| American Fuel & Petrochemical Manufacturers

Question 86: In your experience, what are catalyst best practices to shift FCC yields rapidly between gasoline and diesel maximization and then back again? Many catalyst suppliers are recommending blended catalyst systems. Do you believe this catalyst/additive blending is the best approach?

Co-catalysts are a new product category providing the refiner with the flexibility to change the product slate of the FCC without changing the FCC catalyst. Changing between a maximum gasoline co-catalyst and a maximum LCO co-catalyst will allow the refiner to rapidly capture the most favorable economics at all times – maximizing FCC profitability. Co-catalysts are added to the base catalyst to rapidly change the core performance of the FCC.

Question 85: What is the typical range that you employ for iron content on FCC equilibrium catalyst? What methods are available to determine how iron is accumulated on the catalyst surface? How does the distribution of iron on the catalyst surface impact the FCC operation, yield structure and emissions?

There are several methods available to quantify iron contamination on catalyst. Scanning Electron Microscopy (SEM) pictures are a valuable means to qualitatively assess iron laydown morphology on the catalyst particle.

Question 84: Please describe the function of the critical flow nozzle in relation to the operation of a third stage separator. What are the key process/operations/maintenance considerations you associate with the performance of the nozzle? Can poor performance result in a unit shutdown?

The critical flow nozzle (CFN) is located on the underflow line of the Third Stage Separator (TSS). The purpose of the critical flow nozzle is to continuously help blow down cat fines separated in the TSS. The nozzle is normally designed for 2-4% flue gas and designed to take the same pressure drop as the Expander.

Question 83: What is your experience with regenerator cyclone refractory hex steel failure due to oxidation/corrosion? Do you observe a relationship between these failures and feed sulfur content or refractory type?

The other mode of failure can be the erosion of the CFN holding flanges and cone, which could potentially result in leaking flue gas and catalyst to atmosphere. In either case, a shutdown may be needed if expander blade deposits and expander vibration become unmanageable or the CFN boxes kept on eroding.

Question 82: Immediately after startup of the FCCU, we experienced a hot spot in the regenerator dome and flue gas system. Do you know of any "on the run" acceptable mitigations? Should steam and/or water sprays be applied to the impacted area? Are there reliable analytical techniques to determine if and when the unit should be shutdown for repairs?

Hot Spots are an unfortunate but common problem in cold walled FCC converter vessels and transfer lines. Hot Spots which are not treated can lead to several undesirable effects to the steel envelope. Most refiners typically mitigate these effects by applying steam to the localized hot area.

Question 81: Refiners operating FCCUs producing high levels of propylene have seen different or excessive product contaminants when compared to a less severe operation. In your experience, how has this impacted gasoline or LPG treating unit? What specific contaminants have you identified? What impact have you seen in amine color, consumption, or foaming tendency? What actions have you taken that have mitigated or prevented treating unit issues?

The answer to this question depends on what is considered high levels of propylene and what is the method to achieve it. If the additional propylene is produced by the addition of ZSM-5 to a standard operation, then I would not expect to see additional effects of contaminants. However, if the propylene production is increased through higher severity, ROT, bottoms cracking, etc., then there will be additional contaminant issues.

Question 80: What best practices do you recommend to improve LCO recovery? Do changes in LCO pump around affect LCO recovery? What are common challenges?

There has been a lot of work and discussion on LCO maximization at the FCCU and there is plenty of literature on different options for LCO recovery. This will be a general overview of available options to refiners and some challenges recently experienced at Coffeyville.

Question 79: Backwash containing catalyst fines collected by main column bottoms hydrocyclones, filters or electrostatic precipitators are normally routed back to the FCC reactor riser. In your experience, how does the recycle of catalyst fines in main column bottoms impact particulate emissions from the FCCU?

The distribution of pumparound duties in the Main Fractionator dictates th amount of LCO recovery from the bottom's product. The primary handle to adjust LCO production is the pumparound duty below the LCO section (slurry pumparound or slurry and HCO pumparounds in towers with an), not the LCO pumparound.

Question 78: In your experience, how effective and reliable are hydrocyclones, electrostatic separator, additives, and filters in reducing the ash content of the slurry?

There are basically 3 types of ways to reduce the ash content in slurry oil. They are electrostatic separators, additives with settling and filters. They all have their advantages and disadvantages, and they all do a reasonable job in reducing ash in slurry.

Question 77: How do you minimize the entrainment of inerts from the regenerator which eventually enter the fuel gas system and sulfur recovery units reducing available capacity?

In the Shaw RFCC, we utilize a withdrawal well design that allows the catalyst to deaerate before it enters the RCSP. The withdrawal well achieves a very high catalyst density at a stable flux. It can also help the pressure balance.

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