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From the control room, some officials visited the sewage treatment facility while others saw how the wet limestone scrubbers eliminate 95 percent of the plant's sulfur dioxide from its emissions.
Terry Edwards explained that limestone rock is crushed to a powder with steel balls inside rotating drums the size of buses. The limestone is then mixed with water to create a slurry paste that is sprayed through the flue gas. A chemical reaction changes the gaseous sulfur dioxide into harmless calcium sulfate.
Next, the officials went inside one of the plant's 775-foot-high stacks where the emission monitoring system is housed.
"From an environmental perspective, this is a very important part of the plant,"
"This is where we measure all the air quality in the stack. We have real-time monitors. They're measuring every minute of the emissions. We call them Continuous Emission Monitors, or CEMs."
Inside the clean, quiet, white room, he explained that each stack has probes to gather accurate measurements. The probes remove moisture then pass it through a bank of specialized analyzers and a master computer that sends readings back to the control room.
The CEMs determine the precise amounts of nitrogen oxide, carbon monoxide, carbon dioxide, sulfur dioxide, the stack flow rate and the opacity of the emissions plume- all for EPA reporting purposes.
The Navajo Generating Station consistently stays below EPA-mandated pollution limits because of the installed pollution control technology and the diligence of its operators, he said.
Visitors are often surprised by the cleanliness of the plant and the lack of a smell or the scent of anything burning. The air throughout the plant is odorless and safe.
Although people imagine the entire chimney filled with smoke, in reality the three stacks are lined with massive sleeves and emissions pass through only a section of them, Ostapuk said. A workman can ride the stacks' interior elevator or climb a ladder without harm while the stacks are operating, he said.
What you see coming out, he explained, is primarily water vapor, not smoke. So on hot summer days, it appears to be less. On cold winter days, it appears to be more.
When construction of Navajo Generating Station began in 1969, the plant was built with electrostatic precipitators that remove 99.5 percent of the particulate fly ash after coal is burned. Within each of the power plant's three units are 16 chambers with 96 fields that use electrodes to charge the particles with electricity to collect the ash on oppositely charged plates.
The captured fly ash can then be recycled and sold as a valuable byproduct. It is used to help make concrete flow smoother, set up stronger and reduce energy use by the cement industry.
One company that uses fly ash is Navajo FlexCrete Building Systems, Inc., in LeChee that manufactures light-weight construction blocks as a building material.
In the 1990s, as part of the Navajo Visibility Agreement with the Grand Canyon Trust and the federal government, the Navajo Generating Station invested $420 million to install scrubbers that remove 95 percent of the sulfur dioxide from its emissions.
"This was the primary pollutant we were trying to keep out of the Grand Canyon,"
In 2011, NGS voluntarily completed the $45 million installation of low-NOx burners that reduce 40 percent of the nitrogen oxide from emissions. This also helps to improve visibility by reducing regional haze.
Alden Miller, a ranger at Navajo National Monument who came on the tour, said he was impressed with how much NGS employees care about the power plant.
"It's obvious to me that you take a lot of pride in what you do,"
"It seems like you all have such enthusiasm for sharing it, too."
Terry Edwards agreed.
"These guys are great to work with,"
"Everybody who works here, temporary or fulltime employee, they take pride in their workmanship. They want to do it right."
posted December 7, 2012 5:59 am est