Thermochemical decomposition of tannery sewage sludge in air and nitrogen environment

Abstract

The disposal and the management of sewage sludge from tanneries is a challenging issue for the leather industries because of their adverse effect on the environment. This study describes the detailed characteristics and assessment using thermodynamic and kinetic parameters of the tannery sewage sludge conversion in air and nitrogen. Isoconversional model-free methods like Flynn-Wall-Ozawa (FWO), Friedman and Kissinger-AkahiraSunose (KAS) were employed to investigate the kinetics and the thermodynamic parameters in the air environment. Ea for the Friedman, KAS and FWO were investigated in the study. The curves of DTG at 5, 10, 20 and 40 °C/min shows that the conversion can be divided into three major stages. Along with that, this study also investigates the frequency distribution by applying the DAEM model. There are six pseudo-components involved in the frequency distribution of the air environment while the seven pseudo components involve in the pyrolysis of tannery sewage sludge. For the thermal degradation prediction of the sewage sludge from the tannery, an artificial neural network (ANN) of the MLP-3-7-1 and MLP-3-11-1 model were used for the combustion and pyrolysis. Ea values for the model ranges are Friedman(148.96kJ/mol-395.23kJ/mol), KAS(169.65kJ/mol-383.75 kJ/mol) and OFW (176.44kJ/mol-377.85kJ/mol). Furthermore, the values of ∆H, ∆G, and ∆S are also in good agreement. The negative values of the entropy changes show that they are in good agreement. The model shows that there is a good agreement between the experimental and the predicted values. Overall, this study develops the importance of the ANN model which should be utilized as a suitable model to fit experimental data of thermogravimetric analysis.