Question

Ergun equation is NOT applied in which one of the following unit operations to analyze gas flow behavior:

• A. Blast Furnace
• B. Sintering
• C. Roasting
• D. LD Converter

Hint:

The Ergun equation only applies to gas flow through a packed bed of solid particles; the LD converter has a gas jet blown into liquid metal, not a particle bed.

Answer 1

The Correct Option is D

The Ergun equation is a packed bed formula. It needs a bed of stationary solid particles with a certain voidage $\varepsilon$ and particle size $d_p$ for gas to push through. So the fastest way to answer this question is to check, for each unit operation, whether gas is actually moving through such a particle bed.

1. Blast Furnace: Coke, ore and flux are charged from the top and sit as a tall packed column inside the furnace. Hot blast air is blown in from the bottom and travels up through this solid column. This is a textbook packed bed, so the Ergun equation is used here.
2. Sintering: A layer of ore fines, coke breeze and flux is spread on a moving strand, and air is pulled down through this layer to burn the fuel and sinter the mix. Again, gas is passing through a bed of particles, so the Ergun equation applies.
3. Roasting: Roasting reactors, including packed and fluidized bed types, pass a gas stream through a bed of solid ore particles to drive the roasting reactions. This is once more a particulate bed situation, so the Ergun equation applies.
4. LD Converter: Here the setup is completely different. A jet of pure oxygen is blown at high speed through a lance straight into a bath of liquid steel. There is no stationary bed of solid particles anywhere in this picture, the gas jet is interacting with a liquid, not threading through packed solids. Since the equation needs a voidage and a particle size to even be written down, it simply does not apply to an LD converter.

Three of the four operations, the blast furnace, sintering, and roasting, are all packed bed gas-solid systems where the Ergun equation is the natural tool. The LD converter is a gas-liquid jet system, so it falls outside where the equation can be used at all.

Let's summarize:

• Ergun's equation needs a packed bed of solid particles: bed voidage and particle size must exist for the formula to make sense.
• Blast furnace, sintering and roasting all have gas flowing through such particle beds; the LD converter has an oxygen jet blown into liquid metal instead.

So the Ergun equation is not applied in the LD converter.