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Peer review paper: https://www.cell.com/device/fulltext/S2666-9986(24)00235-7 https://www.cell.com/device/fulltext/S2666-9986(24)00235-7 Executive Summary: Sol

Peer review paper: https://www.cell.com/device/fulltext/S2666-9986(24)00235-7 https://www.cell.com/device/fulltext/S2666-9986(24)00235-7 Executive Summary: Solar heater that can work at temperatures close to 1000C by using semi-opaque materials to absorb solar energy and minimise radiative losses. Not even a proof of concept of an improved smelter. Article text in PopMech is exaggeration of paper and headline is a further exaggeration on top of that.

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mannykannot 2y ago
Ah - a greenhouse that can almost melt copper, though I think you need a mirror to get the "135 suns" input radiation.
scld 2y ago
The paper itself mentions the usefulness of the 1000C threshold: Solar process heat at above 1,000°C can decarbonize key industrial applications such as cement manufacturing and metallurgical extraction. The article is just running with that theme.
- jcranmer 2y ago
  > decarbonize key industrial applications such as cement manufacturing and metallurgical extraction ... so what's the reducing agent, if not carbon?
  - floatrock 2y ago
    Can you explain the chemistry pieces vs. the thermal inputs pieces?
    - jcranmer 2y ago
      The main tasks in converting iron ore to steel is as follows: reduce the iron (which requires a redox reaction), drive out existing impurities (both other metals present in the ore, such as magnesium or aluminum, and other nonmetals like sulfur or phosphorous), and introduce new ones (predominantly, uh, carbon). Note that these don't necessarily all occur at the same time, in the same furnace (steelmaking is a multistep process). These processes require the necessary chemical reagents to cause the necessary chemical reactions to occur. There are multiple roles for heat. Most notably, most of the necessary chemical reactions require high heat to occur at a time. Furthermore, outright melting gives the advantage that impurities tend to sort themselves by density, and your impurities are typically less dense than your main metal (i.e., the slag will float on top of the molten iron). There's also the advantage that high heat can make volatile impurities (e.g., sulfur dioxide) boil out. Historically, the reducing agent was largely charcoal, where you burn the wood in oxygen-poor environment to produce high purity carbon-rich material. The industrial revolution replaced charcoal with coke, where you burn coal in oxygen-poor environment to produce high purity carbon-rich material. In both cases, the furnace converts the fuel largely into carbon monoxide, which is the main actual reducing agent in contact with the iron (whereupon it forms carbon dioxide). The decarbonization assumption has been to replace carbon with hydrogen gas, but as far as I'm aware, hydrogen-based reduction furnaces have only existed in pilot plant form.
  - pfdietz 2y ago
    There's a proposed entirely-thermal iron reduction process that uses sodium as the reducing agent. This produces sodium oxide, which apparently can be decomposed back to sodium and oxygen by vigorous heating. I have my doubts about the overall feasibility of this scheme, but it doesn't involve any electrical energy input.
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mannykannot 2y ago

Ah - a greenhouse that can almost melt copper, though I think you need a mirror to get the "135 suns" input radiation.

scld 2y ago

The paper itself mentions the usefulness of the 1000C threshold: Solar process heat at above 1,000°C can decarbonize key industrial applications such as cement manufacturing and metallurgical extraction. The article is just running with that theme.

jcranmer 2y ago
> decarbonize key industrial applications such as cement manufacturing and metallurgical extraction ... so what's the reducing agent, if not carbon?
- floatrock 2y ago
  Can you explain the chemistry pieces vs. the thermal inputs pieces?
  - jcranmer 2y ago
    The main tasks in converting iron ore to steel is as follows: reduce the iron (which requires a redox reaction), drive out existing impurities (both other metals present in the ore, such as magnesium or aluminum, and other nonmetals like sulfur or phosphorous), and introduce new ones (predominantly, uh, carbon). Note that these don't necessarily all occur at the same time, in the same furnace (steelmaking is a multistep process). These processes require the necessary chemical reagents to cause the necessary chemical reactions to occur. There are multiple roles for heat. Most notably, most of the necessary chemical reactions require high heat to occur at a time. Furthermore, outright melting gives the advantage that impurities tend to sort themselves by density, and your impurities are typically less dense than your main metal (i.e., the slag will float on top of the molten iron). There's also the advantage that high heat can make volatile impurities (e.g., sulfur dioxide) boil out. Historically, the reducing agent was largely charcoal, where you burn the wood in oxygen-poor environment to produce high purity carbon-rich material. The industrial revolution replaced charcoal with coke, where you burn coal in oxygen-poor environment to produce high purity carbon-rich material. In both cases, the furnace converts the fuel largely into carbon monoxide, which is the main actual reducing agent in contact with the iron (whereupon it forms carbon dioxide). The decarbonization assumption has been to replace carbon with hydrogen gas, but as far as I'm aware, hydrogen-based reduction furnaces have only existed in pilot plant form.
- pfdietz 2y ago
  There's a proposed entirely-thermal iron reduction process that uses sodium as the reducing agent. This produces sodium oxide, which apparently can be decomposed back to sodium and oxygen by vigorous heating. I have my doubts about the overall feasibility of this scheme, but it doesn't involve any electrical energy input.
- deleted 2y ago
  [deleted]