Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 1 

### RECIPROCATING INTERNAL CO MBUSTION ENGINE (RICE) SOURCE
CATEGORY

NOx Emission 4

- F actor A nalysis for Reasonable Progress (RP)

I

. Source Description

The review of potential RP sources involved an evaluation all Colorado stationary sources with actual SO2, NOx or PM10 emissions over 100 tons per year based on Air Pollution Emissions Notice (APEN) reports from 2007. The re were one

- hundred

- thirteen (113) sources id entified as exceeding the 100 tons/year threshold for any of the three pollutan ts which were further analyzed, using ArcGIS mapping, to determine the exact distance from the centroid of the source to the nearest Class I A rea (CIA) boundary. The Q/d was ca lculated for each source , where “Q” is the sum of the SO2, NOx and PM10 emissions in tons per year and “d” is the source distance from the nearest CIA in kilometers; which resulted in the identification of s eventeen (17) point

sources with a Q/d 20

. The Q/d threshold was determined based on conducting a sensitivity analysis of previous subject

- to

- BART CALPUFF modeling of BART eligible sources that
indicated a value of 20 represented about 0. 3 deciview of change in visibility impairment

. An evaluation of the 17 RP sources identified only one source directly associated with RICE equipment, a compressor station (Ignacio B Plant) that uses natural gas

- fired RICE . The Ignacio B compressor station is located southeast of Durango on Southern Ute Indian Triba l land which is outside the jurisdiction of the State of Colorado; consequently the Division is unable to provide a 4

- factor NOx control evaluation and associated determination for this particular RP

source.
In addition to individual point sources with a Q /d 20, the Division evaluated categories of sources that were determined to be significant and subject to evaluation under RP

. The Colorado point source emission inventory indicates that stationary internal combustion engine s ( see below table)

, particul arly large industrial natural gas fired reciprocating internal combustion engine s (RICE)

, are a significant so urce category of NOx emissions that represents about 16% of

stat ewide point source NOx emission inventory 1

. Colorado Internal Combustion Engine N Ox Emissions from the PRP 2018b Emission Inventory

Category Subcategory 2018 NOx Emissions (tpy)

Industrial Natural Gas Fired 16,199
Large Bore Engine 256

Distillate Oil (Diesel) 225
Liquefied Petroleum Gas 27

Gasoline 24

Electric Generation All 4,323

Commercial/Institutional All 1,152
Engine Testing All 5

Total: 22,210

1 Total 2018 Statewide Point Source NOx is projected at 101,818 tons per year based on the WRAP PRP2018b emission inventory.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 2 The majority of the RICE operating in Colorado are associated with the oil and gas industry. The p ower generated by these RICE is generally used to compress natural gas for line
transmission or to generate electricity in remote locations

. The designation “large” refers to RICE that have an engine rating of at least 100 horsepower (hp) for the purpose of this
document

. Stationary RICE produce power by combustion of fuel and are operate d at various air

- to

- fuel
ratios (AFR) . If the stoichiometric ratio is used , the air and fuel are present at exactly the ratio to have complete combustion. An air

- to

- fuel ratio controller uses exhaust O 2 to control the
combustion ratio. RICE that are operated with fuel

- rich ratios (exhaust O 2 < 0.05%) at or near stoichiometric , are called rich

- burn engines (RB) , or alternatively RICE that operate with air

- rich
ratios (exhaust O 2 > 7 to 8%) above stoichiom etric , are called lean

- burn engines (LB)

. The

u ndesirable combustion emissions from natural gas fired RICE are primarily nitrogen oxides (NO x , consisting of primarily nitric oxide and nitrogen dioxide), carbon monoxide (CO), and

vo latile organic compounds (VOCs). Oxides of nitrogen are formed by thermal oxidation of nitrogen from the air. CO and VOCs are byproducts of i ncomplete combustion.

There are site specific consider ations for using either type of engine, depending on the parameters that are most important for the operator. RB engines have lower oxygen levels and higher temperatures in the engine exhaust, which allows for the use of a 3

- way catalyst (non

selective catalyst) which is effective at reducing NO x , CO, and VOC s in the exhaust. Because
the air

- to

- fuel ratio is rich with fuel , more fuel is used, which results in increased combustion temperatures

, increased engine power , and decreased engine efficiency

. Higher temperatures result in more NOx being formed during the combustion process

. Conversely, LB engines have higher oxygen levels in the combustion chamber, which decreases the combustion tempera t ure thereby reducing how much NO x is formed

. Because the air

- to

- fuel ratio is lean with fuel , less fuel is used, which results in decreased combustion temperatures, decreased engine power, and increased engine efficiency. T he use of an oxidation catalyst on a lean burn engine similarly
results in decrease s in CO and VOC emissions but the perform ance for controlling NOxColorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 3 emission s is very low because LB engine exhaust temperatures are below the optimum temperature range for effective NOx control due to reduced catalyst reactivity. The above chart provides the relative change in NOx emissions and e ngine exhaust temperature as a function of
air

- to

- fuel ratio.

II. Natural Gas

- F ired RICE Source Category Emissions

- Statewide

Since natural gas

- fired RICE comprise over 73% of the NOx emissions in statewide RICE source category , the analysis will focus ex clusively on NG

- fired RICE

. In 2018, the statewide NG

- fired
RICE source category is projected to contribute the following emissions :

Statewide Natural Gas Fired RICE Source Category Emissions *

Total Number of
Sources with
NG

- fired RICE Pollutant Number
Sources with
RICE > 100 tpy Number

Sources with
RICE

> 40 tpy Number

Sources
with RICE < 2 tpy 2018

Emissions (tpy)

497 NOx 40 85 82 16,199

SO 2 0 0 486 115

* Point Source Natural Gas Fired RICE Emissions based on APEN report data supplied to the WRAP for the PRP2018b Emission Inventory.

Based on the PRP 2018b emission inventory , statewide there are about 4 97 sources using NG

fired RICE and about 40 sources that emit NOx emissions greater than 100 t ons per year. During a recent 2008 rulemaking, t he Division conducted a detailed analysis of RICE outside the 9

- county metro area (referenced as “statewide”) and determined that the re are about 1,340 NG

fired RICE statewide 2 , w hich includes about 593 NG

- f ired RICE over 500 hp as indicated in the
below t able.

Statewide Natural Gas

- Fired RICE Over 500 Horsepower Outside the 9

- County Metro Area

SCC Description Number of RICE
2

- CYCLE LEAN BURN (NG) 84
4

- CYCLE LEAN BURN (NG) 204
4

- CYCLE RICH BURN (NG) 305
Total: 593

In addition to the 593 RICE listed above, the 2004 Denver Early Action Compact rulemaking
identified 139 NG

- fired RICE 3 over 500 hp that were subject to control requirements of non

selective catalytic reduction on 79 RB RICE and oxidation catalyst on 60 LB RICE in the 9

- county metro area. Conseq uently, there are a total of 732 NG

- fired RICE over 500 hp in
Colorado.

It is difficult to readily determine the exact number of NG

- fired RICE below 500 hp but over 100 hp because engines were sometimes grouped together in a single permit. However, a preliminary
review of APEN data indicates that there are approximately 234 NG

- fired RICE below 500 hp but over 100 hp

. The remaining 513 NG

- fired RICE have design capacities under 100 hp.

2 The Statewide RICE count d oes not include RICE in the 9

- county metro area which was subject to an earlier rulemaking , thus the actual number of total RICE in the State of Colorado is higher

. 3 Reference Final Economic I mpact Analysis

– Revisions to Regulation No. 7, February 11, 2004.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 4 III

. NOx Control Technology Evaluation

Step 1: Identify All Available Technologies

Generally in retrofit applications, NOx emissions from engines can be reduced either through combustion controls or adding post combustion emission controls (e.g., catalysts) to the engine exhaust. Catalysts are designed to speed up desired reactions. The rate of chemical reaction is a function of several parameters, including air

- to

- fuel ratio, engine load and exhaust temperature. Catalysts have specific temperature ranges that must be achieved for optimum NOx reduction.
The belo w diagram roughly depicts the catalyst performance for conversion of NOx emissions using a NSCR and SCR on rich and lean burn engines.

Six retro fit technologies have been identified to lower NOx emissions from rich/lean burn natural gas

- fired internal co mbustion engines.

1. Lean Burn

– Air/Fuel Ratio Adjustment

2. Lean Burn

– Ignition or Spark Timing Retard

3. Rich Burn

– Non Selective Catalytic Reduction (NSCR) Catalyst (3

- way)

4. Rich/Lean Burn

– Selective Non

- Catalytic Reduction (SNCR)

5. Lean Burn

– Sele ctive Catalytic Reduction (SCR)

6. Replacement with electric motors

Colorado requires that emissions from rich burn RICE (applicable statewide 4 ) be controlled using a 3

- way catalyst (NSCR) with air/fuel controller if control costs are below $5,000 per ton

. Few of the statewide rich burn RICE demonstrated control costs exceeding the $5,000 cost off

ramp . C onsequently, the state concludes that such NSCR controls are installed on the majority
of rich burn RICE over 500 HP statewide

. Therefore, the following analysis does not evaluate lower benefit NOx controls such as air/fuel adjustment or ignition/spark timing adjustment for
rich burn RICE despite the technical feasibility of such controls

.

4 Reference Colorado Regulation Number 7, see section XVII.E.3.aColorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 5 It is important to clarify that lean burn RICE are not subject to NOx retro fit controls because Regulation 7 requires statewide l ean b urn RICE over 500 HP to install retrofit oxidation catalyst
control , which i s only effective for control of VOC and CO, if the VOC control cost is under $5,000 per ton. This Regulation was effecti ve as of July 1, 2010

.
Step 2: Eliminate Technically Infeasible Options

Technology #1

- LB (

Air/Fuel Ratio Adjustment ) : This technology is technically feasible.

Technology #2

- LB (

Ignition / Spark Timing Retard

) : This technology is technically feasible.

Technology #3

– RB (3

- way NSCR Catalyst): This technology is technically feasible.

Technology #4

– RB/LB (S NCR ) : This technology is technically feasible.

Technology #

5

– LB ( SCR ) : This technology is technically feasible.

Technology #6

– Replace RICE with electric motors: This technology is technically feasible.

Step 3: Evaluate Control Effectiveness of Each Remaining Control Technology

Technology #1

- Lean Burn (Air/Fuel Ratio Adjustment): I n lean burn engines, increasing the air
to fuel ratio decr eases the NOx emissions. Extra air dilutes the combustion gases, thus lowering peak flame temperature and reducing thermal NOx formation. In order to avoid de

- rating, combustion air to the engine must be increased at constant fuel flow, requiring a turbo charger.
An automatic air

- to

- fuel ratio controller also will be required. This control method is most
effective on fuel

- injected engines. Typically, for lean burn engines the air/fuel ratios are increased from normal levels of 50% excess air up to excess air levels of 240%. The upper limit is constrained by the onset of misfiring at the lean limit. This condition also increases CO and VOC emissions. Naturally aspirated engines and engines with fuel injected into the intake manifold plenum do not have i dentical air

- to

- fuel ratios in each cylinder, this results in limited ability to vary the A/F ratio . To maintain acceptable engine performance at lean conditions, high energy ignition systems (HEIS) have been developed that promote flame stability at very lean
conditions. On lean burn RICE, air/fuel ratio adjustment generally achieves about 5

- 30%
reduction 5 in NOx emissions but is very specific to each engine and typical loading.

Technology #2

- Lean Burn (Ignition/Spark Timing Retard): This adjustment l owers NOx emissions by moving the ignition event to later in the power stroke. Because the combustion chamber volume is not at its minimum, the peak flame temperature will be reduced, thus reducing thermal NOx formation. Ignition timing retard is applica ble to all engines. It is implemented in spark ignition engines by changing the timing of the spark, and in compression ignition engines by changing the timing of the fuel injection. For variable loads, an electronic ignition/injection control system is required. On lean burn RICE, ignition/spark timing retard generally achieves about 20% reduction in NOx emissions.

Technology #

3

- Rich Burn NSCR : This technology uses three

- way catalysts to promote the reduction of NOx to nitrogen and water. CO and hydrocarbons are simultaneously oxidized to carbon dioxide and water. NSCR is applicable only to rich burn engines (i.e. those with exhaust oxygen concentration below about one percent). NSCR, in addition to the catalysts and catalyst

5 Reference

– State of the Art (SOTA) Manual for Reciprocating Internal Combustion Engines, State of New Jersey Department o f Environmental Protection, 2003.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 6 housing, require an oxygen sensor and automatic air to fuel ratio controller to maintain an appropriate air to fuel ratio. Some ammonia can be produced particularly as the catalyst ages. The simplified reactions governing NSCR are as follows:

NOx + CO  CO 2 + N 2 NOx + HC  CO 2 + H 2 O + N 2

The exhaust passes over a catalyst, usually a noble metal (platinum, rhodium or palladium) which reduces the reactants to N2, CO2 and H20. Typical exhaust temperatures for effective
removal of NOx are 800

- 1200 degrees Fahrenheit. An oxidation catalyst using additional air can be installed downstream of the NSCR catalyst for additional CO and VOC control. This includes
4

- cycle naturally aspirated engines and some 4

- cycle turbocharged engines. Engines operating with NSCR require a ir/fuel control to maintain high reduction effectiveness typically around 80 to 90 percent NOx control. Extremely tight control of the air to fuel ratio operating range is accomplished with an electronic air to fuel ratio controller.

Technology #4

- Rich/

Lean Burn SNCR: SNCR is applicable to both lean burn natural gas and diesel engines. SNCR involves injecting ammonia or urea into regions of the exhaust w ith temperatures greater than 1200

– 20 00 degrees Fahrenheit. The nitrogen oxides in the exhaust

ar e reduced to nitrogen and water vapor. Additional fuel is required to heat the engine exhaust to the correct operating temperature. Heat recovery from the engine exhaust can limit the additional fuel requirement and concurrent additional emissions from h eating exhaust gases. Ten parts per million of ammonia (slip) is considered reasonable for SNCR. Temperature is the operational parameter affecting the reaction

- as well as degree of contaminant mixing with reagent and residence time. Additional contro l of particulate matter (up to 85% diesel particulate matter), volatile organic compounds (up to 90 percent) and carbon monoxide (up to 70 percent) may be realized by the afterburning effect of this technology. On both rich burn and lean burn RICE, SNCR g enerally achieves about 50 to 95% reduction in NOx emissions.

Technology #

5

– Lean Burn SCR: SCR uses catalyzed reduction of NOx with injected ammonia or urea solution. This technology is applicable to lean burn engines only (i.e., those with greater
tha n about one percent exhaust oxygen, as oxygen is a reagent in the selective reduction reaction.) SCR may be used with lean burn (SI), dual fuel or diesel engines (CI). SCR produces unreacted ammonia (slip) and monitors are necessary to provide correct co ntrol of ammonia injection rates to minimize slip. When used with diesel engines, it is important to use a low sulfur fuel and sulfur resistant catalyst. Sulfur dioxide in the exhaust can be oxidized over the SCR catalyst to sulfuric acid mist, and when combined with unreacted ammonia, produces sulfate particulate.

For an SCR system using urea, the first stage of the catalyst bed is the hydrolysis catalyst, which converts the urea to ammonia. In the second stage of the catalyst, the ammonia and NOx react to form nitrogen gas and water with some unreacted ammonia passing through. Base metal catalysts, typically vanadium and titanium, are used for exhaust gas temperatures between 450 o F
and 800 o F. For higher temperatures (675 o F to 1100 o F), zeolite catalysts may be used. Both the base metal and zeolite catalysts are sulfur tolerant for diesel engine exhaust. Precious metal SCR catalysts are useful for low temperatures (350 o F to 550 o F). When using precious metal SCR catalysts, attenti on should be paid to the fuel sulfur content and the appropriate formulation
selected. This is not a concern with RICE fired with natural gas.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 7 Reactions of NOx over SCR catalyst:

6NO 2 + 8NH 3  7N 2 + 12H 2 O
6NO + 4NH 3  5N 2 + 6H 2 O
4NO + 4NH 3 + O 2  4N 2 + 6H 2 O
2NO + 4NH 3 + 2O 2  3N 2 + 6H 2 O

An SCR system consists of reagent storage, feed and injection system, and a catalyst and catalyst housing. Predictive mapping of engine operating parameters can be used to monitor and control
the SCR r eaction. Precious metal catalysts can reduce NOx by 80%. Zeolite catalysts can reduce NOx by 90% with minimal sulfur dioxide to sulfur trioxide conversion. Exhaust gas temperatures greater than the upper limit (850 F) will pass the NOx and ammonia unrea cted through the cata lyst.

Technology #6

– Replace RICE with electric motors: This control technology results in complete re duction of NOx emissions at the RICE location, although the electric power provided to the motor must be supplied by a power plant located at some distant location. There is a net reduction in NOx emissions from consolidating operations although the amount of reduction depends on the distance from the power plant as transmission line losses reduce the effectiveness
of this control. Another consideration is the proximity to high voltage lines which may limit the practically of this control option in rural areas.

The below table summarizes each available technology and the technical feasibility for NOx
Control.

NG

- Fired RICE

– NOx Tech nology Options and Technical Feasibility

Technology Emission Reduction Potential (%) Technically Feasible? (Y = yes, N = no) Lean Burn (Air/Fuel Ratio Adjustment) 5

- 30% Y Lean Burn (Ignition/Spark Timing Retard) 20% Y
Rich Burn NSCR 80

- 90% Y

Rich/Lean Burn SNCR 5 0

- 95% Y

Lean Burn SCR 80

- 90% Y Replace RICE with electric motors 60

- 100% Y

Step 4: Evaluate Impacts and Document Results

Factor 1: Cost of Compliance

Technology #1

- Lean Burn (Air/Fuel Ratio Adjustment): I n naturally aspirated LB engines and LB engines where fuel is injected into the intake manifold plenum, each cylinder does not have
an identical air

- to

- fuel ratio, thus changes in the A/F ratio are very limited and therefore of little benefit, although the cost of suc h adjustment is minimal. Additional NOx emission reduction benefit is gained through the addition of a turbocharger and an automatic air

- to

- fuel ratio controller. The cost of adding these controls is very specific to the engine size and design but

genera lly ranges between $320 to $8,300 per ton 6 of NOx reduced

.

6 Reference

– Supplementary Information for Four Factor Analysis by WRAP States, EC/R Incorporated, May 4, 2009, see table 3

- 3.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 8 Technology #2

- Lean Burn (Ignition/Spark Timing Retard ): Based on a general analysis of NG
fired RICE for the WRAP states 4 , the cost of this control ranges between $310 to $2,000 per ton
of NOx depending on engine size and firing design.

Technology #

3

- Rich Burn NSCR : Regulation Number 7 requires r ich b urn RICE over 500 HP to install retrofit NSCR controls if the cost of control is under $5

, 000 per combined ton (NOx and VOC) statewide. This Re gulation was effective as of July 1, 2010. No ne of the operators of

r ich b urn RICE outside the metro

- area ozone non

- attainment area submitted information demonstrating control costs in excess of $5,000 per ton cost threshold , consequently, the majority of natural

- gas fired RB RICE over 500 HP must operate an NSCR with an AFR
controller.

Emission Reduction from NSCR Retrofit of RICE > 500 hp Statewide RICE Category * Count** NO
x Reduction (tpy)

Lean Burn 500 HP 288 minimal***

Rich Burn 500 HP 305 5,800

Notes:

* This data represents statewide RICE, excluding the 9

- c ounty metro area (ozone non

- attainment area ) which was addressed in an earlier rulemaking for the Early Action Compact.

** Data obtained from 2008 APENs

*** Retrofit NSCR for lean burn RICE was not required because of minimal NOx reduction

Annualized Costs for Rich Burn RICE Control Device

Item Capital Costs (one time) O&M

(recurring) Total Annualized

Cost (15 yrs)
NSCR with AFR Controller * $35,000

-

$10,851 Operating

- $6,000

Subtotal Costs : $35,000 $6,000

Annualized Costs : $4,851 $6,000

Notes:

* Cost estimates obtained from "Denver Early Action Compact Analysis of Stationary Sources " Nov

. 3, 2003

Costs Associated with Statewide Retrofit of Natural Gas

- fired RB RICE ≥ 500 HP

Category Number of

Devices Annualized

Cos t per Device Total Device

Cost NO
x Reduction

[tpy] $/ton

NSCR & AFR
Controller 305 $10,851 $3,309,555 5,800 $5 71

Technology #4

- Rich/Lean Burn SNCR: SNCR usually requires reheating of the exhaust to achieve the proper temperature range for effective NOx conversion; this is particularly true for lean burn RICE where excess oxygen results in exhaust temperatures well below the required
levels. The Division was unable to acquire cost information for th is control option, thus no cost estimates have been provided. The scarcity of SNCR data on NG

- fired RICE may suggest other post combustion NOx controls are preferred, p articularly SCR which has more reliable control
effectiveness under a variety of load conditions

.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 9 Technology #5

– Lean Burn SCR: Depending on the engine size, catalyst used and the level of sophistication of the control system, S CR costs generally range about $430 to $4,900 per ton of
NOx reduced.

Technology #6

– Replace RICE with electric motors: Depending on the engine size, length and capacity of the power line required , the costs generally range from $100 to $4,700 per ton of

N Ox reduced 7

. These costs do not include any potential impact from increases in electrical load at the power plant. The true cost of replacing RICE with electric motors is dependent on the distance from the power plant and the amount of compression power required. In actuality, larger compressor stations with multiple large engines would produce significant increased
demands at a nearby power plant and possibly significant demands on the line transmission system that would escalate the costs to levels muc h higher than the $4,700 control cost.
Colorado has about 40 large compressor stations, thus the estimation of costs would require a

case

- by

- case analysis which was not done for this RP evaluation. Although, if all statewide RICE (above 500 horsepower) w ere converted to electric motor compression

, then a minimum of approximately 600 MW of extra generating capacity would be required. Realistically, the actual generating capacity required is probably much higher when transmission losses and peak demand cycles are factored into the load demands.

Factor 2: Time Necessary for Compliance

Technology # 1, 2, 4 , 5 and 6 : If Colorado was to decide to adopt a particular control strategy, up to 2 years will be needed to develop the necessary rules and undergo Legislative review. Subject sources may then require up to a year to procure the necessary capital to purchase control equipment. The I nstitute of Clean Air Companies (ICAC) has estimated that approximately 13 months is required to design, fabricate, and install SCR or SNCR technology for NO X control 8

. However, the time necessary will depend on the type and size of the unit being contro lled. For instance, in past rulemakings, typically 18 months may be required to install a particular control technology on hundreds of engines

. Additional time

, up to 12 months may be required for staging the installation process if multiple sources are to be controlled at a single facility. Based on these figures, the total time required achieve the NOx emission reductions for reciprocating engines is estimated at about 5 years.

Technology #

3: This control option is implemented and was effective on July 1, 2010.

Factor 3: Energy Impacts and Non Air

- Quality Impacts

In general, air

- to

- fuel

- ratio adjustments and ignition retarding technologies have been found to increase fuel consumption by up to 5%, with a typical value 9 of about 2.5%. This increased fuel consumption would result in increased CO 2 emissions. Installation of SCR on any type of engine would cause a small increase in fuel consumption, about 0.5%, in order to force the exhaust gas through the catalyst bed

. This would produce an increase in CO 2 emissions. In addition, spent

7 Bar

- Ilan, Amnon, Ron Friesen, Alison Pollack, and Abigail Hoats (2007), WRAP Area Source Emissions Inventory Protection and Control Strategy Evaluation

- Phase II , Western Governors Associatio n, Denver, Colorado, Chpt 4.

8 Institute of Clean Air Companies (2006), Typical Installation Timelines for NO x Emissions Control Technologies
on Industr ial Sources

. 9 Center for Alternative Fuels, Engines & Emissions (2005), Alice Austen Ferry Emissions Tests, M.J. Bradley &
Associates, Manchester , NH, Page 13

.Colorado Department of Public Health and Environment

- Air Pollution Control Division

Reasonable Progress Evaluation for RICE Source Category Page 10 catalyst would have to be changed periodically, producing an increase in solid waste disposal 10

. Replacing RICE with electric motors may require construction of additional power plants to accommodate increased power de mands.

Factor 4: Remaining Useful Life :

Generally t he operational life of a catalyst is approximately 5 to 15 years, depending upon
factors such as how it is maintained and the particular duty cycle of the engine

.
Step 5 : Select Reasonable Progress Contr ol

The state has determined that control technology #3, rich burn NSCR w/air

- fuel controller, represents reasonable progress for the natural gas

- fired RICE source category in this planning period. The estimated reduction of 5,800 tons/year represents about 36% of the NG RICE total
NOx emissions.

The State of Colorado regulates RICE under Colorado Air Quality Control Commission Regulation No. 7 (Reg. 7) Section XVII. Further NOx emission reduction benefits are anticipated in the future because of tight er NOx emission standards in Regulation 7 that require emissions from RICE shall not exceed the following emission performance standards:

Colorado Emission Standards Natural Gas

- Fired RICE

RICE Horsepower Construction or Relocation Date Emission Standards ( grams /hp

- hr)

NOx CO VOC

< 100 Any NA NA NA

≥ 100 and ≤ 500 On or after 1/1/08 2.0 4.0 1.0

On or after 1/1/11 1.0 2.0 0.7

> 500 On or after 7/1/07 2.0 4.0 1.0

On or after 7/1/10 1.0 2.0 0.7

RICE that are subject to an emissions co ntrol requirement in a federal M aximum A chievable
C ontrol T echnology (MACT) standard under 40 CFR Part 63, a Best Achievable Control Technology (BACT) limit, or a New Source Performance Standard under 40 CFR Part 60 are not subject to Reg

. 7 Section XVII.

10 EPA (2002), EPA Air Pollution Control Cost Manual, 6th ed., EPA/452/B

- 02

- 001, U.S. EPA, Offi ce of Air Quali ty Planning and Standards, RTP

.