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Calorific Value

CALORIFIC MEASUREMENT (B.T.U.s)


 

Calorific Value

The following is adapted from the 298 page "Final Report of the Peat Committee."

The calorific value of peat from the various Canadian bogs as shown in the foregoing Tables II and III is determined on the absolutely dry sample. The heating value, however, of the absolutely dry sample is no index as to the effective heating value of the manufactured peat fuel, since the moisture content of the commercial fuel may be anything from a few percent up to 60%. It is usual, for power purposes, to deliver the peat to the power plant with a moisture content of from 25 to 30%,

and all effective heating values are calculated on this moisture content. In all the calculations and the curves plotted from them, the calorific value of the absolutely dry sample of peat has been assumed to be 9,500 B.T.U. per pound. To determine the effective heating value when the moisture content and the calorific value of the absolutely dry peat re known, the following formula may be used:

A = 1 / 100  1120 [100B- X (B+1200)] . . . . . . . . . . (1)

Where A is the calorific value of the wet peat in B.T.U. per pound; B is the calorific value of the absolutely dry peat in B.T.U. per pound; X is the- percentage of moisture contained in the peat for which it is desired to determine the calorific value. The total quantity of heat required to raise one pound of water from 62F to 212F and evaporate it, is denoted by 1,120 B.T.U.

Terminology

Calorific: Capable of producing heat; causing heat; heating.

B.T.U. – British Thermal Unit: The amount of heat needed to raise one pound of water one degree Fahrenheit.

Pound (lb.): British Imperial weight measurement. One pound is approximately 454 grams; one kg is approximately 2.2 pounds.

Fahrenheit: Temperature scale. One Fahrenheit degree is 5 9 of a Celsius degree, or one Celsius degree is 1.8 Fahrenheit degrees.

If it is desired to calculate the calorific value from the ultimate analysis, the following formula (an adap- tation of that of Dulong) may be used:

Y = C 14600 + (H - 1/8 O) 62100 - (9 H + X) 1120. . . (2)

C = weight of carbon; H = weight of hydrogen; O = weight of oxygen; X = weight of water = weight of carbon; H = weight of hydrogen; O = weight of oxygen; X = weight of water = weight of carbon; H = weight of hydrogen; O = weight of oxygen; X = weight of water

In this formula, the loss due to the water formed by the combination of the hydrogen and oxygen of the fuel is taken into consideration; whereas in formula (1) such loss is not taken into account.

The following ultimate analysis of a sample of peat taken from the Alfred bog will be used as an illustration.

Carbon . . . . . . . . . .  .  .  .  .  .  .  .   .  .  .  . . . 56.0%
Hydrogen . . . . . . . .  .  .  .  .  .  .  .  .   .  .  . . .  5.2%
Ash . . . . . . . . . . .  .  . . .  .  .  .  .  .   .  .  .  .  .  6.0%
Oxygen, nitrogen and sulphur by difference . . 32.8%

The nitrogen and sulphur may be taken as 2%, leaving 30.8% as oxygen.

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