I am in the process of completing my system and am adding a drying tank. I will be bubbling washed biodiesel with an aquarium air pump in order to dry the fuel, but need to know whether or not it is necessary to filter the dry biodiesel afterwards. Due to the way my system is currently set up, I am planning to filter the bio after washing yet BEFORE drying. Does anyone have advice on this? Would a filter also be necessary after drying and before storage?
When I used to water wash and air dry I had a pair of CAT 2 micron fuel filter cans as a final polishing filtration before use or storage.
You want to filter AFTER drying 'cause if you have residual soaps in the fuel the can(s) will get most of it. You'll run through filters in a hurry though, which is why I stopped water washing and went with a resin dry wash set up where I demeth the biodiesel first, let it settle out it's soaps and then run through a drum of wood chips followed by twin resin beds and a final CAT 2 micron can.
I personally do not think that only bubbling will get the fuel dry enough unless you have plenty of time to process it that way and the air isn't too humid.
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If you can be sure that no dust , dirt, insects etc can enter your drying system then you might get away with filtering before drying but it is always good practice to filter at the very end of the process, just before you fill your vehicles fuel tank.
I filter with a 5 micron filter and the element lasts 3,500 litres or one year. It still looks perfectly clean at that stage but I change it anyway.