The influence of surface area, temperature and pretreatment on convective hot air oven drying of banana peels biomass

Abstract

Untreated banana peels biomass of 15 x 10, 30 x 20 and 60 x 40 mm sizes were dried at 60 oC while untreated and pretreated (hot water and sulphite treated) biomass of 10 x 10 mm size were dried at 80 – 140 oC, to find out the influence of surface area, pretreatment and temperature on convective hot air oven drying of the biomass. The rate of drying of banana peels increased with increasing surface area and temperature while hot water and sulphite pretreatments reduced the time needed for drying. The drying operation occurred primarily in the falling-rate phase. Effective moisture diffusivities for the drying operations were in the range 5.19 x 10-10 – 1.55 x 10-8 m2 s-1. The activation energies for drying untreated, sulphite treated and hot water treated peels were 24.7, 21.4 and 21.3 kJ mol-1, respectively. The biomass drying kinetics was well described by the Weibull model. Specific energies needed for drying the 15 x 10, 30 x 20 and 60 x 40 mm banana peels biomass at 60 oC were 157.9 – 335.6 kWh/kg while those required for drying both untreated and pretreated 10 x 10 mm sized banana peels biomass at 80 – 140 oC were 33.5 – 93.9 kWh/kg. The rate of drying banana peels in hot air oven can be considerably improved and the energy needed for drying appreciably reduced by increasing the peel surface area, drying at higher temperatures and pretreating the biomass with hot water or sulphite solution.

Keywords

• drying kinetics
• banana peels
• drying pretreatment
• effective moisture diffusivity
• activation energy
• dryingenergy