How to turn plastic waste into diesel fuel cheaply

[wheels]

Hello everyone , new here and hoping for some feedback on my current setup.

Hi and welcome.
I add in my 2 cents starting with the easy part first. Electric or flame! I understand exactly where BBD is coming from, but actually, there is no difference in a Flame or an electrical element when it comes to danger of ignition. The heating element is way beyond the temperature of ignition and in fact, can be an even greater ignition source simply because there is good oxygen content around the element. Where as a flame is using up the oxygen. However, what really must be taken from BBD's comment is that this entire process is dangerous and needs careful thought to all aspects of safety.

Forget a pressure gauge. The bubbler tells you all. By the time you see a pressure rise, the pressure is already there and the fact that a blockage has already occurred and the biggest issue is stopping that pressure rise. If you turn the heat off, there is still pressure rising. It is better to have decent pipe size for good flow as Excalibur suggests.

Don't use copper. Copper acts as a catalyst, but not the right type of catalyst.

Don't use Aluminium. Ally has a melting point of 630degC. You will be getting close to that temperature and that means the vessel material will be losing strength. Should some issue develop, you don't want vessel failure. You want it all to hold together till the temperature drops enough for pressure to drop.

BUT PLEASE!!!!! don't do this inside your Motorhome, just in case you are considering that. It is far far too dangerous, right from fire to explosion to dangerous gasses.

[mindxploration]

Thanks for that better clarification on ignition temp issues. I plan on extensively testing b4 an actual pyrolysis run. I have looked at papr units for better safety around possible fumes. I don't plan on taking any shortcuts etc and I would hope from the looks of my setup that is apparent. I could upgrade to stainless retort but do not see why aluminum should have any problems if kept below 450c and no direct flame contact. Which is why I have steel plates between burner and base of retort. Money is not my concern it's having a proper setup for my needs. I started looking at multifuel diesel generator and electrical heating after bbd's comment but realise that route makes me not want to further explore plastic pyrolysis as I would be in like 6 grand with centrifuge, genny etc...
will move forward with ordering stainless reflux and setting up my thermal siphoning condenser system. Thanks everyone again for the advice. Scares and all.

[wheels]

Thanks for that better clarification on ignition temp issues. I plan on extensively testing b4 an actual pyrolysis run. I have looked at papr units for better safety around possible fumes. I don't plan on taking any shortcuts etc and I would hope from the looks of my setup that is apparent. I could upgrade to stainless retort but do not see why aluminum should have any problems if kept below 450c and no direct flame contact. Which is why I have steel plates between burner and base of retort. Money is not my concern it's having a proper setup for my needs. I started looking at multifuel diesel generator and electrical heating after bbd's comment but realise that route makes me not want to further explore plastic pyrolysis as I would be in like 6 grand with centrifuge, genny etc...
will move forward with ordering stainless reflux and setting up my thermal siphoning condenser system. Thanks everyone again for the advice. Scares and all.

Aluminium is a unique metal in regards to how strength is given to it in the first place. It is work hardened. But by raising temperature above 177degC, it begins to change and the tensile strength begins to change. At temperatures above 200degC, the tensile strength becomes a factor of both time and temperature. In other words, the longer the time it is at a set temp, the less strength it has, or raise the temperature and the faster it loses strength till basically all that tensile strength that was gained in the processing is gone. Once that happens, Aluminium is actually very soft. The other thing to think about is corrosion. As temp rises, the less corrosive resistance the metal has.
What I suggest is that you use the vessel one time only, then do a good clean and inspection of it and make sure all mating surfaces between lid and vessel perfect. By the way, you need a good mechanical seal. There is no other material that can be used as an effective seal.

[mindxploration]

What would be a better choice for retort? Basic cheaper steel vessel cheap to replace when needed or a certified stainless pressure vessel good to 85psi at 100c as pictured? Its looking like one with sanitary fittings is gonna work best for connecting up to my reflux and connecting temp and pressure guages. Should i work on graphite seals or exhaust cement for the sanitary tri clamp connections? You got me rethinking my retort plans bigtime.

[wheels]

What would be a better choice for retort? Basic cheaper steel vessel cheap to replace when needed or a certified stainless pressure vessel good to 85psi at 100c as pictured? Its looking like one with sanitary fittings is gonna work best for connecting up to my reflux and connecting temp and pressure guages. Should i work on graphite seals or exhaust cement for the sanitary tri clamp connections? You got me rethinking my retort plans bigtime.

SST is perfect. Pressure tested even better, even though the process is carried out with no pressure. It simply proves the vessel has very good and tested welds.
Mild steel is still a good choice though. It works, it is cheap, easy to weld, drill, cut, thread etc etc. And should you decide the process is not what you want to continue with, then it has not been an expensive outlay.
Seals are easier to do with Tri-clamps. I think they are a great choice. And this is a very big plus using SST, the fact that there are many fittings off the shelf available, along with Valves and threaded bits and pieces etc, that make adding and changing things easy. And surprisingly, it's not all that much more expensive, apart from the Tank usually, which can make your eyes water re the price.
I make a very simple seal using a soft copper wire ring, that fits in the groove of the Tri-clamp. But you have to weld the wire into a ring. Not so easy for most. So you could cut a thin slice of copper tube/pipe that fits in the groove, or failing that, some copper sheet and cut into a flat seal that is deformed into the groove. The copper exposed is simply not enough to cause any worries.
I have tried all sorts of materials in these tri-clamps and the copper ring has worked the best. In the less hot areas, a flat graphite material or a sealant as a gasket works well and in the very warm down to cold areas, the rubber seal that comes with those fittings works fine. Gasket Silicons will work in temperatures up to 200degC. But NEVER use Gasket Silicons on the retort itself.

[Excalibur]

Give some thought to the grade of stainless. In the dairy industry 316 and 304 are common but are known for cracking at temperatures much less than 400°C+. A crack in a retort at operating temperature would create a runaway fire that would make the 6 o'clock news! A crack would allow hot hydrocarbon liquid or vapor into the flame zone!!

Have a look at this website as a start for making a study. Once you decide on a grade that gives a high safety margin, consider cost, wall thickness, etc.

It might be that the cost outweighs the benefits but in considering the prospect you should allow for cleaning out of the retort so hatches/flanges will be needed. The ability to work/cut/weld stainless is another factor.

Earlier on the forum there was a report of a used stainless vessel as a retort. That vessel cracked and a replacement was made from new stainless of a "heat resistant type".

[mindxploration]

Wouldn't the thickness be just as important as grade? A thin walled vessel of 304 would Crack where a 3 inch thick vessel would have a much harder time cracking. By the way that pressure vessel is not a dairy industry product it's a 125L industrial pressure vessel with a 4 inch sanitary fitting on top. Figured 4"-3" reducer to a 3" x 31" reflux, all stainless. Water cooled dephlegmator and several liebig condensers with needle valves for water flow to control temps.

[Excalibur]

Yes, thickness would be as important as grade. Yes I think thick wall would win for more crack resistance.

Run your existing retort for the experience, so that you'll have a better idea of how to proceed with mk2..

[mindxploration]

I'm not gonna risk ruining a $500 aluminum pressure cooker or risk my safety. That setup has just become my main canner. Rather do things right the first time. Thanks for the help guys.

[wheels]

Wouldn't the thickness be just as important as grade? A thin walled vessel of 304 would Crack where a 3 inch thick vessel would have a much harder time cracking. By the way that pressure vessel is not a dairy industry product it's a 125L industrial pressure vessel with a 4 inch sanitary fitting on top. Figured 4"-3" reducer to a 3" x 31" reflux, all stainless. Water cooled dephlegmator and several liebig condensers with needle valves for water flow to control temps.

I work with SST, so know a bit about it. SST cracks not so much because of the heat, but because it work hardens and then fatigue's due to becoming brittle. The fatigue points tend to be around welds. If by some chance the vessel has a weld around the middle, then that weld edge is something you need to keep an eye on, but it may be totally OK. It depends on how the SST moves. Thickness does not really matter, but a thicker wall section may reduce the ability of movement and thus last a little longer.
Simply, there is no one perfect material. Currently, I use mild steel, because it is cheap and easy to make, because for my processing, it does not last as long. I am processing Plastics that produce Acid. In saying that, I have been working on a whole new design for that part of the process to make my system automated and continuous. I will be going back to SST, but there will not be a retort vessel in this design. Sorry I can't tell you anything more about that part at the moment. But it is a form of FVT (fast vaporisation technique) although there are variances in what FVT can stand for. As well as many different methods.
Anyway, back to discussion. Wall thickness determines how quickly the heat transfers through the wall. SST is not the best at heat transfer so a very thick wall section takes time to transfer heat. A thin wall will transfer it much faster.
The bigger issue to remember is that plastic is terrible at heat transfer. It is a good heat insulator. So don't have too big a vessel, or it takes ages for the heat to get right through the plastic. This is the main reason why there are so many different designs in the commercial realm. All the ideas revolve around trying to get the plastic to the heat as fast and efficiently as possible. As the plastic breaks down and more and more carbon is created, the remaining plastic is more and more insulated from the heat.

[wheels]

SST cracks not so much because of the heat, but because it work hardens and then fatigue's due to becoming brittle. The fatigue points tend to be around welds. .

On re reading my post, I realised I didn't word that well. So let me describe it differently. It is the heat that causes expansion and contraction and it os this constant movement that then causes the work hardening. Because a Weld is slightly thicker than the rest of the vessel and may even be a slightly different chemistry that the parent metal, the expansion/contraction can be ever so slightly different at the edge of the weld. This movement then creates a stress point and the metal will crack. Vibration can do exactly the same thing.
I should also add that excalibur is correct in that there are other SST's that are better with heat than 304 and 316. Only problem with many of them, is that they are very difficult to work with and thus expensive to build a vessel from.
I keep coming back to plain ole Mild Steel as being the best material, because it is easy to work with and cheap.

[ladanivaca]

Mirad que pirolisis

: angel:: angel:https://youtu.be/1Qi54pTAXZ4

[rozier56]

rozier56

A few questions that interest me!
1. In the reflux column we are going to try using metal fans{i.e like radiators} placed in a column. This will provide good surface area and not so easy to block up baffle holes as they are long slits.Easy to remove and clean and one can adjust the amount of fans to achieve best results.
2.What about the use of bitumen as a raw material?{not asphalt with sand added}
3.Best plastics to use seem to be the ones with branched molecules?
4.If one gets a lot of gas escaping through the exhaust pipe does this mean the condenser is not performing enough---our ones are 1.2 metres long and 100mm in diameter. Filled with eight inner pipes.

Couple of good idea's i have introduced.
1. introduced second hatch/opening into bottom side of retort, makes for easy cleaning after run.
2.Filtering finished product through bag filters, firstly ten micron and then 1 micron.Bags are cheap and easy to clean and re-use.product very clean and safe to use.

[Clean Tech]

Some simple questions

Hello everyone,

I have been reading this thread for a while now (admittedly not all of it) and i see where a number of ppl have been having success in converting waste plastic into a fuel. I commend those who have been able to achieve their results thus far and applaud this community for the work that they have done in sharing the knowledge gained so far.

I do have some questions though i wish some of the more experienced members here can help me with.

1. Has anybody ever spoken to one of those plant managers or chemist that work for a commercial pyrolysis operation and without having them give away trade secrets provide insight as to the best way to do this on a smaller scale?
2. would members here be willing to join forces to come up with a standard that can guide those to come on how to do this without much trial and error?
3. Would members be willing to create a diary of sorts that can show the do's and dont's and what has and hasn't worked and why?

The reason i asked these questions is because I am interested in building a plant at a scale that can process about 1-2 tons of waste plastic per day. I know alot of you are manufacturing to support your own domestic needs but i am looking at a small scale commercial, and rather than going the cheap Chinese way (no offense to any member that may be Chinese) I would much rather make something that we could copy around the world for others to model.

[wheels]

Please note that I have answered each of your questions in Blue.

A few questions that interest me!
1. In the reflux column we are going to try using metal fans{i.e like radiators} placed in a column. This will provide good surface area and not so easy to block up baffle holes as they are long slits.Easy to remove and clean and one can adjust the amount of fans to achieve best results.
, why? The reflux column is simply a chamber that allows heavier hydrocarbons to drip back down into the main Vessel to be reheated again and hopefully crack to a lighter Molecule. You don't need anything in the chamber/pipe. It is all about getting the temperature right. It needs to be cooler than the main heating vessel.

2.What about the use of bitumen as a raw material?{not asphalt with sand added}
could try, but you need a lot of heat. Bitumen is Tar obtained by Petroleum Distillation. It is the last product after all the other chains above it have been removed. i.e, Oil, Diesel, Petrol, Solvents etc. So you have to heat it high enough to crack it further. I have never tried it, but I expect it would be slower to process as it will be likely to cycle a few times through the reflux till the chains are light enough to carry on.
3.Best plastics to use seem to be the ones with branched molecules?
There are only three plastics you can safely use. Polyethylene, Polypropylene and Polystyrene. Polystyrene produces ethenylbenzene. It is a product that is more like Petrol, but has an Octane rating of 106.4. Because of such, it can be used by refineries to set the Octane rating of Petrol. It's not much good for anything just on it's own.
4.If one gets a lot of gas escaping through the exhaust pipe does this mean the condenser is not performing enough---our ones are 1.2 metres long and 100mm in diameter. Filled with eight inner pipes.
Are the pipes water cooled? Is there a lot of fuel appearing on top of the water in the bubbler? I think that would be the tell tale sign of the condenser not cooling the gasses enough. But if all you have is clear bubbles and and no fuel floating, then you may be creating too much Gas. Gas is created by Heat and Time. In other words, the cracking is too much and you are turning your liquid fuel into too much Gas. You will always get some gas, but it is a case of getting the most in a liquid.
.

I hope that helps.