Combined Solar Thermal Treatment: Drying Characteristics and Kinetics of Oleochemical Sludge

The objectives of this study are to determine the combined thermal treatment drying characteristics and drying kinetics of palm oil olechemical sludge, impact of ultrasonic pre-treatment on drying duration, the effect of contained heat moisture removal using a solar dryer and the impact of combined drying technology. The drying characteristics for the combinations of all treatments including ultrasonic pre-treatment duration with different operating condition were investigated. When the drying temperatures increases from 70°C to 80°C, the range of drying rate increases from 1.02 – 0.14 g H₂O/g DM (dry basis) for 70°C to 1.20 – 0.06 g H₂O/g DM (dry basis). It was found that the changes on the drying characteristics are not obvious and there is no impact in increasing ultrasonic duration. Solar drying combined with thermal oven drying was conducted and the difference in terms of the effects of energy conservation were compared with thermal drying combined with ultrasonic pre-treatment and thermal drying alone. The period to reach equilibrium for solar drying combined with thermal drying and thermal drying alone is the same which can save two hours of energy for every 600 g of sludge. The cost of electricity can be saved by 22% if using solar drying combined with thermal drying compared with thermal drying alone.