to overcome the resulting increase in flame speed, especially given the common requirement for the burner to operate on both natural gas and high H2 blended fuel. If the designer gets this balance wrong, the flame will propagate back inside the burner. Known as flashback, this can be detrimental to the mechanical integrity of the burner components and thermal NOx emissions levels.
that rely on UV and IR spectral ranges experience weakened peak flame signals, leading to nuisance trips. For scanners utilising the UV spectral range only for flame detection (no IR component), peak response occurs at the OH-radical emission wavelength. Therefore, the absence of carbon in the flame does not impede the scanner’s ability to detect radiation from the target burner.
Figure 2 Zeeco ProFlame Scanner
To overcome this technical challenge, Zeeco has developed a radiant wall burner design capable of firing fuel gas combinations of more than 90% H2 while producing less than 100 mg/Nm3 NOx emissions levels. This burner design utilises a proprietary fuel staging design that produces two separate mixture zones exiting the tip. This combination allows the burner to generate the exit velocity needed in the lean zone to prevent flashback while delaying combustion in the rich zone long enough to mix fuel with inert flue gas products. This burner can be retrofitted in existing ethylene furnaces for firing high H₂ fuels even in challenging furnace applications with extremely tight burner-to-burner and burner- to-tube spacing, still meeting the <100mg/ Nm3 emissions requirement. Flame scanners Conventional flame scanners are configured to detect combustion radiation in the UV, visible, and IR spectra. The exact spectral ranges are based on wavelengths characteristic of the combustion of hydrocarbon fuels. The UV and IR components vary depending on the specific type of fuel used; therefore, conventional scanners have wide spectral ranges, allowing operation on various gaseous and liquid fuels. When firing high H2 fuels, the absence of carbon means the spectral range of radiation produced by the combustion process is significantly narrowed and shifted more towards the UV spectrum. Therefore, scanners
One example is Zeeco’s ProFlame scanner (see Figure 2 ), which can reliably detect 100% H2 flames, a critical furnace safety interlock when firing high H2 fuel. The burner flame may become much shorter “ It is crucial to employ pilot designs capable of firing on pilot gas compositions of up to 90% H 2 without flashback to avoid damage to the pilot itself and any internal components ” when firing high H2 fuels due to increased flame speed. Therefore, it is essential to sight the flame scanner properly to ensure it is aligned with the target flame. This will reduce the chance of unwanted background signals being detected by the flame scanner. Pilots Most pilots used on fired heaters are the self- aspirated type, meaning the air is naturally induced for mixing with fuel gas prior to combustion. When using high H2 pilots, the chance of flashback inside the pilot tube increases. It is crucial to employ pilot designs capable of firing on pilot gas compositions of up to 90% H2 without flashback to avoid damage to the pilot itself and any internal components. For example, some pilot designs utilise an adjustable air door to manually control airflow and prevent flashback when firing high H2
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