Devised to meet new standards set by the US Environmental Protection Agency (EPA PS-12A and/or Part 75 provisions), the Mercury Freedom System (MFS) uses atomic fluorescence analysis to provide continuous monitoring of gases emitted from power plant stacks to detect the presence of mercury, down to levels of parts per trillion.
The system also uses dry mercury conversion technology to minimise maintenance of sensors/instrumentation mounted high on the stack.
“Our Mercury Freedom System, more than two years in development, is an example of our commitment to the power generation industry and stack gas monitoring, and is an extension of our ongoing efforts to help power suppliers comply with regulations mandated under the 1990 Clean Air Act Amendments,” noted Greg Herrema, president of Thermo’s Environmental Instruments Division.
“Recognizing the potential for a mercury monitoring requirement some time ago, we applied our analytical instrument and stack gas monitoring applications expertise to develop a mercury CEMS that we believe is the most cost-effective, accurate, and reliable solution for our customers in the power generation industry.”
In March 2005, the EPA issued the Clean Air Mercury Rule to permanently cap and reduce mercury emissions from coal-fired power plants, making the US the first country to address this source of mercury pollution.
The new standards are expected to lower utility emissions of mercury by nearly 70% to 15 tons per annum (down from 48tpa) once fully implemented in 2018.
The MFS CEMS comprises:
• A mercury analyser able to detect limits as low as 1ng/m3
• A mercury calibrator, which uses Peltier cooler/vapour pressure control and mass flow controllers with a mercury concentration output range between 0.1-300µg/m3, allowing operators to directly calibrate the analyser at post-dilution concentrations and dynamically spike into the sampling probe.
• Zero air supply – the zero air supply provides dry, mercury-free dilution air to the probe, zero gas for analyser calibrations, and air to the mercury calibrator.
• A stack probe and an inertial filter designed to minimise false sampling due to fly ash. All components exposed to sample gas are glass coated, preventing reactions with mercury. The probe incorporates a dilution assembly and calibration gas that can be introduced either upstream or downstream of the inertial filter.
• A high-temperature converter module that prepares vapour phase mercury to elemental phase for analysis. Thermo’s proprietary, high efficiency conversion technology has been demonstrated to meet the EPA criteria of less than 5% of span value deviation from the certified gas value.
• A probe control box, located in the CEM shelter. An umbilical connects the probe to the probe control box and mercury converter. The control unit allows dynamic mercury spiking and auto dilution confirmation; automates probe calibration and dynamic spiking; measures fast loop flow; and automates blowback.
The MFS will be available on Thermo’s recently released advanced iSeries platform.
MFS system
Detects airborne mercury
Levels in the stack
