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Without Further Delay, the Final Risk and Technology Review for the Miscellaneous Organic Chemical Manufacturing NESHAP is Here (Almost)

Posted: June 25th, 2020

Authors: Philip C. 

The much-anticipated Final Risk and Technology Review (RTR) for the National Emission Standards for Hazardous Air Pollutants (NESHAP): Miscellaneous Organic Chemical Manufacturing, otherwise known as “the MON,” is finally here. Well, sort of.  The U.S. Environmental Protection Agency (U.S. EPA) signed the final rule on May 29, 2020 and posted a pre-publication version on their website shortly thereafter.  Although we’re still waiting on official publication in the Federal Register (and all the supporting information to be posted to the docket), affected facilities can do the following to start planning necessary changes to their operations now:

  • Read the final rule! A red-line strike-out version of the rule will be available in the docket upon publication of the final RTR in the Federal Register, and while it’s easier to identify changes in the rule using a red-line version, we recommend reading the pre-publication version now to get a head start on any action you need to take.
  • Evaluate how the new requirements for ethylene oxide described below will affect you. Do you need to gather additional data?
  • Plan projects that will be required for compliance. Develop a timeline and schedule.   Can you accommodate these projects into an already planned outage such that the compliance deadline can be met?
    • Affected sources that started construction after December 17, 2019 must be in compliance with the new requirements on startup, or when the final rule is published in the Federal Register, whichever is later.
    • Existing sources must be in compliance with the new EtO control standards within 2 years of publication, the new equipment leaks standards within 1 year of publication, and the new heat exchange system and gap filling provisions (e.g., SSM and maintenance vents) within 3 years. Electronic reporting of performance tests and evaluations is required within 60 days of publication of the final rule, and the requirement to monitor new or replaced equipment for leaks is effective upon publication of the final rule.
  • Identify what air permitting, if any, will need to be completed to support possible capital projects.
  • Determine what additional information must be monitored and recorded to comply with the revised monitoring, recordkeeping, and reporting requirements.
  • Determine what internal procedures and plans need to be updated as a result of the rule changes.

What are the Most Significant Changes?

Two of the most significant changes are almost identical to those we have seen in other rules:  revised flare requirements and work practices for pressure relief devices (PRD).  However, the most notable changes U.S. EPA finalized are those related to control of ethylene oxide (EtO) emissions.

U.S. EPA found that risks from the source category unacceptable due, in part, to emissions of EtO from process vents, storage tanks, and equipment leaks.  The results of the Agency’s risk assessment were largely influenced by the 2016 unit risk estimate (URE) for EtO from U.S. EPA’s Integrated Risk Information System (IRIS).  U.S. EPA solicited and received several comments on the use of the IRIS value, and ultimately decided to continue using the IRIS value while noting that the Agency is “open” to new values such as the dose response value finalized by the Texas Commission on Environmental Quality (TCEQ) on May 15, 2020.  Although the Agency explained the TCEQ value was not available in time for consideration in the final rulemaking, it’s unclear whether U.S. EPA has any intent to further evaluate risks with a revised URE for EtO at this time.

On top of additional controls to address risk from EtO emissions, U.S. EPA finalized other changes to address startup, shutdown, and malfunction (SSM) events consistent with the 2008 vacatur of the SSM exemptions in the 40 CFR Part 63 General Provisions.  The U.S. EPA also promulgated changes as a result of their technology review and revisions to incorporate electronic reporting requirements.

Miscellaneous Organic NESHAP (MON) Update Webinar

New Standards for Ethylene Oxide Emissions

The final rule contains new standards for process vents, storage tanks and equipment in EtO service.  For purposes of the MON, “in ethylene oxide service” for equipment leaks means any equipment that contains or contacts a fluid that is at least 0.1% by weight EtO.  Process vents in EtO service are those vents that when uncontrolled contain more than 1 part per million (ppmv) by volume of EtO and, when combined, would emit 5 pounds per year or more of EtO. Additionally, any tank storing a liquid that is at least 0.1% by weight of EtO is considered in EtO service.  For vents, storage tanks, and equipment, if information exists that suggests EtO could be present, then the source is considered to be in EtO service unless sampling and analysis is performed to demonstrate otherwise.

For process vents and storage tanks, facilities must vent emissions to a control device that either reduces EtO by 99.9% by weight or to less than 1 ppmv for each process vent and storage tank.  An additional option for process vents is to reduce emissions to less than 5 pounds per year of EtO for all combined process vents.

If you choose to comply with the 99.9% by weight reduction standard, or the 5 pounds per year standard for process vents, you must conduct initial performance testing and establish operating parameter limits for your control device.  Periodic testing is required every 5 years to demonstrate compliance and reestablish operating parameter limits.  Alternatively, if complying with the outlet concentration option (i.e., 1 ppmv of EtO), facilities may use a continuous emissions monitoring system meeting the requirements of Performance Specification 15 of 40 CFR Part 60, Appendix B instead of conducting initial and periodic performance testing.

Any storage tank considered a pressure vessel that is in EtO service must operate with no detectable emissions and must be monitored annually for leaks.  Any reading greater than 500 ppmv is considered a deviation.  Additionally, the pressure vessel must be operated as a closed system that vents to a control device meeting the requirements described above.

For equipment in EtO service, facilities must monitor all pumps in EtO service monthly using a leak definition of 1,000 ppmv and any leaks must be repaired within 15 days of being detected. Connectors must be monitored annually using a leak definition of 500 ppmv and any leaks must also be repaired within 15 days.  If any light liquid pumps or connectors in EtO service are added to a source or replaced, facilities must monitor within 5 days of starting up the new equipment.

PRDs in EtO service must comply with the new monitoring and work practice provisions for PRDs described below with a few exceptions.  Most notably, any release event from a PRD in EtO service is considered a deviation.

Changes as a Result of the Technology Review 

U.S. EPA did not identify any cost-effective developments for process vents, storage tanks, transfer racks, or wastewater as part of the Agency’s technology review; however, the final rule contains revised standards for heat exchange systems and equipment leaks. 

Similar to the recent RTR rule for the Ethylene Production NESHAP at 40 CFR, Part 63, Subpart YY, the final MON rule requires quarterly monitoring for heat exchange systems at existing sources and monthly monitoring at new sources using the Modified El Paso Method and a leak definition of 6.2 parts per million by volume (ppmv) of total strippable hydrocarbon in the stripping gas.  U.S. EPA included an alternative leak definition for systems with a recirculation rate of 10,000 gallons per minute or less of 0.18 kilograms per hour (kg/hr) of total hydrocarbon emitted from the heat exchange system.  Any leaks above a delay action level must be repaired within 30 days.  The delay action level is 62 ppmv, or 1.8 kg/hr for systems with a recirculation rate less than 10,000 gallons per minute. The Agency also added a definition of “heat exchange system” to the rule.

For equipment leaks, U.S. EPA lowered the leak definitions for light liquid pumps at existing batch processes from 10,000 to 1,000 ppmv with monthly monitoring.  The Agency also added provisions that require facilities to monitor any new or replaced equipment within 30 days after initial startup if the equipment is subject to the MON equipment leak standards and is otherwise required to be monitored using EPA Method 21.

Revisions to Address Regulatory Gaps

Pressure Relief Devices 

The MON now contains monitoring and work practice requirements for PRDs similar to those in the Refinery RTR rule at 40 CFR Part 63, Subpart CC and the Ethylene RTR rule at 40 CFR Part 63, Subpart YY.  The final rule includes requirements to develop a PRD management program, monitor PRDs for releases, and perform root cause and corrective action analyses after a release.  Several types of PRDs are exempt from the work practice requirements and facilities should carefully review the list of exemptions to determine which of their PRDs must comply with the new work practices.  U.S. EPA also finalized a requirement that new pilot-operated PRDs must be the “non-flowing” type (pilot valve discharge does not vent continuously during an event).

Bypass Lines, Maintenance Vents, and Storage Tanks 

U.S. EPA finalized the requirement that facilities may not bypass a control device at any time.  If bypass occurs, facilities must include the details of each bypass, including the total quantity of organic HAP released, in the semiannual periodic report.  

The final rule also contains requirements for maintenance vents that are used as a result of startup, shutdown, maintenance, or inspection of equipment where equipment is emptied, depressurized, degassed, or placed into service.  To comply with the maintenance vent provisions, prior to venting, facilities must remove process liquids and depressurize equipment to a flare or control device until one of several control criteria are met (e.g., the vapor is below 10% of the LEL).  The maintenance vent provisions are similar to those for refineries and ethylene production facilities, but the MON contains an option for equipment containing hydrogen halide and halogen HAP.  Equipment that contains hydrogen halide or halogen HAP is allowed to vent to the atmosphere if the vapor in the equipment has an LEL of less than 10% and the outlet concentration of hydrogen halide and halogen HAP is less than or equal to 20 ppmv.

Like the Agency did for the Ethylene RTR, U.S. EPA added storage tank degassing requirements as well.  Emissions from degassing must be controlled until the vapor space concentration is less than 10% of the LEL, for both fixed and floating roofs.  Emissions must be controlled using a flare, a non-flare control device, or routed to a fuel gas system or process.


The final rule contains significant amendments to the operating and monitoring requirements for a subset of flares used as control devices.  U.S. EPA determined that the current requirements are not adequate to ensure the level of destruction efficiency needed to conform with the standards (98% destruction) for flares controlling emissions from sources in EtO service, or from manufacturing chemical process units (MCPU) that produce olefins or polyolefins.  Like the recent Ethylene RTR, these flares are now subject to the Refinery RTR flare definitions and requirements in 40 CFR Part 63, Subpart CC.  In the final rule, U.S. EPA clarified that MCPUs that produce olefins or polyolefins includes only those MCPUs that manufacture ethylene, propylene, polyethylene, and/or polypropylene as a product (by-products and impurities are not considered products).

The subset of flares must operate with a pilot flame at all times and be continuously monitored.  Each 15-minute block where there is at least 1 minute where no pilot flame or flare flame is present when regulated material is routed to the flare will be a deviation from the standard.  Visible emissions are allowed for no more than 5 minutes in a 2-hour period and facilities must monitor for visible emissions on a daily basis.  Additional observation periods are required if visible emissions are observed.

U.S. EPA incorporated the 40 CFR Part 63, Subpart CC requirements for maximum flare tip velocity into the MON as a single equation, irrespective of flare type and facilities must comply with a single minimum operating limit for the net heating value in the combustion zone gas of 270 Btu/scf during any 15-minute period.

The final rule also contains specific requirements for pressure assisted multi-point flares (MPF) in the aforementioned subset.  MPF are not required to comply with the flare tip velocity requirements in 40 CFR Part 63, Subpart CC but must operate with a net heating value in the combustion zone gas of 800 Btu/scf on a 15-minute average basis.  If the MPF uses cross-lighting instead of a pilot on each burner, each burner must be no more than 6 feet apart (unless a cross-lighting demonstration is conducted) and each stage must operate with a flame present with regulated material is routed to the stage.  Each stage must have at least two pilots with one continuously lit.  A deviation occurs if there it at least one minute in a 15-minute block where no pilot flame is present on a stage of burners when regulated material is routed to the stage.  Facilities must also monitor the main flare header pressure and valve positions for each stage to ensure proper operation.  An MPF can continue to operate under an approved alternative means of emissions limitations (AMEL) in lieu of the new MON requirements.

As in the proposed rule, facilities must comply with 40 CFR Part 63, Subpart CC visible emissions work practices for emergency situations; however, as a change from proposal, facilities may not comply with the work practices for velocity limit exceedances during emergencies and instead must comply with the flare tip velocity limits at all times.

The final rule clarifies overlap of the MON standards with other flare regulations.  Flares that are subject to 40 CFR §60.18, §63.11, or §63.987 but that comply with the new standards for flares in the MON rule are only required to comply with the MON.  Except for MPF, flares subject to 40 CFR Part 63, Subpart CC and used as a MON control device are required to comply only with 40 CFR Part 63, Subpart CC flare requirements. 

Non-regenerative Adsorbers and Adsorbers Regenerated Off-site. 

The final MON RTR rule now contains provisions for facilities that use non-regenerative adsorbers and adsorbers regenerated off-site as control devices.  If a facility uses these types of adsorbers, they must operate at least two adsorbers in series.  Operators are required to establish the bed life of the adsorbers based on either a performance test or design evaluation, and the first bed must be continuously monitored for breakthrough according to a specified schedule.  If the adsorbent has more than 2 months of life left, facilities must monitor for breakthrough monthly.  If the bed life is between 2 months and 2 weeks, monitoring is required on a weekly basis.  If the bed has 2 weeks or less of life remaining, daily monitoring is required.  When breakthrough is detected, operators must replace the first bed with the second, and install a new bed in place of the second. 

Other Changes

The final rule contains several other changes including revisions and additions to the definitions, updated overlap provisions, and new recordkeeping and reporting requirements (including electronic reporting requirements).  U.S. EPA also finalized clarifying text and corrections to typographical errors, grammatical errors, and cross-reference errors.

How can ALL4 Help?

ALL4 has a variety of chemical sector experience, including the MON.  We are well versed in the Refinery RTR flare requirements and can assist MON facilities with the new flare requirements including developing monitoring plans, identifying required monitoring systems, and/or preparing procurement specifications for equipment suppliers.  We can also help facilities analyze, plan for, and comply with the new requirements for heat exchange systems, PRDs, and other emissions sources.  Contact Philip Crawford at 984-777-3119 or your ALL4 project manager with questions.


Miscellaneous Organic NESHAP (MON) Update Webinar


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