This is a slide that shows a summary of data taken from several ExxonMobil FCC units showing the correlation of NOx emissions with regenerator design.
In order to put things on a consistent basis, Mobil took samples of spent catalyst and measured their nitrogen contents so that they could determine the % of nitrogen in the coke that goes to NOx in the regenerator.
This takes out the effect of feedstock and looks only at the performance of the regenerator.

Сомневаюсь во фразе "effect of feedstock".

Спасибо.