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Show KEY ISSUES IN THE FORMATION OF POLYCHLORINATED UNSATURATED HYDROCARBONS IN COMBUSTION SYSTEMS Wing Tsang and Valeri Babushok National Institute of Standards and Technology Gaithersburg, M D 20899 ABSTRACT Mechanisms for the formation of polychonnated organics dunng incineration are considered on the basis of fundamental single step reactions. A hypothesis for their formation as a result of the formation of chlorine during lean combustion followed by chlonnation of available organics is presented. The results are tested on the basis of simulations and more detailed requirements for the production of chlorinated organics are deduced. These include the competitions between carbon monoxide and unsaturated hydrocarbon production in rich mixtures, chlonnation of the hydrogen and hydrocarbon by-products and oxidation and chlonnation at a variety of temperatures. INTRODUCTION This paper is concerned with the production of polychorinated organic compounds during incineration [1]. A particularly interesting feature is that such products can be found even in cases where the molecules in the original feed stock were not highly chlonnated[2]. Interest is focussed on gas phase mechanisms. Incineration is largely a gas phase process. Any study of the phenomenon must begin by considering formation and destruction mechanisms in this environment. Although w e will not be discussing the dioxin problem, and will be only concerned with one and two carbon systems, the present result may have some implications on the nature of the precursors responsible for its formation. It will be recalled that the congeners of the polychonnated dibenzo-dioxins contain large quantities of highly chonnated species and indeed the peak concentrations are frequently found about the compounds containing six chlonnes [3]. The approach will be in terms of the fundamental single step thermal reactions that represent the input data for simulation packages such as Chemkin* [4]. These rate expressions, defining the kinetics of the reactions, represent the first transferable element from laboratory to real systems and leads to results that, at least in principle, can be directly related to Certain commerical materials and equipment are identified in this paper in order to specify adequately the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology nor does it imply that the material or equipment is necessanly the best for the purpose. |