How to turn plastic waste into diesel fuel cheaply

[imakebiodiesel]

Nice job waterboost, all that stainless steel and I particularly like the inventive reuse of various vessels. I see that your uncondensable gases are being returned to add to the heat below the retort. You should have a bubbler between the last condenser and the heat source for safety.

[waterboost]

Bubbler

Thankyou imakebiodiesel,

I got the stainless from a process machinery reclamation yard, they wanted too much for everything I looked at... so I asked them what they were sick of seeing...

Good point about the bubbler, I also wanted to fit a gas scrubber and drier.

I was planning on activated carbon for the scrubber and xeolite for the drier.

I'm also concerned about condensate build up in the gas return pipe...

Has anyone on here had a 'flashback'? Not from some youthful acid experience

We make HHO systems and I think we are the only company who do not recommend a bubbler on a vehicle, not even a one-way valve... We use one-way valves on the HHO torches but only because they are not run under a vacuum...

Modern HHO torches are rubbish, just a tube with a tap and a syringe tip, the old ones (I have one from 1976) were designed properly. They have an expansion chamber inside and two holes, I'm not sure how it works, but in the event of a flashback, the flashback smothers itself so you dont even notice.... If this design can be used, it would negate the issue of water being sucked back as the unit cools and creates a vacuum.... and prevent flashbacks.

The gas return pipe is also 1", which I think is a bit big... I'm going to turn the gas return pipe the other way around (away from the reactor) for a test run to see how much gas is made and what kind of variable nozzle/burner head it might require for proper combustion....

I also have a few one-way high pressure, high temperature steam pipe condensate valves of varying designs that may operate as flashback devices...

Anyone any other solutions for safety devices other than a bubbler?

[waterboost]

Bubbler Alternatives

Venture type flashback Arrestors (active) –

Venture flashback arrestors simply create a restriction in the hydrocarbon/air mixture delivery pipe so that the gas velocity is faster than the flame speed, preventing progression of a flashback upstream. Flashbacks in the direction of flow can still happen. Even a partly closed valve can create a high velocity for flashback prevention, but a venture shape creates much lower pressure drop. If gas flow stops, the venture is no longer effective, so methods to measure flow and add makeup gas (nitrogen, for instance) are often included.

Online flame arrestors (passive) – (most commonly used)

Mechanical flame arrestors are filled with metal or ceramic, which absorbs heat from a flashback, quenching it to a temperature below what is needed for ignition. This stops the flame. With a low enough hydrocarbon/air mixture flow rate, if a flame travels to the face of the arrestor, it can become stable at that point. Heating of the arrestor body and internals results. Once the arrestor temperatures increase enough, ignition temperature can be reached on the upstream side of the arrestor and the flashback can proceed. For this reason, a temperature switch is often installed on the flame side of each arrestor (adding an "active" element).

[waterboost]

Pan Scrubs and Cat Litter

Pan Scrubs (Stainless of course) for the flash back arrester - stuffed into the pipe

Cat Litter is usually zeolite... so there the drier...

5minute trip to Asda (Wallmart) and I'm safe

[PLASTICTRIX]

Pan Scrubs (Stainless of course) for the flash back arrester - stuffed into the pipe

Cat Litter is usually zeolite... so there the drier...

5minute trip to Asda (Wallmart) and I'm safe

I made a flashback arrestor using a 8inch black pipe nipple. I installed a union on both ends so it can be removed and inspected periodically. Basically a pipe nipple the same dia of the pipe you are using, loosely pack pipe with S.S. wool and put a 20 mesh s.s. screen disk fit snug at ether end to prevent the wool from moving. I tested it in the middle of a 10 ft length of pipe by loading both ends of the pipe with propane from a torch and lighting one end. I had a friend stand at the other end of the pipe to watch for any flame or flash, after 20 or so flashes not one incident of flame migrating past the s.s.wool. Pretty much anything like this will work, I guess you can use a lot of different packing, BB's,ballbearings, small ceramic/glass beads, kitty litter, rice, beans, fish tank gravel, whole barley, etc.. All it does is create a spot in the pipe with less volume..When a pipe flashes it has to draw an equal amount of air into the pipe to burn, in essence it is like a 50/50 wave of air/fuel, sucking into the pipe while at the same time the same amount of flammable gas is trying to escape while it burns. So when this critical mixture of air/gas with flame hits the packing it disrupts the critical ratio of air/fuel mixture causing it to starve on fuel and or oxygen there for extinguishing itself.
If you build one test it first.

[waterboost]

Sounds perfect

Hi PLASTICTRIX,

Thanks for that... sounds perfect.

The return pipe from my condensers, the one that runs along the floor, has a boss at each end, if I pack this with steel wool and cat litter all the way down, will that suffice do you think?

[mjohnson1]

I made a flashback arrestor using a 8inch black pipe nipple. I installed a union on both ends so it can be removed and inspected periodically. Basically a pipe nipple the same dia of the pipe you are using, loosely pack pipe with S.S. wool and put a 20 mesh s.s. screen disk fit snug at ether end to prevent the wool from moving. I tested it in the middle of a 10 ft length of pipe by loading both ends of the pipe with propane from a torch and lighting one end. I had a friend stand at the other end of the pipe to watch for any flame or flash, after 20 or so flashes not one incident of flame migrating past the s.s.wool. Pretty much anything like this will work, I guess you can use a lot of different packing, BB's,ballbearings, small ceramic/glass beads, kitty litter, rice, beans, fish tank gravel, whole barley, etc.. All it does is create a spot in the pipe with less volume..When a pipe flashes it has to draw an equal amount of air into the pipe to burn, in essence it is like a 50/50 wave of air/fuel, sucking into the pipe while at the same time the same amount of flammable gas is trying to escape while it burns. So when this critical mixture of air/gas with flame hits the packing it disrupts the critical ratio of air/fuel mixture causing it to starve on fuel and or oxygen there for extinguishing itself.
If you build one test it first.

You are full of knowledge. That sounds like an excellent system to use and is relatively cheap to outfit on a unit. What are your thoughts on how this type of flashback arrestor would scale with the unit?

[PLASTICTRIX]

You are full of knowledge. That sounds like an excellent system to use and is relatively cheap to outfit on a unit. What are your thoughts on how this type of flashback arrestor would scale with the unit?

As far as scale..My setup is rather big. On my 125gal retort, i am running 3 inch pipe all the way from the retort to the bubbler. then out of the bubbler i am running a 2 inch pipe 20 feet down hill to a water trap, then a short 2 inch pipe to a plastic 20 gal drum rice dryer, out of the dryer i am running a 10 foot section of 1 inch black pipe with the flash arrestor in the center, then ball valve and 1 inch rubber hose so i can move it around to different burners and equp.

so i start with 3 inch and am reducing to 1 inch throughout my whole system. with the airspace in my bubbler and the airspace in the 20 gal. dryer the pressure is smoothed out from having enough expansion. remember everytime you reduce the pipe size you are increasing gas speed through the hose and pressure in the system can reach higher pressures if you get a spike.
make sure you dry the gas before running it into kitty litter or any organic material that could swell up..the kitty litter can mud up and expand potentially causing a blockage..boom..

I would start big and reduce size untill you get good gas flow without choking the system.

[imakebiodiesel]

Thanks for all this information, Being a belt and braces kind of a guy ill be adding a flash arrester to my outfit. I would agree with plastictrix about using kitty litter as a drier. Some litters are made from clays like bentonite or fullers earth and will swell up considerably when absorbing water or any other liquid. Others are made fron minerals such as sepiolite and zeolite and would be safer,
The best materials would be silica gel or activated alumina. Although more expensive than cat litter these two can be regenerated and used over and over.

[UnclearFizzyCyst]

A few tips from an ex alcohol distiller.

Hi, this was so interesting I signed up

I've only read the first 2 pages (it's a looooong thread).

I first learned how to distill alcohol, courtesy of HMG, at university in a basic organic chemistry course. I later made my own booze, of all kinds, now I'm on the wagon.

I see a lot of people asking about the conical lid and thread. Google USA NPT (National Pipe Thread) and you'll see what is meant, I don't know the UK equivalent. The lid is basically the same but, I guess, machined so it fits nice and snug. Once assembled what you have is a spiral tube around a tapered plug, once tightened the tube is blocked somewhere and is therefore very gas-tight.

Some safety tips-

A low pressure system can become a high pressure one very quickly, with potentially lethal results. An extended bathroom trip resulted in my boiling flask overheating faster than my condensation tubing could cope with, with lab glass just a very expensive mess to clear up. With this kind of set-up I'd recommend some kind of pressure gage, release valve and bolt-hole in case of an imminent explosion. Imagine your molten plastic boiling over into your condenser and you see what I mean.

Sooner or later something won't work as it should (i.e. it breaks or burns out). In my case I once had a vapor box extracting aromatics for gin, one of my support clamps had become loose adding considerably to the amount of weight supported by nothing but glassware. It broke at the narrowest part, sending a torch of flame around 2 feet high, alcohol burns invisibly, what I saw was a cabinet losing its varnish, what I didn't see was what was burning elsewhere. More expense and wifey was a little perturbed too. Make sure you have a safety back-up for everything, even better eliminate it if you can.

Later on I had a thermostat fail. Using glass I could see what had happened immediately so cut the heat. Have some kind of temperature sensitive cut-out AND TEST IT ONCE IN A WHILE.

Some money saver tips -

Make a second set-up and add a well coiled tube to the inside of your metal cage. Load it up so it's ready to go. Use this as your first condensing coil and the heat ($) will be transferred to your sealed container. You may want to burn off your gas under it too, plus any gasoline you're boiling off.

You can keep adding to your array and pretty soon you'll be cutting your fuel bill considerably. The only downside to this is that you need to run a large batch for peak efficiency which means you're gonna have to hang around for more time. Once it's all started to warm up though you'll see the advantages.

I had one thought about the ceramic bricks, it appears there's only one wall. It may be more efficient to have two walls half as thick with each joint covered by the second wall. That is, use a 1/2 brick height on the outer bottom layer and rotate the whole outer wall by 1/2 brick's width.

A doughnut shaped brick on top of the sealed container will also reduce heat loss.

Now, I know a diesel engine is simple but I'm sure that additives are added to the fuel. Perhaps someone could shed some light on this and suggest ways to increase the fuels storage qualities.

I grew up in the UK and now live in the US. I can relate to the problems viz-a-viz the taxman. They're just as greedy here too but law enforcement is so overwhelmed by regular crime there's very little risk involved in this kind of thing. If you don't burn down the neighborhood over here you're pretty much left to your own devices. Have you considered blending with legit diesel?

I'll keep this as a back-burner project right now but I just so love tinkering I may get myself some sort of diesel motor just to try this out.

[PLASTICTRIX]

Thanks for all this information, Being a belt and braces kind of a guy ill be adding a flash arrester to my outfit. I would agree with plastictrix about using kitty litter as a drier. Some litters are made from clays like bentonite or fullers earth and will swell up considerably when absorbing water or any other liquid. Others are made fron minerals such as sepiolite and zeolite and would be safer,
The best materials would be silica gel or activated alumina. Although more expensive than cat litter these two can be regenerated and used over and over.

I am currently using a rice dryer as a separate unit apart from the flash arrestor. Rice works good as long as you leave it well ventilated while not being used to let it dry back out as moisture can end up growing mold and it can get yucky. I just have a plastic drum with 20 lbs of rice in it, I have it set up in the same fashion as a bubbler but instead of water it is rice.
It is piped in after the bubbler and water condense trap. I never have had any moisture of any kind in my rubber gas hose so it must be working fine. My buddy works at a large grocery store so he gets me large packages of expired rice for free.
If you used dried silica gel in this fashion i am sure it would work exceedingly well. They sell large quantities of it at florist supply places.
I am unsure if a flash arrestor and dryer should be used as one unit? it makes sense in some ways but the size of the arrestor is important. IMO the arrestor should be the same size dia. as the pipe used, never bigger. If it is bigger so is the volume of air/gas mixture in it, possibly giving the flash enough air to jump through it.
So if the arrestor is just as small as the pipe dia. filling it with a drying agent, it probably wouldn't last long before becoming saturated.

[Beyond Biodiesel]

flashback arrestor

I found these suggestions PLASTICTRIX, imakebiodiesel, waterboost et al excellent. Thank-you UnclearFizzyCyst for your additional safety suggestions. I think having a flashback arrestor is wise, and having several stages of flashback arrestors even better. The bubbler acts as an effective flashback arrestor.

I also have a diffuser inside my bubbler, which will also work as a flashback arrestor

After my bubbler I also added a gas-water separator, so that I can direct the water to the sewer and the gas back to a burner.

The gas-water separator is packed with steel wool, which not only functions as a refluxing medium to separate bubbler water from the exhaust stream, but it also acts as a flashback arrestor.

A check valve from oxy acetylene torch is also an effective flashback arrestor


I also have a whole house water filter in my exhaust stream. It is after my ice trap and before my bubbler.

I have found that condensables will wet upon the pleated cellulose matrix of the filter and drain down to the holding area at the bottom of the filter, where I can drain them with a tap. The cellulose matrix of the filter medium will work effectively as a flashback arrestor.

However, more stages of flashback arresting is a good idea. Thus, adding metal packing and baffles to the reflux and condensers along the exhaust stream not only aid in condensation, but every stage also acts as a flashback arrestor. Here is a photo of one of my condensing traps which has a baffle separating two stages of metal condenser packing.

Condenser packing can be almost anything that is thermally conductive and highly porous. Stainless steel scrubbies have some advantages in not being highly chemically reactive; however, I use copper scrubbies, aluminum screening, and even the shield from coax cable as effective condenser packing; and, as has been suggested upthread, chemically active metals, such as: copper and aluminum, also offer a neutralizing effect to acids formed in cracking of halogenated hydrocarbons, which can make their way inadvertently in a hydrocarbon cracking medium.

[waterboost]

Bubblers

Have any of you guys had flashbacks as far as your bubbler?

[Excalibur]

Have any of you guys had flashbacks as far as your bubbler?

I haven't noticed any with my set up, though I have the flash back arrestor pictured and described on my blog pages. Also it tee's into the 3 inch forced air duct a few inches from the turk-firebox. This means that firstly the flame has to travel against air current, then negotiate a flame arrestor finally arriving at the bubbler. True, there would be a dozen liters of non-condensable gases in the bubbler at any one time but there's no oxygen been allowed to enter.
That said, I trust flames about as far as I can kick them...

[Beyond Biodiesel]

Have any of you guys had flashbacks as far as your bubbler?

I have had no flash-backs and my exhaust line never ignites, so it looks like I am losing very little hydrocarbon in my process.