Exergy Analysis on Chemical Looping Reforming Process

摘要

The Chemical Looping Reforming (CLR) process developed at The Ohio State University (OSU) converts the coal into H2. In the CLR process, highly reactive metal oxide particles, rather than air or oxygen, are reacted with coal to produce reduced metal particles and an exhaust gas stream containing mainly CO2 and Steam. By condensing the steam, a sequester-ready CO2 stream can be obtained. The reduced metal particles are subsequently regenerated with steam and/or air in a second reactor to produce hydrogen or syngas gas respectively. The reactions oxidize back the oxygen carrier particles to their original state. These particles are then cycled back to the first reactor to react with the coal. This study presents the configuration of the CLR process for the production of H2 from coal. ASPEN plus simulation shows that the energy conversion efficiency of CLR process can be as high as 80% (HHV), much higher than the 64% efficiency obtained by the conventional Coal Gasification-Water Gas Shift (CG-WGS) route. This increase in efficiency for the CLR process is due to the better energy management strategy. In the conventional CG-WGS process mixtures of CO2 and H2 are produced, from which H2 is obtained after several separation and purification steps. Further, the CLR process offers better exergy recuperation compared to the conventional CG-WGS process. In this study, an exergy (availability) analysis on both processes is carried out. The analysis shows that the regenerated particle serves as an exergy carrier, thus improving the overall energy integration in the CLR process.