160 hours of chemical-looping combustion in a 10 kW reactor system with a NiO-based oxygen carrier
Journal article, 2008
Chemical-looping combustion, CLC, is a technology with inherent separation of the greenhouse
gas CO2. The technique uses an oxygen carrier made up of particulate metal oxide to
transfer oxygen from combustion air to fuel. In this work, an oxygen carrier consisting of
60% NiO and 40% NiAl2O4 was used in a 10 kW CLC reactor system for 160 h of operation with
fuel. The first 3 h of fuel operation excepted, the test series was accomplished with the same
batch of oxygen carrier particles. The fuel used in the experiments was natural gas, and a
fuel conversion to CO2 of approximately 99% was accomplished. Combustion conditions
were very stable during the test period, except for the operation at sub-stoichiometric
conditions. It was shown that the methane fraction in the fuel reactor exit gas was
dependent upon the rate of solids circulation, with higher circulation leading to more
unconverted methane. The carbon monoxide fraction was found to follow the thermodynamical
equilibrium for all investigated fuel reactor temperatures, 660–950C. Thermal
analysis of the fuel reactor at stable conditions enabled calculation of the particle circulation
which was found to be approximately 4 kg/s, MW. The loss of fines, i.e. the amount of
elutriated oxygen carrier particles with diameter <45 mm, decreased during the entire test
period. After 160 h of operation the fractional loss of fines was 0.00022 h-1, corresponding to
a particle life time of 4500 h.
Chemical-looping combustion
oxygen carrier
fluidized bed