On evaluation of synthetic and natural ilmenite using syngas as fuel in chemical-looping combustion (CLC)
Artikel i vetenskaplig tidskrift, 2010
Chemical-looping combustion (CLC) is a combustion technique where the CO2 produced is inherently separated from
the rest of the flue gases with a considerably low energy penalty. For this reason, CLC has emerged as one of the more
attractive options to capture CO2 from fossil fuel combustion. When applying CLC with solid fuels, the use of a low
cost oxygen carrier is highly important, and one such low cost oxygen carrier is the mineral ilmenite. The current
work investigates the reactivity of several ilmenites, some which are synthetically produced by freeze granulation
and two natural minerals, one Norwegian ilmenite and one South African ilmenite.
A laboratory fluidized bed reactor made of quartz was used to simulate a two reactor CLC system by alternating
the reduction and oxidation phase. The fuel was syngas containing 50% CO and 50% H2. A mixture of 6 g of ilmenite
with 9 g inert quartz of diameter 125–180μm was exposed to a flow of 900mLn/min syngas in the reduction phase.
During the oxidation phase, a 900mLn/min flow of 10% O2 diluted in N2 was used.
The experimental results showed that all ilmenites give higher conversion of H2 than of CO. Generally, synthetic
ilmenites have better CO and H2 conversion than natural ilmenites and synthetic ilmenites prepared with an excess
of Fe generally showed higher total conversion of CO than synthetic ilmenites with an excess of Ti. Most synthetic
ilmenites and the Norwegian ilmenite showed good fluidization properties during the experiments. However, for two
of the synthetically produced materials, and for the South African ilmenite, particle agglomerations were visible at
the end of the experiment.