THERMODYNAMIC COMPARISON OF HYDROGEN-PRODUCTION PROCESSES

The results are reported of comparisons based on energy and exergy ana lyses of a wide range of hydrogen production processes, including proc esses which are hydrocarbon-based (steam-methane reforming and coal ga sification), non-hydrocarbon-based (water electrolysis and thermochemi cal water decomposition) and integrated (steam-methane reforming linke d to the non-hydrocarbon-based processes). A version of the Aspen Plus process-simulation computer code, previously enhanced by the author f or exergy analysis, is used in the analyses. Overall efficiencies are determined to range widely, from 21 to 86% for energy efficiencies, an d from 19 to 83% for exergy efficiencies. The losses in all processes are found to exhibit many common factors. Energy losses associated wit h emissions account for 100% of the total energy losses, while exergy losses associated with emissions account for 4-10% of the total exergy losses. The remaining exergy losses are associated with internal cons umptions. It is anticipated that the results will prove useful to thos e involved in the improvement of existing and design of future hydroge n production processes. Copyright (C) 1996 International Association f or Hydrogen Energy.