4 The record articles

Chemical and Petrochemical Industry Proposed Updates to EMACT, MON, OLD MACT, and RSR

Posted: May 4th, 2023

Authors: Rawan E. 





What Rules are Changing?

On April 27, 2023, the United States Environmental Protection Agency (U.S. EPA) proposed amendments as a result of reconsideration of the following National Emission Standards for Hazardous Air Pollutants (NESHAP):

  • Generic Maximum Achievable Control Technology Standards [40 Code of Federal Regulations (CFR) Part 63 Subparts XX and YY], specifically for ethylene production, referred to as Ethylene Production Maximum Achievable Control Technology (EMACT);
  • Miscellaneous Organic Chemical Manufacturing (40 CFR Part 63 Subpart FFFF), referred to as MON;
  • Organic Liquids Distribution (Non-Gasoline) (40 CFR Part 63 Subpart EEEE), referred to as OLD MACT; and
  • Petroleum Refineries (40 CFR 63 Subpart CC), referred to as the Refinery Sector Rule (RSR).

The following article summarizes the proposed changes to these rules, as well as how they may affect your facility.

What are the Proposed Changes?

The following table provides the proposed revisions, the affected rules, and a high-level summary of the updates. The sections after the table below discuss each of the revisions in additional detail.

Table 1: Proposed revisions, affected rules, and summary of changes.

Proposed Revision Affected Rules Summary of changes
Removing the force majeure allowance from the work Practice Standards for Pressure Relief Devices (PRDs) and Emergency Flaring. PRDs:
MONEmergency Flaring:
  • Removal of term force majeure from the list of defined terms.
  • Removal of force majeure exemption from violation of the work practice standards for atmospheric PRDs and emergency flaring events.
  • Addition of electronic reporting requirements for event-specific work practice standard data for EMACT.
Degassing of storage vessels. EMACT
  • Floating roof storage vessel may be opened prior to degassing to set up equipment (i.e., connections to temporary control device).
  • Opening must be done in a limited manner and must not actively purge the storage vessel while connections are made.
Pressure-Assisted Flares and Mass Spectrometers. RSR
  • Adding pressure-assisted flares to the definition of “flare” at 40 CFR 63.641.
  • Adding requirements for pressure-assisted flares at 40 CFR 63.670.
  • Adding mass spectrometry as an optional method to determine flare gas composition at 40 CFR 63.671.
Technical corrections, clarifications, and corrections of typographical errors. EMACT

PRDs and Emergency Flaring

The regulations define what constitutes a violation of the work practice standards for atmospheric PRD releases and emergency flaring events. The regulations currently exempt force majeure events (i.e., releases of HAP directly to atmosphere from a PRD or flare from an event beyond the owner/operator’s control as defined in 40 CFR 63.641) from being considered as violations.

During the reconsideration of the rules, the U.S. EPA deemed that the force majeure allowance in the work practice standards may lead to difficulties determining compliance. As part of their proposed reconsideration, the U.S. EPA concluded that the events associated with atmospheric PRD and emergency flaring were infrequent, and force majeure events within those categories were even more rare. Due to the low frequency of force majeure events, the U.S. EPA is proposing to remove the term and the exemption associated with these events. If EPA finalizes the revisions as proposed, facilities will no longer be able to exclude force majeure events when determining whether a violation of the PRD and emergency flare work practice standard has occurred.

Storage Vessel Degassing

The rules associated with degassing standards for storage tanks during shutdown operations require that liquids be removed to the extent practical, and tanks be degassed to a process or control device until the lower explosive limit (LEL) standard is met prior to being vented to atmosphere. The U.S. EPA set the standards regardless of roof type (fixed or floating) and received comments from petitioners that “including a storage vessel degassing standard for floating roof storage vessels was not a logical outgrowth of the proposal and that it was not possible to comment on this standard.” In addition, petitioners requested that U.S. EPA allow facilities to open floating roof storage tanks for the purposes of preparing for degassing, such as connecting the tank to a temporary control device.

The U.S. EPA concluded that degassing standards are required for all storage vessels, regardless of roof type. They are proposing that a floating roof storage vessel may be opened prior to degassing to set up equipment (i.e., make connections to a temporary control device), but this must be done in a limited manner and the facility must not actively purge the storage vessel while connections are made.

Pressure-Assisted Flares and Mass Spectrometers

The U.S. EPA is proposing amendments to the RSR to include the following:

  • Pressure-assisted flares to the definition of the term “flare” at 40 CFR 63.641
  • Requirements for pressure-assisted flares in 40 CFR 63.670 which include:
    • Pilot flame standards;
    • Requirements for cross-lighting;
    • Pressure monitoring;
    • Higher combustion zone operating limits;
    • Requirements to use only the direct calculation methods for determining the flare vent gas net heating value; and
    • Reporting and recordkeeping requirements specific to pressure-assisted flares.
  • Mass spectrometry as an optional method for determination of flare vent gas composition.

These changes are being proposed to align RSR flare requirements with those in the MON and EMACT rules.

Technical corrections, clarifications, and corrections of typographical errors

Many technical corrections, clarifications, and corrections of typographical errors are proposed by the U.S. EPA for EMACT, MON, OLD MACT, and RSR. Some corrections other than those typographical and/or clarifications in nature are discussed below:

  • EMACT :
    • Ethylene Cracking Furnace and delay of burner repair provisions: The U.S. EPA is proposing allowing delay of burner repair beyond one calendar day if the repair cannot be completed during normal operations, the burner cannot be shut down without significantly impacting the furnace heat distribution and firing rate, and action is taken to reduce flame impingement as much as possible during continued operation.
    • Isolation valve inspection and repair: The U.S. EPA is proposing that facilities may wait and rectify isolation valve issues after a decoking operation, provided that the owner or operator can reasonably demonstrate that damage to the radiant tube(s) or ethylene cracking furnace would occur if the repair was attempted prior to completing a decoking operation and/or prior to the ethylene cracking furnace being shut down.
  • MON:
    • Heat Exchange Requirements: The U.S. EPA is proposing that leak monitoring requirements for heat exchange systems at 40 CFR 63.104(b) (also known as water analysis methods) may be used if 99% or more of all the organic compounds that could leak into the cooling water have a Henry’s Law Constant less than 5.0E-6 atmospheres per mole per cubic meter at 25°C instead of using the Modified El Paso Method to monitor for leaks.

What does this mean for your facility?

U.S. EPA is not proposing to extend currently applicable compliance dates for any of the rules, except the new RSR flare requirements apply on the effective date of the final revised rule.

Public comments on the proposed revisions are due to the U.S. EPA on June 12, 2023.

For additional information on how the proposed rulemaking may affect your facility or for assistance commenting on the proposed revisions, please contact Rawan El-Afifi at relafifi@all4inc.com or 281-201-1251. A webinar associated with the updates to the rules discussed and other chemical sector rules is planned for July 2023.


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