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

Technical Analysis for Tilden I Phase III additional 

simulations while applying COEN LNB technology. 

Background 

Simulations 8 thru 11 are newly created simulations. This document provides an overview 

comparative analysis of simulations 8 thru 11, which is Phase III study for Tilden furnaces. 

Simulations 1 thru 3 were created in 2012 as part of Phase I study and were analyzed in a 

previous document. Simulations 4 thru 7 were created and analyzed in a previous 

document in 2013 as part of Phase II study. This document is created for the analysis of 

simulations 8 thru 11. This purpose of this analysis to use current operating data and apply 

it using the latest COEN LNB design conditions required for NOx reduction. Refer to COEN 

report titled “ Final report for Tilden Line 1 (T-1)” for design condition details. 

Simulations 

Phase Simulation Description Conditions 

1 1 Baseline Current operating conditions on natural gas fuel 

with 15.5% stoichiometric primary combustion air 

1 2 100% Stoich Current conditions with 110% stoichiometric primary 

combustion air along with adjusting cooler airflow to 

maintain 1150 °F recouperation (recoup) 

temperature. See stream number 27.

1 3 110% Stoich Current conditions with 100% stoichiometric primary 

combustion air along with adjusting cooler airflow to 

maintain 1150 °F recoup temperature. 

2 4 100% Stoich Current conditions with 100% stoichiometric primary 

combustion air along with adjusting primary cooling 

and recoup airflow airflow to maintain same UDD 

and DDD exhaust gas volume flow. Grate UDD and 

DDD on gas temperatures were maintained the 

same as baseline simulation 1. 

2 5 100% Stoich Current conditions with 100% stoichiometric primary 

combustion air along with adjusting primary cooling 

and recoup airflow airflow to minimize fuel 

consumption.

2 6 100% Stoich Current conditions with 100% stoichiometric primary 

combustion air along with increasing primary cooling 

and recoup airflow airflow by 10% above the flow 

established in Simulation 6.
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 January 13, 2015 

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

Phase Simulation Description Conditions 

2 7 100% Stoich Current conditions with 100% stoichiometric primary 

combustion air along with increasing primary cooling 

and recoup airflow airflow by 20% above the flow 

established in Simulation 6.

3 8 New Gas 

Baseline 

Current operating conditions on 100% natural gas 

as measured and analyzed during the May 23, 2013 

airflow study. 

3 9 COEN Gas 

Stoich Design 

Starting with new gas baseline simulation 8 and 

adjust for latest COEN design information contained 

in report title” COEN final report report for Tilden 1 

(T-1). The design data from COEN for 100% natural 

3 10 New Coal/Gas 

Baseline 

Current operating conditions on 76% coal and 24% 

natural gas as measured and analyzed during the 

June 14, 2012 airflow study. 

3 11 COEN Coal 

Stoich Design 

Starting with new coal/gas baseline simulation 10 

and adjust for latest COEN design information 

contained in report title” COEN final report report for 

Tilden 1 (T-1). The design data from COEN for 

All engineering simulations were developed by holding several of the key process 

parameters used for Simulaton 8 thru 11. The process parameters held were production 

rate of pellets, % green ball moisture, bentonite, flux rate. . 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. Holding these key process parameters also allows for 

comparison to previous simulations 1 thru 7. 

Comparitive Analysis 

Two comparison sets are analyzed. One set for comparing baseline gas with COEN 

LNB gas (simulation 8 compared to 9) and another set for comparing baseline coal with 

COEN LNB coal operation (simulation 10 compared to 11). Data values stated in below 

conclusions will have 8 and 9 values first followed by 10 and 11. 

The LNB COEN simulations were compared to the baseline simulation for several key 

process parameters. NOx emissions values cannot be predicted for COEN 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. Dust emissions (stream 12, 24, 65) were not compared for COEN simulations 

because of the uncertainty of sensitivity of the pellets. Further testing is required to 

determine dust generation. Please refer to attached tables for more comparisons and 

comments. 

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

The comparison values when stated below are stated for gas comparison and then coal 

comparison respectively. The comparison of key process parameters shows a number of 

significant operational and environmental impacts as a result of COEN LNB installation: 

1. Fuel rate is expected to increase 28% and 21%(stream 46) when incorporating LNB 

technology at Tilden I. The fuel rate increase is due to increased heat content in exhaust 

gases, i.e. heat generated but not used to processing pellets. The increase in unheated 

primary combustion air to the burner will require an increase in fuel to replace the heat 

not used from heated secondary combustion air. 

2. A fuel rate increase is also shown between gas firing and coal firing in the kiln. The coal 

firing requires coal grinding mill air be supplied to the kiln burner This amount of air 

accounts for 47% of stoichiometric air requirements as compared to gas firing where 

only 16% stoichiometric air is supplied to kiln burner. The fuel rate between base coal 

firing and gas firing increases 11% due to this. This same phenomenon is the one that 

causes fuel rate to increase when applying COEN LNB burners to Tilden I. The 

significant increase in burner primary air alters the thermal heat balance of the system 

that requires more fuel to be used. 

3. The pellet heat up rate is more aggressive using the LNB simulations. If testing confirms 

that detrimental pellet quality issues occur as a result, it will be necessary to blend 

outside air to reduce process gas temperatures in order to mimic a heat up rate closer to 

the base rate. This additional outside air will increase fuel rate further by increasing heat 

content in exhaust gases further. 

4. The Down Draft Drying (DDD) (stream 24) exhaust gas volumes increased by 20% and 

14% due to higher temperatures and increased air flow rates through the grate. The 

fans that move the DDD exhaust will see an increase in kilowatt usage by the percent 

of additional volume along with additional pressure requirements due to larger pressure 

losses in handling the extra volume. Computational Fluid Dynamics (CFD) modeling of 

process ducts is required to predict pressure requirements from handling the additional 

process air. The modeling will help determine if existing fan capacity can handle the 

increased volume and pressure requirements. 

5. Burner primary air rate increased 709% and 247%. This increase was due to the 

COEN LNB burner requirements of 112% and 116% stoichiometric air rate 

requirements. The burner primary air rate increase is 40% and 35% of the base 

primary cooling air. Since the burner primary air rate is such a large portion of the 

primary cooling the primary cooling air had to be reduced to accommodate the rest of 

the system.. See below for more explanation. 

6. Primary cooling air rate decreased 55% and 60%. This was due to the increase in kiln 

burner primary air rate. The grate and process fans that receive this process gas 

stream cannot handle the increase in gas flow by using same base primary cooling air 

rate along with additional burner primary air rate. 

7. The split of cooling air between primary and secondary cooling will change drastically. 

Although the same amount of total process cooling air to cool the product is required for 

LNB technology, the split of cooling air between the zones in the cooler will change. This 
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Metso Minerals (Pyro Division), 350 Railorad St. Danville, PA, 17821 

change in cooling air split will alter the cooling down cycle of the pellets. Altering the cool 

down cycle may affect pellet quality and dust generation. Secondary cooling air will 

increase while primary cooling air is decreased to accommodate LNB technology 

requirements of high burner primary air. Evaluation of the secondary cooling air fan will 

determine if it can handle the increased flow requirements. 

8. The drastic change of the split between primary and secondary cooling will require rezoning 

of the cooler air. Secondary cooling air has increased so much from original design area 

that the velocity of cooling air through the pellet bed will start to fluidize the pellets. 

Fluidized pellets in the cooler lead to hot spots, thermal inefficiencies, and safety issues 

from handling hot pellets. The increased velocity requires higher underbed pressure to 

supply this increased airflow through the original area. The secondary cooling underbed 

windbox pressure will increase above ” WC while the primary cooling pressure drops to 

around ” WC. The imbalance of pressure between primary and secondary cooling along 

with the high secondary cooling air velocity require the cooler area to be rezoned. When 

rezoning the cooler the location of the gas off-takes such as parallel flow duct, recoup duct, 

cooler stack will have to relocated. 

9. Secondary cooling air exiting the cooler vent stack is projected to increase between 415% 

and 360%. This increase in volume of air required to maintain total cooling air will exit the 

cooler vent stack (stream number 65). The collateral impact to the process, pellet quality, 

and a potential increase in dust loading, will be an important variable to assess during the 

full scale demonstrations. 

10. Dust emissions from UDD and DDD exhaust gas are expected to increase. Dust emissions 

increases will be contributable to two key process changes with LNB technology: process 

dust generation from altered heat up rate and gas cleaning equipment efficiency due to gas 

volume increase through the equipment. The higher volumes of air through the gas cleaning 

equipment increases velocities which may stress existing cleaning systems and may 

decrease cleaning efficiency. 

11. Process dust generation from altered heating and cooling rates may change the dust 

loading to UDD and DDD exhaust gas cleaning equipment. Changes to dust loading at the 

gas cleaning equipment may increase the burden on control equipment and may change 

stack particulate emissions. Process dust generation is not predictable until the sensitivity of 

pellets has been tested. Since the heat-up and cool down profile will change with LNB 

technology, it is expected that dust loading to the control equipment may increase. 

Evaluation of gas cleaning equipment is required to predict exhaust particulate. 

12. Process gas (secondary combustion air) flow rates and temperatures entering the kiln from 

the primary cooling zone will be affected. Individual Computational Fluid Dynamics (CFD) 

analysis is required to fully understand the effects of LNB technology on kiln burner 

combustion zone because each GK system has unique temperatures, flow rates, velocities, 

and blends between the two ports. Expected impacts include but are not limited to: flame 

temperature profile, heat release curve, products of combustion rates, pollutant formations 

such as NOx, and CO. Since GK systems are custom designed, an individual furnace 

analysis is crucial to determine what effects will occur when applying LNB technology. 
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 January 13, 2015 

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

13. LNB technology alters heat up profile. It is recommended that testing and analysis be 

performed to determine what product quality issues are affected. Without further testing 

Metso, as a designed of GK systems, cannot guarantee the effects to product quality and 

production rate without more in depth study. 

14. LNB burner technology alters flame temperature profile. This flame temperature profile is 

critical to obtaining proper time at temperature to produce pellets of proper qualities. The 

final sintering properties are very sensitive to peak temperature and time at temperature. 

Altering the flame temperature profile from the typical grate kiln temperature profile will alter 

pellet sintering quality. Metso cannot predict pellet quality changes due to flame temperature 

profile changes. 

15. The increase in fuel requirements can be shown by the data in the heat loss rows Exhaust 

Gas Heat Loss, Grate Chain Heat Loss, and Total of these two rows. It is shown that the 

lower heat loss correlate to lower fuel rate. The cooler product discharge heat loss is equal 

for all simulations, therefore this heat loss was not shown. One of the goals of the 

simulations was to maintain product discharge temperature. 

16. Increasing heat recovery from the cooler into the process does not always lead to lower fuel 

rates. The increased cooler heat recovery has to be recovered in kiln or grate in order for 

this to lower fuel rates. Passing the increased recover heat into the exhaust gases will not 

improve fuel rate. Process gas heat transfer in the grate bed is more efficient at higher 

temperatures and less mass as compared to lower temperatures and more mass if both 

carry the same amount of heat. 

17. Kiln exit gas temperature was maintained at for all simulations. Because the flame pattern, 

heat release curve, length, etc is not known for LNB kiln burner combustion, the kiln heat 

transfer model was not adjusted for different flame characteristics. 

18. DDD2 Grate on gas temperatures defined in base simulations is known to produce quality 

pellets. All LNB simulations have higher temperatures ϶F and ϶F. Some testing is 

required to determine the effect of this higher temperature on pellet quality. 

19. NOx emissions on a MMBTU basis is expected to decrease from 74% (4.6 to 1.2) but NOx 

be dispersed into the environment will only decrease by 66%. 

Final Conclusions 

The comparative analysis for Phase III of the applying Low NOX technology to Tilden I furnace 

shows similar conclusions as Phase I and Phase II. Using actual design parameters from the 

COEN report titled “Final report for Tilden Line 1 (T-1)” only solidifies the many obstacles, 

performance degradation, fuel penalty, energy penalties already mentioned in previous 

Phase I and Phase II analysis. Phase I and Phase II analysis was based on preliminary 

design information, while Phase III uses vendor required design parameters to meet Low 

NOx operation. 

Attached: 

Tilden I process flow diagram 

Tilden I Data Table, actual data 

Tilden I Data Table, normalized data 
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Metso Minerals (Pyro Division), 350 Railorad St. Danville, PA, 17821 
Simulation 8 Simulation 9 Simulation 10 Simulation 11

Criteria Units No. Actual Actual Actual Actual

Production Rate Lton/hr 67

Fuel Rate BTUg/LTon 46

Primary Air % of stoich 47 15.80 112.00 47.01 116.00

Primary Air lb/min 47

Secondary Air Temperature (°F) 45

Primary Cooling Air lb/min

Secondary Cooling Air lb/min

Secondary Air

Vol. Flow Rate 

(ACFM) 45

Grate PH bed air flow SCFM/grate ft2 36

Recoup Gas Temperature (°F) 27

DDD2 On Gas Temperature (°F) 

Grate pellet disharge Temperature (°F) 44

Cooler pellet discharge Temperature (°F) 67

Exhaust Gas Heat Loss

Heat Content 

(MBTU/min.) 12,24,65

Grate Chain Heat Loss

Heat Content 

(MBTU/min.)

Total

Heat Content 

(MBTU/min.)

UDD Exhaust Gas CO2 (lb/min.) 12

H2O (lb/min.) 12

N2 (lb/min.) 12

O2 (lb/min.) 12

SO2 (lb/min.) 12

NOx (lb/min.) 12

Dust (lb/min.) 12

Mass Flow Rate 

(lb/min.) 12

Vol. Flow Rate 

(SCFM) 12

Vol. Flow Rate 

(ACFM) 12

Temperature (°F) 12

Heat Content 

(MBTU/min.) 12

DDD Exhaust Gas CO2 (lb/min.) 24

H2O (lb/min.) 24

N2 (lb/min.) 24

O2 (lb/min.) 24

SO2 (lb/min.) 24

NOx (lb/min.) 24

Dust (lb/min.) 24

Mass Flow Rate 

(lb/min.) 24

Vol. Flow Rate 

(SCFM) 24

Vol. Flow Rate 

(ACFM) 24

Temperature (°F) 24

Heat Content 

(MBTU/min.) 24

Cooler Stack Gas CO2 (lb/min.) 65

H2O (lb/min.) 65

N2 (lb/min.) 65

O2 (lb/min.) 65

SO2 (lb/min.) 65

NOx (lb/min.) 65

Dust (lb/min.) 65

Mass Flow Rate 

(lb/min.) 65

Vol. Flow Rate 

(SCFM) 65

Vol. Flow Rate 

(ACFM) 65

Temperature (°F) 65

Heat Content 

(MBTU/min.) 65

Note: No. denotes stream flow number for Tilden I 
Criteria Units No.

Production Rate Lton/hr 67

Fuel Rate BTUg/LTon 46

Primary Air % of stoich 47

Primary Air lb/min 47

Secondary Air Temperature (°F) 45

Primary Cooling Air lb/min

Secondary Cooling Air lb/min

Secondary Air

Vol. Flow Rate 

(ACFM) 45

Grate PH bed air flow SCFM/grate ft2 36

Recoup Gas Temperature (°F) 27

DDD2 On Gas Temperature (°F) 

Grate pellet disharge Temperature (°F) 44

Cooler pellet discharge Temperature (°F) 67

Exhaust Gas Heat Loss

Heat Content 

(MBTU/min.) 12,24,65

Grate Chain Heat Loss

Heat Content 

(MBTU/min.)

Total

Heat Content 

(MBTU/min.)

UDD Exhaust Gas CO2 (lb/min.) 12

H2O (lb/min.) 12

N2 (lb/min.) 12

O2 (lb/min.) 12

SO2 (lb/min.) 12

NOx (lb/min.) 12

Dust (lb/min.) 12

Mass Flow Rate 

(lb/min.) 12

Vol. Flow Rate 

(SCFM) 12

Vol. Flow Rate 

(ACFM) 12

Temperature (°F) 12

Heat Content 

(MBTU/min.) 12

DDD Exhaust Gas CO2 (lb/min.) 24

H2O (lb/min.) 24

N2 (lb/min.) 24

O2 (lb/min.) 24

SO2 (lb/min.) 24

NOx (lb/min.) 24

Dust (lb/min.) 24

Mass Flow Rate 

(lb/min.) 24

Vol. Flow Rate 

(SCFM) 24

Vol. Flow Rate 

(ACFM) 24

Temperature (°F) 24

Heat Content 

(MBTU/min.) 24

Cooler Stack Gas CO2 (lb/min.) 65

H2O (lb/min.) 65

N2 (lb/min.) 65

O2 (lb/min.) 65

SO2 (lb/min.) 65

NOx (lb/min.) 65

Dust (lb/min.) 65

Mass Flow Rate 

(lb/min.) 65

Vol. Flow Rate 

(SCFM) 65

Vol. Flow Rate 

(ACFM) 65

Temperature (°F) 65

Heat Content 

(MBTU/min.) 65

Simulation 8 Simulation 9 Simulation 10 Simulation 11 Comments

Normalized Normalized Normalized Normalized

1.00 1.00 1.00 1.00

System flow resistance and existing fan characteristics to be 

evaluated to determine if production rate can be maintained

1.00 1.28 1.00 1.21

Fuel rate increases for LNB simulation due to increase in 

unrecovered heat in exhaust gas streams

1.00 7.09 1.00 2.47

Primary air rate was adjusted to represent a reasonable 

range of primary air for LNB technology

1.00 9.10 1.00 3.09

Primary air rate was adjusted to represent a reasonable 

range of primary air for LNB technology

0.00 326.86 0.00 286.72

Temperature increased greatly due to decreased air flow 

through primary cooling zone.

1.00 0.55 1.00 0.60

Primary cooling decreases due to increase in LNB burner 

primary air rate.

1.00 1.50 1.00 1.54

Secondary cooling increases to maintain final product 

temperature

1.00 0.63 1.00 0.66

Flow rate decreases due to air is displaced by additional 

primary air requirements for LNB technology.

1.00 0.96 1.00 0.96

Simulation 3 airflow was increased to reduce "Recoup Gas" 

temperature

0.00 568.83 0.00 509.19

Recoup gas temperature increases greatly. More testing is 

required to determine if pellet quality will be effected.

0.00 569.15 0.00 509.50

0.00 56.02 0.00 41.09

Temperature increased leading to higher grate chain 

temperatures and degraded chain life.

0.00 -5.88 0.00 -0.83

1.00 1.69 1.00 1.47

This is total heat leaving with UDD, DDD and cooler stack 

exhaust.

1.00 1.63 1.00 1.32 This is estimated heat loss from grate chain. The 

1.00 1.68 1.00 1.45

1.00 0.96 1.00 1.19

1.00 1.08 1.00 1.13

Increased due to higher percentage of drying occuring in UDD 

zone. 

1.00 0.91 1.00 1.10

1.00 0.84 1.00 1.07

TBD TBD TBD TBD

TBD TBD TBD TBD Nox generation values not available from burner supplier

TBD TBD TBD TBD

Dust generation is effected by pellet heat up rate. Further 

testing required

1.00 0.92 1.00 1.10

1.00 0.93 1.00 1.10

1.00 0.95 1.00 1.11

Volume increased due to higher temperatures. Fan 

performance must be evaluated.

0.00 16.82 0.00 7.24

Temperature increased leading to increase in unrecovered 

heat leaving the system.

1.00 1.02 1.00 1.15 Increase in unrecovered heat.

1.00 1.30 1.00 1.20 Increased due to increase in fuel rate.

1.00 1.04 1.00 0.98

1.00 1.04 1.00 1.06

1.00 1.00 1.00 1.04

TBD TBD TBD TBD

TBD TBD TBD TBD Nox generation values not available from burner supplier

TBD TBD TBD TBD

Dust generation is effected by pellet heat up rate. Further 

testing required

1.00 1.04 1.00 1.05

1.00 1.04 1.00 1.05

1.00 1.20 1.00 1.14

Volume increased due to higher temperatures. Fan 

performance must be evaluated.

0.00 105.17 0.00 64.60

Temperature increased leading to increase in unrecovered 

heat leaving the system.

1.00 1.59 1.00 1.31 Increase in unrecovered heat.

1.00 1.00 1.00 1.00

1.00 3.15 1.00 3.10

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

1.00 3.15 1.00 3.10

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

1.00 3.15 1.00 3.10

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

TBD TBD TBD TBD

TBD TBD TBD TBD

TBD TBD TBD TBD

Dust generation is effected by pellet heat up rate. Further 

testing required

1.00 3.14 1.00 3.09

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

1.00 3.15 1.00 3.10

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

1.00 4.15 1.00 3.60

Air flow rate increased to compensate for reduced air flow to 

primary cooling required to maintain cooler pellet discharge 

temperature.

0.00 186.54 0.00 115.17

Temperature increased leading to increase in unrecovered 

heat leaving the system.

1.00 13.89 1.00 5.11 Increase in unrecovered heat.

Note: All values except temperatures have been normalized to base simulation. Temperatures are shown as degrees