OCR Text |
Show the basic aim of the original work was to try to capture the chemistry of flame suppression, no particular effort was made to introduce reactions that can lead to the larger and possibly undesirable side products that can be formed during combustion. Indeed, in the development of the data base an artificial cutoff was introduced. As a result the data base does not contain any fluorinated species containing more than two carbon atoms. This means that while the present data base is probably sufficient t~ describe the destruction of the fluorinated compounds under consideration, it cannot be used to describe the larger products of incomplete combustion that may well be the main issue in the destruction of fluorinated compounds by incineration. Some typical results are summarized in Figures 1-4. In these figures, the data are plotted in terms of the time required to achieve a given amount of destruction (99%) versus the amount of methane present. Each point represents one run. Changing the waste concentration, for example from 1 to 3% have rather small effects ( no more than a factor of 1.5) on the curves. The equivalence ratio, residence time and waste loading represent all the variables that can be readily controlled. In these figures all the area above the line for a particular compound implies greater destruction efficiency. Higher destruction efficiencies are in fact very close to the lines drawn here. This is because the physical picture is of a plug of gas which ultimately ignites to a very high temperature. At these high temperatures there are no particular problems in destroying a compound to as a Iowa level as necessary. The data in Figures 1 and 2 are from simulations carried out at initial temperatures 900 K and 1200 K purely as a matter of convenience. Nevertheless, the differences in the curves are of some significance. At the lower temperature apparently nothing much happens until ignition. At 1200 K, decomposition is already occurring prior to ignition. The data in Figure 3 are for ethane as a fuel. There does not appear to be substantial differences from the results with methane as a fuel. Figure 4 contains results with a waste mixture. It would appear th~t the decomposition of some of the more labile wastes is in essence providing an initiation source. Perfluromethane clearly occupies a unique position. From the data on Tables 1 to 3 it is clear that all pertinent rate constants are much smaller than those for the fuel, methane 16 |