Chemical and Biomolecular Engineering, Department of


First Advisor

Yasar Demirel

Date of this Version

Fall 10-23-2012


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Engineering (Chemical and Biomolecular Engineering), Under the Supervision of Professor Yasar Demirel. Lincoln, Nebraska: December, 2012

Copyright (c) 2012 Nghi Nguyen


A conventional biodiesel plant utilizing two distillation columns to purify unreacted reactants and products is considered in this study. Thermodynamic analyses are used to assess the performance of the existing distillation columns, and reduce the costs of operation by appropriate retrofits in a biodiesel production plant. After the retrofits, the overall exergy loss for the two columns has decreased from 2430.87 kW to 1674.12 kW.

A reactive distillation is developed for esterification of lauric acid with methanol using equilibrium and nonequilibrium models. Equilibrium modeling dominated during last few decades due to their straightforward mathematical modeling. In reality, separation depends on the heat and mass transfer rates between liquid and vapor phases and a more sophisticated nonequilibrium modeling is more suitable to describe the separation process. Further, thermally coupled side-stripper reactive distillation sequence is used to reduce the overall energy consumption of the reactive distillation column and the methanol recovery column of the equilibrium design. The total exergy losses for the columns are reduced by 281.35 kW corresponding to 21.7% available energy saving.

In order to design a new generation biodiesel plant, direct carboxylation and glycerolysis routes are developed to convert a by-product, glycerol, of the biodiesel production plant into a value-added product, glycerol carbonate, to reduce the unit cost of the biodiesel production plant. A direct comparison of the economic analysis based on deterministic and stochastic models of the conventional biodiesel plant, biodiesel-glycerol carbonate production by direct carboxylation plant and biodiesel-glycerol carbonate production by glycerolysis plant is presented. The results show that either route can be used to reduce the unit cost of the biodiesel production plant.

Advisor: Yasar Demirel