pre-tap slurry tank reaches the second target concentration. By adjusting the operating frequency of the outlet pump of the dilution slurry tank, the material that needs to be replenished in the dilution slurry tank is transported to the pre-knock slurry tank within 5 to 7 minutes, so that the material concentration in the pre-knock slurry tank can be quickly restored to the second target concentration; (9) After the material concentration in the pre-knock slurry tank in step (8) is adjusted, the mill starts running again and performs pulping treatment on the material that has reached the second target concentration in step (8). After pulping treatment, the slurry is stored in the post-knock slurry tank. The dilution water pipeline in step (3) is equipped with a dilution water flow metering device. The operating current of the extruder and the material concentration at the outlet of the dilution tank are used as two-level feedback factors to regulate the dilution water volume in steps (3) and (6). The calculation relationship between the operating current of the extruder and the dilution water flow is shown in Formula 1, and the calculation relationship between the material concentration at the outlet of the dilution tank and the dilution water flow is shown in Formula 2. When the dilution water flow values ​​calculated by Formula 1 and Formula 2 are different, the smaller value is used for dilution water volume regulation. The above Formula 1 and Formula 2 are as follows: (Official 1) In the formula: Q'——Dilution water flow rate, m 3 / h; A'——Extruder operating current, real-time monitored quantity, unit is A; Q — The required dilution water flow rate after the material blockage in the extruder forms. This is calculated based on collected historical production data and is a known quantity, expressed in meters (m³). 3 / h; A — The stable operating current after the material blockage of the extruder is formed. It is a known quantity obtained by collecting past production data and is in A. (Official 2) In the formula: Q'——Dilution water flow rate, m 3 / h; A'——Extruder operating current, real-time monitored quantity, unit is A; A — The stable operating current after the material blockage of the extruder is formed. It is a known quantity obtained by collecting past production data and is in A. K — The amount of absolutely dry material conveyed after the extruder plug is formed. It is obtained by collecting past production data and is a known amount, with the unit being t / h. L 稀 —Actual liquid level in the dilution tank, real-time monitoring volume, in percentages (%) V 稀 —Effective volume of the dilution tank, in m³ 3 ; C 稀 — Actual concentration of material at the outlet of the dilution tank, real-time monitoring amount, in wt%; C 稀目 —The first target concentration in the dilution pool, known quantity, in wt%.

2. The method according to claim 1, characterized in that, The first target concentration, the second target concentration, and the third target concentration are 4.0~4.4wt%, 3.7~3.9wt%, and 4.6~4.8wt%, respectively.

3. The method according to claim 2, characterized in that, If the concentration of the material at the outlet of the dilution tank in step (3) does not reach the first target concentration range or the concentration of the material at the outlet of the dilution tank in step (6) does not reach the third target concentration range, the material in the dilution tank will return to the dilution tank through the first self-circulation pipeline for continuous circulation and mixing.

4. The method according to claim 1, characterized in that, In step (8), the material in the dilution slurry tank is returned to the dilution slurry tank via the first concentration detection device and the first self-circulation pipeline. The self-circulation time of the material in the dilution slurry tank is 2-4 minutes. During this period, the first concentration detection device collects the real-time concentration of the material in the dilution slurry tank every 2 seconds. When the self-circulation of the material in the dilution slurry tank ends, the first concentration detection device calculates the average concentration of the material in the dilution slurry tank during the self-circulation period, i.e., the actual concentration of the material in the dilution slurry tank. The material in the pre-tap slurry tank is returned to the pre-tap slurry tank via the second concentration detection device and the second self-circulation pipeline. The self-circulation time of the material in the pre-tap slurry tank is 2-4 minutes. During this period, the second concentration detection device collects the real-time concentration of the material in the pre-tap slurry tank every 2 seconds. When the self-circulation of the material in the pre-tap slurry tank ends, the second concentration detection device calculates the average concentration of the material in the pre-tap slurry tank during the self-circulation period, i.e., the actual concentration of the material in the pre-tap slurry tank. The amount of dilution slurry tank material to be added to the pre-tap slurry tank is calculated based on the actual concentration of the material in the dilution slurry tank, the actual concentration of the material in the pre-tap slurry tank, the actual liquid level of the pre-tap slurry tank, and the second target concentration. The specific calculation is shown in Formula 3. Formula 3 is as follows: (Official 3) In the formula: V 稀 —The amount of diluted slurry material that needs to be added to the pre-tap slurry tank, in m³. 3 ; L 叩 —Actual liquid level in the pre-tapping slurry tank, real-time monitoring volume, unit: % V 叩 —The volume of the pre-thrust slurry pool is known, in cubic meters (m³). 3 ; C 叩 — Actual concentration of material at the outlet of the pre-tapping slurry tank, real-time monitoring amount, in wt%; C 稀 — Actual concentration of material at the outlet of the dilution tank, real-time monitoring amount, in wt%; C 叩目 —Second target concentration, known amount, in wt%.

5. The method according to claim 1, characterized in that, In step (1), the mass of tobacco dust is 1 to 1.8 times the mass of tobacco stems, the mass of water is 5 to 8 times the sum of the masses of tobacco dust and tobacco stems, and the water temperature is 50 to 65°C; in step (2), the density of the extract is 1.048 to 1.057 g / cm³. 3 The dryness of water-insoluble solids is 37-39%.

6. The method according to claim 1, characterized in that, In steps (6) and (8), the actual slurry storage volume of the production line is obtained by collecting the liquid level of each slurry tank in real time, and then multiplying the liquid level of each slurry tank by the volume of each slurry tank. The slurry storage volume is set to be obtained by adding the volumes of each slurry tank in the production line.

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