Class I Air Modeling Report 

Keetac Expansion Project 

Prepared for 

U.S. Steel 

December 2010 

BARR 
2. Project Description 

Currently, Keetac has one operational pellet producing line (Line 2, also referred to as the existing line) 

with an annual production of approximately 6.0 million net tons per year. U. S. Steel proposes to increase 

the capacity at the Keetac facility by restarting a second pellet producing line (Line 1, also referred to as 

the new line). The restart would involve energy-efficient teclmologies in addition to new emission 

controls to exceed current enviromnental standards. The expansion would increase Keetac's iron pellet 

production output by 3.6 million tons to a total annual output of9.6 million tons. This project is referred 

to as the "Keetac Expansion Project". Upgrades to the mining, concentrating and agglomerating 

processes would support the increased production requirements. The project will also include the 

purchase of additional mining equipment and the installation of additional processing equipment. 

Air Emissions 

The project will generate air emissions, including off-road mobile source emissions. As part of the air 

permit, Keetac will take a NOx limit to net out ofPSD requirements for NOx. Keetac will be able to 

comply with the NOx emission limit by using a mixture of natural gas and biomass, coal, or fuel oil. The 

netting evaluation is shown in Attachment E. Since there is no significant increase in NOx emissions the 

project is not subject to PSD requirements to evaluate NOx for increment consumption and NAAQS. 

However, the total facility NOx emissions are included in the evaluation to capture chemical interactions 

with ammonia. In addition, the FLM's have requested that NOx emissions be included in an evaluation 

that compares the change in modeled visibility impacts from the facility baseline period to the expansion 

project combined with the existing facility. NOx emissions will be included with the other pollutants 

including PM10 and S02 for this evaluation. Total emissions modeled are described in Attachment B. 

As discussed with the FLM's and MPCA, Keetac is running a variety of modeling scenarios as described 

in the protocol, which includes a scenario comparing the emissions representative ofKeetac's baseline 

period compared to emissions from the total post project facility. The emissions from these two operating 

scenarios will be used as inputs into the modeling. The differences will be paired in time and space. 

2.1 Baseline Period Modeling (Pre-Scrubber) 

Keetac is pennitting the stationary source NOx emissions for the expansion project as a minor 

modification by netting emissions with the existing line. In the 10 year period preceding this project, 

natural gas was the primary fuel used in the existing line and was the basis for determining a NOx 

baseline value. A 24-month baseline period of November 1999 through October 2001 was chosen to 

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represent baseline emissions for the netting evaluation. Therefore the baseline emissions will be 

calculated using emission factors from the Keetac Phase II Stack Tests July 25-26, 2000 Stack Test for 

S02 and NOx. These tests were used because the emission factors from that time are most representative 

of the indurating process operating conditions for the baseline period. This time period and the emission 

factors used in the netting analysis were reviewed and approved by the MPCA. The MPCA's emission 

inventory rules allow the use of an emission factor derived from a stack test for a period of ten years after 

the test). Additionally, the MPCA has already used these results from the July 2000 NOx test in the 

netting calculations for the permit that authorized construction of the scrubber and fuel switch in 2005 at 

Keetac. The emission factor for PM10 was derived fi·om a stack test performed in July 2000. The baseline 

emissions are summarized by emission group and shown in the Class I Modeling Protocol (November 

2008) (see Attachment A). 

2.2 Final Proposed Facility 

A couple of changes have occurred at the facility since the timeframe associated with the baseline period. 

Understanding and tracking these changes is necessary to define the final proposed facility emissions. 

Post-Scrubber/Fuel Switch Emissions 

Calculation of post scrubber emissions relies on stack test emission factors from two tests at the existing 

Keetac pellet line, one using coal as the primary fuel and one using natural gas as the primary fuel (NOx 

Test Oct 19, 2005 -NG Basis, NOx Test May 31-June 1 2006- Coal Basis). The installation of the 

scrubber in October 2005 also changed the dispersion characteristics for emissions from the existing 

Phase II furnace. Prior to installation of the scrubber there were two stacks on the existing indurating 

furnace. With the installation of the scrubber these two streams were routed to a scrubber with a single 

stack. This modification of the exhaust streams also resulted in changes to the flow patterns in the 

furnace. Following installation of the scrubber two stack tests were conducted, one in 2005 while firing 

natural gas and a second in 2006 while firing coal. Therefore, these stack tests are appropriate to use for 

calculating the emissions for the post scrubber scenario. Additionally, the existing line transitioned from 

use of primarily natural gas for fuel to a combination of natural gas and coal. The existing line will 

continue to operate on these two fuels in the future as well. The post scrubber emissions are detailed in 

the input calculations provided in Attachment B. For purposes of visibility modeling, the proposed 24-

hour emission limits were used as the modeled emission rates. Additional modeling, presented in 

Attachment C, examined impacts using the emission factor for the fuel with the highest NOx contribution 

(natural gas) for modeling maximum potential impacts and a combined fuel (natural gas and coal) 

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emission factor was used for modeling impacts at the permitted emission rate. Additional details of these 

emission factors are provided in Section 2.3 and Attachment B. 

New Source Facility Emissions 

The emissions for the new indurating furnace are based, for most averaging times, on expected permit 

limits based on the BACT determinations for 802, PM10, and PM2.5. NOx emissions are based on the 

proposed 24-hour combined furnace limit. Biomass emissions for the expansion project were calculated 

by applying stack test data from the Minntac facility and scaling it to the Keetac project. Data from 

Minntac is used because biomass is not currently used in the existing furnace at Keetac nor is biomass 

used in any other taconite furnaces. The new Keetac furnace will use a combination of biomass and 

natural gas. The Minntac emission factors used are from a correlation developed by the MPCA from a 

series of stack tests at Minntac. The Minntac results were adjusted and applied to Keetac in accordance 

with a MPCA data evaluation which considers type of pellet (flux vs. acid) and mix offuels (natural gas 

vs. biomass ratio). The new source emissions are summarized by emission groups and shown in 

Attachment B. 

Modified Facility Emissions 

Keetac proposes to permit the stationary source NOx emissions for the expansion project as a minor 

modification by netting emissions with the existing line. To create a credible emission reduction to offset 

the emission increase from the expansion, Keetac will be required to take a federally enforceable permit 

limit on both the new and the existing furnaces to remain below major modification thresholds. The 

proposed 24-hour emission limits for NOx on the combined existing and expansion units is used to define 

potential NOx emission rates for the future scenarios for modeling maximum daily impacts, as well as 

providing a conservative method for modeling annual average impacts. The modified facility emissions 

are shown in Attachment B. 

A change has been made to the emission factors detailed in the Class I modeling protocol for mobile 

sources. Mobile source emissions (diesel trucks) were estimated in the protocol using conservative 

AP-42 emission factors. The AP-42 emission factors were published in 1996 and do not take into 

consideration new emission standards for off-road diesel engines. Keetac has reviewed non-road diesel 

emission regulations and believes that the pending standards associated with non-road diesels are more 

representative of emission from new trucks that will be purchased as part of the expansion project. 

Keetac plans to purchase new haul trucks, shovels, and dozers for the expansion. The old AP-42 emission 

factors were used to estimate emissions fi·om the existing non-road equipment and the new Tier 4 

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emission standards were used to estimate emissions for the new non-road equipment. Additional details 

regarding these calculations are presented in Attachment D. 

2.3 Emission Rate Calculation Basis 

This section discusses how emissions rates that are inputs to the Class I modeling were calculated for both 

the existing and expansion emission units. It also describes how emission rates were calculated for the 

existing facility before the wet scrubber was installed on the existing indurating line. Some small 

rounding discrepancies may appear if you hand calculate the emissions rates using the emission factors 

and throughputs provided in the following sections and compare them to the values in the Attachment. 

The provided emission rates are based on the values calculated in the emission inventory included as pmt 

of the Permit Application submitted in October 2009, with some revisions per subsequent reviewer 

comments, updated emission factors and BACT limits. The emission inventory serves as the primary 

basis for the modeling emission inputs. The actual calculations of emission rates are described later in 

this section. 

2.3.1 Proposed Project Modeled Emission Rates 

A wide range of fuel mixes can be used in both the existing and new indurating lines. U.S. Steel has 

proposed fueling the new line with biomass, natural gas, coal, and fuel oil. The existing line is currently 

permitted to burn natural gas, fuel oil and coal. The mix of fuels used at any one time can vmy from zero 

to 100 percent. In comparing the emission rate of fuel mixes, firing both the existing and expansion lines 

on 100 percent natural gas was determined to be the worst-case emissions scenario for the Class I 

modeling assessment. This scenario represents the maximum NOx emissions, which was determined 

through modeling to be the dominant visibility impacting pollutant. Maximum S02 emissions occur when 

burning 100 percent coal. However the difference in S02 emissions between 100 percent natural gas and 

100 percent coal is not significant because a majority of the S02 comes from sulfur in the ore which is 

liberated from the ore and convetted to S02 in the indurating process. The modeled S02 emission rate for 

the existing furnace is based on an emission factor derived by the MPCA based on CEMs data and 

provided via email dated May 6, 201 0. 

Class I modeling previously conducted for 100 percent natural gas on both the existing and new 

indurating lines indicated visibility impacts above FLM guidance (Attachment C). In addition, the 

frequency and duration at which both lines would be operating on 100 percent gas are limited. Therefore, 

a combined NOx emission rate for the indurating furnaces was developed and modeled corresponding to 

more realistic fuel mixes. Because this is a combined emission rate and the emissions could vary between 

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the new and existing furnace, an analysis was conducted to determine how to distribute the emissions 

between the two lines in order to model maximum impacts. For application of the proposed 24-hr NOx 

emission limit, a sensitivity analysis was performed with respect to the distribution between existing and 

expansion kilns. In this sensitivity analysis emissions were modeled with all emissions coming from the 

existing line only in one run, the expansion line only in another run, and for an even distribution between 

the lines. Results indicated that the existing line's dispersion characteristics results in higher Class I 

impacts than the new lines dispersion characteristics. Therefore, for modeling purposes the existing line's 

emission rate was maximized and then the remaining NOx emissions from the combined total were 

distributed to the new line. This distribution of emissions was used to represent the worst-case impact 

given the proposed NOx emission limit. 

Details of the emission factors and associated rates are provided in the following for the applicable 

emission unit types. These rates were used as the basis for calculating emissions used as inputs for the 

Class I modeling 

2.3.1.1 Facility Expansion 

i. New Indurating Line 

The following four emission points are associated with the new indurating line. Figure 2-1 

shows their relationship to the process flow. Combustion emissions only exit the DDDI stack 

while the other stack emissions are primarily particulates. Some ore related S02 is emitted 

from the TPH stack. 

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1. DDD1 (without consideration of energy efficiency improvements on emission factors) 

NOx: 

Emission Factor Natural Gas (EF11g): 1.726 lb/ston pellets produced 

Emission Factor Biomass (EFbio): 0.854lb/ston pellets produced 

Emission Factor Coal (EFcoal): 0.639lb/ston pellets produced 

Emission Factor Fuel Oil (EFfo): 0.992lb/ston pellets produced 

Basis Natural Gas: Existing facility stack test, 10/15/05 

Basis Biomass: MPCA guidance document sent to Minntac by Hongming Jiang in late 

2004, exponential-decay fit formula for wood combustion combined with Minntac Line 7 

stack test production data (5/21/04). 

Basis Coal: Existing facility stack test, 5/31/06 

Basis Fuel Oil: Existing facility stack test, 7/25/00 

Rated Capacity (RC): 450 tons pellet produced/hr 

Emission Rate Natural Gas (ERng) = EFng * RC = 776.8 lb/hr NOx 

(776.8 lb/hr * hr/3600 sec* 453.6 g/lb = 97.9 g/s) 

(Note: Facility is proposing a combined NOx limit of 1652lb/hr; see Section ii, 

Process Improvement Energy Efficiency Factor for more details.) 

Emission Rate Biomass (ERbio) = EFbio * RC = 384.5 lb/hr NOx 

Emission Rate Coal (ERcoal) = EFcoal * RC = 287.4lb/hr NOx 

Emission Rate Fuel Oil (ERfo) = EFfo * RC = 446.3 lb/hr NOx 

Natural gas is the worst case fuel for NOx emissions. The 10/15/05 natural gas stack test 

emission factor for the existing kiln is used with the rated capacity ofDDD1 to calculate 

the NOx emission rate. 

Page 9 
PM to: 

EF: 0.012 gr/dscf (3-hour averaging time) 

Basis: BACT limit 

RC: 203,967 dscfm 

ER = EF * lb/7000 gr * 60 min/hr * RC = 21.0 lb/hr PM10 

(21.0 lb/hr * hr/3600 sec* 453.6 glib= 2.64 g/s) 

The BACT limit is used with the rated capacity ofDDD1 to calculate a PM10 emission rate. 

The BACT limit will be used for all fuels. 

802: 

EF: 8 ppmv S02 as measured on a wet basis on a 24 hour average at the 19.1 lb 802/hr 

limit for DDD1 

Basis: The DDDI process design, control equipment performance guarantee. 

RC: 203,967 dscfm DDDlER = EF * 60 min/hr * lb mol/385.3 ft3 * 64 lbllb mole* RC = 

= 19.1 lb 802/hr 24-hour average basis 

(19 .1 lb/hr * hr/3600 sec * 453.6 g/lb = 2.407 g/s) 

A total emission rate for DDD I of 19.1 lb SOz/hr is based on a control performance of 8 

ppmv 802 as measured on a wet basis at the rated flow capacity for DDDI. The 8 ppmv 

control basis is used because it reflects worst case expected performance during an 

optimization period. The 24-hr block emission rate is used for visibility modeling since the 

criteria are based on 24-hr block modeling. 

The 23.3 lb 802/hr emission rate on a 3-hour average basis is based on the vendor 

guaranteed control modified to the shmter averaging period. The control equipment 

exhaust 802 concentration at DDD 1 of 5 ppm wet was corrected to 6ppm dry on a 15% 0 2 

wet basis and applied at the rated capacity listed above and the 3-hour average upper 

control limit (UCL, 1.9) of 802 CEMS data from the Minntac plant. The initial vendor 

guarantee of9.7lb/hr was 5 ppm wet at an average flowrate of 160,629 dscfm. The initial 

vendor guarantee was corrected for flowrate (203,967 dscfm) and the UCL. ER =Vendor 

Limit* Flow Correction* UCL ratio= 23.3 lb/hr 802 

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=23.3 lb/hr S02 3-hour average basis (DDD1 only) 

(23.3 lb/hr * hr/3600 sec * 453.6 glib= 2.94 g/s) 

The 3-hr emission rate of23.3 lb S02/hr was used to demonstrate that the modeled impact 

ofthe project is below the S02 SIL concentration (3-hour averaging time). The 24-hour 

modeling rates were used for all other modeling outputs, including acid deposition. 

SAM: 

EF Natural Gas: Uncontrolled SAM emissions of0.030 lb SAM/s-ton pellets produced. 

Basis: SAM stack test while firing natural gas (Minntac, l/13/04). This result gets split 

between DDDI and TPH by Metso modeling estimates of approximately 64% S02 DDD1 

to 36% S02 TPH when firing 100% natural gas as fuel. A control efficiency of95% for 

the CFB was used. 

RC: 450 tons pellet produced/hr 

EF: 0.030 lb SAM/s-ton pellets- uncontrolled 

%SAMtoDDD1: 64% 

SAM Control Efficiency: 95% 

ER = RC *EF *%SAM to DDDl/100% * (0.05) = 0.432lb/hr SAM 

(0.432 lb/hr * hr/3600 sec* 453.6 g/lb = 0.05 g/s) 

A SAM emission rate based on natural gas firing is consistent with the worst case fuel 

scenario for total visibility impacts. 

2. TPH 

NOx: 

No combustion products anticipated for TPH 

EF: 0.012 gr/dscf(3-hour averaging time) 

Basis: BACT limit 

RC: 110,213 dscfm 

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ER = EF * 60 min/hr * lb/7000 gr * RC = 11.3 lb/hr PM10 

(11.3 lb/hr * hr/3600 sec * 453.6 g/lb = 1.43 g/s) 

The BACT limit is used with the rated capacity ofTPH to calculate a PM10 emission rate. 

The BACT limit will be used for all fuels. 

802: 

EF: 5 ppmv S02 as measured on a wet basis at the 6.4 lb 802/hr for TPH (3-hour and 24-

hour averaging time) 

Basis: The TPH process design, control equipment performance guarantee. 

RC: 128,904 scfm (68° F) 

ER = EF * 60 min/hr * 385.3 lb mol/ft3 * 64lb/lb mole* RC = 

= 6.4lb/hr S02 (TPH only) 

The 6.3 lb S02/hr emission rate is the estimated controlled S02 emission rate and was used 

in the air quality modeling analysis initially used to demonstrate compliance with NAAQS. 

The calculated S02 emission rate based on the control equipment guarantee of 5 ppmv S02 

as measured on a wet basis at the rated flow capacity above is 6.4 lb SOz/hr. Given the 

slight difference in these values, an emission rate of 6.3 lb S02/hr was retained to maintain 

consistency with the original air quality modeling analysis. 

(6.3 lb/hr * hr/3600 sec* 453.6 g/lb = 0.79 g/s) 

SAM: 

EF Natural Gas: Uncontrolled SAM emissions of0.030 lb SAM/s-ton pellets produced (3 

hour averaging time). 

Basis: Natural gas SAM stack test (Minntac, 1/13/04). This result gets split between 

DDDI and TPH by Metso modeling estimates of approximately 64% S02 DDDl to 36% 

S02 TPH when firing I 00% natural gas as fuel. A control efficiency of 95 % for the CFB 

was used. 

RC: 450 tons pellet produced/hr 

EF: 0.030 lb SAM/s-ton pellets- uncontrolled 

%SAM to DDDI: 36% 

Page 12 
ER = RC *EF *%SAM to DDD1/100% * (0.05) = 0.243 lb/hr SAM 

(0.24 lb/hr * hr/3600 sec * 453.6 glib= 0.03 g/s) 

3. DDD2 

No combustion products or S02 are expected to be emitted from DDD2. 

EF: 0.012 gr/dscf (3-hour averaging time) 

Basis: BACT limit 

RC: 138,495 dscfm 

ER = EF *lb/7000 gr * 60 min/hr * RC = 14.2 lb/hr PM10 

(14.2 lb/hr * hr/3600 sec* 453.6 glib= 1.79 gls) 

The BACT limit is used with the rated capacity ofDDD2 to calculate a PM10 emission rate. 

4. C4 Cooler 

No combustion products or S02 are expected to be emitted from C4 Cooler. 

PMw: 

EF: 0.012 gr/dscf (3-hour averaging time) 

Basis: BACT Limit 

RC: 191,624 dscfm 

ER = EF * lb/7000 gr * 60 min/hr * RC = 19.7lb/hr PM10 

(19.7lb/hr * hr/3600 sec* 453.6 glib= 2.48 gls) 

The BACT limit is used with the rated capacity of C4 to calculate a PM10 emission rate. 

ii. Process Improvement Energy Efficiency Factor 

NOx emissions are generally related to fuel combustion and therefore improvements in heat 

recovery design can reduce the generation ofNOx emissions by reducing fuel consumption. 

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The new taconite indurating furnace is designed to use approximately 36% to 44% less fuel 

than the existing furnace, on an MMbtu per short ton of pellet produced basis. NOx emission 

rates used in the emission inventory were based on emission rates from the existing furnace and 

were used as model inputs in the previous modeling for both the existing line and new line and 

therefore previous modeling did not account for reductions associated with energy efficiency in 

the new line. The factors for the existing furnace have been reviewed and agreed to by the 

MPCA. The NOx emission rates are based on testing results from the existing furnace which 

has a lower heat recovery and a higher fuel use rate than expected for the new furnace. The 

reduced fuel usage numbers were developed using process design inputs from Hatch. These 

improvements are accomplished by: 

• Expanding the preheat and cooling sections of the furnace to increase the available 

pellet smface for heat transfer 

• Improved air flow patterns for more efficient transfer of heat 

• Optimizing use of recovered energy between heating unfired pellets and combustion 

air 

• Improved air seals to minimize infiltration of cold air into the furnace 

• Improved insulation to minimize heat loss 

The exact relationship between reduced fuel usage and the resulting reduction in NOx 

emissions is not known. Due to the uncertainty associated with the exact reduction in 

NOx emissions that will be achieved, no change was made to the emission rates that were 

used for the original model inputs. 

NOx generation is maximized when the existing line and the new line are running 100% 

natural gas. The range of fueling scenarios was evaluated to understand and define 

ranges reflective of operating conditions for the kilns. 

NOx emissions were calculated by multiplying fuel specific emission factors by the fuel 

mix used and the process throughput to get a totallb/hr rate. 

Fuel specific emission factor (lbs/ton pellet) x max pellet through put (tons/In·)= lbs/hr 

NOx 

Page 14 
Max hourly rates: Expansion kiln- 450tph, Existing kiln- 830 tph 

Total annual production rates do not equate directly to instantaneous hourly max rates 

because it is not feasible to run the line continuously thought out the entire year. 

The expansion kiln emission factor was modified by assuming a conservative 20% 

reduction in NOx emissions due to the heat recovery design of the new furnace. These 

calculations show that an emission rate of 1,652 Ib/hr is an approximate bound on where 

both kilns can run at the same time while one is firing 100% natural gas. 

The 1,652 lb/hr rate was deteJmined primarily by evaluating kiln fueling scenarios by 

using this estimate of improved efficiency for the expansion kiln (applied to the existing 

emission factor with a 20% decrease). 

U. S. Steel is proposing to have a NOx emission limit of 1652 lb/hr for the combination of 

emissions from the existing line and new line. This was derived from the evaluation of 

fueling scenarios for both operating lines. The fueling scenarios range from 100% natural 

gas for both kilns to 0% natural gas/1 00% solid fuel for both kilns. 

Originally, the calculated NOx emission rate was approximately 1660 lb/hr under a 

fueling scenario of 100% natural gas on the existing line and I 00% solid fuel on the 

expansion line. Since this number was calculated, small changes have been made to the 

S02 emission rates. To keep the proposed number of affected days near the original 

proposal, the NOx emission rate was reduced slightly to 1652 lbs/hr. The target operating 

scenario (60% solid fuel existing/50% solid fuel expansion) has a projected emission rate 

below the 1652 limit. When the existing line is operating at its target fueling rate of 60% 

solid fuels and 40% natural gas, the expansion line is capable offueling at 100% natural 

gas and operates below the 1652 lb/Iu· limit. 

(1652 lblhr * hr/3600 sec* 453.6 g/lb = 208.2 g/s) 

(DDD 1 Contribution=Total Limit- Existing Kiln Limit= 208.2-180.5=27. 7 g/s) 

Total Indurating Furnace NOx Emissions =New Indurating Furnace+ Existing 

Indurating Furnace 

Page 15 
New Indurating Furnace Emissions= (% Fuel*EFng+% Fuel*EFbio+% Fuel*EFcoal+ 

% Fuei*EFfo) *Pellet Tput *(1-eng efffactor) 

Existing Indurating Furnace Emissions= (%Fuel *EFng+% Fuei*EFcoal) * Pellet Tput 

iii. Baghouses 

PMIO: 

Emission Factor: 0.002 gr/dscf (3-hour averaging time) 

Basis: PM10 BACT limit 

Rated Capacity: Varies (see Attachment B) 

ER = EF * 60 min/hr * lb/7000 gr * RC =Varies (see Attachment B) 

The BACT limit is used with the rated capacity of the individual baghouses to calculate a PM10 

emission rate. 

iv. Mobile Sources, New Large Diesels 

NOx: 

EF: 2.6 g/(hp-hr) (0.82 lb/mmbtu) 

Basis: Diesel Engine, Tier 4 Standard required in 2011 

RC: 72 mmbtu/hr, total proposed new engines 

ER = EF * RC = 59 lb/hr NOx 

(59 lb/hr * hr/3600 sec* 453.6 glib= 7.4 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate a NOx emission rate. Applicable Keetac equipment includes 13 new trucks, 4 new 

shovels, and 1 new loader. 

PM10: 

EF: 1.94E-02 lb/mmbtu 

Basis: Diesel Engine, Tier 4 Standard required in 2011, PM 0.075 g/(hp-hr), convetted to PM10 

by AP-42 ratio. AP-42, 5th Edition, Section 3.4, 10/96, (PM10/PM=0.0573/0.0697) 

Page 16 
RC: 72 mmbtu/hr, total proposed new engines 

ER = EF * RC = 1.4 lb/hr PMw 

(1.4lb/hr * hr/3600 sec* 453.6 g/lb = 0.18 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate an emission rate. 

S02: 

EF: 1.52E-03 lb/mmbtu 

Basis: Diesel Engine, Tier 4 Standard required in 2011, 15 ppm, and 

AP-42, 5th Edition, Section 3.4, 10/96 

RC: 72 mmbtu/hr, total proposed new engines 

ER= EF * RC = 0.1lb/hr S02 

(O.llb/hr * hr/3600 sec* 453.6 g/lb = 0.01 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate a so2 emission rate. 

Page 17 
v. Mobile Sources, New Small Diesels 

NOx: 

EF: 0.3 g/(hp-hr) (0.0945 lb/mmbtu) 

Basis: Diesel Engine, Tier 4 Standard 

RC: 4 mmbtu/hr, total proposed new engines 

ER = EF * RC = 0.4 lb/hr NOx 

(0.4lb/hr * hr/3600 sec* 453.6 glib= 0.05 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate a NOx emission rate. Applicable Keetac equipment includes 4 new dozers and 1 new 

grader. 

PM to: 

EF: 3.15E-03 lb/mmbtu 

Basis: Diesel Engine, Tier 4 Standard required in 2011, PM 0.01 

g/(hp-hr), all PM assumed to equal PMw 

RC: 4 mmbtu/hr, total proposed new engines 

ER = EF * RC = 0.013 lb/hr PM10 

(0.013 lb/hr * hr/3600 sec* 453.6 g/lb = 0.0016 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate a PM10 emission rate. 

S02: 

EF: 1.52E-03 lb/mmbtu 

Basis: Diesel Engine, Tier 4 Standard required in 2011, 15 ppm, and AP-42, 5th Edition, 

Section 3 .4, I 0/96 

RC: 4 mmbtu/hr, total proposed new engines 

Page 18 
2.3.1.2 

ER = EF * RC = 0.01lb/hr SOz 

(0.01lb/hr * hr/3600 sec* 453.6 g/lb = 0.001 g/s) 

The Tier 4 Standard is used with the rated capacity of the proposed new diesel engines to 

calculate a S02 emission rate. Keetac proposes 4 new dozers and 1 new grader. The emission 

calculations are summarized in spreadsheet EICurrent. 

Existing Facility 

Emission factors and associated rates are provided in the following for the applicable emission unit types. 

These rates were used as the basis for calculating emissions used as inputs for the Class I modeling 

i. Induration 

NOx: 

EF Natural Gas: 1.726lb/ston pellet produced 

Basis: Average stack test result from 1 0/15/05 

EF Coal: 0.639 lb/ston pellet produced 

Basis: Average stack test result from 5/31/06 

EF Oil: 0.9918 lb/ston pellet produced 

Basis: Average stack test result from 7/25/00 

RC: 830 tons pellet produced/hr 

ER Natural Gas= EF * RC = 1433 lb/hr NOx 

(1433 lb/hr * hr/3600 sec* 453.6 g/lb = 180.5 g/s) 

ER Coal = EF * RC = 530 lb/hr NOx 

ER Oil = EF * RC = 823 lb/hr NOx 

The most current natural gas stack test emission factor for the existing kiln is used with the 

rated capacity to calculate a NOx emission rate. 

Page 19 
PM to: 

EF Natural Gas: 0.019 gr/dscf(3-hour averaging time) 

Basis: MACT PM limit (0.0 1 gr/dscf) * 1.86 (PM10/PM stack test ratio, 1 0/19/05). 

EF Coal: 0.014 gr/dscf 

Basis: MACT PM limit (0.0 1 gr/dscf) * 1.38 (PM10/PM stack test ratio, 5/31/06). 

EF Oil: 0.019 gr/dscf(3-hour averaging time) 

Basis: MACT PM limit (0.01 gr/dscf) * 1.86 (PM10/PM stack test ratio, 10/19/05). 

RC: 576,000 dscfm 

ER Natural Gas= EF * lb/7000 gr * 60 minlhr * RC = 91.9 lb/hr PM10 

(91.9 lb/hr * hr/3600 sec * 453.6 glib = 11.6 g/s) 

ER Coal= EF * lb/7000 gr * 60 min/hr * RC = 68.1 lb/hr PM10 

ER Oil= EF * lb/7000 gr * 60 min/hr * RC = 91.9lb/hr PM10 

The MACT limit is combined with stack test results to estimate a PM10 emission factor. That 

emission factor is used with the rated capacity of the kiln to calculate a PM10 emission rate. 

The natural gas emission factor which is the highest was used in all modeling runs. 

S02: 

EF Natural Gas: 0.282lb/ston pellet produced (3-hour averaging time) 

Basis: Natural gas stack test, 10/19/2005 

EF Coal: 0.296 lb/ston pellet produced 

Basis: MPCA email, 5/06/2010 

EF Oil: 0.1154 lb/ston pellet produced 

Basis: Oil stack test, 7/25/2000 

RC: 830 tons pellet produced/lu· 

Page 20 
ER Natural Gas= EF * RC = 233.7lb/hr S02 

(233.7lb/hr * hr/3600 sec* 453.6 g/lb = 29.4 g/s) 

ER Coal= EF * RC = 243.2lblhr S02 

(243.2 lb/hr * hr/3600 sec* 453.6 g/lb = 30.6 g/s) 

ER Oil = EF * RC = 95.8 lb/hr S02 

The stack test data was used with the rated capacity to calculate a S02 emission rate. Coal is 

expected to be the worst case fuel for S02 emissions. For prior submittals, the natural gas test 

showed a higher outlet emission rate and was therefore used for the modeled emissions rate 

for all modeling runs. Subsequent comment by MPCA has yielded higher outlet emission 

rates based on coal fueling. This higher rate is therefore used for the modeled emission rate 

for the updated nms in this report. 

SAM: 

Emission Factor: Ratio of SAM to S02 of 0.120 lb SAM/lb S02 emitted 

Basis: SAM stack test while firing natural gas (Minntac,l/13/04). 

S02 ER: 243.2 Ib/hr so2 

EF: 0.120 lb SAM/lb S02 

ER = S02 ER *EF = 29.2lb/hr SAM 

(29.2lb/hr * hr/3600 sec* 453.6 glib= 3.7 g/s) 

The stack test ratio was used with the S02 rate to calculate a SAM emission rate. The highest 

S02 outlet emission rate is therefore used for the modeled SAM emission rate for all 

modeling runs. 

ii. Pellet Cooler 

No combustion products or S02 are expected to be emitted from the pellet cooler 

Page 21 
PM to: 

EF: 10.1 lb/hr (3-hour averaging time) 

Basis: Title V permit limit ( 49 lb/hr) times 0.205 (PM10/PM ratio from United Taconite 

stack test results, 6/15/04 and 4/17/0 I). 

RC: 8760 hours 

ER = EF * RC = 10.1 lb/hr PM10 

(IO.llb/hr * hr/3600 sec* 453.6 g/lb = 1.27 g/s) 

The Title V PM limit is used with the PM10/PM ratio from a similar emission unit to calculate 

a PM10 emission rate. 

iii. Material Handling/Scrubbers 

PM to: 

EF: 0.008 gr/dscf (3-hour averaging time) 

Basis: PM/PM10 MACT limit 

RC: Varies (see Attachment B) 

ER = EF * 60 min/hr * lb/7000 gr * RC =Varies (see Attachment B) 

The MACT limit is used with the rated capacity of the individual baghouses to calculate a 

PM10 emission rate. 

iv. Mobile Sources, Existing Large Diesels 

NOx: 

EF: 3.2lb/mmbtu 

Basis: AP-42, 5th Edition, Section 3.4, 10/96 

RC: 95 mmbtu/hr, total existing engines 

ER = EF * RC = 304 lb/hr NOx 

(304lb/hr * hr/3600 sec* 453.6 g/lb = 38.3 g/s) 

Page 22 
AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a conservative NOx emission rate. Applicable Keetac mobiles include 16 trucks, 6 

shovels, and I loader. 

PM to: 

EF: 0.0573 lb/mmbtu 

Basis: AP-42, 5th Edition, Section 3.4, 10/96 

RC: 95 mmbtu/hr, total existing engines 

E R = EF * RC = 5.44lb/hr PM10 

(5.44lb/hr * hr/3600 sec* 453.6 g/lb = 0.69 g/s) 

AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a PM10 emission rate. 

S02: 

EF: 5.05E-02 lb/mmbtu 

Basis: AP-42, 5th Edition, Section 3.4, 10/96 

RC: 95 mmbtu/hr, total existing engines 

ER = EF * RC = 4.8 lb/hr S02 

(4.8 lb/hr * hr/3600 sec* 453.6 g/lb = 0.6 g/s) 

AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a conservative S02 emission rate. 

v. Mobile Sources, Existing Small Diesel 

NOx: 

EF: 4.41 lb/mmbtu 

Basis: AP42, 5th Edition, Section 3.3, 10/96 

RC: 7.8 mmbtu/hr, total proposed new engines 

E R = EF * RC = 34 lb/hr NOx 

(34 lb/hr * hr/3600 sec* 453.6 g/lb = 4.3 g/s) 

Page 23 
2.3.2 

2.3.2.1 

AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a NOx emission rate. Keetac currently has 7 dozers and 3 graders. 

PM1o: 

EF: 0.31 lb/mmbtu 

Basis: AP42, 5th Edition, Section 3.3, 10/96 

RC: 7.8 mmbtu/hr, total proposed new engines 

ER = EF * RC = 2.4lb/hr PM10 

(2.4 lb/hr * hr/3600 sec* 453.6 g/lb = 0.30 g/s) 

AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a PM10 emission rate. 

S02: 

EF: 0.0505- lb/mmbtu 

Basis: AP42, 5th Edition, Section 3.3, 10/96 

RC: 7.8 mmbtu/hr, total proposed new engines 

ER = EF * RC = 0.4 lb/hr S02 

(0.4lb/hr * hr/3600 sec * 453.6 g/lb = 0.05 g/s) 

AP-42 emission factor is used with the rated capacity of the existing diesel engines to 

calculate a conservative S02 emission rate. 

Pre-Scrubber Facility 

Existing Facility 

i. Induration 

Induration rates and parameters for the Pre-scrubber facility are based on stack 

tests performed in 2000. The emission factor used for NOx was 1.906 lb/ston and 

for S02 was 0.222 lb/ston. These factors are from a 7/25/2000 stack test as 

revised by Hongming Jiang of the MPCA. At the time, the facility was 

Page 24 
exclusively fired on Natural Gas. The induration exhaust was split between the 

two stacks, SV30 and SV31. 

ii. Baghouses 

Baghouses and other non-combustion sources were modeled utilizing the same 

methods as described above in section l.b.ii, with limited exceptions. The 

exceptions include: 

1) Stacks related to the coal handling system are not included in the PreScrubber scenario (SV53,54,57) because they were not installed at that 

time 

2) Existing stacks with projected increased emissions are modeled at their 

original, pre-project emissions. For example, the product loadout (SV65) 

emission rate will increase with the increased pellet production, however, 

the previous production rates were used for the pre-scrubber facility. 

111. Mobile Sources 

Mobile Sources at the mine include Haul Trucks, Loaders, Bulldozers, Shovels, 

and Graders. Emissions are calculated similar to section 1. b.iii., with one 

exception. For the Pre-project scenario, S02 emission factors were used to 

correlate to 5% Sulfur diesel. As noted in the expansion mobile diesel 

discussion, the proposed project will utilize 0.15% Sulfur diesel. 

Page 25 
Table 2. Scenario 1 -Existing Line- Baseline/Pre Scrubber 

NG NG 

24-hr. Max (lbs/hr) Annual Avg. (lbs/hr) 

PM10 so2 NOx PM10 S02 NOx Comments 

Existing Detailed Emission 

Induration 191.53 183.99 1582.08 160.46 154.14 1325.43 Factors in Appendix E 

New 

Induration NA NA NA NA NA NA 

Other PM sources modeled 

Stationary 50.0 0.0 0.0 50.0 0.0 0.0 at PTE 

Existing 

Mobiles 5.2 4.6 230.5 4.5 4.1 203.7 Data from 2007 rates 

New 

Mobiles NA NA NA NA NA NA 

TOTAL 

(lb/hr) 246.7 188.6 1812.6 215.0 158.2 1529.1 

TOTAL 

(tons/yr) 1081 826 7939 942 693 6697 
Table 3. Scenario 2 - Existing Line- Post Scrubber 

Post Scrubber 

NG Coal NG&Coal 

24-hr. Max (lbs/hr) 24-hr. Max (lbs/hr) Annual Avg. (lbs/hr) Comments 

PM10 SOz NOx PM10 SOz NOx PM10 502 NOx 

Existing Detailed Emission 

Induration 75.6 233.7 1432.9 82.1 212.5 530.0 63.2 176.2 723.2 Factors in Appendix E 

New 

Induration NA NA NA NA NA NA NA NA NA 

Other All PM sources 

Stationary 50.0 0.0 0.0 50.0 0.0 0.0 50.0 0.0 0.0 modeled at PTE 

Existing 

Mobiles 5.2 4.6 230.5 5.2 4.6 230.5 4.5 4.1 203.7 Data from 2007 rates 

New 

Mobiles NA NA NA NA NA NA NA NA NA 

TOTAL 

(lb/hr) 130.7 238.3 1663.4 137.3 217.2 760.5 117.7 180.3 926.9 

TOTAL 

(tons/yr) 573 1044 7286 601 951 3331 516 790 4060 
Emission Rate Calculations for Class I Modeling - Kiln Scenario El 

Pollutant Timeframe 

NOx Nov 99 to Oct 01 NOx 24 HR Maximum 

S02 Nov 99 to Oct 01 502 24 HR Maximum 

PM10 Nov 99 to Oct 01 

PM10 24 HR Maximum 

PM2.5, Filterable Only Nov 99 to Oct 01 PM2.5, Filterable Only 24 HR Maximum 

PM2.5, Total Nov 99 to Oct 01 

PM2.5. Total 24 HR Maximum 

PCA. Hongming Jiang. Original data used 1.9841b/s.ton 

PCA. Hongming Jiang, Original data used 0.2308 Ibis. ton 

PCA, Hongming Jiang, Original data used 0.341 lb/s.ton 

Throughput 

10378670 

830 

10378670 

830 

10378670 

830 

10378670 

830 

10378670 

830 

Emission 

Factor 

Units (lb/unit) Unit Basis 

s.ton pellets/yr 1.906 s.ton 7/25/00 Stack Test [1] 

s.ton pellets/hr 1.906 s.ton 7/25/00 Stack Test [1] 

s.ton pellets/yr 0.222 s.ton 7/25/00 Stack Test [2] 

s.ton pellets/hr 0.222 s.ton 7/25/00 Stack Test [2] 

s.ton pellets/yr 0.231 s.ton 7/25/00 Stack Test [3] 

s.ton pellets/hr 0.231 s.ton 7/25/00 Stack Test [3] 

s.ton pellets/yr 0.073 s.ton 9/24/08 Stack Test [4] 

s. ton pellets/hr 0.073 s.ton 9/24/08 Stack Test [4] 

s.ton pellets/yr 0.098 s.ton 9/24/08 Stack Test [4] 

s.ton pellets/hr 0.098 s.ton 9/24/08 Stack Test [4] 

ata from 9/24/2008 stack test used to ratio PM2.5 emission factors from the original PM10 stack test data (7/25/2000) 

AppendixE 

Class I Emission Calculations 

PSD Baseline 

I 

Emission 

Addition Emissions Rate 

Emissions Units (ton/yr) (s.ton/yr) (g/s) 

9891.47 s.ton/yr 35 9926 285.56 

1582.08 lb/hr NA 199.34 

1150.35 s.ton/yr NA 33.09 

183.99 lb/hr NA 23.18 

1197.51 s.ton/yr NA 34.45 

191.53 lb/hr NA 24.13 

377.32 s.ton/yr NA 10.85 

60.35 lb/hr NA 7.60 

510.51 s.ton/yr NA 14.69 

81.65 lb/hr NA 10.29 
Pollutant Timeframe Throughput Units 

Ox, Nat. Gas Average 2006/2007 2427954 s.ton pellets/yr 

Ox, Coal Average 2006/2007 3357352 s.ton pellets/yr 

otal, NOx Average 2006/2007 

Ox, Nat. Gas 24 HR Maximum 830 s.ton pellets/hr 

Ox, Coal 24 HR Maximum 830 s.ton pellets/hr 

02, Nat. Gas Aver'!ge 2006/2007 2427954 s.ton pellets/yr 

02, Coal Average 2006/2007 3357352 s.ton pellets/yr 

otal, S02 Average 2006/2007 

02, Nat. Gas 24 HR Maximum 830 s.ton pellets/hr 02, Coal 24 HR Maximum 830 s.ton pellets/hr 

M10, Nat. Gas Average 2006/2007 2427954 s.ton pellets/yr 

M10, Coal Average 2006/2007 3357352 s.ton pellets/yr 

otal, PM10 Average 2006/2007 

M10, Nat. Gas 24 HR Maximum 830 s.ton pellets/hr 

M10, Coal 24 HR Maximum 830 s.ton pellets/hr 

M2.5, Filterable Only, Nat. Gas Average 2006/2007 2427954 s.ton pellets/yr 

M2.5, Filterable Only, Coal Average 2006/2007 3357352 s.ton pellets/yr 

otal, PM2.5, Filterable Only Average 2006/2007 

PM2.5, Filterable Only, Nat. Gas 24 HR Maximum 830 s.ton pellets/hr 

PM2.5, Filterable Only, Coal 24 HR Maximum 830 s.ton pellets/hr PM2.5, Total, Nat. Gas Average 2006/2007 2427954 s.ton pellets/yr 

PM2.5, Total, Coal Average 2006/2007 3357352 s. ton pellets/yr 

otal, PM2.5, Total Average 2006/2007 

PM2.5, Total, Nat. Gas 24 HR Maximum 830 s.ton pellets/hr 

PM2.5, Total, Coal 24 HR Maximum 830 s.ton pellets/hr 

tion used with 9/24/08 stack test data to ratio to a PM2.5 emission factor 

on used with 9/24/08 stack test data to ratio to a PM2.5 emission factor 

ta from 9/24/2008 stack test, Assumed 80% control 

Emission 

Factor 

(lb/unit) Unit 

1.726 s.ton 

0.639 s.ton 

1.726 s.ton 

0.639 s.ton 

0.282 s.ton 0.256 s.ton 0.282 s.ton 0.256 s.ton 0.091 s.ton 0.099 s.ton 0.091 s.ton 

0.099 s.ton 0.020 s.ton 0.022 s.ton 

0.020 s.ton 0.022 s.ton 0.185 s.ton 0.185 s.ton 

0.185 s.ton 0.185 s.ton 

Modeling 

PSD Baseline Emission 

Addition Emissions Rate 

Basis Emissions Units (ton/yr) (s.ton/yr) (g/s) 

1 0/19/2005 Stack Test 2095.71 s.ton/yr NA 60.29 

5/31/2006 Stack Test 1071.94 s.ton/yr NA 30.84 

3167.65 91.12 

10/19/2005 Stack Test 1432.84 lb/hr NA 180.54 

5/31/2006 Stack Test 530.01 lb/hr NA 66.78 

10/19/2005 Stack Test 341.75 s.ton/yr NA 9.83 

5/31/2006 Stack Test 429.85 s.ton/yr NA 12.37 

771.61 22.20 

10/19/2005 Stack Test 233.66 lb/hr NA 29.44 

5/31/2006 Stack Test 212.54 lb/hr NA 26.78 

10/19/2005 Stack Test 110.54 s.ton/yr NA 3.18 

5/31/2006 Stack Test 166.20 s.ton/yr NA 4.78 

276.74 7.96 

1 0/19/2005 Stack Test 75.57 lb/hr NA 9.52 

5/31/2006 Stack Test 82.18 lb/hr NA 10.35 

10/19/2005 Stack Test [1 24.54 s.ton/yr NA 0.71 

5/31/2006 Stack Test [2] 36.90 s.ton/yr NA 1.06 

61.44 1.77 

10/19/2005 Stack Test [1 16.78 lb/hr NA 2.11 

5/31/2006 Stack Test [2] 18.24 lb/hr NA 2.30 9/24/08 Stack Test [3] 44.87 s.ton/yr NA 1.29 

9/24/08 Stack Test [3] 62.05 s.ton/yr NA 1.78 

106.92 3.08 

9/24/08 Stack Test [3] 30.68 lb/hr NA 3.87 

9/24/08 Stack Test [3] 30.68 lb/hr NA 3.87