Sludge Gasification Using Iron Bearing Metallurgical Slag as Heat Carrier: Characteristics and Kinetics

Waste heat recovery is a key problem to be solved for metallurgical slag. Furthermore, the heat source is a current bottleneck for sewage sludge gasification technology. At present, there is no complete process system for the thermochemical conversion of sludge driven by metallurgical slag waste heat. To recover the waste heat of slag, a granulation and waste heat recovery system using the sewage sludge gasification reaction is proposed in this paper. The sludge gasification kinetics were analyzed using thermogravimetry (TG). The active catalytic components in both Cu and Ni slag were determined using X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). The results show that the metallurgical slag could improve the decomposition rate of the sludge gasification reaction. The main catalytic components were Fe3O4 and CaO for Cu slag and Ni slag, respectively. The conversion ratio was increased by 7.8% and 11.8%, while the activation energy decreased from 21.09 kJ/mol to 17.36 kJ/mol and 17.30 kJ/mol, respectively, when Cu slag and Ni slag were added. After oxidative modification, the catalytic function was enhanced for Cu slag, whereas it was weakened for Ni slag.