Recovery of Acetic Acid from Wastewater by Esterification in a Reactive Distillation Column: Solvent Design

• Main Authors: Yun-Hsiang Pai, 白雲翔
• Other Authors: Cheng-Ching Yu
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/16051818579655526636

碩士 === 國立臺灣大學 === 化學工程學研究所 === 91 === This work explores the recovery of dilute acetic acid aqueous solution with a typical concentration range of 25-50 wt%. Instead of separating acid from water using distillation, acetic acid is converted to acetate via esterification in a reactive distillation. Three questions then arise. First, what is the most economical alcohol (e.g., ranging from methanol to pentanol) for the esterification: a solvent selection problem. Second, will a standalone reactive distillation design remains economical (based on the total annual cost, TAC) as the acid becomes more and more dilute, compared to the alternative process flowsheet, e.g., purification followed by reactive distillation. Thirdly, does the optimally designed process become operable as feed rate and composition changes? For the solvent selection problem, qualitative analysis based on reactive distillation configurations (homogeneous versus heterogeneous reactive distillation) and water withdraw location is given followed by quantitative TAC analysis. Results show that the water withdraw location plays a dominate role as the acid become more and more dilute and methanol is the candidate solvent as the acid becomes more and more dilute. Following a systematic design procedure for reactive distillation columns, the TAC results indicate that a standalone reactive distillation is more economical than a two-unit process flowsheet (purification plus reactive distillation). Finally, a systematic design procedure is used to generate control structure for the optimal design. Simulation results show that it can handles reasonably range of concentration as well as flow rate disturbances.