A fluidized bed system combining two circulating fluidized bed reactors is proposed and investigated for chemical looping combustion. Direct hydraulic communication of the two circulating fluidized bed reactors via a fluidized loop seal allows for high rates of global solids circulation and results in a stable solids distribution in the system. A 120 kW fuel power bench scale unit was designed, built, and operated. Experimental results are presented for natural gas as fuel using a nickel-based oxygen carrier. No carbon was lost to the air reactor under any conditions operated. It is shown from fuel power variations that a turbulent/fast fluidized bed regime in the fuel reactor is advantageous. Despite the relatively low riser heights (air reactor: 4.1 m, fuel reactor: 3.0 m), high CH 4 conversion and CO 2 yield of up to 98% and 94%, respectively, can be reported for the material tested. V
Two different Ni-based oxygen carriers (OCs) are applied to chemical looping combustion (CLC) of natural gas on a scale of 140 kW fuel power. Both OCs are composed of NiO and a support material which is NiAl 2 O 4 in the case of OC-A and a mixture of NiAl 2 O 4 and MgAl 2 O 4 in the case of OC-B. Fuel reactor temperature and global air/fuel ratio variations are performed and indicate the high reactivity of both OCs. Solids sampling during operation allows the determination of the oxidation degree of the particles in the air and fuel reactors. In general, both OCs show a low degree of oxidation during operation. Despite very low H 2 O/CH 4 molar ratios in the fuel reactor, no carbon formation is observed under any conditions. In reforming conditions (global air/fuel ratio < 1), a complete uptake of the available O 2 is observed in the air reactor.
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