Pulp preparation method using mulberry branches as raw materials

Abstract

The invention belongs to the technical field of pulp preparation, and particularly relates to a method for preparing pulp by taking mulberry branches as a raw material. The preparation method of the pulp comprises the following steps: crushing mulberry branches, and soaking the crushed mulberry branches by adopting a composite chemical reagent system, so that a higher chemical separation effect can be realized at a lower temperature within a shorter time; the materials are treated by innovatively adopting a staged temperature cooking process, so that the problems of fiber damage and excessive lignin residue in a traditional constant-temperature and constant-pressure cooking mode are solved, the separation degree of the fibers can be more effectively controlled, and the yield of the pulp is improved; and finally, the quality of the pulp is remarkably improved through multi-stage countercurrent washing and multi-section bleaching process treatment.

Description

Technical Field

[0001] This invention belongs to the field of pulp preparation technology, specifically relating to a method for preparing pulp using mulberry branches as raw material. Background Technology

[0002] In the papermaking industry, before paper is formed, pulp fibers must be treated using physical methods to change their morphology and structure, such as deformation, crushing, and fibrillation, so that the pulp properties meet the production requirements of the paper machine and the expected quality requirements of the paper. This process of subjecting fibers to friction, shearing, and crushing is called beating. Currently, the papermaking industry uses a wide variety of fiber raw materials. For some fiber raw materials with fibrillated structures, fibrillation also occurs during beating, that is, the process of the fiber body forming finer fibrils under external force. This is specifically manifested in changes such as fiber sheath peeling, loosening of structure, axial splitting, and dissociation. Beating is a physical method to achieve fiber fibrillation. Specifically, it involves dispersing chopped fibers in water and then mechanically beating and grinding them using various beating equipment, resulting in a large number of microfibrillated hairs on the fiber surface, forming highly fibrillated pulp.

[0003] Currently, traditional methods for producing pulp from mulberry branches suffer from problems such as low resource utilization, high energy consumption during production, severe environmental pollution, and unstable product quality. Firstly, traditional pulping methods result in low fiber extraction rates (yield <76%) and the lack of sorting and crushing leads to resource waste. Secondly, single-alkali treatment produces wastewater with a COD >105 kg / t, and the bleaching agent is non-degradable, causing severe pollution. Furthermore, the use of constant-temperature cooking processes can lead to fiber damage or lignin residue, resulting in unstable pulp quality.

[0004] Therefore, there is an urgent need to find a new method for pulp preparation to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing pulp using mulberry branches as raw material. The method provided by this invention not only achieves efficient utilization of resources, but also produces pulp with stable quality.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing pulp, comprising the following steps:

[0008] (1) Chemical treatment: Crush mulberry branches into granules and soak them in a compound chemical reagent for chemical treatment;

[0009] (2) Cooking treatment: The chemically treated mulberry branches are cooked in stages with controlled temperature and pressure.

[0010] (3) Washing and bleaching: The cooked mulberry branch pulp was subjected to multi-stage countercurrent washing and multi-stage bleaching to prepare pulp;

[0011] The composite chemical reagent consists of sodium hydroxide, sodium sulfite, and surfactants.

[0012] Preferably, the particle size of the mulberry branch particles ranges from 5 to 10 mm.

[0013] Preferably, the composite chemical reagent comprises 10-15% sodium hydroxide, 5-8% sodium sulfite, 0.5-1.5% surfactant, and the remainder is water; the surfactant is cashew phenol polyoxyethylene ether, isotretinoin polyoxyethylene ether, or sophorolipid.

[0014] Preferably, the chemical treatment process includes soaking mulberry branch particles in the composite chemical reagent of claim 3 at 60-80°C for 2-4 hours.

[0015] Preferably, the solid-liquid ratio of the mulberry branch particles to the composite chemical reagent is 1:(4-5).

[0016] Preferably, the staged temperature and pressure controlled cooking process includes: an initial stage of cooking at 120-130℃ and 0.1-0.15MPa for 30-50 minutes; and a second stage of cooking at 160-170℃ and 0.5-0.7MPa for 60-90 minutes.

[0017] Preferably, the multi-stage bleaching process includes two or three stages: oxygen bleaching, chlorine bleaching, and soft pulp bleaching.

[0018] More preferably, the oxygen bleaching is 2-4% H2O2, bleaching at 85-100℃ and pH 10-11 for 1-2 hours; the chlorine bleaching is 1-3% NaClO, bleaching at 70-75℃ for 1-1.5 hours; and the soft pulp bleaching is 0.5-1.5% peracetic acid, bleaching at 45-55℃ for 1-1.5 hours.

[0019] Preferably, the preparation method further includes a process of dehydrating and drying the pulp, wherein the moisture content of the dried pulp is 8-10%.

[0020] The beneficial effects of this invention are:

[0021] This invention utilizes a composite reagent combined with a two-stage cooking and multi-stage rinsing process to prepare pulp. Compared with traditional methods for preparing pulp from mulberry branches, the method described in this invention is energy-saving and environmentally friendly, significantly reducing the COD concentration in wastewater; significantly increasing fiber yield; and demonstrating marked improvements in the properties of the prepared pulp, particularly in copper ammonia viscosity and whiteness. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 Photographs of mulberry branch raw materials;

[0024] Figure 2 This is a photo of the pulp after washing.

[0025] Figure 3 This is a photo of the pulp after rinsing. Detailed Implementation

[0026] This invention provides a method for preparing pulp from mulberry branches, which includes pretreatment of mulberry branches, soaking treatment with compound chemical reagents, staged cooking process, integrated washing and bleaching, and subsequent treatment processes.

[0027] This invention involves crushing mulberry branches into mulberry branch particles with a particle size of 5-10 mm, soaking them in a composite chemical reagent at 60-80°C for 2-4 hours. The composite chemical reagent includes 10-15% sodium hydroxide, 5-8% sodium sulfite, 0.5-1.5% surfactant, and the remainder is water. The surfactant is cashew phenol polyoxyethylene ether, isotretinoin polyoxyethylene ether, or sophorolipid.

[0028] The chemically treated mulberry branches are subjected to staged temperature and pressure controlled cooking. The staged temperature and pressure controlled cooking process includes: an initial stage of cooking at 120-130℃ and 0.1-0.15MPa for 30-50 minutes (for material softening); and a second stage of cooking at 160-170℃ and 0.5-0.7MPa for 60-90 minutes (for enhancing fiber separation and lignin dissolution). The pulp is prepared by subjecting the cooked mulberry branch pulp to multi-stage countercurrent washing and multi-stage bleaching. The multi-stage bleaching process includes two or three stages: oxygen bleaching, chlorine bleaching, and soft pulp bleaching. The oxygen bleaching is performed with 2-4% H2O2 at 85-100℃ and pH 10-11 for 1-2 hours. The chlorine bleaching is performed with 1-3% NaClO at 70-75℃ for 1-1.5 hours. The soft pulp bleaching is performed with 0.5-1.5% peracetic acid at 45-55℃ for 1-1.5 hours.

[0029] Furthermore, the method for preparing pulp according to the present invention also includes a process of dehydrating and drying the pulp, wherein the moisture content of the dried pulp is 8-10%.

[0030] On one hand, this invention employs a composite chemical reagent system to impregnate pretreated mulberry branch particles. This composite chemical reagent is composed of sodium hydroxide, sodium sulfite, and a novel environmentally friendly surfactant mixed in a specific ratio. By controlling the impregnation temperature between 60°C and 80°C and the time between 2 and 4 hours, the cellulose, hemicellulose, and lignin components in the mulberry branches are fully separated. Compared to conventional single alkali or acid treatment methods, this composite chemical reagent system can achieve more efficient chemical separation at lower temperatures and in shorter times, while reducing the amount of chemical reagents used and the generation of waste, thus lowering production costs and environmental pollution risks. Furthermore, the surfactant has good biodegradability and will not cause secondary pollution to the environment, meeting environmental protection requirements.

[0031] On the other hand, this invention innovatively employs a staged temperature control and pressure regulation cooking process. First, in the initial stage, the temperature is raised to 120-130℃ at a relatively slow rate, while the pressure is maintained between 0.1-0.15 MPa for 30-50 minutes, allowing the material to begin softening and decomposing under mild conditions. Next, the temperature is rapidly raised to 160-170℃, and the pressure is increased to 0.5-0.7 MPa, maintained for 60-90 minutes, enhancing fiber separation and lignin dissolution. Finally, the temperature and pressure are slowly reduced, allowing the cooking process to conclude smoothly. Compared to traditional constant temperature and pressure cooking methods, this staged control cooking process can more effectively control the degree of fiber separation, avoiding problems such as fiber damage from over-cooking or excessive lignin residue from insufficient cooking, thereby improving pulp yield and quality while reducing energy consumption and equipment wear.

[0032] In summary, the surfactant in the composite chemical reagent of this invention can promote the penetration of sodium hydroxide and sodium sulfite into the interior of mulberry branch particles. Combined with the "softening before separation" mechanism of staged cooking, it can reduce fiber damage caused by excessive lignin dissolution at low temperature stage and efficiently separate residual lignin at high temperature stage, thereby improving yield and reducing COD emissions.

[0033] On the other hand, this invention employs a novel water-saving washing device during the washing process. By optimizing the distribution and direction of the washing water flow, it ensures full contact between the washing water and the pulp, effectively removing residual chemicals and impurities while reducing water waste. The bleaching process utilizes a multi-stage combined bleaching system of oxygen bleaching, chlorine bleaching, and soft pulp bleaching. The bleaching conditions at each stage are precisely controlled, including parameters such as temperature, time, and reagent dosage. In the oxygen bleaching stage, hydrogen peroxide is used to pre-bleach the pulp under alkaline conditions, partially oxidizing and removing lignin. In the chlorine bleaching stage, hypochlorite is used to further remove lignin and pigments. In the soft pulp bleaching stage, a novel soft pulp bleaching agent is used to finely bleach the pulp at a lower temperature, improving the whiteness and brightness of the pulp while reducing fiber damage and environmental pollutant emissions. Compared with existing single bleaching or conventional multi-stage bleaching processes, this integrated washing and bleaching process is more compact and efficient, significantly improving the whiteness and cleanliness of pulp, meeting the raw material requirements of high-quality paper and cellulose products, while reducing water and chemical consumption during production, reducing wastewater discharge and treatment difficulty, and being more environmentally friendly.

[0034] On the other hand, this invention employs a novel, highly efficient dewatering device during the dewatering process. This device combines mechanical extrusion with vacuum suction to rapidly remove moisture from the pulp, reducing drying energy consumption. The drying process utilizes multi-stage temperature control and ventilation regulation to ensure uniform heating of the pulp during drying, preventing fiber clumping and denaturation, and controlling the moisture content of the final product to between 8-10%, meeting storage and transportation requirements.

[0035] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0036] Unless otherwise specified, the production processes, experimental methods, or testing methods involved in the embodiments of this invention are all conventional methods in the prior art, and their names and / or abbreviations are all conventional names in the field, which are very clear and distinct in the relevant application areas. Those skilled in the art can understand the conventional process steps based on the names and apply the corresponding equipment, and implement them according to conventional conditions or the conditions recommended by the manufacturer.

[0037] The various instruments, equipment, raw materials or reagents used in the embodiments of this invention are not subject to any special restrictions on their source. They are all conventional products that can be purchased through regular commercial channels and can be prepared according to conventional methods known to those skilled in the art.

[0038] Example 1

[0039] Crush mulberry branches to a size of 5-10mm and sieve to remove particles larger than 12mm. The raw material is mulberry branches as follows: Figure 1 As shown.

[0040] Prepare a compound reagent: 13% NaOH, 7% Na2SO3, and 0.8% cashew phenol polyoxyethylene ether, and add water to make a 120L solution.

[0041] The crushed mulberry branch particles were mixed with a compound reagent at a solid-liquid ratio of 1:5, and soaked at 75℃ with stirring for 3.5 hours at a stirring speed of 120 rpm. The soaked mulberry branch particles were then placed in a high-pressure cooker for cooking. The first stage was cooked at 125℃ and 0.13 MPa for 45 minutes with a heating rate of 1.5℃ / min; the second stage was cooked at 168℃ and 0.68 MPa for 80 minutes, with pressure fluctuations of ±0.01 MPa during the pressure holding period.

[0042] The cooked mulberry branch pulp was subjected to a three-stage countercurrent washing process: Stage 1: 45℃ warm water, washing for 12 minutes; Stage 2: 50℃ warm water, washing for 10 minutes; Stage 3: 60℃ hot water, washing for 8 minutes. The washed pulp was as follows: Figure 2 As shown.

[0043] The washed mulberry branch pulp underwent oxygen bleaching and chlorine bleaching treatments. The oxygen bleaching stage consisted of 3.5% H₂O₂ at pH 10.8, bleaching at 95℃ for 1.5 hours; the chlorine bleaching stage consisted of 2.5% NaClO at 70℃, bleaching for 1.5 hours. The bleached pulp was then dried using a plate and frame filter press at 0.6 MPa, followed by a drum dryer with an inlet temperature of 120℃ and an outlet temperature of 60℃ until the moisture content reached 8.8%. The bleached pulp was then... Figure 3 As shown.

[0044] Tests showed that the final wastewater COD of the washed mulberry branch pulp was <50 kg / t.

[0045] Example 2

[0046] Crush mulberry branches to 5-10mm and sieve to remove particles larger than 12mm.

[0047] Prepare the composite reagent: 14% NaOH, 6% Na2SO3, and 1.2% isomeric tridecyl alcohol polyoxyethylene ether, and add water to prepare a 120L solution.

[0048] The crushed mulberry branch particles were mixed with a compound reagent at a solid-liquid ratio of 1:4.5, and soaked at 65℃ with stirring for 4 hours at a stirring speed of 120 rpm. The soaked mulberry branch particles were then placed in a high-pressure cooker for cooking. The first stage was cooked at 130℃ and 0.15 MPa for 35 minutes; the second stage was cooked at 170℃ and 0.7 MPa for 75 minutes, with a cooling rate of 2℃ / min.

[0049] The cooked mulberry branch pulp was subjected to a 5-stage countercurrent washing process: the water temperature was gradually increased from 40-60℃, and the washing time was 6-10 minutes. The washed mulberry branch pulp was then subjected to oxygen bleaching and softening bleaching treatments. The oxygen bleaching stage was: 4% H2O2, pH 11, 100℃, bleaching for 1 hour; the softening bleaching stage was: 0.9% peracetic acid, 55℃, bleaching for 1.5 hours.

[0050] The washed pulp is dried, dewatered by screw extrusion, and then dried in a fluidized bed at 60-85℃ until the moisture content is 9.5%.

[0051] Example 3

[0052] Crush mulberry branches into 5-10mm pieces and sieve to remove particles larger than 12mm. Add 50℃ warm water (solid-liquid ratio 1:3), ultrasonically clean for 10 minutes (frequency 25kHz, power 800W), and then drain.

[0053] Prepare a compound reagent: 11% NaOH, 8% Na2SO3, and 1.0% sophorolipid, and add water to make a 120L solution.

[0054] The crushed mulberry branch particles were mixed with a compound reagent at a solid-liquid ratio of 1:5, and soaked at 80℃ with stirring for 2.5 hours at a stirring speed of 120 rpm. The soaked mulberry branch particles were then placed in a high-pressure cooker for cooking. The first stage was cooked at 120℃ and 0.1 MPa for 50 minutes; the second stage was cooked at 165℃ and 0.6 MPa for 90 minutes, with a heating rate of 3℃ / min.

[0055] The cooked mulberry branch pulp was subjected to a four-stage countercurrent washing process: 60℃ water temperature, 7 minutes washing. The washed mulberry branch pulp was then subjected to oxygen bleaching, chlorine bleaching, and softening bleaching. The oxygen bleaching stage consisted of 2.5% H₂O₂, pH 10, 85℃ for 2 hours; the chlorine bleaching stage consisted of 1.5% NaClO, 75℃ for 1 hour; and the softening bleaching stage consisted of 0.8% peracetic acid, 45℃ for 1 hour.

[0056] The rinsed pulp was dried by double-roll extrusion dewatering under a pressure of 0.8 MPa, followed by multi-stage hot air drying (60℃-90℃-70℃) until the moisture content was 8.2%.

[0057] Comparative Example (Traditional Method for Preparing Pulp from Mulberry Branches)

[0058] Raw material pretreatment: 100kg of collected mulberry branches were cleaned of impurities and directly put into a crusher to be crushed to a particle size of 15±5mm.

[0059] Chemical treatment: Immerse in a single sodium hydroxide solution (18% concentration) at 85°C for 5 hours, with a liquid-to-solid ratio of 6:1 (by volume / dry weight).

[0060] Cooking process: Cook at a constant temperature of 160℃ and a pressure of 0.51MPa for 2.5 hours, with a heating rate of 5℃ / min.

[0061] Bleaching treatment: Single chlorine bleaching process (NaClO concentration 3.5%), treated at 65℃ for 2.5 hours, pH controlled at 11-12.

[0062] Washing and drying: Wash three times with tap water, stirring for 15 minutes each time, then air dry naturally until the moisture content is about 12%.

[0063] The key parameters and yield of the comparative pulp preparation are shown in Table 1.

[0064] Table 1 Key parameters and yield

[0065]

[0066]

[0067] The results are shown in Table 2, comparing the preparation process with that of Example 1:

[0068] Table 2 Comparison of Example 1 and Comparative Example

[0069]

[0070] The results are shown in Table 3, comparing the preparation process with that of Example 2:

[0071] Table 3 Comparison of Examples 1-2 and Comparative Examples

[0072]

[0073] The results, compared with the preparation process in Example 2, are shown in Table 4:

[0074] Table 4 Comparison of Example 3 and Comparative Example

[0075]

[0076]

[0077] In summary, the results show that the pulp prepared by the method described in this application has a significantly improved fiber yield, a significantly reduced COD concentration in the wastewater generated during the preparation process, and a significantly improved pulp quality.

[0078] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing pulp, characterized in that, Includes the following steps: (1) Chemical treatment: The mulberry branches are crushed into mulberry branch particles and soaked in a compound chemical reagent for chemical treatment. (2) Cooking treatment: The chemically treated mulberry branches are cooked in stages with controlled temperature and pressure. (3) Washing and bleaching: The cooked mulberry branch pulp was subjected to multi-stage countercurrent washing and multi-stage bleaching to prepare pulp; The composite chemical reagent comprises sodium hydroxide, sodium sulfite, and surfactant.

2. The preparation method according to claim 1, characterized in that, The particle size of the mulberry branch particles ranges from 5 to 10 mm.

3. The preparation method according to claim 1, characterized in that, The composite chemical reagent includes 10-15% sodium hydroxide, 5-8% sodium sulfite, 0.5-1.5% surfactant, and the remainder is water; the surfactant is cashew phenol polyoxyethylene ether, isotretinoin polyoxyethylene ether, or sophorolipid.

4. The preparation method according to claim 1, characterized in that, The chemical treatment process includes soaking mulberry branch particles in the composite chemical reagent described in claim 3 at 60-80°C for 2-4 hours.

5. The preparation method according to claim 1, characterized in that, The solid-liquid ratio of the mulberry branch particles to the composite chemical reagent is 1:(4-5).

6. The preparation method according to claim 1, characterized in that, The phased temperature and pressure controlled cooking process includes: an initial stage of cooking at 120-130℃ and 0.1-0.15MPa for 30-50 minutes; and a second stage of cooking at 160-170℃ and 0.5-0.7MPa for 60-90 minutes.

7. The preparation method according to claim 1, characterized in that, The multi-stage bleaching process includes two or three stages: oxygen bleaching, chlorine bleaching, and soft pulp bleaching.

8. The preparation method according to claim 7, characterized in that, The oxygen bleaching is 2-4% H2O2, bleaching at 85-100℃ and pH 10-11 for 1-2 hours; the chlorine bleaching is 1-3% NaClO, bleaching at 70-75℃ for 1-1.5 hours; the soft pulp bleaching is 0.5-1.5% peracetic acid, bleaching at 45-55℃ for 1-1.5 hours.

9. The preparation method according to claim 1, characterized in that, The preparation method also includes the process of dehydrating and drying the pulp, and the moisture content of the dried pulp is 8-10%.

Images