I was thinking about converting a Riello Gulliver RG0.R to burn rapeseed oil. The oil is readily available here and sells for about half the price of HHO and parts for the Riello are easily accessible. The Riello is a “normal” residential burner with a pump operating at 12 bar. I was thinking about removing the pump and the complete nozzle holder assy and manufacture and install a new assy with a Delavan SNA nozzle including air supply. I would have to modify some of the electrics and add a compressor, heated tank and feed pump. But the general idea was to keep most of the burner parts, eg. Diffuser disc/flame retentioner, ignitor assy, control box, light cell etc.

But I have some questions – any suggestions would be very appreciated:
– The furnace is rated at 20kW, and it seems that the furnaces being discussed in this forum are larger. Is it impossible to burn rapeseed oil in this way at such a firing rate?
– The furnace is only a few years old and features a circular firebox. The diameter is 12” and the depth is 12”. I’ve seen several discussions on the topic of flame length. It seems that the flame is longer with SVO than with HHO. Would my firebox simply be too small to be used with rapeseed oil? It is feasible to retract the complete burner assy to give way for a longer flame?
– The current nozzle is a Danfoss 0.5 GPH 60 degrees. This will be exchanged to a Delavan of a suitable size. But the Delavan spec sheet doesn’t mention which viscosity the oil should have and hence I can’t tell if I can pick the same nozzle size (ie. A SNA .50). Can someone give me a hint?
– Have I completely overlooked something of paramount importance? I know this is lengthy and I apologize for that, but any help would be very welcome.

You will wind up keeping most all your original parts, but my suggestion would be to get a turbine-style diffuser. I would recommend a Kagi but they’re not selling them anymore to us, as they need them for their on production, so I’m looking for a replacement head at the moment. If anyone has leads, let me know. I’m not sure how 20kw converts over to btu’s, so we’ll need a translator for this. I believe 12 inches on the combustion chamber is close to the norm here. The flame length and size can be controlled by the use of that turbine bladed retention head and correctly sizing the nozzle to your chamber, while adjusting the air vanes on the burner and the air pressure on the siphon nozzle. I call it “dialing it in,” but whatever vernacular you use, these are some of the variables that help get the flame cone where you want it. I haven’t seen any viscosity information out at Hago for a siphon nozzle either. Probably because all of the original uses for siphon nozzles were based on heater and filtered waste motor oil. Obviously, pre-heated waste veg oil is slightly more viscous than waste motor oil but it doesn’t have to be an issue as the oil burner just gets set up a little differently. As far as overlooking anything, I think you’ve pretty much nailed it down.

My Buderus was originally fired at about 20kw .6gpm (74000btu output). I have had good luck running a Hago .2gph nozzle with the oil supplied at a few psi. That has worked better than when I was originally using a .5gph siphon nozzle with 2” lift. Since the siphon nozzle has a narrower spray angle than a typical pressure nozzle, the riello flame retention head might give you too long of a flame. Your .5gph nozzle at 12 bar (~200psi) will give you about.7gph. Down firing to between .3 and .5 gph may give you a short enough flame but you will have to try it. 12” is not overly short for a combustion chamber but you still might need a retention head with more swirl. The nozzles are rated with an oil with similar viscosity as HHO at the specified lifts and air pressures but most people have had better luck using a smaller nozzle with a higher air pressure. I usually run between 10 and 13psi.

My gut feeling is that the larger nozzles, if they are firing into a long enough combustion chamber, are less effected by heavy viscosity than the smaller ones. The only reason that I think this is because very large commercial boilers can burn #6 oil with very little heating of the oil. The Kroll burner might also have a very well matched turbulent air flow that enhances the nozzle pattern. Something that they say about good combustion is the “Three T’s”, Time Temperature and Turbulence. The Kroll burner may have it just right for it’s particular firing rate. I know that I spent more time on retention head design than anything else on my burners.