Wikipedia gives; Yellow grease can also refer to lower grades of tallow (cow or sheep fat) from animal rendering plants. A source from 1896..."Yellow grease is made by packers. All refuse material of the packing houses go into the yellow grease tank, togeather with any hogs that may die on the packers hands."
So based on some of the latest sources, lard may be in yellow grease also.
The yellow grease I was planning to use comes from a fast food outlet that uses vegetable oil mixed with pork lard. They cook hamburgers, sausages, chicken portions etc in this and the fats from these meats also dissolve into the oil. Its hard to be precise but I would estimate that this yellow grease is about 30% animal fats. This kind of feedstock is much easier to source than pure liquid wvo and most of us here in Ireland deal with it by adding a proportion of it into each batch throughout the warm summer months. However those homebrewers who have too much of it will be interested in the fractionating process as this might allow them to use it all year round.
The yellow grease I tried out yesterday proved to be unsuitable. It took 2½ hours of boiling to remove the water from 1 litre and then it titrated at 14ml KOH. Im going to try to buy some pork lard from a butcher or supermarket today.
"Dry fractionation of TME (tallow methyl esters) under controlled
conditions resulted in 60-65% yields of liquid fraction characterized by an increase in iodine
value from 41 to 60 and a decrease in CP from 11 to -1ºC (Krishnamurthy & Kellens, 1996).
These 2 guys seem to be the leading experts in the research on fractionation but I cant find any of their work available on the net. Does anyone have access to a college library we could use?
Called into my local butcher this morning to ask about pork lard or beef tallow. They had no lard but were able to sell me some beef tallow which they make themselves. When I told him what I wanted it for his face lit up. He said that they only sold a tiny proportion of the beef tallow that they could make because it was so out of fashion to cook with fats these days. They have their own rendering plant that could make about a hundred litres per batch. Im calling back tomorrow to show him him the results of the process.
So I came home with enough beef tallow to start making biodiesel to try out fractional crystalization. I can only make 1 litre with my mini processor so I made the first litre today exactly as before, drywashed with magnesium silicate and placed into the warm cabinet at 36°C to settle overnight. Tomorrow I will filter off the mag/sil and store the bio in the warm cabinet. Once I have three litres Ill weigh the biodiesel carefully and then begin the FC process. I want to weigh the filter contents so that I have a clear picture of how much precipitates at different temperatures.
Two litres made, one to go.
this is the full title of the article I am trying to get,
Krishnamurthy, R.; M. Kellens. Fractionation and winterization. In
Oil and Fat Products, 5th edition.
Y. H. Hui, Ed. John Wiley and Sons: New York,
1996; pp. 301–337.
Wiley is a commercial publisher and its prohibitively expensive to buy one article. If any students or college staff could locate it for me through their library catalog, I would greatly appreciate it. My own contacts in various colleges are away on holidays and wont be back till September.
Ive just discovered that Amazon.com sell it but even with the free shipping its a bit too expensive at 2,232 dollars!
Many thanks Tallowman, your parcel of what looks like about 10kg of tallow arrived today. That will keep me going for quite a while.
I made the 3rd batch today and the magnesium silicate is settling now. Tomorrow I will filter it and add it to the other 2 batches which are in the warm cabinet at 40°C. Once the temperature stabilizes Ill lower the temperature by 2°C, gently agitate it for 6 hours and then filter it to remove any crystals. And so on till I reach ambient temperature. As you can see this first trial is going to take quite a while but Im sure with practice I should be able to shorten the times considerably. Also its the kind of process that would be very easy to automate, yet another job for my Arduino.
I finished making the last of the tallow biodiesel yesterday and began the fractional crystallization process.
The steps I finally went for was a reduction of 3°C followed by 8 hours of very gentle agitation to encourage crystal growth followed by 2 hours of filtration to remove any hmpes ( in this process hmpes are referred to as stearin).
Ive now done 2 steps, 39 - 36°C and 36 - 33°C. The yield of stearin , as expected, has been very low, only a few grams. As the temperature falls the yield of stearin should increase dramatically.
In the last picture I posted you can see a bottle behind the packet labelled Dripping with some very pale tallow biodiesel that I had cold filtered down to a cloud point of 12°C. Last night the temperature in my workshop fell to 10C and the biodiesel not only clouded but actually gelled.
In my experience the cloud point and gel point of veg oil biodiesel is usually 5 or 6 degrees apart but it would seem that in tallow biodiesel they are much closer, only 2 degrees. This is something I might investigate later but just at the moment I have my hands full with this fractional crystallization process.
imakebiodiesel; I found information on crystallisation in a book "An Introduction To Modern Experimental Organic Chemistry" published by Holt, Rinehart and Winston, Inc, published 1969, International Standard Book Number 0-03-069165-6, on page 38, under Crystallization, "The hot filtrate is allowed to cool slowly by standing at room temperature. Crystallization should then ensue. Rapid cooling by immersion in water, etc., is undesirable because the crystals formed will tend to be quite small....Generally the solution should NOT be agitated while cooling, since this will also lead to the formation of small crystals." For your gravity filtration purposes I suppose it is easier to filter out larger crystals than smaller crystals. I thought growing crystals should be left undisturbed to grow larger crystals. It took a while but I found a reference to confirm this. I suppose tiny powder size crystals will clog the filter paper faster than larger crystals will.
The agitation I have been using is to pump the bio up from the bottom of the bucket and back into the top at a rate of 2 litres per hour. The bucket contains 3 litres of bio so this is very gentle. Ive read several articles on the fractionating of palm oil and gentle agitation was used. This may have been because of the large size of the cooling tanks. Slow stirring would even out the temp in these large tanks but it may not be necessary in my very small bucket.
Ive now proceeded through 5 steps so far and the temp is at 24°C. Each filter is yielding more stearin than the last but it still doesnt seem like a lot. I think I may stop the agitation and see does that increase the yield of stearin.
One good thing about this process is that if it does go wrong I can just heat it all back up and try again.This message has been edited. Last edited by: imakebiodiesel,
The sample cooled to ambient last night and is filtering at this moment. The amount of stearin is roughly doubling each step but still only represents a very small portion of the total. Here are some of the filter contents
I found that when I stopped the continuous agitation the stearin collected on the sides of the bucket so I now stir the bucket briefly just before starting to filter. Once this filtering is completed I will print up the results with times temps yields etc.
Finished this filtering stage and the yield of stearin/hmpe has increased a lot. Below is a chart of the results so far,
I probably could have skipped the first 3 stages and the continuous agitation did not help. A gentle stir before starting to filter works better.
I started with 2670gms of biodiesel and have removed 102gms of hmpes so the yield is 96.2% of liquid fuel.
We are having night time temps of around 10°C so Im going to do a further stage each night until I get it down to 10°C.
This is what the last filter looked like.
This message has been edited. Last edited by: imakebiodiesel,
Oops, got a bit too enthusiastic last night and let the temp drop to 12C. This morning the bio had formed a slurry too thick for the pump to handle. This is what the articles refer to as "entrainment" when the crystals grow into a matrix and trap the liquid.
Ive turned the heater back on and will reheat to 17°C and start again from there. This is the beauty of this method, if you go too fast or make a mistake its a simple matter to reheat and go again.
Methyl biodiesel from beef tallow or pig lard are similar in composition, or so I've read. The composition has something to do with the animal's diet.
I found a break down of the composition of beef tallow in an old organic chemistry book that has a bearing on your fractional crystallization.
These are methyl esters of fatty acids present in methyl biodiesel derived from beef tallow.
Eicosanoic Acid methyl ester, melting point, m.p. 54.5 degrees C, 0.4-1%.
Stearic Acid methyl ester, m.p. 39.1 degrees C, 21-26%.
Hexadecanoic Acid methyl ester, m.p. 30 degrees C, 25-30%.
Tetradecanoic Acid methyl ester, m.p. 19 degrees C, 2-3%.
9-Octadecenoic Acid methyl ester, m.p -19.9 degrees C, 39-42% (methyl oleate).
Hexadecenoic Acid methyl ester, m.p. -0.5 degrees C, 2-3%.
9,12-Octadecadienoic Acid methyl ester, m.p. -35 degrees centigrade, 2% (methyl linoleate).
That's most of the composition of methyl biodiesel made from beef tallow. Biodiesel made from lard is similar. So you recognize, it is a mixed product. It is not stearin.
Its not so simple as taking the mixture of liquids below their melting point. I don't understand it exactly, but there's some ability of a low melting methyl ester to solvate a higher melting methyl ester below the higher melting methyl ester's melting point.
I have read several articles that suggest a similar profile of fatty acid methyl esters for tallow biodiesel and yes, if it was a simple matter of melting points almost all the contents of my bucket would be captured in my filters by now at 17°C. The presence of lmpes seem to prevent the hmpes from crystallizing, possibly in the same way as adding kerosene to biodiesel helps to winterize it.
This leads me to the next part of this process. Krishnamurthy & Kellens found that by dissolving the tallow biodiesel in a solvent the fractionating process was easier, faster and more effective. But this was offset by the bother of having to remove the solvent afterwards by distillation. They tried out several solvents and found that methanol worked best but kerosene and diesel worked also. The big advantage of these last two is that they would not need to be removed.
Once this batch is finished I intend to do another batch with 20% diesel added.
Most of my information on this process has come from the palm oil/biodiesel industry, and in these articles the authors, mostly chemical engineers rather than chemists, refer to stearins and oleins as the solid and liquid fractions, equivalent to our use of hmpes and lmpes. However I take your point and to avoid confusion Ill stick to hmpes, thanks for that.
I still havent found the complete Krishnamurthy & Kellens 1996 article. My information comes from sections of it being quoted in other related articles. Just about every journal article on the subject quotes it a a primary source so I really will have to get my hands on it. I have a friend doing research in University College Cork and he may be able to get it for me.This message has been edited. Last edited by: imakebiodiesel,
Wesley, I have noticed something about the process that may interest you. My little fractional crystallization unit is inside my warm cabinet and the air temp in the cabinet is monitored by a pid controller. I also have a temp probe monitoring the temp of the liquid bio in the bucket. Thoughout the process I noticed that the bio was 2-3°C warmer than the air in the cabinet. Initially I dismissed this thinking that one of the readings was simply wrong. However I have tested both thermometers against my calibrated lab thermometer and they are both correct.
A little research has explained the difference. The crystallization process is exothermic. Its important to be aware of this and to monitor the actual temperature of the bio when fractionating.
imakebiodiesel; I've got a paper about scientific thermometers. I don't remember where I got it, but I think it is correct. "Thermometer facts...Fact #3: If not used properly, thermometers can give inaccurate readings...The liquid column of total immersion thermometers must be immersed to the level of the liquid in the capillary once the temperature has stabilized. Partial immersion thermometers must be immersed to the line marked on the thermometer.* If total immersion thermometers are used at partial depths (or vice versa), inaccuracies will occur. These inaccuracies increase as the temperature increases.
*In the rare case you need to use a partial immersion thermometer in a total immersion application, corrections for emergent stem temperature must be obtained to achieve an accurate reading."
I've got 6 common thermometers on the wall of my room here. The one manufactured in China that cost $2 dollars American money reads about 2 degrees C lower than the other USA made thermometers.
I suppose you usually get what you pay for when buying thermometers.
imakebiodiesel; I looked in a college chemistry book. Your exothermic heat of crystalization maybe a fact and accurate enough. It is the reverse of dissolving a solid in a liquid. It can be exothermic or endothermic, like dissolving potassium hydroxide in water (exothermic), but in reverse. It should reach an equilibrium where the bucket temperature equals the air temperature inside your autoclave. I'm not sure autoclave is the right word for your temperature controlled box, but it might be. There's a concept called heat of solution, that maybe be exothermic or endothermic. Crystalizing out a solid from a liquid is probably the reverse, relative to heat gain or lost. I haven't studied that aspect of chemistry for about 10-11 years.
didn't someone comment on this before (can't remember if it was on this thread Tallowman perhaps).
They were filtering HMPE's out of bio and noticed an increase of temp in the order of @ 10degC! Interesting stuff.
You are absolutely right, Tallowman noticed a sharp increase in temperature when filtering several pages ago. I didnt make the connection.
I have a partial immersion lab thermometer calibrated to BS1704. I use it to check the accuracy of the Chinese made digital thermometers I fit to my biodiesel processors. Normally they are quite good but occasionally one of these can be 3 or even 4 degrees out.
Due to the warm weather we are having night time temperatures are not dropping very low at the moment. I have got the tallow bio down to 17°C and without refrigeration I cant go any further. I do intend to construct a unit that will cool it down further but it will be a few weeks before I can get on with it. The family holiday is coming up soon and I have to go to England to pick up the kit for our new car. My son and I are going to build this over the next year.
Two seats, three wheels, 2 cylinders, no windscreen, no heater, no hood, lots of fun. Only problem it will run on petrol, can anyone suggest a lightweight 2 cylinder diesel engine that would run on biodiesel?This message has been edited. Last edited by: imakebiodiesel,
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