Q&A

(2010) Question 89: In shifting from partial burn to full burn in a side by side unit, what has been your observed impact on the NOx emissions? What is necessary to achieve 20 ppm NOx?

Several Grace customers successfully operate with NOx emissions less than 20 ppm in full combustion without the use of NOx removal hardware in the flue gas circuit.

(2010) Question 90: Does any refiner use an on-line particulate emissions (PM) analyzer to measure PM concentration and/or particle size distribution in the flue gas? Are any of these analyzers using continuous emission monitoring systems (CEMS)? How reliable and accurate have these systems been?

Sunoco currently has a particulate matter (PM) analyzer in one location on the stack of a Wet Gas Scrubber. It is there to measure Filterable PM only, not particle size distribution. This was installed as a requirement of a local environmental permit.

(2010) Question 91: Assuming the FCCU already has a third stage separator, what are the various options you consider for further reduction of particulate emissions (PM) and what is the expected level of PM to be achieved?

The first thing to consider is the fourth stage collector. For designs that re-introduce the collected fines downstream of the expander, a fourth stage collector with fines removal and filter on the TSS underflow gas will aid in reducing PM.

(2010) Question 67: Have you experienced coking or other fouling of reboilers in naphtha distillation service (splitter, debutanizer, etc.)? If so, what operational or design changes did you implement to eliminate this problem?

Two types of fouling are common in naphtha reboilers. The first type of fouling is generated as a result of the more reactive cracked stock hydrocarbons and is typically seen only in units like Cokers or FCCUs with a cracking process. The second type of fouling is a more complicated issue related to the presence of sulfides in the naphtha and can be seen in straight run units like the Atmospheric Crude.

(2010) Question 70: How can you minimize the possibility of ignition and fire in the structured packing of main fractionators after they are opened for maintenance? Do you use chemicals to improve this procedure?

Zyme-flow products have been used in our past FCC turnarounds to mitigate pyrophoric compounds as well as decrease the amount of time to hydrocarbon free the main fractionator and associated pumparound circuits.

(2010) Question 71: For the main column, "tri lines" can be utilized to monitor bottoms level. When other level instruments are being verified or have failed, what are the best operating and safety practices being employed to verify the level? What do refiners use to monitor and control level in the bottom of the main column?

For the main column, "tri lines" can be utilized to monitor bottoms level. When other level instruments are being verified or have failed, what are the best operating and safety practices being employed to verify the level? What do refiners use to monitor and control level in the bottom of the main column?

(2010) Question 72: With advance controls on the FCCU and gas plants, what are refiners doing to train new operators and keep their experienced operators sharp and ready to handle FCCU upsets and emergencies? Are refiners using simulators to help with the training and retraining?

Sunoco employs Dynamic Matrix Control (DMC) on all the FCC gas plants and DMC on reactor and regenerator systems. One FCC has a complete process training simulator, and we are in the process of installing simulators on all of our FCC’s.

(2010) Question 73: What levels of distillate boiling range material do you include in the FCC feeds? Discuss the yield and heat balance implications of varying the feed distillate content. What equipment/technology options do you employ to minimize the distillate levels

There are several examples of how yield data can be used to identify hardware issues in the FCCU. For example, a decrease in cat to oil and/or catalyst circulation (which leads to a decrease in overall conversion and liquid yield) can be the result of a high regenerator dense bed temperature at constant process conditions. Several mechanical/hardware issues can contribute to higher regenerator temperatures.

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