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I posted this on Home made Ventruri as well - so I am sorry if you are double reading this, but the bottom part of my post needs special attention here.

Ok, I have a question that is directly related to Venturi calculations but for a completely different reason. I have 2 situations in my plumbing where under gravity feed, I am changing pipe dimensions - a venturi de facto. I want to avoid this, well at least isolate its impact, and I am thinking to do this by adding a larger pipe to the output side in each case, so that the oil flow can re-equalize back to gravity flow - clearly this last part is an assumption I am making and if I am wrong let me know. See below for the specs, but my question is, what size pipe and length will I need to make this happen - the red areas.

Problem#2 (the one on the right):
Coming off the Centrifuge, which has 1 1/4" outlet pipe and back into my 3"4" pipework. Even though the centrifuge is not "filling" the 1 1/4" pipe, I am going to put some bends in the 3/4" pipe as well as the cross you already see, so I need some leeway so that the flow doesn't back into the CF.

Problem#1 (on the left):
My pressure tank comes with an 1/2" fitting at the bottom. I can grind out this fitting and put in a 3/4" one (well I will probably put a 1" one and use a bushing), but that seems hard/expensive as opposed to adding the "resizer pipe." My big worry here, other than my assumption might be faulty is that I am creating another problem when I do the reverse flow process in the push-pull reactor? I will be using the harbor freight pump which is rated at 330 US GPH (which is that only 5.5 gallons per minute?)

Thanks for any solutions
Doug

ImagePipe_downsize.jpg (32 Kb, 162 downloads) Pipe Downsize Pic
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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quote:
Originally posted by ProjectPurity:
Graham,

have you held a vacuum meter on the main tank for the entire period that the methanol is being distilled? I know earlier it was mentioned that a 10psia vacuum was reached, but was that figure constant?

Since the methanol is boiling off and generating pressure, which the venturi then takes away, what is the variation in vacuum pressure over the time it takes to recover the methanol? Also, if this actually occurs, what is the actual effect of this variation and how do you correct/sidestep it?

JB


Anyone have an answer for this?
 
Registered: April 01, 2005Reply With QuoteReport This Post
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Hi JB

Sorry for the delay in answering, been away on business, just catching up again.

There's no single answer for your question.

The lower the pressure you can achieve with the venturi, the lower will be the boiling point, and we want to keep the temperature as low as possible to minimise back reaction.

Using an adjustable thermostat or PID , with the sensor in the main tank is a handy way of ensuring you don't exceed your target temperature.

So, first off, run the venturi without adding heat to the batch, and keep running it until no more distillate appears. You will now have a cooled batch, close to its boiling point.

Make a note of that temperature, let's say it is 45C

Now, you are running as much vacuum as you can, but there is no more methanol coming out. The boiling point of methanol will keep rising as it becomes less and less concentrated in the mixture.

So turn the thermostat up 5 degrees and you will start to get more distillate appearing, after which it will tail off. The pressure may rise during this period, but will then drop again to your lowest pressure when no more boiling occurs.

Then turn it up another 5 degrees and continue like this until you reach say 80C or whatwever the temperature limit is of your system.

Why don't we just set the thermostat to 80C at the start? You may be able to do this, but I found that if I went up in gradual steps, I got much less foaming. It is a more controlled release of methanol. Rather than an all out blast from the outset.

Ideally, a ramping PID controller could be used. Once you have found a rate of temperature increase which reliably gives no foaming, you can puth that ramp rate into your PID controller and it will automatically raise the temperature for you at a limited rate.

Hope that helps, I'm still learning this too!

All the best

Graham


Rover 75 + Skoda Fabia on B100
http://www.graham-laming.com

Bicycle on G100 12,000 miles p.a. ( http://uk.virginmoneygiving.com/GrahamLaming )
 
Location: UK | Registered: December 04, 2005Reply With QuoteReport This Post
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Yes. That is exactly what i wanted to know. So let me get this straight:

1) You achieve vacuum first and let the amount of methanol boil out that will at that temp/press.

2) Gradually ramp up the temp so as not to create a sudden and large pressure increase and thus a collapse in vacuum.

3) Do that to the limit of your equipment.

Is there an upper practical limit? After draining my glycerine, i usually take my biodiesel up to 220F to remove any glycerine and water from the prewash. It would probably be unnecessary if i had an air scrubbing venturi, but i haven't got around to buying/making one until now.

Thanks again, you've answered yet another question in the unending line that i seem to produce sometimes.

JB
 
Registered: April 01, 2005Reply With QuoteReport This Post
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I was wondering if anyone can give an example on how they are adding the 1/2 teaspoon of phenolphthalein and how they are adding HCL.
 
Location: Vero Beach, FL | Registered: April 03, 2008Reply With QuoteReport This Post
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quote:
Originally posted by snookup:
I was wondering if anyone can give an example on how they are adding the 1/2 teaspoon of phenolphthalein and how they are adding HCL.


Thank You....I've been wondering about this, too.

Graham, will you be posting example pics soon? I am in the begining stages of building a large processor (300 to 350 gals.) and I'm very interested in the push pull method.

Great work Graham !!!
 
Location: Commerce, TX | Registered: June 20, 2006Reply With QuoteReport This Post



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Anyone?
 
Location: Vero Beach, FL | Registered: April 03, 2008Reply With QuoteReport This Post
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quote:
Anyone?

i'm not totally sure about this, but i don't think anyone is doing this yet....

Graham suggested using a capillary feed to introduce it so that it is slow, but i don't know where to get the parts necessary to build that into a biodiesel processor. It would be nice for anyone who knew to post sources of these parts.
 
Registered: April 01, 2005Reply With QuoteReport This Post
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yeah I didnt think to many had one built since its still pretty new, I am in the process of building it right now and was just trying to figure out what I was going to do for this, I guess its time for us to actually use our minds instead of Grahams.
 
Location: Vero Beach, FL | Registered: April 03, 2008Reply With QuoteReport This Post
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My sub-sub scale experiment was in a beaker, so adding phenolpthalein and HCL wasn't difficult, but the ability to add it to my present mixer is still easy. The same suction line used to admit the methoxide would work just fine for a shot of indicator solution and an acid drip. The quantity of acid required was remarkably small, so a syringe might do the trick, as long as there's no danger of back pressure or leaks. Remember the flow doesn't need to be reversed until after the reaction has been neutralized, so all the normal connections still work in their usual fashion.

The experiment convinced me to keep processing the way I have been, since I already have everything set up, but I'm thinking of neutralizing my glycerin and biodiesel separately.
 
Location: Moses Lake, WA, USA | Registered: August 15, 2001Reply With QuoteReport This Post
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The experiment convinced me to keep processing the way I have been, since I already have everything set up, but I'm thinking of neutralizing my glycerin and biodiesel separately.


What made you think you didn't want to change? what would be the point of neutralising the bio seperately once the glyc was gone? I thought the point was to prevent reverse reaction? Are you worried about the small amount of glyc disolved in the meth contributing to a reverse reaction? Once the meth is removed and everything drops out I dont think the bio needs neutralising as there should be no catalyst left in it.


mathematical elegance -- desired result achieved with minimal complication
 
Location: Manchester UK | Registered: June 03, 2003Reply With QuoteReport This Post
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I dont think the bio needs neutralising as there should be no catalyst left in it.


Yeah... there would be no point in neutralizing the two in separate stages. The point is also to remove methanol in one stage so that you eliminate the waiting for separation.

I entertained the idea of using my methoxide port with a dropper at the end of the attached tube, but some degree of capillary feed would be AWESOME!

I'm building my processor to be a GL1, but with the reversable flow plumbing so that i can later transition when budget allows.
 
Registered: April 01, 2005Reply With QuoteReport This Post



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I'm glad everyone likes them... if anything sticks out as poorly designed, PLEASE tell me before i find out the hard way! I've built four appleseeds before so i have a pretty good grasp on reactor design, but anyone can forget something!



Ok, Project & Graham, I am actually starting to assemble your designs with some minor modifications. (I have been trying to build a diagram in SketchUp - the google 3D - for review, but darn the learning curve for that! I have it working but I am so slow.) So I am just going to put it together and take pictures and we can go from there.

With that said: Project, I am having problems actually assembling your design - like how to screw it all together. I am not the greatest plumber and have never built a reactor before so please take my comments with a grain of salt. I think there is a need to add one more union at the inlet of the pump to screw it to the pipework. The only other way I can see to attach the inlet of the pump is to spin the pump itself onto the piping. Is that what you intend or am I missing something? As for the other 2 unions near the pump, I assume they are there because assembly starts at the side holes in the tank and pipe is threaded back towards the the pump, and these unions allow connection to it? Just so anybody reading this knows, the union on the outlet of the pump (the vertical one) also accomadates the assembly of the 2 bends used for the reverse flow (the Tee that redirects the oil from the pipe coming off the bottom of the tank upwards to the outlet.

Also I am going to ask a really novice question. The way you have the methanol inlet piped in (off the Tee on the bottom right of the picture.) Will not oil spill into the methanol tank? I mean is the pump sucking or is it just gravity that fills the pump? If, as I assume, it is both, is the pump is strong enough to pull from both sources and not lets the oil flow into the methanol tank? My question seems stupid, but since I read somewhere not to put the methanol tank above the motor, gravity might be an issue here.


Thanks
Doug
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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Sorry for the delay in answering - been away, just catching up...

Johno came up with a neat idea which simplifies the valving a lot, I've just been able to draw his layout below.

Uses 2 pumps, select either one or the other to run, for forward or reverse pumping. The flow seems to go quite happily thru the idle pump, which probably acts as a semi-static mixer too.



This was the photo Johno sent me....



I've put the heater between them, to minimise the risk of cavitation - both pump inlet ports should have as little restriction in them as possible.

For the capillary feed, you can use a needle valve to limit the flow.

Doug, the methanol tank on the right is for collection of methanol only. The methoxide will feed into the bottom valve on the left, V2

Hope that helps,

all the best

Graham


Rover 75 + Skoda Fabia on B100
http://www.graham-laming.com

Bicycle on G100 12,000 miles p.a. ( http://uk.virginmoneygiving.com/GrahamLaming )
 
Location: UK | Registered: December 04, 2005Reply With QuoteReport This Post
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Hello Graham, nice to have you back.
I have a question: HCL is kinda rough to store and handle, and corrosive to most materials, including even stainless steel. Can other acid be used for neutralizing the lye, like for example, nitric acid?
Nitric acid is not corrosive to SS or bronze, so it would be perfect for making the capillary system you mentioned, but my question is: would the nitric acid affect the BD quality, or create any other issue that would make it a bad choice?


************************

"When you don't think what you say, you say what you think" Jacinto Benavente.

"Wars not make one great" Yoda.

"A pessimist is a well informed optimist"

WWVhaCwgSSdtIGEgZ2Vlay4gU08gV0hBVD8=
 
Location: Miami, Florida. | Registered: April 06, 2008Reply With QuoteReport This Post
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Hi bernyjb

Nitric acid and glycerine would make me nervous!


Rover 75 + Skoda Fabia on B100
http://www.graham-laming.com

Bicycle on G100 12,000 miles p.a. ( http://uk.virginmoneygiving.com/GrahamLaming )
 
Location: UK | Registered: December 04, 2005Reply With QuoteReport This Post
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Graham,

Nice idea. However those are those HF/Northern Tool pumps that produce either 5.5 gpm or 12gpm depending on which version those are. Not sure how this mix speed how this will effect the HCL reaction.

Doug

PS. GRAHAM, have you actually done an HCL reaction on a large batch 35 gallons or higher batch?
 
Location: Los Angeles | Registered: March 25, 2008Reply With QuoteReport This Post
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Nitric acid and glycerine would make me nervous!


Hmmm. But as I understand it, you also need sulfuric to make Kaboom...
Anyways, how about some other acid? Acetic? Phosphoric? My point is to use any acid that'd be less corrosive than HCL... What do you think?


************************

"When you don't think what you say, you say what you think" Jacinto Benavente.

"Wars not make one great" Yoda.

"A pessimist is a well informed optimist"

WWVhaCwgSSdtIGEgZ2Vlay4gU08gV0hBVD8=
 
Location: Miami, Florida. | Registered: April 06, 2008Reply With QuoteReport This Post



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quote:
Originally posted by Doug Weiner:
...The only other way I can see to attach the inlet of the pump is to spin the pump itself onto the piping....


Yes. You've caught me! If this were a little HF pump using 3/4" unions, i would just throw the little $3 bugger on there and be done with it, but 1 1/4" unions get a little more pricey.

If you feel like spending the extra dough, it would be a GREAT place for a union and i may break down and put one there myself as my pump weighs a ton!

For all out there who haven't spent much time building manifolds/reactors, there is one important rule:

In plumbing, you can never make a closed loop without a union. It's just impossible to tighten. My design can actually be assembled, but, as Doug said, will be a bit of a pain to spin the pump on. Putting a union would save this pain.

quote:
the way you have the methanol inlet piped in (off the Tee on the bottom right of the picture.) Will not oil spill into the methanol tank? I mean is the pump sucking or is it just gravity that fills the pump?


I felt as if a general suction port is alright here, because my pump is pretty powerful. However, later i thought about the fact that i already have all of the plumbing to just put the swing/check valve in and be done with it.

I will be posting some pictures/renders shortly with some additions. I feel that many of you will like the revisions to this design.

quote:
Originally posted by Graham Laming:
...
Uses 2 pumps, select either one or the other to run, for forward or reverse pumping....


That's awesome! If i could only afford two ofm my pumps! At the cost of HF/NT pumps, it may just be cheaper to do it that way rather purchasing the extra pipe and fittings necissary to flip the flow!

quote:
Originally posted by bernyjb:
...HCL is kinda rough to store and handle, and corrosive to most materials, including even stainless steel.


My Muriatic Acid is storing just fine in the plastic gallon jug that it came in.... I don't have worries of it being hydrophelic (sp?)... absorbing water... and spoiling.

quote:
Originally posted by Doug Weiner:
HF/Northern Tool pumps that produce either 5.5 gpm or 12gpm depending on which version those are. Not sure how this mix speed how this will effect the HCL reaction.


Good thought! Maybe use a higher flowing pump for the first stage heating/mixing/agitation/HCL neutralization and use the little HF/NT pump for methanol recovery as flow rate isn't really a big deal here.
 
Registered: April 01, 2005Reply With QuoteReport This Post
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Hi Doug,

Yes done 6 x 80 litre batches so far with the HCL neutralizing the whole lot.

I think the extra pump will be OK in there - but I haven't tried it myself yet.

Hi bernyjb, I'm sure you're right - other acids could be used. You'd want something which creates friendly by-products, and HCl just makes salt and water which is easy to deal with.

Sulfuric may raise the sulfur content - sulfur is measured in ASTM - but this may not be an issue.

HCl is not so bad to deal with, and it is in small quantities, and is cheap and easy to get hold of. It is rapidly neutralised and diluted in the glycerol, so I'm fairly comfortable with it, but it would certainly be nice to have a better solution.

Reasonably concentrated is preferred, so that not too much water is introduced.


Rover 75 + Skoda Fabia on B100
http://www.graham-laming.com

Bicycle on G100 12,000 miles p.a. ( http://uk.virginmoneygiving.com/GrahamLaming )
 
Location: UK | Registered: December 04, 2005Reply With QuoteReport This Post
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