A Survey of Seed Cotton Dryers in Cotton Gins in the Southwestern United States

Abstract

Seed cotton drying is an important and costly part of cotton ginning. Seed cotton having a moisture content above 7% cannot be cleaned or ginned properly. In this study, 73 dryers were surveyed by on-site visits in 23 gins located in the southwestern United States during the 2007 to 2010 ginning seasons. Drying systems surveyed included: standard tower, short tower, hot shelf, hi-volume tower, belt, big reel, vertical, hot air cleaner, pipe, cross-flow, hot box, hi-slip, jet, fountain, and collider systems. Forty-eight percent of dryers had the recommended dual temperature controls, while 26% had only a primary temperature control and 26% had only a maximum temperature control. Belt and big reel dryers had the lowest specific airflow rates (0.34 to 0.72 m3/kg of seed cotton) and also had the lowest energy in the conveying air (1.7 kJ/kg of lint or less). Collider, fountain, and hi-volume tower dryers had the highest specific airflow rates (1.9 to 2.8 m3/kg) and hi-slip, hi-volume tower, and standard tower dryers had the highest energy in the conveying air (7.7 kJ/kg or more). Belt, cross-flow, and hot air cleaner dryers had the lowest pressure drop across the dryer (0.5 kPa or less), while hi-slip, pipe, and standard tower dryers had the highest pressure drop (1.8 kPa or more). Fuel use was positively correlated with airflow (r=0.58) and temperature rise (r=0.59). Systems with fountain, collider, belt, big reel, jet, and hot air cleaner dryers had favorable, low values for fuel use (13.7 kJ/kg of lint or less), while systems with crossflow and hi-volume tower dryers had high values for fuel use (30.0 kJ/kg or more).