Greetings Ken
>On 9/13/05, Keith Addison
><<mailto:[EMAIL PROTECTED]>[EMAIL PROTECTED]>
>wrote:
>
>The question does tend to come up every now and then, but recently a
>much higher proportion than usual are inquiring about biodiesel's
>allegedly short storage life.
>
>So many people just browse around the web like gadflies, they don't
>keep much or any record of where they went or what they found there.
>("Hi, I stumbled on your website...") It seems to point back
>somewhere, it might be worth knowing just where.
>
>Anyway, it seems none of us has stumbled on it, yet.
>
>
>Keith,
>
>JtF is an incredible resource.
Thankyou! </blush>
We're way behind with uploads though, as usual. :-/ Well, I guess it
happens when it does, and it does grow rather steadily.
>I am reading something or another every couple of days from one of
>the many topics. Perhaps including some storage expectations and
>debunking disinformation would be of great service. I know that
>you're busy but, it may save you some time in the long run.
Yes it would, and I've been assembling stuff, including some comments
from this current thread.
>I could have sworn that I saw some sort of guideline on JtF but, I
>certainly can't find it. I've tried searching through the search
>engine ("biodiesel storage" or "biodiesel shelf file") and manually
>searching through the pages that I think would likely contain the
>info but, I keep coming up dry. I can find information on other
>websites but, I trust JtF more.
Thankyou again. We no longer trust our site-search engine much, we're
in the process of replacing it. But it got this one right at least.
The only mention of it is in one of the papers in the Biofuels
Library:
"Biodiesel: The Use of Vegetable Oils and Their Derivatives as
Alternative Diesel Fuels", G. Knothe, R.O. Dunn, and M.O. Bagby, in
Fuels and Chemicals from Biomass. Washington, D.C.: American Chemical
Society.
http://journeytoforever.org/biofuel_library/VegetableOilsKnothe.pdf
http://journeytoforever.org/biofuel_library/VegetableOilsKnothe.doc
Storage stability.
While most aspects of biodiesel discussed above have received
considerable attention, relatively few papers (165-167) deal with the
aspect of (storage) stability of biodiesel or fatty alkyl esters.
The use of biodiesel is advantageous compared to conventional diesel
fuel from the aspect of handling and storage safety because of the
higher flash point of both vegetable oils and their methyl esters.
Generally, the stability of fatty compounds is influenced by factors
such as presence of air, heat, traces of metal, peroxides, light, or
structural features of the compounds themselves, mainly the presence
of double bonds. The more conjugated or methylene-interrupted double
bonds in a fatty molecule, the more susceptible the material is to
oxidation and degradation.
Early storage tests gave the following decreasing order of stability
for different refinement grades of various vegetable oils (165):
soybean oil >> degummed soybean oil > refined soybean oil = refined
sunflower oil > degummed sunflower oil = crude sunflower oil. The
stability of the crude and degummed oils was significantly improved
by the addition of diesel fuel (in 1:1 mixtures) but this did not
improve the stability of refined oils. The storage stability of 1:1
mixtures were in the decreasing order of crude soybean oil crude
sunflower oil > degummed soybean oil > degummed sunflower oil >>
refined soybean oil > refined sunflower oil. A degummed oil / diesel
blend with better stability characteristics than that of a refined
oil / diesel blend could be prepared. Additionally, the purity of
the degummed oils was sufficiently improved by the addition of diesel
fuel to meet the required fuel specification.
A study on the stability of the methyl and ethyl esters of sunflower
oil reports that ester fuels (biodiesel) should be stored in airtight
containers, the storage temperature should be < 30 C, that mild steel
(rust-free) containers could be used, and that
tert.-butylhydroquinone (TBHQ), an oxidation inhibitor, has a
beneficial effect on oxidation stability (166). Methyl esters were
slightly more stable than ethyl esters. Light caused only a small
increase in the oxidation parameters of esters stored at the high
temperature level. The changes in the samples were reflected by
increasing acid and peroxide values in storage at 50 C and increases
in ultraviolet (UV) absorption.
Two parameters, namely temperature and the nature of the storage
container, were claimed to have the greatest influence on the storage
stability (167). Samples stored in the presence of iron behaved
differently than those stored in glass. Higher temperature favored
degradation of the hydroperoxide at a faster rate than when it was
stored at room temperature. Secondary oxidation products were formed
in greater amounts in the presence of iron (from the primary
peroxides) while in glass the concentration of primary oxidation
products is higher. Acidity values were also monitored in this work.
Even for samples stored at 40 C, the increase in free acids was
within the limits of technical specifications. The free acids need
to be controlled because they are mainly responsible for corrosion.
---
Ho-hum.
Best wishes
Keith
>Take care,
>Ken
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