[holowoodman]

No, not at all. Coke or hydrogen always only provide additional heat, they are never the main source of heat. The main heat source can either be coal or an electric arc furnace. The coke or hydrogen are just necessary for the chemical reaction, and providing some heat is a side-effect.

[jijijijij]

Sorry, in face of OP’s tone I allowed myself some sarcasm. Obviously there needs to be additional energy. You’d have some equilibrium with those reactions and OP didn’t make any argument why that can’t be controlled in favor of reducing Fe2O3.

It’s also borderline unbelievable OP never heard of hydrogen in future steelmaking, if they are at all invested in the topic. You’d need a special kind of ignorance to think people are hugely throwing money at this, when the basic chemistry is infeasible.

[Borg3]

Yeah, I did not thats why I asked. Water and Steel doesnt like each other. But thanks for the info.. It seems it can be done in controlled way.

Now I wonder how cost effective it is :)

[holowoodman]

Well, actually, thermolysis for water occurs at 2200°C. Thermolysis of CO₂ starts at 1400°C, of CO at 3700°C. The melting point of iron is around 1500°C, similarly its oxides.

So water as a product is actually more stable than CO₂, and doesn't undergo thermolysis at the relevant temperatures for smelting iron. Whereas when going the CO₂ route, there is the risk of producing relevant amounts of CO, which is not as desirable and less efficient because it only absorbs half the oxygen.

Cost is a big question, but it will for sure be more expensive to use hydrogen. Back of the envelop calculation (250$/t coal price, need 1/3t of H_2 for the same effect, so H₂ may cost up to 750$/t, need 40kWh/kg for H₂ electrolysis at 100% efficiency) gives a breakeven electricity price of 1.875ct/kWh. While this happens from time to time due to overproduction, those prices will even out as soon as there is a market for that excess electricity through batteries, storage and electrolysis. Which means that cost-wise, the H₂ route will never be more effective than coal. To make it viable, coal use needs to be made more expensive through taxes and tariffs.

[Borg3]

Can you provide some citation about CO2 themolysis? I found just one paper from China....

[holowoodman]

That stuff is ages old, I doubt you will find current papers on it. Pick a chem textbook or table book, you should find it somewhere in there.

[jijijijij]

> Now I wonder how cost effective it is :)

I believe right now, it's expected to cost about 30% more. But we don't have an hydrogen economy yet, or 1000 years of experimentation as with carbon as reducing agent. There is probably still some room for innovation in material science for every part of the process.