HYDROCARBON
ENGINEERING
26
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Determining New Source Performance Standard (NSPS)
Subparts Kb and OOOO applicability.
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Accounting for maintenance, startup, and shutdown
emissions for air quality construction and operating
permits.
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Navigating guidance from multiple agencies.
This article discusses each of these issues and provides
real world solutions for staying compliant in an
increasingly regulated environment.
Alternative emissions
calculation methods
The TANKS software created by EPA has long been the
industry and regulatory agency standard for estimating
emissions from different types of atmospheric storage
tanks. However, the most recent version of software,
released in 2006, is no longer reliably functional on
computers using newer operating systems.
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EPA recently
confirmed that it would no longer be providing assistance
for this software nor releasing a new TANKS version.
Therefore, industry is left to identify alternative
approaches for calculating emissions going forward.
Popular alternatives include proprietary software and
custom built Excel workbooks. Regardless of which option
is chosen, the following considerations should be taken
into account:
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Which calculation methodology is used? Most
agencies require the use of calculations based on
AP-42 Chapter 7, EPA’s tank emission calculation
procedure.
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Does it meet the specific needs of your operations,
i.e., can it calculate emissions for a specific location,
tank, and storage material?
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Does it include other emission calculations associated
with tank operations, such as emissions from roof
landings, degassing and cleaning, fugitive leaks,
control devices, outbound loading, and even roads?
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Can it calculate speciated emissions and/or short
term emission rates?
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Are calculation methods presented in such a way that
they will be readily understood and accepted by local
agencies?
While many regulatory agencies will continue to
accept the use of TANKS4.0.9d for the foreseeable future,
many companies are beginning to transition to alternative
approaches.
Properly characterising RVP
and TVP
RVP and TVP have long been analysed for refined product
terminals, but, for the most part, have not received the
same level of attention in the crude/condensate storage
sector. Due to the wide range of unrefined products
received by these terminals, many local agencies have
allowed companies to use default or average RVP values
available in the TANKS software to represent their stored
materials. However, in recent years, the accuracy of these
default values has been questioned due to the influx of
higher RVP shale oils and condensates. This has led to
some agencies stipulating more stringent requirements,
such as periodic sampling or the use of higher RVP
defaults for certain crude oil and condensate stocks.
Properly characterising RVP can have a wide range of
implications from emission calculations to air permitting
to regulatory applicability; consequently, many companies
are beginning to reevaluate how they determine RVP in
order to establish more accurate values going forward.
Properly characterising TVP will have similar
implications; one additional concern for TVP is the
method by which it is determined. Traditionally, TVP has
been determined by using RVP and applying a correlation
provided in AP-42 Chapter 7. However this correlation was
developed decades ago using empirical data from
conventional crude oil. It was later identified that for
higher RVP stocks the correlation would over predict
TVP.
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In addition, typical test methods for determining
RVP (ASTM D323) and TVP (ASTM D2879) potentially
misrepresent lighter oil since samples are not required to
be sealed, and lighter carbon components can vaporise
before testing occurs. To account for this
misrepresentation, some operators began performing
ASTM D2879 using a sealed sample, skipping the degassing
step in the method. In a letter dated 28 May 2013, EPA also
approved the use of an alternative test method, ASTM
D6377-10. This field method is well suited for determining
TVP from lighter crude oils since it requires a sealed
sample, and it does not rely on correlating from an RVP
value.
Determining NSPS Subparts
Kb and OOOO applicability
The two US Federal regulations, located in Code of
Federal Regulations (CFR) Part 60 of Title 40, most likely
to affect crude/condensate tanks in the US are NSPS
Subparts Kb and OOOO. Subpart Kb took effect in 1984,
and most operators are already familiar with the specific
applicability and regulations associated with this rule.
However, two issues that have recently become more
challenging to address: modifying or reconstructing
grandfathered tanks, and properly characterising TVP for
determining applicability and control device requirements.
TVP characterisation was discussed in the previous
section. In regards to tank modifications and
reconstructions, a number of companies have
inadvertently triggered one of these while modifying their
facilities as part of an effort to allow for either increased
throughput or higher RVP materials. While there are a
number of exemptions that allow most facilities to avoid
triggering, companies should familiarise themselves with
the definitions of ‘modification’ and ‘reconstruction’
listed in NSPS Subpart A before performing any physical
change to any grandfathered tank or before accepting
higher RVP material.
Subpart OOOO became effective in 2011, and was
intended to regulate crude/condensate storage tanks in
the crude oil production sector as well as in the natural
gas production, transmission, and distribution sectors that
have the ‘potential to emit’ greater than or equal to 6 tpy
of volatile organic compounds (VOC). The crude oil
production sector is defined in the rule as being ‘between
