A Discussion of Concerns if Proposed Refinery Flare Rules are Applied to the Chemical Industry

A Discussion of Concerns if Proposed Refinery Flare Rules are Applied to the Chemical Industry American Flame Research Committee (AFRC) 2015 Industrial Combustion Symposium September 9 - 11, 2015 Troy M. Boley, Ph. D. Sage Environmental Consulting, LP Vice President 600 Chastain Road NW, Suite 320 Kennesaw, GA 30144 Bruce C. Davis, PENY, QEP E. I. DuPont de Nemours and Company DuPont Engineering Research & Technology 140 Cypress Station Drive, Suite 135 Houston, TX 77090 Introduction The EPA proposed expanded refinery flare rules in June, 20141. The comment period on these rules closed in October, 2014 and the rules are scheduled to be adopted by the EPA administrator on or before September 30, 2015. Approximately 200,000 public comments were received by the EPA relating to the total rule package. The rules, when finalized, will be applicable only to the petroleum refining sector, but the principles can be expected to be the basis for future flare rules for other industry groups. Indeed, the next subsequent sets of rules for the chemical industry, where new flare provisions are expected, are anticipated for the ethylene industry. The proposed refinery flare provisions present a number of problems if they are applied as presented, and more significantly if applied directly to the Chemical Industry. In the proposed refinery rules, the EPA has proposed combustion zone performance parameters for only two flare category types - "all flares" and "air assisted flares". The current EPA General Standards for flares (regardless of industry sector) set basic requirements for four categories or flare types: steam assisted, non-assisted, air assisted and hydrogen rich flares. Many suggest that there are possibly seven basic flare categories that may have different performance parameters needing unique considerations so as to be regulated effectively. The seven categories presented herein include: steam assisted, air assisted, non-assisted, hydrogen rich, pressure flares, ground flares and enclosed flares. This paper will briefly review each of these unique flare categories and discuss the potential impact of the proposed refinery rules to these situations. For non-assisted and hydrogen rich flares, historical 1 79 FR 36880, June 30, 2014. 1 flare combustion efficiency test data will be presented demonstrating no change is required from the current regulations for these flare categories. If any of EPA's proposed combustion parameters are forcibly applied to non-assisted or hydrogen rich flares, the implications suggest supplemental fuel addition with inconsequential emission reduction benefit. Discussion Existing Regulations The existing general industry flare rules date back to the 1980's and are provided at 40 CFR 60.18(b) and 63.11(b). These rules basically require:     A pilot flame, A sufficiently low flare tip exit velocity, A minimum heating value of the flared gas (e.g. >300 BTU/scf for steam or air assisted flares, and >200 BTU/scf for non-assisted flares), and Smokeless operation. Additional qualitative and somewhat subjective flare requirements may be implied at EPA citations including: 40 CFR 60.11(d), 60.18(d), 60.482-10(e), 63.6(e), 63.11(b)(1), 63.172(e) which generally reference:   Adherence to the flare's design documents, and Use of good air pollution control practices. The existing flare-related rules deal with four categories of flare operations. These are steam assisted flares, air assisted flares, non-assisted flares and hydrogen rich flares. These rules are currently in the general provisions of NSPS and MACT rules. The flare rules are referenced by the specific regulation and are the same for all regulations per the current organization for 40 CFR Parts 60, 63 and 65. The General Provisions only specify basic monitoring requirements for the presence of the pilot flame and the operation of a flare with no visible emissions. The current rules exempt operational periods of start-up, shutdown and malfunction (SSM) from visible emissions and exit velocity requirements. The Proposed Rules & Reasons for Change The U.S.EPA has concluded that flare combustion efficiency performance tests conducted over the past few years suggest that the current regulatory requirements may be insufficient to ensure that refinery flares are operating consistently with the 98-percent HAP destruction efficiencies that EPA has determined to be the MACT floor. 2 The proposed refinery performance parameters are one size fits all (large, medium and small flare systems) and are proposed to include only two flare category types. The current regulatory parameters will change from one-time or periodic spot measurements of calorific value and tip exit velocity to continuous measurement requirements. The proposed regulations require continuous monitoring/measurement to enable calculation of BTU/scf, or % LFL, or % combustibles in the combustion zone. The new rules require continuous compliance during periods of startup, shutdown and normal operations. Combustion zone parameters imply an accounting for steam or air assist rates, and thus require measuring both flared gas flow and steam or air assist flow. In addition, different measurements (either composition or BTU/scf) will be needed to estimate each of the performance parameters. The EPA is proposing an averaging time of a 15 minute block average for compliance parameters and exit velocity. The EPA Refinery Rule is combining the steam assisted, non-assisted and hydrogen rich flare types into one rule grouping. The proposed grouping for the refinery rules is two groups which are "all flares" and air assisted flares. EXISTING CATEGORIES Steam Assisted Flares Non-Assisted Flares Hydrogen Rich Flares Air Assisted Flares NEW CATEGORIES All Flares to include Steam Assisted, NonAssisted and Hydrogen Rich Flares Air Assisted Flares There are other flare types including pressure flares and ground flares and enclosed flares. Chemical i Industry comments submitted on the proposed refinery rule emphasize that the EPA should not adopt the new category groupings for flares. The current category grouping should be retained, with appropriate operating parameters for steam assisted, non-assisted, air assisted and hydrogen rich flares. Further, pressure flares, ground flares and enclosed flares should be exempt from these standards. The exit velocity behavior and performance for these flares differs significantly from air assisted, steam assisted flares and hydrogen rich flares. The proposed refinery rule combustion zone regulatory parameters are either:    >= 270 BTU/scf, or <= LFLcz 0.15 fraction, or >= % combustibles in the combustion zone of >0.18 fraction. The parameters are all combustion zone (Cz) parameters. The EPA proposed refinery parameters will have subcategories dealing with what EPA is referring to as "hydrogen olefin interactions". Hydrogen-Olefin interactions are assumed to be present when the concentration of hydrogen and olefins in the combustion zone exceed all three of the following criteria: 3 (1) CH2 in the combustion zone is greater than 1.2 % by volume. (2) The cumulative Colefins in the combustion zone is greater than 2.5 % by volume. (3) The cumulative Colefins in the combustion zone + CH2 in the combustion zone is greater than 7.4% by volume. The proposed rules will assign: • • One set of rules for steam, non-assisted and hydrogen rich flares with 3 parameter options (CzNHV, % LFL, % Combustible) o Two subsets of parameters are provided for flares with and without hydrogen olefin interactions applicable to all the flare types One set of rules for air assisted flares with 3 parameter options o Two sub sets of parameters are provided for flares with and without hydrogen olefin interactions applicable to all the flare types Extensive comments were submitted by the API on the hydrogen olefin issue.ii Comments were also submitted on the issue of compliance at all times including compliance during periods of startup, shutdown and normal operations. The focus of this paper is related to the regulation of the seven separate flare types. Each of the 7 flare types are discussed in the following sections. The regulatory approach for each flare type is outlined. An Analysis of Non-assisted Flares The EPA stated in April 2012 that there is not enough data to establish performance parameters for nonassisted flares2. For non-assisted flares, the combustion properties in the combustion zone are the same as the flared gas. Less than 10 % of refinery flares are non-assisted flares according to the 2011 EPA Refinery Information Collection Request database. A change to the non-assisted flare requirements based on steam assisted flare data is not warranted and it is not appropriate to combine non-assisted flares into one "all flares" category. The requirements should be left "as is" until there is test data or related information that supports the need for a change. This analysis compares the performance of non-assisted flares using the CMA/EPA 1983 data. 3 4 The proposed parameters are calculated for each of the ten (10) non-assisted flare test data sets and compared to the test data. The point where it is estimated that less than 98 % combustion efficiency is reached is compared to the new parameters. 2 USEPA, OAQPS. "Parameters for Properly Designed and Operated Flares'. April, 2012.Page 7-1 The CMA/EPA Study Report is available from TCEQ Flare Stakeholders Web Page 4 A write-up of the CMA study is also available at Davis, B. C., "Flare Efficiency Studies", Plant Operations Progress, July, 1983, Vol. 2 No. 3, Page 191 - 198. 3 4 Use of flammability diagrams to analyze flare data is described in this set of comments and in EPA's Flare Parameter Report.5 The approach used for this analysis is described in B. C. Davis' April, 2012 AIChE presentation6 and was originally developed by Shell.7 The data analysis approach involves:     Use of the CMA/EPA test data for non-assisted flares. Construction of a flammability diagram for the test cases. Plotting the test results on the flammability diagram. o Each of the tests corresponds to a % inert (x-axis) and fuel composition (y-axis) on the flammability diagram. Comparing the test results to the new parameters. o Each of the new parameters corresponds to a % inert (x-axis) and fuel composition (yaxis) on the flammability diagram. The subset of data for non-assisted flares is provided in Table 1. These tests were all performed at or near zero steam flow. The incipient smoke point for this data set is roughly 600 - 650 BTU/scf. For the 80/20 propylene/propane mixture inerted with nitrogen, smoking does not occur for mixtures below approximately 600 BTU/scf. At low BTU's minimal smoking occurs and minimal steam is needed. 5 USEPA, OAQPS. "Parameters for Properly Designed and Operated Flares'. April, 2012.Pages 3-1 - 3-5. Davis B. C "A Review of Regulatory & Engineering Issues Dealing with Flares Based on Forthcoming EPA Flare Regulations" presented at @ the 2012 AIChE Spring Meeting, Houston, TX - April 2, 2012 7 Mueller, Gary. "Combustion of Mixtures: A Modified IFC Approach" 2011 AFRC Flare Colloquium, Houston TX, September 19, 2011. 6 5 Table 1 - CMA/EPA Test Data for Non-Assisted Flaring Test Heating Combustion Number Value Efficiency BTU/scf % 16d 634 99.78 16c 519 99.74 16b 408 99.75 16a 339 99.73 11c 364 99.82 11b 342 99.86 11a 305 99.79 60 298 98.92 59b 232 99.33 59a 192 97.95 The proposed flare parameters calculated for each of the CMA flare tests are presented in Table 2. 6 Table 2 - EPA Parameter Calculations for CMA/EPA Non-Assisted Flare Data Test Number 16d 16c 16b 11c 11b 16a 11a 59b 60 59a Heating Value BTU/scf 636 522 411 367 345 341 307 234 210 193 Combustion Efficiency % 99.78 99.74 99.75 99.82 99.86 99.73 99.79 99.33 98.92 97.95 N2 Vol % % 70.84% 76.10% 81.17% 83.20% 84.21% 84.38% 85.95% 89.30% 90.38% 91.14% Fuel Vol CzNHV or LFL Cz % NHVvg % BTU/scf fraction 29.16% 636 0.07 23.90% 522 0.08 18.83% 411 0.11 16.80% 367 0.12 15.79% 345 0.13 15.62% 341 0.13 14.05% 307 0.14 10.70% 234 0.19 9.62% 210 0.21 8.86% 193 0.23 % Comb % 0.29 0.24 0.19 0.17 0.16 0.16 0.14 0.11 0.10 0.09 The data in Table 3 shows that the cut point for 98% combustion efficiency is 193 BTU/scf. The EPA used the CMA/EPA data and other data to adopt the current heating value parameter for non-assisted flares, 200 BTU/scf. The fuel for these tests was an 80/20 propylene-propane mixture. The proposed parameters and the existing parameters for non-assisted flares are provided in Table 4. Table 3 Calculated Flare Parameters in Units of BTU/scf, LFL Cz and % Combustibles Description New EPA BTU/scf Parameter Old EPA BTU/scf Parameter Critical Point New EPA CzLEL Parameter New EPA % Comb Parameter Fuel Vol CzNHV or LFL Cz % NHVvg % BTU/scf fraction 12.37% 270 0.16 9.16% 200 0.22 6.19% 135 0.33 13.46% 294 0.15 18.00% 393 0.11 N2 Vol % % 87.63% 90.84% 93.81% 86.54% 82.00% % Comb % 0.12 0.09 0.06 0.13 0.18 The fuel composition for these calculations is an 80/20 mixture of propylene and propane, respectively. These calculations are composition dependent and will be different for different compositions. The yellow highlighted cells are the parameters in the units expressed in the current and proposed regulations. The CMA/EPA non-assisted flare data brackets these parameters, meaning that the current parameter is adequate and there is no need to change it. The critical point is the composition below which combustion cannot occur based on the flammability diagram. 7 Table 4 - Estimated Supplemental Fuel Heating Value Required to Achieve the New Flare Parameters Description Data Move New EPA BTU/scf Parameter ~ 210 --> ~ 280 BTU/scf New EPA CzLEL Parameter ~ 210 --> ~ 304 BTU/scf New EPA % Comb Parameter ~ 210 --> ~ 400 BTU/scf % Fuel Increase 35.0% 49.5% 90.5% Est CE @ start ~ 98.9 % ~ 98.9 % ~ 98.9 % Est CE @ Finish ~ 99.8 % ~ 99.8 % ~ 99.5 % The data in this table shows the BTU/scf move needed to comply with all of the new parameters. The LFLCz and % combustible parameters are expressed in BTU/scf units in order to easily estimate the amount of fuel needed to achieve the respective operating parameter. The starting point is 210 BTU/scf which is the assumed operating point used to operate the non-assisted flare (10 BTU's above the current standard). This analysis assumes the flare operator controls up to this point and not at higher BTU levels. The operational objective is thus a move to a combustion zone parameter 10 BTU's greater than the respective parameter. The fuel increase if these parameters were adopted for non-assisted flares is a 35 - 90 % increase with a minimal emission benefit based on the CMA/EPA test data. The combustion efficiency goal for good performance is >98 %. Emissions are normally calculated assuming 98 % combustion efficiency. Based on the EPA/CMA test data set, a minimal emission change is predicted to occur if any of the new parameters are applied to non-assisted flares. Further, the added fuel will result in an increase in NOx and greenhouse gas emissions with a minimal improvement in unburned VOC emissions The flammability diagrams for the propylene propane nitrogen mixture are shown in Figures 1 & 2. In Figure 2, the axis has been adjusted to focus on the data for mixtures <20% fuel. The non-assisted data analysis shows that the three new parameters are predicted to result in a 35 to 90% increase in fuel usage for a limited reduction in emissions. The test data showing the >98% efficiency brackets the EPA parameters, indicating that minimal emission benefit is predicted. The analysis indicates that there is no apparent need, based on the data, to change the existing requirements for non-assisted flares. 8 Figure 1 - Zabetakis Diagram Showing All Parameters Against Test Data Zabetakis or Flammability Diagram 80/20 Propylene/Propane Mixture in Nitrogen CzNHV or Showing All Parameters 50% Test Number 45% 16d 16c 16b 11c 11b 16a 11a 59b 60 59a 40% 35% 30% 25% Combustion Efficiency % 99.78 99.74 99.75 99.82 99.86 99.73 99.79 99.33 98.92 97.95 NHVvg BTU/scf 636 522 411 367 345 341 307 234 210 193 Flammability Lines Critical Point 5.51% LEL (800 BTU/scf) 36.6 % Comb 7.35% LEL (600 BTU/scf) 27.5 % comb 20% % Fuel Compostion @ any Point is: Fuel + Inert + Air = 100 11.02% LEL 400 BTU/scf 10.3 % comb Fuel-Inert Comp @ 0 Air Stoich Air Line 6.19% Critical Point 100 BTU/scf 200 BTU/scf 400 BTU/scf 600 BTU/scf 800 BTU/scf 270 BTU/scf Reg Limit 16d 16c 16b 11c 11b 11b 18% Reg Limit (393 BTU/scf) 11 % LEL 15.00% LEL Reg Limit (294 BTU) 18 % 15% 270 BTU/scf Reg Limit 16 % LEL 12 % comb 10% 200 BTU/scf Critical Point, 6.19% (135 BTU/scf) 33 % LEL 5% 100 BTU/scf 0% 0% 10% 20% 30% 40% 50% 60% Flammability of Fuel Mixture in Nitrogen 70% 80% 90% 100% Region shown in Figure 2 % Inert (Nitrogen - 9 Figure 2 Vertical Array of Flammability Diagram Showing Test Data & Flare Parameters 20 18 CzNHV BTU/scf CzLEL fraction % Comb 411 0.11 18.8% Tst 16b - 99.75% 393 0.11 18.0% New % Comb Parameter 367 0.12 16.8% Tst 11c - 99.82% 341 0.13 15.6% Tst 16a - 99.73 % 16 Tst 16b Tst 11c Tst 16a 14 307 0.14 14.1% Tst 11a - 99.79 % Tst 11a 294 0.15 13.5% New CzLFL Parameter Tst 59b Tst 60 270 Fuel Vol % 0.16 12.4% New BTU/scf Parameter 12 Tst 59a Critical Point Old BTU/scf parameter 234 0.19 10.7% Tst 59b - 99.33 % New % Comb Parameter 10 8 210 0.21 9.6% Tst 60 - 98.92 % 200 0.22 9.2% Old BTU/scf parameter Tst 59a - 97.95 % 193 0.23 8.9% 135 0.33 6.2% Move to 18 % Comb Move to 0.15 LFL Move to 270 BTU/scf 6 New BTU/scf Parameter Critical Point 10 New CzLFL Parameter An Analysis of Hydrogen Rich Flares The EPA is proposing to remove from the refinery rule the 8 vol % rule for hydrogen rich flaring. In addition, the EPA is grouping hydrogen rich flares in an "all flares" grouping in the refinery rules. The chemical industry operates many varieties of flares containing hydrogen rich gases from production units such as:     Hydrogenation Reaction Off gases, Syn Gas, Air Oxidation production off gases, and Other sources. These waste gases may have low hydrocarbon contents, generally <5 %, and usually can be flared without steam assist because these gases have a low tendency to smoke when not flared with hydrocarbon rich flared gases. Refinery flare systems receive gases from hundreds of connections and rarely flare low hydrocarbon content hydrogen rich gases. Further, refiners don't flare hydrogen rich streams in non-assisted flares. We believe refinery practice dealing with flaring low hydrocarbon and hydrogen rich streams is different than chemical industry practice. While the 8 vol % rule may not work for hydrogen rich flaring in refineries, the rule appears to work well for the chemical industry practices which flare hydrogen rich steams, usually to unassisted flares with hydrocarbon compositions typically <5 %. Chemical industry practice is different compared to refining for hydrogen rich, low hydrocarbon content flared gases. The 8 % rule works well for chemical industry sources and needs to be retained for these sources as they become subject to flare rules. The data used by EPA to develop the hydrogen rich flare rules was provided in a DuPont sponsored flare study8 which was conducted in 1997. The EPA Basis Purpose Document that supported the rule development was issued in March 1998.9 In the basis and purpose document, the composition ranges for the hydrogen rich gases that were representative of the sources that flare these gases were: "…combust waste gases containing hydrogen (from 13 to 22 volume percent), inert gases (nitrogen, argon, carbon dioxide, and steam), oxygen (in some streams), and various combinations of the hazardous air pollutants (HAP) in the 115 ppm to 5 percent mole fraction (by volume) concentration range." 10 8 Walsh, Peter M, PhD et. al. "Flame Stability Limits and Hydrocarbon Destruction Efficiencies of Flares Burning Waste Streams Containing Hydrogen And Inert Gases" Presented at: American Flame Research Committee, 2002 Fall Meeting, Bellaire, TX 9 USEPA OAQPS. Basis and Purpose Document on Specifications for Hydrogen-Fueled Flares. March 1998 10 USEPA OAQPS. Basis and Purpose Document on Specifications for Hydrogen-Fueled Flares. March 1998, p. 5 11 As an example, a typical composition of the off gas from an air oxidation process that is compatible with the hydrogen rich gas test composition is: Table 1 - Typical Air Oxidation Process Off Gas Composition Flared Gas Compostion Fuel Normalized Fuel Species Vol % Components Composition Hydrogen 23.75% 23.75% 75.48% Oxygen 1.30% 1.30% 4.14% Nitrogen 68.54% 0.00% CO 4.91% 4.91% 15.61% Methane 0.80% 0.80% 2.55% CO2 0.70% 0.70% 2.23% Total 100.00% 100.00% Inert (N2) Fuel Vol Vol % % 68.54% 31.46% Table 2 contains the fuel and flared gas BTU/scf calculations. Table 2 - Off Gas Properties Flared Gas Compostion Normalized Fuel Species Vol % Composition Hydrogen 23.70% 75.48% Oxygen 1.30% 4.14% Nitrogen 68.40% 0.00% CO 4.90% 15.61% Methane 0.80% 2.55% CO2 0.70% 2.23% Other 0.20% Total 100.00% 100.00% Inert (N2) Fuel Vol Vol % % 68.54% Fuel BTU/scf 270 Flared Gas BTU/scf 270 316 896 316 896 276 87 31.46% Table 3 provides the flared gas LFL calculations. 12 Table 3 - Flared Gas LFL Vol % Flared Gas Compostion Fuel Normalized Fuel Species Vol % Components Composition Hydrogen 23.75% 23.75% 75.48% Oxygen 1.30% 1.30% 4.14% Nitrogen 68.54% 0.00% CO 4.91% 4.91% 15.61% Methane 0.80% 0.80% 2.55% CO2 0.70% 0.70% 2.23% Total 100.00% 100.00% Inert (N2) Fuel Vol Vol % % 68.54% Flared Gas LFL Vol % 4.00% 31.46% 12.50% 5.00% 15.41% Table 4 provides the proposed refinery flare parameters. Table 4 - Proposed Refinery Flare Parameters CzNHV >= LFLcz <= Fraction combustible >= 270 BTU/scf 0.15 fraction 0.18 fraction Table 5 provides the properties that lead to the EPA parameter calculations in Table 7 for the operating case. Table 5 Flared Gas Properties Leading to Flared Gas Parameter Estimate NHVvg = LFLvg = NHV @ LFL = 87 15.41% 13.37 LFLcz = NHV@LFL / NHVvg = 0.154 Table 6 presents the flared gas properties normalized to the current 8 % hydrogen volume % rule. 13 Table 6 - Flared Gas Properties Normalized to 8 % H2 Leading to Flared Gas Parameters @ 8% Flared Gas Compostion Normalized to 8% Hydrogen 8.00% 0.44% 89.40% 1.65% 0.27% 0.24% Inert (N2) Fuel Vol Vol % % 89.40% Flared Flared Gas Gas LFL BTU/scf Vol % 270 4.00% 10.60% 316 896 12.50% 5.00% 29 45.74% 100.00% Flared Gas @ 8% H2 Leading to Flared Gas Parameters NHVvg = LFLvg = NHV @ LFL = LFLcz = NHV@LFL/NNHVvg = 29 BTU/scf 45.74% 13.37 BTU/scf 0.46 Table 7 provides the flared gas EPA parameters for the operating case and for the case normalized to 8 % hydrogen. Table 7 - EPA Parameters for Operating Case & Normalized Case to 8 % Hydrogen Description Flared Gas @ 8 % Operating Case N2 Vol % Fuel Vol % % 89.40% 68.54% % 10.60% 31.46% CzNHV or LFL Cz NHVvg BTU/scf fraction 29 0.46 87 0.15 % Comb Fraction 0.11 0.31 This table shows: 1. The current rule in 40 CFR 60.18 cut point at 8 % hydrogen as compared to the proposed EPA refinery performance parameters shows: a. The hydrogen rich system BTU/scf parameter approach does not work. The EPA parameter is greater than 270 BTU/scf. The old parameter was 200 BTU/scf. The BTU/scf value at 8 % hydrogen is 29 BTU/scf. This specific observation is why DuPont sponsored the 1990's flare study to uniquely develop an alternate parameter for this set of flared gases. 14 b. The LFLcz parameter for the 8 % case is 0.46 fraction. The EPA parameter for LFLcz is <= 0.15. The LFLcz parameter here is above 0.15 fraction. A change to move to 0.15 fraction (by adding fuel) is not justified and the LFLcz fraction parameter does not appear to work for this composition set. c. The % combustible EPA parameter is > 0.18 combustible fraction. The parameter at the 8 % hydrogen case is 0.11 fraction. A change to move this parameter to > 0.18 by adding fuel is not justified and the % combustible parameter does not appear to work for this composition set. The same information is displayed graphical form in Figure 1 showing the flammability diagram for hydrogen rich flaring typical of that done in the chemical industry. The fuel increase needed to achieve the various EPA performance parameters is: 1. To achieve 270 BTU/scf requires 385 ft3 natural gas per 1000 ft3 of flared gas @ 8% H2. 2. To achieve an LFL fraction of 0.15 requires 333 ft3 natural gas per 1000 ft3 of flared gas@ 8% H2. 3. To achieve a 0.18 fraction combustibles requires 98 ft3 natural gas per 1000 ft3 of flared gas @ 8% H2 None of these supplemental fuel addition measures would result in improved combustion efficiency or a decrease in emissions. The current data set used to support the use of the 8% volume hydrogen requirements applied to gases with typically < 5% hydrocarbons is well supported and should not be deleted. For hydrogen flares, the current rule contains a maximum velocity limit of 122 ft/sec. This upper velocity limit for hydrogen rich flaring was set based on the capability of the test rig utilized at the time of the test and has no scientific principal limiting its threshold. EPA's basis and purpose document for the rule, the following statement is made: "The maximum tip velocity was set at 37.2 m/sec (122 ft/s) because that was the highest tip velocity tested."11 The EPA should review pertinent literature before setting a maximum velocity limit. Recent testing performed by Dow Chemical shows hydrogen burns efficiently at sonic exit velocities.12 11 12 USEPA OAQPS. Basis and Purpose Document on Specifications for Hydrogen-Fueled Flares. March 1998, p.25 Comment submitted by Lorraine Krupa Gershman, Director, Regulatory/Technical Affairs, ACC p 47 15 Figure 2 - Flammability Diagram Showing EPA Parameter Performance for Hydrogen Rich Flaring @ 8 % 10.6 % fuel or 8 % H2 16 An Analysis of Enclosed Flares An enclosed flare shrouds the flame in an enclosure. This type of flare should be regulated in a separate category. Enclosed flares should be categorically exempt from the refinery rules. The exit velocity behavior and performance for these flares differs significantly from air assisted, steam assisted flares and hydrogen rich flares. EPA has issued several Applicability Determination Indices (ADI) 13 for enclosed flares. In ADI 0000068, EPA states: "In a determination that is posted as Control Numbers 0000019 and M000002 on EPA's Applicability Determination Index (ADI), EPA Region 6 determined that an enclosed flare is not the type of flare that is regulated by the open-flame flare specifications at 40 CFR 60.18. An enclosed flare is characterized by the flame being totally enclosed within the enclosed flare's structure and none of the flame zone is exposed in the atmosphere as it is for an open-flame flare…. Since an enclosed flare is not the type of flare that is regulated by the open-flame flare specifications at 40 CFR 60.18, the enclosed flare, ETOZ6-704, must comply with the testing procedures in section 60.113b(c) of NSPS Subpart Kb for a closed vent system and a control device other than a flare…." Enclosed flares can be regulated separately as control devices, and consideration should be given to exempt these devices from the refinery or chemical sector flare regulations per the logic contained within this ADI. An Analysis of Pressure Assisted Multi Point Ground Flares On February 13, 2015 the EPA proposed an Alternative Means of Emission Limitation for (AMEL) for Pressure Assisted Multi Point Ground Flares3 The comment period has closed and EPA is in the process of analyzing these comments. The current standards that apply to these types of flares point to the operating requirements for flares in the General Provisions to parts 60 and 63, respectively, to comply with the emission reduction requirements. Because pressure-assisted multi-point ground flares cannot meet the velocity requirements in these General Provisions, Dow and ExxonMobil are seeking an AMEL The current standards in the General Provisions apply to low pressure flare operations. The exit velocity limitations in the General Provisions do not apply to pressure assisted flare operations. Pressure assisted flares can operate efficiently at sonic exit velocities. In the AMEL supporting documentation, is a Dow Chemical test report for flare emission testing conducted in November 2013 for which a report 13 U.S. Environmental Protection Agency, Applicability Determination Index Numbers 0000019, M000002 and 0000068. 17 was submitted to EPA in February 2014.14 Table JZ-2 (Page 7) summarizes the results from "pressureassisted" flare tests. These flares are designed to have an exit velocity at or near sonic velocity. Table JZ1 (Page 6) summarizes the results from a relatively small steam assisted flare tip, a John Zink SKEC burner. Please note that tests S1 and S2 also have a very high efficiency and a high exit velocity. These test results demonstrate that flares should burn well especially during situations where the heating value is relatively high and the exit velocity is in excess of 400 ft/sec. Conclusions 1. The proposed refinery rule flare categorization scheme of "all flares" and "air-assisted flares" presents unique challenges for the chemical industry. Enclosed flares, air assisted flares, steam assisted flares, non-assisted flares, ground flares, hydrogen rich flares and pressure assisted flares all require special consideration and should be regulated separately. 2. Based on historical and existing flare test data, there is no need to change the current regulations for hydrogen rich and non-assisted flares. 3. Enclosed flares can be regulated as a separate control device. 4. Based on test work and information submitted in recent AMEL requests, pressure assisted multipoint ground flares can be regulated separately. 14 : Comment submitted by Lorraine Krupa Gershman, Director, Regulatory/Technical Affairs, ACC pp 38 -87. 18 References i ACC Comments are available at: Comment submitted by Lorraine Krupa Gershman, Director, Regulatory/Technical Affairs, ACC ii API Comments are available at: Comment submitted by Matthew Todd, Regulatory & Scientific Affairs API 3 Multi Point Ground Flare AMEL docket is found at: Docket No. EPA-HQ-OAR-2014-0738 19