How to turn plastic waste into diesel fuel cheaply

[wheels]

I think Col is wanting to run the Fuel in a Petrol engined Vehicle, not Diesel.

[Col]

Great, thanks guys. I drive a petrol at the moment but have diesels at work so can use the fuel either way. Thank you for your feedback guys! Looking forward to using this free fuel

[skymagic]

Hi.....i've been following u guys for sometime now, read a good measure of the pages (not all) and I appreciate and respect all your effort.....really u guys are great... thanks....I have some questions that I need your help with..... they might sound stupid but please pardon me

the uncondensable gas that leaves the bubbler finally what is it made off??? is it methane? buthane? or hydrogen?

2) how well does the diesel work when mixed with regular diesel ? say at a ratio of 1:1

[Col]

types of metal - boiler plate

Hey guys.
Years ago at work while digging a trench for a phone line we hit steel plate and pulled it out with the truck. It was a 4.8m x 1.2m x 10mm sheet of boiler plate. We asked the structural engineers next door to drill some 20mm holes around the perimeter so we could use it for a job. Apparently they couldn't penetrate it cold and had to heat it really hot (don't remember what temperature) before their drills would work on it. We still have the sheet and I was thinking boiler plate would be great to use to make the retort on the next system after proving my small pilot plant.
I am doing the welding myself on my small plant but would contract a boiler maker for the next one. Does anyone know what considerations need to made when using boiler plate in this application?
Thanks

[Excalibur]

Hi.....i've been following u guys for sometime now, read a good measure of the pages (not all) and I appreciate and respect all your effort.....really u guys are great... thanks....I have some questions that I need your help with..... they might sound stupid but please pardon me

the uncondensable gas that leaves the bubbler finally what is it made off??? is it methane? buthane? or hydrogen?

2) how well does the diesel work when mixed with regular diesel ? say at a ratio of 1:1

The noncondensable gases are a mixture if I recall. It is highly flammable and a valuable heat source. See member: Wheels posts on the subject of composition, probably within the last 12 months.
There are numerous reports of this diesel being used as fuel on this forum even going back to the 1st pages initiated by Jetijs. Blending with regular diesel is fine and I'd expect a performance improvement because the bought stuff has cetane improvers whereas our DIY stuff is raw. However with our fuel we can optionally target slightly higher specific gravity so it is slightly more energy dense. Preferable for our product would be an additive package containing a cetane enhancer, deposit controller and oxidation stabilizer.
Continue the reading through, it's the easiest best way to learn and as a bonus it's free. If you're like me, you'll need to re-read some parts a few times to get it to sink in. I suggest dedicate 30min a day to reading and call it an investment.

[wheels]

Hi.....i've been following u guys for sometime now, read a good measure of the pages (not all) and I appreciate and respect all your effort.....really u guys are great... thanks....I have some questions that I need your help with..... they might sound stupid but please pardon me

the uncondensable gas that leaves the bubbler finally what is it made off??? is it methane? buthane? or hydrogen?

2) how well does the diesel work when mixed with regular diesel ? say at a ratio of 1:1

As they say, the only stupid question is the one not asked. This Forum is here for Questions and answers and everyone is at different levels in experience. So don't worry about thinking your question may be stupid. Because I am sure the answers will help others as well as yourself.

The Gas output, which is called the "Off Gas", is in fact an interesting question. Mainly it is Hydrogen. But other components are present and what and how much of the what depends on several things.
The Off Gas make up is why the importance of specific Plastics being pyrolized need to be adhered to. PP and PE plastics are the safest as far as the chemicals being released int he Gas. Mainly Hydrogen and a little Methane. However, it does also depend on Retort Temperature and if any catalyst is used and of course, the design of the plant. Design and temperature equates to how much cracking takes place. High temperatures produce a lot more non-condensable gasses. At the extreme end, Propanes, Propenes and can be created. But unlikely in most backyard plants as you need very high temperatures to produce any of them in quantity.
Any other plastic types can produce extremely deadly toxic and corrosive Gasses. The main three are Hydrogen Chloride (Hydrochloric Acid in Gas form), Hydrogen Cyanide and Chlorine Gas. So great care needs to taken that the wrong plastic types do not enter your Feedstock.

[wheels]

Hey guys.
Years ago at work while digging a trench for a phone line we hit steel plate and pulled it out with the truck. It was a 4.8m x 1.2m x 10mm sheet of boiler plate. We asked the structural engineers next door to drill some 20mm holes around the perimeter so we could use it for a job. Apparently they couldn't penetrate it cold and had to heat it really hot (don't remember what temperature) before their drills would work on it. We still have the sheet and I was thinking boiler plate would be great to use to make the retort on the next system after proving my small pilot plant.
I am doing the welding myself on my small plant but would contract a boiler maker for the next one. Does anyone know what considerations need to made when using boiler plate in this application?
Thanks

Interesting. How did you know it was boiler pate? Normally Boiler plate is just a high quality Wrought Iron, which is fairly soft and actually has reasonably good corrosion resistance when in contact with Boiling water. I wonder if it could have been some kind of Alloy like a Stainless Steel, which can still rust when buried, because contamination from Iron on the soil and lack of oxygen can cause it to rust. So it then looks like ordinary steel plate. But an interesting thing can happen with Alloys with age. It is called Precipitation Hardening. Normally it is done with heat to speed up the process, but some Alloy steels have been known to "improve" when left for many years. Otherwise I really don't know of anything that you would find as a Plate that would be so hard to drill.
Some time in the future, I will be experimenting with different metals, but at the moment, I have come to the conclusion that the cheapest method is to use Mild steel, expect it to corrode eventually and replace it. There are some special SST's that have great resistance to heat and corrosive products, but they are expensive and difficult to work with, so getting a Retort built from such materials can be expensive.

[Col]

hmmm, ok thanks. I don't know for sure if it was boiler plate, the engineers suggested it could be, but they were not particularly expert engineers, did big stuff but couldn't be relied on to know everything... can any of us?
It wasn't dead flat, it had a lot of lumps on it, like slugs crawling over it, and it was corroded. We took at it with angle grinders to remove the worst of the lumps and it took a lot of work, grinding discs and time to get through the few lumps we did grind down. I didn't recognise it as stainless steel when grinding it.
But point taken, stick to the common mild steel. Thanks.

[Col]

Comments assuming you are using standard series condenser setup: 60L tank is small for 1000L batch so given this is the case, diesel will be removed before it has had sufficient time to bleed off the lighter volatiles. Therefore some further processing of the removed diesel will likely be necessary. My tank is 500L.

Do you think is it the throughput to holding tank volume ratio that is key here in getting the lighter fraction to evaporate out of the diesel before the diesel is drawn off, or do you think it is the throughput to available surface area for evaporation ratio that is more important? I am thinking of using a 250mm diameter horizontal round pipe (could be 1m long, could be 6m long, just so long as it is kept at the right temperature) - the condenser feeds into one end, the pipe level is kept half full, the condensate flows from one end to the other and out a drain pipe which turns up to a tap at the half full point. The drain pipe could be run back along the length of the 250mm pipe without insulation for cooling before exit. This way achieves a high surface area to volume ratio which I believe is important to efficient vaporisation and identified as the ideal fill point in lab set ups.
Col

[wheels]

Do you think is it the throughput to holding tank volume ratio that is key here in getting the lighter fraction to evaporate out of the diesel before the diesel is drawn off, or do you think it is the throughput to available surface area for evaporation ratio that is more important? I am thinking of using a 250mm diameter horizontal round pipe (could be 1m long, could be 6m long, just so long as it is kept at the right temperature) - the condenser feeds into one end, the pipe level is kept half full, the condensate flows from one end to the other and out a drain pipe which turns up to a tap at the half full point. The drain pipe could be run back along the length of the 250mm pipe without insulation for cooling before exit. This way achieves a high surface area to volume ratio which I believe is important to efficient vaporisation and identified as the ideal fill point in lab set ups.
Col

I use smaller tanks and they are filled with Stainless Steel swarth from the Lathe. This allows plenty of surface area for the condensates to condense out on, but the tank is kept at temperature. So only the fractions of the required weight will condense out and the rest of the vapor flows on through to the next vessel.

[Excalibur]

Do you think is it the throughput to holding tank volume ratio that is key here in getting the lighter fraction to evaporate out of the diesel before the diesel is drawn off, or do you think it is the throughput to available surface area for evaporation ratio that is more important? I am thinking of using a 250mm diameter horizontal round pipe (could be 1m long, could be 6m long, just so long as it is kept at the right temperature) - the condenser feeds into one end, the pipe level is kept half full, the condensate flows from one end to the other and out a drain pipe which turns up to a tap at the half full point. The drain pipe could be run back along the length of the 250mm pipe without insulation for cooling before exit. This way achieves a high surface area to volume ratio which I believe is important to efficient vaporisation and identified as the ideal fill point in lab set ups.
Col

In my opinion evap'ing light fractions from diesel is more about the balance between temperature and residency time. Using a higher temperature will shorten residency time while a lower temperature will lengthen it. In a continuous production plant a diesel holding vessel that is small will inevitably mean the product will be pumped out prematurely meaning any residual light fractions will need to be extracted later.
Consider this example: Diesel vessel is held at say 80°C. When it becomes full the contents is pumped out to side tank where it's dropped to say 50°C. It will still continue to release light fraction but at a slower rate and continue to fall with the temperature decline. One workaround to continue pulling off the light fractions at a good pace would be applying a vacuum which reduces vapor pressure and boiling point.
My preference would be to have the diesel tank with sufficient volume to accommodate the entire run of diesel production.

[wheels]

In my opinion evap'ing light fractions from diesel is more about the balance between temperature and residency time. Using a higher temperature will shorten residency time while a lower temperature will lengthen it. In a continuous production plant a diesel holding vessel that is small will inevitably mean the product will be pumped out prematurely meaning any residual light fractions will need to be extracted later.
Consider this example: Diesel vessel is held at say 80°C. When it becomes full the contents is pumped out to side tank where it's dropped to say 50°C. It will still continue to release light fraction but at a slower rate and continue to fall with the temperature decline. One workaround to continue pulling off the light fractions at a good pace would be applying a vacuum which reduces vapor pressure and boiling point.
My preference would be to have the diesel tank with sufficient volume to accommodate the entire run of diesel production.

As one or two have found, the Cracking and Distillation is very complex. Temp and R Time both have a factor in Cracking. Even though the Fractions have passed the stages of Retort and then Reflux and are now in a much lower temperature environment of the first Still Pot, some Fractions will continue to Crack into the more unwanted unsaturated type Fractions and much lighter fractions are often broken into non condensable Gasses. My Pots have just been re fitted so they can continuously drain off the condensed liquids as they are produced, so as to get the Fractions out of the heat as quickly as possible. This should allow the production of a more accurate range of fractions in each Pot an hopefully allow for a far more stable end product. I will let you know the result end if this week, as the Plant should be running again early in the Week.

[Excalibur]

It's good to try things and test theories because without that you struggle to learn better ways of production. For that matter talking and bouncing ideas around is a wonderful way of finding solutions.

In this case it might be an advantage not keep the diesel at temperature for the duration of the run (8-12hr) because prolonged exposure to heat may encourage more oxidation. Better could be to extract light fractions quickly then quench/chill the diesel. From this point of view a row of diesel condenser vessels could be something to consider.
Consider this example of 3 vessels filled in 'rotation':
Vessel #1 is full and has a light vacuum applied to pull the last of the volatile fractions off.
Vessel#2 is in the process of being filled from retort production.
Vessel#3 is empty, awaiting its' turn.
Once vessel#2 is full, it has vacuum applied, feed gets diverted to vessel#3 and vessel#1 is pumped out, product quench/chilled to storage.
So at any one time, one vessel is empty, one is getting filled and one is under vacuum. More complicated would be valving and pipework. To help evaporation each vessel could optionally have an electric heater & thermostat.

Just a thought...

[wheels]

It's good to try things and test theories because without that you struggle to learn better ways of production. For that matter talking and bouncing ideas around is a wonderful way of finding solutions.
.

Absolutely and as they say, the only stupid question is the one not asked. I have the view that everyone, no matter what experience level, has something to give. Possibly because I am a Kiwi. Living in a very distant and remote Country, especially in earlier years before we had the world shrinking Internet and these kind of Forums, us Kiwis had a very practical view of making things work. We had no one to say it couldn't be done. We just figured out how to do it instead. I was brought up in that Era of how to make something work with the least of resources. Sadly our country has caught up to the rest of the World in being smothered by Red tape and Laws stopping us from doing things.

[wheels]

In this case it might be an advantage not keep the diesel at temperature for the duration of the run (8-12hr) because prolonged exposure to heat may encourage more oxidation. Better could be to extract light fractions quickly then quench/chill the diesel..

Yes. Although it is even more complex than just this. It is also the key reason why everyone's plant designs produce things differently. As in why one can have a nice clear Diesel produced and another ends up with Wax. Every single aspect affects the type of output. For the Amateur backyarder, the output is not so critical, as long as it is a usable Fuel. But if someone is after a specific product or quality of product, the design becomes more and more important and complex in both it's build and understanding in how to design and Build it. As a couple here on this Forum have discovered. It is also why I am very skeptical of the many companies that Build processing plants for sale. Not all of them have designs that actually work or work well.
What you produce as an output is reliant on many factors which I will list below.
Heat energy to melt the plastic. There is actually a required energy input required to pyrolyze plastics correctly. Even though plastics vaporize OK by just applying any decent heat source, there is actually a specific heating time to take Plastic through the various stages to vaporization. This allows for the most efficient energy input, the best Fuel quality output and the least non-condensable Gases produced. This is probably the most important of all aspects, because not enough heat, or too much heat can both be problems and be one of the main causes of Wax production. Wax can be produced in three ways. The temperature at time of Pyrolyzing being too high or too low can both create Waxes. As well as any further cracking on through the Plant, where residence times, which determines the cracking into what weight of Hydrocarbons, can also produce Waxes. Mostly though, too much heat can produce more non condensable gasses and we don't want to waste our Fuel turning into Gas.
Speed of pyrolysis is going to be determined by Spped of throughput and energy input.
Feedstock. This has a major affect on the output type, because what type of Plastic determines what Chain length is mostly produced at the very start of the cracking process. If you start with long chains, then reflux and Catalyst if used, is important to breaking those chains. But if you are starting with shorter chains, then Reflux time or temp could make the chains too short for the type of fuel you want and also produce more Gas.