An LPG tank or compressor tank is a good idea for a retort (reaction vessel); however, a scrap yard might turn up a 50-100L tank with conflat flanges already installed.

Rockwool style insulation is good insulation, but the retort only needs to go to 300c (575F). So, there is no reason to go over the top and build, or buy, a kiln, when you do not need one. I am using a hot plate a pressure cooker and R-Max insulation and getting to 400F (200c) with no problem. I expect to get to 300c (575F) in a few days with only a few minor modification.


I have the first two condensers. The first is just another pressure cooker with no heat sink. It works fine. I installed copper wool column packing in it. It works great to trap the middle fractions.

I made a 6 foot (2 meeter) water jacketed condenser with twisted aluminum flashing for the column packing. It works great to trap the diesel fraction.

I made a 20 foot (6 meter) copper coil in a bucket for the final condenser. It will have ice in it to trap everything from gasoline (petrol) down.

Dump the bubbler. It is useless.
Correct, but it goes to 450c (842F). On the other hand, PTFE (teflon) is good to 500F (260c), so I am going to replace the rubber seals in my pressure cooker with handmade PTFE seals to see if I can get away with it. It means I can reuse the seals.
I wouldn't bet my life, house and kids on it.
Dump the catalyst it is an unnecessary complication. If you use catalyst you will have to figure out how to regenerate it. Whereas, thermal cracking is working just fine for backyard cracking of plastics into diesel fuel.

Welcome to the forum.

It's great to have a fresh perspective! Thanks for making this happen. Thanks for putting in the effort. Thanks for sharing.

I found the reaction is very slow at the 300'C mark. Perhaps if time wasn't important the batch could be left to run??

There's mention of this being a safety feature. In your view is flash-back not an issue even if directing the uncondensible gases back to the reactor to be burned as heat?

Getting rid of catalyst would make things simpler. I'll give some thought to trying that with the next run.

Thanks

Just a few comments on Beyond Biodiesel's ideas. The ideal temperature for cracking plastics such as PE PP and PS is in the 380 -450 C range, rubber or PTFE seals are not going to survive those temperatures.
The bubbler performs two very important safety roles. First it ensures the pressure in the reactor is a little higher than outside so that if there is a leak it will leak vapours out rather than air in. Second it isolates the reactor from the ignition source and prevents the possibility of blow back. Dump the bubbler at your own risk.
Most of us have found that thermal cracking only will produce a waxy product and a catalyst is needed to produce a stable liquid fuel. However if you have managed usable liquid fuel with thermal cracking, well done.

Beyond biodiesel, I got thinking about your comment. Perhaps your feedstock isnt plastic PE, PP etc?? Maybe it's mineral oil?
Please help us... to help each other... so we can all learn and move forward

Thanks for the welcome. I did not mean to offend anyone, but I used to design, build and operate cat cracking units at Chevron Research, and I noticed a few things about this project that should be firmly established from the first, which is SAFETY.

1) Never operate a hydrocarbon cracking, or distillation, unit that is not purged before the heat it turned on and remains on until the the unit returns to ambient temperatures.

2) Always have two operators. One observing the process and one with a LARGE fire extinguisher, who is far enough from the process to not get blown up, and next to a circuit breaker to shut the process down, and next to a phone to call 911.

3) The process should NEVER be left unattended.

4) All hydrocarbon cracking and distillation units MUST be attended by a qualified operator at all times.

5) Never attempt to build or operate a hydrocarbon cracking or distillation unit without acquiring a BS Chem degree, because that is the basic required knowledge set needed.

6) Never operate a hydrocarbon cracking or distillation unit in a residential neighborhood.

7) Build your hydrocarbon cracking or distillation units outside on a cement slab surrounded by a cement or cinder block wall. Never have anything flammable in the structure surrounding such units.

8) If you are going to have a roof over the unit then make sure you have 2" bursting disks that are vented outside, installed on all units.

9) Hydrocarbon cracking, or distillation, units should be constructed far enough from other building that they cannot damage or set them on fire, WHEN (not if) they blow up.

10) Inform the local fire department that you are building and/or operating a hydrocarbon cracking, and/or distillation, unit in their district, so that they can send off fire fighters for petroleum fire control training.
Never be in a hurry to process hydrocarbons. Some of what I have seen as problems here is due to boil-over in the retort. Take the temperature up at a slow series of stages, ie. 25c steps. Hold each stage for at least 1/2 hour to prevent boil-over.

My experiments have taken only 4 hours, but I plan to run it for longer periods.
If you purge the unit, and make sure there is positive flow of purge gas at all times, then there is no need for a bubbler at the end of the run. Although, since most of the people here are building extremely hazardous equipment on a budget, then I can see the bubbler would work as a primitive indicator of progress. When the bubbles are rapid, then you have boil-over, if the bubbles are few and far between, then either the temperature can be increased to the next stage, or the cracking process is over.
There is no need for a catalyst, because it has already been demonstrated here that cracking takes place when long-chain hydrocarbons are brought up to their vapor stage. Clearly, long-chain hydrocarbons are unstable at their vapor stage, or they would not be cracking. So, let that natural process take place, and recycle the uncracked hydrocarbons back into the retort for a another chance to crack.

Cat cracking is a very complicated process. I have built and operated several pilot Cat cracking units from desktop models to single garage-size. The equipment needed to monitor and operate the process and regenerate the catalyst is very expensive, and requires a great deal of technical expertise, for which there is no need.

However, it would be useful to have a Cat cracking unit on a commercial scale to improve the bottom line. However, the unite size and volume that an amateur would operate would not justify the elaboration of the design required to run catalysts through.

A Cat cracking unit requires a delicate balance between cracking and catalyst regeneration, which is a time bomb if it is not extremely carefully monitored. The Cat Cracking Lab, where I worked at Chevron Research was sited in the oldest building on the compound for a reason. Chevron management knew that lab was going to blow up, so why build them a new one?
Agreed, that PTFE seals are good only to 500F (260c); however, most of the action that has been reported here was 300c and below. Your retorts are not being operated under pressure, so once a hydrocarbon has been vaporized it is moving out of the retort and into the condensers.
Good points, imakebiodiesel; however, as has been pointed out above, not purging your entire process from beginning to end of the operating cycle is HIGHLY irresponsible. Depending solely on a bubbler as a check valve is foolish.
Correct, my feedstock is WMO. I recently got into building a distillation unit for WMO to make it work with WVO without ruining my engine. My focus is recycling waste oils into diesel fuel, and I am interested in developing methods and equipment that are safe to operate.

I have plenty of waste oil available to me, so I am not that interested in cracking plastics now. But, I do like the idea of cracking plastics into diesel fuel, and it is an extension of what I am already engaged in, so I am reading through this thread to gain more information. I can see that I might need to understand the process sometime in the future when waste oils become scarce.

To me it is completely irresponsible to promote the biodiesel process for untrained backyard enthusiasts. The biodiesel process requires handling caustics at elevated temperatures; therefore, it should only be handled by properly trained operators. As has been stated above, a properly trained operator is one who has at least a BS Chem degree.

I simply felt compelled to express safety concerns that no one else seems to have taken an interest in.

My mistake, I thought we were discussing cracking waste plastics.

A purging system is simple to incorporate into a reactor. Argon/CO2 gas as used by mig welders can be piped in at a slightly higher pressure than the internal pressure in the reactor. A further advantage of a purging system would be that it would help to keep residence times in the catalyst column and the condensers steady throughout the process.

So far no one has considered regenerating the catalyst. The idea behind using locally sourced clays is that they are cheap and disposable.
As you say regenerating the catalyst mid process is difficult and potentially dangerous.

Jhananda ?

http://www.youtube.com/watch?v=BBpww1WIIT

I have some safety concerns too please tell me how to tackle with pressures & at what points in the process?? which instruments are used & where r they exactly placed

I am worry if oxygen is to remove completely & through out the process?? i mean should i continue purging through out the process?

& one more problem i am facing that should i fill the plastic to the top which is i thought wrong coz we have studied to have some head spaces in reactors otherwise they will be boom in a sec

& yap how did you manage to control the pressure if you purge at the same time coz wouldn't the vapour pressure will add into the pressure of nitrogen gas??

if any one else can help do tell me

This video shows the process in graphic detail:
Ozmotech

...and don't fill reactor to the top! Surely you have found Jetijs' post on how his pipework became blocked with solid plastic!

If we use plastics from 2,4,5,6 (HDPE,LDPE,PS and PP) there would be no oxygen formed as a result of cracking. A little bit of water (from cleaning process) will evaporate before the plastic will start to melt. Remaining oxygen (23% of total air volume inside the tank will be pushed out. As long as the vessel has air tide lid not allowing any leak into it I don't see a problem or need for CO2 or N injection. At least at the scale most of us is doing. Use of catalyst may eliminate the need to run product through for the second time but of course may depend on plastic category being used. This subject has been covered before in earlier pages.
As far as chemistry goes, this process doesn't exceed the knowledge obtained in average high school 30 years ago. Not so sure about current chemistry level in public schools .

Vtech

There's one of you in every bunch,

Thanks for the points. The more ideas the better.

Beyond Biodiesel, What would you consider a suitable checkvalve to be?

In your view, how can it be made safe to flare off the uncondensable gases?

Is there another type of flame trap we should consider?

As someone who has a BSc.Mech Eng, I find Beyond Biodiesel's faith in the education system touching if a bit misguided. Some of the dumbest people I have ever met held college degrees and some of the smartest have no third level education at all.
He does however raise some valid points about safety. A pyrolyzing reactor is a potential fire bomb if wrongly operated and one should give careful consideration to where it is sited.
Never close to a dwelling or public area.
Not in a building made from inflammable materials.
Fire fighting equipment should be close at hand.
Sensible precautions should be taken at all times.
However I personally believe that one should be allowed to take calculated risks with ones own life and property provided it does not endanger other people.

I would only add to imakebiodiesel's comments that a flow meter should be added to the inert gas source so that one could be assured that there is always a positive flow of inert gas. Also, CO2 should be the cheapest possible inert gas source, and should be effective. It could also be the source of fire extinguishing materials. One could install nozzles over the retort and condensers and a main CO2 valve on your fire suppression system a safe distance from the unit. And, yes, keep the purge gas going until the retort is brought below 212F (100c).

I have not read every page on this thread, but i have read quite a lot.

The issue regarding the displacement of O2 prior to beginning, would it not be feasible to have an inlet valve located in the upper region of the reactor lid that bbefore heating any plastic you could run a pipe onto it feeding from an exhaust of car/generator for a period of time, this would fill the chamber with Co2 prior to any heating being initiated.

I am looking at building jetis set up & a seperate distillery set up for refining later.

Question,

Would there be any benefit from using a reflux still in the process after the cracking has been done?

Boka Reflux Still - How To Build - Distillers Wiki

Having the columns packed with materials to create a reflux action?

`Piping in exhaust gases would work fine to purge the system initially but you probably wouldnt want an engine running throughout the whole process. Exhaust fumes contain a lot of water vapour which would mix with the fuel in the condensers.
A neater way to achieve the same result is to add a small amount of water to the waste plastic. This will boil long before cracking begins and evacuate any air in the reactor.
What Beyond Biodiesel proposes is to purge the whole system continuously with an inert gas.
While this is a good idea in a continuous feed system or any system where oxygen can enter, I dont feel that it is necessary in a closed batch system, however I could be wrong and it never hurts to be too careful.
The upper vessel in Jetijs's reactor , and in mine, is both a catalyst column and a reflux column. These two could be separated and this idea is explored earlier in this topic many pages back.

Yes, that's true. It would be better if the water was condensed out first?
The chart below shows the figures. Possibly worse than water is that diesel exhaust has an O2 of 10%
If the issues of exhaust gas can be overcome, it would be a great way of utilizing both nitrogen and CO2, both of which are abundant in exhaust gas and both of which are tipped as the gases to use.
To illustrate how effective exhaust gas can be, back in the early 70's when I was in the workshop, we routinely used car exhaust to purge fuel tanks in preparation for welding repairs. A simple hose was inserted into a gasoline engined cars' exhaust and its' gases were feed into the emptied fuel tank for several minutes. The welding work was completed with the exhaust gas still coming into the tank. To prove the point, the welding flame could be aimed directly into the tank without the vapors igniting! I wouldn't have believed it unless I'd seen it. After the boss initially demonstrated the technique I have used the method ever since.

N2 = Nitrogen
CO2 = Carbon dioxide
H2O = Water
O2 = Oxygen
CxHy (or Hx or HC) = Hydrocarbons
CO = Carbon Monoxide
NOx = Nitrogen oxides
SO2 = Sulphur dioxide
PM = Particulate matter

I do not think the use of PTFE seals anywhere in the system, is advisable due to fire risk. Beyond biodiesel says hes thinking of using as condenser seals. And states that set up should be away from buildings, because it will catch fire. The pyrolysis of PTFE is detectable at 200 °C (392 °F), and it evolves several fluorocarbon gases. At higher temperatures it can release Hydrofluoric acid.

Taken from wiki "Health & safety

Hydrofluoric acid is a highly corrosive liquid and is a contact poison. It should be handled with extreme care, beyond that accorded to other mineral acids. Owing to its low dissociation constant, HF as a neutral lipid-soluble molecule penetrates tissue more rapidly than typical mineral acids. Because of the ability of hydrofluoric acid to penetrate tissue, poisoning can occur readily through exposure of skin or eyes, or when inhaled or swallowed. Symptoms of exposure to hydrofluoric acid may not be immediately evident. HF interferes with nerve function, meaning that burns may not initially be painful. Accidental exposures can go unnoticed, delaying treatment and increasing the extent and seriousness of the injury.[8]

Once absorbed into blood through the skin, it reacts with blood calcium and may cause cardiac arrest. Burns with areas larger than 25 square inches (160 cm2) have the potential to cause serious systemic toxicity from interference with blood and tissue calcium levels.[9] In the body, hydrofluoric acid reacts with the ubiquitous biologically important ions Ca2+ and Mg2+. Formation of insoluble calcium fluoride is proposed as the etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity.[10] In some cases, exposures can lead to hypocalcemia. Thus, hydrofluoric acid exposure is often treated with calcium gluconate, a source of Ca2+ that sequesters the fluoride ions. HF chemical burns can be treated with a water wash and 2.5% calcium gluconate gel.[11][12][13] or special rinsing solutions.[14][15] However, because it is absorbed, medical treatment is necessary;[9] rinsing off is not enough. Intra-arterial infusions of calcium chloride have also shown great effectiveness in treating burns.[16]

Hydrogen fluoride is generated upon combustion of many fluorine-containing compounds such as products containing Viton and polytetrafluoroethylene (Teflon) parts

Polytetrafluoroethylene - Wikipedia, the free encyclopedia
Hydrofluoric acid - Wikipedia, the free encyclopedia

Many people doing this come from less well off countries, and would not have available the medical expertise to deal with Hydrofluoric acid burns.

PTFE are good to 500F (260c) above that use some other seal system.

To mister jetics
my set up is to get diesel from used motor oil.
then in the burner after 4 hours of work a buildup is formed I think is carbon and metal in the oil I think if the oil gets centifuged before entering the kiln I can solve that problem.
then 200 litres are obtained in 14 hours, may be if I go 400 celcius instead of 300 the time of work can be shotened.
one more thing is a smell like sulfur very strong in the final product after the condenser, I hope that after filtering with some other type of fitering I can lower that smell or how can this smell be lowered.
What do I do? what do you think?
regards from mexico.

gerardo, I too am distilling WMO to turn it into diesel fuel. Do keep in mind that even after distilling WMO it will still be too viscous to use as diesel fuel, unless it cracks into diesel fuel. So, I add gasoline (petrol) to my WMO to turn it into diesel fuel.

My goal in distilling WMO is just to get rid of the coke, which you observed above. Coke is made up of mostly ash and carbon. The ash is mostly metals, like silica. The coke will be left behind in your retort, so that when you burn the WMO the coke will not be left behind on your injectors.

Raising the temperature of your retort will not reduce the coke left behind in it. And, it will also not do any more for distilling your WMO, but it could lead to boil-over, which could force dirty WMO into your condensate. To distill WMO all you need is less heat, like 500F (260c).

So, if you can avoid boil-over, then there should be no reason to filter your condensate, and doing so will not eliminate the smell of sulfur in your resulting fuel.

Centrifuging your WMO before putting it into the kiln is just a waste of time, because distillation is far more efficient at removing contaminants than Centrifuging.

Hi all, regards catalyst in reflux, as anybody used Expanded clay aggregate as used in hydroponics and pond filters.?

The clay pellets are inert, pH neutral
The clay is formed into round pellets and fired in rotary kilns at 1,200 °C (2,190 °F). This causes the clay to expand, like popcorn, and become porous. It is light in weight, and does not compact over time.
Does the size of the media effect its suitability. is larger better due to easier gas flow?

I have used it recently but first I had to let it dry a bit because it absorbs a lot of water (that is not bad at all but we need empty "microcaves").

I have to make more tests but I think pumice stone works much better, at least in my case.Maybe a combination of expanded clay and pumice will be the point.

@ dutchdivco
Did you manage to sort out your gas storage problem ?

Its sort of similar in construction.

File:Hydroton.jpg - Wikipedia, the free encyclopedia

When using a catalyst it will quickly become saturated with free-carbon, so it will have to be regenerated every time you run another batch of whatever it is you are cracking.

If this is acceptable, then the easy way to clean your retort, and regenerate your catalyst, will be to flush the retort and reflux column with O2 after all volatiles have been evaporated off. The carbon coating on the retort, and on the catalyst particles will be burned off and turned into CO2.

The process of regenerating catalyst produces so much heat that it can power the retort. The real problem will be in not melting down your whole apparatus in the process, so turn off the heat, and introduce O2 slowly over time, while monitoring the temperature of your retort.

You will find that you can control the temperature of your retort just by regulating the flow of O2 into it after the heaters have been turned off. What you do not want to happen is have the temperature rise above 1200F (650c), or drop below that during the regeneration cycle.

When the temperature begins to drop during the O2 burn cycle is an indicator that C has either been consumed, or you are not putting enough O2 in to power the regeneration cycle.

This may sound like an oversimplification, but would it be possible to remove the C by Reduction, (which is the reverse of Combustion) by heating the catalyst chamber while running CO2 and H2O through it? The result would be H2 + CO, which is combustible. In fact, if clean enough, it can run a spark ignition internal combustion engine, but for the purpose of practicality, the gas can be flared off. I'm not experienced in this field, so please feel free to critique this idea, and thank you all for this great forum


Marso Green

This is an important area we need to discuss. The clay catalysts many of us have been trialling have very short active lives and a lot of catalyst is needed to produce a significant amount of fuel. In my own clay catalyst mix about 100 gms of clay will only produce about 2 litres of usable fuel before "coking".
As I see it there are three possible solutions to this problem.
1 Find more efficient catalysts.
2 Regenerate the catalysts.
3 Use catalysts that are so cheap than they can be disposed of after one use.

The three points are important certainly...
Maybe what is tiring is opening, emptying and recharging the reflux module again and again but our setups are humble and limited, at least mine... .
I was thinking about some kind of interchangeable reflux module between plastic loads.
For easy and fast pipe removals this kind of clamps are needed :
Heavy Duty Clamps
The japanese from Blest company use them as I saw in their videos.