UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

SECTOR POLICIES AND PROGRAMS DIVISION

OFFICE OF AIR QUALITY PLANNING AND STANDARDS

OFFICE OF AIR AND RADIATION

DATE: February 28, 2014

SUBJECT: Updated Review of the Continuous Emission Monitoring and Continuous Opacity 

Monitoring Data from the Pulp and Paper ICR Responses for NSPS Sources

FROM: Kelley Spence (EPA/OAR/OAQPS/SPPD/NRG)

TO: EPA-HQ-OAR-2012-0640

The purpose of this memorandum is to present the results of an updated review of the 

Continuous Emission Monitoring System (CEMS) and Continuous Opacity Monitoring System

(COMS) data provided by the pulp and paper industry in response to the 2011 Information 

Collection Request (ICR). This analysis is part of the U.S. Environmental Protection Agency’s 

(EPA) effort to review the New Source Performance Standards (NSPS) for kraft pulp mills (40 

CFR part 60, subpart BB) in accordance with section 111(b)(1)(B) of the Clean Air Act (CAA). 

Section 111(b)(1)(B) of the CAA mandates that the EPA review and, if appropriate, 

revise the existing NSPS at least every 8 years. The kraft pulp mills NSPS were promulgated in 

1978 and reviewed in 1986. The NSPS regulate opacity and emissions of particulate matter (PM) 

from new, modified, and reconstructed recovery furnaces, smelt dissolving tanks, and lime kilns 

at kraft pulp mills. The NSPS also regulate emissions of total reduced sulfur (TRS) compounds 

from new, modified, and reconstructed digesters, brown stock washers, multiple-effect 

evaporators, condensate strippers, recovery furnaces, smelt dissolving tanks, and lime kilns at 

kraft pulp mills. On December 6, 2011, the Center for Biological Diversity, Greenpeace, and the 

Port Townsend Air Watchers filed a complaint (Clean Air Act citizen suit) against the EPA to 

review the NSPS. This complaint resulted in a consent decree that required the EPA to review 

the NSPS by May 15, 2013 for proposal and requires promulgation by March 14, 2014 for 

promulgation. See docket ID number EPA-HQ-OGC-2012-0730 for a copy of the consent 

decree.

As part of the NSPS review, the EPA reviewed the CEMS and COMS data and presented 

the results of the review in a memorandum to the docket, which included recommendations for 

proposed emission limits and associated monitoring allowances.

1

The proposed new standards 

(40 CFR part 60, subpart BBa) were published in the Federal Register on May 23, 2013. Once 

promulgated, the new standards will apply to affected sources at kraft pulp mills for which 

construction, modification or reconstruction commences on or after May 23, 2013. A number of 

public comments were received after the proposal that raised questions about the CEMS and 

COMS data presented at proposal, which prompted further review and documentation of the data

prior to promulgation of the rule. This memorandum presents the results of the updated 

CEMS/COMS review.
2

Section I of this memorandum provides a summary of the tabulation and quality 

assurance/quality control (QA/QC) analysis of the CEMS/COMS data provided by industry in 

response to the ICR survey. Section II of this memorandum discusses the analysis of the 

QA/QC’d data. 

I. Data Assembly and QA/QC

The CEMS and COMS data were collected from the pulp and paper industry in 2011 in 

response to a CAA section 114 ICR. The three-part survey was distributed by the EPA in 

February 2011 and requested information needed to perform various regulatory reviews, 

including the subpart BB NSPS review. This section of the memo discusses the pre-proposal 

QA/QC of the CEMS and COMS data that were provided in response to the ICR. 

The general approach for processing the CEMS and COMS data was to extract the data, 

as received, from individual ICR responses into a tabulation spreadsheet. Separate tabulation 

spreadsheets were developed for recovery furnace opacity, lime kiln opacity, recovery furnace 

TRS, lime kiln TRS, and TRS from other pulping process emission units. Tabs within each 

tabulation spreadsheet were labeled in the format of RTI facility code followed by emission unit 

ID with a period as a separator for the two values. If data were provided for multiple stacks for a 

given unit, they were also extracted into separate worksheets with the same naming convention, 

followed by an indication of stack location in parentheses. For example, the unit R401 at RTI 

facility 243 has two stacks and was represented by data in two separate worksheets with tabs 

labeled as follows: 243.R401 (N) and 243.R401 (S). A summary worksheet was included in each 

tabulation spreadsheet to link and tabulate the data provided for each emission unit. Emission 

unit ID, RTI facility ID, and NEI site ID were provided to characterize the emission units; the 

“tab name” of each worksheet from which the data are linked was provided; and summary 

information such as annual average emissions, 99th percentiles, and maximum values were

calculated. The count and percent of averaging periods exceeding limits under consideration 

were also calculated on both an annual and semiannual basis. The data from each summary 

worksheet were used for the data analyses discussed in Section II in this document.

Spreadsheet templates for COMS and CEMS data were provided with part III of the ICR 

(P&P CEMS_PIII.xls). The ICR template requested 6-minute average opacity values for a period 

of one year (87,600 opacity averages), as well as 1-hour average and 12-hour average TRS 

values for a period of one year. Alternative formats were also accepted. To some extent, the data 

extracted into the COMS and CEMS tabulation spreadsheets varied in format and type, 

depending on the facility and the unit, likely due to other state reporting and compliance 

requirements. In some cases, respondents did not provide COMS or TRS CEMS data, or 

provided the data in an alternative format (i.e., .pdf or .doc or .txt) that would have required 

extensive manipulation or re-entry of data. Given the abundance of data sets provided in 

spreadsheet form that were “analysis-ready,” it was elected not to tabulate data provided in an

alternative form. Mills that did not provide data in spreadsheet form were excluded from the 

quantitative analysis of the opacity and TRS emission limits, but the information these mills 
3

provided was reviewed qualitatively to confirm that it was comparable to the “analysis-ready” 

information provided by other mills. 

All data provided were reviewed for erroneous COMS or CEMS readings prior to 

proposal, and again following proposal based on comments questioning certain aspects of the 

proposal data sets. The following types of data were removed:

 Negative opacity and negative TRS concentration measurements which were deemed 

suspect and were removed to prevent artificial lowering of a unit’s annual average 

performance.

 Measurements (including abnormally large values) corresponding with periods of 

zero (or negative) production values or periods labeled as “process downtime”

because emissions of opacity or TRS would not be expected when the process is 

down. These were removed to prevent the artificial increase in the annual average 

emissions associated with the unit.

 Measurements recorded during monitoring system malfunctions, out-of-control 

periods or repairs, and monitor QA/QC checks, calibration checks, or zero or span 

adjustments to the extent that these time periods were labeled in the data sets. These 

were removed to be consistent with the proposed rule requirements that these data be 

excluded from compliance calculations.

The cells containing these values were highlighted to indicate removal of data. Large 

values reported during other periods were not deleted from the data sets. Facilities were asked to 

indicate in the ICR if any data were affected by periods of startup, shutdown, and malfunction 

(SSM). Opacity and TRS emissions occurring during periods of SSM were retained in the 

continuous monitoring data averages analyzed in order to evaluate whether the updated NSPS 

should distinguish between periods of startup and shutdown and normal operation as revised 

emission limits were considered.1 In response to comments on the proposal analysis of the 

CEMS and COMS data, EPA also resolved double oxygen (O2) corrections for units pointed out 

by commenters, rechecked calculation references, ensured any O2 correction calculations added 

to the data sets were based on the 12-hour average TRS concentration and 12-hour average O2

concentration (consistent with the rule), and updated other information as needed. The resultant 

“cleaned” data sets after removal of the erroneous/inappropriate data described above were used 

for further analysis of the promulgated standards. The cleaned data sets replace and supersede

the pre-proposal data sets.

Based on the part III survey responses, there were 151 recovery furnaces and 131 lime 

kilns at 98 kraft pulp mills in 2009. Of these, two recovery furnaces were indicated as nonoperational during the year of the ICR, resulting in 149 operating recovery furnaces. These two 

units were the following: RF18 at Longview Fiber and Packaging (RTI 156, NEI42338) and 

EU445A at International Paper in Springfield (RTI 105, NEI45182). 

 

1 Although malfunction data were not removed from the data sets, malfunction data were noted as invalid in 

analyses where these data would have been inappropriate for use (e.g., when setting the upper TRS concentration 

limits). 
4

A summary of the type of recovery furnace COMS and TRS CEMS data received and 

the comments from our QA/QC are listed in Appendix A. Similarly, a summary of the type of 

lime kiln COMS and TRS CEMS data and our QA/QC comments are listed in Appendix B.

A. Recovery Furnace Opacity Data

Continuous opacity monitoring system data were provided for 137 of the 149 operating 

recovery furnaces. Of the 137 units with data provided, 135 were extracted into a compiled 

recovery furnace COMS spreadsheet containing individual worksheets for each unit. There were 

25 units with multiple-stack opacity data. The two units with data that were not extracted into the 

spreadsheet were not provided in Excel format. The data for 117.B21 were provided as .pdf and 

the data for 155.RECOVERY FURNACE were provided in Word format (.doc). Recovery 

furnace design (direct contact evaporator [DCE] or non-direct contact evaporator [NDCE]) and 

air pollution control device (APCD) type were added to the spreadsheet from the part III 

database. In all, adding in emission units with COMS on multiple stacks, 160 COMS data sets 

were available for analysis.

The order of preference for opacity averaging period extracted into the opacity 

tabulation spreadsheet was 6-minute averages followed by 1-hour averages. Of the data 

provided, 5 units were extracted in the 1-hour format (1 unit with multiple stacks) and the 

remaining units were extracted in the 6-minute average format. 

The recovery furnace COMS summary worksheet summarizes the data type as “6-

minute averages,” “hourly averages,” “data not provided,” or indicates if data are provided in 

alternate format. For each COMS, the summary spreadsheet contains the maximum opacity, the 

average (including and excluding exceedances), the standard deviation, the 99th percentile, the 

median, and the number (and percentage) of opacity 6-minute average values over 20 percent

and 35 percent. The number of averaging periods in which valid opacity data were provided is 

also indicated along with the percent of periods that exceeded the limits under consideration.

B. Recovery Furnace Total Reduced Sulfur (TRS) CEMS Data

Total reduced sulfur CEMS data were provided for 135 of the 149 operating recovery 

furnaces. Of the 135 units with data provided, 131 were extracted into a compiled recovery 

furnace TRS CEMs spreadsheet containing individual worksheets for each unit. There were 10

recovery furnaces with multiple stack TRS data. The four units with data that were not extracted 

into the spreadsheet were not provided in Excel format. The data for three of these units were 

provided in Word format and one unit was provided as a PDF document. In all, adding emission 

units with multiple stacks, 141 TRS CEMS data sets were available for analysis.

As noted previously, separate TRS CEMS spreadsheet templates requesting 12-hour and 

1-hour average TRS data for a period of one year were provided with part III of the ICR. The 

1-hour average data were requested in addition to the 12-hour average data in order for EPA to 

explore shorter averaging times should there be a prevalence of shorter TRS averaging times 

required by state regulations. However, based on a review of permit limits and of the CEMS data 

provided, it appears that a 12-hour averaging time is most consistently used for compliance. 
5

Therefore, the order of preference for TRS averaging time extracted into the tabulation 

spreadsheet used was 12-hour averages, followed by 12-hour averages manually calculated based 

on 1-hour averages, with 24-hour averages being least desirable. Of the TRS data provided, 114

recovery furnaces were extracted in the 12-hour average format (9 units with multiple stacks), 10

units in the 12-hour average calculated based on 1-hour averages, and 7 units in the 24-hour 

format (1 unit with multiple stacks). 

The CEMS spreadsheet template that was sent to industry with part III of the survey 

(P&P CEMS_PIII.xls) requested that a facility report the “12-hour average emission value for 

TRS (ppmdv corrected for % O2)” in column I with the instructions “please enter concentration 

(ppmdv) corrected for % O2 as required by subpart BB (8% O2 for recovery furnaces; 10% O2

for other equipment for which data are requested).” The spreadsheet template also requested that 

a facility report the “% O2 correction (by volume, dry basis)” in column J with the instructions to 

enter “the % O2 correction by volume (dry basis) (e.g., 8% or 10%).” For the recovery furnace 

TRS CEMS, it was expected that the O2 correction would be reported as 8 percent in column J. 

The oxygen correction data for 7 units (127.REC1, 171.02, 171.03, 171.04, 183.002, 207.038, 

and 340.005) reported in column J appeared to be raw O2 data instead of the requested corrected 

O2 value of 8 percent. It was assumed, because raw O2 data were reported instead of the 

correction value, that the TRS data provided in column I were also raw data. The raw TRS and 

O2 values were used to determine the corrected TRS value using Eqn. 1 shown below from 40 

CFR 60.284(c)(3).

2

The new TRS column was highlighted in yellow for the 7 units reported for 

which values were calculated. Unit 163.RF1901 had data reported as corrected to 10 percent O2

and unit 242.AA-011 had data as corrected to 5 percent O2. These units were corrected to 8 

percent O2. The data for two units (100.037A, 143.7000) were indicated as raw data. These 

values were also corrected using Eqn. 1 and the corrected TRS value column was highlighted in 

yellow. 

Corrected TRS value = Raw TRS concentration value * ((21-8)/(21-O2 value)) (Eqn. 1)

Data provided for five units (179.RF3, 240.RF04, 240.RF01, 163.RF1901, and 

163.RF2904) may slightly skew the performance values (e.g., annual average, median, 99th

percentile) for those units high because data were reported as “<1” instead of decimal values. 

These values were not removed or edited; therefore, they did not contribute to the performance 

values, but the reporting of the data was considered in the analysis.

3

The summary worksheet in the recovery furnace TRS CEMS spreadsheet indicated the

data type as “12-hr average,” “12-hr calculated from 1-hr averages,” “24-hr average,” “not 

 

2

Commenters expressed concern about the potential for double correction for oxygen in the pre-proposal analysis. 

Upon further examination of the data sets following proposal, we determined that the impact of the potential double 

correction on our conclusions relative to the proposed emissions limits and monitoring allowances is insignificant 

because the number of exceedances of the proposed standard was similar in the original TRS concentration column 

and the potentially double-corrected TRS concentration column of each CEMS data sheet. Therefore, we did not 

burden ICR respondents with follow-up questions on the TRS CEMS data, nor did we remove the 7 potentially 

double-corrected data sets from the analysis.

3 Upon further examination of these units following proposal, these values had no significant effect on any 

conclusions presented in this memorandum. 
6

provided,” or indicated whether data are provided in alternative format. The annual average and 

standard deviation of the corrected TRS parts per million (ppm)4values were calculated for each 

unit (to determine 99th percentiles), as well as the maximum reported average and the number of 

exceedances over 5 ppm. Because most DCE recovery furnaces are not currently subject to the 

NSPS, the 20 ppm emission guideline for DCEs was also used for comparison. The emission 

guideline for NDCEs is 5 ppm (the same as the NSPS, though permitting approaches vary by 

state). Additional details such as APCD type, NSPS applicability, and whether or not the 

recovery furnace burns non-condensable gases (NCG) were imported into the CEMS tabulation 

spreadsheet for analysis.

C. Lime Kiln TRS CEMS Data

Total reduced sulfur CEMS data were provided for 115 of the 131 operating lime kilns. 

Of the 115 units with data provided, 110 units were extracted into a compiled lime kiln TRS 

CEMS spreadsheet containing individual worksheets for each unit. Data for one kiln was not 

used based on public comment that the respondent provided uncorrected data (and did not 

provide the actual O2 percent to correct it with). The four kilns with data that were not extracted 

into the spreadsheet were not provided in Excel format. The data for two of these kilns were 

provided in text format (.txt), one kiln was provided in Word format, and one kiln was provided 

as a PDF document. In all, 110 TRS CEMS data sets were available for analysis.

Similar to recovery furnaces, the order of preference for TRS averaging period for lime 

kilns was 12-hour averages, followed by 12-hour averages calculated based on 1-hour averages, 

with 24-hour averages being least desirable. Of the data provided, 90 kilns were extracted in the

12-hour average format, 12 kilns were extracted in the 1-hour average format, and 8 were 

extracted in the 24-hour format. The 1-hour average TRS data sets were converted to 12-hour

average format for comparison purposes.

The O2 correction data for 7 lime kilns (127.LK1, 127.LK2, 164.P12, 171.009, 171.010, 

183.004, and 340.008) reported in column J of the ICR template appeared to be raw O2 data 

instead of the requested corrected O2 value of 10 percent. The raw TRS and O2 values were used 

to determine the corrected TRS value using Eqn. 1 above.5 Units 119.EQT006, 103.G-65, and 

105.EU455 had data reported as corrected to 8 percent O2; therefore, a new column was added 

(highlighted yellow) with the data corrected to 10 percent. Raw data were reported for unit 

143.6063, which were used to calculate the corrected TRS values. 

 

4 All parts-per-million values reported in this document represent ppm by volume on a dry basis (ppmdv). 

5

Commenters expressed concern about the potential for double correction for oxygen in the pre-proposal analysis. 

Upon further examination of the data sets following proposal, we determined that the impact of the potential double 

correction on our conclusions relative to the proposed emissions limits and monitoring allowances is insignificant 

because the number of exceedances of the proposed standard was similar in the original TRS concentration column 

and the potentially double-corrected TRS concentration column of each CEMS data sheet. Therefore, we did not 

burden ICR respondents with follow-up questions on the TRS CEMS data, nor did we remove the 7 potentially 

double-corrected data sets from the analysis.
7

Data provided for four units (163.LK1501, 163.LK2502, 179.LK3, 240.CA81) may

skew the annual performance values (e.g., annual average, 99th percentile) for those units 

because data were reported as “<1” instead of decimal values. These values were not removed or 

edited; therefore, they did not contribute to the performance values, but the reporting of the data 

was considered in the analysis.6

A summary worksheet was added to the lime kiln TRS CEMS spreadsheet to 

characterize the data provided. Emission unit ID, RTI facility ID, and NEI site ID were provided 

to characterize the emission units. The name of the worksheet for which the data were calculated 

for each row of data was provided as “tab name,” and data type was indicated as “12-hr 

average,” “24-hr average,” “not provided,” or if provided in alternative format. The annual 

average and standard deviation of the corrected TRS ppm values were calculated for each unit

(to determine 99th percentile), as well as the maximum, average and the number of exceedances 

over 8 ppm. Because some lime kilns are not currently subject to NSPS, the 20 ppm emission 

guideline was also used for comparison. Additional lime kiln details such as APCD type, NSPS 

applicability, whether or not the lime kiln burns non-condensable gases (NCG), or uses a whiteliquor NCG pre-scrubber were imported into the CEMS tabulation spreadsheet for analysis.

D. Lime Kiln Opacity Data

Lime kiln opacity data were compiled in order to establish a limit for lime kilns with 

electrostatic precipitators (ESPs) under the NSPS. Continuous opacity monitoring system data 

were provided for 27 lime kilns that utilize ESPs or ESP/scrubber combinations as pollution 

control devices. These were extracted into a compiled lime kiln COMs spreadsheet containing 

individual worksheets for each unit. There were 2 units with multiple stack opacity data. The 

order of preference for opacity averaging period extracted into the opacity tabulation spreadsheet 

was 6-minute averages and 1-hour average. There were 25 units extracted in the 6-minute 

average format and 2 extracted in the 1-hour format. Including kilns with dual stacks, 29 data 

sets were available for analysis.

The lime kiln COMS summary worksheet summarizes the data type as “6-minute 

averages” and “hourly averages.” The maximum opacity, the average, the standard deviation, the 

99th percentile, the median, and the number (and percentage) of opacity average values over 20 

percent were calculated.

II. Data Analysis 

The updated summary data from the recovery furnace and lime kiln COMS and TRS 

CEMS spreadsheets described in Section I were plotted and compared to the current NSPS limits 

in order to evaluate the accuracy of the proposed regulatory options and finalize the regulatory 

options for the NSPS review. Annual average measurements and the 99th percentile of the 

 

6 Upon further examination of these units following proposal, these values had no significant effect on any 

conclusions presented in this memorandum.
8

averaging periods were plotted for each emission unit and used to evaluate each opacity or TRS 

emission limit. The 99th percentile was used as an indicator of the emission limitation 

consistently met by each emission unit. The percent of averaging periods exceeding the opacity 

or TRS limit under consideration was calculated and plotted on both an annual basis (as was 

done for proposal) and on an semiannual basis (in response to comments on the proposal) to 

evaluate appropriate monitoring allowances to be coupled with each opacity or TRS emission 

limit. Distinctions in furnace design and control systems, and current emissions allowances in the 

NSPS, were considered in the CEMS and COMS analyses as described in more detail in the 

following sections. In addition, emission units were identified as either NSPS units (currently 

subject to subpart BB) or non-NSPS units (units that have not triggered subpart BB) when 

appropriate. Emission units that have previously triggered NSPS subpart BB were further 

subdivided into new units and modified units in some cases. 

A. Recovery Furnace COMS Analysis

Opacity limit evaluation. The subpart BB kraft pulp mill NSPS contain a 35 percent limit 

for opacity from recovery furnaces and do not distinguish between recovery furnace design

(DCE or NDCE). The NSPS require opacity to be recorded as 6-minute averages, and allow 6 

percent of the 6-minute averages per quarter recorded to be in exceedance of the 35 percent limit. 

Appendix C contains graphs of the updated recovery furnace opacity data. The horizontal axis 

represents each emission unit, but is not labeled with emission unit IDs because this would make 

the figures too difficult to read. A total of 160 COMS data sets were graphed (including multiple 

data sets for furnaces with separate COMS for dual stacks). The majority (154) of the COMS 

data sets graphed were 6-minute average data. Six data sets were based on hourly average. The 

hourly data sets were generally within the range of the 6-minute average data.

Figure 1 in Appendix C presents the annual average of the opacity readings for each 

recovery furnace COMS data set (160 data sets). Based on this figure, it does not appear that 

recovery furnace design affects opacity. The highest annual average opacity was 17 percent, well 

below the 35 percent NSPS limit. Figures 2 and 3 show annual average opacity by control type 

(within DCE and NDCE groupings in Figure 2). The primary control types are wet-bottom ESP 

(WBESP), dry-bottom ESP with a dry PM return system (DBESP), and dry-bottom ESP with a 

wet PM return system (DBESP-WPR). Figures 2 and 3 reveal no clear distinction between 

recovery furnace control system and opacity.

Apart from the monitoring allowance discussed below, compliance is based on each 

individual averaging period and not the annual average. Therefore, the 99th percentile and 

percent of averaging periods exceeding 35 percent were graphed in order to understand how 

opacity varies. Figure 4 in Appendix C presents the 99th percentile values from each of the 160 

COMS data sets. From Figure 4, it is apparent that the majority of mills are consistently meeting 

the NSPS limit of 35 percent opacity. The subpart MM NESHAP contains a 20 percent opacity 

monitoring action level for new and existing recovery furnaces (40 CFR 63.864(k)(1)(i)). For 

new recovery furnaces equipped with an ESP, subpart MM considers opacity greater than 20 

percent for more than 6 percent of quarterly operating time to be a violation of the subpart MM 

standards (40 CFR 63.864(k)(2)(i)). Figure 4 shows that most (136 of 160 data sets) recovery 

furnace COMS had 99th percentiles below the 20 percent level regardless of recovery furnace 
9

design. Figures 5 and 6 break out 99th percentile opacity by control type (within design

groupings in Figure 5). Figures 5 and 6 show that most control types are capable of meeting 20 

percent opacity consistently, and that all control types are meeting 35 percent consistently. Two 

unique control systems (a parallel DBESP-WPR/DBESP/DBESP system and a two-sided dry 

and wet bottom ESP) had 99th percentiles around 25 and 27 percent, respectively. The annual 

averages for these two unique systems were around 14 and 10 percent, respectively.

Based on Figures 1 through 6 in Appendix C, 20 percent opacity was proposed and 

remains an acceptable regulatory option for the final NSPS review because: (1) 20 percent is 

already a benchmark under subpart MM, (2) all mills had annual average opacity of 17 percent 

or less, and (3) the majority of recovery furnaces are consistently achieving 20 percent opacity. 

The EPA could have considered higher or lower options (e.g., 25 percent or 15 percent), but 

these do not have the benefit of relating to subpart MM. An opacity limit of 20 percent is still 

considered adequately demonstrated for recovery furnaces. 

Monitoring allowance evaluation. In the pre-proposal analysis of the COMS data, 

monitoring allowance calculations for opacity were conducted on an annual basis. Commenters 

on the proposal requested that EPA evaluate the monitoring allowances on the same time period 

as will be used for compliance instead of evaluating the allowance on an annual basis and then 

using a shorter quarterly or semiannual timeframe for compliance calculations of the monitoring 

allowance. A semiannual timeframe was selected for the final rule consistent with the 

semiannual reporting frequency in 40 CFR 60.288a(a). EPA revised the annual monitoring 

allowance calculations presented at proposal using the updated data sets, and added analysis of 

the monitoring allowance on a semiannual basis in response to comments. 

Figures 7 through 9 in Appendix C review the percentage of averaging periods (on an 

annual basis) exceeding the current 35 percent NSPS opacity limit, as compared to the current 6 

percent monitoring exceedance allowance. Similarly, Figures 10 through 12 in Appendix C show 

the percentage of averaging periods exceeding 20 percent opacity. Figures 7 through 9 show that 

the overwhelming majority of mills are performing far better than the 6 percent monitoring 

allowance for opacity above 35 percent regardless of recovery furnace design or APCD type. 

These figures show that a 1 to 2 percent monitoring allowance more accurately represents the 

number of exceedances mills are incurring under a 35 percent opacity limit. Twenty-eight

recovery furnace COMS had zero exceedances of the 35 percent limit.

As to be expected, the percent of averaging periods that are exceedances increases when 

an opacity limit of 20 percent is considered (instead of 35 percent). Nevertheless, Figures 10 

through 12 show that a 2 percent monitoring allowance coupled with a 20 percent limit is 

achieved by many recovery furnaces regardless of design or control system. One of the unique 

control systems mentioned above (the parallel DBESP-WPR/DBESP/DBESP system) would be

challenged to remain under a 2 percent monitoring allowance but because alternative control 

designs are both available and adequately demonstrated, it is not clear if this unique system

would continue to be used if this furnace were to be replaced, modified, or reconstructed. A 6 

percent monitoring allowance would cover nearly all exceedances of the 20 percent opacity limit

and is consistent with subpart MM (but a 6 percent allowance would not provide much incentive 

for improvement compared to a 2 percent allowance). A 2 percent monitoring allowance more 
10

accurately represents the number of exceedances the best performing recovery furnaces were

incurring on opacity limits ranging from 20 to 35 percent. Only 8 of 160 recovery furnaces 

COMS had zero exceedances of the 20 percent opacity limit which supports the need for having 

a monitoring allowance.

As mentioned above, the EPA repeated monitoring allowance calculations based on a 

semiannual reporting period instead of the annual basis used for the proposal. Table 1

summarizes the number of COMS data sets analyzed for new, modified (or reconstructed), and 

existing recovery furnaces. The number of COMS data sets in compliance with the proposed 

opacity standard and monitoring allowance before proposal and in the final data sets is indicated. 

The values presented from the proposal analysis represent calculation of the opacity monitoring 

allowance on an annual basis, while the values from the final analysis reflect the revised data sets 

and calculation of the opacity monitoring allowance on a semiannual basis. Use of a semiannual 

basis for calculating the opacity allowance resulted in only minor differences in the number of 

emission units that would not be in compliance with the proposed opacity standard and 

monitoring allowance. The semiannual allowance calculation would change the compliance 

outcome for only 3 out of 160 recovery furnace COMS data sets.

Table 1. Summary of Recovery Furnace COMS Data Sets Analyzed

Unit NSPS Classification1

Proposal data 

set2

Final data 

set3 Notes

No. of COMS data sets 160

 New 52

 Modified 32

 Existing (not subject to NSPS) 76

No. of COMS meeting 20% opacity 

with a 2% allowance

144 141

 New 45 44

 Modified 30 30

 Existing (not subject to NSPS) 69 67

No. of COMS not meeting 20% 

opacity with a 2% allowance

16 19

 New 7 8 Installation dates ranged from 1978 to 1991. The 

semiannual percentage of periods exceeding 20% 

opacity ranged from 0.59 to 8.05%. Four of the 8 

units in the final data set achieved a 4% 

allowance in both semiannual basis.

 Modified 2 2 Two stacks having separate COMS on a furnace 

that became subject to the NSPS in 1990. The 

semiannual percentage of periods exceeding 20% 

opacity ranged from 1.26 to 7.72%. Neither of 

these COMS achieved a 4% allowance in both 

semiannual periods.

 Existing (not subject to NSPS) 7 9 5 of the 9 units in the final data set achieved a 

4% allowance on a semiannual basis. The 

semiannual percentage of periods exceeding 20% 

opacity ranged from 0.39 to 35.2%.

1. New and modified units are defined in terms of the subpart BB NSPS 1976 applicability date (not the more recent 

subpart MM applicability date).

2. The monitoring allowance was calculated on an annual basis in the proposal data set (Reference 1).

3. This column refers to the monitoring allowance calculated on a semiannual basis using the final updated data set 

presented in this memorandum.
11

Figures 13 through 15 in Appendix C show the percentage of averaging periods 

exceeding 20 percent opacity on a semiannual basis and indicate that that a 2 percent monitoring 

allowance (on a semiannual basis) coupled with a 20 percent limit is achieved by most recovery 

furnaces regardless of design or control system. 

Figures 16 through 18 in Appendix C depict semiannual monitoring allowance 

calculations for only those recovery furnaces that triggered the subpart BB NSPS as new or 

modified units after the 1976 subpart BB applicability date. Figures 16 through 18 show that the 

2 percent monitoring allowance for recovery furnace opacity is achieved by most recovery 

furnaces regardless of their control system or their prior NSPS classification as new or modified 

units. While a few recovery furnaces that became subject to the NSPS when they were installed 

new or were modified did not achieve 20 percent opacity with a 2 percent allowance for one or 

more semiannual periods, it is notable that these units all became subject to the NSPS over 20 

years ago. Recovery furnaces that have come online as new units or been upgraded over the past 

decade showed compliance with the proposed 20 percent opacity limit with a 2 percent 

monitoring allowance.

One commenter on the proposal suggested a 4 percent monitoring allowance for recovery 

furnace opacity. Based on the data in Figures 13 through 18, although a 4 percent allowance

would provide some additional flexibility, it would not resolve the issues noted for all of the new 

and modified NSPS units in Table 1 that did not meet 20 percent opacity with a 2 percent 

allowance. The two modified recovery furnaces that did not meet the 2 percent allowance also 

did not meet a 4 percent allowance in both semiannual periods. 

Recommendation. The figures in Appendix C support the proposed regulatory decision to 

reduce the subpart BB opacity limit from 35 percent to 20 percent and to reduce the monitoring 

allowance from 6 percent to 2 percent for new, modified, and reconstructed recovery furnaces.

Overall, 141 of 160 total recovery furnace COMS data sets demonstrated that the 20 percent 

opacity limit with a 2 percent monitoring allowance proposed for subpart BBa was achieved 

with a semiannual monitoring allowance calculation. Consequently, it is recommended that the 

20 percent opacity limit and 2 percent monitoring allowance for new, modified, and 

reconstructed recovery furnaces be finalized as proposed.

Startup and shutdown periods were included in the data sets used to evaluate the revised 

opacity limit. Therefore, a revised limit of 20 percent opacity with a 2 percent monitoring 

allowance accounts for startup and shutdown periods (as well as normal operation), supporting 

the conclusion that separate opacity limits for startup and shutdown are unnecessary. Continuous 

compliance with the NSPS opacity limit can be demonstrated through monitoring of control 

device operating parameters (e.g., ESP secondary voltage and current or power) during times 

when the 2 percent monitoring allowance is invoked.

B. Recovery Furnace TRS CEMS Analysis

TRS limit evaluation. The subpart BB kraft pulp mill NSPS limit TRS emissions from 

straight recovery furnaces to 5 ppm at 8 percent O2 and from cross recovery furnaces to 25 ppm 

at 8 percent O2. Review of the part III ICR data indicates that no cross recovery furnaces are 
12

currently subject to the NSPS. Likewise, there are no TRS emissions data to analyze for these 

units. Maintaining the current cross recovery furnace TRS limit is recommended for three 

technical reasons. First, the sulfur content of the semichemical liquor is higher than traditional 

kraft liquor. Second, the heat content of the liquor is lower because it contains less organic 

material than kraft pulping liquor because of higher pulping yields. Lastly, the heavier sulfur 

loading and the lower operating temperature puts a restriction on the amount of excess oxygen 

available to oxidize sulfur compounds. We do not project any modified, reconstructed, or new 

cross recovery furnaces being constructed in our analysis. The remainder of this section will 

focus on TRS emissions from straight recovery furnaces.

The subpart BB NSPS require TRS to be recorded as 12-hour averages and allow 1 

percent of the 12 hour averages recorded per quarter to be in exceedance of the 5 ppm limit 

without constituting a violation. As noted previously, the EPA is finalizing a semiannual period 

for the monitoring allowance calculation consistent with the semiannual reporting frequency in 

40 CFR 60.288a(a). EPA revised the annual monitoring allowance calculations presented in this 

section using the post-proposal updated data sets, and added an analysis of the monitoring 

allowance on a semiannual basis in response to comments.

Appendix D contains graphs of the updated recovery furnace TRS data. A total of 131

recovery furnaces are represented by these graphs (including 10 recovery furnaces with multiple 

TRS CEMS for a total of 141 TRS data sets), with the majority reported as 12-hour averages. 

The TRS emission guidelines require a limit of 5 ppm for existing NDCE and 20 ppm for 

existing DCE recovery furnaces. All of the recovery furnace TRS ppm values discussed in this 

section reflect conversion to 8 percent O2.

The plots in Appendix D present the recovery furnace TRS summary data from the 

summary spreadsheet described in Section I. Most of the TRS values shown on the plots are 

based on 12-hour averaging periods; however, seven of the TRS data sets (for non-NSPS 

furnaces) are based on 24-hour average values. The graphs distinguish between NSPS and nonNSPS recovery furnaces because there are separate Federal TRS limits for existing and new 

sources under the emission guidelines and NSPS, respectively. Recovery furnace design and 

NSPS applicability appear to be more relevant than control device type in distinguishing between 

the best performing recovery furnaces for TRS. Process control factors (e.g., good combustion

practices) are expected to play a large role in recovery furnace TRS emissions. 

As shown in Figure 1 in Appendix D, many DCE recovery furnaces that are not subject 

to the NSPS TRS limit exhibit emissions above 5 ppm but below the 20 ppm emission guideline 

on an average basis (i.e., the average of the block averaging periods provided for the year). On 

average, all but one of the NDCE recovery furnaces met the 5 ppm limit, and most of the NDCEs 

averaged below 2 ppm. 

Apart from the 1 percent monitoring allowance, compliance with the NSPS TRS limit is 

based on each 12-hour block average (rather than the average of all 12-hour blocks in a year).

Therefore, we considered the 99th percentile of the TRS averaging periods in Figure 2 as an 

indicator of how consistently the block average limit is achieved. Two 99th percentile outliers 

were omitted from Figure 2 (a non-NSPS DCE with 99th percentile at 126 ppm, and a NDCE 
13

subject to the NSPS with 99th percentile at 43 ppm). When considering the 99th percentile, nearly 

all of the DCE furnaces had TRS emissions above 5 ppm while the majority of NDCE furnaces 

achieved 5 ppm consistently. Most of the DCE furnaces had 99th percentile values between 5 

ppm and 20 ppm, with a few DCE furnaces exhibiting 99th percentile values between 20 and 30

ppm.

We also considered the number of averaging periods in excess of 5 ppm for each 

recovery furnace in Figure 3. Predictably, the DCEs exhibited a high percentage of averaging 

periods (on an annual basis) above 5 ppm because most DCEs are not required to consistently 

meet the 5 ppm limit. The majority of NDCEs achieved the 5 ppm limit consistently with 1 

percent or fewer of the averaging periods (on an annual basis) in excess of 5 ppm. As noted 

previously, subpart BB contains a 1 percent monitoring allowance for recovery furnace TRS. A 

few NDCE furnaces had a relatively high percentage of averaging periods (on an annual basis) in 

excess of 5 ppm, but these were mostly non-NSPS NDCEs.

Only the recovery furnaces subject to the NSPS were plotted in Figures 4 through 6 in 

order to better evaluate the 1 percent TRS monitoring allowance (on an annual basis) and the 

effect of different types of air pollution controls. As shown in Figure 4, two of the three DCEs 

subject to the NSPS exceeded 5 ppm in less than 1 percent of the averaging periods. One of these 

DCEs had zero exceedances. The third DCE (controlled by a WBESP and scrubber) exceeded 

the 5 ppm limit in 46 percent of the averaging periods, which again suggests that DCEs are 

challenged to meet a TRS limit of 5 ppm. Many of the NDCEs (44 of 72) subject to the NSPS 

achieved the 5 ppm limit with zero exceedances during the year reported. An additional 14

NDCEs had some exceedances but remained below the 1 percent monitoring allowance, and 8 

units exceeded 5 ppm for 1 percent of the reporting periods. Six NDCEs exceeded 5 ppm in up to 

8 percent of the averaging periods. 

Figure 5 shows that there is little difference in the performance of various control systems 

used on NSPS recovery furnaces. All systems achieved the 5 ppm limit on an annual basis, with 

the exception of the DCE controlled by a WBESP in conjunction with a scrubber. In Figure 6, 

we observe that control device type does not appear to significantly affect the 99th percentile 

TRS value for the NSPS recovery furnaces. Few recovery furnaces had a 99th percentile TRS 

value in excess of 5 ppm, including a unique system with a two-sided dry- and wet-bottom ESP. 

The 99th percentile values shown on this figure indicate that most of the NSPS recovery furnaces 

are achieving 5 ppm 99 percent of the time, regardless of APCD type. Although the annual 

average of the TRS averaging periods (shown in Figure 5) seems to suggest that a limit lower 

than 5 ppm (e.g., 3 ppm) is achieved, the 99th percentile TRS value in Figure 6 reflects the 

variability exhibited in each block average and affirms that a limit of 5 ppm provides for the 

variability in TRS expected from the best performing sources. 

Figure 7 in Appendix D investigates the effect on DCE recovery furnace TRS emissions 

if multiple-stage black liquor oxidation (BLO) is used prior to the DCE. Of the three NSPS DCE 

recovery furnaces, two units had two-stage BLO systems and one had a single-stage BLO 

system. A total of 12 recovery furnaces with data were indicated as single stage BLO (3 units 

with multiple stacks) and 14 recovery furnaces with TRS data were indicated to have two-stage 

BLO, and four had three-stage BLO systems. The TRS data in Figure 7 are inconclusive as to 
14

whether multiple-stage BLO systems reduce TRS emissions better than single-stage systems. 

Most of the BLO systems did not achieve the 5 ppm NSPS limit. 

Figures 8 and 9 explore the impact of burning NCGs. Figure 8 shows the impact of 

burning NCGs on the annual TRS average, and Figure 9 shows the impact on the 99th percentile. 

Burning NCGs did not appear to significantly increase recovery furnace TRS emissions, but it 

did indicate an increase in the potential for TRS emissions variability as evidenced by the greater 

range in 99th percentiles for the NCG-burning NDCE furnaces in Figure 9.

Monitoring allowance evaluation. In the pre-proposal analysis of the TRS CEMS data, 

monitoring allowance calculations for TRS were conducted on an annual basis. The annual-basis 

analysis was repeated with updated data sets, and a semiannual monitoring allowance calculation 

was added as discussed later in this subsection. As shown in Figure 4 of Appendix D, most 

recovery furnaces subject to the NSPS have achieved a 5 ppm TRS limit with 1 percent or less 

monitoring deviations (on an annual basis) during normal operations and startup and shutdown 

periods. The TRS CEMS data shown in Figure 4 include periods of startup and shutdown, and 

show that many mills comply with the TRS limit in spite of startup and shutdown periods. The 

TRS CEMS data were reviewed closely to determine the impact of removal of the SSM 

exemption in 40 CFR 60.284(e)(1) and continuous application of the 5 ppm limit to startup and 

shutdown periods in addition to normal operations. Periods of malfunction and process 

downtime (i.e., when BLS firing ceases) were excluded from consideration because these are not 

valid operating periods for rulemaking. The TRS CEMS data reveal that some exceedances of a 

5 ppm limit falling within the 1 percent monitoring allowance are associated with periods of 

startup and shutdown. To ensure that the standard is continuous, an upper limit (i.e., a cap) was

determined. Table D-1 in Appendix D shows the CEMS data for periods of startup and 

shutdown. After removing the extreme values for reasons noted in the table, three recovery 

furnaces had values associated with startup and shutdown between 25 and 30 ppm. Thus, 30 ppm

appears to be a representative cap for the 1 percent monitoring allowance. For any of the 

recovery furnaces, up to eight of the 12-hour periods were in excess of the 5 ppm limit. Eight of 

730 possible 12-hour blocks in a year corresponds to about 1 percent of possible averaging 

periods (8/730 = 1.1%).

During periods of startup and shutdown, the EPA observed that corrected TRS 

concentrations may be grossly inflated as a result of the oxygen correction equation. As the stack 

gas concentration approaches ambient conditions, the denominator of the oxygen correction 

equation becomes very small, leading to an oxygen corrected concentration that is artificially 

high, such that an otherwise compliant TRS measurement can exceed the applicable 

concentration because it is corrected for oxygen. Table D-2 in Appendix D shows this inflation. 

The proposed solution to this issue was to allow uncorrected, actual TRS values to be used 

during periods of startup and shutdown for compliance for periods when the oxygen 

concentration is greater than 15 percent. 

Table 2 below summarizes the number of TRS CEMS data sets analyzed for new, 

modified (or reconstructed), and existing recovery furnaces. The number of TRS CEMS data sets 

in compliance with the proposed TRS standard and monitoring allowance before proposal and in 

the final data sets is indicated. The values presented from the proposal analysis represent 
15

calculation of the TRS monitoring allowance on an annual basis, while the values from the final 

analysis reflect the revised data sets and calculation of the TRS monitoring allowance on a 

semiannual basis. Use of a semiannual basis for calculating the TRS allowance resulted in only 

minor differences in the number of emission units that would not be in compliance with the 

proposed TRS standard and monitoring allowance. The semiannual allowance calculation would 

change the compliance outcome for only 2 out of 141 recovery furnace TRS CEMS data sets.

Table 2. Summary of Recovery Furnace TRS CEMS Data Sets Analyzed

Unit NSPS Classification1

Proposal 

data set2

Final 

data set3 Notes

No. of TRS CEMS data sets 141

 New 51

 Modified 28

 Existing (not subject to NSPS) 62

No. of CEMS meeting 5 ppm 

with a 1% allowance

95 93

 New 45 45

 Modified 26 26

 Existing (not subject to NSPS) 24 22

No. of CEMS not meeting 5 

ppm with a 1% allowance

46 48

 New 6 6 Installation dates range from 1977 to 1992.

 Modified 2 2 Modified in 1989 and 1990.

 Existing (not subject to NSPS) 38 40 Includes 33 DCE recovery furnace CEMS. The 

TRS emission guideline for existing DCE recovery 

furnaces is 20 ppm.

4 of these existing units were DCE furnaces in the 

final data set that have since been replaced with or 

converted to NDCE technology (in 2011-2012 

after the data were collected).

1. New and modified units are defined in terms of the subpart BB NSPS 1976 applicability date (not the more recent 

subpart MM applicability date).

2. The monitoring allowance was calculated on an annual basis in the proposal data set (Reference 1).

3. This column refers to the monitoring allowance calculated on a semiannual basis using the final updated data set 

presented in this memorandum.

Figure 10 in Appendix D depicts semiannual monitoring allowance calculations for 

recovery furnaces already subject to the subpart BB NSPS. The monitoring allowance represents 

the percent of TRS CEMS averaging periods exceeding the limit for each emission unit. Figure 

10 shows that the majority of recovery furnaces subject to subpart BB achieved a 1 percent TRS 

monitoring allowance on a semiannual basis. In fact, the majority of the 79 NSPS CEMS data 

sets displayed in Figure 10 reflected zero exceedances of the 5 ppm limit (i.e., 59-60 of the 79 

data sets had zero exceeedances in each semiannual period). Total reduced sulfur data for 

existing sources are not shown in Figure 10 because existing sources are subject to TRS limits 

less stringent than the NSPS limits. Based on this figure, it appears that a 1 percent monitoring 

allowance reflects the level of TRS compliance that has been adequately demonstrated and is 

achieved by the best performing recovery furnaces (on a semiannual basis).
16

Recommendation. Based on the TRS data presented in this section, it can be concluded 

that DCE recovery furnaces would not be expected to reliably meet the current NSPS limit of 5 

ppm. It would also be expected that the current NSPS (at baseline) would require that new 

recovery furnaces be NDCE furnaces and modified or reconstructed DCE recovery furnaces to 

convert to NDCE technology. We did not project any new DCE recovery furnaces being 

constructed in our analysis. The figures presented in Appendix D support the proposed

regulatory decision to maintain a TRS limit of 5 ppm with a 1 percent monitoring allowance for 

recovery furnaces. To ensure the TRS standard is a continuous standard (consistent with the 

decision in of the D.C. Circuit Court of Appeals decision in Sierra Club v. EPA, 551 F.3d 1019 

(D.C. Cir. 2008)), the monitoring allowance was capped a proposal at 30 ppm, which is 

representative of the upper limit achieved by most recovery furnaces. Because the TRS CEMS 

data analyzed include startup and shutdown periods (in addition to normal operational periods), 

there is no need for a separate standard during periods of startup and shutdown. 

It is recommended that the 5 ppm TRS limit and 1 percent monitoring allowance, capped 

at 30 ppm, for new, modified, and reconstructed straight recovery furnaces be finalized as 

proposed. The monitoring allowance would be calculated on a semiannual basis.

C. Lime Kiln TRS CEMS Analysis

TRS limit evaluation. Lime kiln TRS emissions are limited to 8 ppm at 10 percent O2 by 

the subpart BB kraft pulp mill NSPS. All of the lime kiln TRS ppm values discussed in this

section reflect conditions at 10 percent O2. Figures 1 through 9 in Appendix E present updated 

TRS CEMS summary data for each lime kiln (1 unit with multiple stacks, for a total of 110 data 

sets). Most of the data points shown in these figures reflect 12-hour average CEMS data sets. 

However, 7 of the 110 lime kiln CEMS data sets were based on 24-hour averages. The 24-hour 

averages are annotated on the graphs where appropriate. The figures in Appendix E distinguish 

between lime kilns subject to the NSPS and non-NSPS kilns because there were several lime 

kilns that are not currently subject to the 8 ppm NSPS limit (but are more likely held to the 20 

ppm emission guideline), and, therefore, exceeded 8 ppm. 

Figure 1 shows all of the lime kiln CEMS data sets for NSPS and non-NSPS kilns based 

on APCD type: ESP, ESP followed by a scrubber (ESP/SCBR), and SCBR. The 24-hour average 

data sets were noted and fell within the scatter of the 12-hour average data sets. We observed that 

control device performance overlaps, and that ESP/SCBR systems fell within the scatter of the 

ESP-alone and SCBR-alone systems. With no clear distinction in TRS by control device, it is 

expected that process factors (e.g., mud washing, use of uncontaminated scrubber water, and 

NCG burning) have a greater effect on lime kiln TRS emissions than control device type. As 

shown in Figure 1, most of the lime kilns achieved the 8 ppm limit on an annual average basis. 

Figure 2 shows the 99th percentile of the averaging periods for NSPS and non-NSPS kilns based 

on APCD type. As shown in Figure 2, many of the kilns consistently achieved 8 ppm 99 percent 

of the time. However, compliance is based on each 12-hour block averaging period, so the 

percentage of averaging periods in excess of 8 ppm was plotted in Figure 3. Several scrubbers 

and one non-NSPS ESP exceeded 8 ppm for a relatively high percentage of averaging periods.
17

The non-NSPS kilns were removed from the remaining figures in Appendix E in order to 

more clearly examine lime kilns that are required to meet 8 ppm. In Figure 4, it can be observed 

that the overwhelming majority of the NSPS kilns met the 8 ppm limit regardless of control 

device. Most of the kilns were operating with roughly a 4 ppm compliance margin below the 8 

ppm limit based on annual average. The one scrubber-controlled kiln with annual average 

emissions above 8 ppm experienced an uncommon number of startup and shutdown events and 

considerable downtime during the year. 

Figure 5 shows the percentage of averaging periods exceeding 8 ppm for the lime kilns 

subject to NSPS. There is no monitoring allowance for lime kiln TRS CEMS data in the subpart 

BB NSPS (e.g., any average that is an exceedance can be considered as a violation). Although 

some well-controlled kilns had a few exceedances of the 8 ppm limit (which supports the need 

for an allowance), several of the NSPS kilns (33 of 58) achieved zero exceedances of the 8 ppm 

limit regardless of control device type. We note that startup and shutdown periods were included 

in the percentages of averaging periods that exceeded 8 ppm. Startup and shutdown periods 

would be subject to the 8 ppm emission limit, while malfunctions can be handled with 

affirmative defense provisions. The scrubber-controlled kilns appear to be the most challenged to 

remain below 8 ppm.

Figure 6 considers the 99th percentile of the averaging periods for each kiln subject to the 

NSPS. Most of the kilns consistently achieved 8 ppm 99 percent of the time regardless of control 

system. Figure 6 shows that most of the kilns use the compliance margin afforded by the 8 ppm 

limit in order to remain in compliance and that a new source limit more stringent than 8 ppm 

would be difficult for well-controlled kilns to meet consistently. A lower limit would reduce the 

compliance margin, and there is no clear technological basis for achieving a lower TRS limit. 

While ESP/SCBR-controlled kilns all remained below the 8 ppm limit, their 99th percentile 

performance was within the range of that achieved by the lime kilns with ESP or scrubber 

control only. 

Figure 7 shows the 99th percentile for NSPS kilns based on combustion of NCGs. While 

NCGs can contribute to TRS (if not properly combusted), there does not appear to be any clear 

distinction in the TRS emissions of NCG-burning kilns versus non-NCG burning kilns. NCGburning kilns with white liquor pre-scrubbers have similar TRS emissions to NCG-burning kilns 

without pre-scrubbers. Figure 8 shows the percent of periods exceeding the TRS 8 ppm limit for 

lime kilns based on NCG burning. NCG burning appears to result in the potential for additional 

process variability.

Monitoring allowance evaluation. In the pre-proposal analysis of the TRS CEMS data, 

monitoring allowance calculations for TRS were conducted on an annual basis. The annual-basis 

analysis was repeated with updated data sets, and a semiannual monitoring allowance calculation 

was added as discussed later in this subsection. As shown in Figure 5 of Appendix E, all but four 

of the lime kilns subject to the NSPS achieved the 8 ppm TRS limit with 1 percent or less 

monitoring deviations (on an annual basis) in spite of startup and shutdown periods. The TRS 

CEMS data were reviewed closely to determine the impact of removal of the SSM exemption in 

40 CFR 60.284(e)(1) and continuous application of the 8 ppm limit to startup and shutdown 

periods in addition to normal operations. Periods of malfunction and process downtime (i.e.,
18

when lime mud charging ceases) were excluded from consideration because these are not valid 

operating periods for rulemaking. As shown in Appendix E, 12-hour average CEMS data sets 

providing startup and shutdown detail were available for 30 lime kilns controlled by ESP and 

subject to the NSPS. Upon review of these data sets, we observed that a 12-hour block can either 

be partially or completely affected by startup or shutdown periods. Up to 113 of a possible 730 

annual 12-hour averaging periods were affected by startup and shutdown in the data sets 

reviewed for startup and shutdown. On average it takes a lime kiln 24 hours to start up and 12

hours to shut down.

7 Of the 30 data sets with startup and shutdown indicated, 21 of the data sets 

contained no exceedances of the 12-hour 8 ppm limit. Thus, compliance with the 8 ppm limit 

during startup and shutdown has been demonstrated at several mills. However, for 9 other kilns,

compliance with the 8 ppm TRS limit during startup and shutdown has not been adequately

demonstrated because these kilns experienced exceedances in up to seven 12-hour blocks 

affected by startup and shutdown. Seven of 730 possible 12-hour blocks in a year corresponds to 

1 percent of possible averaging periods (7/730 = 1.0%). This percentage of averaging periods 

affected by startup and shutdown is consistent with the information in Figure 5, which shows 54

of 58 NSPS kilns in compliance with the 8 ppm TRS limit in all but 1 percent of averaging 

periods.

Table E-1 in Appendix E shows the maximum TRS 12-hour average ppm values 

occurring during startup and shutdown where there were exceedances of the 8 ppm standard. 

Where available for the higher-end values, 1-hour TRS data sets corresponding with the 12-hour 

averages were reviewed to determine the nature of the TRS emissions during the startup and 

shutdown events. Most of the high-end values were determined not to be representative for 

rulemaking purposes. The 12-hour TRS concentration corrected to 10 percent O2 that appeared to 

be representative of startup and shutdown events was 22 ppm. Similarly, for most NSPS kilns, 

the 99th percentile 12-hour average during all time periods (including startup and shutdown) was 

less than 20 ppm as shown in Figure 6. Therefore, an upper limit 12-hour average of 22 ppm 

appears to be representative of the TRS concentration that has been achieved in practice during 

startup and shutdown events.

As discussed for recovery furnaces, during periods of startup and shutdown, the EPA 

observed that corrected TRS concentrations may be grossly inflated as a result of the oxygen 

correction equation. As the stack gas concentration approaches ambient conditions, the 

denominator of the oxygen correction equation becomes very small, leading to an oxygen 

corrected concentration that is artificially high, such that an otherwise compliant TRS 

measurement can exceed the applicable concentration because it is corrected for oxygen. See 

Table D-2. Consequently, EPA proposed to allow uncorrected, actual TRS values to be used 

during periods of startup and shutdown for compliance for periods when the oxygen 

concentration is greater than 15 percent. 

As noted previously, the EPA is finalizing a semiannual period for the monitoring 

allowance calculation consistent with the semiannual reporting frequency in 40 CFR 60.288a(a). 

 

7Memorandum from K. Hanks, and C. Gooden, RTI International to K. Spence and B. Schrock, EPA. Review of 

Pulp and Paper Information Collection Request (ICR) Responses Pertaining to Startup and Shutdown of Subpart BB 

Equipment. March 22, 2013.
19

In the updated analysis of the TRS CEMS data, the EPA repeated monitoring allowance 

calculations based on a semiannual reporting period in addition to the annual basis used for the 

proposal. Table 3 below summarizes the number of TRS CEMS data sets analyzed for new, 

modified (or reconstructed), and existing lime kilns. The number of TRS CEMS data sets in 

compliance with the proposed TRS standard and monitoring allowance before proposal and in 

the final data sets is indicated. The values presented from the proposal analysis represent 

calculation of the TRS monitoring allowance on an annual basis, while the values from the final 

analysis reflect the revised data sets and calculation of the TRS monitoring allowance on a 

semiannual basis. Use of a semiannual basis for calculating the TRS allowance resulted in only 

minor differences in the number of emission units that would not be in compliance with the 

proposed TRS standard and monitoring allowance. The semiannual allowance calculation would 

change the compliance outcome for only 2 out of 110 lime kiln TRS CEMS data sets.

Table 3. Summary of Lime Kiln TRS CEMS Data Sets Analyzed

Unit NSPS 

Classification1

Proposal 

data set2

Final 

data set3 Notes

No. of TRS CEMS data sets 112 110 2 data sets (for 1 new kiln and 1 existing kiln) 

were removed from the final analysis due to data 

quality issues.

 New 48 47

 Modified 11 11

 Existing (not subject to NSPS) 53 52

No. of CEMS meeting 8 ppm with 

a 1% allowance

68 64 2 data sets (for 1 new kiln and 1 existing kiln) 

were removed from the final analysis due to data 

quality issues.

 New 45 44

 Modified 7 7

 Existing (not subject to NSPS) 16 13

No. of CEMS not meeting 8 ppm 

with a 1% allowance

44 46

 New 3 3 Installed 1997, 1989, and 1994.

 Modified 4 4 Modified in pre-1990, pre-1995, and 2007. 

Scrubber-controlled. Some of these kilns were 

up and down and had data availability issues 

throughout the year.

 Existing (not subject to NSPS) 37 39 The TRS emission guideline for existing lime 

kilns is 20 ppm.

1. New and modified units are defined in terms of the subpart BB NSPS 1976 applicability date (not the more recent 

subpart MM applicability date).

2. The monitoring allowance was calculated on an annual basis in the proposal data set (Reference 1).

3. This column refers to the monitoring allowance calculated on a semiannual basis using the final updated data set 

presented in this memorandum.

Figure 9 in Appendix E depicts semiannual monitoring allowance calculations for lime 

kilns already subject to the subpart BB NSPS. The monitoring allowance represents the percent 

of TRS CEMS averaging periods exceeding the limit for each emission unit. Figure 9 shows that 

the majority of lime kilns subject to subpart BB achieved a 1 percent TRS monitoring allowance 

on a semiannual basis. In fact, the majority of the 58 CEMS data sets displayed in Figure 9 

reflected zero exceedances of the 8 ppm limit (i.e., in each semiannual period there were 40 

CEMS showing zero exceedances). Total reduced sulfur data for existing sources are not shown 
20

in Figure 9 because existing sources are subject to TRS limits less stringent than the NSPS 

limits. Based on this figure, it appears that a 1 percent monitoring allowance reflects the level of 

TRS compliance that has been adequately demonstrated and is achieved by the best performing 

lime kilns (on a semiannual basis).

Recommendation. To summarize, the current 8 ppm TRS limit based on a 12-hour 

average with a 1 percent monitoring allowance during which time emissions must not exceed 22 

ppm is recommended to be finalized as proposed as the continuous lime kiln TRS standard. This

has been achieved in practice. The 1 percent monitoring allowance (not to exceed 22 ppm) is 

recommended to adjust the current 8 ppm limit (with no allowance) for removal of the startup 

and shutdown exemption. This option balances the requirement for a continuous emission 

standard while providing for the operational variability expected from mills under normal, 

startup, and shutdown conditions. It is also recommended that the proposed provision stating that 

the uncorrected TRS concentration can be considered when O2 is near ambient conditions during 

startup or shutdown be finalized.

D. Lime Kiln COMS Analysis

Opacity limit evaluation. The kraft pulp mills NSPS do not contain an opacity limit for 

lime kilns because scrubbers were the dominant technology in 1978 and 1986 when the NSPS 

were originally promulgated and revised, respectively. However, the EPA received COMS data 

for lime kilns that had installed ESPs and are required to monitor opacity under subpart MM. 

Subpart MM requires continuous opacity monitoring for lime kilns and specifies 20 percent as 

the opacity limit for both new and existing kilns. Subpart MM contains an opacity monitoring 

allowance where 6 percent of the 6-minute opacity averages per quarter may exceed the 20 

percent limit without being considered an exceedance.

A total of 29 COMS data sets were graphed (including multiple data sets for two kilns 

with separate COMS for dual stacks), and the graphs are provided in Appendix F. The majority 

(27) of the COMS data sets graphed were 6-minute averages. Two data sets represented hourly 

averages.

Figure 1 in Appendix F presents the annual average of the opacity readings for each lime 

kiln. The highest annual average observed was 8 percent, well below the 20 percent MACT 

limit; however, compliance is based on each averaging period and not the annual average. The 

99th percentile of opacity is shown in Figure 2 based on APCD type. Lime kilns controlled with 

ESP and ESP/scrubber systems consistently achieved 20 percent opacity. The COMS for 

ESP/scrubber systems were usually placed between the ESP and scrubber. Two units exceeded 

the 20 percent opacity, but further investigation shows they did not exceed 20 percent for more 

than the subpart MM 6 percent monitoring allowance.

Monitoring allowance evaluation. In the pre-proposal analysis of the COMS data, 

monitoring allowance calculations for opacity were conducted on an annual basis. Figure 3 in 

Appendix F shows the percent of averaging periods (on an annual basis) in excess of 20 percent 

opacity. All but two kilns consistently achieved 20 percent opacity, with less than 1 percent of 

averaging periods in exceedance of 20 percent. 
21

As noted previously, the EPA is finalizing a semiannual period for the monitoring 

allowance calculation consistent with the semiannual reporting frequency in 40 CFR 60.288a(a). 

In the updated analysis of the COMS data, the EPA repeated monitoring allowance calculations 

based on a semiannual reporting period in addition to the annual basis used for the proposal.

Table 4 below summarizes the number of COMS data sets analyzed for new, modified (or 

reconstructed), and existing lime kilns. The number of COMS data sets in compliance with the 

proposed opacity standard and monitoring allowance before proposal and in the final data sets is 

indicated. The values presented from the proposal analysis represent calculation of the opacity 

monitoring allowance on an annual basis, while the values from the final analysis reflect the 

revised data sets and calculation of the opacity monitoring allowance on a semiannual basis. Use 

of a semiannual basis for calculating the opacity allowance resulted in no difference in the 

number of emission units that would not be in compliance with the proposed opacity standard 

and monitoring allowance. The semiannual allowance calculation would not change the 

compliance outcome for any of the 29 lime kiln COMS data sets.

Table 4. Summary of Lime Kiln COMS Data Sets Analyzed

Unit NSPS Classification1

Proposal 

data set2

Final 

data set3 Notes

No. of COMS data sets 29

 New 23

 Modified 2

 Existing (not subject to NSPS) 4

No. of COMS meeting 20% 

opacity with a 1% allowance

27 27

 New 21 21

 Modified 2 2

 Existing (not subject to NSPS) 4 4

No. of COMS not meeting 20% 

opacity with a 1% allowance

2 2

 New 2 2 Exceedances of the 1% allowance were 1.84% and 

2.19% on a semiannual basis. These ESPcontrolled kilns became subject to the NSPS in 

1997 and 1994, respectively (prior to establishment 

of the subpart MM opacity monitoring 

requirements).

 Modified 0 0

 Existing (not subject to NSPS) 0 0

1. New and modified units are defined in terms of the subpart BB NSPS 1976 applicability date (not the more recent 

subpart MM applicability date).

2. The monitoring allowance was calculated on an annual basis in the proposal data set (Reference 1).

3. This column refers to the monitoring allowance calculated on a semiannual basis using the final updated data set 

presented in this memorandum.

Figure 3 in Appendix F shows the percentage of averaging periods exceeding 20 percent 

opacity on a semiannual basis and indicates that a 1 percent monitoring allowance (on a 

semiannual basis) coupled with a 20 percent limit is achieved by most ESP-controlled lime kilns. 

Figure 4 in Appendix F depicts semiannual monitoring allowance calculations for lime kilns that 

triggered the subpart BB NSPS as new or modified units. Figure 4 shows that the 1 percent 
22

monitoring allowance for lime kiln opacity is achieved by nearly all lime kilns regardless of their 

prior NSPS classification as new or modified units.

Recommendation. In summary, a 20 percent opacity limit with a 1 percent monitoring 

allowance has been adequately demonstrated, and it is recommended that it be finalized as 

proposed as the lime kiln opacity standard. Continuous compliance with the NSPS PM standards 

can be demonstrated through monitoring of control device operating parameters (e.g., ESP 

secondary voltage and current or power) during times when the 2 percent monitoring allowance 

is invoked. Because the data analyzed in arriving at the recommendation included startup and 

shutdown periods, there is no need for a separate standard for startup and shutdown periods.

E. Analysis of TRS CEMS Data for Other Emission Units

TRS limit evaluation. As shown in Table 5, TRS CEMS data were submitted with the 

ICR for four kraft mill processes emitting non-condensable gases. The 12-hour average TRS 

CEMS data sets were reviewed for these systems. As with the lime kiln and recovery furnace 

TRS CEMS data sets, zero emissions values measured during process downtime and negative 

emissions were removed. Emissions measured during startup and shutdown were retained.

The NCG source CEMS data sets were analyzed for maximum and 99th percentile TRS 

averages. These units included a pulp washer, a boiler, and two thermal oxidizers. The pulp 

washer data were provided as actual (uncorrected) TRS emissions because the oxygen correction 

is not required for non-combustion sources. The boiler was characterized as backup control for 

low-volume high-concentration (LVHC) and high-volume low-concentration incineration that 

was used when the recovery furnace (primary control device) was not operational. The two 

thermal oxidizers were used to burn LVHC and stripper off gas streams. These units exhibited 

99th percentile TRS values from 1.33 ppm to 3.88 ppm, but also exhibited maximum values of 

approximately 5 ppm (4.4, 4.8, and 4.9 ppm) up to 16 ppm. 

Recommendation. Based on this limited amount of data, it appears that the current NSPS 

limit of 5 ppm is the appropriate limit for each of these operations, and no changes are 

recommended. 

III. References

1. Spence, K., U.S. Environmental Protection Agency. Review of the Continuous Emission 

Monitoring and Continuous Opacity Monitoring Data from the Pulp and Paper 

Information Collection Request Responses Pertaining to Subpart BB Sources. 

Memorandum to Docket ID No. EPA-HQ-OAR-2012-0640. April 5, 2013.
23

Table 5. TRS CEMS Data for Kraft Pulping Processes Emitting NCGs

RTI 

Code NEI ID

Emission 

Unit ID

Process 

Type APCD Type APCD ID

NCG Sources 

Controlled Notes

Max TRS 

ppmdv @ 

10% O2

99th

Percentile 

TRS 

ppmdv @ 

10% O2

1

186 NEI18334 HWCHEM Pulp 

Washer

Hardwood 

Chemiwasher 

Scrubber

FL34 and 

HWCHME

Washer Because this is a noncombustion control, the 

ppmdv is provided at 

the actual oxygen 

content of the untreated 

(undiluted) gas stream.

4.4 3.29

198 NEI41565 016 Boiler unspecified 016_CD Backup control 

for digester and 

washer (NSPS 

units); also O2

delig and decker

According to Part I, 

Boiler 016 serves as the 

backup control device 

for HVLC control when 

the primary control 

device (recovery 

furnace) is not 

operational.

4.8 1.61

242 NEI34066 AA-016 TO Scrubber - packed 

bed

RC-22 condensate 

stripper, 

evaporator, 

turpentine, and 

digester LVHC

4.9 1.33

112 NEI34064 LVHC01, 

LVHC02, 

LVHC03

TO Scrubber - packed 

bed

AA-113 Digester, 

evaporator, 

turpentine, and 

condensate 

stripper

16 3.88

1. Calculated as the average of the 12-hr average values provided including startup and shutdown.
A-1

APPENDIX A: Summary of Recovery Furnace Data Received
A-2

Summary of Recovery Furnace Data Received

RTI + Emission 

Unit ID

Opacity Data 

Type TRS Data Type Comments on Data

100.037A 6-min averages 12-hr averages Provided raw TRS data - corrected to 8% 

O2. Calculated 12-hr average TRS from 1-

hour data.

102.RB10 6-min averages 12-hr averages

103.G-158 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

104.EUG D6 data not provided not provided

105.EU445C 6-min averages 12-hr averages

105.EU445A unit down unit down

107.08-P1 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

108.RB3 6-min averages 12-hr averages

109.RB4 6-min averages 12-hr averages Commenter confirmed TRS data were 

corrected to 8%.

109.RB3 6-min averages 12-hr averages Commenter confirmed TRS data were 

corrected to 8%.

111.G-44 6-min averages 1-hr averages Calculated 12-hr average TRS from 1-hour 

data.

112.AA-100 6-min averages 12-hr averages

114.U500 6-min averages 12-hr averages

115.RE01 6-min averages 12-hr averages Unit has opacity data for 2 stacks

116.003 6-min averages 12-hr averages

117.B21 data in pdf form not provided Opacity data not tabulated

119.EQT010 6-min averages 12-hr averages

119.EQT008 data not provided not provided

120.F7 6-min averages 12-hr averages

121.000013 6-min averages 12-hr averages

121.000014 6-min averages 12-hr averages

124.001 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

124.019 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

126.RECOV 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

127.REC1 6-min averages 12-hr averages Unit has opacity data for 2 stacks. O2

correction values were not 8%, assumed 

TRS values were raw data and corrected. 

Calculated 12-hr average TRS from 1-hour 

data.

130.1 6-min averages 12-hr averages

130.2 6-min averages 12-hr averages

130.3 6-min averages 12-hr averages

131.5 6-min averages 24-hr averages
A-3

RTI + Emission 

Unit ID

Opacity Data 

Type TRS Data Type Comments on Data

131.6 6-min averages 12-hr averages

132.4RB hourly average 12-hr averages

132.5RB hourly average 12-hr averages Unit has opacity data for 2 stacks

133.10 6-min averages 12-hr averages

135.003-1 6-min averages 12-hr averages

136.EU 005 6-min averages 12-hr averages

137.189 data not provided provided as .doc TRS data not tabulated

137.721 data not provided provided as .doc TRS data not tabulated

138.002 6-min averages 12-hr averages

139.02 6-min averages 12-hr averages

140.55 6-min averages 24-hr averages

142.CU7216 6-min averages 12-hr averages

142.CU7214 6-min averages 12-hr averages

142.CU7215 6-min averages 12-hr averages

143.7000 hourly average 12-hr averages TRS raw data reported - corrected to 8%. 

Calculated 12-hr average TRS from 1-hour 

data.

143.7010 hourly average 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

143.7020 hourly average 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

145.55 6-min averages 12-hr averages

145.54 6-min averages not provided

146.16 6-min averages 12-hr averages

146.8 data not provided 12-hr averages

147.14 6-min averages 12-hr averages Unit has opacity data for 2 stacks

147.5 6-min averages 12-hr averages

148.001 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

148.007 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

149.B011 6-min averages 12-hr averages

150.CREC-1 6-min averages 12-hr averages

151.REC004 6-min averages 12-hr averages

151.REC007 6-min averages 12-hr averages

152.03 data not provided 12-hr averages

153.EQT 0065 not surveyed not surveyed Mill was closed during the development of 

the survey (reopened in 2010)

154.P36 6-min averages 12-hr averages

154.P37 6-min averages 12-hr averages P39 and P37 have own WBESP but vent to 
A-4

RTI + Emission 

Unit ID

Opacity Data 

Type TRS Data Type Comments on Data

combined stack with single COMS (2 TRS 

CEMS)

154.P39 6-min averages 12-hr averages P39 and P37 have own WBESP but vent to 

combined stack with single COMS (2 TRS 

CEMS)

155.RECOVERY 

FURNACE

provided as .doc provided as .doc Not tabulated.

156.RF18 unit down unit down

156.RF19 6-min averages 12-hr averages

156.RF22 6-min averages 12-hr averages

157.RB2 6-min averages 12-hr averages

159.F3 data not provided provided as .pdf Not tabulated.

162.381A 6-min averages 12-hr averages

162.382A 6-min averages 12-hr averages

163.RF2904 6-min averages 12-hr averages TRS data contained "<1" instead of 

decimal values

163.RF1901 6-min averages 12-hr averages TRS data contained "<1" instead of 

decimal values, O2 correct was reported as 

10%, corrected to 8%

164.B08 6-min averages not provided Flue gases from B08 and B10 combine and 

then split into 2 ESPs

164.B10 6-min averages not provided Flue gases from B08 and B10 combine and 

then split into 2 ESPs

165.000013 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

165.000006 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

166.RB01 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

166.RB02 data not provided 12-hr averages

167.005RB 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

169.04 6-min averages 12-hr averages

169.05 6-min averages 12-hr averages

171.002 6-min averages 12-hr averages O2 correction not reported as 8%, assumed 

raw TRS data and corrected

171.003 6-min averages 12-hr averages O2 correction not reported as 8%, assumed 

raw TRS data and corrected

171.004 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks, 

O2 correction not reported as 8%, assumed 

raw TRS data and corrected

172.RB01 6-min averages 12-hr averages

172.RB02 6-min averages 12-hr averages

173.RECOVB 6-min averages not provided Unit has opacity data for 2 stacks

174.G-32 6-min averages 12-hr averages
A-5

RTI + Emission 

Unit ID

Opacity Data 

Type TRS Data Type Comments on Data

174.G-92 6-min averages not provided Unit has opacity data for 2 stacks

175.RB3A 6-min averages 12-hr averages

175.RB2A 6-min averages 24-hr averages

176.RB7 6-min averages 12-hr averages

177.EU0804 6-min averages 12-hr averages

178.08P012 6-min averages 12-hr averages

178.08P013 6-min averages 12-hr averages

179.RF3 6-min averages 12-hr averages TRS data contained "<1" instead of 

decimal values

180.D001 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

181.50 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

181.10 6-min averages not provided Unit has opacity data for 2 stacks

182.037 6-min averages 12-hr averages

183.002 6-min averages 12-hr averages O2 correction not reported as 8%, assumed 

TRS raw data and corrected

184.72 6-min averages 12-hr averages

184.73 6-min averages 12-hr averages

185.02 data not provided 12-hr averages

186.RB15 6-min averages 12-hr averages

188.014RB1 6-min averages 24-hr averages

188.016RB2 6-min averages 24-hr averages

189.SN26 6-min averages 12-hr averages

190.R400 6-min averages 12-hr averages R400 and R401 appear to each have a 

DBESP that vent through a common stack 

(opacity represents combined total)

190.R401 6-min averages 12-hr averages R400 and R401 appear to each have a 

DBESP that vent through a common stack 

(opacity represents combined total)

190.R402 6-min averages 12-hr averages Unit has opacity and TRS data for 2 stacks

195.003 6-min averages 12-hr averages

196.SN-06 6-min averages 12-hr averages

196.SN-14 6-min averages 12-hr averages

197.2 data not provided not provided

198.019 6-min averages 12-hr averages Calculated 12-hr average TRS from 1-hour 

data.

199.002 6-min averages 12-hr averages

200.007RF2 6-min averages 12-hr averages Unit has opacity data for 2 stacks

200.007RF3 6-min averages 12-hr averages Unit has opacity data for 2 stacks

201.SR0001 6-min averages not provided
A-6

RTI + Emission 

Unit ID

Opacity Data 

Type TRS Data Type Comments on Data

202.Recovery 

Furnace EU320

6-min averages 12-hr averages

203.RF#2 6-min averages 12-hr averages

203.RF#3 6-min averages 12-hr averages

205.009 6-min averages 12-hr averages Unit has opacity data for 2 stacks

206.G-32 6-min averages 12-hr averages

206.G-31 6-min averages 12-hr averages

207.038 6-min averages 12-hr averages Unit has opacity data for 2 stacks. O2

correction was not reported as 8%, 

assumed to be raw TRS data and corrected

226.RECB2 6-min averages 12-hr averages

226.RECB1 6-min averages not provided Unit has opacity data for 2 stacks

240.RF04 6-min averages 12-hr averages TRS data contained "<1" instead of 

decimal values

240.RF01 6-min averages 24-hr averages TRS data contained "<1" instead of 

decimal values

242.AA-011 6-min averages 12-hr averages O2 correction reported as 5% - corrected to 

8%

243.R407 6-min averages 12-hr averages

243.R401 6-min averages 24-hr averages Unit has opacity and TRS data for 2 stacks

340.005 6-min averages 12-hr averages O2 correction was not reported as 8%, 

assumed to be raw TRS data and corrected

525.EU18 6-min averages 12-hr averages

531.RF15 6-min averages 12-hr averages

600.G0803 6-min averages 12-hr averages

600.G0806 6-min averages 12-hr averages

606.RB2 6-min averages 12-hr averages

606.RB3 6-min averages 12-hr averages

606.RB4 6-min averages 12-hr averages

610.4 6-min averages 12-hr averages Units 4 and 5 utilize a single stack with 1 

COMS

610.5 6-min averages 12-hr averages Units 4 and 5 utilize a single stack with 1 

COMS

613.001 6-min averages not provided Unit has opacity data for 2 stacks

613.002 6-min averages not provided Unit has opacity data for 2 stacks

615.24 6-min averages 12-hr averages Unit has opacity data for 2 stacks

617.B14 6-min averages 12-hr averages

208228535.001 6-min averages 12-hr averages

208228535.007 6-min averages 12-hr averages
B-1

APPENDIX B: Summary of Lime Kiln Data Received
B-2

Summary of Lime Kiln Data Received

RTI + 

Emission Unit 

ID

Opacity Data 

Type

TRS Data 

Type Comments On Data

100.115 6-min averages 12-hr average

102.LK 6-min averages 12-hr average Separate stacks. A portion of the ESP exhaust gas 

is withdrawn from each stack for use by SMI (a 

PCC plant). This lowers the stack gas flow and 

reduces pollutant mass emissions (though opacity 

remains the same).

103.G-165 NA 12-hr average TRS values reported as corrected to 8%. 

Converted values to 10% correction. Calculated 

12-hr average TRS from 1-hour data.

104.EUG E7 not provided not provided

105.EU455 6-min averages 12-hr average TRS values reported as corrected to 8%. 

Converted values to 10% correction.

Lime Kilns #2 and #3 vent through same stack 

(though LK2 is usually only operated as a backup 

to LK3)

107.11-P14 6-min averages 12-hr average

108.LK1 NA not provided

109.LK1 6-min averages 12-hr average Commenter confirmed TRS data were corrected 

to 10%. 

111.G-35 not provided 12-hr average Calculated 12-hr average TRS from 1-hour data.

112.AA-110 not provided 12-hr average Commenter confirmed TRS data were corrected 

to 10%.

114.U800 6-min averages See note Did not use 12-hour average TRS data in final 

analysis based on public comment that 

respondent provided uncorrected data (and did 

not provide the actual O2 percent to correct with).

115.LK01 6-min averages 12-hr average

116.001 NA 12-hr average

117.P36 NA not provided

119.EQT006 NA 12-hr average TRS values reported as corrected to 8%. 

Converted values to 10% correction.

120.M18 NA 12-hr average

120.M19 NA 12-hr average Calculated 12-hr average TRS from 1-hour data.

121.000011 NA 12-hr average

124.004-1 NA 12-hr average

126.LK not provided 24-hr average

127.LK1 6-min averages 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%. Calculated 

12-hr average TRS from 1-hour data.

127.LK2 6-min averages 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%. Calculated 

12-hr average TRS from 1-hour data.
B-3

RTI + 

Emission Unit 

ID

Opacity Data 

Type

TRS Data 

Type Comments On Data

130.4 NA 12-hr average

130.5 NA 12-hr average

131.18 NA 24-hr average

131.16 NA 12-hr average

132.21LK4 1-hour average 12-hr average

133.14 NA 12-hr average

133.15 NA 12-hr average

135.004-1 NA 12-hr average

136.EU 033 6-min averages 12-hr average

137.511 not provided provided as .txt Did not tabulate

137.512 not provided provided as .txt Did not tabulate

138.001 NA 12-hr average

139.04 NA 12-hr average

140.32 NA 24-hr average

142.P6025 NA 12-hr average

142.P6009 NA 12-hr average

143.6063 hourly average 12-hr average Raw TRS was provided, corrected data to 10%. 

Calculated 12-hr average TRS from 1-hour data.

145.001 NA not provided

146.6 NA 12-hr average

146.30 6-min averages 12-hr average

147.3 NA 12-hr average

147.55 not provided 12-hr average Calculated 12-hr average TRS from 1-hour data.

148.003 NA 12-hr average Calculated 12-hr average TRS from 1-hour data.

148.009 6-min averages 12-hr average Calculated 12-hr average TRS from 1-hour data.

149.P001 NA 12-hr average

150.CAU-12 NA 12-hr average

151.CP002 NA 12-hr average

151.CP001 NA 12-hr average

152.08 NA not provided

153.EQT 0053 NA not surveyed Mill was not surveyed

154.P30 6-min averages 12-hr average

155.LIME 

KILN

NA provided as 

.doc

Did not tabulate

156.143100 NA 12-hr average Lime kiln 3

156.145000 NA 12-hr average Lime kiln 4

156.LK5 6-min averages 12-hr average Lime kiln 5; has 2 separate COMS (north and 

south stacks) but one TRS CEMS
B-4

RTI + 

Emission Unit 

ID

Opacity Data 

Type

TRS Data 

Type Comments On Data

157.KILN NA 12-hr average

159.F4 NA provided as 

.pdf

Did not tabulate

162.371A NA 12-hr average

162.372A 6-min averages 12-hr average

163.LK1501 NA 12-hr average Data contained "<1" instead of decimal values

163.LK2502 NA 12-hr average Data contained "<1" instead of decimal values

164.P12 NA 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%.

165.000019 NA 12-hr average

165.000002 NA 12-hr average

166.LK01 NA 12-hr average

166.LK02 NA 12-hr average

167.004LK NA 12-hr average

169.03 NA 12-hr average

171.010 NA 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%.

171.009 NA 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%.

172.LK03 NA 12-hr average

173.LK1 NA not provided

174.G-18 6-min averages 12-hr average

174.G-95 NA not provided

175.LK1A NA 24-hr average

175.LK2A NA 12-hr average

176.G-5 NA 24-hr average

177.EU0905 NA 12-hr average

178.09P037 6-min averages 12-hr average

179.LK3 6-min averages 12-hr average Data contained "<1" instead of decimal values

180.L001 NA 12-hr average Calculated 12-hr average TRS from 1-hour data.

180.L002 NA 12-hr average Calculated 12-hr average TRS from 1-hour data.

181.01 NA not provided

181.14 NA not provided

183.004 NA 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%.

184.LK1 NA 12-hr average

184.LK2 not provided 12-hr average

185.07 NA 12-hr average

186.LK 6-min averages 12-hr average
B-5

RTI + 

Emission Unit 

ID

Opacity Data 

Type

TRS Data 

Type Comments On Data

188.001LK1 NA 24-hr average CEMS reported to be from all 3 kilns, repeated 

values for the 3 units.

188.002LK2 NA 24-hr average CEMS reported to be from all 3 kilns, repeated 

values for the 3 units.

188.003LK3 NA 24-hr average CEMS reported to be from all 3 kilns, repeated 

values for the 3 units.

189.SN25 NA 12-hr average

190.L600 NA 12-hr average

190.L601 NA 12-hr average

195.002 NA 12-hr average

196.SN-09 NA 12-hr average

196.SN-02 6-min averages 12-hr average

197.1 NA not provided

198.004 NA 12-hr average Calculated 12-hr average TRS from 1-hour data.

199.011 NA 12-hr average

200.007_10 6-min averages 12-hr average

201.SR0003 NA not provided

202.Lime Kiln 

EU340

NA 12-hr average

203.LKScr NA 12-hr average

205.008 NA 12-hr average

206.G-37 NA 12-hr average

206.G-38 NA 12-hr average

207.103A NA not provided

226.LK1 NA not provided

226.LK2 NA not provided

240.CA81 6-min averages 12-hr average TRS data contained "<1" instead of decimal 

values

242.AA-013 not provided 12-hr average

243.LG07 not provided 12-hr average

340.008 NA 12-hr average TRS O2 correction not reported as 10%. Assumed 

data were raw and corrected to 10%.

525.EU17 NA 12-hr average

531.LK7 not provided 12-hr average

600.G0903 NA 12-hr average

600.G0905 NA 12-hr average

600.G0908 NA 12-hr average

606.LK4 6-min averages 12-hr average

610.7 NA 12-hr average
B-6

RTI + 

Emission Unit 

ID

Opacity Data 

Type

TRS Data 

Type Comments On Data

610.8 NA 12-hr average

613.009 NA 12-hr average

615.21 NA 12-hr average

617.P22 6-min averages 12-hr average

208228535.003 NA 12-hr average

208228535.009 6-min averages 12-hr average

NA – Not applicable (for kilns with wet scrubbers)
C-1

APPENDIX C: Recovery Furnace Opacity Data
C-2

0

2

4

6

8

10

12

14

16

18 Annual Average Opacity (including exceedances)

Figure 1. Annual Average Opacity - DCE vs. NDCE

Calculated as the average of the 6-min averaging periods*

DCE NDCE *Two mills provided hourly averages (6 data sets). These 

averages are all within the range of the 6-min averages provided.
C-3
C-4
C-5

0

5

10

15

20

25

30

35

40

45

50 99th Percentile of Opacity (%)

Figure 4. 99th Percentile of Opacity - DCE vs. NDCE

DCE NDCE

Current NSPS opacity limit = 35%

MM action level = 20%
C-6

0

5

10

15

20

25

30

35

40

45

50 99th Percentile of Opacity (%)

Figure 5. 99th Percentile of Opacity - DCE vs. NDCE (Showing APCD) 

DCE - DBESP DCE - DBESP-WPR

DCE - WBESP NDCE - DBESP

NDCE - DBESP-WPR NDCE - DBESP-WPR/DBESP/DBESP

NDCE - DB-WBESP [2 sided dry and wet] NDCE - WBESP

MM action level = 20%

Current NSPS opacity limit = 35%
C-7

0

5

10

15

20

25

30

35

40

45

50 99th Percentile of Opacity (%)

Figure 6. 99th Percentile of Opacity - APCD

DBESP DBESP-WPR

DBESP-WPR/DBESP/DBESP DB-WBESP [2 sided dry and wet]

WBESP

Current NSPS opacity limit = 35%

MM action level = 20%
C-8
C-9
C-10
C-11
C-12
C-13
C-14
C-15
C-16
C-17
C-18
C-19
D-1

APPENDIX D: Recovery Furnace TRS Data
D-2
D-3
D-4
D-5
D-6

0

1

2

3

4

5

6

7 TRS (ppmdv @ 8% O2

)

DCE - WBESP DCE - WBESP/SCBR NDCE - DBESP

NDCE - DBESP-WPR NDCE - DB-WBESP NDCE - WBESP

Figure 5. Annual Average of the 12-hour TRS Averaging Periods by APCD (NSPS Furnaces)

Current NSPS limit for straight RF (DCE and NDCE) = 5 ppm @ 8% O2

Note that compliance is based on each 12-hr average, not the annual average. 
D-7

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15 TRS (ppmdv @ 8% O2

)

DCE - WBESP DCE - WBESP/SCBR NDCE - WBESP

NDCE - DBESP-WPR NDCE - DB-WBESP NDCE - WBESP

Figure 6. 99th Percentile of the 12-hour TRS Averaging Periods by APCD (NSPS Furnaces)

Current NSPS limit for straight RF (DCE and NDCE) = 5 ppm @ 8% O2

One 99th percentile omitted: NSPS NDCE (49 ppm)
D-8

0

5

10

15

20

25 TRS (ppmdv @ 8% O2

)

1 stage 2 stage 3 stage

Figure 7. Comparison of the 99th Percentile of the TRS Averaging Periods for DCE Recovery 

Furnaces with Multiple Stages of Black Liquor Oxidation

*NSPS units are indicated by the hollow data points.
D-9

0

1

2

3

4

5

6

7 TRS (ppmdv @ 8% O2

)

DCE (No NCG) NDCE (No NCG) NDCE Burning NCG

Figure 8. Annual Average of the 12-Hour TRS Averaging Periods for NSPS Furnaces With and Without NCG Burning

Current NSPS limit for straight RF (DCE and NDCE) = 5 ppm @ 8% O2

Note that compliance is based on each 12-hr average, not the annual average. 
D-10

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15 TRS (ppmdv @ 8% O2

)

DCE (No NCG) NDCE (No NCG) NDCE Burning NCG

Figure 9. 99th Percentile of the 12-Hour TRS Averaging Periods for NSPS Furnaces With and Without NCG Burning

Current NSPS limit for straight RF (DCE and NDCE) = 5 ppm @ 8% O2
D-11
D-12

Table D-1: TRS CEMS Data Sets for Recovery Furnaces Subject to NSPS with Exceedances of the 5 ppm Limit During Startup and 

Shutdown (Based on a 12-Hour Average) 

RF 

type ID

No. of S/S Periods No. of 12-hr Periods 

Exceeding 5 ppm 

During S/S

Highest 12-hr TRS 

ppm during S/S Note Control

NDCE 119.EQT010 13 5 45.22*

38.58*

23.22*

20.29*

10.44*

Could not recreate 12-hr averages with 1 hour 

data

DBESP

NDCE 127.REC1 1 1 102.84* Uncorrected for O2; associated with 0 production 

at 19.15% O2. No other valid values reported 

during startup/shutdown. Unclear if the O2

correction near ambient conditions was already 

applied, and could not recreate 12-hour average 

with 1 hour data.

WBESP

NDCE 132.5RB 25 6 25.57

12.54

10.83

9.27

9.04

7.61

DBESPWPR

NDCE 149.B011 15 1 29.62 Production was CBI; labeled as 

“startup/shutdown”

DBESP

NDCE 186.RB15 1 1 15.9 DBESP

NDCE 189.SN26 12 8 27.34

25.78

15.21

11.19

7.49

6.64

6.49

6.23

WBESP

DCE 600.G0803 2 1 16 WBESP

*This value was disregarded for the reason provided in the “Note” column. The value was not considered as representative for rulemaking purposes.

Note: Not shown in the table are 53 recovery furnaces currently subject to NSPS subpart BB that had no exceedances of the 5 ppm limit at any time (including normal 

operations or startup/shutdown). 
D-13

Table D-2: TRS CEMS Data Corrected Based on Various Oxygen Levels

for Lime Kilns and Recovery Furnaces

Recovery 

Furnace 

TRS Raw 

Data

Lime Kiln 

TRS Raw 

Data O2 Reading

Recovery 

Furnace TRS 

Corrected to 

8% O2

Lime Kiln 

TRS 

Corrected to 

10% O2

5 8 0 3.1 5.0

5 8 5 4.1 6.5

5 8 6 4.3 6.9

5 8 7 4.6 7.4

5 8 8 5.0 8.0

5 8 9 5.4 8.7

5 8 10 5.9 9.5

5 8 11 6.5 10.4

5 8 12 7.2 11.6

5 8 13 8.1 13.0

5 8 14 9.3 14.9

5 8 15 10.8 17.3

5 8 16 13.0 20.8

5 8 17 16.3 26.0

5 8 18 21.7 34.7

5 8 19 32.5 52.0

5 8 20 65.0 104.0

5 8 20.5 130.0 208.0

5 8 20.999 65000.0 104000.0
E-1

APPENDIX E: Lime Kiln TRS Data
E-2

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16 TRS (ppmdv @ 10% O2

)

ESP ESP/SCBR SCBR

Calculated as the average of the values for each 12- or 24-hr averaging period. 

Note that compliance is based on each 12-hr average, not the annual average.

Figure 1. Annual Average TRS CEMS Data for Lime Kilns (Including Non-NSPS Kilns)

Current NSPS limit = 8 ppm @ 10% O2
E-3

0

10

20

30

40

50

60 TRS (ppmdv @ 10% O2

)

ESP ESP/SCBR SCBR

Calculated as the average of the values for each 12- or 24-hr averaging period. 

Figure 2. 99th Percentile TRS CEMS Data for Lime Kilns (Including Non-NSPS Kilns)

Current NSPS limit = 8 ppm @ 10% O2
E-4
E-5
E-6
E-7
E-8

0

5

10

15

20

25

30

35 TRS (ppmdv @ 10% O2

)

No NCG NCG Pre-scrubbed NCG

Figure 7. 99th Percentile TRS CEMS Data for Lime Kilns Burning NCGs (NSPS Kilns Only)

Current NSPS limit = 8 ppm @ 10% O2
E-9
E-10
E-11

Table E-1. TRS CEMS Data Sets for Lime Kilns Subject to NSPS Subpart BB with Exceedances of the 8 ppm Limit During

Startup and Shutdown (Based on a 12-Hour Average)1

Emission Unit ID APCD Type

No. of 

S/S 

Periods

No. of 12-hr 

Periods 

Exceeding 8 

ppm During 

S/S

Max 12-hr ppm 

TRS During S/S 

Events at 10% O2

unless otherwise 

noted Comments

107.11-P14 ESP 8 2 67.9*

10.8

 Likely invalid data. 12-hour block contained one 899 ppm spike followed 

by negative 1-hour readings. Actual O2 data unavailable; unclear if O2

correction inflated the ppm. 

 Next highest 12-hr value was 10.8 ppm.

109.LK1 ESP 20 3 167 @ 20.4% O2

48.8 @ 19.6% O2

8.8 @ 15.7% O2

 Mill had two consecutive high O2-corrected TRS 12-hr averages (167 and 

48.8 ppm) and one unrelated 12-hr average in excess of 8 ppm. All three of 

these values would be below 8 ppm after invoking the proposed provision to 

consider uncorrected values when O2 exceeds 15%. The uncorrected values 

would be 9.8, 6.0, and 4.2 ppm).

147.3 SCBR 9 2 17.8 Next highest 12-hr value was 8.1 ppm.

148.009 ESP 1 1 8.035

151.CP002 SCBR (NCG 

scrubbers prekiln + LK ESP]

7 2 37.0*

13*

Although 12-hr data set indicated 37 ppm (with next highest of 13 ppm), the 

corresponding 1-hr data do not show 37 ppm. It is unclear how the 37-ppm 

12-hr average reported was derived because the highest 1-hr value for that 

block was 10.9 ppm. Similarly, all hourly values associated with the 13 ppm 

12-hour average were less than 1 ppm. Data set not considered further.

151.CP001 14 7 57.0*

43.0*

22

20

17

12

10

 Data anomaly. Only one hourly value of 57 ppm was included in the 12-hr 

average because process down time for the other 11 hours is excluded. 

 The 2nd highest value of 43 ppm was associated with 0 production.

 The 3rd highest value was 22 ppm

 Actual O2 data unavailable; unclear if O2 correction inflated the ppm.

180.L002 SCBR 85 2 10.2

8.5

186.LK ESP/SCBR 18 1 8.1

240.CA81 ESP 10 1 9.0

1. Not shown in the table are 21 additional lime kilns that clearly had no exceedances of the 8 ppm TRS standard during startup or shutdown. A total of 33 

lime kilns had no exceedances during any time (normal operation or startup/shutdown).

*Not considered representative for rulemaking purposes.
F-1

APPENDIX F: Lime Kiln Opacity Data
F-2

0

1

2

3

4

5

6

7

8

9Annual Average Opacity (%)

Figure 1. Lime Kiln Annual Average Opacity

Calculated as the average of the 6-min averaging periods for all COMS data sets (except one hourly average set).

ESP ESP/SCBR
F-3
F-4
F-5