Mechanisms Governing Transients from the Batch Incineration of Liquid Wastes in Rotary Kilns

Abstract

When "containerized" liquid wastes, bound on sorbents. are introduced into a rotary kiln in a batch mode, transient phenomena in-volving heat transfer into, and waste mass transfer out of, the sorbent can oromote the raoid release of waste vaoor into the kiln environment. This raoid vaoor release can cause depletion and displacement of the excess oxygen from the primary flame, and formation ofa "puff," which can result in a temporary Failure orthe incinerator system. Parametric studies on a specially designed rotary kiln incinerator simulator showed that puffs are easily generated even with very small quantities of surrogate wastes and at excess air values exceeding 100 percent. Furthermore, their magnitudes and intensities increase with increasing kiln temperature and kiln rotation speed. A theoretical model describing simultaneous heat and mass transfer through a sorbent aggregate, coupled with vapor pressure driven waste vaporization within the sorbent aggregate, was combined with a fragmcntauon model and was able qualitatively to predict experimentally observed effects relating to puff duration, kiln rotation speed, kiln temperature. and stoichiometric oxygen requirement of the surrogate waste. Extrapolation of the model to conditions beyond the experimental test matrix indicated very strong influences of waste boiling point (and consequently latent heat), and of sorbent parameters such as overall void fraction in the container and the sorption characteristics of the individual sorbent particles. The theoretical results support the experimental data from the rotary kiln incinerator simulator and suggest that the experimentally observed trends have general practical validity. The model constitutes a first step in being able to rank wastes and sorbents with respect to their propensity to produce puffs.