Hi Rick,
Yes, I agree. Up to a certain batch size with a given pump, the eductor would seem to be of limited value.

quote:

It's just that monster pumps in general have been proven to give the same gains as an eductor.

Have you seen testing that shows up to what batch size a pump like Murphy's won't be improved by an eductor? If so, can you share it?

Rick,

Above on one of the previous pages, you recommended going up to 1/4" instead of 1/8" to minimize wear on the pump. Will the 1/4" provide enough agitation?

Also, if I install the 1/8" nipple do we know the long term consequences on the NT pump? (how long will they last?)

Thanks.

quote:

Originally posted by RickDaTech:
Ah, ok, you need a smaller nozzle. 3/8" wont develop much pressure and needs a diffuser added to get any mixing action at all. You won't any pressure buildup on these little pumps until you get down to 1/4".

You don't need a smooth taper. If you abruptly change diameters you need about 4-6 diameters of constant bore size to re-establish laminar flow and make a good nozzle.

Beer,

I'm sure you will get some in tank mixing with the 1/4" nipple. I have not tested the 1/4" nipple. I suspect it would be an improvement in mixing, but don't know for certain.

Long term consequences on the pump is anyones guess. 30 psi is well within it's rated loading. The pump will draw a few more amps and run a touch warmer. Leaks by the seals are caused by running the pump dry or under a vacuum, so I doubt the pressure would cause any leaks. It might make a dribbling pump leak badly.

I'd be more concerned about any plastic tubing you may have in the line. It will also be pressurized to 30psi. That kind of pressure would considerably shorten it's useful lifespan. So, I'd recommend using all steel plumbing with an eductor.

Rick,

I am using your biodiesel compatable tubing
http://www.b100supply.com/Biodiesel_Tubing_p/1482.htm

What are your thoughts on its use at these pressures?

Rick:

You carry the Mazzei venturi - did you know they also sell tank mixers?
http://www.mazzei.net/products/nozzles_turbomixer.htm

Beer, Steel is better. I don't mind using the plastic when the pressures are under 2psi but at 30 psi I'd rather use steel.

R2.0, yes, but they don't fit inside an appleseed. Since your not doing an appleseed it will probably work fine for you.

ok Rick and others thinking of adding an eductor to your setup.

I went to Lowe's and bought a 1/2 pipe nipple 18" long, a 3/8 to 1/4 bushing and a 1/4 to 1/8 bushing.

My thought is to thread the interior of the 1/2 pipe nipple and use the busings to step down to a 1/8 diameter. Lowe's didn't have any 1/8 diameter nippes - Since the final 1/4 to 1/8 bushing will be below to surfact or the oil, do I still need a nipple?

Beer,

I've been looking at alternatives from plugging the end of the pipe and drilling a hole through the plug, to using a compression fitting with a short bit of copper for a nozzle.

Since the plumbing has rapid changes in diameter, you need a few diameters of length to bring the flow back to laminar for the best spray. I'm thinking a two inch long nipple may be overkill on the length.

Give it a shot with just the bushing and let us know how it works out. You may need to file out the threads. to get it to spray a tight jet.

Rick - I thought we needed a more turbulent flow to improve the mixing?? That was one of the reasons of using the bushings... thoughts?

quote:

Originally posted by RickDaTech:
Beer,

I've been looking at alternatives from plugging the end of the pipe and drilling a hole through the plug, to using a compression fitting with a short bit of copper for a nozzle.

Since the plumbing has rapid changes in diameter, you need a few diameters of length to bring the flow back to laminar for the best spray. I'm thinking a two inch long nipple may be overkill on the length.

Give it a shot with just the bushing and let us know how it works out. You may need to file out the threads. to get it to spray a tight jet.

The goal is maximum mixing using a coherent, pencil like, high velocity stream to encourage it. You should be able to get that even with the bushing.

A gradual transition in pipe size down to the nozzle opening will do it with slightly less pressure on the pump.

Beer,

The best way I know to explain this is by experiment. Get a bucket of water and throw in some grass clippings. The grass clippings are so you can see how the water is moving inside the bucket. Then break out the garden hose and adjust the spray nozzle on the end for a tight high pressure stream. Stick that in the bucket and watch how it effects the grass clippings. Then open the spray a little so the stream is more cone shaped than pencil like and try it again.

Your observations from such an experiment would vastly outperform my attempts at explaining the goals and how to reach them.

Technically we have two goals, the most important is to prevent the glycerin from settling in the bottom of the tank by keeping things moving around inside the tank. The second, less important goal is to do some actual mixing inside the tank so the methanol does not rise to the surface when we add it in.

Rick

I think I have a simple way to make a nozzle similar to what you have described but out of copper plumbing I can get locally. You mentioned earlier that the nozzle should be parallel the axis of the water heater. My intuition (not always correct I might add) tells me it might be beneficial to have the last 2 " segment at a 45 degree angle to also create a whirlpool effect? Opinions? I'll probably try both versions but I only do 1 batch/week so it will take quite a while to get a good sample of results.

I have been running the 2 stage process (80/20) at 22% methanol. What are the opinions about the impact here? I typically get near 100% yield with about 1 hr/stage mixing at 140F, However, I fail the 3/27 test at 20% methanol with longer (2hr/stage) mixing times. So I think adequate mixing is an issue for me.

Brent

That whirlpool effect does not improve mixing. If the nozzle is pointed straight down (or up) the stream has a better chance of reaching the bottom of the tank. If the pressure stream makes it all the way to the bottom then it will flush up an glycerin trying to concentrate there.

'IF' I get around to changing things to a nozzle going straight down I have a small metal cone that would not reduce the drum capacity too much I want to affix to the bottom. I figure it will create a nice upwelling for mixing with the stream striking it. Right now I don't have the sight tube valved off so it would not be a good idea to add more pressure to the line.

Rick
Good point. The Whirlpool would just spin the whole batch in circles not cause turbulence.

I have made an eductor from parts I got from Home depot. Parts used

3/4" MNPT to 1/2" copper
3/4" FNPT to 1/2" copper
20" 1/2" copper line
1/2" copper to 1/4" FNPT
1/4" MNPT-1/8" FNPT
1/8" NPT Brass nipple (.25" ID)
Total cost about $15



The 3/4" MNPT to 1/2" copper you need to grind out the stops which prevent the copper pipe from sliding through the fitting, so you can make it slide throught the fitting. Have enough above the fitting so you can solder the other 3/4' NPT fitting to it. Then connect to the 3/4 FNPT as you would have on the water heater.

Picture is located here

http://biodieselpictures.com/viewtopic.php?p=1131#1131

With this setup I got about 20 psi pressure from the HF clear water pump, and it drew just under 5 amps

A batch is processing mixed at 20%. which I have never passed without reprocessing. So we'll see what happens

Brent

Great eductor. Be sure to report back on how it did or didn't work for you!

First test did not work well. I think I had excessive water in the oil, my yield was down considerably. I typically loose less than 1/2 gallon on a 33 gallon batch (32.5 gallons bio from 33 gallons oil) This time I lost 1.5 gallons

2nd batch worked like a charm. used only 20% methanol. After the first stage, failed as expected. 15 minutes into the second stage pass crystal clear. Total mixing time was 1:15 at 140F Yield was back up, 32.5 gallons from 33 gallons oil.

This is a significant improvement. Typically I have mixed for a total 1.5 hr at 22%. I have never before passed with anything less than 22% methanol.

So next batch I will drop down to 18%.

Brent

That's great news Brent! Keep us informed as to your progress. I'd love to see you make a good batch with 18% methanol using single stage base.

How long does it take for you to load your methoxide?

I will keep you posted. However, it will be slow. I only do at most 1 batch per week.

AS far as loading the methoxide. I never really checked. My guess is less than 5 minutes for the first 80%. Second stage (last 20%) only a couple of minutes. I will time it next time.

I have been considering trying a single stage process. I have not only because I had trouble getting my process woking when I first started and a 2 stage worked and I have been getting good yield and fuel with it. I suspect most of my problems were a result of insfficent mixing. If I can get a good collection this weekend so I can test with the same oil source I will probably try a single stage at 20% so I can compare the yield. If my yield is the same I'll probably stop running a double stage and drop down to 18% and try again.

Brent