阅读说明：本技术 一种低能耗、高强度的高得率制浆工艺 (Low-energy-consumption high-strength high-yield pulping process ) 是由 周小凡 乔晓龙 田超超 杨佩 于 2021-10-19 设计创作，主要内容包括：本发明公开了一种低能耗、高强度的高得率制浆工艺,属于制浆技术领域。本发明中,借鉴传统化学浆制备方法,将植物纤维原料与化学药品在高浓度条件下混合加热,同时利用双螺杆挤出机的挤压输送搅拌作用,将化学品和原料均匀共混,使二者在高温和高浓度条件下充分作用,使植物纤维原料达到软化目的,与传统高得率制浆工艺相比,其制浆浓度高达50-90％,最佳比例在70-80％,使得化学药品在植物纤维中充分渗透,提高了反应效率,其中,化学药品的最佳添加量为5-15％相对绝干植物纤维原料质量,化学药品的添加量高于现在高得率浆工艺的添加量,使得植物纤维原料能够在高浓和一定温度下塑化,大大降低磨浆能耗。(The invention discloses a high-yield pulping process with low energy consumption and high strength, and belongs to the technical field of pulping. In the invention, by using the traditional chemical pulp preparation method for reference, the plant fiber raw material and the chemical are mixed and heated under the condition of high concentration, meanwhile, the extrusion conveying and stirring functions of the double-screw extruder are utilized to uniformly blend the chemicals and the raw materials, so that the chemicals and the raw materials fully act under the conditions of high temperature and high concentration, the plant fiber raw materials are softened, compared with the traditional high-yield pulping process, the pulping concentration is as high as 50-90%, the optimal proportion is 70-80%, so that chemicals can fully permeate in the plant fiber, the reaction efficiency is improved, wherein the optimal addition amount of the chemicals is 5-15% relative to the mass of the absolutely dry plant fiber raw material, the addition amount of the chemicals is higher than that of the existing high-yield pulp process, the plant fiber raw material can be plasticized at a high concentration and a certain temperature, and the grinding energy consumption is greatly reduced.)

1. A low-energy-consumption high-strength high-yield pulping process is characterized by comprising the following steps:

s101, preparing raw materials, namely performing pretreatment operation on the plant fiber raw materials, uniformly mixing the pretreated plant fiber raw materials with chemicals, and putting the mixture into mixing equipment;

s102, carrying out reaction treatment, namely heating the mixing equipment, continuously feeding the raw materials to improve the concentration, and softening and plasticizing the plant fiber raw materials under the conditions of high temperature and high concentration;

s103, the mixing equipment realizes the separation of plant fibers through the screw extrusion, shearing and dispersion effects, and high-yield pulp with excellent performance is prepared, and the concentration of the pulp is 50-90%.

2. A low energy consumption, high strength, high yield pulping process in accordance with claim 1 wherein the chemicals comprise acids and bases and the acids are inorganic and organic acids.

3. A low energy consumption, high strength, high yield pulping process in accordance with claim 1 wherein the inorganic acid is a mixture of one or more of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, sulfurous acid, and hydrofluoric acid and the organic acid is a mixture of one or more of maleic acid, formic acid, acetic acid, and acrylic acid.

4. A low energy consumption, high strength, high yield pulping process in accordance with claim 1 wherein the alkali is a mixture of one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide and lithium hydroxide.

5. A low energy consumption, high strength, high yield pulping process according to any of claims 1-4 wherein the plant fiber material comprises wood fiber material and non-wood fiber material.

6. A low energy consumption, high strength, high yield pulping process according to any of claims 1 to 4 wherein the chemicals comprise 3 to 30 wt% of the plant fiber material.

7. The low energy consumption, high strength, high yield pulping process of claim 1 wherein the mixing apparatus is set to a temperature of 70-180 ℃.

8. The low energy consumption and high strength high yield pulping process according to claim 1, wherein the mixing device is a co-rotating twin-screw extruder, and the preferred speed of the twin-screw extruder is 100-.

9. The low energy consumption, high strength, high yield pulping process of claim 8, wherein the twin screw multiple stages comprise a conveying stage, an extrusion temperature raising stage, a mixing stage, a discharge stage, and a venting stage, all of which are interconnected in sequence.

10. A low energy consumption, high strength, high yield pulping process in accordance with claim 9 wherein the feeding section is adapted to convey the plant fiber raw material and to mix and agitate the plant fiber raw material;

the extrusion heating section is used for fully extruding, melting and primarily reacting the plant fibers and the chemical materials through heat transfer and friction shearing, and simultaneously realizing softening of the plant fibers;

the pulping section further shears, refines and disperses the size of the plant fiber raw material to form paper pulp fibers, and combines the functions of extrusion, shearing and dispersion with high-concentration mixing of chemicals;

the discharge section is used for conveying and pressurizing, and establishing discharge pressure to ensure that the paper pulp fibers at the die opening have certain compactness;

the exhaust section is used for exhausting water vapor, is arranged at the tail part of the double-screw extruder and is used for exhausting water vapor generated in the pulping process, and exhaust can be controlled through a valve according to the amount of the water vapor generated in the pulping process.

Technical Field

The invention belongs to the technical field of pulping, and particularly relates to a low-energy-consumption high-strength high-yield pulping process.

Background

Chemical mechanical pulp is used as one of high-yield pulping processes, a pulping method of chemical pretreatment and mechanical grinding aftertreatment is adopted, the chemical treatment is favorable for improving the strength performance of pulp and reducing the energy consumption of grinding pulp, firstly, a medicament is used for mild pretreatment (dipping or stewing) to remove part of hemicellulose in wood fiber raw materials, so that lignin is dissolved out less, intercellular layers are softened, then, grinding is carried out by a disc grinder, so that fibers are separated into pulp, the key point of the chemical mechanical pulping is a chemical pretreatment stage, the quality of treatment directly influences the quality of finished pulp and the energy consumption of grinding pulp, and the energy consumption is also one of important indexes for evaluating the chemical mechanical pulp;

the pulping machine is one of the core devices of pulping and papermaking plants, not only directly influences the product quality, but also relates to the production energy consumption and cost of the product, the pulping energy consumption usually accounts for about 1/2 of the total energy consumption of high-yield pulp production, more than 80% of electric energy in the process is converted into heat energy, and only about 20% of energy consumption is converted into useful work, so that the energy consumption of the pulping machine directly influences the economic benefit of pulping and papermaking enterprises;

the double-screw extruding and kneading machine of double-screw extruder, called as third generation pulping machine, can integrate the high-concentration operation processes of conveying, chemical treatment, pulping and washing into one body, and can utilize the extruding, kneading and tearing action of two long screws to implement all the technological processes at one time with high efficiency, so that it has the obvious effect of saving water, electricity, steam and chemicals, and possesses extensive application prospect

In the traditional pulping process by utilizing a double-screw extrusion kneader, raw materials and chemicals are blended in a large liquid ratio, the raw materials and the chemicals mainly play a role in dipping and stirring in the process, disc grinding is still needed subsequently to ensure the quality of finished pulp, the sheet making performance of the prepared pulp is far lower than that of chemical pulp, and the application range of the pulp in the industry is limited.

Disclosure of Invention

The invention aims to: the high-yield pulping process with low energy consumption and high strength is provided in order to solve the problem that the sheet making performance of the traditional double-screw dipping and stirring pulping is far lower than that of chemical pulp, and the application range of the traditional double-screw dipping and stirring pulping is limited in industry.

In order to achieve the purpose, the invention adopts the following technical scheme:

a low-energy-consumption high-strength high-yield pulping process specifically comprises the following steps:

s101, preparing raw materials, namely performing pretreatment operation on the plant fiber raw materials, uniformly mixing the pretreated plant fiber raw materials with chemicals, and putting the mixture into mixing equipment;

s102, carrying out reaction treatment, namely heating the mixing equipment, continuously feeding the raw materials to improve the concentration, and softening and plasticizing the plant fiber raw materials under the conditions of high temperature and high concentration;

s103, the mixing equipment realizes the separation of plant fibers through the screw extrusion, shearing and dispersion effects, and high-yield pulp with excellent performance is prepared, and the concentration of the pulp is 50-90%.

As a further description of the above technical solution:

the chemicals include acids and bases, and the acids are inorganic and organic acids.

As a further description of the above technical solution:

the inorganic acid is one or more of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, sulfurous acid and hydrofluoric acid, and the organic acid is one or more of maleic acid, formic acid, acetic acid and acrylic acid.

As a further description of the above technical solution:

the alkali is one or a mixture of sodium hydroxide, calcium hydroxide, potassium hydroxide and lithium hydroxide.

As a further description of the above technical solution:

the plant fiber raw material comprises wood fiber raw material and non-wood fiber raw material.

As a further description of the above technical solution:

the chemical medicine accounts for 3-30 wt% of the plant fiber raw material.

As a further description of the above technical solution:

the temperature of the mixing equipment is set to be 70-180 ℃.

As a further description of the above technical solution:

the mixing equipment is a co-rotating twin-screw extruder, and the rotating speed of the twin-screw extruder is preferably 100-1200 r/min.

As a further description of the above technical solution:

the twin-screw multiple sections comprise a conveying section, an extrusion heating section, a mixing section, a discharging section and an exhaust section which are sequentially connected with one another.

As a further description of the above technical solution:

the feeding section is used for conveying the plant fiber raw materials and mixing and stirring the plant fiber raw materials;

the extrusion heating section is used for fully extruding, melting and primarily reacting the plant fibers and the chemical materials through heat transfer and friction shearing, and simultaneously realizing softening of the plant fibers;

the pulping section further shears, refines and disperses the size of the plant fiber raw material to form paper pulp fibers, and combines the functions of extrusion, shearing and dispersion with high-concentration mixing of chemicals;

and the discharge section is used for conveying, pressurizing and establishing discharge pressure, so that the pulp fibers at the die opening have certain compactness.

The exhaust section is used for exhausting water vapor; the double-screw extruder is arranged at the tail part of the double-screw extruder and used for discharging water vapor generated in the refining process, and the air discharge can be controlled through a valve according to the amount of the water vapor generated in the refining process.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

1. in the invention, by using the traditional chemical pulp preparation method for reference, the plant fiber raw material and the chemical are mixed and heated under the condition of high concentration, meanwhile, the extrusion conveying and stirring functions of the double-screw extruder are utilized to uniformly blend the chemicals and the raw materials, so that the chemicals and the raw materials fully act under the conditions of high temperature and high concentration, the plant fiber raw materials are softened, compared with the traditional high-yield pulping process, the pulping concentration is as high as 50-90%, the optimal proportion is 70-80%, so that chemicals can fully permeate in the plant fiber, the reaction efficiency is improved, wherein the optimal addition amount of the chemicals is 5-15% relative to the mass of the absolutely dry plant fiber raw material, the addition amount of the chemicals is higher than that of the existing high-yield pulp process, the plant fiber raw material can be plasticized at a high concentration and a certain temperature, and the grinding energy consumption is greatly reduced.

2. In the invention, through the improvement of the structure of the double screw, outside the conveying section at the front section and the final discharging section, a plurality of shearing and conveying elements are arranged on the whole screw, so that the chemical continuously realizes the functions of extrusion, permeation, shearing, re-extrusion, permeation, shearing and dispersion from the surface to the inside of the plant fiber in the process of feeding the screw, and finally forms high-concentration slurry, in a co-rotating double screw extrusion system, because the speed directions of the co-rotating double screws at the meshing position are opposite, one screw pulls the plant fiber raw material into the meshing gap, and the other screw pushes the plant fiber raw material out from the gap, so that the plant fiber raw material is transferred from one screw to the other screw to advance in a wavy shape, the speed change and the relative speed of the meshing area are higher, and the mixing of the plant fiber raw material and the chemical is very favorable, the device can fully permeate chemical medicine from the surface of the plant fiber to the inside of the plant fiber, realizes the permeation softening and chemical reaction of plant fiber raw materials from the surface to the inside, simultaneously, because the meshing clearance is small, the speeds of the screw thread and the screw groove at the meshing part are opposite, the shearing speed is high, the softened surface plant fiber raw materials are dispersed into single fibers through the extrusion shearing action, the full contact of the internal plant fiber raw materials and the chemical medicine is further promoted, the further permeation of the chemical medicine from the surface to the inside is realized by an extrusion module, because a plurality of groups of different mixing and mixing elements are distributed in the middle of the whole device, the chemical medicine can continuously realize the extrusion permeation, shearing, re-extrusion, permeation, shearing and dispersion actions from the surface of the plant fiber to the inside in the screw material walking process, and finally forms high-concentration pulp The chemical mechanical pulp formed under the conditions of high concentration, high extrusion, high shearing and dispersion has very low water content, and is convenient for later storage and transportation.

Drawings

FIG. 1 is a schematic flow diagram of a pulping process according to an embodiment;

FIG. 2 is a scanning electron microscope for fine pulp papermaking of example 1 according to the present invention;

FIG. 3 is a scanning electron microscope for fine pulp papermaking of example 2 according to the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Referring to fig. 1-3, the present invention provides a technical solution: a low-energy-consumption high-strength high-yield pulping process specifically comprises the following steps:

s101, preparing raw materials, namely performing pretreatment operation on the plant fiber raw materials, uniformly mixing the pretreated plant fiber raw materials with chemicals, and putting the mixture into mixing equipment;

s102, carrying out reaction treatment, namely heating the mixing equipment, continuously feeding the raw materials to improve the concentration, and softening and plasticizing the plant fiber raw materials under the conditions of high temperature and high concentration;

s103, the mixing equipment realizes the separation of the plant fibers through the screw extrusion, shearing and dispersion effects, and high-yield pulp with excellent performance is prepared, and the concentration of the pulp is 50-90%, preferably 70-80%.

The chemical comprises acid and alkali, the acid is inorganic acid and organic acid, the inorganic acid is a mixture of one or more of sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, sulfurous acid and hydrofluoric acid, the organic acid is a mixture of one or more of maleic acid, formic acid, acetic acid and acrylic acid, the alkali is a mixture of one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide and lithium hydroxide, the plant fiber raw materials comprise wood fiber raw materials and non-wood fiber raw materials, the chemical accounts for 3-30 wt% and preferably 5-15 wt% of the plant fiber raw materials, the mixing equipment is set at 70-180 ℃ and preferably 80-120 ℃, the mixing equipment is a co-rotating twin-screw extruder, the preferred rotating speed of the twin-screw extruder is 100-, Extruding, heating, mixing, discharging and exhausting;

the feeding section is used for conveying the plant fiber raw materials and mixing and stirring the plant fiber raw materials;

the extrusion heating section is used for fully extruding, melting and primarily reacting the plant fibers and the chemical materials through heat transfer and friction shearing, and simultaneously realizing softening of the plant fibers;

the pulping section further shears, refines and disperses the size of the plant fiber raw material to form paper pulp fibers, and combines the functions of extrusion, shearing and dispersion with high-concentration mixing of chemicals;

the exhaust section is used for exhausting water vapor; the double-screw extruder is arranged at the tail part of the double-screw extruder and used for discharging water vapor generated in the refining process, and the air discharge can be controlled through a valve according to the amount of the water vapor generated in the refining process.

The discharge section is used for conveying and pressurizing, and establishing discharge pressure to ensure that the paper pulp fibers at the die opening have certain compactness;

wherein, the combination of the screw elements in the present embodiment is not limited to the above combination, and different plant fiber raw materials can be used with different combinations of screw elements to achieve the production of high yield pulp with low pollution, high strength and high concentration.

The screw is characterized in that a plurality of shearing and conveying elements are arranged on the whole screw except for a conveying section at the front section and a final discharging section, so that the functions of extrusion, permeation, shearing, re-extrusion, permeation, shearing and dispersion of chemicals from the surface to the inside of plant fibers are continuously realized in the screw conveying process, and finally high-concentration slurry is formed;

the co-rotating twin-screw extruder adopts a building block type structure and mainly comprises the following thread elements:

a conveying element: conveying plant fiber raw materials, and mixing and stirring; the conveying threaded element belongs to a self-sweeping type, is longitudinally open and transversely closed, has a strong conveying effect, short material retention time and good self-cleaning property, and can establish high pressure in a short axial distance; in order to promote the melting of materials, increase the pressure and enhance the mixing effect, and increase the residence time of materials and the input of shearing energy, a reverse thread element is arranged at the upstream of the exhaust area;

a shearing element: the shearing element is mainly a kneading block element commonly used in an intermeshing co-rotating twin-screw extruder, and mainly has the functions of providing high shearing, enabling plant fibers with softened surfaces to fall off from the surfaces, further enabling chemicals to permeate into the plant fibers, realizing extrusion, permeation, shearing, re-extrusion, permeation, shearing and dispersion of the surfaces of the plant fibers, and having a neutral kneading block, a forward kneading block and a reverse kneading block.

Wherein, the kneading blocks with the staggered angle of 90 degrees are called neutral kneading blocks; the kneading discs which are arranged in a staggered way form a spiral angle which is consistent with the spiral direction of the positive thread elements and is called a positive kneading block; the helix angle formed by the kneading disks installed in a staggered manner is consistent with the helical direction of the reverse thread elements and is called a reverse kneading block;

tooth element TME: the non-staggered areas of the toothed discs on the two screws can shunt materials, increase interfaces, provide the minimum input capacity, facilitate the distribution and mixing of plant fiber raw materials and chemicals and generate lower temperature, and the toothed discs on the two screws can shear the materials in a direction perpendicular to the flowing direction in the staggered areas and also facilitate the dispersive mixing;

grooved threaded elements on the thread edges such as SME and ZME elements: the element is formed by forming a plurality of grooves on the screw edge of the screw conveying element.

The grooves can enable adjacent screw grooves to be communicated, so that the propelling effect of the plant fiber raw materials and chemicals between the adjacent screw grooves is facilitated, and longitudinal mixing is promoted.

Wherein, because the spiral arris is provided with the groove, the conveying capacity and the pressure reduction capacity of the spiral arris are reduced, but the fullness of the mixture of the plant fiber raw material and the chemical in the spiral groove is increased, and the retention time of the material is increased;

a strong conveying element: the element has large free volume, the angle of the conveying power direction is directly along the positive axial direction, the element is used for high-filling products, the feeding capacity in unit time can be improved, and particularly, the returning of materials at a feed opening is effectively avoided when straw type low-bulk density raw materials are used;

the "S" shape component: the stretching block is generally conveyed in a positive and negative pair of large leads, can effectively improve the extrusion and shearing functions, and has lower energy consumption and lower heat energy generated by the extrusion and shearing functions;

in the double-screw extruder, a conveying element is used for tightly meshing a mixture of a plant fiber raw material and a chemical by a screw ridge of one screw and a screw groove of the other screw, and the mixture is forced to rotate in the same direction, so that the plant fiber is extruded and fed;

as shown in fig. 1, there is also provided a process for preparing high-yield pulp from wheat straw by alkaline plasticization, comprising the following steps:

(1) uniformly mixing 30g of sodium hydroxide, 300g of absolute dry wheat straw and 200g of water;

(2) setting the temperature of the double screws to be 80 ℃ and the rotating speed to be 600r/min, and extruding slurry;

(3) screening the pulp;

(4) determining the yield;

(5) fine pulp papermaking and pulp residue recycling;

(6) detecting the strength of the paper;

(7) and detecting Chemical Oxygen Demand (COD) of the slurry.

High yield pulp and paper strength properties were measured as in table 1:

TABLE 1 sodium hydroxide plasticized wheat straw preparation of high yield pulp Properties

Example 2

The process for preparing high-yield pulp by plasticizing wheat straw with an alkaline method comprises the following steps of:

(1) uniformly mixing 45g of sodium hydroxide, 300kg of oven-dried wheat straw and 200g of water;

(2) setting the temperature of the double screws to be 80 ℃ and the rotating speed to be 600r/min, and extruding slurry;

(3) screening the pulp;

(4) determining the yield;

(5) fine pulp papermaking and pulp residue recycling;

(6) detecting the strength of the paper;

(7) and detecting Chemical Oxygen Demand (COD) of the slurry.

High yield pulp and paper strength properties were measured as shown in table 2:

table 2: high-yield pulp performance prepared from sodium hydroxide plasticized wheat straw

Example 3

The process for preparing high-yield pulp by plasticizing wheat straw by an acid method comprises the following steps of:

(1)50g of sulfuric acid, 1000g of wheat straw and 1000g of water are uniformly mixed;

(2) setting the temperature of the double screws to be 80 ℃ and the rotating speed to be 200r/min, and extruding slurry;

(3) screening the pulp;

(4) determining the yield;

(5) fine pulp papermaking and pulp residue recycling;

(6) and (6) detecting the strength of the paper.

High yield pulp and paper strength properties were measured as in table 3:

table 3: high-yield pulp performance prepared from sulfuric acid plasticized wheat straw

Comparative example 1

The process for preparing the high-yield pulp by plasticizing the wheat straw with the low-rotation-speed acid method comprises the following steps of:

(1) uniformly mixing 5g of sulfuric acid, 100g of absolute dry wheat straw and 100g of water;

(2) setting the temperature of the double screws to be 80 ℃ and the rotating speed to be 35r/min, and extruding slurry;

(3) screening the pulp;

(4) determining the yield;

the measured yields are as in table 4:

TABLE 4 high yield pulp yield from sulfuric acid plasticized wheat straw at low rotation speed

As can be seen from Table 4, the rotation speed of the twin-screw extruder has a great influence on the pulping effect, when the rotation speed is 35r/min, the shearing force of the screw is not enough to disperse the wheat straw fibers, and the fine pulp yield is relatively low, so that the embodiment 1 is a preferred embodiment of the invention;

the process has the advantages that:

the yield of the wheat straw pulp is over 73 percent, and the pulp concentration is 70-80 percent;

the pulping energy consumption is about 200 kW.h/t, compared with the traditional high-yield pulping process, the energy consumption is greatly reduced, no steam is generated in the whole process, no pulping section is required, no potential dissipation is required, the process flow is simplified, the production efficiency is improved, and the cost expenditure of equipment and the like is reduced;

the fine pulp has thermal plasticity, and the sheet making strength is close to that of chemical pulp;

the production process has no pollution and no VOC emission;

continuous pulping operation can be realized;

the formed slurry is dry slurry with low water content rate, and is convenient for later storage and transportation.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.