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.< 1200C < 1300C Max.
1400-1450C 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 1.0 Fouling Potential (Deposits of Ash in S/H)
Low Medium High Severe Ash Fusion Temp. Higher Ash Fusion Temp.
>1100C 25 >25 >20 FC/VM % 1-1.25 1-1.25 1-1.25 1-1.25
1.4-1.6
