|Title||Regulatory Update for Refinery and Chemical Sector Flares|
|Description||Paper from the AFRC 2017 conference titled Regulatory Update for Refinery and Chemical Sector Flares|
|Abstract||On December 1, 2015, the United States Environmental Protection Agency (USEPA) published amendments to Maximum Achievable Control Technology (MACT) Subparts A, CC, and UUU. These amendments include provisions which affect a number of different refinery process units, including flares. The flare requirements are intended to ensure flares achieve at least 96.5% combustion efficiency when regulated material is sent to them. These requirements are similar (but not identical) to many of the requirements set forth in Consent Decrees between the USEPA and refiners and petrochemical facilities under the Flare Enforcement Initiative, and similar rules are expected to be promulgated for other industries in the near future.; This presentation will provide an overview of these new flare requirements and focus on their applicability to the petrochemical industry as a whole.|
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Paper for AFRC 2017 Industrial Combustion Symposium Houston, Texas September 18-20, 2017 Presenter Herman Holm - Client Service Manager - Sage ATC Environmental Consulting, LLC TITLE - Regulatory Update for Refinery and Chemical Sector Flares On December 1, 2015, the United States Environmental Protection Agency (USEPA) published amendments to Maximum Achievable Control Technology (MACT) Subparts A, CC, and UUU. These amendments include provisions which affect a number of different refinery process units, including flares. The flare requirements are intended to ensure flares achieve at least 96.5% combustion efficiency when regulated material is sent to them. These requirements are similar (but not identical) to many of the requirements set forth in Consent Decrees between the USEPA and refiners and petrochemical facilities under the Flare Enforcement Initiative, and similar rules are expected to be promulgated for other industries in the near future. Source categories within both MACT CC and MACT UUU that utilize a flare as a control device are subject to the flare requirements found in the RSR, which require refineries with affected flares to meet specific operating limits related to: 1. 2. 3. 4. 5. 6. 7. Flow rate monitoring, Vent gas NHV/composition monitoring, Pilot flame monitoring and presence, Visible emissions, Flare tip exit velocity, Net heating value in the combustion zone (NHVcz), and Net heating value dilution parameter (NHVdil) for flares which receive perimeter assist air. The requirements related to pilot flame monitoring and presence, visible emissions, and flare tip velocity were previously found in §63.11 of MACT Subpart A and §60.18 of New Source Performance Standard (NSPS) Subpart A. Refinery flares subject to the provisions of the RSR are required to be in compliance with all flaring provisions no later than January 30, 2019. Flow Rate Monitoring The RSR includes the requirement to monitor the flow of vent gas (which includes any supplemental gas addition) and assist gas (either steam and/or air) to an affected flare [§63.670(i)]. Flow monitoring systems must be capable of correcting volumetric flow to standard conditions, which are defined by the Rule as a temperature of 20°C (68°F) and a pressure of 1 atmosphere. Mass flow meters may be used for monitoring the flow of gas, but the measurements must be converted to volumetric flow using equation (1) shown below: 𝑄𝑣𝑜𝑙 = 𝑄𝑚𝑎𝑠𝑠 × 385.3 𝑀𝑊𝑡 (1) Where Qvol = Volumetric flow rate (standard cubic feet per second [scf/s]) Qmass = Mass flow rate (pounds per second [lb/s]) 385.3 = Conversion factor (standard cubic feet per pound-mole [scf/lb-mol]) MWt = Molecular weight of the gas at the flow monitoring (pounds per pound-mole [lb/lb-mol]) Additionally, according to §63.671(a)(8), "the CPMS must be capable of measuring the appropriate parameter over the range of values expected for that measurement location." This requirement does not specify an accuracy over the entire range of expected flows, but indicates that the range of values measured by the monitor cannot be exceeded by the flow rate encountered. Vent Gas Flow Monitoring The RSR defines flare vent gas as "all gas found just prior to the flare tip. This gas includes all waste gas, that portion of sweep gas that is not recovered, purge gas, and supplemental gas but does not include pilot gas, total steam or assist air." Table 13 of MACT CC specifies the required accuracy of vent gas flow meters as ±20% between 0.1 and 1 foot per second (ft/s) and ±5% above 1 ft/s. If a mass flow meter is used, the readings must be converted to a volumetric basis according equation (1) using the molecular weight location as determined by compositional analysis as described in Section 2.2. Alternatively, if the molecular weight of the vent gas is known, the facility may continuously monitor the temperature and pressure within the header and use appropriate engineering calculations to determine the vent gas flow rate within the flare header. Steam Flow Monitoring For steam-assisted flares, the total volumetric flow of steam (where the total flow of steam is the combined amount of ring [both upper and lower, if applicable] and center steam, if applicable) to the flare must be monitored. Mass flow meters or engineering calculations with continuous temperature and pressure monitoring are allowed in place of directly measuring the volumetric flow of steam. Volumetric steam flow meters are required to meet an accuracy as provided in Table 13 of the Rule of ±5% or 10 cubic feet per minute (cfm) over the normal range of flows measured, whichever is greater. If a mass flow meter is used, it must meet an accuracy specification of ±5% over the normal range of flows measured and the readings must be converted to a volumetric basis according equation (1). A molecular weight of 18 lb/lb-mol is required to be utilized for steam. Table 13 states that the flow meters, other than the vent gas flow meter, must be accurate over the normal range of flows. The Rule does not define the term "normal range," nor does it prescribe how to determine what the normal range would be for a point of flow measurement. Sage ATC is not aware of any documentation or guidance published by the USEPA outside of the RSR which indicates how to determine the normal range. Therefore, Sage ATC believes that the facility has flexibility in how the normal range is to be established. If the facility chooses flow technologies that will not meet the accuracy requirements over the entire flow range, documentation around how the normal range was determined should be created. Assist Air Flow Monitoring For air-assisted flares, the amount of perimeter assist air supplied to the flare at a given time may be determined using the following methods: Direct measurement (either volumetric of mass flow monitoring); Engineering calculations with continuous temperature and pressure compensation; or Monitoring the fan speed or power and using a fan curve to determine the flow of perimeter assist air. An assist air flow meter is subject to the same accuracy requirements as an assist steam flow meter. If a mass flow meter is utilized, the readings must be converted to a volumetric basis according equation (1). The molecular weight of 29 lb/lb-mol is required to be utilized. Supplemental Gas Flow Monitoring Monitoring the flow of supplemental gas depends on whether the supplemental gas is introduced upstream or downstream of the vent gas flow meter and the calculation method chosen for compliance. If the supplemental gas is introduced downstream of the vent gas flow meter or if the feed forward compliance calculation method is chosen, then a supplemental gas flow meter is required. If supplemental gas is added upstream of the flow meter, a supplemental gas flow meter is not required but still recommended in order to accurately determine the amount of supplemental gas being supplied to the flare at a given time. Supplemental gas monitoring is beneficial to determine the contribution of supplemental gas to the vent gas. Depending on the addition point, flow monitoring also allows the contribution of the waste gas components (i.e. the "non-supplemented" flow and NHV) to be differentiated from the vent gas. Additionally, a supplemental gas flow meter would allow for the facility to determine and track costs associated with supplemental gas addition. Based on the definition of vent gas, supplemental gas is considered part of the flare vent gas. As such, if a separate supplemental gas flow meter is necessary to demonstrate compliance with the Rule, the flow meter must meet the same accuracy requirements as the vent gas flow meter. Furthermore, if a mass flow meter is used, the molecular weight of the supplied natural gas will need to be determined to assess if a constant value can be utilized. Vent Gas Composition Monitoring The RSR requires the facility to monitor either the vent gas composition or the net heating value in the vent gas (NHVvg) for each affected flare [§63.670(j)]. The Rule provides several options for complying with this requirement. 1. Install a monitoring system capable of continuously (i.e., at least once every 15 minutes) monitoring (collection and analysis) the concentration of each required constituent of the vent gas; 2. Install a monitoring system capable of directly measuring NHVvg; 3. Install a grab sampling system capable of collecting a sample at least once every eight (8) hours; or 4. Apply for an exemption using the results of sampling a gas stream and establishing a consistent, minimum NHVvg. If the composition of the vent gas is monitored, the concentrations of each vent gas constituent will be used to calculate NHVvg using equation (2) below: 𝑛 𝑁𝐻𝑉𝑣𝑔 = ∑ 𝑥𝑖 𝑁𝐻𝑉𝑖 (2) 𝑖=1 Where i = Individual component in flare vent gas n = Number of components in flare vent gas xi = Concentration of component i in flare vent gas (volume fraction) NHVi = Net heating value of component i as shown in Table 12 of the Rule (British thermal units per standard cubic foot [Btu/scf]) If the facility chooses to install a monitoring system capable of directly measuring NHVvg (i.e., a calorimeter), the RSR also allows for the use of a second instrument to measure hydrogen. This is important because the Rule allows facilities to use the effective NHV of hydrogen of 1,212 Btu/scf, instead of its actual NHV of 274 Btu/scf, if the concentration of hydrogen is measured. If this option is used, the hydrogen concentration will be updated each time that the hydrogen instrument completes a cycle. That value will be used to correct the measured NHVvg from the calorimeter until the next hydrogen measurement is reported. The measurement from the calorimeter can be adjusted, based on the concentration of hydrogen in the vent gas, as shown below in equation (3). 𝑁𝐻𝑉𝑣𝑔 = 𝑁𝐻𝑉𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 + 938𝑥𝐻2 (3) Where: NHVmeasured = NHVvg as measured by the calorimeter (Btu/scf) 𝑥𝐻2 = Concentration of hydrogen in flare vent gas at the time the sample was input into the net heating value monitoring system (volume fraction) 938 = Net correction for the measured heating value of hydrogen (Btu/scf) If the grab sample option is selected, the RSR [§63.670(l)(6)(i) and (ii)] specifies the following procedure for determining which grab sample is to be used for demonstrating compliance with the Rule. i. ii. Use the analytical results from the first grab sample collected for an event for all 15minute periods from the start of the event through the 15-minute block prior to the 15minute block in which a subsequent grab sample is collected. Use the results from subsequent grab sampling events for all 15 minute periods starting with the 15-minute block in which the sample was collected and ending with the 15minute block prior to the 15-minute block in which the next grab sample is collected. For the purpose of this requirement, use the time the sample was collected rather than the time the analytical results become available. Direct compositional or NHV monitoring is not required for flares with a consistent composition or a demonstrated minimum NHVvg. In order to qualify for the exemption, the facility would need to document the conditions which allow the flare to qualify for the exemption and obtain a minimum of 14 daily grab samples which support the assertion that the vent gas maintains a constant or minimum NHVvg. For infrequently operated flare gas streams/systems, seven grab samples must be collected unless other additional information would support reduced sampling. Pilot Presence and Monitoring The RSR [§63.670(b) and §63.670(g)] requires that each affected flare must have a pilot flame present at all times when regulated material is being sent to the flare. For this reason, the flare must be equipped with at least one continuous pilot flame monitoring device capable of detecting that a pilot flame is present. The Rule lists thermocouples, ultraviolet (UV) beam sensors, and infrared (IR) sensors as potential technologies for monitoring the pilot flame. Other technologies, such as an acoustic pilot monitoring system, may also be used. For flares equipped with more than one pilot and more than one pilot monitoring system (i.e. a thermocouple on each pilot), only one of the pilot monitoring devices must indicate a pilot during a minute to demonstrate compliance. Visible Emissions and Monitoring Flares subject to the requirements of the RSR [§63.670(c) and §63.670(h)] must operate without visible emissions except for a total of five (5) minutes during any two (2) consecutive hours when regulated material is sent to the flare and the vent gas flow rate is less than the smokeless capacity of the flare. For flares that have the potential to operate above their respective smokeless capacities, the owner or operator will have to comply with the provisions of §63.670(o)(1) through (7). A single value for the smokeless design capacity of each flare must be specified. In order to comply with the visible emissions limit, the facility must conduct an initial 2-hour visible emissions demonstration for each flare using Method 22. The Rule allows the facility to choose between the two compliance demonstration options described below: 1. At least once per day, conduct a 5-minute Method 22 observation for each flare. If visible emissions are observed at any point during the day, a 5-minute observation will be conducted, even if the daily observation has already occurred. If visible emissions are observed for more than one continuous minute, the 5-minute observation must be extended to two hours, or until five total minutes of visible emissions are observed; or 2. The facility may use a video surveillance camera to continuously record (i.e., at least one frame every 15 seconds, with time and date stamps) images of the flare flame and a reasonable distance above the flare flame at an angle suitable for viewing visual emissions. The video output must be supplied to a continuously manned location, such as a control room. Flare Tip Velocity The RSR flare tip velocity (Vtip) limits [§63.670(d) and §63.670(k)] are similar to the limits found in Subpart A (§63.11) for steam assisted flares. The actual Vtip must either: 1. be less than 60 feet per second (ft/s), or 2. be less than 400 ft/s and the maximum permitted tip velocity (Vmax), as calculated by equation (4) below: 𝑁𝐻𝑉𝑣𝑔 +1,212 850 𝑉𝑚𝑎𝑥 = 10 (4) Where: Vmax = Maximum flare tip velocity (ft/s) NHVvg = Net heating value of the vent gas (Btu/scf) Owners and operators of flares were required to comply with similar requirements under Subpart A; however, the equation by which Vmax is determined has been revised in the RSR. In order to be able to calculate the actual tip velocity for a flare, the vent gas flow rate is required to be continuously monitored. The volumetric flow rate must be cumulative over each 15-minute block period starting at midnight and only needs to include flow during periods when regulated material is sent to the flare. However, including all flows during the 15-minute block period is also allowed under the Rule. Using the flow and unobstructed cross sectional area of the flare tip, Vtip may be calculated using equation (5) below: 𝑉𝑡𝑖𝑝 = 𝑄𝑐𝑢𝑚 𝐴𝑟𝑒𝑎 × 900 (5) Where: Vtip = Flare tip velocity (ft/s) Qcum = Cumulative volumetric flow over 15-minute block average period (actual cubic feet) Area = Unobstructed area of the flare tip (square feet) 900 = Conversion factor (seconds per 15-minute block average) Net Heating Value - Combustion Zone Previous flare regulations (Subpart A, [§63.11(b)(6)(ii)]) have included the requirement that steam and air-assisted flares maintain a minimum NHVvg of 300 Btu/scf. The RSR does not include this limit and establishes an operating limit of 270 Btu/scf for the NHVcz [§63.670(e)]. NHVcz is based on the concept that excess steam or air in the combustion zone dilutes the combustible material and decreases combustion efficiency of the flare. The NHVcz limit applies to all flares subject to the requirements of the RSR. Compliance is determined on a 15-minute block average basis when regulated material is sent to the flare for at least 15 minutes. The Rule allows for compliance with the NHVcz limit to be calculated in one of two ways: the direct or the feed forward calculation method. The direct method utilizes the average of the NHVvg values reported within a 15-minute block in conjunction with the cumulative flows of vent gas and assist gas during that 15-minute block. The feed forward method takes the last NHVvg result reported in the previous 15-minute block and applies it to the current block for the calculation of the NHVcz. The additions of supplemental gas from the current and previous block are also weighted using this method. Equations (6) and (7) show the calculations for each respective compliance method. Direct Compliance Calculation Method 𝑁𝐻𝑉𝑐𝑧 = 𝑄𝑣𝑔 × 𝑁𝐻𝑉𝑣𝑔 𝑄𝑣𝑔 + 𝑄𝑠 + 𝑄𝑎,𝑝𝑟𝑒𝑚𝑖𝑥 (6) Feed Forward Compliance Calculation Method 𝑁𝐻𝑉𝑐𝑧 = (𝑄𝑣𝑔 − 𝑄𝑁𝐺2 + 𝑄𝑁𝐺1 ) × 𝑁𝐻𝑉𝑣𝑔 + (𝑄𝑁𝐺2 − 𝑄𝑁𝐺1 ) × 𝑁𝐻𝑉𝑁𝐺 𝑄𝑣𝑔 + 𝑄𝑠 + 𝑄𝑎,𝑝𝑟𝑒𝑚𝑖𝑥 (7) Where: NHVcz = Net heating value of combustion zone gas (Btu/scf) NHVvg = Net heating value of flare vent gas for the 15-minute block period (Btu/scf) Qvg = Cumulative volumetric flow of flare vent gas during the 15-minute block period (scf) QNG2 = Cumulative volumetric flow of supplemental natural gas to the flare during the 15-minute block period (scf) QNG1 = Cumulative volumetric flow of supplemental natural gas to the flare during the previous 15-minute block period (scf). For the first 15-minute block period of an event, use the volumetric flow value for the current 15-minute block period, i.e., QNG1=QNG2. NHVNG = Net heating value of supplemental natural gas to the flare for the 15-minute block period determined according to the requirements in §63.670(j)(5) (Btu/scf) Qs = Cumulative volumetric flow of total steam during the 15-minute block period (scf). Qa,premix = Cumulative volumetric flow of premix assist air during the 15-minute block period (scf) The facility will need to designate which compliance calculation method will be chosen for each flare and notify the USEPA accordingly. The selected compliance calculation method may be changed; however, the USEPA must be notified at least 30 days prior to changing the method of compliance. Net Heating Value - Dilution Parameter In addition to the NHVcz, flares actively receiving perimeter assist air are also subject to the NHVdil limit [§63.670(f)], which must be greater than or equal to 22 British thermal units per square foot (Btu/ft2) on a 15-minute block average basis when regulated material is sent to the flare for at least 15 minutes. This parameter primarily focuses on the time vent gas spends in the flammability region above the flare tip (i.e., the combustion zone). Flare Management Plan The RSR requires the development of a written FMP as part of the Emergency Flaring Provisions contained within the Rule [§63.670(o)]. The requirements of the FMP are similar to the FMP that was required by NSPS Subpart Ja (NSPS Ja). The RSR FMP is required if vent gas can be potentially sent to the flare at a rate that exceeds the smokeless capacity of the flare. The FMP should address the following topics: A listing of all refinery process units, ancillary equipment, and fuel gas systems connected each affected flare; A minimization assessment; A general description of the flare, including, but not limited to, the smokeless capacity of the flare, the minimum and maximum total steam flow, and, if applicable, a description of the assist air blower and the amount of assist air which can be provided to the flare; A process flow diagram showing all gas lines and their associated monitoring systems; A list of the pressure relief valves vented to the flare, including the type, diameter, set point, and any prevention measures in place; and Procedures to minimize flaring during planned startup and shutdowns. The FMP is required to be submitted to the USEPA by January 30, 2019. Smokeless Design Capacity As part of the FMP, the Rule requires refineries to establish a single value for the design smokeless capacity of each affected flare [§63.670(o)(1)(iii)(B)]. In many cases, the flare manufacturer provides a smokeless capacity as part of the initial design of the flare. This value is typically based on the maximum amount of steam the refinery can provide at the date of purchase and an assumed vent gas composition or molecular weight. Although the USEPA has required a single value for the smokeless capacity of a given flare, in actuality, smokeless capacity is a variable value which will depend on the amount of steam the refinery is able to provide (which is likely now a different amount than when the flare was purchased and can vary depending on conditions elsewhere in the refinery) and the composition of the vent gas (which is likely to be highly variable). The Rule does not define the units or averaging time for smokeless capacity. The smokeless capacity that will be listed in the FMP will be used to determine if a RCA and a corrective action analysis are required. If either of the following conditions are met, the facility will be required to prepare a RCA and corrective action analysis within 45 days of the event. The vent gas flow rate exceeds the smokeless capacity of the flare and visible emissions are present from the flare for more than five (5) minutes during any two (2) consecutive hours during the release event. The vent gas flow rate exceeds the smokeless capacity of the flare and the 15-minute block average flare tip velocity exceeds the maximum flare tip velocity determined using equation (4) [§63.670(d)(2)]. Violations of the Emergency Flaring Work Practice Standard The following events would be a violation of the emergency flaring work practice standard. Any flow event for which a RCA was required and the root cause was determined to be operator error or poor maintenance. Two visible emissions exceedance events which required a RCA that were not caused by a force majeure event from a single flare in a 3 calendar year period for the same root cause for the same equipment. Two flare tip velocity exceedance events which required a RCA that were not caused by a force majeure event from a single flare in a 3 calendar year period for the same root cause for the same equipment. Three visible emissions exceedance events which required a RCA that were not caused by a force majeure event from a single flare in a 3 calendar year period for any reason. Three flare tip velocity exceedance events which required a RCA that were not caused by a force majeure event from a single flare in a 3 calendar year period for any reason. Minimization Assessment Similar to NSPS Ja, the FMP requirement of the RSR also requires an assessment to determine if the flows to an affected flare can be minimized [§63.670(o)(1)(ii)]. This minimization assessment focuses on minimizing flaring during periods of startup, shutdown, and emergency releases. The facility is required to evaluate potential minimization measures and justify whether each method is feasible due to factors such as economic feasibility, technical feasibility, and safety considerations. At a minimum, the RSR requires the facility to consider the following forms of minimization: Modification of startup and shutdown procedures, Implementation of prevention measures for pressure relief devices (PRDs) listed in §63.648(j)(3)(ii), and Installation of a flare gas recovery (FGR) system; and, for facilities that are fuel gas rich, a FGR system with co-generation unit or combined heat and power unit. The prevention measures cited in §63.648(j)(3)(ii) that are applicable to PRDs are: Flow, temperature, level, and pressure indicators with deadman switches, monitors, or automatic actuators, Documented routine inspections, maintenance programs, or operator training, and Inherently safer designs or safety instrumentation systems. The Rule requires a minimum of three prevention measures to be installed for each PRD that releases to the atmosphere; however, prevention measures are not required to be installed on PRDs that relieve to a control device, such as a flare [§63.648(j)(4)]. However, as part of the minimization assessment, the facility must determine what prevention measures each PRD that is routed to the flare is currently equipped with (if any) and assess if installing any additional prevention measures would minimize flaring. Installation of additional prevention measures would be dependent on the economic, technical, and safety considerations mentioned above. Per §63.670(o)(vi), a detailed listing of each PRD, including type, size, set pressure, and a listing of prevention measures must be maintained on site and submitted to the Administrator upon request. Reconsideration of Emergency Flaring Provisions On October 18, 2016, the USEPA granted reconsideration of the emergency flaring provisions contained in the RSR. Written comments on the following topics were due by December 19, 2016: PRD prevention measures, Design smokeless capacity, RCAs and corrective actions, and Violations of the emergency flaring work practice standard. As of the date this paper was written, the USEPA has not published responses to these topics. Conclusion With the publication of the revisions to the RSR, the USEPA has indicated a path forward for the refinery industry with regards to the operational requirements for flares. Based on recent enforcement actions in the chemical sector, it appears that the USEPA is also pursuing these requirements for the chemical sector. As the compliance date approaches and refineries work to come into compliance with the new regulations, it will be important to see what the lessons learned are so that these issues can be addressed in a timely fashion and aid the chemical sector with their compliance paths forward.
|Metadata Cataloger||Catrina Wilson|