quote:

Originally posted by Paulus:
So Jim no acid means no need to add phenolphthalein and therefore no need to check for colour change? I guess if you have a build-up of MeOH-rich glycerine from previous batches waiting for distillation you could add a little into each latest batch and process that way?

Only if you didn't do a prewash as the water will contaminate the Methanol. If you use NaOH with the WBD the glycerol turns to a solid brick in 24hrs.
One advantage of that is I can take it to our local dump for land fill, they won't take liquid.

James,

Yes, I agree that an eductor is simpler than effective use of inline mixers. Testing to show that it is just as effective would be good. I will work on that when I have time.

quote:

A good 3/27:-

I am sure you are aware of the reasons why 3/27 is not a good test to detect a reverse reaction. If you want me to expand, I can.

Also, it seems very likely that some reverse reaction has taken place, based on my understanding of the chemistry involved. If we assume that the reaction has run near completion, as soon as methanol is removed, a reverse reaction begins. Of course mixing and other factors would affect the rate. So, to me, the question is: How much reverse reaction has happened and is that acceptable?

interesting..

jamesurl..have you noticed any heating of the oil without adding heat. ir just because of the eductors?

I forgive me if I divirge for a moment.
I have 2 setups
1. a water heater..static mixing is easy to add. the high volume pump and hot abinent(sp local temps)..I normally don't need to turn on the heating element..NOT AT ALL! infact some cooling would make somethings better..
2. a plastic tank..yes I have had the same self heating problem but not as often.

differences
water heater 50 GPM pump, static mixer( home made, so suspect quality) 3/4" lines. 2 inputs but both near the bottom of the tank.

plastic tank
single output..the drain at the the bottom..reduced to 3/4"
return. 3/4" pipe with several holes..maybe 15 and various angles. more or less causing a circular flow..
pump rate around 20 GPM. measured

other notes. that might be interesting
tank1 the water heater. typically finishes conversion in less 1hr using 27/3 as a measure.
tank2, the plastic tank. also around 1 hour..

oh both tanks use about 60 gallons of oil at a time.

so I would conclude the pumping volume is big factor..sure I like to see what would happen if the 50 GPM pump had a nozzle to increase the mixing..but this tank self heats in the summer. I have had to make BD at 170F without adding heat.
for using the little blue pump..forget!!not enough volume. been there tried that. my little giant te5.5 pump is far better.and it uses less power. 1/3hp vs 1/2 hp.


-dkenny

jim,

i'm yet again impressed :]

i'm running a GL/Appleseed with 2 HF pumps currently. I'm still seeing about 3 hour mix times, even though i have pump inputs on the top and bottom of the tank.

i'm interested in running an eductor. would you see any need for dual pumps on 100-120L batches?

would you think that two pumps would speed the process up even faster?


thanks for your input.

Tim

-I've been the static mixer route with the little blue pump and 160 ltr batch, they help but not much. the pump volume is not enough to make them work properly. Tommorrow I will install 3 4" paint mixers (one on top of the other) in the tank driven by an air drill. I tried one paint mixer in a pail of 50/50 water and wvo they where completely blened with in a couple seconds. One thing I noticed, was the mixing is much beter if the stirer is offset from the center of the tank. I read somewhere that the same hold true for eductors as well. Tom

Teepee

-just finished modifying my processor to get better mixing, finished the third batch yesterday, the reaction was very quick, total cost $45.00. mixers are turned by an air drill, but I'm going to change that to a motor (nt pump) and pully/belt system. Tom

I have been using an eductor all spring/summer on my new 500 gallon processor. After you use and eductor, you will never look back. Full conversion in a fraction of the time as opposed to using just a pump.

quote:

Originally posted by Gregory Kittredge:
I have been using an eductor all spring/summer on my new 500 gallon processor. After you use and eductor, you will never look back. Full conversion in a fraction of the time as opposed to using just a pump.

Eductors are only beneficial when the processor design includes an undersized pump.

The best eductor in the world wont replace a proper pump.

quote:

Eductors are only beneficial when the processor design includes an undersized pump.

The best eductor in the world wont replace a proper pump.

Sure. Or viewed another way: Big pumps are for people with more money than design ability.

quote:

Originally posted by Andrew M:

quote:

Eductors are only beneficial when the processor design includes an undersized pump.

The best eductor in the world wont replace a proper pump.

Sure. Or viewed another way: Big pumps are for people with more money than design ability.

That viewpoint is flawed. Smart people know when to spend money. If you're doing batches bigger than 50 gallons you need a bigger pump than the clearwater blue one.

freesoul

-don't you mean 20 gallons?
-educors and static mixers only work well if you have the fluid force and volume to make them work,
-I've used both in line and in tank static mixers with the nt pump on 160ltr batch, and although they increase conversion rate, it's not by much, thats why I went to the paint mixers in cojunction with the nt pump, now WOW
-would it be easier to go to a bigger pump YES, cheaper NO If I was building a new processor I would use the pump and stir method. Tom

quote:

-don't you mean 20 gallons?

I do 34 gallon batches with the little blue pump. I haven't considered it a problem yet. It just takes more time than a powerful pump would.

just a recent observation I have a 66 gallon water heater and do 48 gallon batches I use a 1/2 blue pump I am building a new 320 propane tank reactor but for right now I know I have inadequate mixing with an 1/2 hp blue pump I have learned to overcome the problem with adding the methoxide just before the pump with a slow injecting the methoxide in over time if I do a 1 step I flow in about 20 minuets and immediately I have a near pass of the 3/27 this has not been consistent for me because I use a ball valve it is hard to control the time that is why I am considering a metering pump for the new reactor and I have considered a needle valve but I still have the ball valve on the tank outlet that will be difficult to control the restriction of negative pressure to regulate methoxide flow I am on the fence on this decision to is a educator or is the metered meth injection and pump shear mixing more efficient? I know the 2 hour time isn't necessary look at the Dr pepper test shake for 30 seconds settle for 15 minuets and a near complete reaction.

quote:

If you're doing batches bigger than 50 gallons you need a bigger pump than the clearwater blue one.

Perhaps. There is some cutoff where better design will produce diminishing returns. Where the cutoff is has not, IMO, been established as hard fact.

But some suggest that the blue pump is not good above 20 gal.

I have done 38 gallon batches with 19% methanol in 45 min. Sure it took a bit more work on the design. It was worth the work to me.

To me, work on the design first. Then, consider a bigger pump. Just my approach. If you have more $ than time, by all means, hit it with a big expensive pump.

My wife agree's. Bigger pump isn't always better. With a smaller pump you put a little more into how you use it (design) and do as good or better job with less($). I have the biggest pump Murphy offers but am using it on a 250 gallon batch which it is on the borderline of being big enough so I am going do it as best as I can and hopefully get a really good reaction. Still undecided Static mixer, eductors,or injection I guess I am leaning toward injection but I am still open minded

kinda of a side comment/note..
are ya'll considering just the cost of new pumps( bigger pumps). or used/pumps on ebay?

I ask because those little blue pumps..don't pump enough!

ok for those that don't know
my batches are in the 60 gallon range.
no big, but not small.

pumps
goulds 3642..50 GPM or so. this setup has a homemade static mixer(please question quality, I know I do)
little giant TE-5.5-md - 30 GPM
neither setup draw from near the top and the bottom..I see this would be a much better setup. just not practicle for my setup..

get the idea 10x to 6x the mixing of the little blue pump...oh cost less than $100 for the goulds and less than $75 for the little giant..the little giant is TEFC magnetic drive pump. both used and on ebay.

mix times..using the 27/3 test
less than 1 hour for each setup. or put another way after 1hr it passes 27/3 or it won't.
by that it won't. I mean even after 12hrs of mixing..no change in the 27/3 test.


gee..so which side of the mixing camp do i sit..larger pumps are better..hand down..now when you start getting to LARGE setups..eductors will be better..

-dkenny

I feel fortunate. I found my current used pump on ebay for $74.00 minus a motor. It's a Goulds ICS 3657 (I think) 90+/- GPM, stainless, viton elastomer, carbon seal, mated to a 2.5HP motor I had laying around and it helps to pass 3/27 in 30 min with 110 gallon batches. I would never have been able to afford the price new. A local plumbing company wanted $1300.00 for the pump and motor combo new. Wasn't gonna happen for this cat.

I use a little blue and that is exactly why I get better results using base/base cause I have to reprocess when I do a single base reaction I don't get any more fallout after about 45 min. whether in 1st 2nd or 3rd step unless if i get the meth mixing timed just right by the way dkenny I'm kg4gvx been to the shelby hamfest for the last 9 years except last year maybe we have met before just didn't know it good to know fellow hams on here KG4GVX

After this discussion I guess I have made my mind up on the eductor for my app. Has anyone got a recommendation for an eductor for between 81 and 94 gpm flow at the head I will be running with 1-1/2 plumbing and a volume of 250 gallon ?

I'm sure there is a formula in the Chem E handbook, but you'd probably be better off with a store bought mixing eductor. Pick a vendor, call them and ask for their recommendations. Be sure you have the pump's head vs flow diagram available for them to cross reference.