Related Questions

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 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
Softening temperature of coal ash is a measure of the __________ of coal.
A Caking tendency
B Coking tendency
C Clinkering tendency
D Size stability
During coking of coal, the ash content (percentage)
A Increases
B Decreases
C Remains constant
D None of these
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
Coal is heated in presence of air to a temperature of about __________ °C, while determining its ash content for proximate analysis.
A 500
B 750
C 950
D 1100
The popular notion that a tree's age can be determined by counting number of internal rings in its trunk is generally true. Howeevr, to help regulate the internal temperature of the tree, the outermost layers of wood of the Brazilian ash often →peel away when the temperature exceeds 95 degrees Fahrenheit, leaving the tree with fewer rings than it would otherwise have. So only if the temperature in the Brazilian ash's environment never exceeds 95 degrees Fahrenheit →elav eing the tree with fewer rings than it would otherwise have. So only if the reliable measure of the tree's age. Which of the following is an assumption on whish the argument above depends?
A The growth of new rings in a trees is not a function of levels of precipitation.
B Only the Brazilaian ash loses rings because of excessive heat.
C One day of temperatures above 95 degrees Fahrenheit will cause the Brazilian ash to lose one ring.
D The internal rings of all tress are of uniform thickness
For making fly-ash building bricks, the following mix of fly-ash, sand and lime, is
A 80 : 13 : 7
B 70 : 20 : 10
C 60 : 35 : 5
D None of these
Calorific value of coal middling generated in coal washeries during washing of coal may be around __________ Kcal/kg.
A 1000
B 4000
C 6000
D 8000

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