Conceptual design and plantwide control of an ethyl acetate process

The conceptual design and control of a "reaction followed by separation" process for producing ethyl acetate via esterification of ethanol with acetic acid is evaluated. A zero waste discharge process flowsheet is synthesized using the residue curve map tool. It consists of a boiling reactor-rectifier, followed by an ester purification section with a liquid-liquid extractor and two distillation columns. Steady state analysis reveals the presence of two types of composition profiles for the reactor-rectifier that achieve the desired production rate and quality. The process is designed for the profile that gives lower total energy consumption. The dominant design variables for the process flowsheet, namely, reactor-rectifier pressure and reactant excess ratio are adjusted to obtain an economic design. The developed process design is similar to 20% more energy efficient compared to extant literature reports. Further, a novel plantwide control structure with the feed to the extractor as the throughput manipulator (TPM) is shown to require no equipment overdesign when using established equipment sizing heuristics. In contrast, conventional control with TPM at a fresh feed requires overdesign ranging from 10 to 20% in recycle loop equipment size. The work illustrates the significant impact of plantwide control structure on the necessary equipment overdesign.