EPA proposes costly new NOx control plan for Wyoming coal units

In a move that has already kicked up opposition, the U.S. Environmental Protection Agency plans to publish in the June 10 Federal Register a Federal Implementation Plan setting stringent new regional haze standards for coal-fired power plants in Wyoming.

Basin Electric Power Cooperative, which saw an advanced copy of the EPA plan, said May 31 that the EPA has re-proposed a FIP that would require expensive new emission control technology at the coal-fired Laramie River plant. Approval of the re-proposed FIP, which requires more expensive selective catalytic reduction (SCR) for NOx control instead of cheaper selective non-catalytic reduction (SNCR), would cost Basin Electric hundreds of millions of dollars in emission control upgrades to Laramie River, said Basin Electric, the plant’s operator.

In the June 10 notice, EPA is proposing to partially approve and partially disapprove a State Implementation Plan (SIP) submitted by Wyoming in January 2011. EPA is also proposing a FIP to address the deficiencies identified in the proposed partial disapproval of Wyoming’s SIP.

“In lieu of our proposed FIP, or a portion thereof, we will propose approval of a SIP revision as expeditiously as practicable if the State submits such a revision and the revision matches the terms of our proposed FIP,” EPA noted. “We will also review and take action on any regional haze SIP submitted by the state to determine whether such SIP is approvable, regardless of whether or not its terms match those of the FIP.”

Written comments on this EPA action must be received within 60 days after the Federal Register notice. A public hearing for this proposal is scheduled to be held on June 24 in Cheyenne, Wyo.

EPA vetoes the state’s NOX determinations for several coal units

EPA is proposing to disapprove the following:

  • The state’s NOx best available retrofit technology (BART) determinations for PacifiCorp‘s Dave Johnston Unit 3, PacifiCorp’s Jim Bridger Units 1 and 2, PacifiCorp’s Wyodak Unit 1, and Basin Electric’s Laramie River Station Units 1, 2, and 3.
  • The state’s NOx reasonable progress determination for PacifiCorp’s Dave Johnston Units 1 and 2.
  • The state’s Reasonable Progress Goals (RPGs).
  • The state’s monitoring, recordkeeping, and reporting requirements in Chapter 6.4 of the SIP.
  • Portions of the state’s long-term strategy (LTS) that rely on or reflect aspects of the regional haze SIP that are being disapproved.
  • The state’s SIP because it does not contain the necessary provisions to meet the requirements for the coordination of the review of the reasonably attributable visibility impairment (RAVI) and the regional haze LTS.

EPA proposed to approve the remaining aspects of the state’s January 2011 SIP submittal. It also previously sought comment on two alternative proposals related to the state’s NOx BART determination for PacifiCorp Jim Bridger Units 1 and 2. It proposed the promulgation of a FIP to address the deficiencies in the Wyoming regional haze SIP that it identified in the proposal. 

In lieu of the proposed FIP, or a portion thereof, EPA previously stated that it would propose approval of a SIP revision if the state submits such a revision and the revision matches the terms of the proposed FIP. EPA said it encouraged the state to submit a SIP revision to replace the FIP, either before or after its final action.

EPA requested comments on all aspects of the proposed action and provided a 60-day comment period, with the comment period closing in August 2012. It also held two public hearings.

EPA says the state had wrong estimates on SCR/SNCR costs, benefits

Wyoming obtained the costs of compliance for controls from the BART applications submitted by sources that were subject to BART. EPA said it in turn relied on these costs in its original proposed rule. EPA has reviewed Wyoming’s cost analyses and has identified what it called deficiencies in various cost assumptions and methods. Accordingly, EPA has subsequently and independently calculated costs of compliance and performed new visibility modeling. In many instances, the BART sources underestimated the cost of SNCR, while overestimating the cost of SCR (both in combination with additional combustion controls), EPA said.

Depending on the particular BART source in question, EPA believes this was due to a number of errors, such as: use of incorrect baseline emissions; overestimation of the ability of SNCR to reduce NOx; underestimation of SNCR reagent (urea) usage and cost; and underestimation of the ability of SCR to reduce NOx.

For example, in the case of Laramie River Units 1-3, Wyoming significantly overestimated the ability of SNCR to reduce NOx, EPA said. The analyses submitted by the source, and in turn used by Wyoming, assumed that after the installation of additional combustion controls, SNCR would reduce NOx from 0.23 lb/MMBtu to 0.12 lb/MMBtu (or by roughly 48%). However, SNCR typically reduces NOx an additional 20% to 30% above combustion controls without excessive NH3 slip, EPA said. NOx reduction with SNCR is known to be greater at higher NOx emission rates than lower rates. Accordingly, EPA has estimated that the NOx reduction from SNCR as 30% for initial NOx greater than 0.25 lb/MMBtu, 25% for NOx from 0.20 to 0.25 lb/MMBtu and 20% for NOx less than 0.20 lb/MMBtu.

Due to the relatively recent installation of overfire air at the Laramie River units, the actual annual emissions in 2012 dropped to around 0.19 lb/MMBtu, even lower than the 0.23 lb/MMbtu rate assumed by Wyoming, EPA added. Therefore, EPA predicts that the reduction that can be achieved with SNCR at the Laramie River units is 20%, which is much lower than the 48% assumed by Wyoming. This significantly reduces the tons reduced by SNCR which is in turn used in the calculation of cost effectiveness. It also affects the incremental cost effectiveness between SNCR and SCR (both in combination with additional combustion controls). In addition, EPA’s analysis of urea prices indicates that producer prices for urea have increased the past three years. This increase in price is not reflected in Wyoming’s estimates for SNCR.

EPA said it has also identified a number of flaws in Wyoming’s cost analyses for SCR. For example, Wyoming assumed that SCR could only achieve a control effectiveness of 0.07 lb/MMBtu. By contrast, EPA has determined that on an annual basis SCR can achieve emission rates of 0.05 lb/MMbtu or lower. Moreover, EPA noted that Wyoming’s SCR capital costs on a $/kW basis often exceeded real-world industry costs. The capital costs for SCR claimed by Wyoming for Dave Johnston 3 and 4, Naughton Units 1-3, and Wyodak are in excess of the range of capital costs documented by various studies for actual installations. Five industry studies conducted between 2002 and 2007 have reported the installed unit capital cost of SCRs, or the costs actually incurred by owners, to range from $79/kW to $316/kW (2010 dollars). By contrast, Wyoming’s SCR costs range from $415/kW to $531/kW. These studies show actual capital costs are much lower than Wyoming’s, particularly for the PacifiCorp units.

EPA generally wants NOx compliance within five years

The NOx compliance findings by EPA for each power plant are:

  • Laramie River – Basin Electric’s Laramie River Station is located in Platte County, Wyo. It has three 550-MW dry-bottom, wall-fired boilers (Units 1, 2, and 3), burning subbituminous coal for a total net generating capacity of 1,650 MW. All three units are subject-to-BART. EPA proposes to find that at an emission limit of 0.07 lb/MMBtu (30-day rolling average), which can be achieved by the installation of new Low NOx Burners (LNBs) with Overfire Air (OFA) plus SCR. It is proposing that the FIP NOx BART limit for Laramie River Units 1-3 is 0.07 lb/MMBtu (30-day rolling average), with five years from when the FIP is final for compliance.
  • Dave Johnston – PacifiCorp’s Dave Johnston plant is located in Converse County, Wyo. Dave Johnston is comprised of four units burning pulverized subbituminous Powder River Basin coal. Units 3 and 4 are the only units subject-to-BART. Dave Johnston Unit 3 is a nominal 230 MW pulverized coal-fired boiler that commenced service in 1964. It was equipped with burners in a cell configuration until 2010, but was then converted to a dry bottom wall-fired boiler. Dave Johnston Unit 4 is a nominal 330 MW pulverized coal-fired boiler that commenced service in 1972. It is a tangential-fired boiler. EPA proposes to find that LNBs with OFA plus SCR at an emission limit of 0.07 lb/MMBtu (30-day rolling average) is reasonable for NOx BART for Dave Johnston Unit 3. EPA proposes that new LNBs with OFA plus SNCR at an emission limit of 0.12 lb/MMBtu (30-day rolling average) is reasonable for Dave Johnston Unit 4. Both units would have five years to comply.
  • Jim Bridger – PacifiCorp’s Jim Bridger plant is located in Sweetwater County, Wyo. It has four nominal 530-MW tangentially-fired boilers burning pulverized coal for a total net generating capacity of 2,120 MW. EPA is seeking comment on a first proposal to approve the regional haze plan submitted by the state for Jim Bridger Unit 1 and Unit 2. EPA also is seeking comment on another alternative approach that would determine that BART for Units 1 and 2 at Jim Bridger is SCR, and would establish corresponding NOx emission limits for these units that would have to be achieved within five years of final action on the FIP. This would have the effect of accelerating the installation of the SCR controls at these units that the state and PacifiCorp had proposed to install in the 2021-2022 time-period. The state determined that BART for these units is LNB plus OFA, and selected the 2021-2022 time-period for SCR-based emission limits as a reasonable progress measure. The timeframe was based on the large number of actions PacifiCorp is undertaking (or helping to finance) at a large number of power units in Wyoming, Utah, Colorado, and Arizona. Under the second proposed approach, EPA would propose that it does not agree with the state’s conclusion that a limit of 0.26 lb/MMBtu is reasonable for BART for Jim Bridger Units 1 and 2, which can be achieved with the installation and operation on LNBs with OFA. Under the second approach, EPA would find that LNBs with SOFA plus SCR at an emission limit of 0.07 lb/MMBtu (30-day rolling average) is reasonable for Jim Bridger Units 1 and 2, with compliance mandated within five years of the final FIP being put in place, advancing the SCR installation schedule under the existing plan.
  • Naughton – PacifiCorp’s Naughton plant is located in Lincoln County, Wyo. Naughton has three pulverized coal-fired units with a total net capacity of 700 MW. Naughton Unit 1 generates a nominal 160 MW, Naughton Unit 2 generates a nominal 210 MW and Naughton Unit 3 generates a nominal 330 MW. All three boilers are tangentially fired boilers. EPA proposes to find that new LNBs with OFA plus SCR at an emission limit of 0.07 lb/MMBtu (30-day rolling average) is reasonable for Naughton Units 1 and 2, with five years given to comply. The state determined that NOx BART for Naughton Unit 3 was existing LNBs plus OFA with SCR with an emission limit of 0.07 lb/MMBtu (30-day rolling average). EPA found this determination to be reasonable. It is also asking if interested parties have additional information regarding the possible conversion of Naughton Unit 3 from a coal-fired unit to a natural gas-fired unit as part of a better-than-BART demonstration. PacifiCorp has indicated that converting the unit to natural gas would reduce NOx emissions to 0.10 lb/MMbtu, and nearly eliminate all SO2 emissions.
  • Wyodak – PacifiCorp’s Wyodak plant is located in Campbell County, Wyo. It has one coal-fired boiler, Unit 1, burning pulverized sub-bituminous Powder River Basin coal for a total net generating capacity of a nominal 335 MW. Wyodak’s boiler commenced service in 1978. EPA proposes to find that new LNBs with OFA plus SNCR at an emission limit of 0.17 lb/MMBtu (30-day rolling average) is reasonable for NOx BART for Wyodak Unit 1, with five years from the final FIP given for compliance.
About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.