OCR Text |
Show temperature of 871°C (1600°F) and a chlorine concentration of 4 percent was performed in triplicate. For all tests, excess air was nominally 11.5 and 7.5 percent oxygen in the kiln and afterburner exit flue gas, respectively. Estimated solids residence time within the kiln was 1 hr. Sampling and Analysis of Flue Gas Particulate Particulate samples were collected from the afterburner exit flue gas using a variation of a Method 17 sampling train (5). For each test, about 19.8 m3 (700 ft3 ) of flue gas was sampled over a 3-hr sampling period, beginning no less than 1/ 2 hr after the start of test mixture feed. The large sample volume allowed at least 1 g of particulate to be collected for each test. The particulate was collected in an oversized alundum thimble placed within the sampling probe. After obtaining the total particulate weight, these samples were divided according to the terminal velocity in air using a No. 6000 Bahco Micro Particle Classifier (centrifugal classifier) in accordance with the procedures in ASME Power Test Code 28 (6). Particulate separation by size was accomplished by sequentially subjecting each sample to increased air velocities. Each air velocity condition separated a particulate sample into two portions-a fine "throw-off" and a coarse "residue." The throw-offs were recovered for each velocity condition and placed into separate vials, while the corresponding residues were placed back into the machine to be subjected to the next higher velocity. This procedure produced nine fractional samples for each starting sample, with each fraction representing a different size range. strictly speaking, the Bahco analysis classifies according to the particle terminal velocity distribution and not by the particle diameter. The conversion of the terminal velocities into actual particle sizes is accomplished through the use of Stokes' Law. The nine fractional samples were recombined to give the five nominal size cuts of less than 2 ~m, 2 to 4 ~m, 4 to 10 ~m, 10 to 30 ~m, and greater than 30 ~m. Each cut fraction was weighed, digested and analyzed for metals. Samples were digested following the procedures of Method 3010 (7). Metals analysis was performed by inductively coupled argon plasma (rCAP) spectroscopy per Method 6010 (7). RESULTS AND DISCUSSION Table 4 summarizes the metal distributions by particle size range in the afterburner exit flue gas particulate. Two groupings of tests appear in the table, each grouping corresponding to a series of tests in which one test variable (kiln exit temperature or waste feed chlorine content) was varied, with the other variable held nominally constant. The 6 |