[Federal Register Volume 63, Number 85 (Monday, May 4, 1998)]
[Rules and Regulations]
[Pages 24436-24445]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-11262]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 60 and 63
[AD-FRL-6003-7]
RIN 2060-AH94
Standards of Performance for New Stationary Sources: General
Provisions; National Emission Standards for Hazardous Air Pollutants
for Source Categories: General Provisions
AGENCY: Environmental Protection Agency (EPA).
ACTION: Direct final rule.
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SUMMARY: This action amends the General Control Device Requirements
applicable to flares in 40 CFR Part 60 which were issued as a final
rule on January 21, 1986, and the Control Device Requirements
applicable to flares in 40 CFR Part 63 which were issued as a final
rule on March 16, 1994. This action amends existing specifications to
permit the use of hydrogen-fueled flares. For additional information
concerning comments, see the parallel proposal found in the Proposed
Rules Section of this Federal Register.
DATES: This direct final rule is effective June 23, 1998 without
further notice unless the Agency receives relevant adverse comments by
June 3, 1998. Should the Agency receive such comments, it will publish
a document withdrawing this rule. The incorporation by reference of
certain publications listed in the rule is approved by the Director of
the Federal Register as of June 23, 1998.
ADDRESSES: Comments. Comments should be submitted (in duplicate, if
possible) to: Air and Radiation Docket and Information Center (6102),
Attention Docket No. A-97-48 (see docket section below), Room M-1500,
U.S. Environmental Protection Agency, 401 M Street S.W., Washington,
D.C. 20460. The EPA requests that a separate copy also be sent to Mr.
Robert Rosensteel (see FOR FURTHER INFORMATION CONTACT section for
address). Comments may also be submitted electronically by following
the instructions provided in the SUPPLEMENTARY INFORMATION section. No
Confidential Business Information (CBI) should be submitted through
electronic mail.
Docket. The official record for these amendments has been
established under docket number A-97-48. A public version of this
record, including printed, paper versions of electronic comments and
data, which does not include any information claimed as CBI, is
available for inspection between 8 a.m. and 4 p.m., Monday through
Friday, excluding legal holidays. The official rulemaking record is
located at the address in the ADDRESS section. Alternatively, a docket
index, as well as individual items contained within the docket, may be
obtained by calling (202) 260-7548 or (202) 260-7549. A reasonable fee
may be charged for copying.
FOR FURTHER INFORMATION CONTACT: Mr. Robert Rosensteel, Emission
Standards Division (MD-13), U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park,
North Carolina 27711, telephone number (919) 541-5608.
SUPPLEMENTARY INFORMATION:
Electronic Filing
Electronic comments and data can be sent directly to EPA at: r-docket@epamail.epa.gov. Electronic comments and data must be
submitted as an ASCII file avoiding the use of special characters and
any form of encryption. Comments and data will also be accepted on
diskette in Word Perfect 5.1 file format or ASCII file format. All
comments and data in electronic form must be identified by the docket
number A-97-48. Electronic comments may be filed online at many Federal
Depository Libraries.
Electronic Availability
This document is available in Docket No. A-97-48, or by request
from the EPA's Air and Radiation Docket and Information Center (see
ADDRESSES), and is available for downloading from the Technology
Transfer Network (TTN), the EPA's electronic bulletin board system. The
TTN provides information and technology exchange in various areas of
emissions control. The service is free, except for the cost of a
telephone call. Dial (919) 541-5742 for up to a 14,000 baud per second
modem. For further information, contact the TTN HELP line at (919) 541-
5384, from 1:00 p.m. to 5:00 p.m., Monday through Friday, or access the
TTN web site at: www.epa.gov/ttn/oarpg/rules.html.
Regulated Entities
Entities affected by this direct final rule include:
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Category Examples of regulated entities
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Industry........................ Synthetic Organic Chemical
Manufacturing Industries; and
Petroleum Refining Industries.
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This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. This table lists the types of entities that the EPA is now
aware could potentially be affected by this action. Other types of
entities not listed in the table could also be affected. If you have
any questions regarding the applicability of this direct final rule to
a particular entity, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.
The information presented in this preamble is organized as follows:
I. Background
A. Existing Flare Specifications
B. DuPont's Request for Specifications for Hydrogen-Fueled
Flares
II. DuPont Test Program For Hydrogen-Fueled Flares
A. Summary of Earlier Relevant Hydrogen-Fueled Flares Tests
B. Objectives of the DuPont Test Program
C. Design and Implementation of DuPont Test Program
D. Results of the Test Program
III. Rationale
A. The Need for Specifications for Hydrogen-Fueled Flares
B. Use of DuPont Test Results as the Basis for Hydrogen-Fueled
Flare Specifications
[[Page 24437]]
C. Selection of Specifications for Hydrogen-Fueled Flares
D. Decision to Proceed With Direct Final Rulemaking
IV. Summary of the Amendments to the Flare Specifications
V. Impacts
A. Primary Air Impacts
B. Other Environmental Impacts
C. Energy Impacts
D. Cost and Economic Impacts
E. Summary of Impacts
VI. Administrative
A. Paperwork Reduction Act
B. Executive Order 12866
C. Regulatory Flexibility Act
D. Unfunded Mandates Reform Act
E. Submission to Congress and the Comptroller General
I. Background
The General Control Device Requirements of 40 CFR 60.18 were issued
as a final rule on January 21, 1986 and are applicable to control
devices complying with New Source Performance Standards (NSPS)
promulgated by the Agency under Section 111 of the Clean Air Act (CAA),
and National Emission Standards for Hazardous Air Pollutants (NESHAP)
issued under the authority of Section 112 prior to the CAA Amendments
of 1990. The Control Device Requirements of 40 CFR 63.11 were issued as
a final rule on March 16, 1994 and are applicable to control devices
used to comply with NESHAP issued under the authority of the CAA
Amendments of 1990, for the control of hazardous air pollutants (HAP).
These existing control device requirements contain specifications
defining required operating conditions of control devices generally.
Specifically, 40 CFR 60.18(b) through (d), and 40 CFR 63.11(b) contain
the operating conditions for flares (i.e., existing flare
specifications). Flares operating in accordance with these
specifications destroy volatile organic compounds (VOC) or volatile HAP
with a destruction efficiency of 98 percent or greater. These existing
flare specifications were written for flares combusting organic
emission streams. The current regulations do not permit the use of
flares not meeting these specifications to satisfy control requirements
under the CAA.
E.I. du Pont de Nemours and Company (DuPont) representatives
requested that the EPA either add specific limits for hydrogen-fueled
flares to the existing flare specifications or approve their hydrogen-
fueled flares as alternate means of emission limitation under 40 CFR
61.484, 40 CFR 61.12(d) and 40 CFR 63.6(g) (Docket No. A-97-48, Item
No. II-D-2). DuPont subsequently sponsored a testing program to
demonstrate that hydrogen-fueled flares in use at DuPont destroy
emissions with greater than 98 percent efficiency. The test program
demonstrated that these hydrogen-fueled flares achieved greater than 98
percent destruction efficiency. Further, the EPA judged the conditions
of the test program to be universally applicable under the
specifications contained in these amendments. Therefore, this notice
provides the background and rationale for this action to add
specifications for hydrogen-fueled flares to the existing flare
specifications.
This notice is being published as a direct final notice since the
EPA does not anticipate relevant adverse comments. For the reasons
discussed in this notice, the EPA believes that hydrogen-fueled flares
meeting the operating specification in this amendment will achieve the
same control efficiency, i.e., 98 percent or greater, as flares
complying with the existing flare specifications. Further, these
specifications will result in reduced emissions of carbon monoxide,
nitrogen oxides, and carbon dioxide formed during the combustion of
supplemental fuel necessary for hydrogen-fueled flares to comply with
existing regulations. By promulgating these amendments some companies
using hydrogen-fueled flares can, as of the effective date of this
amendment, reduce supplemental fuel use resulting in cost savings and
reduced emissions.
A. Existing Flare Specifications
Flares are commonly used in industry to safely combust VOC and
volatile HAP. Flares can accommodate fluctuations in VOC or volatile
HAP concentrations, flow rate, heating value, and inerts content.
Further, flares are appropriate for continuous and intermittent flow
applications. Some organic emission streams can be flared without the
need for supplemental fuel. However, the use of supplemental organic
fuel such as natural gas to ensure the complete combustion of emissions
is common.
The EPA determined the destruction efficiency of flares combusting
organic emissions in the early 1980's and developed the existing flare
specifications as a result of this work. The testing was conducted with
a nominal 8-inch diameter flare head furnished by a vendor (Docket No.
A-97-48, Item No. I-II-12) and pilot-scale flares (Docket No. A-97-48,
Item No. I-II-5). From destruction efficiency testing under a wide
variety of velocities, gas compositions, tip diameters, air and steam
assistance, and the presence or absence of a pilot burner, it was
concluded that the destruction efficiency of flares was above 98
percent when operated within the conditions of the flare
specifications. These specifications list the minimum heat content of
the flame (British thermal units per standard cubic feet of gas, or
Btu/scf), and the tip velocity (feet per second, or ft/s) allowed for
steam-assisted, air-assisted and nonassisted flares.
B. DuPont's Request for Specifications for Hydrogen-Fueled Flares
DuPont operates six flares at three facilities which are used to
combust waste gases containing hydrogen (from 13 to 22 mol percent),
VOC and volatile HAP. These waste streams also contain other
combustible waste gases, inerts, and oxygen. All of DuPont's hydrogen-
fueled flares are nonassisted and use pilot burners.
The concentrations of the combustible gases are low, and since the
heating value of hydrogen per unit of volume is low, the DuPont
emission streams have lower volumetric heat contents than the streams
of flares meeting the existing flare specifications. Because DuPont's
six flares do not meet the existing flare specifications, and three of
these flares are used to control emissions for HAP sources currently
subject to NESHAP, DuPont initiated a process to demonstrate that their
hydrogen-fueled flares achieve the same destruction efficiency as
flares complying with the existing flare specifications. DuPont began
the process by investigating the literature on hydrogen-fueled flares
(Docket No. A-97-48, Item No. II-I-2). The objective of this
investigation was to find any data that may exist in earlier hydrogen-
fueled flare test reports that would support their assertion that
hydrogen-fueled flares achieve a control efficiency for VOC and
volatile HAP of 98 percent or greater. The investigation concluded that
no such historical data exist.
At this point, DuPont wrote a letter to the EPA, discussed in the
introduction to this section, asking the EPA to consider either adding
specific limits for hydrogen-fueled flares to the existing
specifications, or approving their hydrogen-fueled flares as an
alternate means of emission limitation. DuPont stated that they would
provide testing to support this request, and the EPA's Office of Air
Quality Planning and Standards (OAQPS) and Office or Research and
Development (ORD) agreed to review their test plan, observe testing and
review the test report.
[[Page 24438]]
II. DuPont Test Program for Hydrogen-Fueled Flares
A. Summary of Earlier Relevant Hydrogen-Fueled Flares Tests
There has been previous testing of hydrogen-fueled flares. In 1970,
a study was conducted to evaluate the stability of hydrogen-fueled
flares (Docket No. A-97-48, Item No. II-I-6). In this study the
velocity gradient and the volume percent hydrogen were correlated with
the observation of blow out (i.e., when the flame is completely
extinguished) for diffusion flares with hydrogen concentrations in the
50 to 100 volume-percent range. The velocity gradient is defined as the
change in velocity at the boundary of the fuel and air. A critical
velocity gradient for a given volume-percent of hydrogen was
identified, above which the flame was unstable. The significance of
this study was that the stability of hydrogen-rich flares (i.e., 50 to
100 volume-percent) was able to be predicted by calculating the
velocity gradient. Another study was conducted in 1984 (Docket No. A-
97-48, Item No. II-I-9), where the velocity gradient and predictions of
flame stability were investigated, but in the range of hydrogen
concentrations from 4 to 75 volume-percent hydrogen. However, data were
not collected in these tests sufficient to determine destruction
efficiencies.
B. Objectives of the DuPont Test Program
The primary objective of DuPont's hydrogen-fueled flare testing
program was to demonstrate that the hydrogen-fueled flares used at
their facilities were achieving a volatile HAP and VOC destruction
efficiency equal to or greater than that of flares meeting the existing
flare specifications. Specific technical objectives to support this
primary objective were:
(1) To determine the limits of velocity and hydrogen content within
which hydrogen-fueled flares are stable, and;
(2) To measure the destruction efficiencies of a surrogate for HAP
under conditions corresponding to those in industrial hydrogen-fueled
flares.
C. Design and Implementation of DuPont Test Program
The results of the testing program form the basis of these flare
specification amendments. The testing program used a nominal 3-inch
pipe flare with a hood and a stack suspended over the flare to capture
the plume. Stability and destruction efficiency tests were performed on
the test flare.
The first portion of the testing consisted of stability testing. To
determine the flare's stability limit, a stable flame was first
established, then the hydrogen flow rate was slowly reduced while
holding the tip velocity constant. Hydrogen readings were recorded when
the flame lifted off, and again when the flame completely blew out.
This procedure was repeated at different tip velocities in the 16 to
130 ft/s range, for flares with and without pilot burners.
The destruction efficiency of the flare was tested at high gas
velocities and hydrogen contents in the stable range. The gases in the
waste gas stream and in the hood stack were sampled and analyzed for
concentrations of the compound chosen as a surrogate for HAP. Since the
surrogate is a VOC this destruction efficiency also demonstrates the
destruction efficiency of VOC. Destruction efficiencies were then
calculated from these results.
D. Results of the Test Program
1. Flare Stability
The measurements of the hydrogen volume percent at lift off and
blow out for the piloted and unpiloted nominal 3-inch (2.9 inch inner
diameter) pipe flare are shown in Figure 1 as a function of velocity.
Because the hydrogen content at lift off was essentially the same for
flares with and without a pilot burner, a single line was fit to the
data sets of lift off measurements for piloted and unpiloted flares,
this is represented by the upper curve in Figure 1. The data point in
the far upper right corner of the figure is an unexplained outlier that
is inconsistent with all other data points and was excluded from the
linear regression analysis of the lift off data set. The middle and
lower curves in Figure 1 are the blow out curves without and with a
pilot, respectively.
BILLING CODE 6560-50-P
[[Page 24439]]
[GRAPHIC] [TIFF OMITTED] TR04MY98.003
BILLING CODE 6560-50-C
[[Page 24440]]
2. Destruction Efficiency
The measured mean destruction efficiencies and destruction
efficiencies at the 95 percent confidence level are shown in Figure 1.
All the measurements of destruction efficiencies at conditions more
stable than lift off were above 99 percent. Further, control
efficiencies greater than 98 percent were found at hydrogen contents
below the lift off curve.
III. Rationale
A. The Need for Specifications for Hydrogen-Fueled Flares
The EPA is taking this action to amend 40 CFR 60.18 and 40 CFR
63.11 since the EPA sees the need to permit the use of hydrogen-fueled
flares to meet the EPA control requirements. As discussed below,
hydrogen has a lower heat content than organics commonly combusted in
flares meeting the existing flare specifications and cannot, therefore,
be used to satisfy current control requirements. However, since the
combustion of hydrogen is different than the combustion of organics,
and the test report demonstrates a destruction efficiency greater than
98 percent, the EPA believes that hydrogen-fueled flares meeting the
specifications outlined in the amendments will achieve a control
efficiency of 98 percent or greater. This level of control is
equivalent to the level of control achieved by flares meeting the
existing specifications. In addition to achieving the same destruction
efficiency of VOC or organic HAP, the adoption of these amendments has
the added advantage of reducing the formation of secondary pollutants;
since the combustion of supplemental fuel would not be required by
hydrogen-fueled flares to meet the existing flare specifications.
1. The Heat Content of Hydrogen
The heat content of a substance is a measure of the amount of
energy stored within the bonds between atoms in each molecule of the
substance. Hydrogen is a simple molecule consisting of two hydrogen
atoms held together by weak, hydrogen bonds, thus resulting in a low
heat content. In comparison, organic chemicals are larger chains (or
rings) of carbons with hydrogens and other atoms attached to them.
These molecules are held together with a combination of ionic, covalent
and hydrogen bonds, which contain substantially more energy (i.e.,
higher heat content) than the hydrogen bond in the hydrogen molecule.
2. The Difference in Combustion Between Hydrogen and Organics
The first phenomenon to explain the difference in combustion
between hydrogen and organics is related to the thermodynamics of the
combustion reaction. In order for the hydrogen atom to react in the
combustion/oxidation reaction, the weak hydrogen bond between the two
hydrogen atoms must first be broken. Because there is less energy
holding the hydrogen atoms together, less energy (heat) is required to
separate them. Once the hydrogen bonds are broken, the hydrogen atoms
are free to react in the combustion reaction.
The second phenomenon explaining the difference in combustion
between hydrogen and organics is due to hydrogen's upper and lower
flammability limits. The flammability limits are the minimum (lower)
and maximum (upper) percentages of the fuel in a fuel-air mixture that
can propagate a self-sustaining flame. The lower and upper flammability
limits of hydrogen are 4.0 and 74.2 percent, respectively, which is the
second widest range of lower and upper limits of substances typically
combusted in flares (Docket No. A-97-48, Item No. II-I-2).
The third phenomenon explaining the difference in combustion
between hydrogen and organics is the relative difference in diffusivity
between hydrogen and organics in air. Diffusivity refers to how easily
molecules of one substance mix with molecules of another. Further, the
quicker the fuel and air in a flare mix, the quicker the combustion
reaction occurs. The measure of how quickly a substance mixes with
another substances is expressed in terms of the diffusivity
coefficient. The larger the diffusivity coefficient, the quicker the
mixing. The diffusivity coefficient for the mixture of hydrogen and air
is an order of magnitude higher than those for the mixture of air and
volatile HAP with readily available diffusivity coefficients.
Therefore, hydrogen is more diffuse in air compared to organics and
more quickly enters the flammability range than organics.
B. Use of DuPont Test Results as the Basis for Hydrogen-Fueled Flare
Specifications
These tests were conducted by DuPont primarily for their flaring
conditions. However, after reviewing the test plan, observing the
testing, and thoroughly reviewing the test report supplied by DuPont,
the EPA concluded that the test results were applicable to all
nonassisted flares with a hydrogen content of 8.0 percent (by volume)
or greater, and a diameter of 3 inches or greater. The EPA believes
that the test results are universally applicable since all the
effective data points demonstrated a destruction efficiency greater
than 98 percent, with the majority achieving greater than 99 percent
destruction. Therefore, if the test flare can achieve these destruction
efficiencies, then the EPA expects industrial flares meeting the flare
specifications in these amendments to achieve a destruction efficiency
of 98 percent or greater.
In selecting the conditions under which the pilot flare testing was
to be conducted and interpreting the results of the testing, a
``conservative'' decision was made for each choice, that is the
condition that would most likely assure that a full-scale flare would
achieve at least as high and possibly higher destruction efficiency was
chosen. This approach applied to the selection of flare tip design,
flare tip diameter, pilot burner heat input, and characteristics of the
surrogate for HAP for destruction testing. It also applied to the
evaluation of stability testing and destruction efficiency results, as
well as the selection of operating limits applying to hydrogen
concentration and tip discharge velocity.
1. The Selection of the Flare Type
A nonassisted, plain-tip flare was used in the testing program
because all of DuPont's flares are nonassisted. A nonassisted flare is
a flare tip without any auxiliary provision for enhancing the mixing of
air into its flame. The plain-tip means no tabs or other devices to
redistribute flow were added to the rim of the flare. Because the
presence of tabs improves the stability of the flare by channeling the
flare's flow and improving mixing of fuel and air, it was concluded
that the lack of tabs (i.e., plain tip) would result in the least
stable test conditions.
2. The Comparison of the Selected Flare with the Existing Flare
Specifications
A 3-inch flare was selected for the emission test since this was
the same size flare used for the testing to establish the basis for the
existing flare specifications in 40 CFR 60.18 and 40 CFR 63.11.
Stability tests were conducted using propane to determine if the flare
was operating properly and could meet the existing flare
specifications. Test results demonstrated that this flare was stable
when it was expected to be stable and not stable when it was not
expected to be (i.e., as indicated by the existing flare
specifications).
[[Page 24441]]
3. The Size of the Test Flare
Another reason for using the 3-inch flare for these tests is
because a 3-inch flare is small, relative to the size of flares in
industry (as a point of reference, the DuPont flares are 16 to 48
inches in diameter). Research indicates that smaller flares are less
stable than larger flares (Docket No. A-97-48, Item No. II-I-1, Sec 4,
page 6). Specifically, the physical parameter known as the velocity
gradient can be used to predict when a flame will blow out by plotting
the velocity gradient versus the volume-percent hydrogen. The larger
the boundary velocity gradient, the more unstable the flame. Further,
the velocity gradient is inversely proportional to the diameter of the
pipe. Therefore, at a given velocity, the larger the pipe, the smaller
the boundary velocity, and the more stable the flame. The EPA concludes
that if a stable flame can be maintained with a smaller flare pipe,
then a larger flare would be expected to be stable at lower hydrogen
concentrations and higher velocities. Therefore, the EPA believes that
3-inch or larger flares that meet these specifications will have
destruction efficiencies as high or higher than those obtained from the
3-inch pipe flares.
4. The Selection of the Size of the Pilot Burner
The amount of heat input from the pilots on DuPont's full-scale
hydrogen-fueled flares are in the range from 0.05 to 0.6 percent of the
total heat input to the flares. A venturi burner turned down to
approximately one third of its 9,000 Btu/hr capacity was used for the
tests described in this document, and the heat input was equal to 0.3
to 0.6 percent of the pilot flare's total heat input during the
stability and destruction efficiency tests. Therefore, the heat input
from the pilot during the tests was comparable to the heat input for
the full-scale flares operated by DuPont.
The relatively small proportion of heat input from the venturi
burner compared to the total heat input to the test flare would not be
expected to have a significant effect on either the stability or
destruction efficiency results, because this amount of heat is
insignificant compared to the flare's total heat content. Also, the use
of a pilot burner is consistent with EPA's flare specification which
requires that the pilot flame be present at all times.
5. The Selection of Ethylene as the Surrogate for HAP to be used in the
testing
For this study it was desired to select a surrogate for HAP that
was more difficult to destroy than the volatile HAP present in the
large scale flare waste streams, and which could be measured at a
concentration of 10 parts per billion by volume and higher. In general,
the difficulty of destruction for organics increases as the molecular
weight decreases, but the limit of detection decreases as the molecular
weight decreases. It is obvious then that there may be some compromise
necessary in selecting a surrogate for HAP.
In order to compare the relative difficulty to destroy various
species, a linear multiple regression model was used that calculates a
destruction temperature using parameters describing the molecular
structure, autoignition temperature, and residence time as inputs to
the model. The destruction temperatures obtained are theoretical
temperatures for plug flow reactors to achieve specified destruction
allowing a comparison to be made among various chemical species to
estimate relative destructibility (Docket No. A-97-48, Item No. II-I-
14). As a first step the destruction temperatures were calculated for
all the chemical species that were identified as present in DuPont's
full-scale flare waste streams. The next step was to calculate
destruction temperatures for the surrogates for HAP under
consideration. (The results from this analysis are presented in Tables
4-3 and Table 4-4 of Docket Item II-I-14).
In comparing the model's destruction temperature estimates for
candidate surrogates for HAP present in DuPont's flare streams, the
best choice as a surrogate was methane, but the detection limit was too
high to be accepted for the field study. The next choice was methanol
but not only is the detection limit high, it is a HAP and it is also a
liquid at ambient temperatures, presenting handling difficulties. The
next candidate considered was ethylene which was selected for the
study. It has a higher destruction temperature than all the organic HAP
in the study, except methanol, and has an acceptable limit of
detection. Therefore, the most difficult to destroy substance was
chosen for the study that was feasible to use.
6. The Criteria for a Stable Flame
The hydrogen content reported when lift off was first observed was
selected as the criterion for a stable flame, because it was easy and
precise to identify. The EPA concluded that this was a conservative
estimate for the stability limit because destruction efficiencies
greater than 98 percent were noted even for hydrogen contents below the
lift off level.
Another reason why the EPA concluded that lift off was a
conservative criterion for a stable flame was based on a correlation
between the stability ratio and the destruction efficiency observed in
earlier flare testing conducted in the 1980's (Docket No. A-97-48, Item
No. II-I-5). At that time it was demonstrated that the destruction
efficiencies were directly proportional to the ratio of the flare gas
heating value to the minimum heating value for flame stability (i.e.,
stability ratio). Regardless of the substance being combusted, it was
observed that the destruction efficiency plateaued to greater than 98
percent destruction when the stability ratio was above approximately
1.2. For this test program, the destruction efficiency versus the ratio
of actual hydrogen to hydrogen at lift off (analogous with the
stability ratio, and referred to as the hydrogen ratio) was plotted for
this test program. The curve of the data was similar to those obtained
from the flare test programs in the 1980's. Three data points
demonstrated that at stability ratios below 1.0, with the lowest
stability ratio of 0.955, destruction efficiencies greater than 98
percent were achieved. Since the amendments for these flare
specifications require a stability ratio of 1.0 or greater, it is
assumed that a 98 percent or greater destruction efficiency will be
achieved.
7. The Operating Parameters Used for Testing the Destruction Efficiency
(i.e., Hydrogen Content and Flare Tip Velocity)
The destruction efficiency of ethylene for the hydrogen-fueled
flares was tested at high tip velocities (i.e., approximately 100 to
120 ft/sec) because this is the velocity range expected to produce
lower destruction efficiencies. Therefore, if acceptable destruction
efficiencies are observed at high tip velocities, then at least as high
or even higher destruction efficiencies are expected at lower tip
velocities.
The expectation to observe decreased destruction efficiency at high
tip velocities is explained by two phenomena. The first phenomenon is
due to the increased fuel flow. The increased volume of fuel flow
entrains more air, and more eddies are formed at the boundary between
the fuel and the air. These eddies tend to strip off some of the gases'
flow, even before the flame is able to combust the substances, so
uncombusted or incompletely combusted substances may be lost to the
ambient air.
Another phenomenon explaining the expectation of decreased
destruction efficiency at increased tip velocities
[[Page 24442]]
results from comparisons of stability ratios at different tip
velocities. For this test program the ratio of the hydrogen content at
lift off to the hydrogen content at blow out with a pilot was used as
an analogous ratio to the previously mentioned stability ratio.
Further, the value of hydrogen at blow out was used as the minimum
hydrogen content, since at essentially this level of hydrogen, the
destruction efficiencies were above 98 percent for tip velocities of
100 and 120 ft/sec. The DuPont test program's data revealed a trend
where the hydrogen ratios were lower at higher velocities compared to
lower tip velocities, 1.15 to 1.17 versus 1.3, respectively. Since the
test programs in the 1980's demonstrated that the destruction
efficiency is directly proportional to the stability ratio, then it
could be expected that the same or higher destruction efficiencies
would be experienced at lower tip velocities where the hydrogen ratios
are larger.
C. Selection of the Specifications for Hydrogen-Fueled Flares
The operating specification for hydrogen-fueled flares in these
amendments is the maximum tip velocity for a given hydrogen content,
from the equation of the line fitting the data from the stability
testing at lift off conditions as seen in Figure 1. The equation in
these amendments comes directly from the test report. This equation is
presented in the appropriate form in Section IV of this preamble with
the units changed to metric.
There are safety requirements that must be carefully considered for
all flare installations, and this is the case for the user of these
hydrogen-fueled flare amendments. As an example, if the discharge
velocity is too low under certain conditions, the flame could propagate
back into the process with potentially catastrophic results. These
amendments only specify a maximum discharge velocity for the purpose of
assuring efficient destruction of pollutants in waste streams and do
not address any aspect of safe operation. The user of any EPA flare
specifications should carefully consider all features of this
application, not just the limitation on maximum discharge velocity, and
implement all necessary measures to assure a safe operation. Safe
operating conditions are always the responsibility of the owner/
operator at each facility to assure that all applicable safety
requirements are adhered to whether they are company, consensus and/or
governmental requirements.
The EPA did not think that extrapolating the data outside the range
of values tested to be prudent; therefore, the hydrogen-fueled flare
specifications have been restricted to the confines of the conditions
used for the test program. The following restrictions are included in
the hydrogen-fueled flare specifications:
1. Nonassisted Flares
The amendments are applicable to only nonassisted flares because
that is the only type of flare tested for these amendments.
2. Continuous Flame
The existing flare specifications require the presence of a
continuous flame where reliable ignition is obtained by continuous
pilot burners designed for stability. To ensure that the pilot is
continuously lit, a flame detection device is required. These
amendments incorporate the same requirements for the same reason, to
ensure flame stability.
3. Minimum Flare Diameter
The testing was conducted on 3-inch flares, therefore this is the
minimum flare diameter for the amendments.
4. Minimum Hydrogen Content
The minimum hydrogen content in the gas streams tested was rounded
to the nearest whole number, 8.0 volume percent, and set as the
defining minimum hydrogen concentration cutoff for a hydrogen-fueled
flare.
5. Maximum Tip Velocity
The maximum tip velocity was set at 37.2 m/sec (122 ft/s), because
that was the highest tip velocity tested.
6. Flame Stabilizers
Flame stabilizers (often called flame holders) are allowed because
stability and destruction efficiency testing was conducted without
them, so if these tabs stabilize the flame even better mixing, and
potentially greater destruction efficiencies can be achieved.
7. Minimum Flare Tip Velocity
A minimum flare tip velocity was not listed since evidence
indicates that performance will not be diminished due to lower tip
velocities (See the preceding discussion concerning safety
responsibilities).
D. Decision To Proceed With Direct Final Rulemaking
This notice is being published as a direct final notice since the
EPA does not anticipate relevant adverse comments. For the reasons
discussed in this notice, the EPA believes that hydrogen-fueled flares
meeting the operating specification in this amendment will achieve the
same control efficiency, i.e., 98 percent or greater, as flares
complying with the existing flare specifications. Further, these
specifications will result in reduced emissions of carbon monoxide,
nitrogen oxides, and carbon dioxide formed during the combustion of
supplemental fuel necessary for hydrogen-fueled flares to comply with
existing regulations. By promulgating these amendments some companies
using hydrogen-fueled flares can, as of the effective date of this
amendment, reduce supplemental fuel use resulting in cost savings and
reduced emissions.
IV. Summary of the Amendments to the Flare Specifications
The amendments to the flare specifications add requirements for
nonassisted flares that combust 8.0 percent (by volume) or greater of
hydrogen in the stream and have a 3-inch or greater diameter. The
amendments present an equation that calculates the maximum allowable
flare tip velocity for a given volume percent of hydrogen. This
equation format is similar to the one used for air-assisted flares in
the existing flare specifications. The specific equation for the
maximum tip velocity for hydrogen-fueled flares is:
Vmax=(XH2--K1)* K2
Where:
Vmax=Maximum permitted velocity, m/sec.
K1=Constant, 6.0 volume-percent hydrogen.
K2=Constant, 3.9(m/sec)/volume-percent hydrogen.
XH2=The volume-percent of hydrogen, on a wet basis, as
calculated by using the American Society for Testing and Materials
(ASTM) Method D1946-77.
This direct final rule adds specifications for hydrogen-fueled
flares to both 40 CFR 60.18 and 63.11. The amendments to the General
Provisions for NSPS are contained in 40 CFR 60.18. In addition, 40 CFR
60.18 (c)(4)(i) was revised to correct an earlier published
typographical error. The amendments to the General Provisions for
NESHAP are contained in 40 CFR 63.11(b)(9). 40 CFR 63.11(b)(8) was also
revised to make the number of significant figures consistent throughout
the specifications.
IV. Impacts
The impacts discussed in this section are only for six DuPont
flares that are required by current or pending EPA regulations to meet
the existing flare specifications. The EPA does not have information,
and cannot estimate
[[Page 24443]]
impacts for other hydrogen-fueled flares in the United States.
Therefore, the following estimates are limited to these six DuPont
flares.
A. Primary Air Impacts
The amended flare specifications will reduce emissions by the same
amount (i.e., 98 percent or greater) as emissions would be reduced by
using flares meeting the existing flare specifications.
B. Other Environmental Impacts
The Agency estimates that these amendments to the flare
specifications will reduce secondary emissions of pollutants since the
combustion of supplemental organic fuel will no longer be required;
therefore, there will be no emissions resulting from the combustion of
a supplemental fuel. It is estimated that these flare specification
amendments will reduce annual emissions from the six affected DuPont
flares by 147 megagrams (161 tons per year) of criteria pollutants
(i.e., 124 megagrams (136 tons per year) of carbon monoxide, and 22.7
megagrams (25 tons per year) of nitrogen oxides) and 39,900 megagrams
(44,000 tons per year) of carbon dioxide.
In addition to these secondary emission reductions, there may also
be State regulations that require owners/operators to follow the
existing flare specifications, and by allowing the owners/operators to
meet the specifications in these amendments, there may be further
reductions in secondary air emissions. Therefore, these impacts are a
minimal estimate of the potential secondary air emission reductions.
C. Energy Impacts
These amendments to the flare specifications are expected to
decrease the amount of energy used by DuPont's six hydrogen-fueled
flares since these flares will no longer be required to combust
secondary fuel. The expected energy savings is estimated to be 7.75 x
108 cubic feet of natural gas annually (7.75 x
1011 Btu/yr) .
D. Cost and Economic Impacts
Cost savings will be realized due to these amendments by not
requiring the combustion of supplemental fuel (to comply with the
original heat content requirements), and by not requiring the
subsequent resizing of the existing flares that would result from a
requirement to combust supplemental fuel in order to accommodate the
additional flow of supplemental fuel. The cost of natural gas as
supplemental fuel for the six affected flares is estimated to be $2.8
million per year. The capital investment to replace a smaller flare tip
with a larger one is estimated to be approximately $667,000 per flare
or $4 million for all six flares. The total annual savings achieved by
allowing hydrogen-fueled flares that fulfill the specifications of
these amendments are the sum of the annual fuel cost savings, and the
annualization of the capital savings (calculated to be $280,000 per
year). Therefore, total annual savings for the six affected DuPont
flares are estimated to be $3.08 million per year. Since sources using
these hydrogen-fueled flare specifications will experience savings, no
adverse economic impacts will result from this action.
E. Summary of Impacts
This section discussed the cost savings, emission reduction of
secondary pollutants, and energy savings from only the six DuPont
flares subject to current or pending regulations. These flare
specification amendments have the potential to reduce emissions and
save money and fuel from hydrogen-fueled flares of which the EPA is not
yet aware.
VI. Administrative
A. Paperwork Reduction Act
This rule does not contain any information collection subject to
the Office of Management and Budget (OMB) approval under the Paperwork
Reduction Act (PRA), 44 U.S.C. 3501 et seq.
B. Executive Order 12866 Review
Under Executive Order 12866, (58 FR 51735 (October 4, 1993) the
Agency must determine whether the regulatory action is ``significant''
and therefore subject to OMB review and the requirements of the
Executive Order. The Order defines ``significant regulatory action'' as
one that is likely to result in a rule that may:
(1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or tribal governments or
communities;
(2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
(3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs or the rights and obligations of recipients
thereof; or
(4) Raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
It has been determined that these amendments are not a
``significant regulatory action'' under the terms of Executive Order
12866 and, therefore, are not subject to review by the Office of
Management and Budget.
C. Regulatory Flexibility Act
EPA has determined that it is not necessary to prepare a regulatory
flexibility analysis in connection with this final rule. EPA has also
determined that this rule will not have a significant economic impact
on a substantial number of small entities, because this rule imposes no
additional regulatory requirements, but merely expands the types of
flares that may be used to meet the requirements of 40 CFR 60 and 40
CFR 63.
D. Unfunded Mandates Reform Act
Under section 202 of the Unfunded Mandates Reform Act of 1995
(``Unfunded Mandates Act''), signed into law on March 22, 1995, the EPA
must prepare a budgetary impact statement to accompany any proposed or
final standards that include a Federal mandate that may result in
estimated costs to State, local, or tribal governments, or to the
private sector, of, in the aggregate, $100 million or more. Under
section 205, the EPA must select the most cost effective and least
burdensome alternative that achieves the objectives of the standard and
is consistent with statutory requirements. Section 203 requires the EPA
to establish a plan for informing and advising any small governments
that may be significantly or uniquely impacted by the standards.
The EPA has determined that the final standards do not include a
Federal mandate that may result in estimated costs of, in the
aggregate, $100 million or more to either State, local, or tribal
governments, or to the private sector, nor do the standards
significantly or uniquely impact small governments, because they
contain no requirements that apply to such governments or impose
obligations upon them. Therefore, the requirements of the Unfunded
Mandates Act do not apply to this final rule.
E. Submission to Congress and the Comptroller General
The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General
[[Page 24444]]
of the United States. EPA will submit a report containing this rule and
other required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. This rule is not a
``major rule'' as defined by 5 U.S.C. 804(2).
List of Subjects
40 CFR Part 60
Environmental protection, Air pollution control, Incorporation by
reference.
40 CFR Part 63
Environmental protection, Air pollution control, Hazardous
substances, Incorporation by reference.
Dated: April 17, 1998.
Carol M. Browner,
Administrator.
For the reasons set out in the preamble, title 40, chapter I of the
Code of Federal Regulations is amended as follows:
PART 60--STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES
1. The authority citation for part 60 continues to read as follows:
Authority: 42 U.S.C. 7401, 7411, 7414, 7416, 7429, 7601 and
7607.
Subpart A--General Provisions
2. Section 60.17 is amended by revising paragraph (a)(6) to read as
follows:
Sec. 60.17 Incorporation by reference.
* * * * *
(a) * * *
(6) ASTM D1946-77, Standard Method for Analysis of Reformed Gas by
Gas Chromatography, IBR approved for Secs. 60.45(f)(5)(i),
60.18(c)(3)(i), 60.18(f), 60.614(d)(2)(ii), 60.614(d)(4),
60.664(d)(2)(ii), 60.664(d)(4), 60.564(f), 60.704(d)(2)(ii) and
60.704(d)(4).
* * * * *
3. Section 60.18 is amended by revising paragraphs (c)(3) and
(c)(4)(i), and by adding paragraphs (c)(3)(i) and (c)(3)(ii) to read as
follows:
Sec. 60.18 General control device requirements.
* * * * *
(c) * * *
(3) An owner/operator has the choice of adhering to either the heat
content specifications in paragraph (c)(3)(ii) of this section and the
maximum tip velocity specifications in paragraph (c)(4) of this
section, or adhering to the requirements in paragraph (c)(3)(i) of this
section.
(i)(A) Flares shall be used that have a diameter of 3 inches or
greater, are nonassisted, have a hydrogen content of 8.0 percent (by
volume), or greater, and are designed for and operated with an exit
velocity less than 37.2 m/sec (122 ft/sec) and less than the velocity,
Vmax, as determined by the following equation:
Vmax=(XH2-K1)* K2
Where:
Vmax=Maximum permitted velocity, m/sec.
K1=Constant, 6.0 volume-percent hydrogen.
K2=Constant, 3.9(m/sec)/volume-percent hydrogen.
XH2=The volume-percent of hydrogen, on a wet basis, as
calculated by using the American Society for Testing and Materials
(ASTM) Method D1946-77. (Incorporated by reference as specified in
Sec. 60.17).
(B) The actual exit velocity of a flare shall be determined by the
method specified in paragraph (f)(4) of this section.
(ii) Flares shall be used only with the net heating value of the
gas being combusted being 11.2 MJ/scm (300 Btu/scf) or greater if the
flare is steam-assisted or air-assisted; or with the net heating value
of the gas being combusted being 7.45 MJ/scm (200 Btu/scf) or greater
if the flare is nonassisted. The net heating value of the gas being
combusted shall be determined by the methods specified in paragraph
(f)(3) of this section.
(4)(i) Steam-assisted and nonassisted flares shall be designed for
and operated with an exit velocity, as determined by the methods
specified in paragraph (f)(4) of this section, less than 18.3 m/sec (60
ft/sec), except as provided in paragraphs (c)(4)(ii) and (iii) of this
section.
* * * * *
PART 63--NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS
FOR SOURCE CATEGORIES
1. The authority citation for part 63 continues to read as follows:
Authority: 42 U.S.C. 7401, 7411, 7412, 7414, 7416, 7429, 7601
and 7607.
Subpart A--General Provisions
2. Section 63.11 is amended by revising paragraphs (b)(6) and
(b)(8), and by adding paragraphs (b)(6)(i) and (b)(6)(ii) to read as
follows:
Sec. 63.11 Control device requirements.
* * * * *
(b) * * *
(6) An owner/operator has the choice of adhering to the heat
content specifications in paragraph (b)(6)(ii) of this section, and the
maximum tip velocity specifications in paragraph (b)(7) or (b)(8) of
this section, or adhering to the requirements in paragraph (b)(6)(i) of
this section.
(i)(A) Flares shall be used that have a diameter of 3 inches or
greater, are nonassisted, have a hydrogen content of 8.0 percent (by
volume) or greater, and are designed for and operated with an exit
velocity less than 37.2 m/sec (122 ft/sec) and less than the velocity
Vmax, as determined by the following equation:
Vmax=(XH2-K1)* K2
Where:
Vmax=Maximum permitted velocity, m/sec.
K1=Constant, 6.0 volume-percent hydrogen.
K2=Constant, 3.9(m/sec)/volume-percent hydrogen.
XH2=The volume-percent of hydrogen, on a wet basis, as
calculated by using the American Society for Testing and Materials
(ASTM) Method D1946-77. (Incorporated by reference as specified in
Sec. 63.14).
(B) The actual exit velocity of a flare shall be determined by the
method specified in paragraph (b)(7)(i) of this section.
(ii) Flares shall be used only with the net heating value of the
gas being combusted at 11.2 MJ/scm (300 Btu/scf) or greater if the
flare is steam-assisted or air-assisted; or with the net heating value
of the gas being combusted at 7.45 M/scm (200 Btu/scf) or greater if
the flares is non-assisted. The net heating value of the gas being
combusted in a flare shall be calculated using the following equation:
[GRAPHIC] [TIFF OMITTED] TR04MY98.004
Where:
HT=Net heating value of the sample, MJ/scm; where the
net enthalpy per mole of offgas is based on combustion at 25 deg.C and
760 mm Hg, but the standard temperature for determining the volume
corresponding to one mole is 20 deg.C.
K=Constant=
[GRAPHIC] [TIFF OMITTED] TR04MY98.005
where the standard temperature for (g-mole/scm) is 20 deg.C.
[[Page 24445]]
Ci=Concentration of sample component i in ppmv on a wet
basis, as measured for organics by Test Method 18 and measured for
hydrogen and carbon monoxide by American Society for Testing and
Materials (ASTM) D1946-77 (incorporated by reference as specified in
Sec. 63.14).
Hi=Net heat of combustion of sample component i, kcal/g-mole
at 25 deg.C and 760 mm Hg. The heats of combustion may be determined
using ASTM D2382-76 (incorporated by reference as specified in
Sec. 63.14) if published values are not available or cannot be
calculated.
n=Number of sample components.
* * * * *
(8) Air-assisted flares shall be designed and operated with an exit
velocity less than the velocity Vmax. The maximum permitted
velocity, Vmax, for air-assisted flares shall be determined
by the following equation:
Vmax=8.71 + 0.708(HT)
Where:
Vmax=Maximum permitted velocity, m/sec.
8.71=Constant.
0.708=Constant.
HT=The net heating value as determined in paragraph
(b)(6)(ii) of this section.
* * * * *
[FR Doc. 98-11262 Filed 5-1-98; 8:45 am]
BILLING CODE 6560-50-P
