Monday, July 15, 2019
GINNING OF COTTON FIBRES, POST GINNING TREATMENT
GINNING OF COTTON FIBRES:
What is the main object of ginning? How cotton is ginned? As we know that cotton fibres obtained directly from farms have cotton seeds and many other impurities like dirt, dust and plant left with them. Therefore it is necessary to make cotton fibres free from these impurities. Ginning is the first effort to make cotton fibres free from impurities. “Ginning is a process of separation of cotton fibres from cotton seeds”. The main object of ginning is to remove the cotton fibres from cotton seeds. Secondary dirt, dust and leaves are also removed during ginning. Now, this day ginning of cotton is performed by different types of machines available.
WORKING OF GINNING MCHINE:
The working of a ginning machine can be described in the following steps:
• Feeding system.
• Drying system.
• Opening system.
• Cleaning system.
• Seeds separation system.
• Lints collection.
• Cotton feeding system: In the old type of ginning machines cotton arriving in the trailer is fed into the gin through a lattice. Cotton is put onto the lattice. When lattice rotates, it carries the cotton forward with it. The lattice is made of wooden stripes. Cotton is fed in the hopper. Cotton falls onto the lattice automatically due to its gravity. In modern machines, the cotton is directly sucked through a large air suction pipe and is sent into gin. The diameter is of this suction pipe is nearly equal to 16”.
• Drying system: Moist cotton creates difficulties during the opening, cleaning and seed separating action, so that it demands to remove excess amount of moisture. Due to excess water content cotton fibres grip strongly the cotton seeds. Cotton fibres are passed through the dryer and an extra amount of moisture is removed up to the maximum extent. Now cotton is ready for opening and cleaning.
• Opening system: when cotton passes through rotating spikes and saw rollers, modules are broken. In modern machines, modules are broken by suction pipes.
• Cleaning system: Cotton now passes through the cleaning cylinder. This cleaning cylinder has six to seven rotating, spiked rollers. These rollers break clumps of cotton. Foreign material leaves, dust remove here and passes through rods or screens for removal. The stick machine uses centrifugal force to remove larger foreign matter such as sticks and burrs while the cotton is held by a fast revolving saw cylinder.
• Seed separation system: The gin stand uses the teeth of rotating saws to pull the cotton through a series of ginning ribs, which pull the fibres from the seeds which are too large to pass through the ribs. The cleaned seed is then removed from the gin via an “auger system”. The seed is reused for planting or is sent to an oil mill to be further processed into cottonseed oil and cottonseed meal.
• Cotton lints collection system: The lint cleaners again use “saws and grid bars”, this time to separate “immature seeds” and any remaining foreign matter from the fibres. The bale press then compresses the cotton into bales for storage and shipping. Modern gins can process up to 15 tonnes (33,000 lb) of cotton per hour.
• POST GINNING TREATMENT( BALE FORMATION OF COTTON FIBRES):
After ginning cotton lints are ready to send to market. Since cotton fibre has low specific gravity so that it covers more volume and difficulties are faced during shipping and transportation. Compact packing of cotton is done to minimise the volume. Cotton lints are compressed through a hydraulic press. The compact and desired shape of the cotton bale is obtained. Each bale has 500 lbs. weight. compressed bales are banded and wrapped. Moisture resistant wrapping of the cotton bale is done. Cotton or polypropylene may be used for wrapping, which maintains the proper moisture content of cotton. Proper and good wrapping also helps to keep bales clean during handling, storage and transportation. The particular identification number is given to each bale. “Now cotton is ready to send for marketing”.
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