Question
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In the event of an emergency shutdown of the FCCU, coke in the reactor and reactor cyclone may be peeled off. On the other hand, a significant period of time will be required to remove the coke. In the event of an emergency shutdown, how should we determine whether or not coke removal is necessary?
May-2024
Answers
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Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br
Coke deposition in the internals of fluid catalytic cracking units like separator vessels are, unfortunately, a common issue, especially for those units processing atmospheric residue (RFCC) which presents high carbon content in the feed. During emergency shutdowns, the instability and transient operation conditions can lead to coke detachment from the cyclones, for example, leading to the poor separation efficiency of the catalyst which will raise significantly the particulate emissions to the atmosphere, leading inevitably to the shutdown of the processing unit for maintenance considering the current environmental regulations and ESG policies.
Some refiners are applying the strategy to install devices in regions where historically are found coke deposition capable to sustain and attach the coke, avoiding the falling over the equipment internals. These devices can be designed according to the historical of coke deposition in the processing unit and are installed during the planned shutdown for maintenance. Regarding the question of remove or not the coke during an emergency shutdown, this should be a technical and economic decision considering the performance of the processing unit previously of the shutdown, availability of maintenance resources and materials, and the remaining life cycle of the processing unit.
Jun-2024
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