The main purpose of this paper is to find the effects of design and operating parameters, especially the chamber geometry and the overfire air injection method, on the mixing and reaction in municipal solid waste incinerators. 2- and 3-dimensional cold flow experiments, experimental and numerical analyses on hot flow model and numerical analyses on cross flow jets are conducted for this purpose.
Cold flow experiments show the flow characteristics of the counter and the parallel type incinerators and the improvement of mixing by the injection of overfire air. Numerical analysis on hot flow model of the center flow type incinerators is performed for several cases of flow rate distributions and injection angles of the overfire air. It shows that CO emission which indicates the effectiveness of mixing efficiency is strongly dependent on the flow field and it also suggests that the overfire air nozzles over the drying zone of the grate plays a dominant role in mixing and reaction for a given incinerator design.
Numerical analysis on the cross flow jets indicates that the nozzle space/diameter ratio as well as the momentum flux ratio determines the penetration depth, the size of recirculation zone and the degree of mixing with combustion gas. Nozzle space/diameter ratio should be considered as an important parameter in designing overfire air nozzles.
Further study is necessary to establish the optimal method of overfire air injection such as injection points, distribution of flow rate, the nozzle space/diameter ratio, the momentum flux ratio and the nozzle arrangement.
