Working on the well-established principle that if you can’t measure something you can’t control it, regulatory authorities such as the U.S. Environmental Protection Agency (EPA) have for many years insisted on the continuous monitoring of emissions from major sources such as power plants in the utilities and chemical industries.

A continuous emissions monitoring system (CEMS) is “the total equipment necessary for the determination of a gas or particulate matter concentration or emission rate using pollutant analyzer measurements and a conversion equation, graph or computer program to produce results in units of the applicable emission limitation or standard,” according to the EPA.

Now that might be a fairly typical example of all-embracing “officialese,” but the EPA regulations — which had their genesis with the Clean Air Act of 1963 and its subsequent amendments in 1977 and 1990 — go on to specify in much more detail what is expected of the operators of plants emitting gases such as nitrogen oxides (NO_x), sulphur dioxide (SO₂), carbon monoxide and dioxide (CO, CO₂), as well as oxygen. Performance specifications for CEMS are laid down in EPA regulations 40 CFR Part 60 (new source performance standards) and 40 CFR Part 75 (covering utility boilers and turbines under the Acid Rain Program), and are constantly under review to reflect changing technologies and attitudes to possible pollutants.

In the power sector, for example, the Electric Power Research Institute (EPRI), Palo Alto, Calif., is running a CEMS program to help participating member companies keep abreast of the “new” pollutants that power plants will need to begin monitoring in the next few years — the most likely ones being mercury, particulate matter mass concentrations, SO₃, NH₃, HCl and HF. “Some of these measurements can provide more accurate, defensible Toxics Release Inventory (TRI) reporting and others can serve for process control. EPRI established the program to promote the commercial availability of robust, accurate, least-cost CEMS and gas species-based process monitors,” says Chuck Dene, the program’s technical lead.

Focus on mercury

Most CEMS manufacturers are currently concentrating on the upcoming mercury monitoring rules that take effect on January 1, 2009. By then all new and existing coal-fired power plants must have some form of continuous mercury-monitoring capability in operation. This follows the EPA’s promulgation of the Clean Air Mercury Rule (CAMR) in May 2005, which creates a market-based, cap-and-trade program for mercury emissions.

“Mercury is the hot topic right now,” agrees Doug Kriebel, manager of systems and proposals with the Rosemount Analytical Division of Emerson Process Management, Solon, Ohio. “It’s mainly concerned with coal-fired power stations and most of these already have CEMS in place, so for them it’s just an added measurement to their existing system, rather than putting in a whole new system just to measure mercury. So far, though, the EPA has not laid down what it thinks is the best way.”

Such uncertainty is certainly fuelling the market for mercury CEMS’s at the moment. “There are very, very few [mercury systems] installed right now,” notes Frank Duckett, product manager for continuous gas analyzers at Thermo Fisher Scientific, Waltham, Mass., which is one of the largest suppliers of CEMS’s. “So between now and January 2009 there are 800 or so systems that need to be installed in the U.S. We have a very large program here, which we started two to three years ago, to develop an analyzer, calibrator, probes and sampling system specifically for mercury monitoring, and we’ve started to install these over the last six months or so.” Thermo’s Mercury Freedom system has so far met or exceeded all of the EPA’s performance specifications.

Field evaluations of mercury monitors are being carried out on the EPA’s behalf by EPRI, which also has developed its own mercury sorbent trap called QuickSEM. An alternative to continuous emissions monitoring, the trap collects mercury for later laboratory measurement. If the EPA were to allow sorbent traps, EPRI says the savings could be as much as $80,000 per unit compared with CEMS’s.
What is claimed to be the first mercury CEMS destined for continuous operation (as opposed to evaluation tests) in a U.S. coal-fired power plant has recently been ordered by PSEG Fossil for its Hudson Generating Station in Jersey City, N.J. This DM-6 mercury CEMS and data acquisition system is being supplied by Horiba Instruments, Irvine, Calif. It reduces all mercury compounds to elemental mercury at the stack prior to transporting the sample to a continuous cold vapor atomic absorption analyzer.

Other companies offering EPA-field-tested systems include Tekran Instruments, Knoxville, Tenn., with its Series 3300 based on the company’s patented cold vapor atomic fluorescence technology, and Cemtek Systems, Linden, N.J., which offers complete mercury solutions using Tekran and Thermo Instrument’s analyzers for which it is a preferred integrator.

The MIP Division of Ducon Technologies, Farmingdale, N.Y., is one of many other companies looking to that 2009 deadline. Its SM4 mercury monitor is said to be the first instrument to use a thermocatalytic principle to avoid wet chemical sample treatment. Underscoring that interest in mercury monitoring is by no means a U.S. phenomenon. For instance, process analyzer and instrumentation company Sick Maihak, Reute, Germany, and Houston, Texas, offers its TÜV- and EPA-approved (for measurements of 0-45μg/m³) MERCEM stack gas analyzer.

While perhaps not immediately relevant to the many chemical plants that burn oil or gas, the CAMR does indicate how regulation can influence product development. “It wouldn’t surprise me to see other nations bringing EPA-like regulations on board by around 2012 to 2014. In reality though, in the U.S., once you hit January 2, 2009, this market will drop dramatically,” says Alan Matta, manager for Thermo’s industrial hygiene and safety products.