EPA approves haze limits for two coal-fired Wyoming industrial plants

While rejecting some regional haze NOx decisions from the state of Wyoming related to several coal-fired power plants, the U.S. Environmental Protection Agency is proposing to approve regional haze decisions related to two coal-fired industrial facilities in the state.

In a notice to be published in the June 10 Federal Register, EPA said that is proposing a partial disapproval of a State Implementation Plan related to NOx mandates for several coal-fired plants, including PacifiCorp’s Jim Bridger and Naughton facilities. The agency is proposing a Federal Implementation Plan to replace those state NOx standards with its own limits for those power plants.

But in the same June 10 notice, EPA does propose to approve SIP findings for two industrial facilities in the state of Wyoming that fire coal.

FMC’s Westvaco facility is a trona mine and sodium products plant located in Sweetwater County. FMC Westvaco has two existing coal-fired boilers, Unit NS-1A and Unit NS-1B, that are subject to the Best Available Retrofit Technology (BART) standards under the regional haze program. Unit NS-1A and Unit NS-1B each have a design heat input rate of 887 MMBtu/hr and were constructed in 1975. They are both wall-fired, wet-bottom boilers burning subbituminous coal.

Units NS-1A and NS-1B are currently controlled for NOx with combustion air control with a permit limit of 0.7 lb/MMBtu (3-hour rolling average). The state determined that low NOx burners (LNBs) and overfire air (OFA), LNBs and OFA with selective non-catalytic reduction (SNCR), and LNBs and OFA with selective catalytic reduction (SCR) were all technically feasible for reducing NOx emissions here. The state determined that LNBs plus OFA are reasonable for BART. The state has determined that NOx BART emission limit for these units is 0.35 lb/MMBtu (30-day rolling average).

“We agree with the State’s conclusions, and we are proposing to approve its NOx BART determinations for FMC Westvaco Unit NS-1A and Unit NS-1B,” EPA said. “Although the cost-effectiveness for SNCR is reasonable, we find it reasonable for the State not to select this control technology based on the incremental visibility improvement for this control technology.

Unit NS-1A and Unit NS-1B are currently controlled for PM emissions by electrostatic precipitators (ESPs). They each currently have a PM emission limit of 0.05 lb/MMBtu. The state determined that fabric filters on the wet scrubber, addition of an ESP downstream of the wet scrubber, and replacement of the ESPs with fabric filters were technically feasible options. Baseline PM emissions are 197 tpy for each unit based on a heat input rate of 887 MMBtu/hr and 8,760 hours of operation per year.

Given the high cost of controls, which are higher than what EPA, or other states have considered reasonable for PM, FMC did not evaluate the visibility improvement that would result from the PM controls evaluated. Previous visibility modeling analyses from the source indicate that the contribution in visibility degradation from PM is minor when compared to the effects of NOx and SO2. Results from FMC’s visibility modeling screening and analysis confirm this conclusion.

The state agreed with FMC’s conclusions and did not require FMC to perform additional visibility analyses for the PM control options. The state determined that the current ESP control was reasonable for PM BART. The state has determined that the PM BART emission limits for FMC Westvaco Unit NS-1A and NS-1B are 0.05 lb/MMBtu, 45.0 lb/hr, and 197 tpy.

“We agree with the State’s conclusions, and we are proposing to approve its PM BART determinations for FMC Westvaco Unit NS-1A and Unit NS-1B,” EPA wrote.

General Chemical plant also gets NOx and PM approvals from EPA

General Chemical Green River is a trona mine and sodium products plant. General Chemical’s two existing coal-fired boilers, C and D, are co-located at the facility power plant. Both boilers burn low-sulfur bituminous coal, and they supply power and process steam to mining and ore processing operations. Both boilers are tangentially fired using in-line coal pulverizers. The firing rate is 534 MMBtu/hr for Boiler C and 880 MMBtu/hr for Boiler D.

Boiler C and Boiler D are currently controlled for NOx with LNBs plus OFA with a permit limit of 0.7 lb/MMBtu (3-hour rolling average). In August 2009, the state issued a BART permit to General Chemical that required the source to meet a NOx emission limit of 0.32 lb/MMBtu (30-day rolling average) for both boilers. The state assumed the source could meet this emission limit with new LNBs added to the existing OFA. Upon further investigation, the source determined it could not meet a limit of 0.32 lbs/MMBtu with new LNBs and the existing OFA.

In response to the additional information provided by the source, the state re-examined its BART determination for Boiler C and D. It decided that installing separated overfire air (SOFA) in addition to the existing LNBs and OFA could achieve an emission limit of 0.28 lb/MMBtu. Because SOFA in conjunction with the existing NOx controls could achieve better emission reductions than new LNBs plus OFA, the state eliminated the latter from further consideration in the BART analysis. The state determined that SNCR and SCR were also technically feasible. Baseline NOx emissions are 1,167 tpy for Boiler C and 1,816 tpy for Boiler D based on an average of 2001-2003 actual emissions.

The state determined that NOx BART is the existing LNBs with new SOFA, or a comparable performing technology. It said the new limit should be for Boiler C a level of 0.28 lb/MMBtu (30-day rolling average) and that the NOx BART emission limit for Boiler D is 0.28 lb/MMBtu (30-day rolling average).

“We agree with the State’s conclusions, and we are proposing to approve its NOx BART determinations for General Chemical Green River – Boiler C and D,” said EPA. “Although the cost-effectiveness for SNCR and SCR is reasonable, we find it reasonable for the State not to select this control technology based on the low visibility improvement for these control technologies.”

Boilers C and D are currently controlled by ESPs with permit limits of 50 lb/hr and 80 lb/hr, respectively. General Chemical addressed PM emissions through an abbreviated analysis by using PM BART information from FMC Westvaco. The facilities are similar in size and located about ten miles apart. Baseline PM emissions are 98 tpy for Boiler C and 161 tpy for Boiler D based on the average of 2001-2003 actual emissions.

The state determined that the current ESP control was reasonable for PM BART. The state rejected other controls because of their high cost-effectiveness values. The state determined that the PM BART emission limits for Boiler C are 0.09 lb/MMBtu, 50 lb/hr, and 219 tpy, and that the PM BART emissions limits for Boiler D are 0.09 lb/MMBtu, 80 lb/hr, and 350.4 tpy.

“We agree with the State’s conclusions, and we are proposing to approve its PM BART determination for General Chemical Green River Boiler C and D,” EPA said.

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.