Bamboo Pulp Making
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, portable belt conveyor and loader will be the best helper.
After 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 in according with 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 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 pulp washing process into the bottom of pulper, displace the high-temperature black liquor and reduce the temperature in the pulper to 100℃. For bamboo pulp making, it generally adopts kraft process. The kraft process has high digester yield, high strength, less pollution, soft fiber, and mature technology of alkali recovery. Compared to the wood, the 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 typical choice, it not only recovery the rest heat, but also avoid 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 require longer penetration time. Penetration time for raising 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:
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 bamboo pulp washing process includes vacuum washer, pressure pulp washer, and Horizontal belt filter. Generally, the large-scale bamboo pulp production line can use 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 a bad influence on the bamboo paper quality. The bamboo pulp washing adopts multi-section countercurrent washing 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 save water, reduce the 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 the pollution. Because the oxygen delignification and medium consistency technology mature gradually, bleaching process is the short process with 3-4 stages. To meet the strict requirement of environmental protection, 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.