SWEPCO works on emissions retrofits for three coal-fired plants

A new integrated resource plan (IRP) from Southwestern Electric Power (SWEPCO) shows continued faith in coal-fired generation, with new emissions controls installed at and preservation of the Flint Creek coal plant a key part of that plan.

The IRP, covering the 2012-2021 period, was filed Nov. 30 at the Arkansas Public Service Commission, which is also still considering an application filed earlier this year to add a new SO2 scrubber and other emissions controls at Flint Creek. Some parties to that case, including the Sierra Club, claim that there would be better alternatives to what amounts to a life-extension project for Flint Creek.

SWEPCO is a unit of American Electric Power (NYSE: AEP).

“Based on modeling results and engineering analysis, a recommended Plan has been developed for SWEPCO’s solid-fuel generating units at Flint Creek, Welsh and Pirkey,” said the IRP. “For Flint Creek, SWEPCO has performed robust economic analyses around alternatives that would point to the environmental retrofitting of the plant by approximately June 2016 as being the least-cost solution over the economic life-cycle studied when compared to other feasible options. SWEPCO also performed the necessary risk analyses to ensure the recommended unit disposition solution would not likely be altered by key risk drivers — namely, lower natural gas pricing, earlier-than-anticipated impact of (potential) CO2/carbon pricing, and higher retrofit construction costs.”

For Welsh Units 1 and 3, preliminary economic and engineering analysis by SWEPCO and consultant Sargent and Lundy LLC (S&L) supports the option to retrofit with activated carbon injection/dry sorbent injection/fabric filter (ACI/DSI/FF) with provision for future installation of spray dryer absorber (SDA) selected as the most technically and economically viable option to reduce SO2 emissions potentially required by the National Ambient Air Quality Standard (NAAQS) one-hour standard. The installation of ACI in conjunction with FF will reduce mercury emissions to meet the requirements of the new Mercury Air and Toxics Standards. No retrofit consideration was given to Welsh Unit 2 due to its impending retirement, SWEPCO noted.

Initial analysis performed around Pirkey by both S&L and the resulting SWEPCO economic analysis established the least cost compliance option to be, with an ACI system, the conversion of each existing electrostatic precipitator (ESP) casing to a full sized FF. The conceptual engineering, costs, and schedule are currently being developed for Pirkey to be in compliance with MATS based on the selected option.

The recommended plan provides the “lowest, reasonable cost” solution through a combination of traditional supply, renewable and demand side investments, the utility said. Tempered load growth combined with additional renewable resources, increased energy efficiency initiatives, completion of the new, 600-MW Turk coal-fired plant, and capacity purchases, will allow SWEPCO to meet its resource requirements through the planning period. No new uncommitted baseload capacity is required over the term of the forecast period.

SWEPCO and fellow AEP-affiliate Public Service Co. of Oklahoma (PSO) operate in the Southwest Power Pool (SPP) and collectively serve a population of about four million customers (1,053,890 retail) covering a 36,000 square mile area in parts of Arkansas, Louisiana, Oklahoma, and Texas.

SWEPCO’s coal-fired capacity, with its owned shares of applicable plants/units, is: Flint Creek Unit 1 (264 MW); Pirkey Unit 1 (580 MW); Welsh Units 1-3 (1,584 MW); and Dolet Hills Unit 1 (257 MW).

Utility models several options for Flint Creek, included gas-fired replacement

The following four modeling options were performed by SWEPCO around Flint Creek unit disposition:

  • Option #1 – Retrofit Flint Creek with low NOx burner/over fire air (LNB/OFA) technology by 2014, DFGD and ACI technology by about June 2016 and, subsequently, coal combustion residuals (CCR)-related equipment by 2018 and selective catalytic reduction (SCR) technology by 2020 to ensure compliance with an ultimate Regional Haze Rule Arkansas-State Implementation Plan (SIP), known MATS-based emission requirements, Cross-State Air Pollution Rule (CSAPR) NOX emission budgets, proposed EPA CCR rulemaking, as well as any potential future requirements for further NOX reduction under revised National Ambient Air Quality Standards (NAAQS) for NOx/ozone.
  • Option #1A – Eliminate the SCR installation over the study period. This view would essentially mirror SWEPCO’s current position in terms of, particularly, Best Available Retrofit Technology (BART) applicable to NOX control under the Arkansas Regional Haze SIP.
  • Option #1B – Advance the SCR installation to be concurrent with the DFGD and ACI retrofit or by approximately June 2016.
  • Option #2 – Convert Flint Creek to exclusively burn natural gas by Jan. 1, 2016.
  • Option #3 – Retire Flint Creek and replace it with a 50% share of a nominally-rated 608 MW natural gas combined cycle facility at or near the existing brownfield Flint Creek site by Jan. 1, 2016, with attendant gas supply requirements, in recognition of regional transmission/reliability constraints in that NW-AR transmission area, and to ensure environmental compliance.
  • Option #4 – Retire Flint Creek and replace it with a 50% share of a nominally-rated 610 MW natural gas CC facility at a greenfield (or non-identified) site by Jan. 1, 2016, recognizing an incremental bulk transmission investment that would be required to ameliorate those regional NW-AR constraints and to ensure environmental compliance.

Various options also evaluated for Welsh, including new gas-fired capacity

Leveraging combined experience and knowledge, along with studies conducted at Welsh in the 2008-2010 period, SWEPCO, American Electric Power Service Corp. and Sargent and Lundy developed a conceptual design, capital cost and O&M estimates for each of the following environmental retrofit options to bring the Welsh units into compliance with 1-hour SO2 NAAQS standard and MATS requirements:

  • Activated carbon injection (ACI), dry sorbent injection (DSI) and fabric filter (FF);
  • ACI/DSI/FF with provisions for future installation of spray rryer absorber (SDA);
  • ACI/DSI/FF with a phased (or delayed) installation of SDA;
  • NID plus ACI;
  • Conversion of hot side electrostatic precipitator (HS-ESP) to cold side ESP (CS-ESP) allowing for direct injection of ACI/DSI and no FF; and
  • Installation of a 600-MW natural gas combined cycle plant.

No retrofit consideration was given to Welsh Unit 2 due to its impending retirement. Economic and environmental sensitivity analyses’ were conducted for each of the options. Option 2, that includes ACI/DSI/FF with provision for future installation of SDA, was selected as the most technically and economically viable option to reduce SO2 emissions potentially required by the 1-hour SO2 NAAQS standard. The installation of ACI in conjunction with FF will provide for the reduction of mercury to meet the requirements of the MATS rule.

Pirkey work resulted in four options being considered

In response to the U.S. Environmental Protection Agency’s MATS rule, SWEPCO, in consideration of the installation of a fabric filter with ACI for increased mercury (Hg) removal, hired S&L in January 2012 to evaluate options for retrofitting a FF at Pirkey in Hallsville, Texas. S&L conducted a screening study to compare FF technology options in terms of technical, economic, schedule, and outage characteristics.

S&L and SWEPCO evaluated four options:

  • Stand-alone, full-size fabric filters adjacent to each existing electrostatic precipitator (ESP) plus removal of existing ESPs;
  • Polishing stand-alone fabric filters in series with operational ESPs;
  • Conversion of each existing ESP casing to a full sized fabric filter; and
  • Pre-fabricated full-size fabric filters in the location of each ESP plus removal of existing ESPs.

All options would incorporate an ACI system. S&L’s screening study results were in support of an internal SWEPCO economic analysis of the options. S&L’s study and the resulting SWEPCO economic analysis both established the least cost compliance option to be Option 3, the conversion of each existing ESP casing to a full sized fabric filter. The conceptual engineering, costs, and schedule are currently being developed for Pirkey to be in compliance with MATS based on the selected option.

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.