China Nonferrous Metallurgy

Anode carbon residue is a harmful solid waste generated during the aluminum electrolysis process. Enterprises often use the pyrometallurgical process to burn carbon to recover electrolytes from it. The pyrometallurgical process is a commonly used recycling process for the sustainable development of the aluminum industry, but the treatment process has problems such as insufficient combustion, low electrolyte recovery rate, and unclear combustion kinetics. This article uses TG-DSC analysis and dynamic analysis to study the combustion performance and dynamic control conditions of anode carbon slag, analyzes the influence of heating rate on the combustion process, and obtains the following conclusions. The heating rate has a significant impact on the combustion of anode carbon slag. When the heating rate is 30K/min, the ignition temperature and maximum weight loss temperature increase to 525.79℃ and 1085.79℃, respectively. The maximum weight loss rate decreases to 0.22%/℃, the flammability index C decreases, the ignition index Ci increases, and the heat release during ignition increases to 790.38kJ/g. The high electrolyte content of anode carbon slag leads to asynchronous surface and internal temperatures of particles, and the ignition mode is heterogeneous ignition, which is not affected by the heating rate. The calculation results of Coats Redfern integration method show that the combustion fitting results of anode carbon slag at temperatures of 476~886℃ conform to the chemical reaction function model g(α)=(1-α)-^1/2, the limiting step is mainly controlled by chemical reactions. The combustion fitting results at temperatures ranging from 886 to 1100℃ conform to the one-dimensional diffusion integral function model g(α)=α². The restrictive links are mainly controlled by diffusion.