What procedure should be employed to ensure that FCC-LPG is on-spec for sulphur and mecaptants (and to meet copper corrosion specs) immediately following startups from turnarounds or outages? Are there any additional best practices for treaters?
Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
I suppose that your LPG treatment scheme is the following:
LPG is first treated in an amine absorber (extractor) for H2S removal.
Subsequently the LPG is processed in a Merox unit consisting of a caustic prewash and a caustic extraction loop containing a Merox catalyst.
To ensure good H2S and mercaptan removal, you should ensure that all three towers are operating correctly. This means that:
1) the amine should be well regenerated, which means that the amine regenerator should have a high enough overhead temperature.
2) the caustic in the prewash should be of adequate strength (7-10%) and not more than 50-70% spent
3) the caustic in the extraction loop should be of adequate strength (12-17%), not more than 10-20% spent, enough catalyst should be present and enough air should be injected for proper regeneration.
These are some of the basics that you can check to enure proper operation.......