Conventional methods of measuring airborne hazardous air pollutant (HAP) metals in stack gas effluent at Department of Defense (DoD) facilities typically involve manual sampling techniques that are not sufficiently responsive to ensure continuous pollution control. This project validated and demonstrated sustained performance of a prototype Multimetal Continuous Emissions Monitor System (MMCEMS) for HAPs. The MMCEMS employs a shrouded probe for extracting a stream of stack gas, a patented sampling interface for plasma sample introduction, and an argon inductively-coupled plasma (ICP) spectrometer as an elemental analyzer. The MMCEMS is capable of rapid and simultaneous detection, at low part per billion levels, of all 14 of the HAP metals targeted by the U.S. Environmental Protection Agency (EPA), plus virtually any metal in the contained periodic table.

Demonstration Results

The MMCEMS was validated in two separate demonstrations. The first took place on the stack emissions from a munitions deactivation incinerator. Empty 30-mm aluminum cartridge casings containing percussion primers were introduced into the furnace at an average rate of 2000 per hour. Metal emissions from the detonation of munitions in the rotary kiln and from the artificial introduction of other metal aerosols were monitored alongside simultaneous sample collection for comparison through EPA Reference Method 29. Measurement of 8 of the 10 target metal analytes (Ba, Cd, Co, Cr, Mn, Ni, Pb, Sb, Sr, and Y) satisfied and favorably exceeded the 20 percent relative accuracy requirement stipulated in the EPA's PS-10, Draft Performance Specifications for MMCEMS. The second demonstration took place on a Plasma Arc Hazardous Waste Treatment System (PAHWTS) being developed under a separate ESTCP project. The incinerator was fed with surrogate wastes such as contaminated soil, paint mixtures, oily rags and solvents to investigate the effects of stack-gas moisture on MMCEMS operation. Under operating conditions of up to 41 percent moisture in the stack emissions, reasonable agreement (+/- 20 percent) between the MMCEMS and Reference Method 29 were obtained for four target metals (Al, Fe, Pb, and Ti).

Implementation Issues

Operation of the MMCEMS system is entirely automated, requiring only minimum human interaction. Compliance of hazardous waste combustors under the National Emissions Standards for Hazardous Air Pollutants and Compliance Assurance Monitoring rules is enhanced. The MMCEMS also greatly facilitates Resource Conservation and Recovery Act (RCRA) permitting and public acceptance of new thermal treatment processes such as the plasma arc technology.

Relaxation of the margin of error for operating restrictions on waste characterization and tighter waste feed rates with more refined requirements for permit modifications for new feed items may be possible with MMCEMS. While originally intended for use on explosive ordnance deactivation furnaces, the system also has great potential for industrial application. The MMCEMS is now commercially available from Thermo Elemental (Franklin, MA) under the TraceAIRâ„¢ trademark. (Project Completed - 2001)