Q&A

(2016) Question 63: What are your current methods used for regenerator cyclone temperature control? Do you use water sprays or steam injection?

In the early days of FCC, the normal bed and dilute-phase operating temperatures –being less than 1100°F –did not support CO combustion. These units operated with high levels of carbon on catalyst and about 10 vol% CO in the flue gas with almost no excess oxygen in the flue gas.

(2016) Question 64: What are your typical operating guidelines to prevent compressor surge episodes? How closely do your FCCU operators approach the actual surge line of a compressor before adjusting operation?

[United Refining Company (URC)] The unit engineer/compressor manufacturer should be able to provide guidelines to prevent surge episodes. These guidelines may include safe windows of operation for air rates, discharge pressures, and discharge temperatures.

(2016) Question 65: Please comment on which FCC feed types you are currently processing and what chemicals you are using for gas plant corrosion prevention. Is waterwashing sufficient to sustain adequate unit reliability?

Our refinery typically runs Western Canadian Crudes, SYN, and some conventional heavy crudes.

(2016) Question 66: In your experience, how does changing the feed cutpoints impact FCC conversion and product yields? How does the LP (liquefied petroleum) determine where to make these cutpoints?

Deeper cuts will not have as high a conversion as will lighter cuts. For example, an FCC charge API gravity of 22 may have a conversion of 83%, while a lighter gravity of 23 will show conversion one point higher at 84%.

(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 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.

Question 42: What are your best practices to minimize catalyst carry over to the main column on start up?

Catalyst loss events experienced while bringing the FCC online after a shutdown are troublesome as they can add significant cost and delay to the startup. Because the main air blower is run close to design conditions throughout the startup, losses are more frequently observed from the reactor side.

(2019) Question 45: What are your options to maximize light cycle oil from the FCCU (e.g. operating conditions, feedstock, recycle, equipment, catalyst, etc.)?  What are the typical unit constraints?  What projects have been considered at your facility to capture the increased value of diesel?

There are multiple ways to maximize light cycle oil from the FCC including reducing conversion, reformulating the fresh catalyst, utilizing additives, and adjusting fractionation.

(2019) Question 46: How often do you perform steam optimization in the FCC reactor? What process response and benefits do you typically see from performing "step tests" to feed nozzle, lift, and stripping steam flow rates?

How often do you perform steam optimization in the FCC reactor? What process response and benefits do you typically see from performing "step tests" to feed nozzle, lift, and stripping steam flow rates?

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