Corrosion issues in an existing RFCC unit of a refinery

[chengg29]

Hi,

As part of an ongoing exercise in the company to debottleneck a 70 KBPD existing refinery one of the issues that needed a resolution was the corrosion issues in an RFCC unit in order to debottleneck it. Following below are options to debottleneck the same, which under discussion right now:

a) Explore possibility of converting this RFCC to an FCC

b) Blend the feed with Diesel / Middle Distillates, sourced from other units in the refinery with the exception of sourcing from units producing cracked stocks viz. SDA, Visbreaker etc., to dilute the feed to achieve a lower Sulphur content in the RFCC feed

The feed for this RFCC is the Atmospheric Residue (AR) from the CDU without any Hydrotrearting. The crude feed to the CDU is sour with 3.1 wt % Sulphur. The untreated AR has a Sulphur content of 2.9 wt % and a CCR spec. of 5.7 wt. %.

Of course the licensor will be involved once the time comes for that but before that happens I request your opinion on the above i.e whether the options considered for the debottlenecking to address the corrosion issues are truly feasible.

Many thanks in advance

 

[georgeverghese]

Where are the main corrosion spots - riser line, reactor or regenerator in this RFCC ?

 

[chengg29]

Initial investigations found various stages of corrosion in different sections of the fractionator column of this RFCC Unit although the investigation is still ongoing by a team comprising the Licensor and our engineering consultant and we expect to get more information on the extent of the corrosion.

However at this stage we are deliberating on the said options from a future technical and commercial point of view since its known that the original design intent Sulphur content and the CCR have increased significantly since the unit's installation about 6 years ago. Hence that's why the options suggested need to be decided based on their "do-ability" first and then decide on the technical and commercial implications.

 

[Chumpes]

hi chengg29
what is your question ?
what type of corrosion was experienced ? where ?

operating conditions are essential for evaluation of corrosion, what are the operating conditions ?

generalized corrosion by high temperature sulfidation, if it is confirmed to be the actual corrosion mechanism encountered, depends mainly on temperature, sulfur content having less influence. what is the temperature ?

 

[georgeverghese]

Though I only have a layman's knowledge of FCCs', would imagine you'd get higher vapor loadings at the main fractionator / overheads condensors and liquid loadings at associated side strippers also. Have you run a simulation rating check to see where the bottlenecks in the fractionation section are ? What reduction in throughput rates are required to keep these loadings within design limits, and are there any debottlenecking opportunities ?