Compartmented fluidized bed gasifier (CFBG), consisting of two compartments, which are the combustor and gasifier, uses the air blown instead of pure oxygen for syngas production, eliminating the need for the air separation unit and thus reducing the capital cost as distinguished from traditional ones. This paper presents a fluidization quality study on the cold physical model of CFBG for the main bed of the combustor and gasifier without considering the solid circulation inside. Different inert particles (river sand, quartz sand, and alumina) were used to investigate the effects of the distributor free area and the geometry of the compartments (area reduction/expansion) on the fluidization quality in CFBG. The results demonstrate that the combustor compartment can attain good fluidization quality, whereas the gasifier hardly achieves good fluidization because of the occurrence of channeling. The fluidization quality of the gasifier continues to remain poor even after the attempt of changing the distributor design by increasing the distributor free area. Our study shows that the effective diameter, D-e, for the compartmented reactor has a pronounced effect on the fluidization quality if the basic criteria, the distributor/operating pressure drop ratio greater than the distributor/critical pressure drop ratio, has been met. On the basis of the values of D-e found in our study, the CFBG reactor in our real pilot plant is designed according to the partition ratio of 60:40 (combustor/gasifier), with the total diameter of 0.65 m, so that the minimum effective diameter requirement can be achieved at the gasifier side when compared to the originally proposed ratio of 65:35 (combustor/gasifier) at a total diameter of 0.484 m.