Focus of Some Scale-Up issues for Gas-Solid Flows with Group B Particles

Chemical Looping Combustion is an oxy-combustion like technology where oxygen-carrying particles are used to supply oxygen for combustion. The process uses dense group B metal oxide as an oxygen carrier to transfer oxygen from an air reactor to a fuel reactor in a circulating fluidized bed. Process development and scale-up issues require good understanding of particle flow. This paper discusses two important aspects that were investigated in detail. The first one deals with riser flow. Experiments were conducted in a large cold flow model with two monodispersed group B solids having similar density and size, but different shape factors (sand and glass beads). For a given condition, pressure drop in the riser roughly decreases by 50% with the spherical particles. This work, therefore suggests that particle sphericity has a strong impact on the riser hydrodynamic that is not presently accounted by models. The second aspect relates to attrition. Existing knowledge of attrition is mostly based on FCC background using standard tests such as PSRI Jet-Cup apparatus. For group B powders, we found useful to define a new attrition index and also to evaluate with CFD the jet cup internal circulation rate of CLC particles compared to FCC particles.