Performance of Hematite/Ca2Al2SiO7 Oxygen Carrier in Chemical Looping Combustion of Coal

In this work, a novel Ca-enhanced hematite oxygen carrier was developed for chemical looping combustion of coal. Calcium aluminated cement was used to bind hematite particles to enhance its mechanical strength and improve its chemical properties. An anthracite coal was used as the feed stock. Coal gasification and combustion tests at 900 degrees C were carried out with the silica sands particles, calcium aluminate cement particles, pure hematite, and the combined Ca-enhanced hematite oxygencarrier particles in a fluidized-bed reactor at atmospheric pressure. It was found that, by the presence of the contents of CaO, Al2O3, as well as SiO2, a material of Ca2Al2SiO7 with hight melting point was produced. This Ca2Al2SiO7 material was confirmed to improve the mechanical strength for the newly developed oxygen carriers. Also, during the initial reduction process, the coal gasification rate was improved by nearly twice with the addition of the calcium aluminate cement. The physical and chemical properties for the combined oxygen carrier were characterized by X-ray powder diffractometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy and measurements of BET surface area. Multiple cycles tests confirmed that a stable reactivity for the newly developed oxygen carrier. The presence of Ca2Al2SiO7 prevented the sintering process during multiple cycles.