Chemical Looping Combustion of liquid fossil fuels in a 1 kWth unit using a Fe-based oxygen carrier

Abstract

The integrated use of low-value hydrocarbons from the refining of crude oil under Chemical Looping Combustion (CLC) conditions can satisfy the demands of heat and steam of the refining process itself while at the same time reducing CO2 emissions up to 50% in oil refineries. This work evaluated the use of three different fossil liquid fuels, i.e., diesel, mineral lubricant oil and synthetic lubricant oil in a 1kWth CLC unit working with a Fe-based oxygen carrier prepared by impregnation method. The effect of key parameters of the CLC process was studied with the same batch of oxygen carrier particles for a total of 150 operation hours. With regard to the results obtained, every fuel tested was able to achieve 90% combustion efficiency being synthetic lubricant oil the most reactive fuel studied. Hydrocarbon reactivity seems to depend on the nature of the chemical bonds, being higher for alkenes (synthetic lubricant oil) than for alkanes (diesel and mineral lubricant oil). CH4 was revealed as a relatively stable intermediate combustion product for these liquid fuels. Therefore, oxygen carrier's reactivity towards this gas becomes crucial for the overall conversion. The characterization carried out to the oxygen carrier after operation revealed no evidence of changes derived from the sulphur or impurities present in the fuel. Therefore, the Fe-based material herein used seems to be suitable for conversion of fossil liquid fuels.