CN114263062A - Method for preparing straw pulp by continuous hot grinding machine - Google Patents

Abstract

The invention relates to the field of papermaking, in particular to a preparation method of continuous thermomechanical straw pulp. The straw pulp is suitable for producing corrugated paper, box board, bobbin paper, etc. and may be used in producing other kinds of paper for packing. The method comprises the following steps: (1) and (5) washing with water. (2) Conveying by screw conveyer while introducing steam for heating at 60-80 deg.C, and conveying the heated straw raw material into pulping machine for coarse grinding at 60-80 deg.C and pulping concentration of 30-50%. (3) The coarse pulp after coarse grinding directly enters a screw conveyer, steam is continuously introduced into the screw conveyer at the temperature of 60-80 ℃, the heated straw raw material is sent into a pulp grinder through the screw conveyer for fine grinding, the pulp grinding temperature is 60-80 ℃, and the pulp grinding concentration is 30-50%. (4) Screening and concentrating to obtain the straw pulp. Realizes alkali-free pulping, and has the characteristics of environmental protection, low cost and high efficiency.

Description

Method for preparing straw pulp by continuous hot grinding machine

Technical Field

The invention relates to the field of papermaking, in particular to a preparation method of continuous thermomechanical straw pulp. The straw pulp is suitable for producing corrugated paper, box board, bobbin paper, etc. and may be used in producing other kinds of paper for packing.

Background

In the prior art, the fiber raw material can only be made into pulp because lignin and other organic matters in grass (including gramineous) wood are resistant to high temperature, acid, alkali and the like. So the method of acid or alkali is adopted to extract fiber in the world so far for paper making or chemical fiber weaving. Mechanically produced fibers can only be used for papermaking and not for weaving. Taking alkaline pulping as an example, the alkali consumption of chemical pulping is gradually reduced from 20%. The alkali consumption of the semi-chemical pulping is reduced from 14 percent to about 2 percent at present or lower. As long as the alkali (acid) is used for pulping and high temperature is added, a large amount of raw materials are inevitably consumed in water in the pulping process, so that the pollution to the environment is caused, and a large amount of raw materials are required to be put into the environmental treatment.

The hardstocks produced in the past, i.e. the stocks from which the boxboard is produced, are semi-chemical pulping, which is an old process starting in 1925. The old process for producing the same kind of pulp has high raw material consumption, high chemical raw material consumption, high water consumption, high product cost and relatively high harm to the environment. Therefore, the research on new technology for manufacturing the hard pulp of the boxboard ensures that various new pulping technologies with low consumption, low product cost and no environmental pollution are imperative.

At present, only mechanical groundwood pulp is used, and most of the mechanical groundwood pulp is pre-impregnated by alkali, wherein the alkali consumption is generally more than 2% by taking straw as an example; due to the alkali pre-soaking, organic matters such as lignin, hemicellulose and the like in the plant raw materials are hydrolyzed and lost after encountering alkali. The raw material loss is too large; the loss of lignin, hemicellulose and other organic matters in pulping is large, so that the yield of the finished pulp is low. The higher yield of the general grass is only 65-75%; the organic matter loss in pulping is large, so that the content of organic pollutants in pulping wastewater is high, the concentration of concentrated sewage is more than 1.0 percent, and the concentrated sewage is viscous, so that the sewage treatment is difficult, and the environmental protection is very unfavorable. This is the main factor for stopping the pulp and paper mill of gramineous plants in China. A large amount of gramineous straws are burnt and discarded every year in China, and the power consumption per ton of the pulp is increased accordingly, and the power consumption per ton of the pulp is more than 500 kWH. The consumption of gramineous plant raw materials per ton of pulp is high, the consumption of the pulp per ton is 1.8-2.2 tons generally, and the yield of the coarse pulp is 65 percent. The cost of the prior pre-soaking mechanical pulp is higher than that of the process by more than 30 percent due to the reasons. The most important is that the prior process technology depends on the action of chemical raw materials such as alkali, acid and the like, the condition that organic matters such as lignin and the like are not used for resisting heat is not utilized, the plant raw materials which are subjected to thermal expansion are washed by water for cooling in the pulping process, and the fiber raw materials are cooled by cooling, so that the alkali is used more, the macromolecules of a large amount of plant raw materials are broken and peeled into micromolecules which are dissolved in sewage, the pulping yield is reduced, the cost is increased, the wastewater concentration is increased disadvantageously, and if the wastewater is treated without increasing the cost, an enterprise can close a door due to the environmental pollution. Thermomechanical pulp has not been reported.

Disclosure of Invention

The invention aims to provide a method for preparing continuous thermomechanical straw pulp, which is alkali-free pulping, environment-friendly, low in cost and high in efficiency, aiming at the defects.

The technical solution of the invention is as follows: the preparation method of the continuous thermomechanical straw pulp is characterized by comprising the following steps:

(1) washing with water, using rice straw or stalk as raw material (Gramineae), dedusting, washing in pulper, and concentrating.

(2) Conveying the cleaned and concentrated straw raw material by a screw conveyor, introducing steam into the conveying process for heating at the temperature of 60-80 ℃, conveying the heated straw raw material into a pulping machine by the conveyor for coarse grinding at the pulping temperature of 60-80 ℃, wherein the pulping concentration is 30-50%.

(3) The coarse pulp after coarse grinding directly enters a screw conveyer, steam is continuously introduced into the screw conveyer at the temperature of 60-80 ℃, the heated straw raw material is sent into a pulp grinder through the screw conveyer for fine grinding, the pulp grinding temperature is 60-80 ℃, and the pulp grinding concentration is 30-50%.

(4) And screening and concentrating the fine-ground paper pulp to obtain rice straw pulp (continuous thermomechanical pulp).

In the above scheme, the method further comprises:

in the step (3), the pulp can be continuously refined by more than two sections of hot mills or a plurality of refiners.

And (4) after the step (4), refluxing the screened coarse pulp to the screw conveyer in the step (3), heating and softening the coarse pulp, and grinding the coarse pulp into pulp.

In the step (2) or (3), the beating degree is 18-22 DEG SR.

The obtained straw pulp is suitable for producing pulp for corrugated medium paper, boxboard and bobbin paper.

Taking gramineous plants as an example, the straw contains 64 percent of holocellulose and only contains about 11 percent of lignin, and the lignin content is greatly reduced by 17.1 percent and 23.91 percent compared with that of poplar and birch. The average fiber length is 0.92mm, the length is generally 0.47mm-1.43mm, and the average fiber length is about 0.99mm and 0.98mm compared with the average fiber length of the poplar and birch. And the straw is easier to soften. If studies show that cooking starts with a large delignification. Due to the above factors, the present invention has been implemented and made possible. The method has the guiding idea that the straw raw material is subjected to bond and bundle breaking under the conditions of thermal softening and heating, and is thermally ground into pulp, lignin is removed as far as possible, organic matters are not lost, the difficulty of sewage treatment is reduced, clean production is realized, and the environment is protected. Therefore, the method for producing the boxboard straw hard pulp by adopting the method of washing, rough hot grinding and continuous hot grinding is easier and more scientific.

The method has the main problems of guiding thought and solving:

the method guides each production process by using a clean production guide idea.

The previous process does not leave pollution hidden trouble for the next process.

The pollution source is prevented and controlled before production, and the production process is free from diseases and does not treat diseases again.

Because of clean production, various consumptions are less, so the cost is greatly reduced.

The quality of the product is reasonably improved by proper measures under the guidance of the idea of clean production.

More importantly, the present invention is the production of thermomechanical pulp, which requires the cellulose to be obtained while retaining lignin, hemicellulose and other organic matter, rather than dissolving them away. Therefore, the key to distinguish from other pulping is: firstly, washing the raw materials; continuously hot grinding in a whole hot state; no acid is added; chemical raw materials such as alkali and the like are not added, and alkali-free pulping is realized.

The invention mainly solves and is different from several problems of other technologies:

different from other pulping technologies, the raw materials are washed first, and the pulp is cleaned in a state of clean raw materials. The components in the raw materials are kept as much as possible, but are not dissolved and removed.

The method is different from other pulping methods in that the whole process is continuously thermally ground into pulp, and the whole process is continuously thermally ground on the premise of alkali-free pulping.

The invention heats the white steel spiral conveyer. The heating area is 300 mm multiplied by 200mm, and the heating aperture is 3.0mm-5.00 mm.

The prior refining is carried out at low temperature, so the technology solves the problem that the transmission system of the prior refining is high-temperature resistant.

Because the technology is acid-free and alkali-free mechanical pulping, even if waste water and waste residues are generated, the technology can be used for farmland irrigation and fertilization. Can be continuously produced in large scale. The pulp can be used for producing cultural paper and the like after scientific bleaching.

The process technology different from wood grinding is as follows: the continuous thermal grinding machine has a self-feeding device for straw pulp.

Solves the problem that a great amount of waste (burnt) resources of the gramineous straws are wasted every year in China, and the value of the waste straws is more than billions yuan.

Because the technology does not use chemical raw materials such as acid and alkali, and the like, and has no pollution, the pollution problem caused by a large amount of waste paper imported from foreign countries every year in China can be solved by popularizing the technology. The problem of shortage of paper making raw materials is also solved.

The inventor has been engaged in pulping and papermaking for decades and has been through the design, construction and production of chemical wood pulp systems, the production and research of semi-chemical wood pulp, the production and research of semi-chemical straw pulp and the research of mechanical straw pulp, thus promoting the birth of the application.

The invention has the advantages that: 1. the method has the advantages of realizing alkali-free manufacture of straw pulp, not using chemical raw materials, extremely easy treatment, easy recovery and no pollution of the pulper wastewater, solving the treatment difficulty of enterprises on the environment from the source, being beneficial to environmental protection, reducing the production cost and providing the production efficiency. 2. The method conforms to the policy of national support and advocated straw recycling to reduce the atmospheric and environmental pollution caused by field incineration of farmers and increase the economic income of farmers and industrial enterprises. 3. The excessive dependence of paper making enterprises on imported waste paper and domestic waste paper can be reduced, the production cost can be reduced, and the investment cost for environmental protection can be reduced. Easy pulp washing and low water consumption, and the water consumption per ton of pulp is about 6 to 12 tons; the process from coarse grinding to fine grinding is continuous, the production process is compact, coal consumption and power consumption are low, coal consumption per ton of pulp is 80Kg, and power consumption per ton of pulp is 110 degrees. 4. Because chemical raw materials such as acid, alkali and the like are not used and the cooking is not carried out, the plant fiber raw materials are not degraded, the raw material consumption per ton of pulp is low, and only about 1.3 tons is consumed. Therefore, the yield of mechanical straw pulp is 83-86%. Therefore, the mechanical straw pulp produced by the process has the advantages of low raw material consumption and high yield.

Embodiments of the present invention will be described in further detail with reference to examples.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

Examples

Preparation method of continuous hot grinding mechanical straw pulp (SMRM method):

referring to fig. 1, the cleaning process is elaborated to reduce the generation of pollutants, and comprises the following steps:

firstly, an S-section process: the main function of the section is to wash the grass pieces with water. Cutting the straws into segments, wherein the specification of the cut straws is as follows: 30 mm-60 mm (more than 70%). The raw materials are dedusted, sent to a pulper for washing and then concentrated, and the dust, sandy soil, grass leaves and impurities carried by the raw materials are removed. The method is a pretreatment stage of pulping, so that the consumption of heat and the like of the pulping in the next stage is reduced, the raw materials are clean and clean, and more importantly, the waste water in the stage is easy to precipitate, and the method is favorable for recycling the waste water and precipitates.

Second, the first M-segment process: the straw material after S section cleaning, dewatering and concentrating is fed into white steel screw conveyer with diameter of 500mm, and simultaneously steam is introduced for heating, and the temperature is controlled at 60-80 ℃. The heated straw raw material is sent into a high-concentration refiner with the diameter of 600mm by a conveyor for coarse grinding (primary refining), and the refiner is provided with a self-feeding device. The concentration of the refined pulp is 30-50%, and the refining temperature can be controlled between 60-80 ℃. The rotating speed and the material conveying speed of the conveyor are adjustable and are adaptive to the pulping speed of the pulping machine. The straw after the first M section of high-concentration grinding is coarse pulp. The rotation number of the screw conveyer is 60-100 r/min, and the screw conveyer is driven by a speed regulating motor.

Third, the R section process: the coarse pulp after coarse grinding directly enters a white steel speed-regulating screw conveyor with the diameter of 500mm, steam is continuously introduced into the screw conveyor, the temperature is controlled to be 60-80 ℃, heating is carried out while conveying, and if the screw conveyor is long, the screw conveyor can be lengthened, so that the coarse pulp continuously expands and absorbs water. The stage is a temporary short latency stage of the plant fiber raw material after coarse grinding and before fine grinding of the paper pulp. After the coarsely ground raw material is decomposed by the coarsely ground limbs, a large number of pores are generated on the surface of the coarsely ground raw material, a large number of plant cells are exposed outside, the plant block diameter is reduced, and heat and water can easily enter the raw material vertically. When the small-block-diameter raw material enters hot water, the raw material is easy to expand. After the tiny plant fibers are fully expanded, bonds (chemical bonds) are easy to be broken and the 'bundles' are easy to be broken, and the 'bundles' of the fibers are easy to be divided and broomed by a powerful refiner (disc refiner) to be changed into a plurality of fiber states. The fiber bundles are reduced or both ends of the fiber bundles are broomed and fluffed in the middle. To a "hard" pulp suitable for use in the production of linerboards and corrugating medium. The rotation number of the conveyer is 60-100 r/min, the fiber raw material is expanded under the action of steam, partial fibers are subjected to bond breaking (chemical bond) and fiber bundle breaking, so that the fiber bundle is mechanically extruded and torn in a mill in the high-concentration refining stage of the next stage, the fiber bundle is changed into a state of more fibers, and the fiber bundle is reduced or two ends of the fiber bundle are broomed and the middle of the fiber bundle is fluffed. The paper making requirements are met. Depending on the scale of production or on specific requirements, the screw conveyor can also be replaced by a continuous digester at this stage.

Fourth, a last M-stage process: the function of the stage is to pass the softened, expanded, bond-released and bundle-released coarse pulp raw material through 600mm phi pulp grinder (or other models, or multiple serial grinders) to be thermally ground into pulp under the action of high temperature and mechanical action, the pulp grinding temperature is 60-80 ℃, and the fine grinding is realized. Qualified finished pulp with certain yield is produced under the condition of multi-step and multi-section pulp grinding. The concentration of the pulp is 30-50% or higher, and the temperature of the pulp is 60-80 ℃. The pulp is refined at high temperature and high concentration, so that the fiber is broomed more and less damaged during refining, and fiber bundles are changed into single fibers, so that the fiber can get rid of organic constraint of plant stems more easily. This stage may be divided into two stages of hot milling. The high-consistency pulp grinding continuous grinding of a plurality of pulp grinders is beneficial to improving and controlling the quality of the ground fiber. Through the four stages of the pulping process, the pulp also needs to be screened and concentrated. The pulp is washed. The coarse slag returns to the R section to be heated and milled again. The method is abbreviated as SMRM method.

Since the main factor affecting the strength of the paper is the binding force of the fibres. The binding force of the fiber is improved along with the improvement of the beating degree. The number of refiners may be increased or decreased to ensure the desired freeness, depending on the quality requirements of the product.

Namely, the milled paper pulp enters a pulp well, and the recycled water is added to adjust the concentration to 3-5%. The paper pulp after concentration adjustment enters a high-concentration pressure screen through a pump. And returning the screened coarse pulp to a 500mm phi submersible screw conveyor, heating and softening the coarse pulp, and grinding the coarse pulp into pulp. The size of the screen gap of the pressure screen is 0.25 mm-0.35 mm. And (4) concentrating the screened fine pulp in a concentrator. And (4) feeding the concentrated paper pulp into a pulp well (completing the pulping process). The waste liquid of the concentrated pulp enters a recovery liquid storage tank (groove) for recycling. In order to improve the pulp strength, reinforcing agents can be added into the pulp forming well according to requirements so as to improve the quality requirement of individual papermaking products.

The preparation method of continuous hot grinding mechanical straw pulp-process technical conditions are as follows:

1. the cut straw specification: 30 mm-60 mm (more than 70%).

2. The concentration of the pulper is 2-3.5%. (or adjusted according to practice).

3. Outlet concentration of screw conveyor: 30-50%; the grass temperature is 60-80 ℃.

4. The concentration of coarse grinding (slurry) is 30-50%. (can be adjusted according to actual conditions).

5. The rotation number of the screw machine after coarse grinding is 60-100 r/min.

6. The concentration of the pre-soaking (after coarse grinding and before fine grinding), namely the screw conveyer, is 30-50%, and the temperature is 60-80 ℃.

7. The pulping degree is 18-22 DEG SR.

8. Yield of finished pulp: 83 to 86 percent.

And (3) knotting: the technology (process) is characterized in that raw materials are washed firstly (water in the raw materials is easy to recover and treat), and coarse grinding, conveying and heating are carried out, and then the raw materials are thermally ground into pulp. And (4) treating and recovering the water for papermaking.

The main process route is as follows:

grass cutting → grass washing (water recovery) → conveyor (heating) → coarse grinding (heating) → conveyor continuous hot grinding → pulp washing → (reinforcing agent addition) pulp forming → pulp making → paper making (water recovery) → finishing.

The technological process includes secondary coarse and fine grinding and tertiary (layered) water recovery. The whole process is for environmental benefit and product quality.

The first grass washing is beneficial to recycling water, namely, is beneficial to environmental protection. The whole process of hot grinding is to expand the straw so as to be beneficial to removing the constraint of organic matters in the straw to cellulose, hemicellulose and lignin and removing the bonding force of chemical bonds of the organic matters, thereby achieving the purpose of pulping (see figure 1).

Examples of the experiments

The method comprises the following steps of comparing experimental data measured in part:

in the practice of simulating actual production, some key technical conditions, namely data, are necessary and critical to the SMRM (acid-free, alkali-free) continuous thermomechanical pulp technology. The key steps are as follows:

1. the raw material must be washed before refining and pulping, and the waste water in the stage is easy to recover and pollution-free, so that the water consumption per ton of pulp is controlled within 10 tons. Up to no more than 12 tonnes. And the water consumption at this stage is about 2 per ton of pulp.

2. Concentration of coarse grinding: the rough grinding is the basis of the fine grinding, and is prepared for the technique that the fine grinding meets the pulping requirement, and the cut and washed forage is ground into coarse fibers so as to be beneficial to absorbing heat and expanding the fibers. When the concentration of the coarse grinding pulp is reduced to 20-28%, the quality of coarse grinding is not greatly influenced, but the adverse factor is brought to the fine grinding pulp of the next procedure. Firstly, 10% more water can increase the heat absorption and increase the coal consumption; and secondly, more than 10% of water is added, so that the discharge capacity of the wastewater is increased, and the load of wastewater treatment is increased, which is not favorable for environmental protection. And thirdly, high-concentration pulping which is not beneficial to fine pulping is realized due to the reduction of the concentration, the cutting action of a pulping machine on fibers can be increased in the pulping process, the friction action among the fibers is reduced, and the pulping is not beneficial. On the contrary, when the refining concentration is higher than 50%, the resistance of the brown stock in the conveyor increases and the flow resistance in the disc mill increases. The grinding speed is reduced, the grinding yield is reduced, the power consumption and the cost are increased, and the like. Therefore, the concentration of the coarse pulp should be controlled to 30-50%, and the concentration of the fine pulp is preferably uniform.

3. Coarse grinding pulp temperature: the coarse grinding pulp is disadvantageous when the temperature of the coarse grinding pulp is lower than 50 c, and the heat loss from the conveyor to the refiner is too large when the temperature of the coarse grinding pulp is higher than 80 c. And the retention of organic matters in lignin, hemicellulose and grass raw materials is not facilitated due to the overhigh temperature. Because they can be degraded more or less at high temperature, the method is not favorable for environmental protection, and is not favorable for improving the pulping yield and reducing the cost. When the refining temperature is higher than 80 ℃, gas is emitted from a plurality of places, which is not beneficial to energy conservation. Therefore, the temperature of the coarse refining is preferably controlled to 60-80 ℃. Can also be controlled at 55-75 ℃.

4. Concentration of the refined pulp: the high-concentration pulping can increase the friction among fibers, and the extrusion is beneficial to the devillicate and brooming of the fibers, which is the purpose of pulping and pulping. However, too high concentration has poor fluidity, which increases the refining resistance, increases the damage of partial fiber locally, reduces the refining yield, increases the cost, and does not improve the quality of the finished pulp. The grinding concentration is too low, so that the cutting capability of the grinding teeth on fibers is increased, and the grinding is not favorable. Is not beneficial to improving the quality of the finished pulp. The simulation production proves that the concentration of the refined pulp is controlled to be optimal within 30-50%, and the pulp refining in the range is also beneficial to the front and back coordination of the production process.

5. Temperature of fine grinding: the high temperature is beneficial to the swelling and expansion of straw pulp fiber and the devillicate brooming of the fiber. Wood pulp is freed of resin when refined at high temperatures above 50 ℃ causing resin blockage, which is not the case with straw pulp. Through simulation production pulping experiments, the temperature requirement of the fine grinding pulp is well adapted to the coarse grinding pulp, and the effect is optimal from the four aspects of yield, quality, cost and environmental protection.

6. Pulping degree: the strength of the paper is improved along with the improvement of the beating degree. In a simulation production experiment, the temperature and the concentration of the fine grinding pulp have great influence on the finished pulp beating degree, and the rough grinding pulp condition has little influence on the finished pulp beating degree. When the temperature of the refined pulp is 60-80 ℃ and the concentration is 30-50%, the beating degree of the finished pulp can reach 18-20 DEG SR. The highest SR can reach 22 degrees, and the pulp quality is good.

7. Yield of finished pulp: through experimental comparison, the pulping yield is high under the conditions, and is generally 83-86%. The pulping yield is reduced after changing the conditions.

8. Hardness and fiber binding of the pulp: during production, the pulp quality and the fiber binding force are poor due to the fact that the pulping temperature and the pulping concentration are controlled or the various technological conditions are not properly controlled in the initial production stage. When using the poor quality pulp, the following measures can be taken to compensate. Firstly, pulp needs to be ground before papermaking, and the improvement of the beating degree is the first way of improving the binding force of paper fibers. Because the paper is beaten out in the beater. Secondly, some reinforcing agents can be added properly. Thirdly, according to different paper varieties, a certain amount of waste paper pulp is properly prepared. For example, it is not practical to produce newsprint only with groundwood, which must be combined with about 30% bleached chemical pulp, and so on.

In any event, the present process provides better fiber status and binding than hardwood pulp, a result of repeated investigation and experimentation, as evidenced by the pulp samples produced by the process. The pulp sample has good binding force and is incomparable with ground wood pulp. We used domestic commercial groundwood and also in Russian groundwood, and the workers called him was bread pulp, which fell off slag both when moving and transporting the groundwood. Even if the ground wood pulp is refined three times before papermaking, the ground wood pulp is not like straw pulp. Groundwood pulp is a pulp sheet that does not make such fiber bonds. This is mainly determined by the characteristics of the plant material and the production process and technique. Part of the main data is compared with the data in table 1 and table 1.

TABLE 1

TABLE 1

And (4) conclusion:

1. to date, no continuous thermomechanical pulp has been produced abroad, even no pre-preg thermomechanical pulp; the production of semi-chemical straw pulp or presoaked mechanical straw pulp is produced at home, but the production is stopped for a long time due to the problem of environmental pollution; at present, no 'process technology for continuously hot grinding straws (hard') exists in China.

2. The 'continuous hot grinding straw (hard) pulp process technology' is proved in the simulation production process, and the paper pulp produced by the process is suitable for producing corrugated medium paper, box board (as lining pulp), bobbin paper pulp and the like; the pulp can also be used for producing other varieties of packaging paper according to a certain proportion; the pulp (pulp sample) can be prepared into cultural paper and the like after being treated by proper processes such as bleaching and the like.

3. The straw pulp produced by the process technology can replace part of imported waste paper and relieve the contradiction of waste paper supply shortage in domestic markets.

4. The straw pulp produced by the process technology has the advantages of simple process, easy operation, less investment and low cost, so the economic benefits of pulping and papermaking enterprises are good, and the straw pulp can make a contribution to national economic development.

5. Because the process technology does not use alkali and other chemical raw materials for producing the straw pulp, the waste water in the production process is easy to treat and can be recycled, and the environment is not polluted. Is a clean process technology and can be popularized and used.

6. After the 'smrm continuous hot grinding straw (hard) pulp process technology' is used, a large amount of rural waste straws can be utilized every year, so that the pollution caused by using imported waste paper is reduced, and the environmental pollution caused by treating the waste straws in rural areas is reduced. But also brings good economic benefit for rural areas due to the utilization of waste straws. Therefore, the technology of using the smrm continuous hot grinding straw (hard) pulp is feasible and is an improvement for the benefit of the nation and the people.

The method has the following economic benefits:

the gross profit of each ton of pulp exceeds 500 yuan calculated by 1900 yuan market selling price of each ton of air-dried pulp (calculated by 12 percent of water content) and 1400 yuan calculated by the total cost (cost) of each ton of air-dried pulp (12 percent of water content).

If the annual output reaches 2.0 ten thousand tons, the annual profit can be obtained by 848 ten thousand yuan, the income tax payment is 212 ten thousand yuan each year, even if the yield is 35 percent in the first year, the annual profit is 296.8 ten thousand yuan, and the SMRM continuous thermomechanical pulp total cost table is shown in the table 2.

TABLE 2

The foregoing description is only exemplary of the invention and is not intended to limit the spirit of the invention.

Claims (5)

1. The preparation method of the continuous thermomechanical straw pulp is characterized by comprising the following steps:

(1) washing with water, taking rice straws or stalks as raw materials, dedusting, sending to a pulper for washing, and concentrating;

(2) conveying the cleaned and concentrated straw raw material by a screw conveyor, introducing steam into the conveying process for heating at the temperature of 60-80 ℃, conveying the heated straw raw material into a pulping machine by the conveyor for coarse grinding at the pulping temperature of 60-80 ℃, wherein the pulping concentration is 30-50%;

(3) directly feeding the coarsely ground pulp into a screw conveyor, continuously introducing steam at the temperature of 60-80 ℃, feeding the heated straw raw material into a pulp grinder through the screw conveyor for fine grinding, wherein the pulp grinding temperature is 60-80 ℃, and the pulp grinding concentration is 30-50%;

(4) and screening and concentrating the fine-ground paper pulp to obtain the straw pulp.

2. The method for producing mechanical straw pulp by continuous thermomechanical milling as claimed in claim 1, wherein in step (3), the refining can be carried out continuously in more than two stages of thermomechanical mills or in multiple refiners.

3. The method for producing continuous thermo-mechanical rice straw pulp according to claim 1 or 2, wherein after the step (4), the screened-out raw pulp is returned to the screw conveyor in the step (3) to be heated and softened and then ground.

4. A method for producing continuous thermo-mechanical rice straw pulp according to claim 1 or 2, characterized in that in step (2) or (3), the degree of beating is 18-22 ° SR.

5. The method for preparing straw pulp of continuous thermal mill machinery according to claim 4, characterized in that the obtained straw pulp is suitable for producing pulp for corrugated medium, boxboard and bobbin paper.

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