Question

JFN number in LD converter process is defined as:

• A. \( \text{JFN} = \text{Gas pressure} \times \left(\frac{\text{Lance height}}{\text{Nozzle diameter}}\right) \)
• B. \( \text{JFN} = \text{Nozzle diameter} \times \left(\frac{\text{Lance height}}{\text{Gas pressure}}\right) \)
• C. \( \text{JFN} = \text{Gas pressure} \times \left(\frac{\text{Nozzle diameter}}{\text{Lance height}}\right) \)
• D. \( \text{JFN} = (\text{Gas pressure} + \text{Lance height}) \times \text{Nozzle diameter} \)

Hint:

Jet Force Number (JFN) in LD steelmaking helps optimize the oxygen jet impact — it increases with pressure and nozzle size, but decreases with higher lance height.

Answer 1

The Correct Option is C

Step 1: What is JFN Number?
In steelmaking using the LD (Linz-Donawitz) converter process, the JFN (Jet Force Number) is an empirical parameter that governs the force exerted by the gas jet on the molten metal surface. It plays a crucial role in determining the depth of penetration and mixing in the bath. Step 2: Formula
The correct expression for the Jet Force Number is: \[ \text{JFN} = \text{Gas pressure} \times \left(\frac{\text{Nozzle diameter}}{\text{Lance height}}\right) \] This shows that the force of the oxygen jet increases with: - Higher gas pressure, - Larger nozzle diameter, and - Decreases with greater lance height (more distance from the bath). Step 3: Elimination of Incorrect Options
- (A), (B), and (D) are all dimensionally or conceptually incorrect in terms of flow dynamics and energy transfer. Conclusion: JFN is defined as Gas pressure × (Nozzle diameter / Lance height).