For an enclosed combustion device, other than those listed in paragraphs
(d)(1) through (3) and
(7) of this section, or for a flare, continuous monitoring systems as specified in
paragraphs (d)(8)(i) through (iv) of this section and visible emission observations conducted as specified in
paragraph (d)(8)(v) of this section. Additionally, for enclosed combustion devices or flares that are air-assisted or steam-assisted, the continuous monitoring systems specified in
paragraph (d)(8)(vi) of this section.
Except as provided in this
paragraph (d)(8)(ii) and paragraphs
(d)(8)(iii) and
(vi) of this section, use one of the following methods to continuously determine the NHV of the inlet gas to the enclosed combustion device or flare at standard conditions. If the inlet gas stream to the flare or enclosed combustion device does not include streams from processes or equipment where inert gas or other vent gas streams which may lower the NHV of the combined stream are added (e.g., vent streams from acid gas removal (AGR) system amine regenerator still columns, vent streams from glycol dehydrator unit reboilers without water removal, vent streams from compressors in acid gas service, vent streams containing water or CO2 used for enhanced oil recovery, vent streams from storage vessels with high water content where the owner or operator has determined that the vent stream could cause the inlet gas to the enclosed combustion device or flare to not meet the minimum NHV, vent streams from gas plants that receive acid gas from sweetening units, and vent streams from nitrogen removal units (NRU)), the NHV of the inlet stream is considered to be sufficiently above the minimum required NHV for the inlet gas, and you are not required to conduct the continuous monitoring in this
paragraph (d)(8)(ii) of this section or the demonstration in
paragraph (d)(8)(iii) of this section, but you must submit the report in
§ 60.5420b(b)(11)(v)(I) and maintain the record in
§ 60.5420b(c)(11)(vi) indicating that the flare or enclosed combustion device does not receive inert gases or other vent gas streams which may lower the NHV of the combined stream.
(A)
A calorimeter with a minimum accuracy of ±2 percent of span.
(B)
A gas chromatograph that meets the requirements in
paragraphs (d)(8)(ii)(B)(1) through (5) of this section.
(1) You must follow the procedure in Performance Specification 9 of appendix B of this part, except that a single daily mid-level calibration check can be used (rather than triplicate analysis), the multi-point calibration can be conducted quarterly (rather than monthly), and the sampling line temperature must be maintained at a minimum temperature of 60 °C (rather than 120 °C). Calibration gas cylinders must be certified to an accuracy of 2 percent and traceable to National Institute of Standards and Technology (NIST) standards.
(2) You must meet the accuracy requirements in Performance Specification 9 of appendix B of this part.
(3) You must use a calibration gas or multiple gases that includes the compounds that are reasonably expected to be present in the flare gas stream. If multiple calibration gases are necessary to cover all compounds, you must calibrate the instrument on all of the gases. You may only use the compounds used to calibrate the gas chromatograph in the calculation of the vent gas NHV.
(4) In lieu of the calibration gas described in paragraph (d)(8)(ii)(B)(3) of this section, you may use a surrogate calibration gas consisting of hydrogen and C1 through C5 normal hydrocarbons. All of the calibration gases may be combined in one cylinder. If multiple calibration gases are necessary to cover all compounds, you must calibrate the instrument on all of the gases. Use the response factor for the nearest normal hydrocarbon (i.e., n-alkane) in the calibration mixture to quantify unknown components detected in the analysis. Use the response factor for n-pentane to quantify unknown components detected in the analysis that elute after n-pentane.
(5) To determine the NHV of the vent gas, determine the product of the volume fraction of the individual component in the vent gas and the net heating value of that individual component. Sum the products for all components in the vent gas to determine the NHV for the vent gas. For the net heating value of each individual component, use any published values for the net heating value per mole at 25 °C and 1 atmosphere and use 20 °C as the standard temperature for determining the volume corresponding to one mole of vent gas.
(C)
A mass spectrometer that meets the requirements in
paragraphs (d)(8)(ii)(C)(1) through (6) of this section.
(1) You must meet applicable requirements in Performance Specification 9 of appendix B of this part for continuous monitoring system acceptance including, but not limited to, performing an initial multi-point calibration check at three concentrations following the procedure in Section 10.1. A single daily mid-level calibration check can be used (rather than triplicate analysis), the multi-point calibration can be conducted quarterly (rather than monthly), and the sampling line temperature must be maintained at a minimum temperature of 60 °C (rather than 120 °C). Calibration gas cylinders must be certified to an accuracy of 2 percent and traceable to NIST standards.
(2) The average instrument calibration error (CE) for each calibration compound at any calibration concentration must not differ by more than 10 percent from the certified cylinder gas value. The CE for each component in the calibration blend must be calculated using the following equation:
(3) You must use a calibration gas or multiple gases that includes the compounds that are reasonably expected to be present in the flare gas stream. If multiple calibration gases are necessary to cover all compounds, you must calibrate the instrument on all of the gases. You may only use the compounds used to calibrate the mass spectrometer in the calculation of the vent gas NHV.
(4) In lieu of the calibration gas described in paragraph (d)(8)(ii)(C)(3) of this section, you may use a surrogate calibration gas consisting of hydrogen and C1 through C5 normal hydrocarbons. All of the calibration gases may be combined in one cylinder. If multiple calibration gases are necessary to cover all compounds, you must calibrate the instrument on all of the gases. For unknown gas components that have similar analytical mass fragments to calibration compounds, you may report the unknowns as an increase in the overlapped calibration gas compound. For unknown compounds that produce mass fragments that do not overlap calibration compounds, you may use the response factor for the nearest molecular weight hydrocarbon in the calibration mix to quantify the unknown component. You may use the response factor for n-pentane to quantify any unknown components detected with a higher molecular weight than n-pentane.
(5) You must perform an initial calibration to identify mass fragment overlap and response factors for the target compounds.
(6) To determine the NHV of the vent gas, determine the product of the volume fraction of the individual component in the vent gas and the net heating value of that individual component. Sum the products for all components in the vent gas to determine the NHV for the vent gas. For the net heating value of each individual component, use any published value for the net heating value per mole at 25 °C and 1 atmosphere and use 20 °C as the standard temperature for determining the volume corresponding to one mole of vent gas.
(D)
A grab sampling system capable of collecting an evacuated canister sample for subsequent compositional analysis at least once every eight hours. Subsequent compositional analysis of the samples must be performed according to ASTM D1945-14 (R2019) or alternatively GPA 2261-19 (incorporated by reference, see
§ 60.17). To determine the NHV of the vent gas, determine the product of the volume fraction of the individual component in the vent gas and the net heating value of that individual component. Sum the products for all components in the vent gas to determine the NHV for the vent gas. For the net heating value of each individual component, use any published value for the net heating value per mole at 25 °C and 1 atmosphere and use 20 °C as the standard temperature for determining the volume corresponding to one mole of vent gas.
(iii)
As an alternative to the continuous composition monitoring requirements in
paragraph (d)(8)(ii) of this section, a sampling demonstration may be used as specified in this paragraph. Flares or enclosed combustion devices that are not required to monitor flare gas composition because the inlet gas streams to the flare or enclosed combustion device does not include streams from processes or equipment where inert gas or other vent gas streams which may lower the NHV of the combined stream are added (e.g., vent streams from acid gas removal (AGR) system amine regenerator still columns, vent streams from glycol dehydrator unit reboilers without water removal, vent streams from compressors in acid gas service, vent streams containing water or CO2 used for enhanced oil recovery, vent streams from storage vessels with high water content where the owner or operator has determined that the vent stream could cause the inlet gas to the enclosed combustion device or flare to not meet the minimum NHV, vent streams from gas plants that receive acid gas from sweetening units, and vent streams from nitrogen removal units (NRU)), are not required to conduct sampling demonstrations specified in this paragraph. For an unassisted or pressure-assisted flare or enclosed combustion device, if you demonstrate according to the methods described in
paragraphs (d)(8)(iii)(A) through (F) of this section that the NHV of the inlet gas to the enclosed combustion device or flare consistently exceeds the applicable operating limit specified in §
60.5415b(f)(1)(vii)(B) or
(C), continuous monitoring of the NHV is not required, but you must conduct the ongoing sampling in
paragraph (d)(8)(iii)(G) of this section. For flares and enclosed combustion devices that use assist air (including perimeter assist air) or assist steam, if you demonstrate according to the methods described in
paragraphs (d)(8)(iii)(A) through (F) of this section that the NHV of the inlet gas to the enclosed combustion device or flare consistently exceeds 300 Btu/scf, continuous monitoring of the NHV is not required, but you must conduct the ongoing sampling in
paragraph (d)(8)(iii)(G) of this section. For an unassisted or pressure-assisted flare or enclosed combustion device, in lieu of conducting the demonstration outlined in
paragraphs (d)(8)(iii)(A) through (D) of this section, you may conduct the demonstration outlined in
paragraph (d)(8)(iii)(H) of this section, but you must still comply with
paragraphs (d)(8)(iii)(E) through (G) of this section.
(A)
Continuously monitor the inlet stream which is routed to the flare or enclosed combustion device for 14 operating days or collect a sample of the inlet gas which is routed to the enclosed combustion device or flare twice daily to determine the average NHV of the gas stream for 14 operating days with no sampling day to be spaced more than 3 operating days apart from the previous sampling day. If you do not continuously monitor the NHV, the minimum time of collection for each individual sample be at least one hour when technically feasible. When it is not technically feasible to collect individual samples for at least one hour (e.g., low or intermittent flow), the collection time must be as long as possible up to one hour. For samples taken during low or intermittent flow events, the collection time and the reason for not obtaining a full one hour sample must be documented and reported with the NHV sampling results. Samples must be separated by at least 6 hours. If inlet gas flow is intermittent such that there are not at least 28 samples over the 14 operating day period, you must continue to collect samples of the inlet gas beyond the 14 operating day period until you collect a minimum of 28 samples.
(B)
If you collect samples twice per day, count the number of samples where the NHV value is less than 1.2 times the applicable operating limit specified in §
60.5415b(f)(1)(vii)(B),
(C), or this
paragraph (d)(8)(iii) (i.e., values that are less than 240, 360, or 960 Btu/scf, as applicable) during the sample collection period in
paragraph (d)(8)(iii)(A) of this section.
(C)
If you continuously sample the inlet stream for 14 days, count the number of hourly block average (e.g., noon to 1 p.m., 1 p.m. to 2 p.m., etc.) NHV values that are less than the applicable operating limit specified in
§ 60.5415b(f)(1)(vii)(B),
§ 60.5415b(f)(1)(vii)(C), or this
paragraph (d)(8)(iii) (i.e., values that are less than 200, 300, or 800 Btu/scf, as applicable), during the sample collection period in
paragraph (d)(8)(iii)(A) of this section.
(D)
If there are no samples counted under
paragraph (d)(8)(iii)(B) of this section or there are no hourly block average values counted under
paragraph (d)(8)(iii)(C) of this section, the gas stream is considered to consistently exceed the applicable NHV operating limit and on-going continuous monitoring is not required.
(E)
If process operations are revised that could reduce the NHV of the gas sent to the enclosed combustion device or flare, such as the removal or addition of process equipment, and at any time the Administrator requires, re-evaluation of the gas stream must be performed according to
paragraphs (d)(8)(iii)(A) through (D) of this section within 60 days of the revisions to process operations to ensure the gas stream still consistently exceeds the applicable operating limit specified in §
60.5415b(f)(1)(vii)(B),
(C)(1), or this
paragraph (d)(8)(iii). If any of the samples counted under
paragraph (d)(8)(iii)(B) of this section or any hourly block average values counted under
paragraph (d)(8)(iii)(C) of this section are less than the limits in the respective paragraph you must conduct the continuous monitoring required by one of the options
paragraphs (d)(8)(ii)(A) through (D) of this section within 60 days of the re-evaluation of the gas stream.
(F)
When collecting samples under
paragraph (d)(8)(iii)(A) of this section, the owner or operator must account for any sources of inert gases or other vent gas streams which may lower the NHV of the combined stream (e.g., vent streams from AGR system amine regenerator still columns, vent streams from glycol dehydrator unit reboilers, vent streams from compressors in acid gas service, vent streams from enhanced oil recovery facilities, or vent streams from storage vessel with high water content where the owner or operator has determined that the vent stream could cause the inlet gas to the enclosed combustion device or flare to not meet the minimum NHV) that can be sent to the enclosed combustion device or flare. The owner or operator must document in the report in
§ 60.5420b(b)(11)(v)(I) and the records in
§ 60.5420b(c)(11)(vi) must note the operating scenario(s) which may lower the NHV of the combined stream through the introduction of inert gases or other vent gas streams, and whether the sampling included periods where the highest percentage of inert gases or other vent gas streams which may lower the NHV of the combined stream were sent to the enclosed combustion device or flare. If the introduction of inerts or other vent gas streams which may lower the NHV of the combined stream is intermittent and does not occur during the initial demonstration, the introduction of inerts or other vent gas streams which may lower the NHV of the combined stream will be considered a revision to process operations that triggers a re-evaluation under
paragraph (d)(8)(iii)(E). If conditions at the site did not allow sampling during periods where the introduction of inert gases or other vent gas streams which may lower the NHV of the combined stream was at the highest percentage possible, increasing the percentage of inerts will be considered a revision to process operations that triggers a re-evaluation under
paragraph (d)(8)(iii)(E).
(G)
You must collect three samples of the inlet gas to the enclosed combustion device or flare at least once every 5 years. The minimum time of collection for each individual sample must be at least one hour, when technically feasible. When it is not technically feasible to collect individual samples for at least one hour (e.g., low or intermittent flow), the collection time must be as long as possible up to one hour. For samples taken during low or intermittent flow events, the collection time and the reason for not obtaining a full one hour sample must be documented and reported with the NHV sampling results. The samples must be taken during the period with the lowest expected NHV (i.e., the period with the highest percentage of inerts or other vent gas streams which may lower the NHV of the combined stream). The first set of periodic samples must be taken, or continuous monitoring commenced, no later than 60 calendar months following the last sample taken under
paragraph (d)(8)(iii)(A) of this section. Subsequent periodic samples must be taken, or continuous monitoring commenced, no later than 60 calendar months following the previous sample. If any sample taken in accordance with this
paragraph (d)(8)(iii)(G) has an NHV value less than 1.2 times the applicable operating limit specified in §
60.5415b(f)(1)(vii)(B),
(C), or this
paragraph (d)(8)(iii) (i.e., values that are less than 240, 360, or 960 Btu/scf, as applicable), you must conduct the continuous monitoring required by one of the options in
paragraphs (d)(8)(ii)(A) through (D) of this section within 60 days of receipt of the last sample.
(H)
You may request an alternative test method under
§ 60.5412b(d) to demonstrate that the flare or enclosed combustion device reduces methane and VOC in the gases vented to the device by 95.0 percent by weight or greater. You must use an alternative test method that demonstrates compliance with the combustion efficiency limit; you may not use an alternative test method that demonstrates compliance with NHVcz and NHVdil in lieu of measuring combustion efficiency directly. You must measure data values at the frequency specified in the alternative test method and conduct the quality assurance and quality control requirements outlined in the alternative test method at the frequency outlined in the alternative test method. You must monitor the combustion efficiency of the flare continuously for 14 days. If there are no values of the combustion efficiency measured by the alternative test method that are less than 95.0 percent, the gas stream is considered to consistently exceed the applicable NHV operating limit, and you are not required to continuously monitor the NHV of the inlet gas to the flare or enclosed combustion device.
(iv)
Except as noted in paragraphs
(d)(8)(iv)(A) through (F) and (vi) of this section, a continuous parameter monitoring system for measuring the flow of gas to the enclosed combustion device or flare. You may use direct flow meters or other parameter monitoring systems combined with engineering calculations, such as inlet line pressure, line size, and burner nozzle dimensions, to satisfy this requirement. The monitoring instrument must have an accuracy of ±10 percent or better at the maximum expected flow rate.
(A)
Pressure-assisted flares and pressure-assisted enclosed combustion devices are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device if you install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(B)
Unassisted flares are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device if you meet the conditions in paragraphs (d)(8)(iv)(B)(1) and (2) of this section.
(1) You must demonstrate, based on the maximum potential pressure of units manifolded to the flare and applicable engineering calculations for the manifolded closed vent system, that the maximum flow rate to the flare cannot cause the flare tip velocity to exceed the maximum tip velocity as specified in the applicable provisions in § 60.18(c) and (f) of this chapter. You must use the minimum expected value of the NHV of the inlet gas to the flare or enclosed combustion based on previous sampling results or process knowledge of the streams sent to the enclosed flare of combustion device in your demonstration. If there are changes to the process or control device that can be reasonably expected to increase the maximum flow rate to the flare, you must conduct a new demonstration to determine whether the maximum flow rate to the flare is compliant with the applicable maximum flare tip velocity provisions in § 60.18(c) and (f) of this chapter.
(2) You must install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(C)
Unassisted enclosed combustion devices are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device if you meet the conditions in paragraphs (d)(8)(iv)(C)(1) and (2) of this section.
(1) You must demonstrate, based on the maximum potential pressure of units manifolded to the enclosed combustion device and applicable engineering calculations for the manifolded closed vent system, that the maximum flow rate to the enclosed combustion device cannot cause the maximum inlet flow rate established in accordance with paragraph (f)(1) of this section to be exceeded. If there are changes to the process or control device that can be reasonably expected to impact the maximum flow rate to the enclosed combustion device, you must conduct a new demonstration to determine whether the maximum flow rate to the enclosed combustor is less than the maximum inlet flow rate established in accordance with paragraph (f)(1) of this section.
(2) You must install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(D)
Air-assisted flares or enclosed combustion devices that use only perimeter assist air and have no assist steam or premix assist air are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device or the flow of assist air if you meet the conditions in
paragraphs (d)(8)(iv)(D)(1) through (3) of this section, as applicable. For these flares and enclosed combustion devices, NHVcz is assumed to be equal to the vent gas NHV.
(1) You must install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(2) If you are required to monitor vent gas composition for the flare or enclosed combustion device according to paragraph (d)(8)(ii) or (iii) of this section, you must demonstrate, based on the maximum flow rate of perimeter assist air to the enclosed combustion device or flare and applicable engineering calculations, that the NHVdil can never be less than the minimum required NHVdil. The demonstration must clearly document why the maximum flow rate of perimeter assist air will never exceed the rate used in the demonstration. You must use the minimum flow rate of vent gas allowed by your backpressure regulator valve and the minimum expected value of the NHV of the inlet gas to the enclosed combustion device or flare based on previous sampling results or process knowledge of the streams sent to the enclosed combustion device or flare in your demonstration. You must update this demonstration if there are changes to the backpressure regulator valve, the backpressure regulator valve set point, or the maximum flow rate of perimeter assist air. You must also update this demonstration if any sampling results of the NHV of the inlet gas to the enclosed combustion device or flare under paragraph (d)(8)(ii) or (iii) of this section are lower than the NHV vent gas value used in your demonstration.
(3) For air-assisted flares, you must also demonstrate, based on the maximum potential pressure of units manifolded to the flare and applicable engineering calculations for the manifolded closed vent system, that the maximum flow rate to the flare cannot cause the flare tip velocity to exceed the maximum tip velocity as specified in the applicable provisions in § 60.18(c) and (f) of this chapter. You must use the minimum expected value of the NHV of the inlet gas to the flare or enclosed combustion based on previous sampling results or process knowledge of the streams sent to the enclosed flare of combustion device in your demonstration. If there are changes to the process or control device that can be reasonably expected to increase the maximum flow rate to the flare, you must conduct a new demonstration to determine whether the maximum flow rate to the flare is compliant with the applicable maximum flare tip velocity provisions in § 60.18(c) and (f) of this chapter.
(E)
Air-assisted flares or enclosed combustion devices that use only premix assist air and have no assist steam or perimeter assist air are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device or the flow of assist air if you meet the conditions in
paragraphs (d)(8)(iv)(E)(1) through (3) of this section, as applicable.
(1) You must install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(2) If you are required to monitor vent gas composition for the flare or enclosed combustion device according to paragraph (d)(8)(ii) or (iii) of this section, you must demonstrate, based on the maximum flow rate of premix assist air to the enclosed combustion device or flare and applicable engineering calculations, that the NHVcz will never be less than the minimum required NHVcz. The demonstration must clearly document why the maximum flow rate of premix assist air will never exceed the rate used in the demonstration. You must use the minimum flow rate of vent gas allowed by your backpressure regulator valve in and the minimum expected value of the NHV of the inlet gas to the enclosed combustion device or flare based on previous sampling results or process knowledge of the streams sent to the enclosed combustion device or flare in your demonstration. You must update this demonstration if there are changes to the backpressure regulator valve, the backpressure regulator valve set point, or the maximum flow rate of premix assist air. You must also update this demonstration if any sampling results of the NHV of the inlet gas to the enclosed combustion device or flare under paragraph (d)(8)(ii) or (iii) of this section are lower than the NHV vent gas value used in your demonstration.
(3) For air-assisted flares, you must also demonstrate, based on the maximum potential pressure of units manifolded to the flare and applicable engineering calculations for the manifolded closed vent system, that the maximum flow rate to the flare cannot cause the flare tip velocity to exceed the maximum tip velocity as specified in the applicable provisions in § 60.18(c) and (f) of this chapter. You must use the minimum expected value of the NHV of the inlet gas to the flare or enclosed combustion based on previous sampling results or process knowledge of the streams sent to the enclosed flare of combustion device in your demonstration. If there are changes to the process or control device that can be reasonably expected to increase the maximum flow rate to the flare, you must conduct a new demonstration to determine whether the maximum flow rate to the flare is compliant with the applicable maximum flare tip velocity provisions in § 60.18(c) and (f) of this chapter.
(F)
Steam-assisted flares or enclosed combustion devices that have no premix assist air and or perimeter assist air (other than perimeter assist air intentionally entrained in lower and/or upper steam at the flare tip and the effective diameter of the flare tip is 9 inches or greater) are not required to have a continuous parameter monitoring system for measuring the inlet flow of gas to the device or the flow of assist steam if you meet the conditions in
paragraphs (d)(8)(iv)(F)(1) through (3) of this section, as applicable.
(1) You must install, calibrate, maintain, and operate a backpressure regulator valve calibrated to open at the minimum pressure set point corresponding to the minimum inlet gas flow rate. The set point must be consistent with manufacturer specifications for minimum flow or pressure and must be supported by an engineering evaluation. At least annually, you must confirm that the backpressure regulator valve set point is correct and consistent with the engineering evaluation and manufacturer specifications and that the valve fully closes when not in the open position.
(2) If you are required to monitor vent gas composition for the flare or enclosed combustion device according to paragraph (d)(8)(ii) or (iii) of this section, you must demonstrate, based on the maximum flow rate of assist steam to the enclosed combustion device or flare and applicable engineering calculations, that the NHVcz will never be less than the minimum required NHVcz. The demonstration must clearly document why the maximum flow rate of assist steam will never exceed the rate used in the demonstration. You must use the minimum flow rate of vent gas allowed by your backpressure regulator valve in and the minimum expected value of the NHV of the inlet gas to the enclosed combustion device or flare based on previous sampling results or process knowledge of the streams sent to the enclosed combustion device or flare in your demonstration. You must update this demonstration if there are changes to the backpressure regulator valve, the backpressure regulator valve set point, or the maximum flow rate of assist steam. You must also update this demonstration if any sampling results of the NHV of the inlet gas to the enclosed combustion device or flare under paragraph (d)(8)(ii) or (iii) of this section are lower than the NHV vent gas value used in your demonstration.
(3) For steam-assisted flares, you must also demonstrate, based on the maximum potential pressure of units manifolded to the flare and applicable engineering calculations for the manifolded closed vent system, that the maximum flow rate to the flare cannot cause the flare tip velocity to exceed the maximum tip velocity as specified in the applicable provisions in § 60.18(c) and (f) of this chapter. You must use the minimum expected value of the NHV of the inlet gas to the flare or enclosed combustion based on previous sampling results or process knowledge of the streams sent to the enclosed flare of combustion device in your demonstration. If there are changes to the process or control device that can be reasonably expected to increase the maximum flow rate to the flare, you must conduct a new demonstration to determine whether the maximum flow rate to the flare is compliant with the applicable maximum flare tip velocity provisions in § 60.18(c) and (f) of this chapter.
(vi)
If you use a flare or enclosed combustion device that is air-assisted or steam-assisted and that receives streams from processes or equipment where inert gas or other vent gas streams which may lower the NHV of the combined stream are added (e.g., vent streams from acid gas removal (AGR) system amine regenerator still columns, vent streams from glycol dehydrator unit reboilers without water removal, vent streams from compressors in acid gas service, vent streams containing water or CO2 used for enhanced oil recovery, vent streams from storage vessels with high water content where the owner or operator has determined that the vent stream could cause the inlet gas to the enclosed combustion device or flare to not meet the minimum NHV, vent streams from gas plants that receive acid gas from sweetening units, and vent streams from nitrogen removal units (NRU)), you must either meet the applicable requirements in (d)(8)(vi)(A) through (D) of this section or you must use an approved alternative method allowed under §
60.5412b(d)(1)(i) and
(ii) to continuously monitor NHVcz and, if applicable, NHVdil. If you elect to continuously monitor NHVcz and, if applicable, NHVdil using an approved alternative method as provided under §
60.5412b(d)(1)(i) and
(ii), you are not required to monitor NHV of the vent gas as specified in
paragraph (d)(8)(ii) of this section or monitor flow rates as specified in this
paragraph (d)(8)(vi) provided you can demonstrate that the maximum flow rate to the flare cannot cause the flare tip velocity to exceed the maximum tip velocity as specified in the applicable provisions in §
60.18(c) and
(f) of this chapter. You must use the minimum expected value of the NHV of the inlet gas to the flare or enclosed combustion based on previous sampling results or process knowledge of the streams sent to the enclosed flare of combustion device in your demonstration.
(A)
Except as allowed by paragraph
(d)(8)(iv)(E) or
(F) of this section, you must monitor and calculate NHVcz as specified in
§ 63.670(m) of this chapter. Additionally, for flares and enclosed combustion devices that use only perimeter assist air and do not use steam assist or premix assist air, the NHVcz is equal to the vent gas NHV. When NHVcz is equal to the vent gas NHV, you are not required to continuously monitor NHVcz if you meet the requirements in
paragraph (d)(8)(iii) of this section.
(B)
Except as allowed by
paragraph (d)(8)(iv)(D) of this section, for each flare using perimeter assist air, you must also monitor and calculate NHVdil as specified in
§ 63.670(n) of this chapter. If the only assist air provided to the flare or enclosed combustion control device is perimeter assist air intentionally entrained in lower and/or upper steam at the flare tip and the effective diameter is 9 inches or greater, you are only required to comply with the NHVcz limit specified in paragraph (f)(8)(vi)(A) of this section.
(D)
You must determine the flare vent gas net heating value as specified in
§ 63.670(l) of this chapter using one of the methods specified in
paragraph (d)(8)(ii) of this section. Where the phrase “petroleum refinery” is used, for purposes of this subpart, it will refer to flares controlling an affected facility under this subpart. If you are not required to continuously monitor the NHV of the inlet gas because you have demonstrated that it consistently exceeds the applicable operating limit as provided in
paragraph (d)(8)(iii) of this section, you must use the lowest net heating value measured in the sampling program in
paragraph (d)(8)(iii) of this section for the calculations performed in paragraphs
(d)(8)(vi)(A) and
(B). You must update this value if a subsequent sampling result of the NHV of the inlet gas to the enclosed combustion device or flare under
paragraph (d)(8)(iii) of this section is lower than the NHV vent gas value used in your calculations.