How to turn plastic waste into diesel fuel cheaply

[placebo]

That picture of the hopper is similar to something I have in mind. But with my idea, I am thinking of using it as a pre-melt hopper with double valves in the pipe below the hopper instead of the solenoids like you have suggested.

The pre-melt would be achieved by placing the hopper inside of (basically) a chimney. Mine is a 55 gallon drum is a smaller diameter drum inside of it. The exhaust (waste) heat from the burner itself would be routed up through the "chimney" (55 gal. drum) so that the hot air that is no longer hot enough for cracking would melt the plastics that would be in the hopper. Open the top valve, let the pipe fill up, then close the top valve and open the bottom valve to add to the retort. I modified your picture to try to show what I am talking about, its very crude, but I hope it gets the idea across. I think with having the retort under a vacuum, it would pull the melt into the retort, but I am not entirely sure. Might have to pressurize the pre-melt hopper so that if forces the melt into the tube, hold the pressure in the tube, and then the pressure difference would force it into the retort when the lower valve is opened... but then a vacuum would have to be pulled on the retort again for each refill (I would think.)

Thanks, excellent idea. Another thing I have thought of is maybe having the auger and pipe protrude in to the retort so the high temps melt the plastic as it comes of of the pipe.

All good ideas I will look in to as I progress.

[placebo]

The blue water is copper chloride and and HCL. It should be pretty corrosive, unless the copper has fully neutralized it. It will come in a wide range of colors from green to blue. You will get it if you have any PVC or other chlorinated hydrocarbons in your reactor.

I like your vacuum pump idea to evacuate the air out of your feed of ground plastic, but it might be insufficient. To aide in purging you could add a ring with holes in it at the bottom of your hopper, then run CO2 through that ring. CO2 will perculate your ground plastic before it goes into your vacuum pre-chamber.

Thanks for the idea

[Mporse]

Hello everyone,

Just wanted to say: AMAZING THREAD! It is really inspiring to see so many people who are working with a topic like this

I have read the whole thread twice now, and I got inspired to build my own unit with a friends help (just as a prototype in the beginning, to see if I could get it to work).

Anyways, below is a couple pictures of the unit:





The retort is a cylinder of steel, where a disk of steel is welded onto the bottom of the cylinder, in order to keep the cylinder closed:







Afterwards, in order to test the system, we tried putting in the plastic we wanted to turn into diesel fuel (mostly PE, both LDPE and HDPE). We then closed the cylinder using another disk-formed steel lid, with bolts and screws, and we also layed some sealing cord between the cylinder and the lid:







But the test didn't go so well. At first, we could hear that some of the plastic-vapor condensed in our reflux, and then came back down again to the retort, so for us this was a sign that the system somewhat seemed to work. When we reached a temperature of 250-300 degress Celsius, we saw that some greyish/whitish vapor came out from the sides of the lid (mainly where the screws and bolts were placed), and we also started to see vapor coming from the middle of the lid, just around the vertical pipe (where the vapor was supposed to travel from the retort, through the vertical pipe, and then up into the reflux). This was clearly a problem, so we shut down the test.

When we opened up the lid to the retort, and we could see some brownish, waxy substans:



Because of what had happened during the test, we thought that the lid wasn't shut good enough. Therefore, we tried welding the lid shut, and we also welded the vertical pipe onto the lid, where som vapor also came from earlier (of course after we had removed the old plastic and added some new). Afterwards, we covered the welds with heat resistant sealant:





We then ran the test again, but had to stop it because more vapor started to come out of the retort through tiny holes in the welds.

My questions to all of you with knowledge about this topic is:

Why can't we keep our system shut?

Why does vapor keep coming from the lid?

And (most importantly): What do you guys think my friend and I can do to seal the lid, so we can stop the vapor from coming out of the system?

We have both thought about using sealants and silicone to seal the lid, but all of the materials we have found all melt at the cracking temperature for plastic, so we really don't know what to do here.

I know this was quite a long post, but it is really important for us to find out what's wrong, because we can't obviously find the mistake ourselves.

Thanks a lot, and keep up the good work!

[waterboost]

Mmmmm

Brilliant effort guys but it sounds like you need someone who can weld...

If the welds are poor then safety will be an issue.

[Mporse]

Hello everyone,

Just wanted to say: AMAZING THREAD! It is really inspiring to see so many people who are working with a topic like this

I have read the whole thread twice now, and I got inspired to build my own unit with a friends help (just as a prototype in the beginning, to see if I could get it to work).

Anyways, below is a couple pictures of the unit:





The retort is a cylinder of steel, where a disk of steel is welded onto the bottom of the cylinder, in order to keep the cylinder closed:







Afterwards, in order to test the system, we tried putting in the plastic we wanted to turn into diesel fuel (mostly PE, both LDPE and HDPE). We then closed the cylinder using another disk-formed steel lid, with bolts and screws, and we also layed some sealing cord between the cylinder and the lid:











But the test didn't go so well. At first, we could hear that some of the plastic-vapor condensed in our reflux, and then came back down again to the retort, so for us this was a sign that the system somewhat seemed to work. When we reached a temperature of 250-300 degress Celsius, we saw that some greyish/whitish vapor came out from the sides of the lid (mainly where the screws and bolts were placed), and we also started to see vapor coming from the middle of the lid, just around the vertical pipe (where the vapor was supposed to travel from the retort, through the vertical pipe, and then up into the reflux). We could see that this was clealy not smoke from the burned tree beneath the retort, so we shut down the test.

When we opened up the lid to the retort, and we could see some brownish, waxy substans:



Because of what had happened during the test, we thought that the lid wasn't shut good enough. Therefore, we tried welding the lid shut, and we also welded the vertical pipe onto the lid, where som vapor also came from earlier (of course after we had removed the old plastic and added some new). Afterwards, we covered the welds with heat resistant sealant:





We then ran the test again, but had to stop it because more vapor started to come out of the retort through tiny holes in the welds.

My questions to all of you with knowledge about this topic is:

Why can't we keep our system shut?

Why does vapor keep coming from the lid?

And (most importantly): What do you guys think my friend and I can do to seal the lid, so we can stop the vapor from coming out of the system?

We have both thought about using sealants and silicone to seal the lid, but all of the materials we have found all melt at the cracking temperature for plastic, so we really don't know what to do here.

I know this was quite a long post, but it is really important for us to find out what's wrong, because we can't obviously find the mistake ourselves.

Thanks a lot, and keep up the good work!

[Mporse]

Oops!

Sorry, accidentally posted the post again :P

[Mporse]

Brilliant effort guys but it sounds like you need someone who can weld...

If the welds are poor then safety will be an issue.

That sounds like a good idea Waterboost

Unfortunately, we really don't know anyone who is REALLY good at welding, so that might be a problem...

Do you have any other suggestions? For example, do you know a material that can withstand the high temperatures of the cracking process, which we can use to seal our retort?

Or maybe, do you know how to make prober welds?

I guess we can find the answer to the last question by simply making a search on Google
Just thought I would ask in this forum because many people probably know a lot about this.

Thanks again!

[mjohnson1]

I can see a couple problems just by looking at the pictures. The hole for the pipe coming out of your retort looks to be very small in diameter and the hole on the top plate you attached to the retort looks to be even smaller than the diameter of the pipe.

I have a feeling that this small diameter hole combined with the pressure requirements of the bubbler will make your retort leak like you were experiencing.

I would suggest a compressed air test by filling up your entire system with some compressed air and seeing where the leaks are with some soapy water.

I'll be the first to admit my welds don't look the greatest. I would make another pass over the existing welds at a higher temp to help close off the holes.

If you aren't using a catalyst you won't expierence much if any cracking at the 250-300C range. You will need to get to the 400C range if you want to crack without a catalyst.

[mjohnson1]

Why can't we keep our system shut? You have a pressure requirement due to the bubbler water depth which forces vapors/air out of the tiny holes in your unit.

Why does vapor keep coming from the lid? The welds likely have small holes in them allowing vapors to escape. Get rid of the sealant. Do a 2nd welding pass and turn up the heat. Look at some youtube videos on how to weld too. I wouldn't use any type of sealant on these units if you can help it. Welding > sealant.

And (most importantly): What do you guys think my friend and I can do to seal the lid, so we can stop the vapor from coming out of the system? There are two things to consider here. You want to have a perfect seal but you also need a way to reload your retort with plastic. I would suggest looking for steel flanges and welding those on. You then bolt on both flange with a gasket in between them. I'm not sure where you live but I am was able to get a pair of high quality flanges off of ebay for $75 USD including shipping. As a last resort you could make your own flange like you did. I would use graphite gaskets though and not the cord you use. I use high temperature graphite gaskets like someone suggested earlier. If you have a torque wrench use that as it will give you a perfect fit and follow the recommended torque settings for the particular gasket you bought.

[Mporse]

Hey guys,

Thanks a lot for the suggestions

My friend and I will try to make another go with a larger pipe from the top of the retort to the reflux. We will probably try to weld it again, but as mjohnson1 suggested, we will fill our system with compressed air to see where there might be leaks in the system.

If other people in this forum would like to share some suggestions for improvements with me, then I would really appreciate it

Thanks again guys!

[Mporse]

Just saw your latest post now mjohnson, so just ignore my previous post.

Yes, the things you are suggesting would really help us out. I will talk to my friend about this tomorrow, and then we can find a good solution based on what you have suggested.

Thanks a lot

[Beyond Biodiesel]

Hello everyone,

Just wanted to say: AMAZING THREAD! It is really inspiring to see so many people who are working with a topic like this

I have read the whole thread twice now, and I got inspired to build my own unit with a friends help (just as a prototype in the beginning, to see if I could get it to work).

We then ran the test again, but had to stop it because more vapor started to come out of the retort through tiny holes in the welds.

My questions to all of you with knowledge about this topic is:

Why can't we keep our system shut?

Why does vapor keep coming from the lid?

And (most importantly): What do you guys think my friend and I can do to seal the lid, so we can stop the vapor from coming out of the system?

We have both thought about using sealants and silicone to seal the lid, but all of the materials we have found all melt at the cracking temperature for plastic, so we really don't know what to do here.

I know this was quite a long post, but it is really important for us to find out what's wrong, because we can't obviously find the mistake ourselves.

Thanks a lot, and keep up the good work!

That sounds like a good idea Waterboost

Unfortunately, we really don't know anyone who is REALLY good at welding, so that might be a problem...

Do you have any other suggestions? For example, do you know a material that can withstand the high temperatures of the cracking process, which we can use to seal our retort?

Or maybe, do you know how to make prober welds?

I guess we can find the answer to the last question by simply making a search on Google
Just thought I would ask in this forum because many people probably know a lot about this.

Thanks again!

Thanks for the pictures and the post, and good to know that you read through the thread, now don't bother to reinvent the wheel, instead buy some descent flanges and a proper graphite seal that works with those flanges.

[Rich Connell]

Shredded Plastic

Hello,

In a later post you stated that you could obtain 1,000 kg of shredded plastic for about $50. I cannot find any suppliers here in the Southern California area so was hoping you might tell me who or where I should go to get a quote?

Thank you for your assistance.

[Allcanadian]

@Mporse
Wow that is a real interesting weld job, looks like you need way more heat. I imagine you have an AC machine so I would use a 7018 1/8" rod just to cap it. Weld in a horizontal position(work is flat, rod near 45 Degrees) and crank the freaking heat up to at least 100-110 Amps or drop a rod size to 3/32 at 80-90 Amps. I prefer the smaller rod at high heat running it fast.

The trick to a good weld is the puddle, once you strike her up watch the puddle of molten metal behind the rod and if it starts bunching up or getting higher your moving to slow or you need more heat. The puddle is flat and as you move along it does it's own thing and run a test bead then break the slag to make sure it's slightly higher than your work(no undercut) and you have enough heat. As well if your just capping with 7018 then you don't need a lot of pressure and pretend it is just a wax rod touching a hot surface and let it melt in and move at it's own pace, just keep the angle off vertical, 30-45 Degrees with very little pressure.

If you want to really weld it then taper the weld joints and run something like a 6014 rod with more pressure in the root of the weld then cap it with 7018. I use two off the shelf rods, 60 for the root and 7018 to cap and you can weld damn near anything including cast and spring steel. I'm not saying cast is easy or the right way of doing things but it can be done,lol.

P.S. -- I should mention AC welders suck and given the choice a DC machine is definitely the way to go. I have a nice little Miller Econotig that is 12 years old and it has run flawlessly, as well in those 12 years I have never used the AC setting once.

AC

[batwicho]

Yesterday I ran my old machine which experimented 2 years ago ... Still work , simple design and the results here...