Description:  Contaminated soils initially enter the counterflow rotary drier, beginning the journey from the feed end of the unit to the discharge point of the drier.  Flow rates for contaminated soil are consistently rated at 25 to 30 tons per hour.  Contaminant vaporization is caused by heat in the drier chamber.  During the retention time in the rotary drier, the soil is exposed to a heated air stream that elevates the soil temperature to the required level of 600-900°F to vaporize high-boiling-point-type contaminants.  At these temperatures, the contaminants in the soil become volatilized constituents, entrained in the system's heated 12,000 CFM air stream.

Primary Treatment Unit:  The drier system is designed for use with a 12,000 CFM air system and Model 6422 Drier Drum.  The 64"x22' Counterflow Aggregate Drier is constructed of high-strength, abrasion-resistant steel.  Drum tires and trunnions are castings machined to ensure correct operation of the drier burner.  The drier features a saddle chain drive system with a 25-hp drive motor.  Specially designed heat-resistant packet flights begin lifting and veiling the material for drying.  The vaporization of the contaminants is caused by the process of heat.  The counterflow drier system utilizes a 30-million BTU Hauck 150 Star Jet burner.  A 30-hp blower furnishes controlled air directly to the burner.  During the retention time in the rotary drier, the soil is exposed to a heated air stream elevating its temperature to the required level of 600-900°F.  To control exhaust gas temperatures, a patented veil modification plate (VMP) is included.  The VMP provides the ability to adjust the material curtain during the drying operation, affecting gas stream temperature and soil temperature.  The processed soils are discharged from the rotary drier into the discharge and mixing units, which prepare them for stockpiling and reuse.

Particulate Scrubbing:  The volatized contaminants are transported to the filter house for removal of airborne particulate.  The primary section is mounted ahead of the bag modules on the same frame.  Coarse particles are removed to relieve particle loading and abrasion in the secondary baghouse chamber.  The secondary chamber utilizes 224 Polyamide P-84 bags with a maximum temperature rating of 500°F.  The compact portable primary fabric filter dust collectors provide more cloth area per unit size through the use of 10-foot bags.  Exhaust gases pass through bags, depositing particles on the outside.  Exiting gases flow into the top half of the plenum, through the central passage to the exhaust fan.  All welded, reinforced housing is coated inside with epoxy sealer to protect against corrosion.  Bag access panels are tightly sealed to maintain efficiency.  A 25-hp Sullair Compressor furnishes the air supply for the air cannons, baghouse pulse system, and air seals on the plant.  No section of the filter house is shut down as bags are continuously cleaned by a reverse pulse-jet.  This prevents formation of excessive dust cakes.  The pulse-jet is a sharp blast of compressed air jetted through a venturi on the top of the bag.  The sudden influx of air ripples the bag, dislodging the dust, which falls to the collecting hopper.  A drag type conveyor moves collected dust across the floor of the filter house to the dust screw augers, for return to the rotary drier and discharge system.  Two magnahelic gauges, one mounted on the filter house and one in the control house, provide a check on proper operating conditions.  Each gauge shows if pressure differential is rising.  This allows the operator a way to adjust the cleaning cycle to match conditions.  A dual-setpoint digital over-temperature protection system operates the primary section baffle and automatically shuts off the burner if temperature in the bag chambers rises too high.  Drier exhaust, baghouse inlet, and baghouse exhaust temperatures are continuously monitored, ensuring proper operating temperatures and safety requirements.  The cleansed air stream is then ducted through the internal workings of the house and into the thermal oxidizer for contaminant destruction.

Contaminant Destruction:  As discussed, once the air stream has passed through the filter house and has been scrubbed of particulate, the air stream with the volatized contaminants, still entrained, is ducted into the thermal oxidizer.  This is the component within the system responsible for destruction of the vaporized contaminants.  As with the vaporization process, heat is the catalyst that provides contaminant destruction.  The key is to expose the volatile contaminants to an environment containing sufficient levels of heat and retention time so that ignition and combustion of contaminants is accomplished -- therefore, the name thermal destruction.    The oxidizer utilizes a Hauck Beta BBL/G112 furnishing 30 million BTU with a 30-hp blower.  Burners operate on natural gas with the capacity of operating on liquid propane.  For the destruction of compounds, 1800-1950ºF temperatures are maintained with a 1.5-2 second retention time of the air stream within the afterburner.  The resulting air stream was exhausted into the atmosphere with particulate and total stack emissions of 3.35 lbs./hour and 99.9976% destruction and removal efficiency of contaminants, respectively.

Following are the approximate weights and dimensions of the equipment:

Primary Unit - including drier, crushing and screening equipment:
Weight:  80,000 lbs., Dimensions:  Length - 71', Width - 10', Height - 13'6"

Secondary Unit - including genset, baghouse and afterburner
Weight:  85,000 lbs., Dimensions:  Length - 60', Width - 12', Height - 14'6"

3 in 1 Feed Unit - including control house and feed system
Weight:  50,000 lbs., Dimensions:  Length - 71', Width - 10', Height - 14'6"

Consumption of energy - electricity, gas, liquid propane, water, etc.

Water Usage:  approximately 40 gallons per US ton processed.
Water service available and accessible; capabilities of 100 gpm/50 psi should be installed to area dedicated for thermal treatment.

Natural Gas Usage:  approximately 1.5 mmbtu per US ton processed.
If natural gas is available near the subject site, it shall be utilized for treatment operations.  The natural service will be tied into with help of the local utilities and piping will be installed underground to the treatment plant.  A four-inch main is required for the treatment plant.  The line must have the capacity to supply 60 million BTUs and 15 pounds of pressure to the plant burner gas regulators.  If natural gas is unavailable at the site, LP shall be utilized for fuel purposes (approximate usage - 18 gallons of LP per US ton processed).

Electrical:  460v/600 amp, 3-phase electrical service.