Modeling the Conversion Rate of Fuel Reaction for Chemical Looping Combustion in a Bubbling Fluidized Bed

Chemical-looping combustion (CLC), which divides the combustion process into an air reactor and a fuel reactor, has been regarded as an effective method to facilitate carbon dioxide mitigation. This system can be designed similar to a circulating fluidized bed, but with the addition of a bubbling fluidized bed on the return side. Between the two reactors, specific metal-oxide particles, called Oxygen Carrier (OC), are used for oxygen transport. Since OC is the main additional operating cost, it is proposed that low-cost minerals, such as ilmenite, are with great potential to explore. Previous study has shown that, simulation methods are an important tool for the scale-up and detailed design for this kind of system. The objective of this study is to establish a reduction reaction model in a bubbling fluidized bed with ilmenite as oxygen carrier for methane and synthetic gaseous fuels. Due to the agitation affect in the bubbling fluidized bed, it is assumed that the concentration of the oxygen carrier is homogeneous in the dense bed, so the bubbling fluidized-bed reactor can be modeled as a plug-flow reactor. Shrinking core model (SCM) displays the kinetic reaction of oxygen carrier for various fuels in the model. The constructed dynamic model can accurately fit the experimental data performed at the Institute of Nuclear Energy Research (INER). For the parameter R0, the oxygen transport capacities of ilmenite for H2 and CO are higher than that for CH4. By the shrinking core model, the analysis results show that the characteristics of Australia’s and Norwegian’s ilmenite are analogous. Finally, the sensitivity analysis based on two indexes, the specific combustion heat and the heat utilization factor, shows that the efficiency of reactor and fuel can be increased (or decreased) at the same time when varying temperature and OC size.