HCN emissions in fluid catalytic cracking

PTQ - Petroleum Technology Quarterly, 2013 Q2
HCN emissions in fluid catalytic cracking
Xunhua Mo, Bart De Graaf and Paul Diddams, Johnson Matthey
Increased attention to refinery emissions of hydrogen cyanide requires detailed understanding of its formation and conversion in the FCC regenerator
A lot of attention has been paid to controlling NOx and SOx (and particulate) emissions. Today, FCC unit design and additives have been geared to achieve the lowest levels of both SOx and NOx. Recently, however, hydrogen cyanide (HCN) emissions (present in flue gas at up to about 150 ppm) have come under scrutiny in the US. Suddenly, a “new” species is added to FCC chemistry. In the public domain, the origin of HCN in FCC flue gas was poorly understood. In this article, we explain the origin of HCN, its relationship to NOx, and how modern FCC unit design geared to low NOx emissions can induce a trade-off with HCN emissions. Continuous catalytic additive development for regenerator flue gas control helps to bring flue gas chemistry under control. However, flue gas control is a combination of additive and regenerator design working together.
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