Agriculture Reference
In-Depth Information
automatic conveyor belt that feeds them into the module feeder. The module feeder
uses a series of rotating spiked cylinders to break loose the cotton from the edge of the
module. The loosened cotton is transferred to a dryer generally through a pneumatic
conveying system. The dryers in the gin use heated air to remove excess moisture
from seed cotton as necessary. Temperature sensors are used to measure and control
the temperature of the air stream inside the dryer within a desired range, generally by
regulating the gas feed to the burner. Cylinder cleaners remove finer foreign materials
in the seed cotton, such as leaves and dirt, using rotating spiked cylinders coupled with
rods and screens. The stick machine uses the centrifugal force created by a rotating
saw cylinder to remove larger foreign materials, such as sticks and burs. The extractor
feeder performs the final stage of seed cotton cleaning and feeds cotton evenly to the
gin stand. After the seed cotton cleaning process, the gin stand separates the fibers
from seeds using the teeth of a saw rotating between ginning ribs. The saw teeth pull
the fibers through the gaps between the ribs and away from the seeds, which will not
fit through the gaps. The seeds are generally conveyed pneumatically to a storage area.
The fibers are removed from the saw by a brush and conveyed to a lint cleaner. Lint
cleaners remove smaller particles that remain in the lint to improve the grade of cotton.
A saw-type lint cleaner consists of a rapidly rotating saw-cylinder and grid bars. Lint is
cleaned by a combination of centrifugal force and scrubbing action between saw cyl-
inder and grid bars. The bale press is a packaging system that compresses the lint into
dense bales of roughly 227 kg for transportation, storage, and distribution (Anthony
and Mayfield, 1994). Some modern bale presses measure bale compression to deter-
mine when a bale is complete and include automated tying and wrapping systems. A
modern high-speed gin stand is able to gin 20 bales (4540 kg lint) per hour.
6.4.2 C
OTTON
M
OISTURE
M
EASUREMENT
AND
M
ANAGEMENT
Moisture is one of the most important factors affecting fiber quality and operational
practices during cotton harvesting, ginning, and storage. It is necessary to accurately
measure and properly control the moisture content of cotton in various production stages.
Before harvesting, cotton plants should be properly defoliated to minimize the amount
of green trash mixed with seed cotton, which increases moisture content in the module.
The moisture content of the cotton at harvest may be monitored with a portable moisture
meter and should be less than 12% to avoid damage to the fiber and seed during storage
(Anthony and Mayfield, 1994). High moisture content in harvested seed cotton can cause
rapid and continuing rise of temperature inside the module. In the ginning process, mois-
ture content needs to be properly managed. Lower moisture content of the seed cotton
makes it easier to remove the foreign matter. However, when the moisture content is too
low, fiber damage can occur at the gin stand and lint cleaners, increasing the short fiber
content and decreasing the fiber length. In most situations, cotton should be ginned at
6.0-7.5% lint moisture content, whereas 7.0% is ideal. Ginning at the moisture contents
outside this range can also cause the machinery to choke and stop and even damage the
machinery (Anthony and Mayfield, 1994; Mayfield et al., 2011).
Various types of drying systems are used at gins to remove excess moisture in
seed cotton before cleaning processes. Sensors and controls are used in these sys-
tems to limit air temperature as it contacts the seed cotton. According to ASABE
