NOx Formation/CEMs 

Avoidance Team

Project Leader: John Hausman

February 28, 2008
1
VOC / VOB

Voice of the 

Agency

Regional 

Haze Rule from 

EPA.

Known NOx 

emissions levels 

to determine 

major 

contributors to 

NOx formation.

Key Agency 

Issues

NOx 

emissions on 

Iron Range

EPA 

restrictions on 

MPCA

No 

continuous data 

to determine 

Critical Agency 

Reqs

Way to 

continuously 

monitor NOx 

formation in 

indurating 

process.

Install CEMs 

on all 12 stacks.

Reduce 

Critical 

Business Reqs

Product 

Quality

Maintenance 

Costs

Installation 

Costs

Key Business 

Issues

 Increased 

maintenance 

costs ($/ton) 

spent to repair 

the CEMs.

Availability of 

CEMs and effect 

on MPCA 

reporting if 

installed.

Voice of the 

Business

To maintain 

the availability 

of the CEMs 

would be 

difficult. 

Increased 

electrical 

manpower to 

install CEMs.

2

NOx formation.

Known NOx 

emissions levels 

to impose an 

operating limit. 

to determine 

major 

contributors to 

NOx formation 

in indurating 

process. 

Reduce 

overall NOx 

emissions on 

the Iron Range.

RVI < 0.20

STD (resid) / 

Mean (data) < 

0.09 for 

regression. 

installed.

Manpower to 

install CEMs is 

limited.

Cost of CEMs 

($1.65M up front 

costs)

Decreased 

(decreased 

product quality) 

gas flow to 

reduce NOx 

emissions if NOx 

emissions limit is 

required of HTC. 

install CEMs.

Take 

employees from 

working on 

other project to 

maintain CEMs

$1.65M to 

install CEMs 

would increase 

operating costs 

by a significant 

amount and 

CEMs have no 

proven 

effectivness in 

dirty conditions.
Explanation of Agency Requirements

 RVI < 0.20

 “...will be quantified by a RVI defined by the MPCA as 

the ratio of the width of a 95% prediction interval to the 

center of the interval.” 

 STD (resid) / Mean (actual data) < 0.09

3

 “...the residual standard deviation of the random 

differences between the actual measured concentration 

and the regression equation predicted value divided by 

the average NOx concentration is less than or equal to 

0.09 at the midpoint of the predicted concentration.”

* Taken from the Administrative Order given to HTC from the MPCA.
SIPOC

Customers

Transfer House

PLO

MPCA

Process

Outputs

Fired Pellets

Stack Exhaust 

Gasses (1,2,3,4)

Inputs

Green Balls

Moisture

Natural Gas

Reaction Heat

Cooling Air

Suppliers

Concentrator

Balling Drums

4

Balling Down Draft 

Drying

Preheat/Prefiring Firing

Drying Zone Cooling
Initial Financial Impact

Cost Avoidance for not Installing CEMs 

$1.65 Million

Cost Avoidance for Mechanical/Electrical Reliability of 

CEMs

No estimate

DCS Tie-in Cost Avoidance

5

No estimate
6
Quick Win Opportunities

Regression Quick Win was denied by MPCA for the reason 

of not enough data to prove NOx formation equation. 

MPCA determined that we would at least need a 7 day 

stack test (on all stacks) with varying furnace conditions 

to have enough data.

Have data from 7 day stack test performed from 

7

October 25th – November 3rd, 2007.

Regulations set by MPCA

» RVI < 0.20 means that no continuous data is 

needed

» RVI > 0.20 means that continuous data is required.