CRACKING HEATER CONVECTION RETROFIT ITH INTEGRAL SCR

摘要

When faced with a state-imposed mandate to reduce NOx emissions from a steam cracker, Chevron Phillips Chemical Company LP (CPChem) determined that the most advantageous solution would be a retrofit of new convection sections on the existing 13 cracking furnaces, incorporating both integral steam superheating coils and integral Selective Catalytic Reduction (SCR) for NOx removal. This allowed CPChem to reduce stack heat- losses as well as NOx emissions in the cracking heaters, while completely idling a low efficiency steam superheater and avoiding the NOx generated therein.Technical and design issues were addressed by a team incorporating members of CPChem; Lummus Technology Heat Transfer, who provided the heater thermal and mechanical design; and KBR, who engineered the ammonia delivery system and erected the new convection modules. Significant design issues needed to be addressed, in terms of the design of the ammonia delivery system and the Ammonia Injection Grid (AIG). As the revamp of the convection sections required additional heating surface for higher thermal efficiency and also new services (steam superheat), the height of the convection section would increase by 30 feet over the existing design. The associated increases in dead weight and wind load imposed on the structural members and foundations were concerns that ultimately required some additional bracing and fortifications of the supporting steel.