How to turn plastic waste into diesel fuel cheaply

[Excalibur]

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.

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

Dump the bubbler. It is useless.

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?

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

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

Thanks

[imakebiodiesel]

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.

[Excalibur]

retort only needs to go to 300c

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

[Beyond Biodiesel]

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.

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.

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??

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.

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?

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.

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

Thanks

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?

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.

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.

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.

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.

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

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.

[imakebiodiesel]

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.

[mercedes 308]

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.

Jhananda ?

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

[unaiz]

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

[unaiz]

I agree, I think oxygen gets expelled early on in the heating process. The bubbler gives a slight amount of back pressure, denying air the opportunity to enter. In any case it would seem that the air/fuel ratio would be far from ideal combustion, much like over-rich mixture in a gasoline engine. I'm not a chemist but I know a motor will not fire unless the mixture is within a tight range. That said, we need to be very mindful of what we're dealing with.
The continuous feed allowing air into the reactor has me thinking. Plastic would need to be melted to remove the air gaps between the granules, at least. However oil feedstock could be gravity feed from overhead assuming the pipeline was purged to begin with. A third possibilty could be oil with a plastic granules content. My thoughts earlier was to heat the oil to 100'C to drive off any water content before feeding the hot reactor. Any water content might be meet with unwanted reaction!

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

[Excalibur]

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!

[blackchisel97]

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

[thissideup]

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.




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.


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.

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..

There's one of you in every bunch,

[Excalibur]

Thanks for the points. The more ideas the better.

Depending solely on a bubbler as a check valve is foolish.

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?

[imakebiodiesel]

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.

[Beyond Biodiesel]

...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...

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 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).

[Uncorruptable]

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?