Abstract
The world is facing the dangers of an energy crisis due to the depletion of traditional fuel sources such as coal and petroleum. Over the past few years, there has been an increasing awareness and acceptance of biofuels as a viable potential substitute for petroleum. The aim of this work is modelling the mass and energy balances of typical biorefinery in order to optimise the energy and material efficiency. We have shown that there are great potential to improve the energy and economic efficiency of this process by employing process engineering tools. The process steps considered here are: feedstock storage and size reduction, dilute acid pretreatment, detoxification, saccharification, fermentation and distillation and azeotropic separation. The energy balance of the process revealed that the main energy requirement is for heating (96%) compared to work input (4%). Most of the energy input is for pretreatment and distillation (83%). However we have considered two process modifications to reduce the energy requirement for pretreatment and distillation. By designing a recirculating hot oil system for pretreatment based on multiscale models of pretreatment covering all influential steps and adding a solid/liquid separation before distillation it is possible to reduce the energy requirement for distillation and pretreatment by 40% and overall energy efficiency by up to 20%. © 2011 Elsevier B.V.