Abstract: In the manufacture of alumina by the Bayer process, a method comprising the steps of bringing the overflow from a multistage red mud thickener into counterflow contact with the steam generated in consequence of the flashing of bauxite-dissolved slurry so as to effect exchange of heat therebetween, separating and removing sand from the slurry by regulating the rate at which the slurry is discharged from the bottom of the column, and circulating the heated overflow and using it as the wash water in the former stage of the said thickener, all the said operations performed in one and the same column; and a device provided with inlet and outlet pipes for the overflow, an overflow type condenser, inlet and outlet pipes for the slurry, and a pipe for the removal of sand so as to effect the operations of the said method wholly in one and the same column.