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6 Ways to Benefit from Reducing Diesel Sulfur Giveaway

By Optimization Specialist Robert

Aug 09, 2015
 

Quick tips on how to benefit from reducing refinery diesel sulfur giveaway.

 
 

It has been a fairly difficult process preparing the refining industry to produce 15 ppm diesel.  Most refiners had to make substantial capital investment to enable the catalytic capability, but the majority of the global market is now there. 

 

Sulfur giveaway with diesel product in the 15 ppm range is a lot more costly than sulfur giveaway in the 500 ppm range.  Most refiners intuitively understand that “hard sulfur” molecules, such as sterically hindered dibenzothiophene, require a significant amount of Umph to treat.  However, many do not really know how to translate that into actual dollar costs.

 

Have you often wondered what the value of sulfur giveaway is for your diesel product?  Do you feel that there is adequate attention paid to minimizing diesel product giveaway at your refinery?  If not, the tips below will provide methods to accurately access the value of diesel sulfur giveaway. 

 

 

 

 

1. Hydraulic Capacity

 

The Umph required to hydrotreat diesel streams comes from two primary means.  The first is having adequate catalyst activity, and the second is having sufficient hydrogen partial pressure.  If your diesel product has sulfur giveaway, you can likely recover some unit throughput by manipulating hydrogen partial pressure. 

 

For refiners that are diesel hydrotreating capacity limited, increased rate capability can have significant dollar benefits.  To change hydrogen partial pressure, you have two options to consider:

 

Reduce Unit Pressure

Depending on unit configuration and downstream hydrogen handling options, some units have the ability to reduce overall unit pressure.  This is more likely the case if there is no hydrogen recycle compressor on the unit (i.e. once through hydrogen).  Since pressure drop is proportional to the square of flow-rate, an increase in total unit rates can be achieved by increasing the allowable pressure drop through the reactor system.

 

Reduce Hydrogen Circulation

Since hydrotreaters operate with a high hydrogen to hydrocarbon ratio, reducing the hydrogen circulation is often an effective way of taking advantage of product sulfur giveaway.  Consideration must be given to the potential rate increase in catalyst activity loss, but often times this is not a limiting factor, or economics still favor the move. 

 

Reduced hydrogen circulation can be achieved for hydrotreater units with once through hydrogen or recycle capabilities.  In addition to increased hydraulic capacity, reducing hydrogen circulation has potential benefits of reducing energy consumption as well as reducing hydrogen consumption (i.e. aromatic saturation).  Reducing hydrogen consumption may or may not be a benefit depending on refinery hydrogen balance and diesel product aromatics/cetane balance.

 

 

2. Diesel Yield                                                       

 

Reducing diesel sulfur giveaway can often times translate to higher diesel yields.  Many refiners under-cut diesel endpoint to ensure that product specs are met.  However, the converse move of increasing diesel endpoint when product sulfur giveaway exists does not often occur.  If there is room on 90% spec, you should give good consideration to increasing diesel recovery though higher endpoints.

 

 

 

 

3. Product Upgrading

 

Increasing the amount of cycle oil processing in a diesel hydrotreater can often yield strong benefits.  Some refiners limit cycle oil processing due to catalyst runlength concerns.  For refineries with diesel sulfur giveaway, this opportunity can often translate to increased LCO processing.  This can be a $5 or $10/bbl upgrade depending on market conditions. 

 

 

4. Increase Unit Runlength

 

If there are strong economic drivers, why not simply operate the hydrotreater at reduced severity to increased runlength duration?  A good rule of thumb many ULSD units can utilize is that 1 ppm sulfur reduction is equivalent to roughly 3 months runlength.  Over-treating diesel product by 2 ppm has the potential to cut runlength short by 6 months!  

 

 

"Over-treating diesel product by 2 ppm has the potential

to cut runlength short by 6 months!" 

 

 

Longer diesel hydrotreater runlenghts can  enable more optimal refinery shutdown pairings.  Refiners can also reduce annualized catalyst expenses or even increase annualized refinery utilization with longer catalyst runlengths. 

 

 

5. Reduce Catalyst Expense

 

I bet your refinery expense budget increased significantly when switching production from Low Sulfur Diesel to Ultra Low Sulfur Diesel.  It’s likely that many refiners over-designed their unit capabilities to ensure performance success.  If your refinery diesel product has sulfur giveaway, here’s a potential opportunity to recover some of that expense creep.  Re-assess your catalyst loading scheme and see if you can reduce expenses by reducing catalyst activity in your next fill.

 

 

6. Reduce Energy Expense

 

Energy may be cheap these days, but it doesn’t mean that you have to waste it.  Fire down your heaters and reduce refinery fuel gas requirements as a quick way of capturing benefits for reducing diesel sulfur giveaway. 

 

 

 

Whether you are a process engineer or a planning analyst, many people often find it challenging understanding the value of diesel product giveaway.  Listed above are 6 ways to capitalize on sulfur giveaway, and all have very astounding benefits.  

 

 

Most opportunities maximize diesel yield as a means of increasing refinery profits. The most appropriate opportunity for your refinery may even be a combination of items above since some are synergistic and some compete against others. 

 

 

At the end of the day, it’s easier to focus an organization on improving performance once they have a credible value driver to target.  Define what option provides maximum benefit and capture your reward!

 
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  • Eric Vetters :   One important additional factor that must be considered in reducing sulfur giveaway is the cost of making off spec product. Before making changes the refinery should consider the cost of off spec product and the likelihood of making before making changes. If not done, the cost savings could be easily overwhelmed by the costs of making bad product. The refiner should also consider future unknowns and flexibility when making decisions. Steps like reducing pressure or hydrogen circulation will negatively impact run length and can take away flexibility to run poorer quality feeds or increase rate down the road. Steps like reducing temperature to stay on spec may have smaller immediate benefits but they retain flexibility that can allow the refiner to gain even bigger benefits down the road.

    Aug 12, 2015

  • Stefano Cefaratti :   I see following additional savings: more high sulphur crude that can be processed (less expensive than sweet one), less lubricity improver consumption (sulphur helps lubricity)...

    Aug 13, 2015

  • Vishvedeep Bhat :   Reduce pressure in steps of 5 bars at a time and see the benefit on H2 consumption and RGC/MUGC utility cost. Evaluate H2 consumption vs product yield. Product yield vol% will go down so less profit $$, H2 consumption will go down so you will save some$$. Done it few times. Try to also find out the limits by aromatic saturation/C.I/CN. Drop the kerosene cut in the diesel stream if the hydrotreater has a main fractionator within limits of flash point. It will further improve sulfur. It can be done outiside units in tanks also. To study the effect on catalyst of pressure reduction, you need to wait for few weeks before making the next move. At EOR conditions Diesel give away benefits wont be that attractive or even feasible.

    Apr 13, 2016

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