Performance Assessment Of Local Biomass Powered Cereal Drier Used By Small-Scale Kenyan Farmers
Madaraka F. Mwema, Kimayu S. Musau, Ngugi J. Mburu
Index Terms: Aflatoxin, Biomass, Drying, Empirical control, Maize, Temperature
Abstract: Recent studies have revealed that drying maize using biomass driers increase the quality of grains, delays insect infestation, mold and aflatoxin contamination in relation to direct sunlight drying. Most importantly, biomass drying takes shorter time. It is therefore important to undertake performance of these driers to investigate the possibility of empirical control of such systems in remote areas. In this paper, we present results of thermal performance of typical biomass-powered drier (batch type). The results show that under natural convection, temperature behavior within the drying chamber is unpredictable. However, the use of exhaust fan (forced convection) gives predictable temperature distribution within the drying chamber. For burner shutter open at 50% and using maize cob as the fuel for forced convection, the drying chamber attained a maximum temperature of 93˚C after 28 minutes and minimum temperature of 69˚C after 37 minutes in the lower tray (tray 1). For burner shutter open at 100%, the drying chamber attained a maximum temperature of 91˚C after 41 minutes and minimum temperature of 67˚C in tray 1. With burner 50% open, tray 2 attained a maximum temperature of 62˚C after 30 minutes and minimum temperature of 56˚C after 40 minutes. With the burner 100% open, tray 2 attained a maximum temperature of 61˚C after 39 minutes and minimum temperature of 52˚C after 52 minutes. From these results, the optimal operating conditions of the burner operation were achieved when the shutter was open at 50%. It took 76 minutes to dry 5kg of maize with about 0.8kg (including dampness from rains) moisture content in tray 1. It took 140 minutes to dry the same quantity and moisture content of maize in tray 2. These results show that it is possible to control empirically biomass cereal (maize) driers.
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