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).

Determination of Volatile matter

A = (W2-W1) / Wt of coal taken

V.M % = (A-Moisture %)*100

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

Classification Of Coal By UHV GRADE

Calorific value range (kcal/kg)

A >6200

B 5600-6200

C 4940-5600

D 4200-4940

E 3360-4200

F 2400-3360

G 1300-2400