Continuous biodiesel processor

The processor consists of 12 main parts

The processor is intented to produce 200 litre/day. This requires a main mixer with a capacity of 8 litre to allow a 1 hour residence time. Approx. flow is 140ml/min. By keeping the volume as small as practical the heat input is reduced compared to a batch system as it is more suitable for heat recovery and will be easier to insulate. The system should require no more than a 15A 240V supply. Where ever possible the system will use standard production parts or easily fabricated parts.

The oil is first heated to 150 deg C to boil off any water. This is done by passing it over a hot plate controlled at 150-160 deg C. When heated the water sinks to the bottom of the oil. By spreading it over a large surface area (minimum depth) the water will flash off easily.

The oil then moves into the hot oil store. It's temperature is too high to go straight into the main processor. It will be cooled by a) a heat exchanger heating water to maintain temperatures throughout the rest of the system and b) by heating a still to reclaim methanol from the biodiesel.

The oil then enters the metering pump which runs in parallel with the methoxide metering pump. These will be pneumatic pumps. The air supply will be controlled by air solenoids which in turn are controlled by automotive indicator relays to provide the pulses. The timing can be controlled by external variable resistors. The main mixer will be an oscillatory flow mixer which can be view at http://www.cheng.cam.ac.uk/groups/polymer/OFM_page.html

The mixing action will again use a pneumatic pump, this time double ended connected to either end of the processor. The mixer will be constructed of 50mm bore ERW steel tube. The baffles will be automotive core plugs drilled with a 25mm hole in the centre. These will be spaced at 75mm throughout the 4m overall length. To make the mixer more compact it will consist of 4x1m tubes. These will be housed in a 75mm dia. water jacket.

The outlet will be feed back to the still contained within the hot oil store. The recovered methanol will be cooled by the exhaust air from the pneumatic valves. Any spare heat will be recovered by passing it through the main oil store before it goes to the settling and washing tanks.

To increase the capacity the mixing tube would need to be proportionally longer the metering pumps re-calibrated/enlarged and the drying heater enlarged.