Method and apparatus for treating waste material in a counter-current incinerator

A method of treating waste material in a multiple hearth furnace having a plurality of vertically spaced hearths, wherein the waste material is introduced to the furnace at the top thereof and moves downwardly in a generally serpentine fashion alternately inwardly and outwardly across the hearths and is discharged at the bottom of the furnace, while simultaneously the gases of combustion are caused to flow in counter-current direction wih respect to the material being processed and are exhausted at the top of the furnace, and wherein the furnace has a natural tendency to form zones of processing including sequentially from the top of the furnace to the bottom thereof, a drying zone, a charring and volatile burning zone, a fixed carbon burning zone, and an ash cooling zone, said method further comprising the steps of adding air and water vapor in the fixed carbon burning zone.

Apparatus for treating waste material comprising, in combination, a multiple hearth furnace having a plurality of vertically spaced hearths, a rotatable center shaft extending through the center of the furanace and passing through each hearth, a plurality of spaced rabble arms secured to the center shaft and extending radially outwardly over each hearth, alternate hearths having drop holes disposed towards the center shaft and the other hearths having drop holes disposed toward the outer periphery thereof, said furanace having an upper material inlet and a lower material dispensing outlet, and said furnace having an upper exhaust gas outlet, said furnace having a natural tendency to form zones of processing including sequentially from the top thereof to the bottom, a drying zone, a charring and volatile burning zone, a fixed carbon burning zone and an ash cooling zone, and means for adding an oxidant including air and water vapor to the fixed carbon burning zone.