[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: a-and-
[email protected]. 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.       
------------------------------------------------------------------------

    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