A carbon runaway or “snowball” occurs in an FCC that is operating in partial CO combustion mode and very high CO levels. In the runaway situation, the carbon on regenerated catalyst (CRC) rises to levels such that additional coke that is laid down on the catalyst cannot be burned from the catalyst in the regenerator, causing the CRC to continue rising like a snowball that gets bigger and bigger as it rolls down a hill.

[United Refining Company (URC)] Our FCC unit has five operators per shift. Typically, two people are inside running the DCS (distributed control system) and board-mounted controls while the other three are doing rounds in the unit.

This is a three-part question. The first question is: When is the return on investment (ROI)adequate to justify installing a desalter to treat purchased FCC feeds? The capital and operating costs of an FCC feed desalter are supported by improvements in performance, operating costs, and reliability.

Amines have been used in refinery steam systems for decades. When properly applied, the amount of amine that may make it to the crude fractionator towers should be very small; the partial pressure contribution should be so low that the steam condensate amines should not contribute to salt formation.

Besides the use of flow-normalized pressure drop, another observable parameter that can be used is the distillation overlap of the overhead distillation curves.

There are many types of level controllers for desalters, so an exhaustive response is not possible here. Generally, each type has comparative merits based on how robust it is with regard to the various contaminants in desalters, resolution, or cost. Traditional capacitance probes, and also float-type level controllers, have a broad application in desalters and have been used for many years in the industry.

From the various articles and presentations on this subject, plus our own experience, we have found that LTO, in itself, is not an issue. Rather, LTO mixed with crudes containing asphaltenes is the issue. Industry seems to agree that precipitation of asphaltenes is one of the main fouling mechanisms.

Fluor's standard design to measure overflash that is not pumped uses a simple loop and an orifice plate. Having adequate elevation difference to route the overflash return to the top stripping tray is needed. It is easy to do on a new unit, and sometimes more difficult to do on a revamp.

Coker LPG contains various species of mercaptans and other organo-sulfur compounds, besides other contaminants. Depending on capacity and impurity levels, coker LPG treatment in a coker may include amine treating for CO2and H2S, as well as a coker LPG mercaptan removal unit.

Ensure that the following scenarios or standards are met.