Hacker News Reader

Comment by loons2 | Hacker News Reader

“... the technology to make fossil-free steel is already currently operating with natural gas...”

Natural Gas IS a fossil fuel!

Yes. The technology is in use, just using natural gas instead of hydrogen because of cost.

If/when hydrogen becomes cost-effective via direct market forces or mandated at gunpoint by government, the technology is ready.

Got bad news, you can reduce iron electrolytically and bypass the electricity to hydrogen/hydrogen reduction steps.

Is there a well developed industrial process doing that?

There is a paper by a member of a Norwegian research group that ran a pilot plant in the 1950's using iron sulfide as a starting material. I think their efficiency was ~4kwh/kg. On a straight balance sheet it's not competitive against unexternalized fossil fuel based processes. It has the same problem I mentioned with hydrogen reduction. If you're using fossil fuels to create electricity to reduce iron, you can skip that generate electricity step and use the fossil fuel directly. Which is why there has been very little work in this area.

In a world where you have electricity from wind and solar with regular oversupply. And high taxes on carbon based fuels. then I think electrowinning is viable.

Fun fact, since you mentioned Norway -- in the early 1900s, Norwegian industry also used the Birkeland-Eyde process to produce nitric acid for fertilizer from atmospheric nitrogen.

The process is not energy-competitive with other processes, but since the plants in question had very cheap hydropower energy that couldn't be exported for use elsewhere, this was not a dealbreaker.

I'm thinking that energy-intensive industry in early hydropower-friendly regions could get away with using simple but inefficient processes, since the energy couldn't be used for anything better anyway. Sort of like creating a minimum viable product of an industrial process, before optimizing and getting great efficiency increases.

bostonmetal.com

I don’t know whether this counts as “well-developed”.

It is not well developed, but there are at least two approaches being investigated at lab or pilot scale.

The first involves electrolysis of molten iron oxide.

https://www.bostonmetal.com/moe-technology/

The other approach involves electrolysis of iron ore powder in alkaline aqueous solution.

https://www.siderwin-spire.eu/sites/template.drupal.pulsarte...

I found the Boston Metal link particularly interesting. If you consider it, combined with a small form factor nuclear reactor, you could build an iron ingot producing plant right on top of the deposits in places that would otherwise be forced to ship ore out for external processing.

They're both interesting, but the aqueous approach has some advantages. Keeping materials working at extreme temperature is difficult: basically anything above 1000C gets very hard. And a low temperature approach has the potential very big advantage of being highly dispatchable, since it would not have to be kept running to keep from freezing up. Dispatchable electrochemistry is like half a battery, just great for dealing with intermittent power sources like renewables.

The second link is interesting. I've only seen the paper on the old Norwegian pilot plant before that slide show. The Norwegians were dealing with Iron Sulfide waste from copper mining as the feed stock. Being able to directly reduce solid iron oxide is probably better.

I have also wondered if you could use the iron rich gangue from bauxite mining as a feed source.

That's not bad news!

How do the capital costs compare?

The paper I saw was doing it using an aqueous process at ordinary temperatures. Capital costs of the actual cells would likely be very low. Though feed stock processing might not be.

One of things that struck me is if the capital costs are low enough an aqueous process should be something you can bring online and offline rapidly depending on current market rates. Consider Germany already had a few late nights in winder where rates went negative. You can see where I'm going here.

Yeah but the labor costs for an on-call backshift will eat you.

You can't just replace natural gas with hydrogen. Biggest issue is the piping.

Here in the Netherlands we have a lot of natural gas infrastructure (it used to be mandated that every house gets a gas pipe for central heating and cooking). We would like to reuse it for hydrogen, but the pipes we have right now would leak horribly.

Beyond the issues of containing hydrogen, there is another difference. You can't (easily) liquefy hydrogen, whereas liquefied natural gas (LNG) is a big thing.

Yes, but the amount of electrons per gram of carbon is three times as high with CH4 as with C.

CH4 + Fe2O3 >> CO + 2H2O + 2 Fe

3 C + Fe2O3 >> 3 CO + 2 Fe

In air: 2 CO + O2 >> CO2

CO2 is not produced directly at high temperatures because it decomposes at 900 C to CO and O2.

A bigger problem with natural gas is the methane released to the atmosphere when it is extracted. This is actually the largest source of atmospheric methane IIRC.

I'd have figured the methane would be reformed to H2 first: nominally,

H2O + CH4 -> CO + 3 H2 + H2O -> CO2 + 4H2 3H2 + FexOy -> H2O + Fe

about 1.2-1.4x the methane winds up as CO2 (some extra is burned for heating in the reforming step). In this order H2 could be just as easily, but far more expensively, produced via green methods.

Another green way would be to use aluminum to refine iron, Al + FexOy -> Fe + Al2O3. Exothermic, rapid, 'green', but expensive because it costs electricity to make Al.

Also to your main point in modern blast furnaces I believe CO is either recycled or allowed to react with Fe2O3 at lower temperature to go all the way to CO2, saving money on coke: Fe2O3 + 3CO → 2Fe + 3CO2 or Fe2O3 + 3C -> 4Fe + 3CO2

> believe CO is either recycled or allowed to react with Fe2O3 at lower temperature to go all the way to CO2, saving money on coke:

I think in typical blast furnace the CO in the exhaust is used as fuel to run the plant/heat the air blast.

That's why opposition to gas flaring is ridiculous. It's far better for the environment to burn it and turn leaking methane into CO2 + water vapor than let it escape (even if the burning can't be locally used to power anything).

Reply on news.ycombinator.com