Question
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We’re encountering fines build-up in the drum overhead into the fractionator of our delayed coker. Solutions please.
Nov-2021
Answers
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Marcello Ferrara, ITW Technologies, mferrara@itwtechnologies.com
In the delayed coking process foam formation is one of the most common operational issues.
As the coke drum completes the filling cycle the distance between the coke bed and the outlet line decreases and this, of course, increases fines carry-over. Froth or foam in the coke bed exacerbates the problem, entraining coke fines.
Foam is highly stabilised inside the coke drums because it finds the ‘perfect’ environment to form: a liquid phase, a vapour phase, and solids.
When not controlled the foam will lead to coke carry-over at the drums outlet and hence at the main fractionator.
The coke fines will be further carried over in the overhead, by following the vapour flow. And then build up in the accumulator.
The injection of an antifoamer will address foam formation/control and proper injection strategy will be part of the solution.
A silicon based antifoamer will, however, create problems in the downstream units.
Silica is indeed a poison for the catalysts in that it promotes catalyst sintering, thereby reducing the active surface and hence performance.
ITW can provide an effective non-silicon based antifoamer which will address the foaming problem while eliminating the downside of catalyst poisoning.
Nov-2021
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