Trace metal analysis of solvents used as fuel in a cement kiln

The kilns used to manufacture Portland cement provide an excellent environment for the safe disposal of certain combustible, hazardous wastes. Moreover, the fuel value of these wastes may yield significant savings in fuel costs.In order to evaluate part of the air pollution potential associated with these fuels, spent solvents were analyzed for trace metals using flame atomic absorption spectroscopy. Lead, zinc, chromium, nickel, selenium, cadmium, beryllium and arsenic levels were examined in 55 samples of solvents that had been obtained by a single distillation of unblended spent solvents, 185 samples of undistilled solvents, and 10 samples of coal. All samples of distilled solvents showed metal concentrations near the limit of detection.The mixed, undistilled solvents showed metals concentrations that were relatively higher than the distilled product, and very scattered except for cadmium, beryllium and arsenic, which were always below the limit of detection. The average values (mg/l) for lead, zinc, chromium, nickel and selenium were 42, 58, 30, 14 and 4, respectively.In order to determine the potentialnet increase or decrease of trace metals in the stack gases, ten coal samples were tested. These coal samples were obtained from a nearby cement kiln. The average concentrations for coal were 20 mg/l lead, 38 mg/l zinc, 43 mg/l chromium (corrected), 60 mg/l nickel 2 mg/l beryllium, and <0.62 mg/l cadmium. No determinations were made for selenium and arsenic. Most of the metal content of the spent solvents was contained on or in the participate matter in the solvents. It follows that the supernatant liquid from a settling tank should be a relatively safe fuel for use at cement kilns.