Fuels and Combustion

Question: In high temperature carbonisation of coal compared to low temperature carbonisation
[A].

yield of ammonia is less.

[B].

aromatic content of tar is low.

[C].

H2 content in the coke oven gas is more.

[D].

calorific value of the coke oven gas is lower.

Answer: Option C

Explanation:

No answer description available for this question.

Question: Anthracite can be used for
[A].

recarbonising steel.

[B].

making carbon electrodes;

[C].

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

[D].

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

Answer: Option D

Explanation:

No answer description available for this question.

Question: Combustion of pulverised fuel
[A].

requires larger combustion chamber than rich gaseous fuel.

[B].

in a metallurgical furnace does not contaminate the product in the furnace by ash from fuel.

[C].

suppresses the discharge of fine dust and grit into atmosphere

[D].

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

Answer: Option A

Explanation:

No answer description available for this question.

Question: Nitrogen in coal
[A].

is present upto 1-2%.

[B].

comes from protein in parent vegetable matter.

[C].

is recovered as ammonia during its carbonisation.

[D].

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

Answer: Option D

Explanation:

No answer description available for this question.

Question: Froth floatation is used for
[A].

washing fine coal dust (< 0.5 mm size).

[B].

washing lump coal (> 80 mm size).

[C].

removing ash from the coal based on difference in specific gravity of coal and ash.

[D].

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

Answer: Option A

Explanation:

No answer description available for this question.

Question: As the equilibrium moisture content of the coal increases, its
[A].

calorific value increases.

[B].

swelling number decreases.

[C].

swelling number increases.

[D].

bulk density decreases.

Answer: Option B

Explanation:

No answer description available for this question.

Question: Caking coal is desirable for
[A].

burning on travelling grate.

[B].

coke making.

[C].

burning on firebars.

[D].

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

Answer: Option B

Explanation:

No answer description available for this question.

Question: Fuel gases containing hydrocarbons (ie.g. coke oven gas) are not preheated before burning, mainly because
[A].

the hydrocarbons crack thereby choking and fouling the heat transfer surface by carbon soot.

[B].

it reduces its calorific value tremendously.

[C].

it reduces its flame temperature tremendously.

[D].

there are chances of explosion during preheating.

Answer: Option A

Explanation:

No answer description available for this question.

Question: Gross calorific value will be equal to the net calorific value for
[A].

H2

[B].

C2H2

[C].

CO

[D].

C2H6

Answer: Option C

Explanation:

No answer description available for this question.

Question: 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 (a), (b) and (c).

Answer: Option D

Explanation:

No answer description available for this question.