Pyrolysis Characteristics and Kinetics of the Preparation Process of Sludge-Based Activated Carbon by ZnCl₂ Activation Method

Xin Li¹, Guang-Zhi Wang¹, Wei-Guang Li^1,2, Ping Wang¹

(1.School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China;2. State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China)



Abstract:

To obtain the pyrolysis characteristics and kinetics of preparation process of sludge-based activated carbon by ZnCl₂ activation method (i.e. the pyrolysis process of the sludge with ZnCl₂ activation), the characteristic of mass loss and gas products generated during pyrolysis of the sludge with ZnCl₂ activation were analyzed by thermogravimetric analysis coupled with Fourier Transform Infrared Spectroscopy (TG-FTIR). The kinetic parameters were calculated by the Coats-Redfem method and the mechanism models were established. The role of ZnCl₂ in the pyrolysis process of the sludge with ZnCl₂ activation was also illustrated through the comparison of the pyrolysis characteristics and kinetics of the sludge with and without ZnCl₂ activation. The results showed that the pyrolysis process of the sludge with ZnCl₂ activation can be divided into four stages including the dehydration of sludge and initial depolymerization of a small portion of organics matters, the decomposition of large molecular organic matters into small molecular intermediates, the further degradation of intermediates and volatilization of ZnCl₂, and the decomposition of inorganic minerals and undecomposed organic matters. CO₂, CO, CH₄, H₂O, some aldehydes and carboxylic acids are the major pyrolysis gaseous products. The activation energies and pre-exponential factors are in the range of 28.84-206.42 kJ/mol and 9885.16-8.08×10¹¹ min-1, respectively. During the pyrolysis of sludge, ZnCl₂ not only can function as a dehydration agent and inhibit the formation of tar, but also can peptize the organic matters in the sludge, making them easier to be decomposed.

Key words:  sludge  ZnCl₂  activation  pyrolysis

DOI：10.11916/j.issn.1005-9113.2013.06.005

Clc Number:X705

Fund: