Abstract:
In this research, effects of temperature and reaction time on chemical - looping combustion using calcium sulfate as an oxygen carrier were studied. Experiments were carried out in a fixed bed reactor. In the reduction reaction, the results showed that an increase in temperature gave more CH4 conversion and CO2 production. At higher reaction time, CH4 conversion and CO2 production were increased. However, it was observed the formation of CaO via the side reaction, which is a major problem of using CaSO4 as an oxygen carrier. This CaO is hard to be converted back to CaSO4, resulting in a significant drop in regeneration of the oxygen carrier. This work examined an effect of adding magnesium oxide on performance of calcium sulfate in the reduction reaction. It was found that, in case of 5 wt.% and 10 wt.% of MgO mixed with CaSO4, the main reaction between CaSO4 and CH4 was moved forward. Moreover, the side reaction, forming CaO, was decreased. In addition, cyclic experiments of reaction oxidiation reactions (the chemical-looping combustion) were investigated using 10, 30 and 50 wt.% of MgO mixed with CaSO4. Results were compared to that obtained in case of using pure CaSO4. An increase in MgO in CaSO4 exhibited the amelioration of carrier recyclability