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Posted by Boo on April 13, 2008, 5:10 am
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Hi,
The question is as per title : I suppose it must vary a bit depending on the
steel and the plant, but can anyone here tell me how much carbon is typically
releaseed into the atmosphere during the production of a ton os steel ?
Many thanks,
--
Boo
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Posted by Peter Fairbrother on April 13, 2008, 6:59 am
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Boo wrote:
> Hi,
>
> The question is as per title : I suppose it must vary a bit depending
> on the steel and the plant, but can anyone here tell me how much carbon
> is typically releaseed into the atmosphere during the production of a
> ton os steel ?
>
> Many thanks,
>
Varies a bit: a COREX plant can be up to 2.2 tons CO2 per ton of hot
iron (but some of that will be as export gas), and a modern HIsmelt or
DIOS plant might only produce about 1.2 tons of CO2 per ton of hot iron
- but this is at the lowest end.
Say 1.5 - 2.5 tons per ton of rolled steel overall, probably averaging a
little under 2 tons CO2/ton steel.
(I have ignored electric smelters, as the electricity to run them has to
come from somewhere - if the lekky is carbon-free and natural gas is
used as the reductant it might go as low as 0.7 tons CO2/ton steel, but
this is impractical)
-- Peter Fairbrother
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Posted by Cheshire Steve on April 13, 2008, 2:55 pm
Please log in for more thread options > Boo wrote:
> > Hi,
>
> > The question is as per title : I suppose it must vary a bit depending
> > on the steel and the plant, but can anyone here tell me how much carbon
> > is typically releaseed into the atmosphere during the production of a
> > ton os steel ?
>
> > Many thanks,
>
> Varies a bit: a COREX plant can be up to 2.2 tons CO2 per ton of hot
> iron (but some of that will be as export gas), and a modern HIsmelt or
> DIOS plant might only produce about 1.2 tons of CO2 per ton of hot iron
> - but this is at the lowest end.
>
> Say 1.5 - 2.5 tons per ton of rolled steel overall, probably averaging a
> little under 2 tons CO2/ton steel.
>
> (I have ignored electric smelters, as the electricity to run them has to
> come from somewhere - if the lekky is carbon-free and natural gas is
> used as the reductant it might go as low as 0.7 tons CO2/ton steel, but
> this is impractical)
>
> -- Peter Fairbrother
Peter,
I had to look up Corex, I am a little out of date. Isn't that just
iron production, so leaves all the steel production side. Which takes
a fair bit of energy, as does the casting, soaking pits, and rolling -
I assume you don't just want a 1 tonne ingot ?
Steel plant will include a considerable fraction of recycled steel, so
a big fraction of iron stays in circulation once extracted.
I once contacted an organisation (was it the energy saving trust),
regarding the benefit of keeping an old car going compared to buying a
new more economical model. They came up with a fairly rational answer,
and certainly for my regular car it there is no sound environmental
reason to dump it even though it is 13 years old.
Steve
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Posted by Peter Fairbrother on April 14, 2008, 2:11 am
Please log in for more thread options Cheshire Steve wrote:
>> Boo wrote:
>>> Hi,
>>> The question is as per title : I suppose it must vary a bit depending
>>> on the steel and the plant, but can anyone here tell me how much carbon
>>> is typically releaseed into the atmosphere during the production of a
>>> ton os steel ?
>>> Many thanks,
>> Varies a bit: a COREX plant can be up to 2.2 tons CO2 per ton of hot
>> iron (but some of that will be as export gas), and a modern HIsmelt or
>> DIOS plant might only produce about 1.2 tons of CO2 per ton of hot iron
>> - but this is at the lowest end.
>>
>> Say 1.5 - 2.5 tons per ton of rolled steel overall, probably averaging a
>> little under 2 tons CO2/ton steel.
>>
>> (I have ignored electric smelters, as the electricity to run them has to
>> come from somewhere - if the lekky is carbon-free and natural gas is
>> used as the reductant it might go as low as 0.7 tons CO2/ton steel, but
>> this is impractical)
>>
>> -- Peter Fairbrother
>
> Peter,
>
> I had to look up Corex, I am a little out of date. Isn't that just
> iron production,
Yes, COREX and HIsmelt/DIOS smelters produce "hot iron" (molten iron,
usually about 4% carbon) from iron ore and coal - these are usually
co-located with steelmaking converters and a steel mill though.
Smelting is the most energy-requiring and CO2 producing part of the
steelmaking process.
{ COREX is the major smelting technology used today. HIsmelt and DIOS
are the new kids on the block. They replace the old blast furnace and
coke oven - the coal is used in the smelters directly, rather than being
made into coke, which has many pollution-related and efficiency advantages }
so leaves all the steel production side. Which takes
> a fair bit of energy,
The input energy for hot iron -> hot steel can be considered to be just
pumps, cranes and conveyors.
Conversion gives off a bit of CO2 from burning the carbon in the hot
iron though (the heat from which is used to melt the scrap). The export
gas from the COREX process, or part of it, may also be used to melt (or
usually just preheat) extra scrap, so the ratio of scrap can be higher.
{ steel is produced today by the basic oxygen process, a steelmaking
furnace is charged with a mixture of scrap and hot iron and oxygen is
blown through it. The 4% carbon in the hot iron burns, the heat from
which is used to melt the scrap - the hot iron from the smelter/blast
furnace is already molten. }
as does the casting, soaking pits, and rolling
Casting uses little energy (the metal is already molten), soaking pits
and rolling can use quite a bit (but less than smelting).
> I assume you don't just want a 1 tonne ingot ?
>
> Steel plant will include a considerable fraction of recycled steel, so
> a big fraction of iron stays in circulation once extracted.
Typically about 20% of the steelmaking converter charge is scrap, the
rest is hot iron from the smelter. Larger scrap ratios are possible but
unusual in primary steel production.
The process map can be insanely complex (!!), and just talking about
single bits of it often doesn't give more than a rough idea of what's
going on. Plus a detailed map with figures is going to be a proprietary
secret, so you have to estimate a bit.
When you have a combined smelter, converter and steel mill it can get
really complex, with various interactions between them like the use of
export gas in the soaking pits.
In calculating CO2 release you also have to consider the CO2 from the
lime used as flux, the extra steel produced from scrap, the 96%
composition of hot iron, the treatments (eg desulphurisation uses
magnesium, which costs a whole lot of energy to produce - but the
desulphurisation reaction gives off a lot of heat) - and so on.
I have tried my best, without doing lots of research.
A COREX smelter will typically operate at about 1.8 tons CO2/ton hot
iron, the converter and mill will use the rest.
About 2.0 tons CO2/ton steel seems a reasonable figure for developed
world COREX-based production, and about 1.9 tons CO2/ton steel for
HIsmelt/DIOS - but note that the figure for secondary production in the
developing world will be higher, sometimes much higher.
Though new large primary plants in China, India etc are often COREX plants.
-- Peter Fairbrother
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Posted by Boo on April 13, 2008, 3:21 pm
Please log in for more thread options > Varies a bit: a COREX plant can be up to 2.2 tons CO2 per ton of hot
> iron (but some of that will be as export gas), and a modern HIsmelt or
> DIOS plant might only produce about 1.2 tons of CO2 per ton of hot iron
> - but this is at the lowest end.
>
> Say 1.5 - 2.5 tons per ton of rolled steel overall, probably averaging a
> little under 2 tons CO2/ton steel.
>
> (I have ignored electric smelters, as the electricity to run them has to
> come from somewhere - if the lekky is carbon-free and natural gas is
> used as the reductant it might go as low as 0.7 tons CO2/ton steel, but
> this is impractical)
>
Thanks !
--
Boo
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>
> The question is as per title : I suppose it must vary a bit depending
> on the steel and the plant, but can anyone here tell me how much carbon
> is typically releaseed into the atmosphere during the production of a
> ton os steel ?
>
> Many thanks,
>