OCR Text |
Show while flowing through a water-jacketed duct into a collection cyclone. The selected char sample contained 61% carbon and 36% ash and, based on low magnification electron microscopy, was assumed to contain only char and mineral ash. Lampblack was prepared as needed by burning commercial kerosene-based fuel in a wick lamp and collecting the deposit on a water-cooled stainless steel surface. Since this material was prepared from a liquid distillate fuel it was assumed to be pure soot without char or mineral ash. Fly ash from a commercial power plant was used as the third component of the mixtures. This fly ash contained less than 3% carbon, and was assumed to be mineral ash with only trace amounts of either char or soot. Procedures evolved during the course of the study and the following is the final procedure which was used for the reported results. A sample of fly ash (nominally 0.01 g) was weighed using a Mettler Model AE240 analytical balance. All tare and sample weights were double checked and reweighed if the valued differed by more than ±0.0002 g. The sample was placed in a 20 x 150 m m test tube with 20 ml of 200 proof ethyl alcohol and agitated using a Aquasonic Model 75HT ultrasonic cleaner for 5 minutes. The test tube was then placed in a rack and allowed to settle for 60 ± 5 minutes. The top 18-19 ml of the suspension was decanted into a second test tube and the tube containing the bottom fraction was refilled with ethyl alcohol. Both tubes were again ultrasonically agitated and the settling was repeated. The process continued, as shown in Figure 1, to produce a top product fraction which contained material which was in the decanted liquid twice (T2) and a bottom fraction which contained material that had settled three times (B3) respectively. The product fractions were transferred to 50 ml beakers and placed in an oven to begin evaporating the alcohol. As the suspensions became more concentrated the liquid was poured, approximately 3 ml at a time, into tared ceramic crucibles and oven dried. The crucibles were weighed to give the net sample mass and the carbon analysis was performed using a Leco Model 521 apparatus with a Model 577-200 absorption train. A spreadsheet was set up to record the raw data and to perform the calculations. The measured top and bottom mass fractions, the Char and Soot 6 September 4, 1998 |