Ilmenite with addition of NiO as oxygen carrier for chemical-looping combustion
Journal article, 2010
The naturally occurring mineral ilmenite, FeTiO3, has been examined as oxygen carrier for chemical-looping
combustion. NiO-based particles have been used as an additive, in order to examine if it is possible to
utilize the catalytic properties of metallic Ni to facilitate decomposition of hydrocarbons into more reactive
combustion intermediates such as CO and H2. Firstly, ilmenite was examined by oxidation and reduction
experiments in a batch fluidized-bed reactor. These experiments indicated moderate reactivity
between ilmenite and CH4, which was used as reducing gas. However, adding 5 wt.% of NiO-based particles
to the ilmenite improved the conversion of CH4 greatly, resulting in an increase in combustion efficiency
with a factor of 3. Secondly, 83 h of chemical-looping combustion experiments were conducted in
a small circulating fluidized-bed reactor, using ilmenite as oxygen carrier and natural gas as fuel. A wide
range of process parameters and different levels of NiO addition were examined. Occasionally, there were
problems with the circulation of solids between the air reactor and fuel reactor, but most of the time the
experiments worked well. The products were mostly CO2, H2O and unconverted CH4. Adding small
amounts of NiO-based particles to the reactor increased the conversion of the fuel considerably. For
the base case conducted at 900, the combustion efficiency was 76% for pure ilmenite and 90% for the
corresponding experiments with 1 wt.% NiO-based particles added to the reactor. The properties of
ilmenite were found to change considerably during operation. Used particles had lower density, were
more reactive and more porous than fresh particles. These changes appear to have been physical, and
no unexpected chemical phases could be identified.
Ilmenite
Natural Gas
Chemical-looping combustion