August 2008

Getting ready to scrub the SO2

Randy Crawford is testing instruments for the December start-up of Bull Run’s scrubber.

Everyone is talking about the need for cleaner air. Across TVA, folks like Randy Crawford are doing something about it.


Randy Crawford at the new Distributed Control System racks used for controlling the scrubber systems

A 17-year TVA employee, Crawford started last August as senior instrument mechanic on the scrubber project at Bull Run Fossil Plant near Oak Ridge, Tenn. When the scrubber goes into service in December, it will be the next step in TVA’s long-term program to improve air quality. In fact, the scrubber is expected to reduce the plant’s sulfur-dioxide emissions by 95 percent in 2009.

To prepare for that start-up, Crawford is doing the operational testing, monitoring inputs for controls, and making sure every system works the way it should. “It is a big project,” says Crawford.

What is a scrubber

Scrubber is shorthand for a “flue-gas desulphurization system,” designed to remove sulfur-dioxide emissions from the flue gas released from a coal-fired plant.

Here’s how it works:
The flue gas is blown through curtains of liquid limestone slurry spray, which absorb the SO2 from the gas. The liquid moves by gravity to the bottom cone drain, and the cleaned gases leave the scrubber at the top outlet.


The Bull Run scrubber will be the 8th to go into operation in the TVA fossil system. TVA has invested more than $4.8 billion so far on all clean-air controls. “I believe TVA is very serious about reducing emissions,” says Crawford.

The scrubbers currently in operation, along with the use of low-sulfur coal, have reduced the SO2 emissions from TVA plants by 82 percent compared with 1977 levels.

To reduce nitrogen-oxide emissions, TVA has installed various combustion controls on all 59 coal-fired units and selective catalytic reduction technology on 21 of the units. Since 1995, TVA has reduced NOx emissions during the summer (when ozone levels increase) by about 81 percent.

“The scrubber will definitely help,” says Crawford, who – along with the rest of the Bull Run scrubber team – takes pride in helping TVA do its part to reduce emissions.

Crawford and his wife, Mary Beth, a teacher at Grace Christian Academy, have three children. Amanda, 20, and Ashleigh, 18, are studying at Pellissippi State Technical Community College to be teachers. Chris, 11, is a fifth grader at Grace Christian.