CHEMICAL LOOPING COMBUSTION WITH OXYGEN UNCOUPLING (CLOU) OF COAL CHAR IN A FLUIDIZED BED REACTOR

The present paper addresses chemical looping combustion with oxygen uncoupling (CLOU) as a mean to overcome the inherent limitations of direct and gasification-enhanced CLC of solid fuels. The validity of this concept has been tested by means of experiments with a bituminous coal char in a bench scale fluidized bed reactor. Experiments were carried out in oxygen-free atmosphere, using commercial reagent-grade CuO-dispersed alumina particles as oxygen carrier. Combustion was monitored by continuous analysis of gases at the exhaust. Regeneration of the carrier was carried out in the same reactor at constant temperature in air. The reactivity of the carrier was determined over multiple oxidation/reduction cycles in order to investigate the occurrence of deactivation. A complementary activity was carried out in a thermogravimetric apparatus in order to assess the inherent extent and rate of oxygen uptake of the carrier over repeated oxidation/reduction cycles. Results were compared with those of pure copper oxide. Based on the experimental results the possibility of application of the carrier in chemical looping processes is discussed. In addition, XRD analysis on both fresh and processed carrier was carried out to investigate the chemical-physical transformations subjected by the carrier during the CLOU process.