Energy optimization of bioethanol production via gasification of switchgrass

• Published in: AIChE journal Vol. 57; no. 12; pp. 3408 - 3428
• Main Authors: Martín, Mariano, Grossmann, Ignacio E.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01-12-2011; Wiley; American Institute of Chemical Engineers
• Subjects: Applied sciences; Biodiesel fuels; bioethanol; biofuels; Catalysis; Catalysts; Catalytic oxidation; Catalytic reactions; Chemical engineering; Chemical synthesis; Chemistry; Distillation; energy; Exact sciences and technology; Gas composition; Gasification; General and physical chemistry; Membrane separation (reverse osmosis, dialysis...); Optimization; process synthesis; Reactors; Reforming; Superstructures; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Distillation; Catalytic reaction; Water gas; biofuels; Dehydration; Fermentation; Synthesis gas; Modeling; Partial oxidation; Optimization; Heat recovery; Molecular sieve; process synthesis; Design; Membrane separation; Superstructure; Production; Gasification; Steam reforming; bioethanol; Pervaporation; energy
• ISSN: 0001-1541; 1547-5905
• DOI: 10.1002/aic.12544

In this article, we address the conceptual design of the bioethanol process from switchgrass via gasification. A superstructure is postulated for optimizing energy use that embeds direct or indirect gasification, followed by steam reforming or partial oxidation. Next, the gas composition is adjusted with membrane‐PSA or water gas shift. Membrane separation, absorption with ethanol‐amines and PSA are considered for the removal of sour gases. Finally, two synthetic paths are considered, high alcohols catalytic process with two possible distillation sequences, and syngas fermentation with distillation, corn grits, molecular sieves and pervaporation as alternative dehydration processes. The optimization of the superstructure is formulated as an mixed‐integer nonlinear programming problem using short‐cut models, and solved through a special decomposition scheme that is followed by heat integration. The optimal process consists of direct gasification followed by steam reforming, removal of the excess of hydrogen and catalytic synthesis, yielding a potential operating cost of $0.41/gal. © 2011 American Institute of Chemical Engineers AIChE J, 2011