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I don’t get this. We already use direct reduction using about half hydrogen, and that can be increased to over 90%. Producing ammonia via the Haber process mean

I don’t get this. We already use direct reduction using about half hydrogen, and that can be increased to over 90%. Producing ammonia via the Haber process means losing 40% or so of the energy (and potentially more as you convert it back), so why not just use hydrogen directly? Simply because moving hydrogen is harder than ammonia? I think it makes way more sense to just make and use the hydrogen on-site.

azernik 4y ago
This isn't using ammonia to transport hydrogen; the nitrogen is what's reacting with the iron. And yes, ease of transportation and reactivity is a big motivator. From the abstract: "Ammonia is an annually 180 million ton traded chemical energy carrier, with established transcontinental logistics and low liquefaction costs. It can be synthesized with green hydrogen and release hydrogen again through the reduction reaction." Also: "The authors show that ammonia-based reduction of iron oxide proceeds through an autocatalytic reaction, is kinetically as effective as hydrogen-based direct reduction, yields the same metallization, and can be industrially realized with existing technologies."
- thereisnospork 4y ago
  >the nitrogen is what's reacting with the iron. Only in a supplementary manner to form a nitride coating as rust proofing - the primary reducing agent is hydrogen, forming water. relevant snippet: >>The nitride formation is another key advantage of ADR, as nitriding improves the aqueous corrosion resistance of iron.[29] The nitride passivated the otherwise highly active reduced iron, offering a safety-critical benefit for handling and logistics. Otherwise, for the downstream processing of the reduced material, the porous sponge iron is prone to re-oxidation and strong exothermic reactions with oxygen or moisture due to its high surface-to-volume ratio (typically above 40 vol% porosity[4]). Thus, the sponge iron produced by HyDR must be compacted into hot briquetted iron to reduce the porosity for shipping and handling, which is not necessary with ADR.
gumby 4y ago
You said it: transporting, storing, and otherwise handling ammonia is easier than H2. Amd handling a lump of coke is even easier, which is why we started there.
- jojobas 4y ago
  If hydrogen is electrolytic you can as well make it on site. Steel mills are continuous operations and there is not much need to pool/smooth demand.
  - yxhuvud 4y ago
    Shifting electric prices due to wind power is a strong motivation to pool it though.
    - jojobas 4y ago
      So far it's easier and more efficient to reserve/contract some hydro (dam) storage than store/pool hydrogen for continuous operations.
      - yxhuvud 4y ago
        That sounds very location dependant and not necessarily feasible at all given higher and higher share of wind power being used. That hydro will be needed during periods of low wind to stabilise everything else.
        jojobas 4y ago
        The whole point of the grid is to de-localize power. Direct hydrogen reduction plants pretty much don't exist yet, might as well build them where electricity can be stored efficiently. Some of the biggest hydro plants were built specifically to power aluminium smelting nearby.
PaulHoule 4y ago
i think the question is how far you are shipping the hydrogen. If, say, people are making hydrogen in (say) the Middle East and shipping it to (say) Europe then the overhead of liquifying or compressing H2 is on the same order as converting to ammonia. In that paper they demonstrate that you can just use the ammonia directly to reduce iron and not have a separate system to convert it back. If you have a big wind power or solar complex like the ones being built in the North Sea or Australia you might be better off using hydrogen directly.
- philipkglass 4y ago
  I would guess that even better than shipping ammonia or hydrogen to European steel plants would be to build new steel plants near the hydrogen producers, wherever they may be, and shipping iron ore there while shipping steel back out. Since iron ore and steel are much denser than either ammonia or hydrogen and do not need pressure vessels or chilling they can be shipped at lower speeds (save transport energy consumption) and save money too.
  - tonyarkles 4y ago
    I'm asking this 100% from a place of curiosity because I don't know the answer. From iron ore to steel, how much waste is there? If the waste fraction is large, people might balk at the idea of either leaving that waste behind in the hydrogen-host country or burning fossil fuels to ship it around to have a carbon-free extraction process.
    - adastra22 4y ago
      Anywhere you have water you have hydrogen.
      - to11mtm 4y ago
        Interestingly, the paper mentions that the reactions do produce (some) hydrogen, which could perhaps be recaptured. However, a bigger concern upon a glance is that this process does produce NOx emissions...
algo_trader 4y ago
> Producing ammonia via the Haber process means losing 40% or so of the energy This seems wrong. I believe that green HB process would be 80%-90% efficient since the heat is re-used? I have read conflicting papers. Of course, HB is still a capex-heavy process. Maybe the 40% number is for fossil methane to ammonia?
twawaaay 4y ago
I also think so. Rather than move hydrogen, move the electricity or the iron. Produce hydrogen on site and even on demand to get rid of most of the need to store/transport it. As to cost, who can quantify me the risks of having and transporting so much ammonia?

azernik 4y ago

This isn't using ammonia to transport hydrogen; the nitrogen is what's reacting with the iron. And yes, ease of transportation and reactivity is a big motivator. From the abstract: "Ammonia is an annually 180 million ton traded chemical energy carrier, with established transcontinental logistics and low liquefaction costs. It can be synthesized with green hydrogen and release hydrogen again through the reduction reaction." Also: "The authors show that ammonia-based reduction of iron oxide proceeds through an autocatalytic reaction, is kinetically as effective as hydrogen-based direct reduction, yields the same metallization, and can be industrially realized with existing technologies."

thereisnospork 4y ago
>the nitrogen is what's reacting with the iron. Only in a supplementary manner to form a nitride coating as rust proofing - the primary reducing agent is hydrogen, forming water. relevant snippet: >>The nitride formation is another key advantage of ADR, as nitriding improves the aqueous corrosion resistance of iron.[29] The nitride passivated the otherwise highly active reduced iron, offering a safety-critical benefit for handling and logistics. Otherwise, for the downstream processing of the reduced material, the porous sponge iron is prone to re-oxidation and strong exothermic reactions with oxygen or moisture due to its high surface-to-volume ratio (typically above 40 vol% porosity[4]). Thus, the sponge iron produced by HyDR must be compacted into hot briquetted iron to reduce the porosity for shipping and handling, which is not necessary with ADR.

gumby 4y ago

You said it: transporting, storing, and otherwise handling ammonia is easier than H2. Amd handling a lump of coke is even easier, which is why we started there.

jojobas 4y ago
If hydrogen is electrolytic you can as well make it on site. Steel mills are continuous operations and there is not much need to pool/smooth demand.
- yxhuvud 4y ago
  Shifting electric prices due to wind power is a strong motivation to pool it though.
  - jojobas 4y ago
    So far it's easier and more efficient to reserve/contract some hydro (dam) storage than store/pool hydrogen for continuous operations.
    - yxhuvud 4y ago
      That sounds very location dependant and not necessarily feasible at all given higher and higher share of wind power being used. That hydro will be needed during periods of low wind to stabilise everything else.
      - jojobas 4y ago
        The whole point of the grid is to de-localize power. Direct hydrogen reduction plants pretty much don't exist yet, might as well build them where electricity can be stored efficiently. Some of the biggest hydro plants were built specifically to power aluminium smelting nearby.

PaulHoule 4y ago

i think the question is how far you are shipping the hydrogen. If, say, people are making hydrogen in (say) the Middle East and shipping it to (say) Europe then the overhead of liquifying or compressing H2 is on the same order as converting to ammonia. In that paper they demonstrate that you can just use the ammonia directly to reduce iron and not have a separate system to convert it back. If you have a big wind power or solar complex like the ones being built in the North Sea or Australia you might be better off using hydrogen directly.

philipkglass 4y ago
I would guess that even better than shipping ammonia or hydrogen to European steel plants would be to build new steel plants near the hydrogen producers, wherever they may be, and shipping iron ore there while shipping steel back out. Since iron ore and steel are much denser than either ammonia or hydrogen and do not need pressure vessels or chilling they can be shipped at lower speeds (save transport energy consumption) and save money too.
- tonyarkles 4y ago
  I'm asking this 100% from a place of curiosity because I don't know the answer. From iron ore to steel, how much waste is there? If the waste fraction is large, people might balk at the idea of either leaving that waste behind in the hydrogen-host country or burning fossil fuels to ship it around to have a carbon-free extraction process.
  - adastra22 4y ago
    Anywhere you have water you have hydrogen.
    - to11mtm 4y ago
      Interestingly, the paper mentions that the reactions do produce (some) hydrogen, which could perhaps be recaptured. However, a bigger concern upon a glance is that this process does produce NOx emissions...

algo_trader 4y ago

> Producing ammonia via the Haber process means losing 40% or so of the energy This seems wrong. I believe that green HB process would be 80%-90% efficient since the heat is re-used? I have read conflicting papers. Of course, HB is still a capex-heavy process. Maybe the 40% number is for fossil methane to ammonia?

twawaaay 4y ago

I also think so. Rather than move hydrogen, move the electricity or the iron. Produce hydrogen on site and even on demand to get rid of most of the need to store/transport it. As to cost, who can quantify me the risks of having and transporting so much ammonia?