Aloha Jon h.

What kind of pump have you been using for pulling vacuum on your setup?

quote:

dewater the oil

jon h, how successful is this? Do you heat the oil? How and when do you filter it? Is the energy requirement lower for this kind of dewatering?

Paul

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I've been drawing a deep vacuum (28-30"Hg) on a 40 gallon and now an 80 gallon hot water tank processor for a little over a year now. I use it dewater the oil and to remove the methanol from finished BD and glycerin. No problems to date. As mentioned earlier, keep the head space to a minimum.

Thank you. That's the kind of info that could save me a ton of money...

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Originally posted by GrahamLaming:
Hi bernyjb

Can you sketch a drawing of what you have in mind?

I can't quite picture it in my mind.

V3/V4 and V7/V8 work to allow the flow to be reversed.

Flow down = V3 and V7 open when V4 and V8 closed
Flow up = V3 and V7 closed when V4 and V8 open

Feel free to comment - I wouldn't be here if I didn't welcome comments! All part of the fun, and helps the ideas develop.

All the best

Graham

Wow. I am not into this making bio diesel enough to even know what your doing but it sounds good!
I'm learning and I understand somethings but do you have any real time pictures of your setup complete? Are you using a poly cone tank?

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Wow. I am not into this making bio diesel enough to even know what your doing but it sounds good!

AHA...!! I see you've got the bug...huh?

oh ya, made it, making it faster.

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I am open to suggestions before I start locking everything down and permently mounting everything.

I would seriously re-evaluate the plumbing design so that you don't have to use so many fittings and end up with a "ball of yarn" worth of plumbing. The key to reactor design (aside from the safety stuff like moving that element as per others comments) is to make each valve do as much as it can. I managed to shave a ball valve out of Graham's diagram and adapt his plumbing diagram to a more "appleseed" looking plumbing (pump on ground, etc). I'll probably be posting a SolidWorks rendering of my new reactor this week with all of the plumbing in place... maybe i'll upload a scan of a sketch in the meantime.

On a side note, due to the foam trap, i don't think an appleseed can effectively accomplish this designs goals... just not enough fittings. I have a couple ideas, but i'm not positive that they will work until i get a better sence of processor.

Graham,
I do have a question about the foam trap. is there any size requirements for this? would a mechanism made from 2" black iron pipe + fittings packed with scrubbies work?

Also, how much vacuum does this draw, roughly?

JB

An interesting test would be to take an empty 205 drum and connect it to the vac port on the venturi. Seal it all up well with grease or ptfe tape. Turn on the venturi and see if it can actually collapse a drum or if some limiting factor kicks in first.

Film it if you can, maybe just a mobile phone type thing whatever the best you can do is. Just in case it does collapse. An after collapse pic would do.

If it don't collapse then a water heater prolly won't either. If it does then take one and fill it with water. Lower the headspace an inch or six at a time and try and collapse it again. Keep going untill it gives to some extent. Tell us what the headspace was and show us how it gave. Keep pushing it untill it really fails and tell us what that headspace was too.

That should establish a safety margin to work with on water heaters without wrecking any precious water heaters.

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Hmmm. Do you think a water heater would take the vacuum? Confused Confused

My super sucker is made out of 2, presently, but soon to be 3 water heater tanks mounted and plumbed together. I'm never had any issue with my dual tank unit, and I pull to 20"Hg of so.

And some point I calculated back from the 300psi failure pressure rating for a WH tank and came up with a 33 or 35"Hg failure vacuum...or something like that. It wasn't far beyond what is possible, but was beyond what is common.

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Originally posted by paulb3:
Aloha Jon h.

What kind of pump have you been using for pulling vacuum on your setup?

I started off using a refrigerator compressor salvaged from the local transfer station. It worked for a while, then it quit. It came off a refrigerator that had to be 20-25 years old. Since then I have acquired a belt driven laboratory grade vacuum pump. I also use it to draw a vacuum on my super sucker tank.

quote:

Originally posted by Paulus:

quote:

dewater the oil

jon h, how successful is this? Do you heat the oil? How and when do you filter it? Is the energy requirement lower for this kind of dewatering?

Paul

I think it is very successful though I have never done any quantitative testing. My oil is usually pretty dry, every once in a while I get some wet oil - thats why I bother to do it at all. I only heat the oil up to processing temp (130-140F) before drawing a vac on the tank. It takes me about 30 minutes to dewater wet oil (once the reactor has reached temp).

I really don't recommend you use an oil drum...

http://needmore.physics.indiana.edu/~rickv/barrel.html

Also, look 2/3 down this link

There are so many different drum grades, ages, states of disrepair etc, I think they are just too flimsy to confidently rate for vacuum use, even if partly filled.


Hi JB

The foam trap I have is made from 3" diameter steel tube about a foot long. The inlet half is loosely stuffed with 'scrubbies'

I wasn't suggesting anyone actually use an oil drum. The premise was that oil drums are cheap or free and flimisier than a water heater. So anything a drum can take a water heater could take as well or better. Therefore crushing a few oil drums would be a cheap way to explore how headspace effects vacuum resistance.

quote:

Also, look 2/3 down this link

That link specifically says

"even a heavy duty oil drum will be crushed if it has nothing inside to balance the pressure. "

Clearly implying that having something inside to balance the pressure will make a difference. In an empty drum that is air until you suck it out. In a fullish drum it is oil/bio with only the headspace holding vacuum.

If one were to try and actually use a drum instead of just using them as sacrifical test bodies I would agree that condition is vital and only new condition, heavy duty ones, well maintained and never subjected to vacuum unless almost full would be essential precautions.

Having said that I would still suggest avoiding them except for destructive testing in the interests of establishing the effect of headspace on vacuum resistance.

Even if the testing provided some very repeatable and consistant evidence to show there was a well defined safty zone there would always be the problem of mistakenly applying vacuum when you shouldn't. We all make mistakes. Even the best of us. And most of us are a little less than tne best. Just one of the others like all the rest. And thats good really. Elitism sucks big time. Nothing wrong with praise from ones peers for those who do do outstanding work though. Recognition and respect are different to elitism. Sorry to slide off a bit there.

This message has been edited. Last edited by: Ant,

Graham: I was looking at the diagram, and it seems to me that V10 could also be eliminated, and even V9, if you put a restrictor on top of the tube.
What do you think?

Ok here is another try at it simplified the plumbing as suggested and also mounted the heater element horizontal. Elimited the sight tube perhaps with the lower temps we could use the clear re-enforced tubing as the top inlet.

push-pull-small.JPG (40 Kb, 192 downloads) Another Try

Hi bernyjb

Thanks for the suggestions, but let me explain my reasons for V9 and V10 being there ...

V10 is right at the processor outlet, because I want to ensure that NO glycerol can get into the pipework before draining, or if you need to postpone draining for any reason, or it will quickly solidify.

You could probably eliminate it if V7, V8 and V9 were right up at the outlet together, but this is not really practical to achieve, so I chose a single 'master' isolating valve.

It is also useful if you have to make any changes to the pipework while the processor is full. For example if the pump needs attention, you can confidently shut of the madster V10 and move pipework without risking a leak. (Bitter experience!)

V9 is handy to have, because it allows you to regulate the flow through the sight tube, and allows you to isolate the sight tube completely.

During reverse flow, when you are pumping hot liquid into the base of the tank, you should close V9, so as not to pressurise the sight tube with hot liquid.

During acid dosing, you regulate V9 to get a good flow of dosed biodiesel thru the sight tube, so you can see the colour change clearly.

All the best,

Graham

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For example if the pump needs attention, you can confidently shut of the madster V10 and move pipework without risking a leak. (Bitter experience!)

Ditto. If anything goes wrong with your pump or pipework you really want to be able to isolate the tank full of hot oil/bio as I too have realised in my past experiences.

GL What is the lowest and highest amount of acid that has been required for any batch you have tried and how does that relate to grams per litre of catalyst left in the mix?

Thanks guys.
This is one of the cases when experience proves to be invaluable.
I have another question:
I know there's a relation between the vacuum applied to the methanol and the heat needed to vaporize it. Do you have something like a table with the different temperatures for the different vacuums, or is there a temperature and vacuum at which the demething is more efficient?