Conclusions

The laboratory research into slow and rapid carbonisation of MP and HP, and anode pastes based on these products, has been studied. The dynamics and the content of the main products formed (gases, tar containing PAHs, carbon residue) during slow (1°/min) carbonisation of MP and HP have been studied.

It was shown that during rapid (70°/min) carbonisation of anode pastes, the yields of tar are about 10 times higher and yields of carcinogenic PAHs are about 5-30 times higher than with slow carbonisation . Based on this, the most significant source of carcinogenic danger of Soderberg cells was found to be the open hole during the process stage of repositioning the current-carrying studs. Despite the finding that this stage contributes 60-70% of the carcinogenic emissions of PAHs to the atmosphere, this source is traditionally not considered.

Specific yields were determined for tars, BaA, BaP and DBA from the main sources of PAHs in aluminium production using vertical stud Soderberg cells with anode pastes based on MP and HP. It was shown that use of HP in the anode pastes results in a considerable decrease of specific tar yields from all sources, as compared with MP, while the specific yields of BaP and other carcinogenic PAHs does not change significantly. A replacement of MP with HP in aluminium production using Soderberg technology does not reduce the carcinogenic danger of this production technique.

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