Q&A

(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 41: What effective practices do you deploy to improve the removal of inorganic contaminants in crude such as iron and calcium? What has been the industry success rate with these practices?

Cracked feedstocks can be introduced into the crude unit from several sources; the most common of which in North America are diluted bitumen from Canadian sources, diluted crude oils from South American sources, and slop streams from cracking units onsite that are recycled into the reprocessed slop oil blended into the crude unit feedstream.

(2018) Question 42: Some of the lighter waxy crudes have higher paraffin melting points making it difficult to treat and remove solids, salts in the desalter. What practices do you deploy to manage these higher melting point waxy crudes?

Some of the lighter waxy crudes have higher paraffin melting points making it difficult to treat and remove solids, salts in the desalter. What practices do you deploy to manage these higher melting point waxy crudes?

(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.

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