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
Answer: b
Clarification: The process to mix different types of coal at the same time to increase the efficiency of coal is called blending of coal. This is due to the fact that different types of coal are produced during the coal processing.
9. Which of the following is a disadvantage of storing coal for a long period of time?
a) Increase in the friability of coal
b) Decrease in its ignition temperature
c) Increase in its calorific value
d) Increase in the proportion of fine
Answer: d
Clarification: When the coal is stored for a long period of time, it leads to slow oxidation which causes deterioration of the coal. This process causes an increase in the proportion of fine which are not easy to cure. Also the oxidation of coal can lead to its spontaneous combustion.
10. How do the chances of spontaneous combustion of coal can decrease?
a) Decrease in the maturity of coal
b) By washing the coal time to time
c) Increase in the maturity of coal
d) By the reducing the quantity of coal
Answer: c
Clarification: The coal of high maturity (anthracite) contains less impurities due to which it does not gets oxidise easily, also the volatile matter present in them is less. Washing of coal can cause an increase in moisture content due to which the coal produced will not be of good quality.