Q&A

(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.

(2011) Question 49: What criteria do you use to predict coke drum hot spots (leading to blowouts) during the cutting cycle? How do you modify your standard cutting procedure if you anticipate hot spots?

Coke drum hot spots can be difficult, if not impossible, to predict but there are operating practices that can help minimize the occurrence of coke drum hot spots/blowouts.

(2011) Question 50: What unique challenges do you consider when designing a safety instrumented system (SIS) for a delayed coker heater?

We are currently constructing two new delayed coker heaters at our El Dorado, Kansas facility. As part of this project, we have performed both a process hazard analysis (PHA) and a safety integrity level (SIL) evaluation.

(2011) Question 51: What are some steps that can be taken to minimize re-foaming while steaming to the fractionator? Are there ways to predict re-foaming tendencies of different crudes or coker feed properties?

After a Coke drum is taken offline, it is steam stripped with ‘little’ steam @ 2.5 t/hr for 30 minutes (28 ft drum) to main fractionator to recover volatile hydrocarbon material.

(2011) Question 52: What test methods do you use to predict desalter performance when switching to new crudes or a blend of several crudes?

Standard laboratory tests include salt, BS&W, gravity, viscosity, and filterable solids. The amount, and type of filterable solids can be the greatest factor to consider for interface emulsion resolution and predicting performance.

(2011) Question 53: Asphaltenes are known to destabilize at higher crude preheat temperature. Are there guidelines that can be used to determine the maximum allowable desalter operating temperature before the asphaltenes begin to drop out of solution and come out in the desalter brine?

We have worked with several refining organizations that process heavy Canadian crude oils to find the optimum desalter operating temperature. In general, raising temperature reduces the crude oil viscosity, which is desirable from a Stokes’ Law stand point as it makes breaking the emulsion easier.

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

Q&A