Conceptual design of an efficient Hydrogen production process from Natural Gas using an extension to the “G-H” methodology

Abstract

Conceptual design of novel efficient hydrogen production processes is essential to realizing a future clean energy scenario. Traditional approaches to process design involve detailed modelling of unit operations followed by simulation and optimization steps. However, several implicit assumptions may be made in the detailed models and these limit the efficiency of the overall process. In addition, potentially efficient novel technologies may not be considered. In this paper, fundamental thermodynamic principles are used within the framework of the “G-H” methodology (G denotes Gibbs free energy and H denotes enthalpy) for synthesis of an efficient hydrogen production process. The optimal chemical route is determined and termed the “1-step reaction”. However, the G-H methodology assumes complete conversion, which may not be optimal or even feasible for all reactions. Thus, this paper extends the G-H methodology to make it more realistic by including conversion as a variable. This methodology is then applied to a case study of flowsheet synthesis that uses separation and recycle to achieve 80% conversion. The flowsheet is simulated using Aspen HYSYS and an exergy analysis is performed. An overall exergetic efficiency of 81.8% is achieved and this represents an ideal target to motivate future technology improvements. © 2018 Elsevier B.V.