Fuels and Combustion - Chemical Engineering Questions and Answers

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Coking coals are invariably

lignites

bituminous coals

semi-anthracites

anthracites

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Which of the following accounts for maximum energy loss in a boiler ?

Flue gases.

Ash content in the fuel.

Incomplete combustion.

Unburnt carbon in flue gases.

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'Fuel' can be defined as a substance which produces heat by

combustion.

nuclear fission.

nuclear fusion.

all (a), (b) & (c).

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Washing of coal

reduces its sulphur and ash content.

controls its ash fusibility and increases its calorific value.

improves its coking properties.

all (a), (b) and (c).

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High ash coals

are soft & friable (poor strength and size stability).

require longer time of carbonisation as ash offers resistance to heat transfer.

produce larger quantity of coke oven gas.

none of these.

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Which of the following is not a by-product fuel ?

Pitch

Blast furnace gas

Petrol

Refinery gas

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Preheating of combustion air is done to

increase the adiabatic flame temperature.

increase the calorific value of the fuel.

complete the combustion of fuel.

reduce its requirement for effecting the complete combustion.

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Gross heating value of coal is __________ the net heating value.

higher than

lower than

same as

either (a) or (b); depends on the type of coal

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Anthracite can be used for

recarbonising steel.

making carbon electrodes;

blending with highly coking coal to check its swelling which helps in saving coke even walls from damage and to produce high strength coke.

all (a), (b) and (c).