What is the best tool for heating or evaporating chemical solutions?

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Most members use corning ware to put the beaker in on an electric hot plate.
You can put a sand layer in to protect the glass beaker from the heat.
https://goldrefiningforum.com/threads/corning-ware-a-guide-of-whats-what.23620/#post-249217There are also electric heating mantels for round bottom flasks.
I would have loved to have one, I have so far never found any Pyroceram vessels.
I regularily check the used stores thrift shops and so on, with no luck.
So I have been using these baking vessels with grate care.
I have been lucky so far :)(y)
 
This is very broad and general question. It could be broken down to few categories of approach.
Most straightforward is indirect heating, like sreetips is using - corningware placed on top of the heater, and beaker inside. This offers even heat transfer and support in case of any boil over or spill during the operation. One disadvantage is - heat transfer from the hotplate, through ceramic and then through glass is somewhat limited. So it takes quite a bit of time.

Second option is to use immersable heating element directly inside the vessel - this is one of the most efficient ways how to evaporate down the solutions - as little heat is wasted to the surrounding enviroment, thus efficiency of heating is greatly improved. Disadvantage is - you need to find glass heating element that withstand very harsh corrosion enviroment.

Another way is to use induction heater with block of graphite, immersed into the vessel. This solution is very nice as you can heat solutions inside plastic vessels of large volumes (using some spacer, which eliminates direct contact of plastic with hot graphite). But donĀ“t forget a fact that graphite is porous - so it tend to absorb quite a lot of the liquid. Which is then painful to macerate out of it without incineration of the whole block. Nice solution to the repeatedly encountered situation - you use that same "saturated" graphite for one task over and over again.

Because in situations like "we need to evaporate these 100 L of solution to like 5 L... Selection of the vessel in which you will do it is pretty limited :) so you need to improvise.

And not lastly, plan your operations in a way that you does not need to evaporate the solution, as it is apart from hassle with the very nature of this operation also extremely energy consuming.
 
And not lastly, plan your operations in a way that you does not need to evaporate the solution, as it is apart from hassle with the very nature of this operation also extremely energy consuming.
Except that as refiners we can not always plan on ending up with solutions that don't need evaporation & in fact can often find ourselves in situations where we have to plan for evaporation simply because we find ourselves in situations where we have to do A LOT of washing to get the values washed out of the materials we are leaching which results in VERY diluted solutions & as we know VERY diluted solutions can/will result in ULTRA fine precipitation of our target PM metals which in turn can result in settling &/or filtering problems &/or washing problems of the PM precipitate --- so we are better served to evaporate before dropping our PMs from solution

Examples -----------

1) washing the electrolyte out of the silver crystals from your silver cell - the electrolyte is quite dilute to start with & so should actually be evaporated before cementing the silver out of it or the silver cement will come down VERY fine (this is just the first decant of the electrolyte) then you still need to wash the electrolyte tied up in the crystals out - this takes multiple washings to insure all the silver nitrate is washed out before drying the crystals - (testing a sample of each wash with HCL until no AgCl cloud forms) this results in a VERY diluted silver nitrate solution that NEEDS evaporation before recovery of the silver from the electrolyte & wash

2) IC chip ash (even as concentrates) requires A LOT of washing to insure all the values are washed out so again ending up with a very diluted solution (stannous testing of each wash) that needs evaporation before recovery of the values from the solution

This is especially true if you are processing BGA chips where the green fiber part can't be separated from the black epoxy part of the chip - that is because of the fiberglass sheet in the green fiber part of the chip which turns to fine fiberglass hairs/fluff that will tie up & hold bond wires after milling & sifting & as well there is gold plating involved in these chips so you can't really do a proper concentration wash on these type chips (without losing gold) so if you are after all the gold in these type chips you really need to leach the whole of the ash/fiber after incineration & milling - meaning A LOT more washing to get the values out of the leached ash/fiber so VERY diluted solutions that needs evaporation --- for what it is worth that is why these type BGA should ALWAYS be processed completely separate from other type chips --- if you try to process them together with other chips the glass fiber/fluff will cause lost gold when running the milled ash on a concentrator table

3) Leaching MLCCs - I posted about that yesterday in the "Processing MLCCs" thread ----------

I said -----

IF (the BIG IF) you are going to leach MLCCs

The reason I posted that in bold print is that IMO (In My Opinion) leaching MLCCs - even in small batches is one of the worst ways to go about recovering the Ag & Pd from MLCCs for a number of reasons

1) during the leaching - the ceramic breaks down into an ULTRA fine mud - like clay which is impossible to filter --- so you have to let the ceramic mud settle then decant the leach - then wash with water - let settle & decant again AND you have to do that multiple times AND it is next to impossible to get all the Ag/Pd washed out - at the very best at least traces of Ag/Pd will stay tied up in the ceramic mud

2) So you will end up with a LOT of VERY diluted Ag/Pd solution which you will then want to evaporate back down - otherwise when you go to drop the Ag as AgCl - the AgCl will come down ULTRA fine - so fine it will likely cause washing/filtering problems when you go to wash the still dissolved Pd out of the AgCl

3) washing the Pd out of the AgCl presents the same problem as washing the Ag/Pd out of the ceramic mud - it takes a LOT of washing to get all the Pd washed out resulting in a VERY diluted solution again (if you are not set up to vacuum filter --- vacuum filtering does NOT work on the ceramic mud - but will on the AgCl)

Added note; - due to the amount of washing required - to get ALL the values out of leaching MLCCs - you will more then likely not only have to evaporate after washing the Ag/Pd out of the original leach - but evaporate again after washing the Pd out of the AgCl

So as much as I agree that avoiding the need for evaporation in the first place is good advice - there are situations where evaporation becomes necessary

Kurt
 
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Except that as refiners we can not always plan on ending up with solutions that don't need evaporation & in fact can often find ourselves in situations where we have to plan for evaporation simply because we find ourselves in situations where we have to do A LOT of washing to get the values washed out of the materials we are leaching which results in VERY diluted solutions & as we know VERY diluted solutions can/will result in ULTRA fine precipitation of our target PM metals which in turn can result in settling &/or filtering problems &/or washing problems of the PM precipitate --- so we are better served to evaporate before dropping our PMs from solution

Examples -----------

1) washing the electrolyte out of the silver crystals from your silver cell - the electrolyte is quite dilute to start with & so should actually be evaporated before cementing the silver out of it or the silver cement will come down VERY fine (this is just the first decant of the electrolyte) then you still need to wash the electrolyte tied up in the crystals out - this takes multiple washings to insure all the silver nitrate is washed out before drying the crystals - (testing a sample of each wash with HCL until no AgCl cloud forms) this results in a VERY diluted silver nitrate solution that NEEDS evaporation before recovery of the silver from the electrolyte & wash

2) IC chip ash (even as concentrates) requires A LOT of washing to insure all the values are washed out so again ending up with a very diluted solution (stannous testing of each wash) that needs evaporation before recovery of the values from the solution

This is especially true if you are processing BGA chips where the green fiber part can't be separated from the black epoxy part of the chip - that is because of the fiberglass sheet in the green fiber part of the chip which turns to fine fiberglass hairs/fluff that will tie up & hold bond wires after milling & sifting & as well there is gold plating involved in these chips so you can't really do a proper concentration wash on these type chips (without losing gold) so if you are after all the gold in these type chips you really need to leach the whole of the ash/fiber after incineration & milling - meaning A LOT more washing to get the values out of the leached ash/fiber so VERY diluted solutions that needs evaporation --- for what it is worth that is why these type BGA should ALWAYS be processed completely separate from other type chips --- if you try to process them together with other chips the glass fiber/fluff will cause lost gold when running the milled ash on a concentrator table

3) Leaching MLCCs - I posted about that yesterday in the "Processing MLCCs" thread ----------

I said -----

IF (the BIG IF) you are going to leach MLCCs

The reason I posted that in bold print is that IMO (In My Opinion) leaching MLCCs - even in small batches is one of the worst ways to go about recovering the Ag & Pd from MLCCs for a number of reasons

1) during the leaching - the ceramic breaks down into an ULTRA fine mud - like clay which is impossible to filter --- so you have to let the ceramic mud settle then decant the leach - then wash with water - let settle & decant again AND you have to do that multiple times AND it is next to impossible to get all the Ag/Pd washed out - at the very best at least traces of Ag/Pd will stay tied up in the ceramic mud

2) So you will end up with a LOT of VERY diluted Ag/Pd solution which you will then want to evaporate back down - otherwise when you go to drop the Ag as AgCl - the AgCl will come down ULTRA fine - so fine it will likely cause washing/filtering problems when you go to wash the still dissolved Pd out of the AgCl

3) washing the Pd out of the AgCl presents the same problem as washing the Ag/Pd out of the ceramic mud - it takes a LOT of washing to get all the Pd washed out resulting in a VERY diluted solution again (if you are not set up to vacuum filter --- vacuum filtering does NOT work on the ceramic mud - but will on the AgCl)

Added note; - due to the amount of washing required - to get ALL the values out of leaching MLCCs - you will more then likely not only have to evaporate after washing the Ag/Pd out of the original leach - but evaporate again after washing the Pd out of the AgCl

So as much as I agree that avoiding the need for evaporation in the first place is good advice - there are situations where evaporation becomes necessary

Kurt
I simply cannot use evaporation because I do not have time nor means how to do it in place where I work with PM recovery. This led me to develop techniques, which completely avoid evaporation. And where it cannot be eliminated, I need to be rather distilling off the liquid, otherwise I would wreck the fume hood and fan, which are not desined to deal with large quantity of corrosive wet HCL fumes etc.

So for IC chips ashes, I never leach them, I smelt them down. Too much hassle with decantation and filtration, time consuming and for me not worth the spent time.
MLCCs - I smelt them directly, too. All hydrometallurgy treatment of MLCCs lead to culprits along the way, so I invested in time and equipment before I started facing these problems, and completely obviated this by using induction furnance and pyrometallurgy.

Cementing low grade values out of stockpots or diluted washes - if that happen to unfortunately be the case, I use flocculents or adsorbents such as Celite to conveniently scrub the values from the solution and make it filterable. And yeah, not always it work as planned. But most of the times, two or three days settling problem is solved under an hour. If not, I have large tall vessels for convenient decantation of solutions. Let the dust settle, mix some indiferrent microparticle solid as celite on the top of the liquid column and let it cover the microparticles which you settled. Then decant.

Practically, only time I use the evaporation (in my setup, regular distillation for sake of fumehood) is when de-noxing PGMs solutions before precipitations of PGMs. And I am not happy at all that this cannot be done otherwise. So we are currently developing chlorine electrolyzer which will serve us instead of nitric acid for PGMs operations and dissolution. Oxidizer as oxidizer :)
 
One of the important things to understand about evaporation is that the larger the surface area (top surface of the liquid you are evaporating) the better &/or more efficient the evaporation --- in other words more water vapor comes off a large surface then off a small surface

Also - the closer to the rim of the evaporation vessel the liquid is the better

Examples --------

The 5 liter Vision Ware pot I posted a link to yesterday compared to a 5 liter beaker

The Vision Ware pot has a larger surface area then the beaker & is also therefore shallower - so -----

Experiment ----------

Take both the pot & the beaker - fill each of them with one liter of water - put them both on a hot plate & set both hot plates to the same temp setting

You will evaporate the water out of the pot in about (plus/minus) half the time as it takes to evaporate the water out of the beaker

That is because with the pot more water vapors are able to come off the larger surface area AND as well the vapors don't need to climb as high to reach the rim of the pot & expel out into the air above the pot

Where as with the beaker fewer vapors are coming off the smaller surface area AND they need to climb much high before reaching the rim of the vessel & expelling into the air AND so - because those vapors have to climb so much high before reaching the top rim - it allows some of those vapors to condense & fall back down into the beaker --- you will likely see the vapors condensing on the walls of the beaker & running back down - which you won't see happening with the pot

Kurt
 
So for IC chips ashes, I never leach them, I smelt them down. Too much hassle with decantation and filtration, time consuming and for me not worth the spent time.
MLCCs - I smelt them directly, too. All hydrometallurgy treatment of MLCCs lead to culprits along the way, so I invested in time and equipment before I started facing these problems, and completely obviated this by using induction furnance and pyrometallurgy.
Per the bold print - I completely agree with you on this one Orvi - smelting of the above materials (& so much more) really is the way to go IMO

Investing in a furnace that takes a #40 crucible for smelting in order to eliminate leaching low grade &/or DIRTY crap was one of the best investments I ever made

It reduced my low grade/dirty recovery time - increased metal recovery & reduced chemical waste BY A LOT

Sadly - thanks to You Tube & even this forum - leaching is the go to method in so many cases where smelting would actually better serve people

Leaching - when smelting is actually a better option - is one of the BIG reasons we VERY often find yourselves trying to fix the BIG messes people come here with

Kurt
 
I would always advise you to buy a good quality secondhand Laboratory hotplate.
I know you can find low-quality cheap two and one-ring heaters meant for Hotel rooms and other domestic appliances.
But they will simply not hold up to the rigor involved with highly corrosive environments.
For just a few quid more you can invest in a unit that will serve you for years.
So anything less is a false economy.
Evaporation and reductions are an intrinsic part of our processes.
People always try and bend the real world to their needs. which is not always appropriate or prudent.
https://www.ebay.com/itm/3245955672...3g/1Fg=|tkp:Bk9SR4zilZmOYQ&LH_ItemCondition=4
 
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I would always advise you to buy a good quality secondhand Laboratory hotplate.
I know you can find low-quality cheap two and one-ring heaters meant for Hotel rooms and other domestic appliances.
But they will simply not hold up to the rigor involved with highly corrosive environments.
For just a few quid more you can invest in a unit that will serve you for years.
So anything less is a false economy.
Evaporation and reductions are an intrinsic part of our processes.
People always try and bend the real world to their needs. which is not always appropriate or prudent.
https://www.ebay.com/itm/3245955672...3g/1Fg=|tkp:Bk9SR4zilZmOYQ&LH_ItemCondition=4
I only add to the "corrosive enviroment" issue.

Typical 10euro electric hotplate, 2kW roughly has only ONE regulation and switching contact - bimetal temperature probe, which is manually adjustable. We all know how things are manufactured now :)
Even when not in the "full throttle" mode, itĀ“s just a P-type regulator = on/off. Nothing else. So the ONLY switching mechanism, without any safety features is the thing you rely upon.

It is no secret that contacts of these cheap bimetals are often just bare copper thin sheets, without any contact point. Working with AR, nitric, chlorine and other corrosive stuff will badly damage the insides of the hotplate, counting also the crucial bimetal switch. And not so uncommon - freeze the contacts.

That said, your hotplate will go full throttle, even that you set it to the lowest heat, boil out all the liquid, and eventually catch fire and keep heating till hard-soldered leading wires fall off the spiral.

Not nice scenario to think about :) never leave anything on hotplate without your supervision, if it is this type of junk one :) there is nothing bad about having one for the "hard" work, but it has certain limitations, which shouldnĀ“t be underestimated.
 
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