Effectiveness of direct fired rotary dryers in cleanup of petroleum contaminated soils

Direct fired rotary dryer technology is being used in remediation of soils contaminated with number-sign 2 fuel oil and Gasoline. Soils were processed at the rates exceeding of 20 TPH in a Mobile Unit. The Mobile unit is mounted on trailers and the entire load is on 4 trailers. The soils are heated between 450 to 600F in the dryer. While the soils are being heated, the gasoline or the number-sign 2 Fuel oil is evaporated. These vapors are carried away by the exhaust gases to a fabric filter, where the dust is removed from the gas stream, the relatively dust free gases are passed onto a fume incinerator. The hydrocarbon vapors are then incinerated in the thermal oxidizer and clean gases are exhausted to atmosphere. Both contaminated soils and cleaned soils were sampled regularly. Soils contaminated with Gasoline contained 6,600 PPM hydrocarbons before cleanup, when cleaned, benzene was not detectable, Total Aromatic Hydrocarbon were less than 100 ppb and oil and grease were not detectable. Similarly, soils containing 7,600 PPM number-sign 2 fuel oil initially were cleaned such that PAH's were not-detectable. Results of a bench scale rotary dryer are also described in which soils containing 10,000 ppm Total hydrocarbons were cleaned at 850F to a final concentration of 120 ppm TPH. The paper discusses results from other experiments and cleanup operations. A comparison of the counterflow and parallel flow rotary dryer technology is made