Synthesis and systematic evaluation of solvent recovery pathways

<br/>With the rapid expansion of the chemical market over the next decade, the concerns for environmental sustainability have increased due to excessive disposal of chemical solvents. Chemical solvents are typically used as extraction, cleaning, and purification agents and account for up to 90% of the process by mass. To date, there is no proper mitigation plan to handle the inevitable rise in waste volume. These solvent wastes are typically incinerated or released after a single-use. However, incineration and direct release are not “green” methods because of the potential detrimental effects to the environment. A solvent recovery framework has been developed that considers multiple alternative recovery and purification technology options simultaneously to recover solvents through a superstructure-based approach. The technologies were represented as mathematical models, which included material and energy balances, utility requirements, design, and industrial constraints. The recovery of solvent from multi-component waste streams was modeled as a mixed-integer nonlinear programming problem and solved using programming and optimization tools in GAMS (General Algebraic Modeling Systems). The results showed that appropriate selection of solvent recovery options could result in lower costs when compared to typical incineration and reduced emission of GHGs (greenhouse gases) and other harmful substances into the environment. Furthermore, sustainability analysis was carried out for the recovery process and juxtaposed to that of incineration using the SPI (sustainable process index) methodology. Thus, we were able to demonstrate the capability of the solvent recovery framework to obtain environmentally friendly and economically viable solvent recovery pathways.