Possibility of VRC Dehydration for Energy Production from Wet Biomass

Abstract

Wet biomass comprises diverse organic wastes, which are discarded in large amount from our society. Energy production from them, therefore, poses great challenges both in quality and in quantity. However, anaerobic digestion is practically the only method currently available and due to its limited applicability, the alternative technologies are desired. In this paper, an energy-efficient dryer called the VRC (vapor re-compression) dehydrator that the author have developed for years, is proposed to be applied to wet biomass. The dried biomass would be used as a fuel for thermochemical energy conversions.
The VRC dehydrator compresses evaporated steam and recovers its latent heat, which is used for the subsequent evaporation. Test results on a prototype dehydrator showed that the compression energy is as little as one tenth of the latent heat of water evaporation. Based on the experience, generated electricity from the hypothetical wet biomass was estimated in two processes: VRC dehydration followed by the ther-mochemical generation; and anaerobic digestion followed by the biogas generation. It was found that the VRC dehydration process would obtain more electricity than the anaerobic digestion process, even after the dehydrator's consumption was subtracted from the generator output. Additional advantages and future possibilities of the VRC dehydration system are also mentioned.