Waste Vegetable Oil As A Diesel Replacement Fuel

Index of Waste Vegetable Oil As A Diesel Replacement Fuel
Introduction
Properties of Triglycerides as Fuels
Oils and their melting point and Iodine Values
In Car installation
Problems Costs Exhaust emissions and Cost efficiency
Saturated oils and possible improvements

In Car installation

The oil tank was fitted with a heat exchanger comprising one metre of 12 mm copper tube. This was connected to the engine coolant system and pre-heats the oil in the tank. The tank was located in the engine bay to maximise heat transfer to the tank and to keep the coolant lines short. The finished tank had a useable capacity of seventeen litres. This gave a range of up to 240 km between refuelling.
Additional filtering was installed with an internal preheater. The pre-heater, a 24 V diesel glow plug, together with a relay and thermostat was installed so that if a solid fat was used for fuel, any solidified fat in the filter chamber could be quickly melted. The filter used (Ryco Z30) provides filtration to 30 micron.
A vacuum gauge was fitted after the fuel filter and it was found that at start-up with cold canola oil, fuel flow was insufficient causing a vacuum in the fuel line and filter. An extra in-line fuel pump was added before the filter and this alleviated this problem and has increased fuel filter life.
The heated oil fuel line was one metre of 5/16" semi rigid nylon tube encased in a 5/8" rubber coolant pipe. Brass fittings were used to ensure minimal corrosion and leakages of coolant.
The three port, 12 Vdc solenoid valve was mounted in close proximity to the fuel pump to minimise changeover lag. The fuel return line to the diesel tank was redirected to the fuel pump suction side between the solenoid valve and fuel pump. This was done to prevent the oil in the return line going to the diesel tank. A disadvantage of this is that the fuel system became rather intolerant of air in the system.
A run-on timer was installed using a modified ‘ turbo timer’ . After the solenoid valve is switched back to diesel, the timer keeps the engine running for a period of time, even if the vehicle is parked and the key removed from the ignition.
During this period, the oil in the injector pump is gradually replaced by diesel and after several minutes, only diesel remains in the fuel pump, filter, fuel lines and injectors. The correct time was found by a trial and error. A manual override switch was also installed to allow emergency, or short duration stopping of the engine.

The supplier of the used oil (a fast food outlet) filters the oil and puts it into containers for collection. To ensure that the oil is clean, the oil is heated and additionally filtered through a 5 micron bag filter. It was found that the used oil usually becomes cloudy and this was found to be a combination of the oil starting to solidify due to partial de-unsaturation of the oil from use and minor water content. If water content is suspected of being excessive, the oil is heated above 100’ C to evaporate the moisture.

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