How to turn plastic waste into diesel fuel cheaply

[wheels]

(needing big heating and at the same time creating huge pressure)

Wow, back up the Horse there mate. What do you mean by Huge pressure? There should be no pressure. None at all. Except for the very little the water level in the Bubbler creates. If you raise pressure, you increase the point in temperature that the Plastic will boil at. In fact if it were easy to do, pyrolysis under a Vacuum is the best way to carry out the process. A Vacuum means you need a lot less heat which means less energy and you get a much more stable Fuel and far less nasties being produced. If you have pressure and need more heat to create the gas, then you run the risk of having the boiling point of the plastic in the range of where it will produce Dioxins and be a Fuel that will tend to oxidize easily and quickly.
But the biggest concern is a large volume Vessel under pressure and heat that has not been designed for such.

because temp was precisely controlled through pid controllers

So with such a large installation, how do you use the PID to control the heat?

outlet pipes are also 60%size of that of retort that is 60 mm

You need to design the diameter in relation to back pressure. You want next to no back pressure at all. So you calculate the Volume of gas and see if that will pass through the diameter and length of Pipe with no back pressure. For every Bend in the Piping, you add considerable restriction and that needs to be calculated as well. For instance, a 90deg bend will result in the need to increase the pipe size by 25mm squared.

also i think here also the size of cyclone must be reviewed

This is where you need to know Volume and Velocity of the Vapor and you then design the Cyclone to work the most efficiently at that. Many make the mistake of making a large diameter cyclone. You would be surprised at just how small a Diameter you need. The Vapor needs to spin as fast as possible to allow the very fine carbon dust to settle out.

[Beyond Biodiesel]

To add to BBD and give some of you a little heads up to what you are playing with. If you take 60mls of Petrol and vaporize it, you now have close to the same explosive power as an entire stick of Dynamite. Now consider just how much vaporized fuel you have in your Retort, at a temperature of 400DegC and consider just what will happen should oxygen ever get into the system.
I missed the comment sunilkm153 made about the Retort being designed re the welding and heat. You can not design any metal vessel for what they are being put through. Cracks are inevitable, because that is what Steel will do in heat. Regular Inspection/Testing of the welds need to be carried out. Failuer to do so will get you on the local 6 Oclock news after you have just leveled the Town. Unfortunately you may not be around to watch it.

Just to add to wheels excellent reality check here. ALL pyrolysis units MUST be leak tested EVERY time they are used. I do not believe that leak testing has been described here, so this is one of many ways to leak test a pyrolysis unit. Before loading a pyrolysis unit, with it cold, close off the outlet, and pressurize the entire pyrolysis unit from retort to bubbler to about 5PSI, then spray soapy water over every weld, and every fitting, and every joint. Pay close attention to any bubble formation. If you see bubbles, then tighten the fitting, or re-weld the weld, before running the unit again. You will need to have easily removable insulation to accommodate leak testing.

You are welcome, sunilkm153.

[sunilkm153]

Wow, back up the Horse there mate. What do you mean by Huge pressure? There should be no pressure. None at all. Except for the very little the water level in the Bubbler creates. If you raise pressure, you increase the point in temperature that the Plastic will boil at. In fact if it were easy to do, pyrolysis under a Vacuum is the best way to carry out the process. A Vacuum means you need a lot less heat which means less energy and you get a much more stable Fuel and far less nasties being produced. If you have pressure and need more heat to create the gas, then you run the risk of having the boiling point of the plastic in the range of where it will produce Dioxins and be a Fuel that will tend to oxidize easily and quickly.
But the biggest concern is a large volume Vessel under pressure and heat that has not been designed for such.

So with such a large installation, how do you use the PID to control the heat?


You need to design the diameter in relation to back pressure. You want next to no back pressure at all. So you calculate the Volume of gas and see if that will pass through the diameter and length of Pipe with no back pressure. For every Bend in the Piping, you add considerable restriction and that needs to be calculated as well. For instance, a 90deg bend will result in the need to increase the pipe size by 25mm squared.


This is where you need to know Volume and Velocity of the Vapor and you then design the Cyclone to work the most efficiently at that. Many make the mistake of making a large diameter cyclone. You would be surprised at just how small a Diameter you need. The Vapor needs to spin as fast as possible to allow the very fine carbon dust to settle out.

my intention to say big heating and huge pressure is that in case of static vertical retort you have to put all 5000 kgs of stuff in retort at one time which need big heating and in case of blockage or any other complication a huge pressure buildup is there where in my case at a time here only 150 - 200 kgs of raw material will be there in kiln
so dear friend is it possible to blow a whole town with just 150 kgs of waste plastics which gets processed at atmospheric pressure with professional safety controls
secondly I mentioned data from my 100 mm dia retort having processing capacity of 300-350 kg / day which is not easily but effectively controlled through PID controllers where in case of 5000 kg plant I am willing to go for PLC-SCADA controls
thirdly for designing pipe size or cyclone or condensors only vapour density and volume are not sufficient you also need molecular weight and molar density of the gas

Just to add to wheels excellent reality check here. ALL pyrolysis units MUST be leak tested EVERY time they are used. I do not believe that leak testing has been described here, so this is one of many ways to leak test a pyrolysis unit. Before loading a pyrolysis unit, with it cold, close off the outlet, and pressurize the entire pyrolysis unit from retort to bubbler to about 5PSI, then spray soapy water over every weld, and every fitting, and every joint. Pay close attention to any bubble formation. If you see bubbles, then tighten the fitting, or re-weld the weld, before running the unit again. You will need to have easily removable insulation to accommodate leak testing.

You are welcome, sunilkm153.

DEAR BBD To avoid any possible leakages radiographic and ultrasonic weld testing are the most commonly used methods used to check weid joint and naturally I am going to get the kiln checked with this methods when my bigger capacity rotary kiln gets fabricated which is under fabrication by professional certified boiler manufacturer Also the kiln is checked under pressure 40-50 psi also after completely checked a blown over valve (2.5 -3 psi) is added to kiln which is also linked to hot air generator in case of blown over it not only releases the pressure from the kiln but also shuts down hot air generator and feeding line

[Excalibur]

Thanks for the idea an inclined vertical outlet pipe will be an good option but here in my case from one end of centre axis plastics are feeded while through other centre axis vapours are taken out and exactly below this outlet pipe carbon removal screw is placed so if refluxed heavy fractions got back through outlet pipe they get directly over carbon removal screw wetting dry powdery carbon and disturbing the process so please if you suggest any other possible solution .

How about piping the reflux return to the feed end of the kiln? In this idea, the vapours get fed into the upper part of a reflux chamber. When uncracked hydrocarbon vapour condenses in there, it drains out from the reflux bottom and is piped to the kiln infeed end. The reflux needs to be high enough so that there is sufficient fall.
A further thought was to have a hollow auger shaft and use this the vapour channel and/or reflux return.
Sadly without pictures I'm struggling to visualize your construction so these ideas may not be possible or applicable.
Hope this helps.

[jonathan]

retort question

my uncle give me some exhaust insulation wrap and i am doing some tests.i have question. i make pressure cooker to a 3l glass condenser. i try lunchbags in small pieces and i got over 0.5 litres. in 5 hours with small gas burner.my question is this i try it another time but i dont cut the lunchbags in small pieces i fire the gas burner and after 2 hours reflux tempreture was 330degrees celcius but no oil coming out after a while reflux tempreture begun decrease to 253 i leave it for 6 hours and i find about 0.3 litres oil. i was thinking why it take over 8 hours and tempreture decrease. do you thing because i dont cut them in small pieces? thanks in advance

[Beyond Biodiesel]

DEAR BBD To avoid any possible leakages radiographic and ultrasonic weld testing are the most commonly used methods used to check weid joint and naturally I am going to get the kiln checked with this methods when my bigger capacity rotary kiln gets fabricated which is under fabrication by professional certified boiler manufacturer Also the kiln is checked under pressure 40-50 psi also after completely checked a blown over valve (2.5 -3 psi) is added to kiln which is also linked to hot air generator in case of blown over it not only releases the pressure from the kiln but also shuts down hot air generator and feeding line

Good to know.

my uncle give me some exhaust insulation wrap and i am doing some tests.i have question. i make pressure cooker to a 3l glass condenser. i try lunchbags in small pieces and i got over 0.5 litres. in 5 hours with small gas burner.my question is this i try it another time but i dont cut the lunchbags in small pieces i fire the gas burner and after 2 hours reflux tempreture was 330degrees celcius but no oil coming out after a while reflux tempreture begun decrease to 253 i leave it for 6 hours and i find about 0.3 litres oil. i was thinking why it take over 8 hours and tempreture decrease. do you thing because i dont cut them in small pieces? thanks in advance

plastics are going to melt long before 30degrees celcius, so cutting them up is not likely the problem, but cracking temperature is 425c, so you did not get it hot enough.

[Babataku]

Mild Steel Thickness

Hi All,

I am planning an upgrade to a system that can process 200Kg of Plastic per Batch. I plan to heat this using a light oil / Diesel Burner rated at 30Kw. I intend to have a max of 2 Runs per day. I will use a Mild Steel tank of 6mm thickness guage and will be placed in direct contact of the burners flame.

My question is how long can this material last (6mm Mild Steel), if i have 2 runs per day? How often do you think i will need to replace the tank due to the constant heat cool cycles / metal fatigue& Cracking? i dont mind replacing every 6 - 12 months...Mild steel is cheaper and readily available in my country..

Any advice...

[jonathan]

retort problem

thanks bbd but it is normal that reflux tempreture was 330 in 2 hours then begun to decrease to 253? because as i say the different between 2 test was plastic cut in small pieces.in first test when reflux tempreture was 210 after a while decrease to 200 and continue to rise. thanks

[sunilkm153]

How about piping the reflux return to the feed end of the kiln? In this idea, the vapours get fed into the upper part of a reflux chamber. When uncracked hydrocarbon vapour condenses in there, it drains out from the reflux bottom and is piped to the kiln infeed end. The reflux needs to be high enough so that there is sufficient fall.
A further thought was to have a hollow auger shaft and use this the vapour channel and/or reflux return.
Sadly without pictures I'm struggling to visualize your construction so these ideas may not be possible or applicable.
Hope this helps.

once again excalibur without indulging into unnecessary complications you simply made your suggestion I also tried to elevate reflux height to get heavy condensate directly piped to kiln's inlet but in that case I had very low output of oil I thought in that case gas velocity and temperatures both get reduced which finally affects yield of oil now I am planning to insulate & heat the pipe between reflux and kiln to regain temperature and gas velocity if it still don't work simply I will try to replicate your second suggestion dear friend soon I will post pictures

[wheels]

Hi All,

I am planning an upgrade to a system that can process 200Kg of Plastic per Batch. I plan to heat this using a light oil / Diesel Burner rated at 30Kw. I intend to have a max of 2 Runs per day. I will use a Mild Steel tank of 6mm thickness guage and will be placed in direct contact of the burners flame.

My question is how long can this material last (6mm Mild Steel), if i have 2 runs per day? How often do you think i will need to replace the tank due to the constant heat cool cycles / metal fatigue& Cracking? i dont mind replacing every 6 - 12 months...Mild steel is cheaper and readily available in my country..

Any advice...

You shouldn't have too much of an issue with the heating/cooling in this situation. The heat is constant for the run time and then it cools. That is very different to a rotating vessel going in and out of the heat constantly. In your case, it will be the inside of the vessel you will need to keep an eye on, due to the acids that are created which will slowly eat away at the inside of the vessel. However, that is not to say that you should ignore the outside of the vessel. You still need to inspect it often to ensure all is well.

[sunilkm153]

Hi All,

I am planning an upgrade to a system that can process 200Kg of Plastic per Batch. I plan to heat this using a light oil / Diesel Burner rated at 30Kw. I intend to have a max of 2 Runs per day. I will use a Mild Steel tank of 6mm thickness guage and will be placed in direct contact of the burners flame.

My question is how long can this material last (6mm Mild Steel), if i have 2 runs per day? How often do you think i will need to replace the tank due to the constant heat cool cycles / metal fatigue& Cracking? i dont mind replacing every 6 - 12 months...Mild steel is cheaper and readily available in my country..

Any advice...

200 kgs of plastic per batch and two batches per day and heated through direct flame 6mm mild steel will not withstand longer also security concerns are there instead try to get 10mm thickness

[wheels]

once again excalibur without indulging into unnecessary complications you simply made your suggestion I also tried to elevate reflux height to get heavy condensate directly piped to kiln's inlet but in that case I had very low output of oil I thought in that case gas velocity and temperatures both get reduced which finally affects yield of oil now I am planning to insulate & heat the pipe between reflux and kiln to regain temperature and gas velocity if it still don't work simply I will try to replicate your second suggestion dear friend soon I will post pictures

You don't have to use a Reflux vessel. Reflux is just a simple way of returning the very heavy fractions back to the retort so they can be heated again and hopefully cracked. You can forget the reflux vessel and crack the heavy fractions in it's very own vessel as part of the distilling process. You can even use a catalyst to speed up the process and for the need of less heat, at that point as well.

Earlier I asked about how you control the heat with the PID or whatever you are going to use. I was meaning, how does the temp device actually control the heat? I assume it is controlling the fuel in someway, but just wondered how.

[wheels]

200 kgs of plastic per batch and two batches per day and heated through direct flame 6mm mild steel will not withstand longer also security concerns are there instead try to get 10mm thickness

You will be surprised at how well Mild Steel lasts. Unless you use a very exotic SST, Mild steel is the best choice. Remember that there is, or should be no oxygen, so you do not get corrosion on the inside. You do get etching from the Acids though, so the Steel will slowly eat away. Mild steel withstands the heating and cooling cycles far better than most other metals. If the seams have been welded with mild steel electrodes, the welds behave just like the rest of the vessel metal. But if it has been MIG welded, MIG weld is hard low Hydrogen and will present a "different metal"composition at the weld interface. Two different metals, even though they are both steel, can cause a galvanic action with the Acids and heat. So the Welds need to be inspected regularly.
Wall thickness of 6mm is not too bad for 200ltrs, but I wouldn't go any larger in vessel without increasing the wall thickness. Certainly 10mm would last longer, but remember you also need to get the heat through the vessel wall efficiently. Plus the cost of rolling a vessel with 10mm wall thickness and not to mention the vessels weight would make anything heavier much more difficult.

[Excalibur]

once again excalibur without indulging into unnecessary complications you simply made your suggestion I also tried to elevate reflux height to get heavy condensate directly piped to kiln's inlet but in that case I had very low output of oil I thought in that case gas velocity and temperatures both get reduced which finally affects yield of oil now I am planning to insulate & heat the pipe between reflux and kiln to regain temperature and gas velocity if it still don't work simply I will try to replicate your second suggestion dear friend soon I will post pictures

Yes, of course. The vertical inclined outlet pipe leading to the reflux vessel will itself be a reflux. Even lagging it may not be enough as the outright pipe temperature ideally should be at (or above) kiln temperature.
Two options come to mind. 1/. Maintain the pipe at kiln temperature, or 2/. position the reflux below the outlet and pump any condensate to the kiln infeed.
Hope this is helping. Pics would be great. Thanks.

[Excalibur]

my uncle give me some exhaust insulation wrap and i am doing some tests.i have question. i make pressure cooker to a 3l glass condenser. i try lunchbags in small pieces and i got over 0.5 litres. in 5 hours with small gas burner.my question is this i try it another time but i dont cut the lunchbags in small pieces i fire the gas burner and after 2 hours reflux tempreture was 330degrees celcius but no oil coming out after a while reflux tempreture begun decrease to 253 i leave it for 6 hours and i find about 0.3 litres oil. i was thinking why it take over 8 hours and tempreture decrease. do you thing because i dont cut them in small pieces? thanks in advance

My guess is the volume of vapor generated by the retort declined so this was reflected in reduced reflux temperature. What was the temperature of the retort throughout this test?
On Monday I'm doing some testing. I'll have two probes in the retort so hopefully something can be learnt regarding probe placement, retort behavior, etc