The process of collecting and filtering the oil can best be described as a an industrial art. Handling this non-polar substance requires a fair bit of patients and a mountain of paper towels. The goal of any waste veggie oil (WVO) processing system is to make it as closed as possible. The more containers and transfers one must undertake, the more spills and splatters one must contend with. Cardboard has become my best friend, creating an absorbent foundation for the oil that seeks freedom from the fuel tank.
The design of the system allows for me to insert oil in the start (heated settling tank) and run it through from there to the storage through a closed pipe system. Linking the components reduces the chances of spilling oil. Leaks exist, but losses are negligible and are caught up by containers and cardboard.
My filtering setup was inspired by many other systems used by many other home wvo processors. The idea is simple, start with used fryer oil and end with fuel oil. Generically speaking, the processing sequence is as follows:
- Settling
- Progressive filtering
- Final filtering/water removal
The design of the system allows for me to insert oil in the start (heated settling tank) and run it through from there to the storage through a closed pipe system. Linking the components reduces the chances of spilling oil. Leaks exist, but losses are negligible and are caught up by containers and cardboard.
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| System Diagram |
The collection stage, not pictured here, helps to settle the oil. I collect and hold it in 5 gal buckets for at least a week if not longer. I then pour it into a cubie (fryer oil is sold in these 5 gal plastic containers), letting it settle again for at least a week.
Settling the oil reduces the filtering overhead and helps to remove some of the entrained water. Despite the generalization that water and oil don't mix, fryer oil has varying degrees of water both trapped in both the food particles and suspended/emulsified in varying quantities. From a thick substance unaffectionately referred to as "mayonnaise" (the culinary version being a water/oil emulsion) to molecules dissolved throughout the oil, water is one of the more difficult substances to remove. Extended settling and decanting goes a long way to eliminating the bulk of the water.
From settling, I transfer the oil into the first stage of my system. The previous post How reused fryer oil builds a house, shows this stage. The key here is that the heated oil in the top tank flows out through a raised drain pipe, leaving behind the bottom 3 inches of oil which contains the heaver, water laden sediment. That layer is drained off from time to time and sent to the oil recycler. The oil passes through a 200micron mesh sock filter. For comparison, a human hair is roughly 90 microns (fun fact: merino wool is down around 25 microns).
The oil is then pumped up into the CF (centrifuge) feed tank. Gravity fed through an inline heater The oil feeds into the centrifuge and then out to the storage tanks. I purchased a bowl centrifuge from WVO Designs. The inline heater was built from scratch using a 1100watt hot water heater element. It heats the oil between 140 and 170 deg F.
The tank in the background is the CF Feed Tank. It's filled through the exposed barb on the left. The inline heater element is protected by the purple cup (exposed terminals) and you can see the path thie oil takes as it flows from the CF tank through the black hose, up through the inline heater and then over to the top of the centrifuge. Spinning at 3000 rpm, the centrifuge forces the heaver particles to the bowl sides while the clean oil flows up and over, draining into the storage tank (left foreground). I'm working on dialing in the flow rate. Notice the three feed holes on top of the centrifuge. From the open holes vapor vapor wafts out as the hot oil spatters into the spinning bowl allowing the hot dissolved water to break free.
From left to right, the Raw oil collected from the fryer, the oil after settling/200 micron filtering, and finally, the fuel! At 14 mpg, this half pint on the right represents just under one mile of fuel.
Left behind in the bowl is the darker, heaver oil and free water. Plastered against the bowl sides is a think, black sludge of the larger, solid particles removed from the oil.
The oil is then pumped up into the CF (centrifuge) feed tank. Gravity fed through an inline heater The oil feeds into the centrifuge and then out to the storage tanks. I purchased a bowl centrifuge from WVO Designs. The inline heater was built from scratch using a 1100watt hot water heater element. It heats the oil between 140 and 170 deg F.
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| Running through the centrifuge |
The tank in the background is the CF Feed Tank. It's filled through the exposed barb on the left. The inline heater element is protected by the purple cup (exposed terminals) and you can see the path thie oil takes as it flows from the CF tank through the black hose, up through the inline heater and then over to the top of the centrifuge. Spinning at 3000 rpm, the centrifuge forces the heaver particles to the bowl sides while the clean oil flows up and over, draining into the storage tank (left foreground). I'm working on dialing in the flow rate. Notice the three feed holes on top of the centrifuge. From the open holes vapor vapor wafts out as the hot oil spatters into the spinning bowl allowing the hot dissolved water to break free.
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| Stages of oil |
From left to right, the Raw oil collected from the fryer, the oil after settling/200 micron filtering, and finally, the fuel! At 14 mpg, this half pint on the right represents just under one mile of fuel.
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| Sludge |
Left behind in the bowl is the darker, heaver oil and free water. Plastered against the bowl sides is a think, black sludge of the larger, solid particles removed from the oil.
