Abstract: A process is provided for carrying out the cryogenic cooling of a material which comprises introducing material to be cooled into an elongated cryogenic tunnel housing on means for conveying said material from an inlet end to an outlet end, spraying liquid cryogen onto said material as it travels through said tunnel at a position proximate said outlet end, passing vapor or gas derived from said liquid cryogen in counter-current flow over said material passing through the tunnel, removing from said tunnel at a position proximate said inlet end an exhaust comprising said vapor or gas and atmospheric air entrained thereby through said inlet end, determining the rate of flow of the exhaust and the content of molecular oxygen in said exhaust, and calculating from the rate of flow of the exhaust and its oxygen content the rate of consumption of said liquid cryogen.

Abstract: The invention provides a process for recovering aluminum values from aluminum-containing minerals, such as oxides of aluminum and aluminosilicates.The process involves heating an intimate mixture of an aluminum-containing mineral and a solid carbonizable organic material, preferably a fibrous cellulosic material, so as to carbonize the organic material, and chlorinating the solid residue from the carbonization step. The solid residue contains carbon in very finely divided form distributed throughout the aluminum-containing mineral. The surface area and reactivity of this carbon is much higher than that of powdered coal and the chlorination reaction thus takes place in a most efficient manner.