Analysis of Fuel Ethanol Plant Liquor with the Composition Explicit Distillation Curve Method Thomas J. Bruno,* Arron Wolk, and Alexander Naydich Thermophysical Properties DiVision National Institute of Standards and Technology Boulder, Colorado ReceiVed January 27, 2009. ReVised Manuscript ReceiVed March 25, 2009 Although the use of ethanol and ethanol blends as motor fuels dates back to the earliest vehicles, ethanol has recently received extraordinary attention as a renewable liquid fuel. In the United States, the application of this fluid is mainly as an additive used to lower emissions (carbon monoxide and ozone), enhance antiknock index, and to extend gasoline stock. Elsewhere, such as in Brazil, mandated use raises ethanol to the level of a primary motor fuel. A major barrier to increased application of ethanol is the cost relative to gasoline, something that can be addressed to some extent by processing improvements, especially the distillation steps. Such improvements are not possible without the infrastructure of sound thermophysical property measurements, especially the distillation curves of the major plant streams. In this paper, we present the results of measurements made with the advanced distillation curve technique applied to five different process streams of a Brazilian ethanol plant. The advanced distillation curve method was recently introduced, and features: (1) a composition explicit data channel for each distillate fraction (for both qualitative and quantitative analysis); (2) temperature measurements that are true thermodynamic state points that can be modeled with an equation of state; (3) temperature, volume, and pressure measurements of low uncertainty suitable for equation of state development; (4) consistency with a century of historical data; (5) an assessment of the energy content of each distillate fraction; (6) trace chemical analysis of each distillate fraction; and (7) corrosivity assessment of each distillate fraction. We note that the head product from the stripping column is nearly identical to the residual flow from the molecular sieve columns, as is optimal since both streams are routed to the rectifier column. The head product from the rectifier column is a constant boiling azeotrope of ethanol and water, and the tail product from the rectifier column is nearly pure water. Introduction Fuel Ethanol. Fuel ethanol is usually made by the fermenta- tion of simple sugars, followed by the distillation of the fermentation product, much the same way as potable alcoholic beverages are made. The main use of fuel ethanol in the United States has been as an additive for gasoline. It has been used as an oxygenate, to lower carbon monoxide emissions, and to improve antiknock properties (an octane booster). 1-4 Ethanol has also been suggested as an additive for diesel fuel. 5 The Clean Air Act Amendments of 1990 increased the usage of ethanol, since these acts required production of reformulated gasolines that mandated oxygenates. 6 This has been largely superseded by the Energy Policy Act of 2005, which established a renewable fuels standard (RFS). This mandates the addition of ethanol as a renewable extender in gasoline. 7-9 In the United States, most fuel ethanol is made from corn, 75% of which is processed by dry milling, the remainder by a chemical process called wet milling. 3,10 Outside the United States, the largest producer and user of fuel ethanol is Brazil, where the primary feedstock is cane sugar. 11,12 There is an inherent difference in the processing economics as a conse- quence of the feedstock. The use of cane sugar results in the byproduct waste called bagasse, the fibrous residue remaining after sugar extraction. The bagasse is usually used as a fuel for plant steam production, and this steam is used to power the distillation steps. Moreover, excess energy that might be available from this step is used for cogeneration. The large scale production of fuel ethanol in Brazil came about. 13 This effort, begun in response to the first oil crisis in 1975, was meant not only to produce a fuel but also to stabilize * Author to whom correspondence should be addressed. E-mail: bruno@boulder.nist.gov. (1) Wang, M.; Saricks, C.; Wu, M. Fuel-cycle Fossil Energy Use and Greenhouse Gas Emissions of Fuel Ethanol Produced from U.S. Midwest corn, Report for the Illinois Department of Commerce; Center for Transportation Research, Argonne National Laboratory: 1997. (2) Niven, R. K. Renewable Sustainable Energy ReV. 2005, 9, 535– 555. (3) Yaccobucci, B. D. Fuel Ethanol: Background and Public Policy Issues, CRS Report for Congress, RL33290; Congressional Research Service: Washington, D.C., March 3, 2006. (4) Bonnema, G.; Guse, G.; Senecal, N.; Gupta, R.; Jones, B.; Ready, K. L. Use of Midrange Ethanol/Gasoline Blends in Unmodified Passenger Cars and Light Duty Trucks 1999Final Report - http://ethanol.org. (5) Hansen, A. C.; Zhang, Q.; Lyne, P. W. L. Bioresour. Technol. 2005, 96, 277–285. (6) Yaccobucci, B. D. AlternatiVe Fuels and AdVanced Technology Vehicles: Issues in Congress, CRS Issue Brief for Congress, IB10125; Congressional Research Service: Washington, D.C., May 8, 2008. (7) Keefe, R.; Griffin, J. P.; Graham, J. D. Risk Analysis 2008, 28 (5), 1141–1154. (8) Yaccobucci, B. D. Biofuels IncentiVes: A Summary of Federal Programs, CRS Report for Congress RL33572; Congressional Research Service: Washington, D.C., July 25, 2006. (9) Yaccobucci, B. D. Ethanol Imports and the Caribbean Basin InitiatiVe, CRS Report for Congress, RS21930; Congressional Research Service: Washington, D.C., March 18, 2008. (10) Arnold, F. H. Eng. Sci. 2008, 71 (2), 12–19. (11) Upadhiya, U. C. Production of ethanol from sugarcane. In Iberia Sugar TEC-254; Iberia Sugar: New Iberia, LA, 1996. (12) Buchanan, E. J. Sugar J. 2002, 65 (6), 11–17. (13) Soccol, C. R.; Vandenburgehe, L. P. S.; Costa, B.; Woiciechoski, A. L.; Carvalho, J. C.; Medeiros, A. B. P.; Francisco, A. M.; Bonomi, L. J. J. Sci. Ind. Res. 2005, 64 (11), 897–904. Energy & Fuels 2009, 23, 3277–3284 3277 10.1021/ef900077t This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society Published on Web 04/16/2009