How to turn plastic waste into diesel fuel cheaply

[wheels]

Quick question for those who have done some WMO&RUG blends 80%WMO and 20%Gasoline...

My question is which is better quality diesel fuel? The one produced from pyrolysis process of WMO or simply blending WMO with gasoline? Or its just the same?

I have access to free WMO and want to know if there is any benefit for me to process in my small plastic pyro plant or I can just blend and pour in my tank...this will be simpler for me.

I know Excalibur has done WMO blends in the past and currently doing WMO pyrolysis as well as beyond biodiesel...

All comments are well come.

It is not really possible (in the backyard type plant) to turn Petrol into Diesel, or more accurately speaking, to take two short hydrocarbon chains and join them, to make a longer one. So the best thing to do, is to add the Petrol to Diesel at a rate of no more than 10%. At that rate, the Diesel engine will burn the fuel OK with out too much problem. If you put in too much Petrol, the engine will suffer from too much heat being produced and from too much punch from the combustion at ignition, which makes that Diesel rattle sound really harsh.
I would never use WMO without it ever being processed first, if I understand one of your questions correctly. It will be full of too much gunk and stuff you will never want to go through your engine.

[Babataku]

It is not really possible (in the backyard type plant) to turn Petrol into Diesel, or more accurately speaking, to take two short hydrocarbon chains and join them, to make a longer one. So the best thing to do, is to add the Petrol to Diesel at a rate of no more than 10%. At that rate, the Diesel engine will burn the fuel OK with out too much problem. If you put in too much Petrol, the engine will suffer from too much heat being produced and from too much punch from the combustion at ignition, which makes that Diesel rattle sound really harsh.
I would never use WMO without it ever being processed first, if I understand one of your questions correctly. It will be full of too much gunk and stuff you will never want to go through your engine.

Thanks Wheels for the reply...

I read that if you add petrol to WMO in the following ratio: 20%Petrol & 80%WMO and allow to settle for 1 - 7days...the gunk and dirt will settle to the bottom and can be easily drained off and the remainig blend can be used as "black" diesel...

I am just exploring my options...as I have access to free WMO.

Also read that Vegetable Oils can be mixed with Petrol in a similar fashion and used as Diesel without all the hassles of producing biodiesel...

I am looking for a simple solution to my Diesel needs...and anyone who has tried this before please help

[Excalibur]

Thanks Wheels for the reply...

I read that if you add petrol to WMO in the following ratio: 20%Petrol & 80%WMO and allow to settle for 1 - 7days...the gunk and dirt will settle to the bottom and can be easily drained off and the remainig blend can be used as "black" diesel...

I am just exploring my options...as I have access to free WMO.

Also read that Vegetable Oils can be mixed with Petrol in a similar fashion and used as Diesel without all the hassles of producing biodiesel...

I am looking for a simple solution to my Diesel needs...and anyone who has tried this before please help

Though not perfect, petrol/WMO or petrol/WVO blends will work. I first started blending about 12 years ago. These days I aim to pyrolize WMO or PE but otherwise I blend petrol with clean waste oil.
One downside to blending is the product will have a poor cetane number. This happens because the petrol component has octane which is the exact opposite of cetane. Another issue is the initial boiling point of petrol. Here it's 40°C but diesel has a boiling range of 180–360°C. Both these effects deteriorate as more petrol is added.
In summary, blending takes less effort though I do have to buy the petrol. Pyrolizing takes dedicated time though boiling point can be specifically targeted and cetane will not be seriously impacted though to get the diesel as good as bought product, cetane improvers would need to be added.
Blending oils that are contaminated and/or black as coal are best rejected.

[Babataku]

Though not perfect, petrol/WMO or petrol/WVO blends will work. I first started blending about 12 years ago. These days I aim to pyrolize WMO or PE but otherwise I blend petrol with clean waste oil.
One downside to blending is the product will have a poor cetane number. This happens because the petrol component has octane which is the exact opposite of cetane. Another issue is the initial boiling point of petrol. Here it's 40°C but diesel has a boiling range of 180–360°C. Both these effects deteriorate as more petrol is added.
In summary, blending takes less effort though I do have to buy the petrol. Pyrolizing takes dedicated time though boiling point can be specifically targeted and cetane will not be seriously impacted though to get the diesel as good as bought product, cetane improvers would need to be added.
Blending oils that are contaminated and/or black as coal are best rejected.

Thanks for the clear explanation. I guess I will have to stick with pyrolizing the WMO as I cannot tell for sure what other contaminates have been dumped into it. Unless of course I happen to bump into some clean WMO or WVO.

[wheels]

Thanks for the clear explanation. I guess I will have to stick with pyrolizing the WMO as I cannot tell for sure what other contaminates have been dumped into it. Unless of course I happen to bump into some clean WMO or WVO.

As excalibur states, Centane is an issue, but only if perfect performance is required. I always used to joke that a Diesel engine will run of rubber gumboots if you could get them in the engine. The Diesel Engine was originally designed with the fuel in mind being Peanut Oil. Then Oil was discovered and the world changed.
One of the most abrasive substances to be in your engine, are carbon particles. They withstand extreme temperatures and will simply act as grinding paste on all the metal engine parts. These Carbon particles are what makes the engine oil turn black and the entire point of changing the Engine oil is too remove the buildup of those particles. So adding them back to the engine in your Fuel will simply work at wearing out your engine.
The next issue is that there are other components like Acids and moisture and resins, which are all created during combustion, which the old oil is now full of. Plus you never know what was ever put into WMO, if it has come from some workshop source. There could be Brake Fluid, Antifreeze, Cleaning Solvents etc etc that will all be very bad for the engine and most importantly, the Fuel Pump.

[Excalibur]

Thanks for the clear explanation. I guess I will have to stick with pyrolizing the WMO as I cannot tell for sure what other contaminates have been dumped into it. Unless of course I happen to bump into some clean WMO or WVO.

The clean waste is available but too often it's not free due to competition from folks wanting to recycle as chain bar lube etc.
I had to dump several hundred liters of oil because the contaminants were so bad. I thought it would distill OK but it just created too many problems. I know it had ethylene glycol coolant so this looks likely to be the cause of my boil-over problems recently. There was no real way of knowing what else it contained. The color was pitch black and it didn't look quite right in the way it poured and the way it sat. I hope that explains it.
With regard to clean waste oils, I use them to adjust my pyrolized fuel specific gravity. I use heavy or lighter to bring the fuel into a usable range. These days I've reduced my SG target to .83 ~.84 firstly because I found my vehicle fuel filter won't pass it with enough ease and partly because of winter.

[rozier56]

rozier56

Thanks Wheels and Excal for your comments on my last requests. I have since removed the one way valve's due to blockages and no increase in production rates.
I believe some of my production rate could be because my distillation column is to big.I notice that during a normal run at temps 350*C floe rate is good whilst the burner is on.When the burner shuts off at the desired point the rate reduces a lot waiting for the switch back on temp control. The fluctuation in temp is during the off stage of the burner. Burner switches off at 350*C, the temp continues to rise to 360*C and then reduces slowly to 345*C when the burner switches back on.
Maybe reducing the distillation column size will allow better forces present in the system to maintain steady flows on the shut off period.
What size distillation column do you folks have relating to your retort size? My distillation unit is one third the size of my retort.
I have also noticed that during my diesel runs that i am producing a small amount of grayish sediment in the fuel. this product sits on the bottom of the collected fuel and is liquid.It is not ash/carbon as this is all filtered out.If it was a wax surely it would float. When i filter it out and inspect it feels waxy?
Thanks folks.

[Excalibur]

Thanks Wheels and Excal for your comments on my last requests. I have since removed the one way valve's due to blockages and no increase in production rates.
I believe some of my production rate could be because my distillation column is to big.I notice that during a normal run at temps 350*C floe rate is good whilst the burner is on.When the burner shuts off at the desired point the rate reduces a lot waiting for the switch back on temp control. The fluctuation in temp is during the off stage of the burner. Burner switches off at 350*C, the temp continues to rise to 360*C and then reduces slowly to 345*C when the burner switches back on.
Maybe reducing the distillation column size will allow better forces present in the system to maintain steady flows on the shut off period.
What size distillation column do you folks have relating to your retort size? My distillation unit is one third the size of my retort.
I have also noticed that during my diesel runs that i am producing a small amount of grayish sediment in the fuel. this product sits on the bottom of the collected fuel and is liquid.It is not ash/carbon as this is all filtered out.If it was a wax surely it would float. When i filter it out and inspect it feels waxy?
Thanks folks.

For comparison my retort to reflux ratio is now about 4.5:1 however it needs to be insulated to achieve target temperature. In my opinion, the burner should be switched by a sensor on the retort not the reflux chamber. I would constrain the retort temperature within a fairly tight range. Once this parameter is determined, the reflux temperature should be manipulated by adding/removing insulation or increasing/decreasing vessel size. The reflux temperature setting will then dictate product weight.
So the retort/reflux dynamics are finely balanced and in harmony with each other. Each needs to be run at pace that is not too fast or too slow.
Ultimately the operators' job is to establish the temperature settings based not on just performance but product quality as well. Drive the process too fast and the risk is boil-over which isn't distilling. Too slow and the downside is slow speed.

[wheels]

I believe some of my production rate could be because my distillation column is to big.I notice that during a normal run at temps 350*C floe rate is good whilst the burner is on.When the burner shuts off at the desired point the rate reduces a lot waiting for the switch back on temp control. The fluctuation in temp is during the off stage of the burner. Burner switches off at 350*C, the temp continues to rise to 360*C and then reduces slowly to 345*C when the burner switches back on.
Maybe reducing the distillation column size will allow better forces present in the system to maintain steady flows on the shut off period.

I know exactly what your problem is here.
The Hydrocarbon chains are all wriggling around due to the heat energy being provided. The more heat, the faster they move around. The faster they move, the more space they create between each other. It's just like driving a Car around a corner. The faster you go, the more of the corner you need to use. So the chains require more and more space to move around in, the hotter they get. This is what is called heat expansion and affects all materials that expand and contract with temperature. Of course every material has a different rate of expansion. Gasses have the highest rates of expansion, because the Chains are free to move around in space.
Now lets just briefly side step here.
Remember that the vapor inside the Retort is at a very low pressure. Pressure affects the amount of room the molecules are allowed to take up. This is why increasing pressure requires more heat energy to bring something to the boil. If the Retort were under high pressure, the Vapors would still force their way out for a time, after you have removed the heat energy. But in our case, the Retort is at near zero pressure. So as soon as you remove the heat, the chains very quickly respond by maintaining their energetic state. As long as the solid plastic is producing new vapor, then the vapor already created gets pushed out of the Vessel. But if the heat is removed completely, the Molecules very quickly start to slow down and thus they don't need as much room and the vapor in the retort very quickly contracts. If the contraction continues, then the new vapor production does not push the already made vapor through the outlet. If the energy is removed long enough, the creation of the gasses in the plastic stops as well. This is because it takes energy to break apart the Solid plastic and release the vapor. Take the energy away and the breaking apart stops.
So basically, as soon as you stop the heat, the gas coming out of the Retort stops very quickly. You need to find away to maintain the temperature without turning off the burner. You need to try and either direct some excess heat away from the retort, or reduce the flame somehow. The other thing is to allow a higher Retort temperature and see if it reaches it's own natural temperature level. The most efficient range is about 460degC. But the hotter you go, the more non condensable gasses you produce. 460degC tends to be the sweet spot of most liquid to non condensable gas ratio. Processing WMO does not produce Wax, so you have no problem with waxes being produced by increasing the temp.

[Col]

Heat exchanger / condenser orientation

Hi. Can I bounce this question off you guys?
I am about to put the heat exchanger / condenser into the system. It is a single pass shell and tube condenser, much like Excalibur's. It is 2.5m long (bit of an overkill for this smaller system but has extra capacity for the next upgrade). I was originally going to mount it horizontally with a bit of fall, but then thought about mounting it vertically. If I mount it vertically I will need to add a riser after it to get the discharge height back up to a practical level to enter the diesel holding tank.
If I use a riser the condenser will always be full up to the over-flow point of the riser. I was figuring I would set that point to the full height of the condenser. If I do this I think it will create back pressure and could bottleneck uncondensed gases at the condenser entry point. Perhaps then the heavier chains would be forced to condense but the light ends might be trapped and accumulate at that point.
So I figure mounting it horizontally is the better way to go, with a few degrees fall.
Thanks.
Col

[Excalibur]

Col, I pondered over similar thoughts when I looked at heat exchanger / condenser orientation. I wanted it vertical mounted but the downside was my shed wasn't high enough. I didn't favor a riser because of the back pressure issue. I elected to mount it inclined from horizontal. Any liquid product that reaches it will favor the 1 or 2 lower tubes. Vapor can choose any of the tubes.
I believe it will be mostly liquid because of the several meters pipe run to initially get to the h/e. More recently I elected to run this pipe closer to horizontal. The h/e was also re-oriented with shallower fall. The reason was to force the liquid to travel slower and have a longer residence time.

[Col]

Condenser

An added benefit of a near horizontal heat exchanger is there will be no hold up of product after the run. If I want to accurately test my results from each batch I will need to end up with all process liquids split off into their respective holding tanks, not mixed up in the condenser.

[Excalibur]

An added benefit of a near horizontal heat exchanger is there will be no hold up of product after the run. If I want to accurately test my results from each batch I will need to end up with all process liquids split off into their respective holding tanks, not mixed up in the condenser.

Agreed. I think a condenser that freely drains into the diesel tank is the best compromise.

Snippet:
Interestingly while my diesel tank target temperature remains at 70°C which of course I control via condenser coolant flow, I had a dramatic drop in petrol production last run. I attribute this to the waste mineral oil feedstock having significantly less volatile content (solvents, etc.) Also boil-over episodes have disappeared. I noted that diesel product begins to darken in the sight glass with retort temperatures above 420°C. I hope to retest this next time out.
Also I aim to start out with a near empty retort and trial running the level much lower. My retort level indicator which I have now pictured on DiyDiesel is working much better than earlier iteration so am hoping to test various levels back-to-back for comparison.

[Col]

Vacuum distillation / cracking

Am I right in saying vacuum would be of little benefit to us in cracking plastic or oil into diesel? We could boil out the diesel fraction that already exists in the oil under vacuum thereby reducing the amount of heat required to recover that part of the diesel fraction. But we are relying on heat and time in heat to crack the remaining long chains into shorter ones so if we applied vacuum we may reduce the temperature to the point where cracking does not occur. So even though the high temperatures can lead to destabilization we need those high temperatures to get the cracking done. Our alternative is catalysts right?

[wheels]

Am I right in saying vacuum would be of little benefit to us in cracking plastic or oil into diesel? We could boil out the diesel fraction that already exists in the oil under vacuum thereby reducing the amount of heat required to recover that part of the diesel fraction. But we are relying on heat and time in heat to crack the remaining long chains into shorter ones so if we applied vacuum we may reduce the temperature to the point where cracking does not occur. So even though the high temperatures can lead to destabilization we need those high temperatures to get the cracking done. Our alternative is catalysts right?

Correct in that you will not achieve what you want to achieve. Vacuum reduces Boiling point and that is all. So under a Vacuum, you can achieve getting the plastic to release the Gasses at a much lower temperature. But that is all. Nothing else really changes.
Col, if you read my comments in reply to Rozier56, I described that increasing heat causes the Molecules to bounce around faster and thus they take up more space which is what we see as expansion. So now if you were able to get your hands around a bunch of those molecules and squeeze them, you restrict there ability to move around. This is what pressure does. So you now need more heat to get them to overcome your squeezing and create space again. Air pressure is doing the same thing as our hand would be. It is squeezing the molecules with a force of 14.7 PSI or 101.3Kp. If we take all that air pressure away, the molecules can now bounce around much more freely.
Plastic and WMO work very differently in a Pyrolysis environment. You are not actually pyrolysing Oil. You are distilling it. Where as Plastic, being a solid, gives up it's hydrocarbons differently once it reaches a high enough temperature. With WMO, the very light fractions, of which have a low boiling point, will vaporize first. Each longer chain will require just that little more heat to vaporize it. So you will never get just the Diesel range without the lighter fractions. You can stop heavier chains by not allowing the heat to rise above 260degC.
When it comes to cracking, that is something very different and is done in two ways. By increasing heat, we are causing those Molecules to bounce around energetically again. The heavy weight fractions are more correctly called "Long Chain Hydrocarbons". If you make a long chain bounce around vigorously with heat energy, it will eventually break. The "eventually" part means it takes time and that time is not precise. Breaking a chain is what is called cracking. But heat does not cause the chain to break in a precise way each time. It tends to be random, so you can get chains of all types.
The other way is using a Catalyst. This causes a chain to crack by a reaction. Using a Catalyst will cause the chain to crack in a more precise place and produce more of what is wanted than unwanted. But getting that part right so you get exactly what you want is difficult or even impossible for us Amateurs.
I hope that helps.