HEX retrofit enables smelter capacity expansion

Abstract

Aluminium Bahrain (Alba) is one of the largest producers of primary high quality aluminium in the world, and continues to consider further expansions such as the planned new line 6. In parallel the amperage on the existing AP30 pot lines 4 and 5 will be increased further. A vary typical bottleneck in the amperage creep projects concerns limitations on gas flow and temperature to the existing gas treatment centers (GTCs). Cooling can be provided by adding dilution air, or water injection, but in both cases additional scaling, HF emissions and higher costs are expected, as well as the potential for reduced lifetime of filter bags due to increased hydrolysis. A new way to consider is to install heat exchangers that are integrated into each compartment in the existing GTCs (IHEXs) to cool the potgas. Stable heat transfer and pressure drop, and successful avoidance of scaling are demonstrated. The performance is compared to the HEX data collected for 26 months at Alcoa Mosjøen.