Related Questions

Prime coking coal is always blended with medium or non- coking coal before ear-bonisation
A To check against its excessive swelling during heating, which may exert high pressure and damage coke oven walls
B Because, it alone produces unreactive coke
C Both A & B
D Neither A nor B
The coking process normally mostly used in Indian oil refineries is the __________ coking process.
A Delayed
B Flexi
C Fluid
D Contact
Ash content in the middling coal (a byproduct of coal washeries) in India ranges between __________ percent.
A 15 to 25
B 35 to 45
C 55 to 75
D 75
Mineral matter content (M) and ash content (A) in coal are approximately related as
A M = 1.1A
B M = A
C M = 1.5A
D M = 2A
A good coking coal should have high __________ content.
A Ash
B Sulphur & phosphorus
C Moisture
D None of these
Volatile matter content in coking coal may be about __________ percent.
A 1
B 7
C 22
D 46
Softening temperature of coal ash is a measure of the __________ of coal.
A Caking tendency
B Coking tendency
C Clinkering tendency
D Size stability
A coal with high ash content
A Has higher calorific value
B Is harder and stronger
C Is not subjected to washing
D Has low quantity of mineral matter
Fusion point of coal ash increases with increase in its __________ content.
A Iron sulphate
B Iron silicate
C Lime and magnesia
D All of the above
A coal with high ash content is undesirable, as
A It is abrasive to the coal pulveriser (ie.g. ball mill) and the combustion chamber
B The ash in molten condition gets absorbed in the pores of the refractory lining of the furnace and causes its spalling due to different co-efficient of expansion/contraction of the refractory and the ash
C The ash retains the sulphur & phosphorus and thus affects the quality of products in metallurgical furnace apart from increasing the slag volume. Besides, it may fuse and stick to the boiler tubes thereby reducing the heat transfer
D All of the above

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