Q&A

(2011) Question 89: Are there advances in cyclone lining material or cyclone designs to make them more erosion resistant allowing higher cyclone velocity or longer run lengths?

We limit the regenerator cyclone inlet velocity to 75 fps to make 4-5 year runs between turnarounds. Reactor cyclone inlet velocity limit is 80 fps if there is a rider termination device that reduces the catalyst loading to the cyclones.

(2011) Question 90: Do you have experience with slide/plug valve independent movements without any controller action?

There are 5 categories of initial causes which may lead to erratic slide valve movements in auto mode. These are oil contamination, servo valve amplifier tuning, part failure, mechanical linkages, and electrical connections. Oil contamination is the initial cause a vast majority of the time.

(2011) Question 91: What methods other than jack hammering, water jetting and low charge explosives have you used to remove coke during turnarounds? What are the advantages and the risks for these methods?

Jack hammering is the most popular method for coke removal as it is effective and is the lowest risk to equipment. As stated early, jack hammering can be used effectively around refractory as long as the refractory has stainless steel needles. The chipping hammer will through sparks when the chipping hammer cuts through coke and starts to hit refractory.

(2011) Question 92: Aside from erosion failures, what is your experience with newly installed lining failures in vibration-cast cold wall risers and standpipes? What caused the failures? What can be done to prevent or mitigate the failures?

Valero has experienced this at one of our revamped FCC units on very long regenerated catalyst standpipe, near the top of the reactor riser in two other units. There are numerous hot spots that can be quenched with steam lances.

(2011) Question 93: We are aware of at least one refiner who replaces the regenerator head, including cyclones, at every turnaround to eliminate the time required for inspection and repair. What are the key factors you consider when assessing the economics of replacing the regenerator and/or reactor head(s) versus the traditional procedure of internal inspection and repair? How does the size of the regenerator and/or reactor play into the decision?

Valero has experience with replacing the regenerator cyclones by cutting off the regenerator head and replacing with a new head and cyclones when the cyclones are at end of life.

(2011) Question 94: What is your experience regarding corrosion of hexmesh anchorage in regenerators using non-phosphate bonded abrasion resistant lining materials?

The fact that a significant number of full burn regenerators have suffered severe abrasion resistant lining failures in recent years due to under-lining corrosion is not in dispute.

(2011) Question 95: What NOx reduction additives have been successfully used to rapidly decrease NOx during operational excursions or hardware failure? What alternatives to additives and hardware exist for NOx reduction? Is there a synergy for combining NOx reduction control methods that may reduce operating or project costs?

Intercat has developed a line of highly successful NOx abatement additive for use in the FCC unit. These additives tend to be most effective when added on a steady state basis. These include a platinum free combustion promoter and an additive designed to reduce NOx emissions for those refineries not using platinum promoters.

(2011) Question 96: What are your experiences using SOx reduction additives formulated with lower rare earth content?

Cerium oxide functions as an oxidant and oxygen carrier: the mixture of two oxidation states Ce(III) and Ce(IV) creates defect sites in the crystal structure where oxygen ions are missing (oxygen vacancies) – these get filled up in the regen and ceria acts as a kind of monatomic oxygen sponge.

(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.

(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.

Find the answer to your technical question in AFPM's extensive Q&A database.

Q&A