Difference between revisions of "Winter waxing"

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(Separation by settling)
 
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==Feedstock related waxing==
 
==Feedstock related waxing==
  
Turning vegetable oils into biodiesel lowers the overall melt point of the liquid, that is to say that the resultant fuel will still be liquid at temperatures where the source oil would have become solid.  However, making biodiesel from feedstocks 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).
+
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==
 
==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]].
+
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 their presence may go undetected, as they remain liquid.  In winter a layer of cream may form after a few days of settling.
+
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 waxing winter==
+
==Surviving winter waxing==
  
Additives such as petrol typically do not prevent wax formation, though the level may be reduced.  Treatment is by water washing or separation.
+
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===
 
===Water washing===
  
As mono and diglycerides are emulsifiers, they can be removed by [[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.
 
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===
 
===Separation by settling===
  
The initial level of waxes in the produced fuel may also be reduced by doing a [[Water Prewash]] before settling soaps.
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Doing a [[water prewash]] may help with reducing the level of waxing on settling after demething.
  
If water it not used in your process at all, and the fuel is only gravity settled after demething, liquid biodiesel can be drawn from the top of a settled batch, and the creamy liquid at the bottom put into the next batch for reprocessing.
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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.
 
 
Only a very small amount of methanol and catalyst will be required for reprocessing the cream (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.
 
  
 
===Separation by filtering===
 
===Separation by filtering===
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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.
 
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.
  
 
<gallery caption="Waxing" widths="200px" heights="200px" perrow="3">
 
<gallery caption="Waxing" widths="200px" heights="200px" perrow="3">

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