Process Simulation of Chemical Looping Combustion for a Mixture of Biomass and Coal with Various Oxygen Carriers—Part II

Abstract

Chemical Looping Combustion (CLC) is an emerging technology that has shown great promise for the capture of almost pure CO₂ in combustion of fossil fuels in power plants. In this chapter, the CLC process is modeled in ASPEN Plus and then validated using experimental data from the combustion of three types of biomass as fuels, and Hematite (Fe₂O₃) as an oxygen carrier (OC). The three types of biomass used in the simulation are Pine Sawdust, Almond Shells, and Olive Stones. The effect of the fuel reactor temperature on gas concentrations (namely CO₂, CO, H₂, and CH₄) in the fuel reactor, and the carbon capture efficiency are examined. It is found that all three biomass types have very high carbon capture efficiencies, with Pine Sawdust and Almond Shell reaching nearly 100% capture efficiency for temperatures equal to or greater than 950 °C, while Olive Stones reaches a capture efficiency of nearly 100% at temperatures greater than 980 °C. It is also found that fluctuations in CO₂ concentrations in the fuel reactor vary across the three biomass types. The effect of using Mn₂O₃ as the OC in place of Fe₂O₃ was also investigated. It was found that switching the oxygen carrier to Mn₂O₃ caused the concentrations of CO and H₂ in the fuel reactor to decrease slightly, while the concentration of CO₂ increased slightly. Furthermore, changing the OC to Mn₂O₃ had no effect on the carbon capture efficiency. Additionally, a mixture of coal and biomass at 895 °C was used with each of the two oxygen carriers, and the results were compared. It was found that the system using Fe₂O₃ had a greater power output than the one using Mn₂O₃, and that power output increased as the fraction of coal in the coal-biomass mixture increased.