How to turn plastic waste into diesel fuel cheaply

[ndsunil]

Heating and cooling cycle

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.

Heating and cooling cycle will be facing thermal fatigue and so one has to be careful while selecting the thickness of plate for reactor . One should consider thermal fatigue property while designing batch type reactor

[jonathan]

retort problem

thanks excalibur l dont have probe in retort but i think retort tempreture was hi enough. do you think retort tempreture was low or too hi?

[jonathan]

retort problem

thanks excalibur l dont have probe in retort but i think retort tempreture was hi enough. do you think retort tempreture was low or too hi? or it can be because there is to much wind because i have insulation on retort/reflux only? thanks

[Excalibur]

thanks excalibur l dont have probe in retort but i think retort tempreture was hi enough. do you think retort tempreture was low or too hi? or it can be because there is to much wind because i have insulation on retort/reflux only? thanks

It's great that you are using a test model to try things out on. They are quick and cheap to add changes to. Start by buying some more k type thermocouples. Put one in the retort. Another could go on the flame temperature. Get these reading known good values and then work on any other problems that arise.
If you are only heating the base of the retort vessel, this is likely to be causing frustration. I think heating 80 -90% of the retort vessel outer area is a good target. The insulation should be outside of that heat zone.
I recorded some temperatures recently when my plant was really working well with an excellent flow rate cracking WMO.
Retort 397°C
Reflux 339°C
Flame heat 439°C
Exhaust stack 240°C
These readings should be regarded as a 'snapshot' only. The next run will see more insulation for the retort plus a revised retort probe.

[jonathan]

retort problem

thanks excalibur for help. i will try like as you said.but how can i heat 90% of retort with gas burner. are you meaning that i leave gas burner heat the base of retort and put retort in oil barrel insulated

[Excalibur]

Jonathan.. In this schematic example the retort is surrounded by (red)flame... which is in turn surrounded by (blue) insulation!



The Orion instrument panel. All run from K-type TC. The housing is a recycled PC chassis with wooden sides. To be tested shortly.

[jonathan]

retort problem

thanks excalibur i will try it like that on monday i will buy iron sheet and make a cabinet insulated. thanks alot great photos and very interested website. i hope to see updates soon. keep it up

[Beyond Biodiesel]

Thanks, Excalibur, for sharing the new photos. Your system is looking very professional.

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...

6mm Mild Steel seems plenty thick enough to me. 425c is not very high temperature, so oxidation on the outside is not likely to be significant, and the inside is going to be coated with coke, so it will be protected.

The real problem will be how to cool off your reactor quickly enough to load it again in a 24 hour period. My reactor tended to be 100c after 12 hours of cooling.

The other issue that you will have to deal with is decoking the inside of your reactor. You will have to do it from time to time, because coke is an excellent insulator, so you will see that it will take more and more fuel and/or more time to get to your control point as the coke layer grows from successive run cycles.

Also the reactor will have to be almost ambient temperature to manually scrape off all of the coke.

The petroleum industry burns the coke off by raising the temperature of the retort to 650c once all of the volatiles have been evaporated. Then air, or O2 is metered in. You do it slowly at first, while closely monitoring the retort temperature.

At first when O2 is admitted the retort temperature will rise. You just regulate the O2 or air to keep the temperature at 650c. When all of the coke has been burned you will see the temperature start to drop off sharply. That is when you can shut off the O2 or air inlet, let the retort drop to 425c, then purge the O2 out, and blow the ash out a bottom valve, then add more melted plastics to start your next run.

[Babataku]

The real problem will be how to cool off your reactor quickly enough to load it again in a 24 hour period. My reactor tended to be 100c after 12 hours of cooling.

The other issue that you will have to deal with is decoking the inside of your reactor. You will have to do it from time to time, because coke is an excellent insulator, so you will see that it will take more and more fuel and/or more time to get to your control point as the coke layer grows from successive run cycles.

Also the reactor will have to be almost ambient temperature to manually .

Thanks for the replies. Well, my plan is that after i have processed a full batch within 4 - 5 hours, i will remove the insulation on the top part of the retort and i have noticed from my current small unit that after about an hour the temperature drops to about 250 deg celc. I will then open the lid and then start adding more plastics when temp is around 160deg, close and tighten the lid and start heating again.

[sunilkm153]

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.

by controlling flow of fuel and speed of blower

[wheels]

by controlling flow of fuel and speed of blower

OK. So I assume your PID output will switch either on or off. So how do you use that exactly?
I am upgrading from the Electric element, to a 27Kw Burner and have been trying to figure out just how to control the heat. I have some ideas, although the Burner hasn't arrived yet, so I haven't yet been able to try any of the ideas. Hence I was curious as to how you controlled your burner. Do you simply switch it on and off?
I would rather have the heat dial back rather than just switch hard off and then on again, as that is going to cause too much up and down of temperature inside the retort.
One idea I did have was to have a bypass control gate steer the Burner exhaust to flow around the retort, or slowly open and bypass the heat directly to the Flue. That way I can have greater control of the retort heat and still take heat from the burner to heat the Reflux vessel.

[jonathan]

retort problem

excalibur...today was calm very little wind so i do another test. i put lunchbags but not to much and fire gas burner in about 45 minutes reflux tempreture rise to 330 and oil begun coming out for about 30 minutes and stop then reflux tempreture begun to decrease to 204 this time i leave system fired and after a while tempreture rise again to 280 and about another 300ml oil comes out so i stop system and leave it to cool.i open retort and was empty.i only find little ash like burn paper.so as you said.vapor generated by the retort declined so this was reflected in reduced reflux temperature. but do i understand you well? is this proplem because i only heat base of retort and not 80-90% of retort? thanks

[wheels]

excalibur...today was calm very little wind so i do another test. i put lunchbags but not to much and fire gas burner in about 45 minutes reflux tempreture rise to 330 and oil begun coming out for about 30 minutes and stop then reflux tempreture begun to decrease to 204 this time i leave system fired and after a while tempreture rise again to 280 and about another 300ml oil comes out so i stop system and leave it to cool.i open retort and was empty.i only find little ash like burn paper.so as you said.vapor generated by the retort declined so this was reflected in reduced reflux temperature. but do i understand you well? is this proplem because i only heat base of retort and not 80-90% of retort? thanks

Hi Jonathan, This reply is going to start of sounding complicated with lots of numbers, but please bare with me.
Firstly, what you have seen happen is actually very normal.
You have to keep in mind just how much 400 and even 330 deg actually is and that even a small percentage of difference in temperatures results in a very large difference. For instance, if we were working in much lower temperatures, say 30 and 40 deg, then the difference between then maybe a huge 30%, but the difference is actually just 10deg. But at 300 and 400 deg, the same % but actual difference is 100 deg. So at high temperatures, small changes in anything happening inside the Retort can result in very large changes in temperature or output and so on.
Also remember that inside such a very hot Retort, if there is very little Vapor, then there is very little anything. With nothing, you have an almost perfect insulator. The only way heat can travel is via the Steel wall of the vessel, which is not very efficient. Only when Vapor is produced can heat travel again. So what you have seen is really not that abnormal. What will most likely have happened is that a crust may have formed on the surface of the little remaining plastic. Then the crust finally broke and released the remaining Vapor and that gave you another short final temperature increase.
Something else to consider is that Plastic bags trap a lot of Air. A way to help reduce that air is to stuff all the plastic bags into one plastic bag and then suck all the air out of it. The plastic bag will shrink right down and squeeze out the air from all the others. You end up with a very tight dense ball of plastic bags.
Remember that Oxygen inside is bad. Not just for risk of explosion, which actually is not that easy if most of the air has been removed anyway, but mainly in what nasties can be made. Small amounts of oxygen and temperatures over 400Deg can produce Diaoxin and cause oxidation of some of the Hydrocarbon vapors.

[jonathan]

retort proplem

Thanks. Wheels for answer me too. I put bags as you said but next time I try wmo and then try like excalibur retort try heating 90 percent of retort I think it is good idea..thanks

[sunilkm153]

OK. So I assume your PID output will switch either on or off. So how do you use that exactly?
I am upgrading from the Electric element, to a 27Kw Burner and have been trying to figure out just how to control the heat. I have some ideas, although the Burner hasn't arrived yet, so I haven't yet been able to try any of the ideas. Hence I was curious as to how you controlled your burner. Do you simply switch it on and off?
I would rather have the heat dial back rather than just switch hard off and then on again, as that is going to cause too much up and down of temperature inside the retort.
One idea I did have was to have a bypass control gate steer the Burner exhaust to flow around the retort, or slowly open and bypass the heat directly to the Flue. That way I can have greater control of the retort heat and still take heat from the burner to heat the Reflux vessel.

bypassing heat through flue may also work but then unnecessary wastage of fuel is there now answer to your question No I am not turning blower motor on and off through PID To go through my idea you must understand logic of PID . PID has two states simply say 1 & 2 as it reaches setpoint it change its state from 1 to 2 and viceversa I convert my 1140 rpm motor of blower in two speed motor having three states that means off , low speed and high speed similarly diesel supply to burner is made by modifying fish aqurium motor to two speed one . Now i get these two motors connected through PID at speed 1 and speed 2 (not zero) so when the desired temp. is gained it doesn't switch off the motor but it goes to lower speed and lower diesel supply resulting lower temp. and similarly get reversed at another set point I feel very sorrry that due to some obligations this time I cannot post any of the pictures but as soon as my 5000 kg plant gets completed I will post pictures
what type of catalyst are you using and what are the end results