This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Fuels and Combustion”.
1. In presence of which gas is the fuel burnt to generate energy in form of heat?
Explanation: The fuel is burnt in presence of oxygen to generate energy in form of heat. This heat energy can be used for electrical power generation in steam power plants and for propelling ships, automobiles and locomotives etc.
2. Which are the main constituents of fuel from given options?
a) Carbon and Nitrogen
b) Oxygen and Hydrogen
c) Carbon and Hydrogen
d) Helium and Oxygen
Explanation: Carbon and Hydrogen are the main constituents of a fuel. In addition to them, fuel also contains sulfur, oxygen and nitrogen in minimal quantities. Depending on the fuel, the percentage of carbon ranges from 50-95%, hydrogen (H2) 2-6%, oxygen (O2) 2-4%, sulfur (S2) 0.5-3% and Nitrogen (N) 5-7%. A solid fuel may also contain 2-30% ash. In a fuel carbon, hydrogen and sulfur are combustible elements whereas nitrogen and ash are incombustible elements. Since the major combustible elements in fuel are carbon and hydrogen it can also be called as Hydrocarbon fuel.
3. Which fuel is used widely in steam power plants?
Explanation: Coal is the oldest form of fuel and is still used in large scale throughout the world by steam power plants as well as all power generation plants. Coal is a heterogeneous compound and its constituents are always carbon, hydrogen, oxygen, sulfur, nitrogen and certain mineral non combustibles.
4. What is phenomenon of formation of coal called?
Explanation: The phenomenon by which the buried vegetation consisting wood, grass, shrubs etc, transformed into coal is known as metamorphism. The nature of coal will depend upon the type of vegetation buried and nature and duration of metamorphism. There are different types of metamorphism namely contact metamorphism, regional metamorphism, cataclastic metamorphism, hydrothermal metamorphism, burial metamorphism and shock metamorphism.
5. On what basis is the coal classified?
a) Period of formation
b) Depending on capacity to burn
c) Region/area where is it formed
d) Physical and chemical composition
Explanation: The coal is classified on the basis of its physical and chemical composition. The proximate and ultimate analyses are the common tests which are used to find the commercial value of the coal. The proximate analysis gives characteristics of coal such as percentage of moisture, ash and volatile matter. Analysis of coal gives an indication about fusion temperature and heating value of the coal.
6. What is the use of electrostatic precipitations in steam power plant?
a) To remove the steam
b) To draw the coal powder into boiler
c) To remove the feed water
d) To remove fly ash
Explanation: The electrostatic precipitators are extensively used in the steam power plant for removal of fly ash from the electric utility boiler emission. Since the water inside the boiler is converted into steam, the fire for converting is fuelled by burning the coal which produces high amount of fly ash, so that the ash’ can be reused. The use of electrostatic precipitators is growing rapidly because of the new strict air code and environmental laws. An electrostatic can be designed to operate at any desired efficiency.
7. Why is ‘make-up water’ added to drum continuously?
a) To remove the impurities in tube
b) To replace the water that has been converted into steam
c) To keep the system cool externally
d) To compensate for water loss trough blow down
Explanation: Make-up water is added to compensate for the losses of water incurred by blow downs or leakages occurring in boiler, and also to maintain desired water level in boiler steam drum. Blow down and leakages are common since there is continuous flow of condensate from condenser to boiler.
8. What causes failure of boiler tube?
a) Heating the tubes, when desired water level is not maintained
b) Induced pressure in the water
c) Over use of boiler
d) Hardness of water
Explanation: Hardness of water causes failure of boiler tube. Hard water consist of calcium and magnesium salts. Hardness in water will form deposits on the tube water surfaces which will lead to overheating and failure of tubes. Thus the salts have to be removed from water.
Sanfoundry Global Education & Learning Series – Energy Engineering.
To practice all areas of Energy Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.