Synthesis and optimisation of demethaniser flowsheets for NGL recovery

A discussion on a demethanizer process, which was characterized by interactions between the complex distillation column and other flowsheet units, including the turbo-expander, flash units, multistream exchangers, and refrigeration system, covers a systematic approach for demethanizer flowsheet synthesis to generate cost-effective designs; a semi-rigorous boundary value method for the design of complex demethanizer columns for application within an optimization framework for process synthesis and evaluation; a simplified flowsheet simulation model based on shortcut models to account for various configurations and inter-connections in the demethanizer process; a methodology accounting for heat integration in multistream exchangers; a generalized superstructure for demethanizer flowsheet synthesis that includes various structural combinations in addition to the operational parameters; application of a stochastic optimization technique, simulated annealing, to optimize the superstructure and generate energy-efficient and cost-effective flowsheets; and a case study relevant to natural gas processing to apply the synthesis methodology. This is an abstract of a paper presented at the 2012 AIChE Spring National Meeting and 8th Global Congress on Process Safety (Houston, TX 4/1-5/2012).