Are the max yield and the yield efficiency numbers mixed up?
The reason I ask is I wonder if the carbon could be used as a soil amendment to help replenish top soils in agriculture, or as a growing medium generally. But this would only be conceivable if it's just carbon.
Things like crystallization reactions will produce very pure products, some other reactions will absorb more contaminants.
If you collect the pollutants before emitting them and turn them into stable products, you aren't polluting.
Ergo, clean.
Why is that disqualifying?
The problem is combustion’s emission of sequestered carbon. If you don’t have that you don’t have this problem.
You concluded it’s processed dirtily at the source based on that premise (“which means”). If you’re independently asserting that, you’d have a point.
That and if you just encourage more exploration, and it's cheaper to just burn the stuff anyways, guess what happens in the price conscious free market?
Given that construction currently uses a huge amount of concrete, and given that concrete emits huge amounts of CO2[1], if this could partially replace concrete in construction, it might actually be clean. At least compared to what we're doing now.
I doubt foundations are going to be made out of carbon nanotubes, but they might be useful for the structure (columns, beams, etc.).
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[1] "4-8% of total global CO2" according to https://en.wikipedia.org/wiki/Environmental_impact_of_concre...
How long will the C atoms in those "stable product" stay there?
Burning wood is clean energy: it does not increase the number of atomic C in the upper layers. Natural gas is not, unless you find a way to store those C.
Carbon fouling is also a major block to scale. 15-20% of carbon deposits as soot on reactor walls. At a 1MW scale thats 15-30 kg/h of crud degrading the catalytic heat transfer. Continuous cleaning or scheduled downtime would drive OPEX out of possible realities.
Hot hydrogen loops are a son-of-a-bitch and equal continuous embrittlement of pipes, valves, pumps. Seals that work at temperature. H2 Leak detection. Some real heavyweight process safety engineering here.
The reactor chemistry is solved. The paper proves it works.
The scale-up is where clean-tech startups go to burn money and die.
Aluminum red mud is 40% iron.
Is hydrogen useful for plasma enhanced CVD?
Are there electrical plasma improvements to CVD specifically for CNT carbon nanotube production?
What optimizations of CVD produce nonmetallic aligned carbon nanotubes (with band gaps useful for semiconductor production for FET field-effect transistors, and integrated optical components)?
From gemini3pro, for human consideration;
> [ PECVD: Plasma-enhanced CVD] allows VA-CNT synthesis at temperatures as low as 450–650°C
> High-flux hydrogen (H_2) carrier gas is used in floating-catalyst CVD (FCCVD) to reduce the number of nuclei, favoring isolated semiconducting nanotubes over bundled metallic ones.
> Electric Field Alignment: PECVD uses the built-in electric field of the plasma sheath to guide nanotubes into vertical or horizontal alignment as they grow.
> [ Kite growth CVD with nonmetallic seeds like nanodiamond grow in tip-growth mode ]
Which would be useful for FET in Carbon-based chips
Couldn't hydrogen (cold) plasma clean a CVD reaction chamber?
Currently H2 is clean only at the usage stage, not at the production stage. Just like electricity for EVs in Germany :)
As a fuel, the alternatives are electricity for land and biofuels for land and sea.
But as a chemical feedstock the alternator is dirtier hydrogen.
So wasting this as a fuel means that you aren’t replacing dirty hydrogen with it, but rather cleaner electricity.
dupe: https://news.ycombinator.com/item?id=46368776
It didn't show any matching posts when I shared the URL.
ENH: HN: search for matching articles on debounced update to the submit URL field
Then wouldn’t you have a cleaner energy system then burning the methane directly?
> And the energy content of the hydrogen output is less than the methane input plus the heat dumped in. This is thermodynamics.
You are right, but you forgot something. You are not creating the methane. You are extracting it from the ground. The energy content of the hydrogen is only 60% of the energy content of the methane you use to get it, and if you account for the energy to split the CH4, you are left with only 50% of the original energy of the methane. But then you get hydrogen that can generate emissions-free electricity. It's a good trade off.
[1] https://en.wikipedia.org/wiki/Standard_enthalpy_of_formation...
PaulHoule•1mo ago
https://www.aga.org/its-time-to-pay-attention-to-turquoise-h...
in contrast to "Grey Hydrogen" [1] made by steam reforming
https://en.wikipedia.org/wiki/Steam_reforming
The self-taught ChemE in me worries a little about any process that makes a solid product since that product could plate out inside the machine and clog it up, but maybe that's not really a problem here.
[1] "Blue" if you capture the CO2