Analyses of one-step liquid hydrogen production from methane and landfill gas

Abstract

Conventional liquid hydrogen (LH 2) production consists of two basic steps: (1) gaseous hydrogen (GH 2) production via steam methane reformation followed by purification by means of pressure swing adsorption (PSA), and (2) GH 2 liquefaction. LH 2 produced by the conventional processes is not carbon neutral because of the carbon dioxide (CO 2) emission from PSA operation. A novel concept is herein presented and flowsheeted for LH 2 production with zero carbon emission using methane (CH 4) or landfill gas as feedstock. A cryogenic process is used for both H 2 separation/purification and liquefaction. This one-step process can substantially increase the efficiency and reduce costs because no PSA step is required. Furthermore, the integrated process results in no CO 2 emissions and minimal H 2 losses. Of the five flowsheets presented, one that combines low and high temperature CO/CH 4 reforming reactions in a single reactor shows the highest overall efficiency with the first and second law efficiencies of 85% and 56%, respectively. The latter figure assumes 10% overall energy loss and 30% efficiency for the cryogenic process.