Ethyl Acetate Design Project

Ethyl Acetate Design Project University of California Santa Barbara Omid Borjian Executive Summary The catalytic conversion of ethanol to produce ethyl acetate has shown to be a profitable market. We designed a plant to optimize the production of ethyl acetate, while minimizing operating and production costs and undesired side products. We found that the reaction was best suited for a 41m3 plug flow reactor operated at 285 oC and 1 atm. Feeding 120 MM kg/yr of ethanol into the reactor produced 100 MM kg/yr of ethyl acetate to be sold along with 5 MM kg/yr of hydrogen for a total profit before taxes of a total of $43.6 MM$/yr. To start the plant a total capitalized investment (TCI) was approximated to be $28.8 MM with a net present value of the project (NPVproj) to be $102 MM and net present value percent (NPV%) of 32.7%. The internal rate of return (IRR) was found to be 113.5%. The discussed numbers are approximations, and flexible approach should be considered when plant production commences. The plant design accounted for market fluctuations, and the process control was purposely designed simplistically. They are, however, a good basis to gain an understanding of the plant’s general function and expectations. Goals and Introduction With an increasing industrial demand for ethyl acetate, many have found successful ways to create a marketable business for the production and distribution of ethyl acetate. This increasing demand has also initiated industry to develop commercial processes, such as that by DAVY Process Technology, for large production of ethyl acetate. The GSI Process Feasibility Group has developed a plant that will be in direct competition with Davy Process Technology. In this plant, ethyl acetate will be synthesized via the interaction of ethanol with a catalyst consisting of 94% copper oxide, 5% cobalt oxide, and 1% chromium oxide. Unfortunately, under these conditions ethanol can react to form ether acetaldehyde or diethyl ether. Diethyl ether is a side product that is of lesser importance and may not be profitably sold. While diethyl ether does not need to be disposed of and can be burned, in this initial profitability design and analysis, heat exchange interactions were not taken into account and any credits able to be obtained from burning the diethyl ether were not accounted for. In addition to ethyl acetate and diethyl ether, this system of reactions will also produce hydrogen and water. Through the use of a flash drum, the hydrogen will be separated from the system and be sold for further profit. The primary challenge is to create an optimally profitable amount of ethyl acetate, while working around an azeotropic solution involving the ethyl acetate, ethanol, and water. Since in this system the selectivity is constant over reactor conversion, a higher conversion was able to be chosen without loss of selectivity. Once a specific conversion is selected, a separation system is able to be designed and the equipment and streams of the system are able to be cost and implemented into a cost diagram. To ensure profitability, an economic analysis will be run on the five most important economic parameters. Conceptual Design Various factors were taken into consideration when making design decisions to optimize the plant profitability. These factors consisted of reactor volume, reactor temperature and pressure, along with other equipment constrictions. The system was found to be optimized at a reactor conversion of 90% with a recycle stream to the reactor. Using Douglas’s Conceptual Design hierarchy (Douglas, 2011), ideal stoichiometric mole balances were developed to find the flow rates of the inlet, outlet, and ideal recycle streams. Using the kinetic data provided from the GSI technical data sheet, a graph of reactor volume versus reactor conversion was constructed for varying temperatures and pressures (Doherty, 2011). Analysis of the chart provided a minimal reactor volume, which facilitated the selection of optimal operating conditions. It essential that a minimal reactor volume is shown for cost analysis shows reactor cost grows exponentially as a function of reactor volume. The reactor optimally operated at 285 oC and 1 atm. The reaction was run in a heat exchanger with circulating heating fluid because in order to run the endothermic reaction isothermally. A shell-and-tube heat exchanger was utilized to combine the costing of the reactor and heat exchanger. Maintaining the heating fluid at the desired temperature was the primary factor regarding the reactor operating cost. To approximate the heat produced in the reactor, and thus cost the reactor, the heat capacities were assumed to be constant with respect to temperature. The separation consisted of a split block that separated out the diethyl ether, a flash drum that separated out the hydrogen, two distillation columns that separated out ethyl acetate, and one distillation column that removed water in the process, purifying the ethanol recycle stream. The flash drum was optimized at 1 atm and 255 K, allowing for approximately 100% of the hydrogen to exit the column in the vapor stream. It was particularly challenging to separate the ethanol, ethyl acetate, and water because they contain azeotropes that prevent separation of individual species. Each distillation column was designed at specific pressures and temperatures that avoid azeotropes by analysis of ternary maps as shown in Appendix B. Flash drum calculations were designed in the attached MATLAB code (Appendix D) and the three distillation columns were designed in ASPEN as shown in Appendix .........................................CONTINUED....................................................