Interesting paper on biodiesel

[Julian]

Been doing some reading on thin layer chromatography, with the lovely acronym of TLC.  It appears it may be possible with biodiesel, but not yet sure if it's withing "shedman's" capabilities.    Anyhow, I stumbled upon this paper ... http://www.crses.sun.ac.za/files/research/completed-research/bio_energy/e_prah.pdf  in the course of my Googling ...

It seems to contain quite a lot of interesting stuff on testing bio.  Only skipped through the first few pages, but it mentions quite a bit about feed stock pre-treatment.  Of interest was water washing and treatment with methanol ...

2.5 Feed stock pre- treatment

Vegetable oils are obtained by the extraction or expression of the oil from the oil seed
source. This extraction is done by solvent extraction or pre-press/solvent extraction. The oil
at this stage could be referred as “crude” oil. ”Crude” oils at this stage contain varying
amounts of naturally occurring non-glyceridic materials. In order to achieve a biodiesel
product that meets standard specification, these substances should be removed or reduced
prior to the transesterification reaction. It should however be noted that, not all non-glyceridic
materials should be considered as undesirable elements in the biodiesel. For instance,
tocopherols act as an anti-oxidant in the biodiesel. Pre-treatment of the oil is necessary so
as to ensure that the biodiesel meets the required standard as set in bodies like the
ASTMD6751 or EN14214. Some of the pre-treatment techniques employed include the
following:


2.5.1 Degumming

This involves the removal of high levels of phosphatides in the feed stock. It includes the
treatment of the crude oil with a limited amount of water to hydrate the phosphatides and
make them separable by centrifugation. High levels of phosphatides in the final product
increase the turbidity of the product. (Brunner et al., 2001) recommended the addition of
methanol to the feed stock as this makes the phosphatides swell and precipitate.
2.5.2 Neutralization
This is performed on the feed stock to reduce its content of the free fatty acids (FFA). Higher
levels of FFA inactivate the catalyst for the transesterification reaction and thus reduce the
mass percent (%) ester yield. An alkali glycerol phase of a subsequent transesterification
step is employed to neutralise the FFA (Turck, 1999).This results in the FFA being converted
to high specific gravity soaps. After this, the oils are washed with water to remove the
residual soaps.


2.5.3 Hydrogenation/partial hydrogenation

Hydrogenation is intended to reduce the amount of unsaturation in the oil as this relate to the
stability of the fuel. This process can have detrimental consequences especially in temperate
climates as the conversion of unsaturation in the oil will lead to an increase in the presence
of saturated fatty acids giving rise to biodiesel with poor cold flow properties a situation that
is unwanted in cold zones. The technique involves the passing of H2(g) through the oil at
elevated temperatures in the presence of a suitable catalyst, such as platinum (Mcmurry,
2004). The unsaturation is destroyed and a saturated fatty acid is created

(equation here wouldn't copy and paste)


The hydrogenation process is easily controlled and could be stopped at any desired point. If
the hydrogenation is stopped after only a small amount of hydrogenation has taken place,
the oils remain a liquid.


2.5.4 Dehydration

The final stage in the pre- treatment of the feed stock before transesterification is
dehydration. This involves the removal of traces of water from the feed stock. The presence
of water in the feed stock decreases the conversion rates and may therefore result in the
inability of the biodiesel to meet the minimum requirement of 96.5% conversion rate.
Dehydration is done by passing nitrogen gas through the oil.

This afternoon I tried a shake up test with some WVO awaiting production and the water certainly removed something from the oil ... it was a real dirty colour.  I think I may have a bash at water washing the feed stock prior to the next batch ... it'll be interesting to see if successive washes result in clear wash water.

[Manfred]

It states that after a limited amount of water has been added it then needs centrifuging to remove the phosphatides. How do you intend to remove them if they need extreme G to be separated from the oil. It sounds like Methanol has a similar effect but then the oil doesn't need to be dried excessivley before production. Still needs a centrifuge though. Isn't the dirty water that you got just that ?

[Julian]

It may well be just dirty water. 

If the phosphatides (what ever they are) will separate by centrifuging, they may separate under gravity ... you don't know unless you try.

They also mention drying the oil with nitrogen, so perhaps they like making things more complicated than necessary.

[dgs]

Julian,
Isn't the part of the paper that you posted referring to new pressed feedstock that hasn't been pre-treated for food use. My understanding was that freshly pressed oil had a high % of FFA's and they were removed and the oil purified by various methods and then dried before being sold as veg oil for food use.

I have found that an intensive glyc pre treatment results in oil that has virtually the same colour as the finished biodiesel product.

Give the water wash a go, you have nothing to loose if you bench test it.

[Head Womble]

Seems to me that Julian just needs to find new ways of forming an emulsion.

[Jamesrl]

I remember reading a similar paper several years ago.

[Julian]

Seems to me that Julian just needs to find new ways of forming an emulsion.

You know me ... always looking for new ways of doing things!

[Julian]

Haven't been out in the shed since doing the "shake up test", but I checked this morning and the sample had indeed split into three phases ... dirty water, a thin gloopy, khaki coloured layer and murky WVO on top ... presumably murky due retaining some of the wash water.

So I'll go ahead and try washing the next full batch in the processor.

[Manfred]

What % water are you going to try and what method of introduction. Please don't say the Frankin pump for all things bio.
 Watching with acid at the ready.

[Julian]

Am I that predictable?

I added 10 ltrs water to 80 ltrs WVO via the venturi and mixed using Frankinpump ... and guess what?

I'll see if the emulsion has split by the morning.

[Manfred]

Quality. Sorry for your misfortune but it is funny. That is when it's someone else. The thing is though when you split it hopefully you will have succeeded. Try with salt first as I remember someone drying whites with a brine mix and found it to work ok.

[Head Womble]

Am I that predictable?

I added 10 ltrs water to 80 ltrs WVO via the venturi and mixed using Frankinpump ... and guess what?

I'll see if the emulsion has split by the morning.

Uuuum.

[Julian]

Things are looking up a little!

The emulsion sample from last night pretty much broke over night, but the stuff in the processor didn't.

I tried another sample with a little acid and that didn't seem to work ... I may have over done the acid.

So I heated the oil to 90°C, drained what had separated and then ran the venturi and Frankinpump until the outlet of my SHHE ran cold (my usual indication that the oil is pretty much dry).

There was a noticeable dark, oily layer between the water and clean oil when I drained the free water from the processor.

This was the result, washed oil on the left ....



The comparison with the unwashed oil is not really a fair one.  The unwashed oil is not exactly the same batch, it's just typical of my feed stock, it's not dried and it's at ambient temperature where as the washed sample is approximately 85°C.

All the same the washed oil shows a marked difference.  Despite the emulsion, I may try again on the next batch and see if I can make a fairer comparison with samples.