|A wide variety of monitoring technologies exist that help EGUs comply with the Mercury Air and Toxics Standard (MATS). Facilities working toward MATS compliance will need several different monitoring instruments in operation by April 2015. Typically, it is necessary to install one monitoring instrument for each regulated element or compound emitted. Photo courtesy: Thermo Fisher Scientific|
By Michael Corvese, Thermo Fisher Scientific
The U.S. Environmental Protection Agency’s (EPA) Mercury and Air Toxic Standards (MATS) rule has been in place for new coal-fired electric generating units (EGUs) since 2012, but the regulation has yet to take effect for existing units. Existing EGUs and their management teams were allotted additional time (including an option to apply for an extension with their state agency if necessary) to define their strategy and decide whether retrofitting or retiring existing facilities would make the most business sense for them.
We are only five months from the April 2015 deadline for MATS compliance – and while many EGUs already have comprehensive plans in place, a surprising amount do not.
Meeting the compliance deadline takes significant planning and preparation; the closer EGUs get to April 2015, the more difficult (and costly) it becomes to have all the necessary pieces in order on time. This is especially true if the decision is made to retrofit an existing facility, as the EGU must then begin managing outside vendors and ensuring that all equipment is in place to meet the new requirements. April 2015 is rapidly approaching, and that puts EGUs under significant pressure to develop and begin executing a compliance plan.
Vendor schedules will continue to fill up as the deadline approaches, and that means more and more options will become unavailable. The later the decision to upgrade an EGU is made, the more limited and hasty the decision-making process becomes. While this isn’t necessarily problematic, it is generally true that decisions made under pressure deliver worse outcomes than those planned well in advance. Making compliance decisions early gives plants the opportunity to thoroughly explore all options available to them and formulate a knowledgeable, achievable plan.
Every EGU is different, so the decision to upgrade or retire a facility in response to MATS must incorporate all relevant factors. Decision-makers must consider state-level regulations, taxes, the condition of the facility and more. While MATS will certainly make operating older coal-fired EGUs more difficult – at least in the short term – it is important that plant operators understand that technology exists that can help limit the disruption caused by this additional regulatory burden. Without fully understanding existing MATS compliance technologies, coal-fired EGU operators cannot make well informed retrofitting or retiring decisions.
EGUs that are considering upgrading and continuing operation under MATS should have that MATS technology review completed at this point. If the decision is made to upgrade, the EGU will need to have a comprehensive plan for achieving compliance by the April 2015 deadline. For facilities that have yet to formulate their own compliance plan, these five steps can serve as a broad outline for developing one.
Step 1: Rule Interpretation
MATS will affect every EGU in a slightly different way depending on the configuration of the plant. Some facilities will already have certain monitoring equipment installed, while others will have to start from a more rudimentary stage. Most EGUs will need a combination of both emissions control and emissions monitoring technologies to meet the MATS requirements. Emissions control equipment may include flue gas desulfurization (FGD), activated carbon injection (ACI), and dry sorbent injection (DSI); necessary emissions monitoring technologies for MATS compliance include mercury (Hg) monitors, hydrogen chloride (HCl) monitors, sulfur dioxide (SO2) analyzers and particulate matter (PM) monitors.
Some EGUs will already have some of this equipment installed for another reason, such as compliance with an existing state-level regulation. Facilities preparing to achieve MATS compliance should take a comprehensive audit of their existing emissions control and monitoring equipment in order to identify how and where new technology is most needed. This will also provide a useful starting point for discussions with instrument manufacturers; most of them will have significant experience helping EGUs achieve MATS compliance, and additional information on a facility’s unique compliance challenges will help them formulate more effective recommendations. This increases efficiency and improves results for both parties.
Step 2: Instrument Selection & DAHS Integration
A wide variety of monitoring technologies exist that help EGUs comply with MATS. Facilities working toward MATS compliance will need several different monitoring instruments in operation by April 2015. Typically, it is necessary to install one monitoring instrument for each regulated element or compound emitted.
Many facilities already have existing mercury monitoring systems, most of which were installed in response to the Clean Air Mercury Rule (CAMR). After CAMR was vacated in 2009, a number of these EGUs continued to operate their systems to meet the requirements of state and local agencies.
EGUs that do not already have a mercury monitoring system have many elements to consider. One example is the instrument’s ability to measure different types of mercury. An instrument being used to achieve MATS compliance should be able to measure elemental, ionic and total mercury output. One technology that offers this capability is Cold Vapor Atomic Fluorescence (CVAF).
CVAF systems work by bombarding gases leaving the stack with ultraviolet light and measuring the response of the mercury within the gas. While older systems were hobbled by their need for expensive carrier gases (such as argon), gold amalgam traps and a source of distilled water, modern CVAF systems use direct measurement methods to capture mercury from the ambient air for analysis. In addition to reducing the need for expensive equipment and consumables, direct measurement also offer more reliable and continuous measurement.
Hydrogen Chloride (HCl) and/or sulfur dioxide (SO2)
The levels of these two compounds have a fixed ratio in most facilities, which means that the vast majority of coal-fired EGUs will not need to measure both of them to achieve MATS compliance – instead, they can simply use the level of one to determine the level of the other. This means that deciding which compound to measure is a critical part of any MATS compliance plan.
Facilities that decide to monitor HCl have a number of options available. One of the most reliable techniques for this application is Fourier transform infrared (FTIR), which uses infrared light to measure the molecular contents of stack gas. FTIR continuous emissions monitoring systems (CEMS) are capable of measuring up to 10 stack emission components – including HCl – simultaneously.
EGUs that choose to measure SO2 also have several different options. One of the most highly recommended is pulsed fluorescence technology, which measures SO2 content in stack gas using pluses of ultraviolet light. This technique can accurately measure concentrations of SO2 as low as 50 parts per trillion (ppt).
Particulate Matter (PM)
MATS also requires facilities to measure and report their PM output. For existing EGUs complying with MATS, PM measurements act as a surrogate for all toxic metal emissions. In some cases, certain subcategories of EGUs can use alternative measurements to PM, such as total non-mercury metal air toxics. However, the vast majority of facilities will find that PM measurement is the most effective option for MATS compliance. EGUs that believe that they may have other applicable measurement options should fully explore them during the “Rule Interpretation” step.
The most common PM monitoring technologies include light-scattering, beta attenuation, light extinction (essentially a measurement of opacity) and inertial microbalance. Because beta attenuation uses emissions from radioactive materials to measure the contents of a stack, it is typically only recommended in cases where no other analysis techniques are possible. Introducing radioactive materials adds an additional level of regulatory complication that is rarely worthwhile for this application.
One of the best solutions is to combine both light-scattering and inertial microbalance into one measurement instrument. Light-scattering is a precise continuous monitoring technique, but it is also prone to decalibration over time. Inertial microbalance is a much less drift-prone technique, but it cannot perform continuous measurement like light-scattering can.
Once all the necessary monitoring instruments have been chosen, work must be done to ensure that the collected compliance data is compatible with all existing plant systems. Most importantly, all instruments must be integrated with the plant’s existing data acquisition and handling system (DAHS). Successful integration usually requires bringing in the plant’s DAHS provider to manage the process and confirm that the newly modified system is able to meet all state-specific DAHS requirements. Starting the process early allows EGUs to give themselves the necessary time to deal with any unexpected issues that may come up in the DAHS integration process. This extra time is especially critical when several new instruments are being brought online for MATS compliance, as each one must be fully integrated and functioning reliably before the compliance deadline.
Step 3: Site Preparation
MATS compliance requires significant investment in new instrumentation, and installing all that new equipment can be disruptive to plant operations if it isn’t planned around. A rushed compliance process increases the chances that these disruptions will occur. Problems with MATS compliance preparations can lead to cost and time overruns which, if they are severe enough, can derail the entire process.
To avoid these complications, EGUs must create a detailed site preparation and equipment installation plan. This plan should include at least four months for instrument delivery and installation. Additionally, time should be budgeted for required physical plant upgrades, which can include everything from new communications and electrical lines to construction of equipment shelters and changes to plant air systems.
Installation operations get even more complicated the farther up the stack they go. Instrumentation being installed in the stack’s annular space can cause additional logistical challenges. Because of space limitations, existing instruments in the annular space may have to be moved to accommodate new measurement equipment. Ensuring that instruments high up the stack get the proper voltage and amperage needed for safe and reliable operation can also be a challenge.
Planning for RATA
Site preparation plans should also include some basic preparations for the facility’s first MATS relative accuracy test audit (RATA). All EGUs subject to MATS will have to undergo at least one RATA per fiscal year for each installed monitoring instrument. Mercury monitors, for example, must demonstrate performance accuracy within 20 percent of the reference instrument’s reading to pass a MATS RATA. If the monitor fails, all data from the system are considered invalid by the EPA until the problem is fixed.
Preparing for a RATA is stressful, as is scheduling one. The U.S. currently has a limited number of stack testers, so appointments must be scheduled far in advance. EGUs that plan ahead for MATS compliance will have an easier time setting a meeting with a RATA tester, and can even have time to perform some internal testing before their first RATA.
Step 4: Service, Service, Service
Coal-fired EGUs have very strict data availability requirements under MATS, so it is critical to ensure that everything is ready to go by April. This includes maintenance schedules; calibration and planned maintenance do count against a facility’s data availability statistics, so limiting unplanned maintenance and other downtime also reduces blank spots on the monitoring record. All monitoring instruments require regular servicing, including diagnostic checks, calibrations and adjustments; the more this service can be preplanned the better.
In addition to onsite maintenance, some instruments are also capable of being remotely serviced by their manufacturer. To facilitate this process, EGUs should also plan to have a data link set up during installation. Setting up remote access with the manufacturer in advance of the compliance deadline can save significant time, effort and cost down the road.
Step 5: Productive, Compliant EGU
Achieving compliance with MATS is not the easiest or most pleasant part of operating an EGU. However, it will soon be necessary for all facilities, old and new: April 2015 is only a half-year away. In six months, retrofitted old facilities will have to comply with MATS.
Demonstrating MATS compliance is a burden on businesses, but it only becomes more difficult when a facility is not adequately prepared.
Beginning the compliance process as early as possible makes meeting the deadline much easier. The countdown to April 2015 is already well underway, and EGUs that don’t already have a formal compliance plan in place should start formulating one now.
Michael Corvese is director of Business Development for Environmental and Process Monitoring at Thermo Fisher Scientific.
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