Crude Furnace Burner Tip Coking issue

Is it coke or other impurities (metals, salts)?
If it is coke then you may not have enough excess air, or you are outside the flow range for the burner.

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P.E. Metallurgy, Plymouth Tube

Another cause of coking I've seen has been fuel risers projecting through the windbox of a balanced draft furnace with an air preheater. Olefins in the fuel gas can polymerize when they heat up and deposit gunk which can coke up.

White deposits sounds more like metals in the fuel gas though. Got a good coalescer/knockout on your fuel gas? Would behoove you to test the deposits before making any changes based on assumptions...

Nathan Brink

Agreed, there may be one or more of these:
a) poor vapor liquid separation upstream
b) poor hydrocarbon dewpointing of the fuel gas

High backpressure in the firebox could be due to degradation of the fins in the convective section of the furnace ( from corrosion which may be due to fuel gas with H2S , NH3 etc; and/or poor materials selection for the fins)

AMONIUM OR SODIUM CHLORIDE SALTS COULD BE CAUSE FOR YOU BURNER TIPS PLUGGING. DO YOUR FUEL GAS BURNERS PIPING HAVE FILTERS?