Systems and methods for producing high-purity hydrogen

Abstract

A system for producing high-purity hydrogen fuel gas may include a chilling train configured to receive a purified, compressed cracked gas and produce one or more condensed liquid streams and a tail gas stream; and a demethanizer tower downstream of the chilling train configured to receive at least a portion of the one or more condensed liquid streams and produce a demethanizer overhead stream and a demethanizer bottoms stream. The system may be configured such that the tail gas and demethanizer overhead streams are not mixed. Rather, the system may be configured to process the tail gas stream in a multi-stage hydrogen expansion unit to produce a hydrogen stream for the high-purity hydrogen fuel gas and process the demethanizer overhead stream in a methane expander and drum unit to produce a methane stream. The hydrogen stream and methane stream may be used as a refrigerant in the chilling train.