As well known, Sugarcane is one of the materials for sugar making. Sugarcane bagasse is a by-product of sugar mills and is a raw material for papermaking with regional characteristics. How much do you know the sugarcane bagasse paper? how to make paper from sugarcane wastes?
Sugarcane is a raw material of stem fiber grown in a year, which is equivalent to the length of hardwood fiber. The data shows that the fiber form of various sugarcane is different, planting area, climatic conditions, and growth period may also cause fiber morphology. Generally, the length of the sugarcane fiber is 1.0 to 2.0 mm, the width is 14 to 28 um, the width ratio is 60 to 80, and the wall cavity ratio is much smaller than 1, with the character of medium length, large width, and small wall cavity ratio. Compared with wood fiber, the length of bagasse fiber is only half of that of softwood, which is basically equal or even better than that of hardwood. The width is smaller than that of softwood but similar to that of hardwood fiber. The length ratio is similar to that of most wood fiber. The ratio is much smaller than the wood material. Among the grass-based raw materials, the length of the bagasse fiber is relatively long, the width is much larger than other varieties, and the wall-to-cavity ratio is the smallest among the grass materials. In general, when fiber length is less than 45, it will lose their value of papermaking due to their lack of interlacing ability and low paper strength. When the fiber wall cavity ratio is greater than 1, the fiber is stiffer.
The bagasse is a good raw material for papermaking after demyelination. Sugarcane bagasse is a kind of grass fiber, easy to be cooked and bleached, and fewer chemicals needed. Although the silicon content is higher than that of wood, it is lower than other grass fiber materials. Therefore, the technology and equipment of bagasse pulping and alkali recovery process are mature and simpler than other grass fiber materials like.
Bagasse papermaking process
Material preparation
After sugar press, about 50% of the sugarcane bagasse can be used for papermaking. However, some of the cane marrow (myeloid cells) have no interweaving force and should be removed before the pulping process. Therefore, it is necessary to prepare materials before pulping. The traditional bagasse preparation is firstly carried out in the sugar factory for the first semi-dry decontamination and then packaged and sent to the paper mill for dry storage. Then the horizontal or vertical degumming machine is used for dry removal.
pulp production from bagasse
The pulping process includes cooking → washing → screening → bleaching. The most common cooking equipment for bagasse pulping is digester. Because bagasse is relatively easy to cook, it is more suitable for small-scale enterprises to use rotary digester as cooking equipment because of the advantages of low investment, simple operation and high flexibility.
For modern bagasse pulp making, the pulp cooking process adopts soda pulping and cold blow. The cooking equipment uses a horizontal tube continuous digester.
significant advantages as following:
- the cooking time is short, less consumption of alkali and steam; high pulp yield (under the same K value, the yield is increased by 5% on average compared to other fibers), high and strong. The ratio of wood pulp can be reduced;
- The macro process design is compact and easy to operate and manage;
The whole system is centrally controlled, adopting advanced and reliable DCS interlock control, and the cooking equipment runs safely. Less maintenance and low labor costs; suitable for large-scale pulp and paper production from sugarcane bagasse..
The use of cold blow can reduce the damage of the fiber, the pulp strength is high, and it is beneficial to the heat recovery. Since the bagasse has light bulk density, large compressibility, easy formation of a plug, and strong absorption capacity of the liquid, the continuous cooking equipment is relatively reliable and suitable.
The most commonly used equipment for pulp washing equipment is the vacuum drum washer. Because of its low operating cost, simple operation and high black liquor extraction rate, many pulp mills use this equipment as a pulp washing equipment.
In the past, the traditional screening system is an open low-concentration screening system with a screening concentration of 0.8-1.0%. the pulp mill usually adopts CX sieve and low-concentration desander. The water consumption per ton of pulp is up to 100m3, and the sewage is discharged 75m3, which directly increases the production cost. Now, to change the situation that the conventional screening and purification system has large water consumption, large screening and purification system, poor quality of the slurry after screening, the large amount of wastewater and difficult treatment, the bagasse pulp, and paper mill adopt the medium-concentration closed screening system.
Sugarcane bagasse pulp is easier to be bleached. Ordinary CEH three-stage bleaching can bleach the bagasse pulp to 80% ISO, so the old sugarcane bagasse pulp plant basically uses CEH three-stage bleaching. However, in recent years, chlorinated organic compounds such as dioxin which is carcinogenic in the waste liquid discharged from chlorine bleach have been internationally recognized. The environmental pressure of the CEH three-stage bleaching process is relatively high, sooner or later, less chlorine or even chlorine-free bleaching will be widely adopted.
Alkaline recovery
Conventional alkali recovery systems use evaporation, combustion, causticization techniques to treat black liquor and recycle chemicals and heat. Short-tube four-effect evaporation station, jet burner with venturi or electrostatic precipitator, continuous causticization, clarifier clarification white liquor, vacuum slag washer washing white mud, traditional bagasse pulp recovery technology and equipment are currently mature, and run better. The disadvantage is that the scale is relatively small (not suitable for pulp mills with an annual production scale of more than 50,000 tons), and the dryness of white mud produced is low (about 40%).
sugarcane bagasse papermaking
Sugarcane bagasse pulp is a short fiber with low tearing and is similar in nature to hardwood pulp. For most kind of paper and paperboard, sugarcane bagasse pulp can almost completely replace hardwood pulp. After mixing with a certain amount of long fibers, the bleaching chemical bagasse pulp can be used to make a variety of high-grade culture and household papers, such as coated base paper, copy paper, double-adhesive paper, high-grade toilet paper, napkins, etc. Using a suitable papermaking process, you can even make high-quality copper base paper and newsprint.
Conclusion
As the saying goes, “There’s no such thing as waste, Only stuff in the wrong place” For bagasse that was previously burned as fuel, if it is used as a raw material for papermaking, the use value is increased by 3 to 5 times. As a raw material for papermaking, each ton of bagasse can replace 0.5 to 0.8 m3 of papermaking materials, making full use of sugarcane bagasse papermaking, which can alleviate the shortage of resources and play an active role in environmental protection.