Feasibility analysis of isopropanol recovery by hybrid distillation/pervaporation process with the aid of conceptual models

Abstract

In this contribution, main results of a techno-economic feasibility study to recover spent isopropyl alcohol (IPA) from a pre-treated waste stream composed by IPA (95.64 wt.%) and water (4.36 wt.%) are presented. Based on conceptual models for the unit operations, a quasi-optimal design for a hybrid process combining pervaporation and distillation is found under process specifications given by a pharmaceutical company. The proposed procedure allows a separated design of each unit with the aid of conceptual models. While distillation is evaluated from pinch theory, the conceptual model for pervaporation considers that the maximum driving force (i.e., no liquid temperature drop) is maintained across the membrane unit. A brief performance comparison for different membranes is also performed as part of the assessment to the company. For this purpose, the pervaporation separation index (PSI index) defined as the product of the permeate mass flux and the separation factor was used for membranes for which either literature data or membrane supplier brochures were available. In the case of the membrane PERVAP 2216 from Sulzer, several pervaporation experiments at 80 °C and permeate pressure of 1.52 kPa were carried out. The PSI index was then redefined as the overall separation factor times the inverse of the minimum membrane area required to perform a given separation. The results obtained emphasize the usefulness of conceptual modeling in all steps of process design.