Deadburning
Upgraded calcined magnesia is finely ground and compressed into briquettes for deadburning. The purpose of the grinding and briquetting steps is to prepare the magnesia such that the deadburning can proceed efficiently with even flow through the kilns, producing the highest quality magnesia with respect to homogeneity and density.
The briquettes are heated to 2,300°C in three gas-fired vertical shaft kilns (VSK's) to form sintered or deadburned magnesia. The furnaces are fired by natural gas, with cooling air introduced through the bottom or discharge end. The discharge temperature of the product remains high, with further air cooling being provided in the product storage bins. The capacity of the DBM plant is currently 110,000tpa.
Product grades are characterised by chemical composition, bulk specific gravity, and periclase crystal size (PCS). Both the SUPER and EXTRA grades have chrome oxide added to enhance the BSG.
DBM is stored on site prior to trucking to the port of Gladstone for export. Full capacity storage at Gladstone is 20,000mt, from where the product is loaded in bulk shipments mainly to Europe and North America.