Chemical Looping Combustion and Chemical Looping with Oxygen Uncoupling Experiments in a Batch Reactor Using Spray-Dried CaMn_(1-x)M_xO_(3-δ) (M = Ti, Fe, Mg) Particles as Oxygen Carriers

摘要

Chemical looping combustion and chemical looping with oxygen uncoupling (CLOU) with oxygen carrier particles consisting of CaMn_(1-x)M_xO_(3-δ) (M = Ti, Fe, Mg) has been studied by consecutive oxidation and reduction experiments in a fluidized-bed batch reactor. The examined particles were produced by spray drying, and all did show a significant release of gas-phase oxygen to the inert atmosphere at 900 and 1000 °C. All particles also provided very high reactivity with syngas and methane. Some of the examined particles showed unfavorable fluidization characteristics, i.e., they formed dust during operation or showed agglomeration or defluidization tendencies. The crushing strength of the particles that formed dust was typically <1.2 N. The desired perovskite structure was detected in all samples by X-ray diffractometry. The materials that included iron and titanium had these elements incorporated in the perovskite structure, substituting manganese. When magnesium had been included, it was not incorporated into the crystal structure; instead, it was present as a separate phase of MgO. In addition to a perovskite phase, most samples also contained small amounts of marokite (CaMn2O4). Particles doped with MgO calcined at 1300 °C showed good fluidization behavior, as well as particularly high reactivity with fuel.