## API Comments

on RMACT 1 and 2 Startup and Shutdown and Special Operating Scenarios

The following is a preliminary tabulation of startup and shutdown and other separate operating scenarios where the normal RMACT 1 and 2 requirements cannot be met. Inability to comply with normal requirements associated with other regulations, preventive maintenance, and with malfunctions is not included in this tabulation.

RMACT 1

Process Vents
Requirement: Control Group 1 vents at all times.

Situation: During sh utdown of equipment, process vents generally can continue to be controlled until the control is no longer effective. For most types of controls a point is reached where the vent no longer has adequate pressure to reach the control. For combustion controls, a point can be reached where the inert content of the process vent is so high that sending it to combustion can be unsafe and/or upset the operation of the combustion device. For other types of controls, control efficiency can fall below require d levels at very low vent stream flows.

Recommendation: As has been done in the Polymer and Resins 1 NESHAP for flares ( see §63.485(w ) ) , provide a n exception from the control requirements for situations, during shutdown periods, where the process vent ha s inadequate pre ssure to reach the control device or is no longer a process vent (i.e., contains <50 PPM HAP). Expand this exception to include all types of control devices, when that emission limit cannot be achieved due to the process vent flow , pressur e , or composition.

RMACT 2
Fluid Catalytic Crack ing (FCC )
Each FCCU features its own unique configuration and operating envelope that impacts emissions. Partial b urn and f ull b urn refer to the combustion mode of the regenerator of an FCCU. A partial burn unit operates with limited oxygen in the regenerator and has CO levels of 3% to 6% out of the regenerator. Partial burn units complete the combustion of the flue gas (includin g CO) downstream in a CO boiler. Because of these high levels of CO when the CO boiler is not available (versus the 500 ppm normal operation limit), averaging is not an effective way of addressing startup and shutdown emissions for partial burn CO emissio n limits. A full burn unit operates with excess oxygen to ensure complete combustion and has CO levels of about 10

- 100 ppm out ofAPI Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 2 the regenerator during normal operation. Full b urn u nits are generally not equipped with CO boilers.

1. FCC Regenerator V ent
- General Startup and Shutdown
Requirement: 500 ppm CO (hourly avg.)

Situation: High temperature is required to fully combust CO into CO 2 . In normal operation, the required heat is derived from the combustion of coke. From a cold startup, FCC’s use a natural gas fired heater to heat the regenerator to about 600

– 800

° F

. We discuss the fired heater operation separately in the next item. These auxiliary burners and regenerator internals are not designed to heat the reg enerator to temperatures required to start the FCC unit cracking reactions (>1000F). Torch oil 1

Recommendation s : 1. CO limits should not apply when torch oil is being combusted during startup or shutdown

. is needed to heat the regenerator beyond the capacity of the auxiliary burner. Thus, d uring a typical start

- up , and during some shutdowns and standby operatio ns of an FCC unit, there is a period of time when torch oil is added to the regenerator to facilitate the unit heat

- up to operating temperature. Upon the addition of feed to the unit, catalytic coke will start to burn in the regenerator along with the tor ch oil. Feed ramp up is fairly quick, during which time the torch oil is backed out during normal startups, but can be longer if refractory repairs were made because of the need to raise temperatures slowly so as not to damage the new refractory . The per iod of torch oil addition (i.e. th e period when the bed temperature is relatively low) results in increased CO during the start

- up period.

2. If there must be a limit, follow the C onsent D ecree (CD) model and make the 500 ppm limit a short

- term limit that excludes periods of SU/SD and add a long

- term limit that includes periods of SU/SD ( i.e ., 365

- day average).

Requirement: Opacity (6 mi nute rolling avg.), PM emissions, 500 ppm CO (hourly avg.), e.g., 8 0 ppm NOx (7

- day avg.), e.g., 50 ppm SO 2 (7

- day avg.)

1 “Torch oil” is a term which is usually applied to gas oil that is burned in FCC regenerators, to supply necessary heat requirements during startup, shutdown, or feed

- outage conditions, when coke is not being produced in the reactor. Typically, it is injec ted through dedicated nozzles which discharge into the dense catalyst bed of a regenerator.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 3 Situation: Prior to introducing feed into an FCC unit hot air is used initially to heat up the regenerator. The hot air is typically supplied from a natural gas fired air

- preheater that is only used for start

- up. If refractory repairs were made , a refractory dry

- out is required and the regenerator temperature must be raised slowly (e.g., at a rate of 50

– 100F/hr) to prevent water from damaging the refractory. Emissions from the regenerator vent during this time are from the air heater.

Recommendation: Clarify that the FCC regenerator emission limits are only applicable when hydrocarbon is being fed to the unit and that comb ustion exhaust used to heat an FCC during start

- up are subject to combustion source limits, not FCC regenerator limits

.

2. FCC Regenerator Vent

- General Startup and Shutdown

– Full Burn Units
Requirement: 500 ppm CO (hourly avg.)

Situation: For full burn FCC units, there is a relatively short period of time during startup when the unit operates in partial burn mode resulting in a n additional period of higher CO. This partial burn period can result from heat imbalances during this transition state or may be required for safety because o peration at regenerator temperatures high enough for complete combustion while establishing catalyst circulation or introducing feed can result in exceeding metallurgical temperature limits.

The unit is inhere ntly unstable as feed is being put into the unit. It is a balancing act that requires operators to manually balance heat consumed to vaporize the feed and sustain the cracking reaction as additional feed is being put on the unit with the heat being brough t into the reactor from the regenerator via catalyst circulation, which is a function of regenerator operating conditions. This is an extremely complex operation with numerous variables that operations must manage until the unit can be lined out.

Recommen dation: For full burn FCC’s CO limits should not apply until feed and full burn operation is stable and normal heat balance can be maintained.

3. FCC Regenerator Vent

- General Startup and Shutdown

– Partial Burn Units
Requirement: 500 ppm CO (hourly a vg.)

Situation: For a partial burn unit, the required CO boilers add an additional step to unit
start

- up. Additional time is required from the point that the regenerator enters partial burn until the time the flue gas is all routed through the CO boiler(s). The CO boi ler(s) must be brought up separately from the regenerator to protect them from swings of the regenerator flue gas quality during the start

- up process, which can result in temperatureAPI Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 4 excursions , damage to CO boiler internals and/or trip of the CO boiler(s)

. A CO boiler trip must be avoided because it could ultimately lead to a refinery shutdown due to a drastic decrease in steam production ( a very large proportion of the refinery’s steam supply is typically provided by the CO Boilers), resulting in excess emissions at other units , significant flaring , production loss, and potentially equipment damage

. Since the regenerator flue gas initially bypasses the CO boiler, the CO is not further combusted. Once the regenerator is stable, the flue gas is added to th e CO boilers and CO emissions drop to normal levels. Prior to lining up the regenerator flue gas to the CO boiler, the unit is operating in a mode with higher CO emissions for a short period of time.

Recommendation: For partial burn FCC units , CO limit s should not apply until the CO boiler (s) operation is stable and all regenerator gas is routed to the boiler (s)

.

4

. FCC Regenerator Vent

- Hot Standby
Requirement: Opacity (6 minute rolling avg.), PM emissions, 500 ppm CO (hourly avg.), e.g., 8 0 ppm NOx (7

- day avg.)

Situation: There are operational situations where it is necessary to remove feed from an FCC unit to accommodate unit repairs, respond to an upstream or downstream malfunction or maintenance outage , and/ or to delay full startup due to dow nstream issues. Although processing is stopped, the FCCU maintains temperature by burning torch oil, which can result in higher CO and NOx emissions during this period of operation. PM/Opacity will also be higher for FCC units with ESP PM controls, since, as discussed below, it is unsafe to operate the ESP during torch oil firing. A standby mode of up to 7

– 10 days presents fewer safety risks and total environmental emissions than a complete FCCU shutdown and minimizes production losses

.
The ability t o operate in hot standby mode allows the FCC to stay ready for startup when otherwise it would have to go through a full cold shutdown with catalyst removal, which adds days to the downtime, operationally intense startup/shutdown activities, potential unit damage due to thermal cycles, and potential for increased emissions. This is an extremely important operation that is routinely employed , and the impact should not be underestimated. In addition to minimizing overall emissions, this operation minimizes the time to get products (e.g. gasoline) to the public. Further, it doesn’t introduce reliability issues inherent with cold shutdowns that could result in even further delays in returning to production.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 5 One refinery reports that during a recent hurrica ne the refinery experienced numerous unit shutdowns associated with lost utilities and hurricane related damage. The refinery was able to recover the FCC unit and establish stable operations in hot standby ready for startup. However, downstream units were not prepared for startup. Consequently, the FCCs idled in this condition until downstream facilities were brought back on line. Being able to stay in hot standby meant the FCC did not have to go through a cold shutdown whil e refinery resources were dedicated to recovering other units. Other refineries report similar situations, riding out hurricanes with the FCC unit in hot standby, thereby allowing the refineries to get gasoline back to the public faster than if the FCC un its had to go through a cold shutdown and restart.

Recommendation: Exclude the “hot standby” operating mode from the regenerator emission limits.

5

. FCC Regenerator Vent

- CO Boiler Shutdown
Requirement: 500 ppm CO (hourly avg.)

Situation: For FCC units with a single CO boiler, i t is sometimes necessary to operate partial burn FCC units when the CO boiler is down for inspection or , in particular, for repair. During such times the C O limit cannot be met. We discuss the reasons why the FCC unit needs to continue to operate during these times in the previous item.

Recommendation: For partial burn FCC units do not apply the CO emission limit when the CO boiler is out of service for inspection or maintenanc e.

6

. FCC Regenerator Vent

- Wet Gas Scrubber (WGS) Control
Requirement: Wet gas scrubber operating parameters , e.g., 8 0 ppm NOx (7

- day avg.) , e.g., 50 ppm SO 2 (7

- day avg.)

Situation: Many FCC units monitor wet gas scrubber operating parameters as surrogates for opacity and PM, because the normally required COMS are not functional in a wet gas environment. The WGS gas/liquid ratio and delta P requirements may not be able to be met duri ng the initial startup period due to low regenerator gas flow; similarly on shutdown , at some point the regenerator flow will drop off as feed is removed

.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 6 N O x and SO 2 may be above the RMACT 2 limits on startup for FCC units equipped with LoTOx controls s ince the ozone generation and routing to the WGS may not happen until after the FCC unit is fully operational at stable feed rates. Ozone cannot be sent to the vent until there is enough NOx and SO 2 in the flue gas to assure that the o zone is reacting (NO x) or being scavenged (SO2) into scrubber solution and not just being emitted to atmosphere.

Recommendation: For FCC units with wet gas scrubbers do not apply operating parameter limits during startup or shutdown. For FCC units using LoTOx controls do not apply the NOx or SO 2 limits until ozone generation has been started and routed to the regenerator vent.

7

. FCC Regenerator Vent

- Selective Catalytic Reduction (SCR) Control
Requirem ent: e.g., 8 0 ppm NOx (7

- day avg.)

Situation: At many FCC units, SCR controls have been installed to reduce NOx. SCR controls use a NOx reduction catalyst along with ammonia injection to reduce NOx. The required ammonia injection cannot commence until the SCR reaches operating temperature (nominally 600+ °F). This results in an unavoidable delay in controlling the NOx and resultant higher short term NOx emissions. In addition, for a partial burn FCC unit, the regenerator flue gas must bypass the CO bo iler(s) during start

- up because the SCR needs to be protected from potential regenerator catalyst carryover. If the SCR is plugged, this will reduce the overall NOx reduction efficiency during normal operation

. Additionally, for FCC Units with more than one CO boiler, the NOx limit cannot be achieved when one CO Boiler is out

- of

- service, because at the reduced FCC unit rate there is inadequate heat for maximum SCR efficiency.

Recommendation: NOx emission limits must not apply to FCC units with SCR control unless the SCR unit is at operating temperature, ammonia injection is at normal levels, and all regenerator gas is routed to the SCR unit. (Note: This is a general issue for all SCR NOx controls.) Some CDs allow an annual average approa ch, but it is unclear if that would work in every case.

8

. FCC Regenerator Vent

- Electrostatic Precipitator (ESP) Control
Requirement: Opacity (6 minute rolling avg.) , PM emissions , 500 ppm CO (hourly avg.)

Situation: On FCC units equipped with an ESP , the ESP must be powered off or bypassed, during an FCCU and/or CO B oiler startup and shutdown. In fact, m any FCC unit s have critical safety instrumentation which automatically shuts down the ESP inAPI Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 7 case of unusual operations or equipment malfunctions, such as loss of circulation differential pressure, air blower trip, high ESP inlet temperatures, and other similar types of issues.
During startup and shutdown operations of the FCC unit, the regenera tor flue gas may become combustible from either direct torch oil firing, from high levels of CO and/or with the unintentional introduction of hydrocarbon into the regenerator. For this reason and, at a minimum, the ESP should be OFF/Bypassed for the steps of torch oil firing and feed introduction/removal, as well as transitory operations (e.g. CO B oiler malfunction or shutdown, other FCCU process upsets or equipment failures). There is a similar point in the SD process where fresh feed rates are unstable and/or torch oil is fired where similar precautions must be taken.
Because the ESP must be operating in order to meet PM and opacity limits, but for safety reasons, the ESP should be powered off or bypassed during FCC startup and shutdown operations, impos ing a PM or opacity limit during such periods forces owners and operators to choose between compliance and safety to employees and equipment. In all cases, safety concerns are paramount and following proper safety procedures should not result in a potenti al non

- compliance of an emission limit.

Recommendation: PM and o pacity limits cannot apply during periods when regenerator offgas cannot be safely routed to the ESP.

9

. FCC Regenerator Vent

- Cyclone Controls
Requirement: Opacity (6 minute rolling avg. ), PM emissions

Situation: During startup and shutdown of FCC units, gas flows are not always adequate for cyclones to work properly and thus opacity and PM limits can be exceeded. Startup operations require passing through transient operations that are not ideal for cyclone performance. This will impact opacity. This is especially apparent during catalyst addition. There is also a fair amount of unit variability as air and catalyst levels are varied during startup operations.

Recommendation: PM and opacity limits cannot apply during periods when regenerator offgas flow is below cyclone minimum design flow.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 8 10

. FCC Regenerator Vent

- Feed Hydrofiner Outages
Requirements: e.g., 8 0 ppm NOx (7

- day avg.), 50 ppm SO 2 (7

- day avg.)

Situation: Approximately 45% of FCC units in industry are using catalyst additives to meet EPA Consent Decree requirements. In the majority of these applications, the FCC feed is hydrotreated in an upstream Cat Feed Hydrotreater (CFH) to remove impurities and improve feed quality. The majority of limits established through the Consent Decree process have a short

- term limit on a 7

- day rolling average and a long

- term limit on a 365

- day rolling average. However, the CD recognizes that the operation of the FCCU feed hydrotreater is integral in complying with this short term limit, and thus the CD s include an exemption from the short term limits provided that the FCCUs comply with good air pollution control practices for minimizing emissions consistent with an approved plan.
It is a common industry practice to change catalyst in the CFH unit while the FCC continues to operate. Under this scenario, refiners may not be able to meet the short

term limit without adding expensive, redundant hydroprocessing capacity. The EPA will need to consider the capital costs associated with installing such redunda nt capacity for use for only short periods and the cost of adding wet gas scrubbers to units without them.

Recommendation s : 1. A much more reasonable approach is to provide short

- term exemptions of any 7

- day rolling average limit during periods of startup, shutdown, or malfunction of the CFH, including CFH catalyst change

- out or turnaround periods. The EPA rulemaking could accomplish this by requiring facilities to prepare a CFH Outage Plan, outlining the specific steps to be taken to minimize FCCU emissions during this period.
2. If there must be a limit, follow the CD model and exclude periods of SU/SD from the short term limits and add a long

- term limit that includes periods of SU/SD ( i. e ., 365

- day average).

Sulfur Plant s

1 . Catalyst sulfidation
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation: During startup, the Claus System (and “ SCOT ” unit, if present) must be warmed up and the tail gas catalyst must be activated (i.e., sulfided) before full H 2 S removal can occur. Sulfiding must be done at low temperatures to avoid catalystAPI Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 9 damage. During these low temperature periods there can be incremental slip of reduced sulfur from the unit or to the tail gas inc inerator, result ing in high SO 2 or TRS until the
reactors are activated and on temperature.

Recommendation s : 1. Follow the NSR CD model of having a short

- term limit that excludes SU/SD emissions and a long

- term limit that includes SU/SD (e.g., 365

- d ay average).

2. Establish an allowable mass of SO 2 from each SRU for SD

– justified by the unit’s design.

2

. Sulfur flashing
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation : In some SRP configurations, during startup, the gas from the Claus System
must bypass the t ail g as u nit and vent directly to the incinerator. The sulfur in the line can solidify and cause a high temperature flash which can send excess sulfur to the inci nerator and cause the SO2 limit to be exceeded.

Recommendation s : 1. Follow the NSR CD model of having a short

- term limit that excludes SU/SD emissions and a long

- term limit that includes SU/SD (e.g., 365

- d ay average).

2. Establish an allowable mass of S O 2 from each SRU for SD

– justified by the unit’s design.

3

. Hot sweep
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation: During some shutdown s , high temperature natural gas and air or oxygen must be added to the Claus System during hot sweep to ensure sulfur stays in liquid form. Measurement of O 2 in the convert outlets becomes unreliable under these conditions and can result in is too much O 2 . If there is too much O 2 , there is a potential for burn off of sulfur in the catalyst bed creating excess sulfur to the incinerator.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 10 Similarly, i f the shutdown is not for total catalyst replacement, the unit must be operated as close to stoichiometric as possible because excess air will result in the combustion of sulfur within the reactors that could lead to an Incinerator excursion or excessive temperatures within the catalyst bed that could result in catalyst and/or equipment damage. Due to system and control variability this operation can result in

r unning air deficient . An air deficient operation can result in soot formation (i.e. incomplete combustion) that will result in reactor plugging thereby reducing unit capacity or in the reduction (i.e. deactivation) of the Tail Gas Catalyst which c an substantially impact sulfur recovery efficiency.

Recommendation s : 1. Follow the NSR CD model of having a short

- term limit that excludes SU/SD emissions and a long

- term limit that includes SU/SD (e.g., 365

- d ay average).

2. Establish an allowable mass of SO 2 from each SRU for SD

– justified by the unit’s design.

4

. Hot strip prior to shutdown
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation: During shutdown, there is holdup of sulfur in catalyst, vessels, piping and ductwork that needs to be removed for inspection and maintenance. A portion of this sulfur can be transferred to sulfur pits, but additional sulfur can only be r emoved by combusting (“burning”) it following shutdown of tail gas units (because excess oxygen can damage the tail gas units) . The amount of sulfur held up depends in part on the configuration of the Claus unit, with some units having lesser ability to route sulfur to pits. These incidents have been reported to EPA in Acid Gas/Tail Gas incident reports required under refiner’s NSR consent decrees.

Recommendations: 1. Follow the NSR CD model of having a short

- term limit that excludes SU/SD emissions and a long

- term limit that includes SU/SD (e.g., 365

- d ay average).

2. Establish an allowable mass of SO 2 from each SRU for SD

– justified by the unit’s design.API Comments on RMACT 1 and 2 Startup and Shutdown a nd Special Operating Scenarios

April 10, 2012 Page 11 5

. Single train refinery shutdown
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation: Single train refineries are required to have total refinery shutdowns on occasion. For these facilities, all acid gas sources are taken out of service, and, in turn, all Claus trains have to be taken out of service (i.e., no acid gas feed available). I n these instances, the Claus unit(s) are shutdown in conjunction with the shutdown of acid gas producing units. During the Claus unit shutdown, the tail gas unit remains in service prior to introducing oxygen to the Claus reactor. By design, the tail gas unit generates acid gas, which is normally routed back to the front of the Claus reactor. When the first of multiple Claus units is shutdown, this tail gas (acid gas) can be routed to another operating Claus unit. Eventually, however, the final Claus un it is being shutdown, with no Claus unit to receive the acid gas and the gas must be purged to the atmosphere

. These incidents have been reported to EPA in NSR CD Acid Gas/Tail Gas incident reports.

Recommendations: 1. Follow the NSR CD model of having a short

- term limit that excludes SU/SD emissions and a long

- term limit that includes SU/SD (e.g., 365

- d ay average).

2. Establish an allowable mass of SO 2 from each SRU for SD

– justified by the unit’s design.

6

. Hot nitrogen sweep
Requirement: 250ppm SO 2 (12

- hr avg.) at the incinerator outlet or 300 ppm TRS (12

- hr avg.) and 10 ppm H 2 S (12

- hr avg.)

Situation: When the sulfur plant is not operating (no feed), a hot nitrogen sweep is maintained. The CEMS can register > 250 ppm during this situation, due to residual sulfur in the unit or interference f ro m the hot nitrogen.

Recommendation: Be clear that SO 2 limit only applies when the SRP is operating with acid gas feed to the unit and not when it is in hot standby mode.