How Can We Do Steel In A Coal-Depleted Future?

[Eclipse Now]

“a complete replacement of 520 million tonnes of coke [based on 2008 requirements for steel production] (setting aside those nontrivial matters of differences in compressive strength and furnace size) would require nearly 2.1 billion tonnes of wood. Even if that wood were to come from such high-yielding species as tropical eucalypts, producing about 10 tonnes per hectare/year, today’s iron smelting would require harvesting annually an area of 210 million hectares of well-managed tropical wood plantations –- or an area equivalent to half of Brazil’s Amazon tropical rain forest.”

 

http://www.vaclavsmil.com/wp-content/uploads/docs/smil-article-20090917-iron-age.pdf

[Essay]

“a complete replacement of 520 million tonnes of coke [based on 2008 requirements for steel production] (setting aside those nontrivial matters of differences in compressive strength and furnace size) would require nearly 2.1 billion tonnes of wood. Even if that wood were to come from such high-yielding species as tropical eucalypts, producing about 10 tonnes per hectare/year, today’s iron smelting would require harvesting annually an area of 210 million hectares of well-managed tropical wood plantations –- or an area equivalent to half of Brazil’s Amazon tropical rain forest.”

 

http://www.vaclavsmil.com/wp-content/uploads/docs/smil-article-20090917-iron-age.pdf

Yikes!

 

 

Well this is just amazing. Thanks!

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As the paper points out, wood-based charcoal (derived from pyrolysis) is basically the same as coke (coal-based charcoal) --with the caveats mentioned about mechanical strength, etc.-- and so it can be used as a substitute for the coke needed during iron production.

 

The problem is the large amount of wood needed to provide that charcoal.

 

The solution is to instead use large amounts of waste biomass to provide that charcoal.

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I recently heard the figure of more than a gigaton per year of waste biomass, from the U.S. alone, that could be made available for producing cellulosic ethanol (just in case somebody figures that one out). And that accounted for the waste biomass that needs to be retained as a soil conditioner...for producing humus. And it may not have counted forest wastes either, but....

But until that waste biomass is dedicated for cellulosic ethanol....

 

Any pyrolyzed waste biomass (from plastics to algae) will produce charcoal suitable for iron production at some level, but pyrolysis of industrial-scale waste biomass such as nutshells, or pelletized biowastes will produce charcoal with higher mechanical strength.

 

"Although it is often assumed ...[charcoal] is the result of solid-phase reactions in which devolatilized biomass leaves behind a carbonaceous residue (primary char), in fact... [charcoal] is also formed by decomposition of organic vapours (tars) to form coke (secondary char). This secondary ...[charcoal] is as chemically reactive as the primary ...[charcoal] despite differences in its formation (Chen et al, 1997)." ~BEM* -p.137

 

Essentially, somebody needs to invent synthetic coke. There are already ways of adjusting the pyrolysis process to maximize specific properties of charcoals designed for various uses such as different activated charcoals, artist's charcoals, etc. It shouldn't be hard to adjust the process to maximize the coking properties of charcoal, say by using pelletized algae for the primary (structural) charcoal, and using plastics for developing the secondary (coking) charcoal....

 

[...as the organic (plastic) vapors deposit, cleave, fractionate, and re-deposit on the primary carbonaceous structure... (just fyi)].

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So does this make sense? Does it seem like waste biomass is a resource out there that we could use instead of vast forest tracts? Maybe collecting and processing that waste biomass at industrial-scale facilities could replace all the coal miner jobs, but it would probably require more jobs and they'd be distributed more evenly across the country.

 

~ :)

[Eclipse Now]

What about our sewerage flowing out onto huge brownfields or desert areas and growing algae or hemp?

[CraigD]

As usual, Vaclav Smil raises good and interesting points about iron/steel making in this 2009 paper The Iron Age & Coal-based Coke: A Neglected Case of Fossil-fuel Dependence. As usual, my impression of his speech and writing is that he underemphasizes the flexibility of engineering technology, focusing more on emerging challenges than emerging solutions.

 

This thread’s title question, “How Can We Do Steel In A Coal-Depleted Future?”, could be misleading. By conservative estimates, easily obtainable coal reserves will last at least 150 years – as Smil says in the closing line of his paper, “There can be no doubt: coal-derived coke will be with us for generations to come.” The main driver behind a shift from coal to less environmentally damaging fuels is not, I think, near-term scarcity of coal, but the need to reduce the emission of carbon into the atmosphere.

 

Technically, there’s nothing new or difficult about making steel using electricity – nearly all “secondary steel” making – steel made from recycling iron and steel scrap – uses it. So any power source that produces electricity, such as solar photovoltaic, is suitable for steelmaking. The power requirements (520 billion tons/year of coal is about 500 TW (5e14 W)) isn’t beyond the feasible range of such sources.

 

In short, I think primary steel making – steel and iron from ore – can be sustained for many centuries following a shift from coal coke to electric or other non-combustive energy sources. Engineering ingenuity will be needed, but isn’t, I think, a scarce commodity.

 

It’s also worth noting, I think, that materials such as carbon are potentially better than metals in many applications currently dominated by steel and other metals. We may well be passing from the iron age into a new “carbon age” (or, more poetically, “diamond age”), in which steel and other metals as bulk structural engineering materials will be less common than carbon-based materials. Already, graphite is common in many vehicles and other high-strength applications.

[Eclipse Now]

Hi Craig,

yeah, some good points but I'm not sure Vaclav was saying that coking coal was for the energy source but an ingredient in making the steel. As a fan of GenIV nukes that breed up lower uranium ores into good reactor fuel, I'm convinced Integral Fast Reactors could power the world indefinitely and give us all the electricity we need for electric arc smelting of metals.

 

But steel requires masses of carbon to be flushed through it. That's the problem here. Wikipedia on steel lays it out in the first few sentences...

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron

 

But the recycling wiki gives us some hope.

It is cheaper to recycle steel than to mine iron ore and manipulate it through the production process to form new steel. Steel does not lose any of its inherent physical properties during the recycling process, and has drastically reduced energy and material requirements compared with refinement from iron ore. The energy saved by recycling reduces the annual energy consumption of the industry by about 75%, which is enough to power eighteen million homes for one year.[5].....

 

 

....Recycling 1000 kilograms of steel saves 1,100 kilograms of iron ore, 630 kilograms of coal, and 55 kilograms of limestone.[8]

http://en.wikipedia.org/wiki/Ferrous_metal_recycling

 

Vaclav's work shows that the coke above is all ingredients.

 

Coke, made by pyrolysis of coal, has several critical roles in the smelting process: it high

mechanical strength supports the ore and limestone charge, it provides a permeable medium for

the ascent of reducing gases and the descent of molten slag and metal within the furnace, it acts

as the reducing agent (upward moving hot CO-rich gases reduce ore oxides into elemental iron)

and it energizes the high-temperature melt. The total amount of coke charged per unit of

produced iron has been gradually reduced by better furnace design and operation, by injecting oil

or natural gas and more recently by resorting to high injection rates of pulverized coal and even

by using pelletized plastic waste. As a result, average worldwide ratio of dry coke:hot metal

declined from about 1:1 in 1950 to 0.65:1 by 1970 and to just 0.45:1 by 2008.

 

This means that the global iron production still needed about 420 million tonnes of coke in 2008

and hydrocarbons and coal injected into blast furnaces added up to an equivalent of another 100

million tonnes of coke. In a non-fossil world the only option would be to replace coal-derived

coke (and injected fossil fuels) with charcoal made from woody biomass. Charcoal, nearly pure

carbon produced by pyrolysis wood, is an excellent reducing agent and all cast iron was

produced with it until the middle of the 18th century when Abraham Darby’s pioneering use of

coke began to spread among the English ironmakers. Traditional ironmaking used the fuel very

inefficiently (commonly 8-10 tonnes of charcoal per tonne of hot iron) but modern smelting

practices need no more than 0.75 tonne of charcoal per tonne of hot metal.

 

our grandchildren are in trouble?

 

The World Coal Institute says we only have 119 years of coal left!

http://worldcoal.org/resources/co­­al-statistics/

[Eclipse Now]

Anyone else actually excited by solving this problem? Think about it. If we can divert enough carbon out of our agriwaste or forestry each year to manufacture enough steel, just think what that means for Carbon Sequestration! WOW! It's up there with biochar! (But maybe competing with biochar?)

 

In other words, the steel industry moves from being an enormous carbon emitter to being a carbon negative industry, to the tune of half a billion tons of coal a year! (However that actually works out in tons of Co2 gas / year).

[Eclipse Now]

Anyone else had thoughts on this? I really don't think we're going to make headway with banning coal or capping carbon. It's just too easy and convenient. We're just going to burn the crap, whatever the consequences! I foresee us ignoring global warming until it is too late, and then being forced into powerding the sky white with the sulphur gun to stop global warming! Sad, but that's the level of cynicism I have about our governments kowtowing to King Coal and Big Oil.

 

So the end result is we burn all the cheaply available hydrocarbons and then steel prices rise exponentially as we can't afford the unconventional, hard to get at hydrocarbons. We flush .5 billion tons a year of hydrocarbons through iron ore to make steel.

 

Our grandchildren are going to wonder what was wrong with us!

[CraigD]

... I'm not sure Vaclav was saying that coking coal was for the energy source but an ingredient in making the steel.

I don’t have any experience or much knowledge about making iron and steel (which is a pretty complicated process), but from Varclav Smil’s paper and general articles on the subject and specifications of various grades or iron and steel, I pretty certain it’s wrong to say that the carbon in coal coke is an ingredient in iron and steel. Rather, it’s part of a catalyst. From Smil’s paper,

… [coke’s] high mechanical strength supports the ore and limestone charge, it provides a permeable medium for the ascent of reducing gases and the descent of molten slag and metal within the furnace, it acts as the reducing agent (upward moving hot CO-rich gases reduce ore oxides into elemental iron) and it energizes the high-temperature melt.

What this is saying is that when smelting ore to get iron to make steel, you need primarily to carry away the oxygen with which the ore’s iron is compounded. The easiest way I know to illustrate this is to write the main chemical reaction of iron smelting:

[ce]Fe_2O_3 + 3C0 \to 2Fe + 3CO_2[/ce]

 

Key to the process is lots of heat and carbon monoxide gas ([ce]CO[/ce]) to strip the oxygen from (“reduce”) the ferric oxide ([ce]Fe_2O_3[/ce]). Coke is a good source of [ce]CO[/ce] for this process, but is molecule doesn’t end up in the final pig iron product of the process, but in its waste exhaust.

 

If we can divert enough carbon out of our agriwaste or forestry each year to manufacture enough steel, just think what that means for Carbon Sequestration! WOW! It's up there with biochar! (But maybe competing with biochar?)

Some rough number checking makes me think steel isn’t a very good place to sequester carbon, because most steel has very little carbon in it, and even “high-carbon steel” doesn’t have very much. Here’s a little table I threw together when reading about various grades of iron and steel:

18/10 stainless steel                < 0.15% carbon  18% chromium   10% nickel
240 SMO stainless steel                                                         > 6% molybdenum
316 LVM stainless steel              < 0.03% carbon             
Martensitic  stainless steels   0.12 - 1%    carbon  12% chromium  < 2% nickel
low-carbon steel                0.05 - 0.15% carbon
mild steel:                     0.16 - 0.29% carbon
high-carbon steel               0.6  - 0.99% carbon
cast iron                       2    - 4%    carbon
pig iron                        3.5  - 4.5%  carbon

As we can see from these various recipes, carbon’s a key, but not a quantitatively major ingredient in most steel.

 

Current steel production is about 1.4 billion tons per year, of which about 70% is from recycling scrap (which doesn’t sequester any new carbon), so guessing at 0.5% carbon steel as an average, steel removes about 2 million tons of carbon per year. This is a small fraction of the estimated sequestration by methods such as biochar’s “1 to 2 billion tons per year”, or the release rate of about 5.5 billion tons per year from fossil fuels and concrete making.

 

Worse, because most primary (from ore) steel production burns coal, oil, gas, and other carbon-based fuels, is releases about 70% as much carbon into the air as the mass of the steel produced , so even the highest carbon content iron sequester only about 1/16th of the carbon their production releases. (data source: this industry group webpage. see “table: GHG emissions of various materials”, noting that the “CO2 equivalent” in this table must be multiplied by 12/44 to give carbon mass).

 

In other words, the steel industry moves from being an enormous carbon emitter to being a carbon negative industry, to the tune of half a billion tons of coal a year! (However that actually works out in tons of Co2 gas / year).

This could happen, if steel production shifts from carbon-based fuel energy sources, but as I show above, the sequestration will be insignificantly small.

 

Now, if we make the big “iron to carbon age” shift in main engineering materials to graphemes, or the even bigger “diamond age” shift to diamondoids, we could sequester a lot of carbon, as every large machine and structure we built would be primarily pure carbon. But such a shift is, IMHO, at least 10 years in the future.

 

Anyone else had thoughts on this? I really don't think we're going to make headway with banning coal or capping carbon. It's just too easy and convenient. We're just going to burn the crap, whatever the consequences!

Sadly, I agree. :( I hope we’re both wrong.

 

I foresee us ignoring global warming until it is too late, and then being forced into powerding the sky white with the sulphur gun to stop global warming! Sad, but that's the level of cynicism I have about our governments kowtowing to King Coal and ItBig Oil.

Wow! “Dr Evil” Lowell Wood’s ides and studies on climate geoengineering awe me! According to them, a fleet of less than a dozen [ce]SO_2[/ce]tanker airplanes could reverse polar ice melting. The cost of something like that would be negligible.

 

That there’s not more enthusiasm for this 5-year-old scheme, especially from the rest of the “forces of evil”, big oil, etc., puzzles me somewhat. I suspect Wood, a master of both technology and politics, concluded rightly:

"To talk openly about geoengineering, you would first have to admit there is a problem," Wood says. "And right now, no one is willing to do that in Washington. The issue is completely polarized."

(from the 2006 magazine article Can Dr. Evil Save The World?)

[Eclipse Now]

Oh I see, so carbon is flushing out the Oxygen but then reentering the atmosphere? OK, my apologies! Thanks for that clarification, I really appreciate it.

 

(I'm not a scientist at all, but can only *just* make out what's happening in the equations above).

 

Do you think the syngas that comes off plasma-burners might help replace the coal?

 

http://eclipsenow.wordpress.com/recycle/

 

But such a shift is, IMHO, at least 10 years in the future.

 

Are we really that close? I thought it was still sci-fi and that they were still testing safety issues with nano-particles and that it was still prohibitively slow and expensive?

 

That there’s not more enthusiasm for this 5-year-old scheme, especially from the rest of the “forces of evil”, big oil, etc., puzzles me somewhat. I suspect Wood, a master of both technology and politics, concluded rightly:

"To talk openly about geoengineering, you would first have to admit there is a problem," Wood says. "And right now, no one is willing to do that in Washington. The issue is completely polarized."

 

Yes, it is a bit of a mind-job isn't it? Artificially replicating the effects of volcanoes. And boffins keep coming up with ways to make it cheaper, such as using floating hoses to dump the sulphur instead of flying it up. Interesting times hey?

[geko]

If only there was a way to allow new technology to become economically viable quicker...

 

Oh wait, it exists already under capitalism :rolleyes:

 

...sorry, couldn't resist the dig /hug