Technological Implication of Coal Quality Improvement for Power Stations by Beneficiation and Blending

1
Technological Implication of Coal Quality
Improvement for Power Stations by Beneficiation
and Blending
Kalyan Sen N. S. Das A. Choudhury
S. G. Chowdhury R. Dasgupta
S. Biswas
Central Fuel Research Institute, Dhanbad
2
INDIAN RAW COALas Feed to TPS
Constraints

• Genetic high inertinite content,
  high moisture
• Operational mechanized mining in
  large OCP
• Organizational multiple sources/
  linkages

3
Net result

• high ash content
• heterogeneity in size
• deterioration in heat value

Need
Beneficiation to a limited extent that meets the
desired qualities
4
Probable alternates for Improvement

• mixing cleans of coarse fractions with untreated
  smalls
• blending a part of raw coal with its cleans
• blending low ash imported coal with high ash
  indigenous coal
• mixing cleans of all fractions (whole coal
  beneficiation )

5
Alternate 1 to 3, only meet the mandate on
overall ash and moisture content but, combustio
n qualities ?
6
LIMITATIONS
Alternate 1
20-40 of finer fraction (5-10 of whole coal) is
obvious dirt
Alternate 2
Multiple sources - variable feed
Alternate 3
Blending coals of widely different ranks causes
differential combustion behaviour in boilers
Alternate 4
Needs finer fractions to be beneficiated
7
Beneficiation of Finer Fractions
to be or not to be !
8
Case Study
9
Quality of Raw Coal and Screened Fine Fraction
Type Coal Overall Finer
frac. Ash Ash 1) A
37 27 2) B C 43-38
34-37 3) D 47 44
10
Beneficiation schemes adopted
Schemes Optimization parameter I
Only coarse coal overall ash 34 II
Whole coal at Ep 0.12 a. overall ash 34
( Jig) b. corresponding to l
55 III Whole coal at Ep 0.04 a. overall ash
34 ( HM washer) b.
corresponding to l 55
11
Result of the study
Coal Schemes Upgradn. Yield Remarks
(UHV level) () A I
1 gt90 gt15 of cleans is
II(a), III(a) 1 gt90 obvious
dirt II(b),III(b) 2 75
lt 5 B I 1
65-69 7-10 II III-a
1 67-85 with l 55, lt5 C
II III-b 1 70-85 dirt D
I not achievable
II III-a 2 45-57 lt 5
II III-b 1 62-65
overall ash may be gt34
12
Densiometric Distribution of simulated products
from coal A
0
Raw coal A
Amount of undesired particles having ash content
gt55 (above sp.gr. 1.80-1.85)
10
I (Ash34)
20
IIa (a34)
IIb (lambda 55)
30
IIIb (lambda55)
40
Yield,
50
60
70
A
I
80
IIa
IIb
90
100
IIIb
0
10
20
30
40
Ash,
13
Suggestions

• Beneficiation of whole coal, particularly, where
  crushing to finer size does not help in
  liberation
• washing coal at a specific gravity determined
  from l 50-55. This will minimize the presence
  of non-combustibles