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Show 1. INTRODUCI10N Implementation of federal regulations controlling the treatment and disposal of hazardous wastes has stimulated interest in hazardous waste incineration. Many hazardous wastes are organic containing liquids and are candidates for incineration in spray-fIred combustors. Proper design of incinerators to handle these materials depends on understanding vaporization and combustion of both sprays and droplets, and on determining the extent of conversion of the hazardous components, potential production of toxic intennediates, and possible flame-out failure modes. Two factors can inhibit robust burning in the combustion of hazardous wastes and thus are the focus of fundamental research: halogenation and low heat of combustion. In the present study we have experimentally quantified the vaporization and combustion rates of droplets of pure chlorinated hydrocarbons and their mixtures with n-alkanes. Several insights into the combustion of hazardous wastes were gained. In the following sections we present the experimental methodology, results and discussion, and practical implications of our work. 2. EXPERIMENTAL METHODOLOOY The droplet combustion apparatus, schematized in Figure 1, is similar to that of Randolph and Law (1986) in which a stream of monodisperse droplets with controlled spacing is downwardly injected into the post-combustion region of a flat-flame burner. Upon heating, the droplets undergo either pure vaporization or vaporization and combustion depending on the temperature and oxygen concentration of the environment. The instantaneous droplet size and composition are determined by photomicrography and liquid phase sampling. Droplets with initial diameters varying between 200 and 300 micrometers, initial relative velocities of about 1 mis, and spacing greater than 100 droplet diameters are produced. The temperature in the reactor is approximately 1100 K and the oxygen concentration is 18% by volume for the burning experiments and 0% for the vaporizing experiments as described by Randolph (1986). The compounds studied include pure n-alkanes, pure I-monochloroalkanes, and mixtures of 1,1,2,2-tetrachloroethane (C2H2C4) plus n-alkanes. Although monochloroalkanes are not considered to be important hazardous wastes, understanding their combustion behavior in contrast to that of n-alkanes provides useful insight into the effects of chlorination on droplet burning. On the other hand, C2H2C4 is an important hazardous waste and is a heavily chlorinated compound with a very low heat of combustion. In fact, we shall demonstrate that droplets of pure C2H2C4 do not burn in our apparatus. The purpose of our investigation of mixtures is to explore blending strategies through which highly chlorinated hydrocarbons can be successfully incinerated. 3. RESULTS AND DISCUSSION Pure Compounds A plot of the square of the instantaneous droplet diameter versus time for a burning hexadecane (C16H34) droplet is presented in Figure 2 in accordance with the classical D2-law. The data show an initial intense droplet heating period during which the droplet size changes very little, and a prolonged period of steady burning accompanied by mild 2 |