Appendix A. NPS Comments on Milton R. Young Station (MRYS) Baseline Emissions

Minnkota p4-3: 4.1 RANK OF NOX CONTROL OP TIONS BY EFFECTIVENESS The first step in this supplemental “top-dow n” BACT evaluation is to determine the expected control effectivene ss of the hypothetical applicatio n of tail end and low-dust SCR technology alternatives, so that they may be compared and ranked relative to the technically-feasible NO X control techniques and technolog ies included from the initial NO X BACT Analysis Study report. To do this, we start with the basis for determining the NO X emissions control effectiveness, which is the historic baseline emissions expressed in pounds per million Btu of heat input from the five-year lookback period.

NPS: Use of historic baseline emissions is pe rmissible only if they are documented and do not determine the outcome of the analysis/or constraints are enforceable, and provided that the cost-effectiveness is compared to similar sources using similar approaches. According to the NSR Workshop Manual [ emphasis added ]:

“...baseline emissions are essentially uncontrolled emissions, calculated using realistic upper boundary operati ng assumptions.”

“...in developing a realistic upper boundary case, baseline emissions calculations can also consider inherent physical or oper ational constraints on the source.

Such constraints should accurately reflect the true upper boundary of th e source's ability to physically operate and the applicant should submit docume ntation to verify these constraints . If the applicant does not adequately verify these constraints, then the reviewing agency should not be compelled to consider these constraints in calculating baseline emissions. In addition, the reviewing agency may require the applicant to calculate cost effectiveness based on values exceeding the upper bou ndary assumptions to determine whether or not the assumptions have a deciding role in the BACT determination. If the assumptions have a deciding role in the BACT determinat ion, the reviewing agency should include enforceable conditions in the permit to assure that the upper bound assumptions are not exceeded.

In addition, historic upper bound operating data, typical for the source or industry, may be used in defining baseline emissions in evaluatin g the cost effectivene ss of a control option for a specific source. For example, if for a source or industry, historical upper bound operations call for two shifts a day, it is not necessary to as sume full time (8760 hours) operation on an annual basis in calculating baseline emissions. For comparing cost effectiveness, the same realistic upper boun dary assumptions must, ho wever, be used for both the source in question and other sources (or source categories) that will later be compared during the BACT analysis. ”MRYS #1 Baseline Emissions

Minnkota p4-4: Unit 1 boiler’s baseline pre-cont rol emissions at Milton R. Young Station are based upon the same highest ro lling 12-month averag e unit emission rate (lb/mmBtu) and corresponding hi ghest rolling 12- month aver age gross heat input rate (mmBtu/hr) that were reported in 2001-2005:

• MRYS Unit 1’s highest 12-month NOX ma ss emissions averaged 0.849 lb/mmBtu at a corresponding average unit heat input rate of 2,744 mmBtu/hr and unit gross electrical output of 244.5 MWg.

• During this lookback time period, Unit 1 at Milton R. Young Station was typically operated in a base-loaded manner.

NPS: MRYS #1’s highest annual NO X mass emissions averaged 0.866 lb/mmBtu in 1995 and 0.843 in 2004. MRYS #1’s highest annual averag e unit heat input rate of 2,761 mmBtu/hr occurred in 2003. MRYS #1’s highest annual availability of 97% occurred in 2001 and again in 2004.

In its 2009 BART determination, NDDH stated that MRYS #1 had a Boiler Rating of 3,200 x 10 6 Btu/hr , with 2000 – 2004 NO x emissions averaging 8,665 tons/year (tpy) and 0.81 lb/mmBtu. NDDH used a baseline emission rate of 9,032 tpy. The subsequent NDDH BART permit again stated th e rated capacity as 3,200 mmBtu/hr and limited NO x emissions to 0.36 lb/mmBtu on a 30-day ro lling average; there were no limits on annual emissions.

In its 2010 BACT determination, NDDH stated that MRYS Unit 1 had a heat input of 2,728 mmBtu/hr and 2003 – 2007 NO x emissions averaging 9,081 tpy and 0.840 lb/mmBtu. NDDH calculated a maximum emissi on rate of 9,676 tpy and used a baseline emission rate of 9,934 tpy. ASOFA would achieve 0.513 lb/mmBtu

.

According to Tom Bachmann of NDDH (4/26/10 e-mail), “the Title V Permit to Operate limits NO x emission from Unit 1 to 2752 lb/hr

... This effectively caps annual emissions...” to 12,054, tpy at 8760 hr/yr operation which is equivalent to 0.86 lb/mmBtu @ 3,200 mmBtu/hr @ 100% utilization. It is clear that NDDH is using 3,200 mmBtu/hr heat input, 100% utilization, and 0.86 lb/mmBtu in conducting its BART analyses and developing its Title V permit.

2In the absence additional constraints, baseline emissions for the purpose of evaluating the cost-effect iveness of additional NO x controls should be estimated at 0.86 lb/mmBtu and SCR cost-effectiveness sh ould be assumed at 0.513 lb/mmBtu @ 3,200 mmBtu/hr with 100% capacity utilization. 1 This yields a baseline NO x emission rate of 12,054 tpy for the uncontrolled situation and 7,190 tpy for the emissions into the SCR.

MRYS #2 Baseline Emissions

Minnkota p4-4: Unit 2 boiler’s baseline pre-cont rol emissions at Milton R. Young Station are based upon the same highest ro lling 12-month averag e unit emission rate (lb/mmBtu) and corresponding hi ghest rolling 12- month aver age gross heat input rate (mmBtu/hr) that were reported in 2001-2005: • MRYS Unit 2’s highest 12-month NO X mass emissions averaged 0.786 lb/mmBtu at a corresponding average un it heat input rate of 4,885 mmBtu/hr and unit gross electrical output of 440 MW. • During this lookback time period, Unit 2 at Milton R. Young Station was typically operated in a base-loaded manner.

NPS: MRYS #2’s highest annual NO X mass emissions averaged 0.856 lb/mmBtu in 2007. MRYS #2’s highest annual average un it heat input rate of 5,230 mmBtu/hr occurred in 1997. MRYS #2’s hi ghest annual availability of 95% occurred in 2000 and again in 2008.

In its 2009 BART determination, NDDH stated that MRYS #2 had a Boiler Rating of 6,300 x 10 6 Btu/hr , with 2000 – 2004 NO x emissions averaging 14,705 tons/year and 0.81 lb/mmBtu. NDDH used a baseline emi ssion rate of 15,507 tpy. The subsequent NDDH BART permit again stated th e rated capacity as 6,300 mmBtu/hr and limited NO x emissions to 0.35 lb/mmBtu (excluding star tup) on a 30-day rolling average; there were no limits on annual emissions.

In its 2010 BACT determination, NDDH stated th at MRYS #2 had a heat input of 4,691 mmBtu/hr and 2003 – 2007 NO x emissions averaging 14,858 tons/year and 0.835 lb/mmBtu. NDDH calculated a maximum emissi on rate of 15,818 tpy and used a baseline emission rate of 15,793 tpy. ASOFA would achieve 0.489 lb/mmBtu

.

1 According to the NSR Workshop Manual, “For comparing cost effectiveness, the same realistic upper boundary assumptions must, however, be used for both the source in question and other sources (or source categories) that will later be co mpared during the BACT analysis.” In its Table 8, NDDH has used costeffectiveness data from permits issued by Wyoming to Basin Electric for its Dry Fork PC boiler and to Black Hills Power for its Wygen 3 PC boiler. Because both of those cost-effectiveness an alyses were based upon 100% utilization of the PC boilers, NDDH must use the same 100% capacity utilization for comparison to MR Young. (At 97% availability, the historic maximum availability for MRYS #1, the baseline NO

x emission rates would be 11,704 tpy for the uncontrolled situation and 6,982 tpy for the emissions into the SCR.)

34 According to Tom Bachmann of NDDH (4/26/10 e-mail), “the Title V Permit to Operate limits NO x emission...to...5418 lb/hr from Unit 2. This effectively caps annual emissions...” to 23,731, tpy at 8760 hr/yr operation which is equivalent to 0.86 lb/mmBtu @ 6,300 mmBtu/hr @ 100% utilization. It is clear that NDDH is using 6,300 mmBtu/hr heat input, 100% utilization, and 0.86 lb/mmBtu in conducting its BART analyses and developing its Title V permit.

In the absence additional constraints, baseline emissions for the purpose of evaluating the cost-effect iveness of additional NO x controls should be estimated at 0.86/b/mmBtu and SCR cost-effectiveness should be assumed at 0.489 lb/mmBtu @ 6,300 mmBtu/hr with 100% capacity utilization. 2 This yields a baseline NO x emission rate of 23,731 tpy for the uncontrolled situ ation and 13,493 tpy for the emissions into the SCR.

2 At 95% availability, the historic maximum availability for MRYS #2, the baseline NO

x emission rates would be 22,652 tpy for the uncontrolled situation and 12,880 tpy for the emissions into the SCR.)