Q&A

Question 29: How are crudes with high filterable solids crude managed to mitigate their impact on the operation? What levels of solids do you see and how are they measured?

Several major refiners have begun to use a water wash step at the end of the D4807 test to determine the actual non-water-soluble filterable solids. This method is more reflective of actual solids contained in the crude.

(2018) Question 30: When injecting wash water upstream of the cold train in a 2-stage system, do you use fresh wash water or brine water from the 2nd stage desalter?

For two stage desalting, injecting all the fresh wash water upstream of the second stage desalter provides the opportunity to use the lowest salt water on partially desalted crude which should result in the lowest level of salt in the desalted crude oil. Water from the second stage desalter is then used to provide wash water for the first stage. This water is typically split between being injected upstream of the exchanger train and upstream of the mix valve for the first stage desalter.

(2018) Question 34: What is considered your practical limit on TAN (Total Acid Number) of blended crude diet before monitoring, treatment, or metallurgy upgrades should be considered to avoid naphthenic acid corrosion issues?

Understanding the mechanism of naphthenic acid corrosion, we model the hot circuits looking at the potential TAN of the stream, metallurgy and fluid velocity within the circuit. Once this has been done, we evaluate the options, if the corrosion potential is high enough.

(2018) Question 35: For deep cut vacuum tower designs what is your experience with heater coking and typical run lengths? Are you using on-line cleaning (like coker heater spalling)?

For a properly designed vacuum heater, it should be possible for the heater to last the entire run between cycle ending turnarounds without having to decoke the heater. This requires the heater to have been designed with the appropriate heat flux and mass flux rates.

(2018) Question 36: How do you manage the potential negative impacts of H2S Scavengers in imported coker feed?

How do you manage the potential negative impacts of H2S Scavengers in imported coker feed?

(2018) Question 37: Do you extend the time between de-coking the furnace by cutting coil outlet temperature or cutting furnace charge? How often are spallings done in coker furnaces? What is the temperature recovery after spalling?

Heater fouling is dependent on several variables that include the process film temperature, residence time at temperature and coke precursor concentration. I like to target a coke drum outlet temperature of 825°F before quench injection, which normally requires a Coker heater outlet temperature of 925°F.

(2018) Question 38: How does coke morphology vary with changes in feed quality? What feed tests do you require to quantify the impact on coke quality?

Predicting coke morphology from feed properties has not been 100% successful as the Coker operating conditions can make a difference if the feed is close to the shot coke vs. sponge coke threshold. The traditional approach uses the asphaltene content of the feed divided by the concarbon value of the feed.

(2018) Question 39: What operating conditions increase the generation of coke fines? What reliability issues do you associate with increased fines production?

Coke fine generation is really a function of the coke cutting process. Feed stock and coke drum operations during the actual drum fill cycle have very little to nothing to do with the generation of coke fines.

(2018) Question 40: What is your experience, design and opportunities for on-line crude blending coupled with near infra-red?

What is your experience, design and opportunities for on-line crude blending coupled with near infra-red?

(2018) Question 46: What is your strategy to minimize main fractionator bottoms (DCO/ Slurry) versus LCO production apart from feed quality/catalyst selection?

The primary operational handles to minimize bottoms production is optimization of the cat to oil in the R&R. As the C/O is increased more of the heavy oils will be converted. As with all good things in the FCC this can be taken too far. Limits can be reached on the actual operating equipment in this process.

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

Q&A