Question

The highest grade of coal, whose surface is shining and has the highest calorific value is :
A) Bituminous
B) Peat
C) Anthracite
D) Lignite

Answer 1

Hint: Highest grade of coal will be the one which will have the highest carbon content and fewest impurities. Anthracite contains a very high amount of 80 to 95% of fixed carbon and very little amount of volatile matter.

Complete step by step answer:
The four main types of coal are:
Peat: This coal is formed in the first stage of transformation of wood to coal. It is light brown in colour and is friable. It contains less than 40 to 55% carbon and a high amount of impurities. It burns like wood and produces a lot of smoke, and pollution because it contains sufficient volatile matter and a lot of moisture.

Lignite : It is formed after peat coal and is the intermediate stage of coal formation. It contains 40 to 45% carbon and moisture content is high (over 35%). It is the lowest rank of coal. It undergoes spontaneous combustion. It is also called brown coal.

Bituminous: It is a soft coal and is most widely available. It has 40 to 80% carbon content and the moisture and volatile content is 15 to 40%. It is dense, and is usually of black colour. Its calorific value is sufficiently high due to high carbon content and low moisture. It is the most common type of coal used in electricity generation.

Anthracite: It is formed in the last stage in coal formation. It is the highest quality of coal and is extremely hard. It has a brilliant black submetallic luster and thus has a shiny surface. It contains 80 to 95% carbon, very little volatile matter and hence has the highest calorific value. It burns with a nice blue flame (blue flame means there is complete combustion) and produces practically little or no pollutants. Among all types of coal, anthracite is the highest grade of coal.
So, the correct answer is “Option C”.

Note: Calorific value of a fuel is the amount of heat produced by the fuel when it is completely burned under the standard conditions. Anthracite contains the highest amount of carbon i.e. 80 to 95%, so it produces the maximum amount of heat and consequently has the highest calorific value among all types of coal.