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Our RFCC unit load is limited at 90% because of WGC governor is widely open and it's reaching 100%. Can anybody help with this issue?

Feb-2022

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Adrie Visser, Natref, adrie.visser@natref.com

You need to make sure that you understand the fundamental operating principles of your equipment to guide you in troubleshooting poor performance. Write down the sizing or performance equations of the piece of equipment to help you identify what to look for.

The steam valve being wide open means that there is not enough power available to compress the amount of gas available. This can be caused by either poor performance of the turbine or poor performance of the compressor or both. Or there could be just more gas available than what the compressor and turbine was designed for.
What determines the performance of the turbine? Is the turbine rotor fouled because of bad quality steam that came in? Is the steam pressure and temperature high enough as per design? Is the turbine outlet pressure low enough as per design? Are the turbine inlet nozzles set correctly? And so on and on and on.
Same with the compressor. Are there salt deposits on the impellers requiring a naphtha wash? Relative to design, what is the compressor outlet to inlet pressure ratio, what is the gas mole weight, what is the suction temperature? Back calculate the polytropic efficiency of the compressor? Is it as expected or much lower pointing to fouling?

Understand the process within which the equipment functions and the impact thereof on the performance. Is there a problem on the main air blower that requires the regen and reactor pressures to be lower than design? Has the reactor pressure been dropped for better feed atomisation and vaporisation? As stated by others, has the catalyst performance changed resulting in more gas make?

There are too many things that can be the cause to such an open ended question, but understanding and applying the fundamentals will always guide you in finding the root cause. It is up to you as process engineer to equip yourself so as to improve your troubleshooting skills.

Feb-2022
Mohammad Abdulrahman, Kuwait Integrated l Petroleum Industries Company, m.ghufran@kipic.com.kw

In addition to what Mr. Marco mentioned, simply analyse the trend of dry gas make and its composition. More H2, check your metals. More C1/C2, check your reactor operating condition. Is there more non condensables?. Check with your catalyst supplier as they track regularly I assume your RFCC data. They can figure out from dry gas composition if thermal cracking is more.

However, do consider other factors in case non of the above found as the cause.

Feb-2022
Marco Greco, Petrobras, marco_greco@petrobras.com.br

There is a chance that the gas going to the WGC is lighter than usual. There are a couple of possible reasons for that. First of all try checking molecular weight of the gas compared to historical average. If equilibrium catalyst is high in Nickel you may be facing higher hydrogen content on your wet gas. Another possibility is thermal craking if for any reason you have high temperatures on riser bottom. See also if you pressure profile has changed. Is pressure lower than usual on WGC suction?

Feb-2022