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ArcelorMittal Straight-Grate NOx Reduction

Technology Development Efforts

August 11, 2014
Overview

• ArcelorMittal is fully engaged in developing new technology for use at our straight-gra

indurating furnaces.

• ArcelorMittal retained and Clean Combustion & Energy

(“CC&E”) to assess NOx reduction technologies for Minorca’s straight-grate induratin

furnace.

• These efforts were focused on opportunities to reduce thermally generated NOx at

Minorca’s two main combustion chambers and its eight preheat burners. Primary

efforts have included:

– Initial screening of potential NOx reduction alternatives

– Phased development of a robust CFD model of Minorca’s furnace

– Construction of a laboratory scale model furnace to corroborate and refine the CF

modeling results

– Use of the CFD model and laboratory model to assess the NOx, energy and

operating impacts of water injection

• While further assessment is needed, these efforts indicate emerging technologies ca

reasonably be expected to achieve a 70% NOx reduction on a lb/MMBtu basis.

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Investigation Structure

• Phase 1: Main Combustion Chamber Technology Screening

– Developed a Computational Fluid Dynamics (CFD) model of one of the

two “main combustion chambers” and burners on the pelletizing line at

Minorca Mine

• Phase 2: Preheat Burner Modeling and Analysis

– Developed a CFD model for one of eight preheaters at Minorca Mine

– Initial planning for laboratory model to be completed in Phase 3

• Phase 3: Initial Process Impact Study

– Developed complete CFD model of the pelletizing line at Minorca Mine

– Construction of laboratory scale model furnace

– Initial testing with model furnace to help validate CFD model results for

preheat burners

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Phase 1: Main Combustion

Chamber Technology Screening

• A partial CFD model of one main combustion chamber in the

pelletizing line at Minorca Mine was developed. This phased

approach reduced the initial complexity of the calculations.

• As a result, initial screening of technology could now be

completed more efficiently, with greatly reduced calculation

times.

• Several options were screened for potential feasibility.

Among other initial efforts, this included use of the CFD

model to evaluate a modification for pre-combustion staging.

• This analysis, in conjunction with the Phase 2 and 3 work

described below, led us to focus further assessment efforts

on water injection technology.

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Phase 1: Main Combustion

Chamber Model Layout

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Phase 1: Main Combustion

Chamber Technology Screening

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Phase 2: Preheat Burner Modeling

and Analysis

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• Phase 2 involved the development of a CFD model for one of

Minorca’s eight preheat burners.

• Based on the initial screening analysis, this Phase 2 model

was used to investigate water injection technology.

• This assessment was based on the presumed installation of

burners predicted to achieve a 15% initial reduction

from baseline NOx emissions at the preheaters.

• A water injection lance was installed on the centerline of the

burner in the model and atomized water was injected into the

flame zone.

• The water creates an energy sink to drive down peak flame

temperature, thereby reducing NOx.
Phase 2: Preheater Model Baseline

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Phase 2: Modified Preheater

Configuration With Water Injection

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Phase 3: Initial Process Impact

Study

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• Developed a baseline for the complete indurating furnace

• Applied water injection to that complete baseline model

• Initial optimization of design for a potential water injection spray

system:

– Parameters included water spray, droplet size and injection angle

– Droplet size varied using different spray tips and water pressures

• Extended modeled water injection to all eight preheat burners and

both main combustion chambers

• Validated model results using laboratory experimentation

• Began investigating furnace, process and energy impacts from the

application of water injection
Phase 3: Complete Model Layout

East View

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Phase 3: Baseline Model

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Phase 3: Water Injection Applied

to Main Combustion Chambers

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Phase 3: Water Injection Applied

to Main Combustion Chambers

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Phase 3: Preheat Burner Water

Injection

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Phase 3: Baseline Under-Grate

Temperatures

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Phase 3: Under-Grate

Temperatures With Water Injection

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Estimated Baseline NOx Profile

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NOx Profile with Water Injection

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* Reductions measured on a lb/MMBtu basis

* * *
Phase 3: Laboratory Scale

Experimental Design

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Phase 3: Constructed Laboratory

Scale System

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Phase 3: Status and Conclusions

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• Our Phase 3 efforts indicate:

1. NOx can be reduced using water injection in the preheat and main

burners.

2. Water injection is significantly more effective at reducing NOx in the

preheat burners than the main burners.

3. NOx reduction is sensitive to water droplet size and to a lesser extent

the water spray angle.

4. Water injection does impact the furnace temperature profile.

5. Water injection imposes an energy penalty that increases with the

amount of water injected. This energy penalty erodes the overall mass

NOx reduction that can be achieved.

• Process and pellet quality impacts still need further evaluation,

including how the introduction of additional water may impact the

integrity of pellets and affect drying rates. This requires a detailed

review by furnace engineers.
Current and Next Steps: Combined

Technologies and Additional Alternatives

• We are currently evaluating three additional options for NOx

reduction at straight grate furnaces:

– Pre-combustion Optimizations

– Steam Injection

– Multiple Point Injection

• Viability is being evaluated based on:

– NOx reduction potential

– Impacts to pellet quality and process

– Installation and operational downtime

– Energy penalty (including erosion of NOx mass reductions)

– Capital and operating costs

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Current and Next Steps:

Combined Technologies

• Phase 3 efforts showed water injection technology was less

effective at reducing NOx in the main combustion burners than

in the preheat zone.

• This led us to initiate the further investigation of pre-combustio

alternatives for the main chambers using the CFD model.

• This raises the prospect of optimizing NOx reductions using

both water injection in the preheat zone (where it appears mor

effective) and a pre-combustion approach at the main burners.

• The next slide depicts this approach and includes percent

reductions on a lb/MMBtu basis.

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NOx Profile with Combined

Technologies

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* * *

* Reductions measured on a lb/MMBtu basis
Current and Next Steps:

Combined Technologies

• While this initial CFD modeling of combined water spray and

pre-combustion technologies shows potential, substantial

additional work remains to validate these results and assess th

feasibility of this approach.

– NOx reductions came at the expense of an energy penalty,

which must be evaluated to understand the true mass

reduction potential of this approach.

– Impacts to the process (including potential reduction in coole

capacity) must still be evaluated. Detailed review by a

furnace engineer is necessary.

– Pellet quality impacts also need to be evaluated.

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Current and Next Steps: Steam

Injection

• The phase 3 study of water injection indicated more substantia

NOx reductions in the preheat section than the main combustio

chambers.

• One potential reason for this variance is the different distributio

of water in preheaters and main combustion zones.

• Steam injection to the fuel stream has the potential to provide

better mixing in the flame zone and thus increased NOx

reductions where distribution concerns exist.

• Efforts to evaluate this new alternative are at an early stage, a

additional time is needed to assess its viability based on the

criteria described above.

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Current and Next Steps: Multiple

Point Injection

• Another alternative to reduce NOx formation at the main

combustion chambers is through a number of smaller “surface

spray” injectors.

– Involves spraying fuel at several different locations and combusting it

along the inner refractory surface.

– Rapid combustion and radiant heat release from the refractory surfac

is projected to reduce NOx by short reaction residence times and

reduced peak temperatures.

– This approach has the prospect of a reduced energy penalty (which

would avoid eroding mass NOx reductions through increased fuel

combustion).

• As with steam injection, this concept is in the early stages, and we

plan to initiate a modeling feasibility study to evaluate its prospect

based on the criteria discussed above.

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Conclusions

• ArcelorMittal’s straight-grate NOx reduction strategy

combines emerging new technologies for the preheat

burners and main burners.

• Combined modeling indicates these technologies can

reasonably be expected to achieve a 70% NOx reduction

on a lb/MMBtu basis.

• Further assessment is needed to confirm and refine these

results and to assess pellet quality and process impacts.

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