Waste and Sorbent Parameters Affecting Mechanisms of Transient Emissions from Rotary Kiln Incineration

When “containerized” liquid wastes, bound on sorbents, are introduced into a rotary kiln in batch mode, transient phenomena involving heat transfer into, and waste mass transfer out of, the sorbent can promote the rapid release of waste vapor into the kiln. This rapid vapor release can cause depletion of available oxygen, and the formation of a “puff” which can result in a temporary failure of the incinerator system. A systematic study has been completed examining the effect of waste and sorbent properties on the magnitudes of transient puffs in a laboratory scale rotary kiln simulator. Of primary importance were waste boiling point and waste stoichiometric oxygen requirement. Of secondary importance were sorbent parameters such as bulk void fraction, and the fraction of the adsorbed waste that was contained within the individual sorbent particles. A theoretical model that utilizes a vaporization/surface renewal approach can be used as a guide to explain experimental results for several wastes on sawdust and corncob sorbents. Resin sorbents, on the other hand, are extremely effective at controlling puffs because they appear to be able to bind the liquid waste tightly to the sorbent in such a way that it is not released by a vaporization process. This non-physical waste release process is not described by the current model. In general, the results suggest that the practice of limiting containerized waste feed rates based on the heat of combustion of a given container be modified to provide feed rate limitations based on the stoichiometric oxygen requirements and boiling point of waste in a given container. This modified practice may enable containerized waste feed rates to be optimized, with a view to minimizing both the transient load on the afterburner and the transient emissions from the stack.

Keywords:

• Waste incineration
• rotary kiln
• transient behavior
• organic emissions
• modeling

Notes

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