This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Coal Weighing Methods”.
1. What does ESP stand for in dust collection?
a) Endothermic sensor plate
b) Extrasensory perception
c) Electrostatic precipitators
d) Electronic stability program
View Answer
Explanation: With stringent air quality restriction by the governments, majority of power plants in the world use electrostatic precipitators (ESP’s) for dust removal. An ESP can handle large volumes of flue gases accompanied low pressure drop and high collection efficiency (99.5%). It facilitates easy removal of dust particles.
2. What happens when high voltage is applied to the electrodes in electric dust collectors?
a) Forms uniform electric field
b) Corona is formed
c) The whole system gets charged
d) Ions move from emitting electrode to collecting electrode
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Explanation: When the high voltage is applied, it generates a unidirectional non uniform electric field having greater magnitude at the discharge electrodes. This result in a blue luminous glow called corona around them. This corona is an indication of negatively charged ionized gas molecules which travel from discharge electrodes to grounded collection electrodes.
3. Why is weighment of the coal essential in the plants?
a) For knowing the quantity of the coal present
b) For getting optimum efficiency
c) For knowing which type of coal has good fuel content
d) To separate the grades of coal
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Explanation: The consumption of coal and its cost has major important once as coal forms the basic ingredient of the thermal power plant. Weighment of coal is essential for getting optimum plant efficiency at reduced cost using weighers.
4. Which type of weigher is commonly used all over the world?
a) Electronic weighers
b) Mechanical weighers
c) Pneumatic weighers
d) Nuclear weighers
View Answer
Explanation: Mechanical weigher is commonly used all over world. This based on mechanical principle. This works on a lever system mounted on knife edges and bearings that connected to a resistant like a spring or pendulum. The resultant value obtained by multiplication of load and speed values is displayed by a digital counter.
5. Which type of weighers is used in place where the electronic weighers are not allowed?
a) Pneumatic weighers
b) Mechanical weighers
c) Nuclear weighers
d) Electronic weighers
View Answer
Explanation: The pneumatic weighers use a pneumatic transmitter weigh head and the corresponding air pressure determined by the load applied and is transmitted to the weight indicating receiver may be used where electronic system is not permitted for use.
6. Electronic weighers are based on which principle?
a) Semiconductor principle
b) Electromagnetic principle
c) Load cell principle
d) Junctions
View Answer
Explanation: The operation is based on load cell principle. The load cells produce voltage signals proportional to the applied load. This system maintains high accuracy in measurement. Its performance is affected by temperature, noise, dust and humidity of the air.
7. What types of rays does the nuclear weigher used to measure the weight?
a) Infrared rays
b) Ultraviolet rays
c) Gamma rays
d) X-ray waves
View Answer
Explanation: Nuclear weighing system operates on gamma ray, Works on gamma rays absorption principle. A radio-active source located in the source head emits gamma rays which pass through the material on the conveyor to the detector.
8. What is the main disadvantage of the nuclear weigher?
a) They are not mobile
b) Accuracy depends on speed of material
c) They are big in size, requires large amount of space
d) Consumes large amount of electricity
View Answer
Explanation: Main disadvantage of the nuclear weighing machine is that its accuracy depends on a consistent speed of material movement and the condition of the detectors since this should be kept clean at all times as otherwise absorption value of gamma-rays will be affected.
Sanfoundry Global Education & Learning Series – Energy Engineering.
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