Stabilization of galvanic sludge by microwave pre-treated pyrolysis

Abstract

The study was aimed examine the effect of microwave preheated pyrolysis on the characteristics of volatile metal compounds. In order to monitor the behavior of volatile metals, samples were preheated with microwave oven in varying energy ranges and process durations. In order to determine optimum conditions, 360-, 600- and 900-W microwave power and 3-, 5- and 10-min microwave irradiation were used. Chemical analyses of samples were carried out both before and after experiments by X-ray fluorescence. Pyrolysis experiments were performed in a laboratory-scale fixed-bed updraft stainless steel reactor in the presence of 1 L min(-1) N-2 gas. Content of synthetic gas product obtained via pyrolysis was analyzed by a continuous gas analyzer. Microwave preheated pyrolysis resulted an increase in the weight percentage of calcium oxide, iron(III) oxide, and chromium(III) oxide in galvanic sludge. Similar changes were determined for most of the samples at 600 W and 5 min of microwave preheated pyrolysis. In this point, the weight percentage of calcium oxide, iron(III) oxide, and chromium(III) oxide were measured as 22.47, 16.93, and 5.63 wt% which were 19.86, 10.89, and 3.03 wt% after single pyrolysis. It is concluded that, future analysis are needed to increase the efficiency of stabilization by microwave preheated pyrolysis.