Thermal efficiency of blast furnace stoves used for heating blast (air) may be about __________ percent.

Which of the following facts is/are correct about the blast furnace in Iron metallurgy? Limestone is added to the blast furnace to reduce the iron oxide in the ore to iron. Coke is added to the blast furnace to physically separate iron from other impurities. Carbon dioxide reduces to carbon monoxide.

A

A and B

B

B and C

C

Only C

D

None

Explosion limit of blast furnace gas is 37 to 71% gas in gas-air mixture. It means that the blast furnace gas will explode when burnt in a confined space, if its concentration in the gas-air mixture is __________ percent.

A

[

A.

B. >71%

B

In between 37 & 71%

C

None of these

In the blast furnace, as the oxygen percentage in air blast increases, the
P. flame temperature increases
Q. blast volume increases
R. blast volume decreases
S. flame temperature decreases

A

P, Q

B

P, R

C

R, S

D

Q, S

The bypass factor (B. P. F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil, and td₃ = Dry bulb temperature of heating coil)

A

(td₂ - td₃)/(td₃ - td₁)

B

(td₃ - td₂)/(td₃ - td₁)

C

(td₃ - td₁)/(td₂ - td₃)

D

(td₃ - td₁)/(td₃ - td₂)

The bypass factor (B.P.F.) in case of sensible heating of air is (Where td₁ = Dry bulb temperature of air entering the heating coil, td₂ = Dry bulb temperature of air leaving the heating coil and td₃ = Dry bulb temperature of heating coil)

A

$$\frac{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}$$

B

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}$$

C

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_2} - {\text{t}}{{\text{d}}_3}}}$$

D

$$\frac{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_1}}}{{{\text{t}}{{\text{d}}_3} - {\text{t}}{{\text{d}}_2}}}$$

Blast furnace stoves are meant for heating

A

Air

B

Blast furnace gas

C

Steam

D

None of these

Combustion of furnace oil in a furnace (soaking pit) with preheated combustion air at 400°C results in saving of about __________ percent furnace oil as compared to its combustion with atmospheric air, if the flue gas outlet temperature from the soaking pit is 1200°C.

A

5

B

60

C

20

D

40

Overall thermal efficiency of a lumpy coal fired suitably designed heating furnace, if operated & maintained properly may be about __________ percent.

A

10-15

B

25-30

C

45-50

D

65-70

Overall thermal efficiency of a lumpy coal fired suitably designed heating furnace, if operated & maintained properly may be about __________ percent.

A

10-15

B

25-30

C

45-50

D

65-70

Which property is important for bricks used in the combustion chamber & dome of blast furnace stoves?

A

High refractoriness

B

High resistance to spalling

C

High strength and density

D

All of the above

Thermal efficiency of blast furnace stoves used for heating blast (air) may be about __________ percent.

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