Q&A

(2010) Question 65: What methods do you use for heat recovery from furnace flue gas equipment at ~260°C (500°F)?

Air preheat systems are used for recovery of heat from flue gas down to app. 300 deg F. The 300 deg F temperature is set based on limiting dewpoint corrosion on cold metal surfaces. This temperature will vary depending on the materials employed, the sulfur content of the treated fuel gas, and cold ambient temperature.

(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 68: Do you see any benefit in continuing to steam strip crude tower distillate cuts since these side streams require further processing in down stream hydrotreaters?

We have observed definite benefits to steam stripping the distillate cuts and have been working to determine whether the benefit is worth the cost. The main purpose for distillate side strippers is to control product flash with a secondary purpose of lifting lighter material and affecting the product cuts.

(2010) Question 69: What do you see as the critical considerations for wash bed design in high C-factor vacuum columns? How does one determine bed type, depth, and appropriate wash oil distributor design?

A new vacuum column will typically be designed for a C-factor of 0.36 ft/sec above the wash zone which is normally the section with the highest vapor velocity. A high C-factor situation (say above 0.43) would then involve an existing unit operating well above its original design point.

(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 78: In your experience, how effective and reliable are hydrocyclones, electrostatic separator, additives, and filters in reducing the ash content of the slurry?

There are basically 3 types of ways to reduce the ash content in slurry oil. They are electrostatic separators, additives with settling and filters. They all have their advantages and disadvantages, and they all do a reasonable job in reducing ash in slurry.

(2010) Question 80: What best practices do you recommend to improve LCO recovery? Do changes in LCO pump around affect LCO recovery? What are common challenges?

There has been a lot of work and discussion on LCO maximization at the FCCU and there is plenty of literature on different options for LCO recovery. This will be a general overview of available options to refiners and some challenges recently experienced at Coffeyville.

(2010) Question 85: What is the typical range that you employ for iron content on FCC equilibrium catalyst? What methods are available to determine how iron is accumulated on the catalyst surface? How does the distribution of iron on the catalyst surface impact the FCC operation, yield structure and emissions?

There are several methods available to quantify iron contamination on catalyst. Scanning Electron Microscopy (SEM) pictures are a valuable means to qualitatively assess iron laydown morphology on the catalyst particle.

(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 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.

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