EXERGY ANALYSIS OF SORPTION ENHANCED CHEMICAL LOOPING REFORMING PROCESS FOR HYDROGEN PRODUCTION FROM GLYCEROL

Abstract

This research presents a study on the sorption enhanced-chemical looping reforming process (SECLR) for hydrogen production from glycerol. A thermodynamic approach is used to evaluate the effect of operating parameters on the SECLR process in terms of the hydrogen production and carbon formation. Optimal operating condition is identified at a self-sufficient condition where external heat input is unnecessary. The simulation results show that the yield and purity of hydrogen can be enhanced by carbon dioxide sorption and steam addition. Furthermore, the excess of calcium oxide (CaO) sorbent and steam can inhibit a carbon formation in the SECLR process. A higher hydrogen yield can be obtained at high temperatures and low nickel oxide (NiO)/glycerol molar ratio. When increasing reforming temperatures and reducing NiO/G molar ratios, more energy is also required. At the self-sufficient condition with the highest hydrogen production yield, the process should be operated at the reforming temperature of 580 oC and atmospheric pressure, steam/glycerol molar ratio of 3.2, CaO/glycerol molar ratio of 3 and NiO/glycerol molar ratio of 1.84. Under these conditions, the hydrogen production yield of 4.92 (mol H2/mol glycerol) is obtained. To further improve the process performance, a pinch analysis is performed to design a heat exchanger network. The designed SECLR process is also investigated by performing energy and exergy analyses. The thermal and exergy efficiency of the SECLR process are compared with a conventional process for hydrogen production from glycerol. The result indicates that 79.8% of the energy fed to the process is recovered as the useful product of hydrogen and the exergy efficiency of the process is 75.1%. In comparison with the conventional reforming process, the SECLR process provides higher thermal and exergy efficiency than the steam reforming and auto-thermal reforming of glycerol.