How to turn plastic waste into diesel fuel cheaply

[Beyond Biodiesel]

Pravin, After nearing becoming overwhelmed with Hydrogen Chloride gas (HCL) I stopped my pyrolysis project and spent a few weeks studying the Toxic by products of pyrolysis and how to mitigate them.

Polyethylene (abbreviated PE) or polythene (IUPAC name polyethene or poly(methylene)) is the most common plastic. The annual production is approximately 80 million metric tons.[1] Its primary use is within packaging (plastic bag, plastic films, geomembranes, containers including bottles, etc.). Many kinds of polyethylene are known, with most having the chemical formula (C2H4)nH2. Thus PE is usually a mixture of similar organic compounds that differ in terms of the value of n.

Toxic by products of pyrolysis
Since Polyethylene is no a halogenated hydrocarbon, then the by products of pyrolysis are going to be just petroleum vapors, which are toxic, and flammable; however, they can be effectively handled with simple condensation via a succession of air, water and ice cooled condensers.

Physical properties
Polyethylene is a thermoplastic polymer consisting of long hydrocarbon chains. Depending on the crystallinity and molecular weight, a melting point and glass transition may or may not be observable. The temperature at which these occur varies strongly with the type of polyethylene. For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range 120 to 130 °C (248 to 266 °F). The melting point for average, commercial, low-density polyethylene is typically 105 to 115 °C (221 to 239 °F).

I have just stated a thread on my forum for discussing the toxic by products of pyrolysis. You can find it at the link below.
Toxic by products of pyrolysis

[imakebiodiesel]

Pravin, the short answer is no. both pet and polyester are unsuitable for pyrolysis into fuels.
Sy, welcome to the forum. Would like to hear more details about your small scale experiments. What temperatures, types of plastics etc. I have performed 65 1kg batches in my small pyrolyser and I am still learning new stuff all the time. Im almost finished my larger unit 50-75 kg and hope to be operational by Christmas, would have been sooner but paid work comes first.

[mjohnson1]

beyond bio. i have huge waste of recycled pet & polyester film ( used sun control film 4 auto ). Is it possible to proces them safely commercialy. pls reply.

Yes it could be done safely on a commercial scale however the yields from PET are not good. If you look at the chemical makeup of PET it is much higher in carbon than the other recommended plastics for pyrolysis. Therefore, you will not get good fuel yields.

The oxygen has to be taken care of otherwise you have a big disaster waiting to happen. Terephthalic acid will also be formed which can cause problems. There is a wealth of information on PET pyrolysis if you look around.

[Gints]

Pyrolysis plant

Hi All,

I would like to share with you the info that the pyrolysis unit you can see in the picture will be ready for first tests at the beginning of January, 2013. I will share information on this thread about the capabilities of this plant with pictures, videos and test results. The plant will be installed at landfill area where they have plastic sorting. The capacity of this test plant we will plan approx 200Ltr or 100kg per cycle. Dimensions - 1,5mx2,0x3,0m (without lift beam ccinstruction). As reactor material we use thermal resistant stainless steel with very good insulation from outside.

Best regards.

[kamal11]

Hello Jetijs,

you really did a fantastic job and i have no word to say anything i am really very impressed with your work.

[imakebiodiesel]

hello Gints,

your reactor looks very well thought out. The picture is very small and is hard to make out. It appears to be a cylindrical retort heated by an oil or gas burner with a reflux chamber above. the output from the first 2 condenser is returning to the retort for recracking. There is another vessel and a set of condensers at the back, what are they for?

[Gints]

Pyrolysis unit

hello Gints,

your reactor looks very well thought out. The picture is very small and is hard to make out. It appears to be a cylindrical retort heated by an oil or gas burner with a reflux chamber above. the output from the first 2 condenser is returning to the retort for recracking. There is another vessel and a set of condensers at the back, what are they for?

Hi,

There will be following production steps - reactor, refluctor, heat exchanger, product tank 1, heat exchanger, product tank 2, bubbler, the rest gas goes to burner chamber. So there are will be two stages if it is necessary to go further with condensing process.

[Beyond Biodiesel]

The thermal decomposition of Polyethylene (PETE, PET, HDPE, LDPE) can lead to the production of terephthalic acid; however, studies shows terephthalic acid is of low order of toxicity, and it is non-irritating to the skin and eyes.
www.inchem.org/documents/sids/sids/100-21-0.pdf

[mjohnson1]

The thermal decomposition of Polyethylene (PETE, PET, HDPE, LDPE) can lead to the production of terephthalic acid; however, studies shows terephthalic acid is of low order of toxicity, and it is non-irritating to the skin and eyes.
www.inchem.org/documents/sids/sids/100-21-0.pdf

The problem with terephthalic acid is that it sublimates below 300C which can gum up the pipes and reactor.

[imakebiodiesel]

Gints, those views are much better. With that out fit you should have good control of the quality of the final products. What fuels do you intend to produce?
I can confirm from bitter experience that terephthalic acid solidifies in condensers. In my experiments with PET I almost blew my self up. About half way through a 1kg batch my bubbler suddenly stopped, always a warning sign. While I was trying to figure our what had happened, I suspected a leak, the steel pipe between the reflux and the condenser split open with a loud crack. The welded joint had failed under pressure, which was just as well because if my welding has not failed the pressure could have built up further and my reactor could have exploded.
Later when I took the outfit apart to repair it the pipe and the condenser was completely clogged with what looked like tar. Terephthalic acid may not be very toxic but that does not mean it is not dangerous.

[Beyond Biodiesel]

Just out of curiosity, imakebiodiesel, at the time you plugged your pyrolysis unit trying to crack PET, how large was your retort, and what diameter was the pipe that plugged?

[mjohnson1]

Gints, those views are much better. With that out fit you should have good control of the quality of the final products. What fuels do you intend to produce?
I can confirm from bitter experience that terephthalic acid solidifies in condensers. In my experiments with PET I almost blew my self up. About half way through a 1kg batch my bubbler suddenly stopped, always a warning sign. While I was trying to figure our what had happened, I suspected a leak, the steel pipe between the reflux and the condenser split open with a loud crack. The welded joint had failed under pressure, which was just as well because if my welding has not failed the pressure could have built up further and my reactor could have exploded.
Later when I took the outfit apart to repair it the pipe and the condenser was completely clogged with what looked like tar. Terephthalic acid may not be very toxic but that does not mean it is not dangerous.

Scary stuff.

FeOOH can be used as a catalyst to decompose the terephthalic acid.

[imakebiodiesel]

The batch size was 1kg and the exit pipe was 1 inch. At the time my pressure relief valve was positioned at the top of my reflux column so it got blocked as well. After that incident I fitted the pressure relief valve on it own pipe direct to the retort, a much safer arrangement.
Im aware that there are ways to avoid the problems of terephthalic acid but they are a fair bit more expense and trouble. Clean PET currently is worth 940 euros a metric ton here in Europe which means that if you subtract the tax on fuel, raw unprocessed PET is worth more than the fuel you could make from it.
Soiled, unsorted PE,PP and PS on the other hand is worth almost nothing and is ideal for our process. Thats why my short answer to Pravins question was no.

[pravin]

PET / Polester

Even i faced a similar problem. My entire condenser tubes were choked forming a white powdery kind of layer on all the condenser and accs. Did u find something similar. In that case how to recover or remove terephthalic acid, any idea.
Secondly IMD i get the soiled and cleaned PE,PP and PS at throwaway price. Dats the reason i am considering commercial pyrolysis.

[Gints]

Gints, those views are much better. With that out fit you should have good control of the quality of the final products. What fuels do you intend to produce?
I can confirm from bitter experience that terephthalic acid solidifies in condensers. In my experiments with PET I almost blew my self up. About half way through a 1kg batch my bubbler suddenly stopped, always a warning sign. While I was trying to figure our what had happened, I suspected a leak, the steel pipe between the reflux and the condenser split open with a loud crack. The welded joint had failed under pressure, which was just as well because if my welding has not failed the pressure could have built up further and my reactor could have exploded.
Later when I took the outfit apart to repair it the pipe and the condenser was completely clogged with what looked like tar. Terephthalic acid may not be very toxic but that does not mean it is not dangerous.

Hi,

With this unit I will plan to crack only PE, PP, LDPE, HDPE materials. Also in the pressure sensor will be installed in reactor. When the pressure sensor is triggered a rise in pressure system, the entire system will be switched off.
Thanks for the idea you notice about the bubbler. I think somewhere can be kind of gas meter installed. In cases where the meter stops, the unit also will be switched off.
Best regards.