| 摘要 |
Contaminants are removed from particulate material in an inclined, rotating drum which has an inlet for contaminated material at its upper end, an outlet at its upper end for vaporized contaminants, an inlet for air that is located between the upper end and the lower end, and an outlet for clean particulate material at its lower end. Contaminated particulate material is admitted to the upper end of the drum and conveyed under the influence of gravity and the rotation of the drum to its lower end. A combustion chamber at the lower end of the drum is provided with an air inlet, a fuel burner and an outlet for combustion products. Fuel is burned in the combustion chamber with excess air supplied so that the temperature of the products of combustion is high enough to volatilize the contaminants in the particulate material, but not so high as to incinerate them. A fire tube within the drum conveys the combustion products from the combustion chamber to the upper end of the drum. Heat is transferred from the products of combustion in the fire tube to the particulate material in the drum by radiation as the products of combustion are conveyed through the fire tube. Heated air introduced into the drum through the air inlet contacts the particulate material and also heats it by conduction and convection as it is conveyed under the influence of gravity and the rotation of the drum to the lower end. The heated air entrains the vaporized contaminants and conducts them to the outlet at the upper end of the drum. Clean particulate material is discharged from the drum at its lower end, and vaporized contaminants entrained in air are removed from the drum at its upper end. These vaporized contaminants are conveyed to a second stage treatment unit, where they are removed from the entraining air. |
