Numerical investigation of the load free permanent strain in carbon anode during baking process

Abstract

Baking is the final step of the anode production, which plays a major role in attaining the anode properties required by industry. However, the anode baking is a costly process during which various complex phenomena take place. It is therefore important to ensure good understanding of the impact of these phenomena on the baked anode quality. Regarding the mechanical aspect, various strain mechanisms occur in the anodes during the baking and evolve with respect to the spatial distribution of temperature and its rate of change in the baking furnace. Each of these mechanisms contributes to the stress equilibrium in the carbon anode and can lead, depending on the baking conditions, to poor mechanical properties including cracks when the failure limit is exceeded. In this paper, a specialized thermo-reactive visco-elastoplastic model is presented, which allow the numerical investigation of the stress distribution in the anode during baking. Each strain mechanism considered in the model is presented with a particular attention given to the permanent and non-recoverable strain mechanism occurring before the initial volatile release phase. Finally, the definition of a baking index is discussed to ensure the best approach to be used to quantify the evolution of anode properties during baking