Navajo Generating Station Voluntarily Installs Low-NOX Burners

By Jim Pratt, Salt River Project

Since its inception, the owners of the Navajo Generating Station (NGS) have been diligent about protecting the natural environment of scenic northern Arizona.

Located near Page on the Navajo Nation, the largest American Indian reservation in the country and about 80 miles from the Grand Canyon National Park’s main visitor area on the South Rim, NGS was the first U.S. power plant to be built to comply with the 1970 Clean Air Act. Then, in 1999, wet scrubbers were installed on the plant’s three generating units in a $460 million project that eliminated about 90 percent of sulfur dioxide (SO2) emissions.

This year, workers at NGS finished installing low-nitrogen oxide (NOX) burners and separated overfire air on the final unit to complete a voluntary three-year effort to retrofit all three 750-MW coal generating units at the plant. The $46 million project reduced emissions of NOX by at least 40 percent.

The key word about the most recent emission-control project is voluntary, said John Sullivan, associate general manager of resource management for Phoenix-based Salt River Project (SRP), the plant’s operator.

“As one of the largest and most important sources of energy in the Southwest,” Sullivan said, “it is important that the Navajo Generating Station continues to operate in a responsible manner on behalf of the hundreds of thousands of people who benefit from the electricity produced at the plant. The NGS owners are doing our part to reduce emissions along the Colorado Plateau for future generations.”

Bob Talbot, manager of NGS, said the power plant’s owners share the values of the Navajo people to balance the need for jobs and revenue with protection of the air, land and water of Dine Bikeyah, or Navajoland.

And the owners of NGS are proud of their relationship with the Navajo people. Talbot said the NGS work force of 545 employees is 83 percent Navajo. The owners give preference to Navajos when hiring new employees for the plant; in the past decade, he said, 250 of NGS’s new employees have been Navajo.

Almost as diligent in the NGS owners’ longtime efforts to establish and maintain an abiding legacy of environmental protection, however, has been the push by environmental groups in recent years to close NGS. They’re hoping a sympathetic administration in Washington helps them.

Recently, the Environmental Protection Agency (EPA) pushed back its pending decision on the Clean Air Act’s Best Available Retrofit Technology (BART) Requirements for NGS. The parties have been told that the EPA will make an announcement regarding NOX in 2012.

One possibility is the EPA could require the plant’s owners to reduce NOX emissions by installing selective catalytic reduction (SCR) technology. An SCR consists of a reactor in which ammonia is injected to combine with NOX to form nitrogen and water.

The cost of installing SCRs on all three units at NGS, however, would be about $544 million, Sullivan said.

If baghouses also are required to mitigate the increase in emissions of other pollutants created by the SCRs, the total cost of controls would rise to about $1.1 billion, he said.

Such a significant expense to the NGS owners—and their electric customers in Arizona, Nevada and California—also raises several questions:

ࢗ  Should the six NGS participants—the Department of Interior’s Bureau of Reclamation, Salt River Project, Los Angeles Department of Water and Power, Arizona Public Service, NV Energy Inc. and Tucson Electric Power Co.—decide the plant must be closed rather than spend millions of dollars on SCR technology that might not significantly improve visibility, what happens to the cost of electricity?

ࢗ  What about the future water needs of Arizona? Ninety-five percent of the power used by the Central Arizona Water Conservation District to pump Colorado River water through the Central Arizona Project canal to its thirsty agricultural and residential users as far away as Phoenix and Tucson is generated at NGS, and that electricity would have to be replaced at a significantly higher cost.

ࢗ  What becomes of NGS’s experienced and technically trained Navajo work force? Unemployment on the Navajo Nation historically has been upward of 50 percent, Talbot said. According to the 2010 U.S. census, more than half of the 303,000 enrolled Navajos live off the Navajo Nation, having left to pursue educational and economic opportunities. The Navajo Nation government has expressed concerns that as Navajos continue to leave their homeland for employment and not return, the erosion of the Navajo language, culture and way of life gains increasing momentum.

ࢗ  And, finally, what would replace the $140 million in annual revenue from paychecks, royalties, scholarships and community and charitable contributions to the Navajo Nation that would be lost if NGS closed? Because of those contributions to the Navajo Nation economy, NGS enjoys the strong support of the Navajo Nation government and its dedicated work force.

The Navajo Nation began building casinos three years ago, but even as Navajo leaders seek other forms of economic development, they repeatedly have said they do not wish their gaming enterprise to be the cornerstone of their economy. The Navajo Nation continues to rely on its coal, oil and gas resources to generate 66 percent of the nation’s governmental revenue.

In the meantime, SRP and the other NGS owners only can wait—and keep producing electricity, knowing their most recent emission-control investment already has put the NGS seven years ahead of schedule on NOX-reduction efforts—for further benefit to the region’s parks and wild spaces.

Sullivan said the NGS owners have made significant strides during the plant’s 37 years to reduce emissions along the Colorado Plateau, including at the Grand Canyon, Canyonlands, Mesa Verde and the Glen Canyon National Recreational Area.

When NGS’s three units went online in 1974, 1975 and 1976, respectively, the plant’s original design included some $200 million in electrostatic precipitators, environmental-control equipment designed to eliminate 99.5 percent of particulate matter. The fly ash created is recycled into concrete, cement and a locally produced construction material known as Flexcrete.

Then, under an agreement signed at the Grand Canyon by President George H.W. Bush in 1989 to complete a negotiated settlement involving SRP, Arizona, the Grand Canyon Trust and the EPA, wet scrubbers were installed in a five-year endeavor that still ranks as one of the largest construction projects in Arizona.

Since that scrubber project was completed, NGS has become a top performer in its class in reducing SO2. That, combined with the availability of high-quality, low-sulfur Black Mesa coal with a sulfur content of less than 1 percent, makes NGS especially efficient in SO2 reduction.

The most recent project, which culminated in April, will result in an annual reduction of some 14,000 tons of NOX and, along with the previously installed wet scrubbers, improves regional haze concerns in a geographically unique area surrounded by national parks and the scenic Navajo Nation.

When released into the atmosphere, NOX creates ammonium nitrate particles that absorb sunlight and then can contribute to regional haze.

Other significant contributors to occasional regional haze are automobile emissions, blowing dust and, especially, forest fires and controlled burns.

Nitrogen oxides form when nitrogen in the air and fuel combine with oxygen in combustion processes. NOX impacts visibility in two ways: As a gas, it absorbs light and becomes visible as a local brown plume while additional reactions create ammonium nitrate particles that have a longer residence time in the atmosphere and can impact visibility as a component of regional haze.

Low-NOX burners and separated overfire air are furnace modifications that control air-to-fuel ratios and provide for deep-staged combustion to reduce NOX formation when coal is burned. This type of control technology is a cost-effective way to reduce NOX emissions at NGS by 40 percent without costly chemicals and other potentially negative environmental consequences.

More information about the ongoing environmental developments at the Navajo plant and its role in providing power and water to the Southwest can be found at


Jim Pratt is Salt River Project’s manager of base load generation. SRP is the largest provider of water and power to the greater Phoenix metropolitan area and the third-largest public power utility in the U.S.

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