1 Summary of Alternate Compliance Technology Studies

2 The Company completed eight noteworthy technical studies to evaluate 

3 NOx, PM and SO2 emission control alternative technologies for Naughton Unit 3, 

4 the first of which also apply to the Hunter Unit 1 projects included in this docket 

5 for review. In October 2002, Sargent and Lundy (“SL”) completed a fleet-wide 

6 Multi-Pollutant Control Report as an attorney-client privileged work product; in 

7 January 2005, SL completed a NOx emissions reduction technologies study; in 

8 March 2006, SL completed a Conceptual Design of Replacement Baghouse 

9 PacifiCorp Naughton 3 study; in February 2007, CH2M Hill completed the BART 

10 Analysis for the Naughton Unit 3; in December 2009, SL completed the SCR and 

11 Baghouse Study Report; in October 2012, Alstom completed the Naughton Unit 3 

12 Engineering Study to Evaluate 100% Gas Firing Fuel Heat Input; in November 

13 2012, SL completed the Naughton Station Conversion of Unit 3 to 100% Natural 

14 Gas Firing study; and in March 2013, Alstom completed the Naughton Unit 3 

15 Engineering Study to Evaluate 100% Gas Fuel Input Including Evaluation of Flue 

16 Gas Recirculation and Low Load Operation. 

17 1. The Multi-Pollutant Control Report provided an early investigation of the cost 

18 and necessity of NOx, particulate matter (“PM”) and sulfur dioxide (“SO2”) 

19 emission controls on the units.

20 2. The 2005 NOx emission reduction technologies study compared sixteen 

21 emission control technologies, status of the technology development, 

22 predicted performance, approximate initial capital costs, and approximate 

23 incremental fixed and variable operational and maintenance (“O&M”) costs. 
24 3. The Conceptual Design of Replacement Baghouse PacifiCorp Naughton 3 

25 study established initial capital costs for PM emissions control alternatives.

26 4. The BART Analysis for the Naughton Unit 3 was conducted for criteria 

27 pollutants NOx, PM10 and SO2. The Company conducted the BART analysis 

28 and determination to analyze the effects on visibility in nearby Class I areas 

29 (Bridger, Fitzpatrick and Mt. Zirkel Wilderness Areas). A BART analysis is a 

30 comprehensive evaluation of potential NOx, PM and SO2 retrofit 

31 technologies, and a BART determination is an emissions limit established by 

32 the application of potential retrofit technologies for each unit. The specific 

33 steps in a BART analysis are established in 40 CFR 51 Appendix Y, Section 

34 IV. The analysis must include: (1) the identification of available and 

35 technically feasible retrofit alternatives; (2) consideration of any pollution 

36 control equipment in use at the source (which affects the availability of 

37 alternatives and their effects); (3) the costs of compliance with control 

38 alternatives; (4) the remaining useful life of the facility; (5) the energy and 

39 non-air quality environmental impacts of compliance; and (6) the degree of 

40 visibility improvement that reasonably may be anticipated from installation of 

41 the BART alternative.

42 5. The SCR and Baghouse Study Report evaluated and established design criteria 

43 and specified critical equipment features to mitigate design risks for a SCR 

44 and baghouse technology alternative.

45 6. The Naughton Unit 3 Engineering Study to Evaluate 100% Gas Firing Fuel 

46 Heat Input assessed the boiler thermal performance impacts; firing system 
47 performance and emissions impacts; controls impacts; and potential boiler 

48 pressure part and firing system component modifications that may be required 

49 to add natural gas firing capability to the unit based on operation with 100% 

50 fuel heat input at full load. 

51 7. The Naughton Station Conversion of Unit 3 to 100% Natural Gas Firing

52 study investigated the scope of work and estimated costs for converting the 

53 unit from a base loaded coal unit to a natural gas fueled peaking unit while 

54 leaving coal firing capability intact to the greatest extent practicable. 

55 8. The Naughton Unit 3 Engineering Study to Evaluate 100% Gas Fuel Input 

56 Including Evaluation of Flue Gas Recirculation and Low Load Operation

57 assessed thermal performance of the unit at low load and provided an 

58 evaluation of NOx emissions control using a FGR alternative at both high and 

59 low loads.

60 Key Study Points

61 Salient points from these eight studies, and related information from other 

62 sources, are presented with following statements:

63 The Multi-Pollutant Control Report indicated that combination “in64 combustion” (Low NOx Burners with Over Fire Air) and “post combustion” 

65 (Selective Catalytic Reduction) would need to be installed on Hunter Unit 1 to 

66 achieve a presumptive NOx emission rate of less and 0.10 pounds per million 

67 British thermal units (lb/mmBtu)

68 The Multi-Pollutant Control Report indicated that a combination of “in69 combustion” and “post-combustion” controls (namely a SCR) would need to be 
70 installed on Naughton Unit 3 to achieve a presumptive NOx emissions limit of 

71 less than 0.10 pounds per million British thermal units (“lb/mmBtu”). 

72 The Multi-Pollutant Control Report indicated that the Hunter Unit 1 ESP 

73 could achieve a particulate emission level of 0.030 lb/mmBtu with reasonable 

74 modifications and upgrades, and it further indicated that that maintenance costs 

75 would need to increase over time to facilitate the rebuilds necessary to keep the 

76 current equipment operational at historic levels. In order to achieve an emission 

77 level below 0.020 lb/mmBtu, the Multi-Pollutant Control Report indicated a 

78 polishing baghouses retrofit would need to be completed.

79 The Multi-Pollutant Control Report indicated that Naughton Unit 3 would 

80 require extensive modifications to the existing ESP or a “polishing baghouse 

81 retrofit” must be completed to meet a presumptive PM emissions limit of less than 

82 0.030 lb/mmBtu. The Naughton Unit 3 ESP is the smallest in the Company’s coal 

83 fleet, is about 40 years old, and is in poor condition. It does have a flue gas 

84 conditioning system to improve its performance. Historical operating data 

85 establishes that the existing ESP’s best PM emissions rate is only approximately 

86 0.04 lb/mmBtu.

87 The Multi-Pollutant Control Report indicated that the Hunter Units 1 FGD 

88 system could achieve a removal efficiency of 90% with the following system 

89 upgrades: (1) close the scrubber bypass damper (2) upgrade the existing mist 

90 eliminators (3) add vertical flow mist eliminators (4) improve inlet gas 

91 distribution (5) upgrade existing reheat system (6) upgrade spray header and 
92 nozzle system (7) replace existing spray pumps (8) convert to a forced oxidation 

93 system (9) restore and upgrade dewatering equipment.

94 The Multi-Pollutant Control Report, and other sources, indicated that a 

95 FGD upgrade SO2 removal efficiency of 90% would be achieved on the existing

96 Naughton Unit 3 FGD with only minor changes including: (1) improvements to 

97 the inlet gas distribution; (2) the liquid to gas contact point would need to be 

98 reviewed; (3) reagent and waste delivery systems needed to be upgraded; (4) a

99 reagent adjustment; and (5) consideration of a conversion to an open spray type 

100 absorber. 

101 At units with high baseline NOx emissions (high is defined here as being 

102 greater than 0.40 lb/mmBtu), it is common utility industry practice to initially 

103 obtain a NOx emissions reduction through the installation in-combustion 

104 modifications, similar to the LNBs installed on the units, and then control the 

105 remainder of any required NOx emissions reduction with post-combustion control 

106 systems, typically either SCR or a selective non-catalytic reduction system 

107 (“SNCR”). 

108 NOx control technologies are grouped as either in-combustion control, 

109 post-combustion control or emerging types:

110 • In-Combustion Controls include: (1) LNBs with overfire air (“OFA”); (2) 

111 more precise combustion control of fuel and air; (3) combustion optimization 

112 using a Neural Network system; and (4) Nalco Mobotec rotating opposed fire 

113 air (“ROFA” or “rotating opposed fire air”) which is a next generation OFA 

114 system.
115 • Post-Combustion Controls include: (1) SNCR, typically limited to only 10 to 

116 40 percent NOx emissions reduction and have higher ammonia slip rates; and 

117 (2) SCR with 80 to 90 percent NOx emissions reduction and a low ammonia 

118 slip rate.

119 • Other emerging NOx reduction technologies (and that might become 

120 commercially available, or more commercially feasible, within the next 

121 decade) with the capability to achieve required NOx removal percentages 

122 include: (1) Regenerative Activated Coke Technology; (2) Powerspan Electro123 Catalytic Oxidation; (3) BOC LoTOx System; (4) Airborne Process; (5) 

124 Consolv Technologies Absorption Process; (6) Lean Gas Reburning; (7) Rich 

125 Reagent Injection; (8) SNCR plus SCR hybrid systems; (9) Aptech CST 

126 SNCR type systems; and (10) other reagent injection developments.

127 Of the technology alternatives mentioned herein, only LNB with OFA, 

128 ROFA, SNCR with LNB, and SCR with LNB were considered BART analysis 

129 feasible alternatives for NOx reduction across the fleet. 

130 In a SCR, ammonia (“NH3”) reacts with NOx contained in the flue gas 

131 exiting the boiler as either nitrogen oxide (“NO”) or nitrogen dioxide (“NO2”) in 

132 the presence of catalyst to form molecular nitrogen (“N2”) and water (“H2O”). 

133 Catalyst enhances the reaction between ammonia and NOx. The injected air134 diluted ammonia is adsorbed on the catalyst surfaces in the SCR reactors and 

135 reacts with oxygen and NOx present in the flue gas according to the following 

136 chemical reaction equations:

137 4NH3 + 4NO + O2 → 4N2 + 6H2O

138 4NH3 + 2NO2 + O2 → 3N2 + 6H2O
139 SNCR technology is similar to SCR because it involves injection of an 

140 amine reducing agent like urea solution. The reduction chemistry, however, takes 

141 place in the boiler without the aid of any catalyst. SNCR relies on appropriate 

142 injection temperatures, proper mixing of the reagent and flue gas, reagent 

143 injection kinematics, and prolonged boiler detention time in place of the catalyst. 

144 SNCR operate at higher temperatures than SCR. The effective temperature range 

145 for SNCR is 1,600 to 2,100 degrees F. SNCR is sensitive to temperature changes. 

146 Table NT3-5-1 summarizes a comparison of NOx emissions control 

147 technologies results adapted from the BART Analysis for the Naughton Unit 3 on 

148 a 2007 cost year basis: Other environmental project costs not included in the

149 BART estimates include: boiler and air preheater casing structural reinforcements, 

150 flue gas path structural reinforcement, a high and low temperature EEGT control 

151 system, demolition, auxiliary power system upgrades, Owner’s project costs and a 

152 contingency allowance. 
Table NT3-5-1: Oxides of Nitrogen Emissions Control Technologies Comparison

(Adapted From CH2M Hill BART Analysis)

Technology

Projected 

Emission 

Rate

(lb/mmBtu)

Projected 

Emission % 

Reduction

(%) (b)

Capital Cost

($ x million)

O&M Cost 

Fixed + 

Variable

($ x million)

Annual 

Power 

Usage

(1,000 

MWh/yr)

First Year 

Avg. Cost For 

NOx Removal 

($/ton)

Baseline 0.50 (a) 0% 0.0 0.0 0.0 0

LNBs with 

OFA 0.35 22.2% 0.0 (c) 0.1 0.0 0

ROFA 0.28 37.8% 14.7 1.9 35.3 1,326

Selective NonCatalytic 

Reduction and 

LNBs with 

OFA

0.28 37.8% 15.8 0.9 2.6 984

Selective 

Catalytic 

Reduction and 

LNBs with 

OFA

0.07 84.4% 92.0 2.6 15.7 2,049

(a) Emissions from PI data in table below; prior to LNB and OFA installations on Unit 3, the uncontrolled 

emissions rate was approximately 0.50 lb/mmBtu

(b) Technology reduction rates from the CH2M Hill BART analysis shown

(c) Currently installed on Naughton Unit 3

153 The baseline NOX concentration of 0.50 lb/mmBtu was established from 

154 Naughton Unit 3 performance historian (“PI”) data and confirmed with 

155 continuous emissions data and flue gas testing. 

156 PM emissions control technologies evaluated for Naughton Unit 3 include: 

157 (1) install a stand-alone baghouse to replace the existing ESP; (2) install a 

158 polishing fabric filter (Compact Hybrid Particulate Collector or (“COHPAC”)) to 

159 operate in series with the existing ESP; (3) rebuild the existing ESP; and (4) 

160 replace the existing ESP with a Reversing Gas Fabric Filter (“RGFF”), which is a 

161 PM cleaning device currently not often selected for use in steam electric plants.

162 Feasible technical alternatives to meet a PM emissions compliance limit of 

163 0.015 lb/mmBtu are: (1) install a polishing baghouse and operate it in series with 
164 a rebuilt ESP; and (2) install a stand-alone baghouse. The Design of Replacement 

165 Baghouse PacifiCorp Naughton 3 study established initial capital costs in 2006 

166 dollars for these two alternatives.

167 The Naughton Unit 3 Engineering Study to Evaluate 100% Gas Firing 

168 Fuel Heat Input reported that the unit can be converted from the current coal 

169 firing configuration and made capable to operate at full load on 100% natural gas 

170 without significant boiler equipment or pressure part modifications. NOx 

171 emissions of approximately 0.09 to 0.12 lb/mmBtu were predicted with natural 

172 gas firing, consequently indicating it would be necessary to install a post173 combustion SNCR process or other post-combustion NOx control process if a 

174 NOx emissions limit of approximately 0.08 lb/mmBtu is required. An alternative 

175 FGR was proposed instead of adding a post-combustion NOx control system. The 

176 FGR can simultaneously achieve the desired NOx emissions limit at 0.08 

177 lb/mmBtu while also achieving design steam temperatures more easily and over a 

178 broader load range. Alstom offered an opinion that potential furnace 

179 modifications that include FGR and or waterwall refractory alternatives would 

180 provide greater flexibility for NOx and carbon monoxide (“CO”) control when 

181 firing 100% natural gas, and would be necessary from a performance standpoint if 

182 the boiler were to be operated at low loads.

183 The Naughton Unit 3 Engineering Study to Evaluate 100% Gas Fuel Input 

184 Including Evaluation of Flue Gas Recirculation and Low Load Operation

185 reported that Naughton Unit 3 can be converted from the current coal firing 

186 configuration and made capable to operate at full load on 100% natural gas 
187 without significant boiler or pressure part modifications. The addition of a FGR is 

188 required to mitigate steam temperature reductions when attempting to attain 

189 required NOx emissions at full load. A FGR is also required to maintain high final 

190 reheat steam temperatures at a low load of approximately 85 MW. Alstom 

191 reported an FGR operated at about 20% FGR at full load, operated in conjunction 

192 with Alstom’s recommended natural gas firing system and the existing SOFA 

193 system, is predicted to result in a NOx emissions range of 0.06 to 0.09 lb/mmBtu 

194 and a CO emissions rate at less than 0.15 lb/mmBtu.

195 Beyond the eight studies discussed above, The EPSCO International, Inc., 

196 Phase III Recommendations study of the Hunter and Huntington electrostatic 

197 precipitators (ESP) was used as the basis for the decision to convert the Hunter 

198 Unit 1 ESP to a baghouse. The decision making process began when the same 

199 type of conversion was made at Huntington Unit 2 (2004-2006). The ESP at 

200 Hunter Unit 1 and Unit 2 and Huntington Unit 1 and Unit 2 are identical and in 

201 2003 it had become apparent that the ESP’s were having operational difficulties. 

202 EPSCO International, Inc. was hired to study the situation, identify options and 

203 make recommendations for the Huntington and Hunter units. The EPSCO report 

204 titled Phase III Recommendations was published in November 2003.