How to turn plastic waste into diesel fuel cheaply

[Beyond Biodiesel]

I was simply referencing the OP. I have a 6 gallon (23L) retort, I put in 5 gallons (20L) of WMO, and get out 4.5 gallons (17L) of distillate. Therefore I do not need a 55-gallon (220L) retort to get 4.5 gallons (17L) of distillate. Not that I do not plan to make a 55-gallon (220L) retort so that I can process solids into liquid fuel. My point is, if you have access to WMO, then distill it, before bothering with shredding and pyrolyzing plastics, because a smaller retort makes for a simpler design.

[Tplane37]

Shredder

Has anyone come up with an innovative way to shred the plastics cheaply yet? It was talked about several pages back, but seems to have gone no further.

As Beyond Biodiesel was saying, volume-wise, it seems that we are wasting a lot of heat due to the excessive space taken up by the plastics in the retort. As mjohnson1 pointed out, the weight of your feedstock can vary drastically based on volume.

The best way I can think of to increase the weight per volume is to shred the plastics, as has been discussed off and on throughout this very informative thread. But with keeping in mind that whenever you shred anything, heat is going to be generated, and that heat can cause the plastics you are trying to shred to gum up the blades of a shredder. This is the issue I have come up with being the primary drawback of shredding plastics, and the option of sitting around for hours on end with a razor blade and scissors (or even the chainsaw mentioned earlier for splitting a mountain of plastic barrels) doesn't seem all that appealing either.

I have brought another guy on board with me to help figure out some various issues that may come up in the entire process, from acquisition of feedstocks, preparing feedstocks, to acquisition and assembly of the test units. We have both gasoline (petrol) and diesel fired equipment we intend to run off of the end products.

He mentioned using an old belt driven lawn mower deck with a custom cover built with safety guards in place. The cover would allow the user to manually feed the plastics through a tube and they would discharge out of the other end. For the larger plastic items like barrels, we are thinking a brush hog/field mower deck. I think the concept would work well for most of the plastics we acquire, but the wall thickness of the barrels has me concerned for feeding through the shredding unit. Another thing I think we would have to keep an eye on is keeping the mower blades sharp, I don't know how fast the blades will dull with plastics. We might even have to either heat or cool the unit to aid in the shredding process (I am thinking we'd have to cool it if anything). The purpose of using a belt driven deck is an additional safety feature... if the shredder clogs for any reason, the belt could slip to keep things from flying apart. If a shaft driven deck is used, a custom adapter would need to be built using a grade 5 or softer bolt as a shear pin to allow the shaft to "break loose" and spin freely if the shredder clogs up.

Thoughts?

[Excalibur]

Perhaps look at purchasing redundant plant from industry. Unless you happen to have 3phase power, a granulator could be repowered with a petrol motor but don't underestimate the HP required. The HP to drive these is bigger than most would think so what about a car engine for the task?
When you feed a cubie into one of these machines, you want that cubie to come off second best. No stalling. Trying to clear jammed plastic is a nightmare, so use big power and a big flywheel as well.
I worked on such machines at a plastics blowmold factory. All the granulators had metal detectors because a piece of steel would do a lot of damage to the blades quick smart.

[waterboost]

Chemist anywhere?

I have a major problem. My fuel, as I have posted, is beautiful and we have petrol in abundance but the last two days the fuel has been naughty.

Yesterday, as the machine was producing fuel, I took 4x 200 ml samples in seperate jars and left them on the shelf. The rest of the fuel was poured into two demijohns (4.5l)

The demijohns were both half full of fuel made previously, one amber coloured and one only slightly yellow (nice stuff!)

This morning one of the demijohns is solid with wax and the other is full of wax crystals...

So the fuel from yesterday has repolymerised along with the fuel we had previously??? However... the samples, kept seperate, are still clear as water!
It is about -1 degrees but even our worst diesel is ok until we freeze it (-20)

I'm gutted, I was using the last of the propane to make liquid fuels for my new oil burner... as the oil burner is fitted to my new, continuous, auger machine (not quite ready yet) we wanted to self fuel and close the loop.
(burner: X Series oil burner range | EOGB Energy Products Ltd)

Any ideas? I know it can be reprocessed (theoretically) but this is worse than when we did a whole batch of polystyrene.... now that did make jelly and wax...

The Reflux is kept below 200 degrees but can occasionaly spike at 220...

I keep thinking that this maybe similar to cooking, fresh coffee in a cold mug damages the oils in the drink, large bongs with a smoke chamber make the smoke tickley because the oils coalesce. Has the hot/fuel reacted with the cold fuel because of the rapid temperature change?

The samples kept seperate have not phase shifted into wax...

[Excalibur]

I seem to recall Jetijs having this problem with PE. At one stage he used clay catalyst. Another solution if I recall was to reduce the reflux temperature to... I'm thinking 150c.

post562
http://www.energeticforum.com/renewa...tml#post146172

post614
http://www.energeticforum.com/renewa...tml#post147106

[Beyond Biodiesel]

waterboost, it sounds like some heavier fractions have made it through your 220c refulx, which is to be expected. I would suggest just running your fuel samples back through your retort to re-fractionate them, and give the heavier fractions another chance to crack.

One of the problems I see in these various pyrolysis units is people are trying to get too much done with one condenser trap. I have about 7 condenser traps and I am planning on adding more. My reflux temperature is 400c, and my first trap operates at 300c, then 200c, then 100c, then 25c, then 0c with a few extra traps just for good measure.

When I do a pyrolysis run I get fluids in all of my traps. I have found wax slowly accumulating at points down to 25c, even though it should have dropped out at 300c.

[imakebiodiesel]

Waterboost, you put your finger on the problem yourself, repolymerization. Any polymerization reaction can ,given the right conditions, become a chain or radical reaction. So the reaction which began in your fresh fuel spread into the old fuel. Ive seen this happen before and I suspect that it is because the fuel contains a high proportion of unsaturated alkenes. These alkenes are highly reactive and want to hook up with any other substance available. If there is nothing else to hook up with they begin to recombine with each other.
The problem is how to prevent it. one test might be to bubble air through the fuel, that gives the alkenes air to combine with (oxidation) rather than repolymerization.
However with the batch you have it is too late, reprocessing is the only solution.

[imakebiodiesel]

You can test your fuel for unsaturates by the Bromine test or with Baeyers test (potassium permanganate).

[Excalibur]

A question for the brains trust.

I'm just finalizing my flanges for the new retort. They are made from 1inch steel with v-groove seal machined directly. The question of optimum sizing and configuration for the reflux attaching to the retort arose.

My original plan for the 200mm (8") retort cylinder was to attach a 100mm (4")diameter refux directly on top but bore the connecting hole at 50mm.

Elsewhere I see the retort and reflux connected by a narrower, short length of pipe almost making the reflux "remote".

So I'm just throwing the topic up for comment while there's time to make changes. Currently the flange sits in the lathe chuck

Thanks

[Beyond Biodiesel]

An 8" retort going to a 4" reflux via 2" all sounds good to me. Since you are building all of this, and working toward a larger ultimate design, then today's retort could be tomorrow's reflux, and today's reflux could be tomorrow's condenser trap, etc.

I just move the old equipment down stream from the larger retort when I get it. In this way I started with 1 gallon (4L) retort, and moved up to 3 gallon, then 5 gallon, then 6 gallon, and now I am preparing a 10-gallon, but all of the old retorts are now down stream condenser traps. And, I am looking for a 20-50 gallon retort.

[Tplane37]

[double Post, Please Remove]

[Tplane37]

A question for the brains trust.

I'm just finalizing my flanges for the new retort. They are made from 1inch steel with v-groove seal machined directly. The question of optimum sizing and configuration for the reflux attaching to the retort arose.

My original plan for the 200mm (8") retort cylinder was to attach a 100mm (4")diameter refux directly on top but bore the connecting hole at 50mm.

Elsewhere I see the retort and reflux connected by a narrower, short length of pipe almost making the reflux "remote".

So I'm just throwing the topic up for comment while there's time to make changes. Currently the flange sits in the lathe chuck

Thanks

I think, on the topic of the sizes for piping and plumbing coming out of the retort, it was determined that 2"-3" piping should be utilized to keep it from plugging up.

But further testing has been done since that conversation, and it was determined that the plugging of the lines was the result of overfilling the retort or with heating temperatures and the speed in which the retort was heated, causing solid material to be "splashed" into the piping or by uncracked/partially-cracked hydrocarbons exiting the retort.

With that said, I think the 1" piping would be fine considering you heat your retort slowly and have tested enough to achieve optimal temperatures. However, there is one step that I am considering, and you may wish to test the same. Where the pipe exits the retort, weld a "shield" of sorts that should prevent solids from entering the pipe, but still allow the gases to pass through. such as:

_____________|..|______
|.................................|
|..................\____/......|
|.................................|
|.................................|

(Ignore the "....." above, the forum did not recognize blank spaces for the sketch.)
***
Please excuse the crude sketch, but I think it gets the concept out there. The idea is that the gases will be forced to hit the lid of the retort, and then go out the piping instead of a straight shot out, thus deflecting some or all of the air-borne solids. While this should work to keep the solids from splashing into the pipe, consideration must still be given to the temperatures and speed of heating to prevent incomplete cracking of the feedstock.

I have been gathering materials for my retort, and so far I have $0 invested. With that said, I have access to a good amount of 1" "black pipe" that I am hoping to use on my system. I have the retort welded into a 55 gallon oil drum already, and I have a removable lid on my retort. I am still gathering plumbing and temperature sensors and working on trying to control the heat input for a fuel-oil fired retort. The temperature sensors will control the speed of a 12V blower motor from an old truck I have out back, so I will have 4 fan speeds to work with for adjusting the temperature, but I have to figure out what sensors/switches to put in. For example, if I have four separate sensors that make contact at different temperatures, when a certain temperature is reached, each switch will put through a different resistance to the fan motor to either speed it up or slow it down... not a fully automated system, but allows some automation (in theory) depending on what temperature switches I can locate, but they should be a simple on/off temp switch, and hopefully something I can pickup at the local auto parts store. I have the 185°, 195°, and 210° (F) temperatures figured out, but higher figures are going to have to be located. And since I don't really have the money to be doing this, I am having to get creative!

[Excalibur]

All good food for thought, thanks.

Sorry, I forgot to post the direct link to the retort pictures

A connecting pipe of 2 -3inch diameter appeals at the moment for a couple of reasons. The insulation refractory would be easier to construct plus more free area of the top flange for other equipment such as probes and feedstock inlets, etc.

On a note of safety.
My earlier prototypes have shown signs of coking the pipework from the retort to reflux, so I would just caution about using too small a diameter pipe.

[imakebiodiesel]

My 1 kg reactor has 1" pipe between retort and reflux and it is just about sufficient for that small amount of material. 1 kg of plastic barely 1/3 fills the retort. Keep in mind that if that pipe blocks you have a bomb on your hands.
My new 50 kg retort has a 3" pipe and Im fairly confident it will be big enough.

[Beyond Biodiesel]

Thanks, Tplane37, for the excellent recommendation of a "shield" before the reflux. That shield is known as a 'baffle' in the petroleum industry. Baffles are common features installed in retorts, condensers, cat crackers, fractionation columns, etc., by the big boys. So, we DIY back-yard petroleum scientist-want-a-bes could install them wherever we can in our pyrolysis units, but as imakebiodiesel cautions, any obstruction to the flow of hydrocarbons can be a potential blockage as well.