# 1/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821 

# Technical Analysis for applying LNB technology to UTAC L2 Grate Kiln (GK) while minimizing product quality issues

Background Metso, as a designer of grate kiln (GK) indurating technology, was asked to analyze the effects of Low NOx Burner (LNB) technology for the UTAC Line 2 GK process facility at United Taconite Mine in Eveleth, Minnesota while minimizing pellet quality issues. Metso used previously modeled conditions summarized in the March 12, 2014 “Updated Technical Analysis for applying LNB technology to UTAC L2 Grate Kiln (GK)” report. Simulation 4 was used as the base case for comparison since this had the latest operating conditions for the facility while producing quality pellets. Two simulations were performed using hi stoich LNB burners while mitigating product quality as much as possible. Quality issues are affected by changes to airflow, temperature, and pressure. The changes will cause pellet quality issues including, but not limited to, the following. 1. Pellet breakage from increased pressure drop, i.e. increased down forces, across the pellet bed. 2. Pellet breakage from increased drying rate and exploded the pellets from rapid steam escape. 3. Pellet fusing from limited cooling in primary section of cooler. To mitigate these issues, current plant operations, as tested during airflow study from April 30, 2013, were used as a baseline for heat up and cool down profiles and pellet bed pressure drops. Minimizing changes from baseline conditions minimizes but does not eliminate pellet quality effects. While flow, temperature and pressures, referred to as process variables, can be maintained, gas composition cannot. This altered gas composition will affect chemical reactions that rely on specific gas compounds and concentrations. Magnetite oxidation, for example, relies on oxygen to complete the reaction. This simulation does not explore mitigations of pellet quality issues from changes to oxygen levels or other chemical reactions within the furnace. Almost all of the process air in a GK system is introduced thru the cooler. A small amount of air is introduced thru the kiln burner. This process air is then used throughout the system to process pellets as efficiently as possible while making quality pellets. For these simulations cooling air in primary and secondary cooling was maintained to properly cool the pellets and minimize pellet fusing issues. This air was vented to atmosphere where it could not be returned to the process. Since hi stoich LNB burners require greater airflow (115% stoich), i.e. unheated primary air, through the burner compared to current burner designs at 15% stoich, airflow from primary cooling to the kiln had to be reduced to maintain airflow thru the kiln and on to the grate preheat (PH) zone. The grate receives its process gas from two sources, the kiln and recoup gas stream from cooler. These two sources of airflow were maintained. This then allowed the drying heat-up rate on the grate to be matched and maintain pellet bed pressures.

# 2/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821 

# The primary cooling air stream was maintained to properly cool the pellets. 100% of this air normally enters the kiln, since more air is introduced through the kiln burner for hi stoich burner operation, the amount of primary cooling air to kiln was reduced. The remaining unused primary cooling air was vented. This air had to be vented and could not be used as hot recoup air due to its high temperature. The high temperature would lead to broken or exploded pellets from rapid drying. By venting this air it then maintained recoup gas temperature. This would ensure drying rate on the grate was maintained as current conditions dictate. The vented stream heat was not recovered into the kiln; therefore more energy from fuel had to be used to satisfy the process. Since more fuel is burned in the kiln, there are more combustion products, (CO2, H2O, N2) in the kiln gases. The increase in combustion products reduces the concentration of oxygen exiting the kiln and entering the PH zone. For plants processing magnetite ore, this will reduce the magnetite oxidation reaction on the grate. The completion of this reaction will then be pushed to the cooler. Since this reaction is exothermic, i.e. generates heat, there is less reaction heat generated on the grate to heat the pellets, therefore the pellets will discharge into the kiln at a lower temperature Similarly the reaction heat in the cooler will increase pellet temperature above baseline conditions. More cooling air will be required into the cooler to maintain final pellet temperature. This analysis report can be used in conjunction with the previous analysis dated September 14, 2012 and March 12, 2014. For references to flow stream numbers in this document please refer to attached UTAC L2 process flow diagram and UTAC L2 data tables. For reference to zones or equipment in this document refer to UTAC L2 process flow diagram.

# 3/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821 

# Simulations Two new simulations 6 and 7 were created: Simulations 1, 2, and 3 were part of the 2012 report. Simulations 4 and 5 were part of the March 12, 2014 report. Simulation Description Conditions 4 Baseline Updated (April 30, 2013) operating conditions on natural gas fuel with 14.0% stoichiometric primary combustion air 5 115% Stoich Updated operating conditions with 115% stoichiometric primary air.

6 115% Stoich

Mitigation 1 Updated operating conditions with 115% stoichiometric

primary air while mitigating pellet quality issues.

7 115% Stoich

Mitigation 2 Updated operating conditions with 115% stoichiometric

primary air while mitigating pellet quality issues.

All engineering simulations were performed using natural gas fuel, maintaining peak pellet temperature, and maintaining final product temperature. The total air supplied to the cooler was adjusted as needed to maintain final product temperature across all simulations. Maintaining these parameters ensures that fuel changes are not due to altered processing requirements. This study was designed to isolate the effects to various process parameters when applying hi stoich LNB technology to UTAC L2 while minimizing pellet quality challenges. Simulation 4 conditions were simulated for updated operating conditions. Simulation 5 conditions were used to simulate a stoichiometric primary combustion air rate representing updated COEN LNB technology while trying to unsuccessfully balance fuel requirements and pellet quality issues. Simulation 6 conditions were used to simulate hi stoich burner operation while mitigating pellet quality issues. The cooler was modeled as though the cooler primary cooling zone was broken into 2 sub zones. The first sub zone reports secondary combustion air to kiln. The second sub zone is vented to atmosphere. The first sub zone would produce higher air temperatures then the second. Simulation 7 conditions were used to simulate hi stoich burner operation while mitigating pellet quality issues also. The cooler was modeled as though the cooler primary cooling zone was maintained as one zone with only a fraction of the mixed air reporting to kiln as secondary combustion air. The remaining air not sent to kiln is then vented to atmosphere. Since all the primary cooling air is mixed from the entire zone before it is used in the kiln, it will produce lower temperature secondary combustion air to the kiln than simulation 6.

# 4/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821 

# Comparison Analysis The LNB simulations, while mitigating product quality issues, were compared to the base simulation for several key process parameters. NOx emissions values cannot be predicted for LNB simulations due to limited information from burner suppliers and would not be accurate until full scale demonstration testing. Dust generation is affected by pellet heat up and cool down rates. Since heat up and cool down rates are similar to current conditions, dust generations from heat up changes should be minimal. Where dust generation needs to be analyzed is due to lower pellet discharge temperature into the kiln. The lower pellet temperature produces pellets with less strength that can break down in the kiln. Dust emissions (stream 8, 12, 55) were not compared for LNB simulations because of the uncertainty of sensitivity of the pellets. Further testing is required to determine dust generation. Please refer to attached tables and comments. Since most airflow, temperatures, and pressures were maintained for the purpose of minimizing pellet quality issues, the main conclusion is drastically increased fuel rates, green house gases, and particulate release into the atmosphere. Conclusions The comparison of process parameters shows significant operational and environmental impacts as a result of mitigating pellet quality impacts from high stoich LNB installation: 1. Fuel rate is expected to increase between 212% and 220% (stream 36) when incorporating LNB technology at UTAC L2 with 115% stoichiometric air while maintaining current pellet quality. The increase in fuel requirements can be justified from the increase in system losses, i.e. heat generated and not used to satisfy heat requirements of pellets. The increase in system loss is made up in primary cooling vent, secondary cooling vent, and slight increase in grate exhaust gas loss. The primary cooling vent and secondary cooling vent is included in stream 55. 2. Because PH gases from the kiln have less oxygen concentration, the oxidation reaction will slow down. This shifts more reaction heat to the cooler. In order to maintain the same product temperature as current operation more air had to be introduced into the cooler. The existing secondary cooling fan is currently operating at 100% capacity. It does not have available capacity to supply the volume increase requirements. 3. The reduced oxidation heat on the grate as described above produces lower pellet temperatures leaving the grate and entering the kiln. This lower pellet temperature will have to be analyzed to determine if the pellets have sufficient hardness to handle kiln mechanical action without causing pellet breakage. 4. Fuel rate increases will substantially increase green house gases such as CO2 and particulate. CO2 will increase 167%. 5. Cooler vent will increase between 274% and 298%. This will increase the amount of particulate into the atmosphere. 6. The cooler vent is now made up of two streams, partial primary cooling vent and the secondary cooling vent. There currently is not a vent connection for primary section of

# 5/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821 

# the cooler. This would require engineering analysis to determine the location and how to direct this vent stream to atmosphere. It is imperative to fully analyze each GK system when incorporating LNB technology due to the large variability in operating parameters associated with system designs due to feed materials, product specifications, fuels, and burner configurations. Since Minntac’s reduction data is used as the baseline for NOx reduction in EPA’s proposed BART FIP, one must analyze the effects from features such as, feed materials chemical heat addition, i.e. hematite vs. magnetite, low flux vs. high flux, ported kilns and PH burners to determine the NOx reduction that can be achieved in GK systems without these features. Attached: UTAC L2 process flow diagram UTAC L2 Data Table, actual data UTAC L2 Data Table, normalized data

# 6/9

August 07, 2014

Metso Minerals (Pyro Division) , 350 Railorad St. Danville, PA, 17821Criteria Units No. Simulation 4 Simulation 5 Simulation 6 Simulation 7

Production Rate Lton/hr 57
Fuel Rate BTUg/LTon 36 Primary Combustion Air % of stoich 37 13.50 115.00 115.00 115.00 Secondary Combustion Air Temperature (°F) 43 Secondary Air Vol. Flow Rate (ACFM) 43 Grate PH bed air flow SCFM/grate ft2 26
Recoup Gas Temperature (°F) 16 Grate pellet disharge Temperature (°F) 34 Cooler pellet discharge Temperature (°F) 57 Grate pellet oxidation % complete 34 Primary Cooling Air Vol. Flow Rate (ACFM) 40 Primary Cooling Air Pressure (In. H2O) 40 Secondary Cooling Air Vol. Flow Rate (ACFM) 47 Secondary Cooling Air Pressure (In. H2O) 47

DDD Exhaust Gas CO2 (lb/min.) 8 H2O (lb/min.) 8 N2 (lb/min.) 8 O2 (lb/min.) 8 NOx (lb/min.) 8 Dust (lb/min.) 8 Mass Flow Rate (lb/min.) 8 Vol. Flow Rate (SCFM) 8 Vol. Flow Rate (ACFM) 8 Temperature (°F) 8 Heat Content (MBTU/min.) 8 Cooler Stack Gas CO2 (lb/min.) 55
H2O (lb/min.) 55
N2 (lb/min.) 55
O2 (lb/min.) 55 NOx (lb/min.) 55 Dust (lb/min.) 55
Mass Flow Rate (lb/min.) 55
Vol. Flow Rate (SCFM) 55
Vol. Flow Rate (ACFM) 55 Temperature (°F) 55 Heat Content (MBTU/min.) 55Criteria Units No.

Production Rate Lton/hr 57
Fuel Rate BTUg/LTon 36 Primary Combustion Air % of stoich 37 Secondary Combustion Air Temperature (°F) 43 Secondary Air Vol. Flow Rate (ACFM) 43 Grate PH bed air flow SCFM/grate ft2 26
Recoup Gas Temperature (°F) 16 Grate pellet disharge Temperature (°F) 34 Cooler pellet discharge Temperature (°F) 57 Grate pellet oxidation % complete 34 Primary Cooling Air Vol. Flow Rate (ACFM) 40 Primary Cooling Air Pressure (In. H2O) 40 Secondary Cooling Air Vol. Flow Rate (ACFM) 47 Secondary Cooling Air Pressure (In. H2O) 47

DDD Exhaust Gas CO2 (lb/min.) 8 H2O (lb/min.) 8 N2 (lb/min.) 8 O2 (lb/min.) 8 NOx (lb/min.) 8 Dust (lb/min.) 8 Mass Flow Rate (lb/min.) 8 Vol. Flow Rate (SCFM) 8 Vol. Flow Rate (ACFM) 8 Temperature (°F) 8 Heat Content (MBTU/min.) 8 Cooler Stack Gas CO2 (lb/min.) 55 Simulation 4 Simulation 5 Simulation 6 Simulation 7 1.00 1.00 1.00 1.00
1.00 1.61 2.12 2.25
1.00 8.52 8.52 8.52
0.00 102.81 123.43 0.31
1.00 0.65 0.53 0.48 1.00 0.99 1.00 1.01

0.00 510.09 0.25 6.33
0.00 92.91 -33.27 -20.44 0.00 -3.99 -0.79 -0.12
1.00 1.11 0.88 0.89 1.00 0.62 1.05 1.00 1.00 1.00 1.00 1.00
1.00 1.24 1.11 1.13 1.00 1.00 1.14 1.00 1.00 1.37 1.67 1.75 1.00 1.06 1.12 1.14 1.00 0.96 1.00 0.99 1.00 0.91 0.91 0.91
TBD TBD TBD TBD
TBD TBD TBD TBD

1.00 0.97 1.00 1.00 1.00 0.97 1.01 1.01
1.00 1.01 1.02 1.02
0.00 26.80 5.91 6.69
1.00 1.14 1.05 1.06 1.00 1.00 1.00 1.00
H2O (lb/min.) 55
N2 (lb/min.) 55
O2 (lb/min.) 55 NOx (lb/min.) 55 Dust (lb/min.) 55
Mass Flow Rate (lb/min.) 55
Vol. Flow Rate (SCFM) 55
Vol. Flow Rate (ACFM) 55 Temperature (°F) 55 Heat Content (MBTU/min.) 55 1.00 1.58 1.86 1.97

1.00 1.58 1.86 1.97

1.00 1.58 1.86 1.91 1.00 1.00 1.00 1.00
TBD TBD TBD TBD

1.00 1.57 1.86 1.96

1.00 1.58 1.86 1.96

1.00 1.93 2.74 2.98
0.00 246.41 523.30 575.34
1.00 2.30 3.81 4.16 Note: All values except temperatures have been normalized to base simulation. Temperatures are shown as degrees °F change.Criteria Units No.

Production Rate Lton/hr 57
Fuel Rate BTUg/LTon 36 Primary Combustion Air % of stoich 37 Secondary Combustion Air Temperature (°F) 43 Secondary Air Vol. Flow Rate (ACFM) 43 Grate PH bed air flow SCFM/grate ft2 26
Recoup Gas Temperature (°F) 16 Grate pellet disharge Temperature (°F) 34 Cooler pellet discharge Temperature (°F) 57 Grate pellet oxidation % complete 34 Primary Cooling Air Vol. Flow Rate (ACFM) 40 Primary Cooling Air Pressure (In. H2O) 40 Secondary Cooling Air Vol. Flow Rate (ACFM) 47 Secondary Cooling Air Pressure (In. H2O) 47

DDD Exhaust Gas CO2 (lb/min.) 8 H2O (lb/min.) 8 N2 (lb/min.) 8 O2 (lb/min.) 8 NOx (lb/min.) 8 Dust (lb/min.) 8 Mass Flow Rate (lb/min.) 8 Vol. Flow Rate (SCFM) 8 Vol. Flow Rate (ACFM) 8 Temperature (°F) 8 Heat Content (MBTU/min.) 8 Cooler Stack Gas CO2 (lb/min.) 55 Comments
Fuel rate increases for LNB simulation due to increase in unrecovered heat in exhaust gas streams Primary air rate was adjusted to latest COEN estimates for LNB operation Temperature increased for simulaiton 6 hottest air from primary cooling was directed into kiln. Flow rate decreases due to air is displaced by additional primary air requirements for LNB technology. Grate air flow was maintained Recoup gas temperature increases greatly. More testing is required to determine if pellet quality will be effected. Pellet temperature slightly less because of less oxidation
Oxidation less on grate because reduced oxygen concentration Primary Cooling was maintained Cooler area was adjusted to match pressure. Volumetric flow rate increases. More cooling required because oxidation reaction shiftd to cooler Cooler area was adjusted to match pressure. Increased due to increase in fuel rate.

Nox generation values not available from burner supplier Dust generation is effected by pellet heat up rate. Further testing required
Volume increased due to higher temperatures. Fan performance must be evaluated. Temperature increased leading to increase in unrecovered heat leaving the system.
Increase in unrecovered heat. Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge H2O (lb/min.) 55
N2 (lb/min.) 55
O2 (lb/min.) 55 NOx (lb/min.) 55 Dust (lb/min.) 55
Mass Flow Rate (lb/min.) 55
Vol. Flow Rate (SCFM) 55
Vol. Flow Rate (ACFM) 55 Temperature (°F) 55 Heat Content (MBTU/min.) 55 primary cooling required to maintain cooler pellet discharge temperature. Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge temperature. Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge temperature. Dust generation is effected by pellet heat up rate. Further testing required Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge temperature. Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge temperature. Air flow rate increased to compensate for reduced air flow to primary cooling required to maintain cooler pellet discharge temperature. Temperature increased leading to increase in unrecovered heat leaving the system. Increase in unrecovered heat. Note: All values except temperatures have been normalized to base simulation. Temperatures are shown as degrees