The co-owners of the coal-fired Columbia power plant are seeking an approval from the Wisconsin Public Service Commission for an upgrade project that includes replacement coal pulverizers and a 95-MW plant uprate.
A Certificate of Authority application was filed July 31 with the commission by Wisconsin Power and Light (WPL), Wisconsin Public Service Corp. (WPS), and Madison Gas and Electric (MGE). They are requesting authorization to upgrade the coal pulverizers and steam turbines at the Columbia Energy Center.
The applicants jointly own Columbia, with WPL holding a 46.2% share, WPS holding a 31.8% share, and MGE owning a 22% share. WPL operates the facility.
“The Applicants have identified a combination of upgrades to the Units that will enable greater efficiencies from the existing units, accruing benefits to customers,” they told the commission. “Since the Columbia units were placed in operation, several advances in the design of turbine and pulverizer technology have occurred. Examples include advanced three dimensional modeling software, which allows for more efficient design, and finite element analysis software, which allows for the design of components such that they carry lower stress and are less susceptible to failure.”
The capital improvement project the utilities are proposing utilizes this newer technology to design and install new turbine components and replacement pulverizers. The primary benefits of the technology improvements are an estimated reduction in the heat rate of approximately 440 Btu per Kilowatt hour on each unit, and a total plant operating capacity increase of about 95 MW.
The heat rate reduction equates to about a 4% efficiency improvement on each unit, and the capacity increase equates to approximately a 9% increase in daily average energy production from each unit. With the efficiency and energy benefits, reduced by the capital and operating costs, the project is estimated to provide a net customer benefit of $103m in present value of revenue requirements (PVRR).
The alternative would be to address the pulverizer and turbine maintenance issues with a combination of repairs and replacement components. However, the alternative would utilize the same technology that was deployed when the units were placed in service in the 1970s, and would not include improvements to efficiency or energy production, the utilities noted.
The capital investment required for the project is estimated at $130m, but has a payback within approximately five years of the first full year of operation.
The applicants are proposing to complete the project by the second quarter of 2017 with material procurement beginning in the second quarter of 2014. The twelve coal pulverizer replacements are proposed for sequential installation beginning in the second quarter of 2015 and ending in the second quarter of 2017. The pulverizers do not require an outage for installation. The turbine upgrades are proposed for installation during major outages in first and second quarters of 2016 and the first and second quarters of 2017 for Unit 2 and Unit 1, respectively.
Current nameplate capacities for each unit are 512 MW and 511 MW
The Columbia Energy Center consists of two units – Units 1 and 2 – each of which is a tangentially-fired boiler and an associated turbine generator. The nameplate capacities for Units 1 and 2 are 512 MW and 511 MW, respectively.
The facility has two General Electric (GE) turbines which were installed during the construction of Unit 1 in 1975 and Unit 2 in 1978. Each of the turbines consists of one dual flow combined high pressure and intermediate pressure (HP/IP) section and two dual flow low pressure (LP) sections and is connected to a GE generator rated for 617.8 megavolt-ampere (MVA). The facility also has twelve Combustion Engineering (now Alstom) coal pulverizers, six per unit, which were installed during the construction of Unit 1 and Unit 2.
Over the past several years, the turbines have begun to show signs of wear and degradation that require additional maintenance investment, the utilities noted. For example, the LP turbine rotors have a corrosion condition known as “stress corrosion cracking.” This condition is common to a significant number of turbine rotors of this vintage with the “dovetail” design. The dovetail refers to the geometry of the connection used to attach the turbine blades to the turbine rotor.
U.S. Energy Information Administration data shows that Columbia earlier this year was taking Powder River Basin coal from suppliers like Arch Coal (NYSE: ACI), Cloud Peak Energy (NYSE: CLD) and Alpha Natural Resources (NYSE: ANR).