Exercise 08 ENG

Pagina 1

Chemical Processes and Technologies (Prof. Laura Pellegrini) Solvent extraction A solution of 30% by weight of acetic acid in water should be treated with isopropyl ether for reducing the acid cont ent. At the operating temperature of 293 K, the system comprising i sopropyl ether and water presents a miscibility gap. The equilibrium data for the ternary system are reported in the table below (the data on the same row correspond to the compositions of the two liquid phases at equilibrium). Having to treat 10 ton/h of solution using pure isopropyl ether:  depict all the equilibrium data on a triangular diagram;  determine the content of aceti c acid obtainable with a single stage extraction, using 2.5 kg ether/kg solution;  determine the content of acetic acid obtainable with three cross -current theoretical stages, equally splitting the flow rate of isopropyl ether among the three stages;  determine the number of counter -current theoretical stages needed to obtain, if possible, a content of 2% by mass of acid using the same relative mass flow rate of solvent. Table. Liquid-liquid equilibrium for the system water (A), acetic acid (C) and isopropyl ether (B) at 293 K and 1 atm: composition are expressed in weight %. Aqueous phase Organic phase xC xA xB yC yA yB 0.69 98.1 1.2 0.18 0.5 99.3 1.41 97.1 1.5 0.37 0.7 98.9 2.89 95.5 1.6 0.79 0.8 98.4 6.42 91.7 1.9 1.93 1.0 97.1 13.3 84.4 2.3 4.82 1.9 93.3 25.5 71.1 3.4 11.4 3.9 84.7 36.7 58.9 4.4 21.6 6.9 71.5 44.3 45.1 10.6 31.1 10.8 58.1 46.4 37.1 16.5 36.2 15.1 48.7 Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta” POLITECNICO di MILANO