# Iron Making Questions and Answers – TFT and RAFT

This set of Iron Making Multiple Choice Questions & Answers (MCQs) focuses on “TFT and RAFT”.

1. The least hearth temperature is known as the _______
a) Critical Hearth Temperature
b) Critical Temperature
c) Critical Blast Temperature
d) Critical Furnace Temperature

Explanation: The least hearth temperature is known as the Critical Hearth Temperature. It is about 1400–1450°C. Minimum hearth temperature has to maintain for the efficient operation to get free running, fluid slag.

2. Tuyere Flame Temperature (TFT) is __________
a) 1800–2000°C
b) 1600–2000°C
c) 1800–2100°C
d) 1900–2200°C

Explanation: Combustion zone temperature has to maintain in the range of 1800–2000°C to ensure rapid transfer of heat. This temperature is known as the Tuyere Flame Temperature (TFT).The requirement of free running, liquid slag decides the lower valve of Tuyere Flame Temperature.

3. The heat of the flame is used to calculate its ___________
a) Temperature
b) Heat capacity
c) Enthalpy
d) Entropy

Explanation: The heat of the flame is used to calculate its temperature. This temperature is known as Raceway Adiabatic Flame Temperature (RAFT). This heat is also called as sensible heat. There is a direct relation between the heat and the temperature.

4. Oxygen enrichment of the air blast increases the RAFT.
a) True
b) False

Explanation: Oxygen enrichment of the air blast increases the RAFT (Raceway Adiabatic Flame Temperature). This also reduces the volume of the blast air as less nitrogen is there. This also lowers the mass of air in the flame.

5. The 100°C increase in blast temperature increases the RAFT by 82°C.
a) True
b) False

Explanation: The 100°C increase in blast temperature increases the RAFT by 82°C. Changes in the furnace conditions change the RAFT temperature correspondingly. RAFT stands for raceway adiabatic flame temperature.

6. What is the effect of1% increase in methane on RAFT temperature?
a) Decrease the RAFT by 56°C
b) Increase the RAFT by 56°C
c) Decreases the RAFT by 6°C
d) Decreases the RAFT by 5°C

Explanation: The 1% methane added to blast C decreases the RAFT by 56°C. Changes in the furnace conditions change the RAFT temperature correspondingly. RAFT stands for raceway adiabatic flame temperature.

7. What is the effect of 5 g/Nm3 increase in the blast moisture on the RAFT temperature?
a) Decrease the RAFT by 28°C
b) Increase the RAFT by 28°C
c) Decrease the RAFT by 8°C
d) Decrease the RAFT by 2°C

Explanation: The 5 g/Nm3 increase in the blast moisture decreases the RAFT by 28°C. Changes in the furnace conditions change the RAFT temperature correspondingly. RAFT stands for raceway adiabatic flame temperature.

Sanfoundry Global Education & Learning Series – Iron Making.

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