Furnace Operations to Reduce Dross Generation

Abstract

While it is generally acknowledged that dross generation should be kept to a minimum, too often, the importance of maximising the aluminium content of the dross is overlooked. Some mistakenly believe that a low metal content is a good thing and that the aluminium is being kept in the furnace. In reality, this metal is most likely being lost due to insufficient cooling and thermiting. Much can be gleaned from looking at the dross that is generated in a casthouse; in fact, the quality of dross can provide a good indication of the overall efficiency of the operation. Even with the very low aluminium prices of today, of circa. US$1400 per tonne, a reduction in dross generation within the furnace can provide huge savings per year. Effective dross management also results in better metal quality, improved fuel efficiency, prolonged refractory life and improved yield in the entire facility. This paper will look at how dross is generated within the furnace in the first place, followed by ways to minimize the dross generation within the furnace using continuous and sub-surface circulation which can also provide significant energy and CO2 reductions. A separate paper will discuss dross processing options and possibilities. In summary, by careful attention to the equipment and process techniques around the furnace and the follow-on dross management significant cost savings and environmental benefits can be realized by cast house operations.

Review of measures for improved energy efficiency in production-related processes in the aluminium industry – From electrolysis to recycling

“…The temperature gradient between the top and bottom of a furnace can be reduced with the help of either stirring or metal pumping [27,28]. This can reduce the dross generation by as much as 25% [27,28]. Both energy use and CO2 emissions associated with the energy use are reduced [28].…”

“…This can reduce the dross generation by as much as 25% [27,28]. Both energy use and CO2 emissions associated with the energy use are reduced [28]. An energy saving of 10-20% and an increase in energy efficiency of 15-35% can be achieved with metal pumping in a reverberatory furnace [27].…”

“…An energy saving of 10-20% and an increase in energy efficiency of 15-35% can be achieved with metal pumping in a reverberatory furnace [27]. Other benefits are improved refractory life [28], increased productivity [27] and improved alloy homogeneity [3,27].…”

Preparation and Melting of Scrap in Aluminum Recycling: A Review

“…Exhaust gas recirculation, regenerative burners, and molten metal pumps have obtained important results [70,71].…”