This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Artificial Solid Fuels & Liquid Fuels”.
1. Which fuel is produced by slow pyrolysis?
a) Dung cake
Explanation: Charcoal is produced by slow pyrolysis. It is prepared by heating wood with limited supply of air below 280°C. It contains 80-90% of carbon. It is used for domestic purpose namely cooking, heating and metallurgical purpose. Charcoal is the light weight black carbon and ash residue produced by removing water and other volatile constituents from animal and vegetation substances. There are different types of coal namely sugar charcoal, activated charcoal, lump charcoal, etc.
2. Which fuel is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber?
d) Briquette coal
Explanation: Coal is prepared by heating bituminous coal continuously for 15 to 18 hours in closed chamber in the absence of air 500oC to 700oC. During this process the volatile matter is removed from the coal, leaving a dull black color to coke. It is a hard porous structure and smokeless. It contains 85 to 95% carbon. When the bituminous coal is heated between 900oC to 1000oC, hard coke is produced. It is used in gas producing plants and blast furnaces.
3. Which fuel is prepared by moulding finely ground coal under pressure?
c) Briquette coal
Explanation: Briquette coal is prepared by moulding finely ground coal under pressure with or without the addition of binding material. Most commonly used binding materials are coal tar, crude oil and clay. By using briquette coal, the fuel loss through boiler grates can be avoided.
4. Which fuel is produced by powdering low grade coal with high ash content?
b) Pulverized coal
d) Briquette coal
Explanation: Pulverized coal is prepared by powdering low grade coal with high ash content. Dry coal is pulverized in pulverizing mills. It burns most efficiently when mixed with air and hence it is used in most of the power plants.
5. Which is the correct advantage of solid fuels out of the given option?
a) They have low ignition temperature
b) They produce small amount of smoke
c) They have higher calorific value
d) They do not form any clinker
Explanation: They have low ignition temperature’. Ignition temperature is the minimum temperature at which a substance starts to burn. Different fuels have different ignition temperature. Some fuels have low ignition temperature and some have high ignition temperature. The fuels that have low ignition temperature are highly inflammable and burn quickly at the spark of fire. While some fuels that have high ignition temperature do not burn quickly. They require heating to burn. For e.g., kerosene oil does not burn unless it is heated up to its ignition temperature.
6. Choose the proper disadvantage of solid fuels out of the given option?
a) They produce lot of smoke
b) They have low ignition temperature
c) They are high in production cost
d) They cannot be easily transported
Explanation: Solid fuels tend to produce lot of smoke because they have large percentage of ash content. They are also brittle in nature and they contain some amount of ash in it when they are in ground. Due to their brittleness, it is common nature of solid fuels that they break into pieces while mining and transporting and form ash.
7. In what forms are liquid fuels available in nature?
a) Light distillate
b) Petroleum spirit
c) Petroleum naphtha
d) Crude petroleum
Explanation: Liquid fuels are available in nature in the form of crude petroleum. All commercial liquid fuels are derived from crude petroleum or crude oil. The crude oil, as it comes out from oil wells contains 83-87% carbon, 10-14% hydrogen and small percentages of sulfur, nitrogen, oxygen and gases containing mainly ethane and methane.
8. Name the process used to eliminate impurities present in crude oil?
Explanation: The impurities present in the crude oil are eliminated by the process of refining oil by distillation. It is based on the principle that boiling points of various hydrocarbons increase with an increase in molecular weight and when distilled, the crude oil is separated into gasoline, kerosene, fuel oil or reduced crude oil.
9. Which fuel has the lightest liquid petroleum fraction?
Explanation: Petrol has the lightest liquid petroleum fraction and highly volatile in nature. It is also called gasoline. It has a specific gravity ranging from 0.70 to 0.78. It is obtained between 65 to 200oC and it is a mixture of a number of hydrocarbons. It is light yellow in color and it is used as a fuel in automobiles and aero planes.
10. Which fuel is heavier than petrol but less volatile and it is commonly used as domestic fuel?
b) Distilled fuel
Explanation: Kerosene is heavier than gasoline but less volatile than it. It has a specific gravity ranging from 0.78 to 0.85. It is obtained between 150 to 300oC. It is mainly used in aviation gas turbines as jet fuel and also in lams and stoves. It is miscible in petroleum solvents but immiscible in water.
11. Which fuel is slightly heavier than kerosene and is produced in petroleum fractions?
b) Crude oil
Explanation: Distillate is slightly heavier than kerosene and is used as fuel and domestic fuel. It is liquid fuel usually distilled from crude petroleum and produced in fractions. Distillate fuel is a type of fuel for internal combustion vehicles with either mechanical transmissions or electric transmissions. They are used in automobiles locomotives and agricultural machinery as well as space heaters and power generators.
12. Which fuel has higher thermodynamic efficiency in liquid fuels?
Explanation: Diesel is heavier than kerosene. It has specific gravity ranging from 0.86 to 0.95. It is obtained between 200 to 370oC. It is used in diesel engine. Diesel engines have found broad use as a result of higher thermodynamic efficiency and fuel efficiency.
13. Which liquid fuel has a wider composition than diesel and used in furnaces of oil fired boiler?
a) Fuel oil
Explanation: Fuel oil is similar to diesel but has wider composition than diesel. It is used in furnaces of oil fired boilers. Broadly speaking, fuel oil is any liquid fuel that is burned in furnace or boiler for the generation of power, except oil is having a flash point of approximately 42oC and oils burned in cotton or wool-wick burners.
14. Which is the artificial liquid fuel obtained by fermentation process?
a) Fuel oil
Explanation: Alcohol is an artificial fuel obtained from vegetable matter by fermentation process. It is used in many chemical processes. The first four aliphatic alcohols (methanol, propanol, ethanol and butanol) are of interest as fuels because they can be synthesized chemically or biologically. The general chemical formula for alcohol fuel is CnH2n+1OH.
15. Which among the following fuels need excess amount of air for complete combustion?
a) Natural fuels
b) Liquid fuels
c) Gaseous fuels
d) Artificial solid fuels
Explanation: Artificial solid fuels need excess amount of air for complete combustion because they have low calorific value compared to liquid fuels and the rate of combustion of solid fuels cannot be easily controlled. They have tendency to form clinkers at high temperatures.
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