OCR Text |
Show f ac t e xam i n a t ion of the da t a , r es ulted in mechanistic rationaliza-tions of the observed sta bilities t ha t can be used to fu r the r im pr ove the rankings based on extrapolat ion and theory. Our results were, at times, complicated by some POHCs apparently being formed as PICs from other POHCs. Although efforts were made to minimize this possibility, it was almost unavoidable for some molecules. This raises the serious question of how propensity for PIC formation should be included in this ranking. Currently, our policy is to avoid it wherever possible. Incineration is a complex process and relating laboratory deter-mined thermal stability to full scale incinerability is a tricky process. Our consideration of the problem suggests that determina-tion of the impact of thermal versus mixing failure modes is the key issue in developing a universally applicable ranking . . If thermal failure is relatively unimportant, then mixing may be the dominant failure mode, and a pyrolysis based ranking is appropriate. On the other hand, if thermal failure is important, the low. temperature oxidative pathways may be responsible for some organic emissions. In this case we would need both an oxidation and pyrolysis based ranking and a method for applying them. In addition, vaporization of solids and liquids may also playa role in determining pollutant emissions. Our laboratory/field data comparisons are encouraging that we are on • the right course, but more research into the above mentioned issues is clearly indicated. A complementary approach to developing a ranking of hazardous waste incinerability is to develop surrogate POHC/PIC mixtures. These mixtures would contain stable POHCs and compounds that produce |