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

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.