Biodiesel Test-Batch Mini-Processor For One or Two Liters

Introduction This mini-processor is easy to make from not very much, mostly kitchen stuff and a couple of tools. It's effective and safe, closed and virtually air- tight, with no splashing or leaking of hot fumes. It will make one- or two-liter batches for test-batch or demonstration purposes, suitable for single-stage or two-stage processes, with full agitation and temperature control. And you can take it anywhere. There's no need to follow this prescription exactly -- use what's to hand, improvise. For instance, if you don't have a plastic drill-grip that will fit a plug spanner to use for the drill-stand as described below, we made a second stand using a piece of angle iron and a strip of 3/32" steel half an inch wide bent to fit round the drill and clamped in place with bolts.

Materials Three-liter HDPE container with two lids; Spaghetti-cooker -- the bottom and sides of the inner pot are full of holes like a colander; Electric drill; Plastic grip for drill; Stand for the drill; Sparkplug spanner; Stirrer; Portable gas cooker (canned gas) or electric hot-plate; Two half-liter PET bottles. Cost -- in our case, zero: this was all discarded junk, including the drill, and all in perfect working order.

Materials The drill stand is rigged from scrap angle iron and welded together, but it could just as easily be bolted. The bit that holds the drill consists of the tough plastic grip that came with the drill, a plug spanner, which conveniently fits inside the grip, held in place by two bolts (extra holes mean you can move the drill in and out from the stand), and the plug spanner is welded to an extra bit of angle iron bolted inside the vertical section, again with extra holes above and below for adjustment. The stirrer is a length of 6mm steel rod with a slot cut in the end and a piece of flat steel brazed into the slot, cut to size so it fits through the larger of the two HDPE container lids.

Materials The lid is fitted with a wooden bush cut from hardwood with a 6mm hole drilled through it to take the stirrer shaft. Make it a tight-fitting hole, then heat a piece of the same steel rod as the stirrer and push it carefully through the hole -- not too hot, just enough to scorch the surface of the wood inside the hole, not char it. Add a few drops of biodiesel for lubrication. of the two HDPE container lids. Cut a square hole in the lid the exact size and shape of the bush; cut another hole in the lid insert. Saw two shallow grooves on all four side of the bush, immediately above and below where it will fit the lid. Push the bush into the hole in the lid; push the insert into the lid around the bush. Secure with epoxy resin -- push the resin firmly into the grooves to hold the bush in position. Some silicon round the seams helps.

Processes Heat up the oil in a saucepan on the gas cooker and pour it into the mini-processor. Slide the business end of the stirrer inside the processor and slide the bush in the lid over the other end; screw the lid on firmly. Fill the two half-liter PET bottles with water at or above the processing temperature. Put the processor into the spaghetti cooker; wedge in position with a PET bottle on either side. Add hot water to the cooker to just below the height of the oil -- as much water as it will take before the processor begins to float. Use the gas flame to adjust the water temperature to the processing temperature, then turn off the gas. Attach the drill to the stand, tighten the stirrer in the chuck, switch on and start stirring.

Processes We mix methoxide for test batches in HDPE chemical bottles, which have a strong lid and a bung. Drill two holes in a lid and fit two short sections of plastic or 1/8" (4mm) copper piping, fix on both sides with strong epoxy resin. To one, on the inside, fix a length of rigid 1/4 (6mm) plastic tubing that will reach almost to the bottom of the bottle. To the other, on the outside, fit a length of flexible 1/4 plastic tubing. Fit a third section of copper piping to the small lid of the processor. To add the methoxide, remove the lid and bung from the bottle of pre-mixed (cool) methoxide and screw on the transfer lid tightly.

Processes Fit the other end of the length of flexible 1/4 plastic tubing to the inlet pipe in the small lid of the processor. Now, carefully, lift the methoxide bottle above the processor and turn it upside down. Air goes into the open pipe to the bottom (now the top) of the bottle, methoxide drains out of the second pipe through the processor lid into the oil to be mixed. When all the methoxide has drained, turn the bottle right way up and put it down on the table beside the processor. Any stray methanol fumes that don't condense inside the processor will vent into the methoxide bottle and condense there.

Processes Monitor the temperature with a thermometer, turning on the heat when necessary -- this is quite safe, even with gas, as is running the drill motor, as no methanol fumes escape during processing. The temperature only needs adjustment twice in an hour at normal room temperature. The HDPE container is translucent rather than fully transparent but it's clear enough to see the reaction going on inside, and the changing color and viscosity of the oil.

Processes When the process is finished, disconnect the drill, remove the container and stand it on its side to settle, small lid down; later, to drain off the by-product, simply tip it up, hold it over a container and loosen the small lid, tightening again when you hit the yellow biodiesel.