Alumina-based dry gas scrubbers are employed for capturing fluoride from the gases evolved from the aluminum smelting process (e.g., from electrolytic cells). The dry scrubbing and secondary (reacted) alumina handling systems may be hampered by accumulations of scale, such as hard gray build-up (HGB). If not systematically addressed with cleaning and maintenance procedures, this scale may, for example, reduce the removal efficiency of gaseous fluoride in the dry scrubbers, reduce the capability to convey alumina at suitable rates, reduce filter life, alter the concentration of fluoride on secondary alumina and reduce the feed rate of alumina to smelting pots.