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

Conventional liquid hydrogen (LH2) production consists of two basic steps: (1) gaseous hydrogen (GH2) production via steam methane reformation followed by purification by means of pressure swing adsorption (PSA), and (2) GH2 liquefaction. LH2 produced by the conventional processes is not carbon neutral because of the carbon dioxide (CO2) emission from PSA operation. A novel concept is herein presented and flowsheeted for LH2 production with zero carbon emission using methane (CH4) or landfill gas as feedstock. A cryogenic process is used for both H2 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 CO2 emissions and minimal H2 losses. Of the five flowsheets presented, one that combines low and high temperature CO/CH4 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.