Optimal design and operation for simultaneous shale gas NGL recovery and LNG re-gasification under uncertainties

Abstract

Both shale gas and liquefied natural gas (LNG) contain certain amounts of C2+ hydrocarbons (NGL), which might profitably be recovered. To accomplish this, the shale gas stream needs cold energy to chill down and scrub NGL; while the LNG stream needs hot energy to evaporate and separate from NGL. Thus, integrating both processes of shale gas processing and LNG re-gasification, so as to utilize cold energy from LNG re-gasification process to assist the NGL recovery, has potentially significant benefits on both energy savings and high-value product productions. In this paper, a new methodology to guide the conceptual design and operation for such a process synthesis has been developed, where the uncertainty of shale gas feed rate changes has been considered. The methodology includes four steps of work: superstructure development and data preparation, synthesis model development and solution identification, heat exchanger network design, and final process validation via rigorous simulations. Compared with the recent study of Wang et al. (2013), the paper has two major contributions: (1) a new MILP model with more precise process presentations; and (2) process synthesis with consideration of the uncertainty of shale gas feed rate, which enhanced future operational flexibility of the conceptual design.