(106c) Full Hydrogen Firing in Furnace Revamps - Safety Considerations

Firing of fuel gas (generated from the cracker plant) in the steam cracking furnaces constitutes about 90-95 percent of the overall CO₂ emissions of the ethylene plant. An option to reduce cracking furnaces CO₂ emissions is to increase the hydrogen content in the fuel gas. By moving to almost full hydrogen firing, CO₂ emissions from the furnace stack can be reduced by about 95 percent for liquid crackers (using typically 10 vol.% H₂ in fuel gas) to 85 percent for ethane crackers (using typically 85 vol.% H₂ in fuel gas).

Utilizing hydrogen as a fuel gas presents different characteristics compared to methane-rich fuel gas. Full hydrogen fuel gas is easier to ignite, has a wider flammability range, a higher flame speed, a hotter flame temperature, a lower density, a higher rate of dispersion, requires lower combustion air and generates lesser flue gas.

Due to the different characteristics of full hydrogen fuel gas, it is required to perform an in-depth analysis to ensure safe furnace design and operation. This presentation discusses the anticipated design considerations involved when applying full hydrogen firing, in the areas of safety, furnace performance and furnace operation.