OCR Text |
Show Destruction of Waste Feed The primary function of any detoxification process is, of course, the destruction of the hazardous components of the process stream being treated. The data for the photothermal conversion of T C E , D C B z , M C B z , and T C B shown in Figures 7 through 10, respectively, clearly show that the photothermal process can indeed effectively destroy organic air toxics ranging from low molecular weight volatile solvents to high molecular weight semivolatile compounds. In each example a significant portion of the waste feed was destroyed at 300°C, the lowest temperature for which data is typically taken. Furthermore, the extent of conversion steadily increases until complete destruction (taken as > 9 9 % destroyed) is achieved. Specifically, in the case of T C E , 12.2% of the sample was destroyed at 300°C, which increased to 81.3% by 500°C, a temperature where there are still no significant thermal reactions taking place. In the case of D C B z 28.7% was destroyed at 300°C, and 55.4% by 600°C. Similarly, 30.2% of the M C B z was destroyed at 300°C, increasing to 75.3% at 600°C. And in the case of T C B , only 5.7% of the sample was destroyed at 300°C, but this increased to 74.4% by 600°C. The data shown in Figures 7 through 10 show that the temperature required for complete photothermal destruction is comparable to that for purely thermal destruction. This illustrates that the exposure conditions used in the LS-PDU (e.g., exposure times, radiation sources, and radiation levels) are inappropriate for a full-scale system. However, as will be discussed below, these data provide the valuable fundamental information needed to predict the exposure conditions required for complete destruction at lower temperatures. Destruction of Organic Products of Incomplete Conversion The ultimate goal of a waste destruction process is to convert the hazardous components of a process stream to innocuous products (e.g., carbon dioxide, water, hydrogen chloride, etc.). One criticism of prior photochemical processes, and even some thermal technologies, is that they fail to completely mineralize the waste feed. Therefore, it is important to demonstrate that the photothermal process is capable of destroying any organic products of incomplete conversion (PICs) which may be produced. Note that the identification of the PICs in the discussion that follows were assigned by mass spectral inteipretation and confinned by analytical standards, when available. In cases where standards were not available, stmcturally similar compounds were used. Much of the early work on photothennal detoxification involved the destruction of semivolatile compounds such as T C B and chlorinated dioxins because these types of materials would absorb the radiation source (i.e., artificial sunlight) being used for these tests. A common result of these tests was that the photothermal process seemed to suppress the formation of organic PICs. The two examples given here from this work (i.e., M C B z and T C B ) are not the best examples available, but they do offer the most complete analysis of photothennal organic products of incomplete conversion (PICs) available to-date. 10 111-19 |