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Author: Subject: Condensing chlorine gas, price of ethane!!!!
Panache
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[*] posted on 17-6-2008 at 20:55
Condensing chlorine gas, price of ethane!!!!


Given Cl2 has a bp of ~34C i suppose condensing it and storing it in a cylinder would be relatively simple. The reason i ask is i recently purchased two ultra-low freezers but intend to sell them and i'm trying to think of things to do with them before they go. The one that works sits quite happily at -85. and is big (i can get into it but is rather terrifying when the double doors are closed on you). I wish i could keep it but i have no real use for it.
i use chlorine gas once in a blue moon and usually generate it when needed. I have condensed dimethyl ether often enough and it stores happily in a cylinder. having cl2 on tap would be a luxury. I would simply use len1's tcca chlorine generator and condense through a glass coil into the cylinder, venting the system through the normal devices, drying.

Looking around it appears it usually is just stored in stainless cylinders with monel or stainless valves. To me this implies it is not a storage hazard. Could i get away with a mild steel LPG cylinder, say 9kg one?

Any advice or warnings from those skilled in the art would be appreciated


I also received a second slighter larger ultra-low freezer but its second stage compressor had been drained of it's ethane refrigerant, so i rang up the refrigeration supplies so i could ensure i would not get ripped off by the fridgey (refrigeration mechanic) when he came to re-charge it. $157.00/kg. WTF, i couldn't believe it is it extra special magical ethane. I understand now why the second fridge had been drained of ethane!!
I thought i should sideline in ethane theft, stealing it from freezers in hospital pathology labs
Incensed i downloaded my town gas composition and ffs it's 5-7% ethane. I dare not calculate how much that would cost me, maybe $0.35!!!!

[Edited on 17-6-2008 by Panache]




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[*] posted on 18-6-2008 at 04:52


The main hassle with condensing your own chlorine into cylinders is adequately drying the chlorine. Perfectly dry Cl2 will not attack steel, but a trace of moisture and you have a corrosion problem and soon a leak. Stainless steel cylinders are expensive even in lecture bottle sizes.

Much easier to condense Cl2 into Florence-form Dewars and use the stuff quickly.




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[*] posted on 18-6-2008 at 07:24


Since you only use HCl in occasion then you might benefit from this............solo

http://www.erowid.org/archive/rhodium/chemistry/hclgas.argox...




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Panache
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[*] posted on 18-6-2008 at 14:52


Quote:
Originally posted by solo
Since you only use HCl in occasion then you might benefit from this............solo

http://www.erowid.org/archive/rhodium/chemistry/hclgas.argox...


thks for this solo did you link it because you know the details of cylinder and regulator maintenance mentioned specific to HCl(g) are be equally pertinent to Cl2(g) or did you misread my post that said i use Cl(g) only rarely?




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[*] posted on 18-6-2008 at 15:50


If it goes to -85°C then you can use it to make dry ice by condensing CO2 from a tank or even as it's made from a burner. That's a use worth keeping it for. I can't believe you're selling it.:(

About ethane, you can make it by kolbe electrolysis of acetic acid. At -85°C it takes only 20psi or so to condense, so you should be able to fill a cylinder pretty easily. Just be careful of its low critical point of 31°C and high vapor pressure at room temp.

[Edited on 18-6-2008 by kilowatt]




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[*] posted on 18-6-2008 at 17:31


Quote:
Originally posted by Panache
Quote:
Originally posted by solo
Since you only use HCl in occasion then you might benefit from this............solo

http://www.erowid.org/archive/rhodium/chemistry/hclgas.argox...


thks for this solo did you link it because you know the details of cylinder and regulator maintenance mentioned specific to HCl(g) are be equally pertinent to Cl2(g) or did you misread my post that said i use Cl(g) only rarely?


...........i clearly misread your post.....pardon my brain fart......solo




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Panache
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[*] posted on 18-6-2008 at 18:41


Quote:
Originally posted by kilowatt
If it goes to -85°C then you can use it to make dry ice by condensing CO2 from a tank or even as it's made from a burner. That's a use worth keeping it for. I can't believe you're selling it.:(

About ethane, you can make it by kolbe electrolysis of acetic acid. At -85°C it takes only 20psi or so to condense, so you should be able to fill a cylinder pretty easily. Just be careful of its low critical point of 31°C and high vapor pressure at room temp.

[Edited on 18-6-2008 by kilowatt]


I wasn't going to mention it in the original post, only by implication but if i precooled the natural gas to say -70 using the refrigerator, then cooled it further through liquid nitrogen dewar i should condense the ethane out at atmospheric pressure and the methane will vent. The main problem with this i see is methane's solubility in liquid ethane. i imagine it's appreciable. you would have to boil off some of your ethane after condensing some it to remove as much methane as you can. Again they have you because at no stage can realsitically pay back your setup costs by making the 2 litres of ethane you need. I have always wanted to do a very low temperature fractionation though and am hardly even going to find a better reason than this.

I will lookup the kolbe synthesis though as i have also never done any electrochemistry (except for at uni but pfftt).

Oh and believe me i so desperately want to keep them but i only bought them promising myself i would sell them (they were very very very cheap, AUS$2K together, but still more than i would allow myself to spend on something i really didn't need)




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[*] posted on 18-6-2008 at 19:43


I think once you sell them, you will later find that you really did need them, and regret selling them deeply since you will never get such a good deal again. You really should keep them if you aren't that desperate for money, especially if you live in Australia where nearly anything useful is banned. Do you really have anything better to do with the money you'd get from them?

Anyways enough of my trying to talk to you into keeping the coolers. I don't think there is much ethane in natural gas, if any. Firstly, the ethane is intentionally removed to be used as industrial feedstock. Secondly, ethane would condense in the high pressure gas mains and never make it to your house anyway. I don't think methane and ethane form any azeotropes, but even if they did, that's what you'd be getting out and that wouldn't help much. If there is any ethane in there at all it's probably only on the order of a percent, and would not be economical at all. You're much better off with a synthesis. Kolbe is probably the easiest, but not the only way. You could also crack larger hydrocarbons to make ethane.

About the chlorine, just bubble it through some concentrated sulfuric acid before condensing it if you want to use a metal tank. A stainless tank isn't much (if any) better than regular steel at holding up to moist chlorine, and in fact might even be worse, so don't think that will save you from having to dry it. Monel, Inconel, and other such alloys do however have a good degree of resistance to such things. Of course, the low temperature condensing process will crystallize out most of the water anyway and allow it to be removed with a fritted filter or something. It might be beneficial to condense it, filter the ice out, then re-evaporate it and bubble it through the dessicating acid to remove the last of the water, then condense it again. Another option is to just make it in an anhydrous manner in the first place, like by thermal decomposition of an anhydrous higher chloride like FeCl3, fused salt electrolysis, or any number of other methods.

[Edited on 18-6-2008 by kilowatt]




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Panache
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[*] posted on 19-6-2008 at 21:19


Quote:
Originally posted by kilowatt
I think once you sell them, you will later find that you really did need them, and regret selling them deeply since you will never get such a good deal again. You really should keep them if you aren't that desperate for money, especially if you live in Australia where nearly anything useful is banned. Do you really have anything better to do with the money you'd get from them?

Anyways enough of my trying to talk to you into keeping the coolers. I don't think there is much ethane in natural gas, if any. Firstly, the ethane is intentionally removed to be used as industrial feedstock. Secondly, ethane would condense in the high pressure gas mains and never make it to your house anyway. I don't think methane and ethane form any azeotropes, but even if they did, that's what you'd be getting out and that wouldn't help much. If there is any ethane in there at all it's probably only on the order of a percent, and would not be economical at all. You're much better off with a synthesis. Kolbe is probably the easiest, but not the only way. You could also crack larger hydrocarbons to make ethane.

About the chlorine, just bubble it through some concentrated sulfuric acid before condensing it if you want to use a metal tank. A stainless tank isn't much (if any) better than regular steel at holding up to moist chlorine, and in fact might even be worse, so don't think that will save you from having to dry it. Monel, Inconel, and other such alloys do however have a good degree of resistance to such things. Of course, the low temperature condensing process will crystallize out most of the water anyway and allow it to be removed with a fritted filter or something. It might be beneficial to condense it, filter the ice out, then re-evaporate it and bubble it through the dessicating acid to remove the last of the water, then condense it again. Another option is to just make it in an anhydrous manner in the first place, like by thermal decomposition of an anhydrous higher chloride like FeCl3, fused salt electrolysis, or any number of other methods.

[Edited on 18-6-2008 by kilowatt]


Great post!!
Thanks, everything was correct but simply hadn't occured to me. What a relief not having to mull over those decisions now. Working alone has its advantages but sometimes you go around and around the same thing in your head. And the steel cylinder answer is also completely obvious. I will just be especially pedantic in dry the feed gas and i will condense a few kilograms over the weekend and i won't have to make it again for
-current usasge @50g/year,
-3000g i'll make
3000g/50g

EVER!!!!
what colour is the liquid chlorine i wonder.
perhaps it will inspire me to keep the freezers, i can store my body in them after i die.




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[*] posted on 20-6-2008 at 02:19


in gas form it is yellowish green.
at liquid temps, it tends more over to the yellow coloration with a hint of green.




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[*] posted on 20-6-2008 at 16:08


I've got a sealed ampoule of pressurized liquid chlorine and it is indeed more yellow than green. Kind of a similar color to overcooked string beans. Quite yellow, but you can see some hint of green inside of it.



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[*] posted on 30-6-2008 at 15:31


Question...how is bubbling the chlorine through H2SO4 going to do anything? If there is any HCl present, bubbling the mixture though H2SO4 isn't going to do squat since HCl has a very low solubility in H2SO4 (one can use this insolubility to make HCl in situ by adding NaCl to conc H2SO4).
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[*] posted on 30-6-2008 at 16:25


<< Question...how is bubbling the chlorine through H2SO4 going to do anything? If there is any HCl present, bubbling the mixture though H2SO4 isn't going to do squat since HCl has a very low solubility in H2SO4 (one can use this insolubility to make HCl in situ by adding NaCl to conc H2SO4). >>


The idea is not to get rid of the HCl but rather to get rid of any water since perfectly dry Cl2 will not attack monel, inconel etc alloys.

dry HCl doesn't either I think, but it would take a lower temp to liquify that anyways so at -34 deg you should have pretty pure Cl2 except for any HCl that is soluble in Cl2 at that temp




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[*] posted on 30-6-2008 at 16:26


H2SO4 is an extremely powerful dessicant. It is used to remove water from gases like chlorine or HCl.



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[*] posted on 2-7-2008 at 15:18


When I generated some chlorine gas for my collection a few years ago, I dessicated it by taking the newly generated gas and passing it through some "fluffy" calcium carbonate to neutralize any acid vapors going through there and any Cl2 that made it through would be pretty danged pure. Granted, the CaCO3 had to be refreshed fairly frequently, but it worked.



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[*] posted on 3-9-2008 at 12:33
Cheap low temp - musing


Quote:
Originally posted by Panache
(...) i recently purchased two ultra-low freezers but intend to sell them and i'm trying to think of things to do with them before they go. The one that works sits quite happily at -85. and is big (...)


Could you achieve a comparable degree of refrigeration by stacking two freezers "in series", ie one inside the other?

The inner refrigerator (if fluid-based) would probably need some modification, eg a lower-freezing fluid suitable for use in the colder environment.

Alternatively, Peltier-type iceboxes come cheap and can theoretically work in a broad temp range...the efficiency could be increased with a liquid circuation system between the inner and outer boxes.

Estimated cost (new): $300 (outer), $100 (inner), $100 (intermediate circulation including fluid, piping and motor; facultative).

[Edited on 3-9-2008 by jarynth]
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[*] posted on 4-9-2008 at 15:03


This is known as a cascade cooler, but commercial units do not really resemble what you describe of course. They may have two or three or possibly more stages.

The inner freezer would at least have to have an oil separator, as common refrigerant oils would become too viscous or solid at such low temperature. A lower temperature refrigerant like ethane would likely be required too.

It would be much more practical of course to use the evaporator coils in just one freezer box for the cold side of cascade, while changing the condenser entirely for a block or other heat exchanger that has both condenser ports/coils for the cold system and evaporator ports/coils for the hot system in it. A much larger compressor (preferably about 2-4x the thermal transfer) is then used for the hot side, with its condenser being air or water cooled. This is far more efficient than relying on air to transfer the heat from the condenser of the cold system to the evaporator of the hot system. You need a much larger compressor for the hot system because it must contend with the waste heat from the cold system.

Peltier cascades exist too but are extremely inefficient, with each stage requiring at LEAST 4x the thermal power transfer of the next. Peltier coolers are notoriously inefficient for any application with large temperature differences.

[Edited on 4-9-2008 by kilowatt]




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[*] posted on 4-9-2008 at 20:33


Quote:
Originally posted by kilowatt
This is known as a cascade cooler [...]
There's a modification of the cascade called an autocascade that uses a single compressor, a refrigerant blend, and clever arrangement of nozzles and heat exchange that successively volatize the various fractions of the refrigerant.
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[*] posted on 11-12-2008 at 14:18
Liquifying Chlorine and bottling/cylindering(?)


So I finally got around to generating some chlorine gas, condensing it and storing it in a cylinder. I ran through a few variants of my basic idea until i found the easiest way i think.
It goes something like this.
Using Tcca+HcL to generate the Chlorine is convenient on the lab scale but for making a couple of liters of condensed chlorine liquid it presents some difficulties.
The first difficulty with the system is the tendency of the TCCA to clump after it is wetted/reacted, to overcome this issue i used a 20L polyethylene drum attached to the top of a flask shaker (one that turns in non-concentric circles such that the agitation is only in two dimensions.). I Initially attempted to make a cement-type mixer from a 20L solvent bottle but the challenge of creating two seals that could overcome rotation and not leak chlorine gas were beyond my skills. (That said i have a 20L rotary evaporator now, std pressure though no vacuum.) The difficulty is one must provide for entry of HCl(aq) and exit of the Chlorine gas, with a rotating vessel this is a challenge.
Thus i went to the shaking vessel and conceded to myself that some efficiency in the conversion would be lost, but hell its not like TCCA is expensive.
The 20L drum was fitted with a t-piece that allowed for the hcl to be added through a small hose section and the Cl gas to be exited. A peristaltic pump salvaged from a commercial dishwasher detergent dosing unit was used to pump in the HCl(aq). It ran about 10L/hr.

The Cl gas was run through two u-tubes filled with CaCl2 and into a stainless coil that was immersed in methanol/dry ice, the coil exited to a 1L Schott lab reagent bottle, that had a small pin prick hole in the lid. The reagent bottle was sitting in dry ice. I pressure tested the system by holding my finger over the prick in the reagent bottle and witnessed the 20L drum swelling like a balloon (well kind of like a balloon).
I ran argon through the setup overnight to remove water from the lines and then i charged the system with a small run intially which would hopefully yield 500mL of liquid, from memory this amounted to ~9.5L of 15% Hcl and ~3000g of TCCA. The system worked well and i ended up with 300mL of Chlorine gas at the end of the HcL addition, with around an extra 50mL coming over over the next 30mins. I decided this was good enough and sealed the reagent bottle and put it in the ultra-low freezer at -85C. In the freezer i had the cylinder i intended to use to store the Chlorine in. It was basically a brand new 3.5kg camping cylinder with a brass valve, i had degassed it and argon flushed it thrice and left it sealed with a vacuum in the freezer with hose attached. to transfer the liquid Chlorine into the cylinder i warmed the very end of the hose attached to the cylinder and placed a short glass tube into it, i immersed this tube into the chlorine liquid and opened the valve on the cylinder. The liquid sucked straight in with any vaporization. A few drops remained the the reagent bottle, these were destroyed with NaOh solution.
I then sat and watched the cylinder come to temperature, nothing happened and i felt alright about it. The following morning i notice some corrosion had peeled the paint away at the point the valve screws into the cylinder. I assumed it was caused by the storage of the chlorine as it was a new cylinder, however perhaps it was already corroded. For safety sake i am storing the cylinder in the ultra-low temporarily, until i replace it.
its all relatively doable for those considering it and having a cylinder of chlorine I imagine will be markedly more convenient for the odd occasion i might want to use some.




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