zompist bboard

I'm working on a little alt-history conworld. The idea is, a people on a little island somewhere in the Mediterranean come up with a method for extracting metal from seawater, which they sell and get rich. I'm having some issues with the technology here; it will probably have to be pretty low on the historical realism scale, but I'd like to avoid the most glaring violations of basic physics.

The process goes something like this: Seawater is lead into a series of giant greenhouses. The sunlight heats up the greenhouses to the boiling point, and pipes lead the steam out from them. By the afternoon, the water is down to about 1/7 of the volume; this is as concentrated as salt water can get. Then the water flows into the next step, where some sort of futuristic handwavy chemistry extracts various metals. This might possibly include electrolysis, which might possibly be powered by the steam. Lastly, the brine ends up in some kind of reservoir where the last water is allowed to evaporate, so you get plain old salt.

There are a whole range of fun products you can get from this.
- First of all, useful metals like iron, aluminium, titanium, silver and gold, presumably all very pure. This can be used to make cool stuff like titanium armour, etc.
- Magnesium and strontium, which are not particularly useful in general, but they are fun to set on fire.
- Potassium, which does fun things when thrown in water. I'm thinking you could make coins from it, which the other peoples might use in sacrifice rituals.
- Steam, which you can obviously use to power things, as well as other thing where you need hot water (soup, maybe?).
- Possibly hydrochloric acid, which I guess you can use to clean things.
- Salt. Probably the easiest way to make money. With the amounts you would get, you could probably also make buildings from it.

But I have a couple of problems I'm thinking about.

Problem one: Unlike normal iron production, this would (I assume) give iron completely free from carbon impurities. Back in ancient times at least, iron was much too brittle because of the carbon. But in a strange twist, completely pure iron is also not very useful, at least for weapons, since it's too soft instead. Are there any alloys that can make it hard, without adding carbon?

Problem two: They would need to process an awful lot of water. To get a few kg of iron, you'd need a megaton of brine or so. It's hard to explain how the process could be that fast.

Problem three: According to my calculations, sunlight on an average day is enough to evaporate 6 mm of water. That would require a huge area for evaporation. An alternative would be boiling it with some kind of fuel, but that hardly seems more feasible.

Any other fun ideas for this conworld?

Er... I don't think you've begun to hit on the problems.

First, you say boil, but then you say evaporate. Those two are very different things. You won't get steam by evaporation. You can boil water with sunlight, but we only know two ways, so far as I know: a great big parabolic mirror and a very small amount of water, or some sort of enzymatic process with specially designed nanoparticles. The latter has only just been invented and is apparently Big News. Parabolic mirrors, meanwhile, are very difficult to make, are prone to breaking, and require sophisticated mathematics and industrial technology, at least to make big ones.

Then you get the turning everything into salt bit. This is tricky, because it's almost impossible. We've been trying it for about 150 years and still haven't discovered a way to do it anything like economically. Largely because you need ten million tons of seawater to get one kilogram of gold. And the more pressing point for pre-19th century people is: given that there's no way of even detecting the gold at such minute levels without modern technology, why would anyone build a massive apparatus to evaporate ten million tons of seawater when they've no reason to think that there's any gold there in the first place?

If you do get iron, it's obvious what you do with it: add carbon, make steel. Why would you want an alloy without carbon in it, that would be more expensive and less useful? There are other iron alloys, in particular nickel-iron alloys, several of which were invented in the 19th century... but unless you're dealing with 19th/20th century technology these are both impossible to make and mostly useless (their main use is in extreme hot and cold, because they don't expand or contract much).

People are unlikely to make coins out of a substance that burns their hand off if they touch it while sweating. Plus, it's about as hard as portsalut.

Salt is a poor building material, except in extremely arid climates, because it dissolves in water.

In any case, you haven't considered something: suppose you do reduce water to rare salts? Then you have a big pan filled with salt. All this salt is basically salt-like in appearance, and all mixed up together. Even supposing you can extract the elements, how do you make sure you get all the titanium in one place and all the gold in another, exactly? Most people probably can't tell one powder from another, particularly when they've never heard of titanium before.

Adding carbon to completely pure iron seems trivially easy to me: just dunk thin sheets of it in burning coals and step on the bellows.

Water you have an infinite supply of, so don't worry about that... I *do* think the problem is, even if you were to manage to filter out the tiny bits of iron and potasium and so on and so forth, however, about salt. For every kilo of iron you'd need to evaporate a shitload of liters of water, which would yield something like 1/10 of a shitload of salt. a megaton of salt, say, just to produce a couple of frying pans and maybe horsehoes for two mares <never mind titanium, which even if you were to obtain an ingot of via magical chemistry you'd still have trouble working with>

The real problem is that the amount of labour it would take to move all that salt around back to the ocean <preferably somewhere far away from the evaporators> would make the whole thing impractical, methinks. I mean, any process that generates the sheer volume of waste salt that this process would generate seems incredibly labour-expensive. Salt is, at any rate, a harmful compound in great concentrations: building houses out of salt means that even with zero rain mere wind erosion means that you would make the surrounding land entirely inimical to plant life: I mean there are some plants that can deal with salty grounds, but not many. And then again, only in normal concentrations. Salt is harmful to people as well! I've put my foot into saltpans in Atacama and let me tell you, it hurts like a bitch. Plus salt is relatively heavy and it corrodes metals: say these people carry the salt back into the ocean on carts: the axles and metal joints would corrode away in a matter of years! <thus having to be replaced>. If people carry the salt in bags on horseback or something then you have the problem of feeding those animals fresh water and food <which doesn't grow nearby because of all the salt>... which brings me to the point of what do the workers of this huge facility eat in the first place? breathing salt is probably bad for you as well: not in normal air concentrations near the ocean, but surely in the concentrations associated with the huge mountains of salt that would have to be moved around for this facility to function. And we're not even getting into the subject of evaporation taking up heat so that you either need to do this somewhere close to the equator <where it rains and the whole thing goes to shit> or in the middle of a desert <which makes the freshwater problem even more dire>.

All in all I suppose that if you have some magical process by which you can extract a few ppm of useful stuff from brine it could work... but it would be a veritably nightmarish place. <kind of how mines were back in the day>

probably its best to invent some handwavy filter.

Torco wrote:Adding carbon to completely pure iron seems trivially easy to me: just dunk thin sheets of it in burning coals and step on the bellows.

Water you have an infinite supply of, so don't worry about that...

For context, to produce one kilogram of gold, you need seawater equivalent to the total hourly discharge of the Nile*.
Yes, the water does exist in the world. But you need to move that water, store it, process it, and them remove it.
Let's say that the water is pumped in at one tenth the rate of the Nile, which is still a pretty noticeable river. So that's ten hours to pump it in, ten hours to pump it out, and lets say the baking takes ten hours as well (you say 'by the afternoon' but that's only part of the process, so let's take a nice round number). OK, so maybe with more advanced industry they could spead this up by using multiple pools and filling one while the other is baking, but let's stick with 30 hours for start-up levels.

That's 30 hours to get 1kg of gold. Until the recent gold bubble came along, so going back 15 years now, a kilo of gold was worth about £6500 in modern money. Let's say £6600, and then divide by 30, and you're making £220 an hour.

At UK minimum wage, you could therefore employ 38 people. Assuming you don't want any profit, and assuming that the machinery doesn't cost money to maintain, and that no energy is used, and that the process doesn't use up any resources.

Of course, 38 people are unlikely to be able to construct an irrigation channel to divert a river the size of the Thames, not to mention managing to produce a periodic flow with it (you can't constantly be refilling the baking pools, so the water supply has to be turned on and off somehow).

Sure, in a pre-modern setting wages will be a little lower and you can employ more people, and maybe gold prices are a little higher. But in any near-earth scenario, the point remains: this is a megaproject on a scale totally disproportionate to what you can actually get out of it.



*Using wolfram to calculate this, I discovered something for conspiracy nuts: apparently, the average US college lecture lasts exactly as long as ten times the half-life of uranium-241. Good to know.

Hmm... good point, controlling the opening and closing of the flood gates itself would demand quite a bit of labour on its own. In chuma's defense, however, you're not only getting gold out of the deal: if his magical filtering device is in place you'd get, in that 30 hours you'd be getting the kilogram of gold, plus a couple more kilos of iron, some silver and tungsten and all kinds of other stuff... I do grant that it wouldn't be productive at all at british minimum wage standards, even if you were to forget the small matter of moving tons and tons of salt around.

Which is why I suggested having slave labour take care of it

Sorry, one more problem: what are the pipes made of? Steam is powerful stuff, and with salt added it's corrosive. The reason you have steam-powered toys but not steam-powered factories in ancient Rome is that they didn't have steel of a quality to make big boilers.

Basically, if you have steam plus plentiful strong steel, you are industrial.

All problems and no solutions, huh? Okay, I can work with that.

First, a few clarifications.
I imagine this in a bronze age setting, so they would be hanging out with the early Greeks etc. I don't know if medieval technology would have helped much anyway, so perhaps it doesn't matter for realism.
I first figured it would be good to build greenhouses to speed up evaporation or even boil the water, but I'm not sure whether that would be much help. Maybe it's easier to just use big ponds. So, less steampunk, more... metalpunk?

Salmoneus wrote:You can boil water with sunlight, but we only know two ways, so far as I know: a great big parabolic mirror and a very small amount of water, or some sort of enzymatic process with specially designed nanoparticles.

Strictly speaking, you could also use a kettle and a solar panel. But anyway. Is it somehow impossible to heat a greenhouse above the boiling point?

Salmoneus wrote:Then you get the turning everything into salt bit. This is tricky, because it's almost impossible.

I'm not sure what you mean. Extracting salt isn't difficult, right? If you're talking about extracting metals, yes, that's difficult (from what I've heard, it's been done economically for some metals, but certainly not gold). That's sort of the main fictional bit. It might be worth pointing out though, that we can extract several metals today, and the reason we're not doing it is because we have other options. Also, while extracting gold would be kind of fun as a curiosity, other metals would probably be much more important. Anyway, all in all, I think it falls within my limits - historically implausible, but not blatantly violating the laws of physics.

Salmoneus wrote:And the more pressing point for pre-19th century people is: given that there's no way of even detecting the gold at such minute levels without modern technology, why would anyone build a massive apparatus to evaporate ten million tons of seawater when they've no reason to think that there's any gold there in the first place?

Quite true. But stranger things have happened, at least in fiction.

Salmoneus wrote:If you do get iron, it's obvious what you do with it: add carbon, make steel.

Now here's a very interesting point I'm not finding much information on. Is carbon really the best possible thing to add? Consider that we've had iron with (often too much) carbon throughout history, simply as an artefact of the production, it seems like a weird coincidence if that just happens to be the best thing to put in it. Of all the elements, isn't there anything at all better than carbon?

Salmoneus wrote:There are other iron alloys, in particular nickel-iron alloys, several of which were invented in the 19th century... but unless you're dealing with 19th/20th century technology these are both impossible to make and mostly useless

Useless may be true, but would they be difficult to make, if you have the elements? Nickel is more common than iron in seawater, so if we accept the premises, there should be enough nickel.

Salmoneus wrote:People are unlikely to make coins out of a substance that burns their hand off if they touch it while sweating. Plus, it's about as hard as portsalut.

Hm, that could be an issue, yes. Maybe magnesium could work for coins, then - I know that doesn't burn your hands off quite so easily, at least.

Salmoneus wrote:Salt is a poor building material, except in extremely arid climates, because it dissolves in water.

That it certainly does. I figured it could be covered in something, maybe, or else used for various indoor things.

Salmoneus wrote:In any case, you haven't considered something: suppose you do reduce water to rare salts? Then you have a big pan filled with salt. All this salt is basically salt-like in appearance, and all mixed up together.

I imagined extracting them directly from the brine. I'm fairly sure that's how you do it with electrolysis, altho I was hoping to do it with some other (hitherto unknown) method.

Torco wrote:The real problem is that the amount of labour it would take to move all that salt around back to the ocean <preferably somewhere far away from the evaporators>

As above, I think regardless of the intricacies of the method they would be working with brine, not dry salt. As for getting it far from the evaporators (so you don't get "depleted" salt back into the process) I think the currents in the sea should take care of that.

There's still, now that I think about it, a slight logistic problem when it comes to getting rid of the brine. Presumably the evaporation ponds (or greenhouses, or whatever) would be just below sea level, so the water can come flowing in. But then how do you get rid of the water when you're done with it? The tide might help, but apparently the tide level difference on for example Crete is only about 1 m.

Torco wrote:never mind titanium, which even if you were to obtain an ingot of via magical chemistry you'd still have trouble working with

Would you? I'm no blacksmith, I don't know much about this, but I thought the difficulty was just obtaining it. The melting point is higher than for iron, but not by much.

Torco wrote:building houses out of salt means that even with zero rain mere wind erosion means that you would make the surrounding land entirely inimical to plant life

Good point, I didn't think of that. But it seems like you'd have to cover a pretty huge area with evaporation ponds, so maybe there's no space for plants anyway...

Torco wrote:say these people carry the salt back into the ocean on carts: the axles and metal joints would corrode away in a matter of years!

Not that it matters, but I think they would have wooden carts.

Salmoneus wrote:That's 30 hours to get 1kg of gold.

That's a far higher rate than I had imagined. At that rate, we would also get 30 kg of silver and 90 kg of copper.

Salmoneus wrote:At UK minimum wage, you could therefore employ 38 people.

A different comparison: In Babylon in 1780 BC, a worker would earn about 2 g silver per day (which happens to be just below £1 with current silver prices). With a comfortable 10 h work day, the silver alone would then pay for 5 000 workers. The same amount could also buy 200 slaves.

But silver and gold wouldn't be important. We would further get 100 kg each of aluminium and titanium, which isn't worth much now, but would as I understand it likely be more valuable than gold at the time. Then we would get some 300 kg of iron; even if iron working had been invented, I assume this would be fairly expensive.

Suppose you have one evaporation cycle per day. (That may be a bad idea, but we can use it for calculations.) You fill the ponds with 7 mm of water, let the 6 evaporate, and are left with 1. So you would get 1 kg of brine for each m^2, or one megaton for each km^2. Getting one kg of gold, as in Sal's example, would require 13 km^2, if I'm not mistaken, which seems a bit over the top. I was hoping at least to settle for 1 km^2 (which would apparently mean a flow equal to that of the Loire).

zompist wrote:Sorry, one more problem: what are the pipes made of?

Not sure, but there should be plenty of options. If they are able to extract all the stuff that's in seawater, they would have half the periodic table to choose from.

zompist wrote:Basically, if you have steam plus plentiful strong steel, you are industrial.

Hm, well, yes. But the rest of the world could still be preindustrial.

...how could they even make greenhouses!? If they're in the bronze ages, they're about three thousand years away from inventing the greenhouse. Well, maybe two. And yes, the Romans did sort of have greenhouses, but because transparent glass hadn't been invented they had to use thicker and more opaque sheets, like cloth, selenite or mica, which were much less effective. In any case, mediaeval greenhouses could only heat up the air a few tens of degrees, were incredibly expensive, and were very expensive to run. And how do you get any large size of glass without advanced metalworking to produce the frames to hold it up? And then again there's the size - you're talking tens of square kilometres? For context, the Crystal Palace was considered one of the great wonders of the world in the 19th century, the pinnacle of technology, and it was only just over 500m long.

I'm sorry, I just don't think any of this really makes sense. You seem to be saying: what if a bronze age tribe suddenly and for no reason developed the economy and technology of the 21st century? Well... how can we evaluate that premise?

It's not one bit that's a problem, it's all of it. I mean, take the idea that because they have a bunch of elements they can make pipes out of whatever they want. Well... how? You can't just put iron or titanium in a fire meant for melting copper and suddenly develop ferrous (titanious?) metallurgy. You can deal with copper in a pottery kiln, but you need to specially design an iron furnace (it's not just the higher melting point, it's that it has to be worked when very, very hot, whereas copper you can just heat up a little to soften it enough to be malleable).

Take something as simple as making steel with the right carbon content, not too much and not too little. It took until the 19th century before the technology existed to do that en masse (previously it had to be done crucible-by-crucible, taking weeks, and costing an order of magnitude more).

So I guess my point is: even if these people do do their handwavy magic and get a big heap of elements out the end of it... they wouldn't know what to do with them.

As for tens of km^2 of greenhouses - no, that seems a bit much. I had hoped that greenhouse heating should be powerful enough that something much smaller would be enough, but that doesn't seem to be the case - from what I've been able to find out, greenhouses don't seem to help evaporation speed noticeably, so I'll probably skip that idea and just let it be open ponds. That should also remove the need for pipes.

Apart from that, I guess my unrealism threshold is higher than yours.

Some notes on a couple of the metals:

Aluminum: Very hard to get the pure metal, can't be made from the same process to get iron (reduction with carbon).
Titanium: Even worse to deal with than aluminum, as in addition to to needing a special process to get the pure metal, the pure metal has to be melted in an environment without oxygen or nitrogen. There's a reason it wasn't obtained as a pure metal until 1910.
Potassium: Must be kept away from oxygen and water if you want to keep the pure metal, it rapidly corrodes in air (in seconds) and I don't think anyone wants their pockets exploding every time it rains if you use it for coins. Never mind that the corrosion in air produces potassium superoxide, which is explosive all on it's own...

Magnesium could probably work for coins or other uses.

Check Wikipedia or something to see the details of how to actually get these metals in a pure form.

furthermore, having your money made of flammable material is a terrible, terrible idea. If you pay me in flamable metals I would run and change that wealth into a nonflammable form as soon as possible.

Torco wrote:furthermore, having your money made of flammable material is a terrible, terrible idea. If you pay me in flamable metals I would run and change that wealth into a nonflammable form as soon as possible.

Good thing how in the real world nobody ever makes money out of paper.

Paper money doesn't explode if it gets dampened.

Any who, the idea was more like Chinese ghost money.

Exactly

and even so: have you tried burning money? as far as paper goes, its decently flame retardant: magnesium, on the other hand, is used on flares!

Chuma wrote: Strictly speaking, you could also use a kettle and a solar panel. But anyway. Is it somehow impossible to heat a greenhouse above the boiling point?

Unless you can find a way to insulate it such that energy can go in but not out and at the same time change the humid air often enough to get fresh dry air in there, then I don't think so. Atleast, at that size and quantity?

Salmoneus wrote:If you do get iron, it's obvious what you do with it: add carbon, make steel.

Now here's a very interesting point I'm not finding much information on. Is carbon really the best possible thing to add? Consider that we've had iron with (often too much) carbon throughout history, simply as an artefact of the production, it seems like a weird coincidence if that just happens to be the best thing to put in it. Of all the elements, isn't there anything at all better than carbon?

No idea, but it's so easy to put carbon into iron that I'd be very surprised if the extra benefit was worth the extra labour to do it in terms of practical day to day use of the items.

Salmoneus wrote:In any case, you haven't considered something: suppose you do reduce water to rare salts? Then you have a big pan filled with salt. All this salt is basically salt-like in appearance, and all mixed up together.

I imagined extracting them directly from the brine. I'm fairly sure that's how you do it with electrolysis, altho I was hoping to do it with some other (hitherto unknown) method.

Do you suppose a Baghdad battery might be strong enough to work with?

Torco wrote:never mind titanium, which even if you were to obtain an ingot of via magical chemistry you'd still have trouble working with

Would you? I'm no blacksmith, I don't know much about this, but I thought the difficulty was just obtaining it. The melting point is higher than for iron, but not by much.

I've only worked with titanium once, and it was back in blacksmithing school when they were teaching us to identify metals based on how they spark. A quick search on the internet shows me people do actually forge with it though.

I have worked with quite a bit of aluminum (race plates and navicular shoes), and that works completely different from iron. It doesn't glow or really change in appearance hardly at all. It doesn't get gradually softer as it gets warmer like iron does, instead it stays fairly hard up until it's about to melt, and as soon at it hits melting it all turns into a puddle at once, unlike iron which gives allot of warning and melts almost like an icecube does. You can also quench half of it and the other half will stay really hot right up to the quench line with no visual clues. Someone once played a really nasty trick on someone else at horseshoeing school by quenching half a hot aluminum bar shoe and holding that half while handing the hot half to someone, oi...

So what all I mean by this tangent into aluminum is it could work very differently from iron, and might not be feasible without modern techniques. I sure know I'd hate to forge with aluminum in a coal forge because of the inconsistant temperature.

zompist wrote:Basically, if you have steam plus plentiful strong steel, you are industrial.

I thought being industrial was more a matter of division of labour and type of economy than what materials are used? Wouldn't it still be industrial if you have towns of people in the paleolithic sitting around making axe heads all day and doing nothing but that to trade other cultures for everything they need to live? Then again, I suppose even by that definition this culture would fall under that.

Daistallia wrote:Paper money doesn't explode if it gets dampened.

I was making fun of Torco using the word flammable; explosive money is quite a different thing, of course!

Torco wrote:have you tried burning money?

No. Have you? Are you rich or something?

mouse wrote:Unless you can find a way to insulate it such that energy can go in but not out and at the same time change the humid air often enough to get fresh dry air in there, then I don't think so.

Insulation should just be a matter of adding more layers of glass. And if you do reach the boiling point, that should mean that you don't need dry air, right? You can have a valve that lets steam out, but nothing needs to go in.
Again, probably not efficient, but in principle (and with modern technology) it seems doable.

mouse wrote:Do you suppose a Baghdad battery might be strong enough to work with?

I doubt it very much. As far as I know, aluminium production requires huge amounts of electricity.

mouse wrote:It doesn't get gradually softer as it gets warmer like iron does, instead it stays fairly hard up until it's about to melt, and as soon at it hits melting it all turns into a puddle at once, unlike iron which gives allot of warning and melts almost like an icecube does.

Although I wouldn't say that ice cubes get gradually softer.

mouse wrote:

zompist wrote:Basically, if you have steam plus plentiful strong steel, you are industrial.

I thought being industrial was more a matter of division of labour and type of economy than what materials are used? Wouldn't it still be industrial if you have towns of people in the paleolithic sitting around making axe heads all day and doing nothing but that to trade other cultures for everything they need to live? Then again, I suppose even by that definition this culture would fall under that.

Well, several things happened at once in 18C England. But division of labor and capitalist economy had existed for centuries-- we generally wouldn't call 16C North Italy "industrial". You get the industrial revolution precisely when massive amounts of power were available, due to steam. The amount of power allowed you to do impressive things, and the capital investment required led to huge centralized factories.

come on you don't have to be rich to be able to afford burning a couple of dollars. if you can afford starbucks you can afford to burn a few banknotes.

Or if you're a science teacher.