Sciencemadness Discussion Board

pyrolysis of plastic and plastic products

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Oxirane - 29-10-2014 at 13:42

Your results seem very similar to mine. The HCl water trap got contaminated with yellow-browish tint, which probably could be purified to some extent by filtering it through ceramic or silica sand filter and maybe even activated charcoal, if it doesn't absorb HCl on it's own. Very good cooling of pyrolysis gases seems to be important, but because I noted that there condensed thick gunk which could potentially block some of the lines, the fumes should be led directly to a submerged condensing flask and then exhausted through reflux condenser into a tube and out to the water trap for HCl collection.

blogfast25 - 29-10-2014 at 14:15

8 g of liquid pyrolysis products out of 237 g PVC and after 85 minutes of runtime seems a little... underwhelming, considering your effort. You'll need a longer run or continue this one to see if more 'goo' can be squeezed out...

Like oxirane suggested, active charcoal may remove the worst of the colour.

Hard to distil such small quantities too. For that I suggest a temporary mini-still cobbled together from a boiling tube, some glass tubing and a cooled receiver test tube, for a crude single plate distillation. De-water the 'goo' first, though. And hope extending the run will give more 'goo'...

I'm a bit unclear about how you capture the 'goo' though. It is supposed to go into the white PE or PP large bottle but I see only 1 inlet/outlet (the ball valve)? Why not collect the 'goo' directly in the first of the two conical flasks (the vac flask, tssk, tssk!)?


[Edited on 29-10-2014 by blogfast25]

aga - 29-10-2014 at 16:07

That'd be the anti-suck back too full then, to be any use as anti-suck-back innit.

Idea was to let any Liquid phase stuff leaving the condenser drop into the bottle, while Gas phase stuff carries on into the anti-suck-back, and then into the water.

Personally i see the experiment as a dismal failure, but then, that's what experimenting is all about - Discovery, Trial and error, hopefully Learning.

From Observation, Stuff Happens at 300 C+
For this Rig, that means Log On more often.

The drops in temperature correlated nicely with Lack of action.

So, next run will be chopped up sun loungers or chairs, whichever gets Discovered (i.e. discarded) first.

Should Benzene burn easily ?

Some of the leaking fluid was absorbed onto some paper, and it it didn't burn at all.

aga - 29-10-2014 at 16:20

Quote: Originally posted by Oxirane  
Your results seem very similar to mine. The HCl water trap got contaminated with yellow-browish tint, which probably could be purified to some extent by filtering it through ceramic or silica sand filter and maybe even activated charcoal, if it doesn't absorb HCl on it's own. Very good cooling of pyrolysis gases seems to be important, but because I noted that there condensed thick gunk which could potentially block some of the lines, the fumes should be led directly to a submerged condensing flask and then exhausted through reflux condenser into a tube and out to the water trap for HCl collection.

My HCl collector is mostly Clear, with what looks like black Oily crap floating on top.

Likely SOS left over from the Wood pyrolysis.

Even though the Gasses do not even get all of the copper pipe Warm, never mind Hot *before* they enter the condenser, all products left the condenser Cool, i.e. < 45 C.

Some gasses were seen leaving the second pot.

plante1999 - 29-10-2014 at 17:42

I heard HDPE is one of the best substrate for BTX production.

Preferable temp appear to be 600 C

deltaH - 29-10-2014 at 21:53

Loved your rig Aga!

A suggestion if I may... I don't know if you're after the HCl as a co-product, but it sounds to me more of a pain than its worth (especially to your apparatus). What about mixing your PVC with lime and then pyrolysing? This way the lime reacts with the HCl formed in situ to generate water and solid calcium chloride and plus the lime would also act as a heterogeneous base catalyst to the pyrolysing melt that may (or may not) help.... making tar/coal being the worst case scenario :D

If it works your condensate would consist of a two phases, water and aromatics. I presume if any aromatic oxygenates (e.g. phenols, cresols, etc) form, they would concentrate in your aqueous phase.

I cannot say for sure about the potential dangers of doing so, though... For example, the reaction between the lime and the PVC would probably be exothermic once it gets going (potentially a good thing if not too exothermic), but this could lead to a thermal runaway. A test tube sized test prior to employing your rig may be a prudent precaution. Also be aware that poisonous CO could also be produced. Heck, now that I think about it, it might just make lots of syngas and 'carbon', aka black crap... :o

[Edited on 30-10-2014 by deltaH]

blogfast25 - 30-10-2014 at 05:58

aga:

Yes, benzene is quite flammable. Which is why you should be very careful with any joints on the pyrolyser being fully airtight. You've got open flames there!

I still don't really understand your set up: seems to me there's only one inlet into the intended organics collector (the large plastic bottle) and no outlet.

I think 300 C is still way too low. Try a charcoal fire or a combination of wood and charcoal, with lots and lots of air. The more air, the more combustion, the higher the temperature. Think BBQ.

At 300 C only a small part will depolymerise or it will take a century to get to say 80 % depolymerisation.


[Edited on 30-10-2014 by blogfast25]

aga - 30-10-2014 at 06:59

Ah. So if it *had* worked as planned, it could have exploded.

Excellent.

Maybe the photos don's show the setup too well.
Out of the condenser is a T-piece, the bottom part of the T is where the plastic bottle is.
The orange pipe takes the Gas into the buchner on the Left, via the spout.
A bung in the top has a glass pipe, connecting to the clear plastic pipe leading to the Buchner on the right, which also has a glass pipe leading from the bung down to just below the level of the water, which is Only in the right hand flask.

The Outlet is the spout on the right hand buchner.
In the event of suckback, the left hand flask would catch some liquid until the level of water in the right hand one fell by about 5mm, after which air could flow freely through both flasks.

Oxirane - 30-10-2014 at 08:26

Minor leaks are not hazardous since the apparatus is filled with HCl and vapors which dispalce oxygen, so only the leaks would ignite after exiting the vessel.

You should apply heat liberally, plastic pyrolysis occurs mostly at temperatures over 300, usually between 350 to 600 degrees. Even though PVC starts to decompose at 200-250, the decomposition products do not differ unless the temperature gets so high the molecules start to decompose, but I find no risk for anyone here getting such high temperatures unless electric heaters or forced oxygen flames are used. I applied 6kw propane heater under a 200x300mm cylindrical reactor which had 100mm layer of rockwool insulation all around it except bottom and the HCl generation rate became quite high at the end of it. With your setup I see a chance for very slow decomposition, so bring the pot closer to the flame.

But afterall, PVC is not a good source for benzene, but HCl. It will generate almost 50% by weight of hydrogen chloride, whileas only 1-10% will be recovered as benzene and rest will be carbon monoxide, dioxide and hydrocarbons of different sizes and lengths. Polyethenes with or without zeolite catalysts are better for obtaining BTX as said before. PVC should only be regarded as a viable source for HCl.

aga - 30-10-2014 at 09:35

Quote: Originally posted by Oxirane  
PVC should only be regarded as a viable source for HCl.

PVC is certainly good for HCl, and Plenty of it.

My observation was that around 270+ C things start happening.

Perhaps Benzene was being a little too ambitious.

Here's a photo of the poor old PVC post-pyrolysis.

pvc after.JPG - 222kB

blogfast25 - 30-10-2014 at 10:30

Aga:

Explosion/fire would only occur with direct leakage from the pyrolysator and proximity of open flame. DO make sure any seals on that part are secure.

I see what you mean now and it is what I thought it was: the T-junction acts as inlet/outlet on the plastic collector. That's far from ideal: think of what happens when you empty a full bottle into a glass or container: the liquid is trying to exit at same time air needs to enter the bottle. Here's it's the reverse: condensate tries to enter the bottle while air must try to get out at the same time. It won't work very well when your condensate flow is larger.

"PVC is certainly good for HCl, and Plenty of it." Did you titrate the HCl? It could be a good way to follow progress of the pyrolysis.

Oxirane:

"[...] but I find no risk for anyone here getting such high temperatures unless electric heaters or forced oxygen flames are used."

Hmmm... even my paint can charcoal fired furnace melts copper (at a push). With good geometry and plenty air, charcoal fire will melt steel!


[Edited on 30-10-2014 by blogfast25]

aga - 30-10-2014 at 11:59

660 C is relatively easy with charcoal and a hairdryer (melting Al)

Not so sure i want a partially sealed 10 gallon tank at 660 C next to me in a field though.

No, i have not yet titrated the HCl.

As before, with the 1L can, there is a stack of HCl left floating about in the reactor, which escapes and gasses you when you open the door.

I closed the door before the cloud was big enough to cause serious Weather Events and squirted some water into the other end to absorb it.

Makes the skin on your arm sting a bit when you stick it into a vat full of HCl gas.
(grabbing that lump of carbon for the photo)

blogfast25 - 31-10-2014 at 05:39

Quote: Originally posted by aga  
660 C is relatively easy with charcoal and a hairdryer (melting Al)

Not so sure i want a partially sealed 10 gallon tank at 660 C next to me in a field though.



A smaller reactor would be safer. Something like a defunct car fire extinguisher, for instance.

aga - 31-10-2014 at 14:25

Quote: Originally posted by Oxirane  

You should apply heat liberally, plastic pyrolysis occurs mostly at temperatures over 300, usually between 350 to 600 degrees.

OK. So lots and lots of heat. Thanks !

Think i can do that.

The leaks worry me, in that Stuff goes where it should not, so they will be fixed for the next run.

In deference to the flammability of any 'products' that may occur, i'll make the tank exit pipe longer, and maybe live to tell the tale.

blogfast25 - 1-11-2014 at 06:57

Quote: Originally posted by aga  

In deference to the flammability of any 'products' that may occur, i'll make the tank exit pipe longer, and maybe live to tell the tale.


That's not really the issue, IMHO, because the cooled 'products' are already much less flammable. The real danger is where the reactor exhaust connect to the reactor: gasses/vapours are still very hot at that point, there's plenty air (for leaked product vapours) and nearby open flame and possibly cinders flying off the wood.

What kind of seal are you using to seal that connection? I would suggest to have a piece of steel pipe welded properly to the hole in the reactor. You can then further down the line connect the steel to the copper pipe that goes into the condenser.

Are there any other vulnerable points in the reactor, like where you load the PVC into it, maybe?

Another issue remains the connection between the tube and the product collector. Looking at one of the photos on the previous page, I can see (shock, horror!) than the thread from the T-piece doesn't even match the thread in the defunct milk bottle (or whatever it was in a previous life)! That's a recipe for losing HCl.

I'm a bit loathe to say [considering your effort] that this project would have much benefited from a lab bench apparatus comprised of no more than some well connected boiler tubes, an ice bath and a HCl scrubber, for higher temperatures and much more quantitative work. :( Weighing everything (walk in Lavoisier's footsteps!), determining HCl obtained, accurate temperature control and decent mass balances could throw so much light on this most interesting problem that your more dangerous ad hoc apparatus can not.


[Edited on 1-11-2014 by blogfast25]

Waffles SS - 1-11-2014 at 08:51

Why pyrolysis of PVC when you can try another interesting pyrolysis?

Pyrolysis of used tires

dl-lemonene is major product and also below compounds as minor products:

2,7,7-trimethylbicycloheptane
1,4-dimethyl-1,3-cyclohexadiene
1-methyl-4-ethylbenzene
1-methylpropylbenzene
1-methyl-3-isopropylbenzene (m-cymene)
2-methyl-1-propenylbenzene
2 or 3-tert-butylthiophene
Diethylthiophene
4-methyl-1-isopropylcyclohexene
Indane
4-methylene-1-isopropylcyclohexene
Butylbenzene
Butenylbenzene
1-methyl-5-isopropenylcyclohexene
2-ethenyl-1,4-dimethylbenzene
Diethylbenzene
Dimethylethylbenzene
Trimethylbenzene
Ethyl-3,5-dimethylbenzene
Quote:

Various samples of used car and truck tires were pyrolyzed in a batch mode under vacuum
and in a continuous feed reactor. The pyrolysis temperature varied in the range of
440–570°C. dl-limonene is a major product formed during the thermal decomposition of
rubber under reduced pressure conditions. The pyrolysis oils were distilled to obtain a
dl-limonene-rich fraction. The difficulty of obtaining a pure dl-limonene fraction is discussed.
A high pyrolysis temperature decreases the dl-limonene yield due to the cracking of the
pyrolysis oil. Several secondary organic compounds produced by cracking were identified by
gas chromatography/mass spectrometry (GC/MS) analysis. These compounds had a boiling
point similar to dl-limonene. The dl-limonene yield decreases with an increase of the
pyrolysis reactor pressure. The mechanism of the thermal degradation of tires leading to the
formation of dl-limonene is discussed. A dl-limonene-rich fraction was obtained following a
series of distillation. Sulfur-containing compounds in the dl-limonene-rich fractions were
analyzed by GC using a sulfur specific detector. Several thiophene-derivatives were identified.
Quantitative analysis of the sulfur compounds in the dl-limonene rich fractions was made.
An olfactometry test was performed on a standard thiophene sample in d- and dl-limonene
solutions to establish an approximate threshold value to detect the thiophene odor.

Production of dl-limonene by vacuum pyrolysis of used tiresPakdel, HJournal of Analytical and Applied Pyrolysis2001, 57: 91–107.doi:10.1016/S0165-2370(00)00136-4




[Edited on 1-11-2014 by Waffles SS]

blogfast25 - 1-11-2014 at 09:38

Quote: Originally posted by Waffles SS  
Why pyrolysis of PVC [...]


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

aga - 1-11-2014 at 10:04

Quote: Originally posted by blogfast25  
I'm a bit loathe to say [considering your effort] that this project would have much benefited from a lab bench apparatus comprised of no more than some well connected boiler tubes, an ice bath and a HCl scrubber, for higher temperatures and much more quantitative work. :( Weighing everything (walk in Lavoisier's footsteps!), determining HCl obtained, accurate temperature control and decent mass balances could throw so much light on this most interesting problem that your more dangerous ad hoc apparatus can not.

I agree totally.
The 'experiment' was useless in any Scientific sense.

Seeing as i'd not know Benzene if i met it, all rather pointless too.

Welding up the rig and firing up a 10 gallon pot was fun though.

I think i have a fire extinguisher, and will take you up on your previous suggestion.

[Edited on 1-11-2014 by aga]

blogfast25 - 1-11-2014 at 12:30

Quote: Originally posted by aga  
The 'experiment' was useless in any Scientific sense.



No, not useless, just flawed.

Oxirane - 1-11-2014 at 13:18

Easiest way for benzene is to get benzoic acid or sodium benzoate and pyrolyse it with sodium hydroxide. If you go hardcore, you can catalytically oxidize toluene to benzoic acid under pressure and heat. There was a patent concerning this. Otherwise, I would still head for polyethenes if I wanted benzene. Who seeks for it, should search internet with "plastic pyrolysis benzene".

And Mr. SS, you will certainly get hundreds of compounds out of plastics and tires, but try you to separate those into useful fractions! If you've got a chemical plant with tens of feets high vacuum fractionating columns side by side and tons of tires to pyrolyse in a continuous process, go for it. Did you know that you can get phenol, aniline an ammonia in tons from common coal - if you happen to have tens of thousands of tons that for turning into coke? But for average amateur chemist with his glassware and utilized fire extinguisher reactors, only residues with few useful fractions are reliably separated. Yes, you can make HCl from PVC, yes you can make styrene from polystyrene, but no, you probably can not separate Indane from car tyre residue oil.

aga - 1-11-2014 at 14:51

Hmm.
Both of my fire extinguishers have Aluminium casings.
Lidl is getting unreliable these days.

A small propane tank might be better.

Car boot time.
Maybe a Butane bottle. They're steel.

[Edited on 1-11-2014 by aga]

aga - 2-11-2014 at 01:53

300 C isn't even half way there.

"The maximum BTX aromatics yield was obtained at 719 °C"
http://pubs.acs.org/doi/abs/10.1021/ef901127v?journalCode=en...

blogfast25 - 2-11-2014 at 06:14

Quote: Originally posted by Oxirane  
Easiest way for benzene is to get benzoic acid or sodium benzoate and pyrolyse it with sodium hydroxide.


http://www.sciencemadness.org/talk/viewthread.php?tid=325

(very long thread)
Quote: Originally posted by aga  
A small propane tank might be better.

Car boot time.
Maybe a Butane bottle. They're steel.

[Edited on 1-11-2014 by aga]


Defunct CO<sub>2</sub> Sodastream bottle? Quite small.
Quote: Originally posted by aga  
300 C isn't even half way there.

"The maximum BTX aromatics yield was obtained at 719 °C"
http://pubs.acs.org/doi/abs/10.1021/ef901127v?journalCode=en...


From the abstract:

"The maximum BTX aromatics yield was obtained at 719 °C, with a value of 18 wt % of the organic product."

That caught my eye: 18 % is not a lot, the rest being 'char', I suppose. Interesting also how they suppressed chlorine by addition of oyster shells (limestone, basically) to the feed.

And then there's this:

"Besides the pyrolysis oil, a combustible gas was also obtained. The main components of the gas were CH4, C2H4, C3H6, C4H6, and C4H10."

That is something that really should be checked too: add a gazometer after the HCl scrubber to capture non-water soluble gases. If only for safety. Part of it will be air of course.

[Edited on 2-11-2014 by blogfast25]

plante1999 - 2-11-2014 at 10:08

Burn the off gases under the tank to help sustain the reaction. Use polyethylene instead of PVC.

aga - 2-11-2014 at 11:46

I got ample supplies of sun-loungers and chairs made of PVC, so needs to be PVC for me.

Eating all these oysters to get raw material is making me Fat, and fishy.

I'd just use some CaO, but i have no idea how to make it into oyster shells.

[Edited on 2-11-2014 by aga]

Oxirane - 3-11-2014 at 19:36

Cyclohexanone is used for production of nylon. So could nylon be pyrolysed back to cyclohexanone?

Etaoin Shrdlu - 3-11-2014 at 20:07

No. Cyclohexanone is used to produce adipic acid and caprolactam, it is not a direct precursor to nylon.

UnintentionalChaos - 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]

aga - 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

blogfast25 - 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.

aga - 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]

blogfast25 - 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]

aga - 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 ?

blogfast25 - 8-11-2014 at 13:50

Quote: Originally posted by aga  

Smear Al2O3 paste onto the threads maybe ?


No, wait: graphite!

plante1999 - 8-11-2014 at 14:17

fire cement or asbestos is generally used in industry for such purposes.

Little_Ghost_again - 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

aga - 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]

plante1999 - 8-11-2014 at 15:16

sodium silicate can be used too.

aga - 8-11-2014 at 15:18

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

Cool ! I got some of that. Cheers.

blogfast25 - 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]

Little_Ghost_again - 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

pesco - 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

aga - 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.

pesco - 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




Boffis - 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.

halogen - 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?

pesco - 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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