For Questions That Don't Merit Their Own Thread

[K^2]

This one seems to have been quickly contained. But two's a pattern. Somebody should be at least investigating the fire safety procedures for any weakness.

[Nuke]

scott manley on why its stupid to send a mass simulator to the moon when the rover they were planning to send is ready to go, due to some congressional shenanigans.

was supposed to go into science facts, but im stupid.

Edited July 19 by Nuke

[farmerben]

  Aluminum is about 5 times the price of steel.  Why is aluminum so much more expensive than steel?

[RKunze]

9 minutes ago, farmerben said:

  Aluminum is about 5 times the price of steel.  Why is aluminum so much more expensive than steel?

Because you need way more energy to go from aluminium ore to aluminium metal than to go from iron ore to steel.

That is why Iceland's second most important export (after fish) is aluminium, even though both the ore needs to be shipped in and the finished product needs to be shipped out. But Iceland has lots of cheap electricity to run the smelters.

[DDE]

57 minutes ago, RKunze said:

That is why Iceland's second most important export (after fish) is aluminium, even though both the ore needs to be shipped in and the finished product needs to be shipped out. But Iceland has lots of cheap electricity to run the smelters.

Ditto for Soviet Union/Russia, all aluminum plants gravitate towards hydroelectric mega-powerplants.

[farmerben]

OK, then how much different would it be to recycle aluminum on solar power.   Solar has more capacity than hydro, but you have the issue of nighttime.  How easy is it to speed up or slow down aluminum production?  How big a battery would it take to keep an aluminum plant going over night?

 

Part of the difference compared to steel production is that steel furnaces are mostly heated by fossil fuels directly without requiring electricity.  Do aluminum furnaces burn fossil fuels as well?

Edited July 21 by farmerben

[StrandedonEarth]

33 minutes ago, farmerben said:

OK, then how much different would it be to recycle aluminum on solar power.   Solar has more capacity than hydro, but you have the issue of nighttime.  How easy is it to speed up or slow down aluminum production?  How big a battery would it take to keep an aluminum plant going over night?

 

Part of the difference compared to steel production is that steel furnaces are mostly heated by fossil fuels directly without requiring electricity.  Do aluminum furnaces burn fossil fuels as well?

Steel is an iron-carbon alloy, so it requires a source of carbon and energy to reduce the iron ore; coal works nicely that way but electric arc furnaces and direct hydrogen reduction is gaining steam. If ‘green’ hydrogen is available then it’s a carbon-neutral process 

Aluminum smelting is an electrolytic process, requiring only electricity. Lots of electricity, hence the nickname “frozen electricity”.  To run a smelter on solar/wind, simply overbuild the renewables and store the excess with pumped hydro for nighttime. 
 

Another instance of placing a smelter in a remote area near abundant hydropower is Kitimat in northwestern BC. It required boring the penstocks through a mountain range…

[farmerben]

1 hour ago, StrandedonEarth said:

 

Aluminum smelting is an electrolytic process, requiring only electricity. Lots of electricity, hence the nickname “frozen electricity”.  To run a smelter on solar/wind, simply overbuild the renewables and store the excess with pumped hydro for nighttime. 

I like that idea of "frozen electricity".  How much power does a typical commercial aluminum plant use?

[magnemoe]

2 hours ago, farmerben said:

OK, then how much different would it be to recycle aluminum on solar power.   Solar has more capacity than hydro, but you have the issue of nighttime.  How easy is it to speed up or slow down aluminum production?  How big a battery would it take to keep an aluminum plant going over night?

Melting down aluminum for reuse is very common  and don't take much energy compared to steel because low smelting point. 

Now making aluminium is not something you can't cycle on / off easy, same with most other melting processes you want to be huge and have an constant capacity. 
You don't aluminum  oxide or iron to turn solid in the furnace, so if power you has to handle it, dumping is an option. 

[StrandedonEarth]

1 hour ago, farmerben said:

I like that idea of "frozen electricity".  How much power does a typical commercial aluminum plant use?

Well, a little googling on the aforementioned Kitimat smelter gives me two link: https://www.northernsentinel.com/local-business/rio-tintos-kitimat-smelter-returns-to-full-capacity-6834462 which gives a capacity of 432 kilotons a year. Wiki gives https://en.wikipedia.org/wiki/Kemano_Generating_Station#:~:text=The smelter at Kitimat consumes,sold to BC Hydro's Powerex. which says: 

Quote

The Kemano Generating Station is... providing hydroelectricity for Alcan's Kitimat Aluminum smelter. The powerhouse is built in a cavern created 427 m (1,400 ft) inside the base of Mt Dubose. It produces 896 MW of power from its eight generator units, 

The smelter at Kitimat consumes about 80-85% of the plant's electricity, and the remainder is sold to BC Hydro's Powerex.[4

So figure the smelter consumes up to 760MW to produce 432kt per year. But that still won't give the number I want. Try again:

https://www.statista.com/statistics/1116216/aluminum-smelting-energy-intensity/#:~:text=In 2021%2C globally averaged%2C primary,one metric ton of aluminum.

Quote

In 2021, globally averaged, primary aluminum smelting requires around 14,114 kilowatt hours of energy to smelt one metric ton of aluminum

14 MWh for one ton. Yeah, ouch.

[farmerben]

Double check my math:  900 MW of power from 300W/m2 solar panels is about 3 square kilometers. 

[AckSed]

1 hour ago, farmerben said:

Double check my math:  900 MW of power from 300W/m2 solar panels is about 3 square kilometers. 

No good at numbers, but I can offer an example: https://en.wikipedia.org/wiki/List_of_photovoltaic_power_stations

https://en.wikipedia.org/wiki/Noor_Abu_Dhabi is pretty close to an ideal monolithic solar farm. Its capacity is 1.177 GW, it covers 8 square kilometres, it uses robots and no water to keep the panels clean and it supplied 2000 GWh in a year.

Edited July 22 by AckSed
Correction

[StrandedonEarth]

Running more numbers, using  14,114 MWh per ton and sustained max production of 432kT/yr yields  6.1  TWh per year. 800MW for a year is 7TWh. @AckSed, your article says 2000GWh, so 2 TWh. out of 8sqkm of solar in a prime location. PV is a good use of otherwise useless (ecologists my beg to differ) desert, while agrivoltaics allows for dual0use of land.

[AckSed]

While it's not a complete overlap, I'm willing to bet that a lot of bauxite mining is in deserts. There's already a trickle of electrification in the mining industry, and since it makes sense to generate the power onsite with solar and batteries, I wonder if someone would make the jump to on-site smelting to take advantage of the abundant sunny days. Export both Al ingots and excess power, or do carbon capture on the side with any overcapacity. Profit?

Mostly I'm amused at the possible switch from "wet climates with lots of hydroelectricity" over to "dry climates with lots of sun".

[StrandedonEarth]

Hmmm, enough batteries to provide 800MW for the night… 10GWh, at least? That’s a honking big battery. The ideal site is desert next to mountains  with  convenient pumped hydro reservoirs

[kerbiloid]

12 hours ago, farmerben said:

Do aluminum furnaces burn fossil fuels as well?

1 t of aluminium requires spending of 600 kg of graphite electrodes, ru-wiki says.

Alternatively, you can reduce it chemically from chloride with sodium or potassium amalgam (the historicaly first process, used in mid-XIX), much more expensive.

Or you can reduce it with CO at 2000+ C temperatures, which is also not the easiest and the cheapest way.

The alumina together with silica are one of the most stable compounds in the universe, that's why the rockey planets consist mostly of them.
So, as Mercury is solid, the direct splitting of the alumina with solar power looks having problems.
Iirc, to the date the real achievement was to split  several hundred grams of stones, and just to extract the oxygen.
As the solid waste would consist of aluminium, magnesium, titanium, and iron, and be polluted with sulfur, so their further separation will result into something not very different from the current process. Maybe also, they will need to oxidize them to separate the stable Al2O3 from others, lol.

9 hours ago, farmerben said:

How much power does a typical commercial aluminum plant use?

Quote

Для производства 1000 кг чернового алюминия требуется 1920 кг глинозёма, 65 кг криолита, 35 кг фторида алюминия, 600 кг анодных графитовых электродов и около 17 МВт·ч электроэнергии (~61 ГДж)

"To produce 1000 kg of raw aluminium, you need 1920 kg of alumina, 65 kg of cryolite (Na3AlF6, sodium hexafluoroaluminate, the deposists are very rare, but is produced from fluorite), 35 kg of aluminium fluoride (still requires fluorite), 600 kg of anode graphite electrodes, and about 17 MWh = 61 GJ of electric energy."

Edited July 22 by kerbiloid

[AckSed]

12 hours ago, StrandedonEarth said:

Hmmm, enough batteries to provide 800MW for the night… 10GWh, at least? That’s a honking big battery. The ideal site is desert next to mountains with convenient pumped hydro reservoirs

I'm getting attached to my desert refinery idea. I note that thermal batteries are being touted (essentially electrically-heated bricks), and they're capable of 20MW of thermal energy output at 1000-1500 deg. C and 300MWh of heat storage each, in a form-factor that could fit in a shop-front car-park. I wonder what percentage of the cryolite heating is down to the electricity, and if so, how many electrical batteries could it replace?

[farmerben]

I'm wondering whether it is possible to build a scaled down recycling plant.  Recycling forgoes those other ingredients.  There are economies of scale, but also inefficiencies of large scale.  Not knowing the industry, I'm not sure where the sweet spots are.  It depends on how big the equipment is, and how many of each piece of equipment you need.  The other big efficiency would be to turn down the system to just simmer at night and start up easily in the morning.  This could be done by just by holding a full crucible at high temperature all night.    

[darthgently]

Excess heat would be great for making thermal depolymerization of plastics even more efficient. 

The big expense of recycling is re-centralizing the feedstock and reliably accurate separation of streams.  Scaled down local recycling could alleviate the former and robotics and sensor improvement could improve the latter.

[StrandedonEarth]

When it comes to recycling plastics, the biggest challenge is getting clean, sorted feedstock. Human nature being what it is, there are many places where people are too lazy, too rushed, or simply don’t have facilities available for proper cleaning and sorting. So I say cut to the chase and just pyrolyze it all back into crude. It doesn’t matter how mixed or contaminated it was s then. Contaminated compost could be thrown in too.
 

Of course, this apparently is only practical when the thermal energy is cheap enough. 

[darthgently]

1 hour ago, StrandedonEarth said:

When it comes to recycling plastics, the biggest challenge is getting clean, sorted feedstock. Human nature being what it is, there are many places where people are too lazy, too rushed, or simply don’t have facilities available for proper cleaning and sorting. So I say cut to the chase and just pyrolyze it all back into crude. It doesn’t matter how mixed or contaminated it was s then. Contaminated compost could be thrown in too.
 

Of course, this apparently is only practical when the thermal energy is cheap enough. 

Thermal depolymerization can provide its own heat of course, but yeah, the more the merrier

[kerbiloid]

Afair, the most clean and ultimate recycling plants first turn the wastes into plasma, then run a shockwave in it.

Probably, the adiabatic compression causes a short-term overheating, which destroys any molecules, turning the complex chemical compounds into the simplest ones.

[magnemoe]

An railway question an line I use has been down for 3 weeks, doing work on it, they replaced the rails but they also replaced the sleepers and the ballast gravel, at least on the two stations I seen. looks like they might reused gravel other places as its darker.
The station I used was rebuild 20 years ago. 
Are the sleepers and gravel consumables? Yes I get that you want to re-set the line especially at stations as trains are stopping and starting all the time and to get dirt out of ballast but replacing the concrete sleepers and the gravel, its don't sounds like consumables for me? 

[AckSed]

They can get contaminated with oil and dust.

However, some concrete sleepers are fully recyclable, because they are made with sulphur concrete. Stick them in oven, bake for an hour and the steel reinforcing and staples can be pulled out: https://www.youtube.com/watch?v=n32rArqcc44

 

[kerbiloid]

The creosote, they are dark from, is cancerogenic.

Unless they use an eco-friendly green creosote.