CALORIFIC VALUE OF FUEL USING JUNKER’S GAS CALORIMETER

CALORIFIC VALUE OF FUELSIt is defined as the heat liberated in kJ by

complete combustion of 1 kg of fuel, solid or liquid.

For gases it is the heat liberated in kJ per cubic metre at STP.

For example:Fuel kJ/kg kCal/kg

Hydrogen 141900 33900

Butane 49200 11800

Diesel 45000 10700

Anthracite 27000 7800

Wood 15000 3600

Natural Gas 54000 13000

TYPES OF CALORIFIC VALUESHigher Calorific Value: It is the total heat

liberated when all the products of combustion are brought back to pre-combustion temperature and in particular, condensing any vapour produced. (kJ/kg)

Lower Calorific Value: It is determined by subtracting the latent heat of vaporization of the water produced from the Higher Calorific value. (kJ/kg)

Thus, (HHV)p = (LHV)p + m hfg (HHV)v = (LHV)v + m(ug – uf)

COMPARISON OF HCV AND LCVHere is a comparison of HCV and LCV of

some fuels.FUEL HCV (MJ/kg) HCV (kj/mol) LCV (MJ/kg)

Hydrogen 141.80 286.00 121.00

Butane 49.50 20900 45.75

Gasoline 47.30 - 44.40

Propane 50.35 2220 46.35

Anthracite 2700 - -

Kerosene 46.20 - 43.00

Paraffin 46.00 - 41.50

THE JUNKER’S GAS CALORIMETER

APPARATUS The apparatus mainly consists of a

cylindrical shell with copper coil arranged in two pass configuration with water inlet and outlet to circulate through the copper coil, a pressure regulator, a wet type gas flow meter & a gas Bunsen burner, temperature sensors for measuring inlet, outlet water temperature, and for flue gas temperature and a measuring jar.

WORKING PRINCIPLE This Gas Calorimeter works on the Junker's

principle of burning of a known volume of gas and imparting the heat with maximum efficiency to steadily flowing water and finding out of the rise in temperature of a measured volume of water.

The formula, Calorific Value of Gas X Volume of Gas = Volume of water X Rise in Temperature, is then used to determine the Calorific Value of the Gas (assuming that heat capacity of water is unity).

DETERMINATION OF CALORIFIC VALUEThis Calorimeter covers a wide range

between 120 BTU (1000 to 26000 K Cal/m3).The Calorimeter is fixed on a tripod stand

having levelling screws to keep the Calorimeter in perfectly vertical position.

 A constant water head maintenance device provided in the feed water pipe along with the inlet water flow regulator is fixed  to the outer housing of the calorimeter.

PROCEDURE(Contd.)The gas source is connected to the pressure

regulator, gas flow meter and the burner respectively in series.

The water and gas flows are started to flow at a constant rate and the burner is lighted outside the calorimeter.

The gas flow is regulated at a steady state to any designed flow (volume).

The burner is inserted into the calorimeter and the outlet water is allowed to attain a steady temperature.

PROCEDURE(Contd.)The outlet is let into a 1000mL flask and

started and the initial gas flow rate is noted.The time taken for the 1000mL flask to be

filled and the final gas flow rate is also noted.

FORMULA TO BE USED CVg=( Vw x w x CPw x ∆T ) / Vg x gℓ ℓ

where ℓw is the density of waterVw is the volume of water

collected in litresCPw is the specific heat of water∆T is the change in temp. of waterVg is the volume of gas burnt in

litresℓg is the density of the gas burnt

APPLICATIONSPetroleum IndustriesCoke Oven BatteriesThermal Power HousesCement IndustriesFuel Gas Producers & ConsumersSteel PlantsFertilizer Units