(2a) NOx, NOx, Who's There - Steam Cracker or Smr? a Tutorial and Wrap-up

Now that the remaining pieces of the puzzle have fallen into place, it is instructive to revisit NOx abatement measures for steam cracking and steam-methane reforming (SMR) with updated information.  Although they are totally different on the process side, combustion is much the same on the furnace side, where thermal NOx is generated and emitted to the atmosphere in the flue gas.  The extent of NOx formation and its control are strikingly similar and predictable such that experience with one process can be readily transferred to the other.   

          Specifically, this paper discusses:

• Simplified process descriptions – including conditions, feeds, products, and fuels
• Similarities and differences between the two processes
• Measured burner NOx emissions from commercial furnaces
• The correlation of burner NOx as a function of burner type; fuel composition; excess oxygen; and fuel, combustion-air, and furnace temperatures
• Treatment of burner NOx emissions in excess of allowable limits by selective catalytic reduction (SCR) 
• Degradation of SCR catalyst by chromium species originating from the exterior of alloy coils and tubes exposed to the hot furnace flue gas
• Integration of combustion in the furnace with gas turbine exhaust 

          Further details are contained in the original sources cited and their supporting references.