Abstract

Distillation and absorption are techniques used to separate mixtures, utilizing energy and absorbent materials as separation agents. These two processes are often combined for gas mixtures to enhance the recovery of key components while also reducing energy consumption. The operation of the distillation column influences not only its own performance but also that of the absorption column, and vice versa. A simplified model of combined absorption and distillation columns has been developed to analyse their performance concurrently. This model examines the relationship between the intermediate stream and the operating parameters of both units, yielding qualitative rules that can help minimize energy consumption and guide the optimization of the combined process. In the case of the methanol-to-olefins (MTO) process, the columns for demethanation and ethylene recovery have been qualitatively analysed using the proposed method, thus enabling efficient optimization of both columns. The optimal ethylene molar concentration at the top of the distillation column is found to be 0.5. Additionally, the corresponding reflux ratio is 1.6029, while the flow rates for the distillate and absorbent are 902.3 kmol/h and 900 kmol/h, respectively.