Construction and operation of a 10 kW CLC unit with circulation configuration enabling independent solid flow control

Chemical Looping combustion (CLC) is an oxy-combustion technology in which the oxygen required for combustion is supplied by metal oxides known as oxygen carriers (OC). The OC particles are employed to continuously transfer oxygen from an air reactor to a fuel reactor where oxygen is delivered to the fuel. This technology is regarded as one of the most promising CO2 capture technology in terms of efficiency penalty and cost reduction. Various CLC configurations have already been developed and tested in laboratory pilot plant scales. However more investigations are required to achieve optimized process operation. Among the different points to address, control of solid circulation rate between reactors is of highest importance regarding its effect on determination of oxygen transfer rate and solid oxidation state. A novel CLC configuration is proposed here where reactions are carried out in interconnected bubbling fluidized beds. Solid circulation rate control is achieved independent from gas flow rate in rectors through use of pneumatic non-mechanical valves as high temperature limits use of mechanical valves. Loop seals are also employed to minimize gas leakage problem. A 10 kW prototype CLC unit based on this configuration has been designed and built at IFP-Lyon in cooperation with TOTAL to operate with nickel-based oxygen-carrier particles. Successful operation has been obtained with CH4 as fuel resulting in more than 99% CH4 conversion to CO2. The effect of operating variables, reactor temperature and degree of reduction of particles on the gas conversion will be discussed in this paper.