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Chementator:  A dynamic way to reduce NOx emissions from FCCs  

By Edited by Gerald Ondrey |

A system for controlling oxides-of-nitrogen (NOx) emissions from catalyst regenerators in fluid catalytic crackers (FCCs) has cut NOx output to below 40 ppm (and as low as 25 ppm under certain conditions) in its first commercial installation, according to its developer, Shell Global Solutions (Houston, Tex.; edlinks.chemengonline.com/7373-531). This compares with about 20 ppm for selective catalytic reduction (SCR), the most effective way to control NOx, says Ye Mon Chen, the company’s regional manager for catalytic cracking. However, he notes that Shell’s method costs only 10 – 15% as much as an SCR system. In Shell’s process, spent catalyst is introduced into the bottom-center of the regenerator and fluidized by air. However, instead of the conventional uniform airflow, Shell introduces two air streams into the bottom of the vessel: a high-velocity stream near the middle and a low-velocity stream in the annulus. This arrangement creates a rolling, dense-phase catalyst bed in which spent catalyst moves up through the middle, circulates to the annulus, and is removed from the bottom near the vessel wall. Chen points out that most NOx emissions in FCC fluegas come from feed-bound nitrogen, which is released during…
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