Split thread on HMPE's.

[Julian]

Not sure how to split a thread, so this is a new thread derived from "Biodiesel troubleshooting flow chart?" thread.

Have you tried "wintron synergy" Julian? something i noticed when doing the winteriser testing
http://www.vegetableoildiesel.co.uk/forum/viewthread.php?tid=14224
i took all the samples down to -17 and made hmpe,s form in all the samples except the one dosed with synergy,i never took it any further as im not really a member of "Tonys winter club"
I could send you a sample if you want and if your really nice some synergy as well

I think it was Wintron I used a couple of years ago, but I still seemed to have trouble.  Used Coldflow last year and had problems again.  I wouldn't mind a little Wintron and I'll treat the washed sample of my last test and compare it with the unwashed.  I've made a little device which will cool two jam jars simultaneously, running off my beer chiller ...



These were the results after three days at -3.5°C ...

Un-washed ...



Washed ...



And this was the mini wash tank I made to run the washing tests ...





When I was playing last year, I found that freezing to -18°C and thawing, never evolved HMPE's.  It seemed to need prolonged periods of cold, but not necessarily very cold.  For example, I've wash tested three batches, each with feedstock from different sources. A couple of days at 2°C yielded HMPE's in two of the three un-washed samples, when the washed samples remained clear.  The third sample (my normal supplier) I took down to -3.5°C and you can see the result above.

I'm wondering if we are all not looking at exactly the same thing, but labelling it HMPE's.  For instance, HMPE's in a settling drum appear as gel like crystals, but in a sealed container in the fridge or as a door step sample, as fluffy clouds, just slightly more dense than the bio.  K.H says he get's them after freezing and I don't ... just gets more and more confusing!

Edit ... messed up with the wrong photos ... ok now!

[K.H]

In that case i guess it was not HMPE,s i saw,ive never seen them under normal conditions anyway
When i took all the samples down to -17 i got a gel like crystal in all the samples except the Wintron,when i raised the temp they remained until near 0C,it seemed that once you create them they remain even at lesser below freezing temps
In the tests i described them as crystals,i think somewhere along the line i must have just assumed they were HMPE,s
If you want a small sample of Wintron send me your address Julian,this winter i shall use all the samples i got for testing so im going to be on many different coldflow additives

[Julian]

Thanks Keith.  I'll send you a PM.  It only need be a very small sample, enough to treat a jam jar full.

I'm not saying what you had wasn't HMPEs, just wondering if we are observing different issues.  Other than they are a pain in the backside, we really don't know for sure what we're looking at.  A VOD member did offered to get samples tested in a university lab, but unfortunately it never happened.

Water washing, pain that it is, certainly seems to improve things down to 2°C on some oils, but I'm not sure that it's the complete cure for what I'm calling HMPEs.  With the Wintron, can you send me a jam jar sample of your washed bio and I'll try that at -3.5°C for the same period of time?  Might be an interesting comparison.

[Julian]

The samples arrived from "Tosser Towers", thanks Keith.

I treated my washed sample with 0.3% Synergy and chilled it along side Keith's washed sample.  After 24hrs at -4.4°C this was the result ...








No obvious HMPEs in my sample (but it may need longer to give them a chance to form), but Keith's sample was about 40% wax. So, first question to Keith ... was the sample you sent treated with an additive?  If not I'll treat it and repeat the test.

[K.H]

Nope,no additives in it

[Julian]

Ok, thanks Keith.

I'll add 0.3% Synergy in and rerun the test, might have to wait until next weekend though.

What was the feedstock out of interest?

[K.H]

My collections are normally a soy/rape mix but ive been having RM,s crud and adding that to the mix

[Tony]

Perhaps it is all the same stuff, but the speed of cooling affects crystal formation.  After all, not all snow is the same and that's made from the same stuff

[Julian]

By "all the same stuff" do you mean what we've come to call HMPEs and solidifying effect at reduced temperatures?  If so it I think that's possible.  The "wax" type stuff in Keith's bio melted by the time it got to +5°C and similarly the fluffy stuff in my bio from the previous test melted over time, but perhaps not so quickly.  Both looked very different from one another though.

From last year's experience, what I had in my bio may well have been different to what appeared in the tests this year as last years stuff didn't melt until around 30°C.

I'll see if the Synergy keeps Keith's Bio liquid at -4.5°C, if it does then I'll check for similar fluffy stuff.

[Julian]

Quick up date ...

Treated Keith's Bio.

Both samples have been chilling for around three hours, have reached -3.9°C and are perfectly clear.

[Julian]

Just over 24 hrs, current temperature -4.8°C.  Keith's sample shows no signs of gelling, so the Synergy seems to work very well in that respect, but both are showing fluffy looking strands adjacent to the chilling pipes (assume the temperature is far lower around the pipes).

[Tony]

By "all the same stuff" do you mean what we've come to call HMPEs and solidifying effect at reduced temperatures?

From my understanding all oil is made of triglycerides with a mix of fatty acid chains.  IE Rapeseed is, according to wikipedia:

60% Oleic acid
21% Linoleic acid
11% Alpha-linolenic acid
7% Saturated fatty acids
4% Palmitic acid
2% Stearic acid
0.4% Trans fat

So if we know the point at which the Methyl Ester of each acid freezes, then we can predict the quantity of what we call HMPEs will be formed for any temperature.

For the example above, chosing Palmitic Acid Methyl Ester (synonym Methyl Palmitate) the melt point is either 29C or 17C - if it's branched at the end, whatever that means.  In the latter case we may find 4% of Rapeseed derived bio starts to solidify below 17C, if that makes sense.

Ideally we'd have a table of all the melt points of each Methyl Ester, then you could estimate for any given oil when it'll start to crystallise, and how much.  I've tried to compile a table in the past but finding this information for all the acids is bit of an arduous task

[Julian]

Sorry to have taken so long to post the final photos, but I've had some camera battery issues!

In the end the treated samples were chilled for 5 days and the pipe work accumulated quite a coating of ice ....



The only obvious signs of any change was immediately around the chilling pipes in both samples. Having removed the chilling pipes, this is what both samples looked like.

Keith's ....



and mine ...



Both showed signs of gelling and/or fluffing, but both returned to being perfectly clear at ambient.


Keith's sample showed more gelling around the pipes immediately after removal (right-hand set) ...




But after a couple of days in an ambient of around 15°C, mine (left-hand set) showed more un-melted deposits than Keith's.  Assume these are HMPEs ...



Compared to previous tests Synergy certainly seems to make quite a difference, but doesn't appear to be a complete cure for HMPEs.

Thanks for sending the Synergy and bio sample, Keith.  It made for an interesting comparison.  Unfortunately I've stocked up on Coldflow, but once that's gone I change to Synergy.

That said, my heated filter is complete and operating quite well ... when I get a chance, I'll post some pics and details.

[K.H]

Yes as i commented on in the VOD additive testing thread,the drip/freezer test sometimes isnt the whole picture,although it is a good comparison,taking into account what my bio looked like when chilled and the way it returned to normal i would always choose synergy over the others,for my feedstock anyway

[Chug]

Here is a description of what happens as bio cools courtesy of Van Gerpen, Knothe et al,
http://www.scribd.com/doc/54171412/The-Biodiesel-Handbook-Knothe-Van-Gerpen-and-Krahl

Cloud Point and Pour Point
Initially, cooling temperatures cause the formation of solid wax crystal nuclei thatare submicron in scale and invisible to the human eye. Further decreases in temperature cause these crystals to grow. The temperature at which crystals become visible [diameter (d )≥0.5µm] is defined as the cloud point (CP) because the crystals usually form a cloudy or hazy suspension.
Due to the orthorhombic crystalline structure, unchecked crystalline growth continues rapidly in two dimensions forming large platelet lamellae . At temperatures below CP, larger crystals (d ~ 0.5–1 mm×0.01 mm thick) fuse together and form large agglomerates that can restrict or cut off flow through fuel lines and filters and cause start-up and performance problems the next morning. The temperature at which crystal agglomeration is extensive enough to prevent free pouring of fluid isdetermined by measurement of its pour point (PP). Some petrodiesel fuels can reach their PP with as little as 2% wax out of solution