Industrial Byproduct Hydrogen Recovery: Mixed Solvent Design, Process Optimization, and Assessment

Abstract

Recovering industrial byproduct hydrogen helps to minimize the environmental impact associated with hydrogen production. In this study, we propose an innovative approach for hydrogen recovery using an ionic liquid (IL)–methanol mixed solvent. By solving a computer-aided ionic liquid design-based mixed-integer nonlinear programming optimization problem, butylmethylammonium tetrafluoroborate ([N4,1,0,0][BF4]) is identified as the best cosolvent candidate. Subsequently, two process designs for hydrogen recovery using the [N4,1,0,0][BF4]-methanol mixed solvent are proposed and then rigorously simulated in Aspen Plus, followed by a comprehensive process assessment study. Results indicate that the absorption process making use of the IL–methanol mixed solvent is not competitive due to its demand for a large amount of solvent, leading to high energy consumption, carbon emissions, and total annual cost (TAC). Conversely, the IL–methanol-based extractive distillation process achieves notable energy savings of 26.0%, a 24.2% reduction in carbon emissions, and a 10.2% decrease in TAC compared to a benchmark hydrogen recovery process. This study underscores the flexibility and potential of the IL–methanol-based extractive distillation technology in industrial hydrogen recovery applications, paving the way for sustainable and efficient hydrogen production processes.