TESTING OF IRON SIZE ORE (PHYSICAL TESTING)

SHATTER TEST:

It is essentially consists of dropping of certain amount of material from certain height for certain number of drops. the amount of material, retained on or passed through a certain sieve size expressed as percentage of the original weight is indicated as shatter index.

PROCEDURE: Take 20 kg of size ore of (+ 5mm to 18 mm) in size and drop four times from a height of 2mts.The material is then screened and determine the particles below 5mm size.

Wt of sample taken = W₁ grams (+ 5 mm)

Wt of sample after falling from 2mts height 4 times= W₂ grams (+ 5mm)

Wt of (-) 5mm material = (W₁ – W₂) grams.

 Shatter index  =SI

  (shatter index of less then 1% is best for sponge iron making through DRI method)

TUMBLING AND ABRASION TEST:

Tumbling is a method in which a constant weight of material of certain size is rotated in a standard drum, at a fixed speed for a fixed number of revolutions. The percentage of material passing through or retained in a fixed sieve is the tumbling index.

Sample size –  5mm to 15mm or 5mm to 18 mm

Sample weight –  15 kgs

Drum diameter  –   1.0  mts

Drum length  –    0.5 mts

No of lifters   –   2

Size of lifters –  50 mm

RPM (speed) – 25 ±  1

No of revolutions – 200

Sieves required –  5 mm and 500μm

Take 15 kg of sample (+ 5 mm) ,dry it and put it in tumbler drum and rotate 200   revolutions. After revolution remove the sample and sieve through 5mm screen and 500μm screens

Tumbling index =TI

W₁ = wt of sample taken

W₂ = + 5mm after rotating in a drum.

POROSITY TEST :

 It is a difficult property to measure and is expressed as the volume of pores to total volume. Open porosity is measured by fluid method where as closed porosity cannot be measured.

Take 50 gms of iron ore and dry it Take weight. Dip the sample in dry kerosene (having specific gravity of 0.80gm/cc) for 2 to 3 hours till no bobbles are observed. Remove the sample from kerosene and weight it.

W₁  =Weightt of sample

W₂ = Weight t of sample after dipping in kerosene

D₁ = Specific Gravity  of ore

 D₂ = Specific Gravity  of kerosene

% Porosity = P

REDUCIBILITY TEST :

 The reducibility test essentially aim at measuring the rate of reduction of iron bearing material in a kiln at reducing atmosphere. The use of reduction temperature in the range of 900-1000^oC and a reducing gas of CO or CO₂ +N₂ of constant composition is increasingly being used. The sample is a known weight of certain fixed size and is placed in a furnace in the form of static bed of fixed dimension during reduction studies.

1. Gakushin test
2. Verein deutscher eisenhuttenleute method(V.D.E.)
3. Center national de recherches mettallugiques(C.N.R.M.)
4. Chiba test
5. Non isothermal test.

DECREPITATION TEST :

When iron ore is suddenly exposed to high temperature of flue gases, breakdown may occurs due to thermal shock. This is known as decrepitating.

500 grams of sized iron ore is dropped in a furnace previously heated to a temperature of 400^oC and retained there for 30 minutes under a flow rate of 5000 litres of N₂ gas per hour. The sample is then removed and cooled. It is sieved through 0.5 mm and 5.6 mm.

      Decrepition rest at ( -)0.5 mm  is the material below  (-) 0.5mm and calculated as % of total ore feed for testing.

Decrepition rest at 5.6mm is the material retain between (+) 0.5mm and ( -) 5.6mm and calculated as % of total ore feed for testing.

tion

LOW TEMPERTURE BREAKDOWN TEST  (L.T.B.T.):

The test consist of subjecting the ore to static bed reduction at low temperature in a rotating furnace for a fixed durations.

Sample weight = 500 gms

Tube dia = 140mm

Tube length = 650 mm

Lifters = four

Lifter height = 20mm

Temperature (^oC) of reduction =600

Tube speed = 10 rpm

Reducing phase =%CO =24

                             %CO₂ =16

                             %N₂ = 60

Flow rate =15 liters/minute

Test time = 1 hours

L.T.B.T.Index = %material of +6.35 mm and % -30mm mesh(0.5mm)

REDUCTION DEGRADATION INDEX :

500 grams of ore in the range of 8 mm to 18 mm is charged in a reacting vessel(700mm length X75mm diameter) made of Inconnel steel 600 grade.The vessel is pushed into a electric muffle furnace maintained at 550 ^oCentrigrate .

Pure N₂ gas is passed (5littes/minutes) till temperature becomes 550^oC.Then a mixture of N₂ and CO in the ratio of 70:30is passed for 30 minutes(15litres/minutes).The sample is then cooled down passing N₂  gas(5litres/minutes)

Reacted sample is then rotated in a small tumbling drum(the drum size is 200mm lengthX 130mm diameter) at 30 rpm for 30 minutes. Sample is screened at 6.3 mm sieve and 3.15mm sieve.

RDI index = %  (+) 3.15 mm.

RI ( REDUCEBILITY TEST):

If the temperature of the sample is to rised to 900^oC and mixed gas(N₂ : CO = 70 : 30) @15litress/minutes  is passed for 3 hours.The sample is cooled and % wt loss is taken out.

W = weight loss in grams

RI = Reducibility Index

SWELLING TEST :

60±2 grams of sample is taken and their apparent volume is tested by dipping in mercury. The sample is then reduced in a static bed at temperature  =1000^oC  ,

{reducing gas =40%COand60%N₂.

gas flow = 1000 lts /minute, pre heating =under nitrogen atm.}

The percentage of reduction is calculated from weight loss. The apparent volume is measured by mercury method.  The swelling is correlated to degree of reduction in graphical form.