How to address corrosion caused by recycled flue gas
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In my catalytic antifreeze unit, severe corrosion occurs in the catalyst reactor during regeneration. Currently, liquid ammonia is injected at the flue gas outlet, but this approach does not yield very good results; moreover, the liquid ammonia odor is quite strong when the regenerated flue gas is vented. Is there any effective way to address this issue of flue gas corrosion?
The corrosion of the regeneration reactors in catalytic cracking units is mainly caused by acid corrosion resulting from sulfur oxides and nitrogen oxides in the presence of water vapor. About 14 or 15 years ago, I was involved in an investigation into the causes of corrosion in the regeneration reactors of Sinopec’s catalytic cracking units, and that was the main conclusion reached. This situation is related to the operating conditions of the regeneration reactor, as well as to the material used, the sulfur and nitrogen content of the feed oil, and the regeneration aids; it is complex and variable. Controlling the excess oxygen in the regeneration process is a good measure, but too low an oxygen level can affect the regeneration efficiency. If the regenerated flue gas has a strong ammonia smell, it indicates oxygen-deficient regeneration, with little to no excess oxygen; as an excess of oxygen would lead to a decrease in ammonia levels (if no ammonia is added). There are generally no nitrogen oxides in flue gas, but sulfur oxides are definitely present.