A continuous bamboo filament cooking method

Abstract

The application provides a bamboo filament continuous cooking method, which comprises a bamboo filament pretreatment step and a continuous cooking step. In the bamboo filament pretreatment step, the bamboo filament is treated with hot water containing NaOH and alkali such as guanidine hydrochloride for 1-2 hours. The continuous cooking step is carried out by using a horizontal tube continuous digester. Through in-depth study of the chemical and physical changes in the cooking process, the application uses suitable cooking parameters and treatment methods to ensure that the pretreatment process reduces the damage to the papermaking required holocellulose while dissolving the lipid substances and lignin; and improves the silicon retention effect of CaO in the cooking process, so that a small amount of CaO can be used to effectively retain silicon in the cooking process, thereby reducing the difficulty of black liquor treatment and the reactor fouling rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of papermaking, and specifically, the present application provides a continuous cooking method of bamboo filament. BACKGROUND

[0002] Bamboo raw material is an important non-wood raw material in the papermaking industry, which has a long history of use in China due to its simple propagation, short growth cycle, high fiber content, and pulp quality not inferior to many wood materials.

[0003] Cooking is an essential step in the papermaking process of bamboo raw materials. Bamboo raw materials are more compact than general wood raw materials, and the cooking process is difficult to penetrate with chemicals, resulting in insufficient product quality uniformity and time extension during the cooking process. The lipid substances in it also interfere with the subsequent process. Therefore, how to adjust the processing and cooking technology of bamboo materials is a key factor in optimizing the papermaking process of bamboo raw materials. At present, the problem is solved by pretreating the raw material with NaOH or Na2S. The main problem is the contradiction between the removal of lignin and lipid and the loss of time of holocellulose in the pretreatment process.

[0004] Another common problem in bamboo raw material papermaking is its high ash content. The silicate formed by the reaction of silicon and alkali in black liquor makes it difficult to extract and process black liquor. It is generally believed that leaving silicon in the pulp has no significant effect on the subsequent process and product. However, the process of leaving silicon, whether it is oxide leaving silicon or aluminum salt leaving silicon without additional equipment, or so-called flue gas black liquor desilication without additional reagents, has its shortcomings. SUMMARY

[0005] In view of the above, on the one hand, the present application provides a continuous cooking method of bamboo filament, which comprises a bamboo filament pretreatment step and a continuous cooking step, and the bamboo filament pretreatment step uses hot water containing alkali to treat bamboo filament for 1-2h.

[0006] Further, the bamboo filament pretreatment step uses 60-80℃ water containing 10-15g / L NaOH and 1-5g / L guanidine salt to treat bamboo filament for 1.5-2h.

[0007] Further, the guanidine salt is guanidine hydrochloride or guanidine carbonate.

[0008] Further, the bamboo filament pretreatment step uses 70℃ water containing 12g / L NaOH and 3g / L guanidine hydrochloride to treat bamboo filament for 1.5-2h.

[0009] Further, the bamboo filament pretreatment step uses 70℃ water containing 12g / L NaOH and 5g / L guanidine hydrochloride to treat bamboo filament for 2h.

[0010] Further, the continuous cooking step uses a Pandya horizontal tube continuous digester, steam temperature 240-250℃, pressure 0.75-0.78MPa, alkali dosage 17% w / w dry raw material mass based on NaOH, sulfidity 25%; 1-1.5% dry raw material mass of CaO is added in the continuous cooking step.

[0011] According to the equipment and methods commonly used by the applicant enterprise, a Pandya horizontal tube continuous digester is used in the embodiments of the present application. A vertical continuous digester and a batch cooking device can also be used in the method of the present application after suitable adjustment.

[0012] Further, 1% dry raw material mass of CaO is added in the continuous cooking step.

[0013] Further, the bamboo filaments are green bamboo filaments or Cymbidium filaments.

[0014] Further, the bamboo filaments are prepared by extrusion and cutting methods, and have a length of not more than 50mm, a width of not more than 10mm, and a thickness of not more than 2mm.

[0015] The bamboo filaments in the present application refer to bamboo pieces in an elongated shape processed by extrusion, cutting and the like. Those skilled in the art can select different sizes according to the equipment and raw materials, and the size is not limited to "length of not more than 50mm, width of not more than 10mm, and thickness of not more than 2mm" used in the embodiments, and can be used alternately with "bamboo pieces".

[0016] The method of the present application ensures that the dissolution of lipid substances and lignin is achieved while reducing the damage to the holocellulose required for papermaking by adding an appropriate amount of guanidine hydrochloride in the pretreatment process of the bamboo filaments; at the same time, the silicon retention effect of CaO in the cooking is improved, and a small amount of CaO can effectively retain silicon, thereby reducing the difficulty of black liquor treatment and the reactor fouling rate. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure shows the change in holocellulose content of the product after 1h when different amounts of guanidine hydrochloride and guanidine carbonate are added in the pretreatment.

[0018] Figure 2 The figure shows the effect of different amounts of CaO on the silicon content in the pulp. DETAILED DESCRIPTION

[0019] Main equipment and methods:

[0020] Main detection methods:

[0021] Paper pulp Kappa number: GB / T 1546-2008;

[0022] Benzene-ethanol extract: GB / T 10741-2008;

[0023] Holocellulose: GB / T2677.10-1995;

[0024] Lignin: GB / T2677.8-1994;

[0025] Ash: GB / T2677.3-1993;

[0026] Silica content: GB / T7978-1987

[0027] Raw materials:

[0028] Green bamboo raw materials were purchased from Guangxi and cut into bamboo filaments / pieces with a length of no more than 50 mm, a width of no more than 10 mm, and a thickness of no more than 2 mm (unqualified bamboo filaments / pieces were no more than 10%), and air-dried for about 1 month. The raw materials contained about 11% water, about 20% lignin, about 75% holocellulose, and about 2% benzene-ethanol extractives and ash content; the same batch of green bamboo raw materials were selected for the comparative experiment.

[0029] NaOH, guanidine salt, CaO and other raw materials were all domestic.

[0030] Cooking equipment:

[0031] Pandiya horizontal tube continuous digester: Rida Biomass Technology Co., Ltd.

[0032] Example 1 Bamboo filament pretreatment process

[0033] The bamboo raw material has a more compact structure than the general wood raw material, and the penetration of the cooking liquor is more difficult during cooking. Therefore, bamboo filament pretreatment is a necessary step in the bamboo filament cooking process. In the pretreatment, the benzene-ethanol extractives and lignin are dissolved as much as possible to make the subsequent cooking liquor penetration more sufficient / time and energy consumption less, and to reduce the interference of lipid components; at the same time, the cellulose component must not be dissolved too much to affect the subsequent beating performance. The applicant determined that using 12 g / L NaOH hot water at 70°C for 1 h is a more ideal condition, which is also the condition used in actual production, through condition screening experiments.

[0034] To further improve the pretreatment effect, the applicant tried to add part of guanidine salt, such as guanidine hydrochloride and guanidine carbonate, to the pretreatment solution to improve the treatment effect, and tried the use amount of 3 g / L and 5 g / L. The effects of the pretreatment on the benzene-ethanol extractives, lignin, and holocellulose content of the treated material after 1 h are shown in Table 1. Figure 1

[0035] ​The results show that, compared with using NaOH only, the addition of guanidine salts can reduce the loss of holocellulose during pretreatment, especially 3-5 g / L guanidine hydrochloride within 1.5-2 h only reduces the holocellulose content by less than 1.5%; while using NaOH only, the lignin content is reduced by more than 6% after about 2 h, which will significantly affect the subsequent beating and papermaking processes.

[0036] The applicants further verified the changes in lignin and benzene alcohol extract content caused by the addition of 3, 5 g / L guanidine hydrochloride within 1.5-2 h, and the results are shown in Table 1.

[0037] Table 1 Effect of 3, 5 g / L guanidine hydrochloride on the lignin and benzene alcohol extract content of the product

[0038] 3 g / L guanidine hydrochloride Lignin content % Benzene-ethanol extract content % 1h 22.12±0.07 1.48±0.05 1.5h 21.34±0.11 1.32±0.04 2h 19.79±0.18 1.17±0.07 5 g / L guanidine hydrochloride 1h 21.95±0.12 1.42±0.03 1.5h 21.28±0.06 1.29±0.03 2h 20.02±0.07 1.09±0.02

[0039] The results show that within 1.5-2 h, the delignification effect and benzene alcohol extract content continue to decrease, especially the benzene alcohol extract content decreases by about 30%, significantly reducing the interference in subsequent applications.

[0040] In addition, the applicants also used Guangxi's Cibiyu as raw material to verify the above method, and the results showed that within 1.5-2 h, 3-5 g / L guanidine hydrochloride can also reduce the loss of holocellulose and improve the effect of delignification and reducing benzene alcohol extract content.

[0041] Table 2 Effect of 5 g / L guanidine hydrochloride on the holocellulose, lignin and benzene alcohol extract content of the product in Cibiyu.

[0042] Lignin content % Benzene-ethanol extract content % Hemicellulose content % 1h 20.78±0.12 1.39±0.01 71.27±1.04 1.5h 20.04±0.05 1.22±0.05 70.05±0.84 2h 18.85±0.11 1.03±0.03 69.54±0.79

[0043] Example 2 Silicon retention in continuous cooking

[0044] Basic continuous cooking method

[0045] The pretreated raw material is added to the digester, the steam temperature is 240-250℃, the pressure is 0.75-0.78 MPa, the alkali dosage is 17% (calculated by NaOH, w / w of absolute dry raw material), the sulfidity is 25%; the continuous cooking time is 240 min (CaO is added at the beginning of cooking). After cooking, the pulp is washed and screened, and pulp samples at 5 different points are selected for testing.

[0046] Oxide silicon retention is a feasible way to retain silicon in pulp, and its cost is lower than that of aluminum salt method when using CaO, but a large amount of CaO is needed to achieve good silicon retention effect (as shown in Table 3, the silicon retention capacity is significantly enhanced only when the dosage is more than 2.5% w / w of absolute dry raw material), at this time the scaling problem will be very significant. Figure 2

[0047] ​Based on the pretreatment method described in Example 1, the applicant found that adding 5 g / L of guanidine hydrochloride to the raw material during the pretreatment stage resulted in better performance in the oxide silica retention method.

[0048] Table 3. The effect of adding guanidine hydrochloride on the silica retention of CaO in raw materials (silica content in pulp %).

[0049] CaO dosage % 3 g / L guanidine hydrochloride 5 g / L guanidine hydrochloride 0 0.045±0.007 0.045±0.003 0.5 0.122±0.009 0.264±0.016 1 0.189±0.013 0.468±0.024 1.5 0.223±0.023 0.491±0.012 2 0.301±0.011 0.502±0.006 2.5 0.438±0.007 0.511±0.021

[0050] contrast Figure 2 According to the data, 3 g / L guanidine hydrochloride has no significant effect on the effect of CaO on silica retention, while 5 g / L guanidine hydrochloride can significantly reduce the amount of CaO used, requiring only about 1% CaO to achieve an effect similar to the original 2.5% CaO.

[0051] The applicant anticipates that the presence of a higher amount of guanidine hydrochloride alters the spatial structure of the fiber morphology, making it easier to retain the added, smoother silica-containing particles.

[0052] The complete process flow confirmed that the addition of 5 g / L guanidine hydrochloride and 1% CaO in the pretreatment stage had no significant impact on the fine pulp yield (47-29%), kappa number (15-17), etc., and the properties of the product were completely within the controllable range.

Claims

1. A continuous bamboo filament cooking method, characterized by, The bamboo filament continuous cooking method comprises a bamboo filament pretreatment step and a continuous cooking step. In the bamboo filament pretreatment step, the bamboo filament is treated with 60-80℃ water containing 10-15g / L NaOH and 1-5g / L guanidine salt for 1.5-2h; the guanidine salt is guanidine hydrochloride or guanidine carbonate; In the continuous cooking step, a Pandia horizontal tube continuous digester is used, the steam temperature is 240-250℃, the pressure is 0.75-0.78MPa, the alkali dosage is 17% w / w of the mass of the absolute dry raw material, and the sulfidity is 25%; 1-1.5% of the mass of the absolute dry raw material of CaO is added at the beginning of the continuous cooking in the continuous cooking step.

2. The method according to claim 1, wherein in the bamboo filament pretreatment step, the bamboo filament is treated with 70℃ water containing 12g / L NaOH and 3-5g / L guanidine hydrochloride for 1.5-2h.

3. The method according to claim 2, wherein in the bamboo filament pretreatment step, the bamboo filament is treated with 70℃ water containing 12g / L NaOH and 5g / L guanidine hydrochloride for 2h.

4. The method according to claim 1, wherein 1% of the mass of the absolute dry raw material of CaO is added at the beginning of the continuous cooking in the continuous cooking step.

5. The method according to claim 1, wherein the bamboo filament is green bamboo filament or Dendrocalamus latiflorus filament.

6. The method according to claim 1, wherein the bamboo filament is prepared by extrusion and cutting, the length of the bamboo filament is not more than 50mm, the width of the bamboo filament is not more than 10mm, and the thickness of the bamboo filament is not more than 2mm.

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