Alignment ensured that the models used similar

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alignment ensured that the models used similar assumptions and rigor in both process and economic calculations. By-products of this alignment were simplified ASPEN Plus and Excel versions of the NREL lignocellulose process model that were less complex and more user friendly. This simpler model provides the same results as the more rigorous version. IV.1 History of the Models IV.1.1 Starch Model A process and economic model of a dry milling ethanol facility was developed several years ago by the USDA-ARS to assist researchers in reducing the cost of ethanol from corn. This model, incorporated in commercial process simulation software, ASPEN Plus, was based on data from ethanol producers, engineering firms, equipment manufacturers, and a USDA-sponsored study. 19 This model includes process flows, details of the capital and operating costs of the equipment, raw materials, utilities, and the co-products involved in ethanol production. This model has served as a base case to evaluate the cost advantages of various process alternatives such as continuous high-gravity fermentation with stripping. 20 IV.1.2 Lignocellulose Model A process and economic model of the conceptual lignocellulose-to-ethanol process was initially developed by NREL in 1995. A database of physical properties for the components of lignocellulosic feedstocks was developed. 21 The rigorous ASPEN Plus model was developed to help the DOE Biofuels program direct research in the development of ethanol from lignocellulosic feedstocks in two ways. Modeling the process and its economics provides an objective way to evaluate research ideas and results, and it also provides DOE with process economic details about the lignocellulose process. The model has been refined each year by NREL engineers with data obtained through formal subcontracts with engineering construction firms and vendors, and informal contact with the corn ethanol industry, culminating in the design report, published in 1999. 16 The methodology for design and costing of the lignocellulose-to- ethanol process is outlined in this report and the process design and model described was the starting point for the creation of the simplified model used for this project. Assumptions about yields, operating conditions and other process design parameters for this study were taken from the Best of Industry case in the above referenced report.
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12 IV.2 Methodology for Achieving the Same Basis Because the primary goal of this work was to compare the two processes° economics, it was necessary to align model methodology. This included normalizing inputs to the ASPEN Plus model and the economic spreadsheet. In ASPEN Plus, the components, unit operations, physical properties and model rigor, and complexity were compared. The NREL model was simplified to make its evaluation easier. In the Excel spreadsheet, the costing methods and cost scaling methods were aligned. The Excel workbooks were made more user-friendly with simple variables like plant life, cost year basis, and feedstock cost inputs that can be changed by the Excel user.
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  • Spring '10
  • BLANCHE
  • The Land, ........., corn ethanol industry

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