Chemical Engineering and Processing, Vol.128, 19-35, 2018
Application of microwave-assisted drying on specific energy consumption, effective diffusion coefficient and topological changes of crumb natural rubber (Cis-1, 4-polyisoprene)
A laboratory scale hot air assisted microwave dryer was built and applied to dry natural rubber (Cis-1, 4-polyisoprene). Drying kinetics and the effects of properties change in comparison to hot air treated natural rubber were compared. The drying rate of crumb natural rubber was significantly improved five folds with microwave convective drying i.e. from 0.012 g H2O/g dry matter. min to 0.06 g H2O/g dry matter. min, whereas 89% and 50% of drying time were saved from convective hot air drying and microwave drying respectively. As predicted, the drying rate of crumb rubber sample was mostly affected by the dynamic air change generated by the heated air as well as the magnitude of microwave energy. The supply of heated air from the regenerative blower with a magnitude of 5.18 +/- 0.28 m/s enhances the drying rate whereas slow drying rate was observed when air flow reduced to 2.78 +/- 0.18 m/s. The topological and composition analysis of microwave-treated and hot air-treated rubber revealed the existence of micro-pore in microwave-dried sample improve the moisture diffusivity and promote rapid drying.