Alliant Energy‘s (NYSE: LNT) Wisconsin Power and Light subsidiary, plus Madison Gas & Electric and Wisconsin Public Service Corp., on July 2 jointly filed a request with the Public Service Commission of Wisconsin (PSCW) to install air emissions technology at the coal-fired Columbia Energy Center near Portage, Wis.
“This project will improve the environment, create jobs and support Wisconsin businesses,” said John Larsen, President of Alliant Energy’s Wisconsin utility. “This air quality control system will help us provide customers with cleaner, reliable and efficient electricity for decades to come.”
The application covers a selective catalytic reduction system (SCR) at Columbia Unit 2 that will reduce NOx emissions by approximately 50%. The SCR project is expected to begin construction in 2016 with an anticipated completion in 2018.
Alliant Energy and its co-owner utility partners are completing their first major environmental investment at the plant. This year, baghouse and SO2 scrubber systems will be put into operation at Columbia Units 1 and 2 that will reduce SO2 and mercury emissions by approximately 90% on each unit.
These projects are part of Alliant Energy’s plan to invest in air quality control systems at its newer, larger and most efficient generating units.
The SCR project will enable the applicants to comply with the NOx emission requirements of a Consent Decree submitted to the U.S. District Court for the Western District of Wisconsin in April 2013. This Consent Decree was entered into with the U.S. Environmental Protection Agency and the Sierra Club to resolve certain claims under the Clean Air Act.
Also, the project will promote compliance with interstate transport rules, and may assist in comporting with the Clean Air Visibility Rule (CAVR) and potential requirements associated with a possibly more stringent ozone national ambient air quality standard.
Conventional SCR chosen as the preferred option
The technology proposed at Columbia Unit 2 is a conventional SCR system. This technology removes NOx from the flue gas via a catalyzed reaction with an ammonia-based reagent. Three types of SCR technologies (conventional, in-duct and hybrid SCR) were evaluated based on the ability to meet Consent Decree requirements, the feasibility of implementation on Columbia Unit 2, and capital and operating cost considerations. Based on this evaluation, the conventional SCR system was chosen as it is a proven, cost-effective, commercially-available technology that can achieve the level of NOx removal required.
The estimated capital costs for the Columbia Unit 2 SCR is about $150m, excluding allowance for funds used during construction (AFUDC).
The utilities identified and evaluated four plans to meet their air compliance needs. Plan 1, the proposed plan, includes the installation of an SCR on Columbia Unit 2, and continued operation of the unit through the year 2038. Plans 2 through 4 each assume the retirement of Columbia Unit 2 at the end of 2018 with replacement capacity and energy resources. The preferred Plan 1 is lower cost than plans 2, 3 and 4 by approximately $579m, $571m, and $562m, respectively, on a present value of revenue requirements (PVRR) basis.
Columbia Unit 2 consists of a tangentially-fired boiler and steam turbine generator with a nameplate capacity of 511 MW. It is equipped with low NOx burners (LNB) and separated overfire air (SOFA) to reduce NOx emissions. Columbia Unit 2 is also equipped with a cold-side electrostatic precipitator (ESP) for particulate control and activated carbon injection (ACI) to reduce mercury. A dry flue gas desulfurization (dry FGD) system, comprised of spray dryer absorbers (SDAs) and a baghouse, is being placed in operation in 2014 on Columbia Unit 2 to reduce SO2, further reduce particulate matter and reduce acid gas emissions.
On Jan. 18, the Wisconsin commission approved a project to upgrade the steam turbines and replace the pulverizers on Columbia Unit 2. That project includes the installation of new HP/IP and LP turbine rotors and inner casings and replacement of all six existing pulverizers. The project, scheduled for completion in fourth quarter 2017, will improve the efficiency, capacity, reliability, and safety of the unit with no increase in gross heat input.
Columbia Unit 1 began operation in 1975 and has a nameplate capacity of 512 MW. Columbia Unit 2 began operation in 1978 and has a nameplate capacity of 511 MW. Both units are jointly owned by Wisconsin Power and Light (46.2%), Wisconsin Public Service (31.8%), and Madison Gas and Electric (22%). The units are operated by WPL.