3 ms·

I read an old paper from the 60's on electrowinning iron from a sulfate solution. They claimed around 4.5kwh/kg. Read a more recent paper (2019) reporting on sa

I read an old paper from the 60's on electrowinning iron from a sulfate solution. They claimed around 4.5kwh/kg. Read a more recent paper (2019) reporting on same process with modern separators[1] got energy requirements down to 3.5kwh/kg. 3.5 kwh/kg is probably 20 cents worth of electricity. [1] Separators are used to isolate the anode and cathode in electrolytic cells in order to suppress side reactions. Modern separators allow specific ions to pass while blocking others.

SECProto 5y ago
> 3.5 kwh/kg is probably 20 cents worth of electricity. Your phrasing implies this is a small number - but 20 cents per kg is 20000c/tonne or $200 per tonne. The current spot price for iron ore is $200, which itself is twice as much as it was a year ago. So the additional cost of electricity could take the spot price as high as $400, four times as much as it was in July 2020. It's still an important for the environment to do this & remove carbon from the industry, but need to acknowledge the costs.
- jjk166 5y ago
  You're ignoring the current price of fuel. For context, in 2019 the cost of coke was $143 per ton of steel produced. Also it takes about 1.6 tons of iron ore per ton of steel, so that's currently about $320 in iron ore costs. Combined, that means 3.5 kwh/kg is roughly 12% more expensive raw material-wise than the current process. So it's an increase, but a drop in the bucket compared to the 200% increase in cost that happened over the past year; in fact its smaller than any YOY price change since 2015. Assuming it is phased in over the course of a few years, we likely wouldn't even notice the price increase.
  - Gibbon1 5y ago
    What tantalizing to me is solar and wind are unique in that the marginal cost of production is near zero. Meaning very unlike coal and natural gas energy sources. That leads to a energy grid characterized by frequent over supply. My thinking is electrowinning iron and mini-mills could easily absorb excess capacity. Aqueous electrolytic cells should be able to just sit idle for hours to days. And electric furnaces draw easily 10-100MW. That makes them a good match for a renewable grid.

SECProto 5y ago

> 3.5 kwh/kg is probably 20 cents worth of electricity. Your phrasing implies this is a small number - but 20 cents per kg is 20000c/tonne or $200 per tonne. The current spot price for iron ore is $200, which itself is twice as much as it was a year ago. So the additional cost of electricity could take the spot price as high as $400, four times as much as it was in July 2020. It's still an important for the environment to do this & remove carbon from the industry, but need to acknowledge the costs.

jjk166 5y ago
You're ignoring the current price of fuel. For context, in 2019 the cost of coke was $143 per ton of steel produced. Also it takes about 1.6 tons of iron ore per ton of steel, so that's currently about $320 in iron ore costs. Combined, that means 3.5 kwh/kg is roughly 12% more expensive raw material-wise than the current process. So it's an increase, but a drop in the bucket compared to the 200% increase in cost that happened over the past year; in fact its smaller than any YOY price change since 2015. Assuming it is phased in over the course of a few years, we likely wouldn't even notice the price increase.
- Gibbon1 5y ago
  What tantalizing to me is solar and wind are unique in that the marginal cost of production is near zero. Meaning very unlike coal and natural gas energy sources. That leads to a energy grid characterized by frequent over supply. My thinking is electrowinning iron and mini-mills could easily absorb excess capacity. Aqueous electrolytic cells should be able to just sit idle for hours to days. And electric furnaces draw easily 10-100MW. That makes them a good match for a renewable grid.