ADT Environmental Thermal Treatment Services

Evaporative Desorption (Soil Oven) is a patented thermal soil treatment technology. Brady Environmental, Inc. developed the technology to reduce remediation costs. We have found that excavation is the most certain remedy for contaminated sites. Removal of contaminated soils not only improves groundwater quality, it improves the value of the property.

The system uses a batch process that allows operators to complete soil treatment at the same time they are conducting other remedial task, (such as demolition, excavation or back filling). The process does not require screening of debris, further reducing costs. Using this patented technology, labor costs are cut by more than 50 percent.

Soils treated with the Soil Oven technology do not have the characteristic brown burned color that is typical of the older thermal desorption technologies. Soil handling and dust conditions are greatly improved with the Soil Oven technology.

The system uses dry hot air to evaporate contaminants rather than boiling them off. Using the evaporative process, especially during the early stages of treatment, reduces energy costs. Air is passed through an activated alumina bed to remove all moisture from the air stream, which increases the carrying capacity of the air. The air is then routed through a ceramic element to heat the air to approximately 1,100 degrees F.

The unit shown above is for smaller projects and is very mobile. Units can be sized to fit the needs of any job from a few thousand tons to 100’s of thousands of tons.

The air is directed to an insulated oven where specially constructed soil roll off bins are situated. Vapor extraction lines located at the bottom of the soil bins withdraw air from the oven. All of the air in the oven passes through the soils in the bins. The extracted vapors are passed over precious metal catalysts to destroy the contaminants prior to discharge to the atmosphere. Extracted vapors can also be chilled to condense contaminants. Carbon filtration is generally used to follow the condensation process.

Since no open flame is used as a heat source, no combustion by-products (such as NOX) is formed. The oven temperature is maintained below the NOX-formation temperature of 1,300°F. The technology produces far less air emissions than the standard thermal desorption process.

Since the treated soils are not rotated during treatment, the soil structure is maintained (no fine powder or discoloration) which minimizes dust emissions during and after treatment. The unit is specifically designed to remove petroleum hydrocarbons from soil, rather than a retro-fitted asphalt plant, which is designed to add hydrocarbons to aggregate.

This technology has minimal moving parts that can break down. The modular design of the air flow system allow for quick replacement, if required, which minimizes down time.

This picture shows both treated and untreated soils at the Togiak Fisheries fixed base soil treatment facility. The stockpile to the left is treated soils that meet the State of Alaska cleanup standards. The pile to the right is contaminated soils before treatment. Both piles are placed on engineered soil storage pads. As can be seen, the untreated soils (right) contained free product which discolors the soil. The natural color of the soil is restored after treatment.

Treatment Method Summary

The Evaporative Desorption Treatment Unit utilizes a patented method and apparatus for the removal of petroleum hydrocarbons from excavated soil. The process utilizes a non-combustive heat source in which desiccated air is heated to temperatures just below the oxides of nitrogen formation temperature. The heated, desiccated air is introduced into a vessel containing a specially designed open top container, which is filled with petroleum-contaminated soil. The soil within the container is heated by two mechanisms.

First, the exterior walls of the soil container are heated by the flow of heated air into the treatment vessel and the soil is in turn heated by conduction from the heated container walls.

Secondly, heated desiccated air is also drawn into the soil by action of a vapor extraction line located within the bottom portion of the soil treatment container, which results in convective heating of the soil. The resulting increase in soil temperature and the flow of desiccated hot air through the soil allows for evaporation and subsequent removal of soil moisture and petroleum hydrocarbons through the vapor extraction line.
The vapor phase petroleum hydrocarbons can be recovered or destroyed by a variety of conventional methods, the selection of which is dependent upon project specifications.

The photo above depicts the fixed base Evaporative Desorption Units located in Togiak Bay, Alaska. The units in the photos are in operation; note the lack of emissions. These units can handle 300 yards each and process time is 24 hours. Three similar units can process 1000 tons a day.