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Comment by roenxi | Hacker News Reader

> The Oregon group’s setup generates essentially as much chlorine gas as it does iron

I'd much rather be dealing with industrial quantities of CO2 than Cl2, if that stuff gets into the atmosphere in bulk I doubt it'd end well. The article seems to suggest that the chlorine can be solved commercially so the argument seems to be that it is economical to sequester the chlorine rather than the carbon dioxide.

There are some obvious risks of being left with large amounts of Chlorine to try and find a home for, but the idea is at least plausible on face value.

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> I'd much rather be dealing with industrial quantities of CO2 than Cl2

The costs of CO2 - the real costs, not the subsidized ones - are extraordinarily high, possibly leading to the worst global catastrophe in human history. What is the cost of Cl2?

Parts of your lung flying out of your mouth. It was the first chemical weapon for a reason.

Is gassing the frog or slowly boiling it crueler?

With the passing of time the answer might not be so clear.

Well, you gas your frogs and I put mine in 2 degrees warmer ponds and we see which one are happier ?

Time for some dark humour! After careful analysis of the situation...

The frogs in the 2 degree warmer pond will be complaining a lot more than the other frogs, so that must be worse.

Last I checked (many years ago) the estimated long term cost from climate change due to all CO2 so far released was only in the low trillions (making WW2 a much bigger catastrophe), do you have an updated figure?

You talking about the area under an initial section of a hockey stick curve.

Swapping all the CO2 in the atmosphere for Cl would kill us all within 30 minutes (at 400ppm). It's way more dangerous.

I realise this is a silly thought experiment but the point of comparison should be, at the very most, the human industry generated CO2, not all natural CO2. The CO2 from this particular process is probably more relevant and since this process generated 1 ton of Cl per ton of Steel and the normal process generated 3 tons of CO2, we should give it a 66% discount.

> I realise this is a silly thought experiment but the point of comparison should be, at the very most, the human industry generated CO2, not all natural CO2

The pre-industrial levels of CO2 were around 280ppm, while the current CO2 levels are around 440ppm.

For Cl2, in occupational-health situations the permissible exposure is around 1ppm per hour, or 3ppm for 15 minutes. So the 160ppm we'd throw into the atmosphere in this thought experiment (or even the 52ppm at the suggested discount) is going to cause some pretty big problems pretty rapidly.

Arguably the most deadly part of CO2 is that it kills sooooooo slowly. Vent CO2 and nobody blinks. Vent Cl and everyone is gonna hate you immediately for immediately present negatives.

That's not the alternative option; nobody is suggesting swapping. Swapping CO2 for fission waste products would also kills us. Swapping it for H2O would drown us!

I think there's like 3 orders of magnitude more water in our atmosphere by weight than CO2, so a swap wouldn't drown us. But the point you were trying to make is clear.

Yes, but as long as we're having some fun with the concept: The problem with CO2 isn't the absolute CO2 in the atmosphere; most(?) of it was already there. It's the changes caused by the added CO2.

The problem with H2O wouldn't be the absolute amount, but the changes brought on by the added H2O. For one thing, it would rain pretty much 24/7 in Florida. :) (Yes, I know it's not at all that predictable.)

It won't necessarily accumulate though - there's a reason it was quickly abandoned as a chemical weapon. I would rather worry about its compounds, as it would quickly react with anything it touches.

I imagine Cl2 being way easier to capture by virtue of its weight. It is also a very useful byproduct for downstream applications.

It's also incredibly reactive, so it's going to be a lot easier to recover in general.

You can avoid any CO2 production in the iron production process via replacing the natural gas inputs to the Direct Reduced Iron (DRI) method with hydrogen. To compare DRI with carbon vs only hydrogen:

with carbon and hydrogen from natural gas/coal gasification: CH4 + CO2 -> 2CO + 2H2 Fe2O3 + 3CO -> 2Fe + 3CO2 (exothermic in >50% H2 environment)

with water-sourced hydrogen: 2H2O -> O2 + 2H2 Fe2O3 + 3H2 -> 2Fe + 3H2O (endothermic, requires energy input)

There are two issues with using hydrogen, which can be overcome:

>"The energy balance of the shaft furnace is affected by the absence of the exothermic carbon monoxide reduction. . . Thus, it is necessary to add energy to the shaft furnace to carry heat in the burden."

>"The second issue is the resulting DRI carbon content; the DRI will have 0% carbon with pure hydrogen. The majority of DRI is used in EAFs, and EAF steelmaking practice generally employs carbon addition... Under current melting practices, it will be necessary to add hydrocarbons at some place in the process to achieve the desired carbon level... However, this added carbon will then be converted to CO2 in the EAF... Alternatively, carbon from a renewable source (like biomass) could be used."

https://www.midrex.com/tech-article/ultra-low-co2-ironmaking...

Isn't Cl gas commercially valuable, people are making it. edit: the article says that this process would make too much...

The process results in a lot of sodium hydroxide as well. Mix it with chlorine and water, and you're back to what you started with: seawater.

And energy! Maybe you can even recover some of the energy from your new warm seawater.

I mean people are intentionally making industrial quantities of chlorine, via electrolysis, and have been for an century.

I did some quick searches thinking I'd find we produce vastly more iron than chlorine, and we surprised to learn that we only use sixteen times more iron.

Being so reactive I imagine. If chlorine were much much cheaper we would find many more uses.

https://en.wikipedia.org/wiki/Polyvinyl_chloride

Big use-case, problem is that in case of fire lots of dioxins are produced.

Yes, and chlorine is the stuff that no one wants, so it's turned into polyvinylchloride, which isn't really useful unless with copious quantities of plasticizer.

For something nobody wants it costs several hundred dollars per ton to buy

The price of chlorine though is much lower still and it has been very stable until recently. How elastic is demand for PVC?

but at scale? how much cl2 are we talking about?

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