7837 SDMS DocID

N DEVELOPMENT OF AN INDIRECTLY HEATED

THERMAL DESORPTION SYSTEM FOR PCB CONTAMINATED SOIL

As Presented at the 1995 Superfund XVI Conference

Anthony J. Pisanelli Neal A. Maxymillian Maxymillian Technologies

IAXYMILLIAN Technologies

EXECUTIVE SUMMARY

ermal Desorption is effective in removing organics to established cleanup standards from contaminated soils, sludges and sediments. Maxymillian Technologies, Inc. (MT) has developed the Indirect System, which is an indirectly heated thermal desorptibn system for decontaminating soils contaminated with PCBs. Refer to the following photograph of the Indirect System during the early stages of assembly. This innovative system is mobile and trailer-mounted for easy transport to remediation sites to treat contaminated soils. The system is designed to effectively decontaminate PCB soil to below 2 ppm at a rate of 10 to 20 tons per hour. MT developed the Indirect System to meet a growing need for cost-effective, mobile, high-throughput technologies that effectively remediate soils contaminated with PCBs. To develop the Indirect System, Maxymillian Technologies entered into a Joint Development Agreement (JDA) with General Electric Corporation's Corporate Research and Development (GE CRD) group. In this relationship, GE CRD provides the basic research and science upon which the technology is based, and MT provides the process and implementation. The Indirect System is scheduled to undergo a Research and Demonstration Test at the South Glens Falls Drag Strip Site, a PCB contaminated site in Moreau, New York, in the fall of 1995.

BACKGROUND OF INDIRECT SYSTEM DEVELOPMENT

lychlorinated biphenyls (PCBs) were once widely used as industrial chemicals because their high stability made them superior transformer oils, hydraulic fluids and dielectrics. However, their stability also makes them persistent environmental contaminants which have been found to bioaccumulate. In order to decrease the hazard to human health and the environment, many technologies have been developed to remediate PCB contaminated sites. Remediation technologies include chemical processes, biological techniques and thermal treatment.

Maxymillian Technologies has been actively involved in the remediation of PCBs for 20 years. Since 1989, MT has designed, constructed and operated mobile thermal treatment systems for remediating contaminated soil. These systems have included both separation (thermal desorption) and destruction (incineration) technologies. During this period, MT has observed several significant trends in the market for thermal technologies which drive technological innovation. At the same time, GE's Corporate Research and Development (GE CRD) Group had been conducting research into the basic science of PCB removal from soils. A relationship between MT and GE CRD evolved, consummating in an agreement to design, construct a thermal desorption system which would meet the following criteria:

• A cost-effective solution to remediate PCB contaminated soils to less than 2 ppm. • A highly mobile technology with a compact footprint. • A fully indirect system, which will meet the emerging definition of desorption as proposed

by EPA's Draft Implementation Guide on Thermal Desorption Treatment (June 1994).

INDIRECTLY HEATED THERMAL DESORPTION SYSTEM # W A y AXYMILLIAN Technologies

Joint Development Agreement

Maxymillian Technologies has undertaken a Joint Development Agreement (JDA) with General Electric Corporate Research and Development (GE CRD) of Schenectady, New York, to develop the Indirect System. The system uses proprietary science developed at GE CRD's laboratory and enhanced by MT's field-experienced engineers. Throughout the system design, GE CRD will continue to be responsible for R&D and scientific issues, whereas MT will be responsible for system design, fabrication, assembly and field operations. MT has designed and constructed the Indirect System and has complete responsibility for commercializing the unit.

Maxymillian Technologies. Inc.

MT has extensive experience thermally treating contaminated soils. To date, MT has treated in excess of 325,000 tons of contaminated soils to regulatory cleanup standards, using several thermal treatment technology configurations. Contaminants treated include petroleum products, VOCs, SVOCs, PAHs and PCBs. During field remediation projects, MT has developed research into the limitations of thermal desorption, including temperature limitations, material properties (including moisture content), organic concentrations and Btu value. This research has entered into the design of the Indirect System.

General Electric Corporate Research & Development r

General Electric Company has been researching alternatives for treating PCB contaminated soils for many years. GE's Corporate Research & Development (GE CRD) group has been experimenting with methods to enhance desorption of PCBs from soils at a bench scale level. Based on initial successful results, GE CRD expanded their experimentation and conducted complete Design of Experiments (DOE) Modeling of their methods. The Modeling was conducted varying factors that influence PCB concentrations in soil including, among others:

• soil temperature • length of processing time • steam flow rate

Through the DOE Modeling, GE CRD developed a 5-term equation to predict residual PCB concentrations, and they successfully demonstrated thermal desorption of PCBs from soil with reproducible and robust results. The Model withstood verification and demonstrated an excellent fit of pre and post DOE data to it. Results from the laboratory scale tests served as partial basis for the engineering design parameters selected for the full scale Indirect System.

System Development

The design process for the thermal desorption system involved focused refinement of GE's basic science, coupled with process innovations derived from MT's field experience. The resulting system, the Indirect System, addresses all of the original design gcJals.. Significant attributes include: v

• Indirectly fired - The primary desorption chamber is heated by a completely indirect-fired source.

• Non-oxidative - The system uses non-destructive air pollution control devices. • Small footprint - The mobile system fits on only 3 trailers plus a water treatment trailer. • Cost effective - The system will remediate PCB contaminated soils to less than 2 ppm at

throughputs greater than 10 tons per hour.

Final design and construction of the system involved multiple engineering disciplines. MT purchased selected components from specialized vendors. Other components were designed, fabricated and constructed in-house using MT personnel. Refer to the following photographs of Indirect System fabrication and assembly. Process design hurdles were overcome through collaboration between GE research scientists and MT design engineers.

Overview of Indirect System

Indirect System is an indirect-fired rotary desorber, with collection of organics in the offgas by condensation and adsorption. A proprietary steam process enhances desorption efficiency. Condensed contaminants and water are processed through a mobile water treatment system where contaminants are removed, concentrated and collected.

The system indirectly heats soil in an enclosed rotary drum volatilizer where contaminants are desorbed from the soil. The non-oxidative atmosphere of the Indirect System minimizes the formation of secondary by-products that may be formed during oxidative combustion processes. Contaminants are both filtered and condensed from the carrier gas, and are treated and removed from the liquid stream. Vapors are carried through HEPA filters for particulate removal and then through a vapor phase carbon filtration system. The vapor stream is treated to remove contaminants and any secondary by-products that are present. Remediated soils are stockpiled and tested to verify decontamination. An Induced Draft (ID) fan maintains negative pressure throughout the system. The majority of soil contaminants are captured, separated and treated in the liquid phase. Treated gas emissions do not contain contaminants at levels that are of regulatory concern.

The Indirect System incorporates several proprietary and unique design features to maximize the system's performance. One specific design feature is a proprietary technique of using steam to strip residual contaminants from the soil. Steam stripping is a separate process that occurs after

ermal desorption in the rotary drum volatilizer. MT and GE CRD hold several patents pending the method and apparatus related to steam stripping.

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INDIRECT SYSTEM Fabrication and Assembly /M^ lAXYMFLLIAISl

Technologies

Waste Applicability

MT designed the Indirect System to handle a variety of soil types and consistencies at a high throughput for a mobile desorption system. The Indirect System is capable of treating soil contaminated with PCBs, SVOCs and VOCs at a variety of concentrations. Preliminary bench-scale studies have been successfully conducted at GE CRD on materials with PCB concentrations greater than 88,000 ppm. The system is not limited "by Bru value or contaminant concentrations of the soil. The unit is designed to treat material with a moisture content of up to 20%, however, it has been MT's experience that waste streams with higher moisture contents can been effectively desorbed at lower throughputs and/or with significant materials handling prior to thermal treatment.

Proprietary methods researched by GE CRD and implemented by MT allow the Indirect System to maintain a small, easily transportable size of 3 to 4 trailers while still achieving a high throughput. Similarly, MT has included unique engineering design features to allow the system to accept a wide variety of material types.

PROCESS AND EQUIPMENT DESCRIPTION

The Indirect System is a modular, completely transportable system. Individual components on three separate trailers are linked together and controlled by a System Operator. A fourth trailer ;ontains a mobile water treatment system. In keeping with one of the original design goals, the

Indirect System was designed to be easily transportable with a small footprint for optimal space utilization. The system's compact footprint measures approximately 70 feet by 80 feet.

The Indirect System is comprised of multiple components to treat contaminated soils and the associated vapor and liquid streams which result from the process. The system consists of:

1. material feed system 2. indirectly heated desorber to volatilize contaminants from feed materials 3. high temperature baghouse 4. steam stripping system 5. materials discharge system 6. vapor treatment system to filter contaminants from the vapor stream 7. liquid treatment system to collect and treat contaminants from the liquid stream

Refer to the following Process Flow Diagram and Trailer Layout. The Indirect System components are described in the following subsections.

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INDIRECT SYSTEM l A K Y M l L L I A N Jy^ Process Flow Diagram Technologies

u Process Water Cooling

Quench V a t e r Cooler

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+/- 70' Gen Set

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Boghouse Soil Disclnarge

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Desorber

INDIRECT SYSTEM Trailer Layout / M A X lAXYMILLIAN

Technologies

The Indirect System is designed for a throughput of 10 to 20 tons per hour. For utilities, the system requires 300 kW, 440 volt, 3 phase electricity and water ranging from 0 to 20 gallons per

inute. Unique design features, as mentioned earlier, allow the system to operate at optimum temperatures which yields energy efficient operations. These selected operating temperatures

allow for minimal fuel usage. The Indirect System requires only 415,000 cubic feet/hour of natural gas or heating value equivalent. MT has experience operating thermal desorbers on both fuel oil and natural gas. The type of fuel selected may be site specific. During the R&D Test scheduled for the fall of 1995, MT will use propane since natural gas te not readily available at the Drag Strip Site.

Material Feed System

Material is fed via front-end loader into a Screen/Feed Hopper. From the hopper soil travels along a feed conveyor to a feed auger, where it is fed into the Indirectly Heated Desorber. A soil seal is maintained in the feed pugmill to ensure that ambient air does not enter the Indirectly Heated Desorber. At the entrance to the feed pugmill, soil is sampled and analyzed to determine average PCB concentration.

Indirectly Heated Desorber

From the feed pugmill, contaminated material is fed into the Indirectly Heated Desorber. The Desorber consists of an inner rotating shell surrounded by an outer shell. The soil travels ffrough the rotating shell, while burners placed along the outside of the shell fire into the annular space between the inner and outer shells. These burners can be modified to operate on natural gas or propane as described above. The burners are specially designed to produce a flat flame to most effectively heat the inner shell. Heat is transferred through the inner shell thereby indirectly heating the soil to the required temperature. The mild steel outer shell is insulated and refractorized to minimize heat loss.

MT carefully controls temperatures throughout the length of the Indirectly Heated Desorber. The Indirect System is designed to operate over a wide range of temperatures from 250°F to 1000°F. Combustion gases do not come in contact with the soils, volatilized contaminants or desorbed gases. To prevent ambient air leakage, efficient seals are located at both ends of the inner shell, and the entire system is kept under negative draft by an ID fan.

Steam Stripping

Decontaminated material exits the inner shell of the Indirectly Heated Desorber and enters the exit breach hopper. This material, combined with clean particulate removed from the gas stream by the baghouse, now enters the steam stripping system. In the steam stripping system, a proprietary technique uses steam to enhance PCB removal from the soil. The steam from the "stem combines with the hot gas stream exiting the Indirectly Heated Desorber.

The clean material then exits the Indirectly Heated Desorber and enters the material discharge system. The material discharge system contains a pugmill which cools and remoisturizes the clean material using clean water recycled from the downstream stage of the system. The liquid treatment system is described later in this process description'. • ̂ radial stacking conveyor stockpiles the processed material in batches to await decontamination verification sampling. Discharged material is moved with a front-end loader dedicated to handling treated material to prevent cross contamination.

Gas Treatment System

The gas stream containing volatilized contaminants, vaporized water and entrained participate exits the Indirectly Heated Desorber breach and enters a high temperature baghouse. Using high efficiency bags, the baghouse filters gases to remove any particulate from the gas stream. Maintaining a high temperature in the baghouse ensures that the particulate removed from the waste stream is clean. The clean particulate is then combined in the exit breach hopper with clean material exiting the Indirectly Heated Desorber.

The particulate-free gas stream enters the quench, where it is cooled to approximately 180°F. During this cooling process organics are removed from the gas stream and are condensed in the quench sump. T,he cooled gas stream then enters a shell and tube condenser to further separate and capture contaminants from the gas stream. The condenser is designed to yield a gas stream exit temperature of approximately 80°F. In order to achieve this gas exit temperature, process water from the condenser is cooled through a chiller. Process water for the chiller circulates through an enclosed system, so it does not come in contact with the gas stream. Condensed liquids are separated from the gas stream and further treated by the liquid treatment system.

The gas stream exiting the condenser is drawn through the air pollution control system. Vapor treatment in the Indirect System begins with a carbon pre-heat unit. The unit is designed to reduce relative humidity thereby increasing carbon efficiency. The pre-heat unit increases the gas stream temperatures from 80°F to 110°F. At 110°F the gas stream is safely below the ignition temperature for any vapors in the stream. Vapors then enter a HEPA filter for fine particulate removal.

The majority of contaminants reside in the aqueous phase and are treated by the liquid treatment system. The vapor phase carbon filtration system removes trace quantities of contaminants. Two carbon vessels operate in series. The vessels can switch from lead to lag to allow the vessel with the greatest adsorptive capacity to be last in the series. At the completion of the vapor treatment phase the vapors are exhausted to the atmosphere. The pollution control mechanisms for vapor phase contaminants are maintained under negative draft by an Induced Draft (ID) Fan. The ID fan maintains negative pressure throughout the system up to and including the feed pugmill.

The air pollution control equipment and all interconnected piping are grounded against static electricity. The ID fan is constructed of non-sparking materials with an explosion proof drive system. These safety measures eliminate the potential for ignition of vapors in the gas stream.

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Liquid Treatment System

As previously stated, the gas stream enters the quench where it is cooled by water sprays. Organics are removed from the gas stream through the cooh'ngiprocess. The cooled gas stream enters a condenser to further remove contaminants. Condensate from the condenser and blowdown from the quench sump contains a mixture of contaminants and water and is stored in a frac tank prior to treatment. Contaminated condensate stored in the frac tank is treated through Maxymillian Technologies' Series IIIA water treatment system. MT has designed and constructed several mobile water treatment systems to remove organic and inorganic contaminants from liquid waste streams. The Series IIIA represents an upgrade of an existing design modified to work in conjunction with the Indirect System. Refer to the following photographs of the Series IIIA water treatment system.

The water and contaminant mixture is pumped from the frac tank to a head tank in the Series IIIA for pH adjustment, and then to an oil/water separator. The aqueous phase discharges to a flocculator, where the pH is adjusted a second time and flocculant is added. In the next component, the clarifier, flocculant is recycled and contaminant laden sludge settles, concentrates and is collected. This sludge is then drawn off to a decant chamber, where liquid decanted from the sludge returns to the flocculator. Water from the clarifier then passes through dual particulate filters. Flow can be directed to only one filter to allow the other filter to be replaced while the system is on-line. The final stage in the treatment process includes a liquid phase granular activated carbon system and a polymer polish, as necessary. The clean water effluent is recycled to the discharge pugmill to cool and remoisrurize discharge material.

PCBs and other organic contaminants are removed as they flow through the components of the system. Samples of influent condensate/wastewater and effluent water are taken to verify treatment and removal efficiencies. MT intends to use all of the clean water effluent to remoisturize treated soil. However if any excess water exists, it will be stored in a holding tank until results from PCB analysis demonstrate that it meets appropriate discharge requirements.

Waste Streams

MT designed the Indirect System maximizing the use of non-contact and closed loop systems for heating and cooling process materials. These closed loop systems isolate the contaminated material, thereby minimizing waste streams requiring treatment or disposal. The Indirect System produces six separate waste streams which MT will collect, store and recycle or dispose. Where appropriate, these wastes are analyzed for PCBs or other applicable contaminants to demonstrate that PCB concentrations are less than original concentrations in the feed stock. Wastes include:

1. filter cake from the filter press 2. spent HEPA filters 3. vapor and liquid phase carbon that has exhibited breakthrough 4. concentrated liquid condensate, if present in a separate distinct phase 5. personal protective clothing 6. equipment decontamination cleaning solution

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SERIES IIIA Water Treatment System ^ lAXYMILLIAN

Technologies

PLANNED STUDY ACTIVITIES

Following fabrication, assembly and shakedown, the Indirect System was mobilized to the South Glens Falls Drag Strip Site, a PCS contaminated site in Moreau, New York. This site will be the location of field research and R&D testing, followed by a TSCA demonstration test. Refer to the following photographs of the Indirect System at the Drag Strip Site.

MT will begin by conducting a Research and Demonstration (R&D) Test using contaminated soil from the site. MT has submitted an application to EPA Headquarters for a R&D permit to conduct this testing. During R&D testing, MT expects to treat several hundred tons of PCB contaminated soil at a throughput of 10 to 20 tons per hour. MT plans on performing several field runs with varying PCB mass feed rates. Additionally during the R&D Test, MT may vary operating temperatures, residence times, volume of steam added, etc. It is Maxymillian Technologies' intent to demonstrate that soil treated during the R&D Test has PCB concentrations below EPA's 2 ppm criterion.

Upon satisfactory results from the R&D Test, MT will proceed with a demonstration test of the system, under the oversight of the EPA. The demonstration test will measure and confirm successful parameters established during R&D activities.

SUMMARY

Maxymillian Technologies is developing an innovative thermal desorption system for remediating PCB contaminated soils. The system, developed in partnership with General Electric Corporate Research and Development, provides a highly mobile system to cost-effectively remove PCBs from a variety of soil matrices. The benefits of MT's Indirect System include:

• Addressing EPA's guidance on alternatives to incineration • Thermal desorption in a non-oxidative environment • Off-gas filtering and condensation to minimize air emissions • On-site decontamination of PCB, SVOC and VOC contaminated soil • Easily transportable system comprised of four trailers with a small footprint

This system is scheduled to perform a Research and Demonstration (R&D) Test in the fall of 1995. Following a successful R&D Test and confirmation by the EPA, the Indirect System will be commercially available to remediate contaminated sites throughout the country.

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INDIRECT SYSTEM South Glens Falls Drag Strip Site /M^ lAXYMILLIAN

Technologies Moreau, NY