Apparatus and method for calcining sand

Apparatus for calcining sand, which comprises:

• an elongate, refractory-lined drum having a longitudinal axis, a generally cylindrical side, and opposite generally circular closed ends;
• means defining a material inlet in one end of said drums;
• means defining a material outlet in the other end of said drum;
• means for supporting said drum for at least partial rotation about its longitudinal axis;
• means for effecting oscillation of said drum over a predetermined arc about its longitudinal axis;
• a plurality of burners located at longitudinally spaced intervals in the side of said drum;
• means defining an exhaust flue in the said other end of said drum;
• indexing structure located inside said drum opposite said burners for mixing the sand for maximum exposure to said burners to effect calcination, and for advancing the sand from the inlet to the outlet responsive to oscillation of said drum;
• means for receiving and precooling the calcined sand discharged from the outlet of said drum;
• and
• means for receiving the calcined, precooled sand and for classifying it into sand of a predetermined granular size for further use.

A system for calcining, precooling and classifying sand, which comprises:

• an elongate, refractory-lined drum having a longitudinal axis, a generally cylindrical side, and generally circular opposite closed ends;
• means defining a material inlet in one end of said drum;
• means defining a material outlet in the other end of said drum;
• means for supporting said drum for at least partial rotation about its longitudinal axis;
• means for effecting oscillation of said drum over a predetermined arc about its longitudinal axis;
• a plurality of burners located at longitudinally spaced intervals along the side of said drum;
• means defining an exhaust flue in the said other end of said drum;
• a plurality of plows located at longitudinally spaced intervals opposite said burners within said drum, said plows being arranged in two staggered rows with each plow having a generally transverse front surface facing the material inlet, an inclined top surface, and an angled back surface facing the material outlet, for mixing the sand for maximum exposure to said burners while advancing the sand toward the material outlet responsive to oscillation of said drum;
• an aerator pipe extending between the rows of plows for injecting air into the sand to facilitate mixing and advancement thereof, and for adding combustion air to said drum to facilitate thorough calcination of the sand by said burners in said drum;
• a slidable door mounted for adjustable positioning over the material outlet in said drum;
• an arcuate bottom wall secured to said drum for oscillation with said drum, said bottom wall being located beneath the material outlet for receiving calcined sand and having upper and lower surfaces;
• index structure mounted on the upper surface of said bottom wall for mixing and advancing the sand;
• an underlying tank of liquid coolant for cooling said bottom wall by partial immersion in the coolant, to precool the sand thereon;
• inner and outer perforated arcuate plates secured to said bottom wall for receiving precooled sand therefrom responsive to oscillation of said drum, said inner plate being of relatively larger perforation than said outer plate to classify the sand;
• and
• a hopper underlying said perforated plates for receiving the classified sand.

A method for calcining sand, comprising the steps of:

• providing a generally horizontal refractory-lined drum having burners along the upper side adapted to heat the interior of the drum, and having predetermined internal indexing structure along the lower side of the drum adapted to mix and advance sand responsive to oscillation of the drum about its longitudinal axis;
• supporting the drum for partial rotation about its longitudinal axis;
• feeding sand to be calcined through an inlet located in one end of said drum;
• oscillating said drum over a predetermined arc centered on its longitudinal axis;
• heating the interior of said drum with the burners sufficiently to incinerate any resins and binders on the sand and thereby effect thermal reclamation of the sand;
• and
• discharging the hot, calcined sand out of an outlet located in the other end of said drum.