In order to improve low combustion efficiency of typical incinerators like a stoker type, a new unique cyclone combustor, three-way swirling combustion (TSC), is being introduced through a commercial scale pilot plant experiment for refused plastic fuel (RPF). TSC provides air curtain insulation, substituting the refractory brick and lowering the generation of flying ash, for clinker prevention at the boiler. Its excellent emission measurement has also been reported. Through the study of three-dimensionless numbers (swirl number, Strouhal number, and Reynolds number) and previous researches conducted on cyclone combustors, their design criteria—geometrical and operational parameters—has been identified and suggested for future designs.