Estimating the solids circulation rate in a 100-kW chemical looping combustor

- Experiments with a novel oxygen carrier were conducted by adding batches of fuel.
- The O2 dip in the AR that followed after each fuel batch could be used to model circulation.
- By making several batch experiments at varying circulation, a general model was obtained.
- The circulation correlated strongly to the internal mass flow in the AR riser.
- The internal mass flow in the AR riser could be used to calculate the solids circulation.

Chemical looping combustion (CLC) is a technology of CO2 capture that can drastically reduce its cost. The solids circulation inside a 100-kW chemical looping combustor was investigated using a novel oxygen carrier called Sinaus by adding fuel batches to the fuel reactor. The decline and subsequent rise of oxygen concentration in the air reactor after each addition was used to determine the residence time of solids in the fuel reactor and adjacent vessels. The obtained residence time, in combination with the solids inventory, determined the solids circulation for a particular batch experiment. After performing a number of such experiments, the above circulation was correlated with other experimental data, revealing a good correlation between the solids flow at the top of the air reactor riser and the actual circulation obtained using batch tests. The relationship between global circulation, ṁ, and the mass flow in the air reactor riser, ṁriser, was found to be linear within the investigated interval, being described as ṁ=6.6+0.057ṁriser. Although this correlation was valid only for the investigated reactor system, the approach used to obtain the solids circulation could be used to derive a similar correlation for any dual fluidized bed system.