How to turn plastic waste into diesel fuel cheaply

[Col]

machined flanges for sight discs

Yes, the bolts are overkill, but that is what suits the flanges available off the shelf at the fittings store. I know we're not expecting any pressure in our systems but so much talk earlier of retort flanges not sealing led me to think better over kill than under done.
I've attached a picture of the flanges now machined to have a step to retain the sight glass and a recess to locate the O-ring. All four flanges have been machined so there is an O-ring on each face of the glass.
Planning on pressure testing the system this week.
For low pressure relief I have a bath plug sitting in a hole in the final bubbler lid. For high pressure relief I intend to use a boiler relief valve at the retort. But I expect if I wind it back off it won't seal very well. Will see.
Regards
Col

[Beyond Biodiesel]

Yes, I agree, the bolts and flanges are massive compared to the brittleness of Pyrex. The suggestion of an o-ring on both sides of the glass is good, verses a thin fiber seal.

You would want to have about .5cm of thickness of the seal on both sides to afford some flexibility.

Also, you will not need more than a slight compression of the o-ring. The problem was most probably differential thermal expansion in the sun. So, a thick seal will allow some flexibility in the seal if it is not fully compressed.

[wheels]

Thanks guys
Spoke with the manufacturer of the sight discs. He insists the discs are made of Schott Borofloat 33 which he says is a German product within the Borosilicate family. He says the English call it Pyrex. There are a number of names for it but it is definitely borosilicate. He was very surprised they were breaking, suggested a couple of things to look at such as flatness/smoothness of flanges, method of tightening, machine a step into flanges for placement of discs, agreed the O-rings would be a good and more acceptable method than the low-compression NAF gaskets.
Here are a couple of photos.
I'll go get a step and O-ring groove machined into the flanges and see how I go after that.
Col

The breakage has been caused by stress due to the plates being too tight and the seals having not enough thickness to allow for the movement. Fibre seals like you are using are not right for this situation.
Excalibur has good advice re springs on the bolts and the use of an O-ring as the seal.

[rozier56]

Hi Excalibur, When you start up your system, whilst climbing to your required temp i.e 330*c in your reflux, you must produce some water and paraffin products. What are you doing with this and how do you discharge them?
Also notice your temp probe for the retort is placed on the retort top!
Is this a long probe that measure the liquid phase? Other wise it must be similar to the reflux temps!

[Excalibur]

The way it's broken suggests it's not toughened glass.

For Viton or silicone rubber o-rings I suggest a crush of the rubber to about 70% of the original thickness, so if a seal was 3.5mm, crush to say 2.5mm. I have o-rings on both sides of the glass. One chipped once because the steel housing came into contact with glass edge. As an afterthought I fit a rubber band around the glass perimeter to isolate it from direct steel contact on the periphery. I made it from old motorcycle inner tube though it needs replacing once in a while.
Later I thought the ideal seal would be a "right angle corner section" so it fits on the face and the rim perimeter of the glass at the same time.

Those are serious bolts! How about a spring under each nut so the rubber seal squish can only be as tight as the spring tension. The fact is we're not running our machines at any real pressure to speak of.

[Col]

Sight Glass / Discs

Thanks guys
Spoke with the manufacturer of the sight discs. He insists the discs are made of Schott Borofloat 33 which he says is a German product within the Borosilicate family. He says the English call it Pyrex. There are a number of names for it but it is definitely borosilicate. He was very surprised they were breaking, suggested a couple of things to look at such as flatness/smoothness of flanges, method of tightening, machine a step into flanges for placement of discs, agreed the O-rings would be a good and more acceptable method than the low-compression NAF gaskets.
Here are a couple of photos.
I'll go get a step and O-ring groove machined into the flanges and see how I go after that.
Col

[sunilkm153]

Hi everyone
I bought some borosilicate sight discs (111mm diameter x 15mm thick) and sandwiched them between standard 3" flanges using NAF (non-asbestos fibre) gaskets. Carefully torqued it up and thought it was job done. The next day one of the discs shattered. I replaced it, this time not as tight. I left the project for a couple of months and came back to it yesterday. Left it in the sun for a couple of days and the other sight disc shattered. Lucky I bought 4 sight discs!
There is not much compression or give in a NAF gasket. I suppose I had the bolts done so tight it was just below the shattering point of the glass, then on a hot day the sun heated up the flanges and the extra expansion added too much pressure on the glass.
Excalibur - what has been your experience with the O-rings in your sight glass set up? Which material worked best - Silicon, Viton or Nitrile? How thick are the O-rings?
Does anyone else have experience or thoughts on this?
Much appreciated.
Col

borosilicate never shatter in sunlight Excalibur sighted right that it simply may be toughened glass regarding seals Compressed Asbestos Fiber (CAF) Jointing Sheets are best where temperature is less then 200 - 250 degrees . BE CAUTIOUS IF IT IS NOT BOROSILICATE YOU MAY BE AT RISK

[Excalibur]

Could it be the glass is not borosilicate but toughened or tempered glass? Has the glass crumbled into small granular chunks? Tempered glass is specifically made to break in the manner it does for safety reasons. Hence the name "safety glass".
Both silicon and viton seals have worked though I haven't measured the temperature they're subjected to. Probably 150°C at the most, only a guess though. They're 3.5mm thick

[Col]

Sight Glass / Discs

Hi everyone
I bought some borosilicate sight discs (111mm diameter x 15mm thick) and sandwiched them between standard 3" flanges using NAF (non-asbestos fibre) gaskets. Carefully torqued it up and thought it was job done. The next day one of the discs shattered. I replaced it, this time not as tight. I left the project for a couple of months and came back to it yesterday. Left it in the sun for a couple of days and the other sight disc shattered. Lucky I bought 4 sight discs!
There is not much compression or give in a NAF gasket. I suppose I had the bolts done so tight it was just below the shattering point of the glass, then on a hot day the sun heated up the flanges and the extra expansion added too much pressure on the glass.
Excalibur - what has been your experience with the O-rings in your sight glass set up? Which material worked best - Silicon, Viton or Nitrile? How thick are the O-rings?
Does anyone else have experience or thoughts on this?
Much appreciated.
Col

[Excalibur]

At least 2 hours

[rozier56]

rozier56

Thks Excalibur,will make the changes and observe.
How long does it normally take you to get to your desired temps in your retort?

[Excalibur]

The exact vessel sizes are quoted on the respective pages of my DIYDiesel blog. I think they are within the region of about 1/4 to 1/5. Yours is closer to 1/8 which is a size I've not tested. You could also try separating the two vessels with a short length of pipe, I used 3"( see blog pics).
You could also try bringing the retort temperature up in stages. On my rig cracking WMO I start by bringing the temperature up to 380° then reducing the flame heat so as just to tickle the vessel contents. If I get product flow I hold the temperature there for a while. Then I increase a few degrees and reduce the flame again to tickle the contents at the higher temperature. Then I go higher, step by step. In this way the lighter fractions are lifted off progressively. This avoids boil-over.
It's normal for the reflux to lag behind retort in temperature because it requires flow of vapor to raise its' temperature. I add or remove insulation to/from the reflux to help control its' temperature however I keep the retort pinned at its' own temperature target irrespective of what the reflux is doing.
So at the beginning I might have the reflux fully wrapped with insulation but at the end I may have removed some/most.

[rozier56]

rozier56

Thanks for your response.
I think my problem could be my reflux column."Beyond" once suggested the reflux should be approx 70% of the retort size. My current plant has capacity 250 lt in volume and the reflux has only 30lt by volume. I think i need to make the reflux volume around 90lt/volume. This will create less forces/gas been passed through and make the system easier to control.
Excalibur, out of interest ,what sort of capacity volumes do you have when comparing retort and reflux?

[Excalibur]

rozier56,
The wax is a clear sign that uncracked hydrocarbon is passing through the reflux. Ordinarily, heavier weight hydrocarbon will condense in the reflux and run back to the retort. In this way light and heavy is automatically separated.
There could be a combination of factors causing wax. You should consider all the plant parameters as a fine balance, vessel size, applied heat, temperatures etc.
Possible causes: reflux not effective enough to deal with the volume of vapor. Reflux temperature too high. Retort temperature too high or too much applied heat causing the reflux to be overwhelmed.
Crude oil and plastic are both hydrocarbons so the same laws of physics apply.
If your burner has just one power setting, I suggest work out a way where the flame temperature can be turned down once the retort reaches target temp. In this way you can match the flame temp to actual retort requirement.

[rozier56]

rozier56

Thks Excalibur.
Some plants are producing product that sits at 0.78-0.79 on the hydrometer reading.When you increase the temp range very slightly you start to produce wax. This is confusing as when you look at normal crude oil distillation plants the process shows production as diesel[heavy molecule] first ,then parrafin and petrol later at cooler temps?Any reason way we different?