Plasma Hearth Process at the Science and Technology Applications Research (STAR) Center, Idaho Falls, Idaho

Site Name:

STAR Center

Location:

Idaho Falals, ID

Period of
Operation:

1993 through 1997

Cleanup
Type:

Bench scale and pilot scale

Technology:
Plasma Hearth Process (PHP)
- PHP is a high temperature thermal process that heats waste to a molten form, which is then cooled into a glass/crystalline waste form; equipped with an air pollution control system to remove particulates and volatiles in the offgas
- PHP melt temperature - 1,650-2,200C;
- Three systems tested - nonradioactive bench-scale system (NBS), radioactive bench-scale system (RBS), and nonradioactive pilot-scale system (NPS)
- NBS- batch system with a refractory lined fixed hearth vessel equipped with a 150 KW Retech RP75T transferred arc plasma torch; feed rate of 15 lbs/hr
- RBS - batch system with a plasma chamber equipped with a 150 KW Retech RP75T transferred arc plasma torch; feed rate of 30 lbs/hr; holds eight, 1-gallon waste containers and includes offgas treatment system
- NPS - 6.5 ft by 6.5 ft cylindrical hearth equipped with a 1.2 megawatt Retech RP600T plasma torch; feed rate of 1,000 - 1,500 lbs/hr; holds three, 55-gallon waste drums and includes offgas treatment

Cleanup Authority:
RCRA and NRC

Principal Investigator:
Ray Geimer
SAIC
545 Shoup Ave.
Idaho Falls, ID 83402
Telephone: 208-528-2144
Fax: 208-528-2194
E-mail: Ray Geimer@cpqm.saic.com

Carla Dwight
Argonne National Laboratory - West
P.O. Box 2528
Idaho Falls, ID
Telephone: 208-533-7651
E-mail: carla.dwight@anl.gov
MWFA Product Line Manager:
Whitney St. Michael
Mixed Waste Focus Area
Lockheed Martin Idaho Technologies Company
Idaho National Engineering and Environmental Laboratory
2525 N. Freemont
Idaho Falls, ID 83415
Telephone: 208-526-3206
Fax: 208-526-1061
E-mail: whitney@inel.gov

Contaminants:
Metals and radionuclides
- Nonradioactive cerium used in tests to simulate plutonium
- Metals include arsenic, barium, cadmium, chromium, lead, mercury

Waste Source:
Wastes from DOE facility operations and air pollution control systems

Type/Quantity of Media Treated:
- NBS - Fly ash, soil, sludges, debris (concrete, asphalt, sheet rock, steel), sodium nitrate
- RBS - inorganic and organic sludges, debris (wood, graphite, and fire brick)
- NPS - debris

Purpose/Significance of Application:
Demonstration of a plasma hearth furnace to treat metals and radionuclides in a variety of waste types

Regulatory Requirements/Cleanup Goals:
- RCRA Land Disposal Restriction (LDR) standards
- Federal and state air emissions standards

Results:
- Slag samples passed the RCRA limits for metals
- Cerium oxide (plutonium oxide surrogate) was found to primarily partition to the vitreous slag; slightly higher retention rates were noted for sludges as compared to combustible debris
- All high vapor pressure metals (mercury, cadmium, lead), except barium, partitioned to the offgas system, where they were removed prior to release from the stack
- Stack emissions were generally below the air emission limits, including total particulates and metals, except for mercury
- The process was shown to treat a wide variety of waste types

Cost Factors:
Projected costs for full-scale system include:
- Capitals - $50 to $86.2 million for facility construction and outfitting
- Startup operating cost - $12 to $18 million
- O&M for a 5-yr period - $48 to $62 million
- Assuming 17,000 cubic meters of waste are treated, the projected unit cost for PHP is $7,400 to $10,800 per cubic meter.

Description:
DOE sponsored a series of bench- and pilot-scale tests of the Plasma Hearth Process (PHP) at the STAR Center in
Idaho Falls, Idaho, conducted between 1993 and 1997. PHP is a high temperature thermal process that heats waste to a molten form, which is then cooled into a glass/crystalline waste form. Three PHP systems were tested on a wide range of wastes to evaluate the process for treating different wastes and to determine operating conditions. The three systems were a nonradioactive bench-scale system (NBS), radioactive bench-scale system (RBS), and nonradioactive pilot-scale system (NPS). The types of wastes tested included fly ash, organic and inorganic sludges, and a variety of debris; for the RBS system, nonradioactive cerium was used as a surrogate for plutonium wastes.

The results showed that PHP was capable of treating a wide variety of radioactive and nonradioactive wastes, meeting the RCRA LDR standards for metals and , with the exception of mercury, operating within the air emission requirements for the systems. Differences were noted between the behavior of sludges and debris in the system, such as higher retention rates for cerium oxide for sludges as compared to debris. Additional data are needed to better quantify the treatment of debris using PHP. Other issues to be considered for full-scale deployment include additional data on the behavior of radionuclides compared to the cerium surrogate, and a more detailed evaluation of PHP for high organic waste feeds.