(391b) Operation of a New 10kW C.L.C. Unit with 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. Consequently direct contact between air and fuel is prevented. Thus the combustion products are essentially CO2 and H2O without N2 dilution. .CLC is presently considered as one of the most promising CO2 capture technology in terms of efficiency penalty and cost reduction , but this technology is still in the early stage of development.

Various CLC configurations have been already developed and tested in laboratory pilot plant scales. In general, the system is composed of two interconnected fluidized beds reactors with a high velocity riser for the air reactor and a low velocity bubbling fluidized bed for fuel reactor. In this configuration the solid circulation flow rate is directly dependent of the gas velocity in the riser making it impossible to control the solid oxidation state independently of solid circulation rate.

A novel CLC configuration is proposed where reactions are carried out in interconnected bubbling fluidized beds. Solid circulation rate control is achieved with non-mechanical L-valves. Loop seals are also employed to minimize gas leakage problem. A 10 kWth equivalent cold flow model has been used to validate the concept. A study was conducted with 3 different solids of Geldart's group B classification with average diameter range of 126 - 305 µm and densities of 2650 and 4750 kg/m3. The results demonstrate stable solid circulation with efficient control on solid flow rate and effective gas tightness between the reactors.

Based on this, a 10 kW prototype CLC unit has been built and operated in IFP-Lyon . Stability of operation was confirmed. Combustion of methane or syngas was achieved with nickel-based oxygen-carrier particles in a wide range of operating conditions (temperature, fuel flowrate, oxygen carrier flowrate....)