flexnet.txt
flexnet.txt
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Texas Natural Resource Conservation Commission
Interoffice Memorandum
To: NSR Permit Reviewers
Date: August 25, 1999
Through: FNSR Team
From: Kurt Kind, Ph.D.
Subject: Draft - FNSR Applicability for Flexible Permits
The following discussion provides background for how federal applicability
may be determined for modifications at facilities covered by flexible
permits (within the emission caps). Note that netting may be avoided
altogether if the source has established a Plantwide Applicability Limit
(PAL).
The first section discusses how the endpoints method might be used to
simplify netting for flexible permits. The second section, flexible permit
project increases, provides direction on how to determine project
increases to determine whether netting is required and how those project
increases would be shown in subsequent netting exercises.
Endpoints Method (suggested if flexible permit was issued in the
contemporaneous period)
If netting was performed for the flexible permit and/or there were
significant emission reductions over the implementation of the permit, this
method may limit the calculations necessary to net out of federal review.
In this case, the applicant assumes that the project would trigger netting
for the pollutants of concern.
The two year average actual emissions prior to the first (earliest)
modification in the contemporaneous period are subtracted from the
proposed allowable for each facility. Facilities in a flexible permit may be
lumped together when making this comparison as illustrated below.
This method eliminates the need to consider changes in actual emissions
at each individual existing facility covered by the flexible permit. It also
prevents double counting of emission increases at a facility with more
than one modification during the contemporaneous period. For example,
A flexible permit was issued in 1997, with 100 existing
facilities (some grandfathered, others permitted) and an
initial emission cap of 1000 TPY. Federal PSD applicability
was evaluated at that time and the past 2 years actual
emissions from those facilities were 1010 TPY. All facilities
at the site are in this permit and there were no modifications
at the site in 1995 or 1996.
Modifications were made in 1998 and 1999 which added
new facilities that contributed emissions of 100 TPY each to
the cap. Another modification is proposed in 2000 which
adds facilities that contribute 50 TPY to the cap. The
proposed cap is 1000 TPY (there were reductions as BACT
was phased in).
Emission cap history
Cap Year Original 1998 Amd. (+100) 1999 Amd. (+100) 2000 Proposed (+50)
1997 990 - - -
1998 890 990 - -
1999 850 950 1050 -
2000 750 850 950 1000
2001 720 820 920 970
The net change for the contemporaneous period is 1000 -
1010, or -10 TPY and the project is not subject to federal
review.
This method is limited to major sources that have to net to determine
applicability. It becomes more complex if there are other construction
permits at the site and will also be complicated by any cap reductions
which may have been required by the SIP.
Flexible Permit Project Increases
The applicant must identify facilities to be physically modified and any
resulting upstream and downstream effects (debottlenecking). The
facilities covered by a flexible permit fall into one of these 2 categories for
any modification:
A. Modified, this includes -
i. those that are physically modified
ii. those not have not been physically modified but require an increase in emission cap contribution
B. Not modified.
Project increases are determined as follows for each of the categories:
A. The increase is the difference between the new cap contribution
(total including 9% if applicable) and the past 2 year actual
emissions for that facility. The actual emissions may not exceed
the contribution to the current cap. If actual emissions exceed the
cap contribution, similar facilities (such as tanks) should be
grouped to avoid this; if that is not possible method B should be
used and the basis for the emission cap evaluated.
In all cases, these increases must be at least equal to those
increases that would be determined through method B. Note that
those facilities with a proposed allowable not based on a physical
limitation (such as tanks and loading in most cases) will be subject
to an enforceable allowable emission for those facilities.
B. The increase in emissions is the potential increase in emissions
due to the debottlenecking of the process (incremental increase
that could result at the facility, actual emissions do not come into
play because the facility is not modified).
Note that any creditable decreases must be determined through the
method for category A facilities. Only those changes at facilities covered
in category A will be shown in future netting.
Basis for this approach
A flexible permit allows for the maximum operational flexibility under the
emission caps (which are generally based on design capacity).
Therefore, aside from the emission caps, the facilities have very few
operational restrictions. This method correctly accounts for increases to
the design capacity of the affected facilities without having to show
increases for unaffected emission points in the cap.
Example
A modification is proposed that will affect the following units; reactor
upgrade, new distillation column (DU), increased boiler steam demand,
increased tank turnovers at any one of four tanks (greater than the current
cap contribution).
The project increases are determined as follows for each of the 4 facilities:
reactor - physically modified, total new cap contribution - 2 year actual
DU - new, cap contribution
boiler - not modified, increase based on anticipated increase in
steam demand. In this case, the steam demand necessary
for the modification is equivalent to an increase in boiler load
of 50 MMBtu/hr. Therefore, the project increase at this
emission point would be 50 MMBtu times the NOx emissions
factor, 0.06 lb/MMBtu in this case. The resulting emission
increase is
50 MMBtu/hr(0.06 lb/MMBtu)(4.38 TPYhr/lb) = 13.14 TPY.
This is not dependent on the past actual emissions for this facility.
tanks - modified, in this case one of the 4 tanks has been operating
with emissions above the emission cap contribution and the
product could go to any one of 4 tanks. The increase is total
new cap contribution for the 4 tanks - 2 year actual for the 4
tanks. A separate emission cap or permit condition will be
necessary to make the new allowable for the tanks federally
enforceable.
Forward any questions regarding this memo or other netting issues to the
FNSR team.