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Show Tacoma RDF plant is designed to produce approximately 250 - 300 ton/day ([PD) of fuel for the Steam Plant. Typically, when processing 500 TPD of incoming refuse, this facility produces 250 TPD of fuel, 125 TPD of "heavies", and 125 TPD of "grits" or "middlings" (Ebasco Environmental, 1990). Given the stringent state regulations, and the heterogeneous nature of the fuels being fed to the system, a program of metals management had to be developed to ensure that the flyash would not exceed the IARC compound limits and be classified as "dangerous waste." Further, research had to be performed to facilitate a more realistic approach to the interpretation of ash composition data in order to modify the assumption that 100 percent of any metal (e.g. lead) would be treated as if it existed in IARC compound form (lead phosphate). METHODOLOGY FOR ASH COMPOSITION ANALYSIS AND MANAGEl\1ENT In general, the methodology for managing the metals content of the flyash from Tacoma Steam Plant #2 involves characterizing in detail the trace metals in the fuels and then developing a profile of metal speciation based upon both literature review and combustion modeling. Methodology for Characterizing Fuel Streams The three fuel streams utilized at the Tacoma Steam Plant #2 were independently characterized with respect to proximate and ultimate analysis (see Table 3), and with respect to trace metals. The hogged wood waste and coal were characterized first. The RDF was subjected to more detailed analysis. Finally, for completeness, the bed media and refractory were characterized. Samples of the hogged wood waste and Obed Mountain Coal were obtained from the site and analyzed by Sound Analytical Services, Inc. of Seattle, WA. The hogged wood waste evaluations were used directly. The results of the coal analyses were compared to the coal specification. Laboratory results were employed in subsequent analyses only when the specification was exceeded, or when the specification did not address a specific metal (strontium). The bed media and refractory were characterized in a manner analogous to the hogged wood fuel--samples were obtained and characterized directly with respect to trace metals content. The RDF was characterized by identifying seven basic fractions of the waste stream: glossy paper; non-glossy paper; cardboard; film plastics; rubber, leather, and hard plastics (RL&HP); wood and textiles; and other organics. The entire fuel fraction of the waste stream was sampled for a complete week, and a weighted average composition was developed based upon the proportion of each stream in the mass of RDF being sent to Tacoma Steam Plant #2. The sample point employed was downstream of the air classifier and screening operations, at the discharge point for the "lights" fraction. Four samples of each fraction were taken for laboratory analysis. Each of the 28 samples was analyzed by AMTEST, Inc. for proximate and ultimate analysis, higher heating value, and trace metal content. For trace metals, each sample was digested directly and -4- |
