FROM: David Randall, RTI International

TO: Brenda Shine, EPA/OAQPS

FOR: EPA Docket No. EPA-HQ-OAR-2007-0011

DATE: March 12, 2012

SUBJECT: Impact of Turndown on NO x Emissions from Process Heaters at Petroleum Refineries

1. Purpose
This memorandum presents an evaluation of the effect of turndown on nitrogen oxide (NO x ) emissions from process heater s at petroleum refineries.

2. Background
On December 28, 2008, EPA proposed amendments to the NO x emission limits for process heaters in 40 CFR part 60, subpart Ja (73 FR 78522). In comments on the proposal, several industry representatives noted that the proposed concentration-based NO x emissions limits would be difficult to meet during turndown, which is a period of time when a process heater is firing below capacity (Cade, 2009; Hunter, 2009; Chittim, 2009a; and Chittim, 2009b). Typically, the commenters suggested that proble ms would occur when process he aters are fired at less than 50 percent of the rated capacity, but one co mmenter suggested that meeting the NO x concentration limit becomes problematic at firing rates less th an 70 percent of the design rate. As an alternative to the proposed con centration limits, the commenters suggested that EPA develop mass-based limits that would apply either at all times or at least on the days when the process heaters operates at turndown. One example s uggested by a commenter was to set a daily mass limit based on the mass of NO x emitted while operating at the design firing rate and meeting the lb/MMBtu emission limit specified for that type of process heater.
This analysis is focused on characterizing the performance of combustion technologies for reducing NO x emissions from gas-fired process heaters or boilers in a petroleum refinery. To aid in the analysis, the following information on burner technologies is provided (MACTEC, 2005).

 Low-NO x Burners . Low-NO x burner (LNB) technology utiliz es advanced burner design to reduce NO x formation through the restriction of oxygen, flame temperature, and/or residence time. The two general types of low NO x burners are staged fuel and staged air burners. Staged fuel LNBs are particularly well suited for boilers and process heaters burning process and natural gas wh ich generate higher thermal NO x . The estimated NO x control efficiency for LNBs where applied to petroleum refining fuel burning equipment is generally around 40 percent.2  Ultra-low NO x Burners . Ultra-low NO x burners (ULNB) are similar to LNB but are specific to gas-fired units. These burners use a higher percentage of staged fuel to achieve lower flame temperatures and lower NO x concentrations. The estimated NO x control efficiency for ULNBs is 50-60 percent.

 “Next generation” ultra-low NO x Burners . Next generation ultra-low NO x burners (NGULNB) may incorporate a variety of t echniques including induced flue gas recirculation (IFGR), steam injection, or a combination of techniques. These burners combine the benefits of flue gas recirculation and low-NO x burner control technologies. Rather than a system of fans and blowers (like external flue gas recirculation), the burner is designed to recirculate hot, oxygen depleted flue gas from the flame or firebox back into the combustion zone. Th is leads to a redu ction in the averag e oxygen concentration in the flame without reducing the flame temp erature below temperatures necessary for optimal combustion efficiency. These NGULNB s have yielded reductio n efficiencies of between 75-85 percent.

3. Analysis

To evaluate the effect of turndown on emissions, we examined NO x CEMS data for 27 process heaters. The 27 process heaters are owned by 3 refi ners and are located at 9 refineries. Most of the process heaters have either low NO x burners or ultra low NO x burners (the type of burner was not available for a few of the process heaters). Ov er half of the process heaters are designed with forced draft, four have natural draft, and the design is not ava ilable for five. The amount of CEMS data per process heater ranges from 4 months to 34 months. Nearly all of the forced draft process heaters have combusti on air preheat, which is exp ected to lead to higher NO x emissions than no preheat. Various details of design and operation of the process heaters are summarized in Table 1 (Chittim, 2009c; Feerick, 2008; La ughlin, 2008; Marathon, 2008a; Marathon, 2008b; and Wagner, 2008).
A previous analysis determined that, for normal operation, the incremental cost effectiveness of control is reasonable at an em issions limit of 40 ppmdv for natu ral draft process heaters and 60 ppmdv for forced draft process heaters, with both concentration limits corrected to 0 percent excess air (Lucas, 2010). The same thresholds were also used in this anal ysis of the effect of turndown. All of the 30-day averag es in this analysis were base d on valid data for the preceding 30 calendar days, which meant the averages for some days were based on data for much less than 30 days. (The effect of calculating the averages based on the preceding 30 valid daily values was also examined, and the results were essentially the same.) All available data were included in the analysis, including SSM, except for data related to a CEMS malfunction.3 Table 1. Process heater data

Process heater

ID Company Refinery Draft type a Burner type b Design firing rate (MMBtu/hr) CEMS data dates Unit in which heater is used
FD-1 Marathon Detroit F ULNB 417 5/07 – 4/08 Crude and vacuum units (common stack)
FD-2 Marathon Canton F ULNB 193 5/07 – 4/08 Crude FD-3 Marathon St. Paul Park F ULNB 116 10/07 – 4/08 Gas Oil Hydrotreater
FD-4 Marathon St. Paul Park F LNB 178 5/07 – 4/08 Crude FD-5 Marathon Catlettsburg F ULNB 177 5/07 – 4/08 Crude FD-6 Marathon Catlettsburg F ULNB 178 5/07 – 4/08 Sat. Gas FD-7a Marathon Texas City F ULNB 182 5/07 – 4/08 Topper FD-7b Marathon Texas City F ULNB 182 5/08 – 4/09 Topper FD-8 Marathon Garyville F LNB 283 5/07 – 4/08 Coker FD-9 Marathon Garyville F LNB 295 5/07 – 4/08 Alky FD-10 Marathon Garyville F LNB 226 5/07 – 4/08 Rose Oil FD-11 Marathon Garyville F LNB 323 5/07 – 4/08 Crude FD-12 Marathon Garyville F LNB 315 5/07 – 4/08 Crude FD-13 ConocoPhillips Ponca City F ULNB 180 1/06 – 10/08 Crude Topping FD-14 ConocoPhillips Ponca City F ULNB 110 3/06 – 10/08 Crude Topping
FD-15 ExxonMobil N/A F ULNB 500 1/08 -8/08 N/A
FD-16 ExxonMobil N/A F ULNB 340 1/08 – 8/08 N/A
FD-17 ExxonMobil N/A F ULNB 340 1/08 – 8/08 N/A
ND-1 Marathon Canton N ULNB 242 5/07 – 4/08 CCR ND-2 Marathon Garyville N N/A 231 5/07 – 4/08 N/A ND-3 ConocoPhillips Ponca City N ULNB 330 1/06 – 10/08 Catalytic reforming ND-4 ConocoPhillips Ponca City N ULNB 180 4/06 – 10/08 Catalytic reforming UD-1 Marathon Robinson N/A ULNB 154 1/08 – 4/08 HF Alky Isostripper UD-2 Marathon Garyville N/A N/A 152 5/07 – 4/08 Crude Vacuum? UD-3 Marathon Garyville N/A N/A 152 5/07 – 4/08 Crude Vacuum? UD-4 Marathon Garyville N/A N/A 71 5/07 – 4/08 N/A UD-5 Marathon Garyville N/A N/A 187 5/07 – 4/08 FCC Charge?

a ”F” means forced draft or balanced, and “N” means natural draft.

b ULNB” means ultra low NO x burner, and “LNB” means low NO x burner.
“N/A” means not available.

Effect of Averaging Period and Exha ust Oxygen Levels on Performance Table 2 shows firing rate and NO x CEMS emission data for the 27 process heaters. Overall, 18 (67 percent) of the process heaters exceeded at least one daily threshold, and 11 (41 percent) exceeded the daily threshold 10 or more times. Because short-term fluctuations resulted in fairly frequent exceedances of daily thresholds, we also examined the effect of 30-day averaging periods on moderating the impact of these fluctuations. On this basis, 9 (33 percent) of the4 process heaters exceeded the applicable thre shold on at least one day, and 7 (26 percent) exceeded it 10 or more times. The percentages are the same if the results for each process heater are normalized to an annual operating period. Se e Attachment A for plots of the daily firing rates, NO x concentrations, and oxygen concentrat ions for the 9 process heaters.
Of the 7 process heaters that exceeded 30-day av erage thresholds on 10 or more days, 5 operated with high oxygen levels normally (FD-11, FD- 12, FD-13, ND-3, and ND-4). Although these 5 process heaters often exceeded 30-day thresholds , all except ND-3 met the limits most of the time, generally when operating at lower exhaust oxygen levels. One of the 7 process heaters (FD-14) exceeded the 30-day threshold only on da ys when the exhaust oxygen levels were much higher than normal and the firing rate was 50 percen t of design or less. These high oxygen levels (6 percent to 11 percent) are hi gher than typically required for flame stability at reduced firing rates, and the unit usually operated with NO x concentrations less than 60 ppmdv while firing at less than 50 percent of de sign capacity on days when the oxygen le vels were less than 6 percent. One process heater (ND-2) exceeded the 30-day threshold on every operating day. This process heater operated with exhaust oxygen levels less th an 5 percent, but we do not have confirmation that this process heater was equipped with low NO x burners.
Of the two process heaters with fewer than 10 days exceeding the 30-day average threshold, process heater (FD-7b) exceeded the threshold on ly when the exhaust oxygen levels were much higher than normal ( i.e. , 10 percent or higher) and firing ra tes were less than 50 percent of design. As noted previously, such oxygen levels are much higher than needed to ensure flame stability. See Figure A-2 for a plot of the da ily emissions data for this process heater.
Only one process heater (FD-5) had a few ex ceedances of the 30-day threshold even though it was equipped with ultra low NO x burners and it generally opera ted with exhaust oxygen levels less than 5 percent (even during the period when the exceedances occurred, although the oxygen concentrations during the exceedance periods were slightly higher than during compliant periods). This process heater al so almost never operated with a fi ring rate less than 50 percent of design (2 percent of operating days) and infreque ntly operated with a firing rate less than 75 percent of design (20 percent of operating days). Therefore, its performance issues were not related to turndown. Based on the limited number of exceedances for this process heater, it is expected that this unit could meet a 30-day aver age 60 ppmdv emission limit if such a limit were required.5 Table 2. Summary of process heater firing rates and NO x emissions

Process heater

ID Total no. of days with both

firing and CEMS data No. of days firing relative to design rate Percent of days firing relative to design rate
Preheat

? No. of days applicable threshold was

exceeded b

Comments <50% <75% <50% <75% Individual days 30-day rolling average
Process heaters with forced draft
FD-7a 356 356 356 100 100 Y 0 0
FD-4 338 338 338 100 100 No 10 0 FD-7b 329 329 329 100 100 Y 16 8 Oxygen on days with NO x >60 ppmdv are much higher than for other days with similar and lower firing rates.
FD-14 952 195 952 20 100 Y 53 30
FD-3 196 189 196 97 100 Y 1 0 FD-8 341 69 341 20 100 Y 3 0 Very scattered NO x for only 5 days with firing <30% of design.
FD-2 366 15 298 4 81 Y 0 0
FD-10 338 15 53 4 16 Y 0 0 FD-17 182 12 28 7 15 Y 9 0 No trend >40% of firing rate. All 7 days with high NO xand lower firing rate are clustered at about 22% of design. The 7 days also have the highest oxygen levels.
FD-5 365 9 74 2 20 No 32 8
FD-1 359 6 231 2 64 Y 0 0
FD-16 229 4 38 2 17 Y 3 0
FD-6 366 4 68 1 19 No 11 0 FD-13 1026 4 88 0.4 9 Y 255 271 Trend is more pronounced for firing <50% of design, but based on only four data points.
FD-9 341 1 195 0.3 57 Y 0 0 FD-12 340 1 10 0.3 3 Y 66 52 Very scattered NO x for firing rates <50% of design rate.
FD-11 340 1 9 0.3 3 Y 78 74 NO x data very scattered for firing rates <75% of design rate.
FD-15 227 0 12 0 5 Y 0 0 NO x increases as firing rate increases above 75% of design.
Process heaters with natural draft ND-3 979 254 979 26 100 No 762 855 Oxygen usually >5%, often over 7%, and higher during periods of greatest turndown.6 Process heater

ID Total no. of days with both

firing and CEMS data No. of days firing relative to design rate Percent of days firing relative to design rate
Preheat

? No. of days applicable threshold was

exceeded b

Comments <50% <75% <50% <75% Individual days 30-day rolling average ND-4 917 148 899 16 98 No 268 306 Oxygen usually between 5% and 7%; higher during periods of greatest turndown.
ND-1 366 12 355 3 97 No 0 0
ND-2 327 3 7 1 2 No 343 c 316 Very slight trend based on only 7 data points. Process heater may not have a low NO x burner. Process heaters for which the type of draft is unknown
UD-3 337 5 122 1 36 N/A 1 0 NO x increases as firing rate decreases to about 50% of design, then 3 data points with lower firing rate have low NO x . UD-2 341 4 10 1 3 N/A 3 0 Same comment as for UD-3. UD-1 118 2 118 2 100 N/A 0 0 Only 1 data point for firing rate <50% of design, and it is within wide range of NO x values for firing rate >50% of design. UD-4 340 1 4 0.3 34 N/A 2 0 Nearly all days firing >100% of design.
UD-5 341 0 166 0 49 N/A 0 0

a See the text for descriptions of each category.

b The applicable threshold is 60 ppmdv for forced draft pr ocess heaters and 40 ppmdv for both natural draft process

heaters and process heaters for which the draft type is unknown.

c The number of exceedances of the applicable threshold exce eds the number of days for which both firing rate data

and CEMS data were available because firing rate date were unavailable for several days while NO xCEMS data were available.
“N/A” means not available.

Daily average NO x concentrations are plotted versus daily average exhaust oxygen levels for each of the 27 process heaters in Attachment B. The data show that 8 of the 27 process heaters never exceeded an applicable 30-day average threshold when oxygen levels were less than 5 percent. Another 4 process heaters occasionally exceeded an applicable 30-day threshold, but when oxygen levels were less than 5 percent, the daily NO x concentrations were always or nearly always less than the applicable threshold. Ten additional process heaters had no exceedances of an applicable 30-day threshold even though oxygen leve ls were generally grea ter than 6 percent. Three process heaters had numerous exceedance s of the 30-day thresholds and generally operated with oxygen levels greater than 5 percent to 6 percent; however, NO x concentrations nearly always were below the thresholds on days when oxygen levels were less than 6 percent to 6.5 percent. One process heater operated with ox ygen levels less than 5 percent nearly every day7 while NO x concentrations were over 80 ppmdv; how ever, this process heater may not be equipped with low NO x burners. Only one process heater known to be equipped with low NO x burners nearly always exceeded the applicable 30-day NO x threshold regardless of the exhaust oxygen level, which was nearly alwa ys greater than 5 percent. Th is process heater also operated with firing rates that were less than 50 percen t and 75 percent of the de sign rate on 26 percent and 100 percent of the operating days, respectively. If this process heater cannot be operated safely at lower oxygen levels during turndown operati ons, then it is the only process heater that could have difficulty meeting an emission lim it based on the applicable threshold on a 30-day rolling average basis. However, it would also have difficulty meeting the applicable emission limit regardless of the number of days included in the rolling average. Additionally, while this unit does use ULNB, it does not use the latest technology ( i.e. , NGULNB). It is also unclear if this unit could meet a 60 ppmdv emission limit during turndown if it had the best available burner technology. Table 3 identifies the process heaters in each group.

Table 3. Comparison of NO x concentrations and Exhaust Oxygen Levels

Process heater ID Frequency of 30-day threshold exceedances Exhaust oxygen levels Comments FD-2; FD-4; FD-6; FD-7a; FD-10; UD-1: UD-3; UD-4 None Always or nearly always <5%

FD-5; FD-7b; FD-14; ND-4 Occasional Varied • Typical oxygen levels were <5%, <6%, <8%, and <10% for the four process heaters •Daily NO xwas always or nearly always less than the threshold when oxygen was less than 5 percent FD-1; FD-3; FD-8; FD-9; FD-15; FD-16; FD-17; ND-1; UD-2; UD-5 None Generally >6%

FD-11; FD-12; FD-13 Often generally >5 percent to 6 percent Daily NO xlevels were always or nearly always less than the threshold when oxygen levels were less than 6 percent to 6.5 percent ND-2 Always Always <5% May not have low NO xburners ND-3 Nearly always Typically >5%

Effect of Turndown Operation on NO x Emissions As shown in Table 2, only 4 of the process heater s operated with firing rates less than 50 percent of design all or nearly all of the time, and 10 ope rated with firing rates less than 75 percent of design all or nearly all of the time. Of the 4 process heaters that typi cally operated with firing rates less than 50 percent of design, 3 never exce eded the applicable 30-day threshold, and the fourth exceeded the 30-day threshold on only 8 da ys (or 2 percent of the time). Of the 10 process heaters operating at less than 75 percent of design all or nearly all of the time, 6 never8 exceeded the 30-day threshold, 2 exceeded the thre shold on 2 percent to 3 percent of the days, and 2 exceeded the threshold on a significant number of days. Of the remaining 17 process heaters that infrequently ope rated at turndown, 12 never exce eded a 30-day threshold, and 5 exceeded a 30-day threshold between 2 percent a nd 97 percent of the operating days. As noted in the preceding section, exceedances generally correlated with high exhaust oxygen levels. In addition, 4 of the 9 process heaters that exceed ed 30-day thresholds ope rated at turndown on very few days relative to the number of exceedances. Details are noted below:

 Three process heaters (FD-3, FD-4, and FD-7a) never exceeded the applicable threshold even though they operated with firing rates le ss than 50 percent of design on all or nearly all days.

 Fifteen process heaters that operated with firing rates less than 50 percent of design on between 0 and 69 days (generally over the course of 12 mont hs of operation) also never exceeded an applicable 30-day threshold. These same process heaters also operated with firing rates less than 75 per cent of design on between 4 and 355 days over the same time periods.

 One process heater (FD-7b) operated at firi ng rates less than 50 pe rcent every day and exceeded the 30-day rolling average threshold on 8 days. However, as noted above, these exceedances correlate with a series of days where the oxygen level was high. Furthermore, although firing rates were less than 50 percen t of design on every day, the days with high oxygen levels had so me of the highest firing rates.

 One process heater (FD-5) had 8 exceedances of the 30-day rolling average threshold. This process heater and operate d with firing rates less than 50 percent of design for only 9 days, and the NO x concentrations on these 9 days di d not contribute to any of the 8 exceedances.

 Over nearly 3 years of operation, one proce ss heater (FD-14) had 30 exceedances of the 30-day rolling average threshold and operated with firing rates less than 50 percent of design on 195 days. The days of turn down operation did affect the number of exceedances. However, as noted previously, the high NO x correlated with high oxygen, and many days with similar or lower firing rates had both lower e xhaust oxygen levels and lower NO x concentrations.

 Four process heaters (FD-11, FD-12, FD -13, and ND-2) had between 52 and 316 exceedances of the applicable 30-day threshol d, but they operated wi th firing rates less than 50 percent of design on only 1 to 4 days . Three of these process heaters operated with firing rates less than 75 percent of design on up to 10 da ys, and the fourth operated with firing rates less than 75 percent of design on 88 days. In all cases, the number of days operating at reduced firing rates was mu ch less than the numb er of exceedances. Thus, turndown operation had little e ffect on the number of exceedances.

 Two process heaters (ND-3 and ND-4) both ha d a large number of exceedances (nearly every day for ND-3), and they operated with fi ring rates less than 50 percent of design on numerous days. They also operated with fi ring rates less than 75 percent of design on all or nearly all days. The highest NO x concentrations were associated with the lowest firing rates. Thus, turndown did affect the 30-day average concentrations, and likely affected9 the number of exceedances as well. We do not have data for operation with firing rates at 75 percent to 100 percent of design for th ese process heaters and thus, we cannot determine whether they would have difficulty meeting the 30-day threshold only on days of turndown operation.

To get another perspective, we plotted the daily NO x concentrations versus the daily firing rates and then classified the process heaters in one of the following five categories based on the correlation or trend in the data:

 Category 1 . No correlation or trend between NO x concentrations and fi ring rates, and all or nearly all of the daily NO x concentrations are below 40 ppmdv for natural draft units and 60 ppmdv for forced draft units.

 Category 2 . No correlation or trend between NO x concentrations and firing rates, but daily NO x concentrations often exceed th e 40 ppmdv or 60 ppmdv thresholds.

 Category 3 . NO x concentrations decrease with decr easing firing rates. Generally the decrease is slight, and the NO x data for such process heaters fall in a wide band ( i.e.
, some days with the highest NO x concentrations have the same firing rates as other days with much lower NO x concentrations). The days with the highest NO x also generally have the highest exhaust oxygen levels.

 Category 4 . NO x concentrations increase with de creasing firing rates, and daily NO x concentrations are always or nearly al ways less than the 40 ppmdv and 60 ppmdv thresholds.

 Category 5 . NO x concentrations increase with de creasing firing rates, but daily NO x concentrations often exceed the 40 ppmdv or 60 ppmdv thresholds.

Attachment C contains the plots of the daily NO x concentrations versus the daily firing rates for each of the 27 process heaters. Table 4 identifies the correlation category that applies to the data for each process heater.
Ten of the process heaters show increasing NO x concentrations with decr easing firing rates, but 7 of those process heaters had no ex ceedances of the applicable 30- day threshold. The other three process heaters (FD-13, ND-3, and ND-4) each had more than 270 exceedances of the applicable 30-d threshold out of more than 900 days of da ta. As discussed above, these three process heaters generally operated with high exhaust oxy gen levels, even during normal operation. If those process heaters are being operated as r ecommended for safe operation such that lower excess air levels cannot be achieve d consistently, then they may have difficulty meeting emission limits based on the applicable threshol ds, regardless of the averaging period.
Four of the process heater s showed no trend between NO x concentrations and firing rates, but the 30-day concentration limits were not met on some days. This suggests that the cause of the exceedances is due to something other than turndown.10 Table 4. NO x correlation with firing rate

Process heater ID No. of days firing <50% of the design rate No. of days applicable 30- day threshold was exceeded Category of NO x correlation with firing rate a

1 2 3 4 5 Forced draft process heaters
FD-7a 356 0 1
FD-4 338 0 3
FD-7b 329 8 3
FD-14 195 30 2
FD-3 189 0 1
FD-8 69 0 4
FD-2 15 0 1
FD-10 15 0 3
FD-17 12 0 4
FD-5 9 8 2
FD-1 6 0 4
FD-16 4 0 4
FD-6 4 0 1
FD-13 4 271 5
FD-9 1 0 1
FD-12 1 52 2
FD-11 1 74 2
FD-15 0 0 1 Natural draft process heaters
ND-3 254 855 5
ND-4 148 306 5
ND-1 12 0 1
ND-2 3 316 3 Process heaters for which the type of draft is unknown
UD-3 5 0 4
UD-2 4 0 4
UD-1 2 0 1
UD-4 1 0 4
UD-5 0 0 1

a See the text for descriptions of each category.

Effect of a Mass-Based Emission Limit for Turndown Operation The analysis above shows that some process heaters generate higher NO x concentrations when operating under turndown conditions than under normal conditions. Eight of the 27 process heaters in the analysis also would exceed emissi on limits set at 60 ppmdv for forced draft units and 40 ppmdv for natural draft units, with both lim its calculated as 30-day rolling averages. Although NO x concentrations may be above such limits on some days of turndown operation, the11 mass of emissions may be less than on da ys with normal firing rates (and lower NO x emissions levels) due to lower gas flow ra tes. Thus, a mass-based emission limit may be more appropriate than a concentration based limit, at least on days of significant turndown. To evaluate this possibility we developed a regul atory alternative that combines a mass-based limit and the 30- day rolling average concentration limit.
The general concept of the alterna tive is that a facility could choose to comp ly with either limit on days when the firing rate is less than 50 percen t of the design rate. The facility would then be subject to the otherwise applicable 30-day aver age concentration limit on all other days. The mass limit in this alterative was calculated as the mass of NO x that would be emitted by a process heater that is meeting the applicable concentra tion-based limit and operating at 50 percent of its design firing rate for the entire day. Because the mass limit is related to the capacity of the unit, the limits would vary from one process heater to another. For example, a forced draft process heater with a design firing rate of 200 MMBtu/hr would have a mass-based emissions limit of 144 lb/d (0.06 lb/MMBtu x 0.5 x 200 MMBtu/hr x 24 h/d = 144 lb/d).

To evaluate the effect of the alternative, we a pplied it to each of the 8 process heaters described above that would not meet applicable concentr ation-based 30-d average emission limits every day. The choices that result in the fewest number of exceedances will depend on the specific NO x concentrations for days in 30-day averages th at are affected by excluding certain days that meet the mass limit. In this analysis we considered two approaches for the 8 facilities. First, we assumed the facility would demonstrate complia nce with the mass limit on all days when the mass limit was met (and the firing rate was less than 50 percent of the desi gn rate). These days would then be excluded from the calculati on of 30-day rolling averages of the NO x concentrations for comparison with the applicab le 60 ppmdv or 40 ppmdv limit on all other days. The second approach is similar to the first appr oach except that the facility would demonstrate compliance with the mass limit only if the average NO x concentration on that day exceeded 60 ppmdv or 40 ppmdv. The result s are presented in Table 5.

As shown in Table 5, the alternative would eliminat e exceedances for only 1 of the 8 facilities. (However, this process heater always operated at less than 50 percent of the design firing rate and met the concentration-based limit on days when the oxygen levels were normal. Thus, exceedances for this process heater also could lik ely be eliminated by better control of excess air.) The alternative (either approach) had litt le effect on the number of exceedances for the other 7 process heaters. The primary reason fo r the minimal impact was that most of these process heaters had few days of turndown opera tion. In addition, when they did operate at turndown, relatively few of those days (in comp arison to the number of exceedances) also met the applicable mass limit. Process heater FD -14 did have numerous days firing less than 50 percent of design and meeting the mass limit, but most of those days also had NO x concentrations less than 60 ppmdv, so excluding those days from the 30-day averages had little effect on the number of exceedances.12 Table 5. Effect of regulatory alternative on the number of exceedances

Process heater

ID No. of days exceeding applicable NO x ppmdv threshold based on 30- day averages Total no. of days

firing <50% of design (A) Total no. of days firing

<50% of design and

meeting lb/d limit (B) Total number of days firing <50% of design, meeting lb/d limit, and

exceeding applicable NO x ppmdv threshold Total number of daily exceedances if using the lb/d limit to comply

on days in column (B) Total number of daily exceedances if using the lb/d limit to comply on all days in

column (A)
FD-7b 8 329 329 16 0 0
FD-14 30 195 170 9 20 9
FD-5 a 8 9 8 1 8 8
FD13 271 4 0 0 271 271
FD-11 b 74 1 1 0 74 85
FD12 52 1 1 0 52 52
ND-3 855 254 44 35 811 806
ND-4 306 148 68 28 239 252

a The one day that meet the conditions in column (B ) does not cause any exceedances of a 30-d average.

b The number of exceedances is higher for the approach in column (A) because the one da y that meets the specified

conditions for complying with the lb/d limit has low NO xand the following days have relatively high NO x .

4. Conclusions

 A majority of existing forced draft process heaters cannot continuously meet a daily average emission limit of 60 ppmdv corrected to 0 percent oxygen, and (although the data sample was small) most existing natural draf t process heaters cannot continuously meet a daily average emission limit of 40 pp mdv corrected to 0 percent oxygen.

 Based on current operating procedures, most forced draft and natural draft process heaters can meet the emission limits based on the applicable 60 ppmdv and 40 ppmdv thresholds if compliance is determined on a 30-day rolling average basis, even when including data from periods of turndown in the averages.

 Under normal operation or turndown, some process heaters experience numerous exceedances when exhaust oxygen levels are relatively high, but few or no exceedances when the oxygen levels are lower. Better cont rol of excess air leve ls likely would reduce the number of exceedances.

 An alternative daily mass-based emissi on limit calculated as the mass of NO x that would be emitted when a process heater meets the a pplicable concentration and operates with a firing rate at 50 percent of design for an en tire day would do little to reduce the number of exceedances among process heaters that are un able to meet the 30-day rolling average emission limit.13 5. References

Cade, R. 2009. Letter and Attachments from R. Cade, Marathon Petr oleum Company LLC, to EPA Docket Center. Comments on Proposed Amendments to 40 CFR part 60, subparts J and Ja . February 3, 2009. Docket Item No. EPA-HQ-OAR-2007-0011-0296.

Chittim, R. 2009a. Letter and Attachments from R. Chittim, API, to EPA Docket Center. Comments from API, NPRA, and WSPA on the Proposed Amendments to 40 CFR part 60, subparts J and Ja . February 5, 2009. Docket Item No. EPA-HQ-OAR-2007-0011-0311.

Chittim, R. 2009b. Letter from R. Chitt im, API, to EPA Docket Center. Supplemental Comments from API, NPRA, and WSPA on the Proposed Amendments to 40 CFR part 60, subparts J and Ja . April 8, 2009. Docket Item No. EPA-HQ-OAR-2007-0011-0315.

Chittim, R. 2009c. Letter and Attachments from R. Chittim, API, to K. Hustvedt, EPA/OAQPS. Follow-up to August 12 Call Regarding Process Heaters . September 10, 2009. Docket No. EPA-HQ-OAR-2007-0011.

Feerick, C. 2008. Email communications from C. Feerick, ExxonMobil, to K. Hustvedt, EPA. EM Process Heater NO x Raw Data . September 9 and 12, 2008, and August 27, 2008. Docket Item No. EPA-HQ-OAR-2007-0011-0261.

Hunter, D. 2009. Letter from D. Hunter, ConocoPhillips, to EPA Docket Center. Comments on Proposed Amendments to 40 CFR part 60, subparts J and Ja . February 5, 2009. Docket Item No. EPA-HQ-OAR-2007-0011-0305.
Laughlin, J. 2008. Email communication with attached data files from J. Laughlin, ConocoPhillips, to, B. Shine, EPA. Refinery Heaters—NO x Emissions . October 27, 2008. Docket Item No. EPA-HQ-OAR-2007-0011-0283.

Lucas, B. 2010. Memorandum from B. Lucas, EP A/SPPD, to Petroleum Re finery NSPS Docket No. EPA-HQ-OAR-2007-0011. Revised NO x Impact Estimates for Process Heaters . July 6, 2010.
MACTEC Engineering and Consulting, Inc. 2005. Midwest Regional Planning Organization (RPO) Petroleum Refinery Best Available Retr ofit Technology (BART) Engineering Analysis

. Prepared for The Lake Michigan Air Dire ctors Consortium (LADCO). March 30, 2005. Docket Item No. EPA-HQ-OAR-2007-0011-0036.
Marathon Petroleum Company LLC. 2008a. NSPS Ja Process Heater NO x Concerns. June 6, 2008. Docket Item No. EPA-HQ-OAR-2007-0011-0256.
Marathon Petroleum Company LLC. 2008b. Presen tation slides. NSPS Subpart Ja Process Heater NO x . July 15, 2008. Attachment to Docket Item No. EPA-HQ-OAR-2007-0011- 0264.14 Wagner, J. 2008. Email communication from J. Wa gner, API, to, K. Hustvedt and B. Shine, EPA/OAQPS. Process Heater Information . October 15, 2008. Docket Item No. EPA-HQOAR-2007-0011-0280.

## Attachment AA-2 Figure A-1. Plot of daily data for Process Heater FD-5

Figure A-2. Plot of daily data for Process Heater FD-7bA-3 Figure A-3. Plot of daily data for Process Heater FD-11

Figure A-4. Plot of daily data for Process Heater FD-12A-4 Figure A-5. Plot of daily data for Process Heater FD-13

Figure A-6. Plot of daily data for Process Heater FD-14A-5 Figure A-7. Plot of daily data for Process Heater ND-3

Figure A-8. Plot of daily data for Process Heater ND-4A-6 Figure A-9. Plot of daily data for Process Heater ND-2

## Attachment BB-2 Figure B-1. Plot of daily NO x versus daily oxygen for Process Heater FD-1

Figure B-2. Plot of daily NO x versus daily oxygen for Process Heater FD-2B-3 Figure B-3. Plot of daily NO x versus daily oxygen for Process Heater FD-3

Figure B-4. Plot of daily NO x versus daily oxygen for Process Heater FD-4B-4 Figure B-5. Plot of daily NO x versus daily oxygen for Process Heater FD-5

Figure B-6. Plot of daily NO x versus daily oxygen for Process Heater FD-6B-5 Figure B-7. Plot of daily NO x versus daily oxygen for Process Heater FD-7a

Figure B-8. Plot of daily NO x versus daily oxygen for Process Heater FD-7bB-6 Figure B-9. Plot of daily NO x versus daily oxygen for Process Heater FD-8

Figure B-10. Plot of daily NO x versus daily oxygen for Process Heater FD-9B-7 Figure B-11. Plot of daily NO x versus daily oxygen for Process Heater FD-10

Figure B-12. Plot of daily NO x versus daily oxygen for Process Heater FD-11B-8 Figure B-13. Plot of daily NO x versus daily oxygen for Process Heater FD-12

Figure B-14. Plot of daily NO x versus daily oxygen for Process Heater FD-13B-9 Figure B-15. Plot of daily NO x versus daily oxygen for Process Heater FD-14

Figure B-16. Plot of daily NO x versus daily oxygen for Process Heater FD-15B-10 Figure B-17. Plot of daily NO x versus daily oxygen for Process Heater FD-16

Figure B-18. Plot of daily NO x versus daily oxygen for Process Heater FD-17B-11 Figure B-19. Plot of daily NO x versus daily oxygen for Process Heater ND-1

Figure B-20. Plot of daily NO x versus daily oxygen for Process Heater ND-2B-12 Figure B-21. Plot of daily NO x versus daily oxygen for Process Heater ND-3

Figure B-22. Plot of daily NO x versus daily oxygen for Process Heater ND-4B-13 Figure B-23. Plot of daily NO x versus daily oxygen for Process Heater UD-1

Figure B-24. Plot of daily NO x versus daily oxygen for Process Heater UD-2B-14 Figure B-25. Plot of daily NO x versus daily oxygen for Process Heater UD-3

Figure B-26. Plot of daily NO x versus daily oxygen for Process Heater UD-4B-15 Figure B-27. Plot of daily NO x versus daily oxygen for Process Heater UD-5

## Attachment CC-2 Figure C-1. NO x emissions versus firing rate for process heater FD-1

Figure C-2. NO x emissions versus firing rate for process heater FD-2C-3 Figure C-3. NO x emissions versus firing rate for process heater FD-3

Figure C-4. NO x emissions versus firing rate for process heater FD-4C-4 Figure C-5. NO x emissions versus firing rate for process heater FD-5

Figure C-6. NO x emissions versus firing rate for process heater FD-6C-5 Figure C-7. NO x emissions versus firing rate for process heater FD-7a

Figure C-8. NO x emissions versus firing rate for process heater FD-7bC-6 Figure C-9. NO x emissions versus firing rate for proces heater FD-8

Figure C-10. NO x emissions versus firing rate for process heater FD-9C-7 Figure C-11. NO x emissions versus firing rate for process heater FD-10

Figure C-12. NO x emissions versus firing rate for process heater FD-11C-8 Figure C-13. NO x emissions versus firing rate for process heater FD-12

Figure C-14. NO x emissions versus firing rate for process heater FD-13C-9 Figure C-15. NO x emissions versus firing rate for process heater FD-14

Figure C-16. NO x emissions versus firing rate for process heater FD-15C-10 Figure C-17. NO x emissions versus firing rate for process heater FD-16

Figure C-18. NO x emissions versus firing rate for process heater FD-17C-11 Figure C-19. NO x emissions versus firing rate for process heater ND-1

Figure C-20. NO x emissions versus firing rate for process heater ND-2C-12 Figure C-21. NO x emissions versus firing rate for process heater ND-3

Figure C-22. NO x emissions versus firing rate for process heater ND-4C-13 Figure C-23. NO x emissions versus firing rate for process heater UD-1

Figure C-24. NO x emissions versus firing rate for process heater UD-2C-14 Figure C-25. NO x emissions versus firing rate for process heater UD-3

Figure C-26. NO x emissions versus firing rate for process heater UD-4C-15 Figure C-27. NO x emissions versus firing rate for process heater UD-5