1. STUDY ON REMOVAL OF LOI UNDER CONTINUOUS HEATING
Name:- Sidhant Pati
Roll no. 112MM0414
METALLURGICAL & MATERIALS ENGEENERING
NIT ROURKELA

2. BACKGROUND
• India has the 4th largest iron ore reserve (10.3 billion tonnes) after Russia, Brazil
and Australia. For a large period of time, it has tremendously exploited its rich
iron ore reserve. For a major time it has relying been on the higher grade iron
ores (greater than 60% Fe content), there by completely neglecting the lower
grades.
• Among the various agglomeration techniques utilized, pelletisation seems to be
a promising one.
• The process Pelletisation enables converting iron fines into “uniformed sized
iron ore pellets called as globules” that can be charged into the blast furnaces.
Pellets with their uniform mechanical strength and high abrasive strength
increase the production of sponge iron.
• But apart from the principal ores of Hematite & Magnetite, many other
minerals like Goethite, kaolinite etc are also present, which have herculean
impact on the ore characteristics. Presence of the undesired compounds makes
the pellets soft. The hydroxyl groups weakens the pellets. As a result they may
breakdown during its usage, resulting in huge economic and manpower loss.
Therefore before pelletisation it is required to remove the moisture by heating it
to a very high temperature. This is referred as “LOSS ON IGNITION (LOI)”.

3. WHAT IS LOI?
• LOI refers to a test used in analytical chemistry, particularly in the
analysis of minerals. . It consists of strongly heating ("igniting") a
sample of the material at a specified temperature, allowing volatile
substances to escape, until its mass ceases to change.
• The volatile materials lost usually consist of "combined water"
(hydrates and labile hydroxyl-compounds) and carbon dioxide from
carbonates. It may be used as a quality test.
• It’s primarily concerned with the matrix moisture present with
complex bonding within the material. So in order to break these
bonds a large amount of energy is required. Therefore the material is
heated to a very high temperature of around 11000C.

4. FACTORS AFFECTING LOI
• Variation of temperature
The samples were kept in a muffle furnace over a range of temperature varying from 400 to 11000C. The
temperature was raised by 500C for each observation. For each corresponding change in temperature the
weight was calculated. Thus the change in weight was noted.
• Variation of residence time
It refers to the time interval for which the crucible is kept at a particular temperature. During the
experiments the residence were varied from 5-15 minutes.
• Variation of bed-depth
It refers to the height unto which the iron ore samples were contained in the crucibles. For each
corresponding change in temperature the change of bed height was recorded to be very small to be
neglected.

5. ACTIVATION ENERGY
• Activation energy can be described as the minimum amount of energy that is required to activate
atoms or molecules to a condition in which they can undergo chemical transformation.
• In terms of the transition-state theory, the activation energy is the difference in energy content
between atoms or molecules in an activated or transition-state configuration and the corresponding
atoms and molecules in their initial configuration. The activation energy is usually represented by the
symbol Ea in mathematical expressions for such quantities as the reaction-rate constant,
k = Aexp(-Ea/RT).
• Taking the natural logarithm of Arrhenius' equation yields:
𝒍𝒏 𝒌 =
−𝑬𝒂
𝑹
𝟏
𝑻
+ 𝒍𝒏(𝑨)
𝑬𝒂 = −𝑹
𝝏 𝒍𝒏 𝒌
𝝏(𝟏/𝑻)

6. 1. Crucibles
2. Tray
3. Heating Furnace (Muffle Furnace)
4. Long tongs
5. Densely woven cotton gloves
6. Protection glasses with light filter
7. Desiccator with blue drying agent
8. Weighing machine
9. 4 iron ore samples (namely
A,B,C,D collected from various
places)
MATERIALS REQUIRED

7. EXPERIMENTAL SETUP
Heating of iron ore samples in muffle furnace

8. PROCEDURE FOR REMOVAL OF %LOI
1. Initially 4 iron ore samples namely A, B, C, D were collected in a tray and was put inside an oven at
1200C for 2-3 hours, in order to remove the surface moisture from the sample.
2. After the required time interval, the tray was taken out of the oven. The weight of the tray was recorded in
order to determine the change in wt. after the removal of surface moisture.
3. Then based on our requirement, required weight (1gm, 250gm and 500gm) of the pre-heated sample was
taken in a crucible.
4. The wt. of empty crucible and the wt. of crucible + sample were taken. The crucibles were made from
Alumina refractory which can withstand high temperature.
5. Then the Bed-ht. was recorded. The mouth of the crucibles were kept open. The crucibles were then kept
inside the furnace at required temperature, for required time interval.
6. The wt. of sample taken was 250gm/500gm. Then the crucibles were heated to 4000C and were waited for
5-15min, based on the residence time required. After that the wt. of the sample was taken. There after the
procedure was repeated for every 500C rise in temperature, till 11000C.
7. After measuring the wt. at 11000C, finally the red hot crucibles were allowed to cool. Thus the change in
colour was observed.
% LOI content= ((Dry wt.)-(wt.at corresponding temperature))/ (wt.
of sample taken in crucible)*100

9. PROCEDURE FOR CALCULATION OF
ACTIVATION ENERGY
1. Let A0 represent the activity of the sample at time t=0. And At represent the activity of the
sample at any time ‘t’.
2. Then we have to calculate the logarithmic value of the (A0/At) at each interval for every 500C
rise in temperature.
3. K=(1/t)*ln(A0/At)
Now we have to calculate ln(k) for each observation at regular time interval and with every
500C rise in temperature.
4. Now we have to plot a graph between ln(K) vs 1/T, where T is the Temperature.
𝒍𝒏 𝒌 =
−𝑬𝒂
𝑹
𝟏
𝑻
+ 𝒍𝒏(𝑨)
5. The value of activation energy is determined by,
𝑬𝒂 = −𝑹
𝝏 𝐥𝐧 𝒌
𝝏(𝟏/𝑻)

10. RESULTS AND
DISCUSSION

11. Sam
ple
Crucible
wt.
(in gm)
Sample wt.
(in gm)
Crucible
wt. +
Sample wt.
(in gm)
wt. at
1200C
wt. at 9500C % of LOI
content
A 25.500
0
1.0035 26.5028 26.5003 26.4727 2.76%
B 25.290
9
1.0000 26.2909 26.2884 26.2382 5.02%
C 27.434
2
1.0010 28.4357 28.4310 28.3591 7.19%
D 26.231
9
1.0001 27.2342 27.2267 27.1028 10.59%
For sample wt. 1gm, Calculation of %LOI content
% LOI content= ((Dry wt.)-(wt.at 9500C))/ (wt. of sample taken in crucible)*100

12. Sample Name Fe% Feo% SiO2% Al2O3 LOI%
Sample-A 63.11 0.50 4.15 2.09 2.82
Sample-B 59.75 0.35 5.04 2.29 5.26
Sample-C 57.52 0.21 5.77 2.50 8.04
Sample-D 52.77 0.21 6.89 2.80 11.4
Chemical analysis of the pre-heated iron ore samples
Sample A was collected from Barbil region of Odisha. Sample D was collected from
Zimbawe. Sample B and sample C are prepared by mixing A & D in various proportions. The
particle size is found to be -100 micron for all the 4 samples.

13. % REMOVAL OF LOI

14. REMOVAL OF %LOI CONTENT
0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degree celcius
% of LOI removal with varying temperature (for a sample of 250 gm, residence time 15 mins)
A B C D

15. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degree celcius
% of LOI removal with varying temperature(for a sample wt. of 500 gm of recession time 15 mins)
A B C D

16. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degree Celcius
% of LOI removal with varying temperature(for a sample of 250 gm, Residence time=10 mins )
A B C D

17. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degree celcius
% of LOI removal with varying temperature(for a sample wt. of 500 gm, Residence time=10 mins)
A B C D

18. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degree celcius
% of LOI removal with varying temperature(for a sample wt. of 250 gm of recession time 5 mins)
A B C D

19. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%ofLOIremoval
Temperature in degrees
% of LOI removal with varying temperature(for a sample wt. of 500 gm of recession time 5 mins)
A B C D

20. CALCULATIONS OF
ACTIVATION ENERGY

21. -11
-10
-9
-8
-7
-6
-5
-4
ln(K)
1/T
Activation Energy for 250_15
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

22. -10
-9
-8
-7
-6
-5
-4
Ln(k)
1/T
Activation Energy for 500_15
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

23. -11
-10
-9
-8
-7
-6
-5
ln(k)
1/T
Activation Energy for 250_10
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

24. -10
-9
-8
-7
-6
-5
-4ln(k)
1/T
Activation Energy for 500_10
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

25. -11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
ln(k)
1/T
Activation Energy for 250_5
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

26. -10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
Ln(k)
1/T
Activation Energy for 250_5
ln(K(A)) ln(K(B)) ln(K(C)) ln(K(D))

27. INFLUENCE OF RESIDENCE TIME
0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%LOIremoval
Temperature
% LOI removal for sample A with varying residence time
A(5) A(10) A(15)

28. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%LOIremoval
Temperature
% LOI removal for sample B with varying residence time
Series1 Series2 Series3

29. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%LOIremoval
Temperature
% LOI removal for sample C with varying residence time
Series1 Series2 Series3

30. 0
10
20
30
40
50
60
70
80
90
100
400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100
%LOIremoval
Temperature
%LOI removal for sample D with varying residence time
D(5) D(10) D(15)

31. CONCLUSION
• From the experimental data, the reduction of LOI is prominent in the temperature
800C.
• It is concluded that the heat transfer in static bed is very slow and requires high
residence time and temperature. Further, reduction of LOI depends upon other
parameters such as temperature, depth of the bed and residence time.
• The above study will finally lead to design and development of a fluidized bed
roasting system for effective removal of LOI, which can address the problem faced
by pelletization units for utilization of low grade iron ore fines with high LOI.