Proposed Rulemaking for Ethylene Production NESHAP

On September 5, 2019, Andrew Wheeler, the U.S. Environmental Protection Agency (U.S. EPA) Administrator, signed a notice proposing changes to the National Emission Standards for Hazardous Air Pollutants (NESHAP): Generic Maximum Achievable Control Technology Standards for Ethylene Production.  U.S. EPA is proposing several rule changes as a result of its risk and technology review (RTR) for the Ethylene Production source category.  The Agency is under a court-ordered deadline to finalize the RTR by March 13, 2020.

U.S. EPA is proposing that the health risk from the ethylene production source category is acceptable and that the current NESHAP provides an ample margin of safety; however, several significant changes to the rule requirements are being proposed as a result of the Agency’s technology review.  In addition, U.S. EPA is proposing changes to address startup, shutdown, and malfunction (SSM) events and is adding monitoring and operational requirements for flares.  The major proposed changes are discussed below.

As part of their technology review, U.S. EPA is proposing to reduce the size and vapor pressure applicability thresholds contained in Table 7 to 40 CFR Part 63, Subpart YY for storage vessels that require 98% control or installation of an internal or external floating roof.  Additionally, U.S. EPA proposes to ratchet down the maximum volume and vapor pressure thresholds for storage vessels that require submerged fill. U.S. EPA found these changes cost-effective, but the Agency’s cost and emissions estimates will likely be a focus as industry prepares comments on the rule.

U.S. EPA is also proposing to update 40 CFR Part 63, Subpart XX to require 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.  U.S. EPA is proposing that any leaks above a 62 ppmv action level must be repaired within 30 days.  While some facilities are already using the Modified El Paso Method, many are not and will be required to either secure contract service or purchase new equipment and become proficient in the new test method.  In addition, other facilities currently use test methods which closely match the results of the Modified El Paso Method (i.e., Method 624 at 40 CFR Part 136, Appendix A) and might consider submitting comments supporting these methods as alternatives to avoid, additional and unnecessary, investment in new equipment.

To address SSM, U.S. EPA is proposing to adopt requirements similar to those found in 40 CFR Part 63, Subpart CC (the refinery sector rule) for pressure relief devices (PRDs).  The PRD requirements include release monitoring, implementing release prevention measures, root cause analysis, corrective action analysis, and corrective action.  The proposal contains language that defines which release events are considered violations, such as those due to operator error, poor maintenance, or multiple releases in a given time period.  Certain PRDs are exempt from the proposed requirements, but owners and operators should carefully review the proposed rule to make sure necessary exemptions have been included.

U.S. EPA is proposing to incorporate other refinery sector rule type requirements for SSM events related to maintenance vents.  The current definition of an “ethylene process vent” excludes “episodic or nonroutine releases such as those associated with startup, shutdown, and malfunction.”  Emissions as a result of opening equipment for maintenance activities have generally been grouped with the episodic or nonroutine releases excluded from the process vent definition, but now U.S. EPA is proposing to amend the process vent definition to include streams that are periodically discharged and add work practice requirements for maintenance vents.  “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 50 pounds per day or more.  The proposed maintenance vent provisions require owners and operators to remove liquids from equipment and depressurize to a compliant flare or non-flare control device until one of five conditions are met, such as reducing the lower explosive limit of the equipment vapor to 10% or less, or reducing the gauge pressure to 5 pounds per square inch or less.

The last set of changes to the Ethylene Production NESHAP based on the refinery sector rule is for flares.  As for refineries, U.S. EPA determined the current operating and monitoring requirements for ethylene flares are not adequate to ensure compliance with the existing standards.  The proposed rule language directly references 40 CFR §§63.670 and 63.671 of Subpart CC to incorporate requirements related to operating and monitoring pilot flames, monitoring for visible emissions, meeting flare tip velocity requirements, meeting combustion zone gas net heating value requirements, and work practices during emergency situations.  U.S. EPA is also proposing specific provisions for ethylene production covering the use of pressure assisted multi-point flares.  These requirements are based on previously approved alternative means of emissions limitation (AMEL) requests and include minimum limits on the net heating value of combustion zone gas, requirements on continuous pilot flames, maximum distances between cross-lit burners, visible emissions limits, and requirements to monitor operation of staging valves.  The Agency is also proposing additional ethylene-specific requirements for those facilities that choose to determine net heating values with a continuous process mass spectrometer.  Any flare that receives fuel gas of which 50% or more is derived from an ethylene production unit must also meet the newly proposed flare requirements for ethylene production.

As part of the rule changes, U.S. EPA is proposing to add work practice requirements for ethylene furnace decoking operations (decoking was previously considered shutdown).  All owners and operators would be required to perform daily inspections for flame impingement on ethylene cracking furnace radiant tubes.  Additionally, facilities would be required to follow two of four compliance options which include:

1. Monitoring carbon dioxide (CO₂) at the radiant tube outlet and stop decoking when CO₂ indicates combustion of coke is slow/stopping;
2. Monitoring temperature at radiant tube outlet and reduce temperature at tubes when decoking is too aggressive;
3. Purge tubes with steam and verify all air is removed before returning to normal operations; and,
4. Apply a coating to the interior of tubes before returning to normal operation.

Facilities must also verify isolation of the process before decoking and before returning to normal operation.  Poor isolation must be rectified before proceeding to decoking or normal operation.

U.S. EPA is also proposing changes to several definitions, clarifying bypass provisions, adding electronic reporting requirements, and addressing overlap of equipment leak provisions with 40 CFR Part 60, Subpart VVa.  For the proposed changes, the Agency is proposing a 3-year compliance timeline.

Although this is only a proposed rule, it’s clear several changes are coming down the pipe for ethylene producers in U.S. EPA’s final rule.  Several of these amendments will require the purchase, installation, and operation of new monitoring equipment, development of new standard operating procedures, new recordkeeping and reporting systems, and amendment of operating permits.  The proposed requirements for flares and storage tanks may even require facilities to purchase and install new control devices or make other significant changes to current equipment configuration and operating practices.  Companies will want to review the proposed requirements in detail to understand how their unique operations will be impacted, and to consider submitting comments to assist U.S. EPA in finalizing amendments that continue to protect public health and the environment, while maintaining operational flexibility for new and existing ethylene production facilities.

For additional details on U.S. EPA’s proposal, check out the pre-publication version here.  Interested parties will have 45 days from publication in the Federal Register to submit comments on the proposed amendments and U.S. EPA will only have until March of next year to finalize changes.  In the meantime, if you have questions on this proposal, or other RTRs, reach out to me at pcrawford@all4inc.com or 984.777.3119.

Learn more about air quality compliance