CaMn0.875Ti0.125O3-δ as oxygen carrier in Chemical-Looping with Oxygen Uncoupling (CLOU) - solid fuel testing and sulphur interaction

Artikel i vetenskaplig tidskrift, 2013

Particles of the perovskite material CaMn0.875Ti0.125O3-δ have been examined as oxygen-carrier material for chemical-looping with oxygen uncoupling (CLOU). The aim of the work has been to determine the effect of the fuel to bed mass ratio when oxidizing solid fuels, and to determine the influence of SO2 on the reactivity with fuel. Two solid fuels have been used, a Mexican petroleum coke and a Colombian coal. The oxygen carrier material used in this study was CaMn0.875Ti0.125O3-δ and was developed and manufactured by the Norwegian research institute SINTEF. The experiments were conducted in a discontinuous quartz glass batch fluidized-bed reactor with an inner diameter of 10 mm. The particle bed rests on a porous plate and thermocouples 5 mm under and 10 above the plate was used for measuring the temperature. In the oxidation phase a flow of 1000 ml/min with 5% oxygen in nitrogen was used. During the solid fuel experiments the bed was fluidized with 600 ml/min nitrogen while 0.1 g of solid fuel added to the reactor from the top. Two solid fuels were used; petroleum coke and Colombian coal. In the experiments with gaseous fuels the bed was fluidized with 900 ml/min consisting of 450 ml/min CH4 and 450ml/min with 0.25-0.5% SO2 in nitrogen. It was found that the Colombian coal was oxidized considerably faster than the petroleum coke, which is unexpected since it could be expected that the kinetics for O2 release from the oxygen carrier should determine conversion rate rather than the reactivity of the fuels. The overall rate of conversion increased for experiments with larger bed mass though, which was expected. SO2 seems to have had a negative effect on the reactivity of the oxygen carrier, likely because of formation of CaSO4.