Experimental study of copper modified manganese ores as oxygen carriers in a dual fluidized bed reactor

Chemical-looping combustion (CLC) is a developing CO2 capture technology. CLC makes use of the repeated oxidation/reduction reactions of metal oxide (oxygen carrier, OC) to separate CO2 from fuel combustion and to obtain a pure CO2 stream suitable for compression and storage. Low cost materials, such as natural ores, are required for coal-fueled CLC because the lifetime of the oxygen carrier (OC) is lowered by side reactions with the fuel ash or carryover losses. In this study, five manganese ores were examined as oxygen carriers using CO as the fuel gas in a laboratory batch fluidized bed reactor. All five of the ores were impregnated by copper nitrate solution to evaluate the reactivity enhancement of copper impregnation. The period with full CO conversion can be enhanced 2-100 times for different ores in the single fluidized bed test, which indicated that the Cu impregnation may be a general method to enhance the reactivity of manganese ores. Finally, one manganese ore and the corresponding Cu-modified particles were tested in a dual fluidized bed reactor. The attrition rates of both materials were measured as 0.13 wt.%/h during the 88 h operation in the dual fluidized bed. Both the manganese ore and the Cu-impregnated ore exhibited stable and high reactivity during the continuous test in the dual fluidized bed reactor, even at a low temperature (∼310 °C). Copper impregnation had no obvious influence on the attrition property of the manganese ore.