The Tennessee Valley Authority Board of Directors voted Dec. 30 to add additional air pollution controls on Units 1 and 4 at TVA’s coal-fired Shawnee Fossil Plant near Paducah, Ky.
Under a 2011 Clean Air Agreement with the U.S. Environmental Protection Agency, Kentucky, other states and environmental groups, TVA was required to make a decision by Dec. 31, 2014, to either retire or install additional air pollution controls on Shawnee Units 1 and 4. A third possible option to convert the units to biomass instead of coal had been previously considered and rejected as being economically unfeasible.
After recently completing an environmental assessment that included public input, TVA determined that either option would have no significant environmental impact.
TVA management recommended approval of the additional air pollution controls after analyzing the options from financial, operational and environmental perspectives. The installation of pollution controls at Units 1 and 4 will assist TVA in fulfilling its air quality goals and commitments while also meeting electricity demand and minimizing costs to TVA customers. Shawnee’s relatively small units provide flexibility to the overall power system because they can more easily serve load when demand fluctuates.
Shawnee has nine operating units generating 1,206 MW. Units 2, 3 and 5-9 are not affected by this decision and already have sufficient controls to meet EPA regulatory clean air standards. The additional controls, which will reduce NOx and SO2 emissions, will be installed before Dec. 31, 2017, at an estimated cost of $185m.
Selective catalytic reduction (SCR) would be added to control NOx, and flue gas desulfurization (FGD) for SO2 control.
The SCR systems would be installed in the location of the non-operational electrostatic precipitators which would be removed. The 250-foot tall original emission stacks for Units 1 and 4 would be demolished and the new FGD systems would be located in the area of these stacks. Additional actions include changes to the dry fly ash piping systems, extensions of on-site electrical components, construction of an ammonia receiving and storage facility, and construction of FGD reagent preparation and feed systems.
The FGD systems would be dry systems using calcium hydroxide as the reagent. Coal combustion residuals (CCRs) from Units 1 and 4, consisting of ash and scrubber residue, would be comingled and trucked to the existing onsite dry stack for disposal.