| OCR Text |
Show maximum concentrations provided in the fuel supply contract. It is important to note that the coal being supplied to the facility, Obed Mountain Coal, has relatively low concentrations of trace metals. Examinations of numerous other coal deposits indicate the potential for much higher concentrations of trace metals in this fuel component. Coal sourcing, then, requires attention to the trace metal content given the regulatory climate in the state of Washington. For completeness, the concentrations of trace metals in bed media and refractory are shown in Table 6. Note that the bed media has very low concentrations of trace metals. While the refractory has significant concentrations of chromium (e.g. 139 ppmw), the refractory is only a very minor contributor to flyash once start-up is complete. The concentrations of trace metals in the RDF are shown in Tables 7 - 9; the individual contributors are shown in Tables 7 and 8; and the weighted average trace metal concentrations for the RDF product as a whole are shown in Table 9. Note that, in general, the paper fractions of the waste stream are lower in metal content than the other fractions of the waste stream. Note, also, that the non-glossy paper appears to have a relatively high lead content when compared to glossy paper or cardboard. It should be noted that a few stray inorganic materials also can be present in the RDF; and these stray inorganics such as aluminum cans and other metal films (or paper/metal films) are additional, if relatively minor, contributors to the concentrations of trace metals in the waste-based fuels. With respect to the RDF production process, Table 10 summarizes the trace metal concentrations in the "grits" or middlings from the waste processing facility. Note that in virtually all cases the "grits" contain significantly higher concentrations of trace metals than the "lights" or fuel fraction from the RDF plant. Given the factors of concentration between fuel and flyash, the barium, chromium, and zinc concentrations in the grits are of consequence. Note, also, that the maximum concentrations of barium, cadmium, chromium, and zinc are significant when "grits" are considered as fuel. Trace Metal Concentrations in the Flyash Total metal concentrations in the flyash have been analyzed using 10 tests when coal and wood waste were fired and 16 tests when coal, wood, and RDF were fired in the unit. Table 11 presents the mean concentrations of total metals in the flyash when coal and wood were fired and the mean concentrations of total metals when all three feedstocks were fired. Table 12 presents the maximum measured concentrations of total metals in the flyash under those two conditions. Note that the inclusion of RDF in the fuel mix increases the trace metal concentration in the flyash dramatically in the cases of barium, cadmium, lead, and zinc. Changes in the concentrations of arsenic, beryllium, chromium, nickel, and strontium range from negligible to slight. Even the 12-15 percent decreases associated with nickel and strontium can be attributed to random events. Note, also, that the trace metals reported in Tables 11 and 12 occur when RDF is fired without "grits" included in the fuel mix. The data clearly show that the "middlings" fraction from the RDF plant should not be included in the fuel to the fluidized bed boilers. -7- |
