Q&A

(2014) Question 24: What is the maximum oxygen content you allow for the platinum redistribution step in a fixed bed reformer? What sets the maximum oxygen concentration?

Directionally the higher O2 level is better for metal dispersion during oxidization. UOP recommends aminimum of 5% with typical maximum O2 content of 8-10 mol% based on the seal oil combustion limits. Dry seals or nitrogen purge seals allow higher O2 content without explosive conditions.

(2014) Question 25: What factors contribute to your decision to place the regeneration section of a CCR in standby mode when the unit is operating in a low-coke mode? Discuss the advantages and disadvantages of the different standby modes (black-catalyst circulation, hot-shutdown, cold-shutdown, etc.).

If the coke content is very low in comparison with the coke burn capacity of the CCR unit, the operation can be limited in one of a few ways. A minimum gas flow is required to ensure the catalyst is properly dried before leaving the regenerator and returning for reduction.

(2014) Question 26: What are options for disposition of the caustic regeneration outgas stream associated with an LPG or gasoline caustic treater? What measures have you successfully used to prevent fouling, pluggage, and corrosion in this line?

The caustic treating off gas stream is primarily air that has been partially depleted of oxygen during the oxidation of mercaptides to disulfides in the caustic regeneration step.

(2014) Question 27: What impacts are you seeing in naphtha processing units from contaminants suspected to come from shale crudes (e.g. tramp amines, chlorides, fouling)? What are you doing to mitigate these impacts?

Tramp amines, chlorides, and fouling related to processing of Shale Crudes (or more specifically, Tight Oils) are issues that are of concern on the Crude Unit. I am not aware of issues specific to the gasoline pool and blending downstream of the crude unit.

(2014) Question 56: How will the recently announced EPA requirement to depressure coke drums to below 2 Psig prior to venting to atmosphere regulations impact your coker operation and design?

In order to meet the potential requirement of less than 2 psig prior to atmospheric venting, new units designed to operate at low coke drum pressure will require additional equipment such as an ejector system discharging to a condenser (potentially the blowdown or fractionator overhead condenser) to adequately reduce the coke drum pressure prior to atmospheric venting.

(2014) Question 57: If vacuum tower bottom feed to the Coker unit drops below unit minimum, what are your operating options available?

Increasing amount of tight oil production with hardly any residual fraction will lead to challenges in filling up the Delayed Coking Unit (DCU). In order to maintain the DCU capacity, external purchase of HFO or VR will have to be made.

(2014) Question 58: What are you using for velocity medium in coker heaters? Are you using boiler feed water?

If Condensate or BFW is used as velocity media or to clear the heater tubes during a heater trip, precautions must be taken as excess free water has the potential to overpressure the heater during a shut-in condition.

(2014) Question 59: What is your experience processing a crude oil that has been treated with a pour point depressant and/or wax dispersant agent?

Some laboratory simulation experience has demonstrated that there were no adverse impacts to processing crude oil treated with a certain pour point depressant relative to oil-water separation for desalting.

(2014) Question 60: How does the mercury in crude distribute in your refinery (e.g., what units are affected)? What operating procedures or technology are you using to mitigate this issue?

How does the mercury in crude distribute in your refinery (e.g., what units are affected)? What operating procedures or technology are you using to mitigate this issue?

(2014) Question 61: What measurement and/or predictive methods are you using to determine crude oil blend compatibility?

Various methods exist to determine blend compatibility; one method would be a comparative asphaltene instability point determination via an anti-solvent titration, or another method used is the Wiehe insolubility number to solubility blend number method.

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

Q&A