## Denver Metropolitan Area and North Front Range
8-Hour Ozone State Implementation Plan

Technical Support Document

For Proposed Pneumatic Controller Regulation

DRAFT
November 5, 2008

Colorado Department of Public Health and Environment
Air Pollution Control Division 4300 Cherry Creek Drive South Denver, Colorado 80246Colorado Department of Public Health and Environment / Air Pollution Control Division

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division



# Table of Contents

1. PROPOSED REGULATION

............................................................................................................................... 1

2. WHAT IS A PNEUMATIC DEVICE? ................................................................................................................1

3. WHY WAS THIS PROPOSED REGULATION DEVELOPED? ....................................................................2

4. WHY IS THIS PROPOSED REGULATION REASONABLE? .......................................................................2

4.1. T IMEFRAME

............................................................................................................................... .....................2

4.2. A SSOCIATED C OSTS

............................................................................................................................... .........2

4.3. C ONVERSION E FFECTIVENESS .........................................................................................................................3

4.4. E MISSION T HRESHOLD

............................................................................................................................... .....3

4.5. A PPLYING R EGULATION TO ONLY H IGH -B LEED D EVICES ..............................................................................3

5. DATA AND CALCULATIONS ...........................................................................................................................4

5.1. E MISSION R EDUCTION

............................................................................................................................... .....4

6. REFERENCES

............................................................................................................................... .......................6

ATTACHMENT 1 - PNEUMATIC DEVICE PROPOSED REGULATION DATA AND CALCULATIONS .....7

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division



## 1. Proposed Regulation

Regulation being proposed to the Air Quality C ontrol Commission in Fall 2008 would require that high-bleed natural gas actuated pneumatic contro llers in ozone non-attain ment areas (NAAs) be replaced or retrofit (converted) to low-bleed controllers, unless they are exempt. The proposed regulation would also allow for other means to re duce emissions, such as using a solar device or a device that is actuated, or powere d, using compressed air. Inspections, enhanced maintenance, and recordkeeping would be required for remaining ex empt high-bleed controllers. Implementation of this proposed regulation would l ead to a reduction in emissions of volatile organic compounds (VOCs), which are precursors to ozone.

Most background information and data used to develop the proposed regulation were obtained from either the Environmental Protection Agen cy (EPA) Gas STAR program or Independent Petroleum Association of Mountain States (IPAM S). Both sources use the term pneumatic “device”, while the Colorado Air Pollution Control Division (Division) has chosen to be more specific by using the term pneumatic “controller” in the proposed regulation. A pneumatic device generally consists of a controller and a valve. The term “device” is used throughout this document to be consistent with data provided by EPA Gas STAR program and IPAMS.



## 2. What is a pneumatic device?

Many types of process control devices can be used to operate valves that regulate pressure, flow, temperature, and liquid levels. These devices can be operated pneumati cally, electrically, or mechanically. A pneumatic device is an instrument th at is actuated using gas. Most of the devices used by the natural gas industry are pneumatically operated. Alt hough instrument air is commonly used to power pneumatic devices at gas processing f acilities, since electricity is readily available to power air compressors at the facilities, the majori ty of natural gas industr y pneumatic devices are powered by natural gas since electricity is not readily available at remote locations. 1

As part of normal operation, most pneumatic devi ces emit, or “bleed”, gas to the atmosphere, either continuously or intermittently. Pneumatic devices generally consist of a controller and a

valve. Bleed rates are associ ated with the controller. Gas is vented to atmosphere during actuation when valves open and/or close. Howeve r, vent rates are not significant and are the same whether a high-bleed or low-bleed controller is used. The pr oposed regulation would address bleed rates from controllers that are actuated by natu ral gas. It will not address valve vent rates or controllers actuated by compressed air.

By definition, high-bleed pneumatic devices emit in excess of 6 standard cubic feet gas per hour (scfh) to atmosphere. The highest bleed rate list ed in a table published by the EPA is 42 cubic feet per hour (cfh). 1 The average bleed rate for high-bleed pneumatic devices in the Denver-Julesburg (DJ) Basin is 17cfh. 2 Bleed rates of 6, 17, and 42 cfh natural gas represent emission sources of 0.3, 0.8, and 2.1 tons per year (tpy) VOC, respec tively, assuming a VOC molar fraction of 7.47 percent, which is representative of the DJ Basin. 2

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division



## 3. Why was this proposed regulation developed?

A 2003 EPA study reported that emissions from pn eumatic devices are collectively one of the largest sources of methane emissions in the na tural gas industry. Natural gas is primarily composed of methane, but also contains VOC s and hazardous air pollutants (HAPs). Annual

nationwide methane emissions are estimated to be approximately 31 billion cubic feet (Bcf) from the production sector, 16 Bcf from the processing sector, and 14 Bcf from the transmission sector. 1

VOC emissions from pneumatic devices within the 9-county Denver Me tro Area/North Front Range (DMA/MFR) NAA were estimated to be 24.8 tons per day (tpd) for the 2006 baseline and have been projected to be 31.1 tpd for the 2010 ba seline. These emissions represent 13 and 15 percent of the total VOC emissions from oil and gas sources in the DMA/MFR NAA in 2006 and 2010, respectively. 3 This source category, pneumatic de vices, has the second highest VOC emissions within the oil and gas i ndustry. Therefore, emission re ductions related to this source category have the potential to be si gnificant. It is estimated that if this proposed regulated is implemented, 2010 VOC emissions will be reduced by approximately 23 tpd.



## 4. Why is this proposed regulation reasonable?

4.1. Timeframe
Many companies have already converted hi gh-bleed devices to low-bleed devices voluntarily, as evidenced from responses to a Section 111 information request letter that the Division mailed to industry in June 2008. At a minimum, industry has committed to converting approximately 95 percent of hi gh-bleed devices to low-bleed devices by November 2008. Therefore, if the proposed regulation is adopted in February 2009, it is anticipated that vendors would have enough suppl y on hand to satisfy orders for low-bleed

devices and retrofit kits. There has been enough supply during the recent and ongoing

conversions.

Under the proposed regulation, companies would be prohibited from installing a high-bleed device after February 1, 2009, unl ess the Division grants an exemption. The Division would approve use of a high-bleed device if a company can demonstrate that it is not technically feasible (e.g., safety or process concerns) to use a low-bleed device in a specific application. High-bleed pneumatic devices that are in place as of the anticipated regulation implementation date must be converted to lo w-bleed devices within three months (by May 1, 2009), unless the Division grants an exemption.



### 4.2. Associated Costs
Because implementation of this proposed re gulation would increase the amount of natural gas that industry can sell, companies have the potential to save money. Calculations related to proposed regulation are available in Attachment 1 of this document. Costs (savings) associated with th is proposed regulation include:

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division

• Cost per ton of reduced VOC associat ed with converting existing pneumatic devices and performing enhanced mainte nance on remaining high-bleed devices would represent an estimated savings of $747

• Weighted average annualized cost associ ated with converti ng existing pneumatic devices and performing enhanced mainte nance on remaining high-bleed devices would represent an estimated savings of $1,505

• Weighted average annualized cost associated with installing low-bleed pneumatic devices for new applications and perform ing enhanced maintenance on remaining high-bleed devices would represen t an estimated savings of $1,630

• Payback time period of implementing this proposed regulation is estimated to be 3

to 24 months



### 4.3. Conversion Effectiveness
The service life and process cont rol ability of low-bleed pneumatic devices is comparable to that of high-bleed devices in most applicat ions. Low-bleed devices are no more likely to fail than high-bleed devices. 4 If a device does fail, the process would no longer be controlled. For example, if a level controller fails, the dump valve would remain open.

This would lead to a shortened residence tim e, which would not allow adequate separation between condensate and water. The mixed liqui ds would flow directly to a tank. This failure would be noticed during a regular site visi t. It is anticipated that a device that fails would be repaired as soon as possible.



### 4.4. Emission Threshold
Typically, the threshold to require a permit for VOC sources in a Colorado NAA is 2 tpy. An average high-bleed pneumatic device emission rate in the DMA/MFR NAA is approximately 0.8 tpy of VOC. An average lo w-bleed pneumatic device emission rate in the DMA/MFR NAA is approximately 0.1 tpy of VOC. 2 The proposed regulation is targeting high-bleed devices, which have VOC emissions ranging from 0.3 to 2.1 tpy in the

DJ Basin. While the low end of the emission ra nge is a lower threshold than required for other emission sources, industry is already conve rting most high-bleed devices. Therefore, this proposed regulation repres ents a reasonably simple me ans of ensuring further VOC reductions. If the proposed regulation only a pplied to high-bleed devices emitting above typical thresholds, emission testing for high-bl eed devices may be required to determine how many tons per year VOC were being emitted from each device. That could require

additional resources both for i ndustry and the Division.

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### 4.5. Applying Regulation to only High-Bleed Devices

IPAMS estimated that in 2006 there were 41,494 pneumatic devices in the DMA/MFR NAA. Of those, 5,524 were high-bleed (13% of total), 34,847 were low-bleed (84% of total), and 1,122 were actuated with compresse d air and therefore do not emit any natural gas or VOCs (3% of total).

If 5 percent of high-bleed devi ces receive an exemption from the Division, an estimated

276 devices would be allowed to re main in place based on 2006 data. 2 The percentage of exempt high-bleed devices, 5 percent, is base d on the projection that 95 percent of devices would be converted from high-bleed to low-bl eed devices. The regulation would require

DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division

that enhanced maintenance be performed on a ll high-bleed devices. Enhanced maintenance potentially reduces emissions. It includes cl eaning, tuning, and repairing leaking gaskets, tubing fittings, and seals; t uning to operate over a broader range of proportional band; and eliminating unnecessary valve positioners. Routine inspect ion and recordkeeping would also be required for remaining high-bleed devices.

Emissions associated with low- bleed devices are a fraction of the emission threshold level, 2 tpy, and of high-bleed device emissions. Ther efore, it is reasonable to avoid the burdens of inspection, enhanced maintenance, a nd record keeping for low-bleed devices.



## 5. Data and Calculations

Most data used in calculations performed to support proposed regulations regarding pneumatic devices are from an IPAMS report. 3 Data used to determine the number of devices that would be converted or require enhanced maintenance and em ission reductions as a result of the proposed

rule include:

• Estimated number of devices in 2006 located within the DJ Basin, by device bleed rate

• 2006 VOC device emissions and fraction of wells in each DJ Basin county

• Average VOC fraction and molecular weight in DJ Basin natural gas

Most data used in cost analysis calculations we re obtained from vendors. Costs include purchase, installation, operation, maintenance, and the bene fit earned from sale of natural gas that had previously been emitted to the atmosphere. Costs were obtained to replace or retrofit two of the most common types of devices, liquid level controll ers and pressure controllers. Costs of these four scenarios were averaged into one scenario.

All data and calculations used to support proposed regulations regarding pneumatic devices are available in Attachment 1, Pneumatic Device Proposed Regulation Data and Calculations.



### 5.1. Emission Reduction
To calculate the reduction of VOC emissions that would occur in the NAA if the proposed regulation is implemented, the following st eps were followed. The calculations are

available in Attachment 1.

1. Obtain emissions for baseline cases: 24.8 tpd (baseline 2006) , 31.1 tpd (baseline 2010)

2. Obtain total bleed rate emissions from high bleed devices in the NAA by adding bleed rate emissions of each high bleed device in the NAA: 150,885 cfh (calculation for each type of high-bleed device based on number and bleed rate of each type of device; see Attachment 1 spr eadsheet, sheet “device calc”, column S)

3. Obtain total bleed rate emissions fr om low-bleed devices in the NAA by adding

bleed rate emissions of each low-bleed device in the NAA: 30,823 cfh (calculation for each type of low-bleed device based on number and bleed rate of each type of device; see Attachment 1 spreadsheet, sheet “device calc”, column T):

4 4. Obtain 2006 baseline emissions (emissions in terms of bleed rate) by adding the total bleed rate emissions of high bleed de vices in the NAA to the total bleed rate

DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division

emissions of low-bleed devices in the NAA: 150,885 cfh + 30,823 cfh = 181,708

cfh

5. Obtain the 2006 total bleed rate emissions of low-bleed devices in the NAA (baseline): see step 3 (same parameter; 30,823 cfh)

6. Obtain the 2006 total bleed rate emissions of low-bleed devices in the NAA (converted from high-bleed if proposed regulation had been implemented) by adding bleed rate emissions of each conve rted low-bleed device in the NAA: 10,148 cfh (calculation for each type of converted low-bleed device based on number and bleed rate of each type of de vice; see Attachment 1 spreadsheet, sheet “device calc”, column U)

7. Obtain the 2006 total bleed rate emi ssions of high-bleed devices in the NAA (remaining 5%, taking into account enhan ced maintenance) by adding bleed rate emissions of each remaining high blee d device in the NAA taking into account

bleed rate reductions from enhanced ma intenance: 4,782 cfh (calculation for each type of high-bleed device based on number and bleed rate of each type of device taking into account bleed rate reductions from enhanced maintenance ; see Attachment 1 spreadsheet, sheet “device calc”, column W) 8. Obtain 2006 projected emissions (emissions in terms of bleed rate) by adding the

total bleed rate emissions of low-bleed de vices in the NAA (baseline) to the total

bleed rate emissions of low-bleed devices in the NAA (converted from high-bleed if proposed regulation had been implemented) and total bleed rate emissions of highbleed devices in the NAA (remaining 5%, taking into account enhanced maintenance): 30,823 cfh + 10,148 cfh + 4,782 cfh = 45,754 cfh 9. Obtain reduction percent obtained from implementing proposed regulation based on 2006 baseline emissions and 2006 projected emissions (as if proposed regulation had been in place) (emissions in terms of bleed rate): (181,708 cfh – 45,754 cfh) / 181,708 cfh = 0.75 or 75% 10. Obtain 2010 projected emissions base d on 2010 baseline emissions and reduction percent obtained from implementing proposed regulation: 31.1 * (1-0.75) = 7.8 tpd

11. Obtain VOC emission reduction that woul d occur in NAA if proposed regulation is implemented by subtracting 2010 project ed emissions from 2010 baseline emissions: 31.1 tpd – 7.8 tpd = 23.3 tpd

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DRAFT - Denver Metro Area/North Front Range 8-hr Ozone SIP Technical Support Document for Proposed Pneumatic Controller RegulationColorado Department of Public Health and Environment / Air Pollution Control Division



## 6. References

1 . US EPA, Lessons Learned: Options for Reducing Me thane Emissions from Pneumatic Devices in the Natural Gas Industry

2. ENVIRON, Buys and Associates, and IPAMS, Development of Baseline 2006 Emissions from Oil and Gas Activity in th e Denver-Julesburg Basin , February 7, 2008

3. ENVIRON, Buys and Associates, and IPAMS, Development of Baseline 2006 Emissions from Oil and Gas Activity in th e Denver-Julesburg Basin , March, 2008

4. Conversations between the Division and industry/vendor s; additionally, doc ument available at http://www.fossil.energy.gov/programs/oilgas /publications/environ_be nefits/14fsprod.pdf

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## Attachment 1 - Pneumatic Device Proposed Regulation Data
and Calculations

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