How to turn plastic waste into diesel fuel cheaply

[Beyond Biodiesel]

...I find it interesting that some of us here (including myself) are so keen in the initial stage to prove this concept that we will quickly set up a crude system to get a quick batch test done without really considering possible (safety and other) complications of the process we are starting.

About a year ago I wacked a heavy gauge 20L pot on top of a high pressure propane burner, put 3L of WMO in it, welded a couple of baffles into a riser, threaded on a 2" brass Y strainer with mesh removed so I could have a temp probe up in the branched vapour exit. Used copper pipe to direct the vapours to a 20L tank with 6m of 1/8th copper tube coiled inside, with a pump circulating water from a 10KL water tank through the cooling tank (I guess the water temp was about 19 degrees C). I didn't even know what a bubbler was, or purge gas, or what temperature to aim for.

All went well enough, no explosions, and I got some product out, initially water, then a mixture of water and light ends, then the stuff I was after. The product stunk like dirty, burned oil but was much thinner and had a lot of suspended particulate in it, it was very dark. I did not get 3 L of product out as I struggled to maintain a high enough temperature (I had no insulation at all).

Your vapor stream probably just refluxed back into the boiler with little making it to your condensers

I turned the unit off at the end of the day part way through the batch. The next day I couldn't get the temperature very high at all, no condensate exited the system.

What I am guessing happened is that I never reached cracking temperatures and so instead distilled off the light fractions on the first day and was left with heavy oil in the pot. Is it the case that the distillation process itself will generate heat? Perhaps it is endothermic to a point then is (partially?) exothermic? If so then the combination of the propane flame and the exothermic reaction involving distillation of the lighter ends may have produced enough heat to maintain the process on day one but day two didn't have any light ends to distill therefor no exothermic heat so day two had less combined heat and couldn't reach a high enough temperature to cause the heavy oil to vapourise. It was over a year ago, no notes or photos, so I do not remember the temperatures reached.

No, your problem was a combination of heat loss due to no insulation, and on the second day you had too little WMO in your boiler to give you sufficient thermal enertia to push anything through your unheated and uninsulated refluxing zone.

Anyway, what might interest you guys is what I got from the condensate. There has been talk about the colour of the fuel being indicative of the type of fuel. But if you look at my photo you'll notice that the two samples are very different in colour, yet came from the same collection pot. Because the condensed fuel stunk and was dark I figured I'd soak it in some activated carbon and see if that cleaned it up. Soaking for 30 mins to a few hours didn't help. I left it over night and drained it through some filter paper to ensure I didn't get carbon fines in the clean sample. What I ended up with was the amber sample. It smelled better and looked great. (the thickness of the dark layer on the bottom of the jar is exaggerated in the image. It is a molasses-like substance, gum from oxidation I guess? Has only appeared gradually over the past year) After the weekend I wanted to dry out the activated carbon to use it for something else so I drained the remaining liquid out (through filter paper again) and ended up with the nice yellow product. I have had both of these samples air tight for over a year, only opening the jars a few times to test the odour of the fuel.

It would seem that either the activated carbon selectively soaked up the longer molecules, leaving just the lighter coloured fuel or cut longer chains into shorter ones, or somehow bleached the fuel. I threw out the original condensate when we relocated the business so only have the very small samples you see in the photo. I do not have sensitive enough scales to perform the BP test and determine what the fuel is comprised of using such a small sample. What are your thoughts? I do not believe the activated carbon was acid washed as I have used it with my fish tank at home and had no ill affect (though it is a big tank, and no I didn't use the same carbon as I put the oil through, didn't think the fish would appreciate it).

I will not be repeating the same system. My next set up will be different having read these many pages. Thank you for your input everyone.

Col

Color of the condensate has been discussed here before. I was under the impression that the heavier the fraction the darker it would be, assuming heavier fractions are just darker. However, someone posted a video here on a Spanish commercial WMO recycling refinery, and they showed that their end product is fairly clear. That was when I realized that the reason why our end product is darker the closer we get to the retort is because we all have some boil-over taking place, which you had as well.

Whereas, the reason why the Spanish commercial WMO recycling refinery, has a fairly clear end product is they are most probably triple distilling it. So, I am currently rebuilding my WMO distillation system to accommodate a number of improvements which will include triple distillation and fractionation on the fly.

Hi Col. ...I read from the Shell petroleum book, when a light oil is cracked out of the feedstock, the remainder will be heavier. When still more light oil is cracked out, the remainder will go heavier again, and so on.

This is useful information. I noticed while working at Chevron on a cracking unit that the residue was heavy like tar. Believe tar is mostly heavy fractions plus coke.

I just picked up a pair of high temperature sight glasses made from borosilicate 15mm thick x 100mm. I plan to install these at the entry to the diesel condenser vessel. To be able to see the flow/ drip rate is a very useful indicator of system health.

Nice to have a site glass. I had transparent plastic bottles for collecting samples in after my water traps, but they got to be a problem to seal, so I do not have a sight glass, and for now I understand my process sufficiently that I think I am going to forgo the sight glass complication. But, I might use your idea later on.

Hi folks, busy reading through all the site,notice mention not to use copper in the process as it will act as catalyst. was planning to make condenser coil with copper coil if this is not suitable what metal shall i be using.Thks

Welcome rozier56, not all of us are anti-copper here. I still use copper extensively in my WMO distillation system, and I plan to keep it there. However, it is good to know that copper begins to oxidize heavily above 400c, and it is best kept below 300c, where it works excellently as a heat exchanger.

I am re-reading the whole thing again , but is there a general agreement about how high the pressure inside gets up to? I think I read 1 bar somewhere, but have not found that bit again yet. I am thinking about relief valves.
I presume (a dangerous thing I know) that the back pressure will only be created by the bubbler. Otherwise it would just be naturally aspirated.

It was probably me who mentioned that at Chevron the cracking units I operated were all operated at 1 atmosphere (1bar) above ambient. For backyard operations, such as ours here, I believe it is much better to keep it naturally aspirated through a bubbler.

Excalibur's comments should be noted carefully. Any valve is going to goop up if it is high up the stream closer to the boiler. However, down stream after cooling the fluid below ambient would work fine as a place to put a check valve. The check valve should be as low a pressure as possible, such as one used for an oxy-acetylene torch.

[cornishscrimper]

Thanks

Thanks for the swift replies, all these tips help me form a good design and get a picture of what is needed - particularly on the safety front!
I have been looking around with fresh eyes at old junk lying around and have picked some gas cylinders, some redundant 3'' stainless tubing and general threaded bits and pieces and will slowly gather a pile of 'useful' bits.
One more general question if I may, I have a fairly large piece of ground to set up on eventually but the question is how much 'smell' is generated downwind ? If everything is running OK is it undetectable or does it smell like a 100 year old inspection pit / Thanks again

[Excalibur]

I have been looking around with fresh eyes at old junk lying around and have picked some gas cylinders, some redundant 3'' stainless tubing and general threaded bits and pieces and will slowly gather a pile of 'useful' bits.
One more general question if I may, I have a fairly large piece of ground to set up on eventually but the question is how much 'smell' is generated downwind ? If everything is running OK is it undetectable or does it smell like a 100 year old inspection pit / Thanks again

Good idea on recycling from the junk pile. My sentiments exactly.

The smell can be objectionable if the retort stream is exhausted to atmosphere. You haven't said how you'll heat the retort but if it's by wood, oil or gas etc, then the exhaust gases can be added and burned as heat. Bubblers and other flame traps are advised.
If the heat source is electrical, like Jetijs did then scrubbing the gases has been talked about quite recently.

[Col]

Pressure relief valves

Thanks for your responses guys.

Regarding pressure relief valves (PRV) - on a boiler the PRV must be exhausted straight up to a minimum height to get the exhaust steam away from people. Not sure of minimum height required but ours must go up about 5m?. I was just thinking about what would happen if there was a blockage in the cracking system and one of these PRV actually opened - look out anyone who is standing nearby I expect we would have an explosive flame exiting the PRV. So...

1) We need to pipe the exhaust from a PRV away from our immediate work area.
2) Q - should we put a flame arrestor in the exhaust pipe of the PRV to ensure no flash back into the cracking reactor?

It could be said the PRV can be plumbed into a low temperature condenser to avoid the explosive flame, but we have seen on this forum operators caught by surprise with problems in or close to the hot reactor. So I think it needs to go there.

Have a cracker of a day guys.

Col

[rozier56]

Now thats what is called "cooking with gas". great job.The first pic of what seems to a succeesfull operation. I have some questions to ask you ,do you have an e-mail address and are you on skype? my e-mail is mtroaier56@gmail.com
regards,
Derek

[rozier56]

hi again, the previous post is directed to Alec. thks

[Beyond Biodiesel]

Thanks for the swift replies, all these tips help me form a good design and get a picture of what is needed - particularly on the safety front!
I have been looking around with fresh eyes at old junk lying around and have picked some gas cylinders, some redundant 3'' stainless tubing and general threaded bits and pieces and will slowly gather a pile of 'useful' bits.

Oh yeah, junk is great. When I looked at the warehouse that I am currently doing my pyrolysis research in, the landlord was pulling out his hair because there were piles of junk.

I said," Don't throw anything out. I will take it as is. It made him happy.

At the last warehouse I was in there was a unit across the alley that had 100 gallons of WMO in plastic buckets that were cracking in the sun. The land lord there knew disposal was going to cost him a large amount of money, so he left it there to soak into the soil.

I said, I'll take it, if you will let me.

The handy man came by with the key to the gate the next day and helped me move all of the buckets into my warehouse space.

One more general question if I may, I have a fairly large piece of ground to set up on eventually but the question is how much 'smell' is generated downwind ? If everything is running OK is it undetectable or does it smell like a 100 year old inspection pit / Thanks again

You are going to want to have at least 30 feet (10 meters) between you and your neighbors. If you accidentally (or foolishly) get into halogenated hydrocarbons, then you could kill yourself and your neighbors if you do not have a lot more space. Also, your unit could catch on fire or blow up. So, you want to work on handling the exhaust first, before you turn on your next unit. So, re-read this thread.

Thanks for your responses guys.

Regarding pressure relief valves (PRV) - on a boiler the PRV must be exhausted straight up to a minimum height to get the exhaust steam away from people. Not sure of minimum height required but ours must go up about 5m?. I was just thinking about what would happen if there was a blockage in the cracking system and one of these PRV actually opened - look out anyone who is standing nearby I expect we would have an explosive flame exiting the PRV. So...

1) We need to pipe the exhaust from a PRV away from our immediate work area.
2) Q - should we put a flame arrestor in the exhaust pipe of the PRV to ensure no flash back into the cracking reactor?

It could be said the PRV can be plumbed into a low temperature condenser to avoid the explosive flame, but we have seen on this forum operators caught by surprise with problems in or close to the hot reactor. So I think it needs to go there.

Have a cracker of a day guys.

Col

Yes, you will want to vent your pressure relief valve in a safe direction. Up is good, or I just plan to run it out the exhaust via a T.

[cornishscrimper]

Mistaken ID

Thanks BB and Excalibur for your replies. I know it must be time consuming and even a little annoying at times, being asked questions that are on the thread.
BB I like your story about taking over the 'junk' I would have done the same.

I think you have got me a little mixed up with someone else regarding having / running a unit, I have not even started yet, other than gathering a few bits and a vague solidworks drawing. I have already read the forum right through and am on second read taking detailed notes this time. But thankyou for all the safety warnings . Do not worry I am not a gung - ho '' stuff a can with bags and seal it , stuff a pipe and in the top and cook it and look mum I am making fuel''. I think there should be a disclaimer to enter this site ! Seeing what some people have attempted.
Back to study...

[Beyond Biodiesel]

Thanks BB ...I think you have got me a little mixed up with someone else regarding having / running a unit, I have not even started yet, other than gathering a few bits and a vague solidworks drawing. I have already read the forum right through and am on second read taking detailed notes this time. But thankyou for all the safety warnings . Do not worry I am not a gung - ho '' stuff a can with bags and seal it , stuff a pipe and in the top and cook it and look mum I am making fuel''. I think there should be a disclaimer to enter this site ! Seeing what some people have attempted.
Back to study...

You are correct, there are so many people posting here, and a lot of it, is precisely what you described. So, I tend to err toward preaching safety. Sorry.

[lowriderzzz]

another idea for efficient heating

Hi guys! Today I cam up with another idea for how the heat absorption be made more efficient and I came up with the following design (on the picture below).


I saw on Blest bigger units the retort is actually laying horizontal so why not get heated both ends internally.

Soon my father is coming and we will build an experimental unit and I'll start sharing data.

Can you give suggestions please what is best to experiment with initially.

I will start with different types of plastic (PP and HDPE), the with temperature, then with catalyst and different combinations between those too.

Cheers: Ivo

[cornishscrimper]

no needto apologise

You are correct, there are so many people posting here, and a lot of it, is precisely what you described. So, I tend to err toward preaching safety. Sorry.

I think you guys are doing a marvellous job and there is no need to apologise to me. Safety needs to be number one job in this pursuit !

[Excalibur]

Hi guys! Today I cam up with another idea for how the heat absorption be made more efficient

I saw on Blest bigger units the retort is actually laying horizontal so why not get heated both ends internally.

Your design shows feedstock filled to the top hatch!! Jetijs warned of overfilling and showed graphic pictures !! Leave some gap at the top of the retort!!

Dual heat sources has some advantages. The electric elements can be thermostat controlled very easily and the flame can bring the retort up to temperature. Please be careful that you never get into a boil-over situation because that could lead to plugging of the pipework like Jetijs pics.
You need the patience of a Saint. Watch the bubbler and be aware of the amount of gas flow there is ...or isn't.

[mjohnson1]

I finally got around to testing out a batch of my new catalyst and I wanted to post my results here-

Conversion rate:73% to liquid fuel (have no way to measure noncondensable gasses but significant "smoke" was coming out)

Fuel composition-
89.5% gasoline
8.9% kerosene
1.6% diesel

No waxes.

This is far from ideal as I want a conversion rate to fuel of ~90% with the remaining ~8-9% to be gasses to power the unit.

[lowriderzzz]

Your design shows feedstock filled to the top hatch!! Jetijs warned of overfilling and showed graphic pictures !! Leave some gap at the top of the retort!!

Dual heat sources has some advantages. The electric elements can be thermostat controlled very easily and the flame can bring the retort up to temperature. Please be careful that you never get into a boil-over situation because that could lead to plugging of the pipework like Jetijs pics.
You need the patience of a Saint. Watch the bubbler and be aware of the amount of gas flow there is ...or isn't.

Sure i'll not overflow it. Filling the half or perhaps 1/3 of it will be OK right ?

By the way how do you measure the progress of the process ? How do you exactly when do you shut the system, since there will lots of exhaust gases initially perhaps that will not be able to get weight measured in case i want to measure the amount of weight going out of the retort ???

[cornishscrimper]

Sure i'll not overflow it. Filling the half or perhaps 1/3 of it will be OK right ?

By the way how do you measure the progress of the process ? How do you exactly when do you shut the system, since there will lots of exhaust gases initially perhaps that will not be able to get weight measured in case i want to measure the amount of weight going out of the retort ???

I know the diagram is probably a 'schematic' rather than a plan, but just to test my own thinking - would not making the top large diameter feed tube longer help with the design? Just asking to see if I am getting the principles right. This a question for interest only.