A combustion chamber for use in the incineration of waste products includes an inner refractory wall which extends vertically within an outer protective wall in a spaced relationship so as to define a plenum therebetween. The inner refractory wall is constructed using a plurality of precast, refractory blocks which are stacked and arranged to define a cylindrical interior cavity. The refractory blocks include mating features on adjacent surfaces to facilitate assembly and provide structural support. For additional support, selected blocks are fixedly connected to vertical support tubes by metal tie-back anchors. To facilitate combustion, a selection of the blocks is precast with a tuyere hole in order to deliver a uniform and balanced supply of air from the plenum into the interior cavity. The precast nature of the refractory blocks enables the inner refractory wall to be constructed with great precision, thereby optimizing incineration and minimizing material degradation.