Sammendrag
In the aluminium industry today, smelters often have to rely on
more than one alumina supplier. This creates diversity in the
properties of smelter grade alumina (SGA). A method has been
developed to compare the HF formation from aluminas containing
different amounts of water. The water content of the different
aluminas was determined by loss on ignition tests (LOI) and
thermal gravimetric analysis (TGA). Further, the aluminas were
added to a cryolitic melt kept in a gas tight furnace with a constant
nitrogen flow rate. The HF concentration in the off gas during the
alumina additions was measured in-situ using a tunable diode
laser. A correlation between the quantity of water found from LOI
characterisation and the amount of HF formed has been found. It
was also found that in this laboratory setup, all types of water
contribute to HF formation; structural hydroxyl, physisorbed and
chemisorbed water.
more than one alumina supplier. This creates diversity in the
properties of smelter grade alumina (SGA). A method has been
developed to compare the HF formation from aluminas containing
different amounts of water. The water content of the different
aluminas was determined by loss on ignition tests (LOI) and
thermal gravimetric analysis (TGA). Further, the aluminas were
added to a cryolitic melt kept in a gas tight furnace with a constant
nitrogen flow rate. The HF concentration in the off gas during the
alumina additions was measured in-situ using a tunable diode
laser. A correlation between the quantity of water found from LOI
characterisation and the amount of HF formed has been found. It
was also found that in this laboratory setup, all types of water
contribute to HF formation; structural hydroxyl, physisorbed and
chemisorbed water.