5 ms·

Coal, yes. Iron, wouldn't the iron we moved to the surface be even more accessible? We didn't destroy it, just rearranged and concentrated it?

by gpm 5y ago

ceejayoz 5y ago
Guess what we do most of our iron smelting with?
- x1f604 5y ago
  Primitive iron smelting was done with charcoal, I believe. Correct me if I'm wrong.
  - ceejayoz 5y ago
    Yes. Being stuck at that point would be the problem.
    - Robotbeat 5y ago
      Would it? Most new smelting plants today in the US (any built in the last few decades) use a mixture of hydrogen and carbon monoxide as the reducing gases (natural gas primarily as feedstock, but no reason it couldn’t be about 90% hydrogen produced via, say, hydroelectricity or wind). Coal didn’t overtake charcoal for smelting iron in the US until the latter half of the 19th century, well after the first industrial revolution. Melting down scrap iron is one of the main sources of steel in the US, and that is done straight with electricity in arc furnaces. Coal accelerated the second industrial Revolution, but it was not essential. Far more important for enabling the first industrial Revolution was some of the early scientific knowledge about steam and pressure, such as the work of Robert Boyle, a lot of that based on a sort of reaction to the classics that had been revived in the Renaissance. The biggest argument for coal is indirectly in that it helped the viability of British society (after the island had most its tree cut down over the previous 500 years) which played an important role in the Scientific Revolution (Robert Boyle was Anglo-Irish)… although by the time Britain was playing an important role, the scientific Revolution was already underway on the mainland of Europe. As long as our books are not all destroyed, I think we’d have no problem bootstrapping from charcoal the second time around. (I think a lot about long term data storage… writing in stone or fired clay still seems like one of the best methods for writing that needs to last 10,000 years… it was, after all, preserved Greco-Roman classics that enabled the renaissance and therefore the scientific Revolution.)
      - ceejayoz 5y ago
        I think that vastly underestimates the dependency tree in modern society. Storing hydrogen in useful quantities is tough, requiring fairly sophisticated metallurgy and cryogenics. Finding out we've got a hard to replace left-pad module somewhere far up the tech tree wouldn't be fun.
        Robotbeat 5y ago
        The dependency tree of 19th Century or early 20th century society is a lot more straightforward, however. And no, you don't need such sophistication for storing useful amounts of hydrogen. Storing large amounts of hydrogen (in this case, also mixed with poisonous CO) was solved in the beginning of the 19th Century (well, late 18th century) in Britain and Germany by using very large near-atmospheric storage vessels called Gas Holders: https://en.wikipedia.org/wiki/Gas_holder https://en.wikipedia.org/wiki/Gas_holder Salt caverns can also be used for greater volumes, i.e. for seasonal storage, as are already used for hydrogen storage in a few places in the US and elsewhere. https://en.wikipedia.org/wiki/Underground_hydrogen_storage https://en.wikipedia.org/wiki/Underground_hydrogen_storage
        Retric 5y ago
        Except the Iron Age started around 2000 BC, so the world would largely be without iron for a very long time.
        mcguire 5y ago
        That gas holder article says they contained methane or coal gas. Methane's density is 0.657 kg/m³; hydrogen's is 0.08375 kg/m³.
        Robotbeat 5y ago
        Coal gas is a mix that (by energy) is about half hydrogen, as I said. And hydrogen gas a specific energy of 142MJ/kg vs 55.5MJ/kg for methane.
      - 5y ago
  - f00zz 5y ago
    Yeah, I think we switched to coke during the Industrial Revolution not because it's a better fuel than charcoal, but because we were running out of trees.
    - stan_rogers 5y ago
      Coke was Abraham Darby's doing (around 1709-1710), and that was mostly to corner the market for cheap pots and kettles. There was no way for the charcoal crowd to compete on iron, and the bronze bunch - the norm for that sort of thing up to that point - was left forever in the dust.
- mas147 5y ago
  What?
masklinn 5y ago
> Coal, yes. Iron, wouldn't the iron we moved to the surface be even more accessible? We didn't destroy it, just rearranged and concentrated it? Might depend how long it takes: because rust is porous and friable, rusting iron should eventually degrade to nothing, and the rust would be difficult to re-concentrate then reduce back to iron.
- gpm 5y ago
  Would whatever the rust turns into be any less accessible (ignoring availability of coal) than what we started out with though? I don't pretend to know the entire "iron cycle", but it seems like it ought to just be turning back into the same sort of minerals that we originally extracted it from?
  - masklinn 5y ago
    Iron rusts over historical timescales, metal deposits form over geological ones.
    - gpm 5y ago
      Am I wrong to think of metal deposits as just "rust mixed with rock"? It doesn't seem like the rock part (i.e. the details of what it is mixed with) should be critical for the extraction process?
      - masklinn 5y ago
        > Am I wrong to think of metal deposits as just "rust mixed with rock"? They're concentrated rust mixed with rocks, otherwise it's not economically viable to extract. Like, iron is ridiculously common, relatively speaking: on earth as a whole it's more common than oxygen, for the crust it ranks 4th at 5% by mass, meaning if you went at it randomly you'd need to sift through 20kg of materials to get 1kg of iron. Currently, we exploit formations as low as 15% iron (banded iron formations / taconite), that's the lower limit of the economically feasible, and those results in absolutely enormous amounts of tailings (waste materials). Pre-industrialisation, unless you had no other choice (e.g. only had ironsands to work with) you really wanted to exploit natural (or "direct-shipping") ores, in the 60~70% range, the extraction is way too much work otherwise.
m4rtink 5y ago
Stone coal could be, at least partially, substituted by charcoal - and often was in the past, where reachable underground coal reserves were not available.
- mcguire 5y ago
  "So by weight charcoal and anthracite coal have an energy density of about 30 MJ/kg, while poorer kinds of coal range down to half of that." (https://www.reddit.com/r/askscience/comments/udjl5/charcoal_vs_coal/ https://www.reddit.com/r/askscience/comments/udjl5/charcoal_...) However, the density of charcoal is much less than that of coal: 200 kg/m^3 vs 1500 kg/m^3 (for solid anthracite). Producing 1kg of charcoal requires 3-4kg of wood. (Producing the 900°C for the process is an exercise for the reader.) (https://www.fao.org/3/y4450e/y4450e11.htm https://www.fao.org/3/y4450e/y4450e11.htm)

Coal, yes. Iron, wouldn't the iron we moved to the surface be even more accessible? We didn't destroy it, just rearranged and concentrated it?

by gpm 5y ago

Coal, yes. Iron, wouldn't the iron we moved to the surface be even more accessible? We didn't destroy it, just rearranged and concentrated it?

ceejayoz 5y ago

Guess what we do most of our iron smelting with?

x1f604 5y ago
Primitive iron smelting was done with charcoal, I believe. Correct me if I'm wrong.
- ceejayoz 5y ago
  Yes. Being stuck at that point would be the problem.
  - Robotbeat 5y ago
    Would it? Most new smelting plants today in the US (any built in the last few decades) use a mixture of hydrogen and carbon monoxide as the reducing gases (natural gas primarily as feedstock, but no reason it couldn’t be about 90% hydrogen produced via, say, hydroelectricity or wind). Coal didn’t overtake charcoal for smelting iron in the US until the latter half of the 19th century, well after the first industrial revolution. Melting down scrap iron is one of the main sources of steel in the US, and that is done straight with electricity in arc furnaces. Coal accelerated the second industrial Revolution, but it was not essential. Far more important for enabling the first industrial Revolution was some of the early scientific knowledge about steam and pressure, such as the work of Robert Boyle, a lot of that based on a sort of reaction to the classics that had been revived in the Renaissance. The biggest argument for coal is indirectly in that it helped the viability of British society (after the island had most its tree cut down over the previous 500 years) which played an important role in the Scientific Revolution (Robert Boyle was Anglo-Irish)… although by the time Britain was playing an important role, the scientific Revolution was already underway on the mainland of Europe. As long as our books are not all destroyed, I think we’d have no problem bootstrapping from charcoal the second time around. (I think a lot about long term data storage… writing in stone or fired clay still seems like one of the best methods for writing that needs to last 10,000 years… it was, after all, preserved Greco-Roman classics that enabled the renaissance and therefore the scientific Revolution.)
    - ceejayoz 5y ago
      I think that vastly underestimates the dependency tree in modern society. Storing hydrogen in useful quantities is tough, requiring fairly sophisticated metallurgy and cryogenics. Finding out we've got a hard to replace left-pad module somewhere far up the tech tree wouldn't be fun.
      - Robotbeat 5y ago
        The dependency tree of 19th Century or early 20th century society is a lot more straightforward, however. And no, you don't need such sophistication for storing useful amounts of hydrogen. Storing large amounts of hydrogen (in this case, also mixed with poisonous CO) was solved in the beginning of the 19th Century (well, late 18th century) in Britain and Germany by using very large near-atmospheric storage vessels called Gas Holders: https://en.wikipedia.org/wiki/Gas_holder https://en.wikipedia.org/wiki/Gas_holder Salt caverns can also be used for greater volumes, i.e. for seasonal storage, as are already used for hydrogen storage in a few places in the US and elsewhere. https://en.wikipedia.org/wiki/Underground_hydrogen_storage https://en.wikipedia.org/wiki/Underground_hydrogen_storage
        Retric 5y ago
        Except the Iron Age started around 2000 BC, so the world would largely be without iron for a very long time.
        mcguire 5y ago
        That gas holder article says they contained methane or coal gas. Methane's density is 0.657 kg/m³; hydrogen's is 0.08375 kg/m³.
        Robotbeat 5y ago
        Coal gas is a mix that (by energy) is about half hydrogen, as I said. And hydrogen gas a specific energy of 142MJ/kg vs 55.5MJ/kg for methane.
    - 5y ago
- f00zz 5y ago
  Yeah, I think we switched to coke during the Industrial Revolution not because it's a better fuel than charcoal, but because we were running out of trees.
  - stan_rogers 5y ago
    Coke was Abraham Darby's doing (around 1709-1710), and that was mostly to corner the market for cheap pots and kettles. There was no way for the charcoal crowd to compete on iron, and the bronze bunch - the norm for that sort of thing up to that point - was left forever in the dust.
mas147 5y ago
What?

masklinn 5y ago

> Coal, yes. Iron, wouldn't the iron we moved to the surface be even more accessible? We didn't destroy it, just rearranged and concentrated it? Might depend how long it takes: because rust is porous and friable, rusting iron should eventually degrade to nothing, and the rust would be difficult to re-concentrate then reduce back to iron.

gpm 5y ago
Would whatever the rust turns into be any less accessible (ignoring availability of coal) than what we started out with though? I don't pretend to know the entire "iron cycle", but it seems like it ought to just be turning back into the same sort of minerals that we originally extracted it from?
- masklinn 5y ago
  Iron rusts over historical timescales, metal deposits form over geological ones.
  - gpm 5y ago
    Am I wrong to think of metal deposits as just "rust mixed with rock"? It doesn't seem like the rock part (i.e. the details of what it is mixed with) should be critical for the extraction process?
    - masklinn 5y ago
      > Am I wrong to think of metal deposits as just "rust mixed with rock"? They're concentrated rust mixed with rocks, otherwise it's not economically viable to extract. Like, iron is ridiculously common, relatively speaking: on earth as a whole it's more common than oxygen, for the crust it ranks 4th at 5% by mass, meaning if you went at it randomly you'd need to sift through 20kg of materials to get 1kg of iron. Currently, we exploit formations as low as 15% iron (banded iron formations / taconite), that's the lower limit of the economically feasible, and those results in absolutely enormous amounts of tailings (waste materials). Pre-industrialisation, unless you had no other choice (e.g. only had ironsands to work with) you really wanted to exploit natural (or "direct-shipping") ores, in the 60~70% range, the extraction is way too much work otherwise.

m4rtink 5y ago

Stone coal could be, at least partially, substituted by charcoal - and often was in the past, where reachable underground coal reserves were not available.

mcguire 5y ago
"So by weight charcoal and anthracite coal have an energy density of about 30 MJ/kg, while poorer kinds of coal range down to half of that." (https://www.reddit.com/r/askscience/comments/udjl5/charcoal_vs_coal/ https://www.reddit.com/r/askscience/comments/udjl5/charcoal_...) However, the density of charcoal is much less than that of coal: 200 kg/m^3 vs 1500 kg/m^3 (for solid anthracite). Producing 1kg of charcoal requires 3-4kg of wood. (Producing the 900°C for the process is an exercise for the reader.) (https://www.fao.org/3/y4450e/y4450e11.htm https://www.fao.org/3/y4450e/y4450e11.htm)