Efficient Cooling of an Aluminum Smelting Electrolytic-Cell after Shut Down

Abstract

In the aluminium reduction technology, cooling of the shut-down pot takes from five to nine days. Shortening of this time is paramount in ensuring smelters do not experience a substantial amount of down time induced revenue losses. The aim of this study is to develop a cooling technique which ensures the integrity of the pot shell is maintained and environmental pollution is averted whilst reducing the cooling time after shut down. To this effect, experimental studies were carried out on the pot shell’s material to deduce the effect of various cooling parameters on its microstructural and mechanical properties. Onsite measurements were carried on a full-scale aluminium reduction pot. 3-D Computational Fluid Dynamics (CFD), Finite Element Heat Transfer (FHT) and Finite Element Structural (FES) models of the aluminium reduction pot were developed using the commercial tools FLUENT and Mechanical ANSYSTM Programming Development Language (Mechanical APDL). The CFD models were used to model the flow of air around the complex shaped pot shell, the FHT models were used to model the pot’s heat transfer during cooling and the FES models were used to monitor the mechanical stresses in the pot shell. Model validation was carried out with onsite measured data. Models for different cooling scenarios were developed and cooling procedures which meet the desired requirements were assessed. Results show that applied cooling rates do not affect the microstructural and mechanical integrity of the shell material at its operating temperature. The Finite Element Models’ solutions were in good agreement with onsite measured data. The study presented an interaction between the pot’s heat transfer and its material contents. Side shell cooling techniques are limited by the insulation layers attached to the steel shell. An adequate cooling system requires the extraction of heat from the top surface of the pot. A cooling system by which the pot’s cooling time can be reduced by about 55hrs was deduced. Financial analyses show that these cooling techniques can aid aluminium smelters avert a substantial amount of down-time induced revenue losses. The validated Finite Element Models are delivered for future optimization studies.

Date of Award	Jun 2013
Original language	American English
Supervisor	Youssef Shatilla (Supervisor)