# GRA **TE -** **KILN PELLETIZING SYSTEM** 

## GRATE - KILN SYSTEM VS STRAIGHT GRATE

## Grate - Kiln Benefits 1. Operational flexibility 2. Superior product quality and more uniform quality 3. Significantly lower electrical power consumption 4. Lower fuel consumption

## Grate - Kiln Power Savings

**If the pow er**  **saving betw een**  **is only 1**  **5 kW -**  **hr/ton product,**  **the savings in pow**  **er costs**  **alone w ould**  **pay f** **or the initial equipment**  **cost of Metso’s Grate**  **- Kiln**  **Sy stem after**  **only 2**  **0 y ears.**  

### kW -hr/ton Di ffere nce between Grate-K iln & St ra ig ht Grate Sa vin gs per

ye ar- $ mi llio ns U. S. Sa vin gs

after 10 Years - $ mi llio ns U. S. Sa vin gs

after 20 Ye ars - $ mi llio ns U. S. 10 8. 4 84. 0 168. 0 15 12. 6 126.0 252. 0 20 16. 8 168.0 336. 0 25 21. 0 210.0 420. 0 Based upon 0.12 $U .S . per kW- hour

## Grate - Kiln Fuel Savings

**If the fuel saving betw** **een the grate**  **- kiln**  **and the straight grate**  **is only**  **1 0,000**  **kCal/ton (about**  **14% ), the savings over 20 y** **ears is about $100,000,000**  **U.S.**

Based upon fuel oil costs of 0 .60 $U .S . per liter **kCal/ton Difference betw**  **een Grate-Kiln & Straight Grate**  **Sav ings per y** **ear – $ millions U.S.**  **Sav in**  **gs after 10 Years –**  **$ millions U.S. Sav**  **ings after 20 Years –**  **$ millions U.S. 5,000**  **2.47 24.7**  **49.4 10,000**  **4.94 49.4**  **98.8 15,000**  **7.41 74.1**  **148.2 20,000**  **9.88 98.8**  **197.6**

## G - K vs S - G FLEXIBILTY

DRYING PREHEA TING INDURA TION COOLING STRAIGHT

- GRA TE

**GRA TE**  **SPEED IS CONST**

**AN T**  **THROUGHOUT A**  **REQUIREMENT T O**  **CHA NGE**  **RESIDENCE TIME IN ONE SECTION, SUCH AS** **D RY**  **ING, CHA** **NGES THE RESIDENCE**  **TIME IN EVER Y OTHER SECTION.**  **HA RDER**  **TO OPTIMIZE**  **EA CH**  **ZONE, BECA** **USE AN**  **Y SPEED**  **CHA NGE**  **EFFECTS AL**  **L OTHER P**  **AR TS**  **OF SYSTEM.**  **LESS FORGIVING OF**  **CHA NGES**  **IN FEED OR UPSTREA** **M PROCESSING** 

## G - K vs S - G FLEXIBILITY GRA TE- KILN DRYING PREHEA TING INDURA TION
COOLING

INDEPENDENT VA RIABLE SPEED CONTROL OF DRYING/PREHEA TING , INDURA TION , ANDCOOLING TO ACCOMODAT E VA RY ING FEED CONDITIONS EASY OPERA

TOR CONTROL. EASY TO SWITCH FROM ONE ORE TO ANOTHER WITHOUT PROCESS INTERR UPTION .

## G - K vs S - G PELLET QUALITY

FIRED PELLETS / HEARTH LA

YER STRAIGHT - GRA TE PELLETS

BECA USE OF THE S - G ST AT IC BED , SOME PELLETS ARE OV ERFIRED , SOME ARE UNDERFIRED. THIS IS DUE TOT HE TEMPERA TURE GRADIENT THROUGH THE PELLET BED , WHICH IS CHARACTERISTIC OF A CROSS - FLOW ST AT IC B ED OV ERFIRED

UNDERFIRED PROCESS GA S FLOW TEMPERA

TURE PROFILE

## PELLET QUALITY IN A GRA

TE- KILN SY STEM, THE KILN MIXES THE PELLETS SO ALL OF THE PELLETS SEE THE SAME TEMPERA TURE A HOMOGENOUS PRODUCT IS THE RESUL T MORE HOMOGENEOUS PELLETS MEAN MORE ST ABLE BLAST FURN AC E OR DRI PLANT OPERA TION , ATP OT ENTIALL Y HIGHER TEMPERA

TURES FOR IMPROVED PERFORMANCE. **BECA USE**  **OF UNIFORM FIRING IN THE KILN, THE GRA TE**  **- KILN**  **PRODUCES A**  **PELLET THA**

**T IS OF SUPERIOR QUA**  **LITY GKS**  **SG**

## PELLET QUALITY

**0 10**  **20 30**  **40 50**  **60**

**0-50 50-** 

**100 100-**  **150 150-**  **200 200-**  **250 250-**  **300 300-**  **350 350-**  **400 GK** **S**

**SG DISTRIBUTION OF COMPRESSIVE STRENGTH** 

**COMPRESSIVE STRENGTH, (kg) %** 

## PELLET QUALITY

• G - K REDUCIBILITY (% PER MINUTE ISO 4695) AVERAGED 1.05, WITH A MAXIMUM OF 1.44.
• S - G REDUCIBILITY AVERAGED 0.82.
• REDUCIBILITY RELATES TO RATE OF REDUCTION, HIGHER IS BETTER.

• G - K FINES (LOW TEMPERATURE BREAKDOWN - 0.5mm, ASTM 1072) AVERAGED LESS THAN 3%.
• S - G FINES AVERAGED GREATER THAN 5%.
• FEWER FINES MEANS BETTER PELLET QUALITY AND LESS RECYCLE.

TEST RESUL

TS OF GRA

TE - KILN AND STRAIGHT GRA TE PELLETS FROM INDEPENDENT ISO LABORA

TO RY . MUL TIPLE PELLET SOUR CES .

## G - K vs S - G POWER CONSUMPTION

150 - 180 mm GRA TE CASTINGS GREEN PELLETS
GRA TE- KILN

250 - 450 mm

75 - 150 mm FIRED PELLETS / HEARTH LA

YER STRAIGHT - GRA TE GREEN PELLETS

BECA USE OF THE GREA TER BED DEPTH, A S - G WILL AL WA YSH AV E A HIGHER PRESSURE DROP AND MORE POWER CONSUMPTION THAN A GRA TE- KILN . FA N POWER DEMAND IS DIRECTL Y PROPORTI0NAL TOB ED DEPTH.

GRA TE BA RS

## POWER CONSUMPTION

GRATE- KILN KWH/TON STRAIGHT- GRATE KWH/TON EMPIRE MINE 21.4 HIBTAC 48.6 TILDEN MINE 24.6 MINORCA 37.5 USX MINNTAC 21.5 JINDAL 35.0 FERROMINERA 22.6 KIOCL 36.0 LKAB 18.0 A GRATE- KILN SYSTEM MAY OPERATE AT HALF THE POWER CONSUMPTION OF A STRAIGHT GRATE. PO WER CONSUMPTION FOR EQUIPMENT FROM THE INLET OF BA LLING THROUGH LOA DOUT .

## FUEL CONSUMPTION BECA USE OF : • MAXIMIZED USE OF PREHEA TED COMB USTION AIR

• RADIANT HEA

T TRANSFER IN THE KILN

• LESS LEAKAGE AIR SINCE THE TRAVELING GRA TE OPERA TES ATA

T CLOSE TOA

TMOSPHERIC PRESSURE, NOT THE HIGH NEGAT IVE PRESSURE OF STRAIGHT GRA TES

• NO HEA

T LO SS TOH EARTH LA YER

• SINGLE KILN BU RNER MORE EFFICIENT THAN MUTLIPLE SMALL BU RNERS THE GRA

TE- KILN SYSTEM HAS A LO WER SPECIFIC FUEL CONSUMPTION RA

TE THAN A STRAIGHT GRA TE- SYSTEM.

## AVAILABILITY

• THE GRATE IS THE BIGGEST MAINTENANCE ITEM ON GRATE- KILN OR STRAIGHT- GRATE SYSTEM.
• THE GRATE ON A GRATE KILN IS SMALLER, OPERATES AT LOWER TEMPERATURES AND THEREFORE REQUIRES LESS MAINTENANCE
• GRATE- KILN PLANTS IN THE USA OPERATE AT A +98.5% AVAILABILITY*
• 1 EXTRA DAY OF AVAILABILITY IS EQUAL TO AN EXTRA 21,000 TONS OF PELLETS (7,000,000 TPY PLANT)

*OF SCEHDULED RUNNING TIME

## MAINTENANCE

**GRA TE**  **- KILN**  **STRAIGHT -**  **GRA TE**  **REFRACT ORIES**  **75.0g/ton pellet 60.0g/ton**  **pellet ALLOY**  **P ARTS**  **8.2g/ton pellet 21.0g/ton**  **pellet**



### MAJOR DIFFERENCES

**GRA TE CAR WELDING**  **N/A ADDITIONAL** **S TA**  **FF**

## EQUIPMENT EVOLUTION

Grate width 3.75m 5.65m 5.65m length 29.0m 49m 73m Kiln diameter 3.05m 6.9m 7.47m length 36.6m 39.6m 40m Cooler mean dia. 7.7m 20.1m 28m pallet width 1.3m 3.05m 3.65m Note: the 6,000,000 tpy system is cur re ntly under construction at

L KAB and is sc heduled for start - up in early 2008. 1960’S 1970’S 2000’S

1,000,000 4,000,000 6,000,000 tpy tpy tpy

# GRA

TE- KILN SYSTEM