OCR Text |
Show burning in the primary bed. The backfrred burners were ftred at 40,000 B tu/hr to minimize the quench through the controlled temperature tower. All burners were operated at thirty percent excess air. Once the system equilibrated after start-up, a charge of waste was placed in the chamber. Emitted 02' CO, CO2, NOx, mc, and S02 were monitored continuously after introduction of the waste. Emissions of volatile organics, semi-volatile organics, acid gas, and metals were also measured during the tests using appropriate EPA sampling and analysis procedures. Samples of the solids in the kiln were obtained at several times during the tests. The test conditions used and analyses performed are shown in Table 2. Variations in bed temperature were attained by varying the main burner load. SuperfIcial bed velocities ranged from 0.6 to 1.4 ftls. Results A primary concern of the test program were the residence times and temperatures required to ensure that all of the toxic materials in the waste are destroyed. This was evaluated by examining the ultimate analysis of the original waste and the solids in the bed. The fraction of the original carbon and hydrogen in the waste remaining after a given time is shown in Figures 7 and 8. The hydrogen content of the samples dropped rapidly. In 30 minutes the hydrogen content in all of the samples dropped to below 10 percent of its original value. The carbon content dropped at a much slower rate. This probably indicates that the volatile components of waste containing signiftcant hydrogen are released rapidly followed by the slower release of organic material containing more carbon. Kiln temperature had a pronounced effect on the rate of carbon evolution. At the highest temperature (18()()°F), carbon was almost totally removed in the ftrst 15 minutes, while more than 30 minutes was required to remove the carbon at l000°F. At all of the temperatures tested, the carbon level could be lowered to less than 1 percent of the original value in less than 1 hour of treatment. The organic materials evolved from the kiln were collected during the fIrst 30 minutes of each test. The concentrations and identity of the compounds present were determined. Table 3 summarizes the volatile and semi-volatile organic emissions from the kiln. Only small amounts of a few volatile organic compounds escaped destruction in the kiln. Much higher concentrations of semi-volatile compounds were observed in the exhaust gas. The emitted semi-volatile compounds consisted of both materials that were present in the waste and combustion byproducts. No clear relationship between operating conditions and organic emissions was observed. The concentrations of toxic metals in the original wastes are summarized in Figure 9. A useful way to examine emissions data is to compare the concentration of the metal in the emissions with the concentration in the waste. Metal enrichment is the ratio of the concentration of a metal in the emitted particles to that in the waste. Often the enrichment is normalized by the enrichment of a metal known to be non-volatile to account for the increase in metals concentration -11- |