### NOx Alternative Monitoring Method 11/12/2009 Hibbing Taconite Company (HTC) requests Minnesota Poll ution Control Agency (MPC A) approval to use the following equations to calculate hourly mass emissions of nitrogen oxides (NO x 

### ) for each of its three indurating furnaces (Lines 1 through 3).



### [1] 3 ,2 ,1 ; 4

1 

###   

# 

 

### jQE

i ji j



### W here E j 

### is NO x 

### emissions from the entire furnace of Line j, lb NO x 

### /hr; C ij 

### is the predicted mass emission rate for NO x 

### in the gas stream of Stack i at Line j, lb/hr, the algebraic detail of which can be found in [2] through [4]; Stacks 1 through 4 denote SV 021 through SV 024 for Line 1; SV 028 downward through SV 025 for Li ne 2; SV 029 through SV 032 for Line 3. The following multiple linear regression e quations should be used to calculate C ij


### . )FeTotal(171.66)22Hood(19721.0)Cool2(5925.5)Depth HL(399.18)SWF(064458.07.4607 C nd 1 11   

  )FeWet(737.12)CaO(85.77Fe)Total(59.101)22Hood(17568.0)T Udd(06520.03.6732 C 21 

     )FeWet(122.12)FeTotal(24.5322)Hood(32661.0T) Udd(24631.0)Mspeed(874.133.3846C

31 

  

  )FeTotal(831.8022)od 0.17165(Ho P) .5475(Wex 4)SVen(540.38Gas) S(4258.16.5776 C 4

41  

   

### [2]


##        )FeSat(751.1318 Hood 37644.0T Udd 0.10259 Mspeed 372.16Depth HL5.06713.0801C

12   

   

##        )FeSat(493.4CAF770.218 Hood 247114.0SVen840.24Feed17920.092.856C 2 22  

    

##         18 Hood 29527.0Thru B038051.0PWex 3126.3SWF 0.10228 Gas S0533.176.175C 3

32 

##  

 

  

###         18 Hood 28753.0Mspeed 926.41S WF08543.0SVen 004.32Gas N5379.325.618C 4 4 42  

   

### [3]


##   

#       )FeWet(495.6Silica258.6118 Hood 071846.0Cool24145.1Mspeed 6105.896.29C nd

13 

     

##        )18 Hood(077930.0PWex 5507.2S WF014698.0Gas S1165.1Feed 0.139487 382.190C 2

23 

    

##        GB(6.072T) MD10263.018Hood 208412.0Mspeed 762.41Depth HL9202.617.934C

33 

    

##         CAF9963.418Hood 14823.0P Udd013.30Gas S3162.1Feed 0.28596 04.752C

43      

### [4]

Where,

WF S 1 

### is the water flow rate of the wet sc rubber at Stack 1 (g allons per minute); HL Depth is the furnace hear th layer depth (inches); 2 nd 

### Cool is the second cooling hood pre ssure (inches of water column); Hood 22 is the hood temperature measured at Windbox 22 (degrees Fahrenheit); Total Fe is analyzed for fired pellets (percent); Udd T is the updraft drying (zone) discharg e temperature (degrees Fahrenheit); CaO is analyzed for fired pellets (percent); Wet Fe ++ 

### is wet Fe ++ 

### of concentrate (percent); Mspeed is the linear moving speed of the traveling grate of the i ndurating machine (feet per minute); S Gas is the total nature gas usage of the south firing chamber (thousand cubic feet per hour); Ven S 4 

### is the Venturi differential pressure for the we t scrubber at Stack 4 (inches of water column);Page 2 of 16 

### Wex P is the pressure measured at the windbox exhaust header (inche s of water column); Hood 18 is the hood temperature measured at Windbox 18 (degrees Fahrenheit); Sat Fe ++ 

### is Satmagan Fe ++ 

### , analyzed for concentrate (percent); Feed is the furnace green ball feed rate (wet long tons per hour); Ven S 2 

### is the Venturi differential pressure for the we t scrubber at Stack 2 (inches of water column); CAF is the pressure measured at the cooli ng air fan header (inches of water column); WF S 3 

### is the water flow rate of the wet sc rubber at Stack 3 (g allons per minute); WF S 4 

### is the water flow rate of the wet sc rubber at Stack 4 (g allons per minute); B Thru is the temperature beneath the pellet bed in the firing zone (degrees Fahrenheit); N Gas is the total nature gas usage of the nor th firing chamber (thousand cubic feet per hour); Silica is analyzed for fired pellets (percent); WF S 2 

### is the water flow rate of the wet sc rubber at Stack 2 (g allons per minute); MD Temp is the machine discharge temperature (degrees Fahrenheit); GB is the moisture content of green balls (percent wet basis); Udd P is the pressure measured at the updr aft drying zone (inches of water column);

(Note that some variables in the righ t-hand side of [2] may app ear to be identical to that of [3] and [4]. However, the variables found in [2], [3], and [4] are associated w ith Line 1, Line 2, and Line 3, respectively. With this understanding, the use of subscripts is minimized among the vari ables in the right- hand side of [2] through [4].)

Figures 1, 2, and 3 compare predicted and measured NO x 

### emissions at the furnace level.



## Line 1 NOx (lb/hr): Predicted vs. Measured

R 2 = 0.906

300.00 400.00 500.00

300.00 400.00 500.00

Predicted

Figure 1 . Furnace 1 NO x PredictionsPage 3 of 16


## Line 2 NOx (lb/hr): Predicted vs. Measured

R

2 

### = 0.8666

300.00 400.00 500.00 600.00

300.00 400.00 500.00 600.00

PredictedMeasured

Figure 2 . Furnace 2 NO x Predictions



## Line 3 NOx (lb/hr): Predicted vs. Measured

R

2 

### = 0.9551

200.00 300.00 400.00

200.00 300.00 400.00

PredictedMeasured

Figure 3 . Furnace 3 NO x PredictionsPage 4 of 16 

### Alternative Method Proposals for NO x 

### Emission Monitoring 

### HTC originally submitted three alternative method proposals, one for each indurating furn ace, with its letter to the Minnesota Pollution Control Agency (MPCA) date d June 30, 2008. A CD-ROM was also submitted to provide NO x 

### performance testing results, process operati ng data, and regression modeling detail. The performance testing at Line 2 was conducted first (Oct ober 24 – November 3, 2007), followed with Lines 3 and 1 (March 31 – April 8 and Apr il 9 – 17, 2008, respectively).

For purposes of the modified alternative monitoring method proposal, HTC performe d best subsets regression analysis for each stack with NO x 

### (lb/hr) as the dependent variable and 25 process operating variables as independent variables (predictors); and fitted NO x 

### (lb/hr) with 5 selected pro cess operating variables. In addition, HTC calculated leverage for each st ack, with results summarized in Table 1.

Furnace Line 1 Furnace Line 2 Furnace Line 3

Variable Mean Standard Deviation Variable Mean Standard Deviation Variable Mean Standard Deviation Stack 1 Leverage 0.04027 0.01928 Stack 1 Leverage 0.04225 0.01699 Stack 1 Leverage 0.04580 0.02708

Stack 2 Leverage 0.04027 0.02265 Stack 2 Leverage 0.04225 0.02107 Stack 2 Leverage 0.04580 0.07425

Stack 3 Leverage 0.04027 0.02234 Stack 3 Leverage 0.04225 0.01898 Stack 3 Leverage 0.04580 0.07332

Stack 4 Leverage 0.04027 0.02601 Stack 4 Leverage 0.04225 0.01671 Stack 4 Leverage 0.04580 0.07260

Table 1 . Leverage Calculations for Furnace Lines 1, 2, and 3Page 5 of 16 

### Selection of Predictors for Regression EquationsPage 6 of 16Page 7 of 16Page 8 of 16Page 9 of 16Page 10 of 16Page 11 of 16Page 12 of 16Page 13 of 16Page 14 of 16Page 15 of 16Page 16 of 16