Q & A > Question Details
We have different fired heaters with fuel oil and gas burners in our refinery. It is seen that the metal tube surface is coated with fine layer of powder (slight yellow colour) externally. This is loosely held to its surface (as seen through inspection door) and reduces the heat transfer leading to high skin, arch and stack temperature. My suspicion on the Fuel oil quality became stronger. So I found that Clarified oil from FCC is not going to the Fuel oil tank. Upon testing the IFO for ash content, it came out to be 0.075%. Is this okay? Any other testing is required?
What probably might be the reason for this powder coating and measures to solve the problem?
25/11/2014 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
The yellow deposit may be as a result of high sulphur content during combustion or moisture may have got in if the unit was stood still.
It is important to recognise that the convection bank fins need to be cleaned as approximately 1 mm of deposits insulate such that it reduces performance by up to 20%
The latest way of cleaning instead of using dry ice, chemicals, water etc is with the new robotic convection bank cleaning technique which is the only system to mechanically enter between every row of finned tubes to completely remove the fouling, without refractory damage, thereby reducing stack temperature and improving overall efficiency and energy consumption
24/11/2014 A: Marcello Ferrara, ITW SrL, mferrara@itw.it
Needless to say, you need to analyze the yellow powder, which might come from different sources.
Ash content seems to be okay and low enough to create, as standalone item, the problem.
What is the sulphur content of the fuel oil ?
I'd rather investigate the fuel oil pool and check the single components.
For example, if you blend pyrolysis oil into the fuel oil the yellow material looks more familiar to me.