Speaking of the improper refractory repair, especially in a hot-wall refractory with the coking service, low alloy base metal requires a 300°F preheat along with removal of all sulfides on the metal surface. If you do not do this, you will get weak and brittle welds that will crack easily because of their low weld strength. And therefore, your anchors will break off and your refractory will fail due to the coke growth behind the refractory. 

Most refractory problems are often due to poor installation and cyclic service. Hot spots are observed in the shell due to major refractory failure; but much more commonly, from the circulation behind the refractory. We have experienced gas and catalyst going behind the monolithic refractory lining. In such cases, hot gases are driven through the refractory by the head of the catalyst just above the entry point. The gas then exits from the dilute phase at the lower pressure zone. As the gas continues to travel through cracks and heats up the metal, the metal tries to expand while the refractory does not expand, which leads to refractory failure. 

We installed packing in our reactor stripper in 2006. So far, the only issue we have seen was in 2012. When we went into the reactor, we had refractory and coke debris from various areas of the reactor that had fallen onto the top of the packing and partially clogged and blocked a portion of the packing. We had already made the decision to remove all of the packing to evaluate whether there was any erosion with the new configuration (there was not), but we would have needed to remove at least the top two layers for cleaning anyway due to the debris. 

Feedstock, catalyst, and reactor hardware all play a very major role in the vapor line coking. Coking of the reactor overhead line is a major concern, particularly when we are processing resids. Catalyst formulations designed for higher hydrogen transfer reactions, coupled with high aromatic feed, tend to produce higher boiling point PNAs (polynuclear aromatics), which have a tendency to condense and form coke in the vapor line.

Currently, we do not have the operators monitor or alter operating conditions for sulfidation and corrosion in the main column bottoms. We took a more traditional approach. We did a good process study throughout both FCC units with the total sulfur because that is what is represented on the McConomy curves, not the sulfur speciation.

The short answer is “Yes”, but it would not be a good FCC answer if I did not say the words, “It depends.” The actual effective service life depends on your solids loading in your slurry system, in both typical and upset conditions.

Typical total catalyst losses from both the reactor and regenerator side are somewhere around 0.05 to 0.1 pounds per barrel. A good assumption is that you have about a 50/50 split between your losses. From a maximum loss standpoint, you are looking at anywhere from 0.10 to 0.15 pounds per barrel for both the reactor and the regenerator. 

The first reports of FCC iron poisoning on a large-scale date from the 1990s. Iron was used in drilling liquids for oil recovery. Iron poisoning results in a loss of activity and an increase in slurry yield. The apparent bulk density of the catalyst decreases, which causes a drop in pressure differential over the standpipes and can lead to erratic catalyst circulation. 

The first consideration should be removal or minimization of the contaminant metals upstream of the FCC. Since removing or limiting these contaminants may not be an option, other methods must be considered to address their negative impacts. 

We get fixed on how much 0-to-40 micron catalyst is in the inventory. You need 10% to run the unit well. And as Bob Flanders used to say, “Purgatory was trying to run a Model IV with less than 10% fines in it.” What I would suggest is certainly nothing smaller than 20 microns.