Process analysis and economic evaluation of mixed aqueous ionic liquid and monoethanolamine (MEA) solvent for CO2 capture from a coke oven plant

This study investigates the process and economic impacts of using an aqueous mixture of 1-butylpyridinium tetrafluoroborate ([Bpy][BF4]) ionic liquid (IL) and monoethanolamine (MEA) as the solvent for CO2capture from a coke-oven plant. The gaps highlighted in the literature on the study of an aqueous mixture of IL and MEA for CO2capture include lack of detailed process models or information on the impacts of varying the IL concentration on different process conditions and economics. This study addressed these needs by developing a rate-based, solvent-based CO2capture process model with a mixed IL and MEA solvent and using the model to perform process and economic evaluations. The model was developed with Aspen Plus® and was used to investigate seven different aqueous mixtures of IL and MEA. The MEA concentration was 30 wt% for all the seven aqueous solvent mixtures, and the corresponding IL concentration was 0, 5, 10, 15, 20, 25 and 30 wt% for each combination. The hybrid IL solvent mixtures (i.e. 5-30 wt% IL) have 7-9% and 12-27% less regeneration energy and solvent circulation rate respectively compared to the base case (i.e. 30 wt% MEA). Based on a commercial-scale cost benchmark for the IL, the initial solvent cost for the mixed solution is predictably higher. However, the solvent makeup cost is less for the mixed solvent.