Experience with a commercial wet-scrubber (Alusuisse) used in unconventional seawater environment

An experience gained in the closed aluminum smelter in Sibenik (Croatia) is described in order to highlight possible similar problems anywhere in the world, when commercial wet-scrubber, designed for fresh water, is used in an unconventional seawater environment. Lime treatment process was used to remove fluoride as an insoluble calcium fluoride. Wet-scrubbing in real system is compared with that in model system, using the SOLGASWATER program (ERICSSON, 1979) for heterogeneous equilibria. It is shown that chemical modelling can help to control the wet-scrubbing process and thus to avoid the undesirable breaking of pipelines. The removal of fluoride at pH 5.4 in the form of insoluble cryolite, using lime slurry process and seawater in recirculation, is suggested to be an alternative to precipitation of calcium fluoride. Environmental consequences of partial discharging aluminum and fluoride into the marine environment are discussed in comparison with ecosystem response to volcanic aerosol.