How to turn plastic waste into diesel fuel cheaply

[neophite]

The bottle options

Afternoon gents,

I am working on the propane tank and I have the following questions:

1- Is the standard propane tank 30 bar with a 2.2m thickness?

2- To air on the side of safety I am looking at thicker walls say 5mm or 8mm. will this require additional energy to heat the chamber? When I say additional energy I mean will it double/triple my energy requirements to heat the chamber?

Thanks

[Beyond Biodiesel]

Afternoon gents,

I am working on the propane tank and I have the following questions:

1- Is the standard propane tank 30 bar with a 2.2m thickness?

No, to the best of my knowledge propane is held at 1 atmosphere (1bar/15PSI). 1/8" (.125"/3mm) is good enough.

2- To air on the side of safety I am looking at thicker walls say 5mm or 8mm. will this require additional energy to heat the chamber? When I say additional energy I mean will it double/triple my energy requirements to heat the chamber?

Thanks

1/4"-1/2" (5mm - 8mm) is over-kill, and would take forever to heat up, and take 2-4x the heat to get the job done.

[Col]

Heat capacity of retort

1/4"-1/2" (5mm - 8mm) is over-kill, and would take forever to heat up, and take 2-4x the heat to get the job done.

I have thought about this heat sink issue in regard to a batch set up compared to a continuous system. Would the question not be better phrased like this? (I'm not up to speed on the technicalities so I'll just simplify it to illustrate the principle)
1 - what is the heat capacity of the 2.2mm walled tank? (say 2.2y J/K)
2 - what is the heat capacity of the 5mm walled tank? (say 5y J/K)
(Although I don't know if the relationship between wall thickness and heat capacity is strictly linear or not)
3 - what is the heat capacity of the starting quantity of feedstock in the tank? (say 10y J/K)
If the heat capacity of the feedstock is significantly greater than the heat capacity of the tank then the relative heat capacity of the tank is of less significance.
If you use a batch system and let the tank cool down between batches then the cost of the heat capacity of the tank needs to be taken into account for every batch. But if you run a continuous system and keep it going 24/7 (for the purpose of illustration) then you only need to consider the heat capacity of the tank once (per shut down). Once the tank gets hot it stays hot and transfers further heat application into the feedstock. So the heat capacity of feedstock can be very large relative to the heat capacity of the tank.
The same argument can be applied to choosing whether to use stainless steel or mild steel. If you don't let the retort cool down the heat capacity does not matter. Mild steel has better thermal conductivity than regular stainless steel so will transfer heat to the feedstock better, and has good expansion capabilities so won't crack like regular stainless steel. Supposedly 409 stainless steel will match mild steel in both of these capabilities (used on exhausts).
Note - if you are going to take a batch system and just keep pushing loads through it one after another, make sure you pre-heat the feedstock to extract at least all the water first. Some manufacturers of similar systems heat the feedstock to 200C before letting it enter the retort, but I don't know if this is for safety or just because they don't want to bother refining the light ends. In the case of WMO, one benefit of pre-heating the feedstock is that you can simply boil off the water, naptha, kero and diesel, in a larger and less complicated system, then just feed the remaining heavier oils through the cracking system. This will effectively multiply your throughput many times over, as really, only the thickest portion of the oil needs to be cracked. This reinforces again why a small cracking system is enough. A big boiler and condenser pre-treating the load first will take care of the rest.
Col

[neophite]

2.2mm vs 3.0mm

No, to the best of my knowledge propane is held at 1 atmosphere (1bar/15PSI). 1/8" (.125"/3mm) is good enough.

1/4"-1/2" (5mm - 8mm) is over-kill, and would take forever to heat up, and take 2-4x the heat to get the job done.

Thanks for this Biodiesel! I've found propane gas bottles rated to 30 bar and 2.2mm in thickness. I am having difficulty gas bottles 3mm thick. Any ideas?

Thanks!

[neophite]

Great Col!

I have thought about this heat sink issue in regard to a batch set up compared to a continuous system. Would the question not be better phrased like this? (I'm not up to speed on the technicalities so I'll just simplify it to illustrate the principle)
1 - what is the heat capacity of the 2.2mm walled tank? (say 2.2y J/K)
2 - what is the heat capacity of the 5mm walled tank? (say 5y J/K)
(Although I don't know if the relationship between wall thickness and heat capacity is strictly linear or not)
3 - what is the heat capacity of the starting quantity of feedstock in the tank? (say 10y J/K)
If the heat capacity of the feedstock is significantly greater than the heat capacity of the tank then the relative heat capacity of the tank is of less significance.
If you use a batch system and let the tank cool down between batches then the cost of the heat capacity of the tank needs to be taken into account for every batch. But if you run a continuous system and keep it going 24/7 (for the purpose of illustration) then you only need to consider the heat capacity of the tank once (per shut down). Once the tank gets hot it stays hot and transfers further heat application into the feedstock. So the heat capacity of feedstock can be very large relative to the heat capacity of the tank.
The same argument can be applied to choosing whether to use stainless steel or mild steel. If you don't let the retort cool down the heat capacity does not matter. Mild steel has better thermal conductivity than regular stainless steel so will transfer heat to the feedstock better, and has good expansion capabilities so won't crack like regular stainless steel. Supposedly 409 stainless steel will match mild steel in both of these capabilities (used on exhausts).
Note - if you are going to take a batch system and just keep pushing loads through it one after another, make sure you pre-heat the feedstock to extract at least all the water first. Some manufacturers of similar systems heat the feedstock to 200C before letting it enter the retort, but I don't know if this is for safety or just because they don't want to bother refining the light ends. In the case of WMO, one benefit of pre-heating the feedstock is that you can simply boil off the water, naptha, kero and diesel, in a larger and less complicated system, then just feed the remaining heavier oils through the cracking system. This will effectively multiply your throughput many times over, as really, only the thickest portion of the oil needs to be cracked. This reinforces again why a small cracking system is enough. A big boiler and condenser pre-treating the load first will take care of the rest.
Col

This is great stuff Col! Thanks.

[NickTech]

Hello to everybody

I have a question:

How much time is needed to see diesel production?

My machine ran for 1 hour whithout results so I stopped the fire.

thank you
Nick

[Excalibur]

The answer depends on how big the retort is, how much feedstock inside, how much heat is being applied and how big the heat losses are. If I could see the unit, I'd have a better idea. How about photos?

From memory, all my prototypes took at least an hour. Many would underestimate how much heat is required. Be sure to use thermocouples to monitor progress. A bubbler is also an indicator of gas flow though early bubbling is likely to be water boiling off, followed by a period of calm before gas flow creates bubbles. Soon after will come the first fuel drips probably around mid 300* -400*C.

I suggest to dismantle the unit and check for clogging with solid plastic. If all is well, then resume with thermocouples and bubbler. A sight glass/viewing port is also a good way of understanding what is going on inside.

Edit: I saw your pic after posting. I think there is not enough heat with that gas ring. Also there appears to be no insulation. The plastic bottle as a catch can will melt because the vapors will be exiting at 400*C with almost nothing to cool it before it runs out of the pipe.
Everyone's got to start somewhere. Even my first attempt I didn't make anything, then the second attempt I got 10-15liters of wax. Some upgrades will be necessary before you can produce fuel.

[Excalibur]

1- Is the standard propane tank 30 bar with a 2.2m thickness?

2- To air on the side of safety I am looking at thicker walls say 5mm or 8mm. will this require additional energy to heat the chamber? When I say additional energy I mean will it double/triple my energy requirements to heat the chamber?

By the looks without measuring, my old propane tanks here are 3mm wall. I think use heavier wall thickness for flame fired retorts or the thinner gauge for electrically heated. When I built my last retort vessel, from a safety point I really wanted 5 or 6mm but after several months hunting I settled on heavier. One thought occurred about the 3mm cylinders was to use for a time, then retire them periodically.
If you are happy to go with a heavy wall vessel, then consider converting a large, old oxygen bottle. The one that comes to mind is about 1.5m high and about 200mm diameter.
Logically, a heavy wall vessel will take more energy to initially heat up. They are best suited to using retort gases (or retort diesel) as the heat source. In such cases, the retort is "feeding off itself". The more heat makes more gas, which in turn makes more heat.

[Beyond Biodiesel]

Thanks for this Biodiesel! I've found propane gas bottles rated to 30 bar and 2.2mm in thickness. I am having difficulty gas bottles 3mm thick. Any ideas?

Thanks!

Should work fine as a small-scale prototype, good for a couple of runs.

[rozier56]

Hi folks, here is plant no3.I have changed the distillation column to a 40lt size[300MM X600MM].My retort is 300lt in volume full.I ran the plant at 330*c and could only produce 2lt/hr of diesel as you see attached.Looks like good product.At no stage was my condenser over heated as i have this temp monitored. This rate is far less than when i was using a small distillation column[4,5,LT].Any bright ideas about this?

[Babataku]

increase temp

Hi folks, here is plant no3.I have changed the distillation column to a 40lt size[300MM X600MM].My retort is 300lt in volume full.I ran the plant at 330*c and could only produce 2lt/hr of diesel as you see attached.Looks like good product.At no stage was my condenser over heated as i have this temp monitored. This rate is far less than when i was using a small distillation column[4,5,LT].Any bright ideas about this?

hi there,

1. 330 deg celc is way too low, consider increasing temp to 400 - 420 deg celc for maximum production results.
2. It seems that you are not insulating your lead / flange and since your exit pipe is not directly on the flange / lid, that uninsulated spot will act as a reflux zone and your actual reflux even if you heat it or insulate it will not be effective. consider insulating it.

Hope it makes sense

[rozier56]

Hi excalibur,when you were making approx 30lt/hr, what sort of reflux temps were you using? Babataku mentions 400-450*c.What is your opinion?

[NickTech]

The answer depends on how big the retort is, how much feedstock inside, how much heat is being applied and how big the heat losses are. If I could see the unit, I'd have a better idea. How about photos?

From memory, all my prototypes took at least an hour. Many would underestimate how much heat is required. Be sure to use thermocouples to monitor progress. A bubbler is also an indicator of gas flow though early bubbling is likely to be water boiling off, followed by a period of calm before gas flow creates bubbles. Soon after will come the first fuel drips probably around mid 300* -400*C.

I suggest to dismantle the unit and check for clogging with solid plastic. If all is well, then resume with thermocouples and bubbler. A sight glass/viewing port is also a good way of understanding what is going on inside.

Edit: I saw your pic after posting. I think there is not enough heat with that gas ring. Also there appears to be no insulation. The plastic bottle as a catch can will melt because the vapors will be exiting at 400*C with almost nothing to cool it before it runs out of the pipe.
Everyone's got to start somewhere. Even my first attempt I didn't make anything, then the second attempt I got 10-15liters of wax. Some upgrades will be necessary before you can produce fuel.

Thank you for your answer.

According to you, how I should modify my system to get better results?
Only insulation around the retort and termocuples to control the process is enough?

Thanks
Nick

[Excalibur]

Hi excalibur,when you were making approx 30lt/hr, what sort of reflux temps were you using? Babataku mentions 400-450*c.What is your opinion?

To clarify my figures are:
Retort: 380*C - 425*C
Reflux: 350*C
Diesel vessel: 80*C - 120*C
These temperatures are for runs with WMO. My plastic feedstocks are yet to be trialed. Note, my retort sensor is in the top of the vessel, not actually in the liquid. It gets the heat from the rising vapor. This may account for the fact that I can get quite good gas/condensate flow even at 380*C or possibly it's because the WMO is more lively than plastic feedstocks. I'd expect to have to revise the reflux temperature downward for plastic feedstocks. Please view the figures as a guide to be tweaked to the requirement of your setup, feedstock and conditions.

The upper condenser/water cooled heat exchanger. Does this have some incline as it runs away, toward the diesel reservoir vessel? I suggest at least a couple of degrees fall.

[Excalibur]

Thank you for your answer.

According to you, how I should modify my system to get better results?
Only insulation around the retort and termocuples to control the process is enough?

Thanks
Nick

Have a look at my first attempt in May 2012
There is an old propane 9kg cylinder inside the drum. In this system there is heat all around the 9kg cylinder. The vertical pipe to the right is the flue-stack. The heat is from burning timber.

I realized I was "blind" without thermocouples monitoring the process!

Insulation should go around the outer drum to minimize heat loss. This will give the heat less opportunity to wastefully bleed away to atmosphere.

I suspect your heat source will need upgrading too but fix one thing at a time. Step by step.