Improving the performance of an indirect heated biomass maize dryer

Abstract

Open sun drying is often hampered and interrupted by cloudy and rainy days. This makes adoption of pleasant technologies that are not dependent on weather more relevant for proper grain drying. This study developed an improved maize biomass dyer. The dryer consists of the combustion unit, heat exchanger, primary and exhaust fans, chimney, and the drying bay. Improvements were made on the both fans and the combustion unit. The blades of the primary fan were reduced from eight to four to improve the suction of air into the heat exchanger. The axial fan at the exit end of the heat exchanger was equally replaced with a centrifugal fan to improve air flow within the heat exchanger. The bed of the combustion unit was lowered to facilitate proper flow of heat from the combustion unit to the heat exchanger. Tests indicated that the improved dryer can efficiently increase the drying temperature by over 250C above the ambient temperature. This makes the dryer almost twice more effective than open air drying. The dryer can reduce the moisture content of maize grain from 21% wet basis to 14% wet basis within 3.5 hours using about 26kg of maize cobs. Drying chamber efficiency was on average 52.5%. The biomass dryer is simple in construction and it is suitable for small-scale maize production in Uganda. The study recommends that the dryer be tested with other maize bio-waste materials such as stovers.