Chemical-Looping Combustion with Liquid Fuel — Operation in a 300W Chemical-Looping Combustor

Licentiatavhandling, 2011

Chemical-looping combustion (CLC) is a promising technology for future energy production based on combustion of fossil fuel with inherent CO2 separation. In comparison to other carbon capture technologies there is no need for energy demanding gas separation using CLC in order to obtain pure CO2. In the past, CLC research has mainly focussed on the use of gaseous and solid fuels. This study is a first step towards the use of liquid fuels in chemical-looping combustion. Experiments were conducted in a laboratory scale chemical-looping reactor system with continuous circulation of oxygen carrier particles. An injection system for liquid fuel was designed and tested. The fuel used was a sulphur-free kerosene. Four different oxygen carrier materials were investigated, of which three were synthesized and one was a mineral. The synthesized materials were based on nickel, manganese and copper. The natural material was ilmenite, which is an iron titanium oxide. The highest fuel conversion to CO2 was achieved with the copper- and manganese-based oxygen carriers. The temperature necessary to achieve high fuel conversion however, was considerably lower for copper-based oxygen carrier than for manganese-based oxygen carrier. Of these two materials, the copper-based oxygen carrier showed clear oxygen release properties, meaning that it is likely that a substantial part of the fuel was converted by direct reaction with gaseous oxygen. This is called chemical-looping combustion with oxygen uncoupling (CLOU). Fuel conversion to CO2 and H2O with nickel-based oxygen carrier was high but somewhat lower than with copper- and manganese-based oxygen carrier, which can be explained by thermodynamic limitations. Ilmenite showed the lowest reactivity of all tested oxygen carriers. All the particles were analyzed before and after the experiments using XRD, SEM, BET surface area and particle size distribution. Whereas copper-based and ilmenite oxygen carrier particles showed a high degree of stability, nickel- and manganese-based oxygen carrier particles were subject to particle disintegration and nearly the entire particle batch was destroyed after the experiments.