WO2009015555A1

WO2009015555A1 - Grass paper pulp used by papermaking and preparation method thereof

Info

Publication number: WO2009015555A1
Application number: PCT/CN2008/001377
Authority: WO
Inventors: Songtao Chen; Mingxin Song; Hongfa Li; Jihui Yang; Yanjin Bi
Original assignee: Shandong Tralin Paper Co., Ltd
Priority date: 2007-07-27
Filing date: 2008-07-25
Publication date: 2009-02-05

Abstract

An unbleached pulp and bleached chemical pulp using the grass plant as raw materials, and preparation method thereof. The unbleached pulp is provided with the breaking length 5000-7500m, tearing degree 230-280mN, fold number 40-90, brightness 25-45%ISO, beating degree 32-38ºSR. The bleached chemical pulp is provided with the breaking length 4500-8000m, fold number 20-90, brightness 45-82%ISO, tearing degree 180-280mN, beating degree 32-38ºSR. The preparation process for the unbleached pulp or bleached chemical pulp includes: a high rigidity pulp with the KMnO4 value 16-28 and beating degree 10-24ºSR is made by cookingthe grass raw materials.

Description

Grass pulp for papermaking and preparation method thereof

Technical field

The invention relates to a grass pulp for papermaking and a preparation method thereof, and belongs to the field of pulp and papermaking.

Background technique

The plant fiber raw materials for papermaking generally include: wood fibers and grass fibers.

Wood fiber, divided into softwood and hardwood, the shape of the two fibers is very different. Softwood fiber: Because of its large fiber length, soft fiber, and low content of fine components, it is easy to produce high-strength slurry, so this fiber is an excellent raw material for papermaking. Hardwood fiber: Because the fiber is short, the content of the duct and the parenchyma cells is high, so the paper strength is not as good as that of the softwood pulp. Due to the poor interweaving of the duct and the fiber network, the powder is easily generated, but the fiber is short on the paper. The stiffness and smoothness are favorable.

Grass fiber, due to the high content of miscellaneous cells, the miscellaneous cells have many adverse effects on the paper pulp papermaking, and the interlacing of the fibers is poor, affecting the strength of the pulp. When the population of the hetero cells adheres to the paper surface, the powder is easily lost. The high-cell lignin content is high, it is not easy to bleach, and it is easy to form yellow dust spots on the paper surface, and the pulping and papermaking value is the lowest. In the prior art, it is generally considered that there are many amorphous small cells in the straw, and the content of non-cells is large, so the water filtration of the straw pulp is poor, and the strength of the paper is also poor. The difference in the strength of the paper is usually expressed by the low value of the crack and the tear. The degree of low value and the number of times of folding resistance are small.

Therefore, the most used papermaking in the world is wood fiber, and grass fiber is used less. However, with the growing shortage of forest resources, how to use grass raw materials to prepare high quality pulp is now faced. A serious problem.

The grass pulping technology is a systematic project. The whole process of pulping should be studied according to the heterogeneity of the biological structure of the grass fiber raw materials and the specificity of the chemical composition. The existing grass pulp is used to produce pulp. The methods are: chemical method, mechanical method, chemical mechanical method. Chemical pulping is a widely used pulping method in chemical cooking by removing some of the ingredients in the grass plant fiber raw material by chemical action in the cooking step. Lime method, caustic soda method, strontium-soda method, sulphate method, sulfite method, etc.

In the prior art, it is generally considered that if pulping of grass plants is to achieve a high whiteness chemical pulp, it is necessary to cook and heat for a long time during cooking, so that the pulp is relatively "soft", for example, in 1999. The paper titled "Imagination and Preliminary Practice of Strengthening Grass Preparation and Reforming Cooking" published in the "Journal of Hubei Institute of Technology", Volume 14, No. 3, mentions that the pulp hardness K value is below 10, and the good is 7-8. The yield of pulp is more than 50%, the good is 57%, the crack length is more than 4000m, and the good is more than 7000m. The depth of turf can be obtained, the bleaching is good, the strength is good, the cooking yield is high, Energy saving, pollution reduction, and consumption reduction.

The sulfite method in the prior art uses plant fiber as a raw material, and the process is first prepared and will be carried out. Pre-processed raw materials for the production of pulp into steaming balls, vertical pots and continuous steaming (spherical digester, vertical cooking pot, continuous digester) and other equipment, and then add chemicals such as ammonium sulfite, to steaming balls, vertical pot Or even steaming in steaming, heat preservation for a period of time to obtain a crude slurry. The cooking is first carried out at a lower temperature. At this time, the lignin and the fiber are partially separated. When the temperature is raised for cooking, the lignin, polypentose and the like in the low-temperature reaction product are condensed and attached to the surface of the fiber. It is difficult to wash away from the fiber, so the uniformity of the pulp is poor, the pulp residue is high, the hardness of the pulp is high, and the water filtration capacity is poor. It requires a large amount of water to wash away the black liquor composed of miscellaneous cells, hemicellulose and lignin, resulting in sewage. Polluting the environment, and increasing the cost of producing pulp, also makes the next step of bleaching difficult. This prior art process produces 15-16 tons, or even 18 tons of black liquor per ton of pulp produced, and this black liquor has a high viscosity.

There are many technicians who are working on improving the cooking and cooking effects of grasses, such as: Heilongjiang Papermaking, No. 4, 2003, published an article entitled "Optimization of Cooking Conditions for Rice Straw Ammonium Method". The article discloses the optimized conditions for the cooking of rice straw ammonium, but the cooking time is long in the cooking method, and the amount of ammonium sulfite is large, so that the energy consumed is relatively large, the cost is relatively large, and the quality of the prepared pulp is not high. .

"Heilongjiang Papermaking", No. 4, 2003, published an article entitled "Characteristics and Application of Wheatgrass Ammonium Pulping and Papermaking", which discloses a method for making pulp of wheat grass, a special plant fiber raw material, ammonium imide method. The method has low hardness, long heat preservation time, high temperature of heat preservation, and high concentration of residual ammonium sulfite in black liquor, and the problem that the energy consumption is relatively large and the quality of pulp is not high.

The prior art decontamination process is generally used in the process of preparing wood pulp, such as the patent application CN200410023742.2, the production method of chemical wood pulp disclosed in the "manufacturing method of a chemical wood pulp", including impregnation, extrusion Disintegration, delignification, the extrusion disintegration is carried out before cooking, by which the structure of the wood chip becomes loose, the wood chips become thinner, the bulk density becomes smaller, and a woody group of a three-dimensional network structure is formed, due to the wood The specific surface area of the filaments becomes larger, and it is easy to uniformly absorb the medicine, so that the reaction rate of the delignification is accelerated, and the reactants are also easily dissolved. This stage is to enhance the uniform permeation of the cooking liquid, reduce the amount of cooking chemicals, and reduce the cooking time. And improve the uniformity of cooking into pulp.

In addition, the patent number CN99221397.5 entitled "Wheat Grass Extrusion Disintegrator" patent also discloses a disintegration device, which is mainly used for squeezing and dissolving the softened and moist wheat straw, the purpose thereof is Overcoming the prior art, the raw material of the wheat straw raw material has low impurity rate and serious pollution, which brings many adverse effects to the subsequent pulp and paper production, and also brings great difficulty to the alkali recovery of the cooking black liquor. However, the wheat straw extrusion disintegrator is used in dry preparation, and has no significant effect on the oxygen delignification process of the cooked slurry.

It is generally considered that the slurry prepared for grass plants has more heterogeneous cells and a higher content of hemicellulose, which is easy to hydrate, and the drainage performance is inferior to that of wood pulp, which is difficult to wash, and the wood obtained by the alkali method is used. The pulp is more difficult to wash than the wood pulp obtained by the acid method. For the straw pulp prepared from grasses, when the hardness of the slurry obtained after cooking is high, the viscosity of the slurry is small, resulting in good drainage performance at the beginning, but the final cleaning degree is poor. It is because some of the waste liquid in the cooking is present inside the fiber. For the slurry with high hardness, the fiber is less damaged. The internal waste liquid is mainly diffused from the cell cavity through the paper hole. The pulp with high hardness and the waste liquid in the fiber The diffusion resistance is large and the more difficult it is to wash. It is more difficult to wash the straw pulp obtained by the alkaline method than the wood pulp.

In the 25th issue of May 2006, in the Journal of Pulp and Paper, the article entitled "Combination Process of Drum Vacuum Washer and Double Screw Extruder from Black Liquid Extraction" is published. In order to achieve high extraction rate of black liquor in the washing process, many manufacturers add a double-screw extruder in front of the washing machine to directly extract the concentrated black liquor in the coarse slurry after spraying, and the effect is also good. In the front of the washing machine, a high-concentration black liquor extraction equipment such as a screw extruder is added, and the extraction rate of the black liquor of the wheat straw pulp is increased to more than 90%.

How to effectively remove lignin is a key issue in grass pulping.

The oxygen delignification method is generally used to prepare wood pulp, which is a process that is less polluting to the environment and has a high rate of delignification. However, if it is used to prepare grass plant pulp, the degree of enthalpy increase is too high due to the medium concentration transport of grass fibers, which seriously affects the water filtration performance of the straw pulp. Therefore, it is generally less used to prepare grass pulp. CN1737255 discloses a pulp cleaning bleaching process comprising: (1) single stage double column oxygen delignification; (2) hypochlorite bleaching; (3) activator pretreatment; (4) hydrogen peroxide bleaching. The method uses non-polluting oxygen and hydrogen peroxide to clean the bleaching agent, achieves high-efficiency bleaching by single-stage double-tower oxygen bleaching and activation pretreatment, and has high bleaching efficiency and whiteness of more than 85%. The construction investment is only chlorine dioxide. Less than 1/5 of bleaching; less pollution, AOX is reduced by more than 70%, wastewater discharge is reduced by 70%, COD and Cr emissions are reduced by more than 60%; production line can be used for the construction of pulp bleaching production line or in the existing pulp bleaching production line. It is specially transformed and specially suitable for the clean bleaching of chemical pulp of wood and grass plant materials with a daily output of more than 50 tons. The system is only used on reed pulp and has never been used on rice straw pulp. This method requires oxygen de-lignin from a double column, which is costly, and the subsequent steps require the use of an activator and hydrogen peroxide. Agents, etc., lead to an increase in pulp costs and a complicated process.

CN1616761 discloses a chlorine bleaching method for alkaline sodium sulfite grass pulp, which adopts pre-bleaching acid H202 pretreatment, two-stage oxygen delignification, chlorine dioxide bleaching, oxygen-enhanced alkali extraction and H202 and insurance powder. The H ₂ 0 ₂ /H ₂ S0 ₄ -01-02-D-Eop-PY bleaching process consisting of the final bleaching section was used to complete the chlorine bleaching of the reed slurry. The method requires H ₂ 0 ₂ pretreatment and two stages of oxygen delignification, and also needs chlorine dioxide bleaching and oxygen enhanced alkali extraction, the process is complicated and the cost is high.

In summary, the prior art does not disclose a high quality grass pulp for papermaking prepared from grasses and a preparation method thereof. Therefore, the invention has been specifically proposed.

Summary of the invention

The primary object of the present invention is to provide a grass-like pulp for papermaking, which is made from grasses. Preparation is carried out, which belongs to the unbleached pulp.

In order to achieve the above object, the technical solution adopted by the present invention is:

-7. 5km, tearing degree, the pulverization of the unbleached pulp is 5. 0-7. 5km, tearing degree 5至之间。 The unbleached pulp has a length of 6. 5-7. 5km, a tear of 250-280mN.

The whiteness of the pulp is 25-45% ISO, and preferably the pulp has a whiteness of 35-45%.

The unbleached pulp has a folding resistance of 40-90 times and a beating degree of 32-38 ° SR; preferably, the folding endurance is 65-90 times and the beating degree is 32-36 ° SR.

The preparation of the unbleached pulp includes a cooking step, wherein the cooking comprises: using a grass plant as a raw material to obtain a hardness of potassium borate of 16-28 and a beating degree of 10-24° SR. High-hardness pulp; preferably, the unbleached pulp is steamed after using grasses as raw materials to obtain a high-hardness pulp having a hardness of potassium permanganate of 16-23 and a degree of beating of 10-20 ° SR.

The unbleached pulp prepared by the grass raw material in the invention has a crack length of 5.0-7.5 km, a folding resistance of 40-90 times, a tear degree of 230-280 mN, and a whiteness of 25-45< 3⁄4IS0. The unbleached pulp can be used as a paste for corrugated paper, lunch boxes, offset printing paper, and food wrap. Since the bleaching treatment is not carried out during the preparation process, the obtained slurry is not contaminated by the bleaching agent, and the strength of the slurry is protected, so that the cellulose in the slurry is prevented from being affected by the bleaching. Loss and degradation. Moreover, the grass materials used in the present invention are abundant and inexpensive. In the present invention, in addition to the use of a certain grass plant at a time, it is also possible to mix several grass raw materials so that various raw materials can be used to complement each other, and the advantages of various raw materials can be utilized to prepare high-quality unbleached pulp.

A second object of the present invention is to provide another grass-like pulp for papermaking which is prepared from grasses as a raw material and which is a bleached chemical pulp obtained by bleaching the above-mentioned unbleached pulp.

A grass-like pulp for papermaking, wherein the pulp is a bleaching chemical pulp obtained by bleaching the unbleached pulp, and has a crack length of 4500-8000 meters and a folding resistance of 20-90 times. The tearing degree is 180-280 mN, the beating degree is 32-38 ° SR, and the whiteness is 45-82% IS0. In the preparation process of the bleaching chemical pulp, the grass raw materials are first cooked to a hardness of potassium permanganate. It is a high-hardness pulp of 16-28 and a beating degree of 10-24° SR; preferably, the bleaching chemical pulp has a crack length of 5500-8000 meters, a folding endurance of 35-80 times, and a tearing degree of 220-280 mN. The degree of beating is 32-36 ° SR, and the whiteness is 75_82%IS0. In the preparation process of the bleaching chemical pulp, the grass raw materials are first cooked to a hardness of 18-25 potassium permanganate and a beating degree of 10- High hardness pulp of 20° SR.

For the prior art bleached chemical grass pulp, the crack length is about 3.8 km, and the tearing degree is only about 170 mN. For the hardwood pulp, the crack length is only 3.5-5.3km, and the tearing degree can reach 440-660mN. This is because the shape and size of the fiber cells of the grass plant material are much smaller than the cell shape and size of the wood material. However, the content of the hybrid cells causing the decrease in the physical strength of the pulp is much higher than that of the corresponding wood raw materials. Therefore, the cracking length of the bleached chemical pulp prepared by using the herbaceous plants as the raw material of the present invention greatly exceeds the prior art straw pulp. Even more than hardwood pulp, its tearing is not as good as the existing hardwood pulp, but it also greatly exceeds the existing straw and wheat straw pulp.

In addition, the number of folding resistance is also an important indicator to characterize the strength of pulp, which is mainly determined by the length of the fiber and the bonding force between the fibers. In the prior art, it is generally considered that there are many amorphous small cells in the straw, and the content of non-cells is large, so The water filtration of the straw pulp is poor, and the strength of the paper is also poor. Although the content of fine cells in wheat straw cells is small, the fiber length is similar to that of hardwood pulp. However, the wall cavity ratio of wheat straw cells is much higher than that of hardwood pulp and softwood pulp. It is generally considered that the wall cavity is stiffer than the high fiber. The pulp strength is low. For the prior art wheat straw pulp, the number of folding resistance is 8 times, and the hardwood pulp is 10-23 times, and the number of folding resistance of the straw and wheat straw pulp of the present invention far exceeds them.

Therefore, the bleaching chemical pulp prepared from grasses as raw materials has a beating degree of 32-36° SR, a crack length of 4500-8000 m, a folding resistance of 20-90 times, and a whiteness of 45-82<3⁄4 ISO. The lignin removal rate is 84-98%. The bleached chemical pulp can be used as a slurry for producing high quality cultural paper. Further, the raw materials used in the present invention are grasses, including straw, wheat straw, cotton stalks, bagasse, reeds, etc., which are not only abundant in source but also inexpensive. Because of the excellent performance of the pulp itself, it can be used with less wood pulp when preparing high-quality paper products. Therefore, in the increasingly lack of forest resources, high-quality paper products are greatly alleviated. The contradiction between demand and lack of timber resources also reduces the production cost of enterprises and brings good economic benefits to enterprises.

A third object of the present invention is to provide a method for preparing a grass-like pulp for papermaking, wherein the pulp is an unbleached pulp prepared by using grasses as raw materials, and the cracking length of the unbleached pulp is 5.0-7.5km, tearing degree is 230-280mN, whiteness is 25-45.<3⁄4ISO.

A method of preparing a pulp, characterized in that the method comprises the following steps:

(1) Cooking the grass raw materials to obtain a high-hardness pulp having a hardness of potassium permanganate 16-28 and a beating degree of 10-24° SR;

(2) washing the high-hardness pulp obtained in the step (1) to obtain a washed slurry;

(3) The washed slurry is post-treated to obtain the pulp.

The cooking according to the present invention comprises one of ammonium sulfite cooking, strontium-soda cooking, kraft cooking or alkaline sodium cooking:

When the ammonium sulfite method is cooked, the amount of ammonium sulfite is 9-13% of the amount of the dry raw material;

When the sputum-soda caustic method is cooked, the amount of alkali is 9-15% based on the amount of dry raw materials;

When cooking by the sulphate method, the amount of the dry raw material is 8-11% based on the amount of alkali; In the alkaline sodium method cooking, the amount of sodium hydroxide is 11-15% by weight of the dry raw material, and the amount of sodium sulfite is 2-6% by weight of the dry raw material.

The cooking according to the present invention comprises: one of ammonium sulfite cooking, strontium-soda cooking, kraft cooking or alkaline sodium cooking:

1) In a batch ball cooker or continuous digester:

The ammonium sulfite method is cooked as follows:

1 Adding a cooking liquid to the grass material, wherein the amount of ammonium sulfite is 9-13% of the amount of the dry raw material, and the amount of sodium hydroxide is 0-8% of the amount of the dry raw material, and the liquid ratio is 1 : 2-4;

2 It is heated by steam, heated to a temperature of 165-173 °C, heated, deflated, and insulated for 160-210 minutes;

The mash-soda cooking is as follows:

1 Adding a cooking liquid to the raw materials of grasses, wherein the amount of alkali is 9-15% based on the total amount of dry raw materials, and the liquid ratio is 1:2-4, and the amount of lanthanum added is dry raw material. The amount is 0.5-0.8%. ;

2 is heated by steam, heated to a temperature of 160-165 ° C, heating, small venting, heat preservation time of 140-190 minutes;

The kraft cooking is as follows:

1 adding a cooking liquor to the grass material, wherein the amount of the dry raw material is 8-11%, the liquid ratio is 1 : 2-4, and the degree of sulfurization is 5-8%;

2 It is heated by steam, heated to a temperature of 165-173 °C, heated, deflated, and insulated for 150-200 minutes;

The alkaline sodium solution cooking comprises:

(1) adding a cooking liquid to the raw material of the grass, wherein the amount of sodium hydroxide is 9-15% by weight of the dry raw material, 2-6% of sodium sulfite, 0.04-0.08% of strontium, and the ratio of cooking liquor is 1 : 3-4;

(2) Heating with steam, heating to a temperature of 160-165 ° C, heating, small venting, heat preservation time of 140-190 minutes;

2) In the vertical cooking pot:

The ammonium sulfite method is cooked as follows:

The grass material is filled into the cooking pot from the hot black liquor with a temperature of 120-14 CTC through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. The air in the pot is boosted to 0.6-0.75 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 156-173 ° C, and the temperature is raised, kept and replaced for 180-220 minutes. The pump discharges the slurry to the spraying pot; wherein the amount of the ammonium sulfite is 9-15% of the amount of the dry raw material, and the amount of the sodium hydroxide is 0-8% of the amount of the dry raw material. The liquid ratio is 1: 6-10; the mash-burning method is as follows: The grass material is filled into the cooking pot from the hot black liquor with a temperature of 120-14 CTC through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. The air in the pot is raised to 0.4-0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 147-165 °C, and the temperature is raised, kept and replaced for 160-220 minutes. The pump sends the slurry to the spraying pot; in the cooking agent, the amount of alkali is 9-17% based on the amount of the dry raw material, and the liquid ratio is 1: 6-9. 0.5-0.8% of the dry material amount. The kraft method is as follows:

The grass material is filled into the cooking pot from the hot black liquor with a temperature of 120-14 CTC through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. The air in the pot is boosted to 0.5-0.65 MPa, and the cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 155-168 °C, and the temperature is raised, kept and replaced for 200-250 minutes, and finally the pump is used. Putting the slurry into the spraying pot; wherein the cooking agent, wherein the alkali amount is sodium hydroxide, the amount of the dry raw material is 8-13%, the liquid ratio is 1:6-10, and the degree of sulfurization is 5-9. % ;

The alkaline sodium solution cooking comprises:

The grass raw material is filled into the cooking pot from the hot black liquor at a temperature of 120-140 ° C through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. At the same time, the air in the pot is discharged and boosted to 0.45-0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 152-165 ° C, and the temperature is raised, kept and replaced for 180-230 minutes. Finally, the slurry is sent to the spraying pot by the pump; wherein the amount of sodium hydroxide is 9-17% by weight of the dry raw material, and the amount of sodium sulfite is 4-8 by weight of the dry raw material. %, 蒽醌 is used in an amount of 0.04-0.08% by weight of the dry raw material, and the liquid ratio is 1: 6-10.

The washing described in the present invention includes

(1) The high-hardness pulp having a concentration of 8-15% is introduced from the inlet of the extruder, and the black liquor is squeezed under the action of the pressing force to obtain a slurry after being squeezed at a concentration of 18-25%. The squeezer is a squeezer used in the prior art for extracting black liquor, preferably a reduced diameter single screw extruder, a double screw extruder or a twin roller extruder;

(2) The slurry after the squeezing is carried out with a concentration of 3-6. 2° Be ' and a pH of 8-8. 3 or a temperature of 70-8 CTC in one or both of the water at a temperature of 70-8 CTC. Washing, the washing is carried out in a vacuum washer, a pressure washer or a horizontal belt washer.

The post-treatment of the present invention includes dissolving, and the dissolving comprises treating the slurry obtained after washing with a high-frequency disintegrator, a rake machine, a disc grinder, a disc grinder or a fiber separator in a beating apparatus, Make the fiber structure loose.

The post-treatment of the present invention further comprises oxygen delignification, the oxygen delignification comprising: feeding the obtained slurry into an oxygen delignification reaction tower, the temperature of the slurry at the inlet of the reaction tower is 90至100°C, the pressure is 0. 9— 1. 2MPa; the temperature at the outlet is 95-105 ° C, the pressure is 0. 2—0. 4MPa; the oxygen delignification is used in the amount of alkali The sodium hydroxide meter is used for 2-4% of the dry pulp volume, and the oxygen is added in an amount of 20-40 kg per ton of dry pulp for 60-90 minutes to obtain a pulp having a hardness of 10-14 potassium permanganate. material. Specifically, before the cooking, the grass raw material may be impregnated: the grass fiber raw material is impregnated with the impregnation liquid to achieve a liquid ratio of 1:2-4, and the spiral is at 85 ° C or higher under normal pressure. Immersion and mixing in the impregnator for more than 10 minutes, wherein it is better to mix and mix for 10-40 minutes between 85-95. In this way, the impregnation liquid is sufficiently contacted with the raw material to uniformly impregnate the raw material. The immersion liquid may be a certain concentration of an alkali solution, such as a sodium hydroxide solution having a dry amount of 3-6%, or a mixture of alkali and black liquor, and the concentration of the black liquor used is 11-14. ° Be ' (20 ° C).

The raw material is subjected to immersion pretreatment, so that the temperature and residual alkali of the black liquor are recycled and reused, thereby reducing energy and resource consumption. Due to the pre-treatment of the raw material, the delignification reaction during cooking is facilitated during the heat treatment. Prepare for the next cooking process.

The next cooking process is a key step in pulping. Due to the differences in the structure, microstructure, chemical composition and lignin molecular structure of wood and grass materials, the delignification reaction process is also very high during the cooking process. Big difference. The chemical composition of grasses is high in polypentose content, generally around 20%. The content of sodium hydroxide is high and the content of lignin is low, but the content of ash is relatively high. The ash is mainly silica. Due to the use of high temperature cooking and chemical cooking liquids, certain chemical changes occur in the raw materials of lignin, cellulose and hemicellulose, and other components, which are subject to various degrees of degradation and damage. For the special pulping material of grass plant fiber, in the method of the invention, the chemical cooking liquid is strictly controlled, the concentration thereof is lowered, and the components required for pulping such as cellulose and semi-fiber are reduced. Degradation and damage. At the same time, in the process of high-temperature cooking, the method of the invention adopts the method of reducing the holding time as much as possible, so that the time of the grass plants at high temperature is shortened, thereby reducing the cellulose and hemicellulose in the grass plant raw materials. degradation. Therefore, the cooking method of the present invention largely protects the components required for pulping in the grass plant material as compared with the prior art cooking method, and greatly shortens the holding time and greatly reduces the energy consumption, and The pulping yield has been greatly improved, reaching 50-68%, thus greatly improving production efficiency.

The method of the present invention obtains a high-hardness pulp after cooking, and the hardness of the high-hardness pulp is a potassium permanganate value of 16-28, which corresponds to a Kappa number of 24-50, and a beating degree of 10-24 ° SR; The hardness of the high-hardness pulp is 18-27 for the potassium permanganate value equivalent to the Kappa price of 29-48; the hardness of the high-hardness pulp is most preferably the potassium permanganate value of 20-25, which corresponds to the Kappa price of 34-42.

The oxygen delignification of the present invention comprises: feeding the slurry obtained after cooking or the washed slurry into an oxygen delignification reaction tower, and the temperature of the slurry at the inlet of the reaction tower is 90-100 ° C, the pressure is 0.9-1.2 MPa; the temperature at the outlet is 95-105 ° C, the pressure is 0.2-0.6 MPa; the oxygen delignification in the amount of alkali is sodium hydroxide, the amount of dry pulp 2-4%, oxygen is added in an amount of 20-40 kg per ton of pulp for 60-90 minutes to obtain an unbleached pulp having a hardness of 10-14 potassium permanganate.

Before the oxygen delignification treatment, the high-hardness pulp is heated to 70-8 CTC by a screw conveyor and sent to a slurry tube, and the slurry is quenched and tempered in the slurry tube to remove the air in the slurry. Fluidization. When oxygen delignification is carried out, a magnesium salt such as magnesium sulfate or the like having a weight of 0.2 to 1% by weight of the dry pulp is added as a protective agent. Due to the oxygen delignification treatment of the high-hardness pulp, until the hardness is reduced to the potassium permanganate value of 10-14, the lignin is effectively removed and the fiber degradation is minimized. Choosing the appropriate oxygen delignification conditions ensures that the slurry obtained after washing is mainly reacted in the oxygen delignification tower to remove lignin instead of cellulose degradation, and the lignin from the oxygen delignification process The rate of removal is 86_98%.

The invention adopts single-stage oxygen delignification, which is carried out under the condition of low temperature and relatively long time, mainly for the milder delignification reaction, and avoids degradation of cellulose as much as possible. Oxygen delignification is carried out under medium concentration conditions. The main advantages of concentrated oxygen delignification are: less investment; due to the success of medium-concentration mixing and pumping technology, slurry processing is much easier than high concentration; low slurry concentration, less corrosion of equipment, no The danger of burning in oxygen.

After the completion of the cooking, the obtained high-hardness slurry is diluted with a certain pressure and sprayed into a discharge pot at a pressure of 0.6 to 0.8 MPa. At this time, the concentration of the high-hardness slurry in the spray pot is 8-15%, the hardness of the potassium permanganate value is 16-28, which is equivalent to the Kabo price 24-50, and the beating degree is 10-24° SR. The screw extruders are connected by a transfer pump, and the transfer pump conveys the high-hardness slurry in the spray pot to the inlet of the screw extruder, and the high-hardness pulp enters from the inlet of the screw extruder, after the slurry is squeezed, the above The high-hardness slurry is sent out from the outlet of the extruder, and the concentration of the slurry sent is increased from 8-15% to 18-25%, which becomes a high-concentration high-hardness pulp, the temperature is 70-80 ° C, and the beating degree is 15-28° SR. While the slurry is being squeezed, most of the black liquor is squeezed out and stored in the black liquor tank. The slurry from the outlet of the extruder is diluted with black liquor displaced in a subsequent process, the black liquor is 3-6° Be ' at 75 ° C, or the temperature can be 70 ° C. Dilute by dipping, and send the concentration of the slurry to 2.5-3% to the sieve for screening.

The washing according to the present invention comprises: introducing the high-hardness pulp having a concentration of 8-15% from the inlet of the extruder, and extruding the black liquor under the action of the pressing force to obtain a concentration of 18-25%. Slurry slurry; the pulper is preferably a reduced diameter single screw extruder, double screw extruder or twin roller extruder. The slurry after the pulverization is washed with one or both of a black liquor having a temperature of 70-8 CTC and a concentration of 3-6.2 ° Be ' and pH 8 - 8.3 or with clear water at a temperature of 70-8 CTC. It is carried out in a vacuum washer, a pressure washer or a horizontal belt washer.

The pulp press described in the present invention may be a pulper used in the prior art for extracting black liquor. When using a squeezer for squeezing, the temperature will rise rapidly due to the large squeezing force during the squeezing process, which will cause the fibers to separate, separate, smash, crush, and the primary wall is destroyed. The energy causes a large stress inside the fiber, and the reaction performance of the high-hardness pulp is greatly improved. At the same time, the fibers are fibrillated, and the impurities of the epidermis and interfibers are dissolved in the cooking black liquor, and the fiber purity is greatly improved by discharging through the liquid discharge tank. Some of the ash and impurities in the black liquor are also discharged with the black liquor, which is fully prepared for the next step. More importantly, the pulping degree of the high-hardness pulp changes little before and after the slurry is squeezed. That is to say, the damage to cellulose during the squeezing process is small, and the inherent fiber length of the grass fiber can be kept relatively good, and the fiber damage is minimized. The extruder according to the present invention may also be a twin-screw extruder or a twin-roller, which achieves the same effect. Different from the prior art, the washing in the present invention is to wash the high-hardness pulp having a hardness of 16-28 potassium permanganate equivalent to a Kappa number of 24-50, because the hardness of the pulp is high, so It is easy to wash off ash impurities and the like, so that the slurry maintains a high degree of cleanliness.

In the present invention, the temperature of 70-8 CTC is 3-6.2 ° Be ' and the black liquor of pH 8-8.3 or one or both of the same temperature of the water is washed one or more times, which is utilized. The role of displacement, and diffusion. These two effects are often carried out at the same time. The diffusion effect is: the waste liquid existing inside the fiber can be diluted, causing the difference in the concentration of the solution inside and outside the fiber, so that the dissolved matter in the fiber is diffused, and then concentrated by pressure filtration to separate. The diffusion effect is caused by the difference in concentration, which means that the high-concentration molecules of the higher concentration move toward the lower one, and the water molecules with the lower concentration also migrate to the higher concentration. , replacement. Therefore, the concentration difference of waste liquid inside and outside the fiber is the driving force of diffusion, which has a great influence on the diffusion speed. The diffusion area is related to the type of pulp and its hardness. The diffusion coefficient depends on the penetration of solid matter dissolved in the waste liquid in the fiber. Capacity is related to washing temperature, viscosity and pressure.

The grass raw material described in the present invention is a combination of one or more of straw, wheat straw, cotton straw, bagasse, reed or arundo.

In the preparation method of the present invention, a high hardness slurry is prepared by reducing the amount of the cooking liquid and shortening the cooking time. The reduction in the amount of chemical liquid used during cooking and the shortening of cooking time will greatly reduce the production cost of the enterprise, and the yield is greatly improved, thereby greatly improving the production efficiency. More importantly, the high hardness of the pulp obtained by cooking will minimize the degradation of cellulose and hemicellulose in the raw material, and the inherent length of the grass fiber is better maintained. At the same time, the high-hardness pulp of the present invention can be used as a raw material for preparing unbleached pulp, and the concentration of the liquid medicine used for cooking is lowered, and the cooking and heat preservation time is also greatly shortened, thereby minimizing the amount of pulp in the pulp. Desirable loss and degradation of cellulose and hemicellulose, and the unbleached pulp is not bleached, avoiding degradation of cellulose and hemicellulose due to the bleaching step, maintaining the inherent length of the grass fibers . Therefore, the yield and strength of the unbleached pulp are improved.

A fourth object of the present invention is to provide a method for preparing a grass-like pulp for papermaking, wherein the pulp is a bleaching chemical pulp.

A method of the above pulp, the method comprising the steps of:

(2) washing the high-hardness slurry obtained in the step (1) to obtain a washed slurry;

(3) The washed slurry is post-treated to obtain the pulp, and the post-treatment includes dissolving, oxygen delignification, and bleaching. The post-treatment of the present invention comprises a dehydration, oxygen delignification and bleaching step, wherein the bleaching comprises: chlorination, alkali treatment and hypochlorite bleaching, chlorination: 2.5- of chlorine is used as an absolute dry pulp 3%, the concentration of the pulp is 3-3.5%, the bleaching temperature is 30-45 ° C, the bleaching time is 45-60 minutes; the alkali treatment condition is: the amount of sodium hydroxide added is the absolute dry pulp amount 2 4<3⁄4, the concentration of the pulp is 10-12%, the bleaching temperature is 50-65 ° C, the time is 100-150 minutes; hypochlorite bleaching: the amount of sodium hypochlorite added is 2-4% of the absolute dry pulp amount, The bleaching temperature is 30-35 ° C and the bleaching time is 100-150 minutes.

The bleaching according to the invention comprises: chlorination, alkali treatment and hydrogen peroxide bleaching, chlorination: the amount of chlorine used is 2.5-3% of the dry pulp, the concentration of the pulp is 3-3.5%, and the bleaching temperature is 30- 45 ° C, bleaching time is 45-60 minutes; alkali treatment conditions are: the amount of sodium hydroxide added is 2-4% absolute dry pulp, the concentration of pulp is 10-12%, bleaching temperature is 50-65 °C, the time is 100-150 minutes; the hydrogen peroxide bleaching comprises: the hydrogen peroxide is added in an amount of 4-6% of the dry pulp, the pulp concentration is 10-12%, and the pH is 11-12.5, 敖The mixture is 0.2<3⁄4, the magnesium sulfate protectant is 0.4<3⁄4, the bleaching temperature is 95-99 °C, and the bleaching time is 100-130 minutes.

In the preparation method of the present invention, a high-hardness slurry is prepared by reducing the amount of the cooking liquid and shortening the cooking time. The reduction in the amount of chemical liquid and the shortening of the cooking time will greatly reduce the production cost of the enterprise, and the yield is greatly improved, thereby greatly improving the production efficiency. At the same time, the high-hardness pulp of the present invention can be used as a raw material for preparing a bleaching chemical pulp, and the concentration of the liquid medicine used for cooking is lowered, and the cooking and heat preservation time is also greatly shortened, thereby minimizing the amount of pulp in the pulp. The loss and degradation of cellulose and hemicellulose required, the yield and strength of the pulp are improved. In the preparation method of the bleached pulp in the present invention, since the steps of cooking, washing, dissolving and oxygen delignification have been carried out under the conditions of minimizing cellulose damage and degradation, most of the pulp preparation needs to be removed. Therefore, the use of various bleaching agents in the bleaching process is also greatly reduced, thereby greatly reducing the environmental pollution of the preparation process. detailed description

Example 1

The wheat straw raw material prepared according to the conventional dry method is charged into the steaming ball, and the cooking liquid is added to the steaming ball. The ammonium sulfite is added in an amount of 9% of the dry raw material, and the liquid ratio is 1:3, and the first heating is heated. After heating to 30 ° C for 30 minutes, the secondary heating was raised to 168 ° C, and the heating and holding time were 130 minutes. The hardness of the high-hardness pulp obtained after cooking is a potassium permanganate value of 22 equivalent to a Kappa price of 35.5, a beating degree of 12.4° SR, and then a slurry with a variable-diameter single-screw extruder for high-hardness pulp before being squeezed. The concentration was 8%, the concentration of the slurry after extrusion was 15%, diluted with dilute black liquor to a concentration of 2.5-3.5%, and then washed with an oxygen delignification residual liquid using a prior art vacuum washer. The washed slurry was sent to a high-frequency disintegrator for dissolving, and after the disintegration, the concentration was adjusted to obtain a high-durability slurry having a concentration of 10%, and then the slurry was heated to 70 ° C by a screw conveyor and sent to a medium-thick slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is in the pipeline before entering the reaction tower The oxygen and alkali content of the added 20 kg per ton of pulp are mixed with an alkali solution of 4% by dry weight of sodium hydroxide, and the slurry is heated and heated by steam. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% of the absolute dry pulp. The inlet temperature is 95 ° C, the pressure is 0.9 Mpa, and the residence time is 75 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 100 ° C at the top of the column and a pressure of 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,800 m, a tearing degree of 250 mN, and a whiteness of 40<3⁄4 ISO. The folding resistance is 60 times and the beating degree is 36° SR.

The above unbleached pulp was further bleached. Chlorination: The amount of chlorine used is 2.5-3% of the dry pulp, the concentration of the pulp is 3-3.5%, the temperature of bleaching is 40 ° C, and the bleaching time is 45 minutes. The conditions for alkali treatment are: adding sodium hydroxide The amount of dry pulp is 4%, the concentration of pulp is 12%, the bleaching temperature is 55 ° C, and the time is 150 minutes; hypochlorite bleaching: sodium hypochlorite is added in an amount of 4% of dry pulp, bleached The temperature was 30 ° C and the bleaching time was 100 minutes. A high quality grass pulp with a whiteness of 82% ISO, a crack length of 6,500 meters, a folding endurance of 45 times and a tearing degree of 220 mN can be obtained.

Example 2

The straw raw material prepared according to the conventional dry method is charged into the cooking pot, and the cooking liquid is added to the cooking pot. The ammonium sulfite is added in an amount of 13% of the dry raw material, and the liquid ratio is 1:4, the first heating The temperature was raised to 120 °C, the temperature was kept at a small steam for 65 minutes, the temperature was raised to 168 °C by secondary heating, and the temperature was raised and kept for 145 minutes. The hardness of the high-hardness pulp obtained after cooking is 16 equivalent to the Kappa price of 23, the beating degree is 24° SR, and then the slurry is squeezed by a double-screw extruder, and the slurry concentration is 10% before the slurry is squeezed. Thereafter, the concentration of the slurry was 26%, and the mixture was washed in a pressure washer with a black liquor having a temperature of 75 ° C and a concentration of 5 ° Be ' _P H8-8.3. After washing, the fiber separator was used for dissolving, and after dissolving, the high-density slurry having a concentration of 10% was adjusted, and then the slurry was heated to 70 ° C by a screw conveyor and transferred to a medium-thick slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 32 kg per ton of pulp and the alkali content of the alkali solution of 3.5% of the dry pulp by sodium hydroxide before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% of the absolute dry pulp. The inlet temperature is 90 °C, the pressure is l.lMpa, and the residence time is 85 minutes. The slurry was allowed to undergo a sufficient delignification reaction at a temperature of 100 ° C at the top of the column and a pressure of 0.2 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6000 m, a tear degree of 230 mN, and a whiteness of 353⁄4>ISO. The folding resistance is 90 times and the beating degree is 32° SR.

The above unbleached pulp is further bleached, and hydrogen peroxide is bleached. The amount of hydrogen peroxide added is 4% of the absolute dry pulp, the concentration of the slurry is 10%, the pH is 11, and the amount of the chelating agent is the absolute dry pulp amount. 0.2%, the magnesium sulfate protecting agent is used in an amount of 0.4% of the absolute dry pulp, the bleaching temperature is 95 ° C, and the bleaching time is 130 minutes. After bleaching, the whiteness is 55 % ISO. The high-quality straw pulp with a length of 5,500 m, a folding resistance of 35 times and a tearing degree of 280 mN.

Example 3

The cotton stalk raw material prepared according to the conventional dry method is charged into the steaming ball, and the cooking liquid is added to the steaming ball. The ammonium sulfite is added in an amount of 11% of the absolute dry material amount, and the liquid ratio is 1:2, the first heating The temperature was raised to 130 ° C, the temperature was kept for 30 minutes, and the temperature was raised to 173 ° C. The temperature was raised and kept for 140 minutes. Cooking to obtain a high-hardness pulp with a hardness of 19 equivalent to the Kappa price of 28, a beating degree of 16.3 ° SR, and then a 10% concentration of a single-screw extruder for the extraction of black liquor in the prior art is squeezed and squeezed. After the slurry, a high-durability slurry having a concentration of 32% was obtained, and the black liquor having a temperature of 70 ° C and a concentration of 6.2 ° Be ' and pH 8 - 8.3 was diluted to 2.5%, and then sent to a vacuum washer for washing. After washing, the slurry was disintegrated by a disc grinder, and after the slurried slurry was adjusted to a concentration of 13%, the slurry was heated to 70 ° C by a screw conveyor and sent to a medium consistency slurry tube. The slurry is first subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 38 kg per ton of pulp and the alkali solution of 3% by weight of sodium hydroxide in the pipeline before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount added is 0.8% by weight of the absolute dry pulp. The inlet temperature is 98 ° C, the pressure is 1.05 Mpa, and the residence time is 85 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 102 ° C at the top of the column and a pressure of 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 7,500 m, a tearing degree of 240 mN, and a whiteness of 45% ISO. The folding resistance is 70 times and the beating degree is 34° SR.

The above unbleached pulp is further subjected to bleaching treatment. Chlorination: The amount of chlorine used is 2.5-3% of the dry pulp, the concentration of the pulp is 3-3.5%, the bleaching temperature is 45 ° C, the bleaching time is 45-60 minutes; the conditions of the alkali treatment are: adding hydrogen The amount of sodium oxide is 4% of dry pulp, the concentration of pulp is 12%, the bleaching temperature is 65 ° C, and the time is 120 minutes; hypochlorite bleaching: sodium hypochlorite is added in an amount of 2% of the dry pulp. The bleaching temperature was 35 ° C and the bleaching time was 150 minutes. A high quality cotton stalk slurry with a whiteness of 80% ISO, a crack length of 7,000 meters, a folding resistance of 50 times and a tearing degree of 180 mN can be obtained.

Example 4

The reeds prepared according to the conventional dry method are charged into the steaming ball, and the cooking agent is added to the batch spherical digester. The ammonium sulfite is added in an amount of 10% of the dry raw material, and the amount of sodium hydroxide is the amount of the dry raw material. 8%, liquid ratio 1: 3, the first heating to 140 ° C, heat and small steam for 45 minutes, secondary heating to 175 ° C, heating and holding 155 minutes. After cooking, a high-hardness pulp with a hardness of 28 and a beating degree of 10° SR is obtained, and then the high-hardness pulp is sent to a conventional single-screw extruder for extracting black liquor in the prior art for slurrying, and the concentration is obtained after the slurry is squeezed. For 26% high hardness pulp, the slurry from the extruder is diluted with dilute black liquor to a concentration of 2.5-3.0%, sent to the sieve for coarse slurry screening, and the sieve loss is 0.2%. The high-concentration cleaner removes impurities and loses 0.1%, and then the slurry obtained after the slag is removed into a horizontal belt washer. The washing, the slurry concentration at the time of washing was 2.0%, the concentration of the pulp coming out of the washer was 9%, and the black liquor having a concentration of 4 ° Be ' and pH 8 - 8.3 was washed in a horizontal belt washer. During the washing process, it was kept at 68-70 ° C, and then conveyed to the disintegrator for dissolving. The degree of beating of the reed pulp before the disintegration was 24 ° SR, and the degree of beating of the reed pulp after the disintegration was 27. SR, after adjusting to 10%, the slurry was heated to 80 ° C by a screw conveyor and transferred to a medium consistency slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 30 kg per ton of pulp and the amount of alkali in the pipeline before the entry into the reaction tower, and the amount of alkali is mixed with 4% alkali solution of sodium hydroxide, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the absolute dry pulp. The inlet temperature is 102 ° C, the pressure is 1.2 Mpa, and the residence time is 90 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 105 ° C at the top of the column and a pressure of 0.5 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 7,500 m, a tearing degree of 260 mN, and a whiteness of 453⁄4>ISO. The folding resistance is 60 times and the beating degree is 36° SR.

The above unbleached pulp was subjected to a CEP three-stage bleaching treatment. Chlorination: The amount of chlorine used is 3% of the dry pulp, the concentration of the pulp is 3%, the bleaching temperature is 38 ° C, and the bleaching time is 60 minutes. The conditions for the alkali treatment are: the amount of sodium hydroxide added is absolutely The dry pulp volume is 2-4%, the pulp concentration is 10-12%, the bleaching temperature is 60 ° C, and the time is 120 minutes; hydrogen peroxide bleaching: the hydrogen peroxide is added in an amount of 5% of the absolute dry pulp, pulp The concentration was 10%, the pH was 11.8, the chelating agent was 0.2%, the protective agent was 0.4% magnesium sulfate, the bleaching temperature was 9, and the bleaching time was 120 minutes. The bleaching chemical pulp has a whiteness of 78% ISO, a crack length of 8000 m, a folding endurance of 70 times, and a tearing degree of 250 mN.

Example 5

The wheat straw prepared according to the conventional dry method is charged into the cooking pot, and the cooking liquid is added to the cooking pot, wherein the amount of alkali is 15% of the amount of the dry raw material in terms of sodium hydroxide, and the amount of the raw material is absolutely dry. 0.5% of the amount of raw materials. , liquid ratio 1: 2, the first heating to 140 ° C, heat and small steam for 30 minutes, secondary heating to 160 ° C, heating and holding time of 160 minutes. After cooking, a high-hardness pulp with a hardness of 20 equivalent to a Kappa price of 32 is obtained, and the degree of beating is 13.8° SR. Then, the high-hardness pulp is sent to a conventional single-screw extruder for extracting black liquor in the prior art for sintering. The slurry from the extruder is diluted with a dilute black liquor having a temperature of 75 ° C and a concentration of 6.2 ° Be ' and pH 8-8.3 to a concentration of 3.03⁄4>, sent to a sieve for coarse filtration, and jumped. The sieve loss was 0.6%, and the impurities were removed by a high-concentration cleaner to lose 0.3%. The slurry obtained after the removal was passed to a vacuum washer for washing. The concentration of the pulp from the washer is 12%, and it is kept at 70-80 °C during the washing process, and then sent to the disc grinding and dispersing machine for dissolving. The degree of beating of the straw pulp before the disintegration is 32° SR, after the disintegration The straw pulp has a beating degree of 33 ° SR. After the concentration is increased by 10%, the slurry is heated to 68 ° C by a screw conveyor and transferred to a medium consistency slurry tube. The slurry is firstly subjected to quenching and tempering treatment in the middle thick slurry pipe to remove the air in the slurry to be fluidized, and then transferred to the oxygen de-wooding by a centrifugal medium-concentration pump. Reaction tower. The slurry is mixed with the added oxygen of 35 kg per ton of pulp and the amount of alkali in the pipeline before the entering the reaction tower, and the amount of alkali is mixed with 4% alkali solution of sodium hydroxide, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the absolute dry pulp. The inlet temperature is 100 ° C, the pressure is l. lMpa, and the residence time is 90 minutes. The slurry was allowed to carry out a sufficient delignification reaction at a temperature of 104 ° C and a pressure of 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 5000 m, a tearing degree of 270 mN, and a whiteness of 38<3⁄4 ISO. The folding resistance is 65 times and the beating degree is 35 ° SR.

The above unbleached pulp is further subjected to bleaching treatment. The bleaching includes: chlorination, alkali treatment and hydrogen peroxide bleaching, chlorination: the amount of chlorine used is 2.5% of the dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 40 ° C, and the bleaching time is 60 minutes; the conditions of the alkali treatment are: the amount of sodium hydroxide added is 4% of dry pulp, the concentration of pulp is 10%, the bleaching temperature is 65 ° C, and the time is 120 minutes; the hydrogen peroxide bleaching includes : The amount of hydrogen peroxide added is 5% of the absolute dry pulp, the concentration of the slurry is 10%, the pH is 11, the amount of the chelating agent is 0.2% of the dry pulp, and the amount of the magnesium sulfate protectant is the dry pulp. 0.4%, bleaching temperature is 99 °C, bleaching time is 120 minutes. The obtained bleached chemical pulp had a whiteness of 75% ISO, a crack length of 4500 m, a folding endurance of 30 times, and a tearing degree of 200 mN.

Example 6

After the prepared reed and the Luzhu are mixed at a mass ratio of 1:4, they are put into a spherical digester, and the cooking liquid is added to the spherical digester, and the amount of the alkali is used to determine the amount of the dry raw material. 9 % of the amount of niobium added is 0.8% of the amount of dry raw materials. , liquid ratio 1: 4, the first heating to 135 °C, heat and small steam for 60 minutes, secondary heating to 165 °C, heating and holding time of 130 minutes. After cooking, a high-hardness pulp having a hardness of 20 equivalent to a Kappa price of 30 is obtained, and the degree of beating is 14. 5 ° SR, and the concentration of the high-hardness pulp is adjusted to 14%, and then the high-hardness slurry is sent to the prior art for extracting black liquor. 5-3. 0%, sent to the sieve for coarse slurry screening, skipping. The slurry from the extruder is diluted with dilute black liquor to a concentration of 2. 5-3. 0%. The sieve loss is 0.6%, and the impurities are removed by a high-concentration cleaner to lose 0.3%, and then washed by a conventional washing method, and then the slurry is heated to 78 ° C by a screw conveyor and conveyed to medium concentration. Slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen and the alkali content of the 35 kg per ton of the slurry in the pipeline before the flow into the reaction tower is 2.5% of the alkaline solution in terms of sodium hydroxide, and in the pipeline. The slurry was heated to heat by steaming. After that, the slurry is thoroughly mixed in the mixer and then enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the dry pulp. The inlet temperature is 100 ° C, the pressure is 1. 2 Mpa, and the residence time is 80 minutes. 6MPa。 The pulp was allowed to carry out a sufficient delignification reaction, the temperature was maintained at 0. 6MPa. After the treatment is completed, the slurry is sprayed into a slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 5800 meters, a tearing degree of 260N, and a whiteness of 25% ISO, 50 times of folding resistance, and a beating degree of 35 ° SR.

The above unbleached pulp is further subjected to bleaching treatment. Sodium hypochlorite was added in an amount of 2% of the dry pulp, the bleaching temperature was 35 V, and the bleaching time was 120 minutes. The bleaching chemical pulp has a whiteness of 45% IS0, a crack length of 5500 m, a folding endurance of 40 times, and a tearing degree of 260 mN.

Example 7

The bagasse after the preparation of the bagasse is charged into the cooking pot, and the cooking liquid is added to the cooking pot, and the alkalitity is the ratio of the degree of vulcanization of the dry raw material to the liquid ratio of 1:4, the first heating is heated. At 110 ° C, heat and small steam at this temperature for 30 minutes, and heat up for 30 minutes to a temperature of 165 ° C for 90 minutes. After cooking, a high-hardness pulp having a hardness of 24 equivalent to a Kappa price of 41 is obtained, and the degree of beating is 10° SR, and then the high-hardness pulp is sent to a conventional single-screw extruder for extracting black liquor in the prior art for sintering. After the squeezing, a high-concentration slurry having a concentration of 28% was obtained, and the black liquor having a concentration of 6.2 ° Be ' and pH 8.3 was washed in a horizontal belt washer. The resulting slurry after washing was transferred to a disc grinder for disintegration, and then the slurry was heated to 70 ° C by a screw conveyor and transferred to a medium consistency tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 20 kg per ton of pulp and the alkali content in the pipeline before entering the reaction tower is 4% alkali solution by weight of sodium hydroxide, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1.3% by weight of the absolute dry pulp. The inlet temperature is 95 ° C, the pressure is 0.95 MPa, and the residence time is 70 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 101 ° C at the top of the column and a pressure of 0.3 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,800 m, a tearing degree of 230 mN, and a whiteness of 60<3⁄4 ISO. The folding resistance is 55 times and the beating degree is 33 ° SR.

The above unbleached pulp was further bleached. Chlorination: The amount of chlorine used is 3% of the dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 45 ° C, and the bleaching time is 55 minutes. The condition of the alkali treatment is: the amount of sodium hydroxide added is absolutely 2% dry pulp, 10% pulp, bleaching temperature 63 ° C, time 120 minutes; hypochlorite bleaching: sodium hypochlorite is added in 4% dry pulp, bleaching temperature is 35 ° C, bleaching time is 150 minutes. The bleaching chemical pulp has a whiteness of 82% ISO, a crack length of 6,500 meters, a folding endurance of 45 times, and a tearing degree of 190 mN.

Example 8

The prepared cotton rod is put into the cooking pot, and the cooking agent is added to the cooking pot. The alkali amount is 11% of the absolute dry material amount, the sulfurization degree is 5%, and the liquid ratio is 1:2. The first heating was carried out to 140 ° C, the heat preservation and small steaming were carried out for 65 minutes, the secondary heating was carried out to 165 ° C, and the temperature was raised and kept for 100 minutes. After cooking, a high-hardness pulp with a hardness of 25 equivalent to a Kappa price of 43 is obtained, and the degree of beating is 10° SR. Then, the high-hardness pulp is sent to a single-screw extruder for extracting black liquor in the prior art for sintering, and the slurry is squeezed. After that, a high-durability slurry with a concentration of 32% is obtained, and a black liquor having a temperature of 80 ° C and a portion of the same temperature are used. The clean water is washed in a horizontal belt washer.

The slurry concentration after washing was adjusted to 12%, and after dissolving by a disc refiner, the slurry was heated to 65 ° C by a screw conveyor and transferred to a medium consistency slurry tube. The slurry is first tempered in the middle thick slurry tube to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 20 kg per ton of pulp and the alkali content of the alkali solution of 3.5% by weight of sodium hydroxide in the pipeline before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1.5% by weight of the absolute dry pulp. The inlet temperature is 90 ° C, the pressure is l.lMpa, and the residence time is 60 minutes. The slurry was allowed to carry out a sufficient delignification reaction, the temperature at the top of the column was 100 ° C, and the pressure was maintained at 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 5,700 meters, a tearing degree of 245 mN, and a whiteness of 30<3⁄4 ISO. The folding resistance is 60 times and the beating degree is 35° SR.

The above unbleached pulp was further bleached. The traditional CEH three-stage bleaching is used later, specifically: the chlorine content of the C section is 3% of the absolute dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 42 ° C, and the bleaching time is 45 minutes; The amount of sodium hydroxide is 3% of dry pulp, the concentration of pulp is 11%, the bleaching temperature is 50 ° C, and the time is 150 minutes; the amount of sodium H-sodium hypochlorite is 2.5% of the dry pulp, the temperature of bleaching At 30 ° C, the bleaching time is 150 minutes, and a high quality grass pulp with a whiteness of 75% ISO, a crack length of 5,500 m and a folding resistance of 55 times is obtained.

Example 9

The rice straw and wheat straw with a mass ratio of 1:4 are prepared and put into a cooking pot, and the cooking agent is added to the cooking pot. The alkali amount is 11% of the dry raw material by sodium hydroxide, and the degree of sulfurization is 5. %, liquid ratio 1: 4, the first heating to 110 ° C, heat and small steam for a total of 50 minutes, secondary heating to 168 ° C, heating and holding time 150 minutes. After cooking, the hardness is 19, which is equivalent to the high hardness pulp of Kappa price 29. The degree of beating is 16° SR, and then sent to the conventional single-screw extruder for extracting black liquor to carry out the slurry. The concentration before the slurry is 12%, the concentration of the slurry from the extruder is 15%, diluted with dilute black liquor to the concentration of the slurry to 3.0%, sent to the sieve for coarse slurry screening, the sieve loss is 0.2%, and the high concentration The slag remover removes impurities and loses 0.1%, and then the slurry obtained after the slag is removed into a vacuum washer. The diluted black liquor at a temperature of about 75 ° C and a portion of the same temperature are washed, and the slurry concentration during washing is 3.0%. The concentration of the slurry coming out of the washer is 10%, the temperature during the washing process is about 72 ° C, and then it is sent to the high-frequency disintegrator for dissolving, and the slurry is then subjected to quenching and tempering through the middle thick slurry tube. The air in the slurry is removed to make it fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 25 kg per ton of pulp and the alkali solution of 2% by weight of sodium hydroxide on the basis of sodium hydroxide before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 0.6% of the weight of the dry pulp. The inlet temperature is 99 ° C, the pressure is l.lMPa, and the residence rate is 70. The slurry was allowed to undergo a sufficient delignification reaction at a temperature of 104 ° C and a pressure of 0.38 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and then washed to obtain a The unbleached pulp has a crack length of 6,500 meters, a tearing degree of 280 mN, a whiteness of 40<3⁄4 ISO, a folding endurance of 65 times, and a beating degree of 35 ° SR.

The above unbleached pulp was then bleached. The bleaching is specifically as follows: the chlorine content of the C stage is 3% of the absolute dry pulp, the concentration of the pulp is 3%, the bleaching temperature is 45 ° C, the bleaching time is 50 minutes; the amount of sodium hydroxide added in the E section is The dry pulp volume is 3%, the pulp concentration is 12%, the bleaching temperature is 60 ° C, and the time is 100 minutes. The H-sodium hypochlorite is added in an absolute dry pulp amount of 2.5%, and the bleaching temperature is 32 ° C. Bleaching. The time is 150 minutes, and the high-quality grass pulp with a whiteness of 78% ISO, a crack length of 6,300 meters, a folding resistance of 60 times, and a tearing degree of 270 mN can be obtained.

Example 10

Straw and wheat straw with a mass ratio of 1:3 were prepared. After the preparation, the rice straw was mixed and filled with hot black liquor at a temperature of 135 °C into a vertical cooking pot through a potter. The liquid ratio was 1:8. After closing the lid, add the cooking agent at a temperature of 145 °C to the cooking pot. The amount of alkali is 13% of the amount of dry raw material based on sodium hydroxide. The black liquor and air are discharged and raised to 0.6 MPa. The cooking liquid circulation pump and the tube heater of the cooking pot were turned on to heat the cooking liquid to 155 ° C, and the temperature was raised and kept for 160 minutes. The hot black liquor is replaced with a dilute black liquor, and sent to a hot black liquor tank. After cooking, a high-hardness pulp having a hardness of 19 equivalent to a Kappa number of 29 is obtained, and the degree of beating is 16° SR, and then sent to a conventional black liquor for extraction. The variable-diameter single-screw extruder is used for squeezing. The concentration before squeezing is 8%, the concentration of the slurry coming out from the squeezing machine is 22%, and then diluted with dilute black liquor to the concentration of the pulp to 3.0%. To the sieve for coarse slurry screening, the sieve loss is 0.2%, and the impurities are removed by the high concentration cleaner to lose 0.1%. Then the slurry obtained after the slag is removed into the vacuum washer using a temperature of 75 ° C. The black liquor and part of the water at the same temperature are washed, the concentration of the slurry from the washer is 9%, the temperature during the washing process is about 75 ° C, and then it is sent to the high-frequency disintegrator for dissolving, and then the pulp is re-dissolved. The medium in the slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then transferred to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 30 kg per ton of pulp and the alkali content of the alkali solution of 3% by weight of sodium hydroxide in the pipeline before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1.3% by weight of the absolute dry pulp. The inlet temperature is 95 ° C, the pressure is 0.9 MPa, and the residence time is 65 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 103 ° C at the top of the column and a pressure of 0.35 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained, and after washing, the unbleached pulp is obtained, and the unbleached pulp has a crack length of 6,600 meters. The tearing degree is 270 mN, the whiteness is 40<3⁄4ISO, the folding resistance is 65 times, and the beating degree is 35 ° SR.

The above unbleached pulp was then bleached. The bleaching is specifically as follows: the amount of chlorine in the C section is 3% of the absolute dry pulp, the concentration of the pulp is 3%, the temperature of the bleaching is 40 ° C, and the bleaching time is 50 minutes; the amount of sodium hydroxide added in the E section is The dry pulp volume is 3%, the pulp concentration is 12%, the bleaching temperature is 58 ° C, and the time is 100 minutes; the P-stage hydrogen peroxide is added in an amount of 4% of the absolute dry pulp, the pulp concentration is 10%, and the pulp The pH value is controlled at 11.5, the chelating agent is added in an amount of 0.2% absolute dry pulp, the protective agent is 0.4% magnesium sulfate, the bleaching temperature is 95 ° C, and the bleaching time is 150 minutes, and the whiteness is 78%. ISO, The high-quality grass pulp with a length of 6,300 meters, a folding resistance of 60 times and a tearing degree of 270 mN.

Example 11

The straw raw material is prepared into a ball type digester, and the cooking agent is added to the ball type digester, and the amount of the dry raw material is 15% by the amount of alkali, and the liquid ratio is 1:3. It is 0.6% of the dry raw material amount, and the first heating is heated to 120 ° C. The temperature is kept at this temperature for 40 minutes, and the secondary heating is heated to a temperature of 168 ° C. The temperature is raised and kept for 150 minutes. After cooking, a high-hardness pulp with a hardness of 18 equivalent to the Kappa number of 27 is obtained, and the degree of beating is 18.4° SR, which is then sent to a conventional single-screw extruder for extracting black liquor for slurrying. The slurry concentration before extrusion is 8%, the concentration of the slurry from the extruder is 22%, diluted with dilute black liquor to a concentration of 2.5%, sent to the sieve for coarse slurry screening, the sieve loss is 0.2%, and the high concentration The slag remover removes impurities and loses 0.1%. The slurry obtained after the slag removal is then washed into a horizontal belt washer for a slurry concentration of 3.0%, and the slurry concentration from the washer is 9%. During the washing process, it is kept at 65-75 °C, and then transported to a high-frequency disintegrator for dissolving. After concentration, the slurry is heated to 65 ° C by a screw conveyor and transferred to a medium-concentration slurry tube. The slurry is first subjected to quenching and tempering treatment in the middle thick slurry tube to remove the air in the slurry to be fluidized, and then transferred to the oxygen delignification reaction column through a centrifugal medium-concentration pump. The slurry in the pipeline before entering the reaction tower with the added oxygen of 35 kg per ton of pulp and the alkali content is 2% of the alkaline solution of sodium hydroxide, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the absolute dry pulp. The inlet temperature is 102 ° C, the pressure is 1.12 MPa, and the residence time is 70 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 104 ° C at the top of the column and a pressure of 0.5 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,100 m, a tearing degree of 255 mN, and a whiteness of 40<3⁄4 ISO. The folding resistance is 40 times and the beating degree is 32° SR.

The above unbleached pulp was further bleached. The bleaching is a traditional CEH three-stage bleaching, specifically: the chlorine content of the C section is 4% of the absolute dry pulp, the concentration of the pulp is 3.2%, the bleaching temperature is 45 ° C, and the bleaching time is 45 minutes; The amount of sodium hydroxide added to the E section is 3% of the absolute dry pulp, the concentration of the slurry is 12%, the bleaching temperature is 57 ° C, and the time is 120 minutes; the amount of the sodium segment of sodium hypochlorite is 2% of the absolute dry pulp amount. The bleaching temperature is 30 ° C, and the bleaching time is 150 minutes, and a high quality grass pulp having a whiteness of 76% ISO, a crack length of 5,600 m, a folding resistance of 35 times, and a tearing degree of 235 mN can be obtained.

Example 12

The Arundo donax is prepared, and the hot black liquor with a temperature of 120 °C is charged into the cooking pot through the potter. When the pan is full, the lid is closed, and the cooking pot is replenished at a temperature of 130 ° C, and discharged at the same time. The air in the pot is boosted to 0.45 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 152 ° C, and the temperature is raised, kept and replaced for 180 minutes. Finally, the slurry is sent to the slurry. The cooking pot, wherein the amount of sodium hydroxide is 9% by weight of the dry raw material, the amount of sodium sulfite is 4% by weight of the dry raw material, and the amount of hydrazine is 0.04 by weight of the dry raw material. %, the liquid ratio is 1:10. After cooking, a high-hardness pulp with a hardness of 25 equivalent to a Kappa price of 45 is obtained, and the degree of beating is 10° SR. Then, the high-hardness pulp is sent to a conventional single-screw extruder for extracting black liquor in the prior art for sintering. After the slurry is squeezed, a high-concentration pulp with a concentration of 20% is obtained. After dilution, it is sent to a sieve for coarse slurry screening. The sieve loss is 0.2%, and the impurities are removed by a high-concentration cleaner to lose 0.1%. The slurry obtained after the slag is washed into a horizontal belt washer, and the slurry is washed. The concentration is 3.0%, the concentration of the pulp from the washer is 9%, and the washing process is maintained at 65-75 °C. After washing, it is dispelled by a high-frequency disintegrator, and then adjusted to 8% to be heated by a screw conveyor. The slurry was passed to 80 ° C and transferred to a medium consistency slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 40 kg per ton of pulp and the amount of alkali in the pipeline before the entering the reaction tower, and the amount of alkali is mixed with 4% alkali solution of sodium hydroxide, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, the amount of which is 0.8% by weight of the absolute dry pulp, the inlet temperature is 98 ° C, the pressure is 1.2 Mpa, and the residence time is 85 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 10 rC at the top of the column and a pressure of 0.35 MPa. After the treatment is completed, the slurry is sprayed into a slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,400 meters, a tearing degree of 260 mN, a whiteness of 40<3⁄4 ISO, a folding endurance of 70 times, and a beating degree of 35 ° SR.

The above-mentioned unbleached pulp is further subjected to conventional CEH three-stage bleaching, specifically: the chlorine content of the C section is 5% of the absolute dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 43 ° C, and the bleaching time is 50. Minutes; the amount of sodium hydroxide added to the E section is 2% of the absolute dry pulp, the concentration of the slurry is 10%, the bleaching temperature is 55 ° C, and the time is 150 minutes; the amount of sodium H hypochlorite added is 2.5 of the absolute dry pulp amount. %, the bleaching temperature is 32 ° C, the bleaching time is 100 minutes, and the high-quality grass pulp with a whiteness of 80% ISO, a crack length of 5,500 m, a folding resistance of 50 times and a tearing degree of 275 mN can be obtained.

Example 13

The wheat straw is prepared according to a conventional method, and the hot black liquor having a temperature of 14 CTC is charged into the cooking pot through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a cooking temperature of 16 CTC, and discharged into the pot. The air is boosted to 0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 165 ° C, and the temperature is raised, kept and replaced for 230 minutes. Finally, the slurry is sent to the spray pot by pumping. In the cooking agent, wherein the amount of sodium hydroxide is 17% by weight of the dry raw material, the amount of sodium sulfite is 8% by weight of the dry raw material, and the amount of cerium is 0.08% by weight of the dry raw material. The ratio is 1: 6. After cooking, the hardness is 22% potassium permanganate, which is equivalent to the high hardness pulp of Kappa price 35. The degree of beating is 12.2° SR, and then sent to the conventional single-screw extruder for extracting black liquor for extrusion. The concentration before the pulp is 12%, the concentration of the slurry coming out from the extruder is 25%, diluted with dilute black liquor to the concentration of the slurry to 3.0%, sent to the sieve for coarse slurry screening, and the sieve loss is 0.4%. The impurities are removed by a high-concentration separator to lose 0.1%, and the slurry obtained after the slag is removed into a horizontal belt washer to wash with a black liquor having a temperature of 75 ° C and a portion of water, and the slurry concentration during washing. 3.0%, the concentration of the pulp from the washer is 12%, the temperature during the washing process is about 70 ° C, and then it is sent to the high-frequency disintegrator for dissolving, after dissolving, the concentration is adjusted to 15% and then passed through the spiral. The conveyor heats the slurry to 70 ° C and delivers it to a medium consistency slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 30 kg per ton of pulp and the alkali solution of 4% of the dry pulp by sodium hydroxide before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 0.5% by weight of the absolute dry pulp. The inlet temperature is 95 ° C, the pressure is 0.9 Mpa, and the residence time is 90 minutes. The slurry can be subjected to sufficient delignification reaction, the temperature at the top of the column is 10 rC, the pressure is maintained at 0.25 MPa, and the lignin removal rate during the oxygen delignification process is 86. %. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and the hardness (potassium permanganate value) of the slurry is lowered to 14, which is equivalent to a Kappa price of 19.5. The diluted slurry is then pumped into a two-stage vacuum washer for washing. The unbleached pulp has a crack length of 5,700 meters, a tearing degree of 250 mN, a whiteness of 45<3⁄4 ISO, a folding endurance of 85 times, and a beating degree of 35 ° SR.

The above-mentioned unbleached pulp is subjected to conventional CEH three-stage bleaching, specifically: the chlorine content in the C section is 5% of the absolute dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 38 ° C, and the bleaching time is 50 minutes. The amount of sodium hydroxide added to the E section is 2% of the absolute dry pulp, the concentration of the pulp is 10%, the bleaching temperature is 60 ° C, and the time is 150 minutes; the amount of the sodium segment of sodium hypochlorite is 2.5% of the dry pulp amount. The bleaching temperature is 32 ° C, and the bleaching time is 100 minutes. The high quality grass pulp with a whiteness of 73 % ISO, a crack length of 5,500 m and a folding resistance of 70 times can be obtained.

Example 14

The straw, wheat straw and reeds with a mass ratio of 1: 1 : 1 are prepared by conventional dry preparation, and then the hot black liquor with a temperature of 120 ° C is charged into the cooking pot through the potter, and is closed when the pot is full. The lid is filled with the cooking liquid at a temperature of 140 ° C in the cooking pot, and the air in the pot is discharged and raised to 0.45 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 155 °. C, heating, holding and replacing for 200 minutes, finally pumping the slurry to the spraying pot; in the cooking agent, wherein the amount of alkali is 8%, the amount of the dry raw material is 8%, and the liquid ratio is 1 : 6, the degree of sulphurization is 9%; before spraying, black liquor is added to the steaming ball for dilution, while the pressure is maintained at 0.65 MPa for spraying. The hardness of the pulp is 23 potassium permanganate and the degree of beating is 21.5. ° SR, the residual alkali concentration in the black liquor is 12g / l. The yield of the prepared high hardness pulp was 58%. It is sent to the conventional single-screw extruder for extracting black liquor for slurrying. The concentration of the slurry from the extruder is 35%, diluted with dilute black liquor to the concentration of the slurry to 3.0%, and sent to the jump. Screening for coarse slurry screening, the sieve loss is 0.2%, and the impurities are removed by a high-concentration cleaner to lose 0.1%. The slurry obtained after the slag is removed into a horizontal belt washer for washing, and the slurry concentration during washing. 3.0%, the concentration of the pulp coming out of the washer is 9%, and it is kept at 70-75 °C during the washing process, and then transported to the high-frequency disintegrator for dissolving, and the slurry passes through the middle thick slurry pipe first. The quenching and tempering treatment removes the air in the slurry to make it fluidized, and then transports it to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 20 kg per ton of pulp and the alkali solution of 4% by weight of sodium hydroxide on the basis of sodium hydroxide before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1.5% by weight of the dry pulp. The inlet temperature is 92 ° C, the pressure is 1.0 MPa, and the residence time is 90 minutes. The slurry was allowed to carry out a sufficient delignification reaction, the temperature at the top of the column was 102 ° C, and the pressure was maintained at 0.3 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 5000 m, a tearing degree of 230 mN, and a whiteness of 43<3⁄4 ISO. The folding resistance is 65 times and the beating degree is 35 ° SR.

The above-mentioned unbleached pulp is subjected to conventional CEH three-stage bleaching, specifically: the chlorine content of the C section is 5% of the absolute dry pulp, the concentration of the pulp is 3.5%, the bleaching temperature is 40 ° C, and the bleaching time is 50 minutes. The amount of sodium hydroxide added to the E section is 2% of the absolute dry pulp, the concentration of the slurry is 10%, the bleaching temperature is 55 ° C, and the time is 150 minutes; the amount of the sodium segment of sodium hypochlorite is 2.5% of the dry pulp amount. The bleaching temperature is 32 ° C, and the bleaching time is 100 minutes. The high-quality grass pulp with a whiteness of 65% ISO, a crack length of 4,500 m, a folding resistance of 35 times and a tearing degree of 220 mN can be obtained.

Example 15 After routine dry preparation, the wheat straw is filled into the cooking pot through a potter with a hot black liquor at a temperature of 120 ° C. When the pan is full, the lid is closed, and the cooking pot is replenished with a cooking temperature of 16 CTC, and discharged at the same time. The air in the pot is boosted to 0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 168 ° C, and the temperature is raised, kept warmed and replaced for 250 minutes. Finally, the slurry is sent to the spray by the pump. Putting the pot; wherein the cooking agent, wherein the amount of alkali is sodium hydroxide, the amount of the dry raw material is 13%, the liquid ratio is 1:10, and the degree of sulfurization is 5%; before spraying, adding to the steaming ball The black liquor was diluted while the pressure was maintained at 0.65 MPa for discharge. At this time, the hardness of the slurry was such that the potassium permanganate value of 18 was equivalent to the Kappa number of 28, and the residual alkali concentration in the black liquor was 12 g/l. The yield of the prepared high hardness pulp was 58%.

The high-hardness pulp obtained after the cooking is first squeezed by a single-screw extruder, and the black liquor is extruded through the slurry, and the impurities in the black liquor are also discharged together with the black liquor, and then the obtained slurry is washed with pressure. Machine washing, after washing, the high-hardness pulp is diluted, diluted to a concentration of 12%, and then sent to a high-frequency disintegrator for dissolving and then oxygen delignification, the oxygen addition amount is 4% of the absolute dry pulp amount The amount of alkali is 3% of the dry pulp by sodium hydroxide, 0.8% magnesium sulfate is added as a protective agent, and 10 MPa steam is heated in the pipeline to 100 ° C, and uniformly mixed by a mixer. After entering the oxygen delignification reaction tower, after 80 minutes of oxygen delignification reaction, the unbleached pulp is obtained after washing, and the unbleached pulp has a crack length of 5600 meters and a tearing degree of 270 mN. The whiteness is 403⁄4>ISO, the folding resistance is 65 times, and the beating degree is 35 ° SR.

The above unbleached pulp is further bleached, and the chlorination-alkali treatment-hypochlorite bleaching is carried out under the following conditions: the chlorine content is 3% of the absolute dry pulp, the pulp concentration is 3.5%, and the bleaching temperature is 42°. C, the bleaching time is 45 minutes; the alkali treatment conditions are as follows: the alkali amount is 2% of the absolute dry pulp, the slurry concentration is 12%, the bleaching temperature is 55 ° C, and the time is 100 minutes. Hypochlorite bleaching: Sodium hypochlorite is added in an amount of 3% of the absolute dry pulp, the bleaching temperature is 35 ° C, and the bleaching time is 100 minutes. After the end of the bleaching, a bleaching chemical slurry having a whiteness of 68 < 3⁄4 ISO, a crack length of 5,300 m, a folding resistance of 50 times, and a tearing degree of 245 mN was obtained.

Example 16

After the cotton stalk raw material is prepared, the raw material is charged into the cooking pot through a potter at a temperature of 140 ° C. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 16 CTC. At the same time, the air in the pot is discharged and boosted to 0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the temperature of the cooking liquid to 165 ° C, and the temperature is raised, kept and replaced for 180 minutes, and finally pumped. The slurry is sent to the spraying pot; in the cooking agent, the alkali amount is 17% of the absolute dry material, and the liquid ratio is 1:6, and the amount of the cerium is 0.5% of the dry raw material amount. . . Before the spraying, black liquor is added to the steaming ball for dilution, and the pressure is maintained at 0.75 MPa for spraying. The hardness of the pulp is the potassium permanganate value of 18, which is equivalent to the Kappa price of 26, the beating degree of 19.8 ° SR, cooking. At the end point, the _P H value was 12, and the yield of the high-hardness pulp was 603⁄4>. The high-hardness pulp obtained after the cooking is first squeezed by a single-screw extruder, and the black liquor is extruded through the slurry, and the impurities in the black liquor are also discharged together with the black liquor, and then the obtained slurry is washed with pressure. Machine washing, after washing, the high-hardness pulp is diluted, diluted to a concentration of 8-12%, and then sent to a disc grinding and dispersing machine for decontamination and bleaching, first oxygen delignification, the oxygen addition amount is per ton The dry pulp volume is 20kg, and the alkali amount is 3% of the absolute dry pulp by sodium hydroxide. The 1.2% magnesium sulfate salt of the dry pulp was used as a protective agent. The temperature of the oxygen delignification was 90 ° C, the temperature was maintained for 98 minutes, the temperature at the top of the column was 98 ° C, and the pressure was maintained at 0.3 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,700 m, a tearing degree of 270 mN, and a whiteness of 44<3⁄4 ISO. The folding resistance is 65 times and the beating degree is 36° SR.

The above unbleached pulp is bleached, and the chlorination-alkali treatment-hypochlorite bleaching is carried out under the following conditions: the chlorine content is 2.5% of the dry pulp, the concentration of the pulp is 3.5%, and the bleaching temperature is 45 °C. The bleaching time is 55 minutes; the alkali treatment conditions are as follows: the alkali amount is 4% of the absolute dry pulp, the slurry concentration is 10%, the bleaching temperature is 65 ° C, and the time is 150 minutes; Chlorate bleaching: Sodium hypochlorite is added in an amount of 4% of the dry pulp, the bleaching temperature is 35 ° C, and the bleaching time is 150 minutes. After the bleaching, a bleaching chemical slurry having a whiteness of 82 < 3⁄4 ISO, a crack length of 6,500 m, a folding endurance of 45 times, and a tearing degree of 260 mN was obtained.

Example 17

After the wheat straw raw material is prepared, the raw material is charged into the cooking pot through a potter at a temperature of 120 ° C. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 13 CTC. At the same time, the air in the pot is discharged and boosted to 0.4 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 147 ° C, and the temperature is raised, kept and replaced for 180 minutes. Finally, the slurry is pumped. It is sent to the spraying pot; in the cooking agent, the amount of alkali is 9% by weight of the dry raw material, and the liquid ratio is 1:9, and the amount of cerium added is 0.8% of the amount of the dry raw material. . After cooking, the hardness of the wheat straw pulp is 20 potassium permanganate, and the degree of beating is 22° SR. The wheat straw pulp is pumped to a screw extruder for slurrying, and the extruded black liquor is evaporated as a water reducing agent. The concentration of the pulp increased from 8% before extrusion to 30%. At this time, the pH of the slurry was 8, the concentration of the black liquor to be extruded was 11 o Be (20 ° C), and the concentration of residual alkali was 8 g/L. The obtained slurry was diluted with a diluted black liquor at 75 ° C to a concentration of 2.5%, washed with a vacuum washer, and concentrated with 10%. The wet weight of the washed pulp is 1.8g, the washing degree of the washing is 350ppm, and it is sent to the high-frequency disintegrator for dissolving. The degree of beating of the wheat straw pulp before the disintegration is 24° SR, and the pulp of the wheat straw pulp after the disintegration is beaten. The degree is 26° SR, the temperature of the wheat straw pulp before the disintegration is 60 °C, and the temperature of the wheat straw pulp after the disintegration is 65 °C. The concentrated black liquor obtained from the degraded wheat straw pulp can be used for the subsequent evaporation as a water reducing agent, and the slurry is then subjected to quenching and tempering in the middle thick slurry tube to remove the air in the slurry to be fluidized, and then centrifuged. The slurry pump is delivered to the oxygen delignification reaction column. The slurry is mixed with the added oxygen of 20 kg per ton of pulp and the alkali solution of 4% by weight of sodium hydroxide on the basis of sodium hydroxide before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 0.8% by weight of the dry pulp. The inlet temperature is 100 ° C, the pressure is 1.2 MPa, and the residence time is 60 minutes. The slurry was allowed to carry out a sufficient delignification reaction at a temperature of 103 ° C and a pressure of 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and then washed to obtain the unbleached pulp. The unbleached pulp has a crack length of 6,600 meters, a tearing degree of 230 mN, and a whiteness of 42< 3⁄4ISO, with a folding resistance of 40 times and a beating degree of 35 ° SR. Finally, the slurry is sent to the bleaching process for hypochlorite bleaching at the chlorination-base. The bleaching conditions are as follows: the chlorine content is 3% of the absolute dry pulp, the pulp concentration is 3.5%, and the bleaching temperature is 40°. C, the bleaching time is 45 minutes; the alkali treatment conditions are as follows: the alkali amount is 2% of the absolute dry pulp, the slurry concentration is 12%, the bleaching temperature is 55 ° C, and the time is 100 minutes. Sodium hypochlorite was added in an amount of 4% of the dry pulp, the bleaching temperature was 35 ° C, and the bleaching time was 150 minutes. The bleached slurry was pumped into a vacuum washer for washing, and after bleaching, a bleached chemical slurry having a whiteness of 78% ISO, a crack length of 6,500 m, a folding resistance of 35 times, and a tearing degree of 185 mN was obtained.

Example 18

The straw is prepared according to a conventional dry preparation method, and the raw material is charged into the cooking pot through a potter by a hot black liquor having a temperature of 120 ° C, and the lid is closed after the pot is filled, and the temperature is added to the cooking pot. The cooking agent is 13CTC, and the air in the pot is discharged and raised to 0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 156 ° C, and the temperature is raised, kept and replaced for 180 minutes. Pumping the slurry to the spraying pot; wherein the amount of the ammonium sulfite is 9% of the amount of the dry raw material, and the amount of the sodium hydroxide is 8% of the dry raw material, and the liquid ratio is 1 : 6; The hardness of the straw pulp obtained after cooking is 18 potassium permanganate value, which is equivalent to the Kappa price of 26, the degree of beating is 21 ° SR, and then dissipated by the disc disintegrator, and the degree of straw pulping after disintegration is 27 ° SR, the temperature of the straw pulp after decontamination is increased by about 5-1 CTC relative to the straw pulp before the decontamination. The disintegrated straw pulp is then pumped to a screw extruder for "concentrated" black liquor treatment, and the resulting concentrated black liquor can be used for subsequent evaporation as a fertilizer, and the concentration of the extruded pulp is from the pre-slurry. 10% increase to 24%, the pH value of the pulp is 8, the concentration of black liquor is 9° Be (20 °C), the residual ammonium is 8g/L, and the straw pulp obtained after the slurry is black liquor. Diluted to the concentration of the slurry to 2.5%, sent to the sieve for coarse slurry screening, the sieve loss is 0.3%, and the impurities are removed by the high concentration separator, the loss is 0.2%, and the straw pulp obtained after the sieve is sieved. The washing is carried out by a vacuum washer, and the washing process is maintained at 65-75 ° C, and then the slurry is adjusted to 10% and sent to a high-frequency disintegrating machine for dissolving, and the pulp is then passed through a medium-concentrating tube to be quenched and tempered. The air in the slurry is fluidized and then sent to the oxygen delignification reaction column by a centrifugal medium-concentration pump. The slurry is mixed with the added oxygen of 20 kg per ton of pulp and the alkali content of the alkali solution of 3.5% by weight of sodium hydroxide in the pipeline before entering the reaction tower, and steam is introduced into the pipeline. The slurry is heated to heat. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the absolute dry pulp. The inlet temperature is 0 ° C, the pressure is 0.9 Mpa, and the residence time is 85 minutes. The slurry was able to carry out a sufficient delignification reaction with a temperature of 105 ° C at the top of the column and a pressure of 0.4 MPa. After the treatment is completed, the slurry is sprayed into a slurry tank and diluted, and after washing, the unbleached pulp is obtained. The unbleached pulp has a crack length of 6,900 m, a tearing degree of 235 mN, a whiteness of 40% ISO, a folding resistance of 45 times, and a beating degree of 38 ° SR.

The above unbleached pulp is finally bleached, and the chlorination-alkali treatment-hypochlorite bleaching is carried out under the following conditions: the chlorine content is 2.5% of the dry pulp, the pulp concentration is 3.5%, and the bleaching temperature is 43°. C, bleaching time is 50 minutes; the conditions of alkali treatment are: the amount of alkali is 4% of absolute dry pulp, the concentration of pulp is 10%, the bleaching temperature is 55 ° C, the time is 120 minutes; hypochlorite bleaching: sodium hypochlorite is added in an amount of 4% of the absolute dry pulp, the bleaching temperature is 35 ° C, and the bleaching time is 150 minutes. After the bleaching, a bleaching chemical slurry having a whiteness of 75 < 3⁄4 ISO, a crack length of 6,500 m, a folding resistance of 20 times, and a tearing degree of 210 mN was obtained.

Example 19

The straw is prepared according to the conventional dry preparation method, and the straw raw material is charged into the cooking pot through the potter by the hot black liquor having a temperature of 140 ° C. When the pot is full, the lid is closed, and the temperature is added to the cooking pot. 16CTC cooking agent, while discharging the air in the pot and boosting to 0.75MPa, turn on the system's cooking liquid heating circulation pump and tube heater to raise the cooking liquid to 173 °C, heat up, keep warm and replace it for 220 minutes, and finally use Pumping the slurry to the spraying pot; wherein the amount of ammonium sulfite is 15% of the amount of the dry raw material, and the liquid ratio is 1:10; the hardness of the straw pulp after cooking is 16 high manganese The value of potassium acid is equivalent to Kappa price 24, the beating degree is 10° SR, and the straw pulp is adjusted to 10% with black liquor, and then pumped to a single screw extruder for "concentrated" black liquor treatment. The concentrated black liquor can be used for subsequent evaporation as a water reducing agent. The concentration of the extruded slurry is increased from 10% before the extrusion to 35%. At this time, the pH of the slurry is 8, and the concentration of the black liquor is 9Be. ' (20 ° C), the residual alkali concentration is 8g / L, and then will be squeezed When the temperature of the straw pulp is 60 ° C, the concentration is 6.1 ° Be ' dilute black liquor to dilute the slurry concentration to 3.0%, and send it to the sieve for coarse slurry screening. The sieve loss is 0.3%, and the residue is removed by high concentration. The impurities were removed, the loss was 0.2%, and the straw pulp was washed with a drum vacuum washer. The temperature during the washing process was 65 ° C, and the degree of beating of the coarse pulp entering the washer was 31 ° SR. The mixture is heated and sent to the medium-concentration slurry tube for quenching and tempering treatment. The medium-concentration pump is sent to the oxygen delignification reaction tower for delignification treatment, and then washed again with oxygen delignification black liquor. The wet weight of the washed slurry is 1.8g, the residual liquid after washing is 440 ppm. The concentration of the slurry after washing was 9 < 3⁄4 to obtain an unbleached slurry. The unbleached pulp has a crack length of 7,200 m, a tearing degree of 250 mN, a whiteness of 40<3⁄4 ISO, a folding resistance of 45 times, and a beating degree of 35 ° SR.

The above-mentioned unbleached pulp is sent to a bleaching process for chlorination-alkali treatment-hydrogen peroxide bleaching. The conditions for bleaching are as follows: the chlorine content is 3% of the dry pulp, the pulp concentration is 3.5%, and the bleaching temperature is 45°. C, the bleaching time is 45 minutes; the alkali treatment conditions are as follows: the alkali amount is 2% of the absolute dry pulp, the slurry concentration is 12%, the bleaching temperature is 55 ° C, and the time is 100 minutes. The amount of hydrogen peroxide added is 5% of the absolute dry pulp, the concentration of the pulp is 11%, the pH is 11, the amount of the chelating agent is 0.2% of the absolute dry pulp, and the amount of the magnesium sulfate protecting agent is the absolute dry pulp. 0.4%, bleaching temperature is 98 ° C, bleaching time is 115 minutes. A bleached chemical pulp having a whiteness of 65 < 3⁄4 ISO, a crack length of 6,800 m, a folding resistance of 30 times, and a tearing degree of 210 mN was obtained.

Example 20

The straw which has been prepared by the conventional dry method is immersed in an impregnation screw machine and impregnated with an alkali solution containing 4% of the amount of dry straw by sodium hydroxide in an immersion screw machine, and then sent to a steaming ball, 蒽醌The amount of addition is 0.6% of the dry raw material, the liquid ratio is 1:3, and the steam is heated once to 110 ° C, and the temperature is kept at a low temperature for 50 minutes. The temperature is raised to 165 ° C, and the temperature is raised and kept for 150 minutes. Before the spraying, black liquor is added to the steaming ball for concentration, and the pressure is maintained at 0.75 MPa for spraying. The hardness of the slurry is potassium permanganate. The value 20 corresponds to a Kappa price of 32, a beating degree of 14.6° SR, a _P H value of 11 at the end of cooking, and a residual alkali concentration of 12 g/l in the black liquor. The yield of the prepared high hardness pulp was 60%. The concentration of the slurry in the steaming ball was controlled at 10%, and then the steamed straw slurry was pumped to a screw extruder for "concentrated" black liquor treatment, and the concentration of the extruded pulp was 9% from the time of extrusion. Increase to 21%, the resulting concentrated black liquor can be used for the subsequent water reducing agent, the concentration of black liquor is 10 ° Be ' (20 ° C), residual alkali 10g / L, temperature 75 ° C, and then The straw pulp obtained after the slurry is diluted with black liquor to a concentration of 3.0%, sent to a sieve for coarse slurry screening, the sieve loss is 0.2%, and the impurities are removed by a high concentration separator to lose 0.1%. The straw pulp obtained after slag removal is transported to a disc disintegrator for dissolving. The degree of beating of the straw pulp before the disintegration is 25 ° SR, and the degree of beating of the straw pulp after the disintegration is 28 ° SR, relative to before the disintegration In straw pulp, the temperature of the straw pulp after decontamination rises by about 5-10 °C. The slurried slurry was then heated by a screw conveyor to 80 ° C and transferred to a medium consistency slurry tube. The slurry is firstly subjected to quenching and tempering treatment to remove the air in the slurry to be fluidized, and then sent to the oxygen delignification reaction tower through a centrifugal medium-concentration pump. The slurry was mixed with 4 kg of oxygen per ton of slurry and 4% by weight of sodium hydroxide by weight of the added slurry before entering the reaction column, and steam was heated in the line to heat the slurry. After the slurry is thoroughly mixed in the mixer, it enters the oxygen delignification reaction tower. The protective agent is magnesium sulfate, and the amount is 1% by weight of the absolute dry pulp. The inlet temperature is 95 ° C, the pressure is 1.0 MPa, and the residence time is 75 minutes. The slurry was allowed to carry out a sufficient delignification reaction, the temperature at the top of the column was 100 ° C, and the pressure was maintained at 0.4 MPa. After the treatment is completed, the slurry is sprayed into the slurry tank and diluted, and the hardness of the slurry is lowered to a potassium permanganate value of 13, which is equivalent to a Kappa price of 17.6 and a degree of 30 ° SR. The diluted slurry was then pumped into a two-stage vacuum washer with a pump to obtain an unbleached slurry. The unbleached pulp has a crack length of 5,600 meters, a tearing degree of 270 mN, a whiteness of 40<3⁄4 ISO, a folding endurance of 65 times, and a beating degree of 35 ° SR.

The traditional CEH three-stage bleaching is used later, specifically: the chlorine content of the C section is 3% of the absolute dry pulp, the concentration of the pulp is 3.2%, the bleaching temperature is 40 ° C, and the bleaching time is 60 minutes; The amount of sodium hydroxide is 2.5% of dry pulp, the concentration of pulp is 12%, the bleaching temperature is 58 ° C, and the time is 120 minutes; the amount of sodium hypochlorite added is 3% of the dry pulp, the temperature of bleaching At 30 ° C, the bleaching time is 120 minutes, and a good quality straw pulp with a whiteness of 78% ISO, a crack length of 5200 m and a folding resistance of 45 times can be obtained.

Comparative example

The quality index of the bleached chemical pulp prepared in the present invention is compared with the hardwood pulp and the common wheat straw pulp, and the results are shown in the following table:

As can be seen from the above table, the straw pulp of the present invention has a more excellent quality index than the similar or similar pulp of the prior art.

Claims

Claim

A grass pulp for papermaking, characterized in that the pulp is an unbleached pulp prepared by using a grass plant as a raw material, and the crack length of the unbleached pulp is 5.0-7.5 km, The tearing degree is 230-280 mN; preferably, the unbleached pulp has a crack length of 6.5-7.5 km and a tear degree of 250-280 mN.

The pulp according to claim 1, wherein the pulp has a whiteness of 25 to 45% ISO, and preferably the pulp has a whiteness of 35 to 45%.

The pulp according to claim 1 or 2, wherein the number of folding resistances of the unbleached pulp is 40 to 90 times, and preferably the number of folding ends is 65 to 90 times.

The pulp according to claim 1 or 2, wherein the unbleached pulp has a freeness of 32-38 ° SR; preferably the beating degree is 32-36 ° SR.

The pulp according to claim 1, wherein the preparation of the unbleached pulp comprises a cooking step, wherein the cooking comprises: using a grass plant as a raw material to obtain a hardness of permanganic acid after cooking. Potassium value 16-28, high hardness pulp with a beating degree of 10-24° SR; preferably, the unbleached pulp is cooked with grasses as raw materials to obtain hardness of potassium permanganate 16-23, beating degree High hardness pulp of 10-20 ° SR.

The pulp according to claim 1, wherein the pulp is bleached to obtain a bleached chemical pulp having a whiteness of 45-82% ISO, preferably the whiteness is 55-82% ISO, more Preferably, the whiteness is 65-82% ISO, and most preferably the whiteness is 75-82% ISO.

The pulp according to claim 6, wherein the bleaching chemical pulp has a crack length of 4500-8000 m and a tear degree of 180-280 mN; preferably, the crack length is 5500-8000 m. The tearing degree is 220-280mN.

The pulp according to claim 6, wherein the bleaching chemical pulp has a folding resistance of 20 to 90 times; preferably, the folding endurance is 35 to 80 times.

The pulp according to claim 6, wherein the bleaching chemical pulp has a freeness of 32-38 ° SR; preferably the freeness is 32-36 ° SR.

A method of preparing a pulp according to any one of claims 1 to 5, characterized in that the method comprises the following steps:

(3) The washed slurry is post-treated to obtain the pulp.

11. The method according to claim 10, wherein the cooking comprises one of ammonium sulfite cooking, strontium-soda cooking, sulphate cooking or alkaline sodium smelting:

When cooking in the 蒽醌-caustic method, the amount of alkali is 9-15% based on the amount of dry raw materials;

When cooking by the sulphate method, the amount of the dry raw material is 8-11% based on the alkali amount of sodium hydroxide;

In the alkaline sodium refining process, the amount of sodium hydroxide is 11-15% by weight of the dry raw material, and the amount of sodium sulfite is 2-6% by weight of the dry raw material.

12. The method according to claim 11, wherein the cooking comprises: cooking by ammonium sulfite, hydrazine

- one of caustic soda cooking, kraft cooking or alkaline sodium cooking:

1) In a batch ball cooker or continuous digester:

The ammonium sulfite method is cooked as follows:

1 Adding cooking liquor to the grass material, wherein the amount of ammonium sulfite is 9-13% of the amount of dry raw materials, and the amount of sodium hydroxide is 0-8% of the amount of dry raw materials, and the ratio of liquid to liquid is 1 : 2-4;

2 It is heated by steam, heated to a temperature of 165-173 ° C, heating, small venting, and heat preservation for 160-210 minutes;

The mash-soda cooking is as follows:

The kraft cooking is as follows:

2 It is heated by steam, heated to a temperature of 165-173 ° C, heated, deflated, and insulated for 150-200 minutes;

The alkaline sodium solution cooking comprises:

1 Adding a cooking liquor to the grass material, wherein the amount of sodium hydroxide is 9-15% by weight of the dry raw material, 2-6% of sodium sulfite, 0.04-0.08% of strontium, and 1:3 ratio of cooking liquor. -4;

2) In the vertical cooking pot:

The ammonium sulfite method is cooked as follows:

The grass plant material is charged into the cooking pot through a potter by a hot black liquor having a temperature of 120-14 CTC. Close the lid, add the cooking temperature to 130-16CTC in the cooking pot, and at the same time discharge the air in the pot and raise the pressure to 0.6-0.75MPa. Turn on the cooking liquid heating pump and the tube heater to warm the cooking liquid to the cooking liquid. 156-173 ° C, heating, heat preservation and replacement for 180-220 minutes, and finally pumping the slurry to the spray pot; in the cooking agent, wherein the amount of ammonium sulfite is 9 - for the amount of dry raw materials 15%, the amount of sodium hydroxide is 0-8% of the amount of dry raw materials, and the liquid ratio is 1: 6-10; the strontium-soda cooking is as follows:

The grass plant material is charged into the cooking pot through a potter at a temperature of 120-140 ° C. When the pan is full, the lid is closed, and the cooking temperature is 130-16 CTC. At the same time, the air in the pot is discharged and raised to 0.4-0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 147-165 ° C, and the temperature is raised, kept and replaced for 180 minutes. Finally, the slurry is sent to the spraying pot by pumping; in the cooking agent, the amount of alkali is 9-17% of the dry raw material, and the liquid ratio is 1: 6-9. The amount is 0.5-0.8% of the amount of the dry raw material. The kraft method is as follows:

The grass material is filled into the cooking pot from the hot black liquor with a temperature of 120-14 CTC through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. The air in the pot is raised to 0.5-0.65 MPa, and the cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 155-168 ° C, and the temperature is raised, kept and replaced for 200-250 minutes, and finally the pump is used. Putting the slurry into the spraying pot; wherein the cooking agent, wherein the alkali amount is sodium hydroxide, the amount of the dry raw material is 8-13%, the liquid ratio is 1:6-10, and the degree of sulfurization is 5-9. %;

The alkaline sodium solution cooking comprises:

The grass material is filled into the cooking pot from the hot black liquor with a temperature of 120-14 CTC through a potter. When the pan is full, the lid is closed, and the cooking pot is replenished with a temperature of 130-16 CTC. The air in the pot is boosted to 0.45-0.6 MPa. The cooking liquid heating circulation pump and the tube heater of the system are turned on to raise the cooking liquid to 152-165 ° C, and the temperature is raised, kept and replaced for 180-230 minutes. Pumping and sending the slurry to the spraying pot; wherein the amount of sodium hydroxide used is 9-17% by weight of the dry raw material, and the amount of sodium sulfite is 4-8% by weight of the dry raw material, 蒽The amount of hydrazine is 0.04-0.08% by weight of the dry raw material, and the liquid ratio is 1:6-10.

13. The method of claim 10 wherein said washing comprises

(1) The high-hardness pulp having a concentration of 8-15% is introduced from the inlet of the extruder, and the black liquor is extruded under the action of the pressing force to obtain a slurry after the slurry having a concentration of 18-25%. The pulper is preferably a reduced diameter single screw extruder, a double screw extruder or a twin roller extruder;

(2) washing the slurry after the slurry is washed with a black liquor having a concentration of 3-6.2 ° Be ' and pH 8 - 8.3 at a temperature of 70-8 CTC or with one or both of a temperature of 70-8 CTC. The washing is carried out in a vacuum washer, a pressure washer or a horizontal belt washer.

14. The method according to claim 10, wherein the post-processing comprises disambiguation, and the dissolving comprises using a high-frequency disintegrator, a rake machine, a disc crusher, and beating the slurry obtained after washing. Disc mill or fiber separation in equipment The machine is processed to loosen the fiber structure.

15. The method according to claim 10, wherein the post-treatment further comprises oxygen delignification, and the oxygen delignification comprises: feeding the obtained slurry into an oxygen delignification reaction column. The temperature of the slurry at the inlet of the reaction tower is 90-100 ° C, the pressure is 0.9-1.2 MPa; the temperature at the outlet is 95-105 ° C, and the pressure is 0.2-0.4 MPa; The amount of alkali used is 2-4% of the amount of dry pulp based on sodium hydroxide, and the amount of oxygen added is 20-40 kg per ton of pulp for 60-90 minutes to obtain a hardness of potassium permanganate. 10-14 slurry.

16. A method of preparing a bleached chemical pulp according to any of claims 6-9, wherein the method comprises the steps of:

(3) post-treating the washed slurry to obtain the pulp;

The post treatments include spalling, oxygen delignification, and bleaching.

17. The method according to claim 16, wherein said bleaching comprises: chlorination, alkali treatment and hypochlorite bleaching, chlorination: using chlorine in an amount of 2.5-3% of the dry pulp, pulp The concentration is 3-3.5%, the bleaching temperature is 30-45 °C, the bleaching time is 45-60 minutes; the alkali treatment condition is: the amount of sodium hydroxide added is 2-4% of the absolute dry pulp, pulp The concentration is 10-12%, the bleaching temperature is 50-65 ° C, the time is 100-150 minutes; hypochlorite bleaching: sodium hypochlorite is added in an amount of 2-4% of the absolute dry pulp, and the bleaching temperature is 30 -35 ° C, bleaching time is 100-150 minutes.

18. The method according to claim 16, wherein said bleaching comprises: chlorination, alkali treatment, and hydrogen peroxide bleaching, chlorination: using chlorine in an amount of 2.5-3% of the dry pulp, pulp The concentration is 3-3.5%, the bleaching temperature is 30-45 °C, the bleaching time is 45-60 minutes; the alkali treatment condition is: the amount of sodium hydroxide added is 2-4% of the absolute dry pulp, the pulp The concentration is 10-12%, the bleaching temperature is 50-65 ° C, and the time is 100-150 minutes; the hydrogen peroxide bleaching comprises: the hydrogen peroxide is added in an amount of 4-6% of the dry pulp, the pulp The concentration is 10-12%, the pH is 11-12.5, the amount of the chelating agent is 0.2-0.4% of the absolute dry pulp, the amount of the magnesium sulfate protecting agent is 0.3-0.6% of the absolute dry pulp, and the bleaching temperature is 95. -99 ° C, bleaching time is 100-130 minutes.