EHS Administration, Sustainability

EPA Considers Revising Flare Pollution Regulations

As a result of lawsuits filed by 10 environmental groups, the EPA has signed two consent decrees requiring the Agency to consider updates to toxic air standards for industrial flaring, which is used as a pollution control measure to combust waste gas compounds at petrochemical plants and storage tanks.

These air standards have not been updated for 26 years, reports the Environmental Integrity Project (EIP), the lead environmental group on the lawsuit EIP v. EPA.

The suit, filed in October 2020, was brought to require the EPA to update its general operating requirements for flares under the National Emission Standards for Hazardous Air Pollutants (NESHAP) and New Source Performance Standards (NSPS).

“EPA first issued the general NSPS flare requirements over three decades ago, in 1986, and the general NESHAP flare requirements 28 years ago, in 1994,” according to an EIP Fact Sheet. “The agency has not updated the general flare requirements in the several decades since they were first issued.”

Alternatively, the lawsuit sought to require the EPA to review and revise the NESHAP and NSPS for certain categories of air pollution sources that incorporate the outdated general flare requirements.

In 2021, Concerned Citizens of St. John, the Louisiana Environmental Action Network, and the Sierra Club brought a separate lawsuit concerning the EPA’s review of the air toxics standards for polymers and resins facilities. The second consent decree resolves this lawsuit.

The first and second consent decrees require the EPA to study and consider updates to its air toxics standards for flares and other polluting units at certain polymer, epoxy resin, non-nylon polyamides, and resin petrochemical plants. The Agency is required to sign a proposed rule “containing all ‘necessary’ revisions” by March 31, 2023. The decrees require the same study and consideration of updates to standards for marine tank loading operations, with any “necessary” rule revisions due by December 19, 2025.

The consent decrees will also require the Agency to consider updating its standards for new and modified storage tanks holding volatile organic liquids, including the standards for flares controlling air pollution from those tanks, by September 29, 2023.

Other environmental groups joining in the suit were the Clean Air Council, Air Alliance Houston, Chesapeake Climate Action Network, Earthworks, Environment America, Environment Texas, Hoosier Environmental Council, Penn Environment, and Texas Campaign for the Environment.

The EPA backlog

The Clean Air Act (CAA) requires NESHAP and the NSPS to be updated every 8 years.

The EIP lawsuit highlights the litigious path environmental groups regularly employ to force the Agency to meet its statutory obligations.

An EPA Office of Inspector General (OIG) report dated March 30, 2022, noted the Agency has 93 overdue mandated risk and technology reviews (RTRs) or recurring 8-year technology reviews (TRs) and that 93 of the 169 industrial sources had overdue RTRs or TRs. Those sources with overdue reports include petrochemical plants, according to the EIP lawsuit.

The OIG report recommended the EPA:

  1. “Perform a workforce analysis to determine the staff and resources needed to meet the statutory deadlines for residual risk and technology reviews, initial technology reviews, and recurring eight-year technology reviews, as well as to complete any such reviews that are overdue.
  2. Develop and implement a strategy to conduct (a) residual risk and technology reviews and recurring technology reviews by the applicable statutory deadlines and (b) any overdue residual risk and technology reviews and recurring technology reviews in as timely a manner as practicable.  The strategy should take into account the Agency’s environmental justice responsibilities under Executive Order 12898 and other applicable EPA and executive branch policies, procedures, and directives.”

NSPS and NESHAP regulations for flaring efficiency

A 2012 EPA Enforcement Alert states the minimum federal requirements under the regulations require flares to be:

  • Designed and operated with no visible emissions using EPA Method 22 (except for periods not to exceed 5 minutes in 2 hours).
  • Operated with a flame present at all times, confirmed by the use of a thermocouple or an equivalent device.
  • Used only when the net heating value of the gas to be combusted is 300 British thermal units (Btu) per standard cubic foot (scf) or greater (if the flare is steam- or air-assisted) or 200 Btu/scf or greater (if the flare is nonassisted).
  • Designed for and operated with an exit velocity less than 60 feet per second (ft/sec). An exit velocity of greater than 60 ft/sec but less than 400 ft/sec may be used if the net heating value of the gas being combusted is sufficiently high.

“Since at least 2012, EPA has recognized that its decades-old flare requirements cannot ensure that many flares properly destroy air toxics and other pollutants,” reports the EIP. “For example, in 2015, the agency instituted more stringent requirements for flares at petroleum refineries to reduce their toxic air pollution.  At the time, EPA estimated that the improved refinery flare standards would reduce hazardous air pollution by 3,900 tons per year and emissions of volatile organic compounds by 33,000 tons per year.”

The 2015 Performance Standards made changes that the EPA stated streamlined the compliance approach for refiners by:

  • “Simplifying the requirements to a single net heating value operating limit in the flare combustion zone of greater than or equal to 270 BTU/scf.
  • Allowing refiners to use a higher adjusted hydrogen heating value provided that they have a system to monitor for hydrogen.
  • Allowing refiners to choose between either a 15 minute feed forward or a 15 minute block average to demonstrate compliance.
  • Allowing refiners to use limited sampling to demonstrate compliance for non-variable flare gas compositions.”

Factors impacting flare performance

The EPA identified the following factors affecting the performance of flares.

Flame quenching in the combustion zone. Problems occur because:

  • Facilities mistakenly believe that excess steam or air will allow good combustion.
  • Facilities fail to reduce steam or air when vent gas flow transitions from high to low.
  • Facilities have minimum steam addition rates to protect the flare tip from overheating. During low waste gas flow, the resulting steam-to-vent gas ratio can be very high, causing oversteaming.
  • The steam control equipment associated with a steam-assisted flare lacks adequate flow adjustment precision, which results in excess steam flow at low waste gas flow.
  • The air blower associated with an air-assisted flare lacks adequate flow adjustment, which results in excess air at low waste gas flow.

These problems lead to significantly lower flare combustion efficiencies. Options to correct the problem include:

  • Continuously measure the flow rate of the waste gas, and continuously measure, and then control, the steam or air being added as assist gas.  Follow the manufacturer’s recommendations and publicly available documents in setting proper assist gas rates.
  • Utilize automatic damper actuators or variable frequency drives on the air supply system.
  • Reduce the “minimum” or “cooling” steam rates as low as possible while still being protective of the physical integrity of the flare.

Low heat value in vent gas. Problems occur because:

  • Facilities use flares to control a variety of streams with varying quality.  When only one or a few low-flow sources are venting to the flare, the volumetric flow and combustible material concentrations can be minimal.
  • Batch processes are inherently variable and will have periods of very low flow or high inert (e.g., nitrogen) concentrations. Inert gas lowers the heating value of the gas mixture.
  • Supplemental fuel requirements can be costly; facilities may choose not to incur that cost and will combust the low heating value stream alone.
  • Facilities conduct compliance tests under the maximum conditions where problems with low heating values are unlikely. In practice, flares are not always operated at these “ideal” rates.

These problems lead to lower flare combustion efficiencies. Options to correct the problem include:

  • Ensure that the vent gas meets the current regulatory heating value limits of 300 Btu/scf for assisted flares and 200 Btu/scf for unassisted flares at all times. This will require evaluating the heating value of vent gas over the full range of operating scenarios.
  • Determine the heating value of the vent gas as a whole, not only the hydrocarbons in the vent gas, just before it leaves the flare tip. The heating value evaluation includes nitrogen and any other compounds that make up the gas mixture that is present just inside the flare tip.
  • Monitor the vent gas flow, and automatically supply supplemental fuel if the vent gas does not have sufficient heating value.
  • Evaluate other control options, and limit flare use to true emergency situations.

Issues with frequent flaring

An October 2000 EPA Enforcement Alert notes that “flaring frequently occurs in routine, nonemergency situations or is used to bypass pollution control equipment,” resulting “in unacceptably high releases of sulfur dioxide and other noxious pollutants. …”

“Flaring at the numerous petrochemical plants and storage tanks in the Houston Area is a virtually routine occurrence,” said Jennifer M. Hadayia, executive director of Air Alliance Houston, in an EIP article about the consent decrees. “Just last week, we were subjected to a flare event that emitted enough air pollution to fill 2 million lungs. Houstonians have waited long enough for change, and we join our partners in acknowledging the important first step that EPA has taken today to hold polluters accountable and protect public health.”

The 2000 Enforcement Alert warns against classifying repeated or regularly occurring flaring events as “malfunctions” because they can be anticipated.

“These upsets should be addressed through improved operational control systems, improved and frequent training of operators, and continued optimal performance of the [Sulfur Recovery Plant], not by bypassing or flaring acid gas and sour water stripper gas.”

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