Thermogravimetric analysis and pyrolysis kinetics of tannery wastes in an inert atmosphere

Authors: LUO, LAN - Zhengzhou University; LIU, JIE - Zhengzhou University; Liu, Cheng Kung; Brown, Eleanor - Ellie; WANG, FANG - Zhengzhou University; HU, YADI - Zhengzhou University; TANG, KEYONG - Zhengzhou University

Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2019
Publication Date: 4/1/2020
Publication URL: https://handle.nal.usda.gov/10113/6949589
Citation: Luo, L., Liu, J., Liu, C., Brown, E.M., Wang, F., Hu, Y., Tang, K. 2020. Thermogravimetric analysis and pyrolysis kinetics of tannery wastes in an inert atmosphere. Journal of American Leather Chemists Association. 115(4):123-131.

Interpretive Summary: Both leather-making and fur-making processes often generate a huge amounts of solid and liquid wastes. It has been deemed of great necessity for developing economical and environment-friendly technique for reusing these wastes. In this regard, the value-added utilization and pyrolysis treatment are promising approaches to reclaim energy and materials from tannery wastes. In order to control the pyrolysis process, the determination of pyrolysis model is a prerequisite for the design of pyrolysis reactor, selection of pyrolysis conditions, and optimization of the preparation of composite materials based on tannery wastes. In the present research work, the pyrolysis model for sheep fur wastes (SFW), a blend of discarded leather and wool, was successfully established based on thermogravimetry and master plots method. This model can be used to predict the pyrolysis behaviors of SFW at very low and very high heating rates that are difficult to study by the regular thermogravimetric analysis. The information derived from this research is very useful for designing the pyrolysis reactor and optimizing pyrolysis parameters for SFW.

Technical Abstract: The sheep fur wastes (SFW) from tanneries contain large quantities of water-insoluble proteins, which may be used for the production of composite materials, renewable chemicals and energy. In this work, the pyrolysis kinetics of powdered SFW was studied by thermogravimetry (TG) at different heating rates from room temperature to 600 °C in nitrogen atmosphere. TG results revealed that there are three stages in this process. The overall apparent activation energy (E) in the main pyrolysis stage was determined to be 275.6 kJ mol-1 by modified Kissinger-Akahira-Sunose (MKAS) method. Because the pyrolysis of SFW could not be described by a single-step reaction, the experimental DTG curve of SFW was deconvoluted into three individual peaks, followed by reconstruction of TG curves corresponding to three pseudo components. The average values of E obtained for these pseudo components are 234.7 kJ/mol, 176.4 kJ/mol, and 186.2 kJ/mol, respectively. Generalized master-plots method indicated that the SFW pyrolysis may follow the random nucleation and growth mechanism (Avrami-Erofeev model). Reaction model functions f(a) for these pseudo components could be expressed as: f(a)=3.1(1-a)[-ln(1-a)]0.67; f(a)=3.6(1-a)[-ln(1-a)]0.72, and f(a)=3.9(1-a)[-ln(1-a)]0.74, respectively.