I was wondering if any of you gents (and ladies) have good suggestions for motorized methoxide mixing.

I'd like to design a steel tank that I can pump the methanol into, pour the measured NaOH into, and mix "hands off." I hate having to shake and stir these things to get them dissolved.

Just as a place to start, I'm thinking about using a 12V motor mounted externally on a steel tank. The small motor I've found that I think might work is a 300RPM motor with a 6mm shaft. I know that there's a lot to choose from. I'd probably need some combination of motor, shaft, propeller, sealed bearing, etc.

Tank design might require some thought. I want to prevent the Lye from clogging the drain.

Do you guys see where I'm going with this?

PwrStrk6spd

-I use a steel tank, old propane 60gal tank, and stir with a paint stirer, driven by a small air drill. (no sparks) done in twenty min. Tom

I never liked steel, mostly because its hard to tell how much is in the tank without using a site tube and my perpetual fear of completing some unknown circuit. We have used polyethylene (HDPE) tanks without issue for a few months now to both mix our methoxide and collect recovered methanol. They tend to be a bit cheaper too and only require a bit of modification.

We used a 15 gallon tank, then punched a hole in the side for a recirculation hose. When mixing our methoxide, we are able to use a air driven diaphragm pumpto do the work. It also pumps into the container too, so if you want to keep your methanol out of the shop and pump it in, this will be helpful.

Here are some photos if what I said was a little... hard to read. Dickinson Biodiesel

How big a tank do you want to mix? I just installed a 1/3rd hp, 6-inch prop mixer on a 300 gallon tank this weekend. At home I have a 1/20th hp prop mixer on a 15 gallon tank with a 2-inch prop. Is yours somewere between?

Critical: use a safe motor. A 12-volt motor is likely to have an arcing brush commutator. This is a very real ignition source for methanol fumes. Better choices are 1) explosion-proof rated motors, 2) TEFC "washdown" motors, and 3) induction motors. Ex-proof motors are best, but expensive (I was luck to find a couple at the scrap yard). TEFC motors are a "poor-mans" ex-proof motor, isolating potential ignition sources, but not truely explosion-proof. Induction motors have no spark source, but are usually small hp suitable only for small mixers.

Keep in mind that the control switch is also an ignition source. Either use an ex-proof switch, or put the switch in a remote location.

Air motors work really well, and are really safe. Not many people use them.

For the big tank I used sch-40 1-1/4 inch pipe to mount the bearings in. Some lathe-work is required. The pipe is welded to a mounting plate that fit the curved side of the tank. The shaft is 3/4 inch steel. I threaded the end of the shaft for the prop, which I also made. The prop must be removable in order to install the shaft in the tank through a hole, then the prop is fastened on. A standard lip-type shaft seal was listed as resistant to methanol, and is pressed-in after the bearing. The drive pulley is 6-inch, giving a prop speed of about 700 rpm. The prop "pushes" towards the tank bottom, and is offset to one end of the tank to prevent formation of an air-sucking vortex. This provided near perfect mixing, judging by the crystal-clear appearance of the methoxide less than 5 minutes after adding the KOH.

I'll post some pictures when I get the chance.

Cheers,
JohnO

Well right now I use a 40gal water heater to make 25gal or approx 100L batches. If I move up to a 200L batch, I would need to mix 44L with 1600g of NaOH. So a tank that's larger than 44L to include headspace.

(Hopefully this picture took. Haven't done this before.)

I use an air drill mounted to a keg. Mount is cobbled together with bearings and 6" hole is sealed with sheet silicone. All screwed down tight with wing nuts. Works well in winter temps, (20 minutes to dissolve koh) Fine mesh sink strainer in bottom exit hole.

Sorry, I'll have to try and get a pic up another way later.

Photos from binuya:

Create an account with www.photobucket.com. Upload the pictures. Crop, resize, whatever. Save the modified pic. Then in the "share this image" box, click on the IMG code. It will copy to your clipboard. Then paste it into the text box here on the forum and it will appear like this (minus the outer brackets)

<IMG]http://i230.photobucket.com/albums/ee169/tunemaker7/CIMG0260.jpg[/IMG>

Giving you this:

Gday,My methoxide mixer is a 250 litre tank made from the top half of two water heaters and has a 1 inch shaft up the centre of the tank.I fill the tank with 200 litres of methanol add approximately 14 kilo of KOH and the tank is sealed up and is rotated 36 rpm by a electric motor.The tank does build up heat and pressure and i have measured this and the hottest temp i have recorded is 50 degrees c and the pressure inside the tank has been no more than 7 p.s.i. regards westwinds

JohnO is right on about the 12V motor if it is 12 volt DC.
I am building a mixer tank as well out of an old galvanized steel pressure tank and will be using an air motor with collapsible blades on the prop designed for drum mixing (a friend has one he would like to sell me that was used for mixing ink) or a small TEFC fractional HP motor with a homemade prop on the end. You could also use a shaded pole motor like what is used in forced air electric heaters, window banger air conditioners, dehumidifiers, etc...
The idea is to seal the vessel and have it vented to the outside to avoid fumes around the vessel and use a motor with no arcing, sparking or heat producing apparatus in them that could ignite the fumes.
I have no idea what kind of HP is going to be required for mixing but once I start testing I will be able to give you a better idea...
Jon

also look into mag drive pumps..many are TEFC..also they eliminate the shaft/seal issue.

a small little Giant chemical pump should work fine. you don't need hugh volumes. just do some reseach on the pumps.

here's another thought..
if you're going to mix in a steel container, some thing that will take heat, use 1/3 of the total methanol amount. add the NaOH..YES THIS WILL BOIL..so put a methanol condensor and let it reflux back in..After the boiling..add the rest of the methanol..no pump, no motors..

-dkenny

Here is a link to my small methoxide mixing tank setup.

I've added some bulkhead fittings for filling meth and a lye dump via RV septic gate valve since the post. Also had to remove the upper mixing blades and extend the shaft length so it reaches down to about 1/2 inch off the bottom of the tank for better mixing.

Besides needing a bigger air compressor, it does pretty good after I worked out the bugs.

-Ken

Ken,
Nice rig!
How are you liking the RV gate valve setup? I am thinking of using the same thing...
Jon

quote:

How are you liking the RV gate valve setup?

Went with the 2" valve, overall works fine but the rubber seals around the gate are getting a bit stiff, making it a little hard to open and close. Think it's due to methanol splashing up or the lye collecting moisture and gumming them up. Should work just fine without them, so they might be on the way out.

-Ken