How to turn plastic waste into diesel fuel cheaply

[Excalibur]

Sure i'll not overflow it. Filling the half or perhaps 1/3 of it will be OK right ?

By the way how do you measure the progress of the process ? How do you exactly when do you shut the system, since there will lots of exhaust gases initially perhaps that will not be able to get weight measured in case i want to measure the amount of weight going out of the retort ???

I would say about 3/4 full is about right.

Thoughts on progress. The first thing you may notice is any included water will boil off as steam so it's a good idea to keep the temperature simmering around 100'c while it evaporates off. The bubbler activity is the thing to watch through the steam stage.

The rate of condensable fuels will slow toward the end. A higher relative quantity of non-condensable gas will then be produced. So somewhere around this time, the amount of return doesn't justify spending more energy to extract. This would be especially true if the heat was costing $$.

I'm building in a viewing port into my new refinery at the diesel condenser. The hope is that I can learn a lot from the drip rate and hopefully how the process is progressing.

Hope this helps.

BTW. On my blog I've just posted up 6 more detailed pics of my retort/reflux assembly. See the page titled: Turk-retort vessel mk6, item 4

[Beyond Biodiesel]

Hi guys! Today I cam up with another idea for how the heat absorption be made more efficient and I came up with the following design (on the picture below).


I saw on Blest bigger units the retort is actually laying horizontal so why not get heated both ends internally.

Soon my father is coming and we will build an experimental unit and I'll start sharing data.

Can you give suggestions please what is best to experiment with initially.

I will start with different types of plastic (PP and HDPE), the with temperature, then with catalyst and different combinations between those too.

Cheers: Ivo

Ivo,
1) there are good reasons to have the retort tall, as Excalibur pointed out avoiding over flow due to expansion.
2) The top 1/4 of the retort works well as a refluxing zone
3) Good luck finding an immersion heater that can handle 400c.
4) I use a hot plate on the bottom, plus band heaters on the sides, plus a heat top on the top and refluxing zone.

I finally got around to testing out a batch of my new catalyst and I wanted to post my results here-

Conversion rate:73% to liquid fuel (have no way to measure noncondensable gasses but significant "smoke" was coming out)

Fuel composition-
89.5% gasoline
8.9% kerosene
1.6% diesel

No waxes.

This is far from ideal as I want a conversion rate to fuel of ~90% with the remaining ~8-9% to be gasses to power the unit.

Impressive results.

Sure i'll not overflow it. Filling the half or perhaps 1/3 of it will be OK right ?

By the way how do you measure the progress of the process ? How do you exactly when do you shut the system, since there will lots of exhaust gases initially perhaps that will not be able to get weight measured in case i want to measure the amount of weight going out of the retort ???

Knowing when to turn off your pyrolysis unit is a big challenge. Monitoring the bubbler rate seams to be the best way.

I used to monitor the drip-rate into my kerosene and gasoline collection flasks, but I had trouble with sealing them, so they are now metal, so I cannot see into them. Excalibur view port idea hold merit here.

Early on I just monitored the temperature closely; and kept doing runs that went on all day, and finding the process complete, so I started backing off and found it took 2 hours for my pyrolysis unit to get to 400c, and 2 hours at the control point to complete the pyrolysis run. So, you might try the same thing.

[mjohnson1]

Can anyone else chime in on their overall conversion % by weight for liquid fuels?

[imakebiodiesel]

mjohnson1, as you have probably worked out yourself you have a bad case of overcracking.
My guess is that you are using a very active catalyst such as zeolite or something similar. This produces a very high proportion of the more volatile fractions. It also has a very short working life before it cokes up which would explain the low total conversion ratio.
A smaller amount of your active catalyst mixed with a slower, clay type catalyst might just do the trick.

I am at present submitting a sample of my kerosene for testing to British Standards. I will know in a few weeks whether my fuel is up to the standard of commercial kerosene. Im fairly confident that it will pass on specific gravity, flash point, viscosity, smoke point and distillation test as can test for these myself. It may fail on colour as my fuel is not as pale as commercial kerosene.

In my latest batches in my new processor I am getting 90% conversion. The liquid output is 92% kerosene, 8% light naphtha.
The 10% residue is a black coloured paraffin wax. Both the light naphtha and the paraffin wax are saleable products used in various industrial processes.

Just a note on the use of the word gasoline or petrol to describe the light fractions derived from this process. Calling it gasoline will encourage beginners to put this fraction into the fuel tanks of their vehicles without further processing which will quickly do damage. Strictly speaking this fraction should be called naphtha. Naphtha needs to be upgraded, usually by hydrocracking to make it into gasoline. Naphtha itself is low grade, low octane fuel that has almost no lubrication or detergent qualities. From my own tests up to 25% naphtha can be added to high octane unleaded gasoline without risk of damage to the engine but no more.

[mjohnson1]

imakebiodiesel,

Thanks for your reply. You are indeed correct about the overcracking of the catalysts. I was very surprised when I was losing several grams of liquid fuel per hour just letting the container sit out in ~19C weather. I ran a second test last night and the conversion % increased by 7% and the fractions shifted towards the diesel range with still no waxes being produced. This was using the same batch of catalyst as the first test with no treatment to get the coke off.

Your kerosene could always be bleached with some type of bleaching agent if the color was a big concern.

90% conversion is excellent. Are you able to modify your catalyst to produce more off gases? Ideally, I feel that ~9% off gases will allow the unit to be powered on its own feedstock once an external heat source brings it up to temperature.

Your gasoline explanation is all correct. I should have referred to it as naptha like you said. I wouldn't trust this fuel in my modern car engine.

[mtrans]

Can you give suggestions please what is best to experiment with initially.

I made this for WMO,f110mm OD,heaters are 2x2kw in f70mm OD all IN ONE tube.
+ easy to heat
-not good for clean,easy vacuum put water inside,I DIDN`T get much,etc
I think boiler need some height to do our job.

[lowriderzzz]

I made this for WMO,f110mm OD,heaters are 2x2kw in f70mm OD all IN ONE tube.
+ easy to heat
-not good for clean,easy vacuum put water inside,I DIDN`T get much,etc
I think boiler need some height to do our job.

so what if the boiler is still upright and there is internal heating on the top and the bottom is heated with classic way (fire).

Will this increase heat absorption efficiency ... by much worth ?

[lowriderzzz]

do I get the bubbler design right ?

I read the tread but i didn't noticed exact design of the bubbler or I forgot it.

I made a simple sketch of how it looks like, can you just confirm if I'm right or wrong about the design of it.

Do you actually burn the gasses after the bubbler or you burn it only in case you don't use bubbler ?

[operatorX225]

the gases should come from the condenser and enter the bubbler force itself through the water level and out to the exhaust stream. your arrow saying to condenser should be flipped over and say from condenser.

[Excalibur]

I read the tread but i didn't noticed exact design of the bubbler or I forgot it.

I made a simple sketch of how it looks like, can you just confirm if I'm right or wrong about the design of it.

Do you actually burn the gasses after the bubbler or you burn it only in case you don't use bubbler ?

Yes, it's not always easy to remember everything. It's why I read through the thread a 2nd time. I was surprised how much more made sense. Finding specific info in the thread is another problem though I have had some luck using "Advanced search", particularly when I know whose post I'm looking for as it's possible to specify a user name as well as a keyword.

Basically, the sketch looks OK. Ideal would be a transparent vessel or a window to see the bubbling. A means of filling, topping up and draining the water would be an advantage.

Good idea to burn the gases after the bubbler. This eliminates the smell and reduces the risk of simply having explosive gas floating around the site. The bubbler itself is an effective flame trap because flame can't jump from bubble to bubble.
One problem can be the stop-start-stop-start nature of the bubbles. This will tend to allow any flame to go out. A bubble diffusor might be the answer here. Also I would put a simple flame trap at the burner head. Some sort of igniter at the burner might be necessary on permanent ignition duty.

[imakebiodiesel]

Mjohnson1, interesting result with the "spent " catalyst. There are many scientific articles about converting plastic to oil using "spent" fuel cracking catalyst from refineries.
I have worked hard to reduce both the heavy and the light fractions in my fuel as I am interested in producing a kerosene,middle distillate, fuel. Removing the heavy fraction is easy and can be done simply by managing the reflux temperature. I have reduced the light fraction by using only enough high activity catalyst to get the cracking going quickly and then depending on a lower activity catalyst for most of the run.
Mixtures of catalysts can be designed to produce whatever fuel profile you want.
Reducing the light fraction also reduces the gas output , in fact when my processor is running at maximum output the gas can barely support a flame in a small gas ring.
I can do better than 90% conversion. If I continue the run to the very end I can get 98% conversion and all that is left is a dry carbon char. However it wastes time and fuel going that far and the residue has no commercial value so I stop at 90%.

[Beyond Biodiesel]

so what if the boiler is still upright and there is internal heating on the top and the bottom is heated with classic way (fire).

Will this increase heat absorption efficiency ... by much worth ?

If you can work out way to have an immersion heater that can handle the temperature while maintaining a leak tight seal, you will then be only half there, because the retort as a whole needs to be heated to cracking temperature, or otherwise you will just have your boil refluxing off the sides and lid until they come up to temperature. So, I prefer to heat from the outside in, not from the inside out.

[mtrans]

One problem can be the stop-start-stop-start nature of the bubbles.

It`s problem.
I use LPG burner all the time on minimum.

[Col]

Targeting a particular fuel profile

I expect there is a tendency for single-ingredient catalysts to preferentially react with particular molecular lengths. But could it be said that most catalysts will cut whichever hydrocarbon molecule bumps into it?
I am after the diesel fraction. So if I want to minimise the off-gas and naptha fractions wouldn't I add the catalyst to the retort / reflux column only after all the fractions down to diesel have been distilled off? I will use WMO as feedstock so I only need to boil / distil off the fractions down to diesel, then add the catalyst to the system to cut the remaining longer oily molecules into shorter ones. This way I prevent my target fuel profile from bumping into the catalyst and being cut into naptha and off-gas.
Does that sound reasonable?

[mjohnson1]

imakebiodiesel,

I've looked into the spent catalyst that you speak of but everything ive read says it produces too much off gas/light fractions. I managed to secure a sample and my tests matched those claims.

It never crossed my mind to mix catalysts together. Sometimes the simplest ideas escape my mind.

I was mainly referring to the percentage of off gases generated as I feel it is better to get 80% liquid fuel and 10% off gases when running a continuous unit because the off gases can be used to help maintain the temperature in the unit.

Everyone here is running a batch system, myself included, so the off gases will be somewhat wasted.