13-46: Flexibility of the cogeneration system in the integrated first and second generation ethanol production process from sugarcane

Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Marina O. S. Dias1, Tassia L. Junqueira1, Otavio Cavalett1, Marcelo P. Cunha1, Charles D. F. Jesus1, Carlos E. V. Rossell1, Rubens Maciel Filho2 and Antonio Bonomi1, (1)Laboratório Nacional de Ciência e Tecnologia do Bioetanol (CTBE), Campinas, Brazil, (2)Faculdade de Engenharia Química - UNICAMP, Campinas, Brazil
In the integrated first and second generation ethanol production process from sugarcane, the lignocellulosic material (sugarcane bagasse and trash) may be used either as a fuel in cogeneration systems, to produce steam and electricity, or used as feedstock for second generation ethanol production. If high pressure boilers are employed in the plant for cogeneration, higher electricity surpluses may be sold to the grid.

If electricity prices are favorable, larger fractions of lignocellulosic material can be used as fuel for production of electricity in the integrated first and second generation ethanol production process. In this case, the cogeneration system must include condensing-extracting steam turbines to convert into electricity the amount of steam that exceeds the process requirement. Therefore, depending on the degree of flexibility in this process design, more or less lignocellulosic material will be diverted for electricity production (thus reducing the fraction of lignocellulose available for use as feedstock in second generation ethanol production) for optimizing economic returns.

In this work rigorous simulations of the integrated first and second generation bioethanol production were carried out using Aspen Plus, evaluating different configurations of the cogeneration system in order to assess the impact of its flexibility depending on the relative electricity and second generation ethanol prices. Environmental assessment (LCA) and a preliminary economic analysis were carried out to indicate which configurations lead to the best economic and environmental results, as a possible basis for decision-making. Sensitivity analyses were also carried out to show in which conditions cogeneration flexibility may be of benefit.

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