A number of coal-fired facilities in Alabama, both electric generating units (EGUs) and industrial plants, were evaluated under the U.S. Environmental Protection Agency’s regional haze rules, with a mixed bag of results.
EPA, in a Feb. 28 Federal Register notice, said it is proposing a limited approval of a revision to the Alabama state implementation plan (SIP) submitted by the Alabama Department of Environmental Management (ADEM). This revision addresses the requirements of the Clean Air Act and EPA’s rules that require states to prevent any future and remedy any existing anthropogenic impairment of visibility in mandatory Class I areas (national parks and wilderness areas). States are required to assure reasonable progress towards the national goal of achieving natural visibility conditions in Class I areas.
EPA is proposing, and will take public comment until March 29 on, a limited approval of this SIP revision. EPA has previously proposed a limited disapproval of the Alabama regional haze SIP because of deficiencies in it arising from the remand by the U.S. Court of Appeals for the District of Columbia Circuit to EPA of the Clean Air Interstate Rule (CAIR), which the state relied on for SO2 and NOx compliance under the regional haze program.
Nineteen emissions units identified for a reasonable progress control analysis are EGUs and are subject to CAIR. These EGUs, located at six facilities, are: Alabama Power-Barry Units 002, 003, 004, 005, 006; Alabama Power-Gorgas Units 004, 005, 008; Alabama Power-Gaston Unit 006; Alabama Power-Miller Units 001, 002, 004, 005; Tennessee Valley Authority-Colbert Unit 014; and TVA-Widows Creek, Units 002, 004, 005, 008, 009.
Based on the analysis, ADEM concluded that additional SO2 control measures, beyond those needed to meet CAIR requirements, for Alabama’s EGUs would not be reasonable during this first implementation period based on a consideration of the reasonable progress statutory factors. EPA proposes to find acceptable Alabama’s methodology and determination that no additional controls beyond CAIR are reasonable for SO2 for affected Alabama EGUs for the first implementation period.
As for non-EGUs subject to regional haze Best Available Retrofit Technology (BART) rules, at both the International Paper-Courtland Mill facility and the Solutia Inc. facility, all five units identified as being subject to analysis for reasonable progress for the Sipsey Wilderness Area are subject to BART and subsequently were evaluated for BART controls. ADEM believes that BART is equivalent to reasonable progress for these five units, and thus, is not requiring any additional controls for reasonable progress. EPA proposes to agree with the state’s conclusions that BART satisfies reasonable progress for the first implementation period for these five non-EGU emissions units.
ADEM analyzed whether SO2 controls should be required for a Cargill Inc. stoker boiler (S–407). For the limited purpose of evaluating the cost of compliance for the reasonable progress assessment in this first regional haze SIP for the non-EGUs, ADEM concluded that it was not equitable to require non-EGUs to bear a greater economic burden than EGUs for a given control strategy. Using CAIR as a guide, ADEM used a cost of $2,000/ton of SO2 controlled or reduced as a threshold for cost-effectiveness.
Cargill’s S–407 unit is permitted to burn coal, natural gas, or No. 2 fuel oil. Coal with a sulfur content of 1.2 to 1.3 lbs/MMBtu is the primary fuel source. S–407 emits about 780 tons per year of SO2. Cargill evaluated three control options: lower-sulfur coal, wet scrubbers and dry scrubbers. Lower-sulfur coal could not be used because of its lack of availability. Also, even if lower-sulfur western coal were available, significant boiler modification would be necessary to burn it and the coal would challenge the boiler’s combustion integrity due to its higher dust content.
As for the wet and dry scrubbers, Cargill estimated that it would cost $2,946/ton to control SO2 with these technologies. Although no modeling was submitted, Cargill also questioned whether S–407 contributed to visibility impairment at the Sipsey Wilderness Area. ADEM concluded, based on their evaluation of the Cargill analyses, that no further controls were warranted at this time. EPA is proposing to approve that finding.
Alabama identified 43 facilities with BART-eligible sources. All of Alabama’s 43 BART-eligible sources were required by the state to submit BART exemption modeling demonstrations. Alabama found that three of its BART-eligible sources – Solutia-Decatur, International Paper-Courtland and Escambia Operating Co.-Big Escambia Creek – had modeled visibility impacts of more than Alabama’s threshold for BART exemption. Escambia took permit limits to no longer be subject to BART. Solutia-Decatur and International Paper-Courtland are considered to be subject to BART and submitted state permit applications including their proposed BART determinations.
Of the 41 exempted sources, three were exempted because they emitted only volatile organic compounds in excess of 250 tons per year, three accepted permit limits which reduced their potential to emit to below 250 tons per year of any affected pollutant, and one, Escambia, took permit limits that reduced its impact to below the haze threshold.
Several coal plants escape BART program
The 34 remaining sources are not subject to BART as they modeled visibility impacts less than the threshold. This modeling involved emissions of NOx, SO2 and PM10. Eight of the 34 sources are power plants (i.e., Alabama Electric Cooperative-Lowman, Alabama Power-Barry, Alabama Power-EC Gaston, Alabama Power-Gorgas, Alabama Power-Greene County, Alabama Power-Miller, TVA-Colbert, and TVA-Widows Creek). Only PM10 emissions were used in the modeling for EGU sources. The SO2 and NOx BART-eligible emissions were not modeled, because Alabama opted to have CAIR satisfy BART for SO2 and NOx for affected CAIR EGUs, as allowed under the regional haze regulations. EPA is not taking action in this proposed rulemaking to address the state’s reliance on CAIR to meet certain regional haze requirements.
The remaining 26 non-EGU sources demonstrated that they are not subject to BART since they modeled less than the threshold visibility impact at the affected Class I areas.
Three BART-eligible sources (Solutia-Decatur, International Paper-Courtland and Escambia-Big Escambia Creek) had modeled visibility impacts of more than Alabama’s threshold for BART exemption. Escambia accepted permit limits to reduce its visibility impacts to below the threshold. Only Solutia-Decatur and International Paper-Courtland are therefore considered to be subject to BART. Consequently, they each submitted permit applications to the state that included their proposed BART determinations.
Solutia plant looked at for coal controls
Solutia-Decatur has five BART-eligible emissions units. Boiler No. 5 is a 290 MMBtu/hr coal-fired spreader-stoker boiler; Boiler No. 6 is a 320 MMBtu/hr coal-fired spreader-stoker boiler; Boiler No. 7 is a 536.1 MMBtu/hr pulverized coal-fired boiler; and Coking Boilers No. 1 and No. 2 are each 384 MMBtu/hr coal-fired stoker boilers. Each of the boilers is equipped with an electrostatic precipitator (ESP) for particulate control, and the boilers have SO2 emissions limits to address modeled SO2 NAAQS exceedances in the area. In addition, Solutia has installed a rotating opposed fired air system (ROFA) combustion control to reduce NOx formation on Boiler No. 7. The manufacturer has guaranteed a NOx reduction of 48% with the system. This unit is subject to New Source Performance Standards and has limitations for particulate, SO2, and NOx emissions.
ADEM has concluded that no additional particulate controls would be reasonable for the BART units at Solutia. For Boilers No. 5 and 6, stack tests have shown an overall PM control efficiency for the ESPs to be 98.8%. For Boiler 7, the PM control efficiency has been estimated from stack tests as 99%. Although the coking boilers have not been tested, the particulate control efficiency from the ESPs has been estimated at 96%. ADEM evaluated the option of adding a baghouse to each of the boilers and coking units following the existing ESPs. The cost effectiveness of this control option ranged from $5,462 to $79,995 per ton of particulate.
ADEM determined that no additional controls for Boiler 5, Boiler 6, and the coking boilers would be required for the control of NOx emissions for BART. However, Boiler 7 would be required to meet an emission limit of 0.36 lb NOx/MMBtu with the installation of a ROFA system or a comparable technology. Although the basis for the installation of the ROFA system for Boiler No.7 was the Boiler Maximum Achievable Control Technology rule, the system has been installed and was considered as existing equipment for this case-by-case BART analysis.
Solutia evaluated additional control options for NOx. The available combustion control options included low excess air, burners out of service, biased burner firing, overfire air, low NOx burners, and reburn. Available post-combustion control options included selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). Modeling for all of the additional NOx control options evaluated indicated relatively small to no reduction in visibility impacts.
For the control of SO2, ADEM has determined BART for Boilers 5 and 6 to be an emissions limit of 1.4 lbs SO2/MMBtu. Boiler 7, the largest of the emissions units subject to BART, would be required to meet a limitation of 0.47 lbs SO2/MMBtu with the installation of a flue solvent injection (FSI) system or a comparable technology. ADEM concluded that the addition of any controls for the coking units would negate the viability of the coking units; therefore, no additional controls were proposed for these units.
Solutia evaluated the utilization of lower-sulfur coals, and post-combustion flue gas desulfurization (which would include sorbent injection or wet scrubbers). The use of low-sulfur coal (1.4 lbs SO2/ MMBtu) in Boilers 5 and 6 would provide a reduction of approximately 43%. Currently, Boiler No. 7 is already required to utilize low-sulfur coal. Therefore, the utilization of lower-sulfur coal would only provide a reduction of 7%. In combination with the ROFA system, Solutia has a manufacturer guarantee that the use of a FSI system would reduce SO2 by as much as 60% in Boiler No. 7.
EPA proposes to agree with Alabama’s analyses and conclusions for the BART emissions units located at the Solutia facility.