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Show Compound CO co2 so2 NO-NO °2 Total HC Principle of Operation NDIR NDIR Flame Photometric Chemiluminescence Thermomagnetic Flame Ionization and analyzed after passing through primary and secondary cyclones and being filtered. Flue gas monitoring equipment includes the following instruments: Instrument MSA, LIRA, Model 303 MSA, LIRA, Model 303 Meloy, FPD Thermo-Electron, Series 10 Leeds & Northrup, Model 7803-G Beckman, Model 400 Start-up of the laboratory-scale unit is accomplished by preheating the lower part of the vessel to the desired temperature (=1500°F) by feeding premixed propane gas and air through the conical distributor plate into the bed region. When the vessel reaches the desired temperature, non-combustible bed material is slowly added to the bed region through the limestone-screw feeder. Once the feeding of bed material is complete, fuel feed is started. As the fuel feed continues, the propane gas is gradually cut off as combustion becomes self-sustaining. The entire start-up procedure for the laboratory-scale unit is not representative of (is longer than) what would be achieved in a commercial boiler, and takes about 1 1/2 hours. Chemical Analyses of Tested Shredded Scrap Tires Ultimate analysis and elemental ash analysis of the scrap tires, which were shredded to 1/4-inch x 0 in size are given in Table 3. Based on the chemical analyses, the calcium and zinc to sulfur molar ratio is less than 1.0 (SO.74). In order to meet current EPA sulfur dioxide emission standards, some limestone addition will be required. The heating value of the tested scrap tires, which is also shown in Table 3, was measured at 16,400 Btu/lb. The higher heating value of the scrap tires, as compared to the average bituminous coal, can be attributed to their higher total carbon and hydrogen content. The quantity of volatile matter, as given in Table 1, was also much higher than in bituminous coal. To achieve high combustion efficiency, provision must be made to burn up all the volatile matter. Experimental Results Combustion and emission characteristics of shredded scrap tires in the 6-inch diameter fluidized-bed combustor were investigated at various operating conditions. The test series consisted of six tests. During the first four tests, double screened silica sand of a size between 12 and 28 mesh was used as an inert bed material to obtain the baseline data, particularly for sulfur dioxide emissions. In the last two tests, a limestone bed, which is much lighter than the silica sand bed, was used to observe the effect of fluidization velocity on the combustion characteristics since this, in our earlier tests, had shown profound effect on freeboard combustion. Results of these preliminary tests are given in Table 4. Combustion, emission, and operating characteristics resulting from the six tests are discussed below: 11-21 |