This paper, co-authored by Marc Cremer and Dave Wang of Reaction Engineering International and Jerry Zhang and Deke Lincoln of Norton Engineering Consultants, was originally presented at the American Flame Research Committee 2021 Industrial Combustion Symposium. A full copy of the paper can be downloaded here. The abstract is presented below:
CO boilers are commonly utilized in oil refineries to produce process steam by burning the low BTU, CO-containing gasses that are produced during regeneration of the fluid catalytic cracking
(FCC) catalysts. Supplemental heating through fuel gas burners is necessary to carry out complete oxidation of the CO containing regeneration gases. The regeneration gases may contain varying concentrations of fuel nitrogen species including HCN, NH3, and NO, which can be sources of NO generation along with thermally produced NO in the CO boiler.
This paper discusses the results of a Computational Fluid Dynamics (CFD) based evaluation to guide the design of selective non-catalytic reduction (SNCR) for NOx control in two typical CO
boiler configurations. In addition to the regeneration gases that are combusted in both boilers, a significant quantity of sour water stripper (SWS) vapor is injected into the combustion zone,
subsequently generating fuel NOx emissions. The CFD simulations show the potential for reducing NOx emission by relocating a portion of the SWS vapor from the combustion zone to the
post-combustion zone, where the SWS vapor acts as an SNCR reagent. Potential impacts on H2S emissions by relocation of the SWS vapor are also examined.