OCR Text |
Show 60.96 cm. long. The burner section and the main section rotate, from 0.5 to 2.0 rpm, while the exhaust section remains stationary. The main section and exhaust section are connected with a rotary seal. A charge of waste is loaded into the center of the main section through the rear of the exhaust section by opening a blast-gate valve and inserting the loading chute. Solids are placed in large paper envelopes and then charged into the kiln. After charging, the chute is retracted and blast-gate valve is closed. A window can then be set in place which allows a direct view of the bed. Another window offers an axial view of the burner and bed. Two sets of cooling coils have been cast in the refractory walls of the kiln so that the rate of heat loss from the kiln can be varied. Solid phase residence time in the kiln varies from 1 to 6 hoUrs depending upon the experiment. Solid samples can be taken at any time during the experimental run. The variable swirl burner flres axial and radial gas and produces temperatures up to 1650°C. From the exhaust section, the gas passes through the flue where continuous gas measurements are taken, using two probes. A quartz-lined stainless-steel probe is used for the hydrocarbon analyzers (Beckman total hydrocarbon analyzer and GC/FID). The sample gas passes through a glass-wool filter and Penna-Pure dryer prior to the analyzers to remove paniculates and water. A 304 stainless-steel probe is used for oxygen and carbon dioxide/monoxide analyzers (Beckman Paramagnetic Oxygen Analyzer and Anarad NDIR CO/C02 Analyzer). Particulates are removed with a glass-wool filter and water is removed in a refrigerated condensate knockout drum. The flue gas then enters the afterburner system. The afterburner system consists of two natural-gas flred burners placed facing one another in a 38.10 cm. by 27.94 cm. rectangular combustion chamber. Each burner is rated at 73 kW; at the exit of the afterburner the oxygen concentration is measured. Particle Characterization Reactor Results To date, the experiments in the Particle Characterization Reactor have explored the effects of contamination method, contaminant concentration, and temperature using toluene contaminated sorbent. To detennine if the method of contamination influenced the desorption rate, the sorbent was contaminated in two ways: 1. using liquid toluene, contaminating the solid to 0.60% and 0.44% by weight toluene and allowing the solid/contaminant mixture to sit for one day and for three weeks, and 2. using a 600 ppm toluene gas and adsorbing the solid at ambient temperature, resulting in 0.950/0 by weight toluene in the sorbent. The results, shown in Figure 6 for desorption at 170°C where parts per million of toluene in the exhaust are plotted versus time, indicate that the method and time of contamination didn't appear to influence the rate of desorption. In addition, when the solids were analyzed at the end of the desorption experiments, they contained approximately the same amount of toluene, 170 J..lglgm to 160 J..lglgm. The effect of contaminant concentration is shown in Figure 7 where the mass flow rate of toluene nonnalized to the initial amount of toluene is plotted versus time for desorption at 170°C. For the higher concentration, the rate of desorption was initially higher than for the low concentration, but at the end of the two experiments, 75 to 80 minutes, the flnal concentration of toluene in the two solids was approximately the same, 190 J..lglgm to 160 J..lglgm. The excess toluene, 0.94% versus 0.44%, evolved at the beginning of the experiment, hence the results were not significantly different at the end of the run. Temperature played an important role during the desorption of the contaminant; as the temperature was raised from 20°C to 300°C (Figure 8) for sorbent contaminated with 0.44% by toluene, the evolution rate changed drastically. The ppm of toluene in the exhaust at 20°C was approaching 1 ppm and beginning to level off at the end of 5 hours. At 140°C, the level of toluene in the exhaust was 1 ppm after approximately one hour, |