Thermodynamic analysis of standalone fuel processors for syngas production

Fuel processing reactor is the key component for synthetic gas or H2-rich gas production, which is commonly integrated in fuel cell systems. However, there is no standard methodology to evaluate the performance of standalone fuel processors. The composition of the product gas is one important feature while the thermodynamic conversion efficiency is also of the same importance. Exergetic analysis provides the most decisive method to evaluate the performance of fuel processing alternatives in thermodynamic equilibrium. In this study, exergy analysis is initiated by introducing reference processes with reversible structure. Subsequently, the ideal components are replaced by real components but still in ideal reversible system structure but with non-reversible reactor in thermodynamic equilibrium. Finally the structure of the process is modified by using economic feasible components considering heat recovery. The performance of the real process and the influence of operating conditions can be investigated by this methodology. Investigations within the framework of this thesis show that steam reforming process has the highest exergetic efficiency in an ideal system with ideal components while partial oxidation has the lowest efficiency. The exergetic efficiency of real steam reforming process with heat integration depends strictly on the real components (in this case; heat exchangers) efficiencies and operating temperature. The exergetic efficiency of partial oxidation at the same condition is not significantly affected by the components efficiencies while its exothermicity provides enough thermal energy for the heat recovery system. The calculations have been performed initially for methane and are continued for heavier hydrocarbons. It can be concluded that the exergetic efficiency of steam reforming is decreasing with increasing C-content of the hydrocarbon. Exergetic efficiency of partial oxidation decreases significantly with increasing C atoms of alkanes and remains almost constant for alkenes. The integration of steam reforming in high temperature fuel cells allows the complete conversion of the fuel even at temperatures as low as 500°C. This is the consequence of continues consumption of CO and H2 in the fuel cell which is compensated simultaneously by formation of these gases in integrated reforming.