How to turn plastic waste into diesel fuel cheaply

[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...

[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.

[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

[rozier56]

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

[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 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.

[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

[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.

[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

[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.

[Beyond Biodiesel]

Babataku,
yes I am revising my insulation and burner, will report back
Thanks

I find 4" (10cm) of good insulation works well. The first inch (2.5cm) should be high temperature insulation; after that you can get away with simple cardboard, unless you use a flame for heating.

Thks beyond,the 435*c you talk about is that measured at the retort?Also i am wondering about the reflux column sizing?What info is available regarding sizing of this unit with reference to the retort,i.e.diameter and heights etc.

Yes, I have a thermocouple that goes down to just 1 inch (2.5cm) above the bottom of the retort. I then I have a thermocouple on the exit of the reflux.

The reflux should be about 1/4 the size of your retort.

Hello Everybody

First, I would like to thank Jetis for starting this thread, and then to all the prominent people who are willing to share their knowledge with us, like ImakeDiesel, Beyond BioDiesel, Excalibur and Asad and to all the others who have written about their experience with this process.

It was a long read, but very informative and valuable.

To those of us who wants to start doing this, the newbies, don`t rush, this is a dangerous process, no matter how you look at it, you are working with a bomb under the right circumstances, don`t take things for granted.

...

Once more, thank you to all the people who are willing to part with their knowledge and experience.

In the next week, I will be starting to build my own system based on all I have learned here, I have already gotten most of the raw material together, just need a few electronics and flanges, then I can start. I’m sure that I will need lots of help and guidance, because although the principle of the system is easy to understand the reality is that it is tricky to get what you desire.

Welcome, VAST, and thanks for posting some excellent advice here.

[Excalibur]

Hi folks, please note this is a picture of my finished plant.Note that we are using lpg gas as our heat source.The retort is a 220kg capacity plant going through a retort system into a triple tree condenser,product collected in first tank,gas then collected and pushed through attached water bubbler and returned to retort for burn-off.My question remains at what temps are you burning at and at what point are your measurements taken?I wish to maximise my system.

Up to 425*C retort however if gas flow and drip rate are good I use less. The thermocouple probe is at the top of the retort.
Perhaps you mean flame temperature? I used up to about 800*C measured just after the turk burner head.

(Feedstock mostly Hdpe/LDPE)
Reflux was increased to 4 feet with a series of baffles and catalyst (red Clay).

Fuel out put wasfeedstock was around 100kg
First Condensor: Duel was dark brow/Yellow Clear 20 liters, SG was 0.85
Second condensor (After water cooling) out put was dark brown/yellow clear 9 liters SG was 0.75. I thought this was good as petrol, put it in one of my cars and the engine was missing badly.

Could this be due to pre ignition? too low Octane? kindly help me clarify the problem.

Also the process took ages 2 hours to heat upto 250 C but peaked at 380C.(after 4 hours)
The Gas slowed down after 6 hours and temperature at the water Condensor inlet reduced considerbly, so I thought no vapour flowing so switched the process off.
When i opened the retort i found nearly 30 kg of unburnt yellowy waxy Hydrocarbons, was expecting black Char.
Could somebody clarify why this unburnt?
Can it be due to too low a retort temperature, can the Reflux now be Too big?

Your .75SG is very close to some petrol SG according to SG charts. Does it ignite with a match-stick? I tried some in a lawnmower, it took some convincing to start but ran well enough to mow lawn. Be sure to filter it.
Making effective petrol won't be a simple as diesel. There's octane to consider for one thing.

I agree with others, it sounds as though you don't have enough heating power and/or the heat losses are too big. It takes a surprising amount of heat to bring a retort up to 400*C, more heat than many would think.

Given that the diesel SG is good then one could reason that the reflux is working OK. With increased proposed retort temperature, that balance might change. Be ready to tweak the reflux temps to suit.

It may have been that when the gas flow stopped after the 6hrs, the target boiling point of the feedstock had risen above the 380*C your system peaked at. It would be prudent to notarize the feedstock quantity and balance it against production. In this way, you can be sure how much there is left in the retort.

Thks beyond,the 435*c you talk about is that measured at the retort?Also i am wondering about the reflux column sizing?What info is available regarding sizing of this unit with reference to the retort,i.e.diameter and heights etc.

Yes, 425*C is retort temperature.
Probably 20 -25% is about right for reflux to retort ratio.
I'm thinking of reducing mine slightly in size if I don't get the temperature to stay high enough for my system. (See blog for current dimensions)

Welcome VAST

[VAST]

Wonderful Information

Hello Everybody

First, I would like to thank Jetis for starting this thread, and then to all the prominent people who are willing to share their knowledge with us, like ImakeDiesel, Beyond BioDiesel, Excalibur and Asad and to all the others who have written about their experience with this process.

It was a long read, but very informative and valuable.

To those of us who wants to start doing this, the newbies, don`t rush, this is a dangerous process, no matter how you look at it, you are working with a bomb under the right circumstances, don`t take things for granted.

Read the forum from start to finish, I know we all want to build the best machine from the start, but all the experience that is given through here is so valuable, you will be able to dodge difficulties if you read through the thread from the beginning.

Don`t jump from one place to another, you will miss valuable information which you will have to go and lookup later in any case.

Make notes from the beginning, divide it into sections so that it is easy to refer back to it, copy the whole thread with all the information from who authored the post and the permanent link to that specific post, so that it is easy to find what you are looking for later in all this pages when you want to refer back to a discussion.

Make a big note for yourself about which plastics is save to use and put it right in front of all your information. I think this is one of the most important parts of this discussion so that you don`t blow yourself up by accident or your family and neighbors.

This whole process work by temperatures, if you don`t control your temperatures right, you can either endanger yourself and others or you will not get the results you aim for.

The reflux column is an important aspect to understand for your safety. Make sure you read up about it so that you can exclude the hazard from blockage in your system and the danger that can be caused here if your temperatures and reflux column is not correctly implemented.

In all this, safety should be your first concern, take the correct steps for the worst case scenario. Study what steps should be taken to douse flames that is started by oil or flammable gas, have a kill switch that can stop your process dead in its tracts for in an emergency.

Once more, thank you to all the people who are willing to part with their knowledge and experience.

In the next week, I will be starting to build my own system based on all I have learned here, I have already gotten most of the raw material together, just need a few electronics and flanges, then I can start. I’m sure that I will need lots of help and guidance, because although the principle of the system is easy to understand the reality is that it is tricky to get what you desire.

[rozier56]

Thks beyond,the 435*c you talk about is that measured at the retort?Also i am wondering about the reflux column sizing?What info is available regarding sizing of this unit with reference to the retort,i.e.diameter and heights etc.

[dippy909]

Babataku,
yes I am revising my insulation and burner, will report back
Thanks