Difference between revisions of "Winter waxing"

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<metadesc>High Melt Point Esters, High Melting Point Esters, HMPE, HMPEs, Fatty Acid Methyl Esters, White balls in Biodiesel, Precipitate in Biodiesel</metadesc>
 
<metadesc>High Melt Point Esters, High Melting Point Esters, HMPE, HMPEs, Fatty Acid Methyl Esters, White balls in Biodiesel, Precipitate in Biodiesel</metadesc>
High Melt Point Esters are [[Fatty Acid Methyl Esters]] with melt points above ambient - typically between 10°C to 40°C.
 
  
HMPEs are usually seen in winter as either suspended flakes in the biodiesel, or white/yellow cream at the bottom of drums.  Adding petrol to a warm, melted mix does not prevent the HMPEs re-solidifying on cooling.
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In winter (or in a convenient freezer) some waxing in biodiesel may be observed as either suspended flakes or a white/yellow creamy layer at the bottom of containers.
  
Treatment is by filtering out the solids at the ambient temperature the fuel will be used at, or [[Water Washing]] with cold water. The initial level of HMPEs in the produced fuel may also be reduced by doing a cold [[Water Prewash]].
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[[File:Hmpe2.jpg|300px|thumb|right|Solids found at the bottom of a batch of biodiesel in the winter]]
  
The presence of HMPEs in biodiesel is feedstock related, with processing method playing only a very minor part.  Please note, there is some speculation that the [[Whole Batch Demeth]] method may produce more HMPEs than other methods although this is unconfirmed and needs further research before a final conclusion is reached.
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__TOC__
  
<gallery caption="High Melt Point Esters" widths="200px" heights="200px" perrow="3">
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==Feedstock related waxing==
File:Hmpe1.jpg|HMPEs at bottom of barrel
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Turning vegetable oils into biodiesel lowers the overall melt point of the liquid - the produced fuel will still be liquid at temperatures where the source oil will be solid.  However, making biodiesel from oils containing high melt components such as palm oil will inevitably result in higher melt points in the final fuel.  These components are commonly referred to as high melt point esters (HMPEs).
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==Process related waxing==
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An incomplete reaction, or a partial reverse reaction (such as by removing too much methanol while following the [[whole batch demeth]] method) can result in biodiesel that is rich in monoglycerides and diglycerides.  These often cause cloudyness in the methanol when performing a [[3/27 test]].
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Mono and diglycerides have an elevated melt point.  During the warm days of summer they remain liquid and their presence may go undetected.  In winter a layer of cream can form after a few days of settling.
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==Surviving winter waxing==
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Additives such as petrol typically do not prevent wax formation, though the level may be reduced.  Treatment is by water washing, separation, or a combination of the two.
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===Water washing===
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As mono and diglycerides are emulsifiers, they can be removed by [[water washing]]. 
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Cold water washing may also help remove waxes caused by HMPEs, as the cold will assist their solidification. However not all HMPEs may be washed out, as they are less dense than water.
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 +
===Separation by settling===
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Doing a [[water prewash]] may help with reducing the level of waxing on settling after demething.
 +
 
 +
After gravity settling for a week or so, any waxes should have settled to the bottom of the batch, and liquid biodiesel can be carefully drawn from the top.  Care must be taken not to stir or disturb the batch during this process, as the cream easily can flurry up into suspension.
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 +
===Separation by filtering===
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 +
Waxes may be separated by gravity filtering through sheets, or by centrifuging.
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 +
Pressure filtering, for example with a pump through 10" filter elements, may only remove a small amount of wax - the rest will be extruded through the filter element by the pump's pressure and still be present in the fuel.
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 +
==Reprocessing==
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If you believe the waxes are from monoglycerides rather than HMPEs, then the creamy liquid at the bottom can be put into the next batch for reprocessing.  Only a very small amount of methanol and catalyst will be required to complete their conversion to fatty acid methyl esters, so treat them as already converted biodiesel in the batch, or follow the [[two stage process]] without any changes.
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If the waxes are from HMPEs, then reprocessing will have no effect beyond melting them (they will reform on settling again).
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TODO: Possible to differentiate between HMPEs and monoglycerides by 50:50 shake test with water or cloudy 3/27?  Further testing required.
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<gallery caption="Waxing" widths="200px" heights="200px" perrow="3">
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File:Hmpe1.jpg|Wax at bottom of barrel
 
File:Hmpe2.jpg|A closer look at the ball formation
 
File:Hmpe2.jpg|A closer look at the ball formation
File:Hmpe_balls.jpg|HMPE balls on the side of a barrel
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File:Hmpe_balls.jpg|Wax balls on the side of a barrel
File:Hmpe_settled.jpg|HMPEs after bio is filtered off
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File:Hmpe_settled.jpg|Waxes after bio is filtered off
File:Hmpe_coil1.jpg|HMPEs forming around the coil of a beer chiller
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File:Hmpe_coil1.jpg|Wax forming around the coil of a beer chiller
 
File:Hmpe_coil2.jpg|A closer look
 
File:Hmpe_coil2.jpg|A closer look
File:HMPEs by Bionoob 1.jpg|Severe HMPEs. Source Bionoob
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File:HMPEs by Bionoob 1.jpg|Severe waxing. Source Bionoob
File:HMPEs by Bionoob 2.jpg|Severe HMPEs. Source Bionoob
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File:HMPEs by Bionoob 2.jpg|Severe waxing. Source Bionoob
File:HMPEs by Bionoob 3.jpg|Severe HMPEs. Source Bionoob
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File:HMPEs by Bionoob 3.jpg|Severe waxing. Source Bionoob
 
</gallery>
 
</gallery>
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==See also==
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* [[MSDS - Biodiesel ]]
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[[Category:Biodiesel]]
 
[[Category:Biodiesel]]
[[Category:Biodiesel general]]
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[[Category:Chemicals]]

Latest revision as of 11:50, 10 March 2013

In winter (or in a convenient freezer) some waxing in biodiesel may be observed as either suspended flakes or a white/yellow creamy layer at the bottom of containers.

Solids found at the bottom of a batch of biodiesel in the winter

Feedstock related waxing

Turning vegetable oils into biodiesel lowers the overall melt point of the liquid - the produced fuel will still be liquid at temperatures where the source oil will be solid. However, making biodiesel from oils containing high melt components such as palm oil will inevitably result in higher melt points in the final fuel. These components are commonly referred to as high melt point esters (HMPEs).

Process related waxing

An incomplete reaction, or a partial reverse reaction (such as by removing too much methanol while following the whole batch demeth method) can result in biodiesel that is rich in monoglycerides and diglycerides. These often cause cloudyness in the methanol when performing a 3/27 test.

Mono and diglycerides have an elevated melt point. During the warm days of summer they remain liquid and their presence may go undetected. In winter a layer of cream can form after a few days of settling.

Surviving winter waxing

Additives such as petrol typically do not prevent wax formation, though the level may be reduced. Treatment is by water washing, separation, or a combination of the two.

Water washing

As mono and diglycerides are emulsifiers, they can be removed by water washing.

Cold water washing may also help remove waxes caused by HMPEs, as the cold will assist their solidification. However not all HMPEs may be washed out, as they are less dense than water.

Separation by settling

Doing a water prewash may help with reducing the level of waxing on settling after demething.

After gravity settling for a week or so, any waxes should have settled to the bottom of the batch, and liquid biodiesel can be carefully drawn from the top. Care must be taken not to stir or disturb the batch during this process, as the cream easily can flurry up into suspension.

Separation by filtering

Waxes may be separated by gravity filtering through sheets, or by centrifuging.

Pressure filtering, for example with a pump through 10" filter elements, may only remove a small amount of wax - the rest will be extruded through the filter element by the pump's pressure and still be present in the fuel.

Reprocessing

If you believe the waxes are from monoglycerides rather than HMPEs, then the creamy liquid at the bottom can be put into the next batch for reprocessing. Only a very small amount of methanol and catalyst will be required to complete their conversion to fatty acid methyl esters, so treat them as already converted biodiesel in the batch, or follow the two stage process without any changes.

If the waxes are from HMPEs, then reprocessing will have no effect beyond melting them (they will reform on settling again).

TODO: Possible to differentiate between HMPEs and monoglycerides by 50:50 shake test with water or cloudy 3/27? Further testing required.

See also