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 fiber is the best fiber materials for papermaking after the 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 the hardwood pulp. Due to the cost of bamboo pulp is lower than wood pulp’s, 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.
Because the bamboo pulp has a similar property with softwood pulp and hardwood, the price of the bamboo pulp can reference the price of hardwood pulp.
Bamboo pulp processing can be simply classified into materials preparation, pulp cooking, pulp washing, and pulp bleaching.
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℃.
|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.
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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.
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.
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