OCR Text |
Show MSW. The resulting waste stream chlorine content of eight runs is shown in Table 5. The results are reasonably consistent, with the possible exception of an unusually high Cl content of 0.62 percent in the MSW sample from Run 9. Back calculation of chlorine percent from combustion gas data generally yielded lower percentages. The four t3st conditions shown in Table 5 were all run at 1800 F, removing temperature as a variable; the four conditions form a 2 by 2 factorial subdesign in the factors waste type and spiking by pvc. As an example, the PCDD/PCDF emissions at these four test conditions measured at the boiler outlet are listed in Table 6. A general linear model was fit to the data using the Statistical Analysis System package in order to perform as analysis of variance for an unbalanced design. A statistical analysis of the data at all measurement locations resulted in the conclusion that "There is no evidence that the amount of pvc in the waste affects the levels of PCDDs/PCDFs at any of the measurement locations". Therefore, removal of pvc will have little affect on unwanted emissions and effort towards this end is unjustified. Further, the study concluded that incinerator operating temperature significantly affected the levels of PCDDs/PCDFs at the boiler outlet location, and the levels of PCDDs/PCDFs and carbon monoxide are related. Conclusions Critics of incineration have argued that a reduction of PCDD/PCDF emissions can be based on an overall strategy of lowering the chlorine content of MSW by separating chlorinated plastics, and if necessary, sodium chloride from the refuse. Characterization and analysis of MSW, and test results from actual incinerators refute this hypothesis. Specifically, - There are multiple sources of chlorine in MSW and on the average plastics contribute about 1/3 of the total chlorine. - The level of hydrochloric acid in the flue gases has very little or no effect on the amount of PCDD/PCDF emitted. |