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August 15, 2011

Update to the 4-Factor Analysis of Control Options for Devon Energy - Blaine County #1 Compressor Station – Chinook, Montana

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Introduction

As part of the EPA’s efforts to satisfy the Reasona ble Progress (RP) requirements of the Regional Haze Rule (RHR), a letter was sent to Devo n on November 5, 2010 requesting a RP 4- factor analysis of control options for two large en gines 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 E C/R dated July 17, 2009, includes consideration of information from Devon’s 2011 res ponse document and 2010 documentation supporting EPA’s recent promulgation of National Em ission Standards for Hazardous Air Pollutants (NESHAP) 2

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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. E PA’s November 5, 2010 reasonable progress information request letter to Devon requested an an alysis of control options for the following emission sources:

Two 5500 HP Ingersoll-Rand KVR 616 (4-stroke rich-b urn 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 conducte d by EC/R, dated July 17, 2009, includes information on other emission sources at the facili ty which is not repeated here. With respect to regional haze, the primary pollutant from natural g as-fired RICE is nitrogen oxides (NO x ). Emissions of particulate matter (PM) and sulfur dio xide (SO 2 ) are relatively small (see Table 1). Thus, this analysis is limited to NO x .

**SO 2**  **(lbs/hr) 1**  **NO x** 

**(lbs/hr) 1**  **PM 10** 

**(lbs/hr) 1**  **PM 2.5** 

**(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 Prog ress Information, from Tracy Carter, Regional Vice President, Devon Energy Production Company, L.P., to Venessa H inkle, U.S. EPA – Region 8. February 25, 2011.
2 40 CFR Part 63 Subpart ZZZZ.2

NO x 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 ra tio.

This analysis assumes that the 5500 hp engines at t he 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-bur n. It is noted, however, that the 2011 Devon response document identifies control options approp riate for lean-burn engines, which is not consistent with the rich-burn designation in the MA QP. Devon’s 2011 response document identifies the following control technologies for NO x reduction: continuous exhaust monitoring system wit h an upgraded ignition system and air/fuel ratio cont rol, Dresser-Rand Mixing Kit for each power cylinder, Dresser-Rand Mixing Kit plus Screw in Pre chambers, and selective catalytic reduction (SCR) with oxidation catalyst. Although some of th e 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 precha mbers (a low-emission combustion (LEC) technology), SCR is only applicable to lean burn en gines.

Control options for 4SRB natural gas-fired RICE inc lude 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 wate r/fuel emulsions, and non-selective catalytic reduction (NSCR). These options are brie fly described below and summarized in Table 2.

A/F adjustment Lowering the availability of oxygen in the cylinder can decrease NO x emissions. 3 The IngersolRand engines are already equipped with an electroni c A/F controller, but the system requires manual adjustment. An automatic A/F controller cou ld 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 NO x . 3 An upgraded ignition system could provide greater reduction in NOx than the existing electronic ignit ion system at Devon.

Prestratified charge PSC is a technology that stratifies the fuel and ai r mixture so that a fuel-rich layer is created around the spark plug while providing an overall fu el-lean mixture. This lowers combustion temperatures and reduces NO x emissions. 3

Low emission combustion LEC requires extensive modification of the engine a nd ancilliary systems to increase the A/F ratio and operate in a fuel-lean environment where NO x 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 In ternal Combustion Engines, NJ DEP Division of Air Q uality. 2003.3

filtration and exhaust systems to handle increase f low; 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 t he combustion temperature within the cylinder and inhibiting the formation of NO x . 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 (NO x ), CO, and other hydrocarbons (HC). In NSCR, the engine exhaust is routed to a catalyst bed across which NO X is reduced to nitrogen gas. At the same time, volatile organic compounds ( VOC) and carbon monoxide (CO) are oxidized to water and carbon dioxide (CO 2 ). The 2007 RICE NSPS RIA 6 states that NSCR is estimated to reduce 90% of NOx, 90% of CO, 50% of n on-methane hydrocarbons (NMHC), and 90% of HAP. The 2002 RICE NESHAP RIA 7 also supports the use of the 90% control efficienc y value for NO x reduction with NSCR.

The NSPS and NESHAP support documents highlight app lication 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 NO x and CO standards of new source review (NSR) or preventi on of significant deterioration (PSD) when review is triggered by the installation of new engi nes at a facility. The 2002 RIA also states that NSCR technologies have been installed to meet reaso nably available control technology (RACT) requirements, and it is the method typically used t o control emissions from 4SRB engines. 7 Due to the 2002, 2007 and 2010 NESHAP and NSPS RIA docu ments’ 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 onl y technology evaluated for cost effectiveness in this analysis.

Table 2 provides the control efficiencies and poten tial emission reductions for the control options identified for natural gas-fired rich-burn engines.

4 Alternative Control Techniques Document -- NOx Emi ssions from Stationary Reciprocating Internal Combu stion Engines, EPA453/R-93032
5 Regulatory Impact Analysis (RIA) for Existing Stat ionary Spark Ignition (SI) RICE NESHAP, EPA 452/R-1 0-010. August, 2010.
6 Regulatory Impact Analysis for the Stationary Spar k-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 Recipro cating Internal Combustion Engines NESHAP, EPA-452/ R02-012. November, 2002. NO x 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 NO X NSCR 743.7 90 669.3

Devon Energy - Units 1 & 2 4SRB NO X A/F Adjustment 743.7 20 148.7

Devon Energy - Units 1 & 2 4SRB NO X IT Adjustment 743.7 20 148.7

Devon Energy - Units 1 & 2 4SRB NO X A/F & IT 743.7 30 223.1

Devon Energy - Units 1 & 2 4SRB NO X 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 NO X Water Injection 743.7 30 223.1

Table 2. Estimated Control Efficiencies - Devon En ergy

Blaine County #1 Compressor Station

a Emissions = 84.9 lbs/hr (Devon 2011 response docume nt,Table 1) * 8,760 hrs/yr * 1/2000 lb/tons * 2 en gines = 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% w as used). Because Devon currently operates electro nic A/F controllers and ignition, the efficiency values pro vided for these controls may be overestimated.

4-Factor Analysis

EPA’s November 5, 2010 reasonable progress informat ion 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 require ments for state implementation plans (SIP)). This document will address the same four factors wh ich include: the costs of compliance, the time necessary for compliance, the energy and non-a ir 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 annua l costs and cost effectiveness for retrofitting NSCR. The capital and annual costs were estimated u sing the 2010 control cost memorandum 8 provided by EC/R to EPA and used as the basis for t he cost data presented in the RIA for Existing Spark Ignition RICE NESHAP, August 2010. T he memorandum provides annual and capital cost equations for NSCR based on engine hor sepower:

8 Memorandum from Bradley Nelson, EC/R Inc. to Melan ie King, EPA OAQPS/SPPD/ESG, Control Costs for Existing Stationary SI RICE, June 29, 2010. This i s 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**

**Effectiveness a**  **($/ton)**

Unit 1 NO X NSCR 150,068 31,914 47.7

Unit 2 NO X 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 t he bid evaluation through start-up. 9 The technical support document (TSD) for NO x 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 adequ ate NO x reduction. Emissions of CO increase when there is a lack of oxygen to fully ox idize the carbon, as in a fuel-rich atmosphere. For this reason, maintaining proper air-to-fuel rat ios 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 prec ious metals and do not contain potentially hazardous materials. In addition, many catalyst co mpanies accept the return of spent catalyst material. 4

In addition to its non-air environmental impacts, N SCR can potentially require a 0-5% increase in fuel consumption and a 1-2% reduction in power o utput. 4

Factor 4 – Remaining Useful Life of Potentially Aff ected 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 I nstallation Timelines for NO X Emissions Control Technologies on Industrial Sources.
10 Stationary Reciprocating Internal Combustion Engin es Technical Support Document for NO x SIP Call, EPA, OAR, OAQPS, AQSSD, OPSG. October, 2003.