1 MEMORANDUM
TO: Brian Shrager, US EPA\OAQPS\SPPD
FROM: Amanda Singleton and Graham Gibson, ERG
DATE: January 2011
SUBJECT: Beyond the Floor T echnology Analysis for Major Source Boilers and Process Heaters

1.0 INTRODUCTION
This memorandum describes the methods used to analyze the be yond-the-floor control technology analysis for each subcategory. EP A considered the new source MACT floor emission limits for boilers and process heater s as a beyond the floor option for existing major source boilers and process heaters. The new s ource MACT floor emission limits are based on an analysis of emissions data from the best pe rforming single source for each pollutant and are detailed in a separate memorandum. 1 A discussion of fuel-switc hing and a facility-wide energy assessment as interim beyond-the-floor options are discussed in separate memoranda. 2,3 The beyond the floor control options are not feasible because the cost of reducing an additional ton of pollutant emissions for each subcategory is ex traordinarily high, or th ere are limitations on the technology’s pollutant removal effi ciency in retrofit applications . This memorandum is divided into the following sections:
1.0 Introduction
2.0 Summary of Beyond the Floor Option
3.0 Effectiveness of Beyond the Floor Option
4.0 Plausibility of Beyond the Floor Option
5.0 References Appendix A: Unit-Level Emission Reducti ons and Costs for Beyond the Floor Option Appendix B: Summary of Cost Ef fectiveness of Beyond the Floor Option2 2.0 SUMMARY OF BEYOND THE FLOOR OPTION

In this beyond the floor option, existing units would comply with more stringent new
source emission limitations for carbon monoxide (CO), mercury (Hg), filterable particulate matter (PM), and hydrogen chloride (HCl). Sim ilar to the MACT floor analysis, this beyond the floor option was assessed on a pollu tant-by-pollutant basis. Tabl es 1 and 2 compare the emission limits for existing sources to the beyond the floor emission limits. No beyond the floor emission limits were considered for dioxins/furans give n concerns raised dur ing the public comment period about the significan t presence of non-detect data used to established the MACT floors, the uncertainty surrounding the formation of dioxi n/furan in this source category, and the demonstrated compatibility of dioxin/furan contro l devices on units with such low dioxin/furan
inlet concentrations.

Table 1 – Comparison of Existing and Beyond the Floor Heat Input-Based Emission Limits
Fuel Category Emission Limits for Existing Sources Hg (lb/TBtu) PM (lb/MMBtu) HCl (lb/MMBtu)
Solid 4.6 0.039 0.035 Liquid 3.4 0.0075 0.0003 Non-Continental Liquid 0.78 0.0075 0.0003

Process Gas 13 0.043 0.0017

Fuel Category Beyond the Floor Emission Limits Hg (lb/TBtu) PM (lb/MMBtu) HCl (lb/MMBtu)
Solid 3.5 0.0011 0.0022 Liquid 0.21 0.0013 0.0031 Non-Continental Liquid 0.78 1 0.0013 0.0031

Process Gas 7.9 0.0067 0.0017 1

1 Identical to existing source floor; no beyond the floor cost or emission impacts estimated for this pollutant/subcategory.3 Table 2 – Comparison of Existing and Beyond the Floor Combustor Design-Based Emission Limits

Fuel Category Combustor Design Existing Source Emission Limit Beyond the Floor Emission Limit CO (ppm @ 3% O2) CO (ppm @ 3% O2) Biomass/ Bio-based solid Dutch Oven/ Suspension Burner 470 470 1

Biomass/ Bio-based solid Fluidized Bed 430 260
Biomass/ Bio-based solid Fuel Cell 690 470
Biomass/ Bio-based solid Stoker/Other 490 160
Biomass/ Bio-based solid Suspension/Grate 3,500 1,500

Coal/Fossil Solid Fluidized Bed 82 18
Coal/Fossil Solid Pulverized Coal 160 12
Coal/Fossil Solid Stoker/Other 270 6 Liquid N/A 10 3 Non-Continental Liquid N/A 160 3

Process Gas N/A 9 3

1 Identical to existing source floor; no beyond the floor cost or emission impacts estimated for this pollutant/subcategory.

Existing boilers and process heaters would comply with the beyond the floor emission limits via the addition of add-on pollution contro l devices, similar to compliance with MACT standards. A description of each add-on pollu tion control device is provided in another
memorandum. 2 This section documents the methods and assumptions used to estimate which add-on pollution control devices would be requir ed for beyond the floor compliance. Beyond the floor impacts were not estimated for units with a rated heat input cap acity of less than 10 MMBtu per hour or for units burning natural gas, refinery gas, or other gas 1 fuels (including metallurgical furnaces). For the same reasons pr ovided in the preamble to the final rule for a work practice standard on these units, numerical emission limits, e ither at the MACT floor level or beyond-the-floor level, are unworkable and impractical at these units due to emissions
measurement difficulties.4 2.1 Baseline emissions
In order to estimate the incremental emission reductions associated with this beyond the floor option, baseline emissions were estimated for each unit. The baseline emission levels were equal to the MACT floor emission limits with a few exceptions: (1) if the reported baseline
emission level established in the initial baselin e emissions analysis was less than the MACT floor emission limit, the initial baseline was main tained; and (2) units subject to work practices
in lieu of emission limits were assi gned to a baseline emission leve l that applied a 1 percent fuel and combustion efficiency factor to the original baseline emission estimates. The methods used
to estimate emission reductions associated with a 1 percent fuel and combustion efficiency factor and for MACT compliance are described in another memorandum. 4

2.2 Emission Reductions Beyond the floor incremental emission reducti ons were estimated by subtracting the newly calculated baseline from the beyond the floor emission limits shown in Tables 1 and 2. However, no beyond the floor control options ar e proposed for TEQ dioxins/furans and, thus, no
emission reductions were estimated. Emission reductions of CO, Hg, PM, and HCl were only
estimated if the unit was not al ready expected to install the id entified beyond the floor control technology for MACT compliance discussed in s ection 2.3 below. Although some air pollution control devices can achieve greater efficiencies when multiple controls are employed in series, no units were required to install more than one of each specific control technology in this analysis due to the economic burden and limite d retrofit space availa ble at existing units. Beyond the floor percent reducti ons were estimated for CO, HCl, and PM emissions.
Emissions of THC and VOC were estimated to be reduced based on the calculated percent
reduction in CO. Emissions of HF and SO2 were estimated to be reduced based on the percent
reduction in HCl. Emissions of PM2.5 and total selected metals (TSM) were estimated to be reduced based on the percent reduction in PM. No additional emission reductions were estimated for limited use units, small units (less than 10 MMBtu/hr), and units firing natural gas, refinery gas, or other on-spec gaseous fuels si nce a beyond the floor analysis was not considered for these subcategories. Appendix A shows the unit-specific emission re ductions associated with the beyond the floor option.5 2.3 Add-on Pollution Control Devices Compliance with the beyond the floor emission limits for CO is expected to be achieved via installation of an oxidation catalyst. Boile rs and process heaters not meeting the beyond the
floor CO emission limit would instal l an oxidation catalyst if one wa s not already estimated to be installed for MACT compliance. Emission and cost impacts for CO were not estimated for boilers and process heaters that installed an oxidation catalyst for MACT compliance. The new
source emission limit for CO is identical to the existing source CO emission limit for boilers and process heaters burning process gase s or liquid in non-continental st ates or territories, and thus the beyond the floor analysis was not consid ered for these units for CO control. Compliance with the beyond the floor emission limits for Hg and PM is expected to be
achieved via installation of a fabric filter and ac tivated carbon injection (ACI) system. Boilers and process heaters not meeting the beyond the floor limit for either Hg or PM would install a
fabric filter if the unit did not al ready have a fabric filter installe d or if a fabric filter was not installed for MACT compliance. If a boiler or process heater was not meeting the beyond the floor emission limit for Hg but already had a fabric filter installed, an activated carbon injection (ACI) system was expected to be installed to comply with the beyond the floor Hg emission limit. Emission and cost impacts for Hg were not estimated for boilers and process heaters that already had ACI installed for MACT compliance because there are no other mercury removal technologies demonstrated on industria l/commercial/institutional boilers. Compliance with the beyond the floor emission limit for HCl is expected to be achieved by installing either a fabric filter and dry in jection (DIFF) combination or a wet scrubber. Similar to the assumption made in the MACT floo r impacts analysis, boilers or process heaters
located at facilities without wastewater discha rge permits could not in stall a wet scrubber. Boilers and process heaters not allowed to di scharge wastewater were defined by facilities assigned a North American Industry Classifica tion System (NAICS) code of 321 (wood product manufacturing) or 322 (paper manufacturing). For boilers and process heater s at facilities with allowable wastewater discharge, the cost of DIFF and a wet sc rubber were compared and the cheaper option was assumed to be installed. If a boiler or process he ater already had a wet scrubber installed, the rate of cau stic injection of the scrubber would be increased to a point where compliance is met. Emission and cost imp acts for HCl were not estimated for boilers and6 process heaters that installed DIFF for MACT compliance. Appendix A shows the unit-speci fic control costs associated with the beyond the floor option for each of the target pollutants.

3.0 EFFECTIVENESS OF BEY OND THE FLOOR OPTION

The incremental costs and emission reductions above the cost and emission reductions
achieved from the MACT floor were estimated. Annual costs were estimated for units expected to install additional add-on pollution control devices to comply with the beyond the floor
emission limits. The methods and calculations us ed to estimate cost impacts are described in
another memorandum. 2 Since testing and monitoring w ould be required under both the MACT floor and beyond the floor control options, only th e costs associated with the installation of controls were considered in this analysis. An incremental cost effectiveness was calculated by dividing the incremental costs by the incremental emission reductions, to estimate a dollars per ton of pollutant reduction for the various types of targeted HAP and HAP surrogates. The cost effectiveness estimates for each beyond the floor control option can be found in Appendix B.

4.0 PLAUSIBILITY OF BEYOND THE FLOOR OPTION

Oxidation catalysts were estimated to be instal led on units in all subc ategories in order to comply with beyond the floor CO emission limits. For units firing liquid fuels, the cost of reducing an additional ton of CO emissions is $86,000 in annual costs. For non-continental liquid units and units combusting process gase s, that same cost is over $11,000 for each subcategory. These costs are unfeasibly high. For units combusting solid fuel, the cost for reducing an additional ton of CO emissions is only $2,000 in annual costs. However, combustion of solid fuels results in significant amounts of dust and fly ash, which can plug or blind catalyst reactive sites necessary to oxidize CO . This reduces the efficiency of the oxidation catalyst. To maintain the effectiveness of th e oxidation catalyst, the unit may require shutting down more frequently for cleaning or replacement of the catalyst, incurr ing additional costs on the facility. The insta llation of fabric filters upstream of the catalyst could reduce the amount of dust to which the catalyst bed may be subjected, but this would also impose a significant cost7 burden on a facility if the unit is not already required to install a fabric filter for control of other pollutants. While dust problems could arise for un its required to install an oxidation catalyst for MACT compliance, the probability of this problem s occurring is estimated to be higher for the beyond the floor option considering that a higher efficiency is needed to achieve the more stringent beyond the floor limits. For these reasons, the beyond the floor option of installing an oxidation catalyst for CO contro l is technically infeasible. Other methods of reducing CO emissions, such as upgrading new burners and ov erfire air systems, were not a technically feasible option available to achie ve the beyond the floor emission limits for solid fuel units. In many cases the beyond the floor limits were betw een 30 and 98 percent lower than the MACT floor emission levels for existing solid fuel sources and although combustion improvements could help achieve the MACT floor emission limits , these combustion controls are not capable of constantly achieving these lower emission levels associated with the beyond the floor option. Further many existing units may have been designed with specific furnace heat release rates in order to be able to fire specific fuel blends, and although the best source in each subcategory is demonstrated to meet the emission limit, existing sources may not be able to do so without complete overhaul or replacement of major boile r components at an unreasonably high cost. All non-continental liquid units subject to em ission limits were expected to install a fabric filter for MACT compliance. Theref ore, compliance with th e beyond the floor PM
emission limit would necessitate an additional fa bric filter, doubling the MACT cost for these units in exchange for minimal additional PM redu ctions. Alternatively, these units may require additional particular control devices, such as a cartridge filtration syst em, which would require additional capital and operating expenses and additional energy to power the fans for adequate draft. For each of the remaining subcategories, where an incremental fabric filter is needed to meet the beyond the floor limit, the cost of reduc ing an additional ton of PM emissions is over $100,000 in annual costs. Since PM is the surro gate for non-mercury metallic HAP, the cost effectiveness of removing a small incremen tal amount of non-mercury metallic HAP was between $3.4 and $31 million per additional ton removed. The cost of this beyond the floor option is not justified given the small incr emental reduction in metallic HAP emissions. All units combusting proce ss gases were expected to install a fabric filter in order to meet the beyond the floor PM emission limit. As a result of the fabric filter’s co-benefit of controlling both PM and Hg, no process gas units were estima ted to need an ACI system to meet the beyond8 the floor Hg limit. For each of the remaining subcategories, the installation of an ACI for compliance with beyond the floor Hg limits results in over $85,000 per additional pound of Hg emission reductions. For these reasons, the be yond the floor option of installing ACI for Hg control is economically infeasible. A beyond the floor analysis for HCl was not conducted for the process gas subcategory since the beyond the floor HCl emission limit is e qual to the HCl MACT floor emission limit. All units combusting liquid fuels (including non-continental liquid uni ts) were expected to install either a scrubber or DIFF for MACT compliance. Therefore, no other control option exists to meet a more stringent beyond the floor option. On ly some of the units combusting solid fuels were estimated to be required to install a scr ubber or DIFF for HCl and acid gas control. The cost of reducing an additional t on of HCl from these units firing solid fuels is estimated to be over $166,000 in annual costs. When consider ing reductions in HCl and HF, the costeffectiveness is only reduced to $156,000 in annu al costs. For these reasons, the beyond the floor option of installing a sc rubber or DIFF for HCl control is not economically feasible.9 5.0 REFERENCES

1. Singleton, A., ERG. Revised MACT Floor An alysis for the Industrial, Commercial,
Institutional Boilers and Process Heaters National Emission Standards for Hazardous Air Pollutants – Major Source. January 2011.

2. Singleton, A. and G. Gibson, ERG. Revi sed Methodology for Estimating Cost and Emissions Impacts for Industrial, Commercial , Institutional Boilers and Process Heaters
National Emission Standards for Hazardous Ai r Pollutants – Major Source. January 2011.

3. Singleton, A. and G. Gibson, ERG. Revised Development of Baseline Emission Factors
for Boilers and Process Heaters at Commercial , Industrial, and Inst itutional Facilities. January 2011.

4. Singleton, A. and G. Gibson, ERG. Revi sed Methodology for Estimating Cost and Emissions Impacts for Industrial, Commercial , Institutional Boilers and Process Heaters
National Emission Standards for Hazardous Ai r Pollutants – Major Source. January 2011.10 

### Appendix A

Unit-Level Emission Reductions and Costs for Beyond the Floor Option
(See Excel spreadsheet)11 

### Appendix B
Summary of Cost Effectivene ss of Beyond the Floor Option
(See Excel spreadsheet)