By William C. Schillaci

EPA’s standard focuses on flows to flare

The latest variation of the hot-button environmental topic of polluted air emissions from flaring at petroleum refineries centers on an EPA final rule that amends emissions limits and other requirements for new flares or those that are modified, as the EPA interprets that term. While there is no disputing when a new flare is installed, there appear to be many disagreements between industry and the EPA over when there is a modification that causes an existing flare to be regarded as new. This article summarizes some of those disagreements.

A flare is a safety device that generally comprises a tall stack equipped with burners. Flares combust and dispose of combustible gases resulting from emergency relief, overpressure, process upsets, start-ups, shutdowns, and other operational safety conditions. Planned flare events occur during scheduled maintenance, the start-up of a process unit, or other activities where a refinery or related source can reasonably anticipate the need to dispose of any excess gases these activities may produce. Unplanned flare events occur during emergencies caused by an equipment breakdown, power outage, or other upsets beyond a refinery's control when flares are used to safely burn compressed gases that may otherwise pose risks to workers, the community, or the environment.

Emissions from flaring include carbon particulate matter (soot), unburned hydrocarbons, carbon monoxide, other partially burned and altered hydrocarbons, NOx, and SO2. Properly operated flares achieve at least 98 percent combustion efficiency in the flare plume. Less efficient flares have been linked to environmental and human health problems, particularly in populated areas near refineries.

One of the main problems with regulating flares is that it is extremely difficult, if not impossible, to measure pollutant concentrations in emissions from flares. Regulations are therefore targeted toward pollutants in gaseous flows to the flare. Accordingly, the EPA’s regulations require that flares be equipped with flow and sulfur monitors except in cases where flares are used infrequently or are configured such that they cannot receive high sulfur gas.

Revising 2008 amendments

The EPA’s action revises the Agency’s 2008 amendments to its new source performance standards (NSPS) for refineries (40 CFR Part 60, Subpart Ja) with process heaters constructed, reconstructed, or modified after May 14, 2007, and flares, constructed, reconstructed, or modified after June 24, 2008. In response to that rulemaking, the American Petroleum Institute (API) and other industry members as well as environmental groups requested that the EPA reconsider certain aspects of the rule, particularly regarding emissions limits and monitoring. The EPA agreed to conduct the reconsiderations and issued a stay on some of the regulatory issues raised; the stay was requested by industry but not in the environmental petition. In December 2008 the EPA proposed amendments in response to the petitions. The current action finalizes the proposal.

Industry petitioners specifically asked that the EPA reconsider its new definition of modification for flares; the definition of a flare; sulfur emissions limits for fuel gas combustion devices as they relate to flares; flow limit for flares; total reduced sulfur and flow monitoring requirements for flares; and the NOx limit for process heaters. Among its requests, environmental groups asked that the EPA promulgate standards for carbon dioxide (CO2) and methane emissions.

The new amendments are expected to have a significant effect on the refinery sector. The EPA notes that it projected that its 2008 amendments would affect about 40 flares. Under the revised amendments, that estimate has grown to 400 flares, at an EPA-estimated compliance cost of nearly $500 million. Industry cost estimates for major rules tend to far exceed the EPA’s.

Connections and modifications

Disagreements over when an existing flare is modified and therefore becomes subject to the NSPS center on the definition of modification and EPA’s interpretation of it. In the Clean Air Act, a modification is defined as “any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted.” Industry asserts that the meaning here is clear–the modification provision should focus on physical and operational changes that increase emissions from the flare; that is, a flare is modified only if net emissions from it increase.

But the EPA argues that flares are operated differently from other refinery process units, making it difficult to apply the modification provision. As noted, the EPA does not believe it is practical to rely on measuring emissions increases to determine if a modification has occurred. Instead, the Agency takes the position that determination of whether a flare has been modified must be based on whether there are increases in flow to the flare, which would be “directly indicative” of increased emissions from the flare.

Industry further stated that at least 14 types of connections to flares do not result in increased emissions and therefore should not be considered when determining if a modification has occurred. EPA’s response to each of the 14 cases is summarized below.

• The EPA considers none of the following connections cited by industry to be modifications.
• Connections made to upgrade or enhance (not just to install) a flare gas recovery system

EPA’s comment: Projects to upgrade components of a flare gas recovery system (e.g., addition of compressors or recycle lines) will improve operation of the flare gas recovery system and not result in increased emissions.

• Connections made for flare gas sulfur removal

EPA’s comment: These connections will generally result in a slight decrease in volumetric flow and a large decrease in emissions of SO2.

• Connections made to install backup equipment

EPA’s comment: Connections made to install backup or redundant equipment such as a backup compressor will result in fewer released emissions if there is a malfunction in the main equipment.

• Flare interconnects

EPA’s comment: The issue here is complex. EPA agrees that interconnections between flares will not alter the cumulative amount of gas being flared. In fact, when a large release event occurs, the amount flared by each flare tip will decrease. However, in cases where a regulated flare is interconnected with a flare that is not subject to Subpart Ja, the resulting interconnected flare becomes subject to Subpart Ja.

In addition to the four exempt connections noted here, the EPA lists three additional connections that are not modifications under the standard:

• Connections to install monitoring systems to the flare.
• Connections to install a flare gas recovery system or connections made to upgrade or enhance components of a flare gas recovery system (e.g., addition of compressors or recycling lines)
• Connection made to install backup (redundant) equipment associated with the flare (such as a backup compressor), that does not increase the capacity of the flare
• EPA considers all of the following to be modifications.
• All emergency pressure relief valve connections from existing equipment

EPA’s comment: New connections, even if made to existing equipment, will result in an increase in flow to the flare during periods of process upset.

• Connections to monitoring system purge gases and analyzer exhausts or closed vent sampling systems

EPA’s comment: These connections will increase emissions from the flare.

• Purge and clearing vapors, block and bleeder vents, and other uncombusted vapors where the flare is the control device

EPA comment: The increase in gas flow to the flare will increase emissions from the flare.

• Connections made to comply with other federal, state, or local rules where the flare is the control device

EPA comment: A connection from a process unit to a flare for use as an emissions control device decreases emissions from the process unit being controlled, but increases emissions from the flare.

• Connections to “unregulated gases” such as hydrogen, nitrogen, ammonia, other nonhydrocarbon gases or natural gas, or any connection that is not fuel gas

EPA’s comment: Each of these streams, when directed to a flare, will increase emissions of at least one pollutant (PM, CO, or NOx) that the NSPS is intended to reduce.

• New connections upstream of an existing flare gas recovery system, provided the new connections do not compromise or exceed the flare gas recovery system’s capacity

EPA’s comment: New upstream connections will increase the likelihood of an event that would cause an exceedance of the flare gas recovery system’s capacity even if the new connections do not exceed the flare gas recovery’s system’s capacity under normal conditions.

• Any new, moved, or replaced piping, or pressure relief valve connections that do not result in a net increase in emissions from the flare, regardless of piping or pressure relief valve size

EPA’s comment: Exemptions may apply to moved or replaced piping or pressure relief valve connections of the same size. However, the EPA does not agree with the premise that new or larger connections somehow will not increase emissions from the flare.

• Vapors from tanks used to store sweet or treated products

EPA’s comment: The argument made by industry is that the H2S content in these vapors is below the concentration limit specified for fuel combustion devices. EPA counters that H2S (an indicator of SO2) is not the only pollutant emitted from flares and that other pollutants will be emitted because of the additional flow of sweet gases.

• Temporary connections for purging existing equipment, as these are essentially “existing” connections

EPA’s comment: No exemption is provided for new connections to existing equipment regardless of whether these connections are temporary or permanent.

• Connections of safety instrumentation systems (SIS) described under OSHA process safety standards at 29 CFR 1910.119, EPA’s risk management program at 49 CFR 68, and/or ANSI/ISA-84.00.01-2004

EPA’s comment: These connections should be evaluated on a case-by-case basis to determine whether they result in a modification. If the connections are made for flare monitoring purposes, they are not modifications. If they are made to connect the analyzer exhaust to the flare, they qualify as modifications.

Finally, industry stated that new connections to a flare made to control and combust fugitive emissions such as leaks from compressor seals, valves, or pumps cause de minimis emissions increases and should not be considered modifications of a flare. But the EPA said that industry has provided no data to support a finding that these types of releases are truly trivial or of no value. At least until such data are provided, the EPA says it may not legally exercise its limited authority to promulgate a de minimis exemption.

EPA’s final NSPS amendments for refinery flares and process heaters are at http://www.epa.gov/ttn/oarpg/t1/fr_notices/refineryrule.pdf.