Engineering Chemistry Multiple Choice Questions on “Coal Technology”.
1. How do the non-coking coals are subjected to consumers in India?
a) By washing
b) By sizing
c) By sorting
d) By blending
Answer: b
Clarification: Sizing is done for non coking coal where as for coking coal, coal are beneficiated to washing before their distribution to consumers. Sorting is done for both type of coal.
2. How is the sizing of coal processed?
a) By the use of measuring instruments
b) By the use of computer software
c) By crushing and screening
d) By the mass of the coal
Answer: c
Clarification: Crushing makes the top surface of a coal furnish due to which it becomes easy to handle (by reducing its overall top size). Screening is used to group process particles into ranges by size. By appropriate sizing, transportation of coal becomes easier.
3. By which process does the impurities of coal are generally removed?
a) Screening process
b) Sorting
c) Blending
d) Wet washing
Answer: d
Clarification: Jig washers and water cyclones are used for the removal of impurities of coal by wet washing. Wet washing is affected with the help of water or a dense medium as the sorting liquid. This process is used for making the density of the clean coal and impurities same.
4. Which of the following is used for the removal of impurities by heavy media separation in industries?
a) Magnetite
b) Zinc chloride
c) Bromoform
d) Carbon Tetrachloride
Answer: a
Clarification: For laboratory we can use zinc chloride but for industrial process we have to use magnetite or fine grains of sand. This is due to cost factor and properties of both of them at large scale.
5. For coarse fractions of dewatering of coal, which of the following process is used?
a) Filtration
b) Thickening
c) Flocculation
d) Centrifugation
Answer: d
Clarification: Centrifugation is a separation process that uses centrifugal force to settle the particles of a solid-liquid mixture. Since at the coarse fraction there is some coal reduction during dewatering due to which centrifugation process is used. Filtration, thickening and flocculation processes are used for finer fractions.
6. Froth flotation process is used for ____________________
a) Screening of coal
b) Beneficiation of coal
c) Dewatering of coal
d) Mining of coal
Answer: b
Clarification: Froth floatation is a process for selectively separating a hydrophobic substance. Before froth flotation the coal is crushed and grinded. Selective agglomeration process is also used for beneficiation of coal.
7. Which of the following is not an advantage of the cleaning of coal?
a) It increases the cost of the coal
b) It increases the efficiency of coal
c) It removes the impurities like phosphorous and sulphur
d) It reduces its ash content
Answer: a
Clarification: The cleaning of coal reduces impurities due to which it becomes easy to transport and store, which reduces the cost of the coal. It also increase the calorific value of the coal.
8. What is the main purpose for a blending of coal?
a) To produce more amount of coal
b) To produce good quality of coal
c) To decrease the cost of coal
d) To produce different types of coal at same time