(26c) Processes for High C2 Recovery from LNG – Part I: Schemes Based on Refluxed Demethanizer

Due to the declining domestic natural gas production, the U.S. LNG import is projected to play an important role in the overall natural gas balance. The re-gasified LNG must meet pipeline gas quality requirements and satisfy the gas interchangeability. Many existing and prospective LNG terminal owners consider extracting C2+ components from LNG as a feasible option for compositional adjustments.

The declining domestic natural gas production also implies decreasing NGL output. Currently, the U.S. is the largest NGL producer and accounts for about 30% of global production. Overall, the U.S. produces about 2 MMBPD of NGL which is mostly used as gasoline blends and chemical feedstock. Although increasing oil import to make up the anticipated NGL shortfall is viable, another route would be to extract maximum amounts of NGL from the imported rich LNG.

This work is a continuation to a previous article in which schemes for extracting C2+ components from LNG were discussed. The previous article focused on lowering the heating values of the regasified LNG to meet pipeline specifications. The C2 recovery level was non-restrictive and may go below 50%. This work will focus on improving the C2 recovery levels. A minimum recovery of 95% is set as a criterion. More specifically, the conventional designs based on the refluxed demethanizer will be investigated. In Part II of this work, designs based on expander technology will be studied.