coal analysis
DESCRIPTION
Indian Coal analysisTRANSCRIPT
Coal AnalysisProximate analysis of coal
• Determines only fixed carbon, volatile matter, moisture and ash
• Useful to find out heating value (GCV)
• Simple analysis equipment
Ultimate analysis of coal
• Determines all coal component elements: carbon, hydrogen, oxygen, sulphur, etc
• Useful for furnace design (e.g flame temperature, flue duct design)
• Laboratory analysis
Coal testingSample from Crusher
House/RC Feeder Size 20mm
Crushed to Size 12.5mm
Coning/ quartering
Crushed to size 3.35mm
Coning/ quartering
Pulverized to 212µ
Sample for proximate analysisKept at room temperature for 24hrsAD Basis Proximate analysis
12.5mm coal (1kg)For surface moisture (x)
2.8mm coal (10g)For inherent moisture (y)
Total moistureTM= x+y{(1-x)/100}
For TM basis report=(100-TM moisture)/(100-AD)
Coal testing
Proximate analysis Moisture Content : Moisture in coal must be transported, handled and stored Since it replaces combustible matter, it decreases the heat content per kg
of coal Aids radiation heat transfer 1-2 gm 72 mesh coal at 105-110 C till constant weight
Volatile Matter: Consist of CH4, hydrocarbons, H2 and CO, and incombustible gases like
CO2 and N2 Proportionately increases flame length, and helps in easier ignition of
coal Sets minimum limit on the furnace height and volume 72 mesh coal 900-950 C for 7 minutes
Proximate analysisAsh Content :• Ash is an impurity that will not burn• Reduces handling and burning capacity.• Increases handling costs.• Affects combustion efficiency and boiler efficiency• Causes clinkering• 1-2 gm 72 mesh 800 C (burned)
Fixed carbon: Solid fuel left in the furnace after volatile matter is removed consists mostly of carbon may contains some H2, O2, S and N2
gives a rough estimate of heating value of coal
Moisture Content
Free moisture- Surface moisture present on apparently dry coals, which is dried off when coal is exposed to the air without heating.Inherent moisture- The moisture retained in the process of coal substance when free moisture has evaporated
Total moisture- It is the sum of free and inherent moisture.
Typical range of moisture is 0.5 – 20 %
Air-dry moisture- It is a term used to describe that part of the total moisture retained in the 72-mesh analysis sample after it has been exposed to the laboratory atmosphere and has attained approximately equilibrium with it.
Determination of Air Dried Moisture Weigh accurately 1 gm of sample in a silica
dish (with cover). Spread it thinly, keep it in electrically heated air oven and temperature is controlled at 108 +/- 2oc for 1 hour. Then take out the dish and keep it in a desiccators to cool and weigh, from which calculate the percentage loss as moisture.
% moisture Decrease in weight of coal * 100
= ------------------------------------------- Wt of sample taken
Determination of Ash content
Weigh 1 gm of sample in a silica dish (with cover). Spread it uniformly , keep it in an air electrically heated muffle furnace and temperature is raised to815 +/- 10oc in 1 hour. Maintain it for 1 hour. Then take out the dish and keep it in a desiccators to cool and weigh, from which calculate the percentage of ash.
weight of ash * 100% Ash = -------------------------------------------
Wt of sample taken
Fixed Carbon It is a calculated figure: Fixed carbon = 100
– (moisture + volatile matter + ash), all
expressed as per cent on the same basis.
Its purpose is to measure the coke residue
from the volatile matter determination
Fixed carbon gives a rough idea of the
heating value of coal
Determination of Volatile matter Heat an empty, clean V.M crucible with
lid at 900 +/- 10oc for 07 minutes, remove and cool it for 10 mins in a desiccators, then take empty weight (W1). Take 1 gm of coal in it. Keep on a silica stand in an electrically heated furnace maintained at 900 +/- 10oc for 07 minutes. Take out ,cool for 1 min on a metal plate ,then in a desiccators for 10 min and weigh (W2).
Calorific Value Of Coal Calorific value is the amount of heat per
unit mass that evolved on complete combustion and is expressed in kJ/kg.
This is normally determined at constant volume by burning a known weight of coal in a bomb calorimeter under condition of excess oxygen and measuring the amount of heat evolved.
CV is two types : GCV and NCV
Reporting of AnalysisConcept of TM Basis & AD Basis Analysis is done on AD Basis Reported on TM Basis
TOTAL MOISTURE12.5mm coal (1kg)For surface moisture (x)
2.8mm coal (10g)For inherent moisture (y)
Total moistureTM= x+y{(1-x)/100}
For TM basis report =(100-TM moisture)/(100-AD)ThusReported moisture = T.M.Reported Ash ={(100-TM moisture)/(100-AD)}*AshReported TM basis VM ={(100-TM moisture)/(100-AD)}*VMReported TM basis GCV ={(100-TM moisture)/(100-AD)}*GCV
Weigh 1kg sample in a container expose to lab condition for 24 hrs.Weigh again. Loss in weight represents Surface Moisture (x)
Weigh 1gm sample in a moisture dish and keep it at 1080C for 1.5 to 3 hrs in oven till constant weight Weigh again. Loss in weight represents inherent moisture (y)
Coal Payment
Equilibrated moisture: moisture@400C 60RH Seam Moisture: As calculated by CFRI =9
Thus Total Moisture= 9+EM
TM>9+EM them moisture from outside. Thus main motive of doing EM is to calculate deduction
Deduction for excess moisture =TM-(9+EM)
Net Calorific Value
• NCV is the difference between the GCV and heat absorbed by water (due to combustion and surface moisture.
• NCV= GCV--53 H Kcal/kg where H is the percentage of hydrogen present including hydrogen of moisture and water of constitution of the mineral matter.
Useful Heat Value
• Power coals (non coking coal ) in
India are presently graded by UHV.
• UHV (Kcal/kg)= 8900-138(A+M) for
V.M >19% , A and M at 60% RH &
40OC