Tail slurry recovery and reproduction process and application thereof

Abstract

The invention provides a tail pulp recovery and reproduction process and application thereof, and relates to the technical field of pulping and papermaking production. The tail pulp recovery and reproduction process comprises the following steps: S1, pretreatment: mixing tail pulp with a surfactant, adding xylanase, and performing secondary mixing to obtain pretreated tail pulp; s2, softening: mixing the pretreated tail pulp obtained in the step S1 with an enzyme preparation to obtain softened pulp; the enzyme preparation is a mixture of keratinase, lignin peroxidase and galactosidase; s3, pulp grinding: concentrating the softened pulp obtained in the step S2 until the concentration is 18%-25%, and performing graded pulp grinding to obtain ground pulp; and S4, shoving: shoving the ground slurry obtained in the step S3 until the dryness is 45-65% to obtain the slurry. The prepared paper pulp is good in physical performance and high in strength, and the method is provided for recycling of the tail pulp of the chemical pulp.

Description

Technical Field

[0001] The present invention relates to the technical field of pulp and paper production, and particularly relates to a tail pulp recycling and reproduction process and its application. Background Art

[0002] The components of plant resources such as wood and agricultural straw are mainly cellulose, hemicellulose and lignin. The process of making pulp is to obtain the pulp that can be used to make paper through physical and chemical methods. The important effects involved include the softening, grinding, chemical delignification and hemicellulose of raw materials, etc. Pulp, as a commonly used fiber material, has a high demand. According to the production process of pulp, it can be divided into mechanical pulp, chemi-mechanical pulp (CMP), semi-chemical pulp and chemical pulp. Chemical pulp is a pulp made by chemically removing most of the non-cellulose components (such as lignin) from plant fiber raw materials (such as wood, bamboo, grass, etc.). Its production process is mainly chemical treatment, separating fibers through processes such as cooking and bleaching. The fiber quality is relatively high, but the raw material utilization rate is relatively low.

[0003] The tail pulp generated during the production process of chemical pulp (including fiber residues and unseparated lignin in cooking waste liquor and bleaching wastewater, etc.) is one of the main wastes in the paper industry. Recycling tail pulp is not only an inevitable requirement for reducing the environmental burden, but also a key measure to improve resource efficiency and promote circular economy. Its necessity is reflected in the following aspects: On the one hand, it can reduce environmental pollution and relieve ecological pressure: Chemical pulp tail pulp contains a large amount of lignin, residual chemical agents (such as alkali, sulfide) and organic substances. If directly discharged without treatment, it will cause water eutrophication, soil acidification and release toxic gases (such as hydrogen sulfide). By recycling the fibers and chemicals in the tail pulp, pollutant emissions can be significantly reduced, avoiding long-term damage to the ecosystem. On the other hand, it can improve resource utilization rate and reduce production costs: The production of chemical pulp requires a large amount of wood, water and energy, but only about 40%-50% of the raw materials are converted into usable fibers, and the remaining part is lost with the tail pulp. Recycling the residual fibers (accounting for 10%-20%) in the tail pulp can be reused to produce packaging cardboard or low-grade paper, reducing the demand for virgin fibers; at the same time, recycling the alkali and heat energy in the cooking waste liquor can save 30%-50% of the chemical and energy costs.

[0004] As described in Chinese Patent CN102002878A, a method for recovering pulp from papermaking wastewater specifically involves the following steps: a. Adding a flocculant to the papermaking wastewater in a mixer and mixing thoroughly to produce flocs; b. Feeding the flocs into the inclined concentration section of a belt filter press through a feeding device. Under the action of gravity, as the surface mesh moves, the free water is rapidly removed to form pulp residue; c. The pulp residue dehydrated in the inclined concentration section is transported to the gravity dehydration section of the belt filter press for further dehydration, and then fed into the "S"-shaped pressing section to promote further dehydration of the pulp residue; d. Finally, the pulp residue is scraped off by a scraper to obtain the pulp for reproduction. However, it does not involve the reproduction process of the recovered pulp.

[0005] Moreover, the tail pulp of chemical pulp or chemi-thermomechanical pulp has the characteristics of short, thick, and hard fibers, and the lignin content is relatively low. Especially for the tail pulp of chemical pulp, it is difficult to improve the bonding strength. However, in the existing technology, there is no recycling method for the tail pulp of chemical pulp. Based on this, developing a recycling process for the characteristics of the tail pulp of chemical pulp is the research focus of researchers in this field. Summary of the Invention

[0006] In view of the above problems, the present invention provides a tail pulp recovery and reproduction process. By optimizing the production process, a recycling method for the tail pulp of chemical pulp is provided, and the prepared pulp has good physical properties.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a tail pulp recovery and reproduction process, which includes the following steps: S1: Pretreatment: Mix the tail pulp with a surfactant, add xylanase, and mix again to obtain pretreated tail pulp; S2: Softening: Mix the pretreated tail pulp obtained in step S1 with an enzyme preparation to obtain softened pulp; the enzyme preparation is a mixture of keratinase, lignin peroxidase, and galactosidase; S3: Pulping: Concentrate the softened pulp obtained in step S2 to a concentration of 18%-25%, and perform graded pulping to obtain pulped pulp; S4: Pressing: Press the pulped pulp obtained in step S3 to a dryness of 45%-65% to obtain pulp.

[0008] Preferably, in step S1, the tail pulp needs to be screened first, and the sieve hole diameter is 2-3 mm to remove impurities.

[0009] Preferably, in step S1, the surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate.

[0010] Further preferably, the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 1-3:2-4; more preferably, the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 2:3.

[0011] Preferably, in step S1, the mass of the surfactant is 0.5%-3% of the mass of the tail pulp; further preferably, in step S1, the mass of the surfactant is 1%-2% of the mass of the tail pulp; more preferably, in step S1, the mass of the surfactant is 1.6% of the mass of the tail pulp.

[0012] Preferably, in step S1, the addition amount of xylanase is 0.1%-0.3% of the mass of the tail pulp. Further preferably, in step S1, the addition amount of xylanase is 0.2% of the mass of the tail pulp.

[0013] Preferably, in step S1, the mixing is stirring, the temperature is 40-60°C, and the time is 1-3 h; further preferably, in step S1, the mixing is stirring, the temperature is 45°C, and the time is 1.5 h.

[0014] Preferably, in step S1, the secondary mixing is stirring, and the specific parameters are: the temperature is 40-60°C, the time is 1-3 h, and the pH is adjusted to 6-10.

[0015] Further preferably, in step S1, the secondary mixing is stirring, and the specific parameters are: the temperature is 50°C, the time is 1 h, and the pH is adjusted to 8.

[0016] Preferably, in step S2, the mass ratio of keratinase, lignin peroxidase, and galactosidase is 2-4:5-6:1-2; more preferably, in step S2, the mass ratio of keratinase, lignin peroxidase, and galactosidase is 3:5:1.

[0017] Preferably, in step S2, the addition amount of the enzyme preparation is 0.2%-0.5% of the mass of the pretreated tail pulp; further preferably, in step S2, the addition amount of the enzyme preparation is 0.3% of the mass of the pretreated tail pulp.

[0018] Preferably, in step S2, the mixing is stirring, and the specific parameters are: the temperature is 40-60°C, the time is 3-5 h, and the pH is 8-10; further preferably, in step S2, the stirring, the specific parameters are: the temperature is 55°C, the time is 5 h, and the pH is 9.

[0019] Preferably, in step S3, a high-concentration refiner is used for refining.

[0020] Preferably, in step S3, the specific operation of classified refining is: For the first pulping, the disc gap is 0.3 - 0.4 mm and the rotational speed is 600 - 700 r / min; For the second pulping, the disc gap is 0.1 - 0.2 mm and the rotational speed is 750 - 800 r / min.

[0021] Preferably, in step S3, the beating degree of the pulp after pulping is 22 - 24°SR and the wet weight is 1.8 - 2.5 g.

[0022] Preferably, in step S4, the dryness is 50% - 60%.

[0023] On the other hand, the present invention provides an application of the pulp prepared by the above - mentioned tail pulp recycling and reproduction process in the preparation of paper products.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. By optimizing the pretreatment process, the present invention adds a surfactant and xylanase to the tail pulp and mixes them twice, so that the cellulose and hemicellulose in the tail pulp are fully exposed and preliminarily softened, laying a foundation for subsequent treatment; 2. By optimizing the composition and ratio of enzyme preparations, it is found that keratinase, lignin peroxidase, and galactosidase have a synergistic effect: on the one hand, it better softens the thick and hard cellulose in chemical pulp; on the other hand, it significantly improves the binding strength of cellulose in the pulp and the prepared paper has better physical properties; on the third hand, it efficiently removes the residual lignin in the tail pulp.

[0025] 3. By optimizing the pulping and pressing processes, the present invention further improves the binding strength of cellulose in the pulp and improves the quality of the pulp. Specific Embodiments

[0026] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the present invention will be further clarified below with reference to specific embodiments. However, the following embodiments are only the preferred embodiments of the present invention, not all of them. Based on the embodiments in the embodiments, other embodiments obtained by those skilled in the art without creative work all belong to the protection scope of the present invention. It is worth noting that the raw materials used in the present invention are all ordinary commercially available products, and no specific limitation is made on their sources. The technical and scientific terms used in the embodiments have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] Example 1 A tail pulp recycling and reproduction process includes the following steps: S1: Pretreatment: The tail pulp is sieved, the sieve hole diameter is 2 - 3 mm. After sieving, the tail pulp is added with a surfactant and stirred at 45 °C for 1.5 h. The addition amount of the surfactant is 1.6% of the mass of the tail pulp. Xylanase (the addition amount is 0.2% of the mass of the tail pulp) is added, the pH is adjusted to 8, and it is stirred at 50 °C for 1 h to obtain pretreated tail pulp; The surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate, and the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 2:3; S2: Softening: The pretreated tail pulp obtained in step S1 is mixed with an enzyme preparation (the addition amount of the enzyme preparation is 0.3% of the mass of the pretreated tail pulp), the pH is adjusted to 9, and it is stirred at 55 °C for 5 h to obtain softened pulp; The enzyme preparation is a mixture of keratinase, lignin peroxidase and galactosidase; The mass of keratinase, lignin peroxidase and galactosidase is 3:5:1; S3: Pulping: The softened pulp obtained in step S2 is concentrated to a concentration of 18% - 25%, and a high-concentration pulping machine is used for classified pulping: For the first pulping, the disc gap is 0.3 - 0.4 mm, the rotation speed is 600 - 700 r / min, and the time is 15 - 30 min; For the second pulping, the disc gap is 0.1 - 0.2 mm, the rotation speed is 750 - 800 r / min; the time is 35 - 60 min; S4: Pressing: The pulped pulp obtained in step S3 is pressed to a dryness of 50% - 60% to obtain pulp.

[0028] Example 2 A tail pulp recycling and reproduction process. Compared with Example 1, only the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate in step S1 is changed to 1:4, and the others are the same as in Example 1.

[0029] Example 3 A tail pulp recycling and reproduction process. Compared with Example 1, only the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate in step S1 is changed to 3:2, and the others are the same as in Example 1.

[0030] Example 4 A tail pulp recycling and reproduction process. Compared with Example 1, only the mass of keratinase, lignin peroxidase and galactosidase in step S2 is changed to 4:6:2, and the others are the same as in Example 1.

[0031] Example 5 A tail pulp recycling and reproduction process includes the following steps: S1: Pretreatment: The tail pulp is sieved, the sieve hole diameter is 2 - 3 mm. After sieving, the surfactant is added to the tail pulp and stirred at 60 °C for 3 h. The addition amount of the surfactant is 3% of the mass of the tail pulp. Xylanase (the addition amount is 0.1% of the mass of the tail pulp) is added, the pH is adjusted to 10, and stirred at 40 °C for 3 h to obtain the pretreated tail pulp; The surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate, and the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 2:3; S2: Softening: The pretreated tail pulp obtained in step S1 is mixed with an enzyme preparation (the addition amount of the enzyme preparation is 0.5% of the mass of the pretreated tail pulp), the pH is adjusted to 8, and stirred at 40 °C for 3 h to obtain the softened pulp; the enzyme preparation is a mixture of keratinase, lignin peroxidase and galactosidase; the mass of keratinase, lignin peroxidase and galactosidase is 3:5:1; S3: Pulping: The softened pulp obtained in step S2 is concentrated to a concentration of 18% - 25%, and a high-concentration pulper is used for grading pulping: For the first pulping, the disc gap is 0.3 - 0.4 mm, the rotation speed is 600 - 700 r / min, and the time is 15 - 30 min; For the second pulping, the disc gap is 0.1 - 0.2 mm, the rotation speed is 750 - 800 r / min; the time is 35 - 60 min; S4: Pressing: The pulped pulp obtained in step S3 is pressed to a dryness of 50% - 60% to obtain the pulp.

[0032] Comparative Example 1 A tail pulp recycling and reproduction process. Compared with Example 1, only the surfactant ratio in step S1 is changed. The mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 4:1, and the others are the same as in Example 1.

[0033] Comparative Example 2 A tail pulp recycling and reproduction process. Compared with Example 1, only the surfactant in step S1 is changed. The surfactant is tallow-based dihydroxyethyl betaine, and the others are the same as in Example 1.

[0034] Comparative Example 3 A tail pulp recycling and reproduction process. Compared with Example 1, only the surfactant in step S1 is changed. The surfactant is sodium diisooctyl sulfosuccinate, and the others are the same as in Example 1.

[0035] Comparative Example 4 A tail pulp recycling and reproduction process. Compared with Example 1, only step S1 is changed: S1: Pretreatment: The tail pulp is sieved with a sieve hole diameter of 2 - 3 mm. The sieved tail pulp is added with a surfactant and stirred at 45°C for 1.5 h. The addition amount of the surfactant is 1.6% of the mass of the tail pulp. Adjust the pH to 8 and stir at 50°C for 1 h to obtain the pretreated tail pulp; The surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate, and the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 2:3; Others are the same as in Example 1.

[0036] Comparative Example 5 A tail pulp recycling and reproduction process, compared with Example 1, only changes step S1: S1: Pretreatment: The tail pulp is sieved with a sieve hole diameter of 2 - 3 mm. The sieved tail pulp is added with xylanase (the addition amount is 0.2% of the mass of the tail pulp), adjust the pH to 8, and stir at 50°C for 1 h to obtain the pretreated tail pulp; Others are the same as in Example 1.

[0037] Comparative Example 6 A tail pulp recycling and reproduction process, compared with Example 1, only changes the enzyme preparation ratio in step S2. The mass ratio of keratinase, lignin peroxidase, and galactosidase is 1:4:3, and others are the same as in Example 1.

[0038] Comparative Example 7 A tail pulp recycling and reproduction process, compared with Example 1, only changes the enzyme preparation in step S2. The enzyme preparation is keratinase, and others are the same as in Example 1.

[0039] Comparative Example 8 A tail pulp recycling and reproduction process, compared with Example 1, only changes the enzyme preparation in step S2. The enzyme preparation is lignin peroxidase, and others are the same as in Example 1.

[0040] Comparative Example 9 A tail pulp recycling and reproduction process, compared with Example 1, only changes the enzyme preparation in step S2. The enzyme preparation is galactosidase, and others are the same as in Example 1.

[0041] Comparative Example 10 A tail pulp recycling and reproduction process includes the following steps: S1: Pretreatment: The tail pulp is sieved with a sieve hole diameter of 2 - 3 mm. The sieved tail pulp is added with a surfactant and stirred at 45°C for 1.5 h. The addition amount of the surfactant is 4% of the mass of the tail pulp. Add xylanase (the addition amount is 0.5% of the mass of the tail pulp), adjust the pH to 8, and stir at 50°C for 1 h to obtain the pretreated tail pulp; The surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate, and the mass ratio of tallow-based dihydroxyethyl betaine to sodium diisooctyl sulfosuccinate is 2:3; S2: Softening: The pretreated tail pulp obtained in step S1 is added with an enzyme preparation (the addition amount of the enzyme preparation is 0.6% of the mass of the pretreated tail pulp), mixed, the pH is adjusted to 9, and stirred at 55 °C for 5 h to obtain softened pulp; the enzyme preparation is a mixture of keratinase, lignin peroxidase and galactosidase; the mass ratio of keratinase, lignin peroxidase and galactosidase is 3:5:1; S3: Pulping: The softened pulp obtained in step S2 is concentrated to a concentration of 18%-25%, and a high-concentration pulping machine is used for graded pulping: For the first pulping, the disc gap is 0.3-0.4 mm, the rotation speed is 600-700 r / min, and the time is 15-30 min; For the second pulping, the disc gap is 0.1-0.2 mm, the rotation speed is 750-800 r / min; the time is 35-60 min; S4: Pressing: The pulped pulp obtained in step S3 is pressed to a dryness of 50%-60% to obtain pulp.

[0042] Comparative Example 11 A tail pulp recycling and reproduction process, compared with Example 1, only step S3 is changed: S3: Pulping: The softened pulp obtained in step S2 is concentrated to a concentration of 18%-25%, and a high-concentration pulping machine is used for pulping: The disc gap is 0.3-0.4 mm, the rotation speed is 600-700 r / min, and the time is 50-90 min; Others are the same as in Example 1.

[0043] Test Example The yield and physical properties of the pulp prepared in Examples 1-5 and Comparative Examples 1-11 are shown in Table 1.

[0044] Table 1. Results

[0045] From the data in Table 1, it can be seen that the pulp prepared in the examples of the present invention has a higher yield; its physical properties are better: the burst index is higher, the beating degree is higher, the wet weight difference is not significant, and the fiber bonding strength of the pulp is higher.

[0046] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than a limitation on the protection scope of the present invention. Any simple modification or equivalent replacement of the technical solution of the present invention by those of ordinary skill in the art does not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A tail pulp recycling and reproduction process, characterized in that, It includes the following steps: S1: Pretreatment: Mix the tail pulp and surfactant, add xylanase, and mix again to obtain pretreated tail pulp; S2: Softening: Mix the pretreated tail pulp obtained in step S1 with the enzyme preparation to obtain softened pulp; the enzyme preparation is a mixture of keratinase, lignin peroxidase, and galactosidase; S3: Pulping: Concentrate the softened pulp obtained in step S2 to a concentration of 18%-25%, and perform graded pulping to obtain pulped pulp; S4: Pressing: Press the pulped pulp obtained in step S3 to a dryness of 45%-65% to obtain the pulp.

2. The tail rotor recycling and reproduction process according to claim 1, characterized in that, In step S1, the surfactant is a mixture of tallow-based dihydroxyethyl betaine and sodium diisooctyl sulfosuccinate.

3. The tail rotor recycling and reproduction process according to claim 2, characterized in that, The mass ratio of the tallow-based dihydroxyethyl betaine to the sodium diisooctyl sulfosuccinate is 1-3:2-4.

4. The tail pulp recycling and reproduction process according to claim 1, characterized in that, In step S1, the mass of the surfactant is 0.5%-3% of the mass of the tail pulp.

5. The tail pulp recycling and reproduction process according to claim 1, characterized in that, In step S1, the addition amount of the xylanase is 0.1%-0.3% of the mass of the tail pulp.

6. The tail rotor recycling and reproduction process according to claim 1, characterized in that, In step S1, the mixing is stirring, the temperature is 40-60°C, and the time is 1-3 h; the second mixing is stirring, and the specific parameters are: the temperature is 40-60°C, the time is 1-3 h, and the pH is adjusted to 6-10.

7. The tail rotor recycling and reproduction process according to claim 1, characterized in that, In step S2, the mass of the keratinase, lignin peroxidase, and galactosidase is 2-4:5-6:1-2; the addition amount of the enzyme preparation is 0.2%-0.5% of the mass of the pretreated tail pulp.

8. The tail rotor recycling and reproduction process according to claim 1, characterized in that, In step S2, the mixing is stirring, and the specific parameters are: the temperature is 40-60°C, the time is 3-5 h, and the pH is 8-10.

9. The tail pulp recycling and reproduction process according to claim 1, characterized in that, In step S3, The specific operation of the graded pulping is: First pulping, the gap between the grinding discs is 0.3-0.4 mm, and the rotation speed is 600-700 r / min; Second pulping, the gap between the grinding discs is 0.1-0.2 mm, and the rotation speed is 750-800 r / min; The beating degree of the pulped pulp is 22-24°SR, and the wet weight is 1.8-2.5 g.

10. Application of the pulp prepared by the tail pulp recycling and reproduction process according to any one of claims 1-9 in the preparation of paper products.

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