To investigate the combustion characteristics in a low-pollutant municipal waste incinerator, the generalized multi-block simulation code that can be applied to turbulent reacting flow with gaseous hydrocarbon fuel in a 3D complex geometry has been developed with nongray radiation effects. To deal with the complex geometry, structured multi-block method and the scheme which treats interfaces implicitly are adopted. The developed code is validated through various engineering problems such as curved duct flow, driven cavity flow, gray multi-block radiation, nongray radiation. and combustion in a incinerator.