Multiphase CFD Modeling for a Chemical Looping Combustion Process (Fuel Reactor)

There are growing concerns about increasing emissions of greenhouse gases and a looming global warming crisis. CO2, is a greenhouse gas that affects the climate of the earth. Fossil fuel consumption is the major source of anthropogenic CO2 emissions. Chemical looping combustion (CLC) has been suggested as all energy-efficient method for the capture of carbon dioxide from combustion. A chemical-looping combustion system consists of a fuel reactor and an air reactor. The air reactor consists of a conventional circulating fluidized bed and the fuel reactor is a bubbling fluidized bed. The basic principle involves avoiding direct contact of air and fuel during the combustion. The oxygen is transferred by the oxygen carrier from the air to the fuel. The water in combustion products can be easily removed by condensation and pure carbon dioxide is obtained without any loss of energy for separation. With the improvement of numerical methods and more advanced hardware technology, the time required to run CFD (computational fluid dynamic) codes is decreasing. Hence, multiphase CFD-based models for dealing with complex gas-solid hydrodynamics and chemical reactions are becoming more accessible. To date, there are no reports in the literature concerning mathematical modeling of chemical-looping combustion using FLUENT. In this work, the reaction kinetics models of the (CaSO4 + HA fuel reactor is developed by means of the commercial code FLUENT. The effects of particle diameter, gas flow rate and bed temperature on chemical looping combustion performance are also studied. The results show that the high bed temperature, low gas flow rate and small particle size could enhance the CLC performance.