Controlling Air Pollutants case study
While it's not always easy to determine what's required for compliance, new technologies can help achieve air-pollution control
Selecting air-pollution control equipment can be tricky. It's not only difficult to determine which pollutants must be controlled, but also which type of equipment will best control them to required levels for any given process or facility because there is no 'one-size-fits-all' solution. Technologies that successfully control pollutants in one facility may not work as well in another. Permissible levels in one region sometimes differ from those in another. A similar process may result in different types or levels of pollutants from one plant to the next.
Fortunately, it is possible to solve this puzzle. Experts suggest determining which regulations apply to your facility's pollutants and region; learning about your particular process and the resulting types of pollutants; and, finally, looking, in detail, at the available technologies to figure out which one or which combination will provide the best solution for your worst-case pollution scenario.
Regulations to watch
Regulations concerning mercury, oxides of nitrogen (NOx) and sulfur (SOx), acid gases and particulate matter emissions are of the biggest con-cern to power plants and some chemical and industrial processors. There are several new or anticipated regulations concerning these pollutants that affected processors need to keep an eye on:
MATS. Revised twice and finalized on March 28, 2013, the U.S. Environ-mental Protection Agency's (EPA; Washington, D.C.; www.epa.gov) Mercury and Air Toxics Standard (MATS) created updates of emission limits for mercury, particulate matter, S02, acid gases and certain individual metals for new power plants. Additionally, certain monitoring and testing requirements that apply to new sources were adjusted. 'Two things to know about MATS are that the particulates covered are not what many of us consider 'particulates,'' says Robert Hilton, vice president, power technologies for government affairs with Alstom (Knoxville, Tenn.; www.alstom.com). 'They are actually aerosols that are classified by EPA as particulate. The other important thing to know is that the revised standards affect only new coal- and oil-fired power plants that will be built in the future. The update does not change the final emission limits or other requirements for existing power plants.'
Interstate Air Pollution Transport. As part of the Clean Air Act (CAA), this 'good neighbor' provision requires the EPA, states and processors to address interstate transport of air pollution that affects downwind states' ability to attain and maintain National Ambient Air Quality Stan-dards. Emissions of S02 and NOx can react in the atmosphere to form fine-particle (PM2.5) pollution. Similarly, NOx emissions can react in the atmosphere to create ground-level ozone pollution. The transport of these pollutants across state borders makes it difficult for downwind states to meet health-based air quality standards for PM2 5 and ozone. Recently EPA set dates and locations for meeting with states to discuss regulations regarding air-pollution transport. 'What makes compliance with this difficult is that the ruling is technically in limbo,' says Hilton. 'And this makes it harder to figure out how to control these pollutants, as well as the pollutants regulated by MATS. A lot of what generators need to do to be in compliance with MATS will cover S02, which will also be covered by the Interstate Air Pollution Transport rule.'
CAA and National Ambient Air Quality Standards. Under the CAA, EPA is required to set National Ambient Air Quality Standards for six common air pollutants and then review those standards every five to six years to determine if the technology to further lower the permissible limits exists and, if so, whether it is actually feasible to achieve these lower levels. 'This is expected to happen this year and it is presumed that EPA will attempt to lower acceptable NOx levels,' says Hilton. 'If this happens, it likely will be further out, in a sequenced implementation plan, with a NOx compliance deadline in the timeframe of 2017 to 2019.' Until then, processors in the 23 eastern states must comply with NOx levels currently set by the Clean Air Interstate Rule (CAIR), and the remaining western states must comply with NOx levels currently set by the CAA'and regional haze rules.
So how do processors know which regulations impact their facility? 'You have to look at all the rules, look at your plant, look at the fuel you burn and where you are located, because some regulations are federal and some are state,' says Hilton. 'You have to work with both state and federal agencies to find out which regulations your facility is subjected to and which of those are the most applicable and important for your plant and location to obtain the permits it needs to operate. In most cases you have to meet the stricter of the guidelines to be in compliance.'