1. For manufacturing of metallurgical coke which of the following properties a coal should have?
a) Low volatile matter and high fixed carbon content
b) High volatile matter and high fixed carbon content
c) High volatile matter and low fixed carbon content
d) Low volatile matter and low fixed carbon content
Explanation: Coal having low volatile matter burn with a short flame and have a good heating value due to which it is preferred and high fixed carbon content helps to burn a coal completely. High volatile matter produces long flames and has a low heating value.
2. Ashes with fusion temperature above than 1430oC are called as ___________
a) Fixed ash
b) Free ash
c) Refractory ash
d) Fusible ash
Explanation: The ash which is present within the mass of coal is called as fixed ash. Fusible ash is the ash that has a fusible temperature less than 1200oC. Free ash can be removed by washing of coal.
3. At what temperature should the coal be heated so as to determine the moisture content of coal?
a) 90-100oC
b) 145-155oC
c) 125-140oC
d) 105-110oC
Explanation: Moisture is generally determined by heating a known quantity of air-dried coal to 105-110oC for one hour so as to get an exact value of the percentile of moisture. The loss of weight in coal determines the percentile of moisture in the coal. If the temperature is shifted from this position it will affect the percentile of oxygen.
4.How does the texture of coal changes with its maturity?
a) Becomes hard, less brittle and moderately tough
b) Becomes hard, more brittle and more tough
c) Becomes hard, more brittle and less tough
d) No change
Explanation: The texture of coal tends to the layer present on the coal and its maturity is from lignite to anthracite. The number of layers from lignite to anthracite increases due to which the compactness increase, thus increasing its toughness, hardness and brittleness
5.On what factors does the specific gravity of coal depends?
a) Its calorific value and ash content
b) Its ignition temperature and calorific value
c) Type of coal and ash content
d) Type of coal and calorific value
Explanation: Specific gravity is the ratio of the density/mass of a substance to the density/mass of reference substance. The total ash content represents its mass and
The type of coal is required for its density.
6. Which of the coal have the best heating values in terms of volatile matter?
a) Containing 20% volatile matter
b) Containing 60% volatile matter
c) Containing 30% volatile matter
d) Containing 50% volatile matter
Explanation: Coals containing high volatile matter produces long and smoky flame due to which its heating value decreases. Semi-bituminous coal has the highest heating value due to less volatiles content.
7. Which type of coals have the highest grindability index?
a) Steam coals
b) Gas coals
c) House coals
d) Pulverised coals
Explanation: Grindability is the ease with which a coal can be grounded. The grindability index of pulverised coal is about 100. This is because of the volatile matter present in the coal, the higher the volatile matter of coal, the more will be its grindability index
8. How does the friability of the coal is tested?
a) Drop shatter test
b) Thermal cracking
c) Knocking
d) Proximate analysis
Explanation: Friability is the tendency of the coal to break into pieces. The more the friability, the less will be the quality of coal. Splint and cannel coal are less friable. Knocking is the unusual sound produced by an engine.
9. Which property of coal is tested in Audibert Arnu test?
a) Bulk density
b) Colour
c) Caking and coking
d) Texture
Explanation: This method uses a dilatometer to find out the swelling properties of coal. Caking is the ability to form a coherent cake when the coal is carbonised. If there is residue formed during carbonisation, then the coals formed are called coking coals
10. On which property of coal does the design of bunkers for the storage of coal depends?
a) Specific gravity
b) Bulk density
c) Grindability
d) Friability
Explanation: Bunkers/coal bins are the containers in which the coal can be transported. Bulk density is weight of soil present in coal. According to the bulk density the design of containers are generated.