Q & A > Question Details
One of our fired heater gas burner's riser pipes is frequently plugged with coke-like formations on the internal periphery. Since it was identified that our fuel gas sulphur content was pretty high, my best guess for the cause of black material deposits was iron sulphide. But I read somewhere that fuel gas with high olefins can also coke up inside the riser pipes. Anyone else faced similar problems in their fired heater? If so, what was the mitigative measure taken to overcome this?
09/05/2021 A: Roger Haglund, Eprom, r_haglund44@hotmail.com
It can be coked/carbonised material. If the surface temperature inside the burner tip exceeds 600-700C some of the fuel gas components will form coke/carbon. Seen that in a steam reformer where the tips were exposed to too high temperature causing plugging and the burner tip and the tip was severely damaged by overheating.
It is not directly related to olefins but rather to the carbonisation temperature of the individual components.
To counteract this effect is to increase the flow inside the burner tip and/or to shield the tip from being exposed to high temperature from back radiation from within the heater.
18/04/2021 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Yes. I have come across such a phenomenon. We had 132 large burners spread across 10 heater cells of a crude complex alone. While reduction of olefin content in fuel gas could be the best option, it may not be practical when coker fuel gas is involved. I guess it’s a hazard associated with low NOx processes in which flue gas is recirculated towards achieving NOx reduction to desired levels. The burner tile joints will allow the hot recirculated flue gas in contact with the gas riser tubes which are otherwise cooled by not so hot combustion air. Sealing the tile joints is not advisable. So keeping the large coker gas component, large gas riser (each burner has 6 risers) requirement and the frequency of gas riser failures due to coking, in house riser tube manufacturing was successfully tried in our site. Else one can try insulation of gas riser tubes.
15/04/2021 A: Sarin Reghunath, BPCL - Kochi Refinery, sarinreghunath@gmail.com
Please ensure that your FG supply header tracing / insulation is proper and drain FG KOD / coalescer periodically.
14/04/2021 A: Sudhakara Babu Marpudi, Dangote Oil Refinery Company, m_sudhakarababu@yahoo.com
Yes. I had a similar experience. The primary reason appeared to Olefins in Fuel Gas. But the cooking starts off in Low NOx burners where Flue Gas is recirculated for NOx reduction. The burner tile joints bring the hot flue gas in contact with the gas risers which are otherwise cold in non-low NOx (normal) burners. Reduction of Olefins content in Fuel Gas is the best mitigation but when Coker Gases are involved, this will become an expensive option. We were left with replacing the Fuel Gas risers as soon as we observed the tips of the risers were blown off. Riser tips gets blown off as the velocity of the Gas increases when the Gas path is restricted beyond a limit due to Coking.
14/04/2021 A: RUPAM MUKHERJEE, ENGINEERS INDIA LIMITED, rupammukherjee86@gmail.com
It may be due to condensation of heavy saturates. Try preheating the fuel gas.