Exergy Analysis of Steam Methane Reforming

Steam methane reforming is an energy intensive process. Minimizing energy usage can
reduce operating cost and emission to the environment. It is learned that energy
requirement of the reformer depends on the operation parameters namely temperature,
pressure, and steam to methane ratio. In this work it is intended to perform the exergy
analysis of the reformer at various operating parameters. The exergy analysis will
address both the quantity and quality of energy. Both chemical and physical exergy of
the system are considered in the analysis. The composition of the outlet stream is crucial
for exergy calculation hence the reformer is modeled as an equilibrium conversion
reactor. The model can predict the composition of the outlet stream. The model can also
explain the effect of hydrogen removal in improving the conversion of methane at
milder conditions. Hydrogen removal of I 0% has similar effect on methane conversion
as 15K rise of reformer temperature at the same condition (other parameters remaining
constant). Exergy losses of the reformer for different operating condition were
investigated. Exergy loss per mole of hydrogen produced has the minimum value at
about 111 OK for steam to methane ratio of 3: 1. Both the conventional exergetic
efficiency and the recently proposed utilizable coefficient were calculated. Comparisons
were made on the basis of their suitability as criteria of thermodynamic performance for
the process. It is found that the utilizable coefficient is better criteria for describing
thermodynamic performance. Microsoft Excel is used as computing tool.