Comparative analysis of multi-effect evaporators in an ammonium acetate concentration process for L-methionine production

The process of treating an acetic acid aqueous solution generated during L-methionine production with ammonia and recovering a highly concentrated ammonium acetate aqueous solution using a multi-effect evaporator process was studied. The electrolyte non-random two-liquid model was applied to calculate the activity in the electrolyte solution, and the Hayden-O'Connell model was used to consider the dimerization reaction of acetic acid in the vapor phase. The dissociation equilibrium constant of acetic acid was modeled based on experimental values, and all other thermodynamic property models and parameters were used as implemented in the Aspen Plus software. Economic evaluation was carried out with various sensitivity tests, considering the loss of acetic acid and ammonia, as well as the steam cost. Evaporator operation was found to be more economical when the molar ratio of acetic acid to ammonia was equal, feed concentration was high, feed flow rate was low, and evaporator temperature was low. These results were confirmed in actual plant operations, with significant correlations between the feed flow rate and evaporator temperature. Our findings have significant implications for the development of sustainable and economical L-methionine production methods that enable the recycling of ammonium acetate.