OCR Text |
Show - 6 - Results Figure 1 shows a lean premixed hexane flarne. TIle flame shape and structure is typical for a hydrocartx>n flame. Also shown in this figure is the two-stage flame of a lean premixed oxygenenriched trichloroethylene flame similar to previous experiments [13]. To test the thermodynamic considerations set forth above, lean mixtures of ethylene, molecular chlorine, and oxygen enriched air were burned. As depicted in the bottom of Fig. 1, indeed, these mixtures do show two-stage flame behavior. Hence, in this study, mixtures of ethylene and chlorine were used to simulate a wide range of hazardous-waste mixtures with independently adjustable HlO ratios, C/O ratios, as well as equivalence ratios and oxygen-enrichment levels. Figures 2-5 show sequences of flames for chlorine-doped ethylene mixtures in oxygen-enriched air. The gases flow from the bottom to the top of each frame through the burner nozzle which is faintly visible on the bottom of each frame. Figure 2 depicts flames characterized by equivalence ratios as well as HlCl ratios of unity, a C/Cl ratio of 0.5 and an average exit nozzle velocity of 45 cm/s. From the top to the bottom the oxygen concentration in the oxidant (oxygen and nitrogen) increases from 23% to 27.5%. TIle stoichiometric reaction C.ffI4 + 202 + zCl 2 -+ CO 2 +4HCI + (z-2)CI 2 is used here to obtain equivalence ratios. This overall reaction is similar to that used for chlorinated hydrocarbons [17]. For HlO < 1, this reaction provides an adequate description of the product distribution. For HlCl > 1, water vapor must be included in the product distribution. Note from Table fi, that for HlCl = 1, the equilibrium mole fraction of ~O/HO equals approximately 0.1. The top picture of Fig. 2 (23% oxygen) shows a cone-like flame structure similar to a simple premixed hydrocarbon flame. The appearance of this inner or first flame is faint yellow-brown. The second flame is bright yellow-white in nature and is located on the tip of the first flame. The two flames are separated by a diffuse yellow brown region. TIle two parallel lines across the luminous zone of the second flame is a ridge along the glass chimney which prevents the entrainment of ambient air into the air-stream which shrouds the flame. It is this ridge which allows an indication of position of the flame relative to the burner nozzle. |