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How To Understand Constellation Energy's Scrubber Technology

In 2007, Constellation Energy began construction on a cutting-edge environmental control system for its Brandon Shores coal-fired power plant in Maryland. Three years later, the new technology – featuring emissions-cutting scrubbers – is up and running. Here's how it works.


  • Step 1: Understand the basics Understand the basics. The flue gas desulfurization emissions controls, or "scrubbers," at Brandon Shores are one component of Constellation's ongoing environmental efforts. The scrubbers will remove 95 percent of the existing sulfur dioxide emissions, and 90 percent of the existing mercury emissions -- resulting in cleaner coal power, and cleaner air.
  • TIP: The Brandon Shores scrubbers are "wet scrubbers," which reduce landfill waste by up to 520,000 tons a year versus "dry scrubbers."
  • Step 2: Get the background Get the background. In 2006, Maryland’s Healthy Air Act, one of the strictest environmental mandates in the U.S., was signed into law. It requires that coal-fired power plants reduce nitrogen oxide, sulfur dioxide, and mercury emissions. Constellation's nearly $1 billion investment in environmental upgrades across all its properties, including the new scrubbers, helps make Brandon Shores one of the cleanest coal-burning power plants of its size in the country.
  • TIP: About 2,000 union jobs were created over the three-year construction period of the Brandon Shores scrubber.
  • Step 3: Know how it works Understand the technology. As coal burns, it emits gases. The plant's new system diverts the exhaust past the two old smokestacks into ductwork, where powder-activated carbon, or PAC, is injected. When the mercury in the gas reacts with the PAC, it gets trapped in the carbon particulate. As the mixture moves along the plant's path, the particulate matter containing the mercury is collected and filtered out.
  • Step 4: Understand the scrubber Next, the gas passes through the absorber tank and dual flow tray, where it gets sprayed with a limestone slurry mix. The limestone absorbs sulfur dioxide, and in the process produces gypsum, a safe, recyclable by-product that gets extracted.z
  • TIP: Gypsum is used in the production of wallboard, concrete, and other construction materials.
  • Step 5: Learn what comes out the stack After the scrubber process, the water is then stripped out of the remaining gas. What you finally see coming out of the new stack is harmless water vapor, which may seem especially noticeable in winter, when it meets the cold air. The existing emission stacks will remain in place, but since the gas now bypasses them, nothing will come out the top.
  • TIP: Even with scrubber technologies, all coal power plants will still produce carbon dioxide, a greenhouse gas. Constellation Energy strongly supports actions and policies to tackle these emissions too, including new laws and incentives, energy efficiency, and new investment in the cleanest of energy technologies like nuclear, wind and solar.
  • Step 6: Understand the results Breathe easy. With this new equipment, Constellation strengthens its environmental stewardship efforts and takes another step toward sustainable power, cleaner air, and a greener planet.

You Will Need

  • Coal technology basics
  • Familiarity with Maryland's Healthy Air Act

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