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

Abstract

Chemical looping combustion (CLC) has been as a viable and efficient alternative for coal combustion with CO2 inherent separation. Iron ore is a promising candidate for CLC of coal due to its low cost. Due to a limitation of particle size of the iron ore used in the fluidized bed, the fines for the iron ore after sieving with a particle size of <0.075 mm were reused for reactivation in the present work. The calcium aluminate cement as a very cheap material was used to combine the fines to produce a cement-supported oxygen carrier. The CLC performance with the developed oxygen carriers was experimentally investigated using Chinese traditional anthracite as fuel. In this study, the components of Fe2O3 and cement were optimized to obtain a better reactivity in the coal CLC process. Further, two additives (Ni and K) were added as catalysts during the oxygen carrier preparation process in order to improve the coal conversion rate and gasification rate. The experimental results suggested that compared with the single iron-based oxygen carriers, the oxygen carriers in the presence of additives demonstrated a high carbon conversion rate, gasification rate, and greater oxygen usage. The effect of reducing temperature (850–950 °C) and reducing/oxidizing cycles (20 cycles) on the reaction performance of the oxygen carrier samples developed in this study were evaluated. Also, the attrition behavior during multiple cycles was investigated. The detailed catalytic mechanism under the effect of additives was further discussed.