water & salt removal from biodiesel

[someguy79]

1. Will water emulsify in biodiesel or biodiesel / petro-diesel blends?

2. What methods are avaialable for removing water and water soluble minerals (i.e. sodium and potassium) from biodiesel or biodiesel / petro-diesel blends?

BACKGROUND INFORMATION

I am trying to determine what method of purification I should be using for a biodiesel blend. It leaves the refinery in good shape, but there is a concern that in transit or in storage, some contaminants may sneak in.

The major concerns are leftover materials in delivery tankers, and water accumulation in storage. Biological contamination is a concern, but will be mitigated if water content is controlled, and biocide dosing and mixing is done appropriately.

Centrifuge separators are a common method to remove heavier than fuel components from petro-diesel. I've run into concerns that water can emulsify in biodiesel and then will not mechanically separate.

With mechanical removal, salts stay bound to the water and are thus removed.

The maximum values per the fuel spec are 0.1% water by volume and 1ppmw soduim + potassium.

So far I've found one related thread.

Biodiesel Separation (Oil Water Separator)

http://www.eng-tips.com/viewthread.cfm?qid=242236

 

[bimr]

You can allow the water to settle out. Water can exist in oil as free water (which, if left to sit will settle to the bottom), or as suspended droplets (which may settle to the bottom if the oil is heated and then allowed to sit).

You can boil the water out. Heat the oil to 60°C (140°F) for 15 minutes, and then let it settle from 24 hours to 2 weeks. Pump the top 90% of the oil off the top to use. The bottom 10% can be recycled for additional water removal.

Probably the most widely used method is to boil the water out by heating the oil above 212°F. Mix the biodiesel to prevent dangerous steam pockets from forming. When the boiling has slowed, increase the heat to 265°F for 10 minutes or so. Allow the oil to cool.

You can extract the water with a hydrophilic chemical. Hydrophilic polymer granules are put in a tower. The oil is run through it and it absorbs the water out in minutes. It can be regenerated and reused.

http://en.wikipedia.org/wiki/Biodiesel

http://www.steeltank.com/LinkClick.aspx?fileticket=SmQZA0POL4E=&tabid=36&mid=535