How to turn plastic waste into diesel fuel cheaply

[Excalibur]

Thanks Excalibur, I'm looking forward to making some physical progress in the next couple of weeks. All the thinking drives you crazy wanting to get hands on!

Yes, I'm like a dog-with-a-bone with my project too. It's good that way, else it would be plain hard work!

I tested the heating temperature of a cheap hot plate, maxed out at 277C, but I could hear a thermostat click it out. So I could bypass the thermostat and try again but seeing it is just a domestic one I wonder of the surrounding materials housing the hot plate would handle higher temperatures. Might just melt into a blob.

Yes, I've looked at elements too. Even once I tweaked an ovens' thermostat and got a LPG cylinder-retort inside it to 400*C, made a few liters of diesel. But it wasn't what I was looking for plus my power isn't cheap so I shelved that project.
400*C is a lot more heat than 277, I mean it's exponentially hotter!! I speculate they may not last, don't know for sure as I haven't tested for any length of time. Possibly good for a condenser trap heater if it were to apply.

Excalibur - You were going to do your first ever clean out of your retort? What residue did you end up with in your retort? What retort temperature/s have you been running at?

Today, I removed the reflux and retort flange. I was amazed how little carbon there was, 99% of which was on the retort floor. The residue was black "carbon biscuit'. I had to break it up to dislodge it. It's 1.5m to the base floor and 200mm round so somewhat awkward. I've run the retort for about 24hr+ all up, made about 250L and temperatures of up to 405*C so far in early testing.
Pics are up on a new DIYDiesel blog post. Pages with more details will be added as well in due course.

[Excalibur]

Hello guys, can someone tell to me what's the typical value of pressure reached during the process in the reactor camber? Is there a formule that can be used for the calculation?
Thank you
By
Nick

For our purposes nil pressure is ideal, so zero.

[Beyond Biodiesel]

Thanks Excalibur and BB, comments much appreciated.

Excalibur said - The bigger the retort vessel, the more the need will be to cool the downstream flow. With vapor will travel heat so the more heat generated means the downstream equipment needs to be sufficient to handle the volume.

I have not seen anyone understand condensers on this or mine or other forums dealing with pyrolysis. Just work on your condensers first. Once you have them they will work just fine regardless of whether it is batch or continuous feed; however, if you increase your flow rate, as Excalibur did, then you will need to increase the volume and heat transfer capacity of each of your condensers.

I expect we can consider a continuous flow system to effectively have an enormous retort, as you could run a 5L retort from a feed tank of 5L or 5ML by steady drip feed.

Yes, a continuous feed system can be based upon a small retort, say 5-gallons (20L), which is what I am building. Once my 5-gallons (20L) batch processor is complete, then all I need to do to convert it to a continuous feed process system is work on a feeding system.

However, no, a continuous feed process system is not like a big retort.

So I will need to design my system with the ability to cool the condensers.

No, if you actively cool your early condensers, which should be above ambient, then you are likely to have a plugged vent line. Just reduce the insulation as I described, 1" (2.5cm) reduced for every 100C.

If I run a few narrow pipes through the guts of the condensers and pump cooling water through the pipes (without any valves on the outlet end of the water pipes so there is no obstruction to super-heated water/steam escaping the pipes, and no pressure) then I expect this would do an adequate job of cooling the condensers from the inside while still allowing me to heat the condensers from the outside as required. Maybe pumping the feed oil instead of water through the cooling pipes might be a better idea, to pre-heat it before entering the retort. Also, when heating water flowing though pipes in a boiler type of situation like this I believe I would need to treat the water to prevent scale build up in the pipes. Whereas pumping oil through shouldn't give that issue, so long as I've de-sludged the oil first.

Forget it.

So you run your retort at 425C and your reflux exit temperature at 425C (same chamber in your case). Wouldn't that mean you are trapping molecules heavier than 'diesel' in your first condenser (the MSDS for BP automotive diesel states a boiling range of 180-380C, so wouldn't you want a reflux exit temperature of 380C and a first condenser exit temperature of 180C?)?

From experience in my 300C trap I am getting motor oil, in my 200c trap I am getting heavy hydraulic oil, in my 200c trap I am getting light hydraulic oil, in my 100c trap I am getting diesel fuel, in my ambient temp trap I am getting kerosene, in my 0c trap I am getting gasoline.

The reason why the MSDS for automotive diesel states a boiling range of 180-380C is because the petroleum industry blends fractions back together to make fuel.

So then you blend solvents with this heavier fraction to get it to diesel spec?

Correct. That is what the petroleum industry does.

I thought one of the purposes of the reflux column was to allow heavier molecules to condense and drip back down for another chance at being cracked into the diesel fraction? If we are to expect the heavier molecules to condense in the reflux column doesn't the temperature of the reflux column need to drop lower than the retort temperature? Then you have your reflux exit temperature and your first condenser exit temperature framing the upper and lower limits of the boiling range for your desired fraction.

Hydrocarbon cracking just breaks large molecules into smaller ones. Trying to get only diesel fuel out of cracking a heavier stock is going to be sisyphean.

I think I will have to do all this at work, I have some space there and can keep it away from a residential setting. I can house it in a shipping container there too.

Sounds like a good idea

I will start with a lower temperature, say 425C, and see what residue I am left with. BB - do you end up with dry ash after a batch run at 425C?

I end up with back soot in my retort.

Excalibur - I don't want any tar - what would I do with tar? I don't need to make a driveway. How would I get rid of it? I am not too concerned about efficiency at this stage, I would prefer to lose some efficiency than end up with tar.

You will not have tar, if you can maintain 425c over the entire retort for long enough.

Thanks guys, you fellas are very helpful. Your input and the input of other notable contributors on this forum have saved me both time and probably an injury or worse.

Col

you are welcome.

[Beyond Biodiesel]

I tested the heating temperature of a cheap hot plate, maxed out at 277C, but I could hear a thermostat click it out. So I could bypass the thermostat and try again but seeing it is just a domestic one I wonder of the surrounding materials housing the hot plate would handle higher temperatures. Might just melt into a blob.

Col

There are several different kinds of hot plates. I used a heating element from a standard US electric stove and wired it directly to my PID controller, and took it several times up to 400c with no problem.

[NickTech]

For our purposes nil pressure is ideal, so zero.

Thank you Excalibur.

So the manometer indicates always zero.

Bye
Nick

[rozier56]

rozier56

Hi b&b and Excal, that banter is awesome!!! .Keep it going and hopefully more of us will contribute as we learn more. I am getting close,with my 200lt plant.Oh, yes i went big after all the info gleaned from this forum.As i mentioned before, i am producing good product but poor production rates. Busy with lots of changes, getting close.My landrover still loving the fuel.As soon as i am confident to share real info that is back up by numbers i will share with the forum.thks guys and keep watching this space!!!!!

[Beyond Biodiesel]

Thank you Excalibur.

So the manometer indicates always zero.

Bye
Nick

NickTech, you will have a small amount of positive pressure in the retort as temperatures in their rise. It will serve to push volatiles out and toward the vent. However, the pressure should never be more than a few inches of water, or you may have a plug.

Thanks, rozier56, do keep us posted. There is some value in starting small and working up to a final product. Excalibur has gone through 6 iterations. I have lost track of how many versions I have tried. Basically every time I make a pyrolysis run I find things that need to be changed, so I change them before the next run.

[Excalibur]

NickTech, you will have a small amount of positive pressure in the retort as temperatures in their rise. It will serve to push volatiles out and toward the vent. However, the pressure should never be more than a few inches of water, or you may have a plug.

Thanks, rozier56, do keep us posted. There is some value in starting small and working up to a final product. Excalibur has gone through 6 iterations. I have lost track of how many versions I have tried. Basically every time I make a pyrolysis run I find things that need to be changed, so I change them before the next run.

BB is right, there will be a tiny amount of positive pressure from the heat making vapor which then wants to occupy more volume. The amount would be relative to the degree of restrictiveness of the condenser/pipework array.
If the retort was fitted with a bubbler, it would add to the pressure figure so a manometer (instrument that uses a column of liquid to measure pressure) placed between retort and atmosphere, would see a gyrating effect as bubbles of gas pushed their way through the water.
Google converted: a few inches of water to about 0.1 psi.

Some time ago, I fitted a (0 -85psi) pressure gauge to the diesel condenser/reservoir as a safety feature to monitor for blockage. To date I've not seen the needle move from it's rest point of 0. If it did, there would be "panic stations".

rozier56, join in the banter whenever you feel like it. We're all learning here. No one has all the answers or is right all the time. I keep changing my set up as does BB. It's the nature of the game. Sometimes a change can bring unexpected results and sometimes the result can be a major breakthrough.
Other times a change can be failure but at least you can identify what doesn't work and perhaps more importantly why it doesn't.

Incidentally, I elected not put any plastic in my retort this time around because I don't want to introduce any unnecessary variable. There's plenty of time later on to crack the plastic stocks I have, so only oil for now. I'm getting close to doing another test run. To do is the IP fuel filter/tank, oil feed pump to sort plus the centrifuge remake of the rotor with new bearings.

[Excalibur]

Latest run: 9hours = 180 liters. More info shortly including a summary of issues faced and ideas for improvement. The unit is capable of 30+ L per hour as I had the feed pump delivering that amount using the counter current principle talked about earlier. Reflux temperatures between 320*C and 380*C.

[Beyond Biodiesel]

Congratulations Excalibur, on another successful run. I noticed that you posted your update on my forum, which I only just got up and running again. If anyone is interested the Beyond Biodiesel forum is now up and running again.
BeyondBiodiesel.org - Index

[Excalibur]

I tested the specific gravity at 837gr for a liter. Someone correct me but isn't this on the light side? I can't find my chart of SG ratings. Can someone post a good link with a chart of all the diesel SG. Here the season is going into summer and it looks like it's going to be a hot one.

The fuel color is the same as previous batches. It's dark green with any quantity like when a jar fill is viewed. It's transparent red if light is shined through and it's amber in small amounts like that of a (8mm) 5/16" polyethylene hose. Otherwise it looks clean and bright, though previous experience says it will have particles less than what the eye can physically see.

This run I insulated the diesel reservoir, however it caused the temperature to exceed my 80 -100*C target which in turn caused the sight level indicator hose to deteriorate. Interestingly enough, the diesel reservoir is at 42*C 17hrs after the heat was turned off. I'd really like to get the centrifuge sorted and running before all that heat leeches away. I don't see that happening this time...

The counter-current preheating of the ingoing feedstock has got me excited. I think I'm onto something good with this idea. As is so often the case, there's problems to resolve and one of the more difficult ones is precisely controlling the feed flow. I need to know how many liters per hour and use that as a point of reference. My set up has a crude system of valves but the control is rather sensitive.

The revised turk burner head showed some good signs but the gas feed is proving a pain. There is backfiring if conditions aren't exactly right which isn't what you need when you trying to distill a large vessel of hydrocarbon. For the last 3 or 4 hours I elected to simply flare off the gas with a vintage Bunsen burner. I rued not having a kettle ready ... all that clean burning flame going to waste!

More pics and updates on the blog shortly. Maybe even a video if they turn out any good.

[Beyond Biodiesel]

Good work Excalibur, your diesel SG is spot on, because the engineering tool box says:
Diesel Fuel Oil 2D/3D/4D/5D (60F) (15.6 c) 0.81 - 0.96sg
Liquids and Fluids - Specific Gravities - SG

For flow control you might look into a metering pump, or metering valve to control the input of raw material.

[Excalibur]

Thanks.

According to Chevron, specific gravity for no.2 diesel at 15.6°C, is between 0.88 and 0.82.

Am working on the centrifuge as I urgently need it running. More updates later, including an idea for a retort level indicator.

[rozier56]

Merry Christmas

Merry to all,and a happy new year.I am off to the U.K. to see my grandson for the first time,leaving hot south Africa,Capetown,30*c for London 3*c.Thanks to all for this great project this year and will see you in the new year.
Regards,Derek

[Beyond Biodiesel]

Safe journey rozier56.