Testing of innovative Fe- and Ca-Mn-based oxygen carriers with natural gas in continuous operation

Chemical-looping combustion (CLC) of gaseous fuels, such as natural or refinery gas, could be a viable option in a variety of industries for production of heat and electricity with CCS. Further, CLC can be combined with conventional steam–methane reforming for efficientcarbon-neutral hydrogen production. A series of collaborate European projects have been carried out since 2002, which focused on oxygen-carrier development and upscaling of both the CLC process and oxygen-carrier production with natural gas and refinery gas as fuel. Inthe latest project, SUCCESS (2013-2017), a series of oxygen carriers based on Fe and Ca-Mn materials were developed using commercial and low-cost raw materials. Two commercial methods for particle production were used: impregnation of Fe2O3 on Al2O3 and spray-drying of CaMnO3. In this paper, selected results are presented from investigation of these two promising oxygen carriers using a laboratory-scale unit with continuous operation and a nominal fuel input of 10 kWth. In this unit, the gas velocities in the riser and in the grid jet zone of the gas distributor come close to gas velocities of industrial-scale units and the material is exposed to a large number of redox cycles. Therefore, this unit is highly applicable for judging particle lifetime. Both materials functioned well during operation with natural gas, with little or no agglomeration. The total time with fuel was 30 h and >100 h for the impregnated Fe-based material and the Ca-Mn-based material, respectively. Although the degree of elutriation was high for both materials, the actual fines production