KYAMBOGO UNIVERSITY
BIOMASS ENERGY
TECHNOLOGIES TEEE3205
ASSIGNMENT ONE
ZAVUGA JOHN BAPTIST
21/U/BEL/16950/PD
Determination of Calorific value of any solid biomass fuel.
Procedure
A known amount of fuel (between 0.5-1.0gm) is kept in a crucible supported
over a ring. A fine magnesium wire touching the sample of the fuel is then
stretched across the electrode.
The bomb is placed care fully in a copper calorimeter containing.in gms of
water
After stirring the water temperature t1 is noted
The electrodes are then connected with the battery and the circuit is
completed thus combustion of fuel takes place and heat is liberated
Now stirring of water continued and the final temperature of water t2 is noted
Treatment of Results / Calculations.
let
X = mass in gm of fuel taken in crucible.
W = mass of water in calorimeter.
W = mass equivalent in gm (of calorimeter, stirrer, thermometer, etc).
T1 = initial temperature of water in calorimeter.
T2 = final temperature of mater in calorimeter.
Ʝ = Higher Calorific value of fuel in Cal/gm.
Now.
Heat liberated by burning the fuel = XꞲ
Heat. absorbed by water and apparatus. = (W+W) (t2 -t1)
So
Heat liberated by fuel = Heat absorbed by water and apparatus
XꞲ = (W+W) (t2-tı)
Highest Calorific value of fuel (Ʝ) = (W+W) (t2-t1)/X
Cal/gm or KCal/kg.
Note
Water equivalent of the calorimeter is determined by burning a fuel of known
Calorific value and using the above equation
fuel used for this purpose are: -
Benzoic acid (HCV = 6.325 Kcal/kg)
Nepthalene (HCV = 96.88 Kcal/kg)
Let H be the % of hydrogen in fuel then
LCV = HCV - 0.09H X 589 Cal/gm.
LCV _ lowest calorific value
HCV _ Highest calorific value
Corrections.
To get more accurate result, the following corrections are needed
(I) Fuse wire correction
The heat measured in above described case includes the heat given but by
ignition of fuse wire used hence it must be subtracted from the total value.
(ii) Cooling correction
The time taken to cool water in calorimeter from maximum temperature to
room temperature is noted from the rate of cooling (dT/minute) and the actual
time taken from cooling (t-minutes).
The cooling correction (dT * T) is added to rise in temperature.
(iii) Cotton thread correction.
The correction for cotton thread used for firing is calculated from weight of dry
cotton thread actually used and on the basis of Calorific value of cellulose
which is 4140 Cal/gm.
(IV) Acid correction
Due to high pressure and temperature, Nitrogen and sulphur present in fuels
are oxidised into HNO3 and H2SO4
2S02 + O2 + H2O → 2 H2SO4 + Heat
2N + 2H + 3O2 → 2 HNO3 + Heat
Equations 1 and 2 are exothermic reactionns and so their heat liberated must
be subtracted.
