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(2014) Question 95: What are the key wash nozzle design criteria for an effective FCC main column overhead water wash system? Please discuss the effectiveness of using hollow-cone versus full-cone and the spray angle direction - up flow versus co-current flow?

What are the key wash nozzle design criteria for an effective FCC main column overhead water wash system? Please discuss the effectiveness of using hollow-cone versus full-cone and the spray angle direction - up flow versus co-current flow?

(2014) Question 96: What are the different methods you employ to increase C3 recovery? What are your typical C3 recovery improvements for these various methods?

What are the different methods you employ to increase C3 recovery? What are your typical C3 recovery improvements for these various methods?

(2014) Question 97: What is your optimal pH for wet gas scrubber water and how is this maintained? What are the implications of too high or too low pH?

The optimum pH for a wet gas scrubber treating FCC flue gas is 6.9 to 7.1. This pH is maintained by the controlled addition of sodium hydroxide.

(2014) Question 98: What are the options for removing catalyst fines from the main fractionator bottoms product? Which, ifany, can reduce the ash content to 50 ppm or less?

Slurry oil catalyst fines Settling Aid chemistries have been used for many years in this type of application. Electrostatic precipitators and filtration equipment is also available for minimization of ash content in slurry oil.

(2014) Question 99: We are struggling with high afterburn in the regenerator. What hardware changes (spent catalyst distributor, air distributor, etc.) have you implemented to improve afterburn? What commercial experience exists using computational fluid dynamics (CFD) to resolve such issues?

CFD has been successfully used to predict afterburn in FCC regenerators. A published example was presented as part of the CFD Case Studies workshop at the 2012 AFPM Cat Cracker Seminar.

(2014) Question 100: How do Nitrogen compounds distribute in the product streams of FCC Units? What effect does riser severity and feed properties have on this distribution?

How do Nitrogen compounds distribute in the product streams of FCC Units? What effect does riser severity and feed properties have on this distribution?

(2014) Question 101: What factors influence butylene selectivity in the FCC LPG? What is the relative role of feedstocks, catalysts, additives, and operating conditions?

A number of factors influence butylene selectivity in the FCC LPG stream. Figure 1 summarizes the fundamentals of butylene selectivity and maximization.

(2014) Question 102: What benefits have you realized by installing packing in their FCC strippers? How did this equipment impact your catalyst circulation and unit pressure balance?

What benefits have you realized by installing packing in their FCC strippers? How did this equipment impact your catalyst circulation and unit pressure balance?

(2014) Question 103: We increased reactor severity and noticed an increase in oxygenates in LPG and sour water. Can you explain the mechanism by which phenols and other oxygenates form in the riser?

Since increasing reactor severity will result in an increase in catalyst circulation, it is likely that the increased oxygenate production being observed is from the higher catalyst circulation which is increasing the entrained molecular oxygen carryover to the riser.

(2014) Question 104: How are radioactive surveys and/or gamma scans utilized to optimize FCC operation?

Monitoring parameters of the FCC such as density and height of catalyst beds, gas and/or solid distribution of the cyclones, air distributor, slide valves and standpipes are accomplished through measurements of pressure, pressure drop and temperature at various locations.

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