Transcript Computational Fluid Dynamics: An Introduction

Studies on the Effect of Coal Blend
Crushing and Carbonization Time on
Coke Quality
Presented by:
Praveen Kumar Jha
e-mail: [email protected]
RDCIS, SAIL, Ranchi
INTRODUCTION
 Coke quality is one of the significant factors affecting blast
furnace performance.
 Coke accounts for >50% of hot metal cost,
 Main coke quality parameters influencing productivity and
coke rate in Blast Furnaces






M10,
M40,
CSR (Coke strength after reaction),
CRI (Coke reactivity index),
Coke Ash,
Size distribution of coke
RDCIS, SAIL, Ranchi
INTRODUCTION Contd…
 One point reduction in M10 index improves BF productivity
by 2.5% and reduces coke rate by 2.0%.
 Coke quality depends on following factors





Coal blend quality,
Granulometry (Crushing index) of coal blend,
Pre-carbonisation technology,
Carbonisation conditions,
Post-carbonisation treatment of coke
 With a view to improve coke quality, effects of coal blend
crushing index and coking time have been studied with
blend of one of the SAIL plant.
RDCIS, SAIL, Ranchi
Experimental
 Around 2 ton of coal blend was collected from charging car
of coke oven battery.
 After proper homogenization, coal blend was divided in 6
equal parts for carbonization tests.
 Tests carried out at RDCIS, Ranchi:
 Coal blend properties
 Pilot oven carbonization test
 Coke quality
RDCIS, SAIL, Ranchi
Experimental contd…
 Following coal blend properties were determined






Size analysis
Proximate analysis
Fluidity
Crucible swelling number
Petrographic analysis
Proximate analysis of different size fraction (+10 mm , + 6
mm , +3.2 mm , + 0.5 mm, -0.5 mm)
RDCIS, SAIL, Ranchi
Experimental contd…
 Pilot oven test was carried out in the electrically heated
movable wall pilot coke oven.
 Crushing index, carbonization condition of six different
samples were maintained as shown below:
Sample No
Crushing Index
(-3.2 fraction), %
Coking Period,
hrs.
Coke mass
temperature, 0C
1
71.8
23.5
1000+10
2
3
4
5
6
72.1
79.2
79.8
80.2
85.5
22
23.5
20
22
22
1000+10
1000+10
1000+10
1000+10
1000+10
RDCIS, SAIL, Ranchi
Experimental contd…
 Coke quality of six different coke produced from pilot
oven were determined to asses the quality of coke with
different level of crushing index and coking time.
 Micum indices (M10 & M40)
 Proximate analysis of coke
 Size analysis of coke
RDCIS, SAIL, Ranchi
Results
 Proximate analysis of coal blend
Tests
Proximate Analysis (IS: 1350 Part I- 1984)
Analytical Moisture % (air dried basis)
Volatile Matter, % (air dried basis)
Ash, % (air dried basis)
Values
1.09
24.9
13.1
 Coking Properties
CSN
3.5
Initial Softening Temp, 0C
Max. Fluidity Temp, 0C
Re-solidification Temp, 0C
Plastic Range, 0C
Max Fluidity, ddpm
406
448
481
75
648
RDCIS, SAIL, Ranchi
Results
 Petrographic analysis of coal blend
A. Maceral distribution, % (ISO 7404-3: 1994)
Vitrinite
51.4
Semi-vitrinite (Reactive semi-fusinite)
1.7
Liptinite
3.2
Inertinite
35.8
Mineral Matter
7.9
B. Reflectance , RoR,% (ISO 7404-5: 1994)
1.012
C. MMR, % (ISO 7404-5: 1994)
1.07
RDCIS, SAIL, Ranchi
Results
 Proximate analysis of different size fraction of coal blend
Size
Fraction
(+10mm) (+6mm) (+3.2mm) (+1mm) (+0.5mm) (-0.5mm)
VM, %
24.68
25.18
25.3
25.16
25.38
25.57
Ash, %
20.71
17.91
16.14
13.46
13.06
10.78
1.5
2
2
3
3.5
4.5
CSN
• Ash content increases with increase in size fraction
• CSN deteriorated with increase in size.
RDCIS, SAIL, Ranchi
Results
25.8
25.6
VM, %
24
Ash, %
22
20
25.2
25
18
24.8
16
24.6
14
24.4
12
24.2
10
(-0.5mm) (+0.5mm)
(+1mm)
(+3.2mm)
(+6mm)
Ash, %
VM, %
25.4
(+10mm)
Size fraction
VM & Ash of Different Size fractions of Coal Blend
Due to difference in the plastic and shrinkage behavior of inert rich
particles and rest of the charge, local stresses are developed and cracks
form adversely affecting coke quality.
RDCIS, SAIL, Ranchi
Results
14
82
13
M40, (%)
M10, (%)
78
12
74
M10
11
M40
10
70
68
72
76
80
84
88
Crushing index, (%)
Micum Indices of Coke Vs Crushing Index of Coal Blend
RDCIS, SAIL, Ranchi
+ 25 mm size fraction, %
Results
92
90
88
86
84
82
70
75
80
85
90
CI, %
+ 25 mm fraction of Coke Vs CI of Coal Blend
RDCIS, SAIL, Ranchi
Results
 Coke quality produced from pilot oven with different CI & CT
Parameters
Coking
Period
Sample
Units
Hrs.
#1
#2
#3
#4
#5
#6
23.5
22
23.5
20
22
22
Proximate Analysis
Ash
%
17.5
17.6
17.4
17.3
17.3
17.4
VM
%
0.37
0.41
0.67
0.66
0.6
0.59
Micum Indices
M10
%
13.6
13.0
11.8
12.2
11.8
11.2
M40
%
70.4
73.6
76.4
78
78.0
80.2
RDCIS, SAIL, Ranchi
Results
As coking period was decreased from 23.5 hrs to 22 hrs,
the coke quality in terms of M10 improved for same
crushing index of ~72%.
M40 index also showed an increasing trend with
reduction in coking time.
As the thermal stress in coke layer increases along with
increase of the heating rate and transverse temperature
gradient of coal layer, the size of coke is decreased.
Bigger size coke (+80 mm) is generally weak.
RDCIS, SAIL, Ranchi
Results
 Correlation developed between Micum indices and Coking
time & Crushing Index
M10 = 14.5 + 0.01*CT – 0.05* CI + 0.13* (% +6mm)
R2 = 0.87
M40 = 72.1 – 0.77* CT + 0.3*CI - 0.3* (% +6mm)
R2 = 0.90
CT : Coking time
CI : Crushing index
RDCIS, SAIL, Ranchi
Conclusion
 Bigger size fractions of coal blend have inferior coking
properties.
 For producing good quality coke, crushing index of coal
charge needs to be at least >80%. +6mm fraction in coal
charge should be as low as possible.
 Coke quality improves with reduction in Coking time.
RDCIS, SAIL, Ranchi
RDCIS, SAIL, Ranchi