In an ethanol plant, the mixture of water and ethanol from the beer column distillate contains about

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In an ethanol plant, the mixture of water and ethanol from the beer column distillate contains about 40% ethanol (molar basis) in water, together with the fusel oils described in the previous problem. This mixture is distilled to give an azeotropic mixture of ethanol and water (89% ethanol) overhead, with 99.9% recovery of ethanol. The fusel oil can cause blending problems if it is allowed to accumulate in the distillate. Fusel oil is a mixture of higher alcohols and ethers that can be approximated as a mixture of n-butanol and diethyl ether. This mixture is usually removed as a side stream from the column. When the side stream is contacted with additional water a two-phase mixture can be formed and the oil phase can be decanted to leave an ethanol-water phase that is returned to the column. 

1. Draw a flowsheet for this process. 

2. Estimate the stream flow rates and compositions for a production rate of 200,000 US gal/d of dry (100%) ethanol. 

3. Optimize the distillation column using the cost correlations given in Section 6.3 and assuming that reboiler heat costs $5/MMBtu. Minimize the total annualized cost of the column. 

Data from section 6.3

Table 6.2 Process cost correlations. Process ABS Resin (15% Rubber) by emulsion polymerization Acetic Acid by

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Chemical Engineering Design

ISBN: 9780081025994

6th Edition

Authors: Ray Sinnott, R.K. Sinnott, Sinnott Gavin Towler

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