Numerical and Techno-Economic Analysis of Batch Annealing Performance Improvements in Tinplate Manufacturing

The present study examines the performance improvement in the batch annealing process used in tinplate manufacturing by enhancing the heat transfer towards the steel coils and altering annealing cycle parameters. Presently, the heat transfer in the furnace is non-uniform, resulting in non-uniform temperature profiles and recrystallisation inside the coils, affecting the final coated steel quality. This study modelled a current furnace and four improvement proposals utilising transient computational fluid dynamics, to produce coil temperature profiles and rank the cases by the highest coil temperature uniformity achieved at the end of soaking. By increasing the soaking temperature and time, as well as the coiling tension before annealing and altering the coil size, the aim was to achieve higher and more uniform coil temperatures that could ensure successful recrystallisation with less defects, especially at the cold spot area in the middle of the coil. Then, a techno-economic analysis compared the cost-effectiveness of the scenarios based on the associated costs and the improvement in the scratching defects of the batch-annealed steel. Overall, most cases exhibited positive results regarding temperature uniformity enhancement, but increasing the coiling tension was considered the most promising option, due to the combination of a large defect reduction potential and cost savings per cycle.