How to turn plastic waste into diesel fuel cheaply

[imakebiodiesel]

Lowriderzz, sorry I did not get a chance to look at your design earlier. The pipe exiting the top of the reflux must immediately turn down wards so that fully cracked vapours cannot flow back down into the reflux column. Dont put catalyst in the condenser, it will serve no purpose and it may block the condenser, stainless steel wool or BBs aluminium flyscreen will work better.

The u bend at the fuel outlet looks a little shallow. It must be twice the height of the bubbler depth or you will get vapours coming out of it.
I got caught out when I added my second bubbler. I stupidly thought that 2 bubblers in series each 6 inches deep would create a back pressure of 6 inches in total, but of course they dont. They create a back pressure of 12 inches. So I had to make my fuel u tube 24 inches deep.

[Excalibur]

Excuse my ignorance, but instead of casting 'fire bricks' is there a reason why we wouldn't just make a turk style burner oven out of two drums, one inside the other and fill the space between the two drums with dirt or sand?

I am thinking about shaping the burner chamber, casting bricks, etc. and I just figured that dirt would probably hold the heat about as effectively as bricks would, and be a lot easier and faster. Eventually the wall of the inner drum would burn out and spill dirt into the burner oven, but if that wall was thick enough to handle the heat then this would work?

Thanks
Col

The basic idea gets my vote. In fact so much so that it's the way I've constructed my latest turk powered retort. Better insulation would be perlite or vermiculite. While not as cheap as sand, we are talking about significant savings in energy over a period of time.
I guess I'll soon find out, as I'm just about to buy the vermiculite or perlite on Thursday. I have 125mm of insulation gap between the layers to fill.

[Beyond Biodiesel]

For my condenser water is going through the inner pipe and the vapor remain in the big pipe. What is the difference if the water comes from top to bottom or bottom to top ?

It is best to reverse the position of the vapor stream to the inside smaller pipe, and the water on the outside, because the outer pipe having water on it acts as an insulator as well as a refrigerator for your vapor stream.

Also, if the water enters through the bottom, instead of the top, then any air that was in the condenser will be forced out, because air floats on water. The cooling water will fill all of the recesses inside your condenser forcing all of the air out.

Excuse my ignorance, but instead of casting 'fire bricks' is there a reason why we wouldn't just make a turk style burner oven out of two drums, one inside the other and fill the space between the two drums with dirt or sand?

I am thinking about shaping the burner chamber, casting bricks, etc. and I just figured that dirt would probably hold the heat about as effectively as bricks would, and be a lot easier and faster. Eventually the wall of the inner drum would burn out and spill dirt into the burner oven, but if that wall was thick enough to handle the heat then this would work?

Thanks
Col

Sounds like a good idea to me. I agree with Excalibur that perlite or vermiculite is better than sand, and just about as accessible, and cheap, to most of us. Ash will work excellently as well. Also, the coke that is removed from the cracking unit could be recycled into insulation, although the carbon in the coke will burn, but it will leave ash, which will not burn, and has a very low coefficient of thermal conductivity.

Once the coke has been burned, leaving ash, then the ash can also be used as a free catalyst for cracking your plastics.

[ashiki]

please help me,
i am on my process of making a 20 ltr reacter,
got some troubles. . .
1st thing i need to know

1.will the welding hold on at 400°C
2.how to fit the heating coil to reacter
3.how to make a airtight lid

my reacter vessel dimensions are
diameter- 24 cm
height - 36cm
thickness - 3mm

[imakebiodiesel]

I have a rocket stove and the firebox gets up to 800C. It is insulated with 2 inches of ash(70%) and vermiculite(30%) and you can comfortably put your hand on the outside.
Ashiki, mild steel or stainless steel weld will easily withstand 400C.I dont know what you mean by a heating coil in the reacter. Air tight seals have been discussed many times already on this discussion. Read the complete thread.

[Col]

Fuel u tube

Thanks for your feedback guys.

The u bend at the fuel outlet looks a little shallow. It must be twice the height of the bubbler depth or you will get vapours coming out of it.
I got caught out when I added my second bubbler. I stupidly thought that 2 bubblers in series each 6 inches deep would create a back pressure of 6 inches in total, but of course they dont. They create a back pressure of 12 inches. So I had to make my fuel u tube 24 inches deep.

I don't recall this "fuel u tube" principle coming up and can't locate it in the search. Can you direct me to the posts about it? Thissideup was going to pipe his vapours into a reservoir of fuel in the bottom of each of his condensers. These vapours would then need to boil off again and rise through the packing to get to the next condenser. It adds another stage of separation, some may say it is an unnecessary stage. I expect it would give a slightly better quality product. Does anyone have any experience with this? From IMBD's comment above it appears it would add significantly to the required height of the fuel u tube.

Thanks
Col

[Col]

Is aluminium needed in the system?

Water will also collect in any condenser cooler than 120C. Obviously the water will also settle to the bottom - the same place as the AlCl3 - so, we will have the reaction Heartburn mentioned - producing more HCl, exactly what we were trying to avoid by adding aluminium in the first place. My question is - is there any point putting the aluminium in the system if we just end up with HCl again downstream? I guess it would mitigate the corrosion damage to the system between the aluminium location and the water / HCl collection point? Does the presence of HCl in the condenser vessel cooler than 120C pose a significant risk of system corrosion or toxic by-product formation? If so, should we make that condenser out of stainless steel to deter corrosion?

Thanks
Col

I apologise for quoting myself - just wanting confirmation that we do not need to put aluminium in the system if we have a bubbler dosed with KOH or similar. I expect we don't need it. But... has anyone seen any signs of corrosion in their condensation vessels where this acid water collects? I don't want to have to make the system from stainless steel.

Col

[imakebiodiesel]

I dont think the utube idea has been discussed much. its just the way I remove condensed fuel from the bottom of the condenser without letting air get in.
There is no need to have any aluminium in the process at all. Mild steel and stainless steel are probably better . I use stainless steel wool filling in my reflux and in my condenser but I noticed that BB uses crumpled up flyscreen in his condenser.
If you are worried about aluminium dont use it.

[Col]

size of reflux vessel

Hi Plastictrix - you mentioned a reflux vessel volume of 5-10% of the retort volume works well. Is that 5-10% of the total capacity of the retort or 5-10% of the volume you fill it to? For instance I intend to fill my 170L retort (an old air compressor tank) to half to 2/3rds full with WMO. I expect you mean 5-10% of the total capacity as that is what remains constant throughout the process whereas the quantity of feedstock changes.
Thanks
Col

[lowriderzzz]

It is best to reverse the position of the vapor stream to the inside smaller pipe, and the water on the outside, because the outer pipe having water on it acts as an insulator as well as a refrigerator for your vapor stream.

Also, if the water enters through the bottom, instead of the top, then any air that was in the condenser will be forced out, because air floats on water. The cooling water will fill all of the recesses inside your condenser forcing all of the air out.

.

OK but if i reverse and put the vapor to go through the inner pipe then how will I separate the non condensable gases to go through the bubblers or other condensers ?

[imakebiodiesel]

BB is proposing a completely different design of condenser, where the water jacket is on the outside of the condenser and the vapours travel up the core. he is not proposing that you just swap the connections on your existing unit.
He is right , his design, sometimes called The Plumbers Delight, is more efficient but I find the condenser I have is so efficient that I can turn off the water completely and it still works so it is not worth changing if you already have the condenser built.

[Excalibur]

1.will the welding hold on at 400°C
2.how to fit the heating coil to reacter
3.how to make a airtight lid

+1 for what IMBD said.
Welding needs to be of a good standard and professional quality.

Airtight lid search came up with... Jetijs v-groove seal

There are lots of posts about the subject of lid seals including gasket with industrial ready made flanges...

[Beyond Biodiesel]

Thissideup was going to pipe his vapours into a reservoir of fuel in the bottom of each of his condensers. These vapours would then need to boil off again and rise through the packing to get to the next condenser. It adds another stage of separation, some may say it is an unnecessary stage. I expect it would give a slightly better quality product. Does anyone have any experience with this? From IMBD's comment above it appears it would add significantly to the required height of the fuel u tube.

Thanks
Col

This is one of the upgrades to my fractionation system that I am preasently working on. In large refineries they call them "bubble caps." If you Google alcohol stills, or "moon shine," you will find people who make their own moon shine commonly bubble the vapor stream through the condensate at the bottom of the condenser.

I apologise for quoting myself - just wanting confirmation that we do not need to put aluminium in the system if we have a bubbler dosed with KOH or similar. I expect we don't need it. But... has anyone seen any signs of corrosion in their condensation vessels where this acid water collects? I don't want to have to make the system from stainless steel.

Col

My WMO distillation system is mostly aluminum, brass and copper. I have seen no evidence of corrosion on any of the aluminum, brass and copper components. However, I did find that brass will deform at 800f (425c), so I have stainless steel fittings and tubing there.

The packing I use is also aluminum, copper, and steel. I have found no serious corrosion on those packing materials either.

Hi Plastictrix - you mentioned a reflux vessel volume of 5-10% of the retort volume works well. Is that 5-10% of the total capacity of the retort or 5-10% of the volume you fill it to? For instance I intend to fill my 170L retort (an old air compressor tank) to half to 2/3rds full with WMO. I expect you mean 5-10% of the total capacity as that is what remains constant throughout the process whereas the quantity of feedstock changes.
Thanks
Col

Your plan to fill your retort for distilling WMO to 2/3 seems sound.

OK but if i reverse and put the vapor to go through the inner pipe then how will I separate the non condensable gases to go through the bubblers or other condensers ?

If you research condenser designs, you will find one called the "plumber's friend" or something like that. It is the simplest design. The vapor stream goes through the middle tube. There is a T at both ends. You can actually buy Ts that have one leg of the cross larger than the other 2 legs, so that a larger tube can be soldered between the two larger legs, this is the water jacket. The straight through section is for a smaller tube, and may have to be drilled through to allow the smaller tube to pass straight through both Ts. The side branch is to allow cooling water to pass. See pick below.

This is a tube in tube condenser receiving packing

[Beyond Biodiesel]

Here are some more photos of a simple tube-in-tube condenser.

a 2 foot (60cm) condenser

Closeup of the heat exchanger sweat fittings at each end

[lowriderzzz]

what goes in each orifice ? where comes in and out the water and where comes in and out the gasses ?