In order to achieve power-generation efficiency higher than those of integrated coal gasification combined cycle plants, advanced integrated coal gasification combined cycle systems have been developed. Here, we developed a triple-bed combined circulating fluidized bed gasifier model using the commercial process simulator Aspen Plus (version 8.6) and Excel. The heat balance and reaction kinetics, including the inhibition of steam gasification by H2, were simulated for a combustor temperature of 950 C using porous alumina particles as heat carrying particles. The theoretical maximum cold gas efficiency of the triple-bed combined circulating fluidized bed gasifier model was 85.0% for a gasification temperature of 800 C. However, when the temperature was increased to 900 C, the efficiency decreased to 80.9%. This indicates that, for triple-bed combined circulating fluidized bed gasifiers, a relatively low gasification temperature is suitable for ensuring higher cold gas efficiency and reducing the amount of circulating heat-carrying particles needed. On the other hand, gasification temperatures lower than 850 C resulted in significantly higher bubbling fluidized bed gasifier volumes even when an effective Ca-based catalyst was used. The cold gas efficiency can be increased further by 8.6% by converting and recovering the missing hydrogen as H2 gas. Hence, there is a trade-off between the cold gas efficiency, gasifier size, and heat-carrying particle/coal ratio. The optimal gasification temperature for triple-bed combined circulating fluidized bed gasifier is 850 C.