Pulping method of bleached chemical pulp

Abstract

The invention discloses a pulping method of bleached chemical pulp, which comprises the following steps: (A) adjusting the concentration of pulp after cooking reaction with water, and adding bio-enzyme and oxidizing compound for oxygen removal reaction to obtain pulp after oxygen delignification; (B) bleaching the paper pulp subjected to oxygen delignification with chlorine dioxide to obtain bleached paper pulp; (C) carrying out alkali extraction on the bleached paper pulp to obtain the bleached chemical pulp, the biological enzyme is one or more of xylanase, hemicelluloses hydrolase, laccase, fiber oxidase, lignin peroxidase and multifunctional peroxidase. According to the method, specific bio-enzyme is added in an oxygen removal section, a common oxygen removal section is converted into bio-enzyme and oxygen bleaching delignification, delignification of a rear section is selectively improved, the load of front-section cooking can be released, the use amount of caustic soda for oxygen removal and cooking is reduced, and the production cost is reduced. Meanwhile, the oxygen removal efficiency, the subsequent bleaching efficiency and the sustainable production level of the paper pulp can be improved.

Description

Technical Field

[0001] The present invention belongs to the field of papermaking, and particularly relates to a method for pulping bleached chemical pulp. Background Art

[0002] In the production process of bleached chemical pulp, pulp bleaching is an important process, which is a chemical process for removing residual lignin and other impurities that cause pulp color, and is a process for purifying and improving pulp. It can improve the whiteness of pulp and further increase the use value of pulp. It plays an important role in the production process of pulp and paper making, and is closely related to the quality of pulp and finished paper, material and energy consumption, and environmental impact.

[0003] Traditional pulp and paper industry generally uses chlorine-containing bleaching agents for bleaching. Although its bleaching effect is good, a large amount of toxic and deformed organic chlorides will be produced in the papermaking wastewater when using this method for bleaching, thus causing serious harm to the environment. Due to the requirements of environmental protection, traditional chlorine-containing bleaching has basically been replaced by elemental chlorine-free bleaching (ECF) and totally chlorine-free bleaching (TCF).

[0004] Hydrogen peroxide bleaching is also a common clean bleaching technology in the papermaking industry. Hydrogen peroxide bleaching does not remove the residual lignin in the pulp, but achieves the bleaching effect by destroying the lignin chromophore group to a certain extent and making it become a non-chromogenic group. Hydrogen peroxide bleaching has a good effect and is pollution-free to the environment. It does not produce chlorine derivatives in the pulp suspension, meeting the environmental protection requirements. However, hydrogen peroxide bleaching still has some problems. The oxidizing property of hydrogen peroxide is not very strong, and the effect is not very ideal when treating passivated lignin. Moreover, when the dosage of hydrogen peroxide is too high, it will also significantly damage the physical strength of the fibers.

[0005] Oxygen delignification is considered to be the lowest-cost and simplest delignification method except for the delignification by cooking in the sulfate process. Molecular oxygen is used as the delignifying agent, mainly because it has two unpaired electrons and has a strong reaction performance with organic substances. When molecular oxygen oxidizes lignin, through a series of electron transfers, it is itself reduced and generates peroxy ion free radicals, hydroperoxyl anions, hydroxyl free radicals and peroxy ions according to different pH values. These derived groups play an important role in lignin degradation, so oxygen delignification can combine pulping and bleaching.

[0006] However, existing oxygen delignification processes all require the addition of alkali, and a large amount of alkali needs to be added for cooking before oxygen delignification. The application of a large amount of alkali will increase waste emissions and impose an environmental burden. With the development of economy and technology and the improvement of people's environmental awareness, the call for green technology and green production is getting louder. As environmental protection becomes more and more stringent, the bleaching of chemical pulp is bound to develop in a more environmentally friendly direction. Therefore, it is very necessary to provide a new pulping method for bleaching chemical pulp, which can reduce the usage of caustic soda and chemical reagents while maintaining or improving the whiteness of the pulp, so as to reduce the pollution load of bleaching wastewater in the pulping process. Summary of the Invention

[0007] Based on this, the present invention provides a pulping method for bleaching chemical pulp. In this method, a specific biological enzyme is added in the oxygen delignification stage, converting the ordinary oxygen delignification stage into a process of using biological enzyme in combination with oxygen bleaching for delignification. By selectively enhancing the delignification in the subsequent stage, the load of the previous cooking can be released, the usage of caustic soda in oxygen delignification and cooking can be reduced, and at the same time, the oxygen delignification efficiency of the pulp, the subsequent bleaching efficiency and the sustainable production level can be improved.

[0008] The biological enzyme combined with oxygen bleaching for delignification in the present invention includes three methods: one is to first treat with biological enzyme and then perform oxygen delignification; the second is to first perform oxygen delignification and then treat with biological enzyme; the third is to perform biological enzyme treatment and oxygen delignification simultaneously. Therefore, the present invention includes the following technical solutions:

[0009] On the one hand, the present invention provides a pulping method for bleaching chemical pulp, which comprises the following steps:

[0010] (1) Adjust the concentration of the pulp after the cooking reaction with water, add biological enzyme for treatment to obtain the pulp after biological enzyme treatment;

[0011] (2) Add an oxidizing compound to the pulp after biological enzyme treatment for oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0012] (3) Perform chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp;

[0013] (4) Perform alkali extraction on the bleached pulp to obtain the bleached chemical pulp;

[0014] The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

[0015] On the other hand, the present invention provides a pulping method for bleaching chemical pulp, which comprises the following steps:

[0016] (a) Adjust the concentration of the pulp after the cooking reaction with water, add an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0017] (b) Add a bio-enzyme to the pulp after oxygen delignification for treatment to obtain the pulp after bio-enzyme treatment;

[0018] (c) Carry out chlorine dioxide bleaching on the pulp after bio-enzyme treatment to obtain the bleached pulp;

[0019] (d) Carry out alkaline extraction on the bleached pulp to obtain the bleached chemical pulp;

[0020] The bio-enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

[0021] In a third aspect, the present invention provides a method for making pulp of bleached chemical pulp, the method comprising the following steps:

[0022] (A) Adjust the concentration of the pulp after the cooking reaction with water, add a bio-enzyme and an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0023] (B) Carry out chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp;

[0024] (C) Carry out alkaline extraction on the bleached pulp to obtain the bleached chemical pulp;

[0025] The bio-enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

[0026] In some embodiments of the present invention, the bio-enzyme is preferably one or more of xylanase, laccase and multifunctional peroxidase.

[0027] In the prior art, the application of enzymes is generally carried out under acidic or neutral pH conditions, while effective oxygen delignification must be carried out under the condition of pH greater than 9. Therefore, there is no method in the existing pulp-making methods that will add bio-enzyme in the oxygen delignification stage. In order to improve the effects of oxygen delignification and bleaching, while maintaining or increasing the whiteness of the pulp, reduce the consumption of caustic soda and chemical reagents to reduce the pollution load of bleaching wastewater in the pulp-making process. The inventor of the present invention unexpectedly found in a large number of experimental studies that adding a specific bio-enzyme in the oxygen delignification section can transform the ordinary oxygen delignification section into bio-enzyme combined with oxygen bleaching for delignification. By selectively increasing the delignification in the subsequent section, the load of the previous cooking can be released, the consumption of caustic soda in oxygen delignification and cooking can be reduced, and at the same time, the oxygen delignification efficiency of the pulp, the subsequent bleaching efficiency and the sustainable production level can be improved.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] The pulping method for bleached chemical pulp provided by the present invention reduces the load of pre-cooking, reduces the amount of caustic soda used in the process, and reduces the negative impact of pulping wastewater on the environment.

[0030] The pulping method for bleached chemical pulp provided by the present invention improves the oxygen delignification efficiency. By adding a certain amount of bio-enzyme, the oxygen delignification and bleaching effects of conventional alkali addition can be achieved without adding alkali; and under the original process conditions, the oxygen delignification and bleaching effects can be significantly improved, the brightness and yield of the pulp and the physical properties of the pulp are greatly improved, and the physical strength of the paper will not be reduced.

[0031] The bio-enzyme used in the present invention is a biomass-based material, which is environmentally friendly. Through the combined action of these enzymes, the pulp mill can reduce the use of chemicals such as alkali and bleaching agents, thereby reducing costs and at the same time reducing the pollution load of bleaching wastewater. Description of the Drawings

[0032] Figure 1 It is the final brightness after oxygen delignification treatment with bio-enzyme in Example 1.

[0033] Figure 2 It is the comparison of brightness effects between using alkali and enzyme in Example 1.

[0034] Figure 3 It is the final brightness after oxygen delignification treatment with bio-enzyme combination in Example 2.

[0035] Figure 4 It is the influence of different enzyme combinations on the brightness after bleaching in Example 5.

[0036] Figure 5 It is the process flow chart of the on-machine experiment in Examples 8 and 9.

[0037] Figure 6 It is the change of the brightness (final brightness of the pulp) of the 4# pulp washer after bleaching when the polyenergy enzyme is added at different positions in Example 8.

[0038] Figure 7 It is the comparison of the amount of alkali used for pulping cooking and oxygen bleaching when the polyenergy enzyme is added at different positions in Example 8.

[0039] Figure 8 It is the change of the brightness (final brightness of the pulp) of the 4# pulp washer after bleaching under different enzyme addition amounts in Example 9.

[0040] Figure 9 It is the influence of the dosage of polyenergy enzyme and the amount of oxygen bleaching caustic soda on the oxygen bleaching efficiency in Example 9.

[0041] Figure 10 For the comparison of the unit consumption of cooking alkali in each stage of the experiment in Example 9.

[0042] Figure 11 For the effects of the energy-saving enzyme, oxygen bleaching alkali, and cooking alkali on the Kappa value of the cooked pulp in Example 9.

[0043] Figure 12 For the effects of the energy-saving enzyme, oxygen bleaching alkali, and cooking alkali on the Kappa value of the oxygen-bleached pulp in Example 9.

[0044] Figure 13 For the comparison of the residual alkali concentration of the black liquor before and after the experiment in Example 9 and during the energy-saving enzyme test stage. Detailed implementation manners

[0045] The technical solutions of the present invention will be further described below through specific examples. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0046] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not used to limit the present invention.

[0047] The terms "including" and "having" and any variations thereof in the present invention are intended to cover non-exclusive inclusion. For example, a process, method, device, product, or equipment that includes a series of steps is not limited to the listed steps or modules, but may optionally further include steps not listed, or may optionally further include other steps inherent to these processes, methods, products, or equipment.

[0048] As used in the present invention, "a plurality of" means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0049] In order to reduce the usage amount of chemical reagents such as caustic soda while maintaining or increasing the whiteness of pulp, so as to reduce the pollution load of bleaching wastewater on the environment during the pulping process; or to further increase the whiteness of pulp under the condition of the same alkali usage amount, in one embodiment of the present invention, a pulping method for bleaching chemical pulp is provided, and the method includes the following steps:

[0050] (1) Adjust the concentration of the pulp after the cooking reaction with water, add a bio-enzyme for treatment, and obtain the pulp after bio-enzyme treatment;

[0051] (2) Add an oxidizing compound to the pulp after biological enzyme treatment for an oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0052] (3) Perform chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp;

[0053] (4) Perform alkaline extraction on the bleached pulp to obtain the bleached chemical pulp;

[0054] The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, fiber oxidase, lignin peroxidase, and multifunctional peroxidase.

[0055] In another embodiment of the present invention, a method for preparing bleached chemical pulp is provided, and the method includes the following steps:

[0056] (a) Adjust the concentration of the pulp after cooking reaction with water, add an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0057] (b) Add a biological enzyme to the pulp after oxygen delignification for treatment to obtain the pulp after biological enzyme treatment;

[0058] (c) Perform chlorine dioxide bleaching on the pulp after biological enzyme treatment to obtain the bleached pulp;

[0059] (d) Perform alkaline extraction on the bleached pulp to obtain the bleached chemical pulp;

[0060] The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, fiber oxidase, lignin peroxidase, and multifunctional peroxidase.

[0061] In another embodiment of the present invention, a method for preparing bleached chemical pulp is provided, and the method includes the following steps:

[0062] (A) Adjust the concentration of the pulp after cooking reaction with water, add a biological enzyme and an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification;

[0063] (B) Perform chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp;

[0064] (C) Perform alkaline extraction on the bleached pulp to obtain the bleached chemical pulp;

[0065] The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, fiber oxidase, lignin peroxidase, and multifunctional peroxidase.

[0066] In some embodiments of the present invention, the bio-enzyme is preferably one or more of xylanase, laccase and versatile peroxidase.

[0067] In some embodiments of the present invention, the bio-enzyme is endo-xylanase.

[0068] In some embodiments of the present invention, the bio-enzyme is laccase.

[0069] In some embodiments of the present invention, the bio-enzyme is a combination of endo-xylanase, laccase and versatile peroxidase.

[0070] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase in a mass ratio of 6-8:1.5-2.5:1.

[0071] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase in a mass ratio of 6.5-7.5:1.5-2.5:1.

[0072] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase in a mass ratio of 6.8-7.2:1.8-2.2:1.

[0073] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase in a mass ratio of 7:2:1.

[0074] In some embodiments of the present invention, the upper temperature limit of the bio-enzyme is above 85°C, and the upper pH limit is above 9.

[0075] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.01 kg / t to 5 kg / t. For example, it can be: 0.01 kg / t, 0.02 kg / t, 0.03 kg / t, 0.04 kg / t, 0.05 kg / t, 0.06 kg / t, 0.07 kg / t, 0.08 kg / t, 0.09 kg / t, 0.1 kg / t, 0.12 kg / t, 0.15 kg / t, 0.18 kg / t, 0.2 kg / t, 0.22 kg / t, 0.25 kg / t, 0.28 kg / t, 0.3 kg / t, 0.32 kg / t, 0.35 kg / t, 0.38 kg / t, 0.4 kg / t, 0.42 kg / t, 0.45 kg / t, 0.48 kg / t, 0.5 kg / t, 0.6 kg / t, 0.7 kg / t, 0.8 kg / t, 0.9 kg / t, 1.0 kg / t, 2 kg / t, 3 kg / t, 4 kg / t, 5 kg / t.

[0076] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.04 kg / t to 5 kg / t.

[0077] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.5 kg / t.

[0078] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.4 kg / t.

[0079] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.35 kg / t.

[0080] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.25 kg / t.

[0081] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.22 kg / t.

[0082] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.08 kg / t to 0.22 kg / t.

[0083] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.1 kg / t to 0.2 kg / t.

[0084] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.08 kg / t to 0.12 kg / t.

[0085] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.18 kg / t to 0.32 kg / t.

[0086] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.18 kg / t to 0.22 kg / t.

[0087] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.25 kg / t to 0.32 kg / t.

[0088] In some embodiments of the present invention, the reaction in step (2) is carried out under the condition of adding alkali or without adding alkali.

[0089] In some embodiments of the present invention, the reaction in step (a) is carried out with or without adding an alkali.

[0090] In some embodiments of the present invention, the reaction in step (A) is carried out with or without adding an alkali.

[0091] In some embodiments of the present invention, the alkali in steps (2), (a) and (A) is at least one of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide.

[0092] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 30 kg / t. For example, it can be 0 kg / t, 1 kg / t, 2 kg / t, 3 kg / t, 4 kg / t, 5 kg / t, 6 kg / t, 7 kg / t, 8 kg / t, 9 kg / t, 10 kg / t, 11 kg / t, 12 kg / t, 13 kg / t, 14 kg / t, 15 kg / t, 16 kg / t, 17 kg / t, 18 kg / t, 19 kg / t, 20 kg / t, 21 kg / t, 22 kg / t, 23 kg / t, 24 kg / t, 25 kg / t, 26 kg / t, 27 kg / t, 28 kg / t, 29 kg / t, 30 kg / t.

[0093] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 20 kg / t.

[0094] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 14 kg / t.

[0095] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 12 kg / t.

[0096] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 10 kg / t.

[0097] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in steps (2), (a) and (A) is 0 kg / t to 8 kg / t.

[0098] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 7 kg / t.

[0099] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.5 kg / t.

[0100] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6 kg / t.

[0101] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.5 kg / t; the addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t.

[0102] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.5 kg / t; the addition amount of the bio-enzyme is 0.08 kg / t to 0.25 kg / t.

[0103] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.2 kg / t; the addition amount of the bio-enzyme is 0.18 kg / t to 0.22 kg / t.

[0104] In some embodiments of the present invention, based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 5.8 kg / t to 6.2 kg / t; the addition amount of the bio-enzyme is 0.18 kg / t to 0.22 kg / t.

[0105] In some embodiments of the present invention, the pH for the treatment with the bio-enzyme added is 7 - 12; the pH for the reaction of adding the bio-enzyme and the oxidizing compound is 7 - 12.

[0106] In some embodiments of the present invention, the pH for the treatment with the bio-enzyme added is 8 - 11; the pH for the reaction of adding the bio-enzyme and the oxidizing compound is 8 - 11.

[0107] In some embodiments of the present invention, the pH for the treatment with the bio-enzyme added is 9 - 11; the pH for the reaction of adding the bio-enzyme and the oxidizing compound is 9 - 11.

[0108] In some embodiments of the present invention, the oxidizing compound is selected from at least one of hydrogen peroxide, ozone, and oxygen; preferably oxygen, or a combination of hydrogen peroxide and oxygen.

[0109] In some embodiments of the present invention, the oxidizing compound is oxygen, and the addition amount of oxygen is such that the pressure in the reaction kettle is increased to 0.3 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa.

[0110] In some embodiments of the present invention, the oxidizing compound is a combination of hydrogen peroxide and oxygen; wherein, the addition amount of oxygen is such that the pressure in the reaction kettle is increased to 0.3 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa, more preferably 0.6 MPa - 0.8 MPa; based on the oven-dry weight of the added pulp, the dosage of the oxidizing compound is 5 kg / t to 50 kg / t, preferably 6 kg / t to 10 kg / t.

[0111] In some embodiments of the present invention, the pulp is bamboo pulp, bagasse pulp, softwood pulp, and / or hardwood pulp; preferably hardwood pulp; more preferably eucalyptus pulp.

[0112] In some embodiments of the present invention, the temperature for treating with the added bio-enzyme is 50 °C to 95 °C, and the treatment time is 1 min to 5 h.

[0113] In some embodiments of the present invention, the temperature for treating with the added bio-enzyme is 70 °C to 92 °C, and the treatment time is 5 min to 2 h.

[0114] In some embodiments of the present invention, the temperature of the oxygen delignification reaction is 50 °C to 95 °C, and the reaction time is 0.5 h to 5 h.

[0115] In some embodiments of the present invention, the temperature of the oxygen delignification reaction is 75 °C to 92 °C, and the reaction time is 1 h to 2 h.

[0116] In some embodiments of the present invention, the temperature of the oxygen delignification reaction is 78 °C to 82 °C.

[0117] In some embodiments of the present invention, the temperature of the oxygen delignification reaction is 88 °C to 92 °C.

[0118] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase, and multifunctional peroxidase with a mass ratio of 6 - 8:1.5 - 2.5:1, the temperature of the oxygen delignification reaction is 88 °C to 92 °C, the pulp is eucalyptus pulp or bamboo pulp, and the addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, more preferably 0.08 kg / t to 0.12 kg / t.

[0119] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:1. The temperature of the oxygen delignification reaction is 88°C to 92°C. The pulp is bamboo pulp. The addition amount of the bio-enzyme is 0.08 kg / t to 0.4 kg / t, preferably 0.1 kg / t to 0.35 kg / t, more preferably 0.2 kg / t to 0.32 kg / t, and even more preferably 0.28 kg / t to 0.32 kg / t.

[0120] In some embodiments of the present invention, the bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:1. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.4 kg / t, preferably 0.1 kg / t to 0.35 kg / t, more preferably 0.28 kg / t to 0.32 kg / t.

[0121] In some embodiments of the present invention, the bio-enzyme is composed of a combined enzyme and laccase. The combined enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:1. The mass ratio of the combined enzyme to laccase is 1:0.8-1.2. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.5 kg / t, preferably 0.18 kg / t to 0.42 kg / t, more preferably 0.18 kg / t to 0.22 kg / t.

[0122] In some embodiments of the present invention, the bio-enzyme is endo-xylanase. The temperature of the oxygen delignification reaction is 88°C to 92°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, more preferably 0.08 kg / t to 0.12 kg / t.

[0123] In some embodiments of the present invention, the bio-enzyme is laccase. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, more preferably 0.08 kg / t to 0.12 kg / t.

[0124] In some embodiments of the present invention, adjusting the concentration of the pulp after the cooking reaction with water means adjusting the concentration to 1% to 15%, preferably 1% to 10%, more preferably 1.5% to 8%.

[0125] In some embodiments of the present invention, the conditions for bleaching with chlorine dioxide include: the pulp concentration is 1% - 15%, preferably 1% - 10%, more preferably 2% - 8%, and even more preferably 2% - 4%.

[0126] In some embodiments of the present invention, the conditions for bleaching with chlorine dioxide further include: adjusting the pH to 3 - 4.

[0127] In some embodiments of the present invention, the conditions for bleaching with chlorine dioxide further include: based on the oven - dry weight of the added pulp, the dosage of chlorine dioxide is 5 kg / t - 30 kg / t, preferably 6 kg / t - 20 kg / t, and preferably 8.4 kg / t - 16.8 kg / t.

[0128] In some embodiments of the present invention, the conditions for bleaching with chlorine dioxide further include: the temperature is 30°C - 70°C, and the reaction time is 20 min - 60 min; wherein the temperature is preferably 40°C - 65°C, and the reaction time is preferably 25 min - 50 min, and more preferably 30 min - 45 min.

[0129] In some embodiments of the present invention, the step of alkali extraction includes: diluting the bleached pulp and then adding alkali and hydrogen peroxide for reaction.

[0130] In some embodiments of the present invention, in the step of alkali extraction, the pulp is diluted to a concentration of 1% - 15%, preferably 1% - 10%, more preferably 2% - 8%, and even more preferably 7% - 8%.

[0131] In some embodiments of the present invention, in the step of alkali extraction, the alkali used is at least one of sodium hydroxide and potassium hydroxide, and preferably sodium hydroxide.

[0132] In some embodiments of the present invention, in the step of alkali extraction, based on the oven - dry weight of the added pulp, the dosage of the alkali is 5 kg / t - 15 kg / t, preferably 8 kg / t - 12 kg / t.

[0133] In some embodiments of the present invention, in the step of alkali extraction, the mass concentration of hydrogen peroxide in the hydrogen peroxide solution is 10 - 30%; based on the oven - dry weight of the added pulp, the dosage of the hydrogen peroxide solution is 10 kg / t - 30 kg / t, preferably 10 kg / t - 20 kg / t, and preferably 13 kg / t - 17 kg / t.

[0134] In some embodiments of the present invention, in the step of alkali extraction, the reaction temperature is 45°C - 90°C, preferably 55°C - 75°C; the reaction time is 40 min - 3 h, preferably 60 min - 120 min, and more preferably 80 min - 100 min.

[0135] The "lignin-removing enzyme" in the present invention refers to all bioenzymes that can directly carry out chemical reactions on lignin to change the properties of lignin; and / or bioenzymes that can improve the separation of lignin components from fiber raw materials by carrying out chemical reactions on pulp components (such as hemicellulose, cellulose or other organic components) linked to lignin, thereby increasing the efficiency of lignin removal from pulp. Among them, the bioenzymes that can directly carry out chemical reactions with lignin include laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase; the bioenzymes that can react with pulp fiber components linked to lignin include cellulase, hemicellulase, and fiber oxidase; the ones that can react with other non-fiber components in pulp include lipase, cutinase, and perhydrolase.

[0136] The "Lignin Oxidase" in the present invention is a class of enzymes, including laccase, lignin peroxidase, manganese peroxidase, and versatile peroxidase, etc., which catalyze the oxidation reaction of lignin. Lignin is a complex natural polymer existing in the plant cell wall, which gives the plant cell wall rigidity and corrosion resistance. Lignin oxidase can oxidize the aromatic ring structure in lignin, leading to its degradation and decomposition, and has an important biodegradation effect.

[0137] The "Laccase" in the present invention is a class of oxidases, belonging to the polyphenol oxidase family. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), the international number of laccase is EC 1.10.3.2. Laccase has a wide substrate specificity and can oxidize polyphenolic compounds, such as phenols, polyphenolic dyes, aromatic amine compounds, lignin, etc., to produce corresponding oxidation products. Laccase is an enzyme mainly involved in lignin oxidation. The catalytic process of laccase can be briefly described as: it reduces molecular oxygen through a substrate (such as lignin), thereby oxidizing the substrate, increasing its reactivity, and even directly degrading it into small molecule products, thus improving and accelerating the removal of lignin.

[0138] "Lignin Peroxidase" in the present invention is an oxidase belonging to the peroxidase family and is specifically involved in the oxidation reaction of lignin. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), the international number of lignin peroxidase is EC 1.11.1.7. The catalytic process of lignin peroxidase involves using oxygen while oxidizing the substrate. It can break the aromatic ring structure of lignin through oxidation reactions, leading to the degradation and depolymerization of molecules. This process involves the peroxidase active site within the enzyme molecule, promoting the oxidation reaction of the substrate through electron transfer and oxygen supply. Lignin peroxidase has high specificity and strong oxidation ability, can catalyze the oxidative degradation of lignin, promote its decomposition into smaller molecules, and accelerate the removal of lignin during the pulping process.

[0139] "Versatile Peroxidase" in the present invention belongs to the peroxidase family and has multiple catalytic capabilities, capable of catalyzing the oxidation reactions of different types of substrates. Compared with other peroxidases (such as lignin peroxidase), the characteristic of versatile peroxidase is that it can catalyze multiple substrates with different structures and properties simultaneously, having a broader substrate specificity. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), the international number of versatile peroxidase is EC1.11.1.16. The catalytic mechanism of versatile peroxidase involves using oxygen while oxidizing the substrate, promoting the oxidation reaction of the substrate through electron transfer and oxygen supply at the peroxidase active center. Different from other peroxidases, versatile peroxidase has a broader range of catalytic substrates, including aromatic compounds, phenols, dyes, etc.

[0140] "Chloroperoxidase (CPO)" in the present invention is an oxidase belonging to the heme peroxidase family. It catalyzes the reaction of chloride and hydrogen peroxide in vivo, generating chloride ions and water, and participates in many redox reactions. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), the international number of chloroperoxidase is EC1.11.1.10. The catalytic process of chloroperoxidase involves using hydrogen peroxide while oxidizing the substrate, generating oxidation products and water. It can catalyze the redox reaction of chloride ions and hydrogen peroxide, thereby generating hypochlorite and water. The reaction of chloroperoxidase can also involve other substrates, including the oxidation of certain organic compounds.

[0141] "Manganese Peroxidase" in the present invention belongs to the peroxidase family and can catalyze hydrogen peroxide (H 2 O 2 ) and manganese ions (Mn 2+) The redox reaction between and the substrate relies on the combination of hydrogen peroxide and manganese ions to form an active center, and then promotes the oxidation reaction of the substrate through the electron transfer of oxidizing the substrate. Manganese peroxidase can catalyze the oxidation of various organic substances, such as certain polyphenols, aromatic compounds, etc., and can efficiently decompose organic substances such as lignin in the plant cell wall.

[0142] "Cellulase" in the present invention refers to all bioenzymes that can degrade cellulose. Cellulase refers to the general term for a group of enzymes that can degrade cellulose to produce glucan, including exoglucanase (also known as cellobiohydrolase) (CBH), endoglucanase (EG), and β-glucosidase (BG).

[0143] "Endocellulase" in the present invention refers to endo-1,4-β-D-glucanase (EC3.2.1.4), also called "endo-glucanase (EG)". This type of enzyme mainly acts on the amorphous region inside cellulose, randomly hydrolyzes β-1,4-glycosidic bonds, truncates long-chain cellulose molecules, and produces a large number of small cellulose molecules with non-reducing ends.

[0144] "Exocellulase" in the present invention refers to exo-1,4-β-D-glucanase (EC3.2.1.91). This type of enzyme acts on the end of the linear cellulose molecule, hydrolyzes β-1,4-D-14 glycosidic bonds, and sequentially cuts off a cellobiose molecule, so it is also called cellobiohydrolase (CBH).

[0145] "Hemi-cellulase" in the present invention is a class of enzymes that can degrade hemicellulose polysaccharide molecules. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), hemicellulases are divided into different classes and families, and each family has specific enzyme functions and structural characteristics. The international numbers of some hemicellulases are as follows:

[0146] GH5 family: The hemicellulase belongs to β-1,4-hemicellulase and decomposes hemicellulose by hydrolyzing β-1,4-glycosidic bonds on the cellulose chain. In the GH5 family, the international number is EC 3.2.1.91.

[0147] GH7 family: This family includes some enzymes that can hydrolyze cellulose and other hemicelluloses. They promote degradation by cleaving glycosidic bonds on the cellulose chain. In the GH7 family, the international numbers of some enzymes are EC 3.2.1.4.

[0148] GH10 family: The enzymes in this family mainly focus on hydrolyzing lignin-like hemicellulose. They break down hemicellulose molecules by cleaving the glycosidic bonds on the lignin chain. Among the GH10 family, the international numbers of some enzymes are EC3.2.1.74.

[0149] GH11 family: Similar to GH10, the enzymes in the GH11 family also specifically hydrolyze lignin-like hemicellulose. They break down hemicellulose by cleaving the glycosidic bonds on the cellulose chain. Among the GH11 family, the international numbers of some enzymes are EC3.2.1.78.

[0150] The "Xylanase" in the present invention is a class of enzymes that can hydrolyze xylan (also known as hemicellulose) and belongs to the hemicellulase family. Xylan is a polysaccharide mainly present in the plant cell wall, constituting the main component of hemicellulose, and forms a complex structure of the cell wall together with other hemicelluloses and other polysaccharides. Xylanase accelerates the hydrolysis reaction of xylan and decomposes it into smaller sugar molecules such as glucose. According to the classification of the International Union of Biochemistry and Molecular Biology (IUBMB), xylanases are divided into different classes and families, each family having specific enzyme functions and structural characteristics. The international numbers of some of these xylanases are as follows:

[0151] GH5 family: Xylanase belongs to β-1,4-xylanase and breaks down xylan by hydrolyzing the β-1,4-glycosidic bonds on the cellulose chain. In the GH5 family, the international number is EC 3.2.1.4.

[0152] GH7 family: This family includes some enzymes that can hydrolyze cellulose and other xylans. They promote degradation by cleaving the glycosidic bonds on the cellulose chain. Among the GH7 family, the international numbers of some enzymes are EC 3.2.1.4.

[0153] GH9 family: The enzymes in this family mainly focus on hydrolyzing xylan. They break down xylan molecules by cleaving the glycosidic bonds on the cellulose chain. Among the GH9 family, the international numbers of some enzymes are EC 3.2.1.4.

[0154] "Cellulose Oxidases" in the present invention belong to the oxygenase family. The unique function of these enzymes is that through catalytic oxidation reactions, they make polysaccharide molecules more easily degraded by other enzymes, thereby promoting biomass degradation. The cellulose oxidases of the present invention include polysaccharide monooxygenase (PMO), lytic polysaccharide monooxygenase (LPMO), and glycosyl hydrolase family 61 (GH61). Lytic polysaccharide monooxygenase is a relatively newly discovered enzyme family, containing multiple different types of LPMO, which can be divided into several subclasses, such as AA9, AA10, etc. Among them, LPMO refers to a family of small metalloenzymes with a molecular weight of 20 - 50KDa and containing copper(II), which can carry out oxygenation or dehydrogenation oxidation reactions with the fiber surface, thereby changing the chemical properties of the fiber surface. The catalytic process of lytic polysaccharide monooxygenase involves the oxidation reaction of the substrate (cellulose or hemicellulose), usually involving the reaction of hydrogen peroxide (H 2 O 2 ) and the substrate. Their function is to introduce oxygen atoms into the polysaccharide molecule, resulting in the cleavage and depolymerization of the molecule, thereby making polysaccharide molecules such as cellulose or hemicellulose more easily degraded by other enzymes.

[0155] The "hydrogen peroxide generating enzyme" described in the present invention refers to a bioenzyme that can catalyze an oxidase substrate using oxygen as a substrate (electron acceptor) and simultaneously produce hydrogen peroxide as a product, including but not limited to the following types of bioenzymes: glucose oxidase (glucose oxidase EC1.1.3.4), monoamine oxidase (abbreviation MAO, EC1.4.3.4), xanthine oxidase (I.U.B.: 1.1.3.22), urate oxidase (urate oxidase, EC 1.7.3.3), oxalate oxidase (oxalate oxidase, EC 1.2.3.4), galactose oxidase (galactose oxidase, I.U.B.: 1.1.3.9), cellulose oxidase (polysaccharide monooxygenase,), polyphenol oxidase (polyphenol oxidase, I.U.B.: 1.14.18.1), alcohol oxidase (alcohol oxidase, EC 1.1.3.13) and aldehyde oxidase (aldehyde oxidase, EC 1.1.3.13).

[0156] In the present invention, the "oxidizing compound" refers to a compound that can provide oxidation efficacy, including oxygen, air, oxygen-releasing compounds, ozone, hydrogen peroxide, sodium peroxide, calcium peroxide, potassium peroxide, sodium perborate, etc.

[0157] In the present invention, perhydrolases belong to the esterase family. What is special about them is that they can catalyze the hydrolysis of ester substrates in the presence of hydrogen peroxide. The international standard number of perhydrolases is EC 3.11.1.-. Perhydrolases generally belong to the esterase family, which includes fatty acid esterases, phosphatidylcholine esterases, etc. These enzymes meet their high reactivity to hydrogen peroxide by catalyzing the hydrolysis reaction of ester bonds.

[0158] In the present invention, the enzyme activity test of laccase is carried out by the following two methods respectively according to its acid-base adaptation range.

[0159] 2,2'-Dihydroxy-3,3',5,5'-tetramethyldiphenyl diimide (ABTS) method: This method is based on the oxidation reaction of the substrate ABTS catalyzed by laccase. In acidic conditions, laccase oxidizes ABTS to produce a blue-green product, and its absorption peak is located at 420 nm. The activity of laccase can be evaluated by measuring the change in absorbance.

[0160] 3,3'-Dimethoxybenzidine (DMP) method: This method uses DMP as the substrate. Under alkaline conditions (usually between pH 8.0 and 10.0), the change in absorbance is recorded at about 450 nm. As the reaction proceeds, DMP is oxidized under the catalysis of laccase to produce a colored product, increasing the absorbance.

[0161] In the present invention, the method for testing the enzyme activity of xylanase is the 3,5-dinitrosalicylic acid (DNS) method. This method uses xylanase to hydrolyze the xylan substrate to generate smaller sugar molecules, such as xylose (reducing sugar). Then, 3,5-dinitrosalicylic acid reacts with xylose under alkaline conditions, and the generated product can produce a color change. The absorbance of this product is proportional to the amount of reducing sugar produced. Therefore, the enzyme activity of xylanase can be evaluated by measuring the change in absorbance. The absorbance of the reaction system is measured using a spectrophotometer at an appropriate wavelength (usually 540 nm). The change in absorbance is proportional to the amount of reducing sugar produced, and the enzyme activity of xylanase can be calculated through a standard curve or a calculation formula.

[0162] In the present invention, the test method for the enzyme activity of manganese peroxidase (MnP) is the 3,3',5,5'-tetramethylbenzidine (TMB) method. In the presence of hydrogen peroxide, manganese peroxidase catalyzes the oxidation of the substrate 3,3',5,5'-tetramethylbenzidine to a highly oxidized product, thereby producing a blue product, and its absorbance increases significantly at a corresponding wavelength (652 nm). This change in absorbance can be measured to evaluate the enzyme activity of manganese peroxidase.

[0163] In the present invention, the test method for the enzyme activity of lignin peroxidase (LiP) is the 2,6-dimethoxyphenol (DMP) method. Lignin peroxidase catalyzes the oxidation reaction of the substrate 2,6-dimethoxyphenol (DMP) to form an oxidation product. This oxidation product will produce a significant change in absorbance under alkaline conditions, and the enzyme activity of lignin peroxidase can be evaluated by measuring the change in absorbance (468 nm).

[0164] In the present invention, the test method for the enzyme activity of versatile peroxidase (VP) is the pyrogallol and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method (also known as the diphenol method). The pyrogallol and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) method combines the oxidation reactions of polyphenolic substrates (such as pyridine and diphenol) and the oxidation reaction of the ABTS substrate, and measures the change in absorbance of the reaction system at wavelengths of 420 nm and 734 nm to obtain the catalytic activity of versatile peroxidase on different substrates.

[0165] The enzymes used in the following examples are described as follows:

[0166] The polyenergy enzyme XP-6718 is an endo-xylanase, and its upper temperature limit is 100 °C and the upper pH limit is 9.

[0167] The polyenergy enzyme XP-6719 is composed of xylanase (R-217), laccase (R-615) and versatile peroxidase in a mass ratio of 7:2:1.

[0168] The polyenergy enzyme R-217 is a heat-resistant and alkali-resistant endo-xylanase, and its upper temperature limit is 95 °C and the upper pH limit is 12.

[0169] The polyenergy enzyme R-566 is a heat-resistant and alkali-resistant laccase, and its upper temperature limit is 90 °C and the upper pH limit is 11 (the enzyme activity test method with DMP as the substrate).

[0170] The energy - concentrating enzyme R - 615 is a laccase resistant to high temperature and alkali, with a temperature upper limit of 85 °C and a pH upper limit of 10 (the method for testing enzyme activity with DMP as the substrate).

[0171] The "whiteness" mentioned in the present invention refers to the reflectance of the pulp sheet at a wavelength of 457 nm, expressed as a percentage equivalent to the reflectance of magnesium oxide. The measurement method is as follows: It is measured according to the national standard GB / T 7974 - 2002 "Paper, Board and Pulp - Determination of Brightness (Whiteness) - Diffuse - Vertical Method".

[0172] The "Kappa number" mentioned in the present invention represents the lignin content in the pulp and is one of the indicators reflecting the degree of delignification of the pulp. The measurement method is as follows: It is measured according to the national standard GB / T 1546 - 2004 "Determination of Kappa Number of Pulp".

[0173] The residual alkali concentration of black liquor mentioned in the present invention refers to the content of active alkali remaining in the cooking liquor after cooking. The measurement method is as follows: Use a pipette to suck 10 ml of black liquor into a 100 - ml volumetric flask, add 10 ml of 10% barium chloride solution to precipitate lignin, and at the same time precipitate sodium carbonate and sodium sulfite. Dilute to the scale with distilled water, shake well and let stand. Use a pipette to suck 10 ml of the upper clear liquid, use methyl orange as an indicator, and titrate with 0.1 mol / L HCl standard titration solution until the light yellow turns orange - red. The residual alkali of black liquor ρ (g / L, calculated as Na 2 O) is calculated according to the following formula: Where V is the volume of the hydrochloric acid standard titration solution consumed during titration, in mL

[0174] c is the actual concentration of the hydrochloric acid standard titration solution, in mol / L

[0175] M is the molar mass of 1 / 2Na 2 O, 31 g / mol

[0176] In the present invention, the addition amounts of all chemical reagents are calculated based on the oven - dry weight of the pulp. For example, the addition amount of alkali is 12 Kg / t, which means 12 Kg of alkali is added to each ton of oven - dry weight pulp.

[0177] The alkali used in the following examples is sodium hydroxide.

[0178] The following are specific examples.

[0179] Example 1

[0180] A pulping method for bleached chemical pulp provided in this example includes the following steps:

[0181] (1) Oxygen delignification enzymatic reaction stage: For each group, 10.5 g of absolute dry pulp (pulp from the 5# washer of eucalyptus pulp from the pulp mill, pH 10.30, concentration 14.56%, whiteness 34.28%) was taken and diluted to 3% with 90°C hot water, then placed in a high-pressure reactor. A blank group (without adding enzyme or alkali), an enzyme-added group (without adding alkali, directly oxygen delignified after adding enzyme), and an alkali-added group (dosage added at 12 Kg / t) were set. In the enzyme-added group, enzyme (XP-6719, dosages were 50 ppm and 100 ppm respectively) was added. Each group added oxygen to the reactor until the pressure in the reactor reached 1.0 MPa, the set temperature was 90°C, the stirring speed was 800 rpm. After reacting for 1.5 h, it was taken out and the pulp was rinsed with clear water in a 150-mesh sieve for 2 min until the water was clear.

[0182] (2) Chlorine dioxide bleaching stage (D0): 3.2 g of absolute dry pulp after oxygen delignification was taken, diluted to a concentration of 3% with water, and the pH was adjusted to 3 - 4 with 2 mol / L sulfuric acid. It was placed in a polyethylene sealed bag, and the prepared chlorine dioxide aqueous solution (chlorine dioxide concentration 2%, calculated as available chlorine, dosage added at 8.4 kg / t) was added. It was placed in a 65°C water bath and reacted for 30 min, during which it was kneaded once every 15 min. After the reaction ended, it was taken out and the pulp was rinsed with clear water in a 150-mesh sieve for 2 min until the water was clear, squeezed dry, and all transferred to a new sealed bag for the alkali extraction stage experiment.

[0183] (3) Alkali extraction stage (Ep): All the pulp after the D0 stage reaction (still calculated as 3.2 g of absolute dry) was taken, diluted to a concentration of 8% with water, alkali (dosage added at 10 kg / t) and hydrogen peroxide (concentration 10%, dosage added at 15 kg / t) were added, and they were mixed evenly in a sealed bag. It was placed in a 55°C water bath and reacted for 50 min, then the temperature was raised to 75°C and reacted for another 40 min. During the reaction process, it was kneaded once every 20 min. After the reaction ended, it was taken out and the pulp was rinsed with clear water in a 150-mesh sieve for 1 min until the water was clear. Approximately 3 g of absolute dry pulp was taken, sheeted with a Buchner funnel, dried in an oven at 105°C for 60 min, and then the whiteness was measured.

[0184] The results are as Figure 1 and Figure 2 shown: Without adding alkali in the oxygen delignification stage, after chlorine dioxide bleaching (D0 stage) and alkali extraction (Ep stage), the paper whiteness of the enzyme-added group (dosage 50 - 100 ppm) was improved compared to the blank group; moreover, the effect with an enzyme dosage of 100 ppm was better, and its whiteness was comparable to that of the alkali addition process (adding 12 kg / t of alkali in the oxygen delignification stage).

[0185] Example 2

[0186] A pulping method for bleaching chemical pulp provided in this example includes the following steps:

[0187] (1) Oxygen delignification (O) stage: Take 110 g of oven-dry bamboo pulp sample and put it into a high-pressure cooking pot. Add water to make the pulp concentration 8%. After stirring evenly, add alkali (dosage added at 20 kg / t), and then add H 2 O 2 (dosage added at 8 kg / t), and stir evenly. Start heating to 90 °C, cover the cooking pot, purge the air in the reaction vessel with oxygen, and then adjust the pressure of the reaction vessel to 0.8 MPa. Keep it at 90 °C for 60 min. After the reaction is completed, take out the sample and rinse the pulp with clear water for 2 min until the water is clear. Take about 2 g of oven-dry pulp in a Buchner funnel. Filter and sheet the pulp, and air-dry it for 24 h to measure the whiteness.

[0188] (2) Enzyme reaction (X) stage: Take the pulp after oxygen delignification, with 125 g of pulp per group (8% concentration, 10 g of oven-dry), put it into a sealed bag, and measure the pH (10.0). Add the enzyme sample XP-6719 to each group according to the designed dosage, and knead evenly. Place it in a 75 °C super constant temperature water bath and react for 30 min. Without washing the pulp, add water to 1500 g, defiberize, and then concentrate to 3%.

[0189] (3) Chlorine dioxide bleaching (D0) stage: Take the pulp after the enzyme reaction in step (2), sample 9.0 g of oven-dry pulp per group and dilute it to 3%. Adjust the pH to 3 - 4 with 2 mol / L sulfuric acid solution. Put it into a sealed bag, add an aqueous chlorine dioxide solution (concentration 2%, calculated as 32% of the oven-dry pulp dosage, and the effective chlorine dosage is 16.8 kg / t of pulp), and place it in a 65 °C super constant temperature water bath and react for 40 min. Take it out and rinse with clear water for 1 min until the water is clear, squeeze dry, and use it for subsequent Ep extraction.

[0190] (4) Alkaline extraction (EP) stage: Take the pulp after chlorine dioxide bleaching and dilute it with water to 8%. Add 10 kg / t of alkali and 15 kg / t of hydrogen peroxide, mix evenly, and put it into a sealed bag. Place it in a 75 °C super constant temperature water bath and react for 90 min, kneading once every 20 min during this period. Take it out and rinse with clear water for 1 min until the water is clear. Take about 2.0 g of oven-dry pulp, sheet it with a Buchner funnel, and air-dry it for 24 h to measure the whiteness.

[0191] The results are as Figure 3 shown: After the oxygen delignification stage, before chlorine dioxide bleaching, treat with enzyme for 30 min, bleach at 3% pulp consistency in the chlorine dioxide bleaching stage, and then after alkaline extraction, compared with the group without enzyme treatment, the final whiteness of the group treated with enzyme (50 - 200 ppm) can be increased by 0.5 - 1.2 units.

[0192] Example 3

[0193] This example provides a pulping method for bleaching chemical pulp.

[0194] I. Experimental Raw Materials: Pulp: Pulp from the 5# washer of a certain eucalyptus pulp mill (concentration 14.56%, pH = 10.30, whiteness 34.28%); Enzyme: R-217.

[0195] II. Experimental Methods:

[0196] (1) Oxygen delignification stage:

[0197] Take 10.5 g of oven-dried pulp, dilute it to 3% with 90°C hot water, put it into a high-pressure reactor, simulate the addition of alkali in the general process group (dosage added at 12 kg / t, denoted as alkali addition blank), simulate the oxygen delignification stage without alkali addition (denoted as no-alkali addition blank), and the group with enzyme addition after alkali stopping (enzyme dosages added at 50 ppm and 100 ppm respectively). Add oxygen to the reactor until the pressure inside the reactor reaches 1.0 MPa, set the temperature at 90°C, the stirring speed at 800 rpm, and after reacting for 1.5 h (including the heating process), take it out and rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear. Take about 3 g of oven-dried pulp sample, make a sheet with a Buchner funnel and dry it in an oven at 105°C for 1 h to measure the whiteness.

[0198] (2) Chlorine dioxide bleaching stage (D 0 )

[0199] Take 3.2 g of oven-dried pulp after oxygen delignification, dilute it to a concentration of 3% with water, adjust the pH to 3 - 4 with 2 mol / L sulfuric acid, put it into a polyethylene sealed bag, add the prepared chlorine dioxide aqueous solution (chlorine dioxide concentration 2%, calculated as available chlorine, and its dosage added at 8.4 kg / t), place it in a 65°C water bath and react for 30 min, knead it once every 15 min during this period. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, squeeze it dry, and transfer all of it to a new sealed bag for the alkali extraction stage experiment.

[0200] (3) Alkali extraction stage (Ep):

[0201] Take all the pulp after the reaction in the D 0 stage (still calculated as 3.2 g of oven-dried pulp), dilute it to a concentration of 8%, add alkali (dosage added at 10 kg / t), hydrogen peroxide (concentration 10%, dosage added at 15 kg / t), mix them evenly in a sealed bag, place it in a 55°C water bath and react for 50 min, then raise the temperature to 75°C and react for another 40 min. Knead it once every 20 min during the reaction process. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 1 min until the water is clear. Take about 3 g of oven-dried pulp, make a sheet with a Buchner funnel, and dry it in an oven at 105°C for 60 min and then measure the whiteness.

[0202] III. Experimental Results

[0203] As shown in Table 1: After enzyme treatment in the oxygen delignification stage, after chlorine dioxide bleaching (D0 After the oxygen delignification stage and the alkaline extraction stage (Ep stage), the final whiteness of the obtained pulp first increases and then decreases with the increase of enzyme dosage. The best effect is achieved when the enzyme dosage is 100 ppm, and the whiteness is equivalent to that of the alkali addition process (12 kg / t of alkali addition in the oxygen delignification stage).

[0204] Table 1

[0205]

[0206] Example 4

[0207] This example provides a pulping method for bleaching chemical pulp to test the effect of different enzyme dosages on bleaching.

[0208] I. Experimental raw materials:

[0209] Pulp: Eucalyptus pulp from the 5# pulp washer of a certain pulp mill (concentration 14.01%, pH = 9.64, whiteness 32.64%); Enzyme: XP-6719.

[0210] II. Experimental methods:

[0211] 1. Oxygen delignification stage:

[0212] Take 5.25 g of oven-dried pulp, dilute it to 1.5% with 80°C hot water, put it into a high-pressure reactor, simulate the reaction of stopping alkali and adding enzyme in the oxygen delignification stage (the dosages are added at 100, 150, 200, and 300 ppm respectively). For each dosage, two parallel reactions are carried out in different reactors. Add oxygen to the reactor until the pressure in the reactor reaches 1.0 MPa, set the temperature at 80°C, and the stirring speed at 800 rpm. After reacting for 1.5 h (including the heating process), take it out, mix the two parallel samples evenly, rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear. Take about 3 g of oven-dried pulp sample, make a sheet with a Buchner funnel, and dry it in an oven at 105°C for 1 h to measure the whiteness.

[0213] 2. Chlorine dioxide bleaching stage (D 0 )

[0214] Take 5 g of oven-dried pulp after oxygen delignification, dilute it to a concentration of 3%, adjust the pH to 3 - 4 with 2 mol / L sulfuric acid, put it into a polyethylene sealed bag, add the prepared chlorine dioxide aqueous solution (chlorine dioxide concentration 2%, calculated as available chlorine, and its dosage is added at 8.4 kg / t), place it in a 65°C water bath and react for 30 min, knead it once every 15 min during the reaction. After the reaction, take it out, rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, squeeze it dry, and transfer all of it to a new sealed bag for the alkaline extraction stage experiment.

[0215] 3. Alkaline extraction stage (Ep):

[0216] Take the D0 After the first-stage reaction, all the slurries (still calculated based on 5 g of absolute dry matter) were diluted to a concentration of 8%, and alkali (added at a dosage of 10 kg / t) and hydrogen peroxide (with a concentration of 10% and added at a dosage of 15 kg / t) were added. They were mixed evenly in a sealed bag and placed in a 75°C water bath for reaction for 90 min. During the reaction process, it was kneaded once every 20 min. After the reaction ended, it was taken out and the slurry was rinsed with clear water in a 150-mesh sieve for 1 min until the water was clear. Approximately 3 g of absolute dry pulp was taken, sheeted with a Buchner funnel, and dried in an oven at 105°C for 60 min, and then the whiteness was measured.

[0217] III. Experimental Results

[0218] The results are shown in Table 2: Without adding alkali in the oxygen delignification stage, at a temperature of 80°C, using XP-6719, the brightness of the pulp after bleaching increased with the increase in the enzyme dosage. When the enzyme dosage was 300 ppm, it increased by about 2.1% ISO compared to without adding enzyme.

[0219] Table 2

[0220]

[0221]

[0222] Example 5

[0223] This example provides a pulping method for bleaching chemical pulp to test the effects of different oxygen pressures and different enzyme dosages on bleaching.

[0224] I. Experimental Raw Materials:

[0225] Slurry: Pulp from the 5# washer of eucalyptus pulp in a certain pulp mill (concentration 14.01%, pH = 9.64, brightness 32.64%); Enzymes: R-566, XP-6719.

[0226] II. Experimental Methods:

[0227] (1) Oxygen delignification stage:

[0228] Take 5.25 g of absolute dry pulp, dilute it to 1.5% with 80°C hot water, put it into a high-pressure reactor, simulate the oxygen delignification stage with alkali stopped and enzyme added (dosages added were 100 and 200 ppm respectively) for reaction. For each dosage, two parallel reactions were carried out in two different reactors. Adjust the oxygen pressure in the reactor (0.5, 0.75, 1.0 Mpa), set the temperature at 80°C, the stirring speed at 800 rpm, take it out after reacting for 1.5 h (including the heating process), mix the two parallel samples evenly, rinse the slurry with clear water in a 150-mesh sieve for 2 min until the water is clear, take approximately 3 g of absolute dry pulp sample, sheet it with a Buchner funnel and then dry it in an oven at 105°C for 1 h, and measure the whiteness.

[0229] (2) Chlorine dioxide bleaching stage (D0 ):

[0230] Take 5 g of oven-dried pulp after oxygen delignification, dilute it with water to a concentration of 3%, adjust the pH to 3 - 4 with 2 mol / L sulfuric acid, put it into a polyethylene sealed bag, add the prepared aqueous chlorine dioxide solution (chlorine dioxide concentration 2%, calculated as available chlorine, and its dosage is added at 8.4 kg / t), place it in a water bath at 65°C and react for 30 min, knead it once every 15 min during the reaction. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, squeeze it dry, and transfer all of it to a new sealed bag for the alkali extraction stage experiment.

[0231] (3) Alkali extraction stage (Ep):

[0232] Take all the pulp after the D 0 stage reaction (still calculated as 5 g of oven-dried pulp), dilute it with water to a concentration of 8%, add alkali (dosage added at 10 kg / t), hydrogen peroxide (concentration 10%, dosage added at 15 kg / t), mix evenly in a sealed bag, place it in a water bath at 75°C and react for 90 min, knead it once every 20 min during the reaction. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 1 min until the water is clear, take about 3 g of oven-dried pulp, make a sheet with a Buchner funnel, dry it in an oven at 105°C for 60 min, and then measure the whiteness.

[0233] III. Experimental results

[0234] The experimental results are shown in Table 3 and Figure 4 as follows:

[0235] 1. In the blank group of the oxygen delignification stage, the whiteness increases significantly with the increase of oxygen pressure. After adding R-566, the change rule disappears, and the whiteness change is not obvious. It mainly increases first and then decreases with the increase of enzyme dosage.

[0236] 2. After bleaching and alkali extraction, the whiteness changes irregularly with the change of oxygen pressure, and both increase first and then decrease with the change of dosage. R-566 has a certain enhancing effect on bleaching under different pressures and dosages.

[0237] 3. The combination of R-566 and XP-6719 has no obvious effect in the oxygen delignification stage, and the whiteness decreases slightly with the increase of dosage. After chlorine dioxide bleaching and alkali extraction, the whiteness is improved. When the dosage is 100 ppm for both, the whiteness is increased by about 1.3 units.

[0238] Table 3

[0239]

[0240]

[0241] Example 6

[0242] This embodiment provides a pulping method for bleached chemical pulp to test the effect of R-566 on bleaching at high temperatures.

[0243] I. Experimental raw materials:

[0244] Pulp: Eucalyptus pulp from a certain pulp mill, pulp from the 5# washer (concentration 14.01%, pH = 9.64, whiteness 32.64%); Enzyme: R-566.

[0245] II. Experimental methods:

[0246] (1) Oxygen delignification stage:

[0247] Take 5.25 g of oven-dry pulp, dilute it to 1.5% with 90°C hot water, put it into a high-pressure reactor, simulate the addition of enzyme instead of alkali in the oxygen delignification stage (dosages are 100 and 200 ppm respectively) for reaction. For each dosage, two parallel reactions are carried out in two different reactors. Add oxygen to the reactor until the pressure inside the reactor reaches 1.0 MPa, set the temperature at 90°C, the stirring speed at 800 rpm. After 1.5 h of reaction (including the heating process), take it out. Mix the two parallel samples evenly, rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear. Take about 3 g of oven-dry pulp sample, make a sheet with a Buchner funnel and dry it in an oven at 105°C for 1 h, then measure the whiteness.

[0248] (2) Chlorine dioxide bleaching stage (D 0 ):

[0249] Take 5 g of oven-dry pulp after oxygen delignification, dilute it to a concentration of 3% with water, adjust the pH to 3 - 4 with 2 mol / L sulfuric acid, put it into a polyethylene sealed bag, add the prepared chlorine dioxide aqueous solution (chlorine dioxide concentration 2%, calculated as available chlorine, and its dosage is added at 8.4 kg / t), place it in a 65°C water bath for reaction for 30 min, knead it once every 15 min during the period. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, squeeze it dry, and transfer all of it to a new sealed bag for the alkali extraction stage experiment.

[0250] (3) Alkali extraction stage (Ep):

[0251] Take all the pulp after the reaction in the D 0 stage (still calculated as 5 g of oven-dry), dilute it to a concentration of 8%, add alkali (dosage added at 10 kg / t), hydrogen peroxide (concentration 10%, dosage added at 15 kg / t), mix them evenly in a sealed bag, place it in a 75°C water bath for reaction for 90 min, knead it once every 20 min during the reaction process. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 1 min until the water is clear. Take about 3 g of oven-dry pulp, make a sheet with a Buchner funnel, and dry it in an oven at 105°C for 60 min, then measure the whiteness.

[0252] III. Experimental results

[0253] The experimental results are shown in Table 4: When reacting at 90 °C, the improvement in whiteness after the oxygen delignification stage and bleaching compared to the blank group is relatively small, and the bleaching aid effect is weaker than that at 80 °C.

[0254] Table 4

[0255]

[0256] Example 7

[0257] This example provides a pulping method for bleaching chemical pulp to test the effect of XP-6719 on bamboo pulp bleaching.

[0258] I. Experimental raw materials:

[0259] Pulp: Unbleached bamboo pulp board from a certain pulp mill (dryness 90%, pH = 7.57, whiteness 20%, kappa number 11.64); Enzyme: XP-6719; H 2 O 2 : 10%.

[0260] II. Experimental method:

[0261] (1) Oxygen delignification stage:

[0262] Take 5.25 g of oven-dry pulp, dilute it to 1.5% with 90 °C hot water, put it into a high-pressure reactor, simulate adding enzyme (dosages are 50 ppm and 300 ppm respectively) in the oxygen delignification stage for reaction. Four reactors for each dosage are taken as a group, add H 2 O 2 (dosage is added at 8 kg / t), add alkali (dosage is added at 14 kg / t), add oxygen into the reactor to a pressure of 0.75 MPa, set the temperature at 90 °C, the stirring speed at 800 rpm, take it out after reacting for 1.5 h (including the heating process), mix the four parallel samples evenly, rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, take about 3 g of oven-dry pulp sample, make a sheet with a Buchner funnel and air-dry it for 24 h, and measure the whiteness.

[0263] (2) Chlorine dioxide bleaching stage (D 0 ):

[0264] Take 5 g of oven-dry pulp after oxygen delignification, dilute it to a concentration of 3% with water, adjust the pH to 3 - 4 with 2 mol / L sulfuric acid, put it into a polyethylene sealed bag, add the prepared chlorine dioxide aqueous solution (chlorine dioxide concentration is 2% in terms of available chlorine, dosage is added at 8.4 kg / t), place it in a 65 °C water bath for reaction for 40 min, knead it once every 15 min during the period, take it out after the reaction ends, rinse the pulp in a 150-mesh sieve with clear water for 2 min until the water is clear, squeeze it dry, and transfer all to a new sealed bag for the alkali extraction stage experiment.

[0265] (3) Alkaline Extraction Stage (Ep):

[0266] Take the pulp from Stage D 0 All the pulp after the reaction in Stage D (still calculated as 5 g of absolute dry weight), dilute it with water to a concentration of 8%, add alkali (dosage added at 12 kg / t), hydrogen peroxide (concentration 10%, dosage added at 15 kg / t), mix evenly in a sealed bag, place it in a water bath at 75 °C and react for 90 min. During the reaction, knead it once every 20 min. After the reaction, take it out and rinse the pulp in a 150-mesh sieve with clear water for 1 min until the water is clear. Take about 3 g of absolute dry pulp, make a sheet with a Buchner funnel, and then air-dry it for 24 h and measure the whiteness.

[0267] III. Experimental Results

[0268] The experimental results are shown in Table 5: When the enzyme dosage is 300 ppm, the whiteness after bleaching increases by 1 unit.

[0269] Table 5

[0270]

[0271]

[0272] Example 8: The On-machine Experimental Effect of XP-6718 in Liuzhou Liangmianzhen Paper Industry

[0273] Experimental time: December 5, 2021 - January 20, 2022.

[0274] Raw materials: 100% eucalyptus, enzyme: XP-6718, addition amount is 200 g / t of pulp.

[0275] I. The Liangmianzhen On-machine Experimental Process (as Figure 5 shown)

[0276] 1. Cooking: Eucalyptus chips are cooked at a high temperature of 170 °C under alkaline conditions for 90 min, and then successively pass through the 1-4# pulp washers before bleaching (enzyme addition point 1, temperature 70 °C, enzyme addition amount 0.2 kg / t of pulp, treatment for 40 min), knot remover and sieve, and then pass through the 5# pulp washer before bleaching and are sent to the oxygen bleaching tower.

[0277] 2. Oxygen delignification: The pulp (concentration 8%) passing through the 5# pulp washer before bleaching is added with alkali and oxygen (35 - 37.5 kg / t to make the pressure in the reaction tower 1.0 MPa) at a temperature of 90 °C. After reacting for 90 min, it is discharged under pressure and passes through the 6-7# pulp washers before bleaching (enzyme addition point 2, temperature 70 °C, enzyme addition amount 0.2 kg / t of pulp, treatment for 40 min), and then the pH is adjusted to acidic to prepare for chlorine bleaching.

[0278] 3. Chlorine bleaching: Adjust the pH of the pulp (concentration 2-3%) passing through the 6-7# pulp washer to 2-3, add chlorine (15 kg / t) and chlorine dioxide (2.4 kg / t), react at 40 °C for 30-45 min, and pass through the 1# post-bleaching pulp washer (enzyme addition point 3, temperature 70 °C, enzyme addition amount 0.2 kg / t pulp, treatment for 40 min), then prepare to enter the alkali extraction section.

[0279] 4. Alkali extraction: Add hydrogen peroxide (10 kg / t) and alkali 200 ml / h to the pulp (concentration 7-8%) from the 1# post-bleaching pulp washer. Adjust the pH to 8-9, react at 55 °C for 1.5 h, and after passing through the 2# post-bleaching pulp washer, enter the next section.

[0280] 5. Take the pulp from the outlet of the 4# post-bleaching pulp washer to test the whiteness and other indicators.

[0281] II. Experimental results

[0282] 1. Change in whiteness of the 4# pulp washer after bleaching before and after the test

[0283] Figure 6 For the change in whiteness (final pulp whiteness) of the 4# pulp washer after bleaching with the polyenergy enzyme added at different positions, it can be seen from the figure that when the polyenergy enzyme is added to the 4# pulp washer before oxygen delignification, the final pulp whiteness is the highest, and the whiteness is 1.4 degrees higher than before the test. This shows that adding the enzyme before oxygen delignification can more effectively improve the pulp whiteness compared to adding it after oxygen delignification and after chlorine bleaching.

[0284] 2. Alkali used in cooking and oxygen bleaching before and after the test

[0285] Figure 7 For the comparison of the alkali used in pulp cooking and oxygen bleaching with the polyenergy enzyme added at different positions, it can be seen that after adding the polyenergy enzyme to the 4# pulp washer before oxygen delignification, the alkali used in cooking and oxygen bleaching is the lowest. This shows that adding the enzyme before oxygen delignification can more effectively reduce the alkali consumption compared to adding it after oxygen delignification and after chlorine bleaching.

[0286] Example 9 Experimentation effect of XP-6719 on the paper machine in Guangxi Qinyuan Paper Industry

[0287] Experiment time: From April 16, 2022 to May 31, 2022.

[0288] Raw materials: 100% eucalyptus, enzyme: XP-6719, addition amount 100 - 300 g / t pulp.

[0289] I. Qinyuan paper machine experiment process (as Figure 5 shown)

[0290] 1. Cooking: The eucalyptus chips are cooked at a high temperature of 170°C for 90 minutes under alkaline conditions. Then, they are successively passed through the 1-4# pulp washers before bleaching, knotter, and sieve, and then sent to the oxygen bleaching tower through the 5# pulp washer before bleaching.

[0291] 2. Oxygen delignification: The pulp (concentration 8%) from the outlet of the 5# pulp washer before bleaching (enzyme addition point 1, temperature 70°C, 5 minutes, enzyme addition amount 0.1 - 0.3 kg / t pulp) is added with alkali and oxygen (35 - 37.5 kg / h to make the pressure in the autoclave 1.0 MPa), and enters the oxygen delignification reaction tower. At a temperature of 90°C, after a reaction of 90 minutes, it is discharged and depressurized, and after passing through the 6-7# pulp washers before bleaching, the pH is adjusted to acidic to prepare for chlorine bleaching.

[0292] 3. Chlorine bleaching: The pulp (2 - 3%) passing through the 6-7# pulp washers is adjusted to a pH of 2 - 3, and chlorine (15 kg / t) and chlorine dioxide (2.4 kg / t) are added. The reaction takes place at a temperature of 40°C for 30 - 45 minutes, and after passing through the 1# pulp washer after bleaching, it is ready to enter the alkali extraction section.

[0293] 4. Alkali extraction: Hydrogen peroxide (10 kg / t) and alkali 200 ml / h are added to the pulp (concentration 7 - 8%) from the 1# pulp washer after bleaching. The pH is adjusted to 8 - 9, and the reaction takes place at a temperature of 55°C for 1.5 hours. After passing through the 2# pulp washer after bleaching, it enters the next section.

[0294] 5. Take the pulp from the outlet of the 4# pulp washer after bleaching to test the whiteness and other indicators.

[0295] II. Process and observation of the machine test:

[0296] 1. Observe the blank before the test, from April 16th to April 27th.

[0297] 2. Without changing the existing process in the workshop, add the energy-saving enzyme, with an addition amount of 100 - 300 g / t pulp. The dosage of the energy-saving enzyme is gradually increased from 0.1 kg / t to 0.3 kg / t, from April 27th to May 6th.

[0298] 3. Reduce the alkali used in the oxygen delignification section and adjust the pH value at the enzyme addition point. The alkali used in oxygen delignification is gradually reduced from 12 kg / t to 6 kg / t, 3 kg / t, from May 6th to May 13th.

[0299] 4. Restore the alkali used in oxygen delignification to 6 kg / t and the dosage of the energy-saving enzyme to 0.3 kg / t, from May 13th to May 15th.

[0300] 5. Restore the alkali used in oxygen delignification to 12 kg / t and the dosage of the energy-saving enzyme to 0.1 kg / t, from May 15th to May 22nd.

[0301] 6. Observe the blank after the experiment. The amount of alkali used in the oxygen delignification stage is 12 kg / t, and the time is from May 22nd to May 31st.

[0302] III. Experimental Results

[0303] 1. Figure 8 The following shows the change in the brightness (final pulp brightness) of the 4# washer after bleaching under different enzyme addition amounts. Under the condition that the existing process in the workshop remains unchanged, when adding the energy-saving enzyme to the 5# washer, the brightness improvement is the highest when the addition amount is 100 g / t.

[0304] 2. Figure 9 The following shows the influence of the dosage of the energy-saving enzyme and the amount of caustic soda used in oxygen bleaching on the oxygen bleaching efficiency. Figure 9 The oxygen bleaching efficiency in [[ ]] is represented by calculating the brightness difference between the 7# washer and the 5# washer. The larger the difference, the higher the oxygen bleaching efficiency. As can be seen from [[ ]] Figure 9 under the condition that it is exactly the same before and after the test, that is, without reducing the alkali used in oxygen bleaching, the addition of the energy-saving enzyme significantly improves the oxygen bleaching efficiency. When the alkali used in oxygen bleaching is reduced to 6 kg / t, the oxygen bleaching efficiency is basically the same as that before and after the test.

[0305] 3. Figure 10 The following shows the comparison of the unit consumption of cooking alkali in each stage of the test. It can be seen that under the conditions that the amount of alkali used in oxygen bleaching is reduced to 6 kg / t and the dosage of the energy-saving enzyme is 0.2 kg / t, the unit consumption of cooking alkali is lower than that before / after the test, and it is 27 kg / t lower than that after the test.

[0306] 4. Figure 11 The following shows the influence of the energy-saving enzyme, the alkali used in oxygen bleaching, and the alkali used in cooking on the Kappa value of the cooked pulp; Figure 12 The following shows the influence of the energy-saving enzyme, the alkali used in oxygen bleaching, and the alkali used in cooking on the Kappa value of the oxygen-bleached pulp. It can be seen that through the optimization of the energy-saving enzyme and the alkali used in oxygen bleaching, the unit consumption of cooking alkali can be significantly reduced, and the same Kappa value can be obtained. The maximum reduction in the unit consumption of cooking alkali is expected to reach 20%. Moreover, when the amount of cooking alkali is reduced by 6 kg / t, the Kappa value of the resulting pulp is stable, indicating that the quality of the resulting pulp is stable and the yield is higher.

[0307] 5. Figure 13 The following shows the comparison of the residual alkali concentration in the black liquor before and after the test and during the test stage of the energy-saving enzyme. It can be seen that compared with before and after the test, the residual alkali concentration in the black liquor during the test stage with the addition of the energy-saving enzyme has decreased significantly, with a decrease of 10 - 15%.

[0308] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0309] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for pulping bleached chemical pulp, characterized in that, it comprises the following steps: (1) Adjust the concentration of the pulp after the cooking reaction with water, add a biological enzyme for treatment to obtain the pulp after biological enzyme treatment; (2) Add an oxidizing compound to the pulp after biological enzyme treatment for an oxygen delignification reaction to obtain the pulp after oxygen delignification; (3) Carry out chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp; (4) Carry out alkali extraction on the bleached pulp to obtain the bleached chemical pulp; The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

2. A method for pulping bleached chemical pulp, characterized in that, it comprises the following steps: (a) Adjust the concentration of the pulp after the cooking reaction with water, add an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification; (b) Add a biological enzyme to the pulp after oxygen delignification for treatment to obtain the pulp after biological enzyme treatment; (c) Carry out chlorine dioxide bleaching on the pulp after biological enzyme treatment to obtain the bleached pulp; (d) Carry out alkali extraction on the bleached pulp to obtain the bleached chemical pulp; The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

3. A method for pulping bleached chemical pulp, characterized in that, it comprises the following steps: (A) Adjust the concentration of the pulp after the cooking reaction with water, add a biological enzyme and an oxidizing compound for an oxygen delignification reaction to obtain the pulp after oxygen delignification; (B) Carry out chlorine dioxide bleaching on the pulp after oxygen delignification to obtain the bleached pulp; (C) Carry out alkali extraction on the bleached pulp to obtain the bleached chemical pulp; The biological enzyme is one or more of xylanase, hemicellulose hydrolase, laccase, cellobiose oxidase, lignin peroxidase and multifunctional peroxidase.

4. The method for pulping bleached chemical pulp according to any one of claims 1-3, characterized in that, the biological enzyme is one or more of xylanase, laccase and multifunctional peroxidase.

5. The method for pulping bleached chemical pulp according to claim 4, characterized in that, the biological enzyme is endo-xylanase; or the biological enzyme is laccase; or the biological enzyme is a combination of endo-xylanase, laccase and multifunctional peroxidase.

6. The method for pulping bleached chemical pulp according to claim 5, characterized in that, the biological enzyme is composed of endo-xylanase, laccase and multifunctional peroxidase in a mass ratio of 6-8:1.5-2.5:1; preferably, the biological enzyme is composed of endo-xylanase, laccase and multifunctional peroxidase in a mass ratio of 6.8-7.2:1.8-2.2:

1.

7. The method for pulping bleached chemical pulp according to any one of claims 1-3, characterized in that, the upper limit of the temperature resistance of the biological enzyme is above 85 °C, and the upper limit of its pH resistance is above 9.

8. The method for pulping bleached chemical pulp according to any one of claims 1-3, characterized in that, Based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.01 kg / t to 5 kg / t, preferably 0.05 kg / t to 0.5 kg / t, and more preferably 0.05 kg / t to 0.4 kg / t.

9. The pulping method of bleached chemical pulp according to claim 8, characterized in that Based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.05 kg / t to 0.22 kg / t, or 0.18 kg / t to 0.32 kg / t.

10. The pulping method of bleached chemical pulp according to claim 9, characterized in that Based on the absolute dry weight of the added pulp, the addition amount of the bio-enzyme is 0.08 kg / t to 0.12 kg / t, or 0.18 kg / t to 0.22 kg / t, or 0.25 kg / t to 0.32 kg / t.

11. The pulping method of bleached chemical pulp according to claim 1, or claim 2 or claim 3, characterized in that the reaction in step (2) is carried out under the condition of adding alkali or not adding alkali; the reaction in step (a) is carried out under the condition of adding alkali or not adding alkali; the reaction in step (A) is carried out under the condition of adding alkali or not adding alkali.

12. The pulping method of bleached chemical pulp according to claim 11, characterized in that the alkali in step (2), step (a) and step (A) is at least one of sodium hydroxide and potassium hydroxide, preferably sodium hydroxide.

13. The pulping method of bleached chemical pulp according to claim 11, characterized in that Based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 30 kg / t, preferably 0 kg / t to 14 kg / t, preferably 0 kg / t to 12 kg / t, and more preferably 0 kg / t to 6 kg / t.

14. The pulping method of bleached chemical pulp according to claim 11, characterized in that Based on the absolute dry weight of the added pulp, the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.5 kg / t; the addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t.

15. The pulping method of bleached chemical pulp according to claim 14, characterized in that the dosage of the alkali in step (2), step (a) and step (A) is 0 kg / t to 6.2 kg / t; the addition amount of the bio-enzyme is 0.18 kg / t to 0.22 kg / t.

16. The pulping method of bleached chemical pulp according to claim 15, characterized in that the dosage of the alkali in step (2), step (a) and step (A) is 5.8 kg / t to 6.2 kg / t; the addition amount of the bio-enzyme is 0.18 kg / t to 0.22 kg / t.

17. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that the pH of the reaction between the bio-enzyme and the pulp is 7-12, preferably 8-11, and more preferably 9-11.

18. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the pH of the reaction of the oxidizing compound with the pulp is 7-12, preferably 8-11, more preferably 9-11.

19. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the oxidizing compound is selected from at least one of hydrogen peroxide, ozone and oxygen; preferably oxygen, or a combination of hydrogen peroxide and oxygen.

20. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the oxidizing compound is oxygen, and the addition amount of oxygen is such that the pressure in the reaction kettle is increased to 0.3 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa.

21. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the oxidizing compound is a combination of hydrogen peroxide and oxygen; the addition amount of oxygen is such that the pressure in the reaction kettle is increased to 0.3 MPa to 2 MPa, preferably 0.5 MPa to 1 MPa, more preferably 0.6 MPa - 0.8 MPa; based on the oven-dry weight of the added pulp, the addition amount of hydrogen peroxide is 5 kg / t to 50 kg / t, preferably 6 kg / t to 10 kg / t.

22. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the pulp is bamboo pulp, bagasse pulp, softwood pulp and / or hardwood pulp; preferably hardwood pulp; more preferably eucalyptus pulp.

23. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the temperature for treating with the added bio-enzyme is 50°C to 95°C, and the treatment time is 1 min to 5 h; and / or, the temperature of the oxygen delignification reaction is 50°C to 95°C, and the reaction time is 0.5 h to 5 h.

24. The pulping method of bleached chemical pulp according to any one of claims 23, characterized in that, the temperature for treating with the added bio-enzyme is 70°C to 92°C, and the treatment time is 5 min to 2 h; and / or, the temperature of the oxygen delignification reaction is 75°C to 92°C, and the reaction time is 1 h to 2 h.

25. The pulping method of bleached chemical pulp according to any one of claims 24, characterized in that, the temperature of the oxygen delignification reaction is 78°C to 82°C, or 88°C to 92°C.

26. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, the bio-enzyme is composed of endo-xylanase, laccase and multifunctional peroxidase with a mass ratio of 6-8:1.5-2.5:1, the temperature of the oxygen delignification reaction is 88°C to 92°C, the pulp is eucalyptus pulp or bamboo pulp, and the addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, more preferably 0.08 kg / t to 0.12 kg / t.

27. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:

1. The temperature of the oxygen delignification reaction is 88°C to 92°C. The pulp is bamboo pulp. The addition amount of the bio-enzyme is 0.08 kg / t to 0.4 kg / t, preferably 0.1 kg / t to 0.35 kg / t, more preferably 0.2 kg / t to 0.32 kg / t, and even more preferably 0.28 kg / t to 0.32 kg / t.

28. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The bio-enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:

1. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.4 kg / t, preferably 0.1 kg / t to 0.35 kg / t, and more preferably 0.28 kg / t to 0.32 kg / t.

29. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The bio-enzyme is composed of a combined enzyme and laccase. The combined enzyme is composed of endo-xylanase, laccase and versatile peroxidase with a mass ratio of 6-8:1.5-2.5:

1. The mass ratio of the combined enzyme to laccase is 1:0.8-1.

2. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.5 kg / t, preferably 0.18 kg / t to 0.42 kg / t, and more preferably 0.18 kg / t to 0.22 kg / t.

30. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The bio-enzyme is endo-xylanase. The temperature of the oxygen delignification reaction is 88°C to 92°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, and more preferably 0.08 kg / t to 0.12 kg / t.

31. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The bio-enzyme is laccase. The temperature of the oxygen delignification reaction is 78°C to 82°C. The pulp is eucalyptus pulp or bamboo pulp. The addition amount of the bio-enzyme is 0.05 kg / t to 0.3 kg / t, preferably 0.08 kg / t to 0.22 kg / t, and more preferably 0.08 kg / t to 0.12 kg / t.

32. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, Adjusting the concentration of the pulp after the cooking reaction with water means adjusting the concentration to 1% to 15%, preferably 1% to 10%, and more preferably 1.5% to 8%.

33. The pulping method of bleached chemical pulp according to any one of claims 1-3, characterized in that, The conditions for bleaching with chlorine dioxide include: the pulp concentration is 1% - 15%, preferably 1% - 10%, more preferably 2% - 8%, and even more preferably 2% - 4%.

34. The pulp making method for bleaching chemical pulp according to claim 33, characterized in that, the conditions for bleaching with chlorine dioxide further include: adjusting the pH to 3 - 4; and / or, based on the oven-dry weight of the added pulp, the dosage of chlorine dioxide is 5 kg / t - 30 kg / t; and / or, the temperature is 30°C - 70°C, and the reaction time is 20 min - 60 min.

35. The pulp making method for bleaching chemical pulp according to any one of claims 1 - 3, characterized in that, the step of alkali extraction includes: diluting the bleached pulp and adding alkali and hydrogen peroxide for reaction.

36. The pulp making method for bleaching chemical pulp according to claim 35, characterized in that, in the step of alkali extraction, the pulp is diluted to a concentration of 1% - 15%, preferably 1% - 10%, more preferably 2% - 8%, and even more preferably 7% - 8%.

37. The pulp making method for bleaching chemical pulp according to claim 35, characterized in that, in the step of alkali extraction, the alkali is at least one of sodium hydroxide and potassium hydroxide; and / or, in the step of alkali extraction, based on the oven-dry weight of the added pulp, the dosage of the alkali is 5 kg / t - 15 kg / t; and / or, in the step of alkali extraction, the mass concentration of hydrogen peroxide in the hydrogen peroxide solution is 10 - 30%, and based on the oven-dry weight of the added pulp, the dosage of the hydrogen peroxide solution is 10 kg / t - 30 kg / t; and / or, in the step of alkali extraction, the reaction temperature is 45°C - 90°C, and the reaction time is 40 min - 3 h.

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