Numerical Simulation of Energy Recovery Incinerators

This paper illustrates the utility of developing compu­ ter models to predict and evaluate performance of com­ plex systems, in this case a dual combustion chamber incinerator of the type normally operated with starved air in the primary chamber, and equipped with a heat recov­ ery boiler. Once the model has been written, it can be used for construction of performance curves and examina­ tion of the parameters of operation. These can be used for comparison with actual operation, increasing understand­ ing of operating data, permitting improvements in per­ formance and resolving operating problems. The paper lists the equations which were used to con­ struct the model and briefly describes the method of cal­ culation of results from input, including an evaluation of the efficiencies of the heat recovery incinerator. Figure 4 shows clearly the principles of both starved-air and excess air combustion. As underfire air is increased from zero, partial combustion takes place until stoichio­ metric air is supplied, resulting in the peak temperature. Additional air reduces the product gas temperature. The calculated adiabatic flame temperature based on a com­ posite fuel (unfortunately not specified in this paper) is reduced to about 3300°F (1850°C) by the heat losses in the combustion chamber. Since such high temperatures cannot be tolerated by most refractories, and results in intolerable slagging conditions, some method must be used to achieve acceptable temperatures such as 900°C