Proximate Analysis:

Indicates the contents in the fuels in percentage by weight.

•Moisture•Volatile material•Fixed carbon•Ash

Moisture Content:Water expelled from the fuel by specified methods without causing any chemical change to fuel.

•1 g of fine powdered air dried coal is weighed in crucible.•Crucible is placed inside oven & Temperature is maintained at 105 to 110◦ C for 1 hour.•Then sample is taken out & weighed.•Loss in weight is the moisture content in the fuel.

Loss in weightPercentage of moisture = ------------------------ x 100 Wt. of coal taken

Moisture in coal evaporates during burning taking Latent heat of evaporation, hence moisture lowers the calorific value of fuel.

“Lesser the moisture content, better the quality of coal as a fuel”

Volatile Matter: Dried sample from the crucible is covered with a lid & placed in an electric furnace.

•Temperature is maintained at 925◦ C + 25◦ C for 7 minute.•Then cooled first in air, then in a desiccator & weighed again.•Loss in weight is reported as volatile matter present in coal.

Loss in weight due to removal of volatile matter Volatile material = ------------------------------------------------------------- x 100

Wt. of coal sample taken

High volatile matter content means that high proportion of fuel will distill over as gas or vapour, a large proportion of which escapes as unburnt. It will burns with long flame, high smoke and has low calorific value.

“Lesser the volatile matter, better the rank of the coal”

Ash:

•Residual coal in crucible is heated without a lid in a muffle furnace at 700◦ C + 50◦ C for half an hour.•Then cooled first in air and next in desiccator.•Then weighed and the ash content is reported.

Wt. of Ash left

Percentage of Ash = ---------------------- x 100 Wt. of coal taken

Ash is a useless, non-combustible matter and it reduces the calorific value of coal. •Ash also causes hindrance to flow of air and heat, thereby lowering the temperature.

“Lower the ash content, better the quality of coal”.

Fixed carbon

Percentage of Fixed carbon = 100 - % of ( moisture + Volatile matter + Ash )

“Higher the percentage of fixed carbon, greater is its calorific and better the quality of coal.”

Ultimate Analysis:

Gives the Elementary composition of

•Carbon•Hydrogen•Oxygen•Nitrogen•Sulphur in percentage by Weight

Determination of Carbon & Hydrogen:

•1 g of coal is burnt in current of oxygen in a combustion apparatus.•C & H are converted into CO2 and H2O.•Gaseous products are absorbed in KOH & CaCl2 of known weights.•Increases in weights are determined.

Corbon: Increase in weight of KOH tube * 12

% of C = ------------------------------------------------------ x 100 Weight of coal sample taken * 44

Hydrogen:

Increase in weight of CaCl2 tube * 2 % of H = ---------------------------------------------------- x 100

Weight of coal sample taken * 18

“Greater the percentage of Corbon and Hydrogen, better is the coal in quality and calorific value”.

Determination of Nitrogen:•1g of powdered coal is heated with conc. H2SO4 with K2SO4 as catalyst in a Kjeldal flask.•After solution becomes clear, treated with excess KOH.•NH3 is liberated & absorbed in known volume of standard acid solution.•Unused acid is determined with NaOH.•From the volume of the acid used by NH3 liberated % of N in coal is determined.

Volume of acid used x Normality x 1.4% of N = ------------------------------------------------------

Weight of coal taken

“Nitrogen has no influence in the calorific value. A good quality coal should have very little nitrogen.”

Determination of Sulphur content:

From washings of bomb in bomb calorimeter, Sulphur is converted into into sulphate.

S + 2H +2O2 H2SO4

H2SO4 + BaCl2 BaSO4 + 2HCl

Weight of BaSO4 obtained *32% of S = ------------------------------------------------------------------ x 100

233 * weight of coal sample taken in bomb calorimeter

Determination of Oxygen:

It is determined from the difference.

% of O = 100 – percentage of ( H + S + N + Ash ).

•Oxygen content decreases the Calorific value of coal•Oxygen is in combined form with Hydrogen, thus hydrogen available for combustion is lesser than actual.

“Good quality coal should have low percentage of Oxygen”

Reporting: Fuels are Heterogeneous in Nature so it is essential to

report all the data analytically.

Basis of reporting•Run-of-mine ( ROM ).•As-received.•Air dried.•Dry.•Dry and ash free ( d.a.f ).•Dry and mineral matter free ( d.m.m.f ).•Moist mineral matter free or simply mineral free.