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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-grate indurating furnaces. • ArcelorMittal retained and Clean Combustion & Energy (“CC&E”) to assess NOx reduction technologies for Minorca’s straight-grate indurating 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 CFD 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 can reasonably be expected to achieve a 70% NOx reduction on a lb/MMBtu basis. 2

## 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 3

## 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. 4

## 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

10 • 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

19 * 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 23

## 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-combustion 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 more 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. 24

## NOx Profile with Combined Technologies

25 * * * * 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 the 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 cooler capacity) must still be evaluated. Detailed review by a furnace engineer is necessary.

– Pellet quality impacts also need to be evaluated. 26

## Current and Next Steps: Steam Injection •The phase 3 study of water injection indicated more substantial NOx reductions in the preheat section than the main combustion chambers. • One potential reason for this variance is the different distribution 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, and additional time is needed to assess its viability based on the criteria described above. 27

## 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 surface 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 prospects based on the criteria discussed above. 28

# 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. 29