1. Adhunik Power & Natural Resources Ltd.
Impact of Coal Quality on PlantImpact of Coal Quality on Plant
Life & PerformanceLife & Performance

2. After the liberalization of Import, most of the Power Stations are attracted
towards using Imported Coal due to:
1)Higher Calorific Value
2)Low Ash Content
3)Low Price per Unit of Energy.
Boilers in India are designed for high ash content Coal, which has lead to:
1)Large scale erosion of components leading to high Maintenance Cost
2)Low Availability
3)Lower PLF in due course of time.
Use of Imported coal has lead to Severe Operation Problems & Outages
because of basic Design features particularly in PF & FBC Boilers.
Coal has basically two components:
1)Marcels (Organic Matter) - Responsible for Heat Value
2)Mineral Matter (Inorganic Matter) - Responsible for Ash Components
Distribution of qualities of these two components effect the Coal Combustion &
thereby Boiler designs in Principle.

3. COAL COMBUSTIONCOAL COMBUSTION
COAL ParticleCOAL Particle
HeatingHeating
Formation of CharFormation of Char
Burning of VolatilesBurning of Volatiles
Release of VolatilesRelease of Volatiles
Burning of CharBurning of Char
Ash FormationAsh Formation
Each process has its own time
depending on Characteristic,
distribution & size of Marcels &
Mineral Matter.
Different Analysis is used to Assess
the Coal Combustion Characteristic.
Previously well known analysis were:
1.Proximate Analysis.
(Rank of Coal)
2.Ultimate Analysis
(Elemental Chemical Composition)

4. NEW METHODS FOR ANALYSIS OF MARCELS
1. Differential
thermogravimetic
Analysis (DTG)
Burning profile
Observation
 Profile extends to
higher temp. Range
High Wt. loss at
low Temp.
 High Peak at low
Temp
High Peak at
higher temp
 High Burn out
temperature
Effects
Slow Burning
Coals
Good Burning
Good flame
stability
Increase furnace
temp.
Require
 Large furnace
 Leading to high S/H
temp.
 Consequently tube
failure
No problem
Problem in water wall
higher unburned
carbon

5. 2. Modified Bomb
calorimeter (ISO
Periobol Bomb
Calorimeter)
3. Petro graphic
Analysis
Observation
Heat Release rate
Reactivity
Effects
 Faster heat
Release initially &
slow towards end.
 Slow rate
initially faster
afterwards
Virtinite >62.7%
Virtinite ≤62.7%
Exinites
Intertinite
Require
 Requires high
absorption surface in
furnace zone.
 High furnace vol.
Rise in temp of S/H,
Eco, etc & low Boiler
Efficiency.
Difficult to burn Good
Burning char highly
reactive.
 Less reactive
 High unburned
carbon
NEW METHODS FOR ANALYSIS OF MARCELS
contd…..

6. MINERAL MATTER
Three aspects of mineral matter influences the ash formation
1.Nature of mineral matter (Included/Excluded).
2.Particle size distribution.
3. Form of mineral matter
Ash contains SiO2, Al203, Fe2O3, CaO, MgO, Na2O K2O, TiO2 & SO3
Ash fusion temperature depends upon the quality & quantity of these
oxides.

7. ASH CHARACTERISTICS
Ash Analysis High Iron Content Clinker formation & furnace temp. limitation
Iron > 19%
10-12%
4-8%
Furnace Temp.< 1200⁰C
< 1300⁰C
Max. 1400-1450⁰C
Slagging Index
< 0.6
0.6-2.0
2-2.6
> 2.6
Boiler Slagging (Deposits of Ash on waterwall)
Low
Medium
High
Severe
Fouling Potential
<0.2
0.2-0.5
0.5-1.0
>1.0
Fouling Potential (Deposits of Ash in S/H)
Low
Medium
High
Severe
Ash Fusion Temp. Higher Ash Fusion
Temp.
>1100⁰C
<1100⁰C
No clinkering tendency.
High clinkering tendency.
Erosion Index
<1.0
>1.0
Erosion of Boiler & Mill Internals
Low
High

8. ENVIRONMENTAL RESTRICTION
Most of the Imported coals have high sulpher content
compared to Indian coal. The design of ESP & stacks are
based upon the low sulpher content of Indian coal. In
Europe & other place desulphurization units are mandatory
parts of the boiler system which are absent in India.
Blend rations are to be decided upon keeping in mind the
Pollution norms in India, otherwise Desulphurization
Equipments or increase in the height of stack is must.

9. COAL BLENDING
Keeping in mind the design features & others, we can operate Indian boilers
with blended coal i.e. a mixture of Imported coal & Indian coal, limited to the
blend ratio, which is most nearest to their design. Inspite of best of blending
each particle of coal burns as per their own characteristic. The blend Ratio
can be decided by
1.Full Scale trails on Boiler- Costly and time consuming.
2.Analyzing Burning Profile of Blended coal at laboratory level.
A study of burning Profile of various mix of Indian coal & South African coal
is represented graphically for typical PF boiler. From it is quite clear that a
30% blend Ratio of Imported to Indian coal has nearly similar burning
profile with similar peaking temperature which is a vital parameter of
furnace design. Similar study can be made for available imported coals &
blend ratios can be fixed for all the boilers in our group scientifically
without inviting costly full scale trials.

10. BLENDING METHODS
Proper blending of coal is always a difficult task. Lower the particle size
better is the blending but limited to feeding of size requirement in boiler.
Difficulties:
1.Stoker fired boiler-Improper mix due large size of feed requirement
2.Large area requirement if blending is done in yard.
3.Difficulty in measurement of accurate blends ratio.
Following are the basic guidelines for better blending:
1.Giving feed from two different sources to common pint on conveyor.
2.Proper mixing by tilting at number of transfer pints before crushing.
3.Common crushing, so that further mixing takes place during crushing.

11. EXECUTIVE SUMMARY
INDONESIAN COAL
PROXIMATE ANALYSIS
ASH
%
MOISTURE
%
VOLATILE
MATTER
%
FIXED
CARBON
%
GCV
Kcal/kg
16.41 6.80 36.25 40.54 5696
1. Trail on FBC Boiler i.e. EC4 for 100% blend, gains were Rs. 40,000 per day.
2. Blend ratio to be limited to 30% due to SO2 norms.
3. Gain at 30% Blend Ratio approx. 15000/day in EC4.
4. Gain for EC1 & EC2 to be calculated after trails.
5. Gain will be available for 8-9 months only, i.e. excluding Monsoon Period.

12. PROXIMATE ANALYSIS
ASH
%
MOISTURE
%
VOLATILE
MATTER
%
FIXED
CARBON
%
GCV
Kcal/kg
17.36 3.33 22.23 57.08 5998
SOUTH AFRICAN COAL
1. Loss in Boiler Efficiency due to high unburned carbon.
2. Net Gain Rs. 60,000 per day for 400 TDP steam.
3. Blend ratio to be limited to 25-30% due to SO2 norms & problems of
clinkering & high flue gas temp in PF boilers of EC1.
4. Expected gain on continuous basis shall be approximately 50000-55000/day.
5. Gain will be available for 8-9 months only, i.e. excluding Monsoon Period.

13. COST IMPACT OF MOISTURE ON
C.V.Cost including Freight (Cif) value at 6500 Kcal = Rs. 1160/ton
Landed Cost = Rs. 2145/ton
An increase in 1% Moisture has a reduction of Rs. 11.60/ton as per weight basis.
Whereas for a Reduction in Gross Calorific value because of high moisture by 1%, the
corresponding loss is about 64 kcal.
Conversion factor at 2.5% moisture = (100-{2.5+1})/(100-2.5)
= 6433 kcal
Difference in C.V. = 6500-6433
= 64 kcal
Cost/kcal = 2145/6500
= Rs. 0.33/kcal
= Rs. 33/100 Kcal
Equivalent Cost for 67 Kcal = 33/100 x 67
= Rs. 22
Total Loss = Rs. 22- Rs. 11.60
approx. Rs. 11

14. Unit Stroker Fired Boilers Fluidized Bed
Boilers
Pulveriz
ed Fuel
Boilers
Under Grate Spreader Chain/
Travelling
Gate
Bed
Super
Heater
Convective
Super
Heater
Stationary Moving
Proximate Analysis
Moisture % 0-10 0-10 0-25 0.20 5-10 8-15 5-10
Volatile
Matter
% 30-40 30-40 18-30 30-40 20-40 20-40 15-25
Fixed
Carbon
% 40-50 40-50 50-65 40-50 30-40 30-40 30-50
ASH % 5-10 5-10 5-15 10-20 >25 >25 >20
FC/VM % 1-1.25 1-1.25 1-1.25 1-1.25 1.4-1.6 <1.5 <2.0
C.V. Kcal
/kg
6500-
7500
6500-
7500
5000-
6000
4500-
5500
3000-
4000
5000-
6000
Rank Semi Anthracite Sub Bituminous
Free
Swelling
Index
5 Max 7 Max NA 5Max NA NA NA
HGI NA NA NA NA NA NA 50-70
SPECIFICATION OF COAL

15. Unit Stroker Fired Boilers Fluidized Bed
Boilers
Pulveriz
ed Fuel
Boilers
Under Grate Spreader Chain/
Travelling
Gate
Bed
Super
Heater
Convectiv
e Super
Heater
Stationary Moving
Statutory Req.
Sulphur ^
<0.5 <0.5 <0.5 <0.5 <0.7 <0.7 <0.5
Moisture % 0-10 0-10 0-25 0.20 5-10 8-15 5-10
Ash Characteristics
Erosion
Index (EI)
NA NA NA NA <1.0 <1.0 <1.0
Ash
softening
Temp
⁰C 13501400 1350-
1400
1050-
1100
1125-1175 >1200 >1150 >1100
Slagging
Index
NA NA NA NA <0.6 <0.6 0.6-2.0
Fouling
Indes
NA NA NA NA <0.2 <0.2 0.2-1.0
Origin

16. GRASIM NAGDA
Analysis & Summary of 100% Imported Coal Use in EC4
(INDONESIAN COAL)
SNo Particulars Unit EC4 Remarks
1. Furnace Temperature ⁰C 782 Improved Norm
2. Bed Temperature ⁰C 922 Within Norms
3. Stack Temperature ⁰C 119 No Dev. From SECL Coal
4. Main Steam Flow TPH 89
5. Main Steam- SECL TPH 81
6. Main Steam Flow-Parta TPH 85
7. Coal Consumption
a. Imported
b. 100% SECL
c. Parta
TPD
TPD
TPD
294
313
331
8. Blend Ratio % 100
9. Calorific Value
a. Imported
b. 100% SECL
c. Parta
d. Gain/loss from SECL
Kcal/kg
Kcal/kg
Kcal/kg
Kcal/kg
5700
4807
4833
893

17. Sr. No. Particulars Unit EC4 Remarks
10 Boiler Efficiency
a.Direct Method
b.Loss Method
c.Average
d.SECL
e.Gain/loss from SECL
%
%
%
%
%
81.87
84.58
83.20
83.78
-0.58
11 Cost of Coal
a.Imported
b.SECL
c.Parta
d.Gain/Loss from SECL
Rs./T
Rs./T
Rs./T
Rs./T
2115
1905
1988
-210
Rs 1959 at 4944 kcal
At 4833 kcal, April 99 Parta
12 Coal Cost/100 Kcal
a.Imported
b.SECL
c.Parta
d.Gain/Loss from SECL
Rs T/1000 Kcal
Rs T/1000 Kcal
Rs T/1000 Kcal
Rs T/1000 Kcal
371
396
411
25
13 Cost of steam
a.Imported
b.SECL
c.Parta
d.Gain/Loss from SECL
Rs./T
Rs./T
Rs./T
Rs./T
286
305
324
19
14 Gain/loss From SECL Rs/Day 40570 At 89 TPH Steam
15 Gain /loss from SECL at Parta Steam Rs/Day 38619 At 85 TPH steam

18. Grasim Nagda (SOUTH AFRICAN COAL)
Analysis & Summary of Blending Imported Coal with SECL Coal From 03/07/99-05/07/99
S.N. Particulars Unit EC1 EC2 EC4 TOTAL/Wt
d
Remarks
1 Furnace Temp. ⁰ C 857 643 722 748 Increasing Trend in EC1
2 Bed Temp ⁰ C 891 922 910 Within norms
3 Stack Temp ⁰ C 171 155 119 146 No dev. From SECL Coal
4 Main Steam Flow TPH 141 104 166 411
5 Main Steam- SECL TPH 141 101 158 400
6 Main Steam Flow-Parta TPH 135 105 158 398
7 Coal Consumption
a.Imported
b.SECL
c.Total
d.100% SECL
e.Parta
TDP
TDP
TDP
TDP
TDP
137
342
479
487
491
141
277
418
419
410
166
367
533
533
596
444
986
1430
1439
1497
8 Blend Ratio % 29 34 31 31
9 Calorific Value
a. Imported
b. Blended
c. SECL Blended
d. 100% SECL
e. Parta
f. Gain/loss from SECL
Kcal/kg
Kcal/kg
Kcal/kg
Kcal/kg
Kcal/kg
Kcal/kg
5998
5229
4921
4779
4833
308
5998
5273
4904
4677
4833
369
5998
5194
4830
5025
4833
364
5998
5229
4882
4840
4833
346
As fired basis-10% moisture
Derived Value

19. S.N. Particulars Unit EC1 EC2 EC4 TOTAL/Wtd Remarks
10 Boiler efficiency
a.Direct Method
b.Loss Method
c.Average
d.SECL
e.Gain/loss from SECL
%
%
%
%
%
82.86
86.17
84.48
88.46
-3.98
71.62
80.49
75.80
78.53
-2.73
88.17
81.62
84.77
85.23
-0.46
81.55
82.81
82.05
84.35
-2.30
Bunker level correction
Not accounted for in
EC2 & EC4
11 Cost of Coal
a.Imported
b.Blended
c.SECL
d.Parta
e.Gain/Loss from SECL
Rs/T
Rs/T
Rs/T
Rs/T
Rs/T
2145
2002
1894
1988
-108
2145
2012
1853
1988
-159
2145
1986
1991
1988
5
2145
1999
1918
1988
-81
At 5998 kcal & 10% moisture
Derived value
Rs 1959 at 4944 kcal
At 4833 kcal, April 99 Parta
12 Coal Cost/1000 kcal
a.Imported
b.Blended
c.SECL
d.Parta
e.Gain/Loss from SECL
Rs
T/1000
Kcal
358
383
396
411
13
358
382
396
411
15
358
382
396
411
14
358
382
396
411
14
13 Cost of Steam
a.Imported
b.SECL
c.Parta
d.Gain/Loss from SECL
Rs/T
Rs/T
Rs/T
Rs/T
267
275
302
8
318
322
327
4
277
285
312
8
286
292
313
7
14 Gain/loss from SECL Rs/Day 27072 9984 31872 68928 At 411 TPH steam
15 Gain/loss from SECL at
Parta Steam
Rs/Day 25920 10109 30336 66365 At 398 TPH steam

20. OUR RECOMMENDATIONS
1. Use of Indonesian Coal at 25-30% Blend Ratio.
2. If possible use of South African coal to be avoided because of
clinking nature of coal.