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sample_report - MIT OpenCourseWare http/ocw.mit.edu 2.830J...

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MIT OpenCourseWare http://ocw.mit.edu 2.830J / 6.780J / ESD.63J Control of Manufacturing Processes (SMA 6303) Spring 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
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1 2007-5-18 2.830 Control of Manufacturing Systems Final Project Profit Maximization in Ethanol Production (May 2007) R. Sriram, S. Subramanian, and G. Tomlin Abstract - We document an experimental study to optimize yield of an ethanol distillation process. The yield is expressed in terms of concentration of the ethanol obtained, and the profit from the process. Concentration is a function of six input factors that can be varied within a given range. Profit is a function of the revenue (which depends on the concentration of ethanol achieved) and costs (which vary with the input factor settings). We started by determining a practical operating range for the six input parameters where the constraints of the system (pressure in the distillation column and holding tanks) were not violated. We then conducted a factorial experimental analysis and used a response surface method (path of steepest ascent) to determine an operating point where the desired concentration level is achieved. Finally, we used a space filling experimental design in a narrow region around the operating point to determine the effect of various input parameters on robustness and profit. Index Terms —Ethanol, Design of Experiments, Optimization O I. PROBLEM DEFINITION ur team found a distillation simulator [2] that was used as the basis of a project at Virginia Tech. This simulator can be found at www.stat.vt.edu/~vining . The simulator takes an input of 6 factors and gives outputs of concentration, profit and pressure. The objective is to maximize profit by changing the six factors. The six factors are: Feed Rate (gallons per minute) Feed Temperature (Fahrenheit) Distillate Rate (gallons per minute) Condensate Temperature (Fahrenheit) Reboil Temperature (Fahrenheit) Reflux ratio (percent) Having no knowledge of the operating conditions, we were provided with costs, revenues, and constraints. This gave us a basic understanding of the premise, and we were able to use given pilot values as a starting point for our analysis. The given costs are: Fixed Costs $1,000 per run Heating Costs $0.08 / 100,000 Btu Cooling Costs $0.04 / 100,000 Btu Raw Material Costs $0.015 / gallon The given revenue is: concentration < 80% = $ 0 80%< concentration < 90% = $ .50/gallon 90%< concentration < 95% = $1.00/gallon 95%< concentration < 100% = $1.25/gallon Constraints given are pressure limits. If maximum pressure is exceeded then the process fails, no product is made and repair costs are extraordinary. II. E XPERIMENTS /D ATA A. Determining operating range for experimental factors As described earlier, the ethanol-water distillation column has six factors that can be adjusted. The setting for each factor has a large range. However, every setting for each parameter is not likely to produce ethanol, as some settings would violate the constraints of the system (Eg: Pressure constraint of the holding tank and the pressure constraint of the distillation column).
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