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Author: Subject: pyrolysis of plastic and plastic products
Oxirane
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[*] posted on 3-11-2014 at 19:36


Cyclohexanone is used for production of nylon. So could nylon be pyrolysed back to cyclohexanone?
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Etaoin Shrdlu
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[*] posted on 3-11-2014 at 20:07


No. Cyclohexanone is used to produce adipic acid and caprolactam, it is not a direct precursor to nylon.
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UnintentionalChaos
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[*] posted on 3-11-2014 at 20:17


Quote: Originally posted by Oxirane  
Cyclohexanone is used for production of nylon. So could nylon be pyrolysed back to cyclohexanone?


Not even close. It would help if you looked up how it is used to make nylon. Either it is oxidatively ring-opened to adipic acid which goes into Nylon 6-6 or the oxime undergoes a Beckmann Rearrangement (which Magpie recently posted a procedure for) to caprolactam. This is then ring-opening polymerized to Nylon 6.

http://fire.nist.gov/bfrlpubs/fire86/PDF/f86013.pdf

This paper indicates that Nylon 6 can be inefficiently cracked to its monomer under airfree conditions, but requires a lot of heat. Under partial oxidation conditions, you can get some cyclohexanone and cyclopentanone through some circuitous reactions, but they are mixed with a lot of other junk. Nylon 6-6 pyrolysis looks to be quite messy.

[Edited on 11-4-14 by UnintentionalChaos]




Department of Redundancy Department - Now with paperwork!

'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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aga
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wink.gif posted on 7-11-2014 at 14:47


Swapped a dead car battery for this yesterday at the scrapyard.

13" diameter, Hand/arm sized hole in one end, machined water-tight seal, end-plate with a 1" fitting, other end has a bicycle-type valve, easily replaced with a nut n bolt.

All Steel.

Wooohooo !

Watch out PVC, here we go ... Pyro To The Max (tm)

shere1.JPG - 158kBsphere2.JPG - 159kB




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blogfast25
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[*] posted on 8-11-2014 at 10:24


Quote: Originally posted by aga  
Swapped a dead car battery for this yesterday at the scrapyard.



I'm pretty sure these are parts of a typical Citroen DS air suspension system. Also used on Bentleys.

Spherical is always good.

You might want to lubricate the manifold thread a bit so it will open more easily after firing.




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aga
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[*] posted on 8-11-2014 at 11:06


Quote: Originally posted by blogfast25  
You might want to lubricate the manifold thread a bit so it will open more easily after firing.

PTFE seals better, and won't go liquid & run out under the high heat.

Lithium grease is supposed to be good for high temperatures (no idea how high).

Combining a spanner with the high-mass inertial adjustment tool always works, sometimes with the help of a blowtorch, and large volumes of swearing.

Edit:

I think the sphere is a pressure absorbing/equalising thing for a pool or other closed water system, that prevents 'knocking' due to resonances or pressure pulses. It had a rubber bag inside it, which i should have pyrolised instead of chucking.

[Edited on 8-11-2014 by aga]




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blogfast25
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[*] posted on 8-11-2014 at 13:15


Quote: Originally posted by aga  
PTFE seals better, and won't go liquid & run out under the high heat.



PTFE MP is about 600 K. But probably better than oil anyway.

[Edited on 8-11-2014 by blogfast25]




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aga
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[*] posted on 8-11-2014 at 13:29


Quote: Originally posted by blogfast25  
PTFE MP is about 600 K. But probably better than oil anyway.

I was about to say 'oh bugger', but if the PTFE does melt, then it'll be an easy indication of temperature reached.

Hmm.
That'll only be half way to the target temperature ...

Smear Al2O3 paste onto the threads maybe ?




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blogfast25
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[*] posted on 8-11-2014 at 13:50


Quote: Originally posted by aga  

Smear Al2O3 paste onto the threads maybe ?


No, wait: graphite!




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plante1999
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[*] posted on 8-11-2014 at 14:17


fire cement or asbestos is generally used in industry for such purposes.
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Little_Ghost_again
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[*] posted on 8-11-2014 at 14:41


Quote: Originally posted by aga  
Quote: Originally posted by blogfast25  


Combining a spanner with the high-mass inertial adjustment tool always works,

[Edited on 8-11-2014 by aga]

Ah I think you mean what they call a Scottish screwdriver ;).

Looks like it should do the job!! Just think what you could have got with a live battery lol
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aga
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[*] posted on 8-11-2014 at 15:13


I got no asbestos or fireclay/cement, and my pencil has no lead (joy of vasectomy).
PTFE, Bentonite Clay(cat litter), Al Oxide and Mud i have.

It may be that if the joints are tight enough that they won't leak much anyway.

One easy way to find out what works best ...

Fire ! (maybe airflow assisted)

[Edited on 8-11-2014 by aga]




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plante1999
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[*] posted on 8-11-2014 at 15:16


sodium silicate can be used too.
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[*] posted on 8-11-2014 at 15:18


Quote: Originally posted by plante1999  
sodium silicate can be used too.

Cool ! I got some of that. Cheers.




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[*] posted on 9-11-2014 at 06:48


Quote: Originally posted by aga  
I got no asbestos or fireclay/cement, and my pencil has no lead (joy of vasectomy).
PTFE, Bentonite Clay(cat litter), Al Oxide and Mud i have.

It may be that if the joints are tight enough that they won't leak much anyway.



I wasn't really suggesting to improve leak tightness, only to make opening the sphere after firing easier.

Lubricating graphite and fire cement you should be able to get from a decent hardware store. Fire cement from a domestic boiler expert.

[Edited on 9-11-2014 by blogfast25]




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Little_Ghost_again
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[*] posted on 10-11-2014 at 03:40


Quote: Originally posted by blogfast25  
Quote: Originally posted by aga  
I got no asbestos or fireclay/cement, and my pencil has no lead (joy of vasectomy).
PTFE, Bentonite Clay(cat litter), Al Oxide and Mud i have.

It may be that if the joints are tight enough that they won't leak much anyway.



I wasn't really suggesting to improve leak tightness, only to make opening the sphere after firing easier.

Lubricating graphite and fire cement you should be able to get from a decent hardware store. Fire cement from a domestic boiler expert.

[Edited on 9-11-2014 by blogfast25]


The other place Aga you can get fire cement is a car replace place,no idea if spain has something like halfords but the stuff they put around exhaust manifolds is fire cement (ok you knew that). I just used some on my little kabota
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[*] posted on 14-12-2015 at 13:16


Very interesting tghread.
Especially when I was pyrolysing plastic for long time.
Nice rig Aga.
I'll take some photos of my setup at some point.

Word of caution - if your vessel contains loosely dumped in material with lots of air in-between when the plastics begin to decompose you are getting mix which can be explosive!. It effectively becomes a bomb.
To mitigate it and be on the safe side I used two methods depending on circumstances:
1) pour some water to the vessel before you close it for operation. During heating steam expels all oxygen.
2) squize in some CO2 from fire extinguisher or drop some dry ice. As CO 2 is heavier than air it will purge the O 2 at the beginning of operation.

Option 2) might be much better choice for PVC.


I've never done PVC myself but could do with some extra HCl and have plenty of PVC which I was throwing away till I found this thread. So now I know what it will be my next project :D

Question - how corrosive is hot gaseous HCl ? Would it be better to use steel, SS or Cu pipes and vessel?
I would prefer the rig not to be of "one use only" type :D


Regards
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[*] posted on 14-12-2015 at 13:49


The 'product' smells of burnt plastic for no reason i can imagine ;)

My rig has not been used since, and is a potential source of a lot of iron oxide LG2.




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[*] posted on 14-12-2015 at 15:03


Design I've perfected over the years

Small vessels were made out of 20L veggie oil tanks.
If for heat I used rocket stove fueled by timber/oil/gas (propane, butane, natural gas) I prepared the vessel this way :
1) cut out paper-thin bottom and weld in matching base cut out of 2mm or thicker steel sheet. Make sure you weld it exactly or a bit above original bottom leaving rim for stacking up the drum on top of another
2) cut out the paper-thin top
3) out of 2mm (or tjicker) steel sheet cut out matching top
4) in the new top cut out semi-circle leaving 40-50mm rim and around 100 mm on one side
5) in the 100 mm "flap" drip hole for tank connector to take the copper tube. I used 15mm nearly always.
6) all around semi-circle drill holes around 30-50mm (depending on thickness/rigidity of your sheet) apart and weld domed nuts on the underneath
7) cut out piece of steel sheet to cover the semi-circle cut out overlapping it 30-50 mm and drill matching holes for bolts
8) on the inner side of bolts glue fibreglass rope user for stove sealing. Stove glue works perfect.
9) weld the new lid on place of original paper-thin you cut out.

Now you have easy to load/clean vessel with wide loading port. The flange style cover makes it easy to load it up and clean if needed making good seal at the same time.

Common easy way of making the heating part of the rig. You need 2x20L veggie oil drums and a length of 100mm steel pipe/square tubing
Drum 1 (bottom)
1) drill 100mm hole in the centre of lid to accommodate the pipe (that's why pipe is easier than square tubing)
2) on a side, around 100mm from bottom cut out small section to put you tubing through. It has to be large enough so you can easily insert you tube through. The void you have to cover with another big of steel sheet. Thin stuff will do.
3) cut out the lid to allow easy filling with insulation

Drum 2 (in between drum 1 and pyrolize vessel):
1) cut out the top/lid
2) cut 100mm hole on the bottom to accommodate the tube
3) on a side around 100mm from the bottom on cut out hole for the chimney

Pipe/square tube assembly - cut, bend, weld to make U shape with one arm short and the other when placed inside drum 1 would go through it up to 3/4 of night of drum 2 stacked on top of drum 1.

Assembly:
1) place drum 1 on the ground
2) feed the U snapped pipe assembly through it as described above.
3) fill the drum with insulation. Perlite works best for me. Rock wool and vermiculite are OK, but you have protect them from water (rain) when rignis not in use
4) place drum 2 on top of it. Because the bottom has only small opening for the pipe it will collect the ash which you could use to get some KOH
5) place your pyrolize vessel on top of drum 2
6) mount a chimney to drum 2

Your rig is ready to go! :)

It sounds as its lots of work, but it isn't really. Once you assemble it the way described you can use it for very very long time.
The pyrolize vessel is protected from corrosion on inside by oils pyrolyzed out of plastics (don't use PVC or fluor containing stuff). The other 2 drums are easily replaced as needed due to modular construction.
Drums are free from most kebab shops :)

Because it uses rocket stove as heater it is very efficient on fuel.
Wooden pallets are everywhere for free (don't use psinted pallets - they are chemically treated).


Almost forgot - the 15mm copper pipe mounted to your pyrolyzing vessel goes through 2 condensers. Metal paint cans or fire extinguishers work well. Mount valve on bottom for easy pouring out distillate.
After 2 condensers I run it thorough another can working as bubbler - flash arrestor. At this point you have anly gad fraction of distillate which you should burn to prevent release to the atmosphere. I run it back the rocket stove.
In practice you need a bit of timber to start the process, then it runs of pyrolyzed fad fraction, then you need a little bit more timber to run the process to completion.

Later on when I have some time and it stops pissing down I'll take some photos.

Regards




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Boffis
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[*] posted on 14-12-2015 at 17:26


Have you actually built one or is this just a "design"? I have to say it sounds like you pinched this design from Wallace and Gromit's rock.
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[*] posted on 14-12-2015 at 19:10


"All eyes are on the prize: benzene. Increasingly hard to get for hobbyists. "

There is a theoretical advantage of polyvinyl chloride over polyethylene which is stoichiometry. At a high temperature, it cracks, and releases it's most stable constituents: carbon, and benzene, and "crap".

There's probably a lot of crap besides benzene but all of the aromatic crap ought to react with permanganate to form water soluble species. Benzene doesn't, I seem to recall. So if it's a helpful suggestion?




F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat with the evolution of chlorine.
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[*] posted on 15-12-2015 at 02:51


Quote: Originally posted by Boffis  
Have you actually built one or is this just a "design"? I have to say it sounds like you pinched this design from Wallace and Gromit's rock.


I've built dozens of pyrolysers over last several years. Most were dead end because of various technical problems. The one described is cheap and cheerful but works perfectly well. Greatest thing I like about it (apart from next to nothing coastwise) is its modular design. Got few different " bases" to use various fuels, like the rocket stove with sort of a basin on the bottom for fueling it by oil or plastic. Oil or melted plastic pools in the basin and as it vaporises its burned down the line. Also rocket section with one vertical and one horizontal "in" tubes works best for prills. Vertical "in" has a hopper filled with prills and horizontal "in" has PC fan attached to it. It's Z shaped so there is no line of sight for infrared radiation so the fan doesn't melt. I built this for variation because I got hold of several hundred kg of used active carbon filters (came from restaurant kitchen). The plates in these filters are composed of active carbon prills glued by PVA.

With all the variations the top (pyrolysing vessel) remains the same.
As matter of fact I got few vessels and because of modular design after pyrolysis is completed in one I can detach it and install new full vessel in a matter of seconds. All is done while rocket is operating and there is no risk of burns or scalds. Only risk is getting stinky because of (tiny amount) of smoke :D



[Edited on 16-12-2015 by pesco]
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