4 ms·

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,

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...
  - londons_explore 4y ago
    NOx from big industrial processes tends not to be an issue. Catalytically reducing it to N2 and O2 is easy, and at the same time, you get out 'free' high grade heat, which there is usually some use for elsewhere in the plant.
  - jabl 4y ago
    > Interestingly, the paper mentions that the reactions do produce (some) hydrogen, which could perhaps be recaptured. The hydrogen is used for reducing the iron oxides, that's the whole point of the process! That is, FeXOY + H2 => Fe + H2O
to11mtm 4y ago
> From iron ore to steel, how much waste is there? Depends on how we define 'waste' and at what part of the process. When they start with the rock from the ground/pit, the rocks/etc are often crushed, running through some sort of slurry while basically separating the 'ore' out from silicates/etc that will be around them. I'm guessing this is already done close to the site, since transport cost could be fairly high even by past standards. What you wind up Iron ores that are considered 'worth' mining, the actual Iron content is anywhere from ~48% to ~72%. They'll typically have Oxygen, Possibly also Carbon or hydrogen as the 'impurities'. So, there's still a lot of potential waste in transporting all of that. [0] - Also, that would theoretically be useful in filling the pit back up, one would hope. But not sure on that one.
bigger_cheese 4y ago
I work in the steel industry so can provide some info here. In the mining of iron ore there is a step called "beneficiation" which involves the wet processing of minerals - this is not unique to iron ore and is common to many mining operations for a wide variety of materials, wet processing produces a waste slurry known as "tailings" which are typically stored in a dam or similar (https://en.wikipedia.org/wiki/Tailings_dam https://en.wikipedia.org/wiki/Tailings_dam) - tailings dams have been the cause of major environmental issues in the past. Such as the Brazilian Dam failure in 2019 which killed 250+ people. After beneficiation Iron ore is transported to a steelworks where it is smelted. The smelting process produces a further waste product "slag" (https://en.wikipedia.org/wiki/Slag https://en.wikipedia.org/wiki/Slag) how much slag is generated depends on a few factors such as the efficiency of the plant and the quality of the raw materials. Steelmaking slags can have some further use, for example it can be used in the concrete and cement industry and as a road base but how much if any of it is recycled very much depends on the country and the steelworks in some countries, particularly those with looser environmental restrictions slag is sent to landfill.

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...
- londons_explore 4y ago
  NOx from big industrial processes tends not to be an issue. Catalytically reducing it to N2 and O2 is easy, and at the same time, you get out 'free' high grade heat, which there is usually some use for elsewhere in the plant.
- jabl 4y ago
  > Interestingly, the paper mentions that the reactions do produce (some) hydrogen, which could perhaps be recaptured. The hydrogen is used for reducing the iron oxides, that's the whole point of the process! That is, FeXOY + H2 => Fe + H2O

to11mtm 4y ago

> From iron ore to steel, how much waste is there? Depends on how we define 'waste' and at what part of the process. When they start with the rock from the ground/pit, the rocks/etc are often crushed, running through some sort of slurry while basically separating the 'ore' out from silicates/etc that will be around them. I'm guessing this is already done close to the site, since transport cost could be fairly high even by past standards. What you wind up Iron ores that are considered 'worth' mining, the actual Iron content is anywhere from ~48% to ~72%. They'll typically have Oxygen, Possibly also Carbon or hydrogen as the 'impurities'. So, there's still a lot of potential waste in transporting all of that. [0] - Also, that would theoretically be useful in filling the pit back up, one would hope. But not sure on that one.

bigger_cheese 4y ago

I work in the steel industry so can provide some info here. In the mining of iron ore there is a step called "beneficiation" which involves the wet processing of minerals - this is not unique to iron ore and is common to many mining operations for a wide variety of materials, wet processing produces a waste slurry known as "tailings" which are typically stored in a dam or similar (https://en.wikipedia.org/wiki/Tailings_dam https://en.wikipedia.org/wiki/Tailings_dam) - tailings dams have been the cause of major environmental issues in the past. Such as the Brazilian Dam failure in 2019 which killed 250+ people. After beneficiation Iron ore is transported to a steelworks where it is smelted. The smelting process produces a further waste product "slag" (https://en.wikipedia.org/wiki/Slag https://en.wikipedia.org/wiki/Slag) how much slag is generated depends on a few factors such as the efficiency of the plant and the quality of the raw materials. Steelmaking slags can have some further use, for example it can be used in the concrete and cement industry and as a road base but how much if any of it is recycled very much depends on the country and the steelworks in some countries, particularly those with looser environmental restrictions slag is sent to landfill.