SIMAR, which stands for System Intrinsic Maximum Recovery, is a hypothetical operating scenario in which an expander-based recovery system can draw refrigeration freely from the environment. SIMAR operation is approximated when the feed stream to the system is LNG, because LNG contains abundant refrigeration that it can be treated as unlimited. SIMAR curve represents the envelope formed by plotting the maximum achievable C2 recovery against the recompression duties (or de-methanizer pressures). SIMAR curves are shown to characterize the given C2+ recovery process configurations very well.

The expander-based process for C2+ recovery has been the mainstay technology since the 1970's. For example, there are more than one hundred filed patents in the U. S. alone with individually claimed advantages. Despite the great technical and commercial success, a methodology for objectively evaluating different process configurations remains missing. Two major hurdles prevent the development in this domain: (1) concerns over possible impact on commercial interests, and (2) many process parameters obscure the underlying reasons of claimed advantages. The second hurdle is particularly noteworthy as some proposed configurations actually have adverse impacts on the recovery. However, the adverse impacts can be compensated by artfully performed refrigeration integrations over the entire system.

This work will generate SIMAR curves for a wide spectrum of processes configurations described in the literature. The curves will reveal the underlying efficiencies of the C2+ recovery process configurations. Findings of this work will be presented in ways only to shed light on current practices of the art. The conclusions and recommendations will be useful to guide future developments in C2+ recovery systems.