Energy Engineering Questions and Answers – Types of Fuels

This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of Fuels”.

1. Fuels are classified as primary and secondary fuel based on the __________
a) Capacity to burn
b) Availability
c) State
d) Occurrence
View Answer

Answer: d
Explanation: Based on the occurrence, fuels are classified as primary fuels and secondary fuels. A primary fuel is available in nature E.g., wood, peat, lignite, natural gas, petroleum, etc. A primary fuel is also called as a natural fuel. A secondary fuel is not available in nature, but it is prepared from primary fuel by artificial means e.g. gasoline, diesel, coke gas, blast furnace gas, kerosene etc. A secondary fuel is also known as artificial fuel.

2. Which fuel is partially carbonized and is considered as a primary stage in coal formation?
a) Coal bitumen
b) Anthracite
c) Peat
d) Lignite
View Answer

Answer: c
Explanation: Peat is partially carbonized and decomposed material formed mainly due the transformation of buried vegetation. It is considered as the primary stage in the formation of the coal. It is spongy substance with high moisture content (upto 80%). Hence it has to be dried before use. In dry form, it has a calorific value of about 14560 KJ/kg. It consists of 58% C; 6.3% H2; 30.8% O2; 0.9% N2 and 4% ash.

3. Which fuel is called secondary stage in the formation of coal?
a) Lignite
b) Bituminous coal
c) Peat
d) Anthracite
View Answer

Answer: a
Explanation: Lignite is the secondary stage in the formation of coal. It is brown in color and hence known as brown coal. It is used as a low grade fuel especially for domestic use and also as a boiler fuel. It is the intermediate stage between bituminous coal and peat. It has a calorific value of about 12500 kJ/kg. It consists of 66% C; 5% H2; 20% O2; 1% N2; 1% S and 3.5% ash and other incombustible.
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4. Which fuel is commonly available in both caking and Non-caking forms?
a) Lignite
b) Bituminous coal
c) Peat
d) Anthracite
View Answer

Answer: b
Explanation: Bituminous coal is the most commonly used form of coal. It is available in both caking and non-caking forms. It burns with a yellow flame. It has calorific value of about 32000 kJ/kg. It consists of 81%C; 5%H2; 8% O2; 1.5% N2; 1% S; and 3.5% ash. Caking bituminous coal softens and forms a pasty mass if heated at higher temperature. This coal is used to manufacture coke. Non-caking bituminous coal doesn’t soften on heating and hence it is used in steam power plants.

5. Which fuel is the final stage in the formation of coal?
a) Bituminous coal
b) Anthracite coal
c) Peat
d) Lignite
View Answer

Answer: b
Explanation: Anthracite coal is called final stage of transformation of buried vegetation into coal. It is non-caking and has highest calorific value of about 35500 kJ/kg. It burns at high temperature and is smokeless. It consists of 91% C; 3% H2; 2.5% O2; 0.5% N2; 0.5% S and 2.5% ash. It is also used as a boiler fuel.
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6. Which form of fuel is used as a domestic form of fuel?
a) Wood
b) Bituminous Coal
c) Dung cake
d) Anthracite coal
View Answer

Answer: a
Explanation: wood is mainly used as a domestic fuel. It has low calorific value of about 10500 kJ/kg. It consists of about 48.5% C; 6% H2; 1.5% of ash; 43.5% O2 and 0.5% N2. Wood fuel is used in different forms such as firewood, charcoal, chips, sheets, pellets and sawdust. The particular form used depends upon factors such as source, quantity, quality and application.

7. What is the main purpose of demineralization treatment plant?
a) To remove deposits made on tube
b) To reduce scaling on tube
c) To remove salts
d) To filter the boiler water
View Answer

Answer: c
Explanation: The salts (calcium and magnesium) of hard water have to be removed to overcome all types of effects caused by water on tubes. Demineralization treatment plant generally consists of cation, anion and mixed bed exchangers. These ions are recombined with water to form pure water. Very pure mineralized water becomes highly corrosive once it absorbs oxygen.

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8. What type of gear mechanism is provided to rotate the turbine generator shaft?
a) Mutilated gear mechanism
b) Ratchet gear mechanism
c) Barring gear mechanism
d) Planetary gear mechanism
View Answer

Answer: c
Explanation: Barring gear is the mechanism provided to rotate the turbine generator shaft at very low speed after unit stoppages. Once the steam inlet valve is closed, the turbine comes down towards standstill. When it stops completely, there is a tendency for turbine shaft to deflect or bend if allowed to remain in same position for too long.

9. Which gas cooling is used in large generator units of steam plant?
a) Sulfur dioxide
b) Hydrogen
c) Carbon dioxide
d) Nitrogen
View Answer

Answer: b
Explanation: Hydrogen gas cooling is used for large generator units in steam plant. Because it has the highest heat transfer coefficient of any known heat transfer coefficient of any gas and for its low viscosity which reduces wind-age losses. This system requires special handling during start up, with air in the generator enclosure first displaced by carbon dioxide before filling with hydrogen. This ensures that the highly flammable hydrogen does not mix with oxygen in the air.
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Sanfoundry Global Education & Learning Series – Energy Engineering.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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