Heating fuel oil

[op9]

I am involved with converting an industrial burner from light oil to heavy oil firing. Thats not a problem.

However the fuel storage tank needs heating to about 60-70degC. Normally that would be accompished with steam (if available) or electric heating. They want to use an old bitumen tank which is fitted with a submerged U tube (immersion tube) to which is fitted a small burner firing through the tube. This type of heating is quite common for bitumen but I have never seen it done with fuel oils. The fuel concerned is a recycled oil having a flash point >60degC (typically 90degC), Boiling point >250degC, Visc 40cSt @ 40degC, SG @15degC of 0.9

One of my concerns are, is there any possibilty that the fuel around the tube where the burner flame is,(where there is the high radiant heat), will "coke" onto the steel eventually causing local high temps of the steel? This sometimes happens on bitumen tanks and we usually fire the burner through another inner concentric SS tube (in the flame area)allowing an air gap between it and the main carbon steel tube.

Would appreciate any comments.
Thanks in advance,
Rod

Rod Nissen.
Combustion & Engineering Diagnostics

 

[PetroSynergy]

Do you know how hot the surface of the U-tube can get? If it stays <250degC(max, to be safe I would hope it was 230degC or <) then you should not have to worry too much about coking.

 

[op9]

Hi Petro,
On another installation for heating bitumen we fired the burner through a SS tube, and so allowed an air gap between it and the outer carbon steel immersion tube. A thermocouple installed on the outer metal surface of the immersion tube reads 300degC. The trip is set at 320degC.

So are you saying that >250degC the fuel will oxidise and form carbon?
Thanks,
Rod

Rod Nissen.
Combustion & Engineering Diagnostics