On evaluation of synthetic and natural ilmenite using syngas as fuel in chemical-looping combustion (CLC)

Chemical-looping combustion (CLC) is a combustion technique where the CO2 produced is inherently separated fromthe rest of the flue gases with a considerably low energy penalty. For this reason, CLC has emerged as one of the moreattractive options to capture CO2 from fossil fuel combustion. When applying CLC with solid fuels, the use of a lowcost oxygen carrier is highly important, and one such low cost oxygen carrier is the mineral ilmenite. The currentwork investigates the reactivity of several ilmenites, some which are synthetically produced by freeze granulationand two natural minerals, one Norwegian ilmenite and one South African ilmenite.A laboratory fluidized bed reactor made of quartz was used to simulate a two reactor CLC system by alternatingthe reduction and oxidation phase. The fuel was syngas containing 50% CO and 50% H2. A mixture of 6 g of ilmenitewith 9 g inert quartz of diameter 125–180μm was exposed to a flow of 900mLn/min syngas in the reduction phase.During the oxidation phase, a 900mLn/min flow of 10% O2 diluted in N2 was used.The experimental results showed that all ilmenites give higher conversion of H2 than of CO. Generally, syntheticilmenites have better CO and H2 conversion than natural ilmenites and synthetic ilmenites prepared with an excessof Fe generally showed higher total conversion of CO than synthetic ilmenites with an excess of Ti. Most syntheticilmenites and the Norwegian ilmenite showed good fluidization properties during the experiments. However, for twoof the synthetically produced materials, and for the South African ilmenite, particle agglomerations were visible atthe end of the experiment