OCR Text |
Show and air that mayor may not be combusting. Obviously, the concentration of waste is continuously decreasing, while the temperature and concentrations of reactive radicals in the packet of gas will be generally increasing. On the other hand, cool unreacted waste can quench fuel and oxidant mixtures that is vigorously reacting or on the verge of ignition. It is important to achieve ignition. This is when a large amount of the chemical energy of the fuel and waste is released into the internal energy (temperature) of the system. It will be recalled that rates of reactions are exponentially dependent on temperature. This is the main driving force for destruction. Subsequent to ignition, the temperature may be so high that the chemical constraints are no longer controlling. It is clear that one cannot describe the incinerator as operating at a fixed temperature. Similarly, there is not a single residence time and the stoichiometry is also varying. The proper operation of an incinerator involves setting the conditions so that the distributions of physical conditions are tightly centered about the desired operating ranges. It is difficult to achieve the destruction efficiencies required by regulations purely on the basis of fixed settings of the operational variables for all incinerators. This is not only due to t~e different configurations of incinerators and the complexity of the process, but more important, the input streams may vary over large ranges in terms of chemical and physical properties. The consequence is that validation of incinerator operation must be performance based. Hence the emphasis on the selection of Principal Organic Hazardous Compound(POHC) and the demonstration of their destruction to certain prescribed limits. Inherent in this procedure is the concept of incinerability or the expectation that all other compounds will be more easily destroyed. Probably the major issue in incineration is the nature and quantity of the Products of Incomplete Combustion (PIC) that are formed in the course of incineration. The present approach is to consider the situation on a case by case basis. The consequence is the necessity for a great deal of field testing. This can be very expensive. The procedure for validation that is now used requires test burns for validation and then setting the operational variables on the basis of the test results. This has the tendency of freezing the technology. It does not answer questions regarding the production of toxicants for which detection methods are not available or upset conditions not covered during the test burns. No predictions can be made upon the consequences of 4 |