yet underappreciated opportunity.  Not only can a refinerconvert molecules between gasoline and distillate through jet optimization, but refiners can also convert molecules between distillate and gasoils. 

Many engineers focus primarily on the separation between jet and diesel, and that misses half of the picture.

While every refinery will have different unit configurations and operating constraints, I’ll list the key variables that all refiners should evaluate.  Even if you think some variables may not be applicable to your refinery, I challenge you to think twice as creativity often finds alternate solutions to your status quo.

Jet Flash

Although off-spec flash is very hard to correct, the value driver to maximizing the amount of naphtha a refiner can drop into Jet can be significant.  While most regions have experienced the strength in distillates over the past 5 years, many refiners are slow to close the gaps in base operating fundamentals.  Although the incentive to maximize distillate production can be high, many refiners still leave a lot of flash room on Jet product. 

With up to a $20/bbl incentive to produce Jet instead of gasoline, Jet flash giveaway can often lead to leaving millions of dollars on the table.  From my travels around the world, the best in class refiners can reduce flash giveaway to around 2 deg F.  Compare this benchmark to your refinery’s current operations and assess where you stand.  With accurate lab measurements and focused operations, flash giveaway opportunity can be quickly closed to enhance revenue capture.

Jet Freeze

After pursuing front end distillation optimization with Jet Flash, it’s now time to turn your attention to Jet Freeze optimization.  The most common mistake that many make is assuming that freeze is not worth optimizing because the difference in product value between Jet and Diesel has not been as high as historically seen.  Prior to Ultra Low Sulfur Diesel regulations, Jet premiums often fetched a $5/bbl incentive relative to diesel.  These days a region can often see Diesel prices higher than that of Jet prices.

So while product prices may not largely drive Jet Freeze optimization, I propose that you look at Freeze optimization in terms of maximizing overall distillate yields.  As distillate prices have strengthened, the value of recovering distillates from gasoils has often increased.  And YES, jet freeze optimization can have a big impact on diesel recovery from gasoil. 

"YES, jet freeze optimization can have a big  

impact on diesel recovery from gasoil"

Refiners have two means of managing jet and diesel interface.  One can change the column distillation within a crude atmospheric unit and shift the cutpoint between jet and diesel.  Alternatively, one can externally route jet to the diesel pool through stream routing downstream of the crude unit.  Depending on what options your refinery has, you have two levels of jet freeze optimization.

If your refinery does not have external jet routing capabilities, then jet freeze optimization will be a function of jet vs diesel premiums and diesel spec constraints.  If any of the following constraints exist at your refinery, then maximizing jet freeze giveaway should be considered:

• Diesel T90 limited
• Diesel cloud limited (or any cold flow property equivalent)
• Diesel cetane limited
• Diesel viscosity limited
• Diesel density limited

By maximizing jet freeze giveaway (i.e. minimizing jet/diesel cutpoint), a refiner can increase the amount of jet molecules dropped into diesel to alleviate any of the constraints listed above.  Even when jet prices are above that of diesel, this can be a viable opportunity as the recovery of diesel from gasoil can offset the downgrade of jet to diesel. 

If your refinery does have external jet routing capabilities, then jet freeze optimization will have a different strategy.  In this scenario, it often makes sense to minimize jet freeze giveaway.  Minimizing jet freeze (i.e. maximizing jet/diesel cutpoint) enables a refiner the ability to externally route more jet to the diesel pool. 

Refineries that make a jet cut often have diesel flash giveaway, so maximizing the amount of whole range jet routed to diesel will increase diesel recovery from gasoil if diesel production is constrained by a quality spec listed above.   Best in class performance is 1 deg C freeze giveaway – where does your refinery stand in comparison?

Military Jet Fuel Production

additives (from anti-oxidants, to de-icing inhibitors, etc…), military jet production can be a lucrative opportunity. 

Anytime you deal with government you can extract more money than required effort; however, when evaluating the economics to pursue this keep in mind the Freeze optimization discussion above.    

Mercaptans 

Unlike diesel production, many refiners can still produce on-spec jet without a hydrotreater.   For those refineries with merox units, engineers often focus on process unit troubleshooting while overlooking assay qualities.  In today’s market where the discount on crude sulfur doesn’t carry the same weight as historic, it pays off to ensure assay qualities are updated.  Allow the refinery LP the choice to optimize crude selection based on sulfur content. 

Also, it pays to understand how mercaptans distribute within the jet cut.  Inexperienced refiners often make the mistake of reducing jet cutpoint to manage a meraptan issue when the opposite action is required.  Closer scrutiny of the jet cut for many crude assays indicate that mercaptans concentrate in the lighter portion of jet.  Mercaptan dilution in this scenario comes in the form of increasing jet endpoint – quite counterintuitive for many!  

Naphtalenes

Similar to mercaptans, naphthalenes is a spec that is best managed though assay validation.  Ensure that naphthalene content is updated for LP crude evaluation, and allow the planning tool to optimize accordingly.  Once the crude is procured, distillation then becomes the handle to manage naphthalene content.  

Thermal Stability

This is an entire blog on its own, so I’ll save this topic for another discussion.  In the meantime, I’m sure that I have given you enough meat to chew on for optimizing your refinery jet production.