[?] Subscribe To
In small plant designs the biodiesel infeed tank filters the waste vegetable oil (WVO) and holds it in storage before it is pumped into the processor. If solid oils or fats are used as the biodiesel raw material then the tank may need to be heated.
The filter on top of the tank can be a 1mm mesh, large enough to remove the larger bits of food from the oil. Mosquito or flyscreen makes a fine filter. Some biodiesel makers then pump the oil through a finer 10 micron filter (I even know one person who filters it down less that that). The reason that the oil is filtered it is that food particles hold moisture and this effects the biodiesel reaction. A lot of people do not bother with removing such small particles. They think that they are too fine to make a difference.
In countries where restaurants store their oil outside there may be water present in the oil. This needs to be removed. There are a couple of ways to do this. The first is to heat the oil up above 100 deg C until the water in the oil has boiled off. It is easy to see when this has happened as the oil will stop boiling and the temperature will start climbing quickly.
The other way to dewater the oil is to heat it to 60 deg C and then to let the oil stand. Any water will drop to the bottom of the tank and can be removed. If the biodiesel infeed tank is going to be used for de-watering then it must be made from steel as plastics will not take the temperatures. It is preferable if the tank has a conical bottom which allows for better separation between the oil and the water. Conical tanks are available from Duda Biodiesel. When dewatering use a valve arrangement with a tee.
A good quick test for water in your oil is to heat a frying pan on the stove. When it is nice and hot pour a little oil into the pan. If you see bubbles and steam coming off the oil then the oil needs to be dewatered.