| American Fuel & Petrochemical Manufacturers

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.

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?

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?

Question 94: To reduce the risk of igniting the gas mixture in the electrostatic precipitator (ESP), we are considering safety interlocks for de-energizing the ESP when carbon monoxide content gets too high. Please share your experience regarding (a) setting an appropriate trip point, (b) other interlocks to consider, and (c) advantages over operating procedures.

Automatic trip points should be set so that the CO gas concentration is well below the Lower Explosive Limit (LEL). Consideration should also be given to adding interlocks to trip the ESP based on high concentrations of methane, especially if the ESP is downstream of a CO Boiler or if there are other potential sources of fuel gas/natural gas to the ESP (even during upset conditions).

Question 93: What is your process safety concerns in withdrawing equilibrium catalyst from the FCC regenerator? How do you manage catalyst transfer piping and spent catalyst hopper temperatures? What materials of construction are appropriate (or inappropriate) for these services?

What is your process safety concerns in withdrawing equilibrium catalyst from the FCC regenerator? How do you manage catalyst transfer piping and spent catalyst hopper temperatures? What materials of construction are appropriate (or inappropriate) for these services?

Question 92 What is the impact of high iron you have seen in some tight oil feeds? What level of Fe on the equilibrium catalyst causes problems, and what are the typical symptoms? What changes to FCC units hardware, catalyst and operation have you implemented to manage Fe poisoning? What is the impact of other uncommon contaminants such as K, Ca and Mg?

Tight oil feeds generally have high levels of iron and calcium present in them. Iron can have a negative effect on catalyst performance. While particulate tramp iron from rusting refinery equipment does not have a significant detrimental effect on catalyst, finely dispersed iron particles in feed (either as organic compounds or as colloidal inorganic particles) can deposit on the catalyst surface, reducing its effectiveness.

Question 91: What are the characteristics of FCC catalyst to minimize particulate emissions at the stack?

While there are several operational and mechanical factors that can influence a unit’s particulate emissions, the question asks specifically about the FCC catalyst; as such, the following discussion will address characteristics of fresh catalyst only.

Question 90: What is the most profitable way to schedule the FCC and associated catalytic naphtha hydrotreater turnarounds? Are there benefits in synchronizing the shutdown of these units?

What is the most profitable way to schedule the FCC and associated catalytic naphtha hydrotreater turnarounds? Are there benefits in synchronizing the shutdown of these units?

Question 89: What are the best practices in the industry for profitable LCO maximization? Please elaborate on (a) FCC catalyst/additive technologies, (b) Cetane maximization, (c) process design and operations strategies and (d) any impact on naphtha octane and how you mitigate it?

Maximizing light cycle oil (LCO) is largely a slurry management process. To increase LCO, refiners can simply change operating conditions and lower catalyst activity to shift operations into a lower conversion regime.

Question 88: During a turnaround, how long does it take from oil out to vessel entry? How do you minimize this time? Please specify the unit capacity.

During a turnaround, how long does it take from oil out to vessel entry? How do you minimize this time? Please specify the unit capacity.