Filtering WVO

WVO needs to be filtered before making biodiesel. There are many different types of filters for filtering WVO , and a few different methods of filtering as well, these are discussed below.


Heating the oil:

Heat the oil up to 160°F before you filter; this speeds up the process of filtering WVO, and will not clog the filter with thickened oil.


Pre-filtering/ Straining:

You can pre-filter using something along the lines of an old t-shirt. Get a 5 gallon bucket, put a few 2 inch holes in the bottom, drape the t-shirt in it, attaching it to the top of the bucket with the lid (hole cut out on top). Pour the oil through the hole on top and have something to catch the oil beneath.

When buying a filter, get a 200 or 400-micron filter to get the crispies and other large food chunks out. The higher the micron number, the larger the filter holes.


Gravity Fed Filtering:

WVO is generally gravity fed through filters with the higher micron ratings since the oil will flow pretty quickly through these. This is either accomplished by hand pouring the WVO through the filter, or setting a tank of WVO above a catching tank, allowing the oil to flow down through a filter.


De-watering:

Before you filter out the really small stuff, it is a good idea to de-water it. De-watering before fine filtering will help get out stuff that may clog your filters prematurely. Often, de-watering is done by heating and mixing simontaineously. Over time the water will evaporate out.


Pumped Filtering:

Filters with a lower micron rating are often pumped. The finer filters take longer for the oil to pass through. Some filters, such as cartridge filters, actually require a pump.

Oil can be pumped through bag filters as long as they are encolosed in housing.

The WVO should be filtered down to 5 microns, so the finished biodiesel will not damage the engine.


Settling WVO:

If patience and space allows, I would highly recommend a mix of settling and filtering WVO. I would store enough WVO so that it can settle for 2 weeks. Pump off the top 90%. On the bottom will be the vast majority of the crud and water. I would still put it through a very fine filter as a precautionary measure and do a water test. Doing this, you would save time and money by not having to build an elaborate filtering system and change large amounts of filters.


Examples:

Some people choose to heat their WVO in a 55-gallon drum using a pipe heater cable wrapped around the drum. The drum is also wrapped in insulation to help keep the heat in. They build a homemade rig for their sock filters to hang from on the top, down into the drum. Here is a great example of this kind of set-up.

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