Question

Gross and net calorific value of fuel will be the same:
A. if its ash content is zero
B. under no circumstances
C. if its carbon content is very low
D. if its hydrogen/hydrogen compound content is zero

Answer 1

Hint: When we compare different types of fuel; the one of its basis of comparison is their calorific value. Calorific value is the amount of heat in a given volume of gas. It is the measure of the heat produced by complete combustion of a specified quantity of it. This is expressed in joules per kg.

Complete answer:
Let us see some differences between the two terms to get more updated on the question.

GROSS CALORIFIC VALUE	NET CALORIFIC VALUE
Amount of heat when a unit quantity of fuel is completely burnt and the products of combustion cooled to normal temperature.	Amount of heat when a unit quantity of fuel is completely burnt and the products of combustion leaves simultaneously.
It is also known as higher calorific value.	It is also known as lower calorific value.
Total energy can also be released when products have cooled to room temperature.	Total energy is released when products are hot.
The heat in byproducts can be recovered through condensation.	The heat in byproducts escapes in the surroundings.

The net calorific value is obtained by the formula which is the latent heat of the water vapours formed by combustion of hydrogen or from the moisture present in that fuel subtracted from the gross calorific value.
The gross and net calorific value of a fuel will be the same when the hydrogen compound content is zero.
So, the correct answer is “Option D”.

Note: There is no such big difference between calorific value and heat of combustion. It can be considered as heat of combustion also.
-Calorific value is the total heat released when a substance undergoes complete combustion with oxygen under standard conditions.
-Heat of combustion is defined as the heat released when the complete combustion of a compound occurs in its standard state to form products.