GROSS CALORIFIC VALUE

1
GROSS CALORIFIC VALUE A GUIDE TO OPTIMUMWASHING
OF POWER COALS

• Chandan Das, Senior
  Research Fellow
• 
  and
• Dr Kalyan Sen,
  Prof. Emeritus
• 
  
• Bengal Engineering Science University, Shibpur
• 2nd Asian Mining Congress, Kolkata, 17-19th
  Jan.2008

2
Basic Issue

• Requirement of power plants
• Washed coal with consistent quality
• Quality Parameters GCV, Ash and Moisture- AR
  (as received) basis

3
Introduction

• About 70 coal produced in India is consumed in
  thermal power plants.
• Indian non-coking coals -
• Permian era, optimum maturity and petrological
  composition
• High Volatile Matter
• low Sulphur, Mercury, Nitrogen and Chloride, etc.
• Burn efficiently
• Large amount of Stones and obvious dirt lead to
  loss of sensible heat
• Erosion in coal handling, crushing, grinding, ash
  handling, etc.

4
Gross Calorific Value (GCV)

• Gross calorific value of coal depends upon its
  chemical composition, which is governed by
  geological environment during its coalification
  process, mainly on its maturity.
• Combustible elements present in coal
• Carbon,
• Hydrogen,
• Sulphur, etc
• Non-combustible mineral contents
• Silica,
• Iron,
• Aluminum,
• Calcium, Magnesium, etc.

5
GCV-Ash Relationship
6
GCV Ash Relationship

• Close relation between ash content vs Gross
  Calorific Value (GCV) of coal
• For Central Coalfield (CC) coals
• GCV at zero ash (pure) coal varies from 7000
  to 8000 kcal/kg, av. being 7800 kcal/kg
• GCV becomes zero (completely inert) at very
  high ash content i.e. about 80 to 90, av. being
  88.
• It is also proved that both ash and GCV contents
  are related to the Relative Density (RD) of coal.

7

8
(No Transcript)
9
Yield Quality of Washed Coal

• Fractional yield is a random property varies
  from seam to seam and day to day
• Cumulative yield at any cut point depends upon
  the Limiting GCV vs sp gr of cut and Efficiency
  of Washers
• If the Particle of Limiting GCV is combustible in
  a given furnace, then all other particles are
  ensured to burn

10
Optimum Result an example

• To limit GCV of particles to 3000 kcal/kg, the
  corresponding characteristic ash will be about
  55 at RD of cut 1.875.
• The cumulative GCV of theoretical cleans will be
  5200 kcal/kg and ash content 30 with cumulative
  yield of 85.

11
Conclusion

• Concept of limiting GCV can optimize coal washing
• It is suggested that if the worst particle can
  be effectively burnt in a given system of
  combustion, all better quality particles can be
  used up at ease.
• The actual cumulative yield of cleans and their
  quality will depend upon the raw coal supplied
  from day to day and efficiency of washing.
  However, the efficiency of combustion will remain
  practically the same.
• GCV is suggested to be used as a major factor to
  grade the coal as well as to optimize