Dear Crispin,
As far as I know the difference between kerosene (paraffin) and higher hydrocarbon fractions, including vegetable oils is the fact that they are not distillable under atmospheric pressure. Undistillable hydrocarbons are fed into the fire as a spray of very fine droplets that burn completely. The same could be done with vegetable oils at the combustor end. However, most vegetable oils tend to react slowly with oxygen to form gunk which eventually blocks the passages it has to flow through. So for a stove that burns vegetable oil, the piping from the storage to the burner should be of very simple shape and easy to clean. Realising that producing a spray of fine droplets is out of the question for domestic stoves, we have to find something that feeds the oil to the combustion zone where the carbon, resulting from the decomposition of the oil is burnt as well. Possibly something like a perforated disk where the oil burns in updraft mode and where the holes occupy a sufficient part of the disk area that all the char comes in contact with air. Does the Protos stove have any relation to Siemens. If so they should hang their head in shame, not having read up on the properties of vegerable oil. All the best, Piet
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