Papermaking system surface charge control method

Abstract

The invention relates to the technical field of papermaking, in particular to a papermaking system surface charge control method, which comprises the following steps: improving PCD (Poly Crystal Diamond) of chemi-mechanical pulp by increasing the torque of a squeezing screw, improving the cleanliness of the chemi-mechanical pulp, feeding the chemi-mechanical pulp with high PCD into a chemi-mechanical pulp storage tower for later use according to a normal process flow, and preparing cationic agents with different solid contents at a wet end for switching use; the mesh concentration is adjusted by adjusting the opening degree of a vertical lip plate in the core layer headbox, so that the uniformity is improved; finally, the formed wet paper web is fed into a pressing part; and the squeezed paper is subjected to pre-drying, sizing, post-repair drying, hard calendaring, coating, soft calendaring and curling. Charges are effectively improved, and slurry and cost are saved; the end breaking time of paper sheets is shortened, the use amount of chemicals is effectively reduced, paper products are more uniform, needle leaf planting and felling can be reduced, and sustainable development of resources is promoted; the chemical dosage is reduced, and the wastewater treatment difficulty of a sewage plant is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking, and in particular to a surface charge control method for a papermaking system. Background Art

[0002] At present, the surface charge control of the papermaking system can reduce the break time of paper sheets, effectively control the use of chemicals, and obtain more uniform paper products. It has more corporate value in comparison with paper of the same price. In order to achieve higher speeds, chemical pulp usually increases the freeness and improves the dehydration of the wire section. High freeness greatly affects the strength of the finished paper. The premise for improving the folding endurance and interlayer bonding of the finished paper is to ensure the normal operation of the paper machine. Therefore, the strength cannot be improved by reducing the freeness and bulk. Therefore, the problem that the present invention focuses on solving is to improve the interlayer bonding force, improve the effect of chemicals and sizing agents, and increase the number of hydrogen bonds formed between fibers in normal production. Summary of the invention

[0003] The purpose of the present invention is to address the defects and shortcomings of the prior art and provide a method for controlling the surface charge of a papermaking system, which can effectively improve the charge, save pulp, and save costs; reduce the break time of paper sheets, effectively reduce the use of chemicals, make paper products more uniform, and thereby reduce conifer planting and felling, and promote sustainable development of resources; reduce the use of chemicals and reduce the difficulty of sewage treatment plants in treating wastewater.

[0004] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: it comprises the following steps: the PCD of the chemical mechanical pulp is increased by increasing the torque of the pressing screw, the cleanliness of the chemical mechanical pulp is improved, and then the chemical mechanical pulp with high PCD enters the chemical mechanical pulp storage tower for standby according to the normal process flow, the pulp in the chemical mechanical pulp storage tower enters the pre-beating tower, and whether to pass through the mill is selected according to actual production needs, and the pulp refined by the mill (or not refined) enters the post-beating tower, and then enters the core paper machine pulp pool for sizing; at the same time, Cationic agents with different solid contents are prepared at the wet end for switching; the pulp from the core layer paper machine pulp pool and the surface / bottom layer paper machine pulp pool passes through the remover, pressure screen, and attenuation tank respectively and then enters the core layer headbox and the surface / bottom layer headbox respectively, and then is sprayed onto the forming net, and the opening of the vertical lip plate in the core layer headbox is adjusted to adjust the concentration on the net to improve the uniformity; finally, the formed wet paper web is sent to the pressing section; the pressed paper is subjected to pre-drying, sizing, post-drying, hard calendering, coating, soft calendering, and curling.

[0005] Preferably, the pressing section is a three-pass shoe press, the first press line pressure is 780 kn / m, the second press line pressure is 790 kn / m, and the third press line pressure is 800 kn / m.

[0006] Preferably, the pre-drying improves the dryness of the paper sheets through the combined action of a steam cooling system and a ventilation system.

[0007] Preferably, the wet end is between the core layer paper machine pulp pool and the core layer headbox.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention provides a surface charge control method for a papermaking system, which effectively increases the charge by 200-300u / L, and while maintaining the original production base, saves 5,000 tons of pulp each year, saving 10 million yuan / year in costs; reduces the break time of paper sheets, effectively reduces the use of chemicals, makes paper products more uniform, and thereby can reduce conifer planting and felling, and promote sustainable development of resources; reduces the use of chemicals, and reduces the difficulty of sewage treatment plants in treating wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a flow chart of the present invention.

[0010] Figure 2 Process schemes and strength index data tables of Examples 1 to 2 and Comparative Example 1.

[0011] Figure 3 It is the process scheme and strength index data table of Examples 3 to 5 and Comparative Example 2.

[0012] Figure 4 It is the process scheme and strength index data table of Examples 6 to 8 and Comparative Example 3.

[0013] Figure 5 It is the process scheme and strength index data table of Example 9 to Example 10 and Comparative Example 4. DETAILED DESCRIPTION

[0014] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. The preferred embodiments in the description are only used as examples, and all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

[0015] like Figure 1As shown, this specific implementation adopts the following technical scheme: it includes the following steps: the PCD of the chemical mechanical pulp is increased by increasing the torque of the pressing screw to improve the cleanliness of the chemical mechanical pulp, and then the chemical mechanical pulp with high PCD enters the chemical mechanical pulp storage tower according to the normal process flow for standby, the pulp in the chemical mechanical pulp storage tower enters the pre-knock tower, and it is selected whether to pass through the mill according to actual production needs, and the pulp refined by the mill (or not refined) enters the post-knock tower, and then enters the core layer paper machine pulp pool for sizing; at the same time, cationic agents with different solid contents are prepared at the wet end for switching; the pulp of the core layer paper machine pulp pool and the surface / bottom layer paper machine pulp pool passes through the remover, pressure screen, and attenuation tank respectively. After that, they enter the core layer headbox and the surface / bottom layer headbox respectively, and then are sprayed onto the forming net, and the opening of the vertical lip plate in the core layer headbox is adjusted to adjust the concentration on the net and improve the uniformity; finally, the formed wet paper web is sent to the pressing section; the pressed paper is subjected to pre-drying, sizing, post-drying, hard calendering, coating, soft calendering and curling; the pressing section is a three-pass shoe press, the first press line pressure is 780kn / m, the second press line pressure is 790kn / m, and the third press line pressure is 800kn / m; the pre-drying is improved by the combined action of the steam cooling system and the ventilation system to improve the dryness of the paper sheet; the wet end is between the core layer paper machine pulp pool and the core layer headbox.

[0016] After adopting the above structure, the beneficial effects of this specific implementation are as follows:

[0017] 1. The charge is increased by 200-300u / L, and the retention is increased by 2%-3%;

[0018] 2. The pulp consumption of coniferous pulp per ton of paper is reduced by 5-10%, saving 5,000 tons of pulp every year;

[0019] 3. Through the research on the surface charge control technology of the papermaking system, the charge is effectively increased by 200-300u / L, which can save 5,000 tons of pulp each year while maintaining the original output, and save 10 million yuan / year in costs; reduce the break time of paper sheets, the use of effective chemicals, more uniform paper products, reduce conifer planting and felling, and promote sustainable development of resources; reduce the use of chemicals and reduce the difficulty of wastewater treatment in sewage treatment plants.

[0020] The performance tests of Examples 1 to 10 and Comparative Examples 1 to 4 were conducted using the following methods. The test data are detailed in Figure 2-Figure 5 :

[0021] Test conditions: Ambient temperature and humidity: (23±3)℃, (50±5)%RH

[0022] Interlayer bonding test method:

[0023] Testing steps: ① Cut the sample to a size of 130×25.4mm, and mark the front, back, horizontal and vertical sides of the sample respectively; ② Tighten the 3M interlayer bonding tape parallel to the 5 reference surfaces; ③ Carefully place the sample with the back side facing down on the tape to keep the sample parallel to the tape, and stick another layer of double-sided tape on the sample, and pay attention to keep the bonding flat; ④ Put the angle steel back frame back, turn the sample pressure device inward to drive the pressure ring, the standard clamping pressure is 100psi (pounds per square inch); ⑤ Pneumatic pressure, the green display light CYCLE will turn off, and the clamping pressure will cycle from 0-100-0; ⑥ Turn the sample pressure device to the open position and remove the angle steel back frame along the direction of the sample angle steel , put it aside, bottom down, so that the lower end of the sample angle is half open and there is no wear; ⑦ Use a paper cutter to cut the sample into 5 parts and cut off the excess parts at both ends; ⑧ Use your left hand to press the sample table on the stage, and use your right hand to press the black clamping open button. Note that there is only one way for the sample to rotate on the stage (the long hole of the sample is on the right, that is, the vertical part of the sample angle is on the left); ⑨ Press and immediately release the green pendulum down button to break the sample, grab and suck it horizontally during the pendulum swing back, if the paper is not completely separated, press the DEL switch to eliminate the record input; ⑩ Press AVG to read the average interlayer bonding strength of a group of 5 samples, and press SD to get the standard deviation of the sample bonding strength.

[0024] Quality judgment criteria: interlayer bonding value ≥ 125 is qualified.

[0025] Folding test method:

[0026] Testing steps: Cut the finished paper longitudinally to obtain a 1.5 cm wide paper sample. Under a spring pressure of 9.81 N, fold the paper sample repeatedly at approximately 180° between rollers until it breaks, thereby determining the maximum number of folds the sample can withstand when it breaks.

[0027] Good or bad judgment criteria: The more times the measurement is taken, the better

[0028] Charge titration method:

[0029] First, you need to prepare the instruments and reagents required for titration, including burette, indicator electrode and reference electrode, etc. At the same time, dilute the sample by 10 times, take out 10 ml, inject it into the instrument, turn on the instrument, add the titrant, and add the titrant directly to the sample to be titrated. During the titration process, pay attention to observe the displayed value returning to zero, stop the titration, and observe the volume of the titrant consumed.

[0030] For those skilled in the art, they can modify the technical solutions described in the aforementioned embodiments and make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for controlling surface charge of a papermaking system, characterized in that: It includes the following steps: the PCD of chemical-mechanical pulp is increased by increasing the torque of the pressing screw to improve the cleanliness of chemical-mechanical pulp, and then the chemical-mechanical pulp with high PCD enters the chemical-mechanical pulp storage tower for standby according to the normal process flow; after the pulp in the chemical-mechanical pulp storage tower enters the pre-knocking tower, it is selected whether to pass through the mill according to actual production needs, and the pulp that is refined by the mill or not enters the post-knocking tower, and then enters the core layer paper machine pulp pool for sizing; at the same time, cationic agents with different solid contents are prepared at the wet end for switching; the pulp of the core layer paper machine pulp pool and the surface / bottom layer paper machine pulp pool respectively passes through the slag remover, pressure screen, and attenuation tank, and then enters the core layer flow box and the surface / bottom layer flow box respectively, and then is sprayed onto the forming network, and the opening of the vertical lip plate in the core layer flow box is adjusted to adjust the concentration on the net and improve the uniformity; finally, the formed wet paper web is sent to the pressing section; the pressed paper is pre-dried, sizing, post-dried, hard calendered, coated, soft calendered, and curled.

2. A method for controlling surface charge of a papermaking system according to claim 1, characterized in that: The pressing section is a three-pass shoe press, the first press line pressure is 780 kn / m, the second press line pressure is 790 kn / m, and the third press line pressure is 800 kn / m.

3. The surface charge control method of a papermaking system according to claim 1, characterized in that: The pre-drying improves the dryness of the paper sheets through the combined action of the steam cooling system and the ventilation system.

4. The method for controlling surface charge of a papermaking system according to claim 1, characterized in that: The wet end is between the core layer paper machine pulp pool and the core layer headbox.

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