Description:

Pyrolysis transforms hazardous organic materials into gaseous components, small quantities of liquid, and a solid residue (coke) containing fixed carbon and ash. Pyrolysis of organic materials produces combustible gases, including carbon monoxide, hydrogen and methane, and other hydrocarbons. If the off-gases are cooled, liquids condense producing an oil/tar residue and contaminated water. Pyrolysis typically occurs under pressure and at operating temperatures above 430 °C (800 °F). The pyrolysis gases require further treatment. The off-gases may be treated in a secondary combustion chamber, flared, and partially condensed. Particulate removal equipment such as fabric filters or wet scrubbers are also required.

Conventional thermal treatment methods, such as rotary kiln, rotary hearth furnace, or fluidized bed furnace, are used for waste pyrolysis. Kilns or furnaces used for pyrolysis would be physically similar to the equipment described in Section 4.23 "Incineration", but would operate at lower temperature and with less air supply than would be required for combustion. Molten salt process may also be used for waste pyrolysis. These processes are described in the following sections:

Rotary Kiln

The rotary kiln is a refractory-lined, slightly-inclined, rotating cylinder that serves as a heating chamber.

Fluidized Bed Furnace

The circulating fluidized bed uses high-velocity air to circulate and suspend the waste particles in a heating loop and operates at temperatures up to 430 °C (800 °F).

Molten Salt Destruction

Molten-salt destruction is another type of pyrolysis. In molten-salt destruction, a molten salt incinerator uses a molten, turbulent bed of salt, such as sodium carbonate, as a heat transfer and reaction/scrubbing meduim to destroy hazardous materials. Shredded solid waste is injected with air under the surface of the molten salt. Hot gases composed primarily of carbon dioxide, stream, and unreacted air components rise through the molten salt bath, pass throught a secondary reaction zone, and through an off gas cleanup system before discharging to the atmosphere. Other pyrolysis by-products react with the alkaline molten salt to form inorganic products that are retained in the melt. Spent molten salt containing ash is tapped from the reactor, cooled and placed in a landfill.

Pyrolysis is an emerging technology. Although the basic concepts of the process have been validated, the performance data for an emerging technology have not been evaluated according to methods approved by EPA and adhering to EPA quality assurance/quality control standards. Performance data are currently available only for vendors. Also, existing data are limited in scope and quantity/quality and are frequently of a proprietary nature.

Synonyms:

Applicability:

Pyrolysis systems may be applicable to a number or organic materials that "crack" or undergo a chemical decomposition in the presence of heat. Pyrolysis has shown promise in treating organic contaminants in soils and oily sludges. Chemical contaminants for which treatment data exist include PCBs, dioxins, PAHs, and many other organics. Pyrolysis is not effective in either destroying or physically separating inorganics from the contaminated medium. Volatile metals may be removed as a result of the higher temperatures associated with the process but are similarly not destroyed.

Limitations:

• There are specific feed size and materials handling requirements that impact applicability or cost at specific sites.
• The technology requires drying of the soil to achieve a low soil moisture content (< 1%).
• Highly abrasive feed can potentially damage the processor unit.
• High moisture content increases treatment costs.
• Treated media containing heavy metals may require stabilization.

Data Needs:

Performance Data:

Cost:

References:

Innovative Remediation Technologies:  Field Scale Demonstration Project in North America, 2nd Edition

Abstracts of Remediation Case Studies, Volume 4,  June, 2000, EPA 542-R-00-006

Guide to Documenting and Managing Cost and Performance Information for Remediation Projects - Revised Version, October, 1998, EPA 542-B-98-007

Energy and Environment Research Center, 1994. Thermal Recycling of Plastics. Energy and Environment Research Center, University of North Dakota, Grand Forks, ND.

EPA, 1992. AOSTRA-SoilTech Anaerobic Thermal Processor: Wide Beach Development Site, Demonstration Bulletin, EPA, ORD, Washington, DC, EPA/540/MR-92/008.

EPA, 1992. Pyrolysis Treatment, Engineering Bulletin, EPA, OERR, Washington, DC, EPA/540/S-92/010.

EPA, 1992. SoilTech Anaerobic Thermal Processor: Outboard Marine Corporation Site, Demonstration Bulletin, EPA, ORD, Washington, DC, EPA/540/MR-92/078.

Shah, J.K., T.J. Schultz, and V.R. Daiga, 1989. "Pyrolysis Processes." Section 8.7 in Standard Handbook of Hazardous Waste Treatment and Disposal, ed. H.M. Freeman. McGraw-Hill Book Company, New York, NY.

• DOE Demo: Energy Technology Engineering Center, ORNL, LANL
• HT-V TDI Thermal Dynamics
• Deutsche Babcock Anlagen AG
• Wide Beach Superfund Site NY SoilTech, Inc.
• 

General FRTR Agency Contacts

Government Web Sites

Non Government Web Sites

A list of vendors offering En Situ Thermal Soil Treatment is available from  EPA REACH IT which combines information from three established EPA databases, the Vendor Information System for Innovative Treatment Technologies (VISITT), the Vendor Field Analytical and Characterization Technologies System (Vendor FACTS), and the Innovative Treatment Technologies (ITT), to give users access to comprehensive information about treatment and characterization technologies and their applications.

Government Disclaimer

To be added