Conceptual Model-Based Optimization and Environmental Evaluation of Waste Solvent Technologies: Distillation/Incineration versus Distillation/Pervaporation

Abstract

In this work, a conceptual model-based optimization is performed for designing two waste solvent treatment technologies: i) hybrid process distillation assisted by pervaporation and ii) distillation/incineration.This task was performed resorting to conceptual models or shortcuts for each unit operation involved, which are characterized by their abilities to capture the essence of the process at a low computational cost. Life cycle assessment (LCA) was applied to evaluate the environmental impact of both alternatives. Optimal values for the utilities, i.e., cooling water, electricity and steam needed for distillation and pervaporation were used as the input data to perform the environmental analysis with LCA. Ecosolvent v.1.0.1 was used to calculate inventories data related to the incineration technology (waste solvent incineration and cement kiln) of the first cut of the distillation step for the case distillation/incineration and for treatment of column residues of both alternatives investigated.Applied to the mixture isopropyl alcohol-water, optimal values for per-pass IPA recovery and distillate composition were determined for the alternative distillation/incineration and distillation/pervaporation, respectively. From the analysis of the economic figures, it was concluded that solvent recovery through the hybrid process is the better option mainly due to the savings in the cost of fresh solvent. The LCA results, performed in SimaPro 7.3, show that the main impact is related to the solvent production. Thus, solvent recovery is the best option if minimization of the use of resources is paramount. Nevertheless incineration in a cement kiln becomes relevant in terms of human health for the avoided use of fuels.Furthermore, it was concluded that both process optimization with the aid of conceptual models and LCA are key tools in the decision-making process to determine which technology is the most appropriate for the treatment of waste solvents.