How to turn plastic waste into diesel fuel cheaply

[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]

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.

[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.

[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.

[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!!!!!

[NickTech]

For our purposes nil pressure is ideal, so zero.

Thank you Excalibur.

So the manometer indicates always zero.

Bye
Nick

[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.

[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.

[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.

[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.

[NickTech]

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

[Col]

Residue in retort

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!

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.

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?

Col

[Excalibur]

Using the feedstock oil feed for the heat exchanger/condenser is a good idea. My plan is to pipe the feedstock oil counter-current to the vapor flow. I have a few details to iron out as currently my condenser controls the diesel reservoir temperature by raising or lowering the distillate that drops into it.

180*C might be on the high side for the diesel tank but depending on how much light fraction you want to draw out and send downstream. My recent run, I aimed at 80*C- 100*C and the diesel seemed fine. Certainly the lower this temperature, the more volume of diesel you'll net. The 180*C mark will mean less quench for the condenser.

I'm curious to see if the 380*C reflux target will yield a diesel with a good specific gravity. Try it and tweak from there if necessary. Please record the S.G. for reference.

The reflux purpose is as you say so I think BB's 425*C marker is to liberate a heavier fraction in the first trap, perhaps a lubricating oil.

The shipping container is another great idea. I have one here but it's a bit too close to my shed and I had the materials to make a dedicated shelter. Consider fitting extractor fans.

[Col]

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

BB said - You NEVER want your reflux zone to be lower in temperature than your retort, or the condenser trap it is servicing, or otherwise you will have tar, wax, polymers, or coke blocking your reflux and vent, then you have oops kaboom!! In that case we can only hope you have good insurance.

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

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.

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? 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.

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

[Beyond Biodiesel]

Thanks Excalibur and BB. Sounds like you have great efficiency and tight control over the heating of your system BB.

You are welcome. If you are going to be cracking and distilling hydrocarbons, then you are going to want tight control of the system, or otherwise fire and explosion will be the result.

Something I have been puzzled by is whether (in a continuous drip feed system with very good insulation) I will need to regulate the temperature of the reflux chamber and condensers # 1 or # 2 DOWNWARD. Much has been said of heating and insulating these chambers, and varying the length of pipes between them to manage temperature drops. So I know I will need to heat and insulate these chambers, but do I need to be able to COOL them in a continuous system??

Designing a hydrocarbon cracking and distillation system requires art and science. So, there will be much for you to learn. I have 4" (10cm) of insulation on my retort and reflux. For every 100C drop moving down my line of condensers I remove 1" (2.5cm) of insulation. This means the condenser trap never overheats from the vapor stream and requires a small amount of power to maintain its temperature.

If the vapours are leaving the retort at 500C (I just want to be left with dry ash rather than tar at the end of a cycle) should I build into my system the ability to heat AND cool the reflux zone to strictly keep it at 380C? ie. would a constant flow of vapours from a 500C retort heat the reflux zone above 380C, so I need to cool it a bit? And would a constant flow of 380C vapours from the refluxing zone heat the first condensing chamber above 180C, so I need to cool it a bit?

You NEVER want your reflux zone to be lower in temperature than your retort, or the condenser trap it is servicing, or otherwise you will have tar, wax, polymers, or coke blocking your reflux and vent, then you have oops kaboom!! In that case we can only hope you have good insurance.

I intend to hold the retort at 500C, the reflux at 380C and the first condenser at 180C, then cool the remainder of the vapours after that. So I catch all vapours between 380C and 180C to be used for diesel.

That is fine, but there is no reason to heat your retort above 800F (425c) because all hydrocarbons will be evaporated, or cracked, under that.

Additionally, you can combine the light fractions with the heavy fractions to make diesel fuel. I have been doing it for 7 years, and the petroleum industry has been doing it for about 100 years.

I recognise the answer to this question depends on how 'closed' my system is. But those of you who have experience with the practical limitations of your insulation will have an idea of whether the heat losses through your insulation are enough to pull the temperature down enough between chambers.

I recall way back there was talk of needing to pull insulation off the system to stop it getting too hot. I don't remember if this was because they couldn't regulate their heat source properly or because the vapours carried too much heat to the next chamber?

Using a hot plate and heat bands, will it be enough to just regulate the chamber temperature via thermostat controlled heaters? or will I need to leave some of the chamber walls exposed and cool them with a fan sometimes? BB's experience tells me that in a batch system I can rely on heating only and not need to cool anything. But in a continuous system there will be no heat sink / cold chamber for the vapours to transfer their heat into as the system chambers will be kept hot continuously.

The problem is almost no one who has come to this forum has understood condenser design, including the OP. Just work on your condensers, before you even crack or distill hydrocarbons.

I looked at strict temperature regulation using thermic oil but I would need to pressurise the oil to 400psi to achieve a temperature of 430C. I'm not really interested in hot oil at that pressure.

Thanks
Col

While cracking towers typically operate at above ambient pressures, that is only 15PSI (1 bar). Do not try to get fancy with your early designs. Just work on the basic system first. Get it running, then consider improvements later.