BIVIS
process: a continuous pulping process from cotton linters for high quality
writing & printing papers and special grades. Cotton fibres and
cotton-based papers have a long story, which is still continuing today.
Papers from cotton fibers
For a long, paper
was formerly made from non-wood fibres such as flax or from woody materials,
such as mulberry trees. Even though if pulp and paper industry is using mainly
wood and recycled fibres as raw materials, cotton fibers are still today very
valuable fibers for paper industry. They are used for special grades and high
quality papers.
Cotton fibers
Cotton fibers,
mainly known as a raw material for textile industry, are also a popular raw
material for paper industry. Cotton fibers converting plant, located in cotton
growing countries, are providing long and short fibers.
Long fibres are
also called “staples cotton”. The length of such fibers is between 20 to 50 mm.
They are separated from seeds and short fuzz with gins machines, and then
collected and sent to spinning mills.
Cotton linters, which are short fuzz or short fibers, are separated from
the seeds using delinting machines. They are collected and then used by paper
and chemical industry. The length of cotton linters is generally included
between 1.5 mm and 6 mm.
Cotton fibers used in paper industry
Cotton fibers are
used to produce high quality papers. But, due to high prices of the raw
material, paper industry generally uses cotton wastes. For very special
applications virgin fibers can be used. Paper industry uses different kinds of
cotton fibers.
Wastes from textile industry: cotton combers, cotton threads and cotton rags:
Cotton combers,
waste from combing machines used in textile industry, are long fibers (up to
2cm). Cotton threads and cotton rags allows getting long fibers. Both of these
are wastes from textile industry. These fibers
are used for very high valuable papers such as bank note paper. Morphology of the fibers, different
than the one of cotton linters, allows getting high mechanical and physical
properties required for the end use of paper for some special properties such
as double fold, strength, opacity and printing properties.
Waste from agriculture: Cotton linters
Bleached cotton
linters fibers are used for many applications in paper industry. It is used
alone or mixed with other pulps, for applications such as technical papers,
security paper, insulating paper, filter paper, non- woven fabrics and fine
papers such as art paper. High quality printing & writing papers are also
produced from cotton linters pulp.
Technical information regarding cotton linters
1. General information: Cotton
linters are short fibres (fuzz) located around cotton seeds. These fibres are
separated from cotton seeds using a special machine, called linter machine or
delinting machine. Cotton fibres collected after first pass using the delinting
machine are called “first cut linters” and they are called “second cut linters”
after second pass in the same machine. Third cut linters often called as “hull
fibres” and mill runs are also
available for pulp production. Cotton linters are delivered in bales; the weight
of them depends on country origin. The bale weight is generally around 500
pounds (220 kg).
2. Cotton species and linters: Main cotton
species producing linters is Gossypium Hirsutum Latifolium. Other cotton
species, such as Gossypium Barbadense, have naked seeds, so these species are
not giving linters. Gossypium Hirsutum Latifolium represents roughly 87% of
world cotton fibres production and Gossypium Barbadense around 8% of same
production.
3. Cotton linters properties: Cotton
linters physical properties are summarized in Table 1 and chemical
composition of typical second cut cotton linters is mentioned in Table
2.
Technical information regarding cotton
linters pulping processes
1. Conventional pulping processes: Lot of
conventional processes are discontinuous processes. Main steps of these processes are here after
mentioned:
• Cotton linters bales
handling and dry or wet fibres cleaning.
•
Fibres handling and spherical boilers feeding.
• Cotton
fibres cooking with alkali solution (generally 10 to 15% Caustic Soda) and
steam, using spherical digesters.
•
Drainage of the pulp in “blow tanks” with black liquor recovery.
•
Unbleached pulp washing using belt press.
• Cotton
linters pulp dilution and fibres shortening using refiners for further cotton
pulp pumping using conventional
centrifugal pumps.
• Pulp
bleaching including 2 or 3 bleaching steps performed with bleaching agents such
as Oxygen, Hydrogen Peroxide, Chlorine Dioxide, Sodium Hypochlorite or other. These bleaching steps are using pulp mixers and conventional pulp chests
or bleaching towers. Pulp washing is performed after each bleaching step using
washing drums. Pulp Ph is then adjusted to requirements.
•
Bleached cotton linters pulp may be later screened and cleaned.
2. BIVIS pulping process: At the end
of eighties, CLEXTRAL developed a continuous process for cotton fibres pulping
using BIVIS machines. Since 1989, 11 pulping
lines processing cotton fibers (cotton linters, cotton combers and cotton
wastes for textile industry) using BIVIS process are in operation in the world,
3 of them are processing cotton
linters. The latest pulping plant processing cotton linters started in
Uzbekistan. The pulping line capacity of the mill is 20,000 ADT/year. Bleached
cotton linters pulp is used to produce writing & printing paper.
Cotton linters pulping line at Yanguyul Pulp and Paper Mill
Process
description: BIVIS process is a continuous and automated process.
Main steps of BIVIS process are described hereafter. See process diagram.
• Cotton linters bales handling and dry cleaning: Cotton
linters are delivered to the mill in high density bales. First step of the
process includes bales openers. Cotton fibres are then dry cleaned. Dry
cleaning equipment includes a cyclone used for heavy contaminants removal. A
beater cleaner for dust and foreign matters as well as a metal detector are
then used to complete dry cleaning. Fibers are then air conveyed to a feeding device for further cooking step.
• Cotton fibers impregnation / cooking: Back water
is added and Alkali content is adjusted for cooking operation which is
simultaneously performed together with fibers chopping. Cooking operation is
performed at high pulp consistency (35%) and temperature at BIVIS discharge is
90°C. No steam is required for cooking step because the conversion of
electrical energy into heat during the process is high enough for wax, fat, pectin and proteins dissolving
and cellulosed foreign parts degradation. Cotton fibers treatment is completed
in a dwell unit, consisting on an insulated housed belt or screw conveyor
allowing a 60 minutes retention time.
• Pulp washing and bleaching: Unbleached pulp issued
from retention tank is delivered to a second BIVIS machine unit used for
washing, fibers cutting and pulp bleaching. Pulp washing operation is performed
using 3 first compressing and
shearing sections of the BIVIS machine the barrel of which is equipped with
filters. Generally direct washing is performed; however, counter-courant
washing may be used. Fibers cutting is simultaneously performed together with
washing. Bleaching operation is carried out injecting a hydrogen peroxide
solution and an alkali solution. No chelating agent or stabilizer is used. Washing water and chemicals are added by
mean of volumetric metering pumps. Pulp consistency at BIVIS discharge is
included between 35 to 40%. Bleaching reaction is completed in a second dwell
tank, consisting on an insulated housed belt or screw conveyor allowing a 90
minutes retention time.
• Bleached pulp washing: Bleached
pulp is diluted down to 3.5% and the pulp is then dewatered using a screw
press, which delivers bleached pulp at 35% consistency. After dewatering, the
pulp is diluted using an agitated
dilution chest and pulp consistency is adjusted to 3-3.5%. Pulp Ph is adjusted
to required value in the dilution chest using Sulphuric acid before to be
stored in a dump chest. Bleached cotton linters pulp is then refined and
screened.
Operating parameters: Based
on 1 ADMT (Air Dry Metric Ton) of bleached cotton linters pulp, produced using
here above described process, main operating parameters are:
• Raw linters
consumption, based on 94% dryness cotton linters and depending on linters
quality: 1.14T to 1.27T,
• Cotton linters wastes and
dust from dry cleaning section: 60 to 100 kg, depending on linters quality,
•
Electrical energy consumption: 1000 to 1100 kWh,
•
Steam consumption: 0,
•
Chemicals consumption:
– Caustic Soda (active
product): 60 to 65 kg,
– Hydrogen peroxide (active
product): 45 to 55 kg,
– Sulphuric
acid or Hydrochloric acid: (active product): 5 to 10 kg, depending on clear
water or back water Ph,
• Clear water
consumption for motors cooling and fresh water consumption: 25 m3, 9 m3 of which is later recycled in pulping process.
Pulp properties: Pulp properties, after Valley beater refining,
are summarized in Table 3.
Technical information regarding cotton linters paper process:
Several
paper grades includes cotton linters fibers. The amount of bleached cotton
linters pulp used in the end paper is depending on paper properties required.
Special grade papers and high quality writing and printing papers are produced
using 100% bleached cotton linters pulp. From bleached cotton linters pulp, as
described here above, writing and printing paper is produced using conventional
equipment. Paper production process includes a stock preparation unit and a
Fourdrinier paper machine. For some paper qualities, paper is later calendered.
Description of paper production process:
1. Stock preparation:
• Pulp storage: Bleached half stock is stored in dump
chest.
• Refining: Before pulp refining, fibers length
adjustment is done using a wide angle refiner fit with “cutting” fillings. The
bleached cotton pulp is then refined with disc refiners. Main refining
operating parameters are specific energy required for fibres cutting and pulp
refining is 350 kWh/ADT and drainage index of refined pulp is 50 °SR after pulp
screening.
• Screening: Bleached pulp is screened using conventional equipment including hydro-cyclones.
2. Paper production: Conventional
equipment is used for pulp preparation. Paper produced includes 12% of China clay,
2.5% of Starch (Hiphase 43) and Aluminium Sulphate as retention agent.
80 g/m2 paper is
produced using conventional Foudrinier machine. The paper is then calendered
using a supercalender fit out with 10 rolls.
3. Paper properties: Paper properties are summarized in Table 4.
4. Printing properties:
Printing
properties of 100% cotton linters calendered writing and printing papers were
compared with 2 typical and standard European writing & printing papers.
Compared to other European writing & printing papers, the calendered paper
using 100% Cotton linters fibers is presenting:
•
Better colour and details rendering, therefore less ink consumption,
•
Better gloss,
•
Better printing homogeneity,
•
Less paper blotting.
Conclusion of the Certified Laboratory
“100% Cotton
linters writing and printing paper is presenting printing properties, at least
as good as and often better, than European W & P papers”.
Cotton linters: an available resource for high quality paper:
In 2007, world
cotton fibers (cotton staples) production was 26,243,000 tons. It is generally
considered that cotton linters quantity, which is potentially available in the
world, represents around 18% of cotton staples,
i.e. around
4,724,000 tons for 2007. Cotton linters pulp production in 2007 was estimated
at 400,000 tons, for both paper and chemical industries, requiring around
500,000 tons of linters. So, only less than 9% of potential linters fibers were
used for pulping.
Conclusion:
Courtesy : Papermart
2 comments:
Utilizing hydrogen peroxide for a mouth wash on a normal basis will help maintain healthful levels of bacteria and protect against future canker sores. Get more information about hydrogen peroxide on this website.
Qui peut m'indiquer un ou plusieurs achêteurs de balles de cotton linters (plusieurs tonnes), client(s) se trouvant en Europe ou Asie SVP?
Post a Comment