Fuel oil heating

[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

 

[rmw]

I think you have a valid concern if the flame temperatures are high enough.

I have another concern. Is your fuel homogeneous? Most heavy oils today are mixtures of lots of "junk" some of which might have light fractions that cause me concern in the vicinity of the high radiant zone you mention.

rmw

 

[ione]

I concur your concern is plausible. The coil wall temperature will probably be close to that of the hot gases fired inside it and fuel coming into contact with hot spots could lead to a flammable atmosphere.

 

[FMJalink]

Rod,

I do not know whether a HAZOP review was already held, but one of the mayor points that should be on the list of the review is tube rupture. Just imagine the fuel oil running into the small burner from the wrong side.

Kind regards,
Frank Jalink