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Improved ginning for better cotton.

Cotton ginning technology has changed a lot since March 14, 1794, when Eli Whitney won a patent for a new invention. The cotton gin--which would eventually transform the South's economy and, ultimately, the nation's politics--would also make cotton the "king" of U.S. crops.

Before Whitney's invention, only a slick-seeded cotton variety grown exclusively in Southern coastal regions could be easily cleaned of seeds by textile mills. But the advent of the cotton gin enabled the South to also grow higher yielding varieties.

By today's standards, Whitney's invention was a crude machine, consisting largely of a box in which two revolving cylinders--one covered with spikes and the other with a brush--combed the seeds out of cotton fiber. His cotton gin mechanized the labor-intensive task of manually separating the seeds, or "lint," so the cotton fiber could be sent to textile mills, spun into yam, and woven into fabric.

Today, computerized improvements to Whitney's basic concept still have the same aims as the original: to increase farmer's profit, reduce labor costs, and provide textile mills with a higher quality raw product.

"Ginning today is more than just removing seeds from cotton," says W. Stanley Anthony, an agricultural engineer with the Agricultural Research Service and inventor of the improved technology. "A modem cotton gin does a lot more cleaning and conditioning to the fiber.

"Everything you do with cotton is important to its final quality and to what the farmer will be paid," he adds. "We're trying to improve the odds for both the farmer and textile mills."

Because not all cotton is created equal, researchers at the ARS Cotton Ginning Research Unit in Stoneville, Mississippi, are looking at ways to gin cotton better, based on individual physical fiber properties.

Ginning involves the removal of trash, which includes any type of plant debris that becomes attached to cotton when it's picked from the field. Various ginning steps remove unwanted material both before and after seed is separated from the fiber.

The ginner must also dry cotton to a recommended 6- to 7-percent moisture content, making it easier to separate trash from the fiber. But if the moisture content drops below that level, fiber quality diminishes, Anthony says.

All cotton in today's gins usually receives the same amount of cleaning, however trashy it might be. Factors such as weather during harvest and physical differences between varieties, or even between different fields, can make some cotton cleaner, dirtier, or more or less moist than other cotton.

Anthony and colleagues are developing new modifications to the ginning process so cotton will have to pass through only those cleaning steps that are really necessary.

Four patents were recently issued for a computerized ginning process control system that Anthony has invented.

"Our first task was to set up a system that could analyze trash content and recommend proper cleaning levels," Anthony says. "The computer model that we developed can help make decisions during ginning that can ultimately affect market price."

To determine what ginning steps are necessary to maximize farmer profit, the computer uses five pieces of information to calculate ideal ginning conditions. It looks at cotton moisture, trash content, color, cotton pricing structures, and gin machinery performance characteristics.

The model allows the ginner to process each batch of cotton through the minimum machinery necessary to achieve maximum returns rather than uniformly processing all the cotton. Anthony says, "By using the computerized process, increased returns to the farmer typically range from $6.86 to $23.38 per bale."

Cotton market grade is based on color, trash content, preparation, fiber length, strength, and other quality factors-all of which can be influenced by ginning. When it is sold, a bale of cotton receives a grade based on these criteria. That grade determines how much the farmer will be paid for the bale.

In some cases, many cottons don't need to go through each drying or cleaning step, which could cut energy costs and decrease fiber damage. The primary energy cost is for electricity used to power the equipment.

Once the "brain" behind computerized ginning was developed, scientists turned to devising instruments that could detect information during ginning and transmit it to the computer model. Anthony uses infrared sensors to measure moisture and special video cameras to detect colors and trash as the cotton goes through cleaning and drying.

The cameras were originally developed for use in objective grading of ginned cotton lint samples.

"To control the drying process, sensors and cameras predict lint moisture, color, and trash content by scanning bulk seed cotton that contains both lint and cottonseed," Anthony says.

He paired the sensors and cameras at three locations in a pilot gin at the Stoneville lab: in the area where harvested cotton enters the gin, at a spot just before cotton enters the seed removal stage or gin stand, and at a location prior to baling. The computer controlled the dryer temperatures to ensure fiber quality and lower energy costs.

"Energy costs could be cut by half because the dryers weren't required to run at full throttle," Anthony says.

Cotton color is strongly influenced by weather exposure in the field. However, Anthony says that gin machinery like lint cleaners can blend fibers to help improve the grade.

As cotton travels through the gin, the cameras detect changes in color and trash and relay this information to the computer model. This allows the model to make ginning decisions that will result in the best possible blend in each bale of ginned cotton to help improve grade and farmer profit.

"The cameras are the eyes that allow the brain (computer) to decide which cleaning steps are necessary," Anthony says. "This helps to control valves in the ginning system that will route cotton through the right cleaning machines."

Cotton is conveyed through large pipes from one cleaning step to the next. To keep all the cotton from traveling through the entire system, Anthony installed valves that serve as pass gates.

For example, if cotton contains a lot of trash, the valves remain open and allow the cotton to go through all cleaning steps. But if the cotton is relatively clean, the cameras relay that information to the computer that directs the closing of a valve. This allows cotton to bypass a particular operation and travel to the next ginning step.

"Thanks to the special routing valves, the computer can decide whether to bypass or select any combination of four seed-cotton cleaners, two multi-path dryers, and three lint cleaners," Anthony says. "This is important because if cotton is over-cleaned or overdried, fiber quality and farmer profits decrease."

Since cotton is ginned in a continuous process, it was important for Anthony to ensure that rerouting cotton wouldn't create any traffic jams. In current ginning systems, as much as 50,000 pounds are ginned each hour.

"Computerized ginning is not something that is going to happen overnight," Anthony says. "It is going to essentially require ginners to completely overhaul their operations.

"While the computerized control is the best ginning system in the long run, initial installation costs could hurt many ginners financially--especially the smaller operations," he adds.

So in the interim, one of the patented features--the flapper--is being used as a component of the dryer-control system. It will likely be in use in many gins well before the complete process control system, Anthony says.

The flapper consists of a movable metal valve that works like a door, roughly 6 inches square and perforated with 3/8-inch holes. It can be attached on one of the pathways where cotton flows through the gin, either in the seed cotton or lint cleaning stages.

Because the flapper is perforated, air can flow through the holes when the door shuts, but cotton can't. The door catches the cotton and compresses it against the camera where it is analyzed.

The door then mechanically opens and releases the cotton. Information read by the camera is transmitted to the computer and used to determine the amount of drying or cleaning required.

While the ARS-computerized system may be somewhat costly, Anthony says several ginners have contacted him about the technology. Payback on investment could occur in less than 2 years.

And textile mills looking for high-quality, low-trash cotton to make finished goods may join the movement toward ginning systems capable of consistently producing higher grades of cotton.--By Bruce Kinzel , ARS.

W. Stanley Anthony is in the USDA-ARS Cotton Ginning Research Unit, P.O. Box 256, Stoneville, MS 38776. Phone (601) 686-2385 fax number (601) 686-9965.

* Agricultural engineer Stanley Anthony operates a microgin at the U.S. Cotton Ginning Laboratory in Stoneville, Mississippi. It is the only fully computer-controlled cotton ginning system in the world. (K4840-1)
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Author:Kinzel, Bruce
Publication:Agricultural Research
Date:Dec 1, 1992
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