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The bamboo pulp is one kind of paper pulp like wood pulp, straw pulp or reed pulp. The bamboo pulp is usually made from moso bamboo, phyllostachys pubescens and sinocalamus affinis by sulfate digestion process or soda process. The bamboo fiber morphology and length is intermediate between wood fiber and straw fiber.
Bamboo pulp can be made into bamboo paper. Bamboo paper is strong and it has wide applications. The bleached bamboo paper is used to manufacture offset paper, typing paper and high-grade culture paper. The unbleached bamboo paper is generally applied to package papermaking. Besides, bamboo pulp and wood pulp can be mixed and used to make cable paper, insulation paper, and cement bag paper.
Bamboo pulp market analytics
Bamboo fiber is the best fiber material for papermaking after softwood fiber because some kinds of bamboo have long fiber and the same features as softwood. Bleached bamboo pulp has better tearing strength and evenness compared to hardwood pulp. Due to the cost of bamboo pulp being lower than wood pulp, the need for bamboo pulp increase continuously. In 2010, bamboo pulp takes 0.56% of Chinese pulp capacity. Bamboo pulp has great market potential in China. As for the international market, it is affected by the production or stock of main pulp exporting countries and pulp consumption. In a word, the pulp price is changed by the trend of world economic development. Bamboo chips can be also applied for bamboo activated carbon making and bamboo pellet making.
Because bamboo pulp has similar properties to softwood pulp and hardwood, the price of the bamboo pulp can reference the price of hardwood pulp.
Bamboo pulp processing
Bamboo pulp processing can be simply classified into materials preparation, pulp cooking, pulp washing, and pulp bleaching.
- Due to the seasonality of bamboo cutting, for ensuring the continuous production, the pulp mill must stock a certain amount of bamboo. Generally, the bamboo storage capacity should be used for 3-6 months. New bamboo should be dried by the air and de-greening.
- As for the stacking and unstacking of the bamboo bundle, a portable belt conveyor and loader will be the best helper.
- After the bamboo bundle enters the pulp mill, it is cut into bamboo chips by the bamboo cutter and is stored with other chips. The size of bamboo chips is 10-25mm.
- When the bamboo is stored in the open system, the position in the process should be designed according to the principle of first screening and last storage. This kind of principle can remove the bamboo sawdust from the screening bamboo chips. The fermentation and mildew of bamboo chips are avoidable in the storage of bamboo.
- The qualified bamboo chips are sent to storage. The long bamboo will be back to bamboo cutter and sawdust will be used as waste and burned in the boiler.
- The stored bamboo chips are used according to the first-in-first-out principle. Ensuring the full use of bamboo chips and avoids the stored bamboo chips go bad because of long-term storage.
- It is necessary to wash bamboo chips in the process of materials preparation. Remove the loam among the bamboo chips, which reduce the wearing, scaling of paper pulper and silicon interference.
Bamboo Pulp cooking
The qualified bamboo chips in the preparation through the conveyor enter into the pulper. After bamboo feed into pulper, pour the black liquor from the bottom of the pulper, presoak the bamboo chips, and remove the air from the bamboo chips. Use the high-temperature black liquor and hot white liquor displace the black liquor in the pulper. Control the temperature in the pulper up to 145℃, and heat the pulper with steam, raise the temperature to the cooking temperature and keep it. When the reaction reaches the settled H factor, send the warm and weak black liquor of the pulp washing process into the bottom of the pulper, displace the high-temperature black liquor and reduce the temperature in the pulper to 100℃.
- For bamboo pulp making, it generally adopts the kraft process. The kraft process has high digester yield, high strength, less pollution, soft fiber, and mature technology of alkali recovery. Compared to wood, bamboo is easier to cook because of its composition.
- The paper pulper machine adopts the vertical and continuous pulp digester. In general, the cold blow is a typical choice, it not only recovery the rest heat, but also avoids the leakage of flue gas. Besides, reduce the steam consumption and pyrolysis of pulp, improve the strength of the fiber.
- In the real bamboo pulp processing, due to the dense structure of bamboo and the difficulty of air removing in the conduit, bamboo pulp cooking requires longer penetration time. Penetration time for raising the temperature is 1.5-2h, penetration time for keeping temperature is 2-2.5h. As we all know, there are vertical pulper and horizontal pulper. Different specifications of pulpers for bamboo pulp making as below:
Rotary Spherical Digester
|Vertical Digester||Continuous Tubular Digester|
|Capacity(dry bamboo chips)||180-220kg||220-230kg||110-160kg/min|
|alkali charge(sodium cyanide)||18%-22%||15%-18%||18%-20%|
|maximum cooking pressure(MPa)||0.55-0.65||0.65-0.7||0.6-0.7|
|maximum cooking temperature||–||Around 165||165-170|
|heating method||Direct heating||Indirect heating and direct heating||Direct heating|
|brown pulp hardness||10-18||14-18||14-18|
|residual alkali of black liquor||9-16g/L||10-16g/L||10-16g/L|
We can get a conclusion according to the above specifications that vertical pulper is more applicable.
Bamboo pulp washing and screening
The practice has proven that bamboo fiber is long, and it has good drainability. The bamboo pulp is easier to wash compared with other straw pulp, even the hardwood pulp. The common equipment for the bamboo pulp washing process includes vacuum washer, pressure pulp washer, and Horizontal belt filter. Generally, the large-scale bamboo pulp production line can use a twin roll press or DD washer. Vacuum washer is more suitable in overall consideration.
Bamboo pulp screening and cleaning mainly remove the crude residue, dust, sand. Bamboo pulp making will produce a lot of crude residues, they are the knots that are not cooked sufficiently. These crude residues are not suitable to cook or produce bad influence on bamboo paper quality.
The bamboo pulp washing adopts multi-section countercurrent washing that can efficiently extract black liquor and ensure the alkali recovery. The bamboo pulp adopts close screening system, screening concentrations are 2-3%. This type of technical combination saves water, reduce pollution, and require less treatment of slurry-residue.
Bamboo pulp bleaching
The pulp bleaching is used to improve the pulp whiteness, keep the strength of bamboo pulp, and reduce pollution. Because the oxygen delignification and medium consistency technology mature gradually, the bleaching process is the short process with 3-4 stages. To meet the strict requirement of environmental protection, the bleach agent uses chlorine dioxide to replace. As for the choice of bleaching, there are ECF, TCF, EPP, ZXP, TCF, ECF, CEH, and etc. Currently, the ECF is still the best popular and efficient pulp bleaching process. But from the economic considerations, CEH is more applicable.
Advantages of bamboo pulp
- Bamboo pulp has medium-length fiber, so it is thin and soft, and also has high bulk and tearing strength, low tensile index and burst index.
- Wide raw material sources.
- Simple pulp processing required.
- Low cost required.
- High market potential.
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