OCR Text |
Show ) INTRODUCTION Oxygen enrichment has long been applied to many industrial combustion processes in order to increase product yields and thermal efficiency. The use of oxygen in hazardous waste incineration to augment or enrich oxidant levels in the combustion zones has the potential to improve the destruction and removal efficiencies (OREs) of the principal organic hazardous constituents (POHCs), minimize the formation of products of incomplete combustion (PICs), and allow for better control of the combustion process. The use of oxygen enrichment in rotary kiln incinerators is of interest as a potential method of minimizing transient failure conditions caused by the batch introduction of waste material. Rotary kiln incinerators are unique in that they are designed to allow a portion of their waste load to be charged in batch rather than continuous mode. In this batch mode of operation, solid wastes and "containerized" liquid wastes are introduced through entrance chutes, typically cocurrent with the gas flow. Kiln angle and rotation speed continuously expose fresh surface for oxidation, determine the residence times of non-combustible materials, and provide for continuous ash removal. Upon entry into the incinerator, the liquid waste container, typically cardboard, plastic, or steel drums, ruptures or burns, exposing the contents to the hot kiln environment. The liquid then rapidly vaporizes and reacts with the excess oxygen present in the combustion gases from the continuous primary flame. A possible kiln failure condition arises when the evolution of waste gases from the ruptured container is more rapid than the rate at which the stoichiometric amount of oxygen can be supplied from the primary flame. This transient overcharging condition, unique to batch mode systems, can lead to a "puff" of incompletely destroyed organic material which must 3 |