Thin layer drying of green microalgae (Chlorella sp.) paste biomass: Drying characteristics, energy requirement and mathematical modeling

Abstract

The characteristics, energy requirement and kinetics of open sun, solar, hot air oven (50–70 °C) and microwave (450–700 W) thin layer drying of green microalgae (Chlorella sp.) paste were investigated. Drying took place mainly in the falling rate period. The moisture diffusivities for the open sun, solar, hot air and microwave drying were 4.64 × 10−10, 6.46 × 10−10, 5.91 × 10−10–1.10 × 10−9 and 1.83–3.91 × 10−9 m2 s−1, respectively. Activation energies for hot air and microwave drying were 28.7 kJ mol−1 and 21.4 W g−1, respectively. The specific energies required for hot air and microwave drying were 51.7–55.1 kWh kg−1 water and 26.2–34.9 kWh kg−1 water, respectively. Kinetics of open sun, solar, hot air and microwave drying were suitably described by the Wang and Singh, Wang and Singh, Weibull and Verma models, respectively.