How to turn plastic waste into diesel fuel cheaply

[rozier56]

Hi folks, just a couple of points.
The reflux vessel temp is measured at the top of the reflux{330*c}
The reflux size you mentioned of 1/4 the size of the retort? due you mean a 1/4 of the vessel size, i.e.220kg volume or the height of the vessel.
Thks.

[Col]

Reflux dimensions and size

Hi fellas.
I have a 400L retort (10mm mild steel). I have an air compressor tank of 150L which I plan on using for the reflux. Although this is larger than the recommended 20-25% I am making a continuous feed system (WMO) so I figure so long as I can maintain the reflux temperature the size of the reflux doesn't matter. I think that so long as the reflux exit is at the right temperature and the vapour supply does not stop, the continuous stream of vapours should just keep refluxing and exiting. At the extreme, you could have a 10m high refluxing column and so long as the temperature was controlled from shell to core and the top section was at the right temperature (and lowest temperature within the reflux) it should work fine. Am I missing something?
I plan on heating the reflux with the exhaust air from the retort, spiralling around the reflux on the way up to the flue. If the reflux temperature climbs too high I will open a bypass vent at the bottom of the reflux heating sleeve to let some hot exhaust air escape. This can be automated later.
Thanks, Col

[Excalibur]

Hi folks, just a couple of points.
The reflux vessel temp is measured at the top of the reflux{330*c}
The reflux size you mentioned of 1/4 the size of the retort? due you mean a 1/4 of the vessel size, i.e.220kg volume or the height of the vessel.
Thks.

Retort to reflux ratio is by volume. I think the probe position would work most anywhere in the upper half of the reflux. What's critical is that it gives an important point of reference that helps determine the SG of the product at the 1st condenser trap.

[Excalibur]

Hi fellas.
I have a 400L retort (10mm mild steel). I have an air compressor tank of 150L which I plan on using for the reflux. Although this is larger than the recommended 20-25% I am making a continuous feed system (WMO) so I figure so long as I can maintain the reflux temperature the size of the reflux doesn't matter. I think that so long as the reflux exit is at the right temperature and the vapour supply does not stop, the continuous stream of vapours should just keep refluxing and exiting. At the extreme, you could have a 10m high refluxing column and so long as the temperature was controlled from shell to core and the top section was at the right temperature (and lowest temperature within the reflux) it should work fine. Am I missing something?
I plan on heating the reflux with the exhaust air from the retort, spiralling around the reflux on the way up to the flue. If the reflux temperature climbs too high I will open a bypass vent at the bottom of the reflux heating sleeve to let some hot exhaust air escape. This can be automated later.
Thanks, Col

Good explanation. A reflux could be any size if only its' temperature could be controlled. Heating the reflux gives some interesting possibilities. It could mean that the targeted product would come on stream quicker. It's a good way of recycling waste heat too.
Controlling temperature could be as simple as a bimetallic spring connected to a butterfly valve. These were common in exhaust systems and auto-chokes in cars of 1960's. See this example

[rozier56]

Thks to all for your reply's.My concern seems to have been answered, i just dont want to create any boil-over and have max production.

[Beyond Biodiesel]

Another point on the reflux is it is better for it to be wide than tall, meaning a reflux that is 1/4 the volume of the retort, but 1/10th its diameter would be a poor design; whereas, a reflux that is 1/4 the volume of the retort and about the same to 1/4 its diameter should work fine. Your exit for the retort should be as large as possible as well, or otherwise it could coke or wax up.

Down stream from your first trap the pipe diameter could be quite small depending upon your flow rate.

[rozier56]

Thks BB. It was good to talk to you on skype.

[Karl_Palsness]

Cracking the hydrocarbon

Hey folks,

Been quite sometime since I've been on the form I see a lot has happened the past while.

My question is regarding cracking the hydrocarbon does anybody know if you can crack it in the gas state or do you have to crack it in the liquid state. The point being, can the gases coming off at a lower temperature be cracked and a high temperature state or do you have to bring the whole liquid up to a higher temperature to crack it to lighter hydrocarbons before it boils off under pressure?

I am just sitting here reading the thread from the beginning as I am thinking of the little machine to do this? The cost of fuel is over a $1.50 per liter now and is getting ridiculous to commute to work.

Looking forward to your comments

Karl

[Col]

Reflux design, condenser design

Another point on the reflux is it is better for it to be wide than tall, meaning a reflux that is 1/4 the volume of the retort, but 1/10th its diameter would be a poor design; whereas, a reflux that is 1/4 the volume of the retort and about the same to 1/4 its diameter should work fine. Your exit for the retort should be as large as possible as well, or otherwise it could coke or wax up.

Wide is better than tall - really? My retort was 1200mm tall x 800mm diameter including a dish end floor. I cut it from a pressure vessel twice the height which had been a liquid / gas phase separator, so it had a 300mm thick pad of stainless steel mesh packing part way up it. I cut out a 300mm segment of the tank and put the packing in there with flanges so it was a removable reflux zone. I put a couple of splash plates below the packing to keep it from being doused with violent splashes of black boiling oil. I had intended to operate the two together until BBD pointed out to another forum member that it could be hard to control the reflux temp if the two were part of a 'single tank' so to speak. I recognised the reflux temperature is critical so binned the idea and was about to use an air compressor tank as a separate vessel a little way above the retort. But the air compressor tank is tall and not so wide (1275mm x 420mm) and the mesh filled segment of the first tank is short and wide (300mm x 800mm), same diameter as the retort. Coincidence has it that both are approximately 35% of the volume of the retort (but not 35% of the WMO fill level, which will be about half way down and constant as it will be a continuous feed system, so the reflux will be about 70% of the volume of the WMO in the retort).
I expected that a tall reflux would be better than a short one, more opportunity for separation of molecules of different SG's. Is it that the narrower the column is the faster the flow rate will be and that disturbs the distillation process? Won't a short, wide reflux make it difficult to control the temperatures? less height to allow reduction of temperature from 425C in the retort to the desired reflux exit temperature? More width will also make it more difficult to keep the temperature uniform from core to shell. Perhaps the rising vapours will keep the core the right temperature and the waste heat circling the reflux can keep the shell at the right temperature.
Does anyone have any experience or ideas on whether a reflux zone the same diameter as the retort and attached directly to the retort will be difficult to maintain at the right temperature? I expect I will insulate the retort only, leaving the reflux above, using the waste heat from the retort heating to control the temperature of the reflux zone. I was happy with this concept using the taller air compressor tank but am unsure I can control the temperature in the core using a wide reflux zone.

I have a good condenser I picked up from a neighbouring business shutting down selling off it's factory gear. It is a horizontal tube condenser with 100mm inlet and outlet pipes. I have put a 100mm vapour outlet on the retort / reflux exit. I expect with this set up I should be able to crank up the throughput later after proving the system first.

[Excalibur]

Does anyone have any experience or ideas on whether a reflux zone the same diameter as the retort and attached directly to the retort will be difficult to maintain at the right temperature? I expect I will insulate the retort only, leaving the reflux above, using the waste heat from the retort heating to control the temperature of the reflux zone. I was happy with this concept using the taller air compressor tank but am unsure I can control the temperature in the core using a wide reflux zone.

I've often pondered over the idea of retort-reflux being the same diameter.
It has a number of good things going for it. It could be fabricated using a continuous length of pipe saving time, effort and resources. A plate welded at the desired dividing point between the two chambers would have a center port hole bored. Reflux temperature might be controlled by the insertion of a "reducing bush", so in this way the heat can be manipulated.
For diesel fired plants, the reflux could be heated with the same flue gas and with minimal effort. A set of dampers could be employed to divert the hot flue gas directly to the stack or via the reflux.
These ramblings are untested theory...

[Beyond Biodiesel]

Thks BB. It was good to talk to you on skype.

Yes, it was.

Hey folks,

Been quite sometime since I've been on the form I see a lot has happened the past while.

My question is regarding cracking the hydrocarbon does anybody know if you can crack it in the gas state or do you have to crack it in the liquid state. The point being, can the gases coming off at a lower temperature be cracked and a high temperature state or do you have to bring the whole liquid up to a higher temperature to crack it to lighter hydrocarbons before it boils off under pressure?

I am just sitting here reading the thread from the beginning as I am thinking of the little machine to do this? The cost of fuel is over a $1.50 per liter now and is getting ridiculous to commute to work.

Looking forward to your comments

Karl

Just keep in mind cracking temperature is 425C. Hydrocarbons are in vapor phase at that point.

Wide is better than tall - really?

Not really. You just do not want either your retort or reflux to be tall and skinny. A ratio or 1:4 or 1:3 between the diameter and the height is best.

My retort was 1200mm tall x 800mm diameter including a dish end floor. I cut it from a pressure vessel twice the height which had been a liquid / gas phase separator,

Sounds just right.

so it had a 300mm thick pad of stainless steel mesh packing part way up it. I cut out a 300mm segment of the tank and put the packing in there with flanges so it was a removable reflux zone. I put a couple of splash plates below the packing to keep it from being doused with violent splashes of black boiling oil.

Sounds just right.

I had intended to operate the two together until BBD pointed out to another forum member that it could be hard to control the reflux temp if the two were part of a 'single tank' so to speak.

Huh? I see no problem with your proposed design. If anything if the reflux is just the upper 1/4-1/3 of the report then it is likely to have the same temperature as the retort, which is good. If the reflux is at a lower temperature than the retort, then your fluid for cracking will just reflux for ever.

I recognised the reflux temperature is critical so binned the idea and was about to use an air compressor tank as a separate vessel a little way above the retort. But the air compressor tank is tall and not so wide (1275mm x 420mm) and the mesh filled segment of the first tank is short and wide (300mm x 800mm), same diameter as the retort. Coincidence has it that both are approximately 35% of the volume of the retort (but not 35% of the WMO fill level, which will be about half way down and constant as it will be a continuous feed system, so the reflux will be about 70% of the volume of the WMO in the retort).

I do not see any of this as a problem.

I expected that a tall reflux would be better than a short one, more opportunity for separation of molecules of different SG's. Is it that the narrower the column is the faster the flow rate will be and that disturbs the distillation process?

The point of a reflux zone is to reduce boil over, so you want the velocity of the vapor stream to slow down, to allow droplets of condensate to precipitate out of the stream.

Won't a short, wide reflux make it difficult to control the temperatures? less height to allow reduction of temperature from 425C in the retort to the desired reflux exit temperature? More width will also make it more difficult to keep the temperature uniform from core to shell. Perhaps the rising vapours will keep the core the right temperature and the waste heat circling the reflux can keep the shell at the right temperature.

The vapor stream heats the reflux, but it should be insulated and heated to the desired temperature. There should not just be 1 reflux zone, but several, one for each condenser trap, and the reflux is of course after the desired trap zone, not before it.

I have a good condenser I picked up from a neighbouring business shutting down selling off it's factory gear. It is a horizontal tube condenser with 100mm inlet and outlet pipes. I have put a 100mm vapour outlet on the retort / reflux exit. I expect with this set up I should be able to crank up the throughput later after proving the system first.

Sunds good

I've often pondered over the idea of retort-reflux being the same diameter.
It has a number of good things going for it. It could be fabricated using a continuous length of pipe saving time, effort and resources. A plate welded at the desired dividing point between the two chambers would have a center port hole bored. Reflux temperature might be controlled by the insertion of a "reducing bush", so in this way the heat can be manipulated.
For diesel fired plants, the reflux could be heated with the same flue gas and with minimal effort. A set of dampers could be employed to divert the hot flue gas directly to the stack or via the reflux.
These ramblings are untested theory...

Sounds good

[rozier56]

Hi folks,How is this idea?
My retort is 850mmlengthx333mmwidth radius.=296metres.
Proposed retort to be placed directly on top of retort is 1meter x 12mm width radius =45 meters.
How does that sound keeping in mind that 1/4 of 296 =74meters.
Another point is that the retort temp in my case is always higher than my reflux temp.Temp is measured in retort open area and reflux at the top of the reflux.
THKS.

[Beyond Biodiesel]

Hi folks,How is this idea?
My retort is 850mmlengthx333mmwidth radius.=296metres.

Sorry rozier56, this does not make any sense to me. Are you using the term 'width' to refer to 'diameter' or 'thickness,' or neither? You also switch from MM to meters??

Proposed retort to be placed directly on top of retort is 1meter x 12mm width radius =45 meters.

Same here, it does not add up.

[mercedes 308]

Catalytic Pyrolysis by Heat Transfer of Tube Furnace for Produce Bio-Oil

Came upon this though could be useful here.
Pyrolysis of grasses and leaves to produce bio oil.

[VAST]

Continues Feed System

I was wondering after reading Excalibur`s account of his efforts, if you want to create a continues feed system, should you reduce the amount of feedstock in your retort to get a faster reaction from processing the feedstock?

Will it not be better to have less feedstock with temperatures that can almost instantly convert your continues feed into gas than to heat the feedstock up to the correct temperature because the feedstock level is to high, thereby when introducing new colder feedstock dropping the temperatures in the retort and slowing down the process?

If one would want to create a system that can deliver 50 liter diesel per hour, how big should the reactor unit be to allow for such a system?

If the feedstock level can be kept lower but the pyrolysis takes place on a faster scale, will that allow to have a smaller reactor unit or will that defeat the purpose to try and create a chamber where the reaction can take place faster in a shorter time period? A smaller reactor means a faster time to achieve the heat requirements, less feedstock in the chamber, can also reduce boil over of feedstock, but that also means that maybe you can`t reduce the size of the reactor?

How should you determine the scale for your reactor based on the amount of fuel you want to produce per day or per hour?