MINNTAC AGGLOMERATOR SULFUR BALANCE

Coleraine Minerals Research Laboratory

June 21, 1994

Natural Resources Research Institute University of Minnesota, Duluth 5013 MillerTrunk Highway Duluth, MN 55811 By:

# Un~ .c 

# f"John

# 'Engser Scientist

Approved

# by:~~~L~ .:> Ro y 

### L. Bleif ss Assistant Director

### 1 

## I

TABLE OF CONTENTS
INTRODUCTION
.....................................................1 TEST PROGRAM AND PROCEDURES
......................................1 Sampling
....................................................1 Analytical Procedures
.......................................2 Sulfur Balance
..............................................2 DISCUSSION OF RESULTS
............................................3 Acid Pellet Production Tests
................................3 Natural Gas Line 6 Test
..................................4 Natural Gas Line 4 Tests
.................................4 Wood-Natural Gas Line 4 Tests
............................4 Fluxed Pellet Production Tests
..............................5 Natural Gas Test
.........................................5 Coal-Natural Gas Tests
...................................5 Induration Sulfur Sources
...................................6 Green Ball Sulfur
........................................6 Fuel Sulfur
..............................................7 Pellet Sulfur
...............................................7 Sulfur Removal by the Scrubber
..............................8 Atmospheric Sulfur Emissions
................................8 CONCLUSIONS
......................................................9

### Number
1 2 3 4 5 6 7



### Number

1 

### 2 3 4 5 6 7 8 

### 9 10 List of Tables
Title
Minntac Taconite Pellet Induration Sulfur Balance.**~nntac** 

### Taconite Pellet Induration Sulfur Balance.**~nntac** 

### Agglomerator Samples

- Fluxed Pellet Production. Minntac Agglomerator Samples

- Acid Pellet Production. Sulfur Sources 

### in Green Balls

- Fluxed Pellet Production. Sulfur Sources 

### in Green Balls

- Acid Pellet Production. Minntac Agglomerator Feed Rates, Recycle Rates, Production Rates and Fuel Usage Rates.

List of Figures
Title
Sulfur Balance Acid Pellet Production Line 6 Nov 3, 1993 Sulfur Balance Acid Pellet Production Line 4 Mar 30, 1994 Sulfur Balance Acid Pellet Production Line 4 April 12, 1994 Sulfur Balance Acid Pellet Production Line 4 April 13, 1994 Sulfur Balance Acid Pellet Production Line 4 April 1, 1994 Sulfur Balance Acid Pellet Production Line 4 April 4, 1994 Sulfur Balance Acid Pellet Production Line 4 April 11, 1994 Sulfur Balance Fluxed Pellet Production Line 6 Mar 11, 1994 Sulfur Balance Fluxed Pellet Production Line 6 Mar 15, 1994 Sulfur Balance Fluxed Pellet Production Line 6 Mar 16, 1994INTRODUCTION The production of sulfur dioxide during the induration of taconite pellets is an environmental concern. The sulfur is introduced into the firing process through the taconite concentrate, the fluxstone, the bentonite clay, the water in the green balls, and the fuel. Mr L. Salmela of USX-Minntac, requested that the University of Minnesota
- Coleraine Minerals Research Laboratory (CMRL) perform induration-sulfur balances during the production offluxed pellets and acid pellets while natural gas, coal and wood were being used as the induration fuels.
TEST PROGRAM AND PROCEDURES The scope ofthe program involved sampling and analysis of all the feed streams entering the induration process. It also involved sampling and analysis of the emission (waste) gas and water streams exiting the induration process and the final pellet product. The feed streams that were sampled during acid pellet production included taconite green balls, fuel (coal or wood), filtrate water, scrubber feed water and bentonite clay. Feed streams sampled during fluxed pellet production includedtaconite green balls, fuel (coal orwood), filtratewater, scrubberfeedwater, bentoniteclayandfluxstoneslurry. Samples of the scrubber exit water were taken during each test. The waste gas entering the scrubber and the waste gas exiting the scrubberwere continuously analyzed for sulfur dioxide, oxygen, carbon dioxide and carbon monoxide using CMRL's self contained emission monitoringtrailer. Minntacpersonnelperformedpitot-traverseteststodetermine the emission gasflows foreach test. The natural-gasfuel was notsampled oranalyzed. The two recycle streams that are present in the process are the green ball recycle and the chip regrind recycle. The green ball recycle stream was not sampled. This recycle stream is removed from the feed before any volatilization or oxidation of the sulfur can take place and therefore should contain the same quantity of sulfuras the green balls. Thechip regrind recycle was sampled and analyzed. Chip regrind pellets are pelletsthat have been dried and partially fired in the preheat zone and therefore, could contain a different amount of sulfur than the green balls. Sampling. All ofthe green ball, chip regrind, fluxstone slurry, bentonite, water, pellet, and fuel sampleswere grab samples. The emission gas sampling and analysis was perform bythe analytical instrumentation in the analytical trailer. Analytical readings weretaken and recorded by a computer every 3 minutes. The emission gas was pumped into the gas analysis trailer through a 200 foot long heated umbilical cord. The temperature of the umbilical cordwas maintained at 180 degrees Fahrenheit so that moisture would not condense duringthetransferofthe emission gasto the analytical instruments. Whenthe emission gas entered the analytical trailer, it was split into 2 gas streams. One stream wasdiluted 1in 10 and analyzedforsulfurdioxide;the second gas stream was dried and
1 

## 0 0analyzed for oxygen, carbon dioxide and carbon monoxide. The em1ss1on gas that entered the scrubber was analyzed for moisture on four separate occasions to ensure thatthe calculated moisture that was being used for molecularweight calculations was correct. Emission gasflow measurements were performed by Minntac personnel using standard pilot-traverse techniques. The recycle rate ofthe green ball recycle stream wastaken from the computer readouts of belt scales. This numberwas usually 7 to 9 percent of the feed value. The recycle rate of chip regrind was estimated by timing the quantitythat fell offthe chip regrind belt into a bucket and then weighing that quantity. Scrubberwater flow rates were determined from the water pump settings. Analytical Procedures. The analysis ofthe sulfur in the wood and coal was performed on a Dohrmann DX-20A with a T-631 SulfurCell. In this system. the sulfur is oxidized in aoxygen stream at 1000degrees Celsius. The offgas is bubbled into an iodide-iodate solution and the quantity of sulfur dioxide in the gas stream is measured potentiometrically. NIST Certified Coal Standard 1632b was run with each set of samples. The sulfuranalysis ofthe watersamples was performed on a Fison Inductively Coupled' Plasma (ICP) Spectrometer Model 3410 using standard ICP procedures. The samples were oxidized with hydrogen peroxide addition and acidified with nitric acid prior to analysis. Sodium sulfate, reagentgrade. wasdissolved in dilute nitricacid. This solution was used as the standard stock solution. The sulfur analysis ofthe green ball samples. the chip regrind samples, and the pellet samples was performed by using an oxidizing-acid dissolution and then analyzing the resultant solution on the Model 3410 ICP using standard ICP procedures. Certified standards were run with each set of samples. The oxygen analysis was performed with an infrared analyzeron the dried portion ofthe emission gas stream. The carbon dioxide and carbon monoxide analyses were performed with a dual C02
- CO infrared analyzer on the dried portion of the emission gas stream. The sulfur dioxide analysis was performed with an ultraviolet instrument. The gasthat enteredthe sulfurdioxide analyzerwas a 1in 10 dilution ofthe original gas that enteredthe analytical trailer. The dilution was performedto ensurethat no moisture and therefore, no sulfur dioxide was lost. Certified gas obtained from Matheson Gas Products was used to calibrate each analytical instrument. Sulfur Balance. The total quantity of sulfur (pounds/hour) that entered the induration process was determined from the sulfur analysis of the green balls, the green ball feed rate, the sulfur analysis of the fuel, and the fuel usage rate. The natural gas contained an insignificant amount of sulfur. The amount ofsulfur (pounds/hour) that was recycled


### 2was determined from the sulfuranalysis of the green balls, the green ball recycle rate, the sulfur analysis of the chip regrind, and the chip regrind recycle rate. The recycled sulfurwas subtractedfromthetotal quantityof sulfurthatenteredthe induration process. Thisdifferencewasthetotal sulfur(pounds/hour) availableforoxidationduring induration. The concentration of sulfur dioxide (ppm) in the emission gas stream that entered the scrubberwas measured in the analytical trailer. Thetotal quantity of

## ott gas that exited the induration processwas determined by performing pilot-traversetests. The molecular weight of the emission gas was calculated from the gas analysis. By using the pilottraverse test data, the molecular weight of the emission gas and the sulfur dioxide concentration, thetotal quantityof sulfur (pounds/hour)thatexitedthe induration process was determined. The amount of sulfur that remained in the pellet product was determined by subtracting the amount of sulfurthat exited with the emission gas priorto the scrubberfrom the quantity of sulfur available for oxidation. The quantity of sulfur in the pellet product was verified by sulfur analysis of the pellet product. The amount ofsulfur (pounds/hour)that enteredthe atmosphere (scrubberexit gas)was calculated from the pilot-traverse data, the calculated molecular weight of the emission gas stream, and the sulfurdioxide concentration (ppm) of the emission gas stream that exitedthe scrubber. The sulfurdioxide concentration ofthe emission gaswas measured in the analyticaltrailer. The sulfurdioxide concentration ofthe emission gas wasverified by scrubber water sampling. The verification of the sulfur dioxide concentration in the emission gasstream was performed by calculation usingthe scrubberflow rate data, the scrubber inlet water sulfuranalysis and the scrubber exit water sulfuranalysis. The sulfur content of the green ball, bentonite clay, fluxstone, and process water were determine by chemical analysis. The sulfur in the taconite concentrate was determined by subtractingthe sulfurconcentration ofthe fluxstone, bentoniteclayand waterfrom the total sulfur in the green ball. The sulfur concentration in the taconite concentrate could not be obtained bydirectsulfuranalysis because residual sulfurfrom the water remained with the concentrate when the concentrate sample was filtered and dried. The residual sulfur from the water would then erroneously be analyzed as sulfur in the taconite concentrate.
DISCUSSION OF RESULTS Acid Pellet Production Tests Seven tests were performed during acid pellet production. Four tests were run while natural gas was being used as the indurating fuel and three tests were run when wood and natural gaswere being used in combination as the fuel.



### 3Natural Gas Line 6 Test. The first test was performed during November of 1993 on agglomerator line 6. The emission gas that entered the scrubber was sampled on November3rd andthe emission gasthat exitedthe scrubberwas sampledon November 4th. The waste gas flows increased slightly from the 3rd to the 4th. No solid samples orwater samples were taken during this test andthe quantityof sulfur in the green balls was calculatedfromthe gasanalysisand recycle data. The green ball feed rate was 510 longtons perhour. The scrubberremoved 26 percentofthe sulfurfromthe emission gas stream. The test dataare given in Tables 1and 2. The feed rates and recycle rates are given in Table 7. The sulfur balance forthis test is illustrated in Figure 1. The amount ofsulfurthat entered the kiln was 120 pounds per hourand the amountof sulfuremitted to the atmosphere was 43 pounds per hour. Fifteen pounds of sulfur per hour was removed by the scrubber. Natural Gas Line 4Tests. The remainderofthe natural gastestswere performed on agglomerator line 4. The line 4 tests were run on March 30. 1994, April 12, 1994 and April 13, 1994. The test data are given in Tables 1 and 2. The feed rates and recycle rates are listed in Table 7. The green ball feed rates ranged from 480 long tons per hour to 605 long tons per hour. The amount of sulfurthat entered the kiln ranged from 126 pounds per hourto 142 pounds per hour. The scrubber removed from 46 percentto 60 percent of the sulfurfrom the emission gas stream. The amount of sulfur emitted to the atmosphere during these tests ranged from 45 pounds per hourto 59 pounds per hour. These three tests are illustrated in Figures 2, 3 and 4. The line 4scrubberis moreefficientin removing sulfurfrom the emission gasstreamthan is the line 6 scrubber. The line 4 scrubber removes approximatelytwice as much sulfur asthe line6scrubber. Therearetwo obvious reasons forthis increasedefficiency. First, the line 4 scrubber has a higherscrubber-waterflow rate than the line 6 scrubber, 3400 gallons perminuteand2650 gallonsper minute respectively. Second, the line 4scrubber was installed at a laterdate and has a slightly different des1gn. Wood-Natural Gas Line 4Tests. Three tests were performed when wood was being used in combination with natural gas asthe indurating fuel. Thesewood-gastests were run on April 1, 1994, April 4, 1994, and April 11, 1994. Two tests were run with 25 percent ofthe heat inputcoming from wood and one test was run with 40 percent ofthe heat input coming from wood. The green ball feed rate ranged from 440 long tons per hourto 605 long tons per hour. Feed rates and recycle rates are given in Table 7. The quantity of sulfurthat entered the kiln ranged from 137 pounds per hourto 195 pounds per hour. The scrubber removed from 57.2 percentto 76.5 percent ofthe sulfurfrom the emission gas stream. The total amount of sulfur that was emitted to the atmosphere during these three tests ranged from 28 pounds per hourto 43 pounds per hour. The data for these tests are given in Tables 1 and 2. The tests are illustrated in Figures 5, 6, and 7.

4

### l 

## l

__; The scrubberdata indicate thatwhen 25 percentwoodwas used, the scrubber removed approximately 60 percent of the sulfur. When the wood was increased to 40 percent of the indurating fuel, the scrubber removed about 76 percentofthe sulfur. This increased scrubbing efficiency is probably due to the chemistry of the wood ash. Wood ash is usually high in calcium oxide, which will react with the sulfurdioxide in the emission gas stream forming calcium sulfite. The resulting calcium sulfite will then be removed bythe scrubber. Other oxides in the wood ash will also react with the sulfur dioxide forming water soluble sulfites. The line 4 scrubber removed an average of 52 percent of the sulfurwhen all ofthe fuel was natural gas. The average sulfur removal increasedto 65 percentwhen wood-natural gas was the fuel. The average sulfur analysis for the wood is given in Table 4. The quantity of sulfur introduced into the process by the wood was 2to 4 pounds per hour. This is less than 3 percent of the total sulfurthat entered the induration process. Fluxed Pellet Production Tests Threetests were run during fluxed pellet production on line 6, one with natural gas asthe fuel andtwo with coal-natural gas in combination asthefuel. During the coal-natural gas tests, all of the kiln fuel was coal and all of the preheat fuel was natural gas. Natural Gas Test. The fluxed pellet test with natural gas as the fuel was run on March 11, 1994. The test data are listed in Tables 1and 2. The feed rates and recycle rates are given in Table 7. The green ball feed rate was 550 long tons per hour. The total amount of sulfurthat reported to the induration process was 163 pounds per hour. The line 6scrubber removed 50 percent ofthe sulfurfrom the emission gas stream. The amount of sulfurthat was discharged to the atmosphere was 46 pounds per hour. The sulfur balance is illustrated in Figure 8. As mentioned earlier, the line 6 scrubber removed 26 percent of the sulfur during acid pellet production with natural gas as the indurating fuel. This increased to 50 percent removal during fluxed pellet production. This increase in scrubber efficiency is probably due to the reaction that occurs between the sulfur dioxide and alkaline oxides that are present in the induration dust. The sulfur dioxide in the emission gas reacts with these oxides forming calcium sulfite and magnesium sulfite which are then removed by the scrubber. The calcium oxide dust also aids in neutralizing the hydronium ion concentration ofthe scrubberwater. thus increasing the solubility ofthe sulfurdioxide in the water. Coal-Natural GasTests. Twofluxed pellettestswithcoal-natural gasasthefuel were performed on line 6. The tests were run on March 15, 1994 and March 16, 1994. The green ball feed rate for both tests was 550 long tons per hour. The feed rates and 

### 5recycle rates are given in Table 7. The total amount of sulfur that reported to the induration process was 224 and 230 pounds per hour lor the two tests. The line 6 scrubber removed about 50 percent of the sulfur from the emission gas stream during both ofthese fluxed pellet tests. The average quantity of sulfurthat was discharged to the atmosphere during the March 15test was 81 pounds per hour. During the March 16 test, the average amount of sulfur that was discharged into the atmosphere was 85 pounds per hour. The data lorthese two tests are given in Tables 1and 2. The March 15 and 16 tests are illustrated in Figures 9 and 10 respectively. The sulfur analysis of the coal is given in Table 3. The quantity of sulfur contributed to the process bythe coal was 67 pounds per hour. This was about 30 percent ofthe total induration sulfur. Induration Sulfur Sources. The two main sources of sulfurthat entered the induration process were the sulfurfrom the green ball feed and the sulfurfrom the fuel. Green Ball Sulfur. The sulfur in the green balls was the major source of sulfurthat entered the induration process. When natural gas was the fuel, the green balls contributed essentially all ofthe sulfurthat entered the process. During wood firing, the green ballscontributed about 97 percent ofthe sulfur. The green ballscontributed about 70 percent of the sulfur to the indurating process when coal was the fuel. The sulfur in the acid green balls came from the acidtaconite concentrate, the bentonite clay and the process water. The amount of sulfurthatwas contributed by each ofthese constituents is given in Table 5. The quantity of sulfur lor each constituent that is listed in Table 5 has been calculated from the analyses of the water and bentonite that are found in Tables 3 and 4. The average sulfur concentration in the acid taconite concentrate was 0.009 percent. The sources of sulfur in the fluxed green ball were the flotation taconite concentrate, the bentonite clay, the process waterand the lluxstone. The contribution from each ofthese constituents is listed in Table 5. The percent sulfur that was contributed by each component was calculated from the analyses of the water. bentonite and fluxstone that are listed in Tables 3 and 4. The flotation taconite concentrate contained an average of 0.007 percent sulfur. The main difference between the acid taconite concentrate and flotation taconite concentrate was the amount of silica (Si02) that the two concentrates contained. The acid concentrate was about 5 percent silica and the flotation concentrate was approximately 4 percent silica. Apparently, when the quantity of silica in the taconite concentrate was decreased from 5 percent to 4 percent. the amount of sulfur in the taconite concentrate was decreased from 0.009 percent to 0.007 percent. However,


### 6when fluxed pellets were produced, approximately 8 percentfluxstone was addedto the concentrate. Since the fluxstone contained about 0.05 percent sulfur, the total amount of sulfur in the fluxed green balls was about 0.002 percent higherthan the sulfurwas in the acid green balls. In the future, the sulfurcontribution from the processwaterin the green ball will continue to increase. Taconite contains a small amount of iron pyrite. During the taconite processing, the pyrite reports to the tailings and is pumped to the tailing·basin. In the basin, the pyritic sulfur oxidizes and hydrates to form sulfuric acid. This acid is neutralized by calcium carbonate and magnesium carbonate that are also found in the taconite tailings. This oxidation and neutralization is constantly occurring and therefore, the concentration of sulfuras sulfate ion in the Minntac process waterwill increase. The concentration of sulfur in Minntac water is increasing at an average rate of 15 parts per million of sulfur peryear. At this rate, thequantity of sulfurin the green ball will increase by about 0.00015 percent peryear. This is probably insignificant when comparedto the variability of the sulfur in the bentonite, fluxstone and concentrate. Fuel Sulfur. The amount of sulfur that entered the induration process from natural gas was extremely small when compared to the quantitythat entered with wood orcoal. The sulfur analysis ofthe four wood samples thatwere taken are found in Table 4. The average sulfuranalysis ofthe woodwas 0.059 percent. Thetotal sulfurcontributionfrom the wood if 100 percent ofthe induration fuel was wood. would be lessthan 8 pounds of sulfur per hour. This is less than 7 percent of the total sulfur input. The sulfur analysis of the two coal samples that were taken are listed in Table 3. The average sulfur of the coal was 0.77 percent. The total sulfur contribution from the coal when coal was the only fuel being used in the kiln was 67 pounds per hour. Thiswas about30 percent ofthe total sulfurinput. Ifthe sulfurin thecoal was 1percent, the sulfur contribution of the coal would be about 90 pounds per hour. This would be about 36 percent ofthe total sulfurinput ifthe green ball feed rate was 550 longtons per hour. Pellet Sulfur The average calculated percent sulfur in the acid pellet product was 0.003 percent. The analyzed average sulfur in the acid pellet product was 0.004 percent. The calculated quantity of sulfur in the fluxed pellet product was 0.005 percent. The analyzed average sulfur was 0.005 percent. These calculated and analyzed sulfur quantities agree very well, which is a good confirmation that the sulfur balances are correct.



### 7Sulfur Removal by the Scrubber Two methods were used to determine the rate at which sulfur was removed from the emission gas stream. One method determined the sulfur removal rate by using the difference between the gas analyses into and out of the scrubber; the other method determined the sulfur removal rate by using the difference between the water analyses intoandoutofthe scrubber. The gassampleswere analyzed everythree minutes, while the watersampleswere dailygrab samples. The sulfur removal rates for eachtest using both methods of calculation are given in Table 1. The calculated sulfur removal rates from both methods are in close agreement. The largest difference between the two methods was seen on April 

### 13, 1994. Forthis date, the average sulfur removal rate of the scrubbercalculatedfromthe gas analysiswas 

### 59.2 poundsofsulfurper hourandthe rate calculatedfromthewateranalysis was 

### 68poundsof sulfurperhour. Thisdifference is within the statistical limits of the test as indicated by the following calculations. The standard deviation of the sulfur dioxide analysis into the scrubber was 

### 3.8 ppm. By adding the standard deviation 

### (3.8) to the average scrubber inlet gas analysis 

### (47.9) the resultant inletsulfurdioxideconcentration is

### 51.7ppm. This would result in 

### 126.0pounds of sulfur per hour entering the scrubber and 

### 68.5 pounds of sulfur per hour leaving the scrubber. This indicates that the 

### 68 pounds of sulfur per hourthat was calculated from the wateranalysis is within 1 standard deviation ofthe rate that was calculated from the gas analysis. Atmospheric Sulfur Emissions The quantity of sulfur that was discharged to the atmosphere during the 4 acid pellet natural gastests. ranged from 

### 34.8 pounds ofsulfurperhourto 

### 57.5pounds ofsulfurper hour. The average was 

### 47.1 pounds per hour. During the one fluxed pellet natural gas test. 

### 45.5 pounds of sulfur per hourwas emitted. The sulfur emitted to the atmosphere duringtheacid pellettest on line 

### 6was 

### 43.5pounds of sulfurper hourand duringthe line 

### 6 fluxed pellet test the sulfur discharged to the atmosphere was 

### 45.5 pounds per hour. During the two coal-fluxed pellet tests, the quantity of sulfur that was released to the atmosphere that can be contributedto the fluxed green balls was 

### 50.4 pounds per hour and

### 49.2 pounds perhour. These results indicatethattherewas approximatelythe same amountofsulfur releasedtothe atmosphereduring bothacid pelletproduction andfluxed pellet production. Slightly more sulfurenteredthe induration process dunngfluxed pellet proClUction than dunng acid pellet production, however. due to the lime dust that was present in the emiss1on gasduring fluxed pellet production, the scrubbers removed more sulfurthan they did during acid pellet production. When coal was used as a fuel rather than natural gas forfluxed pellet production, the total amount of sulfurdischargedto the atmosphere increased by about 

### 80percent because ofthe fuel contribution. Whenwood was used as a fuel ratherthan natural gas, the quantity of sulfurthat was discharged to the atmosphere decreased by an average of 

### 15 percent.



### 8CONCLUSIONS 1. Duringthe production offluxed pellets, the Minntac line 6scrubber removedtwice as much sulfur from the emission gas stream as it did during acid pellet production. 2. When both lines4and 6 were producing acid pellets, the line 4 scrubberremoved about twice as much sulfurfrom the emission gas stream as the line 6 scrubber. 3. When 40 percent wood and 60 percent natural gas were used in combination as the indurating fuel rather than 100 percent natural gas, the amount of sulfur emitted to the atmosphere was decreased by 40 percent. 4. The green ball constituents contributed from 70 to 100 percent of the sulfurthat entered the induration process. 5. When coal was being used as the kiln fuel, the coal contributed about 30 percent of the sulfurthat entered the induration process. 6. When wood was being used as the kiln fuel, it contributed less than 3 percent of the sulfurthat entered the induration process. 7_ Fiftyto sixty percent ofthe sulfurthatwas in the green ball wascontributed bythe taconite concentrate. 8. The discharge rate per hour of sulfur into the atmosphere during fluxed pellet production andacid pellet production appearedto be aboutthesamewhen natural gas was the indurating fuel.

9Feed Waste Rate Fuel Fuel Pellet Test Gas line lTon/hr Type Ratio Type Date lbs/min

6 510 Gas 100 Acid 11/3/93 28,560 6 510 Gas 100 Acid 11/4/93 30,360 4 560 Gas 100 Acid 3/30/94 33,453 4 560 Gas 100 Acid 3/30/94 33,453 4 605 Gas 100 Acid 4/12!94 42,500 4 605 Gas 100 Acid 4/12!94 42,500 4 480 Gas 100 Acid 4/13/94 35,225 4 480 Gas 100 Acid 4/13/94 35,225 4 440 Gas/Yood 75!25 Acid 4/1!94 34,214 4 440 Gas/llood 75/25 Acid 4/1/94 34,214 4 540 Gas/Yood 75!25 Acid 4/4/94 35,590 4 540 Gas/Wood 75/25 Acid 4/4/94 35,590 4 605 Gas/Yood 60/40 Acid 4/11/94 41,680 4 605 Gas/Yood 60/40 Acid 4/11/94 41,680

6 550 Gas 100 Flux 3/11/94 28,500 6 550 Gas 100 Flux 3/11/94 28,500 6 550 Coal/Gas 61/39 Flux 3/15/94 32,680 6 550 Coal/Gas 61/39 Flux 3/15/94 32,680 6 550 Coal/Gas 59/41 Flux 3/16/94 31,500 6 550 Coal/Gas 59/41 Flux 3/16/94 31,500 Table 1

Minntac Taconite Pellets Induration Sulfur Balance

From Gas Analysis Avg Wet Standard Molecular Sa""le Average 502 Cone. Deviation Yeight Point Sulfur

ppm S02, ppm of Gas lbs/hr 29.7 4.4 27.70 Scrub In 58.8 20.7 3.9 27.72 Scrub Out 43.5 37.1 2.9 27.72 Scrub In 86.0 15.0 1.5 27.72 Scrub Out 34.8 33.2 5.1 27.74 Scrub In 97.7 17.8 2.0 27.74 Scrub Out 52.4 47.9 3.8 27.76 Scrub In 116.7 23.6 2.2 27.76 Scrub Out 57.5 48.2 4.7 27.76 Scrub In 114.0 18.1 2.9 27.76 scrub out 42.8 46.1 3.8 27.75 Scrub In 113.5 19.7 1.2 27.75 Scrub Out 48.5 41.8 2.1 27.77 Scrub In 120.5

9.8 0.9 27.77 Scrub Out 28.3

46.8 5.0 27.90 Scrub In 91.8 23.2 2.1 27.90 Scrub Out 45.5 73.7 4.1 27.96 Scrub In 165.4 36.3 4.9 27.96 Scrub Out 81.5 77.4 3.6 27.95 Scrub In 167.5 39.2 4.0 27.95 Scrub Out 84.8 ..............**~**

From Gas From Water Analysis Analyzed Analysis

Average s Sulfur in Scrubber Sulfur in in Scrubber Scrubber Flow Scrubber Water lbs/hr Water, ppm GPH Yater(lb/hr) 15.3 No Sarrple 2650 N/A No Sample 51.2 165 3400 56 198 45.3 165 3400 54 197 59.2 169 3400 68 209 71.2 163 3400 73 206 65.0 166 3400 70 207 92.2 162 3400 93 217

46.3 No Sample 2650 N/A 83.9 161 3000 84 217 82.7 158 3000 78 210

## ...........
Table 2

Minntac Taconite Pellets Induration Sulfur Balance Green Ball Feed Average Sulfur Sulfur in Sulfur in Sulfur Sulfur in Pellets %Sulfur Rate Fuel Fuel Pellet Test %sulfur into Kiln GB Recycle Chip Reg in Fuel PelLets Produced in Pel Lets line LTon/hr Type Ratio Type Date in Greenball lbs/hr lbs/hr lbs/hr lbs/hr lbs/hr lton/hr Calculated 6 510 Gas 100 Acid 11/3/93 0.0115* 120 11 4 0 47 418 0.005 6 510 Gas 100 Acid 11!4/93 4 560 Gas 100 Acid 3/30/94 0.0110 126 11 2 0 27 464 0.003 4 560 Gas 100 Acid 3/30/94 4 605 Gas 100 Acid 4112/94 0.0110 136 12 2 0 24 500 0.002 4 605 Gas 100 Acid 4/12/94 4 480 Gas 100 Acid 4/13/94 0.0145 142 10 1 0 14 408 0.002 4 480 Gas 100 Acid 4/13/94 4 440 Gas/Wood 75/25 Acid 4/1/94 0.0150 135 8 1 2 14 380 0.002 4 440 Gas/Uood 75!25 Acid 4/1/94 4 540 Gas/Wood 75/25 Acid 4/4/94 0.0135 149 10 2 2 26 460 0.003 4 540 Gas/Wood 75!25 Acid 4/4/94 4 605 Gas/Uood 60/40 Acid 4111/94 0.0155 191 12 2 4 61 518 0.005 4 605 Gas/Wood 60/40 Acid 4111/94 Average Calculated Pellet Sulfur for Acid Pellets= 0.003 6 550 Gas 100 Flux 3/11/94 0.0145 163 15 5 0 52 433 0.005 6 550 Gas 100 Flux 3/11/94 6 550 Coal/Gas 61/39 Flux 3/15/94 0.0140 157 14 5 67 40 432 0.004 6 550 Coal/Gas 61/39 Flux 3/15/94 6 550 Coal/Gas 59/41 Flux 3/16/94 0.0145 163 15 5 67 43 432 0.004 6 550 Coal/Gas 59/41 Flux 3116/94 Average Calculated Pellet Sulfur for Fluxed Pellets= 0.005 

### *
- No green ball samples taken. This number was calculated from the gas analysis.

### Table 3

Minntac Agglomerator Samples Fluxed Pellet Production
% 

### ppm Average Std Sample Description Sulfur Sulfur Sulfur Dev Coal 0.76 0.77**0.0~0** 0.78 

### Bentonite 0.25 0.30 0.050 0.35 

### Fluxstone 0.056 0.050 0.0098 0.039 0.062**0.04~** 

### Pellet Product 0.004 0.005 0.0005 0.005 0.005 

### Chip Regrind**0.0~~ 0.0~3** **0.00~7 0.0~5** **0.0~4** 

### Concentrate Thickener Water**~64 ~64**  4**~60 ~69** 

### Sample Description Wood

Bentonite
Pellet Product

Chip Regrind Table 4
Minntac Agglomerator Samples Acid Pellet Production
% 

### ppm Average Sulfur Sulfur sulfur

0.067 0.059 0.075 0.043 0.049

0.36 0.33 0.30 0.005 0.004 0.004 0.003 0.003 0.004 0.014 0.018 0.019 0.014 0.015 0.028 

### Concentrate Thickener Water 167 181 184 190 180 182 

### Std Dev 0.013

0.03
0.0007

0.0053

8...........,....

Table 5

Sulfur Sources in Green Balls Minntac Agglomerator Samples

Fluxed Pellet Production
Average Bentonite Minimun Maxinun Minimun Maxirrun *MiniiTlllll *Maxinun Minirrun Maxinun Test %Sulfur XSulfur % Range %s from %s from %s from %s from %S from %S from %S from Xs from line Date in Greenball in Greenball Moisture (lb/LTon) Bent. Bent. Yater Water Fluxstone Fluxstone Tac. Cone. Tac. Cone.

6 3/11/94 0.0145 0.014 8.89 12 to 18 0.00124 0.00326 0.00138 0.00161 0.00240 0.00560 0.00402 0.00948 6 3/11/94 0.015 9.15 6 3/15/94 0.0140 0.013 9.26 12 to 18 0.00124 0.00326 0.00138 0.00161 0.00240 0.00560 0.00352 0.00898 6 3/15/94 0.015 9.11 6 3/16/94 0.0145 0.013 9.06 12 to 18 0.00124 0.00326 0.00138 0.00161 0.00240 0.00560 0.00402 0.00948 6 3/16/94 0.016 9.25 Average XSulfur in green ball from taconite concentrate= 0.007

The Maximum and Minimum numbers are calculated from the average analyses + or - 2 times the standard deviation. *All fluxstone calculations were based on an addition rate of 8 %.Table 6 Sulfur Sources in Green Balls Minntac Agglomerator Samples Acid Pellet Production General Average Bentonite Minimlln Maxinun Mininun MaxiHUn Mininun Maxinun Test XSulfur %Sulfur % Range %s from %s from %s from %s from %s from %s from line Date in Greenbelt in Greenbelt Moisture (lbs/LTon) Bentonite Bentonite Water Water lac. Cone. Tac. Cone.

6 11/3/93 0.0115 • No Saq:>le No Sanple 12 to 18 0.00124 0.00326 0.00138 0.00161 0.00662 0.00888 6 11/3/93 4 3/30/94 0.0110 0.011 8.85 12 to 18 0.00124 0.00326 0.00145 0.00189 0.00585 0.00832 4 3/30/94 0.011 8.92 4 4/12!94 0.0110 0.01 8.88 12 to 18 0.00124 0.00326 0.00145 0.00189 0.00585 0.00832 4 4/12!94 0.012 8.96 4 4/13/94 0.0145 0.014 9.36 12 to 18 0.00124 0.00326 0.00145 0.00189 0.00935 0.01182 4 4/13/94 0.015 9.38 4 4/1/94 0.0150 0.016 9.35 12 to 18 0.00124 0.00326 0.00145 0.00189 0.00985 0.01232 4 4/1/94 0.014 9.25 4 4/4/94 0.0135 0.013 9.16 12 to 18 0.00124 0.00326 0.00145 0.00189 0.00835 0.01082 4 4/4/94 0.014 9.22 4 4/11/94 0.0155 0.015 9.35 12 to 18 0.00124 0.00326 0.00145 0.00189 0.01035 0.01282 4 4111/94 0.016 9.39 Average% Sulfur in green ball from Taconite Concentrate= 0.009

*No green ball samples were taken. This is a calculated number based on the gas analysis.

The calculated minimums and maximums are based on line 6 water analyses The Maximum and Minimum numbers are calculated from the average analyses + or - 2 times the standard deviation.

### Test Line Date

6 11/3/93 4 3/30/94 4 4/12/94 4 4/13/94 4 4/1/94 4 4/4/94 4 4/11/94 6 3/11/94 6 3/15/94 6 3/16/94 

### Table 7
Minntac Agglomerator Feed Rates, Recycle Rates, Production Rates, and Fuel Usage Rates

Green Ball Pellets Green Ball Chip Reg. Feed Rate Produced Recycle Recycle LTonfhr Lton/hr LTonfhr LTon/hr 510 418 46 14 560 464 50 7 605 500 55 8 480 408 34 3 440 380 25 3 540 460 36 5 605 518 38 5 550 433 50 15 550 432 50 15 550 432 50 15 

### Fuel Used MMBtujhr 153 142 137 106 109 129 158 205 231 220

# Sulfur Balance



# ., Green Balls 120 lbs S/hour



# - 

# - Greenball Recycle 11 lbs S/hour
Chip Regrind Recycle 4 lbs S/hour Figure 1



# Acid Line 

# Nov. Off Gas 43 lbs S/hour



# - Scrubber Water 15 lbs S/hour

Pellets 47 lbs S/hour

Fuel In

- Nat. Gas 0 lbs S/hour 

# Pellets 6 Step 3 3, 1993 

# -- -

# Sulfur Balance 

# ' Green Balls 126 lbs S/hour



# - - Greenball Recycle 11 lbs 5/hour
Chip Regrind Recycle 2 lbs S/hour 

### Figure 2

Off Gas 35 lbs S/hour



# ... 

# - Scrubber Water

51 lbs S/hour

. 

### Pellets 27 lbs S/hour

Fuel In

- Nat. Gas

0 lbs S/hour 

# Acid Pellets Line 4 Step 2 Mar. 30, 1994 

# - ...1

# Sulfur Balance

rGreen Balls 136 lbs S/hour



# ..

- 

# -- Greenball Recycle 12lbsS/hour



### Chip Regrind Recycle 21bs S/hour Figure 3**j~** 

### Off Gas 53 lbs S/hour



# -**~** 

### Scrubber Water 45 lbs S/hour

j

### ll Pellets 24 lbs S/hour

Fuel In- Nat. Gas 0 lbsS/hour



# . Ac1d 

# Pellets Line4Step2 April 12, 1994 

# ..

# Sulfur Balance



# ,., Green Balls 142lbsS/hour



# ...



# - 

# - Greenball Recycle 10 lbsS/hour

Chip Regrind Recycle 1 lb S/hour Figure 4

### J~

### Off Gas 58lbsS/hour



# . 

# .. Scrubber Water 59lbsS/hour**j~** Pellets 14lbsS/hour

Fuelin- Nat. Gas 0 lbsS/hour



# . Ac1d Pellets Line

# 4 Step 2 April 13, 1994 • 

# ...

# Sulfur Balance

Green Balls 135 lbs S/hour



# -

- Greenball Recycle 8 lbs S/hour
Chip Regrind Recycle 1 lb S/hour 

### Figure 5

Off Gas 43 lbs S/hour



# ... 

# .. Scrubber Water 71 lbs S/hour

Pellets 14 lbs S/hour

Fuel In

- Gas/Wood 2 lbs S/hour 

# Acid Pellets Line 4 Step 2 April 1, 1994 

# ..

# 1

Sulfur Balance

Green Balls 149 lbs S/hour



# - -



# - - Greenball Recycle 10 lbs S/hour
Chip Regrind Recycle 2 lbs S/hour Figure 6

Off Gas 48 lbs S/hour



# .. . Scrubber Water

65 lbs S/hour

Pellets 26 lbs S/hour

Fuel In

- Gas/Wood

2 lbs 5/hour 

# Acid Pellets Line 4 Step 2 April 4, 1994 • 

# ...1

# Sulfur Balance

•Green Balls 191 lbs S/hour



# .. -



# - - Greenball Recycle 12lbs S/hour



### Chip Regrind Recycle 21bs S/hour Figure 7**j~** 

### Off Gas 28 lbs S/hour



# .. 

# - Scrubber Water 92 lbs S/hour



## •

a 

### Pellets 61 lbsS(hour

Fuel In-Wood/Gas 41bs S/hour



# . Ac1d Pellets Line4Step2 April 11, 1994 

# ... 

# .

# Sulfur Balance

11r Green Balls 163lbsS/hour



# - 

# -

- Greenball Recycle 15lbsS/hour



### Chip Regrind Recycle SibsS/hour Figure 8



### Off Gas 45lbs S/hour



# ... 

# - Scrubber Water

46ibs S/hour



# •• Pellets 

### 52lbs S/hour

Fuel In- Nat. Gas

0 lbs S/hour 

# Fluxed Pellets Line6Step3 Mar. 11, 1994 

# -

# Sulfur Balance

Green Balls 157lbsS/hour



# - ..



# - 

# - Greenball Recycle 14ibs S/hour



### Chip Regrind Recycle Sibs S/hour Figure 9



### Off Gas 81 lbs S/hour



# ... ... Scrubber Water 84lbs S/hour

Fuel inCoal/Gas 67ibsS/hour 

### Pellets 40 lbsS/hour



# Fluxed Pellets Line6Step3 Mar. 15, 1994 

# - -

# ,Sulfur Balance

rGreen Balls 163 lbs S/hour



# - -

- 

# - Greenball Recycle 15lbs S/hour



### Chip Regrind Recycle SibsS/hour Figure 10

.I

### Ill Off Gas 85 lbs S/hour



# ... ... Scrubber Water

82 lbs S/hour



### ll Pellets 43 lbs S/hour

Fuel in- Coal/Gas

67 lbs S/hour 

# Fluxed Pellets Line6Step3 Mar. 16, 1994 -• 

# -