Bhavdip Paldiya
Dept. of Textile Technology
Sarvajanik College of Engineering & Technology, Surat, India
Email: bhavdipk9009@gmail.com
Cotton ginning A cotton ginning is a machine that quickly and easily separates cotton fibers from their seeds, allowing for much greater productivity than manual cotton separation.
The fibers are processed into clothing or other cotton goods, and any undamaged seeds may be used to grow more cotton or to produce cottonseed oil and meal.
HISTORY
The cotton ginning is a machine that is used to pull cotton fibers from the cotton seed. Eli Whitney invented the cotton gin in 1793 or 1794. The invention of the cotton gin caused a revolution in the production of cotton in the southern United States, and had an enormous impact on the institution of slavery in this country.
Before the invention of the cotton ginning machine, not only was the raising of cotton very labor intensive, but separating the fiber from the cotton seed itself was even more labor intensive. Only the largest plantations found raising cotton cost effective. The invention of the cotton gin and its manufacture changed that.
Growing and cultivating cotton became a lucrative and less labor-intensive cash crop, contributing immensely to the rise of cotton production in the Deep South. This, in turn, led to an increase in the number of slaves and slaveholders, and to the growth of a cotton-based agricultural economy in the South.
FUNCTION
Cotton fibers are produced in the seed pods (“bolls”) of the cotton plant; as a result, the fibers (“lint”) in the bolls are interspersed with the seeds. The seeds must be removed from the lint to make the fibers usable.
Historically, this task was performed by hand: production of cotton required hundreds of man-hours to separate the seeds from a useful amount of lint. Many simple seed-removing devices have been invented over the years, but until the invention of the cotton gin most required significant operator attention and worked on a small scale.
Eli Whitney’s patent Gin The modern mechanical cotton gin was invented in the United States in 1793 by Eli Whitney (1765–1825). Whitney applied for a patent on October 28, 1793; the patent was granted on March 14, 1794, but was not validated until 1807.
Fig: Eli Whitney’s patent Gin
MODERN COTTON GINNING MACHINE:
In modern cotton production, cotton arrives at industrial cotton gins either in trailers or in compressed “modules”, which weigh up to 10 metric tons each. Cotton arriving in trailers is sucked into the gin via a pipe, approximately 16 inches (41 cm) in diameter, that is swung over the cotton. This pipe is usually manually operated, but is increasingly automated in modern cotton plants.
The need for trailers to haul the product to the gin has been drastically reduced since the introduction of the module. If the cotton is shipped in modules, the module feeder breaks the modules apart using spiked rollers and extracts the largest pieces of foreign material from the cotton. The module feeder’s loose cotton is then sucked into the same starting point as the trailer cotton.
Fig: Cotton ginning process
Description of each cotton ginning machine is given below:
1. Feeder:
The stationary head feeder employs a dispersing head with spiked rollers for breaking apart the module. the modules are transported to the stationary dispersing head on a series of beds: each bed is the length of a module and is constructed of flat wire-mesh belts or of chains similar to those of the module truck live bed.
A minimum of 1-1/2 beds is required, but additional beds can be added to increase ginning time. The stationary dispersing head is equipped with a series of horizontal spiked cylinders that remove cotton from the face of the module and deposit the cotton onto a conveyor or into an airline for mechanical or pneumatic conveying to the gin.
2. Dryer:
In the first stage of drying, heated air conveys the cotton through the shelves for 10-15 sec. The temperature of the conveying air is regulated to control the amount of drying.
To prevent fiber damage, the temperature to which the cotton is exposed during normal operation should never exceed 350 F. Temperatures above 300 F can cause permanent physical changes in cotton fibers. Dryer-temperature sensors should be located as near as possible to the point where cotton and heated air mix together.
If the temperature sensor is located near the exit of the tower dryer, the mixpoint temperature could actually be 100-200 F higher than the temperature at the downstream sensor. The temperature drops downstream results from the cooling effect of evaporation and from heat loss through the walls of machinery and piping.
3. Cylinder Cleaner:
The drying continues as the warm air moves the seed cotton to the cylinder cleaner, which consists of six or seven revolving spiked cylinders that rotate at 400-500 rpm.
These cylinders scrub the cotton over a series of grid rods or screens, agitate the cotton, and allow fine foreign materials, such as leaves, trash, and dirt, to pass through the openings for disposal. Cylinder cleaners break up large wads and generally condition the cotton for additional cleaning and drying. Processing rates of about two bales per hour per foot of cylinder length are common.
Fig: Cylinder Cleaner
4. Stick Machine:
The stick machine removes larger foreign matter, such as burs and sticks, from the cotton. Stick machines use the centrifugal force created by saw cylinders rotating at 300-400 rpm to “sling off” foreign material while the fiber is held by the saw. The foreign matter that is slung off the reclaimer feeds into the trash-handling system. Processing rates of 1.5-2.0 bales/hr/ft of cylinder length are common.
Fig: Stick machine
5. Extractor Feeder:
The primary function of the extractor-feeder is to feed seed cotton to the gin stand uniformly and at controllable rates, with extracting and cleaning as a secondary function. The feed rate of seed cotton is controlled by the speed of two star-shaped feed rollers located at the top of the feeder directly under the distributor hopper.
Fig: Extractor Feeder
6. Gin Stand:
The modern gin plant typically has multiple gin stands. Cotton enters the gin stand through a huller front. The saws grasp the cotton and draw it through widely spaced ribs known as huller ribs. The locks of cotton are drawn from the huller ribs into the bottom of the roll box.
Fig: Gin Stand
The actual cotton ginning process–separation of lint and seed–takes place in the roll box of the gin stand. The ginning action is caused by a set of saws rotating between ginning ribs. The saw teeth pass between the ribs at the ginning point. Here the leading edge of the teeth is approximately parallel to the rib, and the teeth pull the fibers from the seed, which are too large to pass between the ribs.
Ginning at rates above those recommended by the manufacturer can cause fiber quality reduction, seed damage, and chokeups. Gin stand saw speeds are also important. High speeds tend to increase the fiber damage done during ginning.
7. Lint Cleaner:
It is very important for cotton to flow uniformly and be well dispersed, particularly as it leaves the gin stand. Cotton is conveyed from the gin stand through lint ducts to condensers and formed again into a batt.
The batt is removed from the condenser drum and fed into the saw-type lint cleaner. The batt should be of uniform thickness and be evenly spread over the entire width of the lint cleaner; otherwise, poor cleaning and excessive fiber loss will result.
8. Bale Press:
The cleaned cotton is compressed into bales, which must then be covered to protect them from contamination during transportation and storage. Three types of bales are produced: modified flat, compress universal density, and gin universal density. These bales are packaged at densities of 14 and 28 lb/ft3 for the modified flat and universal density bales, respectively.
Fig: Bale Press
In most gins cotton is packaged in a “double-box” press wherein the lint is initially compacted in one press box by a mechanical or hydraulic tramper; then the press box is rotated, and the lint is further compressed to about 20 or 40 lb/ft3 by modified flat or gin universal density presses, respectively. Modified flat bales are recompressed to become compress universal density bales in a later operation to achieve optimum freight rates.
In 1996, about 96 percent of the bales in the United States were gin universal density bales. Bales should be packaged and tied only in material approved for storage by the Commodity Credit Corporation loan program.
OPERATION PRINCIPLE OF GIN STAND: The gin removes the seeds so that the lint can be packed into tight bales. The quality and price of cotton are determined based on several factors: length of individual fibers, or staple; grade (color, brightness, and amount of foreign material contaminating the final product); and character (diameter, strength, uniformity, and smoothness of individual fibers).
Fig: OPERATION PRINCIPLE OF GIN STAND
The ginning of cotton produces tons of seeds, which were once deemed a waste-disposal problem but are now a valuable by-product. The separated seeds go to oil mills, where they are further delinted of the shorter, fine hairs that adhere to the seed coat after initial ginning. This shorter lint, sometimes called linters, is used to make paper, furniture padding, and the tips of cotton swabs
TYPES OF GIN STAND:
a. SAW-ROLLER GIN,
Fig: SAW-ROLLER GIN
b. KNIFE ROLLER GIN,
Fig: KNIFE ROLLER GIN
c. MACARTHY GIN.
Fig: MACARTHY GIN
Comparison of Saw Ginning and High-Speed Roller Ginning with Different Lint Cleaners of Mid-South Grown Cotton
Four cotton cultivars were ginned with a saw gin equipment line and also with a high-speed roller gin line. The saw gin line using an air-jet and controlled-batt saw-type lint clearer was compared to the high-speed roller-gin line including one of three designs of lint cleaner; either of two versions of an experimental lint cleaner, of a basic design not used with commercial roller ginning, one design with a lint reclaimer and the other without the lint reclaimer or a commercially available mill-type lint cleaner.
The high-speed roller-gin processed the seed cotton at the same rate as the saw gin stand per m of machine width; however, the roller-gin stand is narrower than the saw gin stand.
The roller-gin line produced lint with better fiber length properties than the saw gin line. The roller-gin stand did less damage to the fiber than the saw gin stands and each of the three lint cleaners following the roller gin stand did less damage to the lint than the controlled-batt saw-type lint cleaner. Fewer neps were created in the roller-gin line than the saw gin line.
The experimental lint cleaner did not remove as much non-lint material as the traditional controlled-batt lint cleaner but the measurements of the negative effects of the experimental lint cleaner were significantly lower than for the controlled-batt lint cleaner. The mill-type cleaner removed even less material but added still fewer neps than the experimental lint cleaner and did little damage to the lint.
The fiber processed with the lint cleaner with the reclaimer had lower quality than the fiber processed with the same lint cleaner without the reclaimer; also, the lint cleaner with the reclaimer removed nearly as much material as without the reclaimer. Therefore, the reclaimer will not be included in further testing.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
