Ionic liquid design and process simulation for shale gas separation
Abstract
Shale gas, considered as the clean resource and a substitute for coal, has attracted increasing attention.
It mainly consists of CH4, other light hydrocarbon gases and some impurities such as CO2, N2, H2O. Therefore, shale gas usually goes through a series of processing to obtain the upgrading needed for commercial gas supplied into pipeline or used as feedstocks for petrochemical plants to produce value-added chemicals.
Traditional technology for the shale gas separation could be a solvent-based decarbonization process followed with series of distillation columns for the light hydrocarbon gases separation which consumes large amount of energy.
With its unique properties of being non-volatile, and flexibility in design, ionic liquids (ILs) are regarded as novel potential solvents and alternative media for gas absorption on specific gas separation.
Therefore, a hybrid gas separation scheme of combining traditional technologies with ILbased absorption separation process is proposed. However, the variability of cations and anions makes it a challenge to identify the optimal combinations in one solvent for specific gas separation.
The selection of solvents is one of the most important factors in the early stage of process synthesis. In this work, a three-stage methodology for hybrid gas separation process design and evaluation is proposed: IL screening, where a systematic screening method with two options (database screening and computer-aided IL design based on UNIFAC model) is established.
Aimed to a model shale gas mixture, two suitable ILs are selected as promising candidates from the two options; process design and simulation, where separation schemes and important design issues in the two IL-based processes are determined; process evaluation, where the final separation process results are analyzed and evaluated through energy consumption and economic aspects.
Comparison work between the two design schemes and traditional technologies are presented.