Caesar Joventino M. Tado1, Dexter P. Ona1, John Eric O. Abon1, Eden C. Gagelonia1, Nguyen Thanh Nghi2/span>; and Le Quang Vinh2
A flatbed dryer with a reversible airflow was introduced in the Philippines through a collaborative project between Nong Lam University of Vietnam and the Philippine Rice Research Institute (PhilRice). In this design, airflow is reversed at some point during the drying period to achieve uniform drying without mixing the grain.
An 8-ton capacity dryer was constructed at PhilRice Central Experiment Station in Nueva Ecija to evaluate its performance and adaptability under Philippine conditions. Appropriate and locally available materials were used in the construction of the pilot unit. Nine (9) additional dryers were then constructed at PhilRice stations (Nueva Ecija, Isabela, Negros, Agusan, Central Mindanao University, and Midsayap) that served as pilot units for technology promotion in their respective areas of coverage. Performance of the dryer was evaluated in terms of the following parameters: (1) drying; (2) quality of dried grains; and (3) economic analysis of using the dryer. The performance evaluation was conducted in three drying batches of newly harvested rice seeds.
Paddy dried with the reversible airflow flatbed dryer at full load capacity has a uniform moisture content with one percent (1%) moisture gradient at different layers of the grain mass along the depth and across the drying bin. The drying rate was 1% moisture reduction per hour.
The drying cost of using the reversible dryer is PhP0.74 per kg which is lower than the prevailing mechanical drying cost of PhP1.13 per kg. It has a payback period of 2.5 years and break-even point of 53.0 batches/year. To date, eight (8) privately-owned units have already been constructed and fully operational in the provinces of Nueva Ecija, Quirino, and Bukidnon, with PhilRice receiving inquiries from interested individuals here and abroad regarding the technology.
Keywords: reversible airflow flatbed dryer, drying rate, moisture gradient
Annals of Tropical Research 37(1):97-109(2015)