HEX Retrofit Enables Smelter Capacity Expansion

Aluminium Bahrain 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 existing pot lines will be increased further. A bottleneck in the amperage creep projects is 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 operation costs are expected, as well as reduced lifetime of filter bags due to increased hydrolysis. Another option is to install heat exchangers 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 close to 3 years at Alcoa Mosjoeen.