Thread 16743612

Some years ago I was reading some papers about desalination, and I read that, when frozen, most salt water becomes fresh water, i.e., the salt separates. Then I read about cascaded desalination systems that use heat, and how heating water is actually much more energy-intense than freezing it (specific heat for ice is like half of that of water), and boiling water uses even more energy.

On the other hand, freezing water is more expesinve than reverse osmosis.

All of the above made me think: why aren't there cascaded desalination systems that reuse the differential in temperatures to separate the salt from seawater? Like, you could have a system where seawater is frozen into ice, and heat is transferred from the input water to the ice in a sequential (cascaded) process designed in a way that little energy is lost. Also, heat pumps would make it so that you would be moving heat away from the system for cheap.

Let's say the output ice is at -20°C, and the input seawater is at 20°C. You could transfer heat from seawater at 0°C to ice -20°C, then seawater at 10°C to ice at -6°C, and seawater at 20°C to fresh water at 5°C, and that would be 3 stages. You could have intermediate stages. Maybe even a continuous flow of some sort. Do you think this would save enough energy to make the system worth making?

Here's some reading material: https://www.nature.com/articles/s41545-022-00158-1

Specific heat capacities of water, sea water and ice:
https://www.engineeringtoolbox.com/specific-heat-capacity-water-d_660.html
https://www.engineeringtoolbox.com/sea-water-properties-d_840.html
https://www.engineeringtoolbox.com/ice-thermal-properties-d_576.html

Another idea: in places where the sea is relatively close to the mountains and these mountains actually get cold enough to produce ice during winter, you could get ice (+ salt) "for free" from sea water with a system that simply exposes salt water to the environment.

This water could be moved with solar energy, and this potential could even be used to build small hydroelectric power plants maybe?

Are these ideas valuable or useless/retarded?

>>16743612 (OP)
Freezing water does not remove salt. Heating only works because the water turns into a gas and salt cannot become a gas.

This is dumb you have to physically remove the salt from the water.

However we have plenty of water. We just need to stop wasting it on nonsense.

>>16743642
>Freezing water does not remove salt
Anon... I'm no expert on this, but you you read the paper I left in the OP. Also, google "freeze desalination" or "cryo desalination" or something.

>Stop guessing start learning
The irony. LMAO.

>>16743724
Technically you can remove salt by freezing but it’s not a viable method. As it doesn’t fully get rid of the salt.


It also has problems scaling.

So to make it simple for you.

It doesn’t work.

Like I said earlier

>>16743612 (OP)
>All of the above made me think: why aren't there cascaded desalination systems that reuse the differential in temperatures to separate the salt from seawater? Like, you could have a system where seawater is frozen into ice, and heat is transferred from the input water to the ice in a sequential (cascaded) process designed in a way that little energy is lost. Also, heat pumps would make it so that you would be moving heat away from the system for cheap.
Bro im not going to decipher whatever you want to say but just realize that legions of very smart scientists and engineers, many of them israeli, have already developed desalination to the best it can get taking into account economic factors, not only physical limits. You are not going to come up with a better idea.
If you can understand and implement the existing technology, you could use that as a basis for a business or job.

>>16743612 (OP)
The thing is, so very many of our industrial processes produce waste heat.
Why not put it to do something useful like desalinate water?

>>16743735
>Like I said earlier
Yeah, and like I said earlier, you could have read, or even glanced over, the fucking paper... How difficult can it be?

>>16743744
>noo you won't do better than engineers!!
>but if you do, you could start a profitable business!
Were you trying to add anything beyond the obvious?
Also, what's with the praise for zionist engineers? Most research seems to be done by arabs

>>16743749
I'd guess it's because the amount of energy and the temperatures needed to get fresh water by boiling it are kinda high. Desalination by boiling uses like 7x what a freeze desalination system could use.

Thought about something similar but using repeated step ups in pressure to reach boiling point (unsure if you could do this effectively with the strength of steel or whatever you would plan to use) then filter off the vapour and return the brine you would be left with, to be honest in my country we probably wouldn't need it as we could just build a new reservoir, arid countries might be interested if you could do it with low power or even better none.

>>16743612 (OP)
>FD can treat concentrated brine close to zero liquid discharge either stand-alone17 or integrating with membrane distillation and crystallization18
Reviewers can't be making clickbait accidentally. Reference 18 is going to have the option for very high water recovery, it's not going to violate the mass balance.

>>16743779
>Most research seems to be done by arabs
cheapest desalinzation is done in israel. Arabs cant read and they hired some americans to build them flash evaporators for desalination using waste heat from their wasteful power plants that burn expensive oil.
Same dumb arabs will produce water at a cost of 1 dollar per cubic meter and use 1000 cubic meters to irrigate desert farms to grow 1 ton of wheat, that isnt worth more than $400. Any leftover money is used to fund some random army in Syria for no practical reason and to build The Line!

>>16743821
Im glad someone else realizes how dumb sandniggers are.

Who the fuck builds cities in the desert? Theres literally no resources. And they have to waste tons of energy to get water to their desert.

Saudis use 10% of oil they extract just on desalination.

This is unsustainable.

These idiots will be riding camels in no time

>>16743744
>Bro im not going to decipher whatever you want to say

>>you could have a system where seawater is frozen into ice, and heat is transferred from the input water to the ice in a sequential (cascaded) process designed in a way that little energy is lost.
let's put it this way:
input is seawater at 20°C (ambient temperature)
output from the freezer is ice at -20°C, BUT you actually want potable fresh water at ambient temperature
freeze desalination = freezing your input water to separate as much salt as you can.
to reduce the amount of energy needed to freeze the input water, you could cool the input water in part, in a cascaded process, to exchange heat with the ice/cold water.
this would be the steps before the final freezling process of your input water.

the question is: can this be optimized enough to reduce the amount of energy lost in the process of freezing the seawater, to make it cheaper than reverse osmosis?

consider that specific heat capacity of saltwater is about 2x that of ice, and that you will have to discard some brine left after freezing, so you could lose some energy there. the less brine that is discarded, the better.

>>Also, heat pumps would make it so that you would be moving heat away from the system for cheap.
reverse osmosis systems require a lot of expensive equipment. something like this could even be done in a portable way to produce water at home, in your fridge, maybe.

I can imagine something like a bunch of tubes inside a big tube: the fresh water moves out of the system through smaller tubes and the big tube transports seawater to the freezer, getting colder as it moves.

the last part would be the most complicated: actually making ice, separating the salt and transferring heat from seawater and freshwater ice. the paper shows multiple methods.

but, whatever. the point of this thread was: how would you design a system that wastes the less energy?

>>16743821
>cheapest desalinzation is done in israel.
can you tell me why? is their process really optimized? is it something technical? if so, what's so special about their reverse osmosis systems vs others? or is it their energy cheaper? maybe they are subsidized by the US government?

>>16743833
ok, I guess arabs are retarded. what about taiwanese?

also, accrding to some quick googling, the lowest energy consumption in the worls is 1.861 kWh/m3
from https://www.danfoss.com/en/about-danfoss/articles/hpp/a-new-world-record-in-swro-energy-efficiency-underscores-the-enormous-potential-of-updating-existing-desalination-plants-with-best-in-class-technology/
while the following paper says "SWRO in Israel 3.0–3.4 (3.85)" 1.861 kWh/m3, and apparently that's only 1 of multiple stages
(source: https://arava.org/wp-content/uploads/2015/05/Renewable-energy-fueled-desalination-in-Israel_final.pdf)

>>16743948
Jews always lie. They are always the best according to them. (Their iron dome failed from irans missiles) dont trust everything you read even if its an academic paper.

Jews love to lie

>>16743948
I'm fond of thinking that any process that doesnt break the laws of physics should be possible. Apparently theres a minimum theoretical energy cost to desalination, as you are concentrating salt creating brine and creatng fresh water so lowering the entropy. Typical desalination will use several times the minimum required energy, theres theoretical room to produce multiple times more water (5 to 20 times) per energy expended.
I dont really care, more water is code for niggers.