Ian's vacuum biodiesel processor
Brief description of layout
If you look at the unit photo above, starting from left to right :-
Oil drum = Feedstock holding tank. (FHT)
20 L drum = Filter unit with vacuum pump below.
Mixing pumps, condenser behind, liquid trap below
45 kilo propane bottle = Reactor
Oil drum = biod bubble wash and dry holding tank, switch gear above.
20 L drum = Methoxide Mixer
How it works
Process based on Aleks Kacs' 2 stage process
The waste oil is poured into the FHT and is heated to 100oC -120oC to seperate water. The vaccum unit is then switched on and the Waste Oil is sucked up and into the Filter Unit. The Oil slowly passes through the filter medium and is drawn into the Reactor.
Once full, and the oil at roughly 80 - 90oC the vacuum unit reduces the internal pressure to about 25 hg. This vac pressure is held until no more water collects in the liquid trap. Time dependant on how wet the oil is.
Methoxide is mixed whilst waiting for water to boil out.
Oil is left to cool to around 50oC then with the mixing pumps switched on, a small ammount of vacuum is used to draw 3/4 of Methoxide into the Reactor. It is heated and circulated for an hour.
After 12 hours, the glycerine is drained from the bottom of the Reactor.
The oil is reheated to 50oC and the final 1/4 of methoxide is added and mixed and heated for an hour.
After 12 hours the glycerine is drained from the bottom of the reactor.
Using the mixing pumps, the Biod is then transferred to the bubble wash tank, bubbled for at least 12 hours, then left to settle out.
Drain water from tank, heat and boil off any remaining water.
A few problems do exist, namely the heating in the first and last tanks. The immersion heater elements have a distance of about 2" between elements and the bottom of tanks. Because the heat is not being directly applied to the base of the drums, the water tends to stay in the oil with not much steaming or dropping out. You will be hard pushed to get the temp above 120oC, sometimes its best to get the oil to 130 for a bit. So, resorting to direct under heat has been neccesary, especialy after bubble washing.
The central heating pumps worry me, I'm not too sure on how long the seals will last on the impeller shafts. If this fails, oil could get in to the electrical windings of the pump and create a fire hazard. Keep an eye on the unit whilst mixing.