How to turn plastic waste into diesel fuel cheaply

[mjohnson1]

I borrowed two smaller electric home handyman sized garden chippers. Both of those were absolutely pathetic at plastic. Actually they didn't chip branches that well either. Studying the problem I identified a couple of shortcomings. Firstly the blade type wasn't suited to the task and secondly they were well short of enough power. I've worked on proper industrial plastic chippers to appreciate the difference. Their cutters were mounted on a shaft that resembled a crankshaft! Metal detectors were an important part of running them as even a small piece of steel could do untold damage in a split second..
The pic in BB's link hasn't been tested on plastic that I seen but at least it would have enough power.
One possible way to get a chipper that's up to the task would be to watch out for industrial auctions selling redundant plastics factory equipment. Buy one with or without motor as it would be 3 phase anyway, then fit up a large stationary engine or perhaps a car engine to drive it.
Lastly try to get a machine that would swallow a whole 20L cubie at once otherwise you'll have to slit them first on a bandsaw. I tried cutting cubies once on a circular saw and I don't recommend it.

There are two types of shredders that are predominantly used for plastics. There is the single shaft type shredder and a dual shaft shredder. The single shaft looks like its the best choice for our plastic types. I'm sure you could build one with a welder and some steel pipe and weld on cutting heads. If you look at the design of them i'm sure you could replicate it and make a smaller version.

I have a dual shaft shredder I bought from a gentleman in Germany. It's small, 6 inches long and 3 inches wide. It's great for shredding any household plastics and considering the quality of the materials it wasn't too expensive.

[CRMoore]

Chloride abundance, PVC & dioxin

[QUOTE=Tplane37;225686]I was focused more on the temperatures achieved in incineration than the reset of the process. Though pyrolysis differ from incineration in several aspects, one basic concept exists in both: high temperatures. I was unable to find anything directly related to neutralizing dioxines in the pyrolysis process.

A bit from a dioxin web site

As one of the most abundant chemical entities in the crust of the Earth, chloride is found in numerous organic5 (e.g., PVC) and inorganic compounds (e.g., salts), both natural and synthetic. Many of these compounds are present in waste. (Waste may also contain small amounts of dioxins and furans that are destroyed during properly designed combustion.) In fact, ordinary waste contains more than a million times more chloride than is necessary to produce the quantity of dioxins and furans generated in a modern waste combustor. Only a small fraction of the chloride present in waste reacts to form dioxins and furans. Even air from a combustor may contain nearly 20 times more chloride than is necessary to produce typical amounts of dioxins and furans from waste combustors.6 That is why removing chloride contributed by PVC does not impact dioxin and furan formation when actual mixed waste is burned, and this has been shown in numerous scientific studies.

However since burning over 600 C for over 2 seconds with turbulence is noted to adequately destroy dioxins and furans you should be good if fuel contained until such combustion.

[fibuslitero]

Here is a domestic unit for shredding:

https://www.youtube.com/watch?v=xOw2zNY9lg0

This one is stronger but I find it a bit dangerous:

https://www.youtube.com/watch?v=Nmbzks1RXBM

[imakebiodiesel]

Would simply burning the gas in a conventional gas cooking ring be sufficient? A gas cooking ring flame is certainly above 600C but would the flow of gas through it be too rapid?
The second shredder shown above is a much better design although I agree it needs proper guards and a hopper to be safe. The slow speed avoids the build up of heat that will melt the plastic and also means that the shafts and cutters do not have to be perfectly balanced. The cutters could be cut from mild steel by hand ( laborious) or with a laser cutter ( expensive). Case hardening would make them last a long time

[Beyond Biodiesel]

I was focused more on the temperatures achieved in incineration than the reset of the process. Though pyrolysis differ from incineration in several aspects, one basic concept exists in both: high temperatures. I was unable to find anything directly related to neutralizing dioxines in the pyrolysis process.

A bit from a dioxin web site

As one of the most abundant chemical entities in the crust of the Earth, chloride is found in numerous organic5 (e.g., PVC) and inorganic compounds (e.g., salts), both natural and synthetic. Many of these compounds are present in waste. (Waste may also contain small amounts of dioxins and furans that are destroyed during properly designed combustion.) In fact, ordinary waste contains more than a million times more chloride than is necessary to produce the quantity of dioxins and furans generated in a modern waste combustor. Only a small fraction of the chloride present in waste reacts to form dioxins and furans. Even air from a combustor may contain nearly 20 times more chloride than is necessary to produce typical amounts of dioxins and furans from waste combustors.6 That is why removing chloride contributed by PVC does not impact dioxin and furan formation when actual mixed waste is burned, and this has been shown in numerous scientific studies.

However since burning over 600 C for over 2 seconds with turbulence is noted to adequately destroy dioxins and furans you should be good if fuel contained until such combustion.

Would simply burning the gas in a conventional gas cooking ring be sufficient? A gas cooking ring flame is certainly above 600C but would the flow of gas through it be too rapid?

Yes, it has also been shown that dioxins will form naturally in a forest fire, due to the presence of halons, such as chlorine, which is abundant. So, it suggests that all pyrolysis units are going to produce dioxins, no matter what, so wearing proper safety equipment when handling the equipment and its products is essential; and having a well-designed condenser system is going to condense out more of the distillates. Remember, the dioxins, etc. are high melting point, so they are going to drop out rather easily, verses becoming an inhalation hazard.

However, all any of you have to do is try processing some chlorinated hydrocarbon, such as TCE, and you will never forget the stink that will come out of the exhaust of your pyrolysis unit, or the stink of your distillates.

Now, that I am back to just distilling WMO, the smell of my distillates is like perfume compared to the stink of chlorinated hydrocarbon distillates.

[mjohnson1]

Here is a domestic unit for shredding:

https://www.youtube.com/watch?v=xOw2zNY9lg0

This one is stronger but I find it a bit dangerous:

https://www.youtube.com/watch?v=Nmbzks1RXBM

I purchased the one in the 2nd video. It works great but gets bogged down with LDPE.

[Beyond Biodiesel]

I purchased the one in the 2nd video. It works great but gets bogged down with LDPE.

Thanks mjohnson1, for the video links above. Pyrolysis of plastics would be assisted by making, or purchasing, a shredder to grind waste plastics into small pieces so that they take up less room in the retort upon loading. Both of the videos linked above show homemade plastic shredders, but they both need a larger hopper if they are going to be used for shredding enough plastic for use in even a small retort.

[imakebiodiesel]

I agree that it is unlikely that dioxins would be produces in the anerobic atmosphere of a pyrolyser but they are so toxic it is worth considering measures to deal with them. Dioxins are not soluble in water but they are highly soluble in fats and oils. This is what makes them so dangerous, they lie undissolved on the surface of the soil for years but once ingested the are absorbed by human fats.
If the uncondensable gases were bubbled through vegetable oil dioxins would be absorbed. The oil could be periodically replaced and burned at a high temperature

[fibuslitero]

Imakebiodiesel:
What you say about capturing dioxins through vegetable oil sounds very very interesting
Since I am making biodiesel at a small scale it would be interesting to research about transesterification of oils with dioxins and see percentages in biodiesel and glycerin.
Thank you.

I agree that it is unlikely that dioxins would be produces in the anerobic atmosphere of a pyrolyser but they are so toxic it is worth considering measures to deal with them. Dioxins are not soluble in water but they are highly soluble in fats and oils. This is what makes them so dangerous, they lie undissolved on the surface of the soil for years but once ingested the are absorbed by human fats.
If the uncondensable gases were bubbled through vegetable oil dioxins would be absorbed. The oil could be periodically replaced and burned at a high temperature

[Beyond Biodiesel]

I agree that it is unlikely that dioxins would be produces in the anerobic atmosphere of a pyrolyser

This is not true, because polycyclic aromatic hydrocarbons arethe product of cracking halogenated hydrocarbons, and are not affected by whether oxygen is present or not.

but they are so toxic it is worth considering measures to deal with them. Dioxins are not soluble in water but they are highly soluble in fats and oils. This is what makes them so dangerous, they lie undissolved on the surface of the soil for years but once ingested the are absorbed by human fats.
If the uncondensable gases were bubbled through vegetable oil dioxins would be absorbed. The oil could be periodically replaced and burned at a high temperature

Dioxins, and other Dioxin-like compounds are high melting point, so as long as the condensers in a pyrolysis unit are effective, then they are going to remove the Dioxin-like compounds in the flu-gas stream long before the water bubbler.

Imakebiodiesel:
What you say about capturing dioxins through vegetable oil sounds very very interesting
Since I am making biodiesel at a small scale it would be interesting to research about transesterification of oils with dioxins and see percentages in biodiesel and glycerin.
Thank you.

The transesterification process that produces biodiesel out of esters should have no effect upon Dioxin-like compounds. You may find reading this forum thread useful Toxic by-products of pyrolysis

[karan]

can i use wooden logs to heat up the container filled of chopped plastic? in place to electric current or liquid burners. ??????

[karan]

can i use wooden logs to heat up the solid chopped plastic waste?

[Excalibur]

can i use wooden logs to heat up the container filled of chopped plastic? in place to electric current or liquid burners. ??????

Yes. My first 3 test runs used wood to fire the retort. It has some advantages. Wood can be free, also coal could be used and has great heating capability. Give some thought about controlling the air supply to regulate the fire because the retort temperature needs to be kept within a tight range.
Hope this helps.

[imakebiodiesel]

The idea about veg oil was just a bit of brainstorming but I agree that proper condensers will deal with dioxins. Converting dioxin contaminated veg oil into biodiesel would have no effect on the dioxins.

I have just finished constructing my latest scrubber for my new reactor. It consists if 3 x 20litre bubblers in series.
The first contains plain water and has a ph meter built in to detect acidification. This should deal will HCl and possibly HFl gas.
The second is a solution of potassium hydroxide which should neutralize any acidic gas.
The third is a solution of sodium hypochlorite to neutralize any hydrogen cyanide.
The scrubbed gas then passes through a flash back arrestor and then is burned in a gas cooking ring.
As you can see Im a belt and braces kind of a guy.

A scrubber like this does not mean you can throw any old plastic into the retort however. It just means that if small amounts of the wrong plastics do get in then the they should not cause a danger to the operator.
I still wear a charcoal filter face mask when working on the initial cleaning and loading.

[Beyond Biodiesel]

The idea about veg oil was just a bit of brainstorming but I agree that proper condensers will deal with dioxins. Converting dioxin contaminated veg oil into biodiesel would have no effect on the dioxins.

I have just finished constructing my latest scrubber for my new reactor. It consists if 3 x 20litre bubblers in series.
The first contains plain water and has a ph meter built in to detect acidification. This should deal will HCl and possibly HFl gas.
The second is a solution of potassium hydroxide which should neutralize any acidic gas.
The third is a solution of sodium hypochlorite to neutralize any hydrogen cyanide.
The scrubbed gas then passes through a flash back arrestor and then is burned in a gas cooking ring.
As you can see Im a belt and braces kind of a guy.

A scrubber like this does not mean you can throw any old plastic into the retort however. It just means that if small amounts of the wrong plastics do get in then the they should not cause a danger to the operator.
I still wear a charcoal filter face mask when working on the initial cleaning and loading.

imakebiodiesel's bubbler and scrubber setup sounds very thorough. I plan to make a similar scrubber for my pyrolysis unit.

Additionally, now understanding that copper components in the high temperature zones can promote the formation of Dioxins, and other Dioxin-like compounds I ordered stainless steel plumbing fittings to replace all of the brass and copper fittings I was using in the high temperature zones of my pyrolysis unit.

Last night I did spend some time pondering the likelihood of salt migrating into a pyrolysis unit along with waste plastic, especially in a coastal region, which is high. The question that occurred to me is, how likely is salt [sodium chloride (NaCl)] going to crack into free Na and Cl in a pyrolysis unit at 800F (425c) when the hydrocarbons are cracking? I think it is unlikely, but I do not know.

If it is more likely that that NaCl will require higher temperatures to crack, then Dioxins, and other Dioxin-like compounds are not more likely to form in a pyrolysis unit, if the temperatures are kept at or below 800F (425c), and Halogenated Hydrocarbon are avoided in the source material for the pyrolysis unit. This would require tighter control of the temperature of the pyrolysis unit. However, I agree with imakebiodiesel, it is possible that some Halogenated Hydrocarbon will find its way into a pyrolysis unit due to the logistics of recycling.

It is also just as likely that even if there are no Halogenated Hydrocarbon in the retort, that Dioxins, and other Dioxin-like compounds will form anyway. Therefore it is wise for the operator of a pyrolysis unit to wear proper safety equipment when operating a pyrolysis unit.