Simulation Study of Distillation, Stripping, and Flash Technology for an Energy Efficient Methanol Recovery Unit in Biodiesel Production Processes
Date
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Biodiesel is an important alternative renewable energy source currently produced
by transesterification reaction of oil or fat with methanol. To improve the conversion,
excess methanol is required, which must be recovered from the product stream and
recycled back into the process for further biodiesel production. The intensive energy
requirements for methanol recovery are an important issue that directly impacts the
production costs of biodiesel. To reduce the cost of biodiesel production, an energy
efficient methanol recovery unit (MRU) is crucial.
This work focuses on energy requirement reduction by distillation, flash-based
recovery, and newly-introduced stripping-based methanol recovery units. Four different
continuous methanol recovery units were simulated using Aspen Plus. Energy
requirements with respect to process parameters including percentage of methanol
recovery, operating pressure, and methanol-to-oil ratio for all methanol recovery units
were analyzed. Units were compared in terms of energy requirement and purity of
recovered methanol product.
The simulation results show that energy requirement for methanol recovery units
increases with increase in % methanol recovery and reflux ratio (for distillation), but
decreases with decrease in operating pressure and increase in methanol-to-oil ratio. The
recovered methanol is pure for distillation and stripping-based MRUs. However, for
flash-based MRUs, the purity of recovered methanol degrades at the high heat duty
supplied. Consequently, the single- and double-flash-based MRUs have narrow ranges of
operation. Moreover, double-flash-based MRUs have no significant advantages over single-flash-based MRUs in terms of heat duty. Comparison of heat duty among
distillation, stripping, and single-flash reveals that the single-flash-based MRU is the
most energy efficient followed by stripping and distillation-based MRUs.