1 

 August 15, 2011 

 Update to the 4-Factor Analysis of Control Options for Devon Energy - Blaine County #1 

Compressor Station – Chinook, Montana 

______________________________________________________________________________ 

Introduction 

As part of the EPA’s efforts to satisfy the Reasonable Progress (RP) requirements of the 

Regional Haze Rule (RHR), a letter was sent to Devon on November 5, 2010 requesting a RP 4-

factor analysis of control options for two large engines at the Blaine County #1 Compressor 

Station. Devon responded on February 25, 2011 in a letter titled “Response to Request for 

Additional Reasonable Progress Information”1. This update to the 4-factor analysis, which 

updates an earlier 4-factor analysis conducted by EC/R dated July 17, 2009, includes 

consideration of information from Devon’s 2011 response document and 2010 documentation 

supporting EPA’s recent promulgation of National Emission Standards for Hazardous Air 

Pollutants (NESHAP)2

. 

Source Description

The Devon Energy Production Company, L.P. operates a natural gas gathering, compression, and 

transmission station. The station gathers field gas and compresses the gas to the required 

pressure for the natural gas transmission system. EPA’s November 5, 2010 reasonable progress 

information request letter to Devon requested an analysis of control options for the following 

emission sources: 

Two 5500 HP Ingersoll-Rand KVR 616 (4-stroke rich-burn reciprocating internal combustion 

engines (4SRB RICE)). 

Consistent with EPA’s November 5, 2010 letter, this 4-factor update addresses only the two 5500 

hp engines. The earlier 4-factor analysis conducted by EC/R, dated July 17, 2009, includes 

information on other emission sources at the facility which is not repeated here. With respect to 

regional haze, the primary pollutant from natural gas-fired RICE is nitrogen oxides (NOx). 

Emissions of particulate matter (PM) and sulfur dioxide (SO2) are relatively small (see Table 1). 

Thus, this analysis is limited to NOx. 

SO2

 (lbs/hr)1

NOx

 (lbs/hr)1

PM10

 (lbs/hr)1

PM2.5

 (lbs/hr)1

0.0045 84.9 0.073 0.073

Table 1. Emission Rates

Blaine County #1 Compressor Station

 

1

 Response to Request for Additional Reasonable Progress Information, from Tracy Carter, Regional Vice President, 

Devon Energy Production Company, L.P., to Venessa Hinkle, U.S. EPA – Region 8. February 25, 2011. 

2

 40 CFR Part 63 Subpart ZZZZ. 
2 

NOx Control Technologies

As described in Devon’s 2011 response document, the Ingersoll-Rand engines are currently 

equipped with an electronic air/fuel controller and electronic fuel valves and ignition, which 

provide manual set-point control of the air/fuel ratio. 

This analysis assumes that the 5500 hp engines at the facility are rich-burn and not lean burn. 

This assumption is based on the Montana Air Quality Permit (MAQP) #1626-08, April 16, 2009,

which identifies both engines as 4-stroke, rich-burn. It is noted, however, that the 2011 Devon 

response document identifies control options appropriate for lean-burn engines, which is not 

consistent with the rich-burn designation in the MAQP. Devon’s 2011 response document identifies 

the following control technologies for NOx reduction: continuous exhaust monitoring system with 

an upgraded ignition system and air/fuel ratio control, Dresser-Rand Mixing Kit for each power 

cylinder, Dresser-Rand Mixing Kit plus Screw in Prechambers, and selective catalytic reduction 

(SCR) with oxidation catalyst. Although some of the technologies identified as possible control 

options at the facility can be implemented on rich-burn engines, including upgraded ignition 

systems and A/F control, and installation of prechambers (a low-emission combustion (LEC) 

technology), SCR is only applicable to lean burn engines. 

Control options for 4SRB natural gas-fired RICE include air-to-fuel ratio (A/F) adjustment, 

ignition timing (IT) adjustment (with or without A/F adjustment), prestratified charge (PSC), low 

emission combustion (LEC), water injection and water/fuel emulsions, and non-selective 

catalytic reduction (NSCR). These options are briefly described below and summarized in Table 

2. 

A/F adjustment

Lowering the availability of oxygen in the cylinder can decrease NOx emissions.3 The IngersolRand engines are already equipped with an electronic A/F controller, but the system requires 

manual adjustment. An automatic A/F controller could be installed to maintain an optimum A/F 

ratio. 

Ignition timing adjustment

By moving the ignition event to later in the power stroke the peak flame temperature can be 

reduced, reducing the formation of NOx.

3

 An upgraded ignition system could provide greater 

reduction in NOx than the existing electronic ignition system at Devon. 

Prestratified charge

PSC is a technology that stratifies the fuel and air mixture so that a fuel-rich layer is created 

around the spark plug while providing an overall fuel-lean mixture. This lowers combustion 

temperatures and reduces NOx emissions.3

Low emission combustion

LEC requires extensive modification of the engine and ancilliary systems to increase the A/F 

ratio and operate in a fuel-lean environment where NOx formation is low. Modifications include 

addition/retrofit of a turbocharger and intercooler or aftercooler; retrofitting the air intake, 

 

3

 State of the Art (SOTA) Manual forReciprocating Internal Combustion Engines, NJ DEP Division of Air Quality. 

2003. 
3 

filtration and exhaust systems to handle increase flow; and modifications to the combustion 

chamber or installation of a pre-combustion chamber.

4

 

Water injection and water/fuel emulsions

Water is injected into the intake system reducing the combustion temperature within the cylinder 

and inhibiting the formation of NOx.

3

Non-selective catalytic reduction

As noted in the 2010 RICE NESHAP regulatory impact assessment (RIA)5, NSCR or three-way 

catalyst is used to control HAP emissions from 4SRB engines. In addition to HAP reductions, 

NSCR also reduces the emissions of nitrogen oxides (NOx), CO, and other hydrocarbons (HC). 

In NSCR, the engine exhaust is routed to a catalyst bed across which NOX is reduced to nitrogen 

gas. At the same time, volatile organic compounds (VOC) and carbon monoxide (CO) are 

oxidized to water and carbon dioxide (CO2). The 2007 RICE NSPS RIA6

 states that NSCR is 

estimated to reduce 90% of NOx, 90% of CO, 50% of non-methane hydrocarbons (NMHC), and 

90% of HAP. The 2002 RICE NESHAP RIA7

 also supports the use of the 90% control efficiency 

value for NOx reduction with NSCR. 

The NSPS and NESHAP support documents highlight application of NSCR on rich burn natural 

gas fired engines. The 2002 RIA refers to NSCR as a lowest achievable emission reduction 

(LAER) or best available control technology (BACT) that could be installed to meet the NOx and 

CO standards of new source review (NSR) or prevention of significant deterioration (PSD) when 

review is triggered by the installation of new engines at a facility. The 2002 RIA also states that 

NSCR technologies have been installed to meet reasonably available control technology (RACT) 

requirements, and it is the method typically used to control emissions from 4SRB engines.7 Due 

to the 2002, 2007 and 2010 NESHAP and NSPS RIA documents’ reliance on NSCR as a control 

technology for NOx reduction in rich-burn RICE, in addition to its higher estimated control 

efficiency presented in table 2, it will be the only technology evaluated for cost effectiveness in 

this analysis. 

Table 2 provides the control efficiencies and potential emission reductions for the control options 

identified for natural gas-fired rich-burn engines. 

 

4

 Alternative Control Techniques Document -- NOx Emissions from Stationary Reciprocating Internal Combustion 

Engines, EPA453/R-93032 

5

 Regulatory Impact Analysis (RIA) for Existing Stationary Spark Ignition (SI) RICE NESHAP, EPA 452/R-10-010. 

August, 2010. 

6

 Regulatory Impact Analysis for the Stationary Spark-Ignition New Source Performance Standard (SI NSPS) and 

New Area Source NESHAP, EPA-452/R-07-015. December, 2007. Control efficiencies for NSCR are on pg. 3-1. 

7

 Regulatory Impact Analysis of the Proposed Reciprocating Internal Combustion Engines NESHAP, EPA-452/R02-012. November, 2002. NOx control efficiency for NSCR is on pg. 2-29. 
4 

Source Name

Source 

Type

Pollutant 

controlled Control Option

Emissions 

(tons/yr)a

Estimated 

Control 

Efficiency (%)b

Potential Controlled 

Emissions

(tons/yr)

Devon Energy - 

Units 1 & 2

4SRB NOX NSCR 743.7 90 669.3

Devon Energy - 

Units 1 & 2

4SRB NOX

A/F 

Adjustment 743.7 20 148.7

Devon Energy - 

Units 1 & 2

4SRB NOX IT Adjustment 743.7 20 148.7

Devon Energy - 

Units 1 & 2 4SRB NOX A/F & IT 743.7 30 223.1

Devon Energy - 

Units 1 & 2 4SRB NOX PSC 743.7 87 647.0

Devon Energy - 

Units 1 & 2 4SRB NOX LEC 743.7 87 647.0

Devon Energy - 

Units 1 & 2

4SRB NOX Water Injection 743.7 30 223.1

Table 2. Estimated Control Efficiencies - Devon Energy

Blaine County #1 Compressor Station

a Emissions = 84.9 lbs/hr (Devon 2011 response document,Table 1) * 8,760 hrs/yr * 1/2000 lb/tons * 2 engines = 

743.7 tons/yr 

b All control efficiency values are from reference 4, except NSCR is from 4, 6 and 7 and water injection is from 3 

(the median value of the provided range of 25-35% was used). Because Devon currently operates electronic A/F 

controllers and ignition, the efficiency values provided for these controls may be overestimated. 

4-Factor Analysis 

EPA’s November 5, 2010 reasonable progress information request letter states that the RP 

analysis must address the four factors included in 40 CFR 51.503(d)(1)(i)(A) (Regional Haze 

program requirements under Subpart P of the requirements for state implementation plans (SIP)). 

This document will address the same four factors which include: the costs of compliance, the 

time necessary for compliance, the energy and non-air impacts of compliance, and the remaining 

useful life of the potentially affected sources. 

Factor 1 – Costs of Compliance 

Table 3 provides a summary of the capital and annual costs and cost effectiveness for retrofitting 

NSCR. The capital and annual costs were estimated using the 2010 control cost memorandum8

provided by EC/R to EPA and used as the basis for the cost data presented in the RIA for 

Existing Spark Ignition RICE NESHAP, August 2010. The memorandum provides annual and 

capital cost equations for NSCR based on engine horsepower: 

 

8

 Memorandum from Bradley Nelson, EC/R Inc. to Melanie King, EPA OAQPS/SPPD/ESG, Control Costs for 

Existing Stationary SI RICE, June 29, 2010. This is the cost memo that is the basis for the cost data presented in the 

RIA for Existing Spark Ignition RICE NESHAP, August 2010. 
5 

Capital cost for NSCR and A/F controller = $24.9 x HP + $13,118 

Annual cost for NSCR = $4.77 x HP + $5,679 

Engine

Pollutant 

Controlled Control Option

Estimated 

Capital Cost 

($)

Estimated 

Annual Cost 

($/yr)

Cost 

Effectivenessa 

($/ton)

Unit 1 NOX NSCR 150,068 31,914 47.7

Unit 2 NOX NSCR 150,068 31,914 47.7

Table 3. Estimated Costs of Control - Devon Energy

Blaine County #1 Compressor Station

a

 Cost effectiveness calculated using the estimated annual cost and the potential controlled emissions. 

Factor 2 – Time Necessary for Compliance 

 According to the Institute of Clean Air Companies (ICAC), it typically takes between 8-

14 weeks to install NSCR control technology, from the bid evaluation through start-up.9 The 

technical support document (TSD) for NOx SIP Call states that the time required to install NSCR 

is less than 11 months.10 

Factor 3 – Energy and Non-Air Impacts 

One concern when implementing an NSCR system is the potential increase in CO emissions. 

NSCR systems require fuel-rich A/Fs to ensure adequate NOx reduction. Emissions of CO 

increase when there is a lack of oxygen to fully oxidize the carbon, as in a fuel-rich atmosphere. 

For this reason, maintaining proper air-to-fuel ratios is critical to reduce potential CO emissions 

from an NSCR system. NSCR can cause an increase in CO emissions of ≤ 37 g/hp-hr.4  

The catalysts used in NSCR systems are made of precious metals and do not contain potentially 

hazardous materials. In addition, many catalyst companies accept the return of spent catalyst 

material.4

In addition to its non-air environmental impacts, NSCR can potentially require a 0-5% increase 

in fuel consumption and a 1-2% reduction in power output.4

Factor 4 – Remaining Useful Life of Potentially Affected Sources 

 Devon’s 2011 response document indicates that the remaining useful life of the engines is 23 

years, with replacement required in 2024.1

 

 

9

 Institute of Clean Air Companies (2006), Typical Installation Timelines for NOX Emissions Control Technologies 

on Industrial Sources. 

10 Stationary Reciprocating Internal Combustion Engines Technical Support Document for NOx SIP Call, EPA, 

OAR, OAQPS, AQSSD, OPSG. October, 2003.