阳极炭渣燃烧动力学研究

Study on the combustion dynamics of anode carbon residue

阳极炭渣是铝电解过程中产生的有害固体废物,企业多通过火法工艺燃烧炭来回收其中的电解质,但处理过程存在燃烧不充分、电解质回收率低、燃烧动力学不清晰问题。本文采用TG-DSC分析及动力学分析研究阳极炭渣燃烧性能及动力学控制条件,分析升温速率对燃烧过程的影响规律,得到如下结论。升温速率对阳极炭渣的燃烧影响较大,当升温速率为30 K/min,着火温度和最大失重温度分别升高至525.79℃和1085.79℃,最大失重速率降低至0.22%/℃,可燃性指数C降低,着火指数C_(i)增加,着火时释放热量升高至790.38 kJ/g;阳极炭渣电解质含量高,导致颗粒表面和内部温度不同步,着火模式为非均相着火,不受升温速率的影响;Coats-Redfern积分法计算结果表明,阳极炭渣在温度476~886℃的燃烧拟合结果符合化学反应函数模型g(α)=(1-α)^(-1/2),限制性环节主要由化学反应控制;在温度886~1100℃的燃烧拟合结果符合一维扩散积分函数模型g(α)=α^(2),限制性环节主要由扩散控制。

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 30 K/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 C_(i)increases,and the heat release during ignition increases to 790.38 kJ/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)=α^(2).The restrictive links are mainly controlled by diffusion.