Basic Study Initiated on Improvement of Coal Quality Through Beneficiation for Cleaner Use of Thermal Coals Kalyan Sen, N.S.Das, S.Biswas, S.K.Mitra, A.Seth, D.Gnana Bharathi, S.G.Chaudhuri Central Fuel Research Institute Dhanbad 828 108

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Basic Study Initiated on Improvement of Coal
Quality Through Beneficiation for Cleaner Use of
Thermal CoalsKalyan Sen, N.S.Das, S.Biswas,
S.K.Mitra, A.Seth, D.Gnana Bharathi,
S.G.ChaudhuriCentral Fuel Research
InstituteDhanbad 828 108 Anjani
Kumar, M.M.BhattachryaCentral Mining Research
InstituteDhanbad 826 004
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Present Status of Beneficiation of Indian
Non-Coking Coal

• Piparwar 6.0 mt/y Jig (13mm)
• ACC 0.4 mt/y Barrel washer
• Bina 4.5 mt/y Jig (30mm)
• Dipika 2.5 mt/y HMC, spiral
• Parameter Ash level 34
  Ref. MOEF, Govt.... Of India)

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Purpose of Beneficiation

• To reduce mineral matter content
• To minimize abrasive material
• To improve combustion qualities
• Q ?
• Does 34 ash always assure the desired
  combustion qualities ?
• A
• Ash limit depends on specific combustion
  qualities

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• Task 1
• To evaluate combustion performances of a coal on
  the basis of traditional inspection properties
• Task 2
• To search for optimum quality parameter(s) that
  will reflect the combustion behaviour of the
  prepared coal

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Common Coal Quality Indices
Heating value C- burn out Char behaviour

• Combustion specific

Rank Petrography
Traditional inspection properties

• Size character.
• Grindability Index
• Elements ( S, Cl, N)

• Moisture
• V.M
• Ash

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Problem with inspection properties

• do not substantiate differential behaviour of
  particles
• Two coals having same overall indices exhibit
  different petrographic / combustion behaviour

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Characteristic Ash As Optimum Quality Parameter

• Relationship with specific gravity of individual
  F/S fraction
• general / universal irrespective of coal
• linear
• slope depends on the association of mineral
  matter of different sp.gr. fractions
• zero-ash density reflects the rank maturity
  of coal
• hence, linked to the combustion behaviour of
  Indiv... particles

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CFRI's CONCEPT
Limiting Characteristic Ash at cut point

• For coking coal 25-28
• Cleans
• High petrographic properties
• Superior coking properties
• Proposed
• For non-coking coal 50-55

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Predictable results with the coals studied(Cut
point selected at Char. Ash, 50 -55)
Coal crushed to 100 mm (Ash) optimum parameter Sp.gr. of cut Theoritical yield Ash Washers (Ep value) Practical Yield Coal crushed Ash
Coal A (37.0) 55.0 1.84 79.2 27.7 HM (0.04) Jig (0.12) 78.1 73.4 27.4 27.5
Coal B (38.3) 50.0 1.79 79.7 32.8 HM (0.04) Jig (0.12) 78.0 69.8 33.0 33.6
Coal C (48.3) 50.0 1.78 51.7 33.8 HM (0.04) Jig (0.12) 52.4 51.1 34.9 37.3
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R D INITIATED(Jointly by CFRI and CMRI of
Dhanbad)

• Assumption
• The degree of explosivity and/or ignitability of
  a parent coal may explain its combustibility in
  actual practice
• Quality parameters to study
• Relative inflammability
• Minimum ignition concentration
• Minimum ignition temperature
• Minimum ignition energy
• Maximum explosion pressure and rate of pressure
  rise

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Beyond cut of point (limit. Char. ash 50-55, the
samples behave non-explosively or do not ignite
at all
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Conclusion

• Preliminary study suggests characteristic ash as
  the quality parameter limiting the value to 50 -
  55
• Further studies with major coal sources are
  required to support the concept