[metallurgy]

I've researched through the web but couldn't find any info on combustibility about iron ore dust and other ore dusts used by Blast Furnace in the air environment( Using Air Compressors).

So, is iron ore dust combustible?

[Enthalpy]

I don't believe so, but I'd prefer a better source.

Si, Al, Na, K, Ca are already as much oxidized as possible, Mn is in small amount. I see only Fe₃O₄ from some ores hypothetically capable of oxidizing further to Fe₂O₃ and release heat, but this heat is small, and a combustion would first need to break very stable molecules.

Some meteorites were used as "ore" an contain metallic iron or FeO wustite. Deep sea nodules too can contain FeO. I suppose this isn't your case.

So if the ore is not tainted (by coal for instance) and is the air is not very hot, I wouldn't worry too much. Ore is metal already "burnt" by our atmosphere. But in a flux of oxygen at 1000°C, I'm disconfident of everything.

[metallurgy]

I don't believe so, but I'd prefer a better source.

Si, Al, Na, K, Ca are already as much oxidized as possible, Mn is in small amount. I see only Fe₃O₄ from some ores hypothetically capable of oxidizing further to Fe₂O₃ and release heat, but this heat is small, and a combustion would first need to break very stable molecules.

Some meteorites were used as "ore" an contain metallic iron or FeO wustite. Deep sea nodules too can contain FeO. I suppose this isn't your case.

So if the ore is not tainted (by coal for instance) and is the air is not very hot, I wouldn't worry too much. Ore is metal already "burnt" by our atmosphere. But in a flux of oxygen at 1000°C, I'm disconfident of everything.

Actually this question is for blast furnace dust removal systems (with pulse jet bag filters) and these bag filter plants filtering the air and blast furnace ore dusts etc.
So I dont think the dust of gas temperature is too high. But a little spark may ignite the dusts or the gas inside the bag filters if air compressors used instead of nitrogen gas...

[Enthalpy]

If you're sure the dust consists only of iron ore, air not too hot is pretty safe I guess.

But if the dust may contain pollen, flour, coal powder... then the risk is very serious.

[metallurgy]

coal powder... then the risk is very serious.

Hmm..

Another thing is the pulverised coal: I mean if pulverised coal injection use air compressors -while dragging in silo- instead of nitrogen gas, then there is same possiblity of this risk?

[Enthalpy]

I'd be very disconfident of coal dust dragged by air. To my opinion, it would be an accident waiting to happen.

You might try to build the whole circuit, including downstream the silo, to withstand the deflagration. I don't like this option because explosions tend to have unexpected consequences.

Can you experiment? On a not too small scale, because some explosions happen at a minimum size. And alas, some materials exploded after having being handled for decades with the same procedure.

To save on nitrogen, you might use CO₂ instead. I believe it's easily available at a blast furnace. If you can guarantee it's free of CO, sulphur oxides, phosphorus oxides, nitrogen oxides, then CO₂ isn't more dangerous than N₂.

I thought recent blast furnaces use oxygen? Then nitrogen should be abundant locally, or?