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Final Risk and Technology Review for Ethylene Production NESHAP Brings Substantial Changes to the Current Rule

Posted: April 9th, 2020

Authors: Philip C. 

Early March was a busy time for the U.S. Environmental Protection Agency (U.S. EPA). Between March 11 and 12, 2020 U.S. EPA signed a flurry of final Risk and Technology Review (RTR) rules, including the National Emission Standards for Hazardous Air Pollutants (NESHAP): Generic Maximum Achievable Control Technology Standards for Ethylene Production, otherwise known as “EMACT.”  Although the U.S. EPA determined that risks from the source category are acceptable, and that the standards provide an ample margin of safety, several changes were finalized as a result of U.S. EPA’s technology review.  Other changes were made to address startup, shutdown, and malfunction (SSM) events consistent with the 2008 vacaturof the SSM exemptions in 40 CFR Part 63 General Provisions.  The U.S. EPA also revised the flare monitoring requirements to ensure flares meet the EMACT standards at all times.  Existing facilities must comply with the changes starting 3 years after publication of the final rule in the Federal Register.  New facilities, or facilities that commenced construction or reconstruction after October 9, 2019 must comply with the changes upon initial startup or the date of publication of the final rule, whichever is later.

Back in September of 2019, we covered the proposed changes to the EMACT standards here.  Although U.S. EPA finalized most of the changes as proposed, there are a few key differences.  Some of these differences are a positive step compared to the proposed rule, while others increase the compliance burden for several facilities.

Storage Tanks

The U.S. EPA originally proposed to reduce the size and vapor pressure applicability thresholds for storage vessels requiring control or submerged fill.  However, based on additional information provided by stakeholders, U.S. EPA determined that these changes were not cost-effective and did not include them in the final rule.

The final rule includes a new standard for storage tank degassing as part of the elimination of SSM exemptions.  The standard applies to both fixed and floating roof storage tanks.  Facilities must remove liquids as much as practicable and route vapors to a flare, a control device, or back to the process or a fuel gas system until the vapor space in the storage vessel is less than 10% of the lower explosive limit (LEL).  If emissions are routed to a flare, the new operating and monitoring provisions for flares must be met.  Additionally, if emissions are routed to a control device, facilities must either complete a design evaluation or performance testing and conduct continuous monitoring to ensure a 98% reduction efficiency.

Heat Exchange System Monitoring

The final 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.  As a change from proposal, 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.

Pressure Relief Devices

The final rule contains EMACT specific definitions of “pressure relief device” (PRD) and “relief valve.”  U.S. EPA is also requiring facilities perform monitoring to ensure the PRD is operating below a 500 ppm leak level within 5 days of a PRD release, or replace the rupture disk, if so equipped.  If the PRD consists only of a rupture disk, the disk must be replaced within 5 days of a release, and the facility may not restart the process until the rupture disk is replaced.

The rule also contains work practice provisions for PRDs like those in the Refinery RTR rule at 40 CFR Part 63, Subpart CC, including 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 at 40 CFR 63.1107(h) 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 and Maintenance Vents 

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.  The previous definition of an “ethylene process vent” excluded “episodic or nonroutine releases such as those associated with startup, shutdown, and malfunction.”  The final rule amends the process vent definition to include streams that are periodically discharged.  “Periodically discharged” covers intermittent gas streams with a total organic HAP concentration greater than 20 ppmv and total volatile organic compound (VOC) emissions greater than or equal to 50 pounds per day, including maintenance vents that meet these criteria. 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).

Work Practices for Decoking Operations

U.S. EPA added decoking work practices to the final rule consistent with the removal of the SSM exemptions.  These work practices include daily burner inspections and repair for flame impingement and monitoring during the decoke cycle.  Facilities must comply with two of the following: 1) Monitor CO2 downstream of the last component being decoked and stop decoke when the CO2 concentration consistently reaches a level indicating combustion of coke is complete and site decoke completion assurance procedures have been concluded; 2) monitor temperature at radiant tube outlet and reduce temperature at tubes when decoke is too aggressive; 3) after decoking, but before returning to normal operations, verify that decoke air is no longer being added; 4) inject materials into the steam or feed to reduce coke formation inside tubes.  Facilities must also verify isolation of tubes/furnace/process before decoke and before returning to normal operation.  Poor isolation must be rectified before proceeding to decoke or normal operation. 


The final rule contains significant amendments to the operating and monitoring requirements for flares used as control devices.  U.S. EPA determined that the current requirements for flares are not adequate to ensure the level of destruction efficiency needed to conform with the standards (98% destruction).  EMACT flares are now subject to the Refinery RTR flare definitions and requirements in 40 CFR Part 63, Subpart CC.

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 EMACT 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).  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 EMACT 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 EMACT standards with other flare regulations.  Flares that are subject to 40 CFR §60.18, §63.11, or §63.987 and used as a control device for an emission point subject to EMACT control requirements are required to comply only with §63.1103(e)(4).  Except for MPF, flares subject to 40 CFR Part 63, Subpart CC and used as an EMACT control device are required to comply only with 40 CFR Part 63, Subpart CC flare requirements. 

Other Changes

The final rule contains several other changes including revisions to the definition of an “ethylene process vent,” regulatory 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.

What Should Facilities Subject to the EMACT do Now?

ALL4 recommends the following:

  • Read the final rule and preamble and understand the impacts on your business and facilities.
  • Identify what additional internal and external resources you need to implement the rule.
  • Identify any capital projects that will required for compliance. Develop a timeline and schedule. Can you accommodate these projects into an already planned outage such that the compliance deadline (3 years from publication of the final rule in the Federal Register) can be met?
  • 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. For example, depending on a facility’s current configuration, the flare monitoring requirements in 40 CFR Part 63, Subpart CC may require the installation of a gas chromatograph, a hydrogen analyzer, or a calorimeter.  New flare gas, air, fuel, or steam monitoring and control equipment may also be required.  Facilities should also consider any necessary upgrades to their data acquisition systems.
  • Determine what internal procedures and plans need to be updated as a result of the rule changes.

ALL4 has a variety of chemical sector experience, including ethylene.  We are well versed in the Refinery RTR flare requirements and can assist EMACT 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.


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