Laboratory study of galvanic sludge's influence on the clinkerization process

This paper presents a laboratory scale simulation that aims to investigate the possibility of partially substituting raw meal with galvanic sludge in cement production. The galvanic sludge used in the experiments, was obtained from the chromium electroplating process; the sludge had Cr as the main heavy metal content. Differential thermal analysis tests were performed using cement raw meal and mixtures of cement raw meal and dry sludge. These mixtures contained 0.25, 0.5, 1.0, 2.0, 3.0, 5.0 and 8.0 wt.% of dry sludge. An apparatus was assembled to simulate the thermal cycle imposed to the charge during the clinker production process. A condenser was inserted into the hot chamber to capture the volatile phases produced. The charge had mixtures containing up to 3.0 wt.% of dry sludge. Samples of the different clinkers produced were submitted to leaching tests: atomic absorption chemical analysis, X-ray diffraction analysis and X-ray fluorescence chemical analysis to characterize the samples. This work showed that chromium emission is not significant during the production process of Portland cement clinker using galvanic sludge additives. The addition of dry sludge of up to 2.0 wt.% of the charge did not affect the formation temperatures of C2S (CaO.2SiO(2)), C3S (CaO.3SiO(2)) and liquid phase. This indicates that the galvanic sludge additions up to 2.0 wt.% did not affect the clinkerization process. The leaching tests showed that total Cr and Cr6+ concentrations in the solution were below the limits established by Brazilian Standards. (C) 2000 Elsevier Science B.V. All rights reserved.