Filters

(2011) Question 97: Disposal of catalyst fines from the slurry tank is expensive since they are handled as a hazardous waste. Do you have a way to reinject these tank fines back into the FCC where it would recover? What are other disposal options for these oil laden fines?

I have seen operations at two refineries where FCC slurry tanks were decanted, and the remaining catalyst fines were resuspended with Orbijets and an LCO circulation loop. A slipstream of this LCO slurry was recycled to the riser. In FCC Unit A (~20,000 BPD) the recycled fines partitioned approximately 2/3 to the regenerator side and out with the flue gas and 1/3 partitioned to the reactor side and back out to storage with the main column bottoms product.
Read more

(2011) Question 98 What measures have you taken to minimize catalyst expenses due to rare earth price inflation? Please include an economic comparison of using a high rare earth catalyst at a lower catalyst addition rate versus using a low rare earth catalyst at a higher catalyst addition rate. Are there alternatives to replace rare earth in FCC catalyst? Are there any negative yield shifts with these new technologies?

Rare earth is an integral component of today's FCC catalyst. Rare earth adds catalyst stability and activity, functions as a vanadium trap and is the oxidizing agent within most SOx additives. Rare earth has also increased in price by over 1500% in the last 18 months. Rare earth has a direct impact on the split between LPG and gasoline in the FCC unit. As rare earth concentration is decreased LPG yield will increase potentially leading to wet gas compressor limitations.
Read more

(2011) Question 99: Are there any uncommon FCC metal contaminants showing up on equilibrium catalyst in addition to Ni, V, Fe, Na, and Ca? Are metals traps able to protect the catalyst by selectively capturing Fe, Na, Ca, or any of these uncommon contaminants?

Each of these catalyst poisons may have a significant impact on the FCC catalyst circulating inventory depending upon their concentration. Vanadium will form vanadic acid resulting in the sintering of the zeolite crystal thereby reducing activity. Nickel increases hydrogen yield potentially leading to wet gas compressor constraints and increases delta coke leading to main air blower &/or regenerator temperature constraints.
Read more

(2011) Question 100: What conditions or contaminants will deactivate ZSM-5 additive? What is the half-life of ZSM-5 in clean feed operation? Will contaminants such as vanadium, sodium or other metals adversely affect the propylene selectivity of ZSM-5? What is the best way to monitor the effectiveness of the ZSM-5?

The deactivation mechanism for FCC catalyst is primarily related to unit cell size reduction, and eventually, collapse or sintering of the zeolite crystal. The mechanism of ZSM-5 deactivation is quite different. The deactivation mechanism is simply the dealumination of the ZSM-5 crystal and activity is lost through the loss of active aluminum sites.
Read more

(2011) Question 101: What analytical methods can distinguish between organic and inorganic iron (Fe) compounds in the feed? What type of iron, organic or inorganic, affects catalyst performance? Considering the relatively long reaction residence time of most laboratory test units used to measure activity, will activity testing properly reflect the actual in-FCCU activity under conditions of Fe contamination? What is your best method to monitor the catalyst performance under Fe contamination? Is ther

We have not routinely attempted to identify the organic and inorganic iron components in our feeds. An internal expert suggested two approaches. First to determine the organic iron using ICP-OES, then wash the same sample with DI water, or slightly acidified water, and utilizing atomic absorption, determine the inorganic iron.
Read more

(2017) Question 50: From this list of your top FCC gas plant constraints, which area is your primary constraint: 1) main column (MC) overhead, 2) wet gas compressor, 3) primary or sponge absorber, 4) stripper, or 5) debutanizer bottoms or overhead?

Refining investments in alkylation expansions and gasoline octane improvements require production of additional feedstock for the alkylation unit. The primary source of olefin feedstock for the alkylation unit is the FCC unit. Operating conditions in the FCC unit can be adjusted to favor increased propylene and butylene production. The FCC wet gas compressor becomes the first major bottleneck in recovering the incremental propylene and butylene. Modifications may be required to the compressor, as well as associated cooling, inter-stage, or after-stage equipment. 
Read more

(2017) Question 51: Can you comment on the safety aspects of placing catalyst in a standpipe to help isolate one vessel from the other? Does the existence of catalyst in a standpipe create a ‘seal’?

I would like to mention that we will have a P&P tomorrow on this topic, so I will try to keep my answer short. It is assumed that this question relates to using the slide or plug valve to form a seal between the regenerator and the reactor during shutdowns. I would like to point out that this is a standard practice in an FCC as there is really no other option; and for the most part, it does work. 
Read more

(2017) Question 52: What challenges do you face for implementing safety-instrumented systems that result in closure of the FCC slide valves?

Systems are designed to meet a specific safety integrity level (SIL). Each operating company has a risk-based matrix specific to the company or site. This matrix has severity on one axis and probability on the other axis. High severity and high probability score the highest. Based on this ranking system, the company sets the SIL rating at SIL 1, 2, or 3. SIL 1 and 2 are the most commonly found in typical refinery processes.
Read more