Exergy analysis: An efficient tool for understanding and improving hydrogen production via the steam methane reforming process

Exergy analysis has been shown to be an efficient tool for understanding and improvement of industrial processes. In the present study, exergy analysis has been used to examine the energy consumption of an existing Steam Methane Reforming (SMR) process and then to test for possible savings in primary energy consumption and environmental protection.In the first step, energy and exergy balances of a steam methane reforming process were established to identify the thermodynamic imperfections of the process. Recommendations from this study have contributed to the building of a new and more efficient process. Consequently, a heat exchanger, corresponding to 44.9% of the total required area for the SMR heat exchange, has been incorporated in the SMR for waste heat recovery.The thermal and exergetic efficiencies of the original process are 70% and 65.5%, respectively. For the new process, the thermal and exergetic efficiencies are 74% and 69.1%, respectively. The unused exergy is reduced by 9.3% from 125.9 to 114.2 kJ per mole of H2 produced. One mole of methane produces 2.48 mol of H2 compared to 2.35 mol of H2 produced in the original process. Furthermore, the new SMR process produces the lower greenhouse gas emissions.

► Exergy analysis is used for evaluating a steam methane reforming process and for guiding efficiency-improvement efforts.
► The main part of the processes exergy destroyed occurs in the chemical reactors.
► To improve the exergetic efficiency the system components should be improved and/or the exhaust exergy should be decreased.
► Heat recovery not only helps to save energy but also decreases the environmental impact.