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147530179 proximate n ultimate analysis

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 weight
Percentage 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.



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