Gross Calorific Value By Using Bomb Calorimeter (LECO AC 500)

The bomb calorimeter is used to analyze gross calorific value of any fuel. The amount of heat evolved when a unit weight of fuel is completely burnt and product of combustion cooled to normal Condition (with water Vapor condensed as a result). The heat contained in the water vapor must be recovered In the condensation process.

Principle of Bomb Calorimeter

The operating principle for this calorimeter is the same as in all bomb calorimeters. A weighed sample is burned in an oxygen-filled metal bomb while the bomb is held in a measured quantity of water within a thermal insulating jacket. By observing the temperature rise of the water and knowing the energy equivalent of the calorimeter, the amount of heat released from the sample can be calculated. Test results are commonly expressed in calories per gram (cal/g), British thermal units per pound (Btu/lb) or in the large Calorie per gram units commonly used for foods. They may also be expressed in joules per kilogram (J/kg) as used in the SI system of international units. In this manual the International Table calorie is used. This is defined as equal to 4.1868 joules. The following conversion factors may be used: 1 cal/g = 1.8 Btu/lb 1 cal/g = .001 Cal/g 1 cal/g = 4186.8 J/kg

Method	Isoperibol
RangeJoules/ChargeCalories/ChargeBTU/Charge	14000 – 350003300 – 830013 – 33(6000- 15000 BTU/lb for a 1gram sample)
Precision	≤0.05% RSD*
Resolution	1 BTU/lb; 0.1 cal/g0.001 MJ/kg; 0.1 Kcal/100kg
Analysis Time Regnault-Pfaundler:Precision Mode:Predictive Mode:	20 minutes8 minutes4.5 to 7.5 minutes
Corrections	Acid or % nitrogen, fuse wire, sulfur, moisture, spike weight, ash, and hydrogen
Temperature Measuring Resolution	0.0001◦ C
Gas Requirements	Oxygen 450 psi (31.0 bar) max; 99.99% purity
Electrical Requirements	115/230 V~ (±10%; at max load), 50/60 Hz, single phase, 3.2/1.6 A, 1,300 BTU/hr
Water Requirement	Distilled water only, approximately 16 lit full of water
Required Work Space** Benchtop	32 in. W x 31 in. D x 26 in. H (81.3 cm x 78.8 cm x 66 cm)

From LECO AC 500 Manual

Operation of Bomb Calorimeter

Filling the Bucket: The bucket is filled by DM water with the help of its pipette.

Assembling the Calorimeter: Take a approx… 1 gm of coal sample in crucible placed it in a crucible holder of bomb calorimeter connect the nichrome wire to the both connector and hang on it above 0.5 cm of the coal sample close the bomb. And fill oxygen 420 psi.

The Test Run:  start test run, first 3 min is water temperature equilibrium time and next 5 min is analysis time and after complete test it give automatically calculated GCV.

Calculated Correction: In bomb calorimeter there is a some correction like acid correction https://industrialchemicaltesting.com/acid-correction-in-gcv-sulphuric-and-nitric-acid/, fuse wire correction, sulfur correction, etc.

STANDARDIZING THE CALORIMETER

Standard Samples. A vial of fifty one-gram benzoic acid pellets is furnished with each calorimeter for standardization purposes. Additional benzoic acid pellets or powder can be obtained from Leco. Benzoic acid is usually compressed into tablet or pellet form for standardizing bomb calorimeters because the pellets are easy to handle and they burn more slowly than loose samples, thereby minimizing incomplete combustions.

The term “standardization” as used here denotes the operation of the calorimeter on a standard sample from which the energy equivalent or effective heat capacity of the system can be determined. The energy equivalent, W, of the calorimeter is the energy required to raise the temperature one degree, expressed as calories per degree Celsius or calories per degree Fahrenheit

The procedure for a standardization test is exactly the same as for testing a fuel sample. Use a pellet of calorific grade benzoic acid weighing not less than 0.9 nor more than 1.25 grams. Determine the corrected temperature rise, t, from the observed test data, also titrate the bomb washings to determine the nitric acid correction and measure the unburned fuse wire. Compute the energy of Benzoic Acid Powder and Pellets equivalent by substituting in the following equation:

W= Hm+e1+e2/t

W = energy equivalent of the calorimeter in calories per degree Celsius (Centigrade), or calories per degree Fahrenheit

H = heat of combustion of the standard benzoic acid sample in calories per gram

m = mass of the standard benzoic acid sample in grams

t = net corrected temperature rise in degrees C or F

e1 = correction for heat of formation of nitric acid in calories

e2 = correction for heat of combustion of the firing wire in calories

Bomb Calorimeter Image and Diagrams