A method for controlling stickies in waste paper pulp

Abstract

The application provides a waste paper pulp adhesive control method, which comprises the following steps: conveying waste paper to a hydraulic pulper for disintegration, then conveying the waste paper to a high-concentration heavy-duty degritting device, a coarse screen machine, a low-concentration heavy-duty degritting device, a fine screen machine, a disc thickener, a hot disperser and a low-concentration disc mill in sequence for pulping, storing the pulp in a post-beating tank for stirring and storage after pulping, then conveying the pulp to a pressure screen for feeding and screening, then passing through a headbox, a wire part, a press part, a drying part, a sizing part, a coating part, a calender part and a winding part of a paper machine in sequence to form paper, wherein 2-5 kg / ton of dry pulp of bentonite with a mass concentration of 2-3% is added into the post-beating tank, and white water recycled from the wire part of the paper machine is subjected to deep air flotation treatment. By adding bentonite with a set concentration into the post-beating tank and cooperating with the deep air flotation treatment technology, the content of adhesive in the waste paper can be greatly reduced, and the adhesive removal rate can reach more than 94%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, in particular to a waste paper pulp adhesive control method. BACKGROUND

[0002] Waste paper recycling can save resources and protect the environment. China is short of papermaking fiber raw materials, and low-cost waste paper has become an important part of papermaking industry raw materials. The biggest problem of waste paper recycling is the removal of adhesives. In the waste paper pulping process, the fine adhesives in the pulp are mainly polyacrylate, mainly from the adhesive tape in the raw materials and other product adhesives, and the removal of adhesives is mainly through screening, purification and dispersion. This method can remove most of the adhesives, but the fine adhesives in the system are easy to accumulate in the wet part, dry part and white water, which has a great impact on the formation, drying, appearance quality and printing of the finished paper.

[0003] In the prior art, a Chinese patent with the publication number CN108060599A disclosed a control method for reducing the content of adhesives in the pulping process and a pulping system. The control method comprises the following steps: A pulping, B high-concentration sand removal, C coarse screening, D medium-concentration fine screening, E first-time flotation, F sand removal, G low-concentration fine screening, H post-treatment, and the pulp temperature of steps C coarse screening, step D medium-concentration fine screening, step E first-time flotation and step G low-concentration fine screening is controlled at 35-45℃. The control method of the invention controls the temperature of the white water by passing in steam, and then controls the temperature of the waste paper pulp, controls the pulp temperature of the coarse screening treatment section, the medium-concentration fine screening treatment section, the first-time flotation treatment section and the low-concentration fine screening treatment section at 35-45℃, reduces the softening of the adhesives by heat and the flow into the good pulp from the screen seam, and the adhesives can be removed from the pulping system through each deslagging process, which improves the running efficiency of the paper machine and ensures the quality of the paper sheet. However, the above control method has high process requirements, and the steps are complex, and there are many technical points to be controlled, which is difficult to implement in practice, and the removal rate of the adhesives is difficult to reach more than 90%. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a waste paper pulp adhesive control method. By adding a set concentration of bentonite in the post-kneading pool and cooperating with the deep air flotation treatment technology, the content of adhesives in the waste paper can be purified to below 1068㎡ / kg from 17808㎡ / kg, and the removal rate of the adhesives can reach more than 94%.

[0005] To achieve the above technical solutions, the application provides a waste paper pulp adhesive substance control method, which comprises the following steps: conveying waste paper to a hydraulic pulper for disintegration, then conveying the waste paper to a high-concentration heavy degritting device for high-concentration heavy degritting, then conveying the waste paper to a coarse screen for coarse screening, then conveying the waste paper to a low-concentration heavy degritting device for low-concentration heavy degritting, then conveying the waste paper to a fine screen for fine screening, then conveying the waste paper to a multi-disc thickener for thickening, then conveying the waste paper to a hot disperser for hot dispersion, then conveying the waste paper to a low-concentration disc refiner for pulping, storing the pulp in a post-beating tank for stirring and storage after pulping, then conveying the pulp to a pressure screen for feeding and screening, then conveying the pulp to a headbox of a paper machine for pulp distribution, and then sequentially passing through a wire part, a press part, a drying part, a sizing part, a coating part, a calender part and a paper winding part of the paper machine to be formed into paper, wherein 2-5 kg / ton of absolute dry pulp of bentonite is added to the post-beating tank, the bentonite is made into a liquid mixture for addition, the mass concentration is 2-3 %, and white water reused from the wire part of the paper machine is subjected to deep air flotation treatment and then reused in the hot disperser.

[0006] Preferably, the bentonite is sodium-based bentonite.

[0007] Preferably, the waste paper is 100% OCC waste paper.

[0008] Preferably, the deep air flotation treatment technology is to make air completely dissolve in liquid by high pressure, then make the dissolved gas suddenly exposed to atmospheric pressure by generating pressure difference in a gas release valve, the gas release process generates tiny bubbles, the bubbles are attached to the flocculation, and the bubbles make the suspended solids and colloidal particles in the waste paper pulp physically separated from water and float to the surface of the clarifier.

[0009] Preferably, cationic polyacrylamide with a molecular weight greater than 10 million is added during the deep air flotation treatment.

[0010] Preferably, the addition amount of the cationic polyacrylamide is 0.2-1 kg / ton of absolute dry pulp, and the mass concentration is 0.2-0.5 %.

[0011] The waste paper pulp adhesive substance control method provided by the application has the beneficial effect that the cooperation between bentonite and deep air flotation treatment technology is fully utilized, the content of adhesive substances in waste paper is purified from 17808 m2 / kg to about 1068 m2 / kg by adding 3 kg / ton of absolute dry pulp of bentonite with a mass concentration of 3 % in the post-beating tank and cooperating with the deep air flotation treatment technology, the removal rate of adhesive substances reaches 94 %, and therefore good adhesive substance removal effect is achieved. DETAILED DESCRIPTION

[0012] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. All the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application. Embodiment 1

[0013] A waste paper pulp adhesive control method comprises the following steps: 100% OCC waste paper is transported to a hydraulic pulper for disintegration, then transported to a high-concentration heavy-duty degritting device for high-concentration heavy-duty degritting, then transported to a coarse screen for coarse screening, then transported to a low-concentration heavy-duty degritting device for low-concentration heavy-duty degritting, then transported to a fine screen for fine screening, then transported to a multi-disc thickener for thickening, then transported to a hot disperser for hot dispersion, then transported to a low-concentration disc refiner for pulping, and after pulping, the pulp is stored in a post-kneading pool for stirring storage. During the stirring storage, 3 kg / ton of absolute dry pulp of bentonite is added to the post-kneading pool. The bentonite is made into a liquid mixture for addition, and the mass concentration is 3%. The bentonite is sodium-based bentonite. Then the pulp is transported to a pressure screen for feeding and screening, then transported to a headbox of a paper machine for pulp distribution, and then sequentially passes through a wire part, a pressing part, a drying part, a sizing part, a coating part, a calendering part and a paper winding part of the paper machine to be formed into paper. The white water recycled from the wire part is subjected to deep air flotation treatment, and then recycled to the hot disperser. The deep air flotation treatment technology is to make air completely dissolved in liquid by high pressure, then make the dissolved gas suddenly exposed to atmospheric pressure by generating pressure difference in the air release valve, and the air release process generates micro bubbles. The bubbles are attached to the flocculation to physically separate the suspended solids and colloidal particles in the waste paper pulp from the water, so that they float to the surface of the clarifier. During the deep air flotation treatment, cationic polyacrylamide with a molecular weight greater than 10 million is added. The addition amount of the cationic polyacrylamide is 0.5 kg / ton of absolute dry pulp, and the mass concentration is 0.3%. Embodiment 2

[0014] The addition amount of the cationic polyacrylamide is 1 kg / ton of absolute dry pulp, and the mass concentration is 0.2%. The remaining technical features are the same as those of embodiment 1. Embodiment 3

[0015] 5 kg / ton of absolute dry pulp of bentonite is added. The bentonite is made into a liquid mixture for addition, and the mass concentration is 2%. The remaining technical features are the same as those of embodiment 1.

[0016] Comparative Example 1

[0017] No bentonite is added to the post-kneading pool. The remaining technical features are the same as those of embodiment 1.

[0018] Comparative Example 2

[0019] The position of adding bentonite is a hot disperser, and the rest of the technical features are the same as those of Example 1.

[0020] Comparative Example 3

[0021] The position of adding bentonite is a pressure screen, and the rest of the technical features are the same as those of Example 1.

[0022] Comparative Example 4

[0023] The deep layer air flotation treatment process is omitted, the white water recycled in the wire part is directly recycled into the hot disperser, and the rest of the technical features are the same as those of Example 1.

[0024] Comparative Example 5

[0025] No cationic polyacrylamide with a molecular weight greater than 10 million is added in the flotation process, and the rest of the technical features are the same as those of Example 1.

[0026] The detection method of the content of the adhesive material: 21.7g of absolutely dry pulp is circulated in a sieve plate with a sieve gap of 0.15mm for 20min, the remaining part is uniformly transferred to a filter disc with a radius of 9cm, and an equal circle paper disc with a white coating layer is covered on the filter disc, and then it is placed in a press machine with a temperature of 95℃ and a pressure of 0.4Kpa for about 40~50min, at this time, the sample is taken out, the white coating layer is adhered on the filter disc due to the adhesion of the adhesive material, and other non-adhesive materials (such as coarse fibers, sand and other inorganic substances, etc.) will not be adhered to the coating layer, the area of the coating layer is obtained by scanning with a scanner, which is the content of the adhesive material, and the specific test data are as follows:

[0027] Table 1 Experimental detection data of Examples 1-3 and Comparative Examples 1-5

[0028]

[0029] As can be seen from the data of Examples 1-3, the present application fully utilizes the cooperation between bentonite and deep layer air flotation treatment technology, by adding bentonite with a mass concentration of 2-3% and an addition amount of 2-5kg / ton of absolutely dry pulp in the post-kneading tank, and cooperating with the deep layer air flotation treatment technology, the content of the adhesive material in the waste paper can be purified from 17808㎡ / kg to about 1068㎡ / kg, and the removal rate of the adhesive material is more than 94%, so that a good adhesive material removal effect is achieved, and in the actual production process, the adhesion of the dryer, the guide roller and the dry net can be greatly reduced, the frequency of the scraping knife is reduced from 2~3 times per shift to 1~2 times. The phenomenon of dropping hair and powder of the coating cow card caused by the adhesive material is reduced, the number and density of the dropping powder points are reduced by more than 80%, and the number of wiping the plate when printing with the coating cow card due to the accumulation of the adhesive material and the paper hair is also greatly reduced.

[0030] As can be seen from the data of Comparative Example 1 and Comparative Example 1, the addition of bentonite can significantly improve the effect of glue removal. Compared with Comparative Example 1, the addition of 3 kg / ton of bentonite in the post-beating tank can increase the glue removal efficiency from 86.4% to 94%, an increase of 7.6%. Moreover, as can be seen from the data of Comparative Example 1, Comparative Example 1 and Comparative Example 3, if bentonite is not added, the pressure screen has no glue removal effect.

[0031] As can be seen from the data of Comparative Example 1, Comparative Example 2 and Comparative Example 3, the addition position of bentonite has a significant impact on the final glue removal efficiency. As can be seen from the data of Comparative Example 2, the glue content at the outlet of the post-beating tank is higher than that in the post-beating tank. The reason is that the bentonite wraps and passivates the fine glue, but under the action of the disc mill shearing force, the passivated glue is dispersed and flocculated again, resulting in a higher glue content in the post-beating tank than in the pre-beating tank. Therefore, the scheme is not good. When the bentonite is added to the pressure screen, the glue removal efficiency is reduced by 3% compared with the addition in the post-beating tank. The possible reason is that the bentonite needs a certain time to adsorb the glue after being added. If it is directly added to the pressure screen, the reaction time is too short, which is not conducive to the adsorption of the glue, resulting in poor glue removal effect of the pressure screen. The experimental results show that the best glue removal effect can be obtained when the bentonite is added to the post-beating tank.

[0032] As can be seen from the data of Comparative Example 1 and Comparative Example 4, the white water deep air flotation treatment process has a significant impact on the final glue removal efficiency. If the recycled white water is not treated by deep air flotation, the glue removal rate at the hot dispersion inlet decreases from 80% to 54.9%, and the final glue removal rate decreases from 94% to 80.2%. The possible reason is that the micro-bubbles generated in the deep air flotation treatment process can be attached to the flocculation, making the glue float to the surface of the clarifier, thereby greatly improving the glue removal rate.

[0033] As can be seen from the data of Comparative Example 4 and Comparative Example 5, the addition of cationic polyacrylamide with a molecular weight greater than 10 million has a very obvious effect on flotation. The possible reason is that when the high molecular weight polyacrylamide (PAM) is dissolved in water, it has a positively charged active group, which adsorbs the negatively charged suspended colloidal particles, neutralizes the particle surface charge, eliminates the repulsive force between the particles, makes the glue flocculate, and then floats to the surface of the clarifier through the action of micro-bubbles, thereby greatly improving the glue removal rate.

[0034] Comparative Example 6

[0035] The bentonite added in the post-beating tank is 1 kg / ton of absolute dry pulp, and the remaining technical features are the same as those of Example 1.

[0036] Comparative Example 7

[0037] The bentonite added in the post-kneading pool was 2 kg per ton of absolute dry pulp, and the remaining technical features were the same as those of Example 1.

[0038] Comparative Example 8

[0039] The bentonite added in the post-kneading pool was 4 kg per ton of absolute dry pulp, and the remaining technical features were the same as those of Example 1.

[0040] Comparative Example 9

[0041] The bentonite added in the post-kneading pool was 5 kg per ton of absolute dry pulp, and the remaining technical features were the same as those of Example 1.

[0042] Comparative Example 10

[0043] The bentonite added in the post-kneading pool was 6 kg per ton of absolute dry pulp, and the remaining technical features were the same as those of Example 1.

[0044] Comparative Example 11

[0045] The bentonite added in the post-kneading pool was 7 kg per ton of absolute dry pulp, and the remaining technical features were the same as those of Example 1.

[0046] The content of the adhesive substance of Comparative Examples 6-11 was also determined, and the specific experimental data are as follows:

[0047] Table 2 Experimental detection data of Example 1, Comparative Example 1, and Comparative Examples 6-11

[0048]

[0049] As can be seen from the data of Comparative Example 1, Comparative Example 1, and Comparative Examples 6-11, the amount of bentonite added has a great influence on the removal rate of the adhesive substance. The removal rate of the adhesive substance increases rapidly with the increase of the amount of bentonite added, and when the amount of bentonite added reaches 3 kg per ton of absolute dry pulp, the removal rate of the adhesive substance is basically flat. From the production cost point of view, when the amount of bentonite added is 3 kg per ton of absolute dry pulp, the best cost performance can be obtained.

[0050] The above describes only the preferred embodiments of the present application, but the present application should not be limited to the contents disclosed in the embodiments and the drawings, so any equivalent or modification made without departing from the disclosed spirit of the present application falls within the scope of protection of the present application.

Claims

1. A method for controlling adhesives in waste paper pulp, comprising the following steps: conveying waste paper to a hydrapulper for disintegration, then conveying it to a high-consistency heavy material remover for high-consistency heavy material removal, then conveying it to a coarse screener for coarse screening, then conveying it to a low-consistency heavy material remover for low-consistency heavy material removal, then conveying it to a fine screener for fine screening, then conveying it to a multi-disc thickener for thickening, then conveying it to a thermal disperser for thermal dispersion, then conveying it to a low-consistency disc mill for beating, after beating, storing the pulp in a post-beating tank for stirring and storage, then conveying it to a pressure screen for feeding and screening, then conveying it to the headbox of a paper machine for pulp distribution, and then sequentially passing it through the wire section, press section, drying section, sizing section, coating section, calendering section, and winding section of the paper machine to form finished paper, characterized in that: Add 2-5 kg / ton of oven-dry pulp bentonite to the post-pressing tank. When adding the bentonite, it should be prepared as a liquid mixture with a mass concentration of 2-3%. The white water recycled from the paper machine wire section should be subjected to deep air flotation treatment and then recycled to the hot disperser.

2. The method for controlling adhesives in waste paper pulp as described in claim 1, characterized in that, The bentonite is sodium-based bentonite.

3. The method for controlling adhesives in waste paper pulp as described in claim 1, characterized in that, The waste paper is 100% OCC waste paper.

4. The method for controlling adhesives in waste paper pulp as described in claim 1, characterized in that, The deep air flotation treatment technology involves dissolving air completely into a liquid under high pressure, and then exposing the dissolved gas to atmospheric pressure by creating a pressure difference in the venting valve. This venting process generates tiny bubbles that attach to the flocculants, physically separating suspended solids and colloidal particles from the waste paper pulp in the water and causing them to float to the surface of the clarifier.

5. The method for controlling adhesives in waste paper pulp as described in claim 4, characterized in that, Cationic polyacrylamide with a molecular weight greater than 10 million is added during deep air flotation treatment.

6. The method for controlling adhesives in waste paper pulp as described in claim 5, characterized in that, The cationic polyacrylamide is added at a rate of 0.2-1 kg / ton of oven-dry pulp, with a mass concentration of 0.2-0.5%.

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