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"In the main approach to steelmaking today, iron oxide is placed into a blast furnace with coke, a hard, porous substance derived from coal... This and other st

"In the main approach to steelmaking today, iron oxide is placed into a blast furnace with coke, a hard, porous substance derived from coal... This and other steps in the process pump around 1.7 gigatons of carbon dioxide into the atmosphere annually, ... And that’s before taking into account the fuels required to fire the furnaces." The coke is the fuel that fires the furnaces.

cauldron 8y ago
Maybe it's about the buring needed to make the coke.
- qbrass 8y ago
  Steel is an alloy of iron and carbon. They mix coke with the iron to add carbon to it. The article is talking about the CO2 released from that coke, and not the coke used to fuel the furnace.
  - cauldron 8y ago
    You sound like confused, from my limited knowledge, the making of steel is exactly opposite of what you said, they extract carbon atoms from iron, that makes carbon monoxide into carbon dioxide.
    - SomeAmerican 8y ago
      Iron ore has no appreciable carbon in it before it enters the blast furnace.
  - hexane360 8y ago
    Actually it's 100% the opposite. Look at your iron-carbon phase diagram: https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/illustr/fe_c_phase_diagram_cast_iron.gif https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/illustr/fe_... Cast iron contains a high concentration of carbon, which makes it brittle. To make steel you need a heavy oxidizer to extract the (reduced) carbon. This is usually done using a "basic oxygen furnace", which is basically injecting a high pressure, very high velocity stream of oxygen into the metal to game thermodynamics into combusting the carbon without combusting the iron.
    - foobarian 8y ago
      Wow, TIL. This has some details at "5 year old level:" https://www.quora.com/What-is-the-difference-between-iron-and-steel https://www.quora.com/What-is-the-difference-between-iron-an... The phase diagram is very interesting too. Very little carbon is needed to go from elemental iron to steel, looks like about 0.008%. Thanks for posting that!
  - testrun 8y ago
    This is correct, and the carbon is a byproduct. The reason is to get rid of the oxide in the iron-oxide compound. The way I understand it, is that when mined they get iron-oxide, Fe(2)O(3), or Fe(3)O(4), so there is no carbon present. They use the coke to make carbon monoxide (CO). And this process removes the oxide and adds carbon to iron to create pig iron. From there it will be further processed to create different steels, alloys and iron products. Wikipedia (https://en.wikipedia.org/wiki/Iron_ore https://en.wikipedia.org/wiki/Iron_ore) under the smelting paragraph describes the oxide removal process.
  - SomeAmerican 8y ago
    The coke that is mixed with the iron ore is the coke that heats the furnace. As the coke (carbon) reacts with oxygen, some of the carbon monoxide then strips oxygen from the iron oxide in the iron ore.
Hextinium 8y ago
Blast furnaces do not need fuel to create iron, the process in which iron oxide is converted to iron is endothermic but the coke itself is the fuel in the furnace. It actually is necessary to do this to produce carbon monoxide which reacts with the iron oxide.
- SomeAmerican 8y ago
  "Blast furnaces do not need fuel to create iron" Blast furnaces need fuel to raise the temperature of the blast furnace input to speed up stripping what becomes slag and the oxygen from the iron oxide in the iron ore. Carbon monoxide is what is able to penetrate the iron ore at the high temperatures. My previous comment is criticizing the author for suggesting that yet another fuel produces the heat for the blast furnace.
- bigger_cheese 8y ago
  It can get very complicated. There are a few different reactions which occur in a Blast Furnace some are exothermic some are endothermic. BF is very simplistically a giant counter current reactor. Ore and Coke (the reactants) are added at the top at room temperature and hot gas (the "blast") is injected at the bottom and they flow past each other. CO is not the only reductant that plays a role Hydrogen primarily from the humidity contained within injected gas also plays a role in the heat balance of the furnace. Hydrogen is actually very efficient at reducing iron and avoids the CO2 byproduct. I know in the past some alternative ironmaking methods have looked into using things like hydrogen gas and natural gas (CH4) to directly reduce iron ore using a process abbreviated as DRI (Direct Reduced Iron) and for a while in the '90's this was marketed as a Blast Furnace alternative I haven't really kept up with technology. I started my career as a Metallurgist (Materials Engineer) working at a Blast Furnace they are hugely complicated beasts.

cauldron 8y ago

Maybe it's about the buring needed to make the coke.

qbrass 8y ago
Steel is an alloy of iron and carbon. They mix coke with the iron to add carbon to it. The article is talking about the CO2 released from that coke, and not the coke used to fuel the furnace.
- cauldron 8y ago
  You sound like confused, from my limited knowledge, the making of steel is exactly opposite of what you said, they extract carbon atoms from iron, that makes carbon monoxide into carbon dioxide.
  - SomeAmerican 8y ago
    Iron ore has no appreciable carbon in it before it enters the blast furnace.
- hexane360 8y ago
  Actually it's 100% the opposite. Look at your iron-carbon phase diagram: https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/illustr/fe_c_phase_diagram_cast_iron.gif https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/illustr/fe_... Cast iron contains a high concentration of carbon, which makes it brittle. To make steel you need a heavy oxidizer to extract the (reduced) carbon. This is usually done using a "basic oxygen furnace", which is basically injecting a high pressure, very high velocity stream of oxygen into the metal to game thermodynamics into combusting the carbon without combusting the iron.
  - foobarian 8y ago
    Wow, TIL. This has some details at "5 year old level:" https://www.quora.com/What-is-the-difference-between-iron-and-steel https://www.quora.com/What-is-the-difference-between-iron-an... The phase diagram is very interesting too. Very little carbon is needed to go from elemental iron to steel, looks like about 0.008%. Thanks for posting that!
- testrun 8y ago
  This is correct, and the carbon is a byproduct. The reason is to get rid of the oxide in the iron-oxide compound. The way I understand it, is that when mined they get iron-oxide, Fe(2)O(3), or Fe(3)O(4), so there is no carbon present. They use the coke to make carbon monoxide (CO). And this process removes the oxide and adds carbon to iron to create pig iron. From there it will be further processed to create different steels, alloys and iron products. Wikipedia (https://en.wikipedia.org/wiki/Iron_ore https://en.wikipedia.org/wiki/Iron_ore) under the smelting paragraph describes the oxide removal process.
- SomeAmerican 8y ago
  The coke that is mixed with the iron ore is the coke that heats the furnace. As the coke (carbon) reacts with oxygen, some of the carbon monoxide then strips oxygen from the iron oxide in the iron ore.

Hextinium 8y ago

Blast furnaces do not need fuel to create iron, the process in which iron oxide is converted to iron is endothermic but the coke itself is the fuel in the furnace. It actually is necessary to do this to produce carbon monoxide which reacts with the iron oxide.

SomeAmerican 8y ago
"Blast furnaces do not need fuel to create iron" Blast furnaces need fuel to raise the temperature of the blast furnace input to speed up stripping what becomes slag and the oxygen from the iron oxide in the iron ore. Carbon monoxide is what is able to penetrate the iron ore at the high temperatures. My previous comment is criticizing the author for suggesting that yet another fuel produces the heat for the blast furnace.
bigger_cheese 8y ago
It can get very complicated. There are a few different reactions which occur in a Blast Furnace some are exothermic some are endothermic. BF is very simplistically a giant counter current reactor. Ore and Coke (the reactants) are added at the top at room temperature and hot gas (the "blast") is injected at the bottom and they flow past each other. CO is not the only reductant that plays a role Hydrogen primarily from the humidity contained within injected gas also plays a role in the heat balance of the furnace. Hydrogen is actually very efficient at reducing iron and avoids the CO2 byproduct. I know in the past some alternative ironmaking methods have looked into using things like hydrogen gas and natural gas (CH4) to directly reduce iron ore using a process abbreviated as DRI (Direct Reduced Iron) and for a while in the '90's this was marketed as a Blast Furnace alternative I haven't really kept up with technology. I started my career as a Metallurgist (Materials Engineer) working at a Blast Furnace they are hugely complicated beasts.