Power Systems Multiple Choice Questions on “Fuels”.
1. Which of the following is correct arrangement of different types of coals according to their increasing carbon content?
A. Peat, bituminous, lignite, anthracite
B. Peat, lignite, bituminous, anthracite
C. Bituminous, peat, lignite, anthracite
D. Peat, anthracite, bituminous, lignite
Answer: B
Clarification: Coal is the most commonly used fuel in thermal power plant. Coal contain moisture, carbon, hydrogen, sulphur, Nitrogen, Oxygen and ash. Coals are classified according to their calorific value and carbon content.
2. Which of the following is most suitable fuel for thermal power plant?
A. Peat coal
B. Lignite coal
C. Bituminous coal
D. Anthracite coal
Answer: c
Clarification: Peat and lignite coals have low calorific value and high ash content. Anthracite coals are found in small quantities and are therefore costlier for power generation. Bituminous coals have enough calorific value, low moisture and ash content so most suitable for power generation.
3. Read the below statements.
I. Sulphur is one of the combustible elements
II. The Sulphur content of coal should be less than 1%
A. Only I is correct
B. Only II is correct
C. I and II are correct
D. I and II are incorrect
Answer: C
Clarification: Sulphur content is one of the factors taken into account while selecting coal for steam power plant. Sulphur is combustible element and can produces energy. But its primary combustion product, Sulphur dioxide, is a health hazard due to which sulphur content in coal should be low.
4. Which of the following coal has highest moisture content?
A. Sub-bituminous coal
B. Bituminous coal
C. Anthracite coal
D. Peat coal
Answer: D
Clarification: Peat is the first stage in the process of transformation of buried vegetation into coal. It has about 60% to 90% moisture content and low carbon content (about 5% to 20%). Peat coal is not suitable for use in power plants.
5. Which of the following coal has highest enthalpy of combustion?
A. Peat coal
B. Sami-bituminous coal
C. Semi-anthracite coal
D. Lignite coal
Answer: B
Clarification: Peat and lignite coals have enthalpy of combustion about 3000 KJ/kg and 17600 KJ/kg. Semi-anthracite coals are harder than bituminous coals and have enthalpy of combustion up to 34750 KJ/kg while sami bituminous coals have that up to 35000 KJ/kg.
6. What is the main drawback of liquid fuel in thermal power plant?
A. High handling cost
B. Hard and Adhesive oil slag
C. Difficult to store
D. High cost of liquid fuel
Answer: D
Clarification: Handling and storing cost of oil fuels are less, load fluctuations can be made easily and few operations are needed. There is no disposal of ash. Superheaters are subjected to hard and adhesive oil slag which is often difficult to remove, but other heating surfaces are almost trouble free.
7. A minimum of 4 to 6 percent of ash is required in coal.
A. True
B. False
Answer: A
Clarification: This 3 to 6% of ash is required on hand fire grates and some stokers for protection of grades against overheating.
8. Grindability of coal should be low.
A. True
B. False
Answer: B
Clarification: Grindability index is inversely proportional to the power required to grind the coal to a certain fineness. Higher the grind ability factor index better the coal is.
9. The selection of coal for power plant does not depends on _________
A. Calorific value
B. Nitrogen content
C. Sulphur content
D. Grindability index
Answer: B
Clarification: The selection of coal for power plant depends on the number of factors such as calorific value, weather ability, sulphur content, ash content, particle size, grindability index, and caking characteristics. Nitrogen content is not needed for the selection of coal for power plants.
10. Read the following statements about coals.
I. Lignite coals can be used in thermal power plants
II. Super-anthracite coal are best for thermal power plants
A. Only I is correct
B. Only II is correct
C. I and II are correct
D. I and II are incorrect
Answer: A
Clarification: Lignite have 30 to 50% moisture and 20 to 40% carbon content and can be used in power generation. Super-anthracite coals are very hard with shiny black surface. It is non cooking and is very difficult to ignite and so, it has little importance in power generation.
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