OCR Text |
Show equllibr ium calculations show that the relative conce ntrations of reactive radicals varies strongly as a function of stoic h iometry , although the total concentration remains nearly constant. La bo r ato r y studies have confirmed tha t s t oic hiome try i s a maj o r variable i n deter mining relative incinerability [6]. Cal c ul a t ions using available kinetic data indicate that the emissions observed from full scale incinerators are several orders of ma gnitude higher than those calculated using oxidation kinetics and residence times and temperatures anywhere near the mean values in the post-flame zone of the incinerator. [7] This suggests that oxygen depleted pathways must be responsible for most POHC and PIC emissions since the rate of POHC destruction is significantly slowed and the rate of PIC formation is increased under pyrolysis. Even though the facility may be operating under nominally excess air conditions, poor mixing will result in oxygen-deficient pockets where the rate of POHC destruction is low and PIC formation is favored. Consequently, it is believed that gas-phase thermal stability under sub-stoichiometric oxygen conditions may be an effec-tive predictor of POHC relative incinerability. A recent study compared the incinerability predictions of several proposed ponc ranking methods with results of 10 pilot or full-scale test burns [7]. The ranking methods included heat of ~ combustion, autoignition temperature, ignition delay time, flame failure modes, theoretical flame mode kinetics, thermal stability of pure compounds under excess air conditions, thermal stability of mixtures under oxidative conditions, and the thermal stability of mixtures under oxygen-starved conditions. Correlations of the ) |